CA1228479A

CA1228479A - Heat transfer sheet

Info

Publication number: CA1228479A
Application number: CA000475688A
Authority: CA
Inventors: Mineo Yamauchi; Masaki Kutsukake; Masanori Akada
Original assignee: Dai Nippon Printing Co Ltd
Current assignee: Dai Nippon Printing Co Ltd
Priority date: 1984-03-02
Filing date: 1985-03-04
Publication date: 1987-10-27
Also published as: US4559273A; DE3573235D1; EP0153880A3; EP0153880B1; EP0153880A2

Abstract

ABSTRACT OF THE DISCLOSURE

This invention relates to a novel heat transfer sheet. By providing a heat-resistant protective layer comprising specific ingredients on a first sur-face of a base sheet having a heat transfer layer on a second surface thereof, there is obtained a heat transfer sheet wherein the running of a thermal head is smooth during recording; wherein an image having a high density and exhibiting no surface roughness at printing areas can be provided; wherein when the heat transfer sheet is wound up and stored, a dye does not migrate to the heat-resistant protective layer;
and wherein the adhesion between the heat transfer sheet and a roll or the like does not occur within traveling apparatus.

Description

;
~228~

HEAT TRANSFER SHEET

GROUND OF THE INVENTION
This invention relates to a heat transfer sheet, and more particularly to a heat transfer sheet suit-able or carrying out heat printing in accordance with image information by heating means such as thermal heads in order to form an image onto a heat transferable sheet or a sheet to be heat transferred.
More specifically, this invention relates to a heat transfer sheet provided with a heat-resistant prick-live layer capable of preventing the fusion bonding between the heat transfer sheet and thermal heads in printing or running the thermal heads Heretofore, a heat sensitive color-producing paper has been primarily used in order to obtain an image in accordance with image information by means of thermal heads. In this heat sensitive color-producing paper, a colorless or pale-colored Luke dye (at room temperature) and a developer (such as bisphenol A) provided on a base paper are contacted and reacted by the application of heat to obtain a developed color image However, the heat sensitive color-producing paper as described above has serious drawbacks in that its color disappears and non-image areas form - color when the resulting image is stored for a long period of time. Further, color printing is restrict-Ed to two colors, and thus it is impossible to obtain a color image having a continuous gradation.
On the other hand, products which have been recently used in order to overcome the drakes as described above are a heat sensitive fusing transfer sheet wherein a heat-fusing wax layer having a pigment or dye dispersed therein is provided on a sheet-shaped base; and a heat sensitive sublimation transfer sheet wherein a heat sensitive sublimation transfer lo layer comprising a dye having heat transferability and a binder therefore is provided on a sheet-shaped substrate.
When this heat sensitive fusing transfer sheet is laminated with a heat transferable sheet and then heat printing is carried out from the back of the heat sensitive fusing transfer sheet, the heat fusing wax layer containing the pigment or dye is transfer red onto the heat transferable sheet to obtain an image. According to this printing process, an image having higher durability than that of the heat sense-live color-producing sheet can be obtained, and a multi-color image can be obtained by using a heat sensitive transfer sheet containing three primary color pigments or dyes and printing it many times.
On the other hand, in the heat sensitive Sybil-motion transfer sheet, the binder layer containing the dye having heat transferability is provided on the sheet-shaped base or substrate. When this heat sensitive sublimation transfer sheet is laminated with a heat transferable sheet and then heat printing is carried out from the back of the heat sensitive sublimation transfer sheet, only dye present in the binder layer is heat sublimated and transferred on the heat transferable sheet to obtain an image. In this printing process, a multi-color image can be also obtained by using a heat sensitive sublimation trueness for sheet containing three primary color dyes having heat transferability and printing it many times.
In recent years, there has been a growing demand or a method and means for obtaining an image having a continuous gradation like a color photograph directly from an electrical signal and a variety of attempts have been made to meet this demand.
One of such attempt is a process for directly obtaining a silver salt color photograph from a cathode-xay tube (CRT) picture. However, this process I

is accompanied my the following drawbacks. The run-nine cost is high. When silver salt film is a 35 mm film, the image cannot be instantly obtained because it is necessary to carry out a development treatment after the photographing An impact ribbon process and an ink jet process have been proposed as further processes. however, in these processes, the quality of the image is inf~xior and an image treatment is required. Thus, it is imp lo possible to simply obtain an image like a photograph.
In order to overcome such drawbacks, an attempt has been made to carry out the recording by using the heat sensitive sublimation transfer sheet described above. In this process comprising using this heat sensitive sublimation transfer sheet, the dye having heat transferability present in the heat sensitive sublimation transfer layer is transferred onto the transferable sheet according to the amount of heft energy applied to the heat sensitive sublimation trays- -for sheet.- Accordingly, an image having a continuous gradation can be obtained and recording can be carried out fry a televisioll signal by a simple treatment.
Examples of the bases of the heat transfer sheet -heretofore used are condenser papers, polyester films, polypropylene films, cellophane and cellulose acetate films. The thickness of the base used is of the order of lo microns.
Of these bases, if cost is regarded as being important, condenser paper has been used. If resist-ante to rupture during application processing, operate in simplicity in a printer uniform thickness and smooth surface are regarded as being important, plastic films have been used. Of plastic films, if the strength in the case of tissue paper is regarded as being important, a polyester film has been part-ocularly preferably used.
A heat sensitive sublimation transfer layer comprising a heat sublimable dye and a binder there-for can be provided on such a polyester film, and heat printing can be carried out from the film sun-face provided with no heat sensitive sublimation transfer layer by means of a thermal head. However, when energy required for obtaining an image having a sufficient printing density is applied to the back surface of the film, the base sheet so may fuse with the thermal head. Thus, so-called sticking phenomenon is observed and in some cases it is imp possible to run the heat transfer sheet. In certain vases, the sheet may be broken from the fused port lions.
In ardor to overcome these problems, several attempts have been proposed to provide the back sun-face of the base sheet of a heat sensitive fusing transfer sheet with a heat-resistant protective layer Examples of such heat sensitive fusing transfer sheets are those wherein the back surface of a base is pro-voided with a metallic layer or a silicone oxide layers a wear-resistant layer (Japanese Patent Laid-Open Pub Noah, and Japanese Patent Lowdown Pub. Noah), with a layer of heat-resistant resins such as silicone and epoxy resins (Japanese Patent Laid-Open Pub. Noah), with a resin layer containing a surfactant which is solid or semi-solid at room temperature (Japanese Patent Laid-Open Pub. Noah), and with a layer comprising a lubricating inorganic pigment and a heat-resistant resin therefore (Japanese Patent Laid-Open Pub. No..
155794/19~1).
When the heat resistant protective layer proposed in these Japanese Patent Laid-Open Publications is provided on the back surface of the heat sensitive sublimation transfer sheet to a film thickness of about 3 microns and then printing is carried out by means of a thermal head, in all cases, the sticking phenomenon ye is observed. Thus, the heat-resistant protective layers proposed cannot function as the protective layer.
This is because the heat-xesistant protective layer of tile heat sensitive sublimation transfer sheet described above undergoes high energy in print in. When heat energy required for heat sensitive fusing transfer recording is compared with heat energy for obtaining a sufficient recording density, in a heat sensitive sublimation recording process wherein a sublimable dye is used, energy required for heat sensitive sublimation recording is at least about 1.5 times that required for heat sensitive fuss in recording.
In order to overcome these problems, we have further carried out studies to find heat-resistant resins capable of using in the heat sensitive Sybil-motion transfer sheet and to find systems wherein a lubricating material is incorporated in the resin '20 described above. We have found the following facts.
In order to produce a heat sensitive sublimation Jo transfer sheet provided with a heat-resistant protect live layer by inexpensive processes such as coating rather than expensive processes such as vacuum depot session, it is necessary to use a resin having heat resistance as a assay. In order to prevent the reduction of the heat sensitivity of a polyester film having a , , thickness of from about 6 to 10 microns, it is pie-fireball that the heat-resistant protective lyres a thickness of from about 0.5 to 3 microns. In order to make it possible to carry out printing and running in the case of the heat transfer sheet provided with the heat-resistant protective layer having the thick-news ranges described above, it is necessary to add any lubricating material to the resin base described above. When known inorganic materials such as talc and mica are added to the resin base as the lubricating ~2~8~

