JP3035935B2 - Polyester film for heat-sensitive stencil printing base paper - Google Patents

Description

The present invention relates to a polyester film for heat-sensitive stencil printing base paper. More specifically, the present invention relates to a film for a heat-sensitive stencil sheet having excellent piercing properties, resolution during printing, and printing durability.

[Problems to be solved by conventional technology and invention]

2. Description of the Related Art Conventionally, as a heat-sensitive stencil printing base paper, one obtained by laminating a porous thin paper on a thermoplastic resin film is known.

As the above-mentioned thermoplastic resin filter, films of various resins such as polyester, polyvinyl chloride, and polypropylene are used.However, since the properties as heat-sensitive stencil base paper are significantly affected by the physical properties of these films, Various films have been used according to the required characteristics, and improvements have been attempted.

The following characteristics are required for a film used for such a purpose.

(1) Good heat piercing property. In other words, it has a sufficient heat shrinkage ratio to melt with a small amount of heat and to obtain perforations of an appropriate size so that the image at the time of printing becomes clear.

(2) It has sufficient strength and elasticity to withstand the work of laminating with porous thin paper and printing. Conventionally, a very thin film (usually 1.5 to 3 μm) has been used as a film for the base paper in order to obtain good heat perforation characteristics, and in order to have workability and durability during base paper production and printing, ,
Sufficient strength and elastic modulus are required for the film.

(3) It can withstand organic solvents such as toluene and xylene used for printing ink for a long time.

Further, in addition to these requirements, it is necessary to have excellent productivity during film production. That is, it is necessary that the film has good stretchability and does not cause troubles such as breakage, and has good winding and slitting properties, and does not cause wrinkles or winding deviation during winding.

Further, it must be excellent in handling workability when preparing a base paper using such a film.

Conventionally, as a film used in such an application, a biaxially stretched film intended for a thermoplastic resin, a film having improved printing characteristics by defining its thermal characteristics (Japanese Patent Application Laid-Open No. Sho 62-149596), etc. However, they did not satisfy all of the above requirements.

[Means for solving the problem]

In view of the above problems, the present inventor has conducted intensive studies and found that a biaxially oriented polyester film containing a specific amount of inorganic or organic fine particles and having a surface state and a heat shrinkage ratio satisfying specific conditions is heat-sensitive stencil printing. The present inventors have found that the film is suitable as a base paper film, and have completed the present invention.

That is, the gist of the present invention is a biaxially oriented polyester film containing n kinds of fine particles having an average particle size in a range of 0.2 to 0.6 μm,
Th density of the particles ^{_{ρ i (g / cm 3)}} , the average particle size d _i (mu
m) and the content w _i (% by weight) satisfy the following formula, and the film has a center line average roughness of 0.02 to 0.3 μm, a maximum projection height of 0.2 to 2 μm, and a film after treatment at 150 ° C. for 3 minutes. Wherein the average of the heat shrinkage in the vertical and horizontal directions is 10 to 40%.

Hereinafter, the present invention will be described in detail.

The polyester in the present invention refers to a polyester containing an aromatic dicarboxylic acid as a main acid component and an alkylene glycol as a main glycol component. As aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, 2,6-
And naphthalenedicarboxylic acid. Examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and the like.

Such a polyester may be a polyester starting from one kind of aromatic dicarboxylic acid and one kind of alkylene glycol, but is more preferably a copolymer containing two or more kinds of components. In addition to the above, examples of the component to be copolymerized include diethylene glycol, polyalkylene glycol, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and oxycarboxylic acids such as p-hydroxybenzoic acid.

The thickness of the film of the present invention is preferably 0.5 to 3 μm
And more preferably in the range of 0.5 to 2.5 μm. If the thickness of the film becomes thinner, the heat transfer distance is shortened, and the heat energy required at the time of perforation is also reduced, so that the perforation property is improved, and the resolution and print quality at the time of printing are improved.
When the thickness is less than 0.5 μm, the printing is unclear and uneven density is apt to occur, and the productivity and winding workability deteriorate even in the production of a film. A film having a thickness of more than 3 μm is not preferable because the perforation property is deteriorated and unevenness occurs during printing.

