JPH01168493A - Image receiving sheet for thermosensitive transfer - Google Patents

Abstract

PURPOSE:To prevent shrinkage or curling from occurring due to the heat at the time of receiving an image and obtain favorable clear images, by using a polyester film comprising minute open cells at the surfaces and in the inside thereof. CONSTITUTION:A minute cell-containing polyester film can be easily produced by, for example, a method wherein a specified polypropylene is blended into a polyester, the blended material is extruded into a sheet shape, and the resultant sheet is stretched at least uniaxially to provide a multiplicity of minute cells at the surfaces and in the inside of the film obtained. A crystalline polypropylene homopolymer to be blended in this case is a polymer comprising at least 95mol.% of propylene units. By this, a uniaxially stretched film can be easily obtained which has an apparent specific gravity of 0.4-1.3, a hinding degree of at least 0.2 and an air leakage index of 50-10,000sec.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an image receiving sheet used for thermal transfer recording.

Specifically, by using a polyester film containing fine closed cells on the surface and inside, clear images without printing spots can be obtained, and it has excellent dimensional stability, and has low shrinkage due to heat and no deformation such as curling. The present invention provides an image-receiving sheet for thermal transfer.

[Problems to be solved by conventional technology and invention]

BACKGROUND ART Recent advances in information processing technology have been remarkable, and as a result, hard copy technology has become more multi-functional and sophisticated.

In hard copy technology, a thermal transfer recording method is used as one of the recording methods. The outline of thermal transfer recording is that a transfer sheet having a transfer layer containing a sublimable or vaporizable dye, or a dye that melts with moderate heat, is placed on top of an image-receiving sheet, and the transfer sheet is heated to absorb the dye into the transfer layer. The dye is sublimated, vaporized, or melted to be dyed or transferred onto the image-receiving sheet, thereby forming a dye image on the image-receiving sheet. Currently, recording methods are becoming more multi-functional and sophisticated, and examples thereof include faster printing, higher resolution, and higher print quality.

Now, the image receiving sheet used for such thermal transfer recording is conventionally used for general printing paper such as cellulose paper, gravure paper with calender finish, or paper surface with unevenness and holes made of pigment made of fine particles. Art paper, coated paper, etc., which are coated papers that have been coated to provide a paper surface with excellent smoothness and gloss, are used. Synthetic paper, which has excellent strength, dimensional stability, and dust-free properties, is also used. With the recent progress toward higher functionality, there is a strong demand for higher quality in these image receiving sheets. Specifically, there is a need for an image-receiving sheet that has improved overall properties such as strong mechanical strength, good dimensional stability, excellent heat resistance, white hiding properties, and no printing spots due to thermal transfer. There is. In other words, conventionally used cellulose paper, synthetic paper, and plastic film cannot satisfy all of these requirements.

That is, conventional printing paper such as cellulose paper has drawbacks such as being easily broken due to its low strength, not being able to be made into thin paper, having poor dust-free properties, and low water resistance. Furthermore, since the paper surface has large irregularities, printing spots are likely to occur, making it difficult to obtain clear images.

On the other hand, synthetic paper has higher strength, dimensional stability, and
Although it is preferable in terms of dust-free property, it cannot be said that it necessarily satisfies the demand for high quality. That is, regarding printability, further improvement in flattening is required, and because of poor heat resistance, it cannot be used in applications exposed to high temperatures.

Now, since polyester films have excellent heat resistance, mechanical properties, chemical resistance, weather resistance, etc., they are widely used in various industries. In particular, biaxially oriented poly(ethylene terephthalate) film is particularly excellent in dimensional stability, strength, flatness, etc., so it is printed using a thermal transfer recording method and used for applications such as manuscripts for overhead projectors. However, biaxially oriented poly(
When attempting to use ethylene terephthalate (ethylene terephthalate) film as a material to replace conventional paper in image-receiving sheets for thermal transfer, there were several problems. That is, the biaxially oriented poly(ethylene terephthalate) film is a material that exhibits strong and rigid characteristics, and lacks flexibility, so the adhesion between the transfer sheet and the image receiving sheet in the thermal head section is insufficient.
This caused a basic defect in that a clear image could not be obtained due to printing mottling. Furthermore, when used as an alternative to conventional paper, whiteness and hiding properties are required to prevent set-off, and a method of adding white pigments is used to impart such properties. In order to provide sufficient hiding power in this method, it is necessary to add extremely large amounts of pigment, which makes the film even more rigid and inhibits its flexibility, making it difficult to obtain clear images and causing hand and finger injuries during handling. It is also unfavorable in terms of handling, as it may cause cuts. So, i
'lJ (ethylene terephthalate) film has a high specific gravity of approximately /,'I g/crn3, and if this is used as a material to replace conventional paper, the weight of the document will be extremely heavy, making it difficult to carry and store. 'There's a problem.

