JPH029687A - Polyester film for thermal transfer - Google Patents

Abstract

PURPOSE:To improve the optical characteristics of a printing surface by providing a specific number of projections having a specific height to a surface to which a transfer layer must be provided. CONSTITUTION:20-200/mm of projections having a height of 0.5-1.0mum and 3-40/mm of projections having a height of 1.2-2.0mum are provided to a surface to which a transfer layer must be provided. In order to develop this surface roughness, a particle group mainly forming the projections having a height of 0.5-1.0mum and a particle group mainly forming the projections having a height of 1.2-2.0mum are pref. compounded with a polyester film. The sizes and amounts of two kinds of these particle groups can not be determined unconditionally, because they are changeable according to the shapes of said particle groups, the compatibility thereof with polyester or a stretching condition but, usually, the mean particle size of the particle groups is selected from a range of 0.5-5mum and the compounding amount thereof with polyester is selected from a range of 0.2-10wt.%.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal transfer recording film,
More specifically, the present invention relates to a polyester film for heat-sensitive transfer that has excellent running properties and anti-stinging properties, and provides an excellent visual sensation with less gloss on the printed surface.

[Prior art and problems to be solved by the invention] Various recording methods have been known in the past, but the thermal transfer recording method, which uses a thermal recording device such as a thermal printer, is difficult to operate and maintain. Excellent and widely used. Biaxially oriented films of polyester, especially polyethylene terephthalate, are used as base films for transfer materials for printers because of their high melting point, heat resistance, chemical resistance, and mechanical properties. . It is known that in order to improve the runnability and staking resistance of the film, particles inert to the polyester, such as silicon dioxide or calcium carbonate, having an appropriate particle size are incorporated into the film.

For example, JP-A-40-25714, JP-A-40-2
/7/9'1 Publication, JP-A-42-193119, JP-A-62-193J-27, JP-A-42-29
93g9 and the like describes a method of improving these characteristics by roughening the surface of a base film supporting a medium to be transferred. It is well known that the degree of surface roughening can be adjusted as appropriate, for example, in the range of 0.02 to 1 μm in terms of center line average roughness.

However, when printing on image-receiving paper using a transfer material made of such a base film, the problem of often causing discomfort to the eyes due to the high gloss of the printing surface has come to the fore in recent years.

[Failure to solve the problem]

The present inventors have arrived at the present invention as a result of their efforts to improve the optical properties of the print surface, in addition to the conventional properties necessary for a base film for thermal transfer.

That is, the gist of the present invention is that the height of the surface on which the transfer layer is provided is 0.5
The number of protrusions of ~1.0 μm is 10 to 200/seagull, and the height is 8~0, and the number of protrusions of 0 μm is 3 to yo/WI
A polyester film for heat-sensitive transfer characterized by the following.

The present invention will be explained in more detail below.

Polyester in the present invention refers to terephthalic acid, co-, 6-
It refers to a polyester obtained using an aromatic dicarboxylic acid such as naphthalene dicarboxylic acid or its ester and ethylene glycol as main starting materials, but of course so-called copolymerized polyesters can also be used. In this case, the dicarboxylic acid component includes one or two of terephthalic acid, phthalic acid, isophthalic acid, 1,2,6-naphthalenedicarboxylic acid and its isomers, adipic acid, sebacic acid, and oxycarboxylic acids such as p-oxyethoxybenzoic acid. The above can be used. As the glycol component, one or more of diethylene glycol, propylene glycol, titanium diol, /, cucyclohexane dimetatool, neopentyl glycol, etc. can be used. In any case, the present invention The polyester of the present invention refers to a polyester having more than one ethylene terephthalate unit or an ethylene terephthalate unit or an ethylene t/n-λ, 6-naphthalene unit as a repeating structural unit.

Further, the polyester film of the present invention refers to a polyester film oriented in at least one axis direction using such a polyester as a starting material, and a known method can be used for its production. For example, usually rich O
After melt extrusion into sheets at ~320°C,
After cooling and solidifying at ℃ to form an amorphous sheet, the sheet is biaxially stretched vertically and horizontally, or simultaneously stretched, and heat treated at 0℃ for 10 to 2 degrees (e.g., The method described in Publication No. 39) can be used.

In the present invention, the sum of Young's moduli in the longitudinal and transverse directions of the polyester film thus obtained is 00 Kq
/rm2 or more is preferable, more preferably 900 Kg
/rtaa2 or higher. In addition, its thickness is usually O,
S to 30 μm, preferably 7 to 10 μm.

Incidentally, the feature of the film of the present invention is that the number of protrusions on the surface on which the transfer layer is provided must satisfy certain specific requirements. That is, when measured with a stylus type surface roughness meter, the height is 0.5 to 1.
The number of protrusions (A) of 0 μm is 20 to 200/W, and the number of protrusions (B) of 8λ to 2.0 μm in height is 3 to O
It is necessary that the number is 1/2.

