JPS584157A - Corona discharging method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona discharge method, particularly for coating a hydrophilic layer such as a photographic emulsion layer on a support having a hydrophobic surface.
The present invention relates to a corona discharge method suitable for use in hydrophilizing said hydrophobic surfaces.

Photographic light-sensitive materials are generally produced by coating a support with at least one silver halide emulsion layer, and various supports with hydrophobic surfaces such as polyethylene-coated paper and polyethylene terephthalate film are used depending on the purpose. is used. On the other hand, since the photographic layer applied to the surface of these supports is usually hydrophilic, it will not adhere even if applied directly to a hydrophobic surface, so it is common practice to make the hydrophobic surface of the support hydrophilic before coating. be. Methods for making it hydrophilic include the so-called subbing method, which involves applying a composition that can adhere to a hydrophobic surface and also adhere to a hydrophilic layer, a corona discharge treatment method, a fire treatment method, an ultraviolet irradiation method, and a glow discharge treatment. Although there are many methods, corona discharge treatment has been widely used in recent years, especially for polyethylene-coated paper, from practical aspects such as operability, safety, and cost.

However, the corona discharge treatment method also has various drawbacks. One of the major problems in the production of photographic light-sensitive materials is that coating unevenness occurs in coated photographic layers due to non-uniform charging caused by uneven discharge. Since a photographic layer is generally a thin layer of several microns to several tens of microns, uneven coating has a large adverse effect on photographic properties and significantly reduces the quality of photographic products.

Conventionally, methods to eliminate or reduce such coating unevenness include improving the coating solution to make it less susceptible to the effects of uneven charging due to corona discharge, and applying the coating solution after corona discharge treatment. There are methods to equalize the charging state by leaving it for a certain period of time, and methods to equalize the charging state by applying electricity to the corona-charged surface with a charging device after corona discharge treatment and before applying the coating liquid. Improvements from liquids are not foolproof as there are many other constraints, and it is difficult to eliminate coating unevenness.

The method of leaving the product for a certain period of time after corona discharge treatment increases the number of intermediate products and the number of steps, which increases costs. Furthermore, the charging method has the disadvantage that uniformity of charging is insufficient.

An object of the present invention is to provide a corona discharge method that does not have the drawbacks of conventional methods and can obtain uniform corona charging.

Another object of the present invention is to provide a corona discharge method by which a hydrophilic coating layer without uneven coating can be obtained on a hydrophobic support made hydrophilic by corona discharge treatment.

FIG. 1 schematically shows the pattern of corona discharge.

The earth roll 1 usually has an insulating coating layer 3 made of an insulating material such as silicone rubber on a grounded metal roll 2.
A material having the following is used. Corona discharge electrode 4
Generally, metals such as aluminum and iron are used. A discharge 6 occurs in the discharge interval between the corona discharge electrode 4 and the support 5 with a hydrophobic surface which runs on the earth roll 1.

The object of the present invention is achieved by using an earth roll or roll electrode whose surface is coated with an insulating coating layer containing a high dielectric constant material.

Since the present invention makes the corona discharge itself uniform and obtains uniform charging, unlike the conventional method described above in which non-uniform charging is removed by some means after the corona discharge treatment, non-uniform charging is obtained. There is no inconvenience caused by removing sex.

One embodiment of the present invention will be explained with reference to FIG. 1. As the insulating coating layer 3, a layer containing a high dielectric constant substance is used.

Another aspect of the present invention is to use a roll electrode (not shown) as a corona discharge electrode in place of the electrode 4 in FIG. layer may be omitted), a layer containing a high dielectric constant material is used as the insulating coating layer.

The high dielectric constant substance used in the present invention is preferably in powder form with a dielectric constant of 20 or more, and the powder particles have a diameter of about 50 μm or less, preferably about 10 μm or less. Preferred high dielectric constant materials for use in the present invention include barium titanate porcelain (relative permittivity 1150-3200), zirconium titanate porcelain (relative permittivity 55), and titanium porcelain (relative permittivity 30-90).
Examples include, but are not limited to, ceramic raw materials such as: Among these high dielectric constant materials, barium titanate porcelain is most preferred.

The content of the high dielectric constant material in the insulating coating layer is usually about 0.00 parts by weight of the insulating material forming the insulating coating layer.
The content is preferably in the range of 3 to about 3 parts by weight. As the content increases, the uniformity of corona charging improves, but if the content is too large, the durability of the insulating coating layer deteriorates, and the fraction of the high dielectric constant material becomes uneven, so it is not practical. It is sufficient to take these into consideration when making a decision.

As the insulating material forming the insulating coating layer, rubbers such as silicone rubber, ethylene propylene rubber, . The dielectric constant of these rubbers is usually about 8 or less.

Note that the relative permittivity referred to in the present invention indicates a value measured at a frequency of 100 KHz.

The corona discharge method of the present invention is suitable as a hydrophilic method for coating a support having a hydrophobic surface with a thin hydrophilic layer that requires strict uniformity, such as a photographic emulsion layer.

Supports with hydrophobic surfaces to which the present invention can be applied include polyolefin polymers such as polyethylene, polypropylene, and ethylene-butene copolymers laminated on both or one side of a substrate such as paper, other synthetic films, or metal foils. Although this is a typical example, it can also be applied to other hydrophobic films such as polyethylene terephthalate and polystyrene. These hydrophobic polymer layers may contain pigments such as titanium dioxide and carbon black, and other additives such as dyes, brighteners, and antistatic agents. The hydrophobic surface of these supports may be roughened.

