JPS63283992A - Thermal stencil paper - Google Patents

Abstract

PURPOSE:To obtain a stencil paper being free of release of a porous film material and a thermal stencil layer from each other at the time of high-speed printing and having extremely excellent plate wear characteristics, by setting the water absorption of the porous film material to be not more than 5 mm in terms of a 10-min value measured by the testing method for water absorption of paper by Klemm's method according to JIS-P8141. CONSTITUTION:A thermal stencil paper comprises a coated layer comprising a thermoplastic polymer as a main constituent, as a thermal stencil layer on one side of a porous film material. In the stencil paper, the porous film material is constituted of a paper made from natural fibers, synthetic fibers or a mixture thereof or a nonwoven fabric, the paper or nonwoven fabric having a basis weight of 5-15 g/m<2> and a water absorption of not more than 5 mm in terms of a 10-min value measured by the testing method for water absorption of paper by Klemm's method according to JIS-P8141. When the porous film material with a low water absorption is used, permeation of water into the material is slight, so that a delamination phenomenon is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-sensitive stencil paper having a heat-sensitive stencil layer provided on one side of a porous thin material.

[Conventional technology]

Conventionally, heat-sensitive stencil paper is produced by applying adhesive (including adhesive) to a film made in advance by stretching or inflation, such as polyvinylidene chloride film or polyethylene terephthalate (PET) film. It is manufactured by laminating a porous thin sheet material on this coated surface.

The heat-sensitive stencil paper produced by this method is one in which the above-mentioned film and adhesive layer together constitute a heat-sensitive stencil layer, and the plate is made by perforating these by heating,
During printing, this base paper is wrapped around an ink drum,
Printing is performed by supplying ink from the porous thin material side.

By the way, in such a heat-sensitive stencil paper, when the thickness of the heat-sensitive stencil layer becomes thick, it becomes difficult for ink supplied from the porous thin material side to pass through during printing, and heat melting occurs around it during hot perforation. A large amount of the polymer remains, resulting in poor plate-making accuracy and ink smearing during printing, making it impossible to print with high density and clarity, and reducing printing sensitivity and image quality. There are negative effects.

For this reason, it is desirable for the thickness of the heat-sensitive stencil layer to be as thin as possible. By making the thickness thinner, the precision of plate making increases and printing becomes easier. This also makes it possible to use high viscosity ink, resulting in high density and clear printing. This enables high-quality printing with good sensitivity and image quality.

However, with the conventional heat-sensitive stencil paper, there is a limit to the number of layers of heat-sensitive stencil layers.
It has been difficult to make the thickness less than μm, for example, about 1 μm.

The reason for this is that films such as polyvinylidene chloride film and PET film have a thickness of about 2 μm at most, and thinner films less than this can be made at low cost.
This is because it is difficult to obtain such materials due to film-forming technology and the amount required, and even if they could be obtained, it would be difficult to uniformly laminate them onto a porous thin sheet material using an adhesive. Another reason is that in order to adhere the above-mentioned membrane-formed film to the porous thin material, it is usually about 0.
This is because 5 to 3 g/% (IiJ type) of adhesive is required, and the total thickness of the heat-sensitive stencil layer becomes thicker accordingly.

Therefore, in view of the above-mentioned problems with the conventional heat-sensitive stencil paper, the inventors have made extensive studies, and as a result, the heat-sensitive stencil layer to be provided on the porous thin material is composed of a coating layer of a thermoplastic polymer. In other words, if the above layer is formed by coating a thermoplastic polymer, problems in terms of film forming technology, laminating technology, and economic efficiency when using the conventional film forming film or adhesive can be solved. It is possible to easily form a very thin heat-sensitive stencil layer of 2 μm or less, usually about 0.1 to 1.5 μm, which was difficult in the past, without any problems, and without any hindrance to thinning the adhesive layer. I have already proposed this as a prior invention to this invention.

The heat-sensitive stencil paper according to this prior invention has a unique structure in which the heat-sensitive stencil layer is composed of a single layer (coating layer) of a thermoplastic polymer without an adhesive layer, unlike the above-mentioned conventional stencil paper. It has many advantages, such as being able to easily make the layer thinner, making it easier to achieve higher quality printing, and being able to manufacture it at a lower cost.

[Problem that the invention seeks to solve]

However, according to subsequent research by the inventors, the heat-sensitive stencil paper according to the above-mentioned prior invention has a problem in stiffness resistance during high-speed printing, for example, when the printing speed exceeds 100 sheets/min for 84 paper. It has been found that at such a speed, a phenomenon occurs in which the porous thin sheet material and the heat-sensitive stencil layer peel off.

