JPH11157033A - Thermal stencil printing base paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid plate crease from occurring in printed matter obtained by stencil printing by constituting a porous carrier with thermoplastic resin fiber being elliptic in cross section at laminating a thermoplastic resin film and a porous carrier consisting of thermoplastic resin fiber having no adhesive therebetween. SOLUTION: In constituting a thermal stencil printing base paper by laminating a thermoplastic resin film and a porous carrier consisting of thermoplastic resin fiber without using an adhesive, the thermoplastic resin fiber forming the porous carrier is made elliptic in cross section. In addition, the thermoplastic, resin fiber is made about 1.2 or more with respect to a ratio of A/B in its major axis A and minor axis B in cross section. By making the fiber cross section of the porous carrier elliptic in this way, fiber becomes hard to kind and thereby the flexibility of paper is strengthened, thus improving its crease resistivity. As such, printed matter obtained stencil printing by the use of thermal stencil printing paper has no plate creases, and thus adhesive the improvement of an imaging property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive stencil sheet. More specifically, the present invention relates to a heat-sensitive stencil sheet which is perforated and made by a thermal head, a laser beam or the like, and particularly to a heat-sensitive stencil sheet having excellent wrinkle resistance.

[0002]

2. Description of the Related Art In recent years, thermal stencil printers have been designed to increase the dot density of a thermal head from 400 dpi to 60 to achieve high resolution.
Improvements have been made, such as reducing the plate making energy of the thermal head, in order to increase the plate making speed to 0 dpi and to shorten the plate making speed. For this purpose, high-sensitivity, high-quality heat-sensitive stencil printing base paper (hereinafter referred to as base paper) ) Is required.

[0003] In order to meet these requirements, for example, a film whose melting point is reduced, its thickness is reduced, and its heat shrinkage and heat shrinkage stress are increased for the purpose of improving the sensitivity, and a base paper using the same is used. It has been disclosed. Further, for the purpose of improving the image quality of printed matter, improvements have been made such as making the support fiber thinner and reducing the basis weight.

[0004] However, even if the sensitivity of the film is improved, the conventional base paper having a structure in which the support and the film are bonded to each other with an adhesive has a problem that the binder or the adhesive in the support partially forms aggregates to form an ink. And there is a problem that white spot defects occur in printed matter. In addition, it was found that when the film was made thinner or the fiber diameter and the basis weight of the support were reduced, there were problems such as wrinkling and lamination of the film when the film and the support were laminated.

In order to solve these problems, the present inventors have disclosed Japanese Patent Application Laid-Open Nos. Hei 6-305273 and Hei 7-18.
Japanese Patent Application Laid-Open No. 6565, JP-A-8-25826, and the like have proposed a heat-sensitive stencil printing base paper obtained by thermally bonding an unstretched polyester film and an unstretched polyester fiber and co-stretching them. Since the base paper is formed by integrating a thin film and a support without using any binder or adhesive, a film printed with the base paper has a high perforation sensitivity and a good image can be obtained. However, it has been found that the base paper has a problem that the plate is easily wrinkled.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a heat-sensitive stencil sheet which does not cause plate wrinkles.

[0007]

Means for Solving the Problems In view of the above problems, as a result of diligent studies, the present inventors have found that this can be attained by specifying the cross-sectional shape of the support fiber constituting the base paper, and reached the present invention.

That is, the heat-sensitive stencil sheet of the present invention is a heat-sensitive stencil sheet obtained by laminating a thermoplastic resin film and a porous support made of thermoplastic resin fibers without using an adhesive. The cross-sectional shape of the thermoplastic resin fibers constituting the porous support is elliptical.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has been extensively studied in order to provide a heat-sensitive stencil printing paper which does not cause plate wrinkles, and as a result, by specifying the cross-sectional shape of a support fiber constituting the base paper, It has been found that such a problem can be solved.

