WO1999028133A1

WO1999028133A1 - Biaxially oriented polyester film for thermal transfer

Info

Publication number: WO1999028133A1
Application number: PCT/JP1998/005431
Authority: WO
Inventors: Narihiro Masuda; Shigeyuki Watanabe
Original assignee: Mitsubishi Polyester Film Corporation; Dai Nippon Printing Co., Ltd.
Priority date: 1997-12-02
Filing date: 1998-12-02
Publication date: 1999-06-10
Also published as: DE69813520T2; EP0962332B1; DE69813520D1; EP0962332A1; EP0962332A4

Abstract

A biaxially oriented polyester film for thermal transfer which is a coated film having a thickness of 20 νm or smaller and obtained by applying a coating fluid containing a water-soluble or water-dispersible organic polymer to at least one side of a polyester film whose orientation and crystallization have not been completed and then drying, stretching, and heating the film, characterized by having thickness fluctuations of 10 % or smaller in any 15 m range in the machine direction. When an ink ribbon containing this film as a base is used in printing, prints having reduced image density fluctuation can be obtained with satisfactory color tone reproducibility.

Description

Specification

Biaxially oriented polyester film for thermal transfer

The present invention relates to a biaxially oriented polyester film for thermal transfer. More specifically, the present invention relates to a biaxially oriented polyester film for thermal transfer capable of giving a high-definition image with less density unevenness during printing.

Background art

Ink ribbons of the thermal transfer type, both the fusion type and the sublimation type, have an ink layer on one side of the base polyester film.At the time of transfer, the film is heated from the side opposite to the ink layer with a thermal head or the like. By transferring this heat to the ink layer, the ink is melted or sublimated to be selectively transferred to the transfer target. At this time, the heat applied to the opposite surface is transmitted through the thickness direction of the film and reaches the ink layer. Therefore, if the thickness of the film is large, it is difficult for heat to be transmitted, and if it is thin, heat is easily transmitted. That is, when the film has a thickness variation, a phenomenon occurs in which the print density becomes thin in a thick portion and the print density becomes high in a thin portion. This phenomenon is less problematic for applications that do not depend on the image quality, such as characters and simple color images. However, thermal transfer printing has been remarkably trending toward higher image quality with the recent spread of personal computers and digital cameras, and particularly high-resolution full-color printing such as printing photographic images is required. In this case, fluctuations in printing density due to fluctuations in the thickness of the base film of the ink ribbon may inadvertently change the color tone of the image or cause loss of color reproducibility. ing.

By the way, some polyester films, which are widely used as base films for thermal transfer ink ribbons, are provided with a coating on the surface to provide a special function for thermal transfer. This coating is generally applied by so-called in-line coating, in which a coating liquid containing an organic polymer compound using water as a medium is applied to a film, followed by drying, stretching, and crystallization. For inline coating, for example, a method of applying a coating solution using water as a medium to a film that has been subjected to longitudinal stretching and drying using a preheating zone in the next transverse stretching process is a simple process. It is preferred in terms of convenience and thermal efficiency, and is widely used.

In such an in-line coating process, a coating liquid containing a large amount of water is applied onto the polyester film, so that the heat given to stretch the film is first taken away by the latent heat of vaporization of water. . Then, after the water content of the coating liquid evaporates sufficiently, the temperature of the film rises, and the temperature of the film is more likely to be uneven than when the in-line coating is not performed. Fluctuations increase.

Furthermore, when a relatively thin film is produced for thermal transfer, the ratio of the coating liquid thickness to the film thickness, that is, the ratio of the water content to the polyester content, is inevitably large, and the above-mentioned film thickness variation is further increased. It will be noticeable. Techniques for suppressing thickness fluctuations of polyester films not subjected to in-line coating include, for example, improvements in polyethylene naphthalate films (JP-A-63-67030, JP-A-63-0731). Japanese Patent Application Laid-Open No. Sho 63-670732), Improvements Regarding Polyester Shrink Films (Japanese Patent Application Laid-Open No. Sho 63-146940 (US Patent Nos. 4,985,5) ), Manufacturing method to keep the sound pressure level around the base below a certain value (Japanese Patent Application Laid-Open No. Sho 63-162122), A technique that defines the ratio of the spectrum intensity sum after conversion (Japanese Patent Application Publication No. 9-254424) is known, but the inline coating is applied and the thickness varies. Polyester film with low density and technology for manufacturing it have not been known

Summary of the Invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a base film which provides an ink ribbon for thermal transfer capable of performing printing with little density fluctuation and good color tone reproducibility. The present inventors have conducted intensive studies to achieve the above object, and as a result, if a thermal transfer ink ribbon was manufactured using a polyester film in a specific thickness variation area, high-definition full-color printing was performed. However, the present inventors have found that print density fluctuations are reduced, and have completed the present invention.

That is, the present invention provides a method of applying a coating liquid containing a water-soluble or water-dispersible organic polymer compound on at least one surface of a polyester film before completion of orientation crystallization. In the case of a coated film having a thickness of 20 / m or less obtained by performing a dry 'stretching' heat treatment, the thickness unevenness in an arbitrary 15 m long section in the longitudinal direction of the coated film is 10% or less. Provided is a biaxially oriented polyester film for thermal transfer.

Detailed description of the invention

The polyester of the polyester film used in the present invention is 80 mol of the repeating unit. / ₀ or more, preferably refers 9 0 mole ^_0/0 or an ethylene terephthalate, Oh Rui ethylene one 2, 6-naphthalate, and the cyclo Cyclohexanedicarboxylic methylene terephthalate phthalate what a repeating unit derived from at least one . 80 moles of the above repeating units. If it is / ₀ or more, it may be a copolymer containing other repeating units. Examples of copolymer components that form other repeating units include glycol components such as ethylene glycol, propylene glycol, diethylene glycol, neopentinole glycol, 1,4-butylene glycol, and 1,4- Examples of dicarboxylic components such as cyclohexanedimethylenedaricone and polyalkyleneglycol, and carboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and oxybenzoic acid as dicarboxylic acid components. I can do it. Among the various polyesters, considering the quality and economy, it is most preferable to use polyethylene terephthalate, and by using polyethylene naphthalate having excellent heat resistance, it is possible to effectively reduce the wrinkles of the ink ribbon. You.

The polyester film used in the present invention may contain, as necessary, inorganic particles, an organic lubricant, an antistatic agent, a stabilizer, a dye, a pigment, an organic polymer, or the like as an additional component. In particular, in order to adjust the gloss of the transferred recorded image, or to improve the runnability of the polyester film when it is manufactured or formed into an ink ribbon, the polyester film contains inorganic particles and organic particles. Is preferably roughened. When the average surface roughness of the film is set to 0.3 to 0.2 // m, and more preferably to 0.4 to 0.2, both running property and high-definition image can be compatible. preferable.