The present inventors have found that n kinds of fine particles are present in the film,
The density of the i-th particle ^{_{ρ i (g / cm 3)}} , the average particle size d _i (mu
It has been found that when m) and the content w _i (% by weight) satisfy the following formula, the perforation sensitivity becomes good.

Although the reason for this is not necessarily clear, it is considered that when the polymer is melted by heat and perforation occurs, the perforation spreads around the fine particles as a starting point. Therefore, the greater the number of particles, the greater the effect.
The density of the particles is relevant. That is, in the case of particles having a large particle size and particles having a large density, it is necessary to increase the content in order to increase the number of particles. However, if the number of particles is too large, breakage is likely to occur during film production, stretching or a subsequent heat treatment step, so it is necessary to set a specific range.

When the content of fine particles is small, In the case of (1), the heat piercing property is insufficient, which is not preferable. Also, if the content of the fine particles is too large, even if excellent piercing properties are obtained, breakage will occur frequently during film production,
It is not preferable because productivity is remarkably deteriorated. Therefore, the content of fine particles is Must be satisfied, and more preferably It is.

The fine particles contained for improving the piercing property have an average particle diameter in the range of 0.2 μm to 0.6 μm. Average particle size 0.2μ
If it is less than m, the effect of improving the piercing property cannot be expected. On the other hand, if the average particle diameter exceeds 0.6 μm, when the content is increased to a sufficient number for improving the perforation property, adverse effects such as deterioration in film productivity occur, which is not preferable. The average particle size of the fine particles is more preferably 0.2 μm to 0.5
It is in the range of μm.

Examples of the fine particles that can be used in the present invention, kaolin, talc, magnesium carbonate, calcium carbonate,
Inorganic particles such as barium carbonate, barium sulfate, calcium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, titanium oxide, silicon oxide, carbon black, etc., calcium oxalate, and described in JP-B-59-5216 Organic particles such as a crosslinked polymer fine powder as described above can be used, but are not limited thereto.

In the film of the present invention, it is necessary that the surface shape of the film satisfies specific conditions. That is, the film of the present invention has a centerline average roughness (Ra) of 0.02 to 0.3 μm, preferably 0.03 to 0.15 μm, with respect to the surface shape.
m and the maximum projection height (Rt) is in the range of 0.2 to 2.0 μm, preferably 0.3 to 1.55 μm.

If Ra is less than 0.02 μm, the film will not have sufficient slipperiness due to insufficient slipperiness during film production and stencil printing paper manufacture.In addition, when used as a base paper, it will slip with the thermal head during perforation. It is not preferable because the property is deteriorated. On the other hand, if Ra exceeds 0.2 μm, the resolution during printing deteriorates, which is not preferable.

On the other hand, when Rt exceeds 2.0 μm, it is not preferable because the resolution at the time of printing is deteriorated, and when Rt is less than 0.2, in the film winding process, wrinkles due to air entrapment occur, which is not preferable. .

In order to obtain such a surface shape, in the present invention, particles having an average particle size exceeding 0.6 μm may be contained at the same time as the fine particles contained for improving the piercing property. Since such particles have no significant effect on the improvement of the perforation property, the average particle size and the content thereof are not particularly limited, but the surface shape is in the above range, and the average particle size is preferably in order not to deteriorate the film productivity. Is 2.0 μm or less, more preferably 1.5 μm or less, the content is 0.2 μm to 0.6 μm in average particle size.
The total amount is preferably 2.5% by weight or less, more preferably 1.5% by weight in total with the fine particles of μm.

In the present invention, in order to have a high degree of heat perforation when used as a stencil sheet for stencil printing and to improve the resolution at the time of printing, at 150 ° C. of the film, the heat shrinkage ratio after the treatment for 3 minutes in the vertical and horizontal directions. The average of the directions is in the range of 10-40%, preferably 10-30%. When such requirements are satisfied in addition to the conditions for containing the fine particles, a high degree of heat porosity can be obtained. If the average of the heat shrinkage is less than 10%, a high degree of heat piercing property cannot be obtained, and the resolution at the time of printing becomes poor. On the other hand, if the average of the heat shrinkage exceeds 40%, curl due to shrinkage of the film after the base paper is formed or printing durability deteriorates is not preferable.

The film of the present invention has an average refractive index of usually 1.586 to 1.597, preferably 1.587 to 1.595, as measured by the method described below.
And the degree of plane orientation ΔP is usually in the range of 0.125 to 0.165, preferably 0.127 to 0.155. When such requirements are satisfied, the resolution and print quality at the time of printing are highly satisfied.

Since the film of the present invention is manufactured as an extremely thin film, it is not preferable that the strength is low because the handling workability deteriorates. In the present invention, when the tensile elastic modulus in both the longitudinal direction and the width direction of the film is 300 kg / mm ² or more, preferably 350 kg / mm ² or more, the handling workability and printing durability become more favorable.

The polyester used in the present invention has an intrinsic viscosity of 0.40 or more, preferably 0.45 to 0.90, since the mechanical properties are reduced when the degree of polymerization is too low.

Next, a method for producing the polyester film of the present invention will be described. In the present invention, the polymer is supplied to a known melt extruder represented by an extruder, and is heated to a temperature equal to or higher than the melting point of the polymer to be melted. Next, the molten polymer is extruded from a slit-shaped die, and rapidly cooled and solidified on a rotary cooling drum to a temperature equal to or lower 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 necessary to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

The electrostatic application adhesion method is generally such that a linear electrode is stretched on the upper surface side of the sheet in a direction orthogonal to the flow of the sheet, and about 5 to 5
This method applies a 10 kv DC voltage to impart electrostatic charge to the sheet, thereby improving the adhesion to the drum. In addition, the liquid application adhesion method is a method of improving the adhesion between the drum and the sheet by uniformly applying the liquid to the entire or a part of the surface of the rotary cooling drum (for example, only the part in contact with both ends of the sheet). is there. In the present invention, both may be used as needed.

In the present invention, the sheet thus obtained is
It is stretched in the axial direction to form a film.

When the stretching conditions are specifically described, the unstretched sheet is preferably 50 to 120 ° C, more preferably 60 to 110 ° C.
The film is stretched 2.5 to 7 times in one direction by a roll or tenter-type stretching machine in the temperature range described above. Next, preferably in the direction orthogonal to the first stage, 55 to 125 ° C, more preferably 65 to 115 ° C.
The film is stretched 2.5 to 7 times in a temperature range of ° C. to obtain a biaxially oriented film. A method in which unidirectional stretching is performed in two or more stages can be used, but also in this case, 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 6 to 30 times.

The film thus obtained is preferably subjected to a heat treatment. However, if necessary, the film may be stretched in the longitudinal and / or transverse directions again before or after the heat treatment.

In the present invention, it is necessary that the average of the heat shrinkage in the vertical direction and the horizontal direction at 150 ° C. for 3 minutes is 10 to 40%.
The temperature is in the range of 0 to 200 ° C, preferably 120 to 180 ° C, and the heat treatment time is usually 1 second to 10 minutes. Such heat treatment may be performed at a limited shrinkage or elongation of the film within 20%, or under a fixed length, or may be performed in two or more steps.

In the present invention, about 10% by weight or less of other polymer (for example, polyethylene, polystyrene, polycarbonate, polysulfone, polyphenylene sulfide, polyamide, polyimide, etc.) can be contained based on the total amount of polyester used for film formation. Further, additives such as an antioxidant, a heat stabilizer, a lubricant, a dye, and a pigment may be blended as needed.

Thus, the polyester film of the present invention, by laminating a predetermined porous thin paper according to a conventional method using a known adhesive, has excellent heat perforation properties, and has excellent printing resolution and printing durability. Heat stencil printing base paper.

〔Example〕

Hereinafter, the present invention will be described in more detail by examples,
The present invention is not limited to the following examples unless it exceeds the gist. The method for evaluating the properties of the film of the present invention is described below.