The conditions for measuring the film surface using a stylus surface roughness meter are as follows. That is, the radius of the stylus is 2
μm1 needle force 3omg, measurement length/■, cutoff value o, o
R area, vertical magnification 70,000 times, horizontal magnification 200
It's double. The height of the protrusion is defined as the difference between the level of the peak on the chart of the roughness curve and the level of the bottom of the valley on the left thereof, divided by the vertical magnification magnification.

The present invention is characterized in that two types of protrusions having different heights are each disposed in a certain amount. The center line average roughness (Ra) has been known as a method of expressing the surface roughness of a film in such applications, but the present inventors found that the value is greatly affected by the number of protrusions, and that it is related to the height of the protrusions. Due to the lack of information, Ra cannot evaluate the properties necessary for a base film for thermal transfer, especially the glossiness of the part after printing, and it is only possible to evaluate the quality of the glossiness of the part after printing. We found that there is a correlation.

In the present invention, the number of protrusions (A
) must be 20 to 200 pieces/zone, preferably 30 to 100 pieces j. If this value is less than λO pieces/day, the runnability and staining resistance will be insufficient, and the gloss of the printed surface will be so high that it will cause discomfort to the eyes. On the other hand, if this value exceeds 200 pieces j, the sharpness of the print will be impaired.

In addition, in the present invention, at the same time, the height /, 2 to 2.0 μm
The number of protrusions (B) must be 3 to 41θ pieces/m,
Preferably! ;-20 pieces/fi. The presence of such protrusions improves the optical properties of the printed surface. In other words, due to the combination with the number of protrusions (A), a large number of relatively high protrusions exist on the film surface with some irregularity, and the thickness of the transfer layer changes minutely, causing diffuse reflection on the printed surface. begins to occur spontaneously. As a result, so-called glare on the printing surface is reduced, giving a soft and pleasant impression.If the number of protrusions (B) is less than 3 protrusions/W, the improvement in glare is insufficient, and if this value is 40 protrusions. If it exceeds /mm, printing performance will be extremely poor.

The ratio of the number of protrusions (B) to the number of protrusions (A) is preferably 0.03 to o, r, and more preferably o, o s to 0.3.
It is preferable that

In the present invention, it is preferable that the number of protrusions outside the above height range be as small as possible. In particular, since protrusions exceeding 3 μm in height cause deterioration in printing performance, the number of protrusions/m is preferably 5 or less. On the other hand, protrusions with a height of less than O, S μm are often mixed together, but in this case as well, if they exist in large quantities, the optical characteristics of the printing surface will deteriorate, so this value is preferably 200 or less, more preferably ioo pcs/fi or less is better.

As described above, the present invention is characterized by maintaining the protrusion height and number of protrusions on the film surface on which the transfer layer is provided within a certain range, but in order to develop such roughness, a conventional method is used. take.

That is, in the present invention, particle groups mainly forming protrusions with heights o, s-i, o μm and particles with a height of 7.2 to 2.0 μm are used.
A preferred method is to blend into a polyester film a group of particles that mainly form protrusions. The size and amount of these two types of particles, which are required to develop the surface condition characterized by the present invention, can be changed depending on the shape of each particle, the affinity of the particles with polyester, the stretching conditions, etc., so they cannot be generalized. Although it cannot be determined, the average particle size is usually O,
The amount of S to Sμm1 for polyester is 0.2 to 1
As described above, in the present invention, the surface condition characterized by the present invention can be more preferably obtained by using two types of particles, but of course, only one type of particles or 3fffi 2 or more particles can be used. It is also possible to achieve this with particles.

Examples of the burnt particles used in the present invention include kaolin, calcium carbonate, calcium fluoride, zeolite, calcium phosphate, silicon dioxide, and titanium dioxide. Particles made of heat-resistant organic crosslinked polymers can also be preferably used.

In the present invention, it is preferable that the surface of the film on the opposite side to the surface on which the transfer layer is provided has the same surface roughness. Normally, the surface of polyester film that comes into contact with the cooling drum during melt extrusion tends to be somewhat flat;
It is convenient to use a biaxially stretched film that is substantially between the front and back sides as it is. A heat-resistant protective layer is usually provided on this surface, but of course a polyester layer giving a different surface roughness may be laminated on the side in contact with the protective layer, if necessary.

In the present invention, the type of heat-sensitive transfer layer formed on the base film is not limited, and either a non-reactive type or a reactive type can be used. Non-reactive types include, for example, transfer layers made of hot-melt ink or sublimable dyes, and reactive types include, for example, a combination of leuco dye and color developer. I can do it.

〔Example〕

The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

In Examples and Comparative Examples, "1 part" indicates "parts by weight."

The measurement method used is as follows.