Examples of the thermoplastic resin film and thermoplastic resin fiber of the present invention include polyester, polyamide, polyethylene, polypropylene, their copolymers, and blends thereof.
Polyester and a copolymer or blend thereof are used for both the thermoplastic resin film and the thermoplastic resin fiber. As the polyester, a polyester containing an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or an alicyclic dicarboxylic acid and a diol as main components is preferable. Here, as the aromatic dicarboxylic acid component, for example,
Terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid , 4,4'-diphenylsulfonedicarboxylic acid and the like, and among them, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid and the like can be preferably used. Examples of the aliphatic dicarboxylic acid component include adipic acid, suberic acid, sebacic acid,
Dodecanedioic acid and the like can be used, and among them, adipic acid and the like can be preferably used. As the alicyclic dicarboxylic acid component, for example, 1,4-cyclohexanedicarboxylic acid and the like can be used. One of these acid components may be used alone, or two or more thereof may be used in combination. Further, an oxyacid such as hydroxybenzoic acid may be partially copolymerized. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1.3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1.3-
Cyclohexanedimethanol, 1.4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2′bis (4′-β-hydroxyethoxyphenyl) propane, and the like can be used. Among them, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.

The polyester used in the thermoplastic resin film of the present invention is preferably polyethylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, a copolymer of ethylene terephthalate and ethylene naphthalate, and hexamethylene terephthalate and cyclohexanediphthalate. Copolymers of methylene terephthalate, blends of polyethylene terephthalate and polybutylene terephthalate, and the like can be used. Particularly preferably, a copolymer of ethylene terephthalate and ethylene isophthalate, a copolymer of ethylene terephthalate and ethylene naphthalate, and the like can be used from the viewpoint of perforation sensitivity and stretchability.

In the thermoplastic resin film of the present invention, an organic lubricant such as a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a pigment, a dye, a fatty acid ester, a wax or the like may be used, if necessary. An antifoaming agent such as siloxane can be blended. Further, lubricity can be imparted as required. There is no particular limitation on the method of imparting lubricity, but, for example, clay, mica, titanium oxide, calcium carbonate, kaolin, talc, inorganic particles such as wet or dry silica, acrylic acid, organic particles containing styrene and the like as constituents And the like, a method using so-called internal particles for precipitating a catalyst or the like to be added during the polyester polymerization reaction, a method using a surfactant, and the like.

As the polyester used for the thermoplastic resin fiber in the present invention, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, and the like can be preferably used.
Particularly preferably, polyethylene terephthalate, polyethylene naphthalate or the like can be used from the viewpoint of thermal dimensional stability.

It is important that the thermoplastic resin fibers constituting the porous support of the present invention have an elliptical cross section. Circular cross-sections are not preferred because plate-form wrinkles are likely to occur. By making the fiber cross section of the porous support elliptical, the fibers are less likely to bend and the stiffness of the base paper is increased, so that the wrinkle resistance is improved.

The ratio A / B of the major axis (A) to the minor axis (B) of the thermoplastic resin fiber of the present invention is preferably 1.2 or more, and more preferably 1.5 or more. . A / B
Is preferably 5 or less from the balance with the image quality.

The fineness of the thermoplastic resin fiber of the present invention is preferably from 0.01 d to 10 d, more preferably from 0.04 d to 5 d, particularly preferably from 0.05 d to 2 d from the viewpoint of the smoothness of the film surface. It is.

[0017] Fibers basis weight of the porous support in the present invention is preferably from 4~20g / m ² from the viewpoint of transportability, and more preferably from 6~16g / m ^2.

The thickness of the base paper in the present invention is preferably from 30 to 120 μm, more preferably from 40 to 100 μm, from the viewpoint of ink permeability.

The crystallinity of the thermoplastic resin fiber in the present invention is preferably from 10% to 50% from the viewpoint of storage stability.
More preferably, it is 20% to 50%.

In the thermoplastic resin fiber of the present invention, a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a pigment, a dye, a fatty acid ester, a wax, etc. are used as long as the effects of the present invention are not impaired. Or an antifoaming agent such as polysiloxane.

The thermoplastic resin fiber of the present invention may be subjected to a chemical treatment such as acid or alkali treatment, a corona treatment, a low-temperature plasma treatment or the like, if necessary, on the surface of the fiber.

