JPH07115547B2 - Thermal stencil printing film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive stencil printing film which is perforated by receiving heat from a xenon flash lamp or a thermal head. The principle of this plate making method is described in, for example, Japanese Patent Publication No. 41-7623 and Japanese Patent Laid-Open No. 55-55.
-103957, Japanese Patent Laid-Open No. 143679/1984, and the like.

[Prior Art] As a heat-sensitive stencil printing base paper, usually, a heat-sensitive stencil printing film and a porous support are bonded with an adhesive is used. Vinylidene copolymer films, polypropylene films, and polyethylene terephthalate films have been used, and thin paper, tetron gauze, etc. have been used as the porous support.

In addition, as disclosed in Japanese Patent Publication No. Sho 60-1198, the melting point or softening temperature of the film is 2 in the width direction of the film.
A structure has been proposed in which two kinds of polymers different from each other by ° C or more are alternately arranged.

[Problems to be solved by the invention]

 However, these have the following drawbacks.

1) When a vinyl chloride or vinylidene chloride copolymer film is used as a film for heat-sensitive stencil printing, characters after printing are not clearly displayed.

2) Polypropylene and polyethylene terephthalate films give clear text, but solid printing (●
Symbols or figures such as and ■ that have a large ink adhesion area, hereinafter referred to as solid printing. ) Can not get a clear one.

3) Also, in both cases, light and shade appear on the printed part.

4) In addition, unevenness in the thickness of characters partially occurs.

5) Sensitivity is poor and black thin letters, etc. do not appear.

An object of the present invention is to provide a heat-sensitive stencil printing film which has reduced thickness unevenness during character printing, less uneven density during solid printing, excellent durability, and excellent sensitivity.

[Means for solving problems]

The heat-sensitive stencil printing film of the present invention is a biaxially stretched film made of a polyester resin and having a thickness of 0.5 to 7 μm, and 0.05 to 3% by weight of inorganic particles having an average particle diameter of 0.5 to 2.5 times the film thickness. It is characterized by being dispersed and added.

In the present invention, the heat-sensitive stencil printing base paper is, as described above, a material that is perforated by receiving heat from a xenon flash lamp, a thermal head, or the like, and a heat-sensitive stencil printing film and a porous support are bonded together. It is a thing.

The present invention is an improvement of the film (hereinafter, simply referred to as a heat-sensitive film) used for the base paper for heat-sensitive stencil printing.

That is, the heat-sensitive film in the present invention relates to a film that forms a portion where a portion such as a character of the base paper to be printed is perforated when exposed to flash light or contacted with a thermal head.

The polyester resin in the present invention is not particularly limited as long as it has an ester bond as its main skeleton, and typical examples thereof include terephthalic acid, isophthalic acid, α, β-bis ( 2-chlorophenoxy) ethane-4,4'-dicarboxylic acid, 2,6-naphthalate, dimethyl-5-sodium sulfoisophthalate or other aromatic dicarboxylic acid, or sebacic acid, adipic acid, dodecadioic acid or other aliphatic dicarboxylic acid Dicarboxylic acid,
On the other hand, as the alcohol component, ethylene glycol, diethylene glycol, polytetramethylene glycol,
Mention may be made of polyesters with polyethylene glycol, 1,4-butanediol and the like and mixtures thereof.

In the present invention, the thickness of the biaxially stretched film is 0.5 to 7
It is necessary that the thickness is μm, preferably 1.5 to 3.5 μm
Is. If the thickness is too thin, it is unclear and uneven density is likely to occur, and if it is too thick, a missing portion is generated or the thickness becomes uneven, which is not preferable.

In the present invention, the average particle size of the inorganic particles to be added needs to be 0.5 to 2.5 times the film thickness, and preferably 1.1 to 2.0 times. This is not preferable when the average particle size is more than 2.5 times the film thickness, because film formation and stencil printing are not stable. On the other hand, if the average particle size is too small, sufficient stencil printability cannot be obtained, which is not preferable. Here, the average particle size of the inorganic particles can be measured by a centrifugal sedimentation method. Specifically, the polyester is removed from the film by a plasma ashing method or an o-chlorophenol dissolution method, the residue is dispersed in ethanol, and a centrifugal sedimentation type automatic particle size distribution analyzer (for example, Horiba, Ltd.) is used. It can be measured by determining the volume average diameter by CAPA500).

The inorganic particles used in the present invention have a Mohs hardness of 2.5.
Those having a Mohs hardness of 3.5 to 7.5 are more preferable because those having a Mohs hardness of 3.5 to 7.5 are particularly preferable. As inorganic particles having a Mohs hardness in the range of 2.5 to 8, CaC
Examples include O ₃ , TiO ₂ , SiO ₂ , Al ₂ O ₃ , talc and the like.

