JPS60251962A - Apparatus for applying corona discharge treatment to support - Google Patents

Abstract

PURPOSE:To uniformize charge density distribution in lateral and thickness directions, by forming the shape of the discharge electrode opposed to a support into a knife edge one and providing a feedback circuit for controlling voltage to be applied upon the detection of the variation in the value of the current flowing to said electrode. CONSTITUTION:When the earthing electrode opposed to a discharge electrode 1 so as to hold a support 2 between both electrodes is the conductive roller 3 contacted with the support 2, the surface of the discharge electrode is formed into a circular arc shape. When the discharge electrode 1 is formed into a knife edge shape in this case, strong corona discharge is uniformly generated at the leading end part thereof and the surface charge density distribution of the support 2 in the lateral direction thereof comes to a range of + or -5% and the thickness irregularity of a coating layer is not generated in a coating imparting part 6. Because a high voltage generation power source 4 is equipped with a feedback mechanism 5 for bringing the value of the current flowing to the discharge electrode 1 to a constant one, the surface charge density distribution of the support 2 in the longitudinal direction comes to a range of + or -5% and no thickness irregularity of the coating layer is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coating method. In particular, in the production of photographic light-sensitive materials such as photographic film and photographic paper, photoengraving materials, magnetic recording materials such as magnetic recording tape, pressure-sensitive photocopy paper, thermal copying paper, and other recording materials, continuously running long strips are used. Is it easy to apply photographic emulsion, magnetic agent, etc. to the support (hereinafter referred to as "support")? It concerns the method of application. More specifically, the present invention relates to a corona discharge treatment device that generates an electrostatic charge on the surface of a support by strong corona discharge in order to assist in applying a coating liquid to the support.

[Prior art]

US Pat. No. 3,33/, 3/It discloses an apparatus for treating such a support with a corona discharge.

The effect brought about by this device is that it often occurs when applying a coating liquid to a support that is transported at high speed.
It can be pointed out that the phenomenon that the coating liquid does not wet the support can be suppressed due to the air film entrained in the support. Also, in the first coating when the coating liquid is first applied to the support, a large amount of the coating liquid is applied to the support, resulting in a IIJ-coating area, but is this a thick coating amount? It has a mitigating effect.

It has been confirmed that the cause of the above effect is that the dynamic surface tension of the coated material decreases due to the electric field formed by the electrostatic charges on the support, and that electrostatic attraction acts on the coating solution. .

When an electrostatic charge is generated on the surface of a support to assist in applying a coating liquid to the support, if the electrostatic charge density on the surface of the support has a distribution in the two-dimensional direction of the support, that is, the width direction and the longitudinal direction. Differences in the thickness of the coating liquid occur, resulting in product defects.

If a commonly used nail-shaped filament or filament with a diameter of several microns is used as a discharge electrode, the charge density distribution in the direction of the support may occur to the extent that the thickness of the coating solution varies. ′-! is,
In the method of keeping the voltage applied to the discharge electrode constant, the actual amount of generated ions varies due to deterioration of the discharge electrode and variations in the gap between the discharge electrode, the ground electrode, and the support, resulting in charge density distribution in the longitudinal direction of the support. occurs. Problems caused by the charge density distribution on the surface of these supports include, for example, thin line-shaped differences in the thickness of the coating layer due to the charge density distribution in the width direction. Depending on the charge density distribution in the longitudinal direction of the support, for example, a stepped coating thickness difference occurs. All of these problems are unfavorable to the quality of the product.

[Purpose of the invention]

The present invention is an apparatus that generates a static "U" load on the surface of a support by strong corona discharge in order to assist in the application of [phase] cloth to the support. It is an object of the present invention to provide an apparatus for treating a support with corona discharge that can uniformly distribute the corona discharge.

[Structure and operation of the invention]

The above object of the present invention is to provide a discharge electrode facing a support. Knifetsu shape and % release'M1.11. Did you have a feedback circuit that detects fluctuations in the current flowing through the poles and controls the applied voltage? This is achieved by corona discharge treatment placement on a characterized support.

The apparatus of the present invention will be explained in more detail below with reference to the drawings.

In the present invention, a knife-type discharge electrode 7 in FIG. 1 is used. The support λτ is a support 71 (in the case of the rotary roller 3, the electrode surface is formed in an arc shape), and the ground electrode facing the support 71 contacts the support λτ.

