JP2999883B2 - Masking film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a masking film for plate making, and more particularly to a masking film in which a dimensional change due to humidity is reduced.

[0002]

2. Description of the Related Art In a conventional masking film, a binder resin mainly composed of a thermoplastic synthetic resin and a dye / pigment are dissolved or dissolved in a solvent on one side of a plastic film such as a polyethylene terephthalate film. The dispersed solution was applied and dried to form a light-shielding release layer, and the light-shielding release layer was formed directly on one surface of the plastic film.

[0003] A polyester such as polyethylene terephthalate is used for a plastic film because of factors such as optical suitability (transparency), mechanical strength, heat resistance, versatility and low cost. In recent years, precise pattern cutting has been performed by an automatic drawing machine. Along with the cutting work using a high-precision automatic drawing machine, the expansion and contraction of the masking film due to humidity, which was not a problem in the manual work until then, has become apparent. In other words, when drawing for a long time, if the humidity of the working environment changes during that time, the masking film expands and contracts, the cutting line discrepancy occurs before and after, and the phenomenon that often becomes useless as a mask occurs. I have.

[0004] When such inconvenience occurs, the drawing must be started again from the beginning, resulting in a great decrease in work efficiency. In addition, depending on the storage method, a part of the film is stretched due to moisture absorption due to a change in environmental humidity, the flatness is not maintained, and the film is in a wavy state. Was.

[0005] While a small dimensional change rate due to humidity plastic is also present, optical suitability (transparency), mechanical strength, heat resistance, solvent resistance of any element, could not be used in place of the polyester. Conventionally, to reduce the effects of humidity, expensive air-conditioning systems were introduced to stabilize the work environment (stabilize the humidity). The development of was desired.

[0006] In the field of packaging materials, it is widely used to provide a film of a substance having a low water vapor transmission rate on the surface of a plastic film for the purpose of preventing moisture permeation, preventing food from drying, and preventing odor from entering. However, in order to stabilize the dimensions of the masking film against humidity, a film made of a substance having a low water vapor transmission rate has not been provided on the plastic film.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a masking film which is less affected by humidity.

[0008]

Means for Solving the Problems To achieve such an object, the present inventors have made intensive studies and as a result, by covering both surfaces of a plastic film with a film of a substance having a low water vapor transmission rate, the influence of humidity is reduced. And found that the present invention can be reduced to a very low level, and completed the present invention. The masking film according to the present invention comprises a film of a substance having a lower water vapor permeability than the plastic film provided on both surfaces of the plastic film, and a light-shielding release layer provided on at least one of the films.

That is, a substance having a low water vapor transmission rate transmits only a small amount of water vapor from the atmosphere, and thus limits the amount of water vapor reaching the central plastic film. This is because dimensions can be maintained. Examples of the plastic film used in the present invention include polyethylene terephthalate, polypropylene, polycarbonate, polyvinyl chloride, polyethylene, and polymethacrylate, but are not particularly limited thereto.

The substance having a low water vapor transmission rate used in the present invention includes silicon and aluminum, titanium, selenium, magnesium, barium, zinc, tin, indium,
Inorganic metal compounds such as calcium, tantalum, zirconium, thorium, thallium, etc., or halides alone or in mixtures, ceramics such as glass,
Copolymer of vinylidene chloride with vinyl chloride, acrylonitrile or acrylic, polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkylvinyl ether copolymer ( Synthetic resins such as PFA) are preferred.

Among these substances, inorganic metal compounds and ceramics have a high effect of restricting water vapor permeation even at a thin film thickness as compared with synthetic resins, and hardly dissolve or swell in organic solvents and the like. It is particularly excellent as a substance having a low water vapor transmission rate, for example, there is no restriction on paint design when providing a light-shielding release layer on this film.