Therefore, it is an object of the present invention to further improve the above-mentioned prior invention and provide a heat-sensitive stencil paper with excellent printing durability, in which the porous thin material and the heat-sensitive stencil layer do not peel off during high-speed printing. It is an object.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors selected and used a specific porous thin sheet material to form a heat-sensitive stencil layer consisting of a coating layer mainly made of thermoplastic polymer. It was discovered that by doing so, it is possible to obtain a heat-sensitive stencil paper with extremely high rigidity resistance, which prevents the thin sheet material and the heat-sensitive stencil layer from peeling off during high-speed printing, and led to the completion of this invention. Ta.

That is, the present invention provides a heat-sensitive stencil paper in which a coating layer mainly composed of a thermoplastic polymer is provided as a heat-sensitive stencil layer on one side of a porous thin-sheet material, and the water absorption of the above-mentioned porous thin-sheet material is is 5 tl as a 10 minute value measured by JIS standard P8141 paper water absorption test method by Klemm method.
This invention relates to a heat-sensitive stencil paper characterized by the following.

[Structure and operation of the invention]

The porous thin leaf material in this invention includes manila hemp,
Natural fibers such as kozo and mitsumata, synthetic fibers such as polyester and nylon, paper or non-woven fabrics made by mixing these with a basis weight of 5 to 15 g/d, polyester fibers, silk screen gauze, etc. can be used. It is necessary that the water absorption is 5 mm or less in a 10-minute value measured by the Klemm water absorption test method using JIs standard P8141 paper.

The 10-minute value measured by the above water absorption test method is a beaker filled with water and a width of 15 ui.

A test piece with a length of 120 m or more was
The test piece is immersed in water for a length of fi and left to stand, and the height of the water rising from the water surface after 10 minutes is expressed as the average value in the width direction.The smaller this value, the higher the water absorption. It means low.

In this invention, the water absorption measured in this way is 51
Below, we have found that printing durability can be improved by using a porous thin sheet material with a low water absorption rate of 0, although the reason for this is currently not clear. do not have. The inventors speculate that in a porous thin sheet material with a high water absorption rate different from that of the present invention, water from the ink excessively permeates during printing, causing the material to swell, and this swelling causes the material to become heat-sensitive. It is thought that the interfacial strength between the stencil layer and the stencil layer decreases, resulting in separation between the two, but with the porous thin film material with low water absorption rate, such as the one of this invention, there is little moisture seeping into the material. It is thought that this is because the above-mentioned peeling phenomenon is suppressed.

The above porous thin sheet material with low water absorption used in the present invention can be obtained, for example, by treating the various porous thin sheet materials described above with a sizing agent or a paper strength enhancer. Sizing agents include various rosins, synthetic resin emulsions, starches, povals, waxes, etc. Paper strength enhancers include acrylamide-based and melamine-based ones, but other sizing agents may also be used. Well, there are no particular limitations.

The thermoplastic polymer used in this invention includes:
In order to form the heat-sensitive stencil layer with this polymer, it is sufficient that it is non-adhesive and solid at room temperature, and it is not formed into a film by stretching or the like as in the conventional method.
One or more polymers can be arbitrarily selected from a wide range of conventionally known polymers such as acrylic resins, olefin resins, butyral resins, and ethylene-vinyl acetate copolymers.

These polymers may be a single polymer or a copolymer, and the copolymer may be a random, block or graft copolymer. The molecular weight of the polymer varies depending on its type, but it is generally desirable that the average molecular weight is in the range of 20,000 to 200,000.

Particularly recommended polymers in this invention include thermoplastic polymers having hydroxyl and/or carboxyl groups in the molecule, and the use of such polymers provides good results in terms of not only stiffness but also printing sensitivity. Can be done. The above hydroxyl group and/or carboxyl group may be present at the end of the molecule or at any position within the molecule (including the side chain).

Specific examples of such thermoplastic polymers include polyester resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymers, polyether resins, polybutadiene resins, acrylic polyols, and urethane resins having hydroxyl groups. Examples include epoxy prepolymers, nitrocellulose, cellulose acetate propionate resins, cellulose acetate butyrate resins, ethyl cellulose, and cellulose acetate.

In this invention, the above-mentioned thermoplastic polymer is provided as a coating layer on one surface of a porous thin sheet material, and various additives such as antioxidants, lubricants, plasticizers, and antistatic agents are added to the coating layer. An agent may be included as necessary. The content of these additives is 50% by weight of the entire coating layer.
The following shall apply.

That is, the coating layer may not only consist of a thermoplastic polymer alone, but may also consist of this polymer as a main component, with an appropriate amount of the above-mentioned additives added thereto.