[Means to solve the problem]

The inventors of the present invention have conducted intensive studies to solve these problems, and have found that if a polyester film containing microbubbles that satisfies specific requirements is used, the problems can be solved at once, and compared to conventional paper. It has been discovered that an excellent thermal transfer image-receiving sheet can be obtained in place of synthetic paper, and the present invention has been achieved.

That is, the gist of the present invention is that the apparent specific gravity is in the range of o, ti to /, J, the degree of hiding is 0.2 or more, and the air leakage index is in the range of 50 to 10,000 seconds. The present invention relates to an image-receiving sheet for thermal transfer, characterized in that it is made of a polyester film containing fine cells stretched in at least/the axial direction.

The present invention will be explained in more detail below.

Polyester as used in the present invention refers to aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalene dicarboxylic acid or their esters, ethylene glycol, diethylene glycol, etc. It is a polyester produced by polycondensing glycols such as t-butanediol, neopentyl glycol, and tercyclohexane dimetatool.

Any commonly used method can be used to produce polyester from these acid components and glycol components. For example, by carrying out a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or by directly esterifying an aromatic dicarboxylic acid and a glycol, the bisglycol ester of an aromatic dicarboxylic acid is substantially , or a low polymer thereof, and then polycondensation is performed under reduced pressure at a temperature of 2'10° C. or higher. At this time, conventional catalysts, stabilizers, various additives, etc. can be used as desired.

Typical examples of such polyesters include poly(ethylene terephthalate), poly(ethylene naphthalate), and poly(butylene terephthalate). This polyester may be a homopolymer, a polymer copolymerized with a third component, or a mixture of these polyesters.

In any case, in the present invention, the content of ethylene terephthalate units and/or ethylene naphthalate units and/or butylene terephthalate units is Omo1% or more, preferably gOmO1% or more, more preferably 90mo1%.
Polyesters having the above properties are preferred.

Further, in the present invention, if the degree of polymerization of the polyester is too low, the mechanical strength will decrease, so it is preferable that the intrinsic viscosity of the polyester is 0, xi or more. More preferably O,S~/,2, still more preferably O,SS~o
, gs.

In the present invention, a film is produced using such polyester, and the film has a structure containing fine closed cells on its surface and inside, and the apparent specific gravity of the film is 0. It is necessary that the ratio is 0.4 to 3, preferably 0.4 to 3. If the apparent specific gravity exceeds 7.3, the film contains a small amount of air bubbles, resulting in poor flexibility and uneven printing, which is undesirable. On the other hand, if the apparent specific gravity is less than o or q, the mechanical strength of the film will be insufficient, which may cause tearing during thermal transfer, which is undesirable.

Further, the degree of hiding of the film of the present invention is 0.2 or more, preferably O.3 or more. If the degree of hiding is less than 0.2, the transferred image will have a large set-off, the coyl-last will become unclear, the image will be difficult to see (and the image-receiving sheet will be difficult to decipher), which is not preferable.

Furthermore, the film of the present invention has an air leakage index of 30 to 0.
5.000 seconds, preferably ioo seconds or more. It is desirable that the time be more than o o o seconds. 3
If it is less than 0 seconds, the adhesion with the transfer sheet at the thermal transfer head section will be poor (this is undesirable), as the transfer efficiency will decrease and printing unevenness will increase.On the other hand, if it exceeds io or ooo seconds, the film will deteriorate. This is undesirable because the slipperiness of the paper becomes extremely poor and the running performance during thermal transfer recording becomes poor, causing running troubles such as paper jams.

In the present invention, it is also an important requirement that the film be stretched at least in one direction, and it is desirable that the stretching magnification is at least 3 times the area magnification. That is,
This is because an unstretched polyester film has extremely poor mechanical strength, and cannot ensure sufficient strength and dimensional stability when used as the image-receiving sheet for heat-sensitive transfer of the present invention.

