JPH03208690A - Film for thermal screen printing base paper - Google Patents

Abstract

PURPOSE:To eliminate sticking at the time of printing and the bleeding of an overcoat layer to a support at the time of superposed standing by providing surface projections of 1 - below 2 mum to a film in a density of 500 or more/1 mm<2> and also providing surface projections of 2 mum or more thereto in a density of 10 or less/1 mm<2>. CONSTITUTION:A film has surface projections of 1 - below 2 mum in a density of 500 or more/1 mm<2> and surface projections of 2 mum or more in a density of 10 or less/1 mm<2>. When 500 or more surface projections of 1 - 2 mum are provided to the film for base paper per 1 mm<2>, sticking at the time of printing is eliminated and the contamination of a thermal head is self-cleaned by the film projections at the time of non-printing. Further, the holding power of an overcoat layer is enhanced and bleed speed is made low even when the film is allowed to stand in a superposed state and a bleed equilibrium point can be improved to a large extent. When the projections are set to 2 mum or more, the lowering of heat sensitivity is generated but, when these projections are 10/1 mm<2> or less, there is no trouble substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a base film for heat-sensitive stencil printing base paper that has excellent resolution, print quality, and printing durability.

[Prior art] Conventionally, base paper for heat-sensitive stencil printing, in which a thermoplastic resin film is bonded to a porous support such as porous thin paper using an adhesive or an adhesive, and thermoplastic resin film on one side of the support such as porous thin paper, have been used. A heat-sensitive stencil printing base paper provided with a coating layer mainly composed of a polymer is known.

When making a plate using this thermal stencil printing base paper,
The original is brought into close contact with the film surface or polymer layer surface of the thermal stencil printing base paper, and infrared rays or xenon flash light is irradiated from the porous support side of the thermal stencil printing base paper to generate heat in the black image area of the original. The film or polymer layer of the heat-sensitive stencil printing base paper is melted and perforated by the heat, and then the document and the heat-sensitive stencil printing base paper are separated. Also, an image sensor reads the image of the document, and the heat of the thermal head melts and perforates the film or polymer layer of the thermal stencil printing base paper in accordance with the image.

The heat-sensitive stencil printing base paper made in this manner is wound around an ink drum and printed by supplying ink from the porous thin paper side.

Base paper for thermal stencil printing using the above thermal head (
(hereinafter simply referred to as base paper), a part of the film that makes up the base paper is melted by a thermal head during plate making and adheres to this thermal head, which may cause plate making defects if a large amount is made. It is necessary to properly clean the thermal head. However, this work is complicated.

Further, the base paper is provided with an overcoat layer on the film surface for reasons such as preventing stickiness of the base paper during plate making with a thermal head. However, if the base papers are left on top of each other, the overcoat layer bleeds into the support, resulting in a problem in that the original function cannot be fully achieved.

On the other hand, there are films that have been surface-treated as base paper films. Examples of such materials include a film with a center line average roughness (R a ) of 0.01 to 0.8 μa+ (Japanese Patent Application Laid-Open No. 1-168494) and an embossed film (Japanese Patent Application Laid-Open No. 1983-168494). No. 499, Japanese Unexamined Patent Publication No. 183598/1983), etc. have been proposed. However, even if such conventional surface-treated films are used, the above-mentioned disadvantages have not been solved.

[Problems to be Solved by the Invention] In view of the above-mentioned circumstances, the present invention is capable of self-cleaning dirt on the thermal head without causing sticking to the thermal head during plate making, and in addition, it is possible to self-clean the dirt on the thermal head, and also to clean the base paper from the base paper. It is an object of the present invention to provide a film for base paper that does not cause the overcoat layer to bleed onto the base paper support even when left to overlap and is capable of producing high-quality images.

[Means for Solving the Problems] As a result of intensive research in order to solve these problems, the present inventors have found that by providing the base paper film with 500 or more surface protrusions of 1 to 2 μm per lIIIn2,
It has been discovered that there is no sticking during printing, and the dirt on the thermal head can be self-cleaned by the film protrusions during non-printing, that is, during unheated plate making feeding, and also to use such a film. It was discovered that the holding power of the overcoat layer can be improved, the bleed speed can be slowed down even if the overcoat layer is left to stand, and the bleed equilibrium point can be significantly improved compared to conventional films, leading to the present invention. Ta.

That is, the present invention provides a film for heat-sensitive stencil printing base paper in which the film has surface protrusions of less than 1 to 2 μm.
500 or more per area and 2μm or more of surface protrusions
This is a film for heat-sensitive stencil printing base paper in which the number of particles per IIm2 is 10 or less.

In the present invention, if the protrusions on the film surface are 2 μm or more, uneven heat transfer will occur even if the pressure of the platen facing the thermal head is increased, resulting in uneven perforation, resulting in poor resolution, decreased thermal sensitivity, etc. However, if the number of protrusions of 2 μm or more is 10 pieces/m+s 2 or less, there is no problem in actual purchase.

Moreover, if the protrusion is less than 1 μm, a sufficient cleaning effect will not be achieved and sticks will occur. The same applies if the number of protrusions is less than 500/2 songs.

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

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Si02 particles with an average particle diameter of 1.5 μm were uniformly distributed at 0.2w.
Polyethylene phthalate dispersed in t% was melt-extruded, cooled and solidified to form a sheet, which was then biaxially stretched to obtain a 2.0 μm film.

Example 2 Polyethylene phthalate in which 0.12 wt % of C a C 0 3 particles having an average particle size of 2.3 μm were uniformly dispersed was processed in the same manner as in Example 1 to obtain a 1.9 μm film.

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

Comparative Example 2 6 Polyethylene phthalate in which 0.2 vt% of SiO2 particles with an average particle size of 1.5 μm were uniformly dispersed was processed in the same manner as in Comparative Example 1 to obtain a 2.1 μm film.

Using the films obtained in each of the above examples and comparative examples,
This was laminated onto Japanese paper of approximately 10μ to prepare a heat-sensitive stencil printing base paper. This was subjected to stencil printing using a thermal stencil printing machine Puriport SS930. The results are shown in the table below.

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

stickiness ◎...Stick does not occur at all.

○: Sticking occurs slightly, but does not affect the image.

×: Sticking occurs and plate making is not possible.

Over layer survival rate after storage at 50℃ for 4 weeks in roll state compared to the initial stage ◎...
50% or more remaining ○...30-50% remaining ◎・・・(
Both A) and (B) are good.

0...(A) is good, but (B) is poor.

×...Both (A) and (B) are defective.

[Effects of the Invention] As explained above, by using the film of the present invention, there is no sticking during printing, and even if the overcoat layer is left to overlap, it is difficult to bleed onto the support, and the image It is possible to obtain thermal stencil printing base paper of excellent quality.

Claims (1)

[Claims] In a film for heat-sensitive stencil printing base paper, the film has 1
~500 or more surface protrusions of less than 2 μm per mm^2, and 10 surface protrusions of 2 μm or more per mm^2
A film for heat-sensitive stencil printing base paper, characterized in that the film is less than or equal to 1.