JPH0394871A - Coating method - Google Patents

Abstract

PURPOSE:To eliminate the unstability in end parts and to allow stable multilayer coating by specifying the difference in the dynamic surface tension between the uppermost layer and the lowermost layer to a specific value in the method for applying plural liquids by a slide hopper type curtain coating method on a supporting body. CONSTITUTION:Two layers of the coating liquid 3 (upper layer) and the coating liquid 4 (lower layer) flowing down on a sliding surface form a liquid injector 2 fall by gravity like a curtain between edge guides 5 and are applied on a traveling web 1. The difference in the dynamic surface tension between the uppermost layer and the lowermost layer is confined within 10dyne/cm. The slide hopper is so disposed that the uppermost layer on the sliding surface is the lowermost layer on the supporting body and the lowermost layer on the sliding surface is the uppermost layer on the supporting body. In addition, the difference in the dynamic surface tension between the uppermost layer and the lowermost layer is confined within 15dyne/cm. Thus, the unstability in the end parts at the time of multilayer coating by curtain coating is eliminated and the stable multilayer coating is executed.

Description

[Detailed Description of the Invention] {] Field of Application of ``Santo'' 2] The present invention relates to a method of applying a coating liquid to a continuously running belt-shaped support (hereinafter referred to as ``UJ''), and more specifically, a curtain coating method. The present invention relates to a method for simultaneously applying multiple counterfeits.

(Background of the Invention) The coating method using the free-falling curtain method is a force method in which the coating liquid is made into a thin film and applied by colliding it with a coating at a certain speed or higher.
No. 24133, No. 49-35447, Japanese Unexamined Patent Publication No. 50-7
The technology is disclosed in No. 6151 and the like.

This coating method is known for its simultaneous multi-layer coating, and along with the slide bead coating method, it has also come to be put to practical use in the coating of extremely precise and thin fakes such as photographic materials.

FIG. 1 shows an example of the curtain coating method, with FIG. 1(a) being a side sectional view and FIG. 1(b) being a front view. The second coating liquid 3 (upper layer) and the coating liquid 4 (lower layer) flowing down from the leg care device 2 on the sliding surface naturally flow down in the form of a thin film curtain between the workpiece guides 5 and onto the running web l. is applied to.

In this case, when the web is fed in the A direction in FIG.

Normally, in the case of multi-counterfeit coating, a surfactant is added to the top layer to stabilize the coating after coating, and the measurement sample is measured using a method such as Willhe 1i-Mee method or F Yuzui method capillary rise. Static!
) The quasi-static surface tension is lower than other methods, but in the case of curtain coating, if the surface tension at the free interface between the front and back sides is large, the edges become unstable, Contraction occurs from the side with higher surface tension, causing rupture. Specifically, two liquids with different dynamic surface tensions in a 0-falling liquid film are piled up in a wide range (7) to form a curtain liquid film) and the edge in a free-falling liquid film. The liquid with high dynamic surface tension causes contraction flow, forming an extremely thin film part t.

If sandwiching is carried out in this condition, not only will there be areas at the edges where the thickness distribution of the distorted emulsion cannot be obtained, but also 1.
7) The strength of the free-falling liquid film is significantly degraded φ, which may lead to the entire liquid film θ) being destroyed.

In this way, if the dynamic surface tension is not set appropriately, the car f
1. [Purpose of the Invention] Problems such as doki I. In contrast, the present invention θ) [1) is a curl coating method that eliminates the instability that occurs at the edges when there are multiple counterfeit products due to curtain modification, and allows stable multi-layer coating. This is what we offer.

[Composition of Shumei]

The above object of the present invention is to provide a method for applying a plurality of liquids onto a female carrier using a slide hopper type curtain method.
The difference in dynamic surface tension between the highest and lowest σ) is 10 dyne/
This can be achieved by a multilayer simultaneous coating method characterized by a coating within Cm.

In addition, since the direction of the advancing force of the web is set to direction B, the top layer on the slide surface becomes the bottom layer on the support, and the bottom layer on the slide surface becomes the L layer on the support. The difference in dynamic surface tension between the top layer and the bottom layer is 15 dyne/em. It is sufficient if it is within u.

The present invention will be explained in detail below.

The method for measuring the dynamic surface tension within the coating film in curtain coating is based on Zoyawor of Fluid Ikkanism (
J. 'Fluid Meeh) 1981, Vol. l.
l2-r) p. 'J>(S.443-458)
P. L i. Established from reports such as ``gJ''
]ing. In addition, P. Joos et al.
Science (J. Colloid and Inte
rface Science) Vol. 115. No
2. Feb. (1987) discuss the behavior of surfactants within curtain membranes.

As a result of analyzing the stability of the edge of the falling film in actual multi-counterfeit curtain coating, we found that the stability here is determined by the difference in dynamic surface tension of each counterfeit as measured by the Okiki measurement method, especially the top layer and the top layer. The difference between the lower corals is the fall time in the free fall section of 0.05-
l Q d y n e /c in the range of 0.2 sec
It has been found that this is sufficiently ensured when the value is within m.

