JPH09220867A - Polyester film for screen process printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve plate wear, film rolling properties, perforation sensitivity and resolving degree at the time of printing by using a biaxially oriented polyester film which shows specific values in terms of melting point, coefficient of thermal contraction and modulus of tensile elasticity. SOLUTION: In a biaxially oriented polyester film for screen process printing employed for a thermal stenciling method, a biaxially oriented polyester film is used which has a coefficient of thermal contraction 8 times or more the coefficient of thermal contraction at 65 deg.C, at a melting point of 170-240 deg.C, a modulus of tensile elasticity of at least, 200kg/mm<2> in both longitudinal and width directions and a thickness of 0.5-7μm. When manufacturing this kind of polyester film, first a polymer is supplied to a known melt extrusion device, then is heated at temperatures or higher than the melting point of this polymer, and this molten polymer is extruded from a slit-like die. Further, this molten polymer is quenched and solidified so that its temperatures are below the glass transition temperature level on a rotary cooling drum to obtain substantially amorphous unoriented sheet. Finally this sheet is biaxially stretched into a film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film for screen printing, and more specifically, a thermal head, a xenon plate-making system, a flash valve, which is used by laminating it on a screen woven with fibers of silk, nylon, polyester or the like. TECHNICAL FIELD The present invention relates to a biaxially oriented polyester film for screen printing, which has excellent heat-sensitive perforation properties such as a method.

[0002]

2. Description of the Related Art Screen plate making using a heat-sensitive stencil film is a simple method with a small number of steps for making a plate because it does not use a photosensitive resin, and is a cost-effective method.
There are drawbacks such as poor printing durability and drawing accuracy. The necessary properties of the heat-sensitive stencil film used for screen plate making include printing durability, film winding properties, perforation sensitivity, image resolution during printing, etc., but conventionally it has been used as a heat-sensitive stencil film for screen printing. Vinylidene chloride is insufficient in mechanical strength and inferior in printing durability, and has poor perforation sensitivity. Therefore, the thermal energy required for perforating a film is high, and the above-mentioned necessary properties are not satisfied.
Conventionally, various proposals have been made regarding a device for screen printing, a perforation method, etc., but few proposals have been made regarding a heat-sensitive stencil film for screen printing, and as a heat-sensitive stencil film for screen printing, a new The appearance of thermoplastic resins is awaited.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat sensitive stencil film for screen printing which is excellent in printing durability, film winding characteristics, perforation sensitivity and resolution during printing. .

[0004]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems, and as a result, found that a specific biaxially oriented polyester film is suitable as a film for screen printing, and completed the present invention. Came to do. That is, the gist of the present invention is that the melting point is 170 to 240 ° C., 10
The thermal shrinkage at 0 ° C is 8 times or more of the thermal shrinkage at 65 ° C, and the tensile elastic modulus in both the longitudinal direction and the width direction is 200k.
The present invention resides in a biaxially oriented polyester film for screen printing, which has a g / mm ² or more and a thickness of 0.5 to 7 μm.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
With the screen printing of the present invention, silk, nylon, a screen woven with fibers such as polyester is fixed to a frame,
After forming the opening and non-opening in any shape by various methods on top of it, ink is put into the boat-shaped screen frame, and the inside of the plate is pressed with a rubber spatula called Squeegee.・ By sliding, the ink is pushed out from the image area through the screen to the back surface of the plate for printing. In general, the screen plate making method includes a screen by a manual method, a photoresist screen, a metal screen, a special screen to which the invention of the present application uses a heat sensitive stencil film instead of a photosensitive resin, and the like. Even in special screen plate making, the reflected light from the original is converted into an electric signal, amplified, and discharged from the recording needle to disperse carbon in a thermoplastic resin film such as vinyl chloride or vinyl chloride / acetic acid vinyl chloride copolymer. Discharge type that perforates a sheet with a perforated sheet to make a screen plate, and various screen meshes that are laminated with a thermoplastic film such as vinylidene chloride that is perforated by heat are brought into close contact with the original and the thermal head, xenon plate There is a heat-sensitive method in which holes are formed by heat energy of a method such as a flash valve and a flash valve, and the biaxially oriented polyester film of the present invention is used for a heat-sensitive stencil method of special screen making among screen printing.

