JPS621537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corona discharge treatment apparatus, which is used to make a hydrophobic surface hydrophilic when a hydrophilic layer such as a photographic emulsion layer is coated on a support having a hydrophobic surface. This invention relates to a corona discharge treatment device suitable for.

Photographic light-sensitive materials are generally manufactured by coating at least one silver halide emulsion layer on a support, and various supports with hydrophobic surfaces such as polyethylene-coated paper and polyethylene terephthalate film are used depending on the purpose. It 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. Hydrophilization methods include a so-called subbing method in which a composition that can adhere to a hydrophobic surface and also adhere to a hydrophilic layer, a corona discharge treatment method, a flame treatment method,
There are various methods such as ultraviolet irradiation and glow discharge treatment, but in recent years corona discharge treatment has been widely used, 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 liquid to one that is less susceptible to uneven charging due to corona discharge, and applying the coating liquid for a certain period of time after corona discharge treatment until it is applied. There are methods to equalize the charging state by leaving it as it is, 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 solution. Not only are there many other constraints on improving the method, but it is also 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.

The present inventors have previously developed a grounding method in which the surface of a metal roll is coated with an insulating coating layer containing a high dielectric constant material as a method that does not have the drawbacks of these conventional methods and can obtain uniform corona charging. He discovered a corona discharge treatment method using rolls or roll electrodes and filed it as Japanese Patent Application No. 101832-1983. This corona discharge treatment method does not have the above-mentioned drawbacks of the conventional method and can obtain uniform corona charging. It has been found that when a roll electrode is used, the surface coating layer deteriorates significantly due to discharge and has poor durability compared to one whose surface is coated with an insulating coating layer that does not contain a high dielectric constant substance.

An object of the present invention is to provide a corona discharge treatment apparatus equipped with a ground roll or roll electrode that can obtain uniform charging, has little deterioration of the surface coating layer due to discharge, and has excellent durability.

Another object of the present invention is to provide a corona discharge treatment device equipped with an earth roll or roll electrode that does not have the drawbacks of conventional methods, can obtain uniform charging, does not cause deterioration of the surface coating layer due to discharge, and has excellent durability. is to provide.

The object of the present invention is to provide an earth roll or a roll electrode in which an insulating coating layer containing a high dielectric constant substance is provided on the surface of a metal roll, and an insulating coating layer not containing a high dielectric constant substance is further provided on the layer. This can be achieved by providing a corona discharge treatment device equipped with a corona discharge treatment device.

The present invention makes the corona discharge itself uniform to obtain uniform charging, and unlike the conventional method of removing non-uniform charging by some means after corona discharge treatment, the present invention eliminates non-uniform charging. There is no inconvenience caused by its removal.

One mode of use of the corona discharge treatment apparatus of the present invention is shown in FIG. 1 is earth roll and metal roll 2
It has a structure in which it has an insulating coating layer 3 containing a high dielectric constant substance on the surface thereof, and further has an insulating coating layer 4 not containing a high dielectric constant substance on the surface thereof. Reference numeral 5 represents a discharge electrode, which is usually made of metal such as aluminum, stainless steel, or iron. 6 is a web to be subjected to corona discharge treatment (for example, a support with a hydrophobic surface for photography), and 7 is a schematic representation of the discharge state. In another embodiment of the present invention, when a roll electrode having the same shape as the earth roll 1 is used in place of the discharge electrode 5 shown in FIG. 1, a metal roll with an exposed metal surface may be used as the earth roll.

In the present invention, rubbers such as silicone rubber, ethylene propylene rubber, and Hypalon are usually used as the insulating material forming the insulating coating layer (hereinafter simply referred to as upper layer) that does not contain a high dielectric constant material, but are not limited thereto. The dielectric constant of these rubbers is usually 8 or less.

The thickness of the upper layer is preferably as thin as possible, and is usually used in the range of 0.1 to 2 mm, particularly in the range of 0.1 to 1 mm.
A range of mm is preferred. If the layer thickness becomes thicker than this range, the uniformity of corona charging will deteriorate and uneven charging will occur.

The high dielectric constant material used in the present invention has a dielectric constant of 20
The above powder form is preferred, 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 (relative permittivity: 1150-3200), titanate-grade materials such as zirconium titanate (relative permittivity: 55), and ceramics such as titanium oxide (relative permittivity: 30-90). but not limited to. Among these high dielectric constant materials, barium titanate is most preferred.