The thermoplastic resin film of the present invention comprises:
The melting point is preferably 250 ° C. or less, more preferably 230 ° C. or less, particularly preferably 21 ° C. or less, from the viewpoint of perforation sensitivity.
0 ° C. or less.

The thickness of the thermoplastic resin film in the present invention is preferably from 0.1 to 5 μm, more preferably from 0.5 to 3 μm, particularly preferably from 0.5 to 5 μm, from the viewpoint of perforation sensitivity and film forming property. ２2 μm.

The thermoplastic resin film of the present invention comprises:
The crystal melting energy is preferably from 10 to 50 J / g, more preferably from 10 to 4 from the viewpoint of the stability of the perforated shape.
0 J / g.

The method for producing the heat-sensitive stencil sheet of the present invention is not particularly limited, but the following method is particularly preferred.

That is, it is produced by laminating an unstretched thermoplastic resin film and an unstretched thermoplastic resin fiber having an elliptical cross section and thermally bonding them, or by biaxially co-stretching while thermally bonding. be able to.

The thermoplastic resin film and the thermoplastic resin fiber used in the present invention are, for example, in the case of polyester,
It can be manufactured by the following method. For example, a method in which an acid component is directly esterified with a diol component, and then the product of this reaction is heated under reduced pressure to remove the excess diol component and polycondensate to produce a dialkyl acid. There is a method of using an ester, performing a transesterification reaction between the ester and a diol component, and then performing polycondensation in the same manner as described above. At this time, if necessary, a conventionally known alkali metal as a reaction catalyst,
Alkaline earth metals, manganese, cobalt, zinc, antimony, germanium, titanium compounds and the like can also be used.

The unstretched thermoplastic resin film used in the production of the base paper of the present invention can be produced by extruding a polymer onto a cooling drum by, for example, a T-die extrusion method using the above polyester. The intrinsic viscosity of the polyester used for the film is preferably 0.5 or more, more preferably 0.6 or more, and particularly preferably 0.65 or more. When the intrinsic viscosity is 0.5 or more, the film-forming stability is good, and particularly, casting of a thin film becomes easy.

The unstretched thermoplastic resin fiber used in the production of the base paper of the present invention can be produced in a nonwoven fabric form by a direct melt spinning method such as a melt blow method or a spun bond method. Among them, a melt blown nonwoven fabric is more preferable from the viewpoint of co-stretchability with a film. At this time, by making the hole shape of the spinneret elliptical, an undrawn fiber having an elliptical cross section can be obtained.

The intrinsic viscosity of the polymer used for the melt blown nonwoven fabric is preferably 0.4 or more, more preferably 0.1 wt.
45 or more. If the intrinsic viscosity is 0.4 or more, there is no shot or yarn breakage in the spinning process, and
This is preferable because the fiber does not break during co-drawing with the film. The birefringence of the unstretched nonwoven fabric preferred in the present invention is preferably 10 × 10 ⁻³ or less, and the crystallinity is preferably 5% or less.

In the production of the base paper of the present invention, the unstretched thermoplastic resin film and the unstretched thermoplastic resin nonwoven fabric are thermally bonded and simultaneously co-stretched, so that the thermoplastic resin film and the thermoplastic resin fiber are Can be bonded without using an adhesive. In addition, the thermoplastic resin nonwoven fabrics can be bonded to each other without using an adhesive, which is preferable.

The method of co-stretching the unstretched thermoplastic resin film and the unstretched thermoplastic resin nonwoven fabric is not particularly limited, but biaxial stretching is preferred, and sequential biaxial stretching is particularly preferred.

In the case of sequential biaxial stretching, it is general that transverse stretching is generally performed by a tenter after longitudinal stretching by a group of heating rolls, but may be reversed.

As the material of the heating roll in the longitudinal stretching step, metal, "Teflon", ceramic, silicon rubber and the like are preferably used. The material of the nip roll is particularly preferably silicon rubber. The nip pressure during stretching is preferably in the range of 0.1 to 100 N / cm as a roll linear pressure. The stretching temperature is preferably between 50 ° C and 150 ° C, more preferably in the range of 60 ° C to 130 ° C. Further, in order to uniformly perform heating during stretching, only the thermoplastic resin nonwoven fabric may be preheated alone and then supplied to the stretching roll. Further, in order to uniformly stretch the film and the nonwoven fabric, the heat-bonded unstretched film and the unstretched nonwoven fabric may be heated by an infrared heater or the like immediately before stretching.

