JPS63214487A - Thermal screen printing base paper - Google Patents

Abstract

PURPOSE:To enhance printing sensitivity and printing durability, by using two kinds of specific resins in combination as thermoplastic polymer for forming a polymer coating layer. CONSTITUTION:A polymer coating layer based on a resin having a hydroxyl group in the molecule thereof and a polyolefinic resin is provided to one surface of a porous thin material as a thermal screen printing layer. As the porous thin material, a thin fabric composed of a natural fiber such as Manila hemp, or MITSUMATA, a synthetic fiber such as polyester or nylon, a polyester fiber or silk can be used. As the resin having a hydroxyl group in the molecule thereof, nitrocellulose, ethylcellulose and a polyester resin are designated and, as the mixing ratio of both resins, the ratio of the polyolefinic resin occupying in the total amount of the resins is pref. set to 40-80wt.%. By this method, printing sensitivity becomes especially good, high density printing generating no broken character or blur can be performed and printing durability is enhanced and the generatation of fog can be prevented.

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]

Heat-sensitive stencil paper has conventionally been produced by applying adhesive (including pressure-sensitive 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 heat-sensitive stencil paper, the thickness of the heat-sensitive stencil layer is thick (this makes it difficult for ink supplied from the porous thin material side during printing to pass through, and also heat is generated around it during hot perforation). A large amount of molten polymer remains, resulting in poor platemaking accuracy and ink smearing during printing, making it impossible to print with high density and clarity, resulting in decreased printing sensitivity and image quality. There is a negative effect.

For this reason, it is desirable for the thickness of the heat-sensitive stencil layer to be as thin as possible.Thinness (thinner) improves plate-making accuracy and facilitates printing, and also allows the use of high-viscosity ink. Clear printing, that is, high-quality printing with good sensitivity and image quality, can be achieved.

However, with the conventional heat-sensitive stencil paper, there is a limit to how thin the heat-sensitive stencil layer can be made, and it is difficult to make the heat-sensitive stencil layer thinner.
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 it is difficult to obtain films thinner than this at a low cost due to film-forming technology and demand. However, even if it were available, it would be difficult to uniformly laminate it onto a porous thin sheet material using an adhesive. Another reason is that in order to adhere the above film to the porous thin material, it is usually about 0.5
This is because ~3 g/rd (solid content) of adhesive is required, and the total thickness of the heat-sensitive stencil layer becomes accordingly thicker.

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 the inventors' subsequent research, the heat-sensitive stencil paper according to the above-mentioned prior invention sometimes lacks the durability of the polymer coating layer, and when it is plate-made and printed, the durability of the polymer coating layer is sometimes lacking, and as the number of printed sheets increases, The coating layer deteriorated and fog appeared on the printed matter. Furthermore, for those with few such problems, the printing sensitivity tends to be somewhat insufficient, and in this case, it is difficult to perform high-density printing without blurring or blurring of characters.

Therefore, the present invention further improves the above-mentioned prior invention, and provides high-density printing without missing or blurred characters, as well as printing sensitivity, durability, and rigidity that eliminates the problem of fogging of printed matter due to an increase in the number of printed sheets. The purpose of the present invention is to provide a heat-sensitive stencil paper with good properties.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors found that if a combination of two specific resins is used as a thermoplastic polymer to form a polymer coating layer,
In addition to being able to perform high-density printing without missing or blurring characters,
The durability of the coating layer is significantly improved, the problem of fogging of printed matter due to an increase in the number of prints is avoided, and a higher quality heat-sensitive stencil paper that satisfies both printing sensitivity and rigidity resistance is obtained. This led to the completion of this invention.

That is, the present invention provides a heat-sensitive stencil material characterized in that a polymer coating layer mainly composed of a mixed resin of a resin having a hydroxyl group in the molecule and a polyolefin resin is provided as a heat-sensitive stencil layer on one surface of a porous thin sheet material. This relates to stencil paper.

[Structure and operation of the invention]

The porous thin material used in this invention is made of natural fibers such as manila hemp, kozo, and mitsumata, synthetic fibers such as polyester and nylon, and nonwoven fabrics made from a mixture of these fibers, with a basis weight of 5 to 15 g/n. or polyester fiber.

Silk screen gauze etc. can be used.