Further, when the scrap of the film generated during the production is recycled, a coat layer component on the film surface described later may be mixed. When measured at 30 ° C. in a phenol-no-tetrachloroethane mixed solvent (weight ratio of 50 to 50), the polyester film used in the present invention is 0.45 to: I. 20 dl Zg, and more preferably 0.5 to 50. It is preferable to have an intrinsic viscosity in the range of 0.80 d 1, g in order to maintain continuity during film formation and to keep thickness unevenness within a specific range.

Since the polyester film of the present invention is used as a base film of a thermal transfer material, it is necessary that its mechanical strength, thermal conductivity, operability during production of the thermal transfer material, and the like be good. In particular, in order to obtain a high-definition image, the total thickness (of the coated film) is preferably 20 / m or less, more preferably 10m or less. The lower limit of the total thickness is usually 0.5 / zm, preferably 1 / m.

The biaxially oriented polyester film of the present invention is a film that is biaxially oriented and oriented in the longitudinal direction of the film and in a direction perpendicular to the film (width direction). Poor strength and dimensional stability make it impossible to obtain high-definition transferred images.

The biaxially oriented polyester film of the present invention is obtained by applying a coating solution containing a water-soluble mono- or water-dispersible organic polymer compound to at least one surface of the film before the orientation crystallization is completed, and then drying, stretching, It is a coating film obtained by performing a heat treatment. As the water-soluble organic polymer compound, those which are soluble in cold or warm water or solubilized by adjusting the pH are preferable. Specifically, polyalkylene alcohol, polyvinyl alcohol, polyacrylic acid , Polymetharalylic acid, polyacrylamide, polyvinylpyrrolidone, polystyrenesulfonic acid, gelatin, zein, dextran, cellulose and the like, and derivatives thereof.

The water-dispersible organic polymeric compound, lay preferred those capable of stably finely dispersed in water, specifically, the range of suspension average particle diameter is preferably from 0.001 to 50 ₁ 11, stable It is preferable that the rate of change of the average particle diameter of the suspension after standing at 25 ° C for 3 hours is within 10% of soil.

Fine dispersions of organic high molecular compounds can be prepared by emulsion polymerization, dispersion by applying strong mechanical shearing, or after adding water to the organic high molecular compound solution. It may be a dispersion prepared by a method of distilling off the agent, and a dispersant may be used to disperse the organic polymer compound in water.

Organic polymer compounds that can be finely dispersed in water include polyethylene, polypropylene, polybutadiene, polystyrene, polyacrylate, polymethacrylate, polyacrylonitrile, polyacetate, polyvinyl butyrate, polychloride butyl, and poly. Vinylidene chloride, aromatic or aliphatic polyester, aromatic or lurid aliphatic polyamide, aromatic or aliphatic polyurethane, aromatic or aliphatic polyether, aromatic or aliphatic polyimide, polycarbonate, polyalkyl ketone Compounds such as aromatic, aliphatic or aliphatic epoxy resins, phenolic resins, urea resins, melamine resins, cyanate resins, polyfluoroethylene, polyorganosiloxanes, natural or synthetic waxes, polyamino acids, and the like. Can Rukoto like the body.

These organic polymer compounds may be homopolymers or random, block or graft copolymers containing two or more types of repeating units. Furthermore, not only can the desired organic polymer compound be present in water from the beginning, but also a reactive monomer or polymer can coexist or be present, and after coating, a crosslinking reaction or polymerization reaction can be performed. In this case, a catalyst may be used in combination.

In the present invention, the coating liquid applied to the biaxially stretched polyester film includes, in addition to the above organic polymer compound, for example, inorganic fine particles, an antistatic agent, a fungicide, an antioxidant, a stabilizer, and the like. Additives can be added in amounts as needed.

The medium of the coating liquid containing the organic high molecular compound in the present invention is preferably water, but is used to disperse the organic high molecular compound or to improve the flexibility (followability during stretching) of the coating film. For this purpose, a water-soluble organic solvent can be used in combination. In this case, however, the upper limit of the concentration is preferably set so that the concentration of the organic solvent used in the atmosphere is lower than the explosion limit.

The coating liquid containing the above-described organic polymer compound is applied to at least one side of the polyester film, and this application step needs to be performed in the polyester film production step. That is, it is applied to a polyester unstretched film, Simultaneous biaxial stretching, coating on a uniaxially stretched polyester film, and then stretching in a direction perpendicular to the uniaxial stretching direction, or applying to a biaxially stretched polyester film, and further stretching in the transverse and / or longitudinal directions Method must be used. Among these, the method of applying to a uniaxially stretched polyester film is the most preferred method because it suppresses fluctuations in film thickness and does not impair productivity.

In order to apply the above-mentioned coating solution to the polyester film, a usual coating apparatus, for example, a reverse port-one coater, a gravure coater, a rod coater, an air doctor coater or the like can be used.

The coat layer containing the organic polymer compound described above,

1) As an intermediate layer between the polyester film and the ink layer,

a) Improvement of adhesiveness with ink layer binder for sublimation transfer

b) Improvement of adhesiveness to the melt transfer ink ・ Release of releasability;

2) As an intermediate layer between the polyester film and the back layer,

Improve adhesion with ink ribbon back layer;

3) As the ink ribbon back layer itself, or

4) Add antistatic performance to ink ribbon

It is provided for the purpose of etc.

The biaxially oriented polyester film for thermal transfer of the present invention is required to have a thickness unevenness of 10% or less in an arbitrary length section of 15 m in the longitudinal direction. This thickness unevenness is a value obtained by dividing the difference between the maximum thickness and the minimum thickness in an arbitrary 15 m length section in the longitudinal direction of the film by the average thickness of the film.

If the thickness unevenness exceeds 10%, when printing a high-definition full-color image using an ink ribbon that uses this as a base film, the difference in color tone due to density fluctuations can be seen visually, and the image quality becomes poor. The result is impaired. The range of thickness unevenness is preferably 7% or less, and if it is 5% or less, the difference in color tone is at a level that hardly causes a problem. Ideally, the lower limit is 0%, but for various reasons, the limit is usually around 2%.

On the other hand, it is preferable that thickness unevenness is small in the width direction, but in most cases, Since an effective width of 15 m cannot usually be taken in the width direction, the measurement length is set to 3 m and thickness unevenness is measured. At this time, the thickness unevenness in the width direction is also preferably 10% or less, more preferably 7% or less, and particularly preferably 5% or less.

The biaxially oriented polyester film for thermal transfer of the present invention is obtained by applying a coating solution containing a water-soluble or water-dispersible organic polymer compound before the completion of the orientation crystallization, followed by drying, stretching and heat treatment. The film must be laminated using so-called in-line coating, and the thickness unevenness in the longitudinal direction must be small. However, as described above, when the above-mentioned in-line coating process is performed, the subsequent stretching is more difficult than when the in-line coating is not performed because the coating liquid containing a large amount of water is applied onto the polyester film. There is a problem that temperature unevenness of the film easily occurs in the process, and as a result, the thickness variation of the film becomes large.