(1) Average particle size of fine particles Centrifugal sedimentation type particle size distribution analyzer SA manufactured by Shimadzu Corporation
Particle size was measured by the sedimentation method based on Stokes' resistance law using -CP3 type. The average particle size (d ₅₀ ) was determined using a value of 50% of the integrated (weight basis) in the equivalent spherical distribution of the particles obtained by the measurement.

(2) Fine particle density (g / cm ³ ) Measured according to JIS K7112B method.

(3) Center line average roughness (Ra) and maximum height (Rt) The values of Ra and Rt are determined as follows using a surface roughness measuring instrument (SE-3F) manufactured by Kosaka Laboratory Co., Ltd. I asked. That is,
From the film cross section curve, the reference length L in the direction of the center line
(2.5 mm), and a roughness curve y = f with the center line of the extracted portion as the x-axis and the direction of the vertical magnification as the y-axis.
When represented by (x), the value given by the following equation is [μ
m].

Also, when the extracted portion is sandwiched by two straight lines parallel to the average line of the extracted portion of the cross-sectional curve obtained at this time, the interval between the two straight lines is measured in the direction of the longitudinal magnification of the cross-sectional curve, and the value is maximized. The height (Rt) was represented by [μm].

Ra and Rt were obtained by calculating ten cross-sectional curves from the surface of the sample film and expressing the average of Ra and Rt obtained from these cross-sectional curves. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

(4) Heat shrinkage rate The sample was heat-treated in an oven maintained at a temperature of 150 ° C. in a non-tension state for 3 minutes, and the length of the sample before and after the heat treatment was measured and calculated by the following equation. The film was measured at five points in the vertical and horizontal directions, and the average value of each was used as the measured value.

(5) Average refractive index () and degree of plane orientation (ΔP) Using an Abago refractometer manufactured by Atago Optical Co., Ltd., the maximum value nγ of the refractive index in the film plane, and the refractive index n in the direction perpendicular to the film.
β and the refractive index nα in the thickness direction of the film were measured, and the average refractive index () and the degree of plane orientation (ΔP) were calculated from the following equations. The refractive index was measured using a sodium D line,
C. was performed.

(6) Copy printing characteristics A base paper was produced by laminating a porous thin paper made of polyester on the obtained film. Using the obtained base paper, characters and images printed using RISOGRAPH FX7200 manufactured by Riso Kagaku Co., Ltd. as a plate making machine and AP7200 as a printing machine were visually judged for the following characteristics, and evaluated for thermal piercing property. And

i) Printing quality…: Good printing with no shading or blurring and clear printing.

Δ: Slight unevenness and bleeding were observed, and slightly lacking in sharpness.

×: Uneven shading or bleeding is clearly seen.

ii) Gradation Gradation was evaluated by an image in which the shading changes continuously.

 …: Good without blurring in the dark part and unevenness in the middle part.

 Δ: There is a slight blur in the dark part and a little unevenness in the middle part.

X: There is blurring in the dark part and unevenness in the middle part, and the gradation is poor.

iii) Printing durability ○: Continuous printing of 2000 sheets or more is possible.

 X: Continuous printing is possible only for about several hundred sheets.

(7) Handling workability The handling workability of the film in the winding work and base paper making work at the time of film production was divided into the following three ranks.

 …: Handleability is good and work can be done smoothly.

Δ: The handleability is generally good or slightly lacking in smoothness.

X: The films are easily blocked or wrinkled, and the handleability is poor.

Example 1 82 parts of dimethyl terephthalate, 18 parts of dimethyl isophthalate
Parts, ethylene glycol 64 parts and calcium acetate monohydrate
0.11 part was placed in a reactor and a transesterification reaction was performed.
That is, the reaction start temperature was set to 180 ° C., and the reaction temperature was gradually increased with the removal of methanol. After 4 hours, the temperature was raised to 230 ° C. to substantially end the transesterification reaction.

