JPH02245267A - Applying method - Google Patents

Abstract

PURPOSE:To prevent generation of trouble resulting from a stripe when a sliding hopper is utilized by positioning the collision point of applying liquid and a web to the part upper than the central point of a back up roll and regulating angle of inclination for the horizontal reference face of a device to 5-30 deg.. CONSTITUTION:The collision point of both applying liquid allowed to flow on a sliding face 5 and a web is nearly positioned to a point of the lip part 6 of an applicator. This point is higher than C being the center of a back up roll 1 for application. The web 10 is held by the back up roll 1, traveled and brought into contact with applying liquid allowed to flow on the sliding face 5 through the slots 4 of an applicator 2 of a sliding bead in the lip part 6 of the applicator. A bead 12 being a ribbonlike liquid reservoir is formed in the lip part 6. The applying liquid is applied to the web via this bead. At this time, the bead 12 is stabilized by pulling the bead 12 downward by a decompression device 3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coating method in which one or more coating liquids are simultaneously coated onto a web using a slide hopper device, and more specifically, a coating method suitable for coating photographic materials. Regarding.

[Prior Art] When coating a traveling long flexible strip-shaped support (hereinafter referred to as a web) using a slide hopper device, a coating bridge (hereinafter referred to as A bead (referred to as a bead) is formed through which the web is coated.

When coating with a slide hopper device, it is very important to keep this bead stable.

In other words, when the bead is disturbed or disturbed, various defects occur in the coating layer applied to the web. For example, a particularly noteworthy defect is the occurrence of streak failure in which vertical streaks appear, and the occurrence of this streak failure results in a decrease in the coating yield of the photographic light-sensitive material. This streak failure occurs from the beginning of the application process, from the time when the web passes through the seam, or when foreign matter such as dust adheres to the web even during steady application, and when this foreign matter passes through. etc.

This streak failure occurs more noticeably as the speed and thinner film is applied.

Various improved techniques have been proposed as techniques for preventing the occurrence of muscle failure. For example, (1) creating a pressure difference between the exposed surfaces above and below the bead portion, such as by creating a vacuum on the surface from which the bead portion hangs, as disclosed in U.S. Pat. No. 2,681,294; technology to make
(2) As disclosed in Japanese Patent Publication No. 51-39980,
A lip is provided at the coating liquid outflow end of the hopper device, and the inclination angle of the top surface of the lip is smaller than the inclination angle of the coating liquid outflow surface, so that the thickness of the coating liquid layer on the top surface of the lip is formed. Technology to increase (3)
) As disclosed in Japanese Patent Application Laid-Open No. 60-183064, the inclination angle of the slide surface with respect to the horizontal reference plane is set to 35" to 50".
degree, and the angle formed by the tangent at the point of collision between the coating liquid and the web is 85 degrees to 110 degrees, and the point of collision is above the center of the coating backup roll, (4) Patent Publication No. 58-907 In order to stabilize the rear end of the bead in contact with the hopper, a liquid holding part is provided at the tip of the hopper.

Technologies such as the following have been disclosed.

However, each of these techniques had the following drawbacks.

That is, the technique (1) above is not sufficient to prevent excessive vibration of the bead if the pressure difference between the upper and lower exposed surfaces of the bead portion is too small, so in this case, the degree of vacuum is increased to reduce the pressure difference. However, if the degree of vacuum increases excessively, the bead may be disturbed or burst. Furthermore, although the technique described in (2) above has the effect of minimizing the occurrence of undesirable streak failures on the coating film due to foreign matter such as dust or silver adhering to the tip of the hopper device, it is also effective in minimizing the occurrence of streak failures caused by other reasons. has no effect. Furthermore, in the technique (3) above, when the slope of the slide surface is large, the dynamic pressure of the liquid increases as the coating liquid flows into the coating bead, and although the adhesion force of the coating liquid to the web increases slightly, it actually worsens the problem as a countermeasure against streak failure. Furthermore, the thickness of the liquid film on the slide surface becomes thinner, which is not preferable for preventing muscle damage caused by foreign objects or the like on the slide surface. Although the technique (4) above has a certain effect, it cannot be said to be sufficient. None of these techniques (1) to 4) are effective against streak failures that occur from the start of coating, and it is difficult to prevent streak failures, especially in the case of high-speed thin film coating. Ta. Furthermore, even during steady application, it was not effective against bead disturbances, and it was not possible to prevent streak failure.

[Problems to be Solved by the Invention] To address the above-mentioned problems, an object of the present invention is to provide a coating method that does not cause streak failure, and in particular, it is an object of the present invention to provide a coating method that does not cause streak failure. An object of the present invention is to provide a coating method that does not cause coating failures even when coating liquids in multiple layers using a slide hopper device.

