JP2003126767A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method by which remarkably thin and uniform coating is carried out on a flexible supporting body in a scraping type coating. SOLUTION: An apparatus 10 using the coating method is provided with a pre-coat apparatus 14 for applying an excess of a coating liquid and a doctor blade 16 for scraping the excess portion of the coating liquid. In the pre-coat apparatus 14, the coating liquid having 1-50 mPa.s high shear viscosity and 0.01-5 Pa.s low shear viscosity is applied so that the pre-coat thickness t1 becomes 3-20 times of wet coating film thickness t2.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method.
Docs used in the manufacture of photographic materials and magnetic recording media
The present invention relates to a coating method of a terblade scraping type. [0002] 2. Description of the Related Art Photosensitive materials and magnetic recording media are continuously running.
A flexible belt-like support (hereinafter referred to as “web”)
Apply a predetermined coating liquid such as magnetic liquid on top of the coating film
It is manufactured through a coating process to be formed. In particular, magnetic recording tape
Magnetic recording media such as loops are intended for broadcasting and computers.
The capacity and recording density are improving rapidly, and the film thickness is thin.
In addition, a coating technique that can obtain a magnetic layer with a smooth surface
It has been demanded. As a method of applying a coating solution to a web surface
For example, roll coater method, gravure coat method,
Le Coat plus doctor method, extrusion coating
Method, slide coating type coating method and the like. Among the extrusion type coating apparatuses,
As shown in Japanese Patent Publication No. 5-8065, the tip of the coating head
In the type of applicator that presses the web against the web,
To increase the fluid pressure at the tip of the coating head
Eliminates the air entrained by the web
Since a uniform coating layer can be obtained, the magnetic recording medium
Often used in the field of manufacturing. However, this type of extrusion
Possible coating layer thickness even when coating with a mold coater
Demands to obtain a thin magnetic layer
There is a problem that cannot be answered sufficiently. Furthermore, paint
The application layer is streaked due to the web scraping at the tip of the fabric head.
There is a drawback that it is easy to produce. [0006] From this, it is thinner and coating without stripes.
As a coating apparatus capable of obtaining a fabric layer, Patent No. 261 is used.
Doctor blade scraping shown in No. 4119
There are mold applicators. This coating device is a roll coater type
Apply the excess coating solution on the web with
Excessive coating solution with a doctor blade located downstream
A thin coating layer is obtained by scraping off the minutes.
The In this case, in Japanese Patent No. 2614119,
As a coating device for applying excess coating liquid,
The Le Coater type is used, but it is not necessary to be limited to this.
Pressurized extrusion type, Equipped with backup
Uses a stretch type, gravure slide coater type, etc.
Can be. [0007] However, the prior art
Doctor blade scraping-type coating device
Conventionally, it is 2 μm or less in a wet state like an air recording medium.
Coating thickness distribution occurs when a very thin magnetic layer is formed
There was a thing. This coating thickness distribution is similar to that of conventional magnetic recording media.
In the case of the coating layer thickness required for the body magnetic layer
The coating layer was extremely thin.
It is manifested by. Scrap-off type applicator
This coating thickness is used for ultra-thin and uniform coating
It is necessary to pursue the cause of distribution and eliminate it.
is there. The present invention has been made in view of such circumstances.
Flexible support for scraping-off type application
Providing a coating method that can be applied to the body in an extremely thin and uniform manner
The purpose is to provide. [0009] The present invention achieves the above object.
In order to achieve this, the belt-like support
Excessive amount of coating liquid on the support with a coating device
After applying the coating solution, scrape off the coating surface side of the support.
Relatively press the squeeze member to scrape the excess of the coating solution.
In the coating method to scrape off, the coating is performed by the pre-coating device.
After scraping off the applied thickness with the scraping member
It is characterized by adjusting according to the coating thickness in the wet state of
doing. The inventor of the present invention has found that the wet state is 2 μm or less.
The specific coating thickness generated when the very thin coating below is applied
Application thickness applied by pre-coating equipment as a cause of cloth
(Hereinafter referred to as “precoat thickness”). And
The coating thickness in the wet state after scraping off
Precoat thickness relative to “wet coating thickness”
Depending on the thickness, a coating thickness distribution unique to ultra-thin coatings occurs.
