JP3953035B2 - Curtain film forming method - Google Patents

Description

  The present invention relates to a curtain film forming method for providing a stable curtain film using a curtain coating apparatus.

  The coating liquid that flows down in a uniform layer on the sliding surface of the coater die is dropped from the tip position of the die slip of the coater die to form a thin curtain film of the coating liquid, and the curtain film is conveyed at a constant high speed. 2. Description of the Related Art Conventionally, a method for producing a photosensitive material using a curtain coating apparatus that performs coating continuously while being placed on a long support web is known. In a method for producing a photosensitive material using such a curtain coating apparatus, it is very important to stably form a curtain film. When the coating solution that has flowed down the slide surface leaves the die slip and forms a curtain film, the coating solution that tends to shrink due to surface tension is held by a side bar (or plate) called an edge guide, and the coating solution flows down. The width is secured.

  However, when the edge guide cannot support the force of the coating solution to be shrunk, the film breaks down, making it difficult to form a stable curtain film. Even if the curtain film can not be formed with the conventional technology, or the curtain film can be formed, the coating liquid is pulled in the transport direction of the support due to the lack of the curtain film holding force of the edge guide at the start of application. For some time, the phenomenon that the curtain film at the end portion is broken due to the force has occurred. In order to eliminate these phenomena, various proposals have been made so far.

  That is, in Japanese Patent Application Laid-Open No. 1-99668, in order to improve this and prevent the film from being broken, a means for reinforcing and stabilizing the curtain film by flowing a side liquid separately at both ends is taken. However, even if the curtain film does not break down, the side liquid concentrates and accumulates at the end portion, so that the film thickness on both sides becomes too thick.

  In order to suppress the increase in the film thickness on both sides, as shown in Japanese Patent Application Laid-Open No. 61-477 and Japanese Patent Application Laid-Open No. Hei 6-233594, the curtain film end thick film portion of the edge guide portion is sucked. It has been removed.

  In JP-A-51-57734, the curtain film is stabilized by using a flat plate edge guide. However, even this does not stabilize the curtain film, and it is impossible to form the curtain film depending on the coating solution. Also, the thick film phenomenon at both ends is not eliminated.

JP 51-57734 A

JP 61-477 JP-A-1-99668 Japanese Patent Laid-Open No. 6-233594

As described above, various coating apparatuses have been proposed for forming a curtain film, but satisfactory ones have not been obtained yet.
In the present invention, without adding new equipment or changing the apparatus, the relationship between the dynamic surface tensions of the respective coating liquids is pursued, the formation of the curtain film is further stabilized, and the photosensitive material is manufactured by stable coating. The objective is to find a method that can do this.

This object is achieved by the following technical means (1) or (2).
(1) Using a curtain coating apparatus, the continuous support has 3 layers or more and a total flow rate of 2 . In the method for forming a curtain film in which a coating solution of 0 cc / sec / cm or more is applied simultaneously, among the three or more layers, the minimum value σ of the dynamic surface tension (DST) of an intermediate layer min [mN / m ] And the difference ΔK between the DST maximum values σ out of the layers (the uppermost layer and the lowermost layer) out of the three or more layers, max [mN / m],
ΔK = min in σ−max outside σ ≧ 5 [mN / m]
A curtain film forming method, wherein coating is performed using a coating liquid having a dynamic surface tension configuration as described above.
(2) the curtain film forming method according to claim 1, wherein the coating speed is equal to or is 3m / sec or more.
(3) The curtain film forming method according to claim 1 or 2, wherein the coating speed is 5 m / sec or more.

  That is, as a result of the study by the present inventors, the dynamic surface tension (DST) configuration of the coating liquid is highly dependent on the stability of the curtain film, particularly in a complicated system having three or more layers. found. Further investigation revealed that the relationship between the DST of the intermediate layer and the DST of the outer layer (the uppermost layer and the lowermost layer) of the curtain film greatly depends. As a result of examining each of the 3, 5, 7, 9, and 16 layer systems, it has been found that if ΔK [mN / m] is increased, the curtain film stability and applicability are improved.

