JPH0761748B2 - Biaxially stretched polyethylene naphthalate film for heat-sensitive stencil printing base paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a film for heat-sensitive stencil printing base paper. More specifically, the present invention relates to improvement of perforation property, resolution at the time of printing, and durability of a film for heat sensitive stencil printing base paper.

(B) Conventional technology Conventionally, as a base paper for heat sensitive stencil printing, a porous thin paper (natural fiber, synthetic fiber, semi-synthetic fiber, and a mixture thereof) is applied to a thermoplastic polymer film by heat or an adhesive. Laminated ones are known.

The principle of punching the base paper will be described with reference to FIG. Original 3 which is a subject on the side of the film 1 for heat-sensitive stencil printing base paper in which porous thin paper 2 is laminated on thermoplastic polymer film 1.
To adhere. When flash light irradiation is performed from the side of the porous thin paper 2, the light rays that have passed through the raw paper are absorbed by the black image portion of the original, and that portion generates heat. Accordingly, the portion of the film 1 which is in close contact with the original portion of the original document is melted and shrunk to cause perforation.

The thermoplastic polymer film constituting the above heat-sensitive stencil printing base paper is required to have the following three characteristics.

1) A film with good heat piercing properties. That is, a film having a sufficient heat shrinkage ratio that melts and shrinks with an appropriate amount of heat and that can obtain perforations of an appropriate size so that an image during printing becomes clear.

2) A film having strength and elastic modulus that can withstand laminating with porous thin paper and printing work. Conventionally,
The film used for the base paper is
A very thin film (usually 20μ or less) is used. In order to maintain good workability and durability during the production of base paper and during printing, the film has sufficient strength, elastic modulus, etc. Strength is needed.

3) A film that can withstand organic solvents such as toluene and xylene used for printing ink for a long time.

Conventionally, as the thermoplastic polymer film that constitutes the base paper for heat-sensitive stencil printing, polyethylene, polypropylene, polystyrene, polyvinyl chloride, vinylidene chloride / vinyl chloride copolymer, propylene / ethylene copolymer, ethylene / vinyl acetate copolymer, etc. Various films have been proposed. However, a film which fully satisfies all the above three characteristics has not been obtained. For example, polyvinyl chloride, vinylidene chloride, and vinyl chloride copolymers have excellent thermal piercing properties, but their strength and elastic modulus are not sufficient, so that they are poor in aptitude for attachment to a support and durability, and they are also organic resistant. It is also not solvent-based. Polyethylene, polypropylene, and propylene / ethylene copolymer are excellent in organic solvent resistance, but still have insufficient strength and elastic modulus, and also have poor thermal piercing property.

Therefore, it has recently been proposed to use a copolyester film containing polyethylene terephthalate as a main component for the purpose, and some improvements are being made. However, in the polyethylene terephthalate copolymer film,
It has been pointed out that when the composition is such that the heat piercing property is sufficiently obtained, especially in the case of thin count, the film has a slightly weak waist.

The present inventor has conducted extensive studies to provide a film that eliminates the above-mentioned drawbacks of the conventional heat-sensitive stencil printing base film, and as a result, a polyethylene naphthalate copolymer film having a certain heat of fusion, which satisfies all the above conditions. I found a thing.

(C) Problems to be solved by the invention In view of the above problems, an object of the present invention is to provide a film which solves the drawbacks of the conventional films for heat-sensitive stencil printing base paper. That is, an object of the present invention is to provide a film for heat-sensitive stencil printing base paper, which is excellent in thermal perforation properties, workability during base paper production and printing, and solvent resistance.

(D) Means for Solving Problems As a result of earnest studies to obtain a film free from such defects, the present inventor has found that a polyethylene naphthalate copolymer film having a specific heat of crystal fusion is a polyester film Among them, while maintaining strength, elastic modulus, solvent resistance,
It has been found that it has excellent heat piercing properties.

That is, the gist of the present invention is that the heat of crystal fusion of the film is 6 to 9c.
A biaxially stretched polyethylene naphthalate copolymer film for heat-sensitive stencil printing base paper, which is characterized in that it is al / g.

