JP2008194908A - Polyester film for thermosensitive stencil printing base paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film for a thermosensitive stencil printing base paper, which enables aimed boring of holes to be surely realized in response to the energy sent from a thermal head in proportion to broad image signals and, at the same time, the size of the bored hole to change in proportion to the energy, especially within higher energetic region, prevents the damage of film due to the repeated press-bonding and wear between printing paper edges and the thermosensitive stencil printing base paper from developing while independent boring of holes are maintained without keeping respective bored holes connected with each other, and realizes consequently excellent printing durability. <P>SOLUTION: This polyester film for the thermosensitive stencil printing base paper is made of a polyester composition including 0.1-1.5 pts.wt. of carbodiimide compound to 100 pts.wt. of polyester. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polyester film for heat-sensitive stencil printing base paper. More specifically, the present invention relates to a polyester film for heat-sensitive stencil printing paper having excellent independent perforation properties and printing resistance.

  Conventionally, as a heat-sensitive stencil printing base paper, a thermoplastic resin film such as polyester is laminated with an ink-permeable porous thin paper with heat or an adhesive, and recently, a high-quality image using a combination of a porous resin film and a porous thin paper is used. Printed materials are known, and the properties of the film used are greatly contributing to the quality of stencil printed materials.

  In order to improve printing characteristics, several proposals have been made in consideration of the structure of the heat-sensitive stencil sheet. For example, in Patent Document 1, thin paper made of synthetic fibers having a fineness of 1 denier or less is used as a porous support, and in Patent Documents 2 and 3, heat-sensitive stencil printing in which a porous resin film is provided on one side of a thermoplastic film. A base paper has been proposed. Patent Documents 4 and 5 propose a heat-sensitive stencil sheet that is substantially made of a thermoplastic film and does not use a porous support that does not inhibit ink passage.

  On the other hand, there have also been proposals for improving the perforation characteristics of the film constituting the heat-sensitive stencil printing base paper, and improving the handleability during film formation and stencil paper preparation.

  Conventionally, it is a biaxially stretched film for thermoplastic resin as a film used for such applications, and has improved printing characteristics by defining its thermal characteristics (Patent Document 6), average particle diameter and film thickness Have been proposed (Patent Document 7), a film that defines the surface roughness and the number of protrusions (Patent Document 8), a film that defines heat shrinkage characteristics (Patent Document 9), and the like.

  However, in recent years, in order to obtain high resolution, each thermal head is small, the number of perforations per unit area is increased, and the energy supplied to each head is in the direction of decreasing. Further, in order to obtain a set print image, energy corresponding to the image signal is supplied to adjust the perforation size. With conventional heat-sensitive stencil sheets using film, perforation with low energy is not sufficient due to insufficient film perforation characteristics, and when perforated with high energy, the perforation size is large and adjacent perforations are not possible. A continuous hole is generated. Therefore, there arises a problem that the print quality such as print offset is deteriorated in character printing and solid printing. In addition, printing durability is required so that a large number of copies can be printed on the prepared heat-sensitive stencil sheet. Specifically, it is desirable that the film is not damaged or torn by repeated pressing and abrasion between the printing paper edge and the heat-sensitive stencil sheet.

In other words, the target drilling surely occurs with respect to the energy from the thermal head corresponding to a wide range of image signals, and the drilling size changes according to the energy. A film for thermal stencil printing base paper that realizes excellent printing durability by preventing repeated damage between the printing paper edge and the thermal stencil printing base paper, and abrasion, while maintaining the print quality has been desired. .
Japanese Patent Laid-Open No. 3-193445 JP-A-8-332785 JP 2003-276355 A JP 54-33117 A JP 2001-212925 A JP-A-62-149496 JP-A 63-286396 JP-A 63-227634 Japanese Patent Laid-Open No. 5-116215

  The present invention has been made in view of the above circumstances, and the problem to be solved is that the target perforation surely occurs with respect to the energy from the thermal head corresponding to a wide range of image signals, and the perforation size changes according to the energy. In particular, in the high energy region, the individual perforations are maintained without being connected to each other, while the press edges of the printing paper and the heat sensitive stencil sheet are repeatedly pressed and the film is not damaged by abrasion, resulting in excellent printing durability. The object is to provide a film for a heat-sensitive stencil sheet that realizes the above.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be easily solved by including a specific amount of a carbodiimide compound in a specific polyester film, and the present invention has been completed. .