(1) Center line average roughness (Ra) It is determined as follows using a stylus type surface roughness meter (SE-, ?FK manufactured by Koita Institute) in the same way as the measurement of the linear density of protrusions on the film surface. Ta. The tip radius of the stylus is 1 μm, and the load is 30
■It is. A part with a reference length L (,2, jm) is extracted from the film cross-sectional curve in the direction of its center line, and the center line of this extracted part is set as the X axis, and the direction of vertical magnification is the Y axis, and the roughness curve y = - When expressed as f(2), the value given by the following equation is expressed in μm.

Ra = di fI' + f(x) + dxO The cut-off value is 303 m, and Ra is 5 points in the vertical direction.
A total of 10 left points were measured in the horizontal direction, and the average value was calculated.

(2) Film running properties during printing If transfer ink was applied to the base film. That is, a heat-melting coloring material layer consisting of 35 parts of paraffin wax, 30 parts of carnauba wax, part of low molecular weight polyethylene, and 2 parts of carbon bluff was coated on one side of the film so that the dry film thickness was 9 μm. . Note that a silicon-based heat-resistant protective layer with a thickness of 0.3 μm was provided on the opposite side to the coloring material layer.

Next, Fuji Xerox's facsimile Telecopier 2
'l! Using an R-type machine, the running conditions of the heat-sensitive transfer film obtained as above were evaluated and divided into the following three stages.

○... The feeding condition is good and there is no problem at all Δ... The ribbon may be slightly wrinkled 0 ×... The ribbon is wrinkled and the feeding condition is often poor.

(3) Stick characteristics The stick characteristics were evaluated using the same evaluation machine and film as in the evaluation of film runnability during printing, and were divided into the following three stages.

○...Good with no problems at all Δ...Slight fusion is observed.

×...Fusion often occurs, resulting in poor ribbon conveyance (4) Printability The same evaluation machine and film used to evaluate the film runnability during printing were used to evaluate the printability, and the following three steps were performed: Divided into.

○...Good with no shading or bleeding Δ: Slight unevenness in shading and bleeding are observed.

×: There is clear unevenness in shading or blurring.

(5) Optical characteristics of the printed surface The degree of glare on the surface of the printed characters was visually observed and divided into the following three levels.

O: Gives a soft impression to the eyes with little glare.

Δ: There is a slight glare and the eyes become easily tired.

×: The glare is large and gives a feeling of fatigue to the eyes.

In addition, the glossiness of the surface was also measured using a glossmeter manufactured by Nippon Heavy Industries. In this case, the incident angle of the light beam was 60 degrees. In general, the lower this value is, the more preferable it is.

Example/ In the polyester manufacturing process, transesterification reaction wave average particle diameter: silicon dioxide with an average particle diameter of 0 μm and calcium carbonate with an average particle diameter of 3 μm were mixed in polyester in amounts of 2.0 parts and 0.0 μm. The slurry was added as an ethylene glycol slurry so that the amount of water was increased.

Next, a polycondensation reaction was carried out by a conventional method to obtain an intrinsic viscosity of L0.63.
of polyethylene terephthalate was obtained.

Next, the obtained polyester was dried and then melted at 290°C.
It was extruded through a die and rapidly cooled to obtain an unstretched sheet. Subsequently, the film was stretched 3.3 times in the longitudinal direction and 3.6 times in the transverse direction, and then heat treated in Co. J and S-'C to obtain a λ-axis oriented polyethylene terephthalate film having a thickness of 5 μm.

The resulting polyethylene terephthalate film was coated with a transfer ink and a heat-resistant image retention layer, and evaluated as a heat-sensitive transfer material.

Examples 3 and 3 and Comparative Examples 7 to 3 Types of particles blended into the film in Examples/
A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 1, except that the average particle size and amount were changed, and it was evaluated as a thermal transfer material in the same manner as in Example.

In Example 1, polyethylene 11,6-naphthalate was produced instead of polyethylene terephthalate. Next, a λ-axis oriented polyethylene, 6-naphthalide film having a thickness of 5 μm was obtained in the same manner as in Example 1, except that the polyester was melted at 300° C. and the stretching temperature was increased.

The obtained film was evaluated in the same manner as in Example 1.

The results obtained above are summarized in Table 7.

〔Effect of the invention〕

By using the film of the present invention as a base film for thermal transfer, the running properties of the film, which are easy to peel in the order of thermal transfer time, the staking resistance, and the printing properties are maintained at a high level, but these properties have not been sufficiently improved to date. The optical properties of the printed surface can also be improved, and its industrial value is high.

wish Reason Diafoil Co., Ltd.

Claims (1)

[Claims] (1) The number of protrusions with a height of 0.5 to 1.0 μm on the surface on which the transfer layer is provided is 20 to 200/mm, and the height is 1.2
A polyester film for thermal transfer, characterized in that the number of protrusions of ~2.0 μm is 3 to 40/mm.