JPS6354975A - Simultaneous multi-layer coating method - Google Patents

Abstract

PURPOSE:To enable high-speed and stable coating by forming the coating film of the lowermost layer of water, specifying the wet coated amt. thereon to a specific amt. or below, specifying the coated amt. of the layer adjacent thereon to the amt. larger than the coated amt. of the lowermost layer and forming said layer of a water soluble coating liquid compsn. having a high viscosity. CONSTITUTION:>=2 layers of coating liquid films 14-16 are held in a superposed state and are applied on a continuously traveling web 2. The coating liquid film 14 of the lowermost layer adjacent to the web 2 is formed of the water and the wet coated amt. thereof is specified to <=2cm<2> per m<2> of the web surface. The coated amt. of the layer 15 adjacent onto the lowermost layer is specified to the amt. larger than the coated amt. of the lowermost layer and said layer is formed of the water soluble coating liquid compsn. having the high viscosity. As a result, the wetting between the web and the lowermost layer film is improved and the beat is stabilized. The generation of the inter- layer mixing with the layer thereon and the generation of coating streaks or the like occurring in the lowermost layer are obviated and the coating speed is considerably increased.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to continuous running in the production of recording materials such as photographic film and photographic paper, photolithographic materials, pressure-sensitive recording paper, and heat-sensitive recording paper. Regarding a method of applying a liquid coating composition to a long flexible support (hereinafter referred to as a web), more specifically, a method of applying a liquid coating composition to a continuously running web with two or more coating liquid films superimposed on each other. The present invention relates to a multilayer simultaneous coating method.

(Prior art) Conventionally, as a high-speed coating method in a slide hopper coating device for simultaneous multi-RFA coating method,
There is the following coating method disclosed in Publication No. 34.

That is, in order to achieve the purpose of improving high-speed coating, this coating method uses a low viscosity liquid of 1 to 8 cps for the bottom layer, and applies a wet coverage of 2 to L2 cd per 1M of web surface, and forms a meniscus. This is a method of increasing the application speed by causing swirling to mix only the bottom layer and the eyebrows immediately above it, without affecting the layer above it.

Furthermore, Japanese Patent Application Laid-Open No. 54-1350 discloses that the next layer to the web is 20 to 200 cps at a sliding speed of 100 seconds.
A method has been proposed that utilizes a dilute carrier layer of a pseudoplastic liquid with a viscosity of less than LO cps and a shear rate of too, ooo seconds. That is, in order to improve the instability of the bead portion as described in Japanese Patent Publication No. 56-20534 I, this coating method has a high viscosity in the bottom layer under low shear rates and a low viscosity under high shear rates. It was designed to use a pseudoplastic liquid with viscosity.

[Problem that the invention seeks to solve]

When using the above coating method, the coating liquid forming the bottom layer has a property of exhibiting Newtonian flow.

Further, in this case, it was necessary to select and prepare a special composition for the coating liquid.

The present invention eliminates the above-mentioned drawbacks of conventional application methods, eliminates glabellar mixing between the bottom layer and the layer directly above it, and also eliminates the addition of special and expensive compositions to the bottom layer. The purpose of the present invention is to provide a new multilayer simultaneous coating method that enables high-speed, stable coating while minimizing the increase in drying time.

c. Means for Solving Problems] As a result of intensive experimental studies on a method of high-speed coating using a low viscosity liquid as the bottom layer, the inventors found that they used Newtonian flow water in the bottom layer and Surprisingly, when the wet I11 coating amount is ultra-thin with less than 2 layers per web surface IM, high-speed coating properties are not lost, and mixing between the bottom layer and the layer immediately above due to swirling in the bead is achieved. It was found that this does not occur.