The present invention will be described in more detail below.

The polyethylene naphthalate copolymer referred to in the present invention,
Copolymers containing 75 mol% or more of polyethylene-2,6-naphthalate units, and the remaining less than 25 mol% are other polyesters. As the other monomer of the copolymerization component, all known ones can be used, and examples thereof include dicarboxylic acids such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,7-dicarboxylic acid or lower dicarboxylic acids. Oxycarboxylic acids such as alkyl esters and p-oxybenzoic acid, or lower alkyl esters thereof or propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, diethylene glycol, etc.
Examples thereof include polyhydric alcohols, polyalkylene glycols such as polyethylene glycol and polytetramethylene glycol. In addition, a polymerization regulator, a crystallization regulator, a plasticizer, a matting agent, a stabilizer, etc. may be added during the polymerization.

Also in the film of the present invention, slipperiness may be imparted by containing a fine inert compound. In one of such methods, a metal compound dissolved in the reaction system during the production of polyethylene naphthalate, for example, a phosphorus compound or the like is caused to act on a metal compound dissolved in the system after transesterification to deposit fine particles. There is a so-called precipitation particle method. However, since this method has a limited amount of precipitated particles, another method, that is, the so-called added particle method is preferably used.

That is, the additive particle method is a method in which polyester is blended with inert fine particles in any step from the polyester production step to the extrusion step before film formation, and examples of the inert fine particles include kaolin, talc, and carbonic acid. Magnesium, calcium carbonate, barium carbonate, calcium sulfate,
At least one metal compound selected from barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, lithium fluoride, and terephthalates such as Ca, Ba, Zn, and Mn. Alternatively, carbon black or the like can be used, but the present invention is not limited thereto.

The shape of the inactive compound may be spherical, lumpy or flat, and its hardness, specific gravity, color and the like are not particularly limited. The average particle size of the inactive compound is usually 0.1 to 10 μm, preferably 0.3 to 3 μm in an equivalent spherical system. The content of the film is 0.01 to 1% by weight, preferably 0.02 to 0.8% by weight, more preferably 0.03 to 0.5% by weight.

Further, since the polyethylene naphthalate used in the present invention has poor mechanical properties when the degree of polymerization is too low, its intrinsic viscosity is preferably 0.40 or more, and more preferably 0.40 to 0.90.

If the heat of crystal fusion is 6 to 9 cal / g, the polyethylene naphthalate copolymer film of the present invention may be formed into a film by either the inflation simultaneous biaxial method or the stenter sequential biaxial method. May be.

In the present invention, the heat of crystal fusion of the polyethylene naphthalate copolymer film is 6 to 9 cal / g. Preferably 7-
It is 9 cal / g. A polyester film with a crystal melting heat of 9 cal / g or more requires a large amount of heat for perforation,
For example, even if the perforation is irradiated with a sufficient amount of heat, such a film usually has a small heat shrinkage ratio, so that the perforation having a required size cannot be obtained, and characters are thinned or there are many blurred portions during printing. On the other hand, the heat of crystal fusion of the film is 6 cal / g
The following polyester films have good thermal piercing properties, but do not have sufficient strength and elastic modulus and cannot withstand the work of laminating with porous thin paper and printing. For this reason, it has a good thermal puncture property, and has sufficient strength and elastic modulus, a polyethylene naphthalate copolymer film has a heat of crystal fusion of 6 cal / g or more, 9 cal / g or less, preferably 7 cal / g. Above, it is below 9cal / g.

The density of the polyethylene naphthalate copolymer in the present invention is 1.330 or more and 1.357 or less, preferably 1.330 or more and 1.350 or less.

The density of the polyester film in the present invention is 1.330 to
It is 1.357, preferably 1.330 to 1.350. When the film density is 1.357 or more, the heat shrinkage rate is small, the perforation of the required size cannot be formed when the flash light is irradiated, and the characters become thin and there are many blurred portions during printing, and a clear image cannot be obtained. On the other hand, when the film density is less than 1.330, the heat shrinkage rate is large and excessively large perforations are formed at the time of flash light irradiation, and when printing, characters such as “○”, “□” and figures, “●”,
The image tends to be unclear because of the tendency of "■".