  That is, the gist of the present invention resides in a polyester film for heat-sensitive stencil printing paper comprising a polyester composition containing 0.1 to 1.5 parts by weight of a carbodiimide compound with respect to 100 parts by weight of polyester.

Hereinafter, the present invention will be described in detail.
The bifunctional acid component of the polyester referred to in the present invention is mainly composed of an aromatic dicarboxylic acid or an ester-forming derivative thereof, specifically, terephthalic acid, 2,6-naphthalenedicarboxylic acid, or an ester-forming property thereof. Examples of the derivatives include dimethyl terephthalate and dimethyl 2,6-naphthalenedicarboxylate. Examples of the glycol component include ethylene glycol, butylene glycol, propylene glycol, polyethylene glycol, 1,4-cyclohexanedimethanol and the like.

  Such a polyester may be a polyester starting from one aromatic dicarboxylic acid or an ester-forming derivative thereof and one alkylene glycol, but is preferably a copolymer containing two or more components. In addition to the above-mentioned components for copolymerization, for example, diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, and isophthalic acid, trimellitic acid, and pyromellitic acid Etc. Further, homopolymers each composed of a single component, a copolymer containing a homopolymer and two or more components, and a blend polyester of the copolymers are preferable.

  The carbodiimide compound blended with the polyester of the present invention and the production method thereof are described, for example, in JP-A-9-208649, JP-A-9-296097, JP-A-52-123484, and the like. First, by reacting at least two isocyanates or polyisocyanates with an isocyanate-reactive hydrogen atom-containing compound, an isocyanate prepolymer (a non-recyclable product having at least two free terminal isocyanate groups) is formed. Then, a carbodiimide-forming catalyst such as 1-phenyl-2-phospholene-1-oxide is added to the isocyanate prepolymer thus prepared, and the prepolymer is converted to the corresponding polycarboimide by decarboxylation. can do.

  As starting materials for the production of carbodiimide compounds, the isocyanate-reactive hydrogen atom-containing compounds used are various compounds such as polyolefins, polyacetals, polyamides, polyamines, polytetrahydrofurans, polyesters, polycarbonates, polysiloxanes with suitable end groups. It can be selected from compounds such as polysulfides and mixtures thereof.

  Isocyanates include, for example, aliphatic, araliphatic, cyclic or aromatic isocyanates, as well as isocyanate prepolymers or isocyanate mixtures.

  The compounding quantity of a carbodiimide compound is 0.1-1.5 weight part with respect to 100 weight part of polyester, Preferably it is 0.1-1.0 weight part, More preferably, it is 0.3-0.7 weight. Part. When the blending amount is 1.5 parts by weight or more, the carbodiimide group is crosslinked by heat in the step of kneading the resin and extruding the sheet, so that the viscosity of the film increases and the perforation characteristics are impaired. When the blending amount of the carbodiimide compound is less than 0.1 part, almost no film viscoelastic property change occurs in the perforation temperature range, and when the energy corresponding to the image signal is supplied, the target perforation occurs reliably, And the target perforation size cannot be adjusted. Also, printing durability is reduced.

  Melting | fusing point of the polyester film of this invention is 140 to 240 degreeC normally, Preferably it is the range of 150 to 230 degreeC. When the melting point is higher than 240 ° C., the perforation characteristics and sensitivity are lowered, and when the melting point is lower than 140 ° C., the heat-resistant dimensional stability of the film is poor. There is a tendency that the gradation level of the printed image is deteriorated.