material in a large amount to form a heat-resistant protective layer, running is not smooth and the solid areas become rough. Further, such inorganic mate-fiats may adhere to the thermal head.
In view of these findings, we have carried out further studies. As a result, we have now found that the use of a heat transfer sheet provided with a heat-resistant protective layer comprising specific components affords a heat transfer sheet capable of providing an image having a high density wherein the running of the thermal head is smooth during record-ivy and the printing areas are not rough. The present invention has been developed on the basis of this discovery.
SUMMARY OF THE INVENTION
The present invention has been developed to achieve the following objects.
(a One object is to provide a heat transfer -sheet capable of running a -thermal head without any sticking phenomenon even if it is heated to a consider-ably higher temperature than that of the case of a hoe. sensitive fusing transfer sheet by means of a thermal head.
(h) Another object is to provide a heat transfer sheet wherein surface roughness does not occur at the printing areas.
(c) A further object is to provide a heat trays-for sheet wherein the materials present in a heat-resistant protective layer do not adhere to a thermal head even if heat printing is continuously carried out by the thermal head.
In order to achieve the above objects, according to the present invention, there is provided a heat transfer sheet comprising a heat transfer layer provide Ed on one surface of a base sheet or substrate, and aheat-resistant protective layer provided on the other surface of said base sheet, i.e., the surface provided I

with no heat transfer layer, said heat-resistant protective layer containing (a) polyvinyl bitterly, (b) an isocyanate such as diisocyanate and Tracy-Senate, and (c) a compound selected from the group consisting of phosphoric esters, its alkali metal and alkaline earth metal salts, and mixtures there-ox.
A heat transfer sheet according to the present invention may have a heat melting wax layer comprise in a dye or pigment and a wax material therefore as the heat transfer layer. A heat transfer sheet according to the present invention may have a binder layer containing a dye having heat transferability as the heat transfer layer. It is particularly pro-fireball that a heat transfer sheet according to the present invention has a binder layer containing a dye having heat transferability.
BRIEF DESCRIPTION OF THE DRAWING
_ _ In the accompanying drawing:
Figure is a sectional view of a heat transfer sheet according to the present invention.
retailed DISSUASION OF THE Invention - A preferred embodiment of the present invention shown in the drawing will now be described.
As shown in Figure, a heat transfer sheet 1 according to the present invention comprises a heat transfer layer 3 provided on one surface of a base sheet 2, and a heat-resistant protective layer 4 provided on a surface having no heat transfer layer.
Films such as polyester film, polystyrene film, polysulfone film, polyvinyl alcohol film and cello-plane can be used as the base sheet. Polyester film is particularly preferred from the standpoint of heat resistance. The thickness of the base sheet is 35 from 3 to 50 micrometers, preferably from 3 to 10 micrometers.
The heat transfer layer 3 may by a heat sensitive ply sublimation transfer layer comprising a sublimable dye and a binder resin therefore The heat transfer layer 3 may be also a heat sensitive fusing transfer layer comprising dye or pigment and a wax material therefore In the heat sensitive sublimation transfer layer 3, the subl:imable dye is contained in the binder resin. The thickness of this layer is from about 0.2 to about: 5.0 micrometers, preferably from lo about 0.4 to 2.0 micrometers.
The dye incorporated in the sublimation transfer layer 3 is desirably a disperse dye. This dye desire ably has a molecular weight of from about 150 to about 400. The dye can be selected by considering heat sublimation temperature, hue, weather ability, stability in binder-resin/ and other factors. Exam-pies of such dyes are as follows: Mike ton Polyester Yellow-YL*(C.I. Disperse Yellow-42, manufactured by Mets Toyotas, Japan), Cousteau Yolks Disperse Yellow 77 r manufactured by Nippon Kayak, Japan), TOKYO I. Solvent Yellow 14-l, manufactured by Mitsubishi Casey, Japan Mike ton Polyester Red BSF*
(KIWI. Disperse Red ill, manufactured by Mets Toyotas, Japan), Cousteau Red B*(C.I. Disperse Red B, manufacture Ed by Nippon Kayak, Japan), TRUCK. Disperse Red 50, manufactured by Mitsubishi Casey, Japan), Mike ton Polyester Blue FBL*(C.I. Disperse blue 56, manufactured by Mets Toyotas Japan), PTB-67*(C.I.
Disperse Blue 241, manufactured by Mitsubishi Casey, Japan), Cousteau Blue KIWI. Solvent 112, manufacture Ed by Nippon Kayak, Japan).
While the amount of the dye can vary depending upon the sublimation temperature of the dye, the degree of covering power in a developed color state, the dye is usually present in the heat transfer layer in an amount of about I to 70~ by weight, preferably prom about 10~ to 60~ by weight.
* trade mark . . .

iota Binder resins are those which ordinarily have high heat resistance and do not prevent the transfer of the dye during heating. For example, the follow-in binders can be used.
S (1) Cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethylhydroxy cellulose, hydroxypropyl cellulose, methyl cellulose cellulose acetate and cellulose acetate bitterroot.

