JPH0486293A - Heat transfer image receiving sheet - Google Patents

Abstract

PURPOSE:To form a heat transfer image receiving sheet having excellent flexibility, printability, dimensional stability, and high industrial value by laminating an image receiving layer made of a copolymer polyester layer having specified copolymerization ratio at least on one side surface of a polyester film. CONSTITUTION:A heat transfer image receiving sheet is formed by laminating an image receiving layer made of a copolymer polyester layer having 5-30mol% of copolymerization ratio at least on one side surface of a polyester film. The sum of mol % of copolymer component occupying in total dicarboxylic acid for forming a copolymer polyester and mol % of copolymer component occupying in total dial component is 5-30mol%. If the copolymerization ratio exceeds 30mol%, the strength of an obtained biaxial orientation film is deteriorated, and its shrinkage ratio is excessively increased improperly. On the other hand, if the copolymerization ratio of less than 5mol%, printability of a transfer film using the obtained biaxial orientation film is deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image receiving sheet used in thermal transfer recording. Specifically, the present invention relates to an image-receiving sheet for thermal transfer, which is composed of two or more layers of composite polyester film and has excellent flexibility, printing characteristics, and dimensional stability.

[Background Art and Problems to be Solved by the Invention] 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 as follows.
A transfer sheet having a transfer layer containing a sublimable or vaporizable dye, or a dye that melts with moderate heat is superimposed on an image receiving sheet, and the transfer sheet is heated to remove the dye contained in the transfer layer. The dye is vaporized or melted and dyed or transferred onto the image receiving sheet 1- to form 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.

Image-receiving sheets used for such thermal transfer recording have conventionally been made of general printing paper such as cellulose paper, gravure paper with a calender finish, or paper whose surface irregularities and pores are coated with pigments made of fine particles. smoothness,
Coated art paper with a glossy surface and Yo1~
Paper etc. are used. Synthetic paper, which has excellent strength, judicial 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.

In other words, conventional printing paper such as cellulose paper has low strength and breaks easily, and cannot be made into thin paper.
It had drawbacks such as poor dust-free properties and low water resistance. Furthermore, since the paper surface has large irregularities, printing spots tend 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 necessarily be said that it can satisfy the demand for high quality. In other words, with regard to printability, further flattening improvements are required,
Also, because of its poor heat resistance, it could not be used in applications exposed to high temperatures.

It has been proposed to eliminate these drawbacks by using a polyester film, but the film
Due to its poor flexibility, there is insufficient adhesion between the transfer sheet and the film in the thermal head, which causes printing mottling and makes it impossible to obtain clear images. Improvements were needed.

[Failure to solve the problem]

The present inventors conducted extensive studies to solve the above problems, and as a result, discovered that a polyester film having a certain specific structure is useful for binding image-receiving sheets, and completed the present invention.

That is, the gist of the present invention resides in an image-receiving sheet for thermal transfer comprising a polyester film and an image-receiving layer made of a copolymerized polyester layer having a copolymerization rate of 5 to 30 mol % laminated on at least one side thereof.

The present invention will be explained in detail below.

The image-receiving sheet of the present invention may be a laminated film formed by lamination, but is preferably obtained by stretching and heat-setting a film extruded by a so-called co-extrusion method in which all layers are co-melt extruded from a die. The film is good. Hereinafter, the image-receiving sheet and U2 will mainly be described as a two-layer composite film, but the image-receiving sheet of the present invention is not limited to a two-layer composite, and may be a multilayer of three or more layers.

The image-receiving sheet of the present invention comprises, for example, a copolyester layer (A) which is a layer for forming an image, and another layer (I3).

In the present invention, the copolyester forming the copolyester layer (A) refers to an ester bond obtained by condensation of a dicarboxylic acid component and a diol component in the main chain ai
It refers to a polycondensate having r, which consists of at least two or more dicarboxylic acid components or diol components.

Examples of dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, and sebacic acid, and examples of diol components include ethylene glycol, butanediol, hexanediol, Neohentyl glycol, diethylene glycol, P-kyzylene gelicol, 1,4-cyclohegysan dimethanol, average molecular weight 150-20,
000 polyalkylene glycol and the like.

In the present invention, a dicarboxylic acid component exceeding 50 mol% of all dicarboxylic acid components constituting the copolymerized polyester is referred to as a main carboxylic acid component, and a diol component exceeding 50 mol% of all diol components is referred to as a main diol component. Carboxylic acid components other than the main diol components and diol components other than the main diol component are referred to as copolymer components. As the main carboxylic acid component, terephthalic acid, 2,6-naphthalene dicarboxylic acid, etc. are preferable, and as the main diol component, ethylene glycol, butanediol, hexanediol, etc. are preferable.