Moreover, it is surprising that the very regular coating failures (which occur in the direction of web travel at several n pitches) occur when high-speed coating is carried out in slide hopper coating equipment, which is well known to those skilled in the art. Japanese Patent Publication No. 1983-255172
It has been found that the method of the present invention has a revolutionary effect even on

That is, the present invention provides a multilayer simultaneous coating method in which two or more coating liquid films are superimposed and applied to a continuously running web, in which the lowest layer coating liquid film adjacent to the web is formed of water, The wet coating amount is 2cm3 per 1d of web surface.
This is a multilayer simultaneous coating method characterized in that the coating amount of the layer adjacent to the bottom layer is thicker than the bottom layer and is formed from a water-soluble coating composition having a higher viscosity.

The coating solution used in the present invention is mainly a water-soluble coating composition, and for example, in the production of photographic light-sensitive materials, it is used in photosensitive emulsion layers and undercoat layers containing a small amount of tJsl solvent.

Examples include coating liquids for protective layers, back layers, antihalation layers, etc.

Supports used in the present invention include paper, plastic film, resin coated paper, synthetic paper, metal, 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;
．． Polyamides such as 6-nylon and 6-nylon, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polycarbonates, and cellulose acetates such as cellulose triacetate and cellulose diacetate are used. Further, the resin used for the resin coated paper is typically polyolefin, but is not necessarily limited thereto, and the metal web includes, for example, an aluminum strip.

Distilled water is generally used as the water in the bottom layer in the present invention. The wet coating amount is desirably 2 or less per 1 i of web surface.

The coating amount of the layer adjacent to the bottom water layer is desirably 5 times or more thicker and 15 times or more higher in viscosity than the bottom layer.

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a side sectional view of a slide hopper type coating device for three-layer coating, which is an embodiment of the coating method of the present invention.

In the figure, 1 is a backup roll, 2 is a web, 3 is a bead portion, 4.7.10.13 is a sliding surface, and 5.8.
11 is a slot, 6.9.12 is a manifold, 14 is a water film forming the bottom layer, 15 is a coating liquid film forming the first layer, and 16 is a coating liquid film forming the second layer. The web 2 is transferred to the backup roll 1 by a conveying means (not shown).
It is continuously transported around the circumference in the direction of the arrow.

On the other hand, the water 14 forming the bottom layer is sent by a liquid pump and spread across the width of the hopper by the manifold 6, then passes through the slot 5 and emerges onto the slide surface 4, where it flows on the slide surface 4 by gravity. It flows down by gravity to form a bead 3 and is applied onto the support 2. The amount of wet i11 applied to this land water is adjusted to 2 or less per 1 d of web surface. Similarly, the other coating liquids 15 and 16 forming the first and second layers as products on the bottom layer also pass through the manifolds 9, 12 and the slots 8.11 and onto the slide surfaces 7 and 10, respectively. It flows out and from here slide surfaces 7 and 1
0 by gravity, each coating liquid film 1'5.1
6 and is coated on the support 2 to form a bead 3 in a weighted state with a water film 14 forming the bottom layer.

FIG. 2 shows another embodiment of the coating method of the present invention.
1'ii is a side sectional view of an extrusion type coating device for simultaneous coating.

In the figure, 21 is a backup roll, 22 is a web,
24, 25, and 26 are slots, 27, 28, and 29 are manifolds, 30 is a water film that forms the bottom layer, 31 is a coating liquid film that forms the first WI of the product, and 32 is a coating liquid film that forms the second N. It is.

The web 22 is continuously transported on the circumference of the backup roll 21 in the direction of the arrow by a transport means (not shown).

On the other hand, the water film 30 forming the bottom layer is fed by the liquid feeding pump, spreads in the width direction of the hopper by the manifold 27, passes through the slot 24, is pushed out, and is pushed out from the support 22.
is applied on top of the The amount of water applied to this land water is 1 on the web surface.
Hit resistance adjusted to 2- or less. Similarly, the first layer and the second layer
Other coating liquid films 31, 32 forming N are also forced through the manifolds 28, 29 and slots 25, 26, respectively, and are applied onto the support 22, with the water film 30 forming the bottom layer.