  The film of the present invention preferably has a thermal shrinkage rate of 140 to 3 minutes at 30 to 70%, more preferably 40 to 70%, and particularly preferably 50 to 70%. If the heat shrinkage rate at 140 ° C. is less than 30%, sufficient drilling diameter and drilling probability may not be ensured from the viewpoint of low energy drilling, and if it exceeds 70%, it occurs during storage of the base paper. Curl and the gradation level of the printed image may deteriorate.

  The glass transition temperature [Tg] of the film of the present invention is preferably 60 ° C. or higher. When Tg is less than 60 ° C., plate-making distortion may occur due to film shrinkage around the solid printing due to heat generated by the thermal head, which may deteriorate printing quality. Master curl contributes to a long-time shrinkage at 60 ° C., but if Tg is less than 60 ° C., tension fluctuation during film formation tends to remain as residual strain, and recovery of strain remaining during master storage. Because of dimensional changes, curling is likely to occur at high temperatures and high humidity. When the curl is large, the paper passing property and the conveyance property in the plate-making printing machine are deteriorated. Further, the laminating temperature is preferably laminating at a temperature lower than the Tg of the film, which may be disadvantageous in terms of productivity. Moreover, when Tg of a film exceeds 85 degreeC, there exists a tendency for the perforation by low energy to become difficult.

  As a film characteristic that contributes to the perforation diameter independent perforation property and perforation diameter, the intrinsic viscosity [η] of the film is 0.55 dl / g or more, preferably 0.60 dl / g or more. If the film intrinsic viscosity [η] is less than 0.55, the melt viscosity is low at the temperature of thermal head printing, and the independence of the perforation diameter cannot be maintained, and continuous holes may occur. On the other hand, when it is 0.80 dl / g or more, deformation resistance at the time of drilling is large, unevenness of the drilling diameter tends to occur, and unperforated holes tend to occur.

  The film thickness of this invention is 0.7-3.0 micrometers normally, Preferably it is the range of 1.0-2.0 micrometers. When the film thickness is thicker than 3.0 μm, the heat conduction distance becomes long, the perforation property is lowered, and the resolution at the time of printing and the print quality tend to be lowered. When the film thickness is less than 0.7 μm, the low energy perforation property is excellent. However, the film durability is insufficient and the printing durability may be deteriorated in applications where the film formation stability and the number of printed sheets are large. .

  In addition, the film of the present invention is used to improve the workability during winding process during film production, coating during base paper production, laminating process and printing, or preventing thermal head and film from fusing during thermal drilling. Therefore, it is preferable to roughen the surface to give the film appropriate slipperiness, but for that purpose, fine inert particles may be added to the film. The average particle diameter of the fine inert particles used is preferably 0.2 to 1.0 times the film thickness, more preferably 0.3 to 0.7 times, and particularly preferably 0.3 to 0.00. 5 times. If the average particle diameter exceeds 1.0 times the film thickness, the flatness of the film surface may be impaired, resulting in uneven heat transfer, uneven perforation, poor resolution, and print quality. May be damaged. On the other hand, when the average particle size is less than 0.2 times the film thickness, workability during film production and base paper production tends to deteriorate, such as poor winding properties of the film.

  The amount of particles added is usually 0.05 to 3.0% by weight, preferably 0.1 to 2.0% by weight. If it is less than 0.05% by weight, the winding properties tend to be inferior. On the other hand, if the content exceeds 3% by weight, the degree of roughening of the film surface tends to be too large and heat transfer tends to be uneven, resulting in uneven perforation, poor resolution, and impaired print quality. There are things to do.