As the copolymerized polyester used in the present invention, printing tends to be clearer if one that is relatively difficult to crystallize is used. For example, dicarboxylic acids such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, component,
Diethylene glycol, neopentyl glycol, P-
Diol components such as xylene glycol, 1,4-cyclohexanediol, and polyalkylene glycols having an average molecular weight of 150 to 20,000 are preferred.

The sum of the mol% of the copolymerized component in all the dicarboxylic acid components constituting the copolymerized polyester and the mol% of the copolymerized component in all the diol components (hereinafter referred to as "copolymerization rate")
is 5 to 30 mol%, preferably 10 to 25 mol%, and more preferably 12 to 20 mol%. Copolymerization rate is 3
If it exceeds 0 mol %, the strength of the two-wheel stretched film obtained will be poor and the shrinkage rate will also be too large, making it unsuitable.

On the other hand, if the copolymerization rate is less than 5 mol%, the printability of the resulting transfer film using the biaxially stretched film will deteriorate.

Furthermore, various known additives such as antioxidants, lubricants, antistatic agents, etc. may be added to the copolyester.

On the other hand, the polyester constituting the other layer (B) has a copolymerization rate of usually 10 mol% or less, preferably 5 mol% or less, more preferably 3 mol%. % or less.

Typical examples of such polyesters include polyethylene terephthalate, polyethylene-2,6-Natsuta radical oxygen 1-, and copolymers thereof. Furthermore, the polyester layer constituting the layer (B) may be a polymer blend of these polyesters and other polymers, and examples of other polymers include polyamide, polyolefin, polymer interior-[, etc. be done.

In the present invention, such polyesters are composited by co-melt extrusion, and at least one of the two exposed layers of the composited layers, that is, the two surface layers,
It is preferable that fine particles are contained in order to impart slipperiness to the polyester film.

The fine particles contained include lithium fluoride, kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, calcium phosphate, titanium oxide, and other elements from Groups 1, 2, and 2 of the periodic table. ,
Inert particles made of salts or oxides containing elements selected from Group Ⅰ, etc., high-melting point organic compounds insoluble during melt film formation of polyester resin, inert particles such as crosslinked polymers (added from outside) particles are called external particles)
Alternatively, particles formed inside the polymer during polyester production (particles formed during polyester production are referred to as internal particles) by metal compound catalysts used during polyester synthesis, such as alkali metal compounds, alkaline earth metal compounds, etc. It will be done.

These inert external particles and internal particles can be used alone or in combination of two or more.

The average particle size of these particles is preferably in the range of 0901 to 3.5 μm, and the amount of fine particles contained in C in the film is preferably in the range of 0.005 to 0.9% by weight.

Since the surface of the image-receiving layer (layer A) is desired to be smooth,
It is preferable that the amount and diameter of particles in the polyester (A) layer are smaller and smaller than those in the polyester (B) layer.

In the present invention, in addition to the above-mentioned fine particles, it is also a preferable method to incorporate an organic lubricant into the two exposed layers of the film in order to improve the slipperiness of the film. The type of organic lubricant is not particularly limited, but aliphatic compounds, fatty acid esters, alkylene bis-aliphatic compounds, aromatic amides, and the like are preferred. As the aliphatic compound, those having a large number of carbon atoms such as moncitric acid are preferred. Examples of aliphatic esters include ethylene glycol nisdel montanate and the like. alkylene bis aliphatic and/or aromatic amide; ζ is hexamethylene bis behenamide, hexamethyl bis stearyl amide, N
, N'-distearyl terephthalamide F, and the like. The content of these organic lubricants in the film is usually in the range of O to 500 ppm, preferably in the range of O to 200 ppm. If too many of these lubricants are mixed in,
This is not preferable because the adhesiveness decreases and the color of the film becomes too yellowish.

Furthermore, for the purpose of improving the printability of the film and the adhesion during vapor deposition, it is also suitable to include polyalkylene glycols in the two exposed layers of the film. Examples of the polyalkylene glycol include polyethylene glycol, polytetramethylene gelicol, polypropylene glycol, and the like. Methods for incorporating these polyalkylene glycols into the film include adding them to the reaction system during transesterification or polymerization, blending a polymer copolymerized with polyalkylene glycols,
Any method may be used, such as kneading it during drying or extrusion of polystill. However, in order not to impair the transparency of the film of the present invention, the polyalkylene glycol usually has a molecular weight of 10.000 or less, preferably 8.000 or less.
Use 0 or less. Further, the content in the film is usually 1% by weight or less, preferably 0.5% by weight or less.

Next, the method for producing the film of the present invention will be specifically explained, but the present invention is not particularly limited to the production method described in (1).