(2) Vinyl resins such as polyvinyl alcohol, polyvinyl acetate polyvinyl utterly, polyvinyl pyrrolidone, polyester, and polyacrylamide.
In order to provide such a heat transfer layer

3 on the base sheet 2, the dye and the binder rosin may be dissolved in a solvent or only dye may be disk pursed therein to prepare an ink composition for forming a sublimation transfer layer this ink come position may be provided on the base sheet 2 by suit-able printing processes or application processes.
Optional additives may be admixed in the in compost-lion for forming sublimation transfer layer as needed.
On the other hand, examples of binders for thereat sensitive fusing transfer layer 3 are carnauba wax, paraffin wax, acid wax and suitable synthetic binders. A dye or pigment is used as a colorant The colorant is usually added in an amount of from So to 30% by weight of the binder.
The heat-resistant protective layer 4 is a layer mainly comprising (a) polyvinyl bitterly, (by an is-Senate and (c) a compound selected from the group consisting of phosphoric esters, its alkali metal and alkaline earth metal salts, and mixtures thereof.
Polyvinyl bitterly reacts with an isocyanate to form a resin having Good heat resistance. Preferred polyp vinyl bitterly resins are those having a molecular weight as high as possible and containing a large amount of an -OH group which is a reaction sit with the isocyanate. Particularly preferred polyvinyl bitterly resins are those having a molecular weight of from 60,000 to 200,000, a glass transition temperature of from 60C to 110C and a vinyl alcohol content of from 15% to 40~ by weight.
Specific examples of isocyanate compounds such as diisocyanates and triisocyanates used in forming -the heat-resistant protective layer are para-phenylene-diisocyanate, 1 chloro-2,4-phenylenediisocyanate, 2-chloro-l,~-phenylenediisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, hexamethylene diisocyanate, 4,4'-biphenylene diisocyanate, in-phenylmethane triisocyanate, and 4,4',4"-trimethyl-3,3',2'-triisocyanate-2,4,6-triphenylene isocyanurate.
Diisocyanate or triisocyanate is usually used in an amount ox from about 1% to 100% by weight, prefer-ably from about 5% to 60% by weight of polyvinyl bitterly.
Phosphoric esters and its alkali metal and alkaline earth metal salts are used as a lubricant in -the present invention. The phosphoric esters used - as the lubricant are not in a salt form of alkali metal and alkaline earth metal salts of phosphoric esters described hereinafter. Specific examples of such phosphoric esters for use herein are Ply surf A 208 Available from Douche Cage Seiko, Japan, and GAFAC US availably from Tao Kagaku, Japan.
Such phosphoric esters are used in an amount of from I to 60% by weight, preferably from 5% to 30% by weight ox polyvinyl bitterly. Because the phosphoric ester is added as the lubricant in such a state that the phosphoric ester is molecularly dissolved in a binder, the surface roughness of printing areas does not occur whereas solid lubricants such as mica and talc occur such a surface roughness. In traveling the heat transfer sheet within the printing travel apparatus and the like, the travel problem of the heat transfer sheet may occur by virtue of tension * trade ok applied to this sheet or the printing pressure of a thermal head. In this case, the phosphoric ester is used alone, or used in combination with its metal salt described hereinafter.
An example of an alkali metal or alkaline earth metal salt of the phosphoric acid for use herein is GAFAC ROD availably from Tao Cook, Japan. This alkali petal or alkaline earth metal salt of the phosphoric ester is used in an amount of from 1% to 50~ by weight, preferably from 10% to I by weight of polyvinyl bitterly. Because the alkali metal or alkaline earth metal salt of the phosphoric ester is aided as the lubricant in such a state that it is molecularly dissolved in a binder, the surface rough-news of printing area does not occur whereas solid lubricants such as mica and talc occur such a surface roughness.
Particularly preferred salts of the phosphoric acid esters are sodium salts of phosphoric esters. Examples of such salts are represented by the following general formulae:
[ Sheehan \ //

/ \
HO Ova Rescission / o No OH
[ Sheehan o No Ova RO-[c~2cH2o]n / o [SHEA 2]n Ova ! it * trade mark .. I. ., 8~7~

wherein R is an alkyd or alkylphenyl group contain-in from B to 30 carbon atoms and n is an average addition mole number of ethylene oxide.
When the alkali metal or alkaline earth metal salt of phosphoric ester is compared with the eon-responding phosphoric ester (not salt), the former exhibits a pi of from 5 to 7 in water and the latter exhibits a pi of no more than 2.5. As can be seen from the foregoing, the alkali metal or alkaline earth metal salt of phosphoric ester exhibits a less acridity than the corresponding phosphoric acid. As described herein before, polyvinyl bitterly reacts with isocyanate to form a base of a heat-resistant pro-tective layer At strongly acidic regions, this reaction does not readily proceed. Further, the reaction consumes time and tends to reduce the degree of cross linking per so. Accordingly/ when the phosphoric ester (not salt form) is added to the reaction system of polyvinyl butyral/isocyanate, the reaction of both reactants requires a significantly long period of time, and the cross linking degree of the resulting reaction product tends to be low. On the contrary, when the alkali metal or alkaline earth metal salt of phosphor ester is added to the reaction system of polyvinyl butyral/isocyanates, the reaction of both reactants rapidly proceeds and the reaction product having a high degree of cross linking is obtained. Accordingly, it is believed that, when a heat transfer sheet having a heat-resistant protective layer obtained by adding the alkali metal or alkaline earth metal salt of pros-phonic ester to the reaction system of polyvinyl butyral/isocyanate is wound up and stored, the dye present in the heat transfer layer does not migrate to the heat-resistant protective layer.
When the alkali metal or alkaline earth metal salt of phosphoric ester is used as a lubricating event in the heat-resistant protective layer, the 13 I 7~3 alkali metal or alkaline earth metal salt of pros-phonic ester does not migrate to the heat transfer layer even if the heat transfer layer comes in contact with the heat-resistant protective layer.
Thus, the contamination of the heat transfer layer is not observed.
A filler can be incorporated in this heat-resistant protective layer as needed. Examples of such fillers for use herein are inorganic tillers such as clays, talc, zealots, aluminosilicates, calcium carbonate, Teflon powder zinc oxide, -titanium dioxide, magnesium oxide, silica and carbon;
and organic fillers having heat resistance such as the condensate of bsnzoguanamine and formaldehyde.
The average particle diameter of this filler is no more than 3 micrometers, desirably from 0.1 to 2 micrometers. The filler is used in an amount of from 0.1% to 25% by weight, preferably from 1.0% to 10% by weight of polyvinyl bitterly.
The fusion bonding between the thermal head and the heat transfer sheet is reduced by incorporating such fillers in the heat-resistant protective layer.
Thus, so-called sticking phenomenon is not completely observed. In addition, silicone oil can also be present in an amount of about I of polyvinyl bitterly.
The heat-resistant protective layer 4 can be provided on the base sheet 2 by the following process.
The ingredients described above are dissolved in a suitable solvent to prepare an ink composition for worming the heat-resistant protective layer. The ink composition is applied onto the base sheet 2 by suitable printing processes or application processes.
The whole is then heated to a temperature of from 30 to 80C to dry it and to react polyvinyl bitterly with isocyanate, thereby forming a heat-resistant protect live film.
In preparing the ink composition or forming * trade mark it :,'. Jo the heat-resistant protective layer, it is prefer-able that a filler be previously admixed with the alkali metal or alkaline earth metal-salt Do phosphoric ester to prepare a filler-con~aining composition.
The heat-resistant protective layer 4 has pro-fireball a film thickness of from 0.5 to 5 micro-meters, more preferably from 1 to 2 micrometers If the film thickness is less than 0.5 micrometer the heat-resistant protective layer has not good properties. If the film thickness is more than 5 micrometers, the heat transmission from the thermal ' read to the sublimation transfer sheet becomes in- ' fervor and the printing density is reduced.
It is preferable to heat in order to accelerate the reaction of polyvinyl bitterly and isocyanate.
In order to prevent heat prom affecting the heat transfer layer during heating, it is preferable that the order of providing the heat transfer layer 3 and the heat-resistant protective layer 4 on the base sheet 2 is as follows: the heat-resistant protective layer 4 is provided on one surface of the base shut ' 2 and thereafter the heat transfer layer 3 is,provid-Ed on the other surface ox the base sheet I
While the fundamental structure of the heat transfer sheet according to the present invention is as described above, the following additional treat-mints may be carried out. A primer layer having a thickness of no more than 1 micron may be interposed between the heat transfer layer 3 and the base sheet 2, or between the heat-resistant protective layer 4 I' and the base sheet 2 in order to improve the bonding strength of respective layers. Known primers can be used in the present invention When the prime layer is formed from acrylic resin, polyester resin and polyol/diisocyanate and a polyester resin it used as the material for the base sheet 2, the adhesion of both layers is particularly improved.
In addition to the optional primer layer describe Ed above, a heat-resistant layer can be interposed between the base sheet and the heat-resistant protect live layer. This heat-resistant layer is obtained by curing with a curing agent a synthetic resin capable of curing during heating.
The heat-resistant layer and the heat-resistant protective layer prevent the sticking onto the thermal head and ensure smooth running.
A variety of combinations of a synthetic resin capable of curing during heating and a binder therefore can be used to form the heat-resistant layer. Repro-tentative combinations are polyvinyl butyral/polyhydric isocyanate, acryl polyol/polyhydric isocyanate, cellulose acetate/titanium chelating agent and polyp ester/organic titanium compound. Commercially available synthetic resins, commercially available curing agents, their trade names and their amounts to be incorporated (parts Betty) are shown in the following Tables.
Synthetic resins Nos. 1,2,3,....... in Table 1 are used in combination with curing agentsNos. 1,2,3,...
in Table 2, respectively.