The present inventors conducted further intensive studies to solve this problem. As a result, due to the vibration of the base film of the base material, the coating film having the remaining fluidity had an uneven thickness distribution. However, the temperature distribution of the base film became non-uniform during the process of drying → preheating → transverse stretching, and it was concluded that this was a factor that had a very large effect on the thickness variation in the longitudinal direction. In other words, it was found that by reducing this vibration or making it less susceptible to vibration, the thickness fluctuation in the longitudinal direction of the polyester film can be suppressed.

After coating the coating liquid, it is subjected to the drying step and until the water in the coating liquid evaporates sufficiently (1% by weight of water in the coating film is a guideline). In addition, most of the vibrations that occur in the film are due to the shock generated when the ears of the film are gripped by the tenter clip, and the film being pushed by the hot air blown out by the tenter. Things. In order to reduce these vibrations, for example, a method of suppressing pulsation by using hot air in a tenter by inverter control, a method of reducing the amount of hot air flow itself, gradually increasing the clip width by the amount that expands due to heating of the film Spread out and avoid loosening in the center of the film gripped at both ends with clips.Use a cushioning material on the clips so that the tenter clips grip the ears of the film with less impact. Can be. In addition, in order to reduce the effects of vibration, To minimize the amplitude of vibration by minimizing the distance from the taper to the point where the ear of the film is gripped by the tenter clip. A method may be used in which a drive or a free roll is brought into contact with the film surface, or a single or a plurality of free rolls, so that the propagation of vibration is interrupted in a short period or in a section. Of course, two or more of these methods can be used in combination.

By adopting the method described above, the vibration of the film in the drying section, especially the vibration with large amplitude, is suppressed, and as a result, the thickness unevenness in the longitudinal direction of the biaxially oriented and heat-fixed film is reduced. Can be reduced. At this time, the amplitude of the film due to the vibration in the drying section depends on the width of the tenter, the thickness of the film, and the coating thickness, but is preferably 5 cm or less at most, and more preferably 3 cm or less. In the present invention, in addition to the above-described method of preventing thickness unevenness caused by in-line coating, a known thickness unevenness preventing method can be used in combination. According to the experience of the present inventors, the unevenness in the film thickness tends to be dragged by the process having the worst defect, and the level thereof is determined. Therefore, even if the in-line coating process can be improved by the present invention, it cannot be said that it alone is sufficient, and a comprehensive measure is required.

Hereinafter, preferred embodiments of a process that can be preferably used to obtain the film of the present invention will be described, but the present invention is not limited thereto.

When performing the melt extrusion of the polyester raw material, it is preferable to install a gear pump in the melt line of the extruder in order to suppress the pulsation of the discharge. In addition, it is also preferable to install a static mixer to make the temperature distribution of the molten polyester in the melt line uniform.

In the process of casting and solidifying the molten polyester to obtain an unstretched film, it is preferable to use a so-called electrostatic adhesion method. In the electrostatic adhesion method, an amorphous metal electrode having an edge portion having a thickness of 50 // m or less (Japanese Unexamined Patent Publication No.

And a laminated blade electrode in which a conductive thin film having a thickness of 0.01 to 10 μm is provided on at least one surface of an electric insulator (Japanese Patent Application Laid-Open No. 1-156600 / 1991). It is preferable to carry out the process while effectively bringing the molten polyester into close contact with the cooling drum by using a method described in the gazette. In order to effectively perform the electrostatic adhesion method, the polyester used as a raw material The specific resistance at the time of melting is preferably 1 × 10 ¹ ° Ω · cm or less, more preferably 1 × 10 ⁹ to IX 10 ⁶ Ω · cm. For the same purpose, JP-A-57-190040, JP-A-58-225123, JP-A-59-91121, JP-A-59-172542, JP-A-59-172542 — 182840, JP-A-59-229314, JP-A-60-141 751, JP-A-60-24

Methods described in JP-A-8737, JP-A-62-213841, JP-A-62-236722, JP-A-62-236722 and the like can also be used.

In addition, when the molten polyester is discharged from the die, the slit ratio of the die z If the ratio of the thickness of the cooled and solidified unstretched film is adjusted to 5 to 20, and further to 8 to 15, the thickness of the unstretched film I like it because it can reduce unevenness.

In addition to the above-mentioned method, a prescription such as minimizing the rotation unevenness of the cooling drum and blocking the wind or the like so that the molten polyester at the time of casting adheres to the cooling drum as little as possible can be used. By adopting these methods, when the sheet-like molten polyester touches the cooling drum, the width of the fluctuation of the linear grounding portion (hereinafter abbreviated as “grounding line”) spreading in the width direction on the cooling drum is It is preferable that the width is 1 mm or less, more preferably 0.5 mm or less, in the area corresponding to the effective product width.

It is preferable that the polyester formed into an unstretched film in the casting step is then stretched longitudinally using a roll stretching method. The stretching conditions used at this time vary depending on the composition of the polyester used. For example, in the case of polyethylene terephthalate (PET), the stretching ratio is 2.0 to 3.0 times in a temperature range of 90 to 110 ° C. After stretching the first stage, the longitudinal stretching is divided into two stages, for example, the second stage stretching is performed at a stretching ratio of 1.2 to 2.0 times in a temperature range of 70 to 90 ° C. It is preferable that the stretching temperature of the second step is set lower than that of the first step. In this case, in each stretching step, a nip roll or an appropriate position should be set at an appropriate position to prevent fluctuations in the position where plastic deformation starts and ends in the stretching section on the low-speed roll and high-speed port. It is preferable to perform the process while pressing the film against each roll using an electrostatic adhesion method. The uniaxially oriented film that has been subjected to the longitudinal stretching is subjected to the in-line coating process described above.

After that, transverse stretching is performed with a tenter, and the conditions for transverse stretching also differ depending on the polyester composition used, as in the case of longitudinal stretching. Taking PET as an example, the draw ratio can be set to 3.0 to 5.0 times in the temperature range of 85 ° C to 130 ° C. At this time, it is preferable to suppress the pulsation by blowing the air for heating and cooling the film in the center as much as possible by controlling the inverter. Also, it is described in JP-A-5-301284. As described above, it is also possible to adopt a method of improving the thickness unevenness in the width direction by changing the angle of the outlet with time.

The biaxially oriented film that has been transversely stretched can be further subjected to re-longitudinal stretching and Z or re-lateral stretching.However, it is preferable that re-longitudinal stretching be performed by roll stretching and re-lateral stretching be performed by tenter method. In these cases, it is preferable to use the same method as the above-described thickness unevenness measure used in the roll stretching method and the tenter stretching method.

The biaxially oriented film that has completed the stretching step is then subjected to a heat setting step. It is preferable to use a tenter method for heat setting, but also in this case, the same measures for thickness unevenness as in transverse stretching can be taken. During heat setting, preferably, the temperature is in the range of 180-245 ° C and the time is in the range of 0.5-60 seconds. In addition, during heat setting, it is possible to perform 1 to 10% relaxation in the width direction in the maximum temperature range and the Z or cooling region in order to improve the heat shrinkage in the 畐 direction. It is.