  First, a coating apparatus used in the method for producing a photosensitive material of the present invention will be described with reference to the perspective view of FIG. A long support 2 is wound around the back roller 1 so that it can be conveyed in the arrow direction at a constant speed. A coater die 3 is provided obliquely above the outer side of the back roller 1, and a plurality of coating liquids flow down while forming a uniform layer thickness on the slide surface 4 of the coater die 3. 5 is separated at the position of the tip of 5 and falls while forming a thin curtain film. At that time, both sides of the curtain film are placed on the support 2 being conveyed at the same speed while a uniform film is formed and held by dynamic surface tension (DST) generated between the curtain film and the edge guide 6. A continuous application goes on to be achieved.

And the edge guide 6 is a thing which installed the straight rod-shaped thing vertically as shown in FIG. The rod-shaped edge guide is a round rod or prism made of stainless steel.
In the experiment of the embodiment of the present invention, the number of coating layers simultaneously applied in multiple layers is 3, 5, 7, 9, 16; however, the present invention is not limited to these numbers. .
Hereinafter, the result of the Example of this invention is explained in full detail.

Example 1
Basic conditions of the experiment Composition of each coating solution Gelatin 7% coating solution, adjusted to 30 cp with thickener Total flow 1, 2, 3, 4 cc / sec / cm
Layer structure 3, 5, 7, 9, 16 layers Curtain height 30-300mm
Curtain film durability measurement at coating speed 180, 300, 420 m / min (3, 5, 7 m / sec) Curtain film width 300 mm
Edge guide Symbol for evaluation of stainless steel round bar type and prismatic type ○: Applicable
△: Curtain film cut after application starts
×: Of curtain film can be applied ○ 3: Can be applied up to 3m / sec.
○ 5: Applicable up to 5m / sec.
○ 7: Coating is possible up to a coating speed of 7 m / sec. The DST measurement of each solution used a curtain film destruction method as shown in the schematic diagram of FIG. Further, as a method for evaluating curtain film stability and coating stability, coating speeds (m / sec) that can be coated in each system were compared.
Based on the above, in each case of 3 layers, 5 layers, 7 layers, 9 layers, and 16 layers, the coating film is formed by changing the ΔK value of DSK, the Q value of the total flow rate, and the dimensional shape of the edge guide. That is, the results of implementation of the present invention that verified the stability of the coating state are shown in the following Tables 1 to 5.

From the above, it can be seen that the ΔK value is preferably ΔK ≧ 5 [mN / m], and more preferably ΔK ≧ 10 [mN / m].
By defining the relationship between the dynamic surface tension of each coating liquid without adding new equipment or changing the equipment, the present invention makes it possible to further stabilize the formation of the curtain film and to produce a photosensitive material by stable coating. We have established a method that can be performed.

The perspective view of the curtain film | membrane formation part of the curtain coating apparatus of this invention. The schematic diagram which shows DST measurement by a curtain film destruction method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back roller 2 Support body 3 Coater die 4 Slide surface 5 Die slip 6 Edge guide 7 Curtain film

Claims (3)

Using a curtain coating device, a continuous support with three or more layers and a total flow of 2 . In the method for forming a curtain film in which a coating solution of 0 cc / sec / cm or more is applied simultaneously, among the three or more layers, the minimum value σ of the dynamic surface tension (DST) of an intermediate layer min [mN / m ] And the difference ΔK between the DST maximum values σ out of the layers (the uppermost layer and the lowermost layer) out of the three or more layers, max [mN / m],
ΔK = min in σ−max outside σ ≧ 5 [mN / m]
A curtain film forming method, wherein coating is performed using a coating liquid having a dynamic surface tension configuration as described above. 2. The curtain film forming method according to claim 1, wherein the coating speed is 3 m / sec or more. 3. The curtain film forming method according to claim 1, wherein the coating speed is 5 m / sec or more.

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