The water vapor transmission rate of these substances is determined by using an inorganic metal compound (polyethylene terephthalate 12 µm
If as an example what was deposited ₂ 0.04 .mu.m) is approximately 1g / m ² / 24hrs, water vapor transmission rate is significantly reduced as compared to 40g / m ² / 24hrs only polyethylene terephthalate, synthetic resin in each case, approximately in the thickness 100μm 0.2~1.5g / m ^2/24
hrs and the thickness of polyethylene terephthalate is 10
It has become a little water vapor transmission rate as compared with about 6.9g / m ² / 24hrs at 0 .mu.m.

The method of providing a uniform film of the above-mentioned substance having a low water vapor transmission rate on the surface of a plastic film includes an inorganic metal compound and, in the case of ceramics, a vacuum evaporation method.
A sputtering method, an ion plating method, or the like is used. In the case of synthetic resins, a method in which they are dissolved in an organic solvent and applied and dried, a method in which they are hot-melted and extruded, a method in which a separately prepared synthetic resin film is laminated using an adhesive, and a method in which vacuum is applied Known methods such as an evaporation method and a sputtering method are used.

The thickness of the film of a substance having a low water vapor transmission rate provided on the surface of the plastic film by the above-described method is particularly low in the case of inorganic metal compounds and ceramics having a low water vapor transmission rate. From 0.01 μm to 0.1 μm from the viewpoint that the film can follow the flexibility of the plastic film and the film can be prevented from falling off due to cracks.
The range of 5 μm is suitable, and more preferably 0.02 μm
From 0.3 to 0.3 μm.

[0015] In the case of a synthetic resin, a range of 1 µm to 50 µm is preferable because sufficient dimensional stability is obtained and the masking film is not too thick and can be easily handled. In order to enhance the adhesion of the substance having a low water vapor transmission rate to the plastic film, it is preferable to perform a pre-treatment such as a discharge treatment or a chemical treatment or an anchor treatment in advance on the film surface in order to improve the adhesion.

The light-shielding release layer provided on at least one of the films of the substance having a low water vapor transmission rate is uniformly coated with a solution in which a binder resin mainly composed of a thermoplastic synthetic resin and a dye / pigment are dissolved or dispersed in a solvent. It can be dried. As thermoplastic synthetic resins, vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinylidene chloride copolymer, vinyl chloride / acrylate copolymer, vinyl chloride / vinyl acetate copolymer
Vinyl chloride copolymer such as vinyl acetate / maleic acid copolymer; acrylonitrile / butadiene rubber; cellulose such as nitrocellulose and acetyl cellulose; polyvinyl acetal such as polyvinyl formal and polyvinyl butyral; acrylic resin; polyvinylidene chloride; An ethylene-vinyl acetate copolymer; an acrylic rubber, an acrylonitrile-butadiene rubber; a polyurethane or the like, if necessary, in a mixture of two or more, but is not limited thereto.

As the dye / pigment, the wavelength is 290-580 n
An organic or inorganic substance capable of blocking light of m is used. The content of the dye / pigment with respect to the binder resin is determined by the thickness of the light-shielding release layer, and is usually added so as to have an optical density of 2.5 or more in light transmittance in the light-shielding light wavelength region. In addition, an inorganic or organic filler can be added to the light-shielding release layer as a matting agent, if necessary, to prevent blocking. Further, an antistatic agent may be added.

According to the above-mentioned method, the thickness of the light-shielding release layer provided on at least one of the films of the substance having a low water vapor transmission rate can ensure that the film strength of the light-shielding release layer upon peeling is not insufficient. In the formation, the range of 5 μm to 60 μm, which allows efficient work of coating and drying, is suitable, and more preferably, it is in the range of 10 μm to 40 μm. In order to adjust the adhesion strength of the light-shielding release layer to a film of a substance having a low water vapor transmission rate, it is preferable to previously perform a pretreatment such as a discharge treatment or a chemical treatment or an anchor treatment on the film surface.