Also, considering the orientation of the surfactant, the conditions will be more relaxed if the coating liquid, which is the top layer after coating that usually contains a large amount of surfactant, is on the solid wall side of the slide surface. It has been found that if yes, the difference in dynamic surface tension between the top fake and bottom layer needs to be within 15 dyne/em.

The general application conditions for curtain coating to which the present invention is applied are as follows: Viscosity of one liquid: 1 to 200 cp Flow-N: 0.1 ce/e+m for each layer. see or more, and the total flow rate is Q-5 to 5 cc/cm. within see.

Replacement conditions are curtain height: 0-5-20 cm and coating speed: 60-300 m/win.

The main solvent is water, which is applied to simultaneous multilayer coating of 2 to 20 copies.

There are no particular limitations on the coating solution and web to which the coating method of the present invention is applied, and for example, when applied to the production of photographic materials as shown in the following examples, any materials and techniques known to those skilled in the art can be used.

〔Example〕

Hereinafter, the effects of the present invention will be illustrated by examples.

Example 1 Using the apparatus shown in FIG. 1, two layers of black and white photographic material were simultaneously coated with the web direction A.

Coating speed: 90s*/win, curtain height: 5cm
Is the support made of polyethylene that has been subtracted? Sauce=
1. Film was used.

■Fabric liquid strip M Protective film liquid/viscosity g 30epSwet thickness 20/7+1
1 emulsion: viscosity 60ep, vei thickness 60μrn Static surface tension (#S), dynamic surface tension ((D) width of each pigeon:
dyne/e■ is changed as shown in Table 1 below. ．． ．． 1. The effect on applicability was examined.

Table 1 Case n of Invention 2: The interfacial thickening agent added to the emulsion layer was changed, and uniform coating was achieved.

In the case of the present invention, the dynamic surface tension ax Ai D is ■0
It was set within dyne/am.

Example 2 Same conditions as Example 1, but with Uyu. σ) Feeding force direction 0
Coating was carried out under the surface tension conditions shown in Table 2 below, with the surface of the web being in the direction of B in Figure 1.

Table 2 From the results in Table 1, in the case of Comparative Example 1: A phenomenon in which only the emulsion layer shrank was observed at the end of the falling liquid film, and film breakage occurred from there as soon as coating was started, making it impossible to coat uniformly.

In the case of Honbimei 1: The surfactant added to the protective layer was changed and uniform coating was achieved.

In the case of Comparative Example 2: Although the degree is milder than in the case of Example 1,
A similar phenomenon was observed and uniform coating was not possible. It was.

In the case of Invention 3: Uniform coating was achieved by reducing the amount of protective surfactant.

In the case of 4σ) of the present invention, uniform coating was achieved by adding a surfactant to the emulsion.

In this Example 0'JJ, in both Invention 3.4, the dynamic surface tension is less than 1 5 a y n e i' cm,
The feather height of the present invention 3 is 10 dyne/cm or more, but if the upper and lower layers of the slide are reversed as in the above σ), it is 15 dyne/cm or more F! ′]Bayun~
You can see that Nuricho is Noh.

Example; 3 Using the same apparatus as in Example 1, 5M simultaneous binding was carried out.

The conditions for each fake are as follows.

Curtain height +7cm Application speed: 150 ships/old n
The support is double-sided polyethylene laminate paper, and the protective book is a fake.

The results were as follows.

In the case of Comparative Example 3: At the special point where the liquid film was formed, a uniform film was formed for the time being, but at the same time as the application started, the white mountain range of the liquid between the lower end of the engine guide and the support body swayed unstably up and down. This fluctuation appears as a fluctuation in the application radius, and the application result is ゛C.
The thick film part was large.

In the case of Invention 6: By changing the surfactant in the protective layer, the above phenomenon was not observed and stable spraying was possible.

〔Effect of the invention〕

According to the present invention, it has been possible to provide a curtain coating method that eliminates instability at the edges during multilayer coating by curtain coating and allows stable multilayer coating.

[Brief explanation of drawings]

FIG. 1(a) is a side sectional view showing an example of curtain coating according to the present invention, and FIG. 1(b) is a front view. l: Web 2: Liquid injection device 3 Upper layer liquid 4: Lower layer liquid 5: Esoji guide

Claims (2)

[Claims] (1) In a method of coating multiple liquids on a support by a slide hopper type curtain coating method, simultaneous multilayer coating is characterized in that the difference in dynamic surface tension between the top layer and the bottom layer is within 10 dyne/cm. Method. (2) In a method in which multiple liquids are applied onto a support using a slide hopper type curtain coating method, the top layer on the slide surface becomes the bottom layer on the support, and the bottom layer on the slide surface becomes the bottom layer on the support. The slide hopper is arranged so that the top layer is the top layer, and the difference in dynamic surface tension between the top layer and bottom layer is 15.
A coating method characterized in that it is within dyne/cm.