JP2736432B2 - Application method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a coating method for simultaneously coating one or more coating liquids on a web by a slide hopper device, and more particularly, to a coating method suitable for coating a photographic light-sensitive material. About.

[Prior art] Traveling long flexible belt-shaped support (hereinafter referred to as web)
When coating is performed using a slide hopper apparatus, a coating bridge (hereinafter, referred to as a bead) is formed between an end of a coating machine (hereinafter, referred to as a lip) and a web, and the web is coated via the bead. . In coating with a slide hopper device, it is very important to keep this bead stable. That is, when the bead is disturbed or disturbed, various defects occur in the coating layer applied to the web. For example, a defect that is particularly notable is the occurrence of a streak failure in which a vertical streak appears, and the occurrence of the streak failure results in a decrease in the coating yield of the photographic light-sensitive material. This streak occurs from the start of coating, occurs when the web passes through a seam, or occurs when foreign matter such as dust adheres to the web even in the steady state of application, when the foreign matter passes. There is. This streak occurs more remarkably at higher speeds and thinner films.

Various improved techniques have been proposed as techniques for preventing the occurrence of the muscle failure. That is, for example, as described in (1) US Pat. No. 2,681,294, a technique for generating a pressure difference between exposed surfaces above and below a bead portion by, for example, generating a vacuum on a surface on which the bead portion is suspended. ,
(2) As disclosed in Japanese Patent Publication No. 51-39980, a lip portion is provided at the coating liquid outflow end of the hopper device, and the inclination angle of the lip top portion is smaller than the inclination angle of the coating liquid outflow surface. Technology to increase the thickness of the coating liquid layer on the top surface of the lip by forming
As disclosed in Japanese Patent No. 60-183064, the inclination angle of the slide surface with respect to the horizontal reference plane is 35 ° to 50 °, the angle between the tangent at the collision point between the coating solution and the web is 85 ° to 110 °, and The collision point is higher than the center of the coating backup roll. (4) Japanese Patent Publication No. 58-907 discloses a liquid holding section provided at the tip of the hopper in order to stabilize the rear end of the bead in contact with the hopper. And the like are disclosed.

However, each of these techniques has the following disadvantages.

That is, in the technique (1), if the pressure difference between the upper and lower exposed surfaces of the bead portion is too small, it is not enough to prevent excessive vibration of the bead, and in this case, the pressure difference is increased by increasing the degree of vacuum. Although it is necessary to increase the diameter, there is a possibility that the beads may be disturbed or burst if the degree of vacuum is excessively increased. The technique (2) has the effect of minimizing the occurrence of undesired streak failure in the coating film due to foreign matter such as dust or silver adhering to the tip of the hopper device. Has no effect. Furthermore, in the technique (3), when the sliding surface has a large inclination, when the coating liquid flows into the coating bead, the dynamic pressure of the liquid increases, and the adhesion of the coating liquid to the web slightly increases, but worsens as a countermeasure against streaking. In this case, the liquid film thickness on the slide surface becomes thinner, which is not preferable for preventing a streak failure due to foreign matter or the like on the slide surface. The technique (4) has a certain effect but is not sufficient. Further, none of these techniques (1) to (4) is effective for streak failure occurring from the start of coating,
In particular, in the case of high-speed thin film coating, it was difficult to prevent the line failure. Further, even in the steady application state, it is not effective against disturbance of the bead, and the occurrence of streak failure cannot be prevented.

[Problems to be Solved by the Invention] In view of the above problems, an object of the present invention is to provide a coating method that does not cause streaking, and particularly contains a water-insoluble solid in the lowermost layer. An object of the present invention is to provide a coating method which does not cause a coating failure even when a coating liquid to be applied is multi-layer coated by a slide hopper device.

[Means for Solving the Problems] It is an object of the present invention to provide a method of applying a coating liquid in a multi-layer manner to a continuously running web by using a slide hopper device. (A) The inclination angle of the slide surface of the device with respect to the horizontal reference plane is 5 ° to 30 °. (B)
The angle between the tangent to the back roll and the slide surface at the point where the coating liquid collides with the web is 85 ° to 95 °.
(C) The gap between the tip of the hopper and the web should be 0.2 mm or less.

This is achieved by a coating method characterized by the following.

The present invention is particularly effective when the coating solution forming the lowermost layer in contact with the support contains 2 to 15% by weight of a water-insoluble solid content.

Hereinafter, the present invention will be specifically described. FIG. 1 shows a schematic sectional view of an example of a slide hopper device that can be used in the present invention.

