JPH02174965A - Method and device for coating to double layers - Google Patents

Abstract

PURPOSE:To determine the coated amt. of the 1st coated layer of a base by providing a doctor blade opposite to a back up roller which supports the flexible base and setting the spacing with the side face on the downstream thereof and to form the 2nd coated layer by discharging a coating liquid from the side face on the upper stream side. CONSTITUTION:The flexible base 2 is run while the base is supported by the back up roll 1 and the front end of a coating head 3 is installed to face the back up roll 1. The spacing (b) between the doctor blade 4 positioned on the upper stream side of the head 3 and the surface of the base 2 is made freely settable and the coated amt. of the 1st coated layer 8 applied on the base 2 is adjusted. Further, the 2nd measured coating liquid 9 is sprayed from the spacing between the doctor blade 4 and a smoothing blade 5 on the upper stream side thereof onto the 1st coated layer 8 by which the 2nd coated layer is formed. The formation of the double coated layers is, therefore, stably executed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to the application of a photographic photosensitive liquid, a magnetic liquid, and a surface that protects them to a flexible strip (support) such as a plastic film, paper, or metal foil. The present invention relates to a method and apparatus for applying a coating liquid such as a protective liquid, and particularly to a multilayer coating method and apparatus suitable for use when manufacturing a magnetic recording medium or the like by applying a coating liquid such as a magnetic material.

(Prior Art) Magnetic recording media such as magnetic tapes and photographic films are produced by coating the surface of a flexible support with a coating solution appropriate for the intended use, drying it, and then cutting it into desired widths and lengths. be. The "support" as used in the present invention includes polymeric compounds such as polyethylene terephthalate, cellulose acetate, polyimide, and polyamide, as well as flexible strips made of paper, copper, and metal foil. Further, the "coating liquid" includes a magnetic material dispersion liquid, a photosensitive material coating liquid, a heat-sensitive material coating liquid, a polymer melt, and the like.

Various methods have been used to apply the coating solution in multiple layers (multilayer coating), such as slide hopper type, curtain type, web pressure extrusion type,
There is a method using an extrusion type device with a backup roll.

The slide hopper type is manufactured by Tokuko Sho 33-897.
Although it is described in Publication No. 7, etc., this type of device is
It is not possible to generate a coating pressure near the upstream meniscus (bead) when applying the coating liquid. Therefore, especially during so-called high-speed thin layer coating in which a thin coating layer is formed at high speed, an entrainment phenomenon in which air entrained by the support gets into the coating liquid tends to occur. Further, when the second coating liquid forming the upper layer is made thinner, there are drawbacks such as the coating liquid not being able to be stretched sufficiently and liquid shortage occurring, and it being difficult to apply a high viscosity coating liquid.

Curtain types are U, S, P, 3450894
7 etc. Even in this type of device,
Similar to the slide hopper type device, it was not possible to generate a coating pressure, the properties of high-speed thinning and high viscosity liquid coating were insufficient, and it was difficult to thin the second coating liquid.

A web pressurized extrusion type is described in Japanese Patent Laid-Open No. 58-109162. This type of device can generate coating pressure near the upstream meniscus (bead) when coating the coating liquid, so from this point of view, the characteristics of high-speed thinning and coating of high-viscosity liquids are improved. However, since the web (supporting body) is pressed against the coating head, unevenness in the web's own thickness and uneven Young's modulus can adversely affect web runnability, resulting in uneven coating thickness. was there.

The extrusion type with backup roll is [1, S, P, 3206323. Unexamined Patent Publication 1986-11
It is described in Publication No. 1168, etc. This type of equipment has better high-speed thin layer coating and high viscosity liquid coating characteristics than the slide hopper type and curtain type, and also applies coating pressure to the coating liquid with the coating head, similar to the web pressure extrusion type. Since it can be added, it is easy to make the second coating layer thinner.

However, there was a major drawback in that the area in which the first coating layer could be coated was narrower than in the above three types of methods. This is because the range of the amount of the first layer that can be coated is determined by the gap between the coating head and the backup roll. In other words, when the coating amount of the coating liquid is changed in order to change the thickness of the first layer, the coating pressure changes in response to this change, and a stable coating is formed due to a small change in the coating amount. As a result, it becomes impossible to maintain the desired coating conditions. Therefore, not only is it difficult to operate because the gap must be set with high precision, but also the bead becomes unstable due to the rotatability of the backup roll. Furthermore, especially in the type where the two liquids merge in the coating head, in addition to the stable formation of the bead, the interface between the two liquids may be disturbed during the merging, and the physical properties of the liquid and the coating liquid discharge port may be affected. There was a problem in which the shape of a certain slot, etc. had to be taken into account.

In addition, in recent years, there has been a demand for thinner coating layers, and there has been a strong desire for highly accurate coating and versatile coating methods and devices that can meet this demand.

(Objective of the Invention) Under such circumstances, the present invention aims to solve the above-mentioned problems, that is, to enable high-speed thin-layer coating and multi-layer coating of high-viscosity coating liquids in connection with an extrusion type with a backup roll. To provide a multilayer coating method and apparatus that can easily and stably form a first coating layer under desired conditions with high accuracy and are less susceptible to the effects of non-uniformity of a support. This is the purpose.

(Means for Solving the Problems) The object of the present invention is to apply a liquid to form a first coating layer on the surface of a flexible support that is run in a certain direction; The back side of is held by a backup roll, and the amount of coating of the first coating layer by the liquid is determined by setting the gap between the backup roller and a doctor blade facing the backup roller, and then the downstream side of the doctor blade is A predetermined second coating liquid is discharged from a slot formed by the side surface of the smoothing blade and the upstream side surface of the smoothing blade provided so as to face the first coating liquid.
a multilayer coating method of forming the second coating layer on the coating layer;
and an apparatus that makes it possible to carry out the method, that is, a backup roll that supports the back side of the flexible support coated with the liquid forming the first coating layer, and a doctor provided to face the backup roll. A smoothing blade is provided in which a gap between the doctor blade and the blade can be freely set, and a smoothing blade having a slot surface facing the downstream side surface of the doctor blade and a coating surface facing the backup roll. This can be achieved by a coating apparatus characterized in that the second coating layer, which is an upper layer of the first coating layer, is configured to discharge a second liquid from a slot formed therein.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Note that FIG. 1 is a schematic diagram of a magnetic recording medium coating apparatus for carrying out the coating method of the present invention, and FIG. 2 is an enlarged view of the main part of FIG. 1.

As shown in FIG. 1, the coating device includes a backup roll 1.
This is an extrusion tube coating device with a backup roll, which is composed of a coating head 3 installed so that the tip of the head faces the backup roll 1.

As shown in FIGS. 1 and 2, the coating head 3 has a
It has a structure in which a doctor blade 4 is provided at the tip of the head, which is located on the upstream side in the traveling direction of the flexible support 2, and a smoothing blade 5 is provided on the downstream side. Then, the first coating layer 8
The gap between the backup roll 1 that supports the back side of the flexible support coated with the first liquid forming the The gap h) between the doctor blade 4 and the surface of the support 2 is freely settable.

That is, the coating head 3 is fixed to, for example, a holding member 10, and the holding member 10 is connected to the backup roll 1.
It is possible to move toward or away from the roll 1 (in the direction of arrow B) or away from the roll 1 (in the direction of arrow C) with extremely high precision. Furthermore, the smoothing blade 5 includes a slot surface 5a facing the downstream side surface 4a of the doctor blade 4 and a coating surface 5b facing the backup roll 1, and the downstream side surface 4a and the slot surface 5a The second liquid for forming a second coating layer 9 which is an upper layer of the first coating layer 8 is discharged from the slot 6 formed in the above.

When the wet (undried) film thickness of the first layer of the magnetic recording layer formed on the support 2 is, for example, about 0.015 to 0.03 mff1, the doctor blade 4 for forming the first layer and the The gap with the support body 2 is, for example, 0.03
The forward angle of the tip of the doctor blade 4 may be set to approximately a right angle as shown in the figure, but this range is preferably in the range of 70 to 110 degrees. The dimension g of the slot 6 is 0.15~
2. A range of approximately Qmm is desirable. Furthermore, the coating surface 5b of the smoothing blade 5 is configured to retreat from the backup roll 1 more than the upper end surface of the doctor blade 4, and this retreat dimension is as follows:
A range of approximately 0.005 to 0.050 mm is desirable.

In the coating device configured in this manner, a first coating liquid (magnetic dispersion liquid or second The first coating layer 8 is applied by setting a gap between the backup roller 1 that backed up the back side of the support 2 and the doctor blade 4 facing the backup roller 1. amount can be determined. That is, the excess amount of the first liquid is scraped off by the front end portion of the doctor blade 4, and only a predetermined amount passes between the doctor blade 4 and the backup roll 1. A measured second coating liquid, which is supplied from the liquid supply system 11 to the liquid reservoir 7 and is discharged from the slot 6, is discharged onto the first coating layer 8 that has passed through the second coating layer 8.
can be formed and two-layer multilayer coating can be performed successfully.

Since the size of the gap can be freely changed as in this embodiment, the coating range of the first coating layer 8 can be freely changed, and this is different from the conventional coating apparatus of this type. Improved high-speed thin layer coating, which was difficult to achieve,
Multi-layer coating of high-viscosity coating liquids is possible, and there is no problem such as variation in coating pressure due to non-uniformity of the support, and the first coating layer 8 can be easily and stably coated under desired conditions with high precision. Therefore, the second coating layer 9 can be applied satisfactorily.

In the embodiment described above, the coating head 3 is configured to move, but in the apparatus of the present invention, the backup roll 1 may be configured to be moved, or both may be configured to be movable. Various changes can be made, such as configuring it to adjust the extremeness. Furthermore, although the above embodiments have been described with reference to two-layer coating, the present invention is not limited to two-layer coating, but can also be applied to multilayer coating of two or more layers.

(Effects of the Invention) As explained above, the present invention applies a first coating layer to the surface of a flexible support, holds the back side of the flexible support with a backup roll, and The coating amount is determined by scraping off the first coating layer by setting a gap between the roller and a doctor blade facing the backup roller, and a roller is provided to face the downstream side surface of the doctor blade. The measured second coating liquid is discharged from the slot formed by the upstream side surface of the smoothing blade, and the second coating layer is formed on the first coating layer, so that the gap is large. By freely changing the coating range of the first coating layer, the suitability for high-speed thin layer coating, which was difficult with conventional coating devices of this type, is improved.
The ability to cope with multilayer coating of high-viscosity coating liquids is improved, and since the excess of the first coating layer is scraped off, coating pressure fluctuations due to non-uniformity of the support and the rotational properties of the backup roller are improved. problems such as the above can be minimized, and the first coating layer can be easily and stably formed with high precision under desired conditions over a wide range.
Application of the coating liquid after the coating layer can also be performed satisfactorily.

(Example-1) Next, the effects of the present invention can be further clarified through examples.

In this example, the first coating liquid 8 had a composition as shown in Table 1.

Table-1 And the coating liquid viscosity of the first coating liquid 8 in Table-1 is 7
(2.4P, . . ., closed with l Qsec-'.

On the other hand, the second coating liquid 9 had a composition as shown in Table 2.

Table-2 And the coating liquid viscosity of the second coating liquid 9 in Table-2 is 70
It was closed at 1.9P, i, at 0sec-'.

For support 2, PET with a thickness of 37 μm is made of PET with a width of 500 μm.
[+11B, tension was 7 Kg/5oo-1, and the support was run at a speed of 300 m/min.

Furthermore, the coating head 3 shown in FIG. 2 in the above embodiment is adopted, and each dimension of the coating head 2 is the width t of the doctor blade 4 and the smoothing blade 5 =
5. Q mm, gap g of slot 6 = Q, 7 mm
, the role of the doctor blade 4 and the smoothing blade 5 was set as d=0.02 +y++TI.

Further, the radius of the backup roll 1 was set to R=120 mm.

Further, the setting of the coating thickness of the first coating layer 8 is based on the graph shown in FIG. 3 (when the film thickness of the second coating layer 9 is 11 CC/m2). and the gap were adjusted. Note that this relationship can be determined by the relational expression approximately [(gap or height d)/2]. The adjustment range of the gap is 0.02~0.05mft
I set it to a + value.

(Comparative Example-1) A curtain type coating device as shown in FIG. 4 was used. The structure of this application head 20 is U, S, P, 3
508947, etc., and its dimensions are the dimension t of the top surface of the coating head, =3Q+++m s F
=30mmN each slot width g+=0.7mm, g2=
0.7 mm, inclination angle α of the coating liquid outflow surface of the coating head, -
40° Distance between the head and the support body Fl+=75 mm.

Note that the first coating liquid 8 (lower layer) and the second coating liquid 9 (upper layer)
The conditions such as the composition and transportation of the support 2 are as in Example-1.
The same as

(Comparative Example-2) A web pressure extrusion type coating device as shown in FIG. 5 was used. The structure of this coating head 30 is disclosed in Japanese Patent Laid-Open No. 58-109162, etc., and the dimensions of the coating head 30 are as follows: dimension of the top surface of the head j+=5.0 mm% ta=4.0 mm 5js=6 ．．
Qmm, D=1. Omm, height d+=0. Q7mm
5d2=0. Q9mm % Inclination angle α of the top surface of the head
2=30°, α3・10°, α,=io”, each step o-
) width gi=0.7mm5g4=0.7mm.

The conditions such as the composition of the first coating liquid (lower layer) and the second coating liquid (upper layer) and mold transfer of the support 2 were the same as in Example-1.

The results of Example 1 and Comparative Examples 1 and 2 are shown in Table 3.

In addition, the measurement target N011 in Table 3 is the measured value when the coating amount of the second coating layer is 1lcc/m', and No. 2 is the measured value when the coating amount of the second coating layer is 1lcc/m'
This is a measured value when the coating amount of the coating layer was 31 ee/m'.

In addition, for No. 3, the coating amount of the first coating layer was 31cc/m'
This represents the incidence of coating thickness unevenness when the coating amount of the second coating layer is 1Qce/m2, but this means:
This is coating unevenness due to variations in coating pressure due to non-uniformity in the thickness and Young's modulus of the support.

Table 3 As shown in Table 3 above, the coating limits of the first coating layer and the second coating layer are better in the examples of the present invention than in the comparative examples, indicating that coating is possible. It can be seen that the coating range is widened and that the occurrence of coating unevenness due to external factors such as non-uniformity of the support can be avoided.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a coating device in an embodiment of the present invention,
Figure 2 is an enlarged sectional view of the main parts of the coating head shown in Figure 1, Figure 3 is a graph showing the relationship between the first coating layer and the gap between the doctor blade and backup roll, and Figure 4 is a comparative example of the curtain type. FIG. 5 is a cross-sectional view of the main part of the coating head, and FIG. 5 is a cross-sectional view of the tip of the coating head in a web pressurization extrusion type as a comparative example. Reference numerals in the figure 1... Backup roll, 2... Support body, 3...
・Application head, 4...Doctor blade, 4a
...Downstream side surface, 5...Smoothing blade, 5
a...Slot surface, 5b...Coating surface, 6.
...Slot, 7...Liquid reservoir, 8...First coating layer, 9...Second coating layer, 10...Holding member, 11...Liquid supply system, 20...Curtain type Coating head, 30... Web pressurized extrusion type coating head. 3 other people)

Claims (1)

[Claims] 1) Applying a liquid for forming a first coating layer to the surface of a flexible support that is run in a certain direction, and holding the back side of the flexible support with a backup roll; The amount of the first coating layer coated by the liquid is determined by setting a gap between the backup roller and a doctor blade facing the backup roller, and the roller is provided to face the downstream side surface of the doctor blade. A pre-metered second
A multilayer coating method comprising discharging a coating liquid to form a second coating layer on the first coating layer. 2) A gap between a backup roll that supports the back surface of the flexible support coated with the liquid forming the first coating layer and a doctor blade provided to face the backup roll is configured to be freely settable. Further, a smoothing blade having a slotted surface facing the downstream side surface of the doctor blade and a coating surface facing the backup roll is provided, and the first coating layer is removed from the slot formed by the side surface and the slotted surface. A coating device characterized in that a second coating layer serving as an upper layer is configured to discharge a second liquid.