Coating layers applied to a support having a hydrophobic surface by the corona discharge method of the present invention include silver chloride, silver bromide, silver chlorobromide, silver iodobromide, etc., silver halide emulsion layers, and halation layers. A typical example is a layer containing hydrophilic colloids such as a prevention layer and a subbing layer. Hydrophilic colloids include gelatin, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl methyl ether,
A wide variety of materials are used, such as methyl vinyl ether-maleic anhydride copolymer and styrene-maleic anhydride copolymer. These hydrophilic colloid-containing layers contain developing agents such as hydroquinone, 1-phenyl-3-pyrazolidone,
Pigments and matting agents such as carbon black, titanium dioxide, silica, talc, clay, barium sulfate, zinc oxide, and rice starch, hardening agents such as formalin and chromium bright bread, wetting agents, couplers, and silver precipitates for silver complex diffusion transfer. Nuclei etc. are included as necessary.

Application methods to which the present invention is applied include dip method,
There are many methods such as the air knife method, kiss method, bead method, and curtain method, but high-speed coating methods such as the bead method and curtain method are advantageous. In carrying out the present invention, the hydrophilic organic colloid solution is applied as a single liquid layer or a plurality of liquid layers.

Next, examples of the present invention will be shown, but the present invention is not limited thereto.

Example In the corona discharge device shown in Fig. 1, the surface of the iron metal roll was coated with barium titanate having an average particle size of about 5 μm in the amount shown in the table below per 1 part by weight of the insulating material. Contains porcelain evenly distributed.

An earth roll coated with an insulating coating layer was used. On this ground roll, a support made of a paper substrate with a basis weight of 160 f/m' and both sides covered with a polyethylene layer of 30μ thickness was placed on the ground roll.
While traveling in the direction of the arrow at a speed of 0 m/min, the corona frequency was 110 KH2 and the discharge current was 1. Corona discharge was performed with OA. The thickness of the insulating coating layer was all 4fi, and the distance between the tip of the discharge electrode and the surface of the support was 500μ.

In order to observe the corona charging state of the surface of the support polyethylene layer after corona discharge treatment, the sample subjected to corona discharge treatment was immersed in an electrophotographic liquid developer containing carbon black as a coloring pigment at a concentration of 0.5%. The state of corona charging was determined based on the state of coloring of the surface of the polyethylene layer by toner, and the results are shown in the table below.

In the table, the best corona charging condition with no uneven charging is rated as 1, and the poor one with uneven charging as 4 is rated as 4.
Values are based on the stepwise method.

From the table above, it can be seen that when the insulating coating layer of the earth roll contains a high dielectric constant substance, uneven corona charging on the surface of the polyethylene layer is improved and uniform corona charging can be obtained.

Next, a gelatin-silver halide emulsion was coated on the corona-charged surface of the support immediately after corona discharge treatment in exactly the same manner as in the above method of this example. In sample N11L1, coating unevenness occurred over the entire surface, but in sample No. 2, coating unevenness was observed only partially.

Sample No. 3 was in good condition with almost no noticeable coating unevenness, and Samples No. 4 to 6 were in very good coating condition.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically explaining the pattern of corona discharge. 1... Earth roll 2... Metal roll of the earth roll 3...
...Anis roll insulating coating layer 4-1...Corona discharge electrode 5...Support having a hydrophobic surface 6...
...Discharge procedure amendment (voluntary) June 2z, 19801, Case description 1982 Patent Application No. 1018822, Name of the invention Corona discharge method 3, Person making the amendment Relationship with the case Patent Applicant Address: 4-2 Shiratama-chome, Maruno, Chiyoda-ku, Tokyo Name (598 En 1-4, Goki Co., Ltd.; Agent Address: Inside Mitsubishi Paper Mills Co., Ltd., 3-4-2 Marunouchi, Chiyoda-ku, Tokyo 100) 5. Date of amendment order ip Year Month Day As shown in the attached sheet 1. Specification page 5 lines 8-14 1 Another aspect of the present invention is...
"Use a substance that contains" was corrected as follows: "Another aspect of the present invention is that when a roll electrode (not shown, but of a similar form to the earth roll of FIG. 1) is used as the corona discharge electrode instead of the electrode 4 of FIG. An insulating coating layer containing a high dielectric material is provided on the electrode surface. However, in this case, the earth roll may not have an insulating coating layer. In the present invention, the thickness of the insulating coating layer is not particularly limited, but Usually, a range of about 1 to 10 0, preferably about 2 to qm'a, is used. If the thickness is too thin, dielectric breakdown will easily occur during corona discharge, and the durability of the insulating layer will be shortened due to deterioration of the physical properties of the rubber over time. In addition, if the part is too thick, it is not only disadvantageous in terms of cost but also deteriorates the uniformity of discharge, which is not desirable.'' 2. Specification, page 6, line 2, ``Ceramic raw material.'' was corrected to "ceramic". (1) A corona discharge method characterized by using an earth roll or a roll electrode that coats the surface of an insulating coating layer 1 metal roll containing a high dielectric constant material. (2) The dielectric constant of the high dielectric constant material is 20 or more. (4) Claim 1, wherein the high dielectric constant material is at least one selected from barium titanate porcelain, zirconium titanate porcelain, and titanium porcelain. Corona discharge method described in item 8.'' 11 1982-4157 (5) 355-

Claims (1)

[Scope of Claims] (1) A corona discharge method characterized by using an earth roll or roll electrode whose surface is coated with an insulating coating layer containing a high dielectric constant substance. ('4) The corona discharge method according to claim 1, wherein the high dielectric constant material has a dielectric constant of 20 or more. (3) The high dielectric constant material is made of barium titanate porcelain, zirconium titanate porcelain, titanium porcelain. The corona discharge method according to each claim, which is at least one selected corona discharge method.