Then, after adding 0.07 parts of triethyl phosphate,
Calcium carbonate 0.6 with average particle size 0.81 μm and density 2.7 g / cm ³
And 0.4 part of antimony trioxide were added, and a polycondensation reaction was carried out by a conventional method. In this reaction, the temperature is gradually increased and the pressure is gradually reduced from normal pressure, and after 2 hours, the temperature is increased.
The test was performed at 270 ° C. and a pressure of 0.3 mmHg. Five hours after the start of the reaction, the reaction was stopped, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained copolymerized polyester (A) was 0.67.

Similarly, the starting materials were 84 parts of dimethyl terephthalate, 16 parts of dimethyl isophthalate, and 64 parts of ethylene glycol, and 1.0 part of titanium oxide having an average particle size of 0.3 μm and a density of 3.9 g / cm ³ was added. Polymerized polyester (B)
Was manufactured. The intrinsic viscosity was 0.69.

Next, 50 parts of the obtained copolymerized polyester (A) and (B)
And 50 parts. This is extruded at 280 ° C into a sheet from an extruder, and rapidly cooled and solidified using a rotating cooling drum set at a surface temperature of 40 ° C by using an electrostatic application cooling method to form a 26 μm-thick substantially amorphous sheet. Obtained.

Next, the obtained sheet was stretched 3.80 times at 80 ° C. in the longitudinal direction and 4.1 times at 95 ° C. in the transverse direction, and further heat-treated at 140 ° C. for 7 seconds to obtain a biaxially oriented film having a thickness of 1.8 μm.

Example 2 The content of isophthalic acid was 15 mol% in the same manner as in Example 1.
A copolymer polyester (C) containing 0.4% by weight of calcium carbonate having an average particle diameter of 0.3 μm and a density of 2.7 g / cm ³ and having an intrinsic viscosity of 0.66 was produced. Similarly, the isophthalic acid content was 15 mol%, the average particle size was 0.27 μm, and the density was 2.
A copolymerized polyester (D) containing 0.45% by weight of spherical silica particles of 0 g / cm ³ and having an intrinsic viscosity of 0.70 was produced.

Next, 40 parts of the obtained copolymerized polyester (C),
30 parts of (D) and 30 parts of the copolymerized polyester (A) produced in Example 1 were mixed, and the film forming conditions were the same as in Example 1 to produce a 1.8 μm-thick biaxially oriented film.

Example 3 As in Example 1, 0.5% by weight of silica particles having an isophthalic acid content of 17 mol%, an average particle diameter of 1.1 μm, a density of 2.2 g / cm ³ and an intrinsic viscosity of 0.71 were used. A polymerized polyester (E) was produced. Similarly, the content of isophthalic acid was 14 mol%, the average particle size was 0.22 μm, and the density was 2.2 g.
/ cm ³ of silica particles contained 0.4 wt%, were prepared copolyester (F) having an intrinsic viscosity of 0.64.

Next, 50 parts of the obtained copolyester (E) and 50 parts of (F) were mixed.
A biaxially oriented film having a thickness of 1.8 μm was produced in the same manner as in Example 1, except that

Example 4 The content of isophthalic acid was 16 mol% in the same manner as in Example 1.
Thus, a copolymerized polyester (G) having an intrinsic viscosity of 0.68 was produced. The polymer contains 90 parts of styrene and divinylbenzene.
The crosslinked polymer particles having an average particle diameter of 0.38 μm and a density of 1.1 g / cm ³ obtained from 10 parts were 0.4% by weight. 50 parts of the obtained polymer and 50 parts of the copolyester (A) produced in Example 1 were mixed, and a 1.8 μm-thick biaxially oriented film was produced under the same film-forming conditions as in Example 3.

Comparative Example 1 80 parts of the copolyester (E) produced in Example 3 and 20 parts of the copolyester (B) produced in Example 1 were mixed, and the film forming conditions were the same as in Example 3 to obtain a thickness. 1.8
A μm biaxially oriented film was produced.

