JP3040412B2 - Film for heat-sensitive stencil printing base paper - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a base film for heat-sensitive stencil printing paper excellent in resolution, printing quality and printing durability.

[Prior art] Conventionally, heat-sensitive stencil printing base paper in which a thermoplastic resin film is bonded to a porous support such as porous thin paper with an adhesive or an adhesive, or heat is applied to one surface of a support such as porous thin paper. 2. Description of the Related Art A heat-sensitive stencil sheet having a coating layer mainly composed of a plastic polymer is known.

When making a plate using this heat-sensitive stencil printing paper, the original and the film surface or the polymer layer surface of the heat-sensitive stencil printing paper are brought into close contact with each other, and infrared or xenon flash is applied from the porous support side of the heat-sensitive stencil printing paper. By irradiating light to generate heat in the black image portion of the document, the heat melts and perforates the film or polymer layer of the heat-sensitive stencil sheet, and then the document is separated from the heat-sensitive stencil sheet. The image of the original is read by an image sensor, and the film or polymer layer of the heat-sensitive stencil sheet is melt-punched according to the image by the heat of the thermal head.

The heat-sensitive stencil sheet thus made is wound around an ink drum and printed by supplying ink from the porous thin paper side.

In the heat-sensitive stencil printing paper using the above-mentioned thermal head (hereinafter simply referred to as “paper”), a part of the film constituting the paper melted by the thermal head at the time of plate making adheres to this thermal head, and a large amount of plate making is performed. In this case, plate making defects may occur, and it is necessary to appropriately clean the thermal head. However, this operation is complicated.

Further, the base paper is provided with an overcoat layer on the film surface for the purpose of preventing sticking of the base paper during plate making with a thermal head. However, there is a problem that if the base papers are overlapped and left, the overcoat layer bleeds to the support, and the original function cannot be sufficiently achieved.

On the other hand, there is a film subjected to a surface treatment as a film for base paper. Examples of such a film include a film having a center line average roughness (Ra) of 0.01 to 0.3 μm (JP-A-1-168494) and an embossed film (JP-A-51-499, JP-A-51-163598) has been proposed. However, even if such a conventional surface-treated film is used, the above-mentioned disadvantages have not been solved.

[Problems to be Solved by the Invention] Under the circumstances described above, the present invention enables self-cleaning of dirt on a thermal head without sticking to the thermal head during plate making, It is an object of the present invention to provide a base paper film capable of forming a high-quality image without causing the overcoat layer to bleed on the base paper support even when left overlaid.

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, the film for base paper has at least 500 surface protrusions of 1 to ² μm per 1 mm ² . During printing, there is no sticking during printing, and when the dirt on the thermal head is not printed,
By using the film projections, it can be found that the self-cleaning can be performed, and further, by using such a film, the holding power of the overcoat layer can be improved, and the bleed speed can be reduced even when the sheets are left in a superposed state. The present inventors have found that the bleed equilibrium point can be significantly improved as compared with the conventional film, and have reached the present invention.

That is, the present invention relates to a film for heat-sensitive stencil printing paper, wherein the film has surface protrusions of less than 1 to ² μm by 1 mm ^2.
1 mm ^{2 with} 500 or more per surface and 2 μm or more surface protrusions
This is a film for heat-sensitive stencil printing paper having 10 or less per sheet.

In the present invention, when the protrusion on the film surface is 2 μm or more, even when the platen pressure facing the thermal head is increased, heat transfer unevenness occurs, the perforation becomes uneven, the resolution is poor, the thermal sensitivity is reduced, and the like. Occurs, and a good image cannot be obtained. However, if the number of protrusions of 2 μm or more is 10 / mm ² or less, there is substantially no problem.

On the other hand, if the projection is less than 1 μm, a sufficient cleaning effect is not exhibited, and sticking occurs.
The same applies when the number of the projections is less than 500 / mm ² .

The thickness of the base paper film of the present invention is preferably 1.5 to 6 μm.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 Polyethylene phthalate in which SiO ₂ particles having an average particle diameter of 1.5 μm were uniformly dispersed at 0.2 wt% was melt-extruded to form a cooled and solidified sheet, and then biaxially stretched to obtain a 2.0 μm film.

Example 2 A polyethylene phthalate in which CaCO ₃ particles having an average particle diameter of 2.3 μm were uniformly dispersed at 0.12 wt% was processed in the same manner as in Example 1,
A 1.9 μm film was obtained.

Comparative Example 1 Polyethylene phthalate containing no filler was melt-extruded to form a cooled solidified sheet, and then biaxially stretched to 2.1.
A μm film was obtained.

Comparative Example 2 A polyethylene phthalate in which SiO ₂ particles having an average particle diameter of 1.5 μm were dispersed non-uniformly at 0.2 wt% was processed in the same manner as in Comparative Example 1,
A 2.1 μm film was obtained.

Using the films obtained in each of the above Examples and Comparative Examples, the films were laminated on about 10 μm of Japanese paper to prepare heat-sensitive stencil printing base paper. This was subjected to stencil printing using a prepress SS930 thermosensitive stencil printing machine. The results are shown in the following table.

The evaluation of each item was based on the following criteria.

Stick property…: No stick is generated.

…: Some stick occurs, but does not affect the image.

 ×: A stick occurred and plate making was impossible.

Residual rate of over layer Residual in the roll state after storage at 50 ° C for 4 weeks…: 50% or more remaining…: 30 to 50% remaining ×: Less than 30% remaining Image quality Printed after 3,000 plate making before storage test (A ) And an image printed after plate making of 3000 plates after the storage test (B)…: Both (A) and (B) are good.

 …: (A) is good, but (B) is bad.

 ×: Both (A) and (B) are defective.

[Effects of the Invention] As described above, by using the film of the present invention, sticking does not occur at the time of printing, and the overcoat layer hardly bleeds to the support even when left overlaid. A heat-sensitive stencil sheet of excellent quality can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayasu Nonogaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Yuji Natori 1-3-6, Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Hideyuki Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (56) References JP-A-2-158391 (JP, A) JP-A-1- 168494 (JP, A) JP-A-63-227634 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41N 1/24 102

Claims (1)

(57) [Claims] 1. A heat-sensitive stencil film for a stencil printing paper, wherein the film has at least 500 surface protrusions of less than 1 to ² μm per 1 mm ^{2 and} 10 or less surface protrusions of 2 μm or more per 1 mm ^2. Characteristic heat sensitive stencil film for stencil printing.