[Means for Solving Problems 1] The above-mentioned object of the present invention is to set the point of collision between the coating liquid and the web at the center of the back roll in a method of multilayer coating a coating liquid onto a continuously running web using a slide hopper device. (a) The inclination angle of the slide surface of the sliding device with respect to the horizontal reference plane is 5° to 30°. (B)
At the point of collision between the coating liquid and the web, the angle between the tangent to the back roll and the sliding surface is 85° to 95°.

(c) The gap between the hopper tip and the web should be 0.2+am or less.

This is achieved by a coating method characterized by:

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 water-insoluble solids.

The present invention will be specifically explained below. FIG. 1 shows a schematic cross-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 onto the slide surface 5 at the coating machine lip part 6, and forms a ribbon-shaped liquid pool in the lip part. A bead 12 is formed through which the coating liquid is applied onto the web. At this time, a method is generally adopted in which the bead is stabilized by pulling the bead downward with the decompression device 3. The above mechanism is the same whether it is a single layer or two or more layers, and simultaneous multilayer coating can be performed by flowing a plurality of coating liquids onto the slide surface through a plurality of slots. The case in Figure 1 is an example of two-layer coating,
For example, the emulsion liquid 14 is poured into the lower layer, and the protective film liquid 1 is poured into the upper layer.
This is an example of a case where simultaneous multilayering is performed by flowing 3.

In the figure, in the present invention, the collision point between the coating liquid flowing on the slide surface 5 and the web is approximately at the coating machine lip portion 6, but this point is higher than the center C of the coating backup roll l. According to the results of studies conducted by the present inventors, the collision point is located above the above six points. FIG. 2 is an enlarged view of the vicinity of the collision point, and the application liquid flowing on the slide surface 5 is affected by the heavy splatter, 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) Due to θ, the force F9 due to gravity is divided into two components, one is a component force F■ parallel to the slide surface, and the other is a component force Fh perpendicular to the slide surface.
It is. 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
It is proportional to the product of and sin θ. Therefore, if θ becomes small, Ft
a also becomes smaller, the flow rate of the coating liquid flowing on the slide surface becomes slower, and the liquid thickness becomes thicker. Furthermore, Fh becomes large, and the force that spreads across the width becomes strong. As the thickness of the liquid increases, streaks are less likely to occur on the slide surface, but because Fll is small, the difference in shear rate between the web and the slide surface increases, and the coating liquid is suddenly stretched out at the collision point. As a result, the bead becomes shallow and unstable. As a result of various studies, the inventors of the present invention determined that at coating points where the inclination angle of the slide surface is 5° to 300°, the angle between the tangent to the back roll and the slide surface is 90', and the gap k between the web and the tip of the hopper is 0. We have discovered that if the thickness is 2 mm or less, stable coating can be achieved with significantly less streak failure.

[Example] The effects of the present invention will be specifically explained below with reference to Examples. It goes without saying that the inclination angle of the slide surface is not limited to the values described in this embodiment, and can be selected within the range described in the claims according to other conditions such as coating speed and liquid viscosity.

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

The emulsion is an ortho-sensitized silver iodobromide emulsion (containing 2 mol % of iodine) 35 (contains silver iodobromide 66509 and gelatin 2000y as a protective colloid in one liter).The emulsion contains gelatin 12501? and sodium as a surfactant. -di(
2-ethylhexi 1)-3ulfosuccin
65cc of 1% solution of ate and styrene as a thickener.
2Q of a 4% aqueous solution of maleic acid copolymer was added to form a 65Q solution, which was used as an emulsion layer coating solution. The solid content concentration of this coating liquid was 1000%.

The second layer is a protective film layer, in which the surfactant 8Q 14% formalin solution 31214% is contained in 8% gelatin solution 100Q.
Glyoxal 8Q and a predetermined amount of the above-mentioned thickener were added to prepare a coating liquid for a protective film.

Coating speed 60m/in, coater vacuum degree -35+ma
q, the wet film thickness is 50 pm for the emulsion layer and 15 μm for the protective film layer.
And so.

The viscosity of the coating liquid is 15 cp for the emulsion layer, 15 cp for the protective film layer, and the surface tension is 39 dyne/am% for the emulsion layer and 26 dyn for the protective film layer.
It was e/am. The measurement conditions were as follows: viscosity was measured using a Brookfield viscometer, and surface tension was measured at 35° C. using the Williams method.

Coating with this layer structure was carried out under the following coating equipment conditions.