Table 1 _ _ ............. ._. . _~. . .... .
No Synthetic Resins Capable of Cur- Amount . in During Heating (parts by _ weight) 1 Polyvinyl bitterly Eslec BX-l*
(Sykes Kagaku, Japan) 00 2 Urethane polyol DF30-55*
(Day Nippon Ink, Japan) 100 3 Urethane polyol (1% of Co is added to DF30-55*) 100 Acryl polyol Acryl Deck APE* 100 (Day Nippon Ink, Japan) .
Polyester Pylon 200* (Tub, 100 6 Polyester Pylon 200* 100 7 Polyester Pylon 200* 100 8 Polyester Pylon 200* 100 9 cellulose acetate L20*-(Hercules Incorporated) . 100 Cellulose acetate L20* 100 11 Nitrocellulose Nit cello SS74*
(Damsel, Japan) 20 - 50 12 Chlorinated rubber CRY*
(Assay Dunk, Japan) 100 13 Chlorinated rubber CRY
14 Mailmen Melon I
(Hitachi Casey, Japan) 100 .. _ .. __ .

* trade mark I, I ',~

Table 2 Amount No. Curing Agents (parts by weight) _ .
Diisocyanate ~akenate Dillon* 45 1 (Tweaked Yakuhin, Japan) 2 Polyisocyanate 'Barnock D-750*20 (Dual Nippon Ink, Japan) 3 PoLyisocyanate 'Barnock D-750*20

4 Polyisocyanate 'Barnock D-750*20 Polyisocyanate Barnock D-750* 20 Titanium chelating agent 6 Tile Bond 50* 5 - 10 (Nippon Soda, Japan) 7 Organic titanium compound A-10* 10 (Nippon Soda, Japan) 8 Organic titanium compound -B-10* 10 (Nippon Soda, Japan) Titanium chelating agent 9 Tile Bond ED* 5 (Nippon Soda, Japan) Polyisocyanate Barnock D-750* 10 (Day Nippon Ink, Japan) 11 Polyisocyanate Barnock D-750*50 - 20 12 Polyisocyanate Barnock D-750* 30 13 Organic titanium compound B-10* 10 Para--toluenesulfonic acid 20 * trade mark A filler is preferably incorporated in the synthetic resin described above. Examples of the fillers suitable for this purpose are magnesium carbonate, calcium carbonate, Salk clays, tile-Nemo dioxide and zinc oxide. The amount of the filler used is usually from 5 to 40% of the resin on a weight basis. In corporation is carried out in a three-roll mill or sand mill to provide surf-fishnet dispersion.
If the adhesion of the heat-resistant layer to the base sheet is insufficient, it is preferable to use the suitable primer as described above.
It the heat transfer sheet according to the present invention, the heat-resistant layer mainly comprising (a) polyvinyl bitterly, (b) isocyanate and (c) phosphoric esters, its alkali metal or alkaline earth metal salts is provided on a surface of the base sheet, i.e., surface contacting with the thermal head. Accordingly, the heat transfer sheet according to the present invention has the following effects and advantages.
(a) Even if the heat transfer sheet is heated to considerably high temperatures by means of the thermal head, no sticking phenomenon occurs and the thermal head can run.
tub) Surface roughness does not occur at print-in areas.
(c) Even if heat printing is continuously carried out by means of the thermal head, the in-gradients for the heat-resistant protective layer do not adhere to the thermal head.
While the present invention will be described by Examples hereinafter, the present invention is not limited thereto. Throughout these Examples US quantities expressed in percent (%) and "parts" are by weight.

example 1 An ink composition for forming a heat-resistant protective layer comprising the following ingredients was prepared. The ink composition was applied onto a polyethylene terephthalate film (manufactured by Tub, Japan and marketed under the trade mark "S-PET") having a thickness of 9 micrometers by a Ayers bar ~16 and dried by warm air. A heat curing treatment was carried out for 20 hours in a 60C oven.
The coating weight (on a dry basis) was about 1.8 grams per square metro Ink Composition for forming Heat-_esistant Protective Layer Parts Polyvinyl bitterly (manufactured by Sykes Kagaku, Japan, and marketed under the trade mark "Eslec BX-l") 4.5 Tulane 45 Zoo Methyl ethyl kitten ` 45.5 Phosphoric ester (manufactured by Douche Cage Seiko, Japan, and marketed under the trade mark "Ply surf ASSAY") 0.45 Diisocyanate (manufactured by Tweaked Yakuhin, Japan, and marketed under the trade mark " Take Nate Dillon"; 75~ ethyl acetate solution) 2.0 An ink composition for forming a sublimation transfer layer comprising the following ingredients was then prepared. The ink composition was applied onto a surface opposite to the heat-resistant pro-tective layer by a Mayer's bar lo and dried by warm air. The coating weight of this heat transfer layer was about 1.2 grams per square meter.

.. . ..
, .

