JPH0224115Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a corona discharge electrode, which is used to make a hydrophobic surface hydrophilic when a thin hydrophilic layer such as a photographic emulsion layer is coated on a support having a hydrophobic surface. This invention relates to a corona discharge electrode.

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. As a method of making it hydrophilic, applying a composition that can adhere to a hydrophobic surface and also adhere to a hydrophilic layer.
There are various methods such as the so-called subbing method, corona discharge treatment method, flame treatment method, ultraviolet irradiation method, glow discharge treatment method, etc., but in recent years corona discharge treatment method has become popular due to practical aspects such as operability, safety, and cost. Widely used.

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 uneven residual charges 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.

An object of the present invention is to provide a corona discharge electrode that prevents discharge unevenness.

Another object of the present invention is to prevent uneven coating of a photographic layer coated on a hydrophobic support made hydrophilic by corona discharge treatment.

The object of the present invention is achieved by covering parts of the corona discharge electrode other than the necessary discharge part with an insulating material.

The discharge surface width of the electrode depends on various conditions such as the running speed of the support to be subjected to discharge treatment, the distance between the electrode discharge surface and the support surface to be discharge treated, the degree of hydrophilization of the hydrophobic surface after discharge treatment, and the discharge density. The appropriate width is determined by this. In the present invention, the "required discharge section" means the appropriate discharge surface, and includes the discharge surface of the electrode, the entire discharge surface prepared, and a further appropriate part of the discharge surface originally included as an electrode. include.

The present invention will be explained below with reference to the drawings.

FIG. 1 schematically explains the pattern of corona discharge. In FIGS. A and B, the earth roll 1 is usually a grounded metal roll wrapped with an insulating material such as silicone rubber. The corona discharge electrode 2 located across the discharge space from the earth roll 1 is usually made of metal such as aluminum or iron. On the ground roll 1 there is a support 3 with a hydrophobic surface running in the direction of the arrow. Figure A shows a state when the discharge intensity is relatively weak, and in such a case, a homogeneous discharge 4 occurs only from the discharge surface a, and no coating unevenness occurs. Figure B shows the state when the discharge intensity is relatively stronger than that in A, and the discharge surface a
Discharge 4' occurs not only from the electrode surface b but also from other electrode surfaces b, resulting in a non-uniform discharge state, resulting in so-called "discharge unevenness".

If the running speed of the support to be subjected to corona discharge treatment is relatively slow, even if the corona discharge intensity is relatively weak, the hydrophobic surface of the support will be sufficiently hydrophilized, and the hydrophilic layer applied thereon will be However, if the running speed of the support is increased to increase productivity, the hydrophobic surface of the support cannot be made sufficiently hydrophilic unless the corona discharge strength is increased. Adhesion to the applied hydrophilic layer on the body is also insufficient. Therefore, in order to obtain sufficient hydrophilicity and adhesion, it is necessary to increase the discharge intensity.

2 to 4 are perspective views showing specific examples of the corona discharge electrode of the present invention. In each figure, a indicates the required discharge surface, and b' (black area)
indicates the electrode surface covered with an insulating material.

FIG. 2 is an example of an aluminum corona discharge electrode of the same shape as that used in FIG. Figure A is a perspective view from above, and Figure B is a perspective view from the side. A is a necessary discharge part, and b' is an insulating film of aluminum oxide with a thickness of about 50 μm obtained by anodizing the electrode surface b in FIG.

3 and 4 are perspective views of the corona discharge electrode of the present invention in other shapes, a and b' respectively indicate the same as in FIG. 2, and can be made in the same manner.

In FIGS. 2 and 4, the entire discharge surface is uncovered and exposed, and in FIG. 3, a suitable portion is exposed.

According to the present invention, the corona discharge intensity can be increased without causing discharge unevenness, so even if the running speed of the support to be subjected to corona discharge treatment is increased, the hydrophobic surface of the support can be sufficiently hydrophilized. Even when a hydrophilic photographic layer is coated on a support, it is possible to obtain a photographic material in which the support and the photographic layer are sufficiently adhered to each other without causing coating unevenness due to discharge unevenness.

The present invention is not limited to the application of photographic layers, but can also be applied to corona discharge treatments for applying thin layers, similar to photographic layers, to hydrophobic surfaces. The photographic layer herein includes various layers necessary to constitute a photographic material, such as a silver halide emulsion layer, an antihalation layer, a filter layer, an undercoat layer, and an image-receiving layer for silver complex diffusion transfer.

The electrolytic solution used for anodization may be any one of oxalic acid, sulfuric acid, and chromic acid aqueous solutions. The thickness of the insulating film formed on the electrode surface varies depending on the discharge intensity, but in the case of aluminum oxide obtained by anodizing an aluminum electrode, the appropriate thickness is usually about 10 to 100 microns. The range of coverage with the insulating material does not necessarily have to be all but the required discharge surface, and it is sufficient to selectively cover the electrode surface where unnecessary discharge occurs. The insulating material used in the present invention is preferably one that is not destroyed by high temperature and high voltage during corona discharge.

In addition, even if a corona discharge electrode produces a relatively weak discharge, if it is used for a long period of time, foreign matter that is thought to be oxide of the electrode material will be generated on the electrode surface other than the required discharge surface. Unnecessary discharge occurs from the protrusion, which can also cause uneven discharge, but according to the present invention, the generation of such foreign matter can be prevented, and uneven discharge caused by foreign matter can be prevented. You can also do that.

Using the electrode of the present invention, a strong corona discharge was applied to one side of double-sided polyethylene-coated paper at a high speed of, for example, 60 m/min or more, and a hydrophilic photographic layer was coated online after a few seconds. A photographic layer was obtained which was firmly adhered to the film.

[Brief explanation of drawings]

Figure 1 is a schematic illustration of corona discharge, Figure 2~
FIG. 4 is a perspective view showing a specific example of the corona discharge electrode of the present invention. 1... Earth roll, 2... Corona discharge electrode, 3...
support with a hydrophobic surface, 4 and 4'...discharge,
a...discharge surface that requires discharge, b...electrode surface that does not require discharge, b' (black area)...electrode surface covered with an insulator.

Claims (1)

[Scope of utility model registration request] Located between the earth roll and the discharge space,
A discharge electrode of a corona discharge treatment device used for hydrophilizing the surface of a support having a hydrophobic surface to which a hydrophilic layer running on an earth roll is to be applied, the discharge electrode having the following features: What is claimed is: 1. A corona discharge electrode, characterized in that a coating of an insulating material is provided on a portion other than the discharge portion, and a band-shaped discharge surface is formed in the width direction of the tip of the electrode.