If the ground electrode 3' is a protruding monolithic flat plate close to the support 2 as shown in Fig. 2, will there be any radiation? The surface of the jL' electrode l' is formed into a flat surface. ...When multiple knife-edge discharge electrodes are used as in J1, a strong corona discharge occurs evenly at the tip of the knife.

The surface charge density distribution in the direction of the support is within 2,t [%], and the coating application area t'? in FIG. 1' Even if a coating solution is applied, it does not cause differences in the thickness of the coating layer. The thickness of the tip of the knife at this time is, for example, j~io
[μ] is used as a color. On the other hand, the voltage generating power supply μ in Figure 1 is equipped with a feedback mechanism j that keeps the value of the power flowing to the discharge electrode constant. The voltage applied to the discharge electrode 1 is suppressed by adjusting the internal slider position fttf. Due to the above-mentioned mechanism, the surface charge density IW distribution in the longitudinal direction of the support becomes within the range of 100 to 300 nm, causing a coating layer thickness distribution. At this time, the controllable range of the current value flowing through the discharge electrode is 1, in other words, 0. /
−j [mA].

How to make a knife edge discharge 'city electrode' and the value of the current flowing to the discharge electrode in the voltage generating power supply applied to it? By providing a constant filled pack circuit, the charge sensitivity distribution on the surface of the support can be made uniform to the extent that it does not cause differences in the thickness of the coating layer.

Supports used in the present invention include paper, plastic film, Lenzkocht paper, synthetic paper, and the like. Examples of the material of the plastic film include polyolefins such as polyethylene and polypropylene; vinyl polymers such as polyvinyl acetate, polyvinyl chloride, and polystyrene; 4. Polyamides such as J-nylon and 6-nylon, polyethylene terephthalate, polyethylene,!
, j;-naphthalate, polycarboate, cellulose triacetate, cellulose acetate such as cell O-, (Z-iacetate, etc.), and the like are used.

The resin used for resin coated paper is typically polyolefin, which is used in polyethylene lamps, but it is not necessarily limited to this.

Furthermore, the term "coating liquid" includes liquid compositions of various types depending on the application, such as those used in photographic light-sensitive materials.
Coating liquids for photosensitive emulsion layers, undercoat layers, protective layers, back layers, etc.;
Magnetic layers, subbing layers, and lubricants such as in magnetic recording media
Coating liquid for @, protection j-, back layer, etc.: Other adhesive 1
1 Colored layer, rust prevention layer.

These coating solutions contain a water-soluble binder or an organic binder.

Said onto the support? ? ', Methods for applying l5dk include slide coat, air doctor coat, blade coat, air knife coat, squeeze coat, etc.
Coat, IJ hearth roll coat), transfer roll coat, gravure coat, kiss coat, cast coat, spray coat, etc. can be used, and other methods are also possible. J-2!, pp. 3-277 (Showa μ1.
,3. ．． 20 issue).

〔Example〕

In order to clarify the effects of the present invention, 4111 examples of implementation will be introduced below.

Example 1 (1) Support: A trap using a polyethylene terephthalate L-band-shaped support having a width of 30 cm and a thickness of 00 μm. A thin layer of gerana is applied to both sides in advance, and the surface resistance of that layer is l at room temperature.
It was 013 to 014Ω.

(corona discharge treatment device) The above-mentioned support was passed through the corona discharge treatment device t' shown in Fig. 1 while running at /!Om per minute.The voltage applied to the discharge electrode was /jKV, and this At that time, the charge density on the support surface was txio-'c7m2.

(+*n coating solution silver halide grains? A photographic emulsion with a viscosity μ0cpB containing approximately vM in a gelatin solution was prepared.

(1v) Applying the coating liquid to the support that has passed through the corona discharge treatment device in B Pi (11) using a slide bead coating device at the same traveling speed!
, tml/m'' of the above coating solution <i:) was applied, passed through a set zone, gelled at a low temperature, and then passed through a drying zone 7r. This step was carried out in a dark room.

(vl evaluation) When the completed sample was cut into a length of about 4 og and subjected to halftone fog light and back vision image processing, a uniform colored film with no density unevenness was confirmed as shown in Figure 3. In Fig. 3, the diagonal lines indicate uniform gray coloration.