The biaxially oriented polyester film thus obtained are breaking strength in the longitudinal direction and the width direction, at both 25 kgf / mm ² or more and shrinkage at 180 ° C3 minutes, 5% or less in the longitudinal direction and the width direction both Preferably,

The laminated film of the present invention preferably has an adhesion of 100 gf Zl 25 mm or less, more preferably 50 8 125 ₁ 11111 or less, particularly preferably 30 g or less, as measured by the method described in Examples described later. ₈ £ _/ / 1 25111111 or less. Even if the laminated film is once wound into a roll and then exposed to high-temperature and high-humidity conditions with pressure applied between the films, the films do not stick to each other. This means that the film can be easily pulled out when unwinding. The fixing force is controlled, for example, by adding a cross-linking agent or a cross-linkable polymer to the coating liquid, This is achieved by promoting cross-linking within or between the components of the organic polymer compound during the heat treatment step of the film. Further, with this, in the case of a coating layer for improving the adhesive strength with the sublimation ink, the adhesive strength with the ink can be further improved. To control the fixing force, it is also effective to adjust the type and amount of organic or inorganic particles contained in the base film to increase the surface roughness.

Further, F 5 value in the longitudinal direction and the width direction of the laminated film of the present invention are both 1 3. Is preferably 0 kgf ZMM ² or more. When this condition is satisfied, the elongation of the ink ribbon in the longitudinal direction and the width direction can be further reduced, and as a result, print wrinkles and missing prints can be reduced. The method for measuring the F5 value will be described in Examples described later.

Example

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless departing from the gist of the present invention. In the examples, “parts” or “%” is “parts by weight” or “% by weight” unless otherwise specified.

The method for measuring the characteristics and the method for evaluating the effects are as follows.

(1) Film thickness

As the “film thickness”, the total thickness of the laminate of the base film and the coating layer containing the organic polymer compound was measured using a micrometer.

(2) Film thickness unevenness

Using a continuous film thickness measuring device (using an electronic micrometer) manufactured by Anritsu Corporation, the length of the biaxially oriented film is 15 m long and the width is 3 m long. Sections were extracted. The maximum thickness (μπι) and the minimum thickness (/ zm) were measured for each sample, and the thickness unevenness was calculated from the average thickness (/ zm) force in that section according to the following formula. Was regarded as the thickness unevenness of the sample.

Thickness unevenness (%) = {(maximum thickness-minimum thickness) ÷ average thickness} X I 0 0

The average thickness used here is a value calculated from the measured area, weight, and density of the sample, and the density at this time is 1.0 for polyethylene terephthalate. 3.97, 1.354 for polyethylene naphthalate, and 1.270 for polycyclohexanedimethylene terephthalate.

(3) Average surface roughness

The average surface roughness measured the surface roughness of the polyester base film. When the coating layer has only one side, the surface roughness of the anti-coating side is used.For double-sided coating, use the ME Kacetone etc. to carefully peel off the coating layer so that the surface shape does not change. Was measured for roughness.

The measurement was performed using a non-contact surface shape measurement system (Micromap 512; objective lens, 20 times) manufactured by Micromap Co., Ltd., and SRa was measured. The measurement was performed for 20 fields of view, and the average value was defined as the average surface roughness.

(4) Intrinsic viscosity of polyester film

The intrinsic viscosity of the polyester film can be determined by completely removing the coating layer using an organic solvent such as MEK Paceton, and then using a sufficiently dried film to form a mixed solvent of phenol Z tetrachloroethane (50/50). ) And measured at a temperature of 30 ° C.

(5) Average particle size of suspension

For the suspension containing the organic polymer compound, the particle size distribution was measured using a particle size analyzer UPA 9340 (manufactured by Nikkiso Co., Ltd. (laser Doppler-Z frequency analysis method)), and the average particle size was calculated.

(6) Degree of density fluctuation of printed image

A sublimable ink layer was formed on the coating layer surface of a biaxially oriented polyester sample having an ink-adhesive coating layer on one side, and a back layer was coated on the other side to form an ink ribbon.

In the case of uncoated film, an ink layer was applied to an arbitrary surface, and a back layer was coated on the opposite surface. Sublimable Inkubihiku Le and back layer vehicle composition shown below, so that each dry coating weight of 1 g / m ² after, after sequentially coated by gravure coating, then dried, and cut, the ink ribbon It was created.

Composition of ink and back layer vehicle

Yellow—: Micrex Yellow 6 G (Bayenore) 2 parts Polyvinylacetate KS-5D (Sekisui Chemical) 3 parts Toluene ZMEK = lZl (weight ratio) 9 5 parts Magenta:

Bimicron VP S N 26 70 (manufactured by NO) 3 parts Polyvinylacetoacetal KS-5D (manufactured by Sekisui Chemical Co., Ltd.) 4 parts Toluene ZMEK = 1 1 (weight ratio) 9 3 parts Cyan:

Kaset Blue 7 1 4 (manufactured by Nippon Kayaku Co., Ltd.) 4 parts Polyvinyl acetate / reacetacetol K S-5D (manufactured by Sekisui Chemical Co., Ltd.) 4 parts Toluene ZMEK = 1 1 (weight ratio) 9 2 parts

Poribyurupuchira Ichiru, S-LEC BX- 1 (manufactured by Sekisui Chemical Co., Ltd.) 2 parts polyisobutylene Xia sulfonate Burnock D750- 45 (manufactured by Dainippon Ink and Chemicals, Inc.) 9 parts of phosphoric acid ester lubricants PLYSURF A ² 0SS (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 2 parts Talc, Micro Ace L-1 1 (manufactured by Nippon Talc) 0.3 parts Toluene ZMEK = 1 Zl (weight ratio) 86.7 parts These ink ribbons are incorporated into a commercially available sublimation transfer type color printer to sublimate. Test printing was performed in the transfer mode. The printing paper was a special paper for printer standard.

In the test, based on digital data of human face photographs (data size of about 32 Mb, A4 size image), the same image was printed five times in succession, and the color tone reproducibility was evaluated. The evaluation was done by carefully comparing the overall color tone of the five images visually, and by using the Tokyo Denshoku Color Analyzer TC-1800ΜΚΠ, the skin color of each of the five images was evaluated. The same location was measured, and the maximum value of the color difference (ΔΕ) was determined. The criteria for visual evaluation were classified into the following three ranks for color tone reproducibility.

A: Good reproducibility with no difference in color tone of image

B: There is a difference in color tone in the image, but it cannot be recognized unless you look very carefully C _: Difference in color tone is recognized in the image, and the difference can be recognized at a glance (Not suitable)

(7) Breaking strength of film

Using a tensile tester manufactured by Intesco Intesco Model 2001, a sample film with a length of 50 mm and a width of 15 mm was sampled at a speed of 20 Om / min in a room adjusted to a temperature of 23 ° C and a humidity of 50% RH. The value obtained by dividing the load (kg) at break by the original cross-sectional area (mm ² ) of the test piece from the tensile stress-strain curve was defined as the breaking strength.