I

Ink Composition for forming Heat Sensitive Sublimation transfer Layer . __ _ _ Parts Disperse dye (manufactured by Nippon Kooks, Japan, and marketed under the trade mark "Cousteau Blue 714") 4 Polyvinyl bitterly (manufactured by Sykes Kagaku, Japan, and marketed under the trade mark "Eslec BX-l") 4.3 10 Tulane - 40 Methyl ethyl kitten 40 Isobutanol 10 A synthetic paper having a thickness of 150 micro-meters (manufactured by Ohji Yoke, Japan, and marketed under the trade mark "YUPO-FPG150") was used as a base. An ink composition for forming an image-recep-live layer comprising the following ingredients was applied onto the base by a Mayer's bar #36 to a coating weight of 4.0 grams per square meter (on a dry basis) thereby to produce a heat transferable sheet.
Ink composition for forming Image-receptive Layer Parts Pylon pulsator resin, manufac-lured by Tub, Japan) 8 Elvaloy PEEVE polymer plasticizer manufactured by Mets Polychemical, Japan) ................................. 2 - -- Amino-modified silicone oil (manufactured by Sonnets Silicone, Japan, and marketed under the trade mark "KF-393") 0.125 Epoxy-modified silicone oil (manufac-lured by Sonnets Silicone, Japan, and marketed under the trade mark "X-2~-343") 0.125 Tulane 70 Methyl ethyl kitten 10 Cyclohexanone 20 I The heat sensitive sublimation transfer sheet and the heat transferable sheet obtained as described * trade mark 21 ~284~
above were laminated so that the heat transfer layer and tune image-receptive layer were in mutual contact.
When recording was carried out from the side of the heat-resistant protective layer by means of a thermal head under the conditions of an output of 1 W/dot, a pulse width of from 0.3 to 4.5 milliseconds and a dot density of 3 dots/mm, no sticking phenomenon occurred and no wrinkles were generated. The heat transfer sheet smoothly ran. The reflection density of a highly developed color density portion at a pulse width of 4.5 milliseconds was 1.65, and the reflection density of a portion at a pulse width of 0~3 millisecond was 0.16. Thus, a recording having gradation in accordance with the applied energy was obtained (as measured by a Macbeth densitometer ROD-9 18~) .
Example 2 Recording was carried out in the same manner as described in Example l except that the ink`composi-lion for forming the heat-resistant protective layer was replaced by the following composition.
Parts Polyvinyl bitterly (manufactured by Sykes Kagaku, Japan, and marketed under the trade mark "Eslec BX-l") 4.5 Tulane - 45.0 Methyl ethyl kitten 45.5 Phosphoric ester (manufactured by Douche Cage, Japan, and marketed under the trade mark "Ply surf AXE") 0.45 Diisocyanate (manufactured by Tweaked Yakuhin, Japan, and marketed under the trade mark "Coronae L"; 45~
ethyl acetate solution) I
In this example, the generation of sticking phenol meson and wrinkles was not observed. Solid areas did not exhibit surface roughness and it was possible to I carry out printing.

to , * trade mark Example 3 An ink composition for forming a heat-resistant protective layer, of Example 1 was replaced by an ink composition comprising the following ingredients:
Parts Polyvinyl bitterly (manufactured by Dunk Kagaku, Japan and marketed under the trade mark "Dunk Bitterly ~6000~C") 4.5 10 Tulane 45.0 Methyl ethyl kitten 45.5 Phosphoric ester (manufactured by Tao Kagaku, Japan, and marketed under the trade mark "GAFAC ROY") 0~4 Diisocyanate (manufactured by Tweaked Yakuhin, Japan, and marketed under the trade mark "Coronet L";
45~ ethyl acetate solution) 4.0 The following ingredients were pulverized for 24 hours in a ball mill to prepare an ink composition for forming await sensitive sublimation transfer layer. The ink composition was then applied onto a base sheet my a Myra bar #14 to a coating weight of 1.6 grams per square meter (on a dry basis).
Parts Disperse dye (manufactured by Nippon Kayak, Japan, and marketed under . the trademark "Cousteau Blue 136") 6 30 Ethyl cellulose 5 Tulane 40 Methyl ethyl kitten 40 Isopropyl alcohol 10 The heat sensitive sublimation transfer sheet and the heat transferable sheet thus obtained were used to carry out printing by means of a thermal head under -the same conditions as described in Example 1. In this heat transfer sheet, neither sticking phenomenon nor wrinkles were generated. The printing density ox a portion at a pulse width of 4.5 milliseconds was 1.48~
and the printing density of a portion at a pulse width of 0.3 millisecond was Oily. Thus, a recording having gradation was obtained.
Comparative Example 1 Recording was carried out in the same manner as described Example 1 except that the ink composition or forming the heat-resistant protective layer was replaced by the hollowing composition. When the print-ivy test was carried out by means of a thermal head, it's possible to carry out running. However, the solid printing areas exhibited surface roughness, and the printed matter having a good printing image could not be obtained.
Parts Polyvinyl bitterly (manufactured by Sykes Kagaku, Japan, and marketed under the trademark "Eslec BX-l") 4.5 20 Tulane - 40 Methyl ethyl kitten 50 Talc 0.8 Diisocyanate (manufactured by Tweaked Yakuhin, Japan, and marketed under the-trademark "Take Nate Dillon"; 75% ethyl acetate solution) 2.0 Comparative Example 2 Recording was carried out in the same manner as described in Example 1 except that the ink composition or forming the heat-resistant protective layer was replaced by the following composition.
Parts Polyvinyl bitterly (manufactured by Sykes Ragaku, Japan, and marketed under the trademark "Eslec sol 4.5 Tulane 40 Methyl ethyl kitten 40 Jo `