I found out. For example, precoat thickness is wet film thickness
If it is too thick, apply streaks to an extremely thin coating
Unevenness occurs. Conversely, the precoat thickness is less than the wet coating thickness.
If it is thin, V-shaped coating unevenness appears on the extremely thin coating film.
The The present invention has been made based on such knowledge.
The precoat thickness is in the proper range based on the wet coating thickness.
To obtain an ultra-thin and uniform coating.
It is a thing. The proper range of precoat thickness is wet
When applying an ultra-thin coating of 2 μm or less,
It should be 3 to 20 times. As a result, the streaky coating mud
Very thin with no coating thickness distribution, such as uneven coating of V and V-shaped
A coating film can be obtained. Also, a coating solution to be applied by a precoat apparatus
It has a high shear viscosity of 1 to 50 mPa · s and a low shear viscosity.
It is preferable to use one having a degree of 0.01 to 5 Pa · s. this
The coating liquid with such viscosity was scraped off with a scraping member.
The coating liquid flows smoothly without collecting on the scraping member.
Fall down. Therefore, it is possible to apply a very thin and uniform coating.
it can. [0012] DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.
A preferred embodiment of the coating method will be described in detail. FIG. 1 shows a scraping mold to which the present invention is applied.
It is the conceptual diagram which showed the whole structure of the coating device 10, FIG.
3 is an enlarged view of a tip portion of a doctor blade 16. FIG. As shown in FIG. 1, the coating apparatus 10 is mainly used.
In excess of the desired coating amount on the continuously running web 12
A pre-coating device 14 for applying the coating liquid,
And doctor blade 16 that scrapes off the surplus.
ing. The pre-coating device 14 is a backup device.
An example of an extrusion type coating head with a cap
However, the present invention is not limited to this.
Crustion type, roll coater type, gravure coater
Type, roll coat plus doctor type, slide coat type
Etc. can be used. The precoater 14 is mainly used for
A rouge-type coating head 22 and the coating head 22
The back is disposed in close proximity to the lip surface 24 at the tip of the
And an up roller 26. Within the application head 22
The part has a cylindrical pocket along the width direction of the web 12
28 is formed and the pocket 28 is removed from the pocket 28.
A slit 30 reaching the top surface 24 is formed. slit
30 is a narrow connecting the pocket portion 28 and the lip surface 24.
It is a flow path and extends in the width direction of the web 12. Further, the pocket portion 28 is supplied with a coating liquid.
Line 34 is connected to this supply line 34
Are provided with a flow meter 36 and a pump 38. This flow
While measuring the flow rate through the supply line 34 with a meter 36
By controlling the pump 38, the pocket 28
Is supplied with a precisely weighed coating solution. Application of coating solution
The feed amount is 3 to 3 with the precoat thickness t1 being the wet coating thickness t2.
Try to be 20 times. Also, as a coating solution to be supplied
Has a high shear viscosity of 1 to 50 mPa · s and a low shear viscosity of 0.
A coating solution of 01 to 5 Pa · s may be supplied. Where high
The shear viscosity is a shear rate of 4 measured with a Rotovisco viscometer.
Viscosity at 0000 (1 / s), low shear viscosity and
Is measured with a B-type viscometer (Brookfield viscometer)
Viscosity. The coating liquid supplied to the pocket portion 28 is
After being spread in the width direction of the web 12 by the ket portion 28,
The lit 30 is raised and discharged from the slit discharge port.
The discharged coating liquid is supported by the backup roller 26.
Between the continuously running web 12 and the lip surface 24
It is applied to the web 12 while forming a bead. Na
As a method of feeding the coating liquid to the pocket portion 28,
The other end side of the pocket portion 28 is closed and supplied from one side.
Method, supply from one side of the pocket 28 and from the other end
How to pull out, supply from the center of the pocket 28 and both
Any of the methods of diverting to the side may be used. The doctor blade 16 travels on the web 12.
It is arranged so as to be approximately perpendicular to the direction.
Backup roller on the upstream side of the cutter blade 16
A support roller 18 is provided on the flow side. Backer
The top roller 26 and the support roller 18
It is disposed at a position lower than the tip of the card 16. This
The web 12 that runs continuously is a doctor blade 16.
Is applied to the web 12 by being pressed against the distal end surface 32 of the web.