The biaxially oriented polyester film of the present invention is used as a heat-sensitive stencil sheet for screen printing, and is laminated on a screen woven with fibers of silk, nylon, polyester, etc., and then a thermal head, a xenon plate-making system, a flash valve, etc. It is perforated by heat energy to form a screen printing plate. The difunctional acid component of the polyester in the present invention is mainly an aromatic dicarboxylic acid or its ester-forming derivative, and specifically, terephthalic acid, 2,6-naphthalenedicarboxylic acid, its ester-forming derivative. Dimethyl terephthalate as a derivative,
Examples thereof include dimethyl 2,6-naphthalenedicarboxylate, and among these, terephthalic acid and dimethyl terephthalate are preferable. Examples of the glycol component include ethylene glycol, butylene glycol, propylene glycol, polyethylene glycol and 1,4-cyclohexanedimethanol, and among them, ethylene glycol and butylene glycol are preferable.

The polyester may be a polyester having one kind of aromatic dicarboxylic acid or its ester-forming derivative and one kind of alkylene glycol as a starting material, but it is a copolymer containing two or more kinds of components. Is preferred. In addition to the above as a component to be copolymerized, for example, diethylene glycol, neopentyl glycol,
Examples thereof include diol components such as polyalkylene glycol, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid and cyclohexanedicarboxylic acid, trimellitic acid and pyromellitic acid. Further, homopolymers each composed of a single component, a copolymer containing a homopolymer and two or more components, and a blended polyester of the copolymers may be used. In any case, a polyester obtained by copolymerization or a polyester obtained by blending may be used as long as it satisfies the gist of the present invention.

Further, according to the present invention, recycled products, that is, scraps such as ears generated during film production can be effectively used. The film of the present invention, in order to improve the workability of the winding step during film production, the step of laminating with a screen, etc., it is preferable to roughen the surface of the film to impart appropriate slipperiness to the film, For that purpose, for example, fine inert particles may be added to the film. In one of such methods, a metal compound dissolved in the reaction system at the time of polyester production, for example, a phosphorus compound or the like is caused to act on a metal compound dissolved in the system after transesterification to deposit fine particles. Method,
There is a so-called precipitated particle method. This method is simple and can be industrially easily adopted. As another method, in any step from the polyester production step to the extrusion step before film formation,
There is a method of blending fine particles with polyester, a so-called added particle method, but either method may be adopted.
Examples of fine particles used in the additive particle method of the present invention, silicon oxide, titanium oxide, zeolite, silicon nitride, boron nitride, celite, alumina, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, calcium phosphate, Lithium phosphate, magnesium phosphate, lithium fluoride, aluminum oxide, silicon oxide, titanium oxide, kaolin, talc, carbon black, silicon nitride, boron nitride and JP-B-59-521.
The crosslinked polymer fine particles as described in JP-A-6 can be mentioned, but of course the invention is not limited thereto.

The fine particles may be spherical, lumpy or flat, and their hardness, specific gravity,
There is no particular limitation on the color and the like. The average particle size of the fine particles is not particularly limited, but is usually selected from a range of 0.01 to 10 μm, preferably 0.05 to 8 μm in equivalent sphere diameter. The fine particles to be blended may be a single component, or two or more components may be used simultaneously. The amount of fine particles added is preferably 0.05 to 3% by weight, more preferably 0.1 to 2% by weight. If the amount of the fine particles is less than 0.05% by weight, the film tends to have poor slipperiness and poor winding characteristics. On the other hand, if the amount of the fine particles added exceeds 3% by weight, the degree of roughening of the film surface may be so large that the perforations may become uneven. In the present invention, a film whose surface is appropriately roughened by the method as described above is obtained, but in order to further satisfy workability, resolution during printing, and print quality, the center line average of the film surface is required. Roughness (Ra)
Is preferably 0.01 to 0.20 μm, more preferably 0.02 to 0.15 μm. R
If a is less than 0.01 μm, it tends to be difficult to wind the film, and the film may be wrinkled and the product may not be obtained. On the other hand, when Ra exceeds 0.20 μm, the flatness of the film surface is impaired, the perforations become uneven, and the resolution tends to be poor, and the print quality tends to be impaired.