In the present invention, the addition amount of such inorganic particles is 0.
It is necessary to be 05 to 3% by weight, preferably 0.1
~ 0.8% by weight. This is not preferable when the amount added is more than 3% by weight, and the stencil printability is adversely deteriorated. On the other hand, when less than 0.05% by weight, sufficient stencil printability is obtained. It is not preferable because it cannot be done.

An additive having an absorption peak in the wavelength range of flash light irradiation may be added to the heat-sensitive film.

In order to improve the adhesiveness with the porous support, the surface of the heat-sensitive film may be subjected to corona discharge treatment in air, carbon dioxide gas or nitrogen gas.

The porous support to be attached to the film of the present invention,
As typical examples thereof, but not limited to, bending paper, synthetic fiber gauze paper such as Tetron gauze, various woven fabrics, and non-woven fabrics can be cited.

The basis weight of the porous support to be used is not particularly limited, but is usually ^{2 to 20} g / m ² , preferably about 5 to 15 g / m ² .

When a mesh sheet is used, it is preferable to use a woven fiber having a thickness of 20 to 60 μm, and it is preferable to use a lattice spacing of 20 to 250 μm.

In the present invention, the adhesive used to bond the biaxially oriented film made of a polyester resin and the porous support is not particularly limited, but includes vinyl acetate resin, acrylic resin, urethane resin, polyester A system resin can be mentioned as a typical example.

Next, the method for producing the heat-sensitive film of the present invention will be described, but the present invention is not limited thereto.

First, a raw material to which predetermined inorganic particles are added is prepared. In this case, the method of adding the inorganic particles is not particularly limited, the inorganic particles are dispersed in ethylene glycol, after subjected to boiling heat treatment as needed within 60 hours, such as glass beads as necessary. From the viewpoint of dispersibility, it is preferable to add what is dispersed using a medium during polyester polymerization. At this time, it is preferable to add a particle surface treating agent such as a phosphoric acid compound to the inorganic particles in an amount of 1 to 80% by weight from the viewpoint of stencil printability. The inorganic particles may be added to a specific raw material in a large amount or may be diluted and used, or may be uniformly added to all raw materials.

Raw materials prepared in this way, after sufficiently dried under predetermined conditions, supplied to the extruder and extruded in a molten state from the die,
Wrap around a cooling drum to cool and solidify to form an unstretched film.

This unstretched film is biaxially stretched. In this case, the stretching conditions vary depending on the resin used and are not limited, but usually, the longitudinal direction and the width direction are each 2.5 to 4.5 times, and the stretching speed is 100 to 1 times.
It is stretched by 0 ⁷ %. The stretching order is not particularly limited, and may be sequential or simultaneous, or biaxially stretched and then stretched again. Further, the biaxially stretched film thus obtained may be appropriately heat treated. The heat treatment condition is not particularly limited, but is 100 to 250 ° C.
The relaxation rate is usually 20% or less.

[Action]

The present invention, in the film of a specific thickness, since a specific amount of inorganic particles having an average particle size of 0.5 to 2.5 times the film thickness is added, when heat is applied to create a stencil, the particles and the polymer are It is thought that this is because the interface with and is easily peeled off, but it became possible to obtain excellent stencil printability.

[Measurement method]

 Each property used in the present invention was evaluated by the following methods.

(1) Evaluation of character printing Evaluation of character clarity Characters of JIS No. 1 standard are used as a base paper (original) with a character size of 2.0 mm □, a porous support made of Tetoron gauze and the heat-sensitive film of the present invention (implementation). Examples and comparative examples are also the same), and the ones made by using the "RISO business card pretend" plate making / printing machine (made by Riso Kagaku Kogyo Co., Ltd.) and printed are as follows. And evaluated. Evaluation is A by the naked eye,
There are 3 levels of B and C, A looks like the base paper, B
Unlike the original paper, the line is partially cut or stuck, but it is readable, and the C is cut or stuck until it is almost unreadable.

Evaluation of missing characters Characters were evaluated for how they were missing by performing plate making and printing in the same manner as in the section above.

Those with a clearly missing part were marked as unusable and marked with a cross. The case where there was no chipped portion at all was regarded as good and indicated by a circle. In addition, a mark (Δ) indicates that there was a slight defect (within a legible range) although it was not in a completely missing condition.

Character size 5.0 mm using the same plate making and printing machine as in the evaluation item for uneven thickness of characters
The letter □ was printed, and the printed state was visually evaluated.

Compared to the characters on the base paper (original), those with apparently uneven thickness are marked with an X, indicating that they have a bad appearance and cannot be used, and those without uneven thickness are marked with a good appearance, and are indicated by ◯.

The thickness of characters was printed and printed in the same manner as in the item for evaluation, and the change in the thickness of characters was visually evaluated.