Various methods can be considered for forming a heat-sensitive stencil layer consisting of such a coating layer. However, since most of the thermoplastic polymers used are soluble at 25°C in an amount of at least 1% by weight in organic solvents that are not compatible with water, a solution in which this polymer is dissolved in an amount of 1% by weight or more in the above-mentioned organic solvent. It is most preferable to employ the method described below using This is because, according to this method, a thin and uniform coating layer can be easily formed without infiltrating the thermoplastic polymer into the porous thin sheet material and without causing coating film defects such as fish eyes in the coating layer.

This preferred method includes the steps of sufficiently filling the voids of the porous thin sheet material with low water absorption with water, and applying an organic solvent that is incompatible with water to one side of the water-containing porous thin sheet material, and adding one weight of this water-incompatible organic solvent to one side of the water-containing porous thin sheet material. The method consists of a step of applying a solution containing a thermoplastic polymer dissolved in at least 50% of the thermoplastic polymer and, if necessary, the above-mentioned additives, and a step of drying after this application to sequentially remove the above-mentioned organic solvent and water. .

In this way, when a porous thin sheet material is filled with water and then a solution of a thermoplastic polymer dissolved in an organic solvent that is incompatible with water is applied, the voids in the porous thin sheet material are filled with water. The applied solution is formed into a layer without penetrating into the voids, and by drying it, it forms a layer on the surface of the porous thin material with a thickness of 2 μm or less, usually 0.1 to 1 μm.
．． It is possible to form a uniform polymer coating layer that is as thin as 5 μm and free from coating defects such as fish eyes.

Furthermore, by selecting and using materials that have good affinity for each other, the surface of the porous thin sheet material and the polymer coating layer can be physically and chemically bonded to each other at the interface to form a strong bond.

In the above method, the filling of water into the porous thin film material is
This can be done by various methods such as roll coating and dipping, and the polymer solution can be applied by using applicator coating, fountain coating, goo coating, and the like. These methods themselves are not particularly limited.

Organic solvents that are incompatible with water include hexane, cyclohexane, cyclohexene, benzene, toluene, xylene, chloroform, ethyl acetate, methyl ethyl ketone,
Many organic solvents may be mentioned, such as methyl isobutyl ketone. The thermoplastic polymer is dissolved in one or more of these organic solvents, and if necessary, the above-mentioned additives are added, but the polymer concentration at this time is at least 1% by weight, usually 2 to 10% by weight. In order to form a thin and uniform coating layer, it is desirable to adjust the weight to a certain level.

Drying conditions after application vary depending on the type of organic solvent, but
Normally, the heating time may be about 1 to 10 minutes at 60 to 120°C. By this drying, first, the organic solvent in the coating layer is volatilized, and then the water filled in the porous thin sheet material is volatilized and removed.

In addition to the methods described above, methods for forming the coating layer include, for example, directly melt-coating a thermoplastic polymer onto one surface of a porous thin sheet material, or coating a solution of a thermoplastic polymer on a release paper and then applying it to a porous thin sheet material. There is also a method of heat-transferring one side of a thin sheet material without using an adhesive. However, in these cases, the conditions for melt application and thermal transfer must be selected appropriately to prevent the thermoplastic polymer from penetrating into the porous thin material and to prevent coating defects such as fish eyes from occurring in the coating layer. Should.

The heat-sensitive stencil paper of this invention obtained in this way is
If necessary, a release layer for preventing adhesion during plate making and an anti-sticking layer for preventing sticking with a thermal head may be provided on the surface of the polymer coating layer as a heat-sensitive stencil layer.

Plate making and printing using the heat-sensitive stencil paper of the present invention may be carried out according to conventional methods. For example, plate making can be done by placing an offset printing original on the surface of a heat-sensitive stencil layer and perforating it with heat using a commercially available heat-sensitive stencil maker, and for printing, using a commercially available stencil printing machine, the base paper after the stencil printing is transferred to an ink drum. It is sufficient to wrap the material around the porous thin sheet material and print while supplying ink from the porous thin material side. During this printing, there was hardly any decrease in the interfacial strength between the above material and the heat-sensitive stencil layer, which is thought to be due to excessive moisture permeation into the porous thin-sheet material. Extremely excellent printing durability is exhibited, with no peeling between the above-mentioned material and the heat-sensitive stencil layer.

〔Effect of the invention〕

In the heat-sensitive stencil paper of the present invention, when forming a heat-sensitive stencil layer by providing a coating layer mainly composed of a thermoplastic polymer on one side of a porous thin-sheet material, the above-mentioned specific porous thin-sheet material is used. By selectively using these materials, the same advantages as the previous invention, such as high quality printing due to thinning of the heat-sensitive stencil layer, can be obtained, and in addition, the interfacial strength between the coating layer and the material can be significantly increased. Through this improvement, an exceptional effect can be achieved in that the coating layer and the material do not peel off even during high-speed printing, and extremely excellent rigidity resistance can be exhibited.