Comparative example 1 (1) Support The same support as in Example 1 was used.

(II) Corona discharge treatment device 1 per minute for the above support! While running with Om.

Four conventional corona discharge treatment devices without a feedback circuit were used, including a discharge electrode with a densely packed discharge electrode. The voltage applied to the discharge electrode is /,! ti(V), and the charge density on the surface of the support at this time was also /x/Q-4C/m.

(ii*) Coating liquid The same photographic emulsion as in Example 1 was used.

(Iv) Application of coating liquid The corona discharge treatment apparatus was as described in (11) above, and the other steps were the same as in Example 1.

IJ) Evaluation completed sample? Approximately 1. The length of the orm was cut into strips, exposed to halftone light, and subjected to post-vision image processing (-9 and C). Different color development was observed.

Example 2 (1) Support: A resin-coated long paper strip having a width of 30 cm and a thickness of 110 μm was used. A thin layer of gelatin was preapplied on both sides, and the internal resistance was 10 Ω.

(II) Corona discharge treatment device The above support? Per minute/! 1. Pass through the discharge treatment apparatus shown in FIG. 2 while running at 0.0 m. The voltage applied to the tC0 free'ilt electrode was /1i (V), and the charge density on the support surface was /X/0'07 cm2.

(iii) Coating liquid The same photographic emulsion as in Example 1 was used.

(1■) Applying the coating liquid At the same traveling speed as in (11) above when passing through the corona discharge treatment device Benika, the slide bead coating device was used for 4
The above coating solution (titr) was applied at a rate of 10 ml/m2, gelled at a low temperature through Seritone/Fang, and then passed through a drying zone. This step was also carried out in a dark room.

(Completion of Vl evaluation 1. The sample was cut into a length of about 40 cm and subjected to halftone exposure and post-view image processing. As shown in Figure 3, a uniform colored film with no density unevenness was confirmed. Ta.

Comparative example 2 (1) Support The same support as in Example 2 was used.

(11) Corona discharge treatment equipment The same corona discharge treatment equipment trap as in Comparative Example 1.

(ii+r coating liquid The same photographic emulsion as in Example 1 was used.

(1v) Application of coating liquid The corona discharge treatment apparatus was as described in (11) above, and the other steps were the same as in Example 2.

(V) Evaluation Completed L7u sample was cut into lengths of about 1.0 cm, and then subjected to iron treatment with noheaf tone dew. Different color development was observed in the middle VC transverse thickness.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the configuration of the corona discharge device according to the present invention. Figure 3 is a diagram showing example data. Figures 1 and 5 are diagrams showing comparative data. . i, t'......Knifetsu-like corona emission; Electrode 2......Support Hiro...・・・・・・・・・High voltage generation power supply j・・・・・・・・・・・・・・・Feedback circuit Patent applicant Rakushi Photo Film Co., Ltd. fa 1 Diagram 3 Diagram No. 4 Illustration 5 Illustration Voluntary procedure amendment Mr. Commissioner of the Patent Office 1, Indication of the case Showa zy year Patent Application No. 10?217 2
, Title of the invention Corona discharge treatment device for support 3, Relationship with the case of the person making the amendment Patent applicant Location 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Telephone (406)
) 2537 4. Subject of amendment The contents of the "Detailed Description of the Invention" column 5 of the specification and the contents of the "Detailed Description of the Invention" section are all amended as follows. (1) "Normal temperature" in line μ of page 1 of the specification has been corrected to "normal humidity." (II) Details page i page r fiA/3rd line “adjustment” is corrected to “preparation”. (iii) Insert "of paper at normal humidity" after "as provided" on page 1, line 11 of the specification. that's all

Claims (2)

[Claims] (1) In a device that generates an electrostatic charge on the surface of a support by strong corona discharge to assist in applying a coating liquid to the support, the discharge electrode facing the support is shaped like a knife,
Is it equipped with a feedback circuit that detects the current value flowing through the discharge electrode and controls the applied voltage? Features: Corona discharge treatment equipment for supports. (2) A corona discharge treatment apparatus for a support according to claim 1, wherein the discharge electrode is a plurality of knife-shaped discharge electrodes.