The excess of the applied coating solution is scraped by the doctor blade 16.
It will be dropped off. Doctor blade 1 facing the web 12
As shown in FIG. 2, the tip surface 32 of 6 is 1-30 mm
It is curved with a curvature R, and the web 12 is applied to the distal end surface 32.
Incident angle (θ_in) Wrapped in a range of 0.5 to 2 °
To enter and leave angle (θ_{ou t}) As appropriate. this
Thus, the distal end surface 32 of the doctor blade 16 and the web 1
It is possible to keep the distance to 2 below 2 μm
Then, the coating layer after being scraped off by the doctor blade 16
The thickness can be made very thin with 2 μm or less. The doctor blade 16 is, for example, super
Alloy or fine ceramics, alumina A-15
Hard surface such as 0, zirconia, or the surface part with these materials
The surface is composed of a member coated with
The roughness is 0.5 μm or less, preferably 0.2 mm or less.
Has smoothness of degree. Next, the coating apparatus 10 constructed as described above is used.
The operation will be described. An extremely thin coating layer having a thickness of 2 μm or less was formed.
At this time, depending on the relationship between the wet coating thickness t2 and the precoat thickness t1.
The specific coating thickness that does not occur in the conventional coating thickness
Cloth may be generated. For example, precoat thickness t1
If it is thinner than 3 times the wet coating thickness t2,
-The effect of the liquid physical properties of the surface part scraped off by the blade 16
In response, V-shaped coating unevenness may occur. Ma
In addition, the precoat thickness t1 is more than 20 times the wet coating thickness t2.
If thick, scrape off with doctor blade 16
Since there is too much coating liquid, the scraped coating liquid
-It accumulates on the blade 16 and forms a non-uniform flow.
Will adversely affect the coating and cause streaky coating unevenness.
Sometimes. Such coating thickness distribution is the same as the conventional coating thickness.
As a reference, the wet coating thickness t2
There is no conventional coating method for adjusting the precoat thickness t1.
It was. Therefore, an ultra-thin coating layer is leveled by the conventional coating method.
It was difficult to form in one. In contrast, the present embodiment is a precoat.
The thickness t1 was adjusted to a range of 3 to 20 times the wet coating thickness t2.
Therefore, the liquid material of the coating liquid scraped off by the doctor blade 16
The coating solution that is affected by the properties
It won't form. Therefore, V-shaped or streaky
The occurrence of coating unevenness can be prevented, and the thickness is 2 μm or less.
The lower ultra-thin coating layer can be formed uniformly. In addition, the coating apparatus 10 of the present embodiment is a
The recoating device 14 has a high shear viscosity of 1 to 50 mPa · s,
Apply a coating solution with a low shear viscosity of 0.01 to 5 Pa · s
I am doing it. A coating solution with such a viscosity
When scraping off with the raid 16, the coating liquid scraped off
Smooth and even flow without collecting on the doctor blade 16
It is easy to form this. Therefore, a more uniform ultra-thin coating
Can be formed. The above-described embodiment is a precoat.
By adjusting the thickness t1 and viscosity to an appropriate range,
Uniform flow of coating liquid scraped off by the cutter blade 16
However, the present invention is not limited to this. For example, scraping
Make sure that the dropped coating solution flows smoothly.
-The surface of the blade 16 is processed with high accuracy and its surface roughness
Or the side of the doctor blade 16
May be formed obliquely in the running direction of the web 12. this
Makes the flow of coating liquid scraped off uniform.
Thus, occurrence of uneven coating can be prevented. In the above-described embodiment, excessive application
Scraping member (application
Doctor blade 16 was used as the
It is not fixed. For example, FIG. 3 shows the coating shown in FIG.
In the cloth device 10, instead of the doctor blade 16
A coating apparatus using a rod-type scraping member 40.
The The rod-shaped scraping member 40 is the width of the web 12
A cylindrical rod 42 arranged parallel to the direction, and the rod
And a support member 44 for supporting the web 42, and the web 1
2 contacts the rod 42 with a predetermined wrap angle
Is done. As a result, the pre-coating device 14 applies excessively.
The excess coating liquid is scraped off by the rod 42.
And weighed to the desired amount of coating solution. In this case, the rod 4
2 shows how the web 12 travels by contacting the web 12.