(8) Thermal contraction rate of finolem

The sample film was subjected to free-end heat treatment at 180 ° C for 3 minutes using a hot air circulating oven manufactured by Tabai, and the dimensional changes in the vertical and horizontal directions before and after the film were processed. Expressed as / ₀ .

(9) Sticking force

The two laminated film specimens were superimposed so that one coated surface was in contact with the other opposite surface, and was pressed by a press machine in a constant temperature and humidity room adjusted to 40 ° C and 80% RH. After leaving a rectangular section with a length of 10.0 cm pressed at a pressure of 1 O kgf Zcm ² for 24 hours, release the pressure, change the temperature and humidity chamber to 23 ° C and 50% RH, and leave it for 24 hours I left it.

After that, the specimen was taken out of the constant temperature and humidity chamber, and a tensioned 0.8 mm 0 piano wire was passed between the two superposed specimens, and the pressed rectangle was 12.5 cm wide. While maintaining the position parallel to the above, the piano wire was moved at a speed of 50 cmZ to peel off the above-mentioned pressed part. The average line of the chart of the peeling load (gf / \ 25 mm width) value applied to the piano wire at the time of this peeling was determined and defined as the fixing force.

(10) F 5 value

Using a tensile tester manufactured by Intesco Intesco Model 2001, in a room adjusted to a temperature of 23 ° C and 50% R.Η, a sample film with a width of 15 mm is chucked with a chuck of 5 Omm, Pull at a speed of 200 mmZ, and apply the load (kgf) when elongating 5% from the original length to the original cross-sectional area (mm ² ) of the test piece (use the total thickness of the above laminated film as the thickness) And calculated). Five points were measured in the same manner, and the average of the obtained values was defined as the F5 value. Example 1

0.3 particles with an average particle diameter of 1.2 μm. /. Polyethylene terephthalate pellets having an intrinsic viscosity of 0.66 were sufficiently dried by heating, fed to an extruder, and melt-extruded at 290 ° C. to produce an unstretched film. At this time, the extruder is equipped with a 10 / m-cut filter to remove foreign matter, a gear pump to suppress pulsation and discharge by metering, and to equalize the temperature distribution of the molten polyester in the melt line. A static mixer was installed in order to make it possible to change the condition. The film was extruded from a T-die into a film, and was wound around a cooling drum having a surface temperature of 40 ° C by an electrostatic adhesion method to be cooled and solidified. The slit gap of the die of the T die was 1.1 mm, and the thickness of the unstretched film solidified by cooling was 91 μm (the ratio of the thickness of the unstretched film solidified by cooling to the slit gap was approximately 1 μm). twenty one ) . In addition, in this electrostatic adhesion method, a voltage of 6 kV was applied using a metal monorefass metal blade having a thickness of 20 / zm and a width of 2 mm, made of chromium-molybdenum monocarbon. In addition, the zone for casting was enclosed as a small room to block the effects of wind from air conditioners and other equipment. As a result, the fluctuation of the grounding line where the molten polyester was grounded to the cooling drum could be reduced to almost zero over the entire effective product width.

The obtained unstretched film was led to a longitudinal stretching step. The longitudinal stretching is performed using a roll stretching method, the first-stage stretching is performed at 100 ° C at a stretching ratio of 2.70 times, and the second-stage stretching is performed at 87 ° C at a stretching ratio of 1.6. Went at 0x. At this time, in both the first and second stages of stretching, the low-speed roll and the high-speed roll, which perform stretching using the peripheral speed difference, have the film separated from the mouth and the film at the mouth, respectively. The nip roll was set at the contact position, and the film was pressed against the mouth so that the position where the plastic deformation started and ended in the stretching section did not fluctuate, and the film was moved.

One surface of the obtained uniaxially stretched film was subjected to a corona discharge treatment in air, and the treated surface was coated with a mixture prepared by mixing aqueous dispersions of each component so as to have the following composition by a Daravia coating method. The application amount of the aqueous dispersion was 6 g Zm ² , and the solid content in the aqueous dispersion was 10% by weight.

Aqueous dispersion composition

Polyester resin 40 parts (solid content ratio) Ataryl resin 40 parts (solid content ratio)

Okisazorin based crosslinking agent 2 0 parts (solid content ratio) The dispersion liquid of the polyester resin, terephthalic acid 5 5 moles of the acid component ^_0/0, isophthalic acid 4 0 mole ^_0/0 and 5 Sojiumu and sulfoisophthalic acid 5 molar ^_0/0, Poriesu Tel consisting of di o Ichiru ethylene glycol 6 0 mole ^_0/0 as a component, Jechirenguri Konore 1 3 mode lambda ^ / o and 1, 4-Butanjio one 7 Mo a system resin aqueous dispersion, the dispersion of Akuriru based resin, E chill § chestnut rate 5 0 Monore ⁰ / o, I isobutyrate Honoré methacrylonitrile rate 3 5 Monore ^_0/0, 2 human Dorokishechi / Remetaku Relate 1 0 Mol%, methacrylic acid 5 mol. / ₀ a Akuriru system榭脂aqueous dispersion consisting of the dispersion of Okisazorin based crosslinking agent, styrene 5 8 2 wt%, butyl acrylate 2 1 8 wt%, 2 -.. Biel one 2- Okisazorin 2 0 weight. /. It was a polymer aqueous dispersion comprising:

After this coating treatment, the film was led to a drying and preheating step. At this time, the following measures were taken so that the film coated with the aqueous dispersion was not vibrated as much as possible. First, two free ports are installed at equal intervals (2 m) between the gravure coater and the entrance of the tenter, and a film is placed on the surface opposite to the surface on which the water dispersion is applied. The contact angle was 2 °. Next, both ends (ears) of the film were gripped with a tenter clip, and hot air, whose pulsation was suppressed by inverter control, was applied to the film to remove water from the water dispersion. At this time, the temperature of the film gradually increased as the water content of the coating layer disappeared, and as a result, a phenomenon was observed in which the film thermally expanded and the central portion was loosened. Therefore, the clip width was slightly increased so that it became wider toward the back of the tenter so that the central part would not loosen.

By taking the above measures, the maximum amplitude of the vibration received by the film was 1.5 cm in the drying section from the outlet of the coating solution of the coating solution to the time when the moisture of the coating layer was sufficiently evaporated.

Next, the film was stretched in a transverse direction at 105 ° C. at a draw ratio of 4.5, and heat-treated at 230 ° C. for 2 seconds in a continuous tenter. Thereafter, the clip width is reduced by 5% at 210 ° C to perform a relaxation treatment. A layered biaxially oriented polyester film having a total thickness of 4.5 μm was obtained.

The properties of the obtained polyester film are shown in Table 1 below.

The obtained film is a polyester film having a sublimable ink easy-adhesion layer provided on one side by in-line coating, and is a polyester film with little thickness unevenness. Concentration fluctuation was small.