Examples of resins having a hydroxyl group in the molecule used in this invention include nitrocellulose, ethylcellulose, benzylcellulose, cellulose acetate, polyvinyl butyral, polyvinyl acetal, and polyester resins, and examples of polyolefin resins include polystyrene, polyethylene, Examples include polypropylene, polymethylpentene, and chlorinated products thereof. It is particularly preferable that the average molecular weight of these resins be in the range of tens of thousands to hundreds of thousands, from the viewpoint of sensitivity and stiffness resistance of the base paper finally obtained.

As for the mixing ratio of both of the above resins, the ratio of the latter, that is, the polyolefin resin, to the total amount of the resin having a hydroxyl group in the molecule and the polyolefin resin is 40 to 80% by weight, particularly preferably 45 to 60% by weight. %. If the amount of polyolefin resin is too large, the rigidity resistance will decrease, and if it is too small, the printing sensitivity will deteriorate, so both are not preferable.

In addition, in this invention, one or more types of other thermoplastic polymers such as polyvinyl acetate may be used in combination with the above-mentioned mixed resin. However, in this case, it is desirable that the amount of the other thermoplastic polymers is suppressed to 20% by weight or less of the total weight.

In addition, in this invention, the above-mentioned mixed resin is provided as a coating layer on one surface of the porous thin sheet material, and at this time, various kinds of antioxidants, lubricants, plasticizers, antistatic agents, etc. are added to the coating layer. Additives may be included as necessary. The content of these additives is 50% by weight or less of the entire coating layer.

In other words, the coating layer may not only consist of the mixed resin alone, but may also consist of the mixed resin as a main ingredient and an appropriate amount of the above-mentioned additives contained therein.

Various methods can be considered for forming a heat-sensitive stencil layer consisting of such a coating layer. However, since the above-mentioned mixed resin is a polymer that is soluble at 25°C at least 1% by weight in an organic solvent that is not compatible with water, a solution in which 1% by weight or more of this mixed resin is dissolved in the above-mentioned organic solvent is prepared. It is most preferable to adopt the method described below. This method prevents the mixed resin from penetrating into the porous thin material and causing coating defects such as fish eyes in the coated layer.
This is because a uniform coating layer can be easily formed.

This preferred method includes the steps of sufficiently filling the voids of the porous thin sheet material with water, and mixing an organic solvent that is incompatible with water with at least 1% by weight dissolved therein on one side of the water-containing porous thin sheet material. This process consists of a step of applying a solution containing the resin and, if necessary, the other thermoplastic polymers and additives mentioned above, 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 mixed resin 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 does not permeate into the voids (formed in a layer, and by drying it, it coats the surface of the porous thin material with a thickness of 2 μm or less, usually 0.1 to 1.5 μm).
It is possible to form an extremely thin and uniform polymer coating layer without coating defects such as fish eyes. In addition, by selecting and using porous thin sheet materials and mixed resins that have good affinity for each other, the surface of the porous thin sheet material and the polymer coating layer are physically and chemically bonded at the interface to form a strong bond. It becomes a joined product.

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,
Examples include multiple organic solvents such as methyl isobutyl ketone.The mixed resin is dissolved in one or more of these organic solvents, and if necessary, the other thermoplastic polymers and additives mentioned above are added. In order to form a thin and uniform coating layer, it is desirable that the polymer concentration be at least 1% by weight, usually about 2 to 10% by weight.

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 material is continuously removed.

In addition to the above-mentioned methods, methods for forming the coating layer include, for example, directly melting and coating the mixed resin on one surface of the porous thin sheet material, and coating a solution of the mixed resin on a release paper, and then
There is also a method of heat-transferring this onto one surface of a porous thin sheet material without using an adhesive. However, in these cases,
Conditions for melt application and thermal transfer should be appropriately selected to prevent the mixed resin from penetrating into the porous thin material and to prevent coating defects such as fish eyes from occurring in the coated layer.

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.

〔Effect of the invention〕

In the heat-sensitive stencil paper of the present invention, a coating layer mainly composed of a mixed resin of a resin having a hydroxyl group in the molecule and a polyolefin resin is provided on one side of a porous thin material to constitute a heat-sensitive stencil layer. By making the heat-sensitive stencil layer thinner, it not only provides the same advantages as the previous invention, such as higher printing quality, but also provides particularly good printing sensitivity and high-density printing without blurring or blurring. It is possible to perform printing, and the durability of the polymer coating layer is improved, the rigidity resistance is improved, and the special effect of preventing the occurrence of fogging of printed matter due to an increase in the number of printed sheets can be achieved.