Silicone UP availably from Sonnets silicone, Japan) 0.6 Diisocyanate (manufactured by Tweaked Yakuhin, Japan, and marketed under the trade mark "Take Nate Dillon"; 75~ ethyl acetate solution) 2.0 When the heat sensitive sublimation transfer sheet having this heat-resistant protective layer was used to carry out printing under the same conditions as described in Example 1 by means of a thermal head, printing and running could be carried out without any problem. However, if the heat transfer sheet is in such a state that this heat resistant protective layer is brought into contact with the heat transfer layer, i.e., the heat transfer sheet was in a form of roll in a printer, dye bleeding occurred at the sun-face of the heat transfer layer. If the heat transfer sheet exhibiting such a state is used to carry out printing, scumming was generated.
Example 4-A heat-resistant protective layer was provided on one surface of a polyethylene terephthalate film having a thickness of 9 micrometers in the same manner as described in Example 1. A heat-fusing transfer layer was provided on a surface opposite to the alone-mentioned surface of the polyethylene terephthalate film, as described hereinafter.
Tolylene-2,6-diisocyanate and ethyl cello solve were first mixed so that the molar ratio of -NO to -OWE present in respective molecules was 1:1. Dibutyl-tin laureate was charged into the thus obtained mixture as a catalyst in an amount of 0.01~ of the total amount of the mixture. The resulting mixture was continuously stirred for 5 hours while maintaining the temperature at 100C thereby to prepare a base composition A.
The thus obtained base composition A was mixed with the following ingredients to prepare a composition for * trade mark I '' I
forming a heat-fusing transfer layer comprising the following ingredients:
Come So on for forming Heat-fusing Trays-furler %
Base composition A 50 Tulane 36 Carbon black 10 Softening agent (manufactured by Idemitsu Seiko, Japan, and marketed under the trade mark "SHEA") 2 Polyethylene glycol having an average molecular weight of ~,000 2 This composition for forming the heat-fusing transfer layer was applied onto the foregoing surface of the polyethylene terephthalate film by the wire bar coating process while heating the film to 170C
to a thickness of 2 micrometers, thereby to form a heat-fusing transfer layer. Thus, a heat transfer sheet was produced This heat transfer sheet and a wood-free paper having a basis weight of 50 grams per square meter were laminated. When printing was carried out by means of a thermal printer (SP-3080*available from Shinto Dunk, Japan), sticking did not occur. A
black sharp printing image was formed on the surface of the wood-free paper.
Example 5 The heat sensitive sublimation transfer sheet and the heat transferable sheet were prepared accord-in to Example l except that an ink composition for forming a heat-xesistant protective layer was prepared and used to form a heat-resistant protective layer, as described hereinafter.
An ink composition for forming a heat-resistant protective layer comprising following ingredients was prepared, then applied onto a polyethylene terephthalate * trade mark I"; I' film (manufactured by Tub, Japan and marketed under the trade mark "S-PET") having a thickness of 9 micrometers my a Mayer's bar ~16 and dried by warm air. A heat curing treatment was carried out for 48 hours in a 60C oven. The coating weight (on a dry basis) was about 1.8 grams per square meter.
Ink Composition for forming Heat resistant Protective Layer Parts Polyvinyl bitterly (manufactured by Sykes Kagaku, Japan, and marketed under the trade murk "Eslec BX-1" 4.5 Tulane 45 Methyl ethyl kitten 45.5 Sodium salt of phosphoric ester (sodium salt of aliphatic phosphoric ester, manufactured by Tao gagaku, Japan, and marketed under the trade mark "GAFAC RD-720") 1.35 Diisocyanate (manufactured by Nippon Polyurethane, Japan, and marketed under the trade mark "Coronae L"; 75% ethyl acetate solution) 1.8 Amine catalyst (manufactured by Nippon Polyurethane, Japan, and market-Ed under the trade mark "NY 3 ";
10% ethylene dichloride-ethyl acetate solution) 0.23 The heat sensitive sublimation transfer sheet and the heat transferable sheet thus obtained were laminated so that the heat transfer layer and the imaye-receptive layer were in mutual contact. When recording was carried out from the side of the heat-resistant protective layer by means of a thermal head under the conditions of an output of l W/dot, a pulse width of from 0.3 to 4.5 milliseconds and a dot density of 3 dots/mm, no sticking phenomenon occurred and no wrinkles were generated. The heat transfer sheet smoothly ran. The reflection density 27 7~3 of a highly developed color density portion at a pulse width of 4.5 milliseconds was 1.65, and the reflection density of a portion at a pulse width of 0.3 millisecond was 0.16. Thus, a recording having gradation in accordance with the applied energy was obtained (as measured by a Macbeth densitometer RD-91~ .
When the resulting heat transfer sheet was wound around a paper tube to cause the heat transfer layer to come in intimate contact with the heat-resistant protective layer and then an aging accede-ration test was carried out for 14 days in a 50C
oven, the contamination of the heat-resistant protective layer due to the migration of the dye present in the heat transfer layer and the contami-nation of the heat transfer layer due to the micra-lion of the surfactant present in the heat-resistant protective layer were not observed.
Comparative Example 3 Recording was carried out in the same manner as described in Example 5 except that the ink come position for forming the heat-resistant protective layer was replaced by the following composition.
Parts Polyvinyl bitterly (manufactured by Dunk Kagaku, Japan, and marketed under the trade mark "Dunk Bitterly AYE") 4.5 Tulane 45 30 Methyl ethyl kitten 45 Phosphoric ester (aliphatic pros-phonic ester, manufactured by Tao Kagaku, Japan, and market-Ed under the trade mark "GAFAC
RS-710") 1.35 Diisocyanate (manufactured by Nippon Polyurethane, Japan, marketed under the trade mark "Coronae L"; 75% ethyl acetate solution) 1.

* trade mark Jo Amine catalyst (manufactured by Nippon Polyurethane, Japan, and marketed under the trade mark "NY 3 "; 10 %
ethylene dichloride~ethyl acetate solution) 0.23 In this example, the generation of sticking phenomenon and wrinkles was not observed, and the solid areas did not exhibit surface roughness. It was possible to carry out printing.
However, when the resulting heat transfer sheet was wound around a paper tube to cause the heat transfer layer to come in intimate contact with the heat-resistant protective layer and then an aging acceleration test was carried out for 14 days in a 50C oven, the dye present in the heat transfer layer migrated to the heat-resistant protective layer to cause it to form color. Further, unevenness of the dye density due to the dye removal from the heat transfer layer occurred. When such a heat transfer sheet was used to carry out printing, the disturb-ante of an image and skimming were generated.
Example 6 The heat sensitive sublimation transfer sheet and the heat transferable sheet were prepared accord-in to Example 1 except that an ink composition for forming a heat-resistant protective layer was prepared and used to form a heat-resistant protective layer, as described hereinafter.
Forty parts of calcium carbonate (manufactured by Shrewish Calcium, Japan, and marketed under the trade mark "laconic DUD") and 60 parts of sodium salt of phosphoric acid (manufactured by Tao Kagaku, Japan, and marketed under the trade mark "GAFAC ROD
720") were thoroughly kneaded in a three-roll mill to prepare a filler-containing composition. This was mixed with the following ingredients to prepare an ink composition for forming a heat-resistant protective layer. The resulting ink composition for forming the 29 Lo I
heat-resistant protective layer was applied onto a polyethylene terephthalate film having a thickness of 9 micrometers (manufactured by Tub, Japan, and marketed under the trade mark "S-PET") by Mayer's bar ~16 and dried by warm air. A heat curing treatment was then carried out for 48 hours in a 60C oven.
The coating weight (on a dry basis) was about 1.8 grams per square meter.
Ink Composition for forming Heat-resistant Protective Layer Parts Polyvinyl bitterly (manufactured by Sykes Kagaku, Japan, and marketed under the trade mark "Eslec BX-l") 6 Tulane 47 methyl ethyl kitten 47 Filler-containing composition described above 1.2 Phosphoric ester which is not in a salt form (manufactured by Douche Cage Seiko, Japan, and marketed under the trade mark "Ply surf ASSAY") 1.2 Diisocyanate (manufactured by Nippon Polyp urethane, Japan, and marketed under the trade mark "Coronae L"; 75~6 ethyl acetate solution 2.4 Amine catalyst (manufactured by Nippon Polyurethane, Japan, and marketed under the trade mark "NOAH"; 10% ethylene dichlorides ethyl acetate solution) 0.3 The heat sensitive sublimation transfer sheet and the heat transferable sheet thus obtained were laminated so that the heat transfer layer and the image-receptive layer were in mutual contact. When recording was carried out from the side of the heat-resistant protective layer by means of a thermal head under the conditions of an output of 1 W/dot, a pulse width of from 0.3 to 4.5 milliseconds and I, . ..