Comparative Example 1

The same polyester raw material as in Example 1 was used for extrusion, casting, longitudinal stretching and corona discharge treatment in exactly the same manner as in Example 1, and a similar aqueous dispersion was applied by the same method.

After that, of the film vibration countermeasures in the drying section performed in Example 1, both ends (ears) of the film were fixed with a tenter clip at the interval between the Daravia Coater and the entrance of the tenter without installing a free roll. Gripped. After that, hot air, whose pulsation was suppressed by inverter control, was applied to the film to remove water from the water dispersion. At this time, instead of slightly increasing the width of the clip so that it became wider toward the end of the tenter, the clip was passed through the dry section with the center loosened. Within the drying section, the maximum amplitude of the vibration that the film received was 7 cm.

Next, a biaxially oriented polyester having a total thickness of 4.5 / m, in which a coating layer having a thickness of 0.1 / m was laminated and subjected to transverse stretching, heat fixing and width relaxation exactly in the same manner as in Example 1. A film was obtained.

Table 1 shows the properties of the obtained polyester film.

The obtained film has a sublimation-ink-easily-adhesive layer provided on one side by in-line coating.However, since the film is a polyester film having a large thickness unevenness, an ink ribbon made using this is used when printing. The density fluctuated greatly, making it unsuitable for printing full-color images.

Comparative Example 2

The same polyester raw material as in Example 1 was extruded and subjected to casting, longitudinal stretching, and corona discharge treatment in exactly the same manner as in Example 1. Here, the gravure coater was passed through without applying the aqueous dispersion performed in Example 1. This After that, in exactly the same way as in Comparative Example 1, in order to prevent the film from vibrating in the drying section, at the interval between the gravure coater and the entrance of the tenter, without setting the free roll, use a tenter to clip both ends of the film. ) Was gripped. After that, the film was transported by applying hot air, whose pulsation was suppressed by inverter control, to the film. At this time, instead of slightly increasing the width of the clip so that it became wider toward the end of the tenter, the clip was passed through the dry section with a slack in the center. Within the drying section, the maximum amplitude of vibration experienced by the film was 7 cm.

Subsequently, transverse stretching, heat fixing, and width relaxation were performed in exactly the same manner as in Example 1 to obtain a biaxially oriented polyester film having a total thickness of 4.4 μm without a coating layer.

Table 1 shows the properties of the obtained polyester film.

Although the level of thickness unevenness was good, no sublimable ink easy-adhesion layer was applied by in-line coating, and the ink layer was peeled off with an ink ribbon made using this film, and printing was performed. I couldn't do that.

Example 2

Polyethylene naphthalate (PEN) pellets having an intrinsic viscosity of 0.55 and containing 0.3% of silica particles having an average particle diameter of 1 .5 are sufficiently heated and dried, and then supplied to an extruder to be heated at 30.5 ° C. To give an unstretched film. At this time, the extruder was provided with the same filter, gear-pump, and static mixer as in Example 1. The film was extruded from a T-die into a film, and the obtained film was wound around a cooling drum having a surface temperature of 60 ° C. using an electrostatic adhesion method, and cooled and solidified. In the die of the T die, the slit gap was 1.1 mm, and the thickness of the cooled and solidified unstretched film was 107 / m (the slit gap The ratio of the thickness of the cooled and solidified unstretched film was about 1 0.3). In this electrostatic adhesion method, the same voltage was applied using the same amorphous metal blade as in Example 1. Further, similarly to Example 1, the zone where the casting was performed was enclosed as a small room, and the influence of the wind from the air conditioner and the like was cut off. As a result, the fluctuation of the grounding line where the molten polyester was grounded to the cooling drum could be reduced to almost zero over the entire effective product width.

This unstretched film was then led to a longitudinal stretching step. The longitudinal stretching is performed using the roll stretching method, and the first-stage stretching is performed at 130 ° C at a stretching ratio of 2.70 times, and then further. In the second step, stretching was performed at 123 ° C. at a stretching magnification of 1.8 times. At this time, for both the first and second stages of stretching, the low-speed roll and the high-speed roll are equipped with an Ep roll at the same position as in Example 1, and the position where plastic deformation starts in the stretching section and the end position The film was pressed against a roll so that no fluctuation of the position occurred. One surface of the uniaxially stretched film was subjected to corona discharge treatment in air, and the treated surface was coated with an aqueous dispersion having exactly the same composition as in Example 1 by a gravure coat method in the same coating amount.

After this coating treatment, a drying / preheating step was carried out. At this time, exactly the same means as in Example 1 were taken so that the film coated with the aqueous dispersion was not vibrated as much as possible. By taking this prescription, the maximum amplitude of vibration received by the film was 1.5 cm in the drying section from the coater outlet of the coating solution to the time when the water in the coating layer was sufficiently evaporated.

Next, the film was stretched 4.7 times at 135 ° C. in the transverse direction, and heat-treated at 230 for 2 seconds in a continuous tenter. Thereafter, the clip width was reduced by 5% at 210 ° C. to perform a relaxation treatment, and the film was passed through a cooling zone, and finally, a coating layer having a thickness of 0. m biaxially oriented polyester film was obtained.

Table 1 shows the properties of the obtained polyester film.

Even when PEN was used, as in Example 1 using PET, the obtained film had a sublimable ink easy-adhesion layer provided on one side by in-line coating, and had a small thickness unevenness. Since it was a film, the ink ribbon created using it had little fluctuation in density when printed. Comparative Example 3

Using the same polyester raw material as in Example 2, extrusion was performed in exactly the same manner as in Example 2, casting, longitudinal stretching and corona discharge treatment were performed, and a similar aqueous dispersion was applied by the same method.

After that, among the measures against film vibration in the drying section performed in Example 2, at the distance between the Daravia coater and the entrance of the tenter, do not install the free roll, and use a tenter clip to attach both ends (ears) of the film. Gripped. After that, hot air, whose pulsation was suppressed by inverter control, was applied to the film to remove water from the water dispersion. On this occasion At the same time, instead of slightly increasing the clip width so that it became wider toward the end of the tenter, it was passed through the drying section with the center part loosened. In the drying section, the amplitude of the vibration received by the film was up to 7 cm.

Next, a biaxially oriented polyester having a total thickness of 4.5 // m was obtained by laminating a coating layer having a thickness of 0.1 m by performing transverse stretching, heat fixing, and width relaxation exactly in the same manner as in Example 2. Table 1 shows the properties of the obtained polyester film.

Although the sublimable ink easy-adhesion layer is provided on one side by in-line coating, since the polyester film is a polyester film with a large thickness unevenness, the ink ribbon created using this has a large density fluctuation when printed. However, it was not suitable for printing a full-color image.

The coating agents used in Examples 3 to 6 and Comparative Example 4 below are as follows.

Terefutanore acid 9 0 Monore in the dicarboxylic acid ^_0/0, 5 _ source Jiu Mus Honoré e isophthalate 1 0 Monore ^_0/0, ethylene glycol in the glycated one Honoré Honoré 7 3 Monore ^_0/0, diethylene glycol 2 7 moles ^_0/0 polyester polymer made of.