Copolymerized polyester A and polyester B having the composition of the present invention, which contain an appropriate amount of inorganic particles as a lubricant as necessary, are each dried using an ordinary hopper dryer, paddle dryer, vacuum dryer, etc., and then separately dried. The polyester is melted at a temperature of 200 to 320°C using an extruder (1), and then the two types of polyester are combined in a pipe or a die, extruded, and rapidly cooled to obtain an unstretched film. For extrusion, any existing method such as the T-die method or the Cheebler method may be used. T when obtaining an unstretched film
When a die is used, a film with uniform thickness can be obtained by using a so-called electrostatic adhesion method during rapid cooling.

The obtained unstretched film was then stretched at about f (
Tg-10)'c -1 ("I" c -10)'
C: Area magnification of 1.1 to 50 times in the following temperature range,
It is preferably stretched 6 to 30 times in the longitudinal direction and/or width direction. The above Tg and Tc indicate the glass transition temperature and crystallization temperature upon heating, respectively, of polyester B. The stretching method may be uniaxial or biaxial stretching depending on the purpose.

When biaxial stretching is performed, it may be sequential biaxial stretching, simultaneous biaxial stretching, or a combination thereof.

In addition, in the case of sequential biaxial stretching, a method of stretching in the longitudinal direction and then in the transverse direction is generally preferably adopted.

Further, after biaxial stretching, re-stretching may be performed in the longitudinal direction and/or width direction before subjecting to the next heat treatment step.

The film axially or biaxially stretched in this way is optionally heated in a heat setting zone at a temperature of 10 to 26
Heat treatment is performed at 0° C. for 1 second to 10 minutes.

It is preferable that the maximum temperature of the heat treatment be at least (melting point of polyester A -10)°C and at most 260°C, preferably at least the melting point of polyester A and at most 260°C.

The above heat treatment is usually carried out under tension fixation, but during the heat treatment and/or cooling after the heat treatment, it is also possible to loosen or cum out by 20% or less in the longitudinal and/or width directions of the film. be.

During the stretching step, it is also possible to perform a corona discharge treatment on one side or the front surface of the film before or after stretching to improve the adhesion of the film to the printed layer or the like.

In addition, during the stretching process, coating is applied to one or both sides of the film before or after stretching to improve the adhesion of the film.
It is also possible to improve antistatic properties, slipperiness, light shielding properties, etc.

The film thus obtained is wound up to form a product.

The thickness of the fill J1 obtained as described above is not particularly limited, but the thickness used for boat fishing is 25~25~
The range is 400 μm.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded.

The film was evaluated according to the method shown below.

(1) Cut the print quality film into an A4 size, and paste it into the Sharp CX-
Thermal transfer recording was performed using a 5000 color printer, and the resulting hard copies were visually evaluated for print density, print unevenness, and degree of contrast I on a five-point scale of 1ζ.

Evaluation criteria 5 Excellent 4 Good 3 Average 2 No practical problems 1 Practical problems Comparative example Contains 6% by weight of titanium oxide with an average particle size of 0.3 μm.
Raw material (B, ゛) is a blend of polyethylene terephthalate chips with an intrinsic viscosity of 0.65 and crystalline polypropylene homobolymer typhosate with a melt flow index (MF, 1> of 5) in an amount of 15% by weight, and an average particle size of 0.3 μm. Polyethylene terephthalate 1'(A+') containing 5% by weight of titanium oxide was dried separately and heated to 290"C using an extruder.
After melting B+' and A,'' in an extruder, they were extruded into a sheet into a cooling drum kept at 40°C to obtain an amorphous sheet I. to 8
Stretched 3.0 times at 5°C and 3.2 times in the transverse direction at 95°C,
After heat treatment at 35℃ for 5 seconds, the final film thickness was 100.
A biaxially stretched laminated polyester film of μm was obtained.

When this film was cut into an A-4 size with image receiving sheets 1 to 1 and the print quality was evaluated, the print density was 3 and the print unevenness was 2.
~3, contrast I~4.

Instead of the polyester A I' used in Examples and Comparative Examples, it contained 8% by weight of titanium oxide with an average particle size of 0.3 μm, and the dicarboxylic acid component consisted of 84% by mole of terephthalic acid units and 16% by mole of isophthalic acid units, Stretch film formation was performed in the same manner as in the comparative example, except that a copolymerized polyester having an intrinsic viscosity of 0.72 and consisting of 97 mol% ethylene glycol units and 3 mol% diethylene glycol units was used as the diol component, and a 100 μm film was similarly obtained. . The obtained film is A
When it was cut into 4 plates and the print quality was evaluated as image receiving sheet 1-, the print density, print unevenness, and contrast I/last were all 5, which was extremely excellent.

〔Effect of the invention〕

The image-receiving sheet for thermal transfer of the present invention has excellent flexibility, printing characteristics, and dimensional stability, and has high industrial value.

Claims (1)

[Claims] (1) An image-receiving sheet for thermal transfer comprising a polyester film and an image-receiving layer comprising a copolyester layer having a copolymerization rate of 5 to 30 mol % on at least one side.