The web 10 runs while being held by the coating backup roll 1, and comes into contact with the coating liquid flowing from the slot 4 of the slide bead coating machine 2 to the slide surface 5 at the coating machine lip portion 6, where the ribbon-like liquid pool is formed at the lip portion. A bead
A coating liquid is applied onto the web via the beads. At this time, a method of measuring the stability of the bead by pulling the bead downward by the pressure reducing device 3 is generally adopted. The above-described mechanism is the same in the case of a single layer or a case of two or more layers. Simultaneous multi-layer coating can be performed by flowing a plurality of coating liquids on a slide surface from a plurality of slots. FIG. 1 shows an example of two-layer coating, in which, for example, an emulsion solution 14 is flowed in the lower layer and a protective film solution 13 is flowed in the upper layer to perform simultaneous multi-layering.

In the present invention, in the present invention, the point of collision between the coating liquid flowing on the slide surface 5 and the web is almost at the point of the lip portion 6 of the coating machine, and this point is the center of the coating backup roll 1.
taller than. As a result of the study by the present inventors, the collision point is located above the point C. FIG. 2 is an enlarged view of the vicinity of the collision point. The coating liquid flowing on the slide surface 5 is affected by gravity g, but the inclination angle of the slide surface 5 with respect to the horizontal reference plane H (hereinafter simply referred to as the inclination angle). The force Fg due to gravity is divided into two by θ, one is a component force Fm that is flat on the slide surface, and the other is a component force Fh that is perpendicular to the slide surface. Therefore, the relationship between the magnitudes of these two component forces changes depending on the inclination angle θ of the slide surface. Fm is the above Fg and sinθ
It is proportional to the product of Therefore, as θ decreases, Fm also decreases,
The flow rate of the coating liquid flowing on the slide surface becomes slow, and the liquid thickness becomes thick. In addition, Fh becomes large, and the power to spread over a wide area becomes stronger. When the liquid thickness is thick, streaks on the slide surface are less likely to be generated, but since Fm is small, the difference in shear rate between the web and the slide surface increases, and the coating liquid is suddenly stretched at the collision point. The bead becomes shallow and unstable. As a result of various studies, the present inventors have found that the inclination angle of the slide surface is 5 ° or more.
If the angle between the tangent to the back roll and the slide surface is 90 ° at the application point of 30 °, and the gap k between the web and the tip of the hopper is 0.2mm or less, stable application can be achieved that is unlikely to cause streak failure. Was found.

EXAMPLES Hereinafter, the effects of the present invention will be specifically described with reference to examples.
Note that the inclination angle of the slide surface is not limited to the value described in the present embodiment, and it is needless to say that it can be selected within the range described in the claims according to other conditions such as the coating speed and the liquid viscosity.

Example 1 A 180 μm polyethylene terephthalate base was used as a support, and the following two layers were simultaneously coated thereon by the slide hopper device shown in FIG. 1 under the following conditions.

The emulsion contained 6650 g of silver iodobromide and 2000 g of gelatin as a protective colloid in 35 l of an ortho-sensitized silver iodobromide emulsion (containing 2 mol% of iodine). 1250 g of gelatin was added to the emulsion, and sodium-di (2-etylhexil) -Sulfosuccia was used as a surfactant.
65 cc of a 1% solution of nte and 2 liters of a 4% aqueous solution of a styrene-maleic acid copolymer as a thickener were added, and a solution finished to 65 liters was used as an emulsion layer coating solution. The solid content concentration of this coating solution is 10.2
%. The second layer is a protective film layer, which is an 8% gelatin solution.
8 liters of the above surfactant, 4 liters of 4% formalin solution in 100 liters, 4%
8 l of glyoxal and a predetermined amount of the thickener were added to obtain a coating solution for a protective film.

The coating speed was 60 m / min, the pressure in the coater was -35 mmaq, and the wet film thickness was 50 μm for the emulsion layer and 15 μm for the protective film layer. The coating liquid viscosity is 15 cp for the emulsion layer, 15 cp for the protective layer, and the surface tension is 39 dyne for the emulsion layer.
/ cm, and the protective film layer was 26 dyne / cm. The viscosity was measured using a Brookfield viscometer and the surface tension was measured using Wilhelmy.
It was measured at 35 ° C by the method.

With respect to such a layer configuration, coating was performed under the following coating apparatus conditions.

FIG. 3 is an explanatory diagram showing the positional relationship between the slide surface and the back roll. In the figure, θ is the slide surface angle, and θ ′ is the position of the application point and represents the angle between the center of the back roll and the tip of the coater. Φ is the angle between the tangent drawn on the back roll and the slide surface in the coating bead.

 There is a relationship of Φ = 90 ° + θ′−θ.

When applying, slide surface angle θ is 5 °, 20 °, 30 °,
35 °, 50 °, and for each, Φ 80 °, 90 °, 100 °
And the gap between the coater tip and the web is 0.15
mm, 0.2 mm, 0.25 mm. Under these conditions, the liquid of the basic formulation was applied, and the number of streaks per unit width (1 m) was evaluated. The results are shown in Table 2.