It may be rotated in the same direction as the direction, it will not rotate
You may do it. Alternatively, the rod 42 may be a rotational drive source
Connected to (not shown), the direction opposite to the running direction of the web 12
You may make it rotate. Also used here
The rod 42 is a flat type whose outer peripheral surface is flat.
Wire type with rod and wire wound tightly around the outer surface
Groove engraved type rod with engraved circumferential grooves on the rod, outer peripheral surface
Can be used. In the case of the coating apparatus shown in FIG.
The thickness t1 is 3 to 20 times the wet coating thickness t2 or applied.
The liquid has a high shear viscosity of 1 to 50 mPa · s and a low shear viscosity of 0.
By setting it to 01-5 mPa · s, the wet coating thickness t2 is uniform.
Thus, an extremely thin and uniform coating can be performed. [0028] EXAMPLES Tables 1 and 2 were carried out by changing the precoat thickness.
The result of a test is shown. In the test in Table 1
Uses a die coater as the precoater and paint A
Is coated on an aramid base with a thickness of 4μm and a width of 300mm
The coating was performed at a speed of 400 m / min. And diameter 1.5
The excess film is scraped off with an ultra-hard mm flat bar.
The thickness was set to 1.0 μm by wet. B type of paint A
Viscosity is 1 Pa · sec, high shear viscosity (shear rate 4000)
The viscosity at 0 1 / sec was 10 mPa · sec. In the tests in Table 2, the precoat equipment and
Then, using a support pressurizing die coater, with a thickness of 5 μm
Width 1000 with paint B applied to the surface by a dry film of 2 μm
On a PEN base with a thickness of 200 m / min.
Paint A was applied. And the doctor blade shown in FIG.
Scrape off excess paint A and wet the final film thickness.
The thickness was 0.5 μm. The doctor blade shown in FIG.
The curvature of the end face is 4mm and the blade thickness is 1.5mm.
Side surface is located toward the upstream side of the web running direction
The [0030] [Table 1] [Table 2]As can be seen from Tables 1 and 2, when the final film thickness is 1 μm
(Table 1), 0.5 μm (Table 2)
A certain tendency depending on the precoat thickness relative to the film thickness
It was observed. That is, as in Comparative Examples 1 and 3,
If the coating thickness / final film thickness exceeds 20 times,
Unevenness occurs, as in Comparative Examples 2 and 4, precoat thickness /
When the final film thickness is less than 3 times, V-shaped coating is applied on the coated surface
Cloth unevenness occurred. On the other hand, like Examples 1-6
In addition, the precoat thickness / final film thickness is in the range of 3 to 20 times.
A good coated surface was obtained. Table 3 shows the results of tests with different paint viscosities.
Is shown. In the tests in Table 3, precoat equipment
As a support press type die coater, thickness 5μm
With the surface, the coating B is applied as a dry film with a thickness of 2 μm.
Cyclohexene on paints C and D on 0 mm PEN base
The coating speed is adjusted by adding SANON to adjust the viscosity of the coating solution.
The coating was performed at 200 m / min and a wet thickness of 10 μm.
And with the doctor blade shown in FIG.
The final film thickness was set to 1.0 μm by scraping. [0032] [Table 3] As can be seen from Table 3, the viscosity of type B is independent of paints C and D.
There is a certain tendency of the coated surface according to the value of high shear viscosity.
It was. That is, a comparative example having a B-type viscosity of less than 0.01
5, 8 or Comparative Examples 7 and 10 having a B-type viscosity greater than 5
The coating unevenness occurred. High shear viscosity is less than 1
Comparison examples 5 and 6 and comparison with high shear viscosity greater than 50
Also in Examples 9 and 10, coating unevenness occurred. Against this
B type viscosity is 0.01-5, and high coating viscosity
In Examples 7 to 10 in which is 1 to 50, it is always good coating
A surface shape was obtained. Next, the paints A to D will be described. Each of the paints A to D is made of the following raw materials:
After kneading each component with a kneader,
Dispersed. Then, polyisocyanate is added to the obtained dispersion.