  Examples of inert particles used in the present invention include 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, kaolin, talc, carbon black, and crosslinked polymer fine powder as described in JP-B-59-5216, but are not limited thereto. . At this time, the inert particles to be blended may be a single component, or two or more components may be used simultaneously. In the present invention, the method of blending the inert particles with the polyester is not particularly limited. For example, a method of adding the inert particles to the polyester polymerization step, or a method of melt-kneading before film formation is preferably used. .

  In the present invention, a film whose surface is appropriately roughened by the method as described above is obtained, but in order to satisfy the workability, the resolution at the time of printing, and the print quality more highly, the center line average of the film surface is obtained. The roughness (Ra) is preferably 0.02 to 0.2 [mu] m, more preferably 0.05 to 0.15 [mu] m, and it is desirable to select conditions appropriately so as to be in this range.

Next, the manufacturing method of the polyester film of this invention is demonstrated.
In the present invention, the polymer is supplied to a well-known extruder represented by an extruder, heated to a temperature equal to or higher than the melting point of the polymer, and melted. Next, the molten polymer is extruded from a slit-shaped die and rapidly cooled and solidified on the rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature, thereby obtaining a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and usually an electrostatic application adhesion method is employed.

  The sheet thus obtained is stretched in the biaxial direction to form a film. The stretching conditions will be specifically described. The unstretched sheet is preferably 55 to 95 ° C, more preferably 60 to 85 ° C, and 3.0 to 6.0 times in one direction, preferably 3. Stretch 5 to 5.0 times. Next, the film is stretched 3.0 to 6.0 times, preferably 3.5 to 5.0 times in a temperature range of 70 to 120 ° C, more preferably 75 to 110 ° C, in a direction orthogonal to the first stage, A biaxially oriented film is obtained.

  Note that a method of performing unidirectional stretching in two or more stages can also be used, but in this case as well, it is desirable that the final stretching ratio is in the above-described range. Further, the unstretched sheet can be simultaneously biaxially stretched so that the area magnification is 9 to 30 times.

  The film thus obtained may be heat-treated, and if necessary, may be stretched again in the longitudinal or transverse direction before or after the heat treatment. The heat treatment after stretching is not substantially carried out, or even if it is carried out, the heat treatment is performed at 120 ° C. or lower, further 100 ° C. or lower. Usually, the heat treatment is performed for 1 second to 20 seconds in a relaxed state or under a constant length.

  Further, when producing a heat-sensitive stencil base paper, curling that may be caused by film shrinkage may occur during a drying process of about 40 to 70 ° C. and long-term storage through summer. Therefore, in order to prevent curling in the present invention, when the obtained film is aged at 30 to 60 ° C. for 5 hours to 3 days, preferably at 35 to 50 ° C. for 1 to 3 days, the curling resistance in the environment concerned Becomes better.

  The base paper film for heat-sensitive stencil of the present invention is excellent in printing durability and can surely perforate with a perforation diameter of a desired size with a wide range of perforation energies, contributing to the extension of the life of the thermal head and high-speed plate making. Its industrial value is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. In addition, the physical-property measuring method used by this invention is as showing below.

(1) Measurement of sample component content A solution in which a polymer sample was dissolved in a deuterium trifluoroacetic acid solvent to a concentration of 3% by weight was prepared. Using a nuclear magnetic resonance apparatus (DRX-500 manufactured by Bruker Biospin), a ¹ H-NMR spectrum of this solution was obtained, each peak was assigned, and the content of each component was calculated from the integrated value of the peak.

(2) Thermal contraction rate (%)
In an oven maintained at a predetermined temperature (140 ° C.), the sample was heat-treated for 3 minutes in a non-tensioned state, the sample length before and after that was measured, and the thermal shrinkage rate was calculated by the following formula.
Five points were measured in the longitudinal and lateral directions of the film, and the average value was determined.
Thermal shrinkage = (sample length before heat treatment−sample length after heat treatment) ÷ sample length before heat treatment × 100

(3) Measurement of intrinsic viscosity 1 g of a sample was dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) and measured at 30 ° C.