The content of the high dielectric constant substance in the lower insulating coating layer is usually in the range of about 0.3 to about 3 parts by weight per 1 part by weight of the insulating coating layer forming the insulating coating layer. Good. As the content increases, the uniformity of corona charging improves, but if the content is too large, the physical properties of the insulating coating layer will deteriorate and the dispersion of the high dielectric constant material will become uneven, so these are not practical. The decision should be made taking into consideration.

Insulating substances that form the insulating coating layer include:
As with the upper layer, rubber such as silicone rubber, ethylene propylene rubber, or Hypalon is usually used.
Not limited to these.

The thickness of the lower insulating coating layer is usually about 1 to 10 mm.
It is preferably used in a range of 2 to 7 mm, but is not particularly limited.

In addition, the relative permittivity referred to in the present invention is at a frequency of 100KHz.
Indicates the value measured in

The corona discharge method of the present invention is suitable as a hydrophilization 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 having a hydrophobic surface 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. is a typical example, but it can also be applied to other hydrophobic films such as polyethylene terephthalate and polystyrene. These hydrophobic polymer layers contain pigments such as titanium dioxide and carbon black,
Other additives such as dyes, brighteners, and antistatic agents may also be contained. The hydrophobic surface of these supports may be roughened.

The coating layer applied to the support having a hydrophobic surface made hydrophilic by the corona discharge treatment apparatus of the present invention includes a silver halide emulsion such as silver chloride, silver bromide, silver chlorobromide, silver iodobromide, etc. Typical examples include various hydrophilic colloid-containing layers such as antihalation layers, subbing layers, and packing layers. Examples of hydrophilic colloids include gelatin, polyvinyl alcohol,
Various materials such as polyvinylpyrrolidone, polyacrylamide, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl methyl ether, methyl vinyl ether-maleic anhydride copolymer, styrene-maleic anhydride copolymer, etc. are used. These hydrophilic colloid-containing layers include developing agents such as hydroquinone and 1-phenyl-3-pyrazolidone, pigments and matting agents such as carbon black, titanium dioxide, silica, talc, clay, barium sulfate, zinc oxide, and rice starch. , a hardening agent such as formalin and chromium alum, a wetting agent, a coupler, a silver precipitate nucleus for silver complex salt diffusion transfer, and the like, if necessary.

There are various coating methods to which the present invention is applied, such as a dip method, an air knife method, a kiss method, a bead method, and a curtain method, and 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 1 In the corona discharge treatment apparatus shown in FIG.
The surface of the iron metal roll is coated with an insulating material with a thickness of 4 mm made by uniformly dispersing 2 parts by weight of barium titanate (a high dielectric constant material) with an average particle size of approximately 5μ per 1 part by weight of Hypalon (an insulating material). An earth roll was used which was covered with a coating layer and further covered with an insulating coating layer made of silicone rubber having a thickness of 0.5 mm (the present invention). A photographic support made of a paper substrate with a basis weight of 160 g/m ² coated with a 30 μ thick polyethylene layer on both sides on this ground roll was moved at a speed of 60 m/min in the direction of the arrow, at a corona frequency of 110 KHz and a discharge current of Corona discharge treatment was performed at 1.0A. The distance between the tip of the discharge electrode and the surface of the support was 500μ.

For comparison, the earth roll according to the present invention without the upper insulating coating layer made of silicone rubber was used and subjected to the same corona discharge treatment.

The corona discharge treatment device of the present invention gave a uniform corona charge to the surface of a photographic support for about 8,000 hours, but the comparative corona discharge treatment device showed partial deterioration of the earth roll surface after about 1,000 hours. , uneven corona charging occurred.

Example 2 In the corona discharge treatment apparatus of the present invention used in Example 1, an earth roll having an insulating coating layer made of Hypalon with a thickness of 1.0 mm was used instead of the upper insulating coating layer made of silicone rubber. death,
When similarly subjected to corona discharge treatment, uniform corona charging was given for about 5000 hours.

Example 3 In Example 2, a ground roll having an insulating coating layer made of ethylene propylene rubber was used in place of the upper layer of Hypalon, and when treated in the same manner as in Example 2, uniform corona charging was provided for about 4000 hours.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically explaining the pattern of corona discharge treatment using the corona discharge treatment apparatus of the present invention. 1... Earth roll, 2... Metal roll part, 3
...Insulating coating layer containing high dielectric material, 4...
Insulating coating layer containing no high dielectric material, 5...corona discharge electrode.

Claims (1)

[Claims] 1. A corona discharge treatment device equipped with an earth roll or a roll electrode in which an insulating coating layer containing a high dielectric constant material is provided on the surface of a metal roll, and an insulating coating layer not containing a high dielectric constant material is provided on the layer. .