[0019]

The present invention will be further described with reference to the following examples.
The present invention is not limited to these examples. Example 1 As shown in FIG. 1, on both sides of a 100 μm thick polyethylene terephthalate film which is a plastic film 1, a material film 2, 2 ′ having a low water vapor transmission rate of about 0.04 μm was formed by a sputtering method.
The SiO ₂ film as uniformly provided. Further, as the light-shielding release layer 3, 64 parts by weight of vinyl chloride / vinyl acetate copolymer, 27 parts by weight of acrylonitrile / butadiene rubber,
The Neozapon Orange RE (oil soluble dye) 5 parts by weight, 300 parts by weight of methyl ethyl ketone, 100 parts by weight of toluene, a solution dissolved in ethyl cellosolve 10 parts by weight (light blocking release layer forming solution), SiO ₂ film sided 2 Was uniformly applied and dried so that the dried film became 25 μm to obtain a masking film.

The humidity expansion and contraction rate of this masking film is
J-TAPPI. It was 0.2 × 10 ^{-5 as} measured by the measurement method of No. 28 m, and the expansion and contraction ratio was about 1/5 as compared with the masking film of the comparative example described later. Example 2 Thickness 1 as Plastic Film 1
On both sides of a polyethylene terephthalate film of 00 μm, vinylidene chloride dissolved in methyl ethyl ketone at 10% by weight as material films 2 and 2 ′ having a low water vapor transmission rate.
The acrylonitrile copolymer is applied and dried, and about 5
A uniform coating of μm was provided. Further, as the light-shielding release layer 3, a coating solution in which 82 parts by weight of alcohol-soluble nylon and 9 parts by weight of Spiron Red GEH are dissolved in 730 parts by weight of denatured alcohol is dried on one surface 2 of a vinylidene chloride-acrylonitrile copolymer film. A masking film was obtained by uniformly coating and drying so that the film thickness became 25 μm.

The humidity expansion and contraction rate of this masking film was 0.3 × 10 ^-5 , which was about 1/3 that of the masking film of the comparative example described later. Example 3 Thickness 1 as Plastic Film 1
Quartz glass was sputtered on both surfaces of the 00 μm polyethylene terephthalate film as the material films 2 and 2 ′ having a low water vapor transmission rate, and a uniform film of about 0.05 μm was provided. Further, as the light-shielding release layer 3, the solution for forming a light-shielding release layer used in Example 1 was uniformly applied onto one surface of the quartz glass film 2 so as to have a dry film thickness of 25 μm and dried to form a masking film. Obtained.

The humidity expansion and contraction rate of this masking film was 0.2 × 10 ^-5 , which was about 1/5 that of the masking film of the comparative example described later. [Comparative Example] Thickness 100 as plastic film 1
μm polyethylene terephthalate film on one side,
As a light-shielding release layer, the solution for forming a light-shielding release layer used in Example 1 was uniformly applied and dried so that the dried film had a thickness of 25 μm to obtain a masking film.

The humidity expansion and contraction rate of this masking film is as follows:
It was 1.0 × 10 ⁻⁵ .

[0024]

[Table 1]

As is clear from Table 1, the masking film of the present invention has a smaller humidity expansion / contraction ratio than the conventional masking film, and thus is not easily affected by humidity not only during plate making but also during storage. Flatness can be maintained.

[0026]

As is clear from the above examples, the masking film of the present invention is less susceptible to humidity than the conventionally used masking film, so that the dimensional change and the irregularity of the flatness are unclear. Such a process does not occur, and a plate making operation requiring high dimensional accuracy can be performed under a normal working environment.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a masking film according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Plastic film 2, 2 '... Coating of the substance with low water vapor transmission rate 3 ... Light-shielding release layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08J 7/04 C08J 7/04 Z

Claims (1)

(57) [Claims] 1. A masking film comprising: a film of a substance having a lower water vapor transmission rate than said plastic film; and a light-shielding release layer provided on at least one of said films.