The film of the present invention has a thickness of 0.5 to 7 μm.
m, preferably 0.5 to 6 μm, more preferably 0.
The range is 5 to 5 μm. The thinner the film is, the shorter the heat conduction distance is. As a result, the heat energy required at the time of perforation is reduced, the perforation is improved, and the resolution and print quality at the time of printing are improved. However, when the thickness of the film is less than 0.5 μm, the printing tends to be unclear, uneven shading tends to occur, and the printing durability tends to be significantly reduced. vice versa,
When the thickness of the film exceeds 9 μm, the perforation property is deteriorated, and thus unevenness tends to occur during printing. The melting point of the film of the present invention is in the range of 170 to 240 ° C, preferably 180 to 230 ° C. Melting point 240
If the temperature is higher than 0 ° C, the high perforation sensitivity, which is the object of the present invention, cannot be obtained, and if it is lower than 170 ° C, the gradation of the printed image becomes poor, which is not preferable. In the present invention, the highest melting point (Tm2) and the lowest melting point (Tm2)
The difference from m1) is preferably less than 50 ° C., more preferably less than 30 ° C., but Tm1 and Tm2 may be the same. When the temperature difference is 50 ° C. or more, uniform perforation does not occur in a short time, and the gradation of the printed image tends to deteriorate. In the present invention, in order to make the gradation of the printed image excellent, the heat shrinkage ratio at 100 ° C. is 8 times or more, preferably 10 times or more, with respect to the heat shrinkage ratio at 65 ° C.
When expressing gradation by the size of perforation diameter in stencil printing, 1
If the ratio of the heat shrinkage ratio at 00 ° C. to the heat shrinkage ratio at 65 ° C. is less than 8 times, the size of the perforation diameter cannot be controlled by the difference in thermal energy, and as a result, gradation cannot be expressed in the printed image, which is not preferable. The film of the present invention has a tensile modulus of 200 in both the longitudinal and width directions of the film.
kg / mm ² or more, preferably 220 kg / mm ² or more. When the tensile elastic modulus is less than 200 kg / mm ² , not only the printing durability is inferior such as the film breaking when being pressed and slid by the squeegee, but also the handling workability is deteriorated. Also, it improves the handling workability,
When the film thickness is increased in order to obtain the strength required for printing, a high perforation sensitivity cannot be obtained, which is not preferable.

Next, the method for producing the polyester film of the present invention will be described. In the present invention, the polymer is supplied to a well-known melt extrusion apparatus typified by an extruder, and heated to a temperature equal to or higher than the melting point of the polymer to melt it. Next, the melted polymer is extruded from a slit die and rapidly cooled and solidified on a rotating cooling drum to a temperature not higher than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum.
Alternatively, a liquid application adhesion method is preferably employed. In the present invention, the sheet thus obtained is biaxially stretched to form a film. Describing the stretching conditions specifically, the unstretched sheet is preferably 20 to 100.
C., more preferably in the temperature range of 25 to 80.degree. C., and first stretched in one direction by a roll or tenter type stretching machine to 3.0 to 7 times, preferably 3.5 to 7 times. Next, in a direction orthogonal to the first stage, preferably 20 to 100
℃, more preferably 3.0 in the temperature range of 25 ~ 90 ℃
To 7 times, preferably 3.5 to 7 times, and more preferably 4.0 to 7 times to obtain a biaxially oriented film.

A method in which unidirectional stretching is performed in two or more stages can be used, but in that case as well, it is desirable that the final stretching ratio falls within the above range. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area magnification becomes 10 to 40 times. The film thus obtained may be heat-treated, and if necessary, may be stretched in the machine direction and / or the transverse direction before or after the heat treatment. In the present invention, in order to obtain a film having the above-mentioned heat shrinkage property, the stretching ratio is 15 as the area ratio.
After heat treatment, the heat treatment after stretching is substantially not performed, or even if it is performed, 110 ° C. or less, further 90 ° C. or less, and the heat treatment time is 1 second to 5 minutes, and the film is stretched within 30% or under a fixed length. It is preferable to carry out. In the present invention, other polymers (for example, polyethylene, polystyrene, polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) can be contained in an amount of about 10% by weight or less based on the total amount of polyester used for film formation. In addition, if necessary, an antioxidant,
You may mix | blend additives, such as a heat stabilizer, a lubricant, an antistatic agent, a dye, and a pigment. The thus obtained heat-sensitive stencil film for screen printing of the present invention is a screen excellent in printing durability after being bonded to a screen woven with fibers such as silk, nylon and polyester, which is perforated with high sensitivity by heat energy. It will be plate making.

[0013]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. The physical property measuring methods used in the present invention are shown below. (1) Average particle size of fine particles Centrifugal sedimentation type particle size distribution analyzer SA- manufactured by Shimadzu Corporation
The particle size was measured using a CP3 type by the sedimentation method based on Stokes' resistance law. The average particle size was determined using a value of 50% of the integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement. The particle size distribution value (r) was calculated from the following equation.

## EQU1 ## Particle size distribution value (r) = d ₂₅ / d ₇₅ (In the above formula, d ₂₅ and d ₇₅ are the cumulative volumes of particle groups measured from the large particle side, and 25% and 75% of the total volume of each is measured. Particle size (μm) corresponding to

(2) Ratio of heat shrinkage ratio The heat shrinkage ratio at 100 ° C. is calculated by the following equation by measuring the length (mm) of the sample before and after heat treatment for 10 minutes in an atmosphere of 100 ° C. without tension. calculate.