Comparative Example 2 In the same manner as in Example 1, the content of isophthalic acid was 15 mol%, the average particle diameter was 0.3 μm, the density was 3.9 g / cm ³ , the content of titanium oxide was 1.3% by weight, and the intrinsic viscosity was 0.63. A polymerized polyester (H) was produced. Using this polymer, a film was formed under the same conditions as in Example 1 for film formation. However, in this case, since the addition amount of the fine particles was beyond the range of the present invention, the film was broken in the stretching or heat treatment step, resulting in poor productivity. For this reason, a film having a thickness of 1.8 μm as in the example could not be stably collected, and a film having a thickness of 2.5 μm was unavoidably produced, and the piercing property was evaluated.

Comparative Example 3 A copolymer having an isophthalic acid content of 15 mol%, an average particle diameter of 0.5 μm, a density of 2.0 g / cm ³ , 0.2% by weight of spherical silica and an intrinsic viscosity of 0.65 was prepared in the same manner as in Example 1. Polyester was produced. Using this polymer, a biaxially oriented film having a thickness of 1.8 μm was produced in the same manner as in Example 1 under film-forming conditions.

Comparative Example 4 A film having a thickness of 1.8 μm was prepared in the same manner as in Example 1 except that the same raw material as in Example 1 was used, and that the film formation conditions were also set such that the heat treatment temperature was 117 ° C.
m was prepared.

Comparative Example 5 As in Example 1, the average particle size was 0.81 μm, and the density was 2.7 g.
0.35% by weight of calcium carbonate / cm ³ and an average particle size of 0.3
Polyethylene terephthalate having an intrinsic viscosity of 0.65 containing 0.3% by weight of calcium carbonate having a density of 2.7 g / cm ^{3 and} a thickness of 2.7 μm was produced. However, in this case, the polymerization temperature was increased to 285 ° C.

Using the obtained polymer, a biaxially oriented film having a thickness of 1.8 μm was produced in the same manner as in Example 1 except that the heat treatment temperature was changed to 235 ° C.

As described above, the obtained film was bonded to a porous thin paper according to a conventional method to prepare a heat-sensitive stencil sheet, followed by transcript printing.

The physical properties and copy printing characteristics of the film are summarized in Table 1 below.

The films of Examples 1 to 4 were excellent in handleability during film production and base paper preparation, and the base papers prepared using these were excellent in heat perforation properties and exhibited good copy printing characteristics.

On the other hand, in Comparative Examples 1 and 3, since the content of the fine particles was less than the predetermined amount, the heat piercing property was insufficient and the copy printing characteristics were inferior. Comparative Example 2 is an example in which the content of the fine particles is too large, but in this case, the film productivity is inferior. Comparative Example 4 is an example in which the heat shrinkage ratio is too large, and the bleeding of the printed image becomes conspicuous and the printing durability deteriorates. In Comparative Example 5, the heat piercing property was deteriorated due to the small heat shrinkage, and good copy printing characteristics were not obtained.

[Effects of the Invention] The polyester film of the present invention is suitable for use as a film for heat-sensitive stencil printing paper having excellent copy printing characteristics because the film is easy to handle in film production and base paper making, and has excellent heat piercing properties. Yes, its industrial value is high.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-158391 (JP, A) JP-A-1-168494 (JP, A) JP-A-63-286396 (JP, A) JP-A-63-1986 286395 (JP, A) JP-A-63-227634 (JP, A) JP-A-62-253492 (JP, A) JP-A-62-116194 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) B41N 1/24 102

Claims (1)

(57) [Claims] 1. A biaxially oriented polyester film containing n kinds of fine particles having an average particle diameter in the range of 0.2 to 0.6 μm, wherein the density of the i-th fine particles ρ _i (g / cm ³ ) and the average particle diameter The diameter d _i (μm) and the content w _i (% by weight) satisfy the following expression, and the center line average roughness of the film is 0.02 to 0.3 μm.
m, the maximum protrusion height is 0.2 to 2 μm, and the average of the heat shrinkage in the longitudinal and transverse directions of the film after treatment at 150 ° C. for 3 minutes is 10 to 40.
% Polyester film for heat-sensitive stencil printing base paper.