(4) Melting point and glass transition temperature The melting point and glass transition temperature were measured by using a differential scanning calorimeter (DSC), specifically, DSC-2920 manufactured by TAA Instruments. The sample was heated from 0 ° C. to 300 ° C. at a heating rate of 10 ° C./min, and the crystal melting endothermic peak temperature was defined as the melting point [Tm]. The glass transition temperature [Tg] was set to the center value of the temperature range in which the DSC curve bends due to a change in specific heat when the sample heated to 300 ° C. was rapidly cooled and then heated at a rate of temperature increase of 10 ° C./min.

(5) Practical characteristics of heat-sensitive stencil printing base paper Washi paper was bonded to a film to prepare a base paper. The obtained base paper was printed by Preport VT3950. Character images and 16-step gradation images were made at printing energies at energization control adjustments of -17% (standard), -35% (economy), and -50%. The perforated state of the gradation image portion was observed with a microscope from the film side of the plate-making base paper, and the following items were evaluated.

(A) Perforation sensitivity ◎ ... Predetermined perforation is reliably performed and the size of the perforation is sufficient ○… Predetermined perforation is almost certainly performed, and the size of the perforation is sufficient Δ: Predetermined perforation is almost certain However, there are some cases where the size of the perforations is insufficient. × ... There are many portions where the predetermined perforations cannot be obtained, and the sizes of the perforations are not uniform.

(B) Perforation size The perforation size of the solid print portion at printing energy (−35%) was compared by photographic observation.
◎… The target size is securely drilled ○… Slightly smaller than the target size, but the drill is securely drilled △… Slightly smaller than the target size, there is an insufficient part that is not completely drilled ×… Target size Also, there is a part that is smaller and is not perforated. Further, the following characteristics were visually determined for the characters and images obtained by actually printing using a stencil sheet and using a pre-port VT3950 printer manufactured by Ricoh Co., Ltd.

(C) Print quality ◎… There is no density unevenness and blurring, and it can be printed clearly ○… There is almost no density unevenness and blurring, and it can be printed clearly △… There is little density unevenness and blurring, Lack of clarity ×… Shading unevenness and blur are observed, and lack of clarity

(D) Printing durability A metal drum having a diameter of 25 mm was brought into contact with the metal drum at 180 degrees and repeatedly worn at a speed of 10 mm / second. The abrasion length was 75 mm, and the film surface change or film damage level when repeatedly worn for 2 hours was evaluated in the following three stages.
○: Little change in film surface and little damage Δ: Thin scratches are observed on the film surface, but no significant film wear is observed ×: The film surface is partially destroyed from the perforated part

Example 1:
Starting from 80 parts by weight of dimethyl terephthalate, 20 parts by weight of dimethyl isophthalate, and 60 parts by weight of ethylene glycol, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, and the reaction start temperature is 150 ° C. The reaction temperature was gradually increased as methanol was distilled off, and the temperature was increased to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 1.0 part of spherical silica having an average particle size of 1.1 μm and 0.03 part of antimony trioxide were added to carry out a polycondensation reaction for 4 hours. It was. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.70 dl / g due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure. The obtained polyester-A had an intrinsic viscosity of 0.70 dl / g. Add 0.5 parts by weight of carbodiimide compound (trade name Carbodilite HMV-8CA, manufactured by Nisshinbo Co., Ltd.) to 100 parts by weight of the polyester-A raw material, knead at 280 ° C. using a twin screw extruder, and extrude into a sheet. A rotary cooling drum set at a temperature of 40 ° C. was rapidly cooled and solidified using an electrostatic application cooling method to obtain a substantially amorphous sheet having a thickness of 25 μm. The obtained sheet was stretched 4.0 times at 70 ° C in the longitudinal direction and 4.0 times at 97 ° C in the lateral direction, and heat-treated in a 90 ° C tenter to produce a biaxially oriented film having a thickness of 1.5 µm. did. Next, the obtained film was bonded to a porous thin paper to produce a heat-sensitive stencil printing base paper, which was subjected to copying printing and perforation evaluation.