Fill with 10 parts of Nate and an average pore size of 1 μm
The coating solution was adjusted by filtration using a filter. Each component of the raw material of paint A is ferromagnetic metal fine powder
100 parts of powder, MR110 as vinyl chloride copolymer
12 parts (manufactured by Nippon Zeon) as polyurethane resin
3 parts of UR8200 (Toyobo Co., Ltd.) as α-alumina
10 parts of HIT55 (Sumitomo Chemical Co., Ltd.), carbon black
# 55 (Asahi Carbon Co., Ltd.)
3 parts sulfonic acid, 10 parts butyl stearate, butoki
5 parts ciethyl stearate, isohexadecyl stearate
3 parts rate, 2 parts stearic acid, methyl ethyl keto
180 parts and cyclohexanone 180 parts. The raw material component of the paint B is a non-magnetic powder.
TiO₂Crystalline rutile (average primary particle size 0.035μ
m, specific surface area 40m by BET method²/ G, pH 7, T
iO₂Content 90% or more, DBP oil absorption 27-38g /
100g, surface treatment agent Al₂O _Three, 8% by weight) 80
Part, CONDUCTEX SC-U as carbon black
20 parts (made by Colombian Carbon), vinyl chloride
12 parts of MR110 (manufactured by Nippon Zeon Co., Ltd.) as a polymer
UR8200 (manufactured by Toyobo) as polyurethane resin
5 parts, 4 parts phenylphosphonic acid, butyl stearate
1 part, 3 parts stearic acid, methyl ethyl ketone /
250 parts of clohexanone (8/2 mixed solvent) was used. Each component of the raw material of the paint C is a ferromagnetic metal fine powder
100 parts of powder, MR110 as vinyl chloride copolymer
12 parts (manufactured by Nippon Zeon) as polyurethane resin
3 parts of UR8200 (Toyobo Co., Ltd.) as α-alumina
10 parts of HIT55 (Sumitomo Chemical Co., Ltd.), carbon black
# 55 (Asahi Carbon Co., Ltd.)
3 parts sulfonic acid, 10 parts butyl stearate, butoki
5 parts ciethyl stearate, isohexadecyl stearate
3 parts rate, 2 parts stearic acid, methyl ethyl keto
80 parts and cyclohexanone 80 parts. Each component of the raw material of the paint D is barium ferrule.
100 parts of Ito magnetic powder, MR as vinyl chloride copolymer
5 parts of 555 (manufactured by Nippon Zeon), polyurethane resin and
3 parts of UR8200 (manufactured by Toyobo Co., Ltd.), α-alumina
10 parts of HIT55 (Sumitomo Chemical Co., Ltd.)
# 55 as a rack (Asahi Carbon Co.) (average primary particles
Diameter 0.075μm, specific surface area 35m²/ G, DBP oil absorption
(Amount 81ml / 100g, PH7.7 volatile content 1.0%)
1 part, 2 parts phenylphosphonic acid, butyl stearate
10 parts, 5 parts butoxyethyl stearate,
3 parts hexadecyl stearate and 2 stearic acid
Part, methyl ethyl ketone 80 parts, cyclohexanone
80 parts. [0039] As described above, the coating method according to the present invention.
According to the method, the thickness of the coating liquid applied by the precoat device
By adjusting the viscosity, a uniform and extremely thin coating film is obtained.
be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram showing the overall configuration of a coating apparatus to which the present invention is applied. FIG. 2 is a side view showing the tip of a doctor blade. FIG. 3 is a rod-type scraping member. FIG. 4 is a side view showing the shape of a doctor blade used in the examples. [Description of Symbols] 10 ... Coating device, 12 ... Web, 14 ... Precoat device, 16 ... Doctor blade, 18 ... support roller,
22 ... coating head, 24 ... lip surface, 26 ... backup roller, 28 ... pocket part, 30 ... slit, 32 ...
Doctor blade tip, 34 ... supply line, 36 ...
Flow meter 38 ... Pump 40 ... Scraping member 42 ...
Rod, 44 ... support member

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Claims (1)

[Claims] [Claim 1] An application surface of the support after applying a coating liquid in excess of a desired coating liquid amount to the support by a pre-coating device while continuously running the belt-like support In a coating method in which a scraping member is pressed relatively to the side to scrape off an excess of the coating solution, the coating thickness applied by the precoat device is applied in a wet state after scraping off by the scraping member. A coating method characterized by adjusting according to the thickness.