I
a dot density of 3 dots/mm, no sticking phenomenon occurred and no wrinkles were generated. The heat transfer sheet smoothly ran. The reflection density of a highly developed color density portion at a pulse width of 4.5 milliseconds was 1.65, and the reflection density of a portion at a pulse width of 0.3 millisecond was 0.16. Thus, a recording having gradation in accordance with the applied energy was obtained (as measured by a Macbeth densitometer RD-91~ .
When the heat transfer sheet was wound around a paper tube to cause the heat transfer layer to come into intimate contact with the heat-resistant protective layer and then an aging acceleration test was carried out for 14 days in a 50C oven, the contamination of the heat-resistant protective layer due to the migration of the dye present in the heat transfer layer and the contamination of the heat transfer layer due to the migration of the surfactant present it the heat-resistant protective layer were not observed.
When the heat transfer sheet was traveled by means of a transfer roll, the generation of wrinkles due to the adhesion between the heat transfer sheet and the roll was not observed.
Example 7 Recording was carried out in the same manner as described in Example 6 except that calcium carbonate present in the iller-containing composition was no-placed by talc (manufactured by Nippon Talc, Japan and marketed under the trade mark "Micro-ace L-l").
In this example, the generation of sticking phenol meson and wrinkles was not observed. When an aging accelation test was carried out in the same manner as described in Example 6, no contamination was observe Ed as in Example 6.

* trade mark Example 8 A heat transfer sheet was produced and record-in was carried out in the same manner as described in Example 6 except that calcium carbonate present in the filler-containing composition was replaced by clay (manufactured by Swish Kaolin, Japan, and marketed under the trade mark "ASP 170"). The generation of sticking phenomenon and wrinkles was not observed. When an aging acceleration test was carried out in the same manner as described in Example 6, no contamination was observed as in Example 1.
Comparative Example 4 A heat transfer sheet was produced and recording was carried out in the same manner as described in Example 8 except that sodium salt of phosphoric ester compound (manufactured by Tao Kagaku, Japan, and marketed under the trade mark "GAFAC ROD 720") present in the filler-containing composition was replaced by phosphoric ester which was not in a salt form (menu-lectured by Tao Kagaku, Japan, and marketed under the trade mark "GAFAC RS710"). The generation of sticking phenomenon and wrinkles was not observed.
However, when an aging acceleration test was carried out in the same manner as described in Example 6, the dye present in the heat transfer layer migrated to the heat-resistant protective layer to cause the heat-resistant protective layer to form color and to occur unevenness of the dye density due to the dye removal from the heat transfer layer. When such a heat transfer sheet was used to carry out printing, the disturbance of an image and skimming were general-Ed sample 9 A heat transfer sheet was produced and recording was carried out in the same manner as described in Example 6 except that phosphoric ester (Ply surf Aye) * trade mark !` .

which was not in a salt form was not incorporated in an ink composition for forming a heat-resistant pro-tective layer. The results substantially similar to those of Example 6 were obtained.
Example 10 The heat sensitive sublimation transfer sheet and the heat transferable sheet were prepared accord-in to Example 1 except that the following ink come position for forming a heat-resistant layer was first applied onto a base sheet to form a heat-resistant layer between the base sheet and a heat-resistant protective layer and Cousteau Blue wise used instead of Cousteau Blue 714 as disperse dye. An ink compost-lion I for forming a heat-resistant layer comprising the following ingredients was prepared. This ink come position was applied onto a polyethylene terephthalate film having a thickness of 9 micrometers (base sheet manufactured by Tub, Japan and marketed under the trade mark "S-PET") by a Mayer's bar #8 and dried by warm air.
Ink Composition I for forming Heat-resistant Layer Parts Polyvinyl bitterly resin Eslec BX-1*
(available from Sykes Kagaku, Japan) 4.5 Tulane 45 Methyl ethyl kitten 45.5 Diisocyanate Take Nate Dillon (available from Tweaked Yakuhin, Japan; 75~ ethyl acetate solution) 2.0 The heat sensitive sublimation transfer sheet and the heat transferable sheet thus obtained were laminated so that the heat transfer layer and the image-receptive layer were in mutual contact. Rev cording were carried out from the side of the heat-resistant layer by a thermal head. The recording conditions were an output of 1 W/dot, a pulse width * trade mark it of from 0.3 to 4.5 milliseconds, and a dot density of 3 dots/mm.
No sticking phenomenon occurred, and no wrinkles were generated. The heat transfer sheet smoothly ran. When the printing density was measured by a Macbeth densitormer RD-918*~ the reflection density of a Hayakawa developed color density portion at a pulse width ox 4.5 milliseconds was 1.65 and the reflection density ox a portion at a pulse width of 0.3 Millie second was 0.16. Thus, a recording having gradation in accordance with the applied energy was obtained.
Example if Ink compositions were applied onto a polyester base sheet in the same manner as described in Example lo except that the following ink composition for form-in a heat resistant layer and the ink composition for worming the heat-resistant protective layer ox Example 2 (GAFAC RD720*instead of GAFF Russ phosphoric ester) were used. `
Ink composition II for forming Heat-resistant Layer Parts Polyvinyl bitterly resin Eslec Byway* 4.5 Tulane 45.0 Methyl ethyl kitten OWE
Diisocyanate Coronae L* (available prom Nippon Polyurethane, Japan;
45~ ethyl acetate solution The base sheet provided with the heat resistant layer and the heat-resistant protective layer was heated and cured in the same manner as described in Example lo Thereafter, a heat sensitive sublime-lion transfer layer was wormed thereon. The result-in heat transfer sheet and the heat transferable sheet used in Example lo were laminated, and printing was carried out in the same conditions as described in Example lo * trade mark . . ,, "

In this example, the generation of sticking phenomenon and wrinkles was not observed, and the solid areas did not exhibit surface roughness. Good printing could be carried out.
Example 12 A heat transfer sheet was produced in the same manner as described in Example 10 except that the following ink composition for forming a heat-resistant layer and the ink composition for forming the heat-resistant protective layer of Example 3 were used.
Ink Composition III for forming Heat-resistant Layer Parts Polyvinyl bitterly Dunk Bitterly #6000-C* (available from Dunk Kagaku, Japan) 4.5 Tulane 45.0 Methyl ethyl kitten 45.5 Diisocyanate Coronae L* (45% ethyl acetate solution) 4.0 When printing was carried out in the same manner as described in Example 10, the generation of sticking phenomenon and wrinkles was not observed, and the solid areas did not exhibit surface roughness.
Example 13 The ink composition for forming the heat-resistant protective layer of Example 6 (without amine catalyst) was applied onto the heat-resistant layer of ink composition I which was provided on the base sheet as described in Example 10. The whole was heated for 12 hours in an oven at a temperature of 60C to cure. When printing was carried out in the same manner as described in Example 10, sticking did not occur and the solid areas did not exhibit surface roughness.
E _ pie 14 A heat-resistant layer was provided on one surface of a polyethylene terephthalate film having a thickness * trade mark I,;

of 9 micrometers in the same manner described in Example ion An ink composition for forming a heat sensitive fusing transfer layer obtained by Example was applied onto the opposite surface of the film by the wire bar coating process while heating to 170C to a thickness of 2 micrometers Thus, a heat transfer sheet was produced.
This heat transfer sheet and a woodier paper having a basis weight of 50 grams per square meter were laminated. When printing was carried out by means of a thermal printer (SP-3080*available from Shinto Dunk, Japan), sticking did not occur. A black sharp printing image was formed on the surface of the wood-free paper.
Example 15 An ink composition for forming a heat-resistant layer comprising the following ingredients was prepared.
The ink composition was applied onto a polyethylene terephthalate film (manufactured ho Tub, Japan and marketed under the trade Mark "S-PET")havirig a thick-news of 9 micrometers by a Mayer's bar #8 and dried by warm air.
Ink Composition for forming Heat-resistant Layer Parts Acryl polyol (manufactured by Taipei Kayo, Japan, and marketed 67 under the trade mark "ACRIT6416MA";
45% toluene-ethyl acetate solution) Tulane 50 30 Methyl ethyl kitten 50 Sand-mill dispersion 14 Diisocyanate (manufactured by 7.2 , Nippon Polyurethane, Japan and j marketed under the trade name "Coronae L"; 75% ethyl ace-late solution) *Sand-mill dispersion used herein has the following ingredients.
* * trade mark , ."