[Equation 2] The atmosphere is changed from 100 ° C to 65 ° C, and 65
The heat shrinkage at 0 ° C is calculated, and the ratio of the heat shrinkage at 100 ° C to the heat shrinkage at 65 ° C is calculated by the following formula.

## EQU00003 ## Shrinkage ratio = (shrinkage at 100.degree. C.) ÷
(Heat shrinkage rate at 65 ° C)

(3) Tensile Modulus Tensile Testing Machine Intesco Model 20 manufactured by Intesco Co., Ltd.
Using a type 01, a sample film having a length of 300 mm and a width of 20 mm is pulled at a strain rate of 10% / min in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH. Is calculated by the following equation.

[Equation 4] E = Δσ / Δε (E in the above formula, E is the tensile elastic modulus (kg / mm ² ), Δσ is the stress difference due to the original average cross-sectional area between two points on the straight line, and Δε is between the same two points. (4) Melting point It was measured using a differential calorimeter DSC7 type manufactured by Perkin Elmer Co., Ltd. The DSC measurement conditions are as follows.
That is, 6 mg of a sample film was set in a DSC device, heated at a rate of 10 ° C./min, measured in the range of 0 to 300 ° C., and the melting point was measured as the top of the melting endothermic peak.

(5) Practical characteristics of heat-sensitive stencil printing base paper A polyester screen was attached to the film to prepare a base paper. The obtained base paper was used to make a character image and a 16-step gradation image with a thermal head at applied energies of 0.09 mJ and 0.12 mJ. The perforated state of the gradation image portion was observed with a microscope from the film side of the perforated base paper, and the following items were evaluated. (I) Perforation sensitivity ◎: Predetermined perforation is surely performed and the size of perforation is sufficient and very good ○: Predetermined perforation is almost certainly performed and the size of perforation is sufficient, and Δ: rarely There is a portion where the predetermined perforation cannot be obtained or a portion where the size of the perforation is insufficient. X: There are many portions where the predetermined perforation cannot be obtained, and the size of the perforation is insufficient, which is a practical problem. (Ii) Printing durability Evaluation was made by the number of sheets that can be printed before the film is damaged by a printing machine. If it is 1000 or more, there is no problem in practical use. ◎: 5000 sheets or more can be printed ○: 1000 sheets or more can be printed △: 500 sheets or more can be printed ×: Film is damaged when less than 500 sheets

(Production of Polyester-1) 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol were used as starting materials, and 0.09 parts by weight of magnesium acetate / tetrahydrate as a catalyst was placed in a reactor and the reaction starting temperature was reached. 1
The temperature was set to 50 ° C., and the reaction temperature was gradually raised as methanol was distilled off, and the temperature was set to 230 ° C. after 3 hours. After 4 hours, the reaction mixture, which had been substantially transesterified,
1.0 part by weight of spherical organic crosslinked particles having an average particle diameter of 1.1 μm and a particle size distribution value (r) of 1.2, and an average particle diameter of 1.2 μ
0.04 part by weight of spherical silica having a particle size distribution value (r) of 1.2 and ethyl acid phosphate 0.04
And 0.04 part of antimony trioxide, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C to 280 ° C. On the other hand, the pressure was gradually reduced from the normal pressure, and finally was 0.3 mmHg. After the reaction starts, 4
After a lapse of time, the reaction was stopped, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester is 0.7.
It was 5.

(Production of Polyester-2) In the production of polyester-1, 100 parts by weight of isophthalic acid, 80 parts by weight of dimethyl terephthalate and 2 parts of dimethyl isophthalate are used.
Polyester-2 was obtained in the same manner as in the production of polyester-1 except that the amount was changed to 0 part by weight. The intrinsic viscosity of the obtained polyester was 0.75. (Production of Polyester-3) Dimethyl terephthalate 10
0 parts by weight, 56 parts by weight of 1,4-butanediol, and 0.005 parts by weight of tetrabutyl titanate were placed in a reactor, the reaction starting temperature was set to 150 ° C., and the reaction temperature was gradually raised as methanol was distilled off. 210 ° C after hours
And After 4 hours, 1.0 part by weight of spherical organic crosslinked particles having an average particle diameter of 1.1 μm and a particle size distribution value (r) of 1.2 was added to the reaction mixture which had undergone the transesterification reaction, and an average particle diameter of 1 0.04 parts by weight of spherical silica having a particle size distribution value (r) of 1.2 μm was added, and tetrabutyl titanate was added as a polymerization catalyst in an amount of 0.005 parts by weight, and polycondensation reaction was carried out by a conventional method. That is, the temperature was gradually raised from 210 ° C. to 260 ° C. On the other hand, the pressure was gradually reduced from the normal pressure, and finally was 0.3 mmHg. After starting the reaction
After 4 hours, the reaction was stopped and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester is 0.
It was 90.