Next, the film forming method of the present invention will be specifically described, but the present invention is not limited to this example as long as the necessary characteristics are satisfied.

Polyethylene naphthalate copolymer raw material containing fine particles such as kaolin and silica is dried and usually 240 to 320
A sheet is extruded from the extruder at a temperature in the range of ℃, and cooled to a temperature of 80 ℃ or less to give a substantially amorphous sheet. At that time, it is preferable to use a conventional electrostatic applied cooling method. Then, the sheet-like material is stretched in the machine direction and the transverse direction so that the area ratio is at least 4 times or more to obtain a biaxially oriented film, and the film is further processed at 100 to 210 ° C, preferably 110 ° C.
The polyester film of the present invention can be obtained by heat treatment at a temperature in the range of 180 ° C. In the process, 0.1 to 20% may be relaxed in the width direction and the longitudinal direction in the maximum temperature zone of heat treatment and / or the cooling zone at the heat treatment outlet.

(E) Effect of the Invention The polyethylene naphthalate copolymer film of the present invention is
By laminating porous thin paper on it in accordance with a conventional method, it has excellent heat piercing properties, workability during base paper production and printing, durability, and solvent resistance, and is stronger than polyethylene terephthalate copolymer film. A base paper for heat-sensitive stencil printing can be manufactured.

(F) Examples Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples as long as the gist thereof is not exceeded. In addition, the physical-property measuring method in the following examples is shown.

(1) Heat of Crystal Melting of Film Using a DSC-1 type self-recording differential calorimeter manufactured by Perkin-Elmer,
The sample amount was 7 mg, the temperature rising rate was 16 ° C./min, and the area method was used for conversion.

(2) Density of film Measured after standing in a carbon tetrachloride / n-heptane density gradient tube at 25 ° C for 6 hours.

Example 1 A polyethylene naphthalate copolymer of [η] = 0.62 in which the acid component was composed of 87 mol% of 2,6-naphthalenedicarboxylic acid and 13 mol% of terephthalic acid, and the glycol component was composed of 99 mol% of ethylene glycol and 1 mol% of diethylene glycol. The polymer was melt extruded to obtain an unstretched film. Then in the vertical direction
The film was stretched 4.0 times at 135 ° C. and 4.2 times at 140 ° C. in the transverse direction and heat set at 150 ° C. to obtain a 3 μ film. The physical properties of the film are shown in Table 1.

Comparative Example 1 Acid component is 90 mol% terephthalic acid and 10 mol% isophthalic acid, glycol component is 99 mol ethylene glycol
%, Diethylene glycol 1 mol% [η] = 0.62
The above polyester was melt extruded at 270 ° C. to obtain an unstretched sheet. Next, 4.0 times at 85 ° C in the vertical direction and 3.7 at 95 ° C in the horizontal direction.
The film was double-stretched and heat-set at 150 ° C. The thickness of the obtained film was 3 μm. The physical properties of the film are also shown in Table 1.

On the other hand, polyvinyl acetate was used as an adhesive on these polyester films, and they were attached to a polypropylene porous thin paper having a basis weight of 5 g / m ₂ . This was used as a base paper for plate making with a thermal flash plate making machine and imprinting was performed. As a result, in both cases, an extremely clear image was obtained without any problem at the time of producing the base paper and at the time of initial printing, but when printing a large number of sheets, the film of the example was stronger than the film of the comparative example as shown in Table 1. Since it was excellent in durability, it was extremely excellent in durability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining the perforation principle of a heat-sensitive stencil printing base paper, in which 1 is a thermoplastic polymer film,
2 is a porous thin paper, 3 is a document, and 4 is a light source.

Claims (2)

[Claims] 1. A biaxially stretched polyethylene naphthalate copolymer film for heat-sensitive stencil printing base paper, characterized in that the film has a heat of crystal fusion of 6 to 9 cal / g. 2. The film according to claim 1, wherein the density of the film is 1.330 or more and 1.357 or less.