JP2003126765A - Coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method by which uniform and extremely thin coating free from coating stripe is carried out in a scraping type coating. SOLUTION: In an apparatus 10 using the coating method, the evaporated quantity of a solvent in a coating liquid on a web 12, which is evaporated between a pre-coat apparatus 14 and a doctor blade 16, is controlled so that the concentration of the solid portion in the coating liquid on the web 12 in the position of the doctor blade 16 becomes <=80%. For example, the evaporation time of the coating liquid is controlled to <=0.2 sec or the temperature of the coating liquid to be applied or the temperature of the web 12 is controlled to be lower by >=30 deg.C than the boiling point of the lowest boiling point solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method.
Used in the manufacture of photographic materials and magnetic recording media.
The present invention relates to a blade blade scraping type application method. [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
Demand for a magnetic layer with low film pressure
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.
When an extremely thin magnetic layer is formed, coating streaks occur frequently
There was a thing. This coating stripe is the same as that of conventional magnetic recording media.
Not seen in case of coating layer thickness required for magnetic layer
This is because the coating layer is extremely thin.
It has become obvious. A scraping-type coating device
In order to perform ultra-thin and uniform application, the cause of this application line is added.
It is necessary to eliminate this factor. The present invention has been made in view of such circumstances.
In scraping-type coating,
Providing a coating method that can be applied with ultra-thin and uniform coating
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 the application side of the support
Relatively press the squeeze member to scrape the excess of the coating solution.
In the coating method of scraping off, it was coated on the support
The solid content concentration of the coating solution is 80 at the position of the scraping member.
% From the precoat device so that it does not exceed%.
Evaporates from the coating liquid on the support before the dropping member
The amount of evaporation of the solvent is controlled. The inventor of the present invention has a thickness of 2 μm in a wet state.
Scrape off the excess of coating liquid in ultra-thin coating
The main cause of frequent application streaks
The solid content concentration of the coating liquid on the support at the position of the member
I found out. In other words, supported by precoat equipment
The solvent evaporates from the coating solution applied to the body, increasing the solids concentration.
Ascending is the main cause of coating streaks, especially scraping
If the solid concentration at the position of the member exceeds 80%, 2
It is said that there are many coating streaks in the case of very thin coating less than μm.
Obtained knowledge. The present invention is based on such knowledge.
Of the coating liquid at the position of the scraping member.
By controlling the shape concentration so that it does not exceed 80%.
Thus, an extremely thin and uniform coating is performed. Coating liquid solid
The concentration is between the precoater and the scraping member.
The amount of solvent evaporated from the coating solution on the support
By adjusting the amount of agent evaporation ”)
You can. The solvent evaporation amount is, for example, a precoat
The amount of solvent contained in the coating solution applied by the device (hereinafter referred to as “First
It is recommended that it be 50% or less of the “term content”. As a preferable method for controlling the solvent evaporation amount,
For example, scrape off the coating solution applied with a pre-coating device
The time until scraping with a member (ie, the “evaporation of solvent”
Time ") should be 0.2 seconds or less. This
The amount of agent evaporation can be reduced, and the solid content concentration of the coating solution
Can be made 80% or less. As another method for controlling the amount of solvent evaporation,
Is the temperature of the coating solution applied by the precoater.
Solvent with the lowest boiling point (hereinafter referred to as “minimum”
If it is 30 ° C lower than the boiling point of the "boiling point solvent")
Good. As a result, a low temperature coating solution is applied onto the support.
Therefore, the solvent of the coating solution is difficult to evaporate,
The solid content concentration can be controlled to 80% or less. As another method for controlling the amount of solvent evaporation,
The temperature of the support at the position of the precoater
The boiling point of the low boiling point solvent may be lower by 30 ° C. or more. This
As a result, the coating solution is applied to the low temperature support.
As a result, the solvent of the coating solution is less likely to evaporate and the coating solution is hardened.
The shape concentration can be reduced to 80% or less. [0014] 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.
It is an enlarged view of the front-end | tip part of a doctor blade. 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. And
Coating applied to the pocket 28 of the coating head 22
The liquid is spread in the width direction of the web 12 in the pocket portion 28.
After that, the slit 30 is raised and discharged from the slit discharge port.
Is done. The discharged coating liquid is supplied to the backup roller 26.
The web 12 is supported continuously by the web 12 and the lip surface 24.