(Production of Polyester-4) 50 parts by weight of Polyester-2 and 50 parts by weight of Polyester-3 are uniformly blended to obtain a spherical organic cross-link having an average particle size of 1.1 μm and a particle size distribution value (r) of 1.2. 1.0 part by weight of particles and 0.04 parts by weight of spherical silica having an average particle size of 1.2 μm and a particle size distribution value (r) of 1.2 were compounded, and the temperature was 285 ° C. in a twin-screw extruder with a vent. Polyester-4 was produced below. The intrinsic viscosity of the obtained polyester-4 was 0.75. (Production of Polyester-5) Polyester-1 was produced in the same manner as in the production of Polyester-1, except that 100 parts by weight of isophthalic acid was changed to 65 parts by weight of dimethyl terephthalate and 35 parts by weight of dimethyl isophthalate. Got 5. The intrinsic viscosity of the obtained polyester was 0.75.

Example 1 Polyester-2 was extruded in a sheet form from an extruder at 265 ° C. and rapidly cooled and solidified by using an electrostatic applied cooling method in a rotary cooling drum whose surface temperature was set to 30 ° C. to have a thickness of 21 μm.
A substantially amorphous sheet was obtained. The resulting sheet is stretched 3.5 times in the machine direction at 75 ° C and then in the transverse direction at 80 ° C.
After being stretched to 4.0 times, the film was heat-treated at 90 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 1.5 μm. Then, the obtained film was adhered to a polyester screen to prepare a heat-sensitive stencil printing base paper,
Screen printing was performed. Example 2 In Example 1, polyester-2 was replaced with polyester-
A heat-sensitive stencil printing base paper was prepared and screen-printed in the same manner as in Example 1 except that the number was changed to 4.

Comparative Example 1 In Example 1, polyester-2 was replaced with polyester-
A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the number was changed to 1, and screen printing was performed. Comparative Example 2 In Example 1, polyester-2 was replaced with polyester-
A heat-sensitive stencil printing base paper was prepared in the same manner as in Example 1 except that the number was changed to 5, and screen printing was performed. Comparative Example 3 Polyester-2 was extruded in a sheet form from an extruder at 265 ° C., rapidly cooled and solidified by using an electrostatic cooling method with a rotary cooling drum having a surface temperature set to 30 ° C., and a thickness of 10 μm.
A substantially amorphous sheet was obtained. The resulting sheet is stretched 2.0 times in the machine direction at 75 ° C and then in the transverse direction at 80 ° C.
The film was stretched 2.0 times by heating at 90 ° C. and heat-treated at 90 ° C. for 6 seconds to produce a biaxially oriented film having a thickness of 2.5 μm.

Comparative Example 4 A heat sensitive stencil sheet was prepared in the same manner as in Example 1 except that the heat treatment after stretching was changed from 90 ° C. for 6 seconds to 165 ° C. for 6 seconds. Screen printing was performed. Comparative Example 5 A vinyl chloride film having a thickness of 2 μm was attached to a polyester screen in accordance with a conventional method to prepare a base paper for heat-sensitive stencil printing, and screen printing was performed, but the film was not perforated and printing was impossible. Comparative Example 6 A polypropylene film having a thickness of 2 μm was attached to a polyester screen in accordance with a conventional method to prepare a base paper for heat-sensitive stencil printing, and screen printing was carried out, but the film was not perforated and printing was impossible. The practical properties of the polyester and the heat-sensitive stencil for screen printing thus obtained are shown in Table 1 below.

[0023]

[Table 1]

[0024]

According to the film of the present invention, the perforation sensitivity,
It is possible to provide a high-sensitivity heat-sensitive stencil polyester film for screen printing, which has excellent printing resolution and printing durability, and its industrial value is high.

Claims (1)

[Claims] 1. A melting point of 170 to 240 ° C., a heat shrinkage ratio at 100 ° C. is 8 times or more of a heat shrinkage ratio at 65 ° C., and a tensile elastic modulus in both the longitudinal direction and the width direction is 200 kg / mm.
^A biaxially oriented polyester film for screen printing, which has a thickness of ² or more and a thickness of 0.5 to 7 μm.