Compared to the thickness of the original, those markedly thickened or thinned are marked with x as unusable, and those with no change in thickness are marked with o. Also, those that are slightly thicker or thinner but can be used are indicated by Δ.

(2) Evaluation of solid printing Evaluation of sharpness of solid printing ● Using (1-5 mmφ) base paper (rounded and filled with black), the same plate as above was printed and printed as follows. evaluated.

The size of the base paper was used as a reference, and the judgment was made by the unevenness (partial) of the contour. Those with irregularities of 200 μm or more larger than the size of the base paper were marked with a cross, indicating poor appearance and unclear, and those with irregularities of 50 μm or less were sharp, and indicated by a circle. The intermediate one is indicated by a triangle. Depending on how you use it, you can also use the one marked with a triangle.

Correspondence with the base paper size of solid printing Printing is performed in the same way as in the paragraph, and all directions (0 ° and 180 °, 45 ° and 225
At 90 ° and 270 °, at 135 ° and 315 °), and the correspondence with the size of the base paper was evaluated.
Different from the base paper size by 500 μm or more (when large,
(Sometimes small) is indicated as poor compatibility and is indicated by an X,
Those having a thickness of 50 μm or less are marked with good compatibility and are indicated by a circle. The one in the middle is indicated by a triangle, but it can be used depending on the application.

Print in the same manner as in the evaluation item for uneven density of solid printing and check if there is uneven density of solid printing.
The presence or absence was visually evaluated. Those with uneven density are indicated by x, and those without unevenness are indicated by o.

(3) Sticking to the base paper Printing was performed in the same manner as in the above item, and those having no sticking to the base paper after printing are indicated by ◯. Also, those that can be easily peeled off from the base paper ○
Indicated by.

(4) Evaluation of sensitivity Prepare 5 types of pencil hardness of 5H, 4H, 3H, 2H and H, and write a letter with a pressing pressure of 150g as a manuscript. Whether or not the letter can be read using this manuscript It was evaluated by. When written in 5H, the color is the thinnest and the sensitivity is highest.
As, the black color becomes darker and the sensitivity becomes worse.

(5) Evaluation of Durability The number of sheets that can be printed before the thermal film is damaged by the above-mentioned printing machine (hereinafter referred to as the number of printable sheets) is expressed.

(6) Mohs hardness A test piece having the same structure and structure as the inorganic particles added to the film is prepared, or a mineral before being crushed into particles is used as a test piece and rubbed with a standard mineral for Mohs hardness measurement, From the presence or absence of scratches, the hardness is measured to the unit of 0.1.

〔Example〕

Examples 1 to 11 and Comparative Examples 1 to 5 As inorganic particles, silicon oxide, talc, titanium oxide or alumina having a predetermined average particle diameter was dispersed in ethylene glycol and subjected to boiling heat treatment for 24 hours. Trimethylammonium phosphate was added to this slurry to
10% by weight was added, and the mixture was uniformly dispersed by a media dispersion method and polymerized with dimethyl terephthalate. Intrinsic viscosity is
It was 0.72. Next, polyethylene terephthalate containing no inorganic particles was polymerized (intrinsic viscosity 0.62) and mixed with the above-mentioned inorganic particle-containing polyethylene terephthalate in a predetermined ratio. After fully dried, feed to the extruder at 290 ℃
Melt extrusion, using the electrostatic cast method, surface temperature
It was wound around a casting drum at 30 ° C., cooled and solidified to form an unstretched film having a thickness of 150 μm. After subjecting this unstretched film to simultaneous biaxial stretching at 95 ° C in the length and width directions of 3.8 times each,
After cooling once, it was heat-treated at 150 ° C. while being relaxed by 1.5%. The 2.2 μm-thick film thus obtained was laminated with Tetoron gauze, subjected to plate making and printing, and evaluated.
The results are shown in Table 1. However, in Table 1, PET indicates polyethylene terephthalate.

As is apparent from Table 1, it is understood that good printability can be obtained only when a predetermined range (particle size / film thickness) of inorganic particles is added in a specific range.

[Effects of the Invention] The film of the present invention has the following excellent effects because the particle size and the amount of the inorganic particles to be added are within the specified ranges. That is, (1) clear printing is possible.

(2) Printing with less unevenness is possible.

(3) The durability is improved.

(4) The sensitivity is improved.

Front page continuation (72) Inventor Hideki Yamagishi 1-1-1, Sonoyama, Otsu City, Shiga Prefecture Inside Toga Co., Ltd. Shiga Plant (56) References JP-A-51-2513 (JP, A) JP-B 47- 5139 (JP, B1)

Claims (1)

[Claims] 1. A thickness of 0.5 to 7 made of polyester resin.
It is a biaxially stretched film with a thickness of 0.5 μm.
~ 0.05 to 3% by weight of inorganic particles having an average particle size of 2.5 times
A heat-sensitive stencil printing film, which is dispersed and added.