〔Example〕

EXAMPLES Below, examples of the present invention will be described in more detail.

Example 1 Basis weight 9 whose water absorption is 0 in the lo minute value measured by the Klemm water absorption test method using JIS standard P8141 paper.
After filling porous tissue paper made of Manila hemp with g/rrr with water by dipping method, a 2% by weight toluene solution of ethyl cellulose (ethoxyl content: 48% by weight, average molecular weight: 1100.000) was slit onto the surface. Apply with a 50 μm thick applicator, then apply 10 (
The mixture was dried for 1 minute at 100 ml of heat-sensitive stencil paper to obtain a heat-sensitive stencil paper having a coated layer of ethyl cellulose with a thickness of about 1 μm as a heat-sensitive stencil layer. Wire barcoding was performed on the coated layer surface of this heat-sensitive stencil paper so that silicone oil was applied as a release layer at a rate of 0.1 g/rd.

Comparative Example 1 As a porous thin paper, its water absorption is JIS standard P8141
10 measured by paper Klemm water absorption test method
A heat-sensitive stencil paper was prepared in exactly the same manner as in Example 1, except that one made of Manila hemp with a basis weight of 9 g/rrl and a weight of 15 mm was used. Went to court.

Example 2 A tsubo 31 tsubo whose water absorption is 3 cranes in 10 minutes measured by JIS standard P8141 paper Klemm's water absorption test method.
A porous tissue paper made of Manila hemp with a weight of 8 g/rrf was filled with water by a dipping method, and then cellulose acetate butyrate (average molecular weight 30
,000. A 2% by weight methyl ethyl ketone solution with an acetyl content of 2.0% by weight and a butyryl content of 53% by weight was applied using an applicator with a slit thickness of 50 μm.
Dry at 0°C for 3 minutes to form a heat-sensitive stencil layer of approximately 1 μm.
A heat-sensitive stencil paper having a thick coating layer of cellulose acetate butyrate was obtained. Apply 0.1 g/r of silicone oil as a release layer to the coated layer surface of this heat-sensitive stencil paper.
Wire barcoding was performed so that it became d.

Comparative Example 2 As a porous thin paper, its water absorption is JIS standard P8141
10 measured by paper Klemm water absorption test method
A heat-sensitive stencil paper was prepared in exactly the same manner as in Example 2, except that one made of Manila hemp with a basis weight of 8 g/rd and a paper weight of 15 m in minutes was used. Went to court.

In order to examine the suitability for high-speed printing of each heat-sensitive stencil paper of the above-mentioned Examples and Comparative Examples, an offset printing original was superimposed on the surface of each heat-sensitive stencil layer, and a heat-sensitive stencil maker (trade name: Risograph FX7200 manufactured by Riso Kagaku Kogyo Co., Ltd.) was used. Ordinary manuscript scale 4
Then, printing was performed using a stencil printing machine (trade name: AP?200, manufactured by Riso Kagaku Kogyo Co., Ltd.) at printing speeds of 80 sheets/min and 120 sheets/min.

As a result, when comparing Example 1 and Comparative Example 1, when the printing speed was 80 sheets/min, the number of printed sheets was lo.

Even when the number of printed sheets exceeded 100 sheets, good printed matter could be obtained in both cases, but when the printing speed increased to 120 sheets/min, the heat-sensitive stencil layer On the other hand, with the base paper of Example 1, good printed matter similar to that obtained when the printing speed was 80 sheets/min could be obtained. In addition, when comparing Example 2 and Comparative Example 2, when the printing speed was 80 sheets/min, both were able to obtain good printed matter even if the number of printed sheets was quite large, but when the printing speed was At 120 sheets/min, the heat-sensitive stencil layer and the porous tissue paper peeled off when the number of sheets printed exceeded 1,500 sheets in the base paper of Comparative Example 2, and printing became impossible, while the base paper of Example 2 Even if the number of printed sheets was exceeded, good printed matter similar to that obtained when the printing speed was 80 sheets/min could be obtained.

Claims (3)

[Claims] (1) As a heat-sensitive stencil layer on one side of the porous thin sheet material,
In a heat-sensitive stencil paper provided with a coating layer mainly composed of a thermoplastic polymer, the water absorption of the above-mentioned porous thin material is a 10-minute value measured by the Klemm method water absorption test method for JIS standard P8141 paper. A heat-sensitive stencil paper characterized by having a thickness of 5 mm or less. (2) When thermoplastic polymers are used in organic solvents that are not compatible with water,
A heat-sensitive stencil paper according to claim 1, comprising a polymer that is soluble at 5°C in an amount of at least 1% by weight. (3) The heat-sensitive stencil paper according to claim (1) or (2), wherein the thermoplastic polymer is a thermoplastic polymer containing a hydroxyl group and/or a carboxyl group in the molecule.