The magnification of co-stretching is not particularly limited, but it is usually preferably 2 to 8 times each in the vertical and horizontal directions, more preferably 3 to 8 times.
~ 8 times is appropriate. Also, after biaxial stretching, vertical or horizontal,
Alternatively, the film may be stretched horizontally and vertically again.

After that, it is preferable to heat-treat the base paper of the present invention after the biaxial stretching. The heat treatment temperature is not particularly limited, but is preferably between 100 ° C. and 200 ° C., and the treatment time is usually suitably about 0.5-60 seconds.

After the base paper obtained by the heat treatment is once cooled to about room temperature, it can be further aged at a relatively low temperature of 40 to 90 ° C. for about 5 minutes to 1 week.
When such aging is employed, curling and wrinkles are less likely to occur during storage of the base paper, which is particularly preferable.

It is preferable to apply a release agent to the film surface of the base paper in the present invention in order to prevent fusion with a thermal head or the like. Silicone oil,
Those composed of a silicone resin, a fluorine resin, a surfactant and the like are preferable. In these release agents, various additives can be used in combination as long as the effects of the present invention are not impaired. For example, antistatic agents, heat-resistant agents, antioxidants, organic particles, inorganic particles, pigments and the like can be mentioned.

The thickness of the release agent layer is preferably 0.005 μm.
m or more and 0.4 μm or less, more preferably 0.01 μm or more and 0.2 μm or less. The thickness of the release agent layer is 0.005 μm
If it is above, the runnability of the base paper becomes good, and the thickness is 0.1 mm.
If it is 4 μm or less, there is no contamination of the thermal head.

The release agent may be applied at any stage before or after the film is stretched. The application method is not particularly limited, but the application can be appropriately performed using a roll coater, a gravure coater, a reverse coater, a bar coater, or the like.

Before the release agent is applied, a corona discharge treatment or the like may be applied to the coated surface of the film in air or other various atmospheres as needed.

Next, a method for measuring and evaluating characteristics according to the present invention will be described.

(1) Cross-sectional shape of fiber A cross section of the base paper in the thickness direction was cut out with a microtome, and a photograph at a magnification of 1000 was taken with an electron microscope and observed.

(2) Basis weight (g / m ² ) The base paper was cut into a size of 20 cm × 20 cm, the film portion was carefully peeled off, its weight was measured, and it was converted to the weight per m ² .

(3) Thickness of base paper (μm) Peacock thickness gauge MODEL H (manufactured by Ozaki Corporation)
Was measured at 10 points, and the average value was obtained. (4) Film Thickness (μm) The thickness was measured using a light interference type thickness meter (HIT-25, Toray Techno Co., Ltd.).

(5) Evaluation of plate wrinkles The prepared base paper was supplied to a printing machine “Risograph” (GR375) manufactured by Riso Kagaku Kogyo Co., Ltd., and a plate printing test by confidential plate making was performed 20 times. Was determined.

◎: No wrinkling occurred ◎: once occurred 回: twice occurred △: 3 or more times occurred Δ or above is a level that can be practically used.

(6) Evaluation of Image Properties The prepared base paper was supplied to a printing machine “Risograf” (GR375) manufactured by Riso Kagaku Kogyo Co., Ltd. Using the 8 charts on the manuscript and printing the sample,
It was determined as follows.

Characters and ruled lines without blurring were marked with "O" character, and ruled lines were blurred, but readable characters were marked with "Δ" characters, and ruled lines were severely blurred and some were unreadable.

[0050]

The present invention will be described in more detail with reference to the following examples.