In the table, the gap represents the gap between the tip of the hopper and the web. In addition, θ = 5 ° and Φ = 80 ° are physically impossible arrangements.

In the case of θ = 35 ° and 50 °, the conditions are described in JP-A-60-183064. However, as is clear from Table 1, streaking often occurs, and even if the gap between the hopper tip and the web is changed. It can be seen that there is no significant change in the number of streaks.

On the other hand, under the conditions that the slide surface angles are 5 °, 20 °, and 30 °, the streaks can be greatly reduced by setting the gap to 0.2 mm or less, and the smallest can be obtained by setting Φ = 90 °. Muscle development can occur.

This is presumed to be due to the fact that when the slide surface inclination is made a certain degree or more, the downward movement increases, but rather the coating bead is disturbed.

Example 2 The following emulsion layers 1 and 2 and a protective layer were simultaneously coated at a coating speed of 90 m / min on an undercoated 120 μm triacetate base.

 The wet thickness at this time was 30, 40, and 20 μm, respectively.

Emulsion layer 1 Regularly sensitized silver iodobromide emulsion containing 7 mol% of iodine
6730g silver halide in 30l gelatin as protective colloid
To an emulsion containing 1500 g, a predetermined amount of 4% carboxydextran sulfate as a thickener, a predetermined amount of the same surfactant as in Example 1, and 40 parts of the following yellow coupler
was added and 2.0 kg of gelatin was added to make 100 l.

 The solid content of this coating solution is 6.73%.

1.8 kg of the above coupler was dissolved in 1.8 kg of dibutyl phthalate and 3.6 l of ethyl acetate, added to 30 l of a 5% gelatin solution containing 100 g of sodium lauryl sulfosuccinate, and emulsified and dispersed using a homogenizer type M3 manufactured by Gaulin to complete 40 l.

Emulsion layer 2 Regularly sensitized silver iodobromide emulsion containing 4 mol% of iodine, emulsion containing 6680 g of silver halide and 1750 g of gelatin
In Example 1, a predetermined amount of the thickener used in Example 1 and 1 part of the surfactant were used.
, 1.25 Kg of gelatin, 40 l of the above coupler dispersion and added
Finished to 00l.

Protective layer To 100 l of a 6% gelatin solution, a predetermined amount of the same thickener as in Example 1 and 6 l of a surfactant and 6 l of a 2% mucohalic acid were added.

Coating conditions Viscosity (cp) Surface tension (dy
ne / cm) Emulsion layer 1 20 37 Emulsion layer 2 15 38 Protective layer 10 27 Measurement temperature 38 ° Measurement method Example 1
Same as.

Apparatus conditions Same as Example 1.

However, the angle Φ between the tangent to the slide surface and the back roll at the application point was changed to 70 °, 90 °, and 110 °. Table 2 shows the number of applied streaks in this case.

From the results in Table 2, the slide surface angle was set to 30 ° as in Example 1.
Hereinafter, the gap between the hopper tip and the web shall be 0.2 mm or less,
It can be seen that when Φ is 90 °, the best coating film can be obtained.

〔The invention's effect〕

According to the present invention, it was possible to provide an application method with less occurrence of streak failure, particularly, an application method with less occurrence of streak failure when applying a coating solution containing a water-insoluble solid in the lowermost layer with a slide hopper.

[Brief description of the drawings]

FIG. 1 is a sectional view of a slide hopper device, and FIG. 2 is a partially enlarged view of FIG. FIG. 3 is an explanatory diagram showing the positions of the slide hopper device and the back roll. 1: Back roll, 2: Slide hopper 5: Slide surface, 10: Web 11: Coating film, 12: Bead C: Center of back roll

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-183064 (JP, A) JP-A-49-101455 (JP, A) JP-A-62-95173 (JP, A) 44925 (JP, B1) JP-B-58-907 (JP, B2) U.S. Pat. No. 4,284,443 (US, A) U.S. Pat. No. 3,896,632 (US, A) U.S. Pat. Patent 1268144 (GB, B)

Claims (2)

(57) [Claims] In a method for applying a coating solution to a continuously running web by a slide hopper device, a collision point between the coating solution and the web is located above a center point of a back roll, and Of the slide surface with respect to the horizontal reference plane is 5 ° to 30 °. (B) The angle between the tangent to the back roll and the slide surface at the point of collision between the coating liquid and the web is 85 ° to 95 °. (C) The gap between the tip of the hopper and the web should be 0.2 mm or less. A coating method characterized by the following. 2. The coating method according to claim 1, wherein the coating liquid for forming the lowermost layer in contact with the support contains 2 to 15% by weight of a solid content insoluble in water.