As described above, the polyester film that is the base material of the image-receiving sheet for thermal transfer of the present invention is required to have such properties, but it is a structure containing microbubbles, and as long as it satisfies such properties and requirements, manufacturing The method is not particularly limited. That is, as a method for manufacturing a structure containing such microbubbles, for example, JP-A-Sho! ;0
-, a method of adding a gas or a vaporizable substance as described in Japanese Patent Publication No. 7g765, Japanese Patent Publication No. 7-16-16-56, etc.; A method of adding a substance that generates gas through chemical decomposition as described in ZOB+2H, etc., or JP-A-Sho,! ;/-,,? '1L9AJ Publication, Special Publication Sho Taco, 27AAl.

Examples include a method of adding a soluble substance to a solvent, impregnating it with a liquid after molding, and extracting it, as described in Japanese Patent Publication No. 2003-111000, and any method may be used. However, since these manufacturing methods require special molding equipment and involve complicated manufacturing processes, they cannot necessarily be said to be methods that can be easily adopted.

Therefore, as a method for easily manufacturing the polyester film containing microcells of the present invention, for example, the method disclosed in Japanese Patent Application No. 1983-1982, which was previously proposed by the present inventors, is available. It is preferable to adopt the method of No. 3/3g9A.

That is, by blending specific polypropylene with polyester,
This method involves extrusion molding into a sheet, and then stretching the sheet in at least one axis to form a film. For details, please refer to melt flow index (hereinafter referred to as M) for polyester.
Abbreviated as F, I) O:: J-kOwt% of crystalline polypropylene homopolymer of t~/20 is blended and melt-extruded to form a substantially amorphous sheet, and then the sheet is at least In this method, a polyester film is produced by stretching the polyester film in the uniaxial direction at an area magnification of more than 2 times, thereby creating a polyester film containing a large number of fine air bubbles on the other side and inside the film.

If such a method is adopted, the apparent specific gravity of the present invention is 0. '
1.3, a hiding degree of 0.2 or more, and an air leakage index of 50 to 10,000 seconds, it is possible to easily obtain a film stretched at least in the -axial direction. Moreover, since it does not require any modification of the conventional film forming apparatus and can be produced within the range of normal stretched polyester production conditions, the advantages are significant when taking into account the production cost.

This method will be explained in more detail. The crystalline polypropylene homopolymer blended in such a method is at least? jmo1% or more, preferably 9 g mo1
% or more of propylene units. If the polypropylene used is of inferior quality, the polypropylene bleeds out on the surface of the sheet when it is made into an amorphous sheet, which is undesirable because it contaminates the surfaces of cooling rolls, stretching rolls, etc.

Further, such polypropylene may contain, for example, 1 ethylene unit.
If it is copolymerized in an amount of 0 mo 1% or more, it is not preferable because the stretched polyester film containing the copolymer cannot contain sufficient microbubbles.

M, F, and I of such polypropylene are 0.2 to /20,
Preferably it is o, 5-so. That is, M, F, I
When M, F, and I are less than 0.2, the bubbles generated become extremely large and breakage occurs frequently during stretching. On the other hand, when M, F, and I are 120 or more, the film often comes off from the clip during stretching in a tenter. (In either case, productivity becomes extremely poor, so this is not preferable.

The blending amount of such polypropylene is preferably 3 to 50 wt%, more preferably 3 to 30 wt%, still more preferably 3 to u (7 wt%).

That is, if the blending amount is less than 3 wt%, the amount of microbubbles produced is small (and it becomes difficult to reduce the apparent specific gravity of the film to 7.3 or less. On the other hand, if it exceeds 10 wt%, This is not preferable because the mechanical strength of the film is extremely reduced and breakage occurs during stretching.

In such a method, stretching in the axial direction is also an essential requirement. This is because it is not possible to generate the polyurethane, and it is possible to generate and contain it only by using a stretching process in combination.

There is no need to adopt special conditions for this stretching method itself (
, conditions within the range for manufacturing ordinary polyester films can be adopted.

That is, a substantially amorphous sheet is obtained using a melt extrusion method using a blend of polyester and polypropylene as raw materials. Next, the sheet is stretched in the longitudinal and/or transverse directions at an area magnification of 9 times or more, preferably 9 times or more, and further/
By performing heat treatment at 20-230°C, the present invention produces microbubbles with an apparent specific gravity of O, a~/, 3, a hiding degree of 0.2 or more, and an air leakage index of 50~io, ooo seconds. A film containing the same can be easily produced.

Thus, the film of the present invention can be produced as a white polyester having a low specific gravity and a high degree of hiding, but there is no problem in adding various additives as long as the basic properties are not impaired. Such additives include, for example, antioxidants,
Examples include ultraviolet absorbers, lubricants, antistatic agents, dyes, pigments, fluorescent whitening agents, matting agents, surfactants, etc., and they may be blended in appropriate amounts at any time and by an appropriate method as required.

Further, the film of the present invention can be subjected to various optical surface treatments in order to improve dyeability and adhesion with dyes, or to prevent blocking and charging in a thermal transfer device. Examples of surface treatment methods include coating treatment, flame treatment, solvent treatment, plasma treatment, corona discharge treatment, ultraviolet treatment, ion plating treatment, sandblasting treatment, etc., which can be performed at an appropriate time.

Among such surface treatments, coating treatment is particularly preferably employed in the present invention. The substance constituting the coating layer may be within a range that satisfies the properties of the film serving as the base of the present invention.
The coating material and coating thickness can be freely selected according to the required characteristics and purpose of the pond. For example, a thermoplastic resin, a crosslinkable resin, or a composition in which various additives and the like are blended therewith can be used as required. Examples of additives include dyes, pigments, lubricants, antioxidants, ultraviolet absorbers, antistatic agents, inorganic fine particles, surfactants, etc., and are added in appropriate amounts as necessary.

The method of forming the coating layer is not particularly limited (
It may be applied to a film that has already been made into a film, or it may be applied during the film manufacturing process. For example, when providing a coating layer on a biaxially stretched microcellular polyester film, the coating agent is applied to the film that has been uniaxially stretched in the longitudinal direction, stretched in the transverse direction while the coating agent is dry or undried, and immediately heat-treated. This method is particularly preferably adopted because film formation, coating, and drying can be performed simultaneously, which has a great advantage in terms of manufacturing costs. The coating layer can be formed on one side or both sides, and when it is formed on both sides,
The coating agents may be the same or different.

<Examples> The present invention will be specifically explained below using Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, the measurement and evaluation of the cord characteristics in the present invention were performed by the following method.

(1) Apparent specific gravity: Cut out 5 square pieces of 10CIrL x 10CrrL from any part of the polyester film, measure the thickness of each sample at 9 arbitrary points with a micrometer, and find the average thickness of each sample. After determining the volume, the weight of each cut sample was measured to calculate the number of grams per crrt3, and the average value of the five samples was taken as the apparent specific gravity of the film.

(2) Hiding degree: The density of transmitted light under a G filter was measured using a Macbeth densitometer TD-qoy type. The larger this value is, the higher the degree of concealment is. Measurements were made at three points, and the average value was taken as the measured value.

(3) Air leakage index: JIS Pg//9-/9? The measurement was performed using a Bekk smoothness measuring machine specified in Section B. The larger this number is, the smoother the surface is. Measurements were made at S points, and the average value was taken as the measured value.

(4) Heat shrinkage rate: Calculated using the following formula by heat-treating the sample for S minutes in an atmosphere of /gO°C in a tension-free state and measuring the length of the sample before and after the heat treatment.

Heat shrinkage rate (%) × 100 (5) Flexibility θ (deg): From sheet, width/J mm, length/! ; Cut the test piece in the longitudinal direction by 7
27 After fixing the test piece horizontally so that it sticks out, a 0.9 g weight is attached to the tip of the protruding test piece and it is hung down.

The distance a mm from a point 30 mm vertically below the horizontally fixed point to the film hanging in the horizontal direction was measured from the side of the specimen, and the formula: tan θ = a /
The hanging angle θ (deg,) was calculated from 30 and used as an index of flexibility. Measurements were performed at three points, and the average value was taken as the measured value. The smaller this value is, the better the flexibility is.

(6) Print quality The two films are cut into A1 size sheets, thermal transfer recording is performed on them using a Sharp CX-SOOθ color printer, and the resulting hard copies are visually checked for print density, print unevenness, and contrast. below! Evaluated in stages.

Evaluation criteria S: (very good) G: (good) 3: (no practical problems) Uni (practical problems) l: (poor) (7) Practical suitability: 2Q sheets of film in Aq size The sheets were cut, stacked, and placed in a receiving paper feed cassette of a thermal transfer recording device used in a print quality test. From this state, thermal transfer recording was actually performed on 10 sheets in succession, and the occurrence of operational troubles such as paper jams in the receiving paper feed section and poor running within the apparatus was observed. -0
If no troubles occurred 7 times in the test of 7 sheets, ○
, Those in which tral rolls occurred seven or more times were evaluated as ×.

Example/ A raw material prepared by blending 10 wt % of crystalline polypropylene homopolymer chips of M, F, I5 with poly(ethylene terephthalate) chips of intrinsic viscosity o, be, etc. containing 5 wt % of white pigment 0.3 μm titanium oxide was fed into an extruder. The mixture was melted at 290°C and extruded into a cooled drum sheet by cooling at YO°C to obtain an amorphous sheet with a thickness of 0.7 mm. The sheet was then heated 3 times in the longitudinal direction at 95°C and 3 times in the transverse direction at 95°C.
．． It was stretched twice and heat treated at 0° C. for S seconds to finally obtain a white biaxially stretched polyester film with a film thickness of 100 μm. The apparent specific gravity of the film was 0.9 g, the degree of hiding was O, S, and the air leakage index was tt, o oo seconds.

In addition, the heat shrinkage rate of the film is % in the longitudinal direction / % in the lateral direction /
6%, and the flexibility θ was II Odeg.

This film is cut into A-4 size as an image receiving sheet,
When we evaluated the print quality, we found that the print density was high, the print unevenness was low,
A good image with a contrast of 5 was obtained, and there were no paper jams or poor running during image receiving operations (indicating good practical suitability).

In place of the white pigment-containing poly(ethylene terephthalate) used in Example/Example//, poly(ethylene terephthalate) containing no pigment and having an intrinsic viscosity of o and oso was used, and the blending amount of polypropylene was A white coaxially stretched polyester film having a film thickness of 700 μm was obtained in the same manner as in Example, except that the film was bound by 20 wt%. However, in order to make the final thickness of the biaxially stretched film 100 μm, the amount of polymer extruded from the extruder was adjusted, and the thickness of the amorphous sheet was set to o, , t it. Also in the following comparative example, the thickness of the amorphous sheet was adjusted by changing the amount of polymer extrusion in order to adjust the thickness of the stretched film. The apparent specific gravity of the biaxially stretched film thus obtained is 0. ri/, concealment degree is 0. B. The air leakage index was /, 100 seconds.

In addition, the heat shrinkage rate of the film is 7.2% in the vertical direction and 7.2% in the horizontal direction.
．． It is 9% and the flexibility θ is 3! It was deg. When the printing quality of this film was evaluated in the same manner as in Example, a good image was obtained with printing density S, printing unevenness q, and contrast 5, and the practical suitability was good with no paper jams or poor running.

Example 3 After carrying out longitudinal stretching under the same conditions using the same raw materials as in Example 3, one side was coated with water-dispersible polyester resin/water-dispersible polyester polyurethane resin/surfactant-nio7qq7i (weight ratio). ) was applied onto the sheet and immediately led to a transverse stretching machine (other than Example 2).
In the same manner as above, the final coating layer/μm thickness of ioo
A white biaxially stretched polyester film of μm was obtained. The apparent specific gravity of such a film is 0.72 and the degree of hiding is 0. The air leakage index on the coated layer surface was 500 seconds, and on the opposite side was 7100 seconds. In addition, the thermal shrinkage rate and flexibility θ were the same values as in Example A. The film was subjected to a thermal transfer device so that the image was received on the coated layer side, and the print quality was evaluated. As a result, an extremely good copy image was obtained with print density S, print unevenness S, and contrast 5. In addition, there was no paper jam or poor running in the device (and it was excellent in practical suitability).

Comparative Example/A film was formed in the same manner as in the example except that polyethylene terephthalate with an intrinsic viscosity of o and bso was used as a raw material, and finally an io film was formed.

A biaxially stretched polyester film having a thickness of μm was obtained.

The apparent specific gravity of the film was /, lI, the degree of opacity o, i, and the air leakage index /2000 seconds, and the surface was flat and transparent.

The heat shrinkage rate of the film is 7.2% in the longitudinal direction and 7.2% in the transverse direction.
and the flexibility θ was llF deg.

When the printing quality of this film was evaluated as an image-receiving sheet, the printing density was 3, the printing unevenness was 3, and the contrast was poor. Furthermore, paper jams and poor running occurred frequently within the thermal transfer device, and the practical applicability was also poor.

Comparative Example 10wt% of calcium carbonate particles with an average particle size of Sμm were triblended with the raw materials used in Comparative Example/, and a film was formed in the same manner as Comparative Example/, except that it was fed to the extruder hopper, and the final film was 700 μm thick. A biaxially stretched polyester film was obtained.

The film had an apparent specific gravity of /, 0, opacity of 0, g, and an extremely roughened surface with an air leakage index of 30 seconds. In addition, the heat shrinkage rate is 7.2% in the vertical direction and 7.2% in the horizontal direction.
%, and the flexibility θ was lI3deg. When such a film was used as an image-receiving sheet, no paper jams or running defects occurred and it had good practical suitability, but the print quality was extremely poor with print density, print unevenness, and contrast l-u. It was something.

Comparative Example 3 A material with an intrinsic viscosity of 0.1.0 containing /jwt% of 0.3 μm titanium oxide instead of the raw material used in Comparative Example /. A biaxially stretched polyester film of 100 μm was finally obtained in the same manner as in Comparative Example except that polyethylene terephthalate of kJ was used. The obtained film had a hiding degree of 8-1 and an air leakage index of 7,000 seconds, indicating excellent hiding properties and a flat surface, but the apparent specific gravity was a high value of /5. Ta. In addition, the heat shrinkage rate is 7.0% in the vertical direction and 7.0% in the horizontal direction/
, 7%, and the flexibility θ is y Adeg.

Met. When the printing quality was evaluated using this film as an image-receiving sheet, the contrast was good as shown on the left, but the printing density was poor at 3 and the printing unevenness was poor, indicating that the quality was not satisfactory. Furthermore, troubles such as poor running within the thermal transfer device occurred, and the practical suitability was also poor.

Comparative Example q The amount of polypropylene blended in Example/
An attempt was made to produce a film in the same manner as in Example 1, except that the film was bound by Owt%, but it was found that the film frequently broke during stretching and the productivity was extremely poor. By the way, small
A sheet sample was taken, and the apparent specific gravity of a 700 μm thick portion was measured to be 0. It was ri. However, since the mechanical strength was extremely poor, it was not possible to evaluate the film's physical properties and print quality.

Table 7 summarizes the raw material composition, physical properties of the films obtained in Examples 1 to 3 and Comparative Examples 7 to 3, and the printing quality and practical characteristics when used as image-receiving sheets. The evaluation results of printing quality and practical suitability of the films of Examples 7 to 3 obtained in the present invention were all good. The degree of concealment was also sufficient, and there was no possibility that the image could be seen through the back side. The heat shrinkage rate was also 2% or less in all cases, and the dimensional stability was excellent, so no waving or curling of the film was observed after printing. In addition, since it has good flexibility, it not only has good printing quality and practical characteristics, but also improved handling properties. As described above, the film of the present invention was excellent as an image-receiving sheet for thermal transfer.

On the other hand, since the requirements of the present invention were not satisfied in Comparative Examples/-Q, the effects could not be sufficiently obtained, and evaluation results that were satisfactory as image-receiving sheets for thermal transfer were not obtained.

<Effects of the Invention> The image-receiving sheet for thermal transfer using the polyester film containing fine closed cells on the surface and inside of the present invention has higher strength than conventional image-receiving papers such as cellulose paper and synthetic paper. It has excellent dimensional stability and heat resistance, does not shrink or curl due to heat during image reception, and is dust-free.

In addition, in comparison with a normal polyester film that does not contain microbubbles, it has appropriate unevenness and flexibility, so the printing floor during thermal transfer is extremely small, and a clear image with good contrast can be obtained.

In addition, the appearance of the film is flexible due to the reduction of specific gravity, i.e.
Due to the flexibility imparted to it, running troubles during transfer operations are extremely small (and the image-receiving paper is easy to handle).

Claims (1)

[Claims] (1) The apparent specific gravity is in the range of 0.4 to 1.3, the degree of concealment is 0.2 or more, and the air leakage index is 50 to 10.
An image-receiving sheet for thermal transfer, comprising a polyester film containing fine bubbles stretched in at least one axis for a time of 0.000 seconds.