〔Example〕

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

Example 1 A porous tissue paper made of Manila hemp with a basis weight of 9 g/d was filled with water by a dipping method, and then chlorinated polypropylene (chlorine content 26% by weight, average molecular weight 150.000) and ethyl cellulose were coated on the surface. (Ethoxyl group content: 48% by weight, average molecular weight: 100.000) A 2% by weight toluene solution of a mixed resin in a weight ratio of 1:1 was applied using an applicator with a slit thickness of 50 μm, and then 80°C
The mixture was dried for 1 minute to obtain a heat-sensitive stencil paper having a coating layer of the above-mentioned mixed resin having 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/rrf.

Comparative Example 1 A 2% by weight toluene solution of ethyl cellulose (the same as that used in Example 1) was used as the polymer solution,
A heat-sensitive stencil paper was prepared in the same manner as in Example 1, except that the drying conditions after coating were 80° C. for 1 minute and the dry thickness was approximately 1 μm, and the same silicone coating as in Example 1 was performed. .

Comparative Example 2 A 2% by weight toluene solution of chlorinated polypropylene (the same as that used in Example 1) was used as the polymer solution, the drying conditions after application were 80°C for 1 minute, and the dry thickness was approximately 1 μm. A heat-sensitive stencil paper was prepared in the same manner as in Example 1, except for the above, and silicone coating was applied in the same manner as in Example 1.

Example 2 Polymethylpentene (average molecular weight 4) as a polymer solution
A 1 wt. % methyl isobutyl ketone/cyclohexene solution of a mixed resin with a weight ratio of 1:1 of nitrocellulose (nitrogen content: 12 wt. %, average molecular weight: 123.000) was used, and the drying conditions after application were adjusted. A heat-sensitive stencil paper was prepared in the same manner as in Example 1, except that the temperature was 80° C. for 1 minute and the dry thickness was 1 μm, and the same silicone coating as in Example 1 was applied.

Comparative Example 3 Except that a 1% by weight methyl isobutyl ketone solution of nitrocellulose (the same as that used in Example 2) was used, the drying conditions after application were 80°C for 1 minute, and the dry thickness was 1 μm. A heat-sensitive stencil paper was prepared in the same manner as in Example 1, and coated with silicone in the same manner as in Example 1.

Comparative Example 4 Polymethylpentene (same as used in Example 2)
A thermal stencil paper was prepared in the same manner as in Example 1, except that a 1% by weight cyclohexene solution was used, the drying conditions after coating were 80°C for 1 minute, and the dry thickness was 1 μm. The same silicone coating as in 1 was applied.

In order to examine the printing sensitivity and rigidity resistance of the heat-sensitive stencil papers of the above Examples and Comparative Examples, a 12-dot/fin thermal recording head was used and set so that the heating element was in contact with the coated layer surface of each base paper. Applied voltage 25■, application time'
A plate was made under printing conditions of 1 msec, and then printing was performed using a stencil printing machine (trade name: AP7200, manufactured by Riso Kagaku Kogyo Co., Ltd.).

As a result, when we first compared Example 1 and Comparative Examples 1.2, we found that the base paper of Comparative Example 1 had a slightly thinner text density and some characters were faded and faded, and the base paper of Comparative Example 2 had a print count of 10 sheets. Capri occurred on the entire surface of the printed matter when it exceeded
With the base paper of Example 1, very high-density printing without character loss or blurring could be performed, and no fogging was observed on the printed matter even when the number of printed sheets exceeded 50. Furthermore, when comparing Example 2 and Comparative Examples 3 and 4, the base paper of Comparative Example 3 had a slightly thinner character density, and some character loss and fading were observed.
In addition, with the base paper of Comparative Example 4, capri occurred on the entire surface of the printed matter when the number of printed sheets exceeded 10, but with the base paper of Example 2, very high density printing without missing characters or blurring could be performed, and the number of printed sheets was also reduced. No fogging was observed on the printed matter even after more than 50 copies were printed.

From these results, it is clear that the heat-sensitive stencil paper of the present invention has excellent printing sensitivity and printing durability.

Claims (1)

[Claims] (1) A heat-sensitive stencil paper characterized in that a polymer coating layer mainly composed of a mixed resin of a resin having a hydroxyl group in the molecule and a polyolefin resin is provided as a heat-sensitive stencil layer on one side of a porous thin sheet material.