Example 1 The hole shape was elliptical (major axis: 0.45 mm, minor axis: 0.3 mm)
290 ° C., hot air temperature 295 ° C., hot air flow rate 150 Nm using a melt blow spinning machine having a spinneret of
³ / h, polyethylene terephthalate raw material ([η] =
0.495, Tm = 254 ° C.)
An unstretched nonwoven fabric having a g / m ² and a fineness of 1 d was produced. The unstretched nonwoven has a crystallinity of 3% or less and a birefringence of 0.005.
It was below.

Next, a copolymerized polyester resin raw material ([η] = 0.70, Tm1 = 2) composed of 85 mol% of ethylene terephthalate and 15 mol% of ethylene isophthalate
07 ° C.) using a 40 mm screw diameter extruder at a T die die temperature of 275 ° C., and cast on a cooling drum having a diameter of 300 mm to produce an unstretched film.

The unstretched film and the unstretched nonwoven fabric were superposed and supplied to a longitudinal stretching machine, stretched 3.6 times in the longitudinal direction, and cooled to room temperature. The temperature of the preheating roll of the vertical stretching machine is set to 75 ° C., 80 ° C., 87 ° C., and 92 ° C. in order from the front, the temperature of the stretching roll is 95 ° C., and the nip linear pressure is 10 N /
cm. Immediately before the stretching roll, the film surface side was heated at 1.2 kW by an infrared heater.

Then, it is sent to a tenter type horizontal stretching machine,
The film was stretched 3.7 times in the width direction at a preheating temperature of 92 ° C. and a stretching temperature of 96 ° C., and was further heat-treated at 150 ° C. in a tenter and wound into a roll. A heat-sensitive stencil sheet of the present invention was prepared by applying a silicone release agent to the film surface.

The base paper had a film thickness of 1.5 μm, the basis weight of the support fiber was 11 g / m ² , the fineness was 0.28 d, and the thickness of the base paper was 80 μm. When the cross section of the base paper was observed with an electron microscope, the cross section of the support fiber was elliptical,
The ratio of the major axis (A) to the minor axis (B) was A / B = 1.5.

Comparative Example 1 The procedure of Example 1 was repeated except that an unstretched nonwoven fabric having a basis weight of 120 g / m ^{2 and a} fineness of 1 d was produced using a spinneret having a circular hole shape (diameter: 0.3 mm). Similarly, a film thickness of 1.5 μm and a basis weight of the support of 11 g / m 2
^2. A heat-sensitive stencil sheet having a fineness of 0.28 d and a thickness of 80 μm was prepared. When the cross section of the base paper was observed with an electron microscope, the cross section of the support fiber was circular.

[0057]

[Table 1]

As shown in Table 1, Example 1 using a porous support made of polyester fiber having an elliptical cross section was used.
In the case of No. 1, no wrinkling occurred, and the image quality was good. On the other hand, in the case of Comparative Example 1 using a porous support made of a polyester fiber having a circular cross section, plate wrinkles occurred frequently.

[0059]

The heat-sensitive stencil printing paper of the present invention has a porous support made of thermoplastic resin fibers having an elliptical cross-sectional shape. Wrinkles do not occur and the image quality is good.

Claims (6)

[Claims] 1. A heat-sensitive stencil sheet obtained by laminating a thermoplastic resin film and a porous support made of thermoplastic resin fibers without using an adhesive, wherein the thermoplastic resin constituting the porous support is provided. A heat-sensitive stencil sheet, wherein the cross-sectional shape of the fiber is elliptical. 2. The base paper for heat-sensitive stencil printing according to claim 1, wherein the thermoplastic resin film is a polyester film. 3. The thermoplastic resin film for heat-sensitive stencil printing according to claim 1, wherein the thermoplastic resin fiber is a polyester fiber. 4. The thermoplastic resin fiber according to claim 1, wherein the ratio A / B of the major axis (A) to the minor axis (B) of the cross section is 1.2 or more. The heat-sensitive stencil sheet described in the above. 5. The thermoplastic resin fiber has a fineness of 0.01 d to 0.01 d.
The base paper for heat-sensitive stencil printing according to any one of claims 1 to 4, wherein the base paper is 10d. 6. The porous support has a basis weight of 4 to 20 g / m ^2.
The base paper for heat-sensitive stencil printing according to any one of claims 1 to 5, characterized in that: