JP7270757B2 - die head - Google Patents

Description

The present disclosure relates to die heads.

2. Description of the Related Art A method of forming a desired coating layer on a base material in a coating apparatus equipped with a die head is known.

Patent Document 1 discloses a coating member manufacturing apparatus in which a coating liquid ejection port is formed between a pair of lip tip portions and a coating film is formed on the surface of a member to be coated that moves relative to the ejection port. A manufacturing apparatus for a coating member is disclosed in which the tip of the downstream lip located on the film formation side has a larger contact angle with water than the tip of the upstream lip.

Patent Document 2 discloses a die coater used for forming a transparent conductive layer by coating a transparent conductive layer-forming coating liquid containing at least a metal material on a transparent base material. It has a die head for discharging the coating liquid, a coating liquid tank for containing the coating liquid for forming the transparent conductive layer, and a liquid feeding path for feeding the coating liquid for forming the transparent conductive layer from the coating liquid tank to the die head. , a die coating apparatus in which a liquid-repellent region is formed at least on the surface of the die head located in the direction opposite to the coating direction.

Patent Document 1: JP-A-2002-248399 Patent Document 2: JP-A-2016-68047

In the die head, once the coating liquid adheres to the contact portion of the lip with the coating liquid, it is then covered with the coating liquid (that is, the coating liquid forms a film on the contact portion). will be done). If the portion of the lip that comes into contact with the coating liquid is covered with the coating liquid, the coating streak will occur starting from that portion.
There are two types of coating streaks here. That is, for example, there are two types of coating streaks: coating streaks caused by the lip on the most upstream side and coating streaks caused by the lip on the most downstream side with respect to the conveying direction of the substrate, which is the member to be coated.
Coating streaks caused by the lip on the most upstream side may be streaks caused by the dry product (i.e., solid content) of the coating liquid generated on the land surface or land surface edge disturbing the shape of the bead end, or streaks caused by the land In some cases, streaks are caused by droplets generated by a flow due to the difference in surface tension between the film of the coating liquid formed on the surface and the beads adhering to the edges of the beads. In the former case, linear film thickness unevenness (that is, streaks) extending along the conveying direction of the base material appears singly or continuously, and the width thereof is about 0.1 mm to 5 mm. In the latter case, linear film thickness unevenness (that is, streaks) extending along the transport direction of the substrate appears singly or sporadically, and the width thereof is about 0.1 mm to 5 mm.
On the other hand, the coating streak caused by the lip on the most downstream side is a droplet of the coating liquid or a dried product of the coating liquid (that is, solid content) that reaches the surface of the lip opposite to the slot forming surface and connected to the land surface. However, the streak is caused by disturbing the shape of the bead edge. In the case of this streak, linear film thickness unevenness (that is, streak) extending along the conveying direction of the base material appears singly or continuously, and the width thereof is about 0.1 mm to 5 mm.
Coating streaks caused by the lip on the most upstream side and coating streaks caused by the lip on the most downstream side can be checked by observing the shape of the bead during coating and the surface condition of the formed coating film. This can be confirmed by capturing the shape of the thickness unevenness. In other words, by linking the observation result of the bead shape with the shape of the formed film thickness unevenness, it is possible to determine whether the coating streak is caused by the lip on the most upstream side, or whether the coating streak is caused by the lip on the most downstream side. It is possible to check whether
Here, the surface condition of the coating film may be observed visually, using a magnifying glass, or using an apparatus for observing the surface condition by transmission or reflection. In addition, a microscope may be used to observe the surface condition of the coating film, and depending on the type of the coating film, the crossed Nicols method may be used.

Accordingly, the problem to be solved by one embodiment of the present disclosure is to provide a die head capable of suppressing the occurrence of coating streaks.

Specific means for solving the problems include the following aspects.

<1> having two or more parallel lips and a slot formed between adjacent lips for transferring and discharging the coating liquid,
At least one of the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction, which is connected to the land surface on the side opposite to the slot forming surface, has a dynamic contact angle hysteresis of 20° or less due to methyl ethyl ketone. A die head.

<2> The die head according to <1>, wherein the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction have a ten-point average roughness Rzjis of 1.0 μm or less. .

<3> The die head according to <1> or <2>, wherein the land surface of the lip at the other end in the parallel direction has a dynamic contact angle hysteresis due to the methyl ethyl ketone of 20° or less.

<4> Of the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction, the surface having a dynamic contact angle hysteresis of 20° or less due to the methyl ethyl ketone is a fluorine-containing compound. The die head according to any one of <1> to <3>, comprising a surface treatment layer formed using
<5> The die head according to <4>, wherein the fluorine-containing compound is a compound having a perfluoropolyether group.
<6> The die head according to any one of <1> to <5>, wherein the lip at the other end in the parallel direction has a curved surface at a portion connected to the land surface on the outer surface when viewed from the side.
<7> The die head according to <6>, wherein the curved surface of the lip at the other end in the parallel direction has a curvature radius of 0.2 mm or more.
<8> During application, the lip at one end in the parallel direction is positioned downstream with respect to the application direction, and the lip at the other end in the parallel direction is positioned upstream with respect to the application direction, <1> to <7 The die head according to any one of .

An embodiment of the present disclosure provides a die head capable of suppressing the occurrence of coating streaks.

FIG. 4 is a schematic side view showing an example of a tip portion of a die head in the present disclosure; FIG. 5 is a schematic side view showing another example of the tip of the die head in the present disclosure; FIG. 5 is a schematic side view showing still another example of a tip portion of a die head in the present disclosure;

The die head of the present disclosure will now be described in detail.
The present disclosure is not limited to the embodiments described below with reference to the drawings, and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure. Components shown using the same reference numerals in each drawing mean the same components. Descriptions of components and symbols that are duplicated in each embodiment may be omitted.
Dimensions in the drawings do not necessarily represent actual dimensions and proportions.

In the present disclosure, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.
In the present disclosure, a numerical range indicated using "to" indicates a range including the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges stated stepwise in this disclosure, the upper limit value stated in one numerical range is the upper limit value of the numerical range stated in another stepwise manner, or the lower limit value stated in the numerical range is , may be replaced with the lower limit of the numerical range described in other steps. In addition, in the numerical ranges described in the present disclosure, upper or lower limits described in a certain numerical range may be replaced with values shown in Examples.
In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.
In the present disclosure, "solid content" refers to components other than solvent (preferably organic solvent).

As described above, in coating using a die head, methods for suppressing the occurrence of coating streaks have been studied.
As a result of studies by the present inventors, it was found that the outer surface of the lip on the most upstream side with respect to the conveying direction of the substrate, which is the member to be coated, is connected to the land surface on the side opposite to the slot forming surface, and the outer surface of the lip on the most downstream side. The inventors have found that the generation of coating streaks can be suppressed by setting the dynamic contact angle hysteresis due to methyl ethyl ketone to 20° or less for at least one of the land surface of the lip and the other.
The outer surface and the land surface having a dynamic contact angle hysteresis of 20° or less allow the coating liquid to move quickly even if they are once covered with the coating liquid, and can return to a clean state when a bead is formed. The clean state means that when the die head is viewed from the side, a three-phase interface consisting of a solid (that is, the outer surface and the land surface), a liquid (that is, the coating liquid), and a gas (that is, the atmosphere) is formed on the outer surface and the land surface. is formed.
In particular, by setting the dynamic contact angle hysteresis to 20° or less with methyl ethyl ketone, which has a low surface tension of about 20°, it is possible to obtain the above-mentioned effect of forming a clean state regardless of the type of coating liquid applied to the die head. Conceivable.
When a three-phase interface is formed on the outer surface and the land surface, the amount of the coating liquid remaining on the outer surface and the land surface is reduced, and a film of the coating liquid exists on the outer surface and the land surface. It is thought that the occurrence of coating streaks caused by this can be suppressed.
In the die heads described in Patent Documents 1 and 2, once a film is formed by the coating liquid on the outer surface, the film is not removed, and the outer surface is not exposed, so the three-phase interface is not formed. .

Based on the above knowledge, the die head of the present disclosure has two or more parallel lips and a slot formed between adjacent lips for transferring and discharging the coating liquid, and the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction, which is connected to the land surface on the side opposite to the slot forming surface, has a dynamic contact angle hysteresis of 20° or less with methyl ethyl ketone.
In the die head of the present disclosure, during coating, the lip at one end in the parallel direction is on the downstream side with respect to the coating direction, and the lip at the other end in the parallel direction is on the upstream side with respect to the coating direction. can be suppressed.
Here, the “coating direction” in the present disclosure refers to the direction in which the coating film is formed.
Coating using the die head of the present disclosure is performed by relatively moving the die head and the member to be coated. That is, "relatively moving the die head and the member to be coated" means moving the member to be coated with respect to the fixed die head, moving the die head with respect to the fixed member to be coated, and moving the die head with respect to the fixed member to be coated. and the member to be coated in one direction relative to each other.
When the base material, which is the member to be coated, is transported relative to the fixed die head, the transport direction of the base material is opposite to the "coating direction".
In addition, in the present disclosure, "the outer surface of the lip at the other end in the parallel direction, which is connected to the land surface on the side opposite to the slot forming surface, has a dynamic contact angle hysteresis of 20° or less due to methyl ethyl ketone." Unless otherwise specified, it includes the dynamic contact angle hysteresis of methyl ethyl ketone of 20° or less on the entire or part of the outer surface of the lip on the other end in the parallel direction. On the outer surface of the lip at the other end in the parallel direction, the area where the dynamic contact angle hysteresis of methyl ethyl ketone is 20° or less preferably includes at least the area in contact with the coating liquid.
Hereinafter, the area that comes into contact with the coating liquid will also be referred to as a contact portion.
Furthermore, in the present disclosure, the lower limit of the dynamic contact angle hysteresis of methyl ethyl ketone is 1° in terms of measurement limit, for example, in any aspect.

In conventional die heads (for example, the die heads described in Patent Documents 1 and 2), depending on the type of coating liquid and coating conditions, the lip on the most upstream side with respect to the conveying direction of the base material may cause The amount of occurrence of coating streaks and coating streaks caused by the lip on the most downstream side may differ.
Therefore, in the die head of the present disclosure, the corresponding surface of the lip on the side where coating streaks are likely to occur, that is, the land surface of the lip at one end in the parallel direction and/or the outer surface of the lip at the other end in the parallel direction is moved by methyl ethyl ketone. By setting the effective contact angle hysteresis to 20° or less, the amount of occurrence of coating streaks can be effectively reduced.
In order to more effectively reduce the amount of coating streaks, in the die head of the present disclosure, the land surface of the lip at one end in the parallel direction and the land surface of the lip at the other end in the parallel direction on the side opposite to the slot forming surface In this aspect, the dynamic contact angle hysteresis due to methyl ethyl ketone is set to 20° or less for both the outer surface connected to the .

[Dynamic contact angle hysteresis by methyl ethyl ketone]
First, the dynamic contact angle hysteresis due to methyl ethyl ketone will be described.
The "dynamic contact angle hysteresis due to methyl ethyl ketone" is also simply referred to as "dynamic contact angle hysteresis".
Dynamic contact angle hysteresis refers to the difference [θa-θr] between the advancing contact angle (θa) and the receding contact angle (θr) when a droplet slides down the surface of a solid wall. In the present disclosure, droplets of methyl ethyl ketone are used as the droplets.
Dynamic contact angle hysteresis is based on the advancing and receding contact angles when a droplet is dropped onto the surface of a horizontally supported solid wall, the solid wall is gradually tilted, and the droplet begins to slide down. Calculated.
For the measurement, as described above, the sliding method (i.e., drop the droplet onto the surface of the solid wall supported horizontally, tilt the solid wall gradually, and measure the state of the droplet when it starts to slide down). method) is used. In addition, the measurement is performed in an environment of room temperature of 25° C. and humidity of 50%. The conditions for the measurement are that the surface temperature of the solid wall is 25° C., the droplet temperature is 25° C., and the droplet volume is usually 1 μL. Although it is set to ~4 μL, the liquid volume is not limited from the viewpoint of reproducing a situation close to the actual phenomenon. For the solid wall, the die head itself may be used, or the same surface as the land surface, the outer surface, etc., which is the area to be measured (specifically, it has the same surface treatment layer and the same ten-point average roughness A plate-like object having a surface having a roughness Rzjis may also be used.

The die head of the present disclosure is an extrusion type die head, and forms a bead by accumulating the coating liquid discharged from the slot between the slot for discharging the coating liquid and the member to be coated (for example, the substrate). The coating liquid is applied to the member to be coated through.
That is, a bead is a coating liquid pool formed between the die head and the member to be coated.

The die head of the present disclosure will be described in detail below with reference to the drawings.
FIG. 1 is a schematic side view showing an example of a tip portion of a die head in the present disclosure.

The die head 100A shown in FIG. 1 has an upstream lip 10 located on the upstream side and a downstream lip 20 located on the downstream side with respect to the conveying direction X of the substrate F, which is the member to be coated.
That is, in the embodiment shown in FIG. 1, since the coating liquid is applied onto the substrate F that is transported and moved, the transport direction X of the substrate is opposite to the coating direction.
In FIG. 1, the contact portion 20Cz of the downstream lip 20 is represented as if there is a step with respect to the surface 20C of the downstream lip 20, but this representation is for convenience of explanation, and the contact portion 20Cz does not have a stepped structure with respect to the surface 20C of the downstream lip 20. The same applies to a contact portion 20Cz on the surface 20C of the downstream lip 20 shown in FIG. 2 and a contact portion 50Cz on the surface 50C of the downstream lip 50 shown in FIG. 3, which will be described later.

In the die head 100A, the upstream lip 10 has a slot forming surface 10B and the downstream lip 20 has a slot forming surface 20B, and as shown in FIG. A slot 30 for transferring and discharging the coating liquid L is formed between the side lip 20 and the slot forming surface 20B.
The slot 30 communicates with a manifold (not shown). The manifold is a space extending along the width direction of the die head 100A (that is, the depth direction in FIG. 1), and spreads the coating liquid L supplied to the die head 100A in the coating width direction (that is, the width direction of the die head 100A). The coating liquid L is temporarily stored.

In the die head 100A shown in FIG. 1, a bead B is formed between the slot 30 and the base material F during coating, and the coating liquid L is applied to the base material F via the bead B. As shown in FIG.

In the die head 100A, the land surface 10A of the upstream lip 10 has a dynamic contact angle hysteresis of 20° or less. The land surface 10A is an example of the land surface of the lip at one end in the parallel direction. Also, the dynamic contact angle hysteresis of the contact portion 20Cz with the coating liquid on the surface 20C of the downstream lip 20 is 20° or less. The contact portion 20Cz is a part of the outer surface of the lip at the other end in the parallel direction, which is connected to the land surface on the side opposite to the slot forming surface, and is an example of a contact portion with the coating liquid.
Since the dynamic contact angle hysteresis of the land surface 10A and the contact portion 20Cz with the coating liquid is 20° or less, the above-described three-phase interface is formed at the land surface 10A and the contact portion 20Cz with the coating liquid, As a result, the occurrence of coating streaks can be suppressed.
The area of the surface 20C of the downstream lip 20 in which the contact portion 20Cz with the application liquid is formed may be an area that can come into contact with the application liquid, which is assumed in consideration of the application liquid, the application conditions, and the like. The formation area of the contact portion 20Cz with the coating liquid is set to, for example, an area of 1 mm or more from the edge of the land surface 20A.
From the viewpoint of surface treatment efficiency, etc., it is preferable that the dynamic contact angle hysteresis of the entire surface 20C of the downstream lip 20 is 20° or less.

Further, even if the three-phase interface moves from the contact portion 20Cz to the land surface 20A due to disturbance such as vibration, the formation of the film of the coating liquid on the land surface 20A can be prevented. The land surface 20A also preferably has a dynamic contact angle hysteresis of 20° or less.
Further, the slot-forming surface 10B of the upstream lip 10 and the slot-forming surface of the downstream lip 20 are arranged so that the coating liquid can be easily removed during cleaning of the die head 100A, and failure due to contamination of the slot 30 is less likely to occur when coating is resumed thereafter. 20B preferably has a dynamic contact angle hysteresis of 20° or less.
Here, the land surfaces 10A and 20A both refer to surfaces facing the base material F. As shown in FIG.

In the die head 100A, the distance between the land surface 10A of the upstream lip 10 and the substrate F and the distance between the land surface 20A of the downstream lip 20 and the substrate F both depend on the viscosity of the coating liquid and the coating to be formed. It may be determined according to the thickness of the film and the like.
For example, the distance between the land surface 10A of the upstream lip 10 and the base material F and the distance between the land surface 20A of the downstream lip 20 and the base material F can each be selected from 50 μm to 500 μm. ˜300 μm may be selected.
Here, the above distance refers to the shortest distance between the land surface and the substrate. Such distance can be measured, for example, with a taper gauge.

Next, another aspect of the die head in the present disclosure will be described with reference to FIG.
Here, FIG. 2 is a schematic side view showing another example of the tip portion of the die head in the present disclosure.
The die head shown in FIG. 2 is a die head for multi-layer coating.

The die head 100B shown in FIG. 2 includes an upstream lip 10 on the most upstream side, a downstream lip 20 on the most downstream side, and an upstream lip 10 and a and an intermediate lip 40 between the lip 20 .
The upstream lip 10 has a slot-forming surface 10B, the downstream lip 20 has a slot-forming surface 20B, and the intermediate lip 40 has slot-forming surfaces _40B1 and _40B2 . Between the slot-forming surface 10B of the upstream lip 10 and the slot-forming surface _40B1 of the intermediate lip 40, a slot 30a for transferring and discharging the coating liquid _L1 is formed. A slot _30b for transferring and discharging the coating liquid L2 is formed between the slot forming surface _40B2 of the intermediate lip 40 and the slot forming surface 20B of the downstream lip 20. As shown in FIG.
The slots 30a and 30b communicate with manifolds (not shown). The manifold in die head 100B is similar to the manifold in die head 100A.

In the die head 100B shown in FIG. 2, a bead B of the coating liquid _L1 and the coating liquid _L2 is formed between the slot 30a, the slot 30b, and the substrate F during coating. The coating liquid _L1 and the coating liquid _L2 are applied to the substrate F. As shown in FIG.

In the die head 100B, the land surface 10A of the upstream lip 10 has a dynamic contact angle hysteresis of 20° or less. The land surface 10A is an example of the land surface of the lip at one end in the parallel direction. Also, the dynamic contact angle hysteresis of the contact portion 20Cz with the coating liquid on the surface 20C of the downstream lip 20 is 20° or less. The contact portion 20Cz is a part of the outer surface of the lip at the other end in the parallel direction, which is connected to the land surface on the side opposite to the slot forming surface, and is an example of a contact portion with the coating liquid.
Since the dynamic contact angle hysteresis of the land surface 10A and the contact portion 20Cz with the coating liquid is 20° or less, the above-described three-phase interface is formed at the land surface 10A and the contact portion 20Cz with the coating liquid, As a result, the occurrence of coating streaks can be suppressed.
In the die head 100B as well, the formation region of the contact portion 20Cz with the coating liquid, which occupies the surface 20C of the downstream lip 20, is assumed in view of the coating liquid, the coating conditions, etc., as long as it can be contacted by the coating liquid. good. The formation area of the contact portion 20Cz with the coating liquid is set to, for example, an area of 1 mm or more from the edge of the land surface 20A.
From the viewpoint of surface treatment efficiency, etc., it is preferable that the dynamic contact angle hysteresis of the entire surface 20C of the downstream lip 20 is 20° or less.

Further, in the die head 100B, even if the three-phase interface moves from the contact portion 20Cz to the land surface 20A due to disturbance such as vibration, it is possible to prevent the formation of a film of the coating liquid on the land surface 20A. The land surface 20A of the side lip 20 also preferably has a dynamic contact angle hysteresis of 20° or less.
Furthermore, from the viewpoint of easy removal of the coating liquid during cleaning of the die head 100B, the land surface 40A of the intermediate lip 40 also preferably has a dynamic contact angle hysteresis of 20° or less.
Furthermore, from the viewpoint that the coating liquid is easily removed when cleaning the die head 100B and failure due to contamination of the slots 30a and 30b is less likely to occur when coating is resumed thereafter, the slot forming surface 10B of the upstream lip 10 and the slots of the downstream lip 20 The forming surface 20B and the slot forming surfaces 40B ₁ and 40B ₂ of the intermediate lip 40 also preferably have a dynamic contact angle hysteresis of 20° or less.
Here, the land surfaces 10A, 20A, and 40A all mean surfaces facing the base material F. As shown in FIG.

In the die head 100B, the distance between the land surface 10A of the upstream lip 10 and the substrate F, the distance between the land surface 20A of the downstream lip 20 and the substrate F, and the land surface 40A of the intermediate lip 40 and the substrate F may be determined according to the viscosity of the coating liquid, the thickness of the coating film to be formed, and the like.
For example, the distance between the land surface 10A of the upstream lip 10 and the substrate F, the distance between the land surface 20A of the downstream lip 20 and the substrate F, and the distance between the land surface 40A of the intermediate lip 40 and the substrate F can be selected from 50 μm to 500 μm, and may be selected from 100 μm to 300 μm.

In addition, FIG. 3 is used to describe still another aspect of the die head in the present disclosure.
Here, FIG. 3 is a schematic side view showing still another example of the tip portion of the die head in the present disclosure.
The die head 100C shown in FIG. 3 has an upstream lip 10 on the upstream side and a downstream lip 50 on the downstream side with respect to the conveying direction X of the substrate F, which is the member to be coated.
A die head 100C shown in FIG. 3 has a configuration including a downstream lip 50 instead of the downstream lip 20 in the die head 100C shown in FIG. Components other than the downstream lip 50 shown in FIG. 3 are the same in function and configuration as the components in the die head 100A shown in FIG. 1, so description thereof is omitted here.

The downstream lip 50 in the die head 100C has a land surface 50A, a slotting surface 50B and a surface 50C. A surface 50C of the downstream lip 50 has a contact portion 50Cz with the application liquid. The contact portion 50Cz is a part of the outer surface of the lip at the other end in the parallel direction, which is connected to the land surface on the side opposite to the slot forming surface, and is an example of a contact portion with the coating liquid. The contact portion 50Cz has a convex curved surface at a portion connected to the land surface 50A in a side view as shown in FIG.
In the die head 100C, since the dynamic contact angle hysteresis of the land surface 10A and the contact portion 50Cz with the coating liquid is 20° or less, the above-described three-phase interface is formed on the land surface 10A and the contact portion 50Cz, As a result, the occurrence of coating streaks can be suppressed.
A three-phase interface formed during application of the coating liquid by the die head 100C usually moves in the region of the contact portion 50Cz due to various factors. Since the portion connected to the land surface 50A has a convex curved surface like the contact portion 50Cz, the degree of freedom of movement of the formed three-phase interface can be improved. In other words, the movement of the three-phase interface is not hindered by the corner of the downstream lip 50 . In addition, in the contact portion 50Cz, even if the three-phase interface moves, the liquid does not remain at the corners (even if the liquid separates from the three-phase interface and adheres to the corners, it remains at the corners). ), and the occurrence of coating streaks can be suppressed.
In the contact portion 50Cz, the degree of freedom of movement of the three-phase boundary is improved, so that the occurrence of coating streaks can be more effectively suppressed.

The convex curved surface of the contact portion 50Cz is preferably an arc curved surface from the viewpoint of processing accuracy.
Further, the convex curved surface of the contact portion 50Cz is preferably a curved surface with a curvature radius of 0.1 mm or more, and more preferably a curved surface with a curvature radius of 0.2 mm or more.
The upper limit of the radius of curvature of the convex curved surface is, for example, 10 mm.

Here, the radius of curvature of the curved surface is measured by the following method.
Observe from the side with a microscope (for example, manufactured by KEYENCE CORPORATION), and determine the radius of curvature from the observed image.
The radii of curvature are obtained at 10 points on the curved surface, and the arithmetic average value at the 10 points is taken as the radius of curvature of the curved surface on the outer surface.

A formation region (including a convex curved surface) of the contact portion 50Cz with the coating liquid, which occupies the surface 50C of the downstream lip 50, is a region that can come into contact with the coating liquid, which is assumed in consideration of the coating liquid, coating conditions, and the like. If it is The forming area of the contact portion 50Cz with the coating liquid is set to, for example, an area of 1 mm or more from the edge of the land surface 50A.
From the viewpoint of surface treatment efficiency, etc., it is preferable that the dynamic contact angle hysteresis of the entire surface 50C of the downstream lip 50 is 20° or less.

Further, even if the three-phase interface moves from the contact portion 50Cz to the land surface 50A due to disturbance such as vibration, the formation of the film of the coating liquid on the land surface 50A can be prevented. The land surface 50A also preferably has a dynamic contact angle hysteresis of 20° or less.
When the portion of the contact portion 50Cz connected to the land surface 50A has a convex curved surface like the downstream lip 50, the land surface 50A is a surface facing the base material F and indicates a flat portion. That is, when viewed from the side as shown in FIG. 3, the area indicated by the straight line is the land portion of the downstream lip.

In the die head 100C, the distance between the land surface 10A of the upstream lip 10 and the substrate F and the distance between the land surface 50A of the downstream lip 50 and the substrate F both depend on the viscosity of the coating liquid and the coating to be formed. It may be determined according to the thickness of the film and the like.
For example, the distance between the land surface 10A of the upstream lip 10 and the base material F and the distance between the land surface 50A of the downstream lip 50 and the base material F can each be selected from 50 μm to 500 μm. ˜300 μm may be selected.
Here, the above distance refers to the shortest distance between the land surface and the substrate. Such distance can be measured, for example, with a taper gauge.

The die head of the present disclosure is preferably made of metal, and the body of the die head and the tip of the lip may be made of different metals.
Specifically, as the metal constituting the die head of the present disclosure, in addition to stainless steel, an ultrafine grain alloy (for example, TF15 (Mitsubishi Materials Co., Ltd.)) and a cemented carbide (for example, Nippon Tungsten) used for the tip of the lip Co., Ltd.) and the like.
In addition, in the die head of the present disclosure, as described above, when the contact portion of the coating liquid has a convex curved surface, the convex curved surface may be formed by chamfering.

[surface treatment]
Next, a method for controlling dynamic contact angle hysteresis will be described.
As a method of making the dynamic contact angle hysteresis of the land surface 10A, the contact portion 20Cz with the coating liquid, etc. 20° or less, at least one compound selected from the group consisting of fluorine-containing compounds and silicon-containing compounds is used. surface treatment used.
That is, the land surface 10A, the contact portion 20Cz with the coating liquid, and the like are preferably provided with a surface treatment layer formed using a fluorine-containing compound. For the surface treatment layer formed using a fluorine-containing compound, for example, a composition such as "Fluorine-based ultra-thin coat MX-031" manufactured by Surf Industry Co., Ltd. (specifically, a composition containing a fluorine-containing compound , for example, a coating agent) is preferably used.

(Fluorine-containing compound)
The fluorine-containing compound used for surface treatment is not particularly limited as long as it is a compound capable of reducing the dynamic contact angle hysteresis to 20° or less.
Specifically, the fluorine-containing compound is preferably a compound having a perfluoropolyether group.

The perfluoropolyether groups include -(OCF ₂ ) _n1 -, -(OC ₂ F ₄ ) _n2 -, -(OC ₃ F ₆ ) _n3 -, -(OC ₄ F ₈ ) _n4 -, and these A group in which two or more are linked, and the like. Each of n1 to n4 independently represents an integer of 1 or more, preferably 20 to 200, more preferably 30 to 200. provided that when the fluorine-containing compound contains -(OCF ₂ ) _n1 -, -(OC ₂ F ₄ ) _n2 -, -(OC ₃ F ₆ ) _n3 -, or -(OC ₄ F ₈ ) _n4 -, n1 , n2, n3, or n4 represent an integer of 2 or more.
The verfluoro group in -(OC ₃ F ₆ ) _n3 - and -(OC ₄ F ₈ ) _n4 - may be linear or branched, preferably linear.

In addition, the fluorine-containing compound is preferably a compound having a Si atom-containing group to which a hydrolyzable group or a hydroxyl group is bonded (that is, it also corresponds to a silicon-containing compound) in addition to the perfluoropolyether group.
A group represented by —Si(R ^a ) _m (R ^b ) _3-m is preferable as the Si atom-containing group to which the hydrolyzable group or hydroxyl group is bonded. R ^a represents a hydroxyl group or a hydrolyzable group, R ^b represents a hydrogen atom, an alkyl group having 1 to 22 carbon atoms, or -Y-Si(R ^c ) _p (R ^d ) _3-p , m represents an integer from 1 to 3. Here, Y represents a divalent organic group, R ^c has the same definition as R ^a , R ^d has the same definition as R ^b , and p represents an integer of 0-3.
Examples of the hydrolyzable group include groups that give a hydroxy group (silanol group) by hydrolysis, specifically, an alkoxy group having 1 to 6 carbon atoms, a cyano group, an acetoxy group, a chlorine atom, and an isocyanate group. etc. Among them, the hydrolyzable group is preferably an alkoxy group or a cyano group having 1 to 6 carbon atoms (more preferably 1 to 4), more preferably an alkoxy group having 1 to 6 carbon atoms (more preferably 1 to 4). .
Examples of the divalent organic group represented by Y include an alkylene group, a group in which an alkylene group and an ether bond (--O--) are combined, and a group in which an alkylene group and an arylene group are combined.

For details of the fluorine-containing compound, the fluorine-containing silane compound described in paragraphs 0033 to 0103 of JP-A-2015-200884, the formula (1a) described in paragraphs 0148 to 0223 of WO 2018/012344, ( The description of the compound (perfluoropolyether compound) represented by 1b), (2a), (2b), (3a), or (3b) can be referred to, and the contents thereof are incorporated herein.

As the fluorine-containing compound having a perfluoropolyether group, a commercially available product may be used. Specifically, a composition (e.g., coating agent) containing a fluorine-containing compound having a perfluoropolyether group is available from Daikin Industries, Ltd. "OPTOOL DSX", "OPTOOL DSX-E", "OPTOOL UD100" manufactured by Co., Ltd., and "KY-164" and "KY-108" manufactured by Shin-Etsu Chemical Co., Ltd.

-surface treatment-
For surface treatment using a fluorine-containing compound, for example, the following method is used.
That is, the fluorine-containing compound is applied to the surface-treated part of the die head (specifically, the land surface 10A, the contact part 20Cz with the coating liquid, etc., the area where the dynamic contact angle hysteresis is 20 ° or less), etc. After application, drying and curing are performed.
Examples of means for applying the fluorine-containing compound include brush coating, dip coating, and spray coating.

-Preparation-
Before the surface treatment using the fluorine-containing compound, the surface-treated part in the die head (specifically, the land surface 10A, the contact part 20Cz with the coating liquid, etc.), the dynamic contact angle hysteresis is set to 20 ° or less. It is preferable to perform pretreatment on such areas as
Examples of the pretreatment include acid treatment, alkali treatment, primer treatment, surface roughening treatment, and surface modification treatment such as plasma.

The surface treatment layer preferably has a ten-point average roughness Rzjis of 2.0 or less, more preferably 1.5 μm or less, even more preferably 1.0 μm or less. From the viewpoint of measurement limit, the lower limit of the ten-point average roughness Rzjis of the surface treatment layer is, for example, 0.001 μm or more.
Here, the ten-point average roughness Rzjis is a value measured by the method described in JIS B 0601-2001. As the measuring device, for example, a stylus type surface roughness measuring machine (Surfcom, Tokyo Seimitsu Co., Ltd.) is used.

Subsequently, the base material to be coated by the die head, the conveying means for the base material, and the coating liquid will be described.

[Base material]
The base material F is not particularly limited as long as it is a member to be coated, and may be appropriately selected according to the application of the coating layer. For example, when continuous coating is performed using the die head of the present disclosure, a long substrate may be used. In particular, a polymer film is preferably used as the substrate from the viewpoint of transportability and the like.

For optical film applications, the light transmittance of the substrate is preferably 80% or more.
For optical film applications, when a polymer film is used as the substrate, it is preferable to use an optically isotropic polymer film.
Examples of the substrate include polyester-based substrates (films or sheets of polyethylene terephthalate, polyethylene naphthalate, etc.), cellulose-based substrates (films or sheets of diacetylcellulose, triacetylcellulose (TAC), etc.), and polycarbonate-based substrates. , Poly (meth) acrylic base material (film or sheet such as polymethyl methacrylate), polystyrene base material (polystyrene, acrylonitrile styrene copolymer film or sheet), olefin base material (polyethylene, polypropylene, cyclic or Polyolefin having a norbornene structure, ethylene propylene copolymer film or sheet), polyamide base material (polyvinyl chloride, nylon, aromatic polyamide film or sheet), polyimide base material, polysulfone base material, poly Ethersulfone base material, polyether ether ketone base material, polyphenylene sulfide base material, vinyl alcohol base material, polyvinylidene chloride base material, polyvinyl butyral base material, poly(meth)acrylate base material, polyoxy Transparent base materials such as methylene-based base materials and epoxy resin-based base materials, and base materials made of blend polymers obtained by blending the above polymer materials, and the like can be used.

The base material may be one in which a layer is formed in advance on the above polymer film.
The layers formed in advance include an adhesive layer, a barrier layer against water, oxygen, etc., a refractive index adjusting layer, an orientation layer, and the like.

[Substrate Conveying Means]
In FIGS. 1 and 2, the base material F is conveyed in the conveying direction X, but the means for conveying the base material is not limited to this mode.
In other words, the means for transporting the base material is not particularly limited. For example, from the viewpoint that the base material can be transported in a stretched state and the coating accuracy is improved, the means for transporting the base material during coating with a die head is a backup roll. is preferred.
That is, the application of the coating liquid by the die head is preferably performed on the base material wound on the backup roll.

The backup roll is configured to be rotatable, and is a member on which the substrate can be wound and continuously conveyed, and is rotationally driven at the same speed as the conveyance speed of the substrate.

The backup roll may be heated from the viewpoint of suppressing brushing of the coating film due to a decrease in the film surface temperature (that is, whitening of the coating film due to fine condensation) in order to promote drying of the coating film. .
Moreover, it is preferable that the surface temperature of the backup roll is detected and the surface temperature of the backup roll is maintained by temperature control means based on the detected temperature.
The backup roll temperature control means includes heating means and cooling means. Induction heating, water heating, oil heating, or the like is used as the heating means, and cooling with cooling water is used as the cooling means.

The diameter of the backup roll is preferably 100 mm to 1000 mm, more preferably 100 mm to 800 mm, and further preferably 200 mm to 700 mm, from the viewpoints of easy winding of the base material, easy coating with a die head, and production cost of the backup roll. preferable.

The conveying speed of the base material on the backup roll is preferably, for example, 10 m/min to 100 m/min from the viewpoint of securing productivity and the viewpoint of coatability.

The wrap angle of the substrate with respect to the backup roll is preferably 60° or more, more preferably 90° or more, from the viewpoints of stabilizing the transportation of the substrate during coating and suppressing the occurrence of thickness unevenness in the coating film. Also, the upper limit of the wrap angle can be set to 180°, for example.
Note that the wrap angle is an angle formed by the direction in which the substrate is conveyed when the substrate contacts the backup roll and the direction in which the substrate is conveyed when the substrate separates from the backup roll.

[Coating liquid]
The coating liquid is not particularly limited as long as it can be discharged from a die head.
Since the die head of the present disclosure suppresses the occurrence of coating streaks, its effect is remarkably exhibited particularly when it is applied to form a thin coating film (for example, a wet thickness of 20 μm or less).

The coating liquid applied to the die head of the present disclosure is not particularly limited as long as it is a fluid liquid.
The coating liquid may be a curable coating liquid containing a polymerizable or crosslinkable compound, or may be a non-curable coating liquid.

Also, in the case of a coating liquid containing an organic solvent, coating streaks tend to occur. Therefore, when a coating liquid containing an organic solvent is applied to the die head of the present disclosure, the effect of suppressing the occurrence of coating streaks is likely to appear.
The organic solvent used in the coating liquid is not particularly limited, and any organic solvent that can dissolve or disperse the components contained in the coating liquid may be used.
The content of the organic solvent is not particularly limited.

(Example of coating liquid)
The coating liquid applied to the die head of the present disclosure is not particularly limited as long as it is a fluid liquid. However, in the case of using a coating liquid that tends to cause coating streaks, the use of the die head of the present disclosure provides a significant effect.

An example of the coating liquid is a coating liquid for forming an optically anisotropic layer, which includes, for example, one or more polymerizable liquid crystal compounds, a polymerization initiator, a leveling agent, an organic solvent, and a coating liquid having a solid content concentration of 20% by mass to 40% by mass. This coating liquid may further contain a liquid crystal compound other than the polymerizable liquid crystal compound, an alignment control agent, a surfactant, a tilt angle control agent, an alignment aid, a plasticizer, a cross-linking agent, and the like.

Another example of the coating liquid is a coating liquid for forming the polarizing layer, which includes, for example, a liquid crystalline polymer, a dichroic compound, and an organic solvent that dissolves the liquid crystalline polymer and the dichroic compound. and a coating liquid having a solid content concentration of 1% by mass to 7% by mass. This coating liquid may further contain an interface improver, a polymerization initiator, various additives, and the like.

Still another example of the coating liquid is a coating liquid for forming a hard coat layer, which includes, for example, a polymerizable compound (preferably a polyfunctional polymerizable compound), inorganic particles (preferably silica particles), polymerization A coating liquid containing an initiator and an organic solvent and having a solid concentration of 40% by mass to 60% by mass may be used. This coating liquid may further contain monomers, various additives, and the like.

Still another example of the coating liquid is a coating liquid for forming an alignment layer, which contains, for example, polyvinyl alcohol (preferably modified polyvinyl alcohol having an acryloyl group), water, and an organic solvent. A coating liquid having a concentration of 1% by mass to 10% by mass can be used. This coating liquid may further contain a cross-linking agent and the like.

(Target coating layer)
The target coating layer formed from the coating liquid is not particularly limited, and examples thereof include a hard coat layer, an optically anisotropic layer, a polarizing layer, a refractive index adjusting layer, and the like in the case of optical film applications. .
The thickness of the layer formed from the coating liquid varies depending on the application, but can be, for example, 5 μm or less, more preferably in the range of 0.1 μm to 100 μm.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

<Preparation of base material>
A long triacetyl cellulose (TAC) film (TD40UL, Fuji Film Co., Ltd., refractive index 1.48) having a thickness of 60 μm and a width of 1340 mm was prepared as a substrate.

<Preparation of coating solution>
(Preparation of coating liquid A)
A coating liquid A was prepared by mixing the following components.
・The following polymerizable liquid crystal compound L-9: 47.50 parts by mass ・The following polymerizable liquid crystal compound L-10: 47.50 parts by mass ・The following polymerizable liquid crystal compound L-3: 5.00 parts by mass ・The following polymerization initiator PI-1: 0.50 parts by mass Leveling agent T-1 below (weight average molecular weight: 10,000): 0.20 parts by mass Methyl ethyl ketone: 235.00 parts by mass

In the polymerizable liquid crystal compound L-9 and the polymerizable liquid crystal compound L-10, one of R ¹ and R ² represents a methyl group, the other represents a hydrogen atom, and one of R ³ and R ⁴ represents a methyl group and the other represents a hydrogen atom. That is, the polymerizable liquid crystal compound L-9 and the polymerizable liquid crystal compound L-10 are mixtures of positional isomers having different positions of methyl groups.

In the polymerizable liquid crystal compounds L-9 and L-10, the group adjacent to the methacryloyl group represents a divalent group in which an ethylene group is substituted with a methyl group. Polymerizable liquid crystal compounds L-9 and L-10 are mixtures of positional isomers having different methyl group substitution positions.

(Preparation of coating liquid B)
A coating liquid B was prepared by mixing the following components.
The following liquid crystalline polymer LP1: 4.011 parts by mass (weight average molecular weight: 13,300, structural unit (1) and structural unit (2) in the molecule 80:20 [(1):(2); mass ratio].)
Dichroic compound D1 below: 0.792 parts by mass Dichroic compound D2 below: 0.963 parts by mass Interface improver F2 below: 0.087 parts by mass Interface improver F3 below: 0.073 parts by mass The following interface improver F4 (weight average molecular weight: 10,000): 0.073 parts by mass Tetrahydrofuran (an organic solvent having a boiling point of 80°C or less): 37.6004 parts by mass Cyclopentanone: 56.4006 parts by mass

(Preparation of coating liquid C)
For 500 parts by mass of methyl ethyl ketone, 500 parts by mass of IPA (isopropanol), partially caprolactone-modified polyfunctional acrylate (KAYARAD DPCA-20, Nippon Kayaku Co., Ltd.) 750 parts by mass, silica sol (MIBK-ST, Nissan Chemical Industries ( Co., Ltd.) and 50 parts by mass of a photopolymerization initiator (Omnirad 184 (former Irgacure 184), IGM Resins B.V.) were added to prepare a coating solution C.

(Preparation of coating liquid D)
The following modified polyvinyl alcohol (PVA, degree of polymerization: 1,000): 20 parts by weight, glutaraldehyde (crosslinking agent): 1 part by weight, water: 378 parts by weight, methanol: 120 parts by weight were mixed, and the coating solution was obtained. D was prepared.

In the above (PVA), the numerical value attached to each structural unit of the main chain is the molar ratio.

<Preparation of die head 1>
Using stainless steel (SUS630), a die head 100A having the same configuration as in FIG. 1 was produced.
In the die head 100A shown in FIG. 1, surfaces corresponding to the land surface 10A of the upstream lip 10, the surface 20C of the downstream lip 20, and the land surface 20A of the downstream lip 20 were surface-treated by the following method. .
First, a 0.1% by mass NaOH aqueous solution was deposited on the substrate, and then dried to perform pretreatment.
After that, surface treatment was performed using MX-031 from Surf Industry Co., Ltd.
When the dynamic contact angle hysteresis with methyl ethyl ketone was measured by the above-described method for the surface treatment layer formed as described above, it was 18°.
Moreover, when the Rzjis of the surface treatment layer was measured by the method described above, it was 1.1 μm.

<Preparation of die head 2>
In the same manner as the die head 1, stainless steel ( A die head 100A having the configuration shown in FIG. 1 was produced using SUS630).
After that, the die head 2 was obtained by performing pretreatment and surface treatment in the same manner as the die head 1 .
The surface treatment layer of the die head 2 was measured for dynamic contact angle hysteresis with methyl ethyl ketone by the method described above, and found to be 15°.
Moreover, when the Rzjis of the surface treatment layer was measured by the method described above, it was 0.9 μm.

<Preparation of die head 3>
Using stainless steel (SUS630), a die head 100B having the same configuration as in FIG. 2 was produced.
In the die head 100B shown in FIG. 2, the land surface 10A of the upstream lip 10, the surface 20C of the downstream lip 20, the land surface 20A of the downstream lip 20, and the land surface 40A of the intermediate lip 40 are subjected to surface processed.
First, a 0.1% by mass NaOH aqueous solution was deposited on the substrate, and then dried to perform pretreatment.
After that, surface treatment was performed using MX-031 from Surf Industry Co., Ltd.
When the dynamic contact angle hysteresis with methyl ethyl ketone was measured by the above-described method for the surface treatment layer formed as described above, it was 18°.
Moreover, when the Rzjis of the surface treatment layer was measured by the method described above, it was 1.1 μm.

<Preparation of die head 4>
A die head 4 was produced in the same manner as the die head 1, except that the pretreatment and surface treatment in the die head 1 were changed to the following methods.
That is, in the die head 100A having the same configuration as that of FIG. Fluororesin coating was performed using ethylene resin.
The dynamic contact angle hysteresis with methyl ethyl ketone on the surface coated with the fluorine resin as described above was measured by the method described above, and it was 21°.
The Rzjis of the fluororesin-coated surface was 1.1 μm when measured by the method described above.

<Preparation of die head 5>
A die head 5 was produced in the same manner as the die head 1, except that the pretreatment and surface treatment in the die head 1 were changed to the following methods.
That is, in the die head 100A having the same configuration as that of FIG. 1, the surfaces corresponding to the land surface 10A of the upstream lip 10, the surface 20C of the downstream lip 20, and the land surface 20A of the downstream lip 20 are plated with nickel by electroless plating. and a composite plating layer of polytetrafluoroethylene.
The dynamic contact angle hysteresis due to methyl ethyl ketone was measured by the method described above for the composite plating layer formed as described above, and it was 40°.
Moreover, when the Rzjis of the composite plating layer was measured by the method described above, it was 1.1 μm.

<Preparation of die head 6>
Using stainless steel (SUS630), a die head 100C having the same configuration as in FIG. 3 was produced.
In the die head 100C shown in FIG. 3, surfaces corresponding to the land surface 10A of the upstream lip 10, the surface 50C of the downstream lip 50, and the land surface 50A of the downstream lip 50 were surface-treated by the following method. . As the downstream lip 50, a convex curved surface with a radius of curvature of 0.1 mm was used at a portion of the surface 50C connected to the land surface 50A of the contact portion 50Cz.
First, a 0.1% by mass NaOH aqueous solution was deposited on the substrate, and then dried to perform pretreatment.
After that, surface treatment was performed using MX-031 from Surf Industry Co., Ltd.
When the dynamic contact angle hysteresis with methyl ethyl ketone was measured by the above-described method for the surface treatment layer formed as described above, it was 18°.
Moreover, when the Rzjis of the surface treatment layer was measured by the method described above, it was 1.1 μm.

<Preparation of the die head 7>
A die head 7 was produced in the same manner as the die head 6 except that the downstream lip of the die head 6 was subjected to the surface treatment described above.
That is, the downstream lip 50 used had a convex curved surface with a radius of curvature of 0.2 mm at a portion of the surface 50C connected to the land surface 50A of the contact portion 50Cz.
When the dynamic contact angle hysteresis with methyl ethyl ketone was measured by the above-described method for the surface treatment layer formed as described above, it was 18°.
Moreover, when the Rzjis of the surface treatment layer was measured by the method described above, it was 1.1 μm.

(Example 1)
The die head 1 was arranged as shown in FIG. 1, and the coating liquid A was continuously applied on the TAC film to form a coating film having a thickness of 3 μm and a width of 200 mm.
Specifically, the TAC film was transported onto a backup roll having a surface temperature of 60° C. and an outer diameter of 300 mm, and the coating liquid A was applied to the substrate on the backup roll using the die head 1 . At this time, the wrap angle of the TAC film was 150°, and the conveying speed of the TAC film was 30 m/min.
Furthermore, the distance between the land surface 10A of the upstream lip 10 of the die head 1 and the substrate (TAC film) F is 100 μm, and the distance between the land surface 20A of the downstream lip 20 and the substrate (TAC film) F is 100 μm. Met.
Here, the coating film was formed under the environment of 23° C. and 50% RH.

(Example 2)
A coating film having a thickness of 0.5 μm and a width of 200 mm was formed in the same manner as in Example 1, except that the coating solution A was replaced with the coating solution B.

(Example 3)
A coating film having a thickness of 5 μm and a width of 200 mm was formed in the same manner as in Example 1, except that the coating solution C was used instead of the coating solution A.

(Example 4)
A coating film having a thickness of 1 μm and a width of 200 mm was formed in the same manner as in Example 1, except that the coating solution A was replaced with the coating solution D.

(Example 5, Comparative Examples 1 and 5)
A coating film having a thickness of 3 μm and a width of 200 mm was formed in the same manner as in Example 1 except that the die head 1 was replaced with the die head 2, 4 or 5.

(Example 6, Comparative Examples 2 and 6)
A coating film having a thickness of 0.3 μm and a width of 200 mm was formed in the same manner as in Example 2 except that the die head 1 was replaced with the die head 2, 4 or 5.

(Example 7, Comparative Examples 3 and 7)
A coating film having a thickness of 5 μm and a width of 200 mm was formed in the same manner as in Example 3 except that the die head 1 was replaced with the die head 2, 4 or 5.

(Example 8, Comparative Examples 4 and 8)
A coating film with a thickness of 1 μm and a width of 200 mm was formed in the same manner as in Example 4 except that the die head 1 was replaced with the die head 2, 4 or 5.

(Example 9)
The die head 3 was arranged as shown in FIG. 2, and continuous multilayer coating of the coating liquid A and the coating liquid A was performed on the TAC film to form a coating film with a total thickness of 30 μm (upper layer 5 μm, lower layer 25 μm) with a width of 200 mm.
Specifically, the TAC film was transferred onto a backup roll having a surface temperature of 60° C. and an outer diameter of 300 mm, and the coating liquid A was applied to the substrate on the backup roll using a die head. At this time, the wrap angle of the TAC film was 150°, and the conveying speed of the TAC film was 30 m/min.
Furthermore, the distance between the land surface 10A of the upstream lip 10 of the die head 3 and the substrate (TAC film) F is 100 μm, and the distance between the land surface 20A of the downstream lip 20 and the substrate (TAC film) F is 120 μm. , and the distance between the land surface 40A of the intermediate lip 40 and the substrate (TAC film) F was 70 μm.

(Examples 10 and 12)
A coating film having a thickness of 3 μm and a width of 200 mm was formed in the same manner as in Example 1 except that the die head 1 was replaced with the die head 6 or 7 shown in Table 1 below.

(Examples 11 and 13)
A coating film having a thickness of 0.5 μm and a width of 200 mm was formed in the same manner as in Example 2 except that the die head 1 was replaced with the die head 6 or 7 shown in Table 1 below.

(Observation: confirmation of three-phase interface)
The land surface 10A of the upstream lip 10 and the downstream lip 20 during coating are applied on a glass transparent roll having a camera inside by the same method as in each of the above examples. 20C was observed with a camera inside the transparent roll.
After the land surface 10A of the upstream lip 10 and the surface 20C of the downstream lip 20 are once covered with the coating liquid, the covered areas are exposed again, and a three-phase interface is formed as a solid surface. , the three-phase interface was judged to be “present”.
Table 1 shows the results.

(Evaluation: evaluation of coating streaks)
Observe the bead shape during application in each of the above examples from the front side (that is, the surface 10C side of the upstream lip 10) and the back side (that is, the surface 20C side of the downstream lip 20). At the same time, the formed coating film (width 200 mm × length 5000 mm size) is placed on a light table, transmitted light is applied, and the presence or absence of shading or repetition of shading is visually observed. Coating streaks were evaluated by associating the observation results of the shape with the film thickness unevenness indicated by gradation.
The coating streak 1 was caused by the lip on the most upstream side with respect to the conveying direction of the substrate, and the coating streak 2 by the lip on the most downstream side.
The coating streaks were evaluated by cutting the coating film formed 5 minutes after the start of coating into the above-mentioned sizes, sample 1, and sample 2 cutting the coating film of the above sizes 2 hours after the start of coating, I went about two. The former was referred to as "applied streak after 5 minutes", and the latter was referred to as "applied streak after 2 hours".
The evaluation index is as follows. Table 1 shows the results.

-Evaluation index for coating streaks-
1: No coating streak is observed.
2: Very weak coating streaks were observed.
3: One or more but less than five distinct coating streaks were observed.
4: Five or more distinct coating streaks were observed on the entire surface.

As shown in Table 1, it can be seen that the coating films formed according to the examples suppress the occurrence of coating streaks 1 and coating streaks 2 .
More specific description will be given.
The coating film formed using a die head having a dynamic contact angle hysteresis value of 21° or 40° on the land surface 10A of the upstream lip 10 and the surface 20C of the downstream lip 20, that is, according to Comparative Examples 1 to 8 In all of the coating liquids A to D, coating streaks due to the lip on the most upstream side with respect to the conveying direction of the substrate were observed in the formed coating film. Similarly, in the coating films formed in Comparative Examples 1 to 8, coating streaks due to the lip on the most downstream side with respect to the conveying direction of the substrate were also observed in all of the coating liquids A to D.
On the other hand, the coating film formed using a die head having a dynamic contact angle hysteresis value of 18° or 15° on the land surface 10A of the upstream lip 10 and the surface 20C of the downstream lip 20, that is, Example 1 In all of the coating liquids A to D, coating streaks due to the lip on the most upstream side with respect to the conveying direction of the substrate were not observed in the coating films formed by 1 to 9. Similarly, in the coating films formed in Examples 1 to 9, no coating streaks due to the lip on the most downstream side with respect to the conveying direction of the substrate were observed in all of the coating liquids A to D.

As shown in Table 1, in Examples 10 to 13, the occurrence of coating streak 1 and coating streak 2 was suppressed even after 2 hours. In particular, by setting the radius of curvature of the curved surface of the downstream lip 50 to 0.2 mm or more, it can be seen that the occurrence of coating streaks 1 and coating streaks 2 after 2 hours is effectively suppressed.

The disclosures of Japanese Patent Application 2019-180291 filed on September 30, 2019 and Japanese Patent Application 2020-039221 filed on March 6, 2020 are incorporated herein by reference in their entireties.

10 upstream lip 10A upstream lip land surface 10B upstream lip slot forming surface 10C upstream lip surface opposite to the slot forming surface 20, 50 downstream lip 20A, 50A downstream lip land surface 20B, 50B Slot forming surface of downstream lip 20C, 50C Surface opposite to slot forming surface of downstream lip (that is, outer peripheral surface)
20Cz, 50Cz Contact portion with coating liquid 30, 30a, 30b Slot 40 Intermediate lip 40A Land surface of intermediate lip 40B ₁ , 40B ₂ Slot forming surface of intermediate lip 100A, 100B, 100C Die head F Base material (an example of a member to be coated )
L, L ₁ , L ₂ coating liquid X conveying direction of substrate B bead

Claims (8)

having two or more lips in parallel and a slot formed between adjacent lips for transporting and discharging the coating liquid;
During application, the lip at one end in the parallel direction is positioned upstream with respect to the application direction, and the lip at the other end in the parallel direction is positioned downstream with respect to the application direction,
At least one of the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction, which is connected to the land surface on the side opposite to the slot forming surface, has a dynamic contact angle hysteresis of 20 due to methyl ethyl ketone. ° below the die head. The die head according to claim 1, wherein the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction have a ten-point average roughness Rzjis of 1.0 µm or less. 3. The die head according to claim 1, wherein the land surface of the lip on the other end in the parallel direction has a dynamic contact angle hysteresis due to the methyl ethyl ketone of 20[deg.] or less. Of the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction, the surface having a dynamic contact angle hysteresis of 20° or less due to the methyl ethyl ketone is formed using a fluorine-containing compound. The die head according to any one of claims 1 to 3, comprising a coated surface treatment layer. 5. A die head according to claim 4, wherein said fluorine-containing compound is a compound having a perfluoropolyether group. The die head according to any one of claims 1 to 5, wherein the lip at the other end in the parallel direction has a curved surface at a portion connected to the land surface on the outer surface when viewed from the side. The die head according to claim 6, wherein the curved surface of the lip on the other end in the parallel direction has a curvature radius of 0.2 mm or more. The dynamic contact angle hysteresis of the land surface of the lip at one end in the parallel direction and the outer surface of the lip at the other end in the parallel direction due to the methyl ethyl ketone is 20° or less according to any one of claims 1 to 7. or the die head according to item 1.

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