Examples 2-4:
In Example 1, the carbodiimide compound was changed as shown in Table 1 below, and a heat-sensitive stencil printing base paper was prepared by the same method as in Example 1, and transcribed printing and perforation evaluation were performed.

Comparative Example 1:
A base paper for heat-sensitive stencil printing was prepared in the same manner as in Example 1 except that 100 parts by weight of polyester-A containing no carbodiimide compound in Example 1 was used, and copying was performed.

Comparative Example 2:
A base paper for heat-sensitive stencil printing was prepared in the same manner as in Example 1 except that 2.0 parts by weight of the carbodiimide compound was blended, and copying printing and perforation evaluation were performed.

Example 5:
70 parts by weight of dimethyl terephthalate, 30 parts by weight of dimethyl 2,6-naphthalenedicarboxylate, 58 parts by weight of ethylene glycol, 42 parts by weight of 1,4-butanediol, and 0.005 part by weight of tetrabutyl titanate were added to the reactor to start the reaction. The temperature was set to 150 ° C., and the reaction temperature was gradually raised along with the distillation of methanol to 210 ° C. after 3 hours. After 4 hours, spherical silica particles having an average particle diameter of 1.2 μm were dispersed in this reaction mixture which had substantially completed the transesterification reaction, and 0.5 parts by weight of ethylene glycol slurry was added. Tetrabutyl titanate 0.005 A polycondensation reaction was performed by adding parts by weight. At this time, the temperature was gradually raised from 220 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. The reaction was stopped when 5 hours had elapsed after the start of the reaction, and the polymer was discharged under nitrogen pressure to obtain copolymer polyester-B. The intrinsic viscosity of the obtained polyester-B was 0.65 dl / g. In the same manner as in Example 1, a carbodiimide compound was blended with the above-described polyester-B as shown in Table 1, the temperature of the twin-screw extruder was 255 ° C., and the surface temperature of the rotary cooling drum was 30 ° C. Got the sheet. The obtained sheet was stretched 4.0 times at 83 ° C. in the longitudinal direction and 4.0 times at 84 ° C. in the transverse direction, and heat treated in a 90 ° C. tenter to form a biaxially oriented film having a thickness of 1.5 μm. Manufactured. A heat-sensitive stencil sheet was prepared in the same manner as in Example 1, and transcribed printing and perforation evaluation were performed.

Example 6:
In the production of polyester-A, polyester-C was obtained using the same method as the production method of polyester-A, except that the starting material was dimethyl terephthalate 100 weight. The intrinsic viscosity of the obtained polyester-C was 0.60 dl / g. Polyester-C was used, the raw materials were blended as shown in Table 1, and the film forming conditions in Example 1 were changed such that the longitudinal stretching temperature of the film was 83 ° C and the lateral direction was 103 ° C, and the heat treatment temperature in the tenter Was 100 ° C., and a biaxially stretched film having a thickness of 1.5 μm was produced. Next, a base paper for heat-sensitive stencil printing was prepared in the same manner as in Example 1, and transcribed printing and perforation evaluation were performed.

Comparative Example 3:
A base paper for heat-sensitive stencil printing was prepared in the same manner as in Example 6 except that Polyester-C containing no carbodiimide compound was used in Example 6, and transcribed printing and perforation evaluation were performed.
The physical properties and stencil paper practical properties of the films obtained above are summarized in Tables 1 and 2 below.

  The film of the present invention can be suitably used as a heat-sensitive stencil sheet.

Claims (1)

A polyester film for heat-sensitive stencil printing paper comprising a polyester composition containing 0.1 to 1.5 parts by weight of a carbodiimide compound with respect to 100 parts by weight of polyester.