Parts Acryl polyol (same as the above) 50 Talc (manufactured by Nippon Talc, 35 Japan, and marketed under the trade mark "Micro-ace Lo Cyclohexane 10 Further, 40 parts of talc above mentioned and 60 parts of sodium salt of phosphoric acid (marketed under the trade irk "GAFAC PA 720 from Tao Kagaku, Japan) were thoroughly kneaded in a three-roll mill to prepare a dispersion composition, which was used in the composition shown below.
Ink composition for forming Heat-resistant Protective Layer Parts Polyvinyl bitterly (marketed under the 6 trade mark "EsIec BX-l, from Sykes Kagaku,Japan) Tulane 47 20 Methyl ethyl kitten .~47 Dispersion composition 2.25 described above Phosphoric acid ester 1.2 (marketed under the trade mark of "Ply surf A 208S" from Sykes Keg) Toluene-diisocyanate adduce 2.4 - (marketed under the trade mark of "coronae L" from Nippon Polyurethane, Japan; 75%
ethylacetate-solution) A heat curing treatment was carried out for 12 hours in a 60C oven. The coating weight (on a dry base) was about 1.2 g/m2.
An ink composition for forming a sublimation transfer layer comprising the following ingredients was then prepared. The ink composition was applied onto a surface opposite to the heat-resistant protective layer by a Mayer's bar #10 and dried by warm air.
The coating weight of this heat transfer layer was about 1.2 grams per square meter. A heat transfer sheet was thus obtained.
Ink Composition for forming Heat Sensitive Sublimation Transfer Layer Parts Disperse dye (manufactured by Nippon Kayak, Japan, and marketed under the trade mark "Cousteau Blue 136") 4 Polyvinyl bitterly Manufactured by Sykes Kagaku, Japan, and marketed under the trade mark "Eslec BX-l") 4.3 Tulane 40 Methyl ethyl kitten 40 Isobutanol 10 A synthetic paper having a thickness of 150 micrometers (manufactured by Ohji Yoke, Japan, and marketed under the trade mark "YUPO-FPGl50") was used as a base. An ink composition for forming an image-receptive layer comprising the following ingredients was applied onto the base by Mayer's bar #36 to a coating weight of 4.0 grams per square meter (on a dry basis) thereby to produce a heat transferable sheet Ink Composition for forming Image-receptive Layer _ Parts Pylon pulsator resin, manufac-lured by Tub, Japan) 8 Elvaloy POW polymer plasticizer, manufactured by Mets Polychemical, Japan) 2 Amino-modifed silicone oil (manufactured by Sonnets silicone, Japan, and marketed under the trade mark "KF-393") 0.125 trade mark I

Epoxy-modified silicone oil (manufac-lured by Sonnets Silicone, Japan, and marketed under the trade m~xk "X-22-343") 0.125 Tulane 70 Methyl ethyl kitten 10 Cyclohexanone 20 The heat sensitive sublimation transfer sheet and the heat transferable sheet obtained as described above were laminated so that the heat transfer layer and the image-receptive layer were in mutual contact.
Recording was carried out from the side of the heat-resistant protective layer by means of a thermal head under the conditions of an output of 1 W/dot, a pulse width of from 0.3 to 4.5 milliseconds and a dot density of 3 dots/mm.
My sticking phenomenon occurred and no wrinkles were generated. The heat transfer sheet smoothly ran.
The reflection density of a highly developed color density portion at a pulse width of 4.5 milliseconds was 1.65, and the reflection density of a portion at a pulse width of 0.3 millisecond was 0.16. Thus, a recording having gradation in accordance with the applied energy was obtained (as measured by a Macbeth densitometer RD-91~ .
Example 16 Preparation of the heat transfer sheet and the heat transferable sheet and recording were carried out in the same manner as described in Example lo except for 1.2 parts of phosphoric ester Ply surf A 208* in ink composition for forming heat-resistant protective layer was replaced by 0.3 parts of lecithin (manufactured by Ajinomoto Co. Japan).
In this example, the generation of sticking phenomenon was not observed and solid areas did not exhibit surface roughness.

* tray murk . . , ,.

Claims

WHAT IS CLAIMED IS:

1. A heat transfer sheet comprising a heat transfer layer provided on one surface of a base sheet, and a heat-resistant protective layer provided on the other surface of said base sheet, said heat-resistant protective layer containing (a) polyvinyl butyral, (b) an isocyanate, and (c) a compound selected from the group consisting of phosphoric esters, its alkali metal and alkaline earth metal salts, and mixtures thereof.

2. The heat transfer sheet according to claim 1 wherein said heat-resistant protective layer further contains a filler.

3. The heat transfer sheet according to claim 1 wherein said heat transfer layer is a heat sensitive sublimation transfer layer comprising a dye having heat transferability and a binder resin.

4. The heat transfer sheet according to claim 1 wherein said heat transfer layer is a heat sensitive fusing transfer layer wherein a dye or pigment is dispersed in a wax material.

5. The heat transfer sheet according to claim 1 wherein said alkali metal salt of phosphoric ester is a sodium salt of phosphoric ester.

6. The heat transfer sheet according to claim 2 wherein said filler is selected from the group con-sisting of calcium carbonate, talc, aluminosilicates, clays, zeolites, Teflon powder, zinc oxide, magnesium oxide, titanium dioxide, silica, carbon, and the condensate of benzoguanamine and formaldehyde.

7. The heat transfer sheet according to claim 1 which further comprises a heat-resistant layer interposed between said base sheet and said heat-resistant pro-tective layer, said heat-resistant layer being obtained by curing with a curing agent a synthetic resin capable of curing upon being heated.

8. The heat transfer sheet according to claim 7 wherein the combination of said synthetic resin capable of curing upon being heated and said curing agent from which said heat-resistant layer is produced is selected from the group consisting of polyvinyl butyral/polyhydric isocyanates, acryl polyol/poly-hydric isocyanates, cellulose acetate/titanium chelat-ing agents, and polyester/organic titanium compounds.

9. The heat transfer sheet according to claim 7 wherein said heat-resistant layer and/or said heat-resistant protective layer contain a filler.

10. The heat transfer sheet according to claim 9 wherein said filler is selected from the group con-sisting of calcium carbonate, talc, aluminosilicates, clays, zeolites, Teflon powder, zinc oxide, magnesium oxide, titanium dioxide, silica, carbon, and the condensate of benzoguanamine and formaldehyde.