<Acrylic polymer: B> 35 mol of methacrylic acid. / ₀ , an alkyl methacrylate ₃₅ mol ⁰ / o, an acryl polymer comprising 30 mol% of styrene.

Water-soluble epoxy compound mainly composed of tetraglycerol tetradalicydinole ether.

Crosslinking agent or crosslinking polymer: C 2>

A water-soluble melamine compound consisting mainly of mono-, di- and tri-nuclear melamines of almost tetrafunctional methylol and methoxymethylol melamine.

Example 3

Polyethylene naphthalate pellets having an intrinsic viscosity of 0.55 and containing 0.7% of silica particles having an average particle diameter of 1.2; um are sufficiently heated and dried, and then supplied to an extruder to obtain a temperature of 30.5 °. C was melt extruded to form an unstretched film. At this time, the extruder is equipped with a 10 μππ cut filter to remove foreign substances, and a gear pump to suppress pulsation and discharge by metering.The melt line is used to equalize the temperature distribution of the molten polyester. A static mixer was installed. The molten polyester was extruded from a die into a film, wound around a cooling drum having a surface temperature of 60 ° C. using an electrostatic contact method, and cooled and solidified. The slit gap of the die of the T die was 1.1 mm. In this electrostatic contact method, a voltage of 6 kV was applied using an amorphous metal plate of cobalt-chromium-molybdenum-carbon having a thickness of 20 / m and a width of 2 mm. Furthermore, the casting zone was enclosed as a small room to block the effects of wind from air conditioners and other equipment. As a result, the fluctuation of the ground line where the molten polyester grounded to the cooling drum could be reduced to almost zero over the entire effective product width.

This unstretched film was then led to a longitudinal stretching step. The longitudinal stretching was performed using the roll stretching method.The first stage was stretched to 2.70 times at 130 ° C, and the second stage was stretched to 1.90 times at 123 ° C. Stretching was performed. At this time, at the time of stretching the first and second stages, the low-speed roll and the high-speed roll, which perform stretching using the difference in peripheral speed, are placed at the position where the film separates from the roll, and at the edge of the film. A nip roll was installed at a position where the film contacts, and the film was pressed against the roll to perform longitudinal stretching so that the position where plastic deformation starts and ends does not fluctuate in the stretching section. One side of this uniaxially stretched film is subjected to corona discharge treatment in air, and the treated surface is mixed with each aqueous dispersion or aqueous solution by Daravia coating method so as to have a solid content ratio shown in Table 2 below. Was applied.

After this coating treatment, the drying and preheating process was conducted. At this time, the following measures were taken so that the film on which the coating liquid was applied was not vibrated as much as possible. First, two free rolls are installed at equal intervals (2 m) between the gravure coater and the entrance of the tenter, and a film is placed on the opposite side of the surface where the coating liquid is applied. The contact angle was 2 °. Next, both ends (ears) of the film were gripped with a tenter clip, and hot air, whose pulsation was suppressed by inverter control, was applied to the film to remove water from the coating liquid. At this time, as the water content of the coating layer disappeared, the temperature of the film gradually increased, and as a result, a phenomenon was observed in which the film thermally expanded and the central portion was loosened. Therefore, until the center part no longer loosened, the clip width was slightly increased so that it became wider toward the back of the tenter.

By taking the above prescription, the amplitude of the vibration received by the film was 1.5 cm at the maximum in the drying section from the outlet of the coating liquid coating until the water in the coating layer was sufficiently evaporated. .

Next, the film was stretched 4.8 times at 135 ° C. in the transverse direction, and heat-treated at 230 ° C. for 2 seconds in a continuous tenter. Thereafter, the clip width was reduced by 3% at 180 ° C. to perform a relaxation treatment, and the film was passed through a cooling zone to obtain a laminated film having a coating layer having a thickness of 0.09 / m. This coating layer improves (easy adhesion) the adhesive strength with the sublimation ink.

While trimming this laminated film to a width of 50 mm, it is wound up into a roll of 300 m with an appropriate hardness so that the core with a 6 inch inner diameter and a wall thickness of 1 mm does not slip off. Was.

Table 2 below shows the results of evaluating the properties of the obtained laminated film.

Next, a high-temperature and high-humidity treatment was performed on the wool-shaped laminated film by the method described below, and then a sublimation-type thermal transfer ribbon was prepared and various characteristics were evaluated.

The wool-shaped laminated film obtained above was adjusted to 40 ° C and 80% RH. They were placed in a thermo-hygrostat and treated for 24 hours. After the treatment, the temperature and humidity in the constant temperature and humidity were changed to 23 ° C and 50% RH, and left as it was for 24 hours. After unwinding the unwound laminated film and transporting it on a plurality of rotating rollers, on the opposite side of the coating layer, two copies of Sekisui Kagaku's Polybier Petilal Esrec BX-1 were added. 9 parts of Polyisocyanate Vernock D 750-45 manufactured by Nippon Ink Co., 2 parts of phosphate ester lubricant Plysurf A208 S manufactured by Dai-ichi Kogyo Seiyaku, 0.3 part of Talc Micro Ace L-11 manufactured by Nippon Talc and toluene Z methyl ethyl ketone (hereinafter abbreviated as MEK) = 11 1 (weight ratio) 88.7 parts of coating solution is applied by Daravia coating method, dried and finished to a final thickness of 1.0 / m heat-resistant lubricating layer was provided.

Next, after transporting the film provided with the heat-resistant easy-sliding layer on a plurality of rotating rollers, an ink coating solution having the following composition is applied to the coating layer opposite to the heat-resistant easy-sliding layer, respectively. Coated by gravure coating method, dried and provided with a sublimation type ink layer with a final thickness of 1.0 // m to form an ink ribbon

Ink coating liquid composition

Yellow: Macrorex Yellow 1 6 G (manufactured by Bayenore) 2 parts Polyvinylacetoacetal K S-5D (manufactured by Sekisui Chemical) 3 parts Toluene ME K = 1/1 (weight ratio) 95 parts Magenta: bimicron VP SN2670 (Manufactured by Bayer) 3 parts Polyvinyl acetate KS-5D (manufactured by Sekisui Chemical) 4 parts Toluene MEK = lZl (weight ratio) 93 parts Cyan: Kaset Blue 714 (manufactured by Nippon Kayaku) 4 parts Byuracetoacetal KS-5D (Sekisui Chemical Co., Ltd.) 4 parts Toluene ZMEK = 1 1 (weight ratio) 92 parts Example 4

In Example 3, the thickness of the unstretched sheet was changed so that the final thickness of the polyethylene naphthalate film of the base material was the same as that of Example 3, and the magnification of the second step of longitudinal stretching was 1 Change to 6 times and adjust the solids concentration of the coating solution so that the final thickness of the coating layer becomes the same as in Example 3, and change the magnification of transverse stretching to 4.3 times A laminated film was prepared in exactly the same manner except for the above. Table 3 shows the results of evaluating the properties of this laminated film. Further, in the same manner as in Example 3, after the high-temperature and high-humidity treatment, a sublimation-type thermal transfer ribbon was prepared, and various characteristics were evaluated. Table 3 shows the obtained results.