[For production]

In the present invention, the lowermost RFI coating film adjacent to the web is formed with water and the wet coating amount is 2 cT1 or less per 1 d of the web surface, thereby improving wetting of the coating liquid to the support and coating by swirling of the bead portion. Don't worry about mixing liquids (
Furthermore, there is no occurrence of coating streaks caused by the bottom layer (uniform coating quality can be obtained and the coating speed can be significantly increased).

〔Example〕

Examples will be given to further clarify the effects of the present invention.

A comparative experiment between the coating method according to the present invention and a conventional coating method was conducted under the following conditions using a slide hopper type coating apparatus shown in FIG. The web used was based on triacetate cellulose (TAC) with a width of 18 cm.

Comparative Example-1 1st layer: Antihalation liquid containing an anionic surfactant exhibiting a viscosity of 5 Qcps at 40°C at a flow rate of 75cc/cm-min 2nd layer: 40°C
A gelatin solution containing an anionic surfactant having a viscosity of 20 cps was simultaneously coated in multiple layers at a flow rate of 75 cc/c+s 0 min.

When applied as above, the application speed was 1Q5m/m.
When it became in, a homogeneous coating surface condition could not be obtained.

Example-I Bottom layer: Water having a viscosity of 0.65 cps at 40°C at a flow rate of 2
cc/c1m・min 1st layer: Same as the 1st layer with the layer structure of Comparative Example-1 2nd layer: Same as the 2nd layer with the layer structure of Comparative Example-1 Simultaneous multilayer coating under the above conditions A uniform coated surface was obtained up to a coating speed of 341 m/min.

Comparative Example-2 11'i: Antihalation liquid with viscosity of 60 cps at 40°C, flow rate of 57.5cc/Cm'm+n 21'ii: Gelatin liquid with viscosity of 8 cps at 40°C, flow rate of 38.4cc /am・min When multiple layers were simultaneously coated under the above conditions, very regular coating streaks that ran in the web running direction at several 11 pitches occurred at a coating speed of 99 m/min, resulting in a homogeneous coated surface. Rena (became)

Example-2 Bottom layer: Water with a viscosity of 0.65 cps at 40°C at a flow rate of 2
CC/cIl-min 1st layer: 2nd Fii same as the first layer of the layer configuration of Comparative Example-2
i=same as the second layer of the layer structure of Comparative Example-2 When coated as above, the above-mentioned streak failure did not occur up to a coating speed of 300 m/min, and a homogeneous coated surface was obtained. Ta.

〔Effect of the invention〕

In the present invention, the bottom layer coating film is formed with water, the wet coating amount is 2 or less per 1 m2 of the web surface, and the coating amount of the layer adjacent to the bottom layer is thicker than the bottom layer and is made of water-soluble water-soluble material having a high viscosity. By forming the coating with a coating liquid composition, the web and the lowermost NWA are well wetted and the beat is stable, and there is no mixing between the eyebrows with the layer above it, and the occurrence of coating streaks etc. caused by the lowermost layer. It was possible to significantly increase the coating speed without any problems.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the coating method of the present invention. FIG. 2 is a side cross-sectional view of a slide hopper type coating device for simultaneous three-layer coating. FIG. 2 is a side sectional view of an extrusion type coating device for simultaneous three-layer coating according to the coating method of the present invention. 1.21...Release up roll 2.22...Web' 3.30...Bead portion 4.7.10...Sliding surface 5.8, 11° 24.25, 26. ...Slot 6.9.12°27.28,29. ...Manifold 14.30
... Water film forming the bottom layer 15.31 ... 1st F
Coating liquid film forming layer 1 16. 32... Coating liquid film forming layer 1

Claims (1)

[Claims] (1) In a multilayer simultaneous coating method in which two or more coating liquid films are superimposed and applied to a continuously running web, the bottom layer coating liquid film adjacent to the web is formed of water, and its wetness The coating amount is 2 cm^3 or less per 1 m^2 of the web surface, and the coating amount of the layer adjacent to the bottom layer is thicker than the bottom layer, and is formed from a water-soluble coating liquid composition with a higher viscosity. A multilayer simultaneous coating method characterized by: