JPH0555075B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrostatic recording film. Recently, with the development of CAD and CAM, the output is increasingly being recorded using electrostatic recording. The present invention relates to an electrostatic recording film using a plastic film as a support. [Prior Art] An electrostatic recording film is composed of three layers: a support, a conductive layer, and a dielectric layer. Conventionally, the conductive layer is made of a polymer electrolyte such as a cationic polymer or anionic polymer, or an ionic surfactant. It was a hygroscopic polymer with inorganic ions added to it. However, the conductivity of these ionic materials is dependent on humidity, and when the humidity is low, the conductivity decreases.
It no longer functions sufficiently as a conductive layer, and the electrostatically recorded image becomes unclear. For this reason, an electron conductive material that does not depend on humidity changes was considered for the conductive layer. JP-A-55-133455 discloses the use of a polyaniline material, but this material is not preferred because it is colored. JP-A-51-25140, JP-A-52-113224,
JP-A-53-85590 describes dispersing conductive metal oxide particles in a binder and applying it to paper or the like. However, the conductive metal oxide particles in the above patent have a microscopic size and cause light scattering, making them unsuitable for use in transparent films. By improving this, JP-A-56-143443 describes that both conductivity and transparency can be satisfied by using conductive metal oxide particles of 0.5μ or less as a conductive layer. . However, when fine particles of a conductive metal oxide are dispersed in a binder and used in the conductive layer, the conductivity is often lowered due to the effect of coating the dielectric layer. In other words, when the coating solvent of the conductive layer interacts with the binder of the conductive layer, when the dielectric layer is coated, the solvent in the coating solution permeates into the conductive layer, reducing the conductivity of the conductive layer from its initial value. It often happens. This tendency is particularly remarkable as the conductive metal oxide becomes finer particles. [Object of the Invention] It is an object of the present invention to prevent the above-mentioned drawback from decreasing the conductivity of the conductive layer during application of the dielectric layer. [Means for Solving the Problems] It has been found that the above problems can be solved by using a water-soluble polymer as a binder for the conductive layer and using an organic solvent-soluble polymer for the dielectric layer.
That is, it has been found that when the dielectric layer is coated with an organic solvent, the problem can be solved by using a water-soluble polymer as a binder for the conductive layer, which can prevent penetration of the organic solvent. The water-soluble polymer of the present invention does not need to have ionic conductivity as described in Japanese Patent Publication No. 58-27494, and there is no need to add an electrolyte such as a salt to the water-soluble polymer layer. On the other hand, it is not preferable to add a large amount of electrolyte such as salt because it deteriorates the stability of the dispersed fine particles. The water-soluble polymer used in the present invention is gelatin or water-soluble polyester. A crosslinking agent may be added to these water-soluble materials. The conductive substance used in the conductive layer of the present invention is preferably a conductive crystalline metal oxide, and in order to maintain transparency, the average particle size is preferably 0.5 μm or less, preferably 0.2 μm or less. Examples of conductive crystalline metal oxides include ZnO, SiO ₂ ,
SnO ₂ , TiO ₂ , Al ₂ O ₃ , In ₂ O ₃ , MgO, BaO,
MoO ₃ etc. or composite oxides thereof. The support used in the present invention is a transparent plastic film, and examples thereof include polyethylene terephthalate, polycarbonate, cellulose triacetate, polyether sulfone, polyvinyl chloride, polystyrene, polyethylene, polypropylene, and the like. The conductive layer may be applied directly to the support, or
Corona discharge treatment, glow discharge treatment,
Flame treatment or ultraviolet treatment may be performed, and an adhesive layer between the conductive layer and the support layer may be made of, for example, vinylidene chloride copolymer, styrene-butadiene copolymer,
Vinyl chloride copolymer, vinyl acetate copolymer,
Acrylic ester copolymer, polyester,
A layer of polyurethane, gelatin, etc. may also be provided. Since the dielectric layer must have insulating properties, it is not preferable to use ionic polymers or polymers that dissociate upon absorption of moisture, and it is necessary that the dielectric layer does not contain large amounts of ionic substances and is soluble in organic solvents. Polymers are preferred. Examples of organic solvent-soluble polymers include vinyl chloride, vinylidene chloride, styrene, methylstyrene, butazine, alkyl esters of acrylic acid (alkyl groups from C ₁ to C ₄ ), and alkyl esters of methacrylic acid (alkyl groups from C ₁ to C ₄ ). (alkyl group), homopolymers or copolymers such as vinyl acetate, acrylonitrile, isobutylene, allyl acetate, soluble polyesters, polycarbonates,
Cellulose derivatives such as ethylcellulose, cellulose acetate, cellulose propionate,
Examples include polyvinyl butyral and polyvinyl formal. Examples of coating solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, ethers such as tetrahydrofuran and dioxane, esters such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate, and chlorinated dichloromethane and dichloroethane. Examples include hydrocarbons and alcohols such as methanol, ethanol, and propanol. The heat of the dielectric layer is preferably about 1μ to 5μ and 3μ
It is preferable to add a matting agent of about 10 μm. Examples will be described below, and the surface resistivity was measured using parallel electrodes and an electrometer manufactured by Keithley in an atmosphere of 23° C. and 50% relative humidity. Also, when applying the dielectric, both sides of the conductive layer should be approximately
It was coated so that a thickness of 10 m/m remained, and this part was used to determine whether the resistivity of the conductive layer would change when the dielectric layer was coated. Example 1 A biaxially stretched and heat-set polyethylene terephthalate film with a thickness of 100μ was subjected to glow discharge treatment, a liquid with the following composition was applied as a conductive layer, and the film was heated at 130℃ for 10 minutes.
Dry for a minute. Gelatin 15 (parts by weight) Antimony-doped tin oxide with an average particle size of 0.2μ (the amount of antimony is 5% based on tin oxide)
55 (〃) Sodium salt of 2,4-dichloro-6-hydroxy-s-triazine 0.03 (〃) Water 1000 (〃) On top of this layer, as a dielectric layer, apply a liquid with the following composition to a dry film thickness of 2.5μ. It was applied and dried at 120℃ for 10 minutes. Vylon (manufactured by Toyobo) 50 (manufactured by Toyobo) Rosin ester (manufactured by Arakawa Chemical) 20 Ethyl ethyl ketone 700 Cyclohexanone 100 Ethyl acetate 200 The surface resistivity is shown in Table 1. Example 2 A biaxially stretched and heat-set polyethylene terephthalate film with a thickness of 100 μm was subjected to a corona discharge treatment, and a liquid having the following composition was applied as an undercoat layer, followed by drying at 130° C. for 10 minutes. Vinylidene chloride/ethyl acrylate/acrylic acid copolymer latex (copolymerization ratio 85/10/
5. Solid content 25%) 20 (parts by weight) Water 1000 (〃) Next, a conductive layer and a dielectric layer were sequentially coated in the same manner as in Example 1. The surface resistivity is shown in Table 1. Comparative Example A biaxially stretched and heat-set polyethylene terephthalate film with a thickness of 100 μm was subjected to corona discharge treatment, and a liquid having the following composition was applied as a conductive layer, followed by drying at 130° C. for 10 minutes. Vinylidene chloride/ethyl acrylate/acrylic acid copolymer latex (copolymerization ratio 85/10/
5. Solid content 25%) 40 (parts by weight) Tin oxide doped with antimony with an average particle size of 0.2μ (the amount of antimony is 5% relative to tin oxide)
50 (〃) Water 1000 Next, a dielectric layer similar to that in Example 1 was applied. Table 1 shows the changes in surface resistivity.

[Table] As can be seen from Table 1, when a water-soluble polymer was used as a binder, there was almost no change in surface resistivity even after coating the dielectric layer, but when a vinylidene chloride copolymer was used, The effect was recognized, with an increase of approximately 4 digits.

Claims (1)

[Claims] 1. In an electrostatic recording film comprising at least a substantially transparent support, a conductive layer, and a dielectric layer,
A static electrostatic device characterized in that the conductive layer is made of conductive metal oxide particles with an average particle size of 0.5μ or less and a water-soluble polymer selected from gelatin or water-soluble polyester, and the dielectric layer is made of an organic solvent-soluble polymer. Film for electronic recording.