Comparative Example 4

Using the same polyester raw material as in Example 3, extrusion-casting, longitudinal stretching, and corona discharge treatment were performed in exactly the same manner as in Example 3, and a similar coating liquid was applied by the same method.

After that, among the measures against film vibration in the drying section carried out in Example 3, at the interval between the gravure coater and the entrance of the tenter, without setting a free roll, use a tenter clip to end both ends (ears) of the film. Was gripped. Thereafter, hot air, whose pulsation was suppressed by inverter control, was applied to the film to remove the water content of the coating liquid. At this time, instead of slightly increasing the width of the clip so that it became wider toward the center, the clip was passed through the dry section with the center part loosened. Within the drying section, the amplitude of the vibration experienced by the film was up to 7 cm.

Next, transverse stretching, heat fixing, and width relaxation were performed in exactly the same manner as in Example 3 to obtain a laminated film. Table 3 shows the results of evaluating the characteristics of the laminated film. Further, in the same manner as in Example 3, after a high-temperature and high-humidity treatment, a sublimation-type thermal transfer ribbon was prepared, and various characteristics were evaluated. Table 3 shows the obtained results.

Example 5

Polyethylene terephthalate pellets containing 0.7% silica particles having an average particle diameter of 1.2 / m and having an intrinsic viscosity of 0.66 are heated and dried for + minutes, and then supplied to an extruder for 290 ° C. C was melt extruded to form an unstretched film. At this time, the extruder was provided with the same filter, gear-pump, and static mixer as in Example 3. The film was extruded from a T-die into a film and wound around a cooling drum having a surface temperature of 40 ° C. using an electrostatic adhesion method to be cooled and solidified. The die gap of the T die had a slit gap of 1.1 mm. In this electrostatic adhesion method, the same voltage was applied using the same amorphous metal blade as in Example 3. Further, as in Example 3, the zone where the casting was performed was enclosed as a small room, and the influence of wind from an air conditioner or the like was cut off. As a result, the fluctuation of the grounding line where the molten polyester was grounded to the cooling drum could be reduced to almost zero over the entire effective product width.

This unstretched film was then led to a longitudinal stretching step. The longitudinal stretching is performed using a roll stretching method. The first stage stretching is performed at 100 ° C. at 2.70 times, and the second stage is further stretched at 87 ° C. at 1.60 times. Was done. At this time, the nip roll is set at the same position as in Example 3 for the low-speed roll and the high-speed roll at the time of the first-stage and second-stage stretching, and the position where plastic deformation starts and ends in the stretching section The film was pressed against a roll and stretched longitudinally so that no positional fluctuation occurred.

One side of this uniaxially stretched film was subjected to a corner discharge treatment in air, and the treated surface was changed to the composition shown in Table 2 by a gravure coating method, and the final thickness of the coating layer was changed to Example 3. Coating was performed in exactly the same manner as in Example 3, except that the solid content of the coating liquid was changed so as to be the same as in Example 3.

After this coating treatment, a drying and preheating step was performed. At this time, exactly the same means as in Example 3 were taken so that the film coated with the coating liquid did not vibrate as much as possible. By adopting this prescription, the amplitude of the vibration received by the film was 1.5 cm at the maximum in the drying section from the coater outlet of the coating solution to the evaporation of the water in the coating layer to + minutes.

Then, it was stretched 4.4 times at 105 ° C. in the transverse direction, and heat-treated at 220 ° C. for 2 seconds in a continuous tenter. Thereafter, the clip width is reduced by 3% at 180 ° C to perform a relaxation treatment, and the film is passed through a cooling zone to finally form a laminated film having a coating layer of 0.09 / zm in thickness. Obtained.

Table 3 shows the results of evaluating the characteristics of the laminated film. Further, in the same manner as in Example 3, after a high-temperature and high-humidity treatment, a sublimation-type thermal transfer ribbon was prepared, and various characteristics were evaluated. Table 3 shows the obtained results.

Example 6

A laminated film was obtained in exactly the same manner as in Example 3, except that the composition of the coating liquid was changed to the composition shown in Table 2. Table 3 shows the results of evaluating the characteristics of the laminated film. Further, when an attempt was made to produce a sublimation-type thermal transfer ribbon in exactly the same manner as in Example 3, when the film was unwound and processed into a ribbon, the films were not easily separated from each other, and the processing yield was low. Mari has dropped slightly.

The total thickness of the laminated films obtained in Examples 3 to 6 and Comparative Example 4 was 2.8 μηι.

Table 2 Composition (% by weight) and final coating thickness (μ π) of the total solid content of the coating layer

Table 3

The invention's effect

The biaxially oriented polyester film for thermal transfer of the present invention has a coating for imparting a special function for thermal transfer, and the coating is performed using water as a medium during the film forming process. Despite being applied and laminated, there is little unevenness in film thickness. As a result, according to the ink ribbon using the film of the present invention, it is possible to perform printing with little density fluctuation and good color tone reproducibility.

Claims

The scope of the claims

1. A coating solution containing a water-soluble or water-dispersible organic polymer compound is applied to at least one side of the polyester film before the orientation crystallization is completed, and then dried, stretched and heat-treated to obtain a thickness. A biaxially oriented polyester film for thermal transfer, wherein the coating film has a thickness of 20 / zm or less, and the thickness unevenness in an arbitrary 15 m long section in the longitudinal direction of the coating film is 10% or less.

2. The polyester film according to claim 1, wherein the thickness unevenness in an arbitrary 15 m long section in the longitudinal direction of the coating film is 7% or less.

3. The polyester film according to claim 1, wherein the thickness unevenness in an arbitrary 15 m length section in the longitudinal direction of the coating film is 5% or less.

4. The polyester film according to claim 1, wherein the thickness unevenness of the applied film in an arbitrary 3 m long section in the horizontal direction is 10% or less.

5. The polyester film according to claim 1, wherein the thickness unevenness of the coating film in an arbitrary 3 m length section in the horizontal direction is 7 <½ or less.

6. The polyester film according to claim 1, wherein the thickness unevenness of the applied film in an arbitrary 3 m long section in the horizontal direction is 5% or less.

7. The polyester film has an intrinsic viscosity in the range of 0.45 to 1.20 d1 Zg when measured at 30 ° C in a phenol / tetrachloro / ethane mixture solvent (weight ratio: 5 OZ50). Polyester film according to any one of Nos. 6 to 6.

8. The polyester film according to claim 1, wherein the total thickness of the applied film is 20 / m or less.

9. bonding strength of the coating layer, the polyester film according to any Aru claims 1-8 Noi deviation at 100 ₈ £ 1251 ₁ 1111 or less.

10. longitudinal direction and the width direction of the F 5 value are both polyester film according to claim 1 is at least 13.0 kgf / mm ^2.