FIG. 3 is an explanatory diagram showing the positional relationship between the slide surface and the back roll. In the figure, C represents the slide surface angle. 11 represents the angle formed between the center of the back roll and the tip of the coater at the position of the coating point. φ is the angle between the tangent line drawn to the back roll and the sliding surface in the coating bead.

There is a relationship of φ-90°+I'-1.

When applying, set the slide surface angle I to 5°, 20″, 30″.
, 35°, and 50°, and the numbers are 80° and 90°, respectively.
°, 100°, and the gap between the coater tip and the web was set to 0.15 mm.

It was changed to 0.2+++m and 0.25mm. The above-mentioned basic solution was applied under these conditions, and the number of streaks generated per unit width (1 m) was evaluated. The results are shown in Table 1.

Margin table below: 1 In the table, the gap represents the gap between the hopper tip and the web. Further, I-5'' and φ-80° are physically impossible arrangements.

When I=35°150°, JP-A-60-183064
As is clear from Table 1, under the conditions described in the above issue, many streak failures occur, and even if the gap between the hopper tip and the web is changed, there is no significant change in the number of streaks.

On the other hand, under the conditions where the sliding surface angle is 5°, 20', and 30°, if the gap is set to 0.2 mm or less, the streaks can be significantly reduced, and roughly speaking, if Φ = 90°, The least amount of muscle formation can be achieved.

This is presumed to be because if the slope of the slide surface is increased beyond a certain level, although the dynamic pressure flowing down increases, it actually disturbs the coating bead.

Example 2 The following emulsion layers 1 and 2 and a protective layer were coated on a triacetate base with a 120 μm drag at a coating speed of 90 m/s.
Simultaneous multilayer coating was performed using in.

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

Emulsion layer 1 Regular sensitized silver iodobromide emulsion 3 containing 7 mol% of iodine
Silver halide 673 (h) in 0I2 was added to an emulsion containing gelatin 1500G as a protective colloid, a predetermined amount of 4% carboxydextran sulfate as a thickener, a predetermined amount of the same as in Example 1 as a surfactant, and the yellow color shown below. Add 40Q of coupler, add 2゜0Kg of gelatin,
Finished with 1 o Off.

The solid content concentration of this coating liquid was 6.73%.

(Yellow coupler) I2 1.8Kg of the above coupler is mixed with 1.8K dibutyl phthalate.
g and ethyl acetate 3.6a, added to 5% gelatin solution 3H containing lauryl sulfokoba and sodium phosphate IQOf, and emulsified and dispersed using Gaulin homogenizer type M3 to obtain 404.

Emulsion layer 2 A regularly sensitized silver iodobromide emulsion containing 4 mol% of iodine, 35ff of emulsion containing 6,680 g of silver halide and 1,750 g of gelatin, a predetermined amount of the thickener used in Example 1, and 112 g of a surfactant. , add 9 to 1.25 gelatin and 4012 of the above coupler dispersion! Finished to 00a.

To 100 ff of 6% gelatin solution for the protective layer, add a prescribed amount of the same thickener as in Example 1, and 612 ml of surfactant 6Q 12% mucohalogenic acid.
added.

Coating conditions Viscosity (cp) Surface tension (dyne/cm) Emulsion layer 1 20 37 Emulsion layer 2 15
38 Protective layer 1027 Measurement temperature 38°C Measurement method Same as Example 1.

Equipment conditions: Same as Example 1.

However, the angle φ between the slide surface and the tangent to the back roll at the coating point was changed to 70', 906.1100. Table 2 shows the number of coating streaks generated in this case.

The following margin table gap is the gap between the hopper tip coating and the web - = 5, φ・7
0° is physically impossible. From the results in Table 2, the slide surface angle was set to 30° as in Example 1.
Below, the gap between the hopper tip and the web is 0.211II
It can be seen that the best coating film can be obtained if the diameter is less than I and φ is 90°.

[Effects of the Invention] According to the present invention, it is possible to provide a coating method that causes fewer streaks, particularly when applying a coating solution containing water-insoluble solids in the bottom layer using a slide hopper. was completed.

[Brief explanation of drawings]

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

Claims (2)

[Claims] (1) In a method of coating a continuously running web with a coating liquid in multiple layers using a slide hopper device, the collision point between the coating liquid and the web is located above the center point of the back roll, and (a) the device slides. The angle of inclination of the surface with respect to the horizontal reference plane is 5° to 30°. (b) At the point of collision between the coating liquid and the web, the angle between the tangent to the back roll and the sliding surface is 85° to 95°. (c) The gap between the hopper tip and the web should be 0.2 mm or less. A coating method characterized by: (2) The coating method according to claim 1, wherein the coating liquid forming the lowermost layer in contact with the support contains 2 to 15% by weight of water-insoluble solids.