Applied to the web 12 while forming a bead between
The It should be noted that the coating liquid is fed to the pocket portion 28.
The other end side of the pocket portion 28 is closed and supplied from one side.
Supply method, supply from one side of the pocket 28 and the other end
Pull out from the side, supply from the center of the pocket 28
Thus, any of the methods of diverting to both sides 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 2 upstream of the blade 16
6. A support roller 18 is provided on the downstream side. Ba
The backup roller 26 and the support roller 18 are
-It is arranged at a position lower than the tip of the blade 16. This
As a result, the continuously running web 12 is
Pressed against the tip surface 32 of the web 16 and applied to the web 12
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
_max0.5 μm or less, preferably 0.2 μm or less
The surface is processed with Rasa. By the way, the coating apparatus 10 includes a doctor valve.
Solid coating liquid on the web 12 at the position of the raid 16
Measures are taken to reduce the concentration to 80% or less,
Specifically, the solvent evaporation amount is a predetermined amount (preferably the initial solvent
Solid content concentration by controlling to less than 50%)
80% or less. The solid content here is, for example,
Magnetic powder such as ferromagnetic metal powder and hexagonal ferrite powder
Powder, metal oxide, metal carbonate, metal sulfate, metal nitriding
, Inorganic compounds of metal carbides, thermoplastic resins, thermosetting
Examples thereof include binders such as resins and reactive resins. Also,
Solvents include acetone, methyl ethyl ketone, methyl
Ketones such as isobutyl ketone and cyclohexanone;
Thananol, ethanol, propanol, butanol names
Alcohol system; methyl acetate, ethyl acetate, butyrate
, Ethyl lactate, glycol acetate monoethyl ether, etc.
Ester system: ether, glycol dimethyl ether
, Glycol monoethyl ether, dioxane, etc.
Recall ether type: benzene, toluene, xylene, etc.
Tar system (aromatic hydrocarbon); methylene chloride,
Ethylene chloride, carbon tetrachloride, chloroform, ethyl
Lenchlorohydrin, dichlorobenzene, etc.
The The method for controlling the amount of solvent evaporation is roughly classified into three types.
There is a kind, the solvent evaporation time is controlled by adjusting the evaporation time of the solvent
Solvent evaporation by adjusting the temperature of the coating solution to be applied
How to control the amount, adjust the temperature of the web 12 to be applied
Thus, the solvent evaporation amount is controlled. The following three types
A specific example of the method will be described. The method of adjusting the evaporation time of the solvent is
Precoat device 14 so that the time is 0.2 s or less.
And the doctor blade 16 are arranged at short intervals. This
In other words, by shortening the evaporation time,
Reduces the amount generated and keeps the solid content of the coating solution below 80%
Can be. The position of the doctor blade 16 is
If a mechanism that can be adjusted in the width direction of the web 12 is provided,
Even when the running speed of the web 12 is changed, it can be easily handled.
be able to. In the method of controlling the temperature of the coating liquid,
The liquid temperature is a predetermined temperature higher than the boiling point of the lowest boiling solvent of the coating liquid.
(Preferably 30 ° C.) The temperature is adjusted to a lower temperature. example
If the boiling point of the lowest boiling solvent is 80 ° C,
The temperature of the cloth liquid is controlled to 50 ° C. or lower. In this way, low temperature
The controlled coating solution is applied from the pre-coating device 14
Reduces the amount of solvent evaporation and reduces the solids concentration to 80%.
The following can be suppressed. In addition, temperature control of coating liquid
Supplies the coating liquid to the coating head 22 of the precoater 14.
A heat exchanger (not shown) is installed in the supply line to supply the heat.
The coating solution may be cooled to a constant temperature with an exchanger. In the method of controlling the temperature of the web 12,
The temperature of the web 12 at the position of the precoater 14
Is less than the boiling point of the lowest boiling solvent of the coating solution (preferably
Or 30 ° C.) or lower. For example, at least
If the boiling point of the boiling solvent is 80 ° C, the temperature of the coating solution
The degree is controlled to 50 ° C. or lower. Thus, the low temperature web
The amount of solvent evaporation is reduced by applying the coating liquid to
The solid content concentration can be suppressed to 80% or less.
As a method for lowering the temperature of the web 12, continuous running is possible.
On the upstream side of the pre-coating device 14
Or spray on the pre-coating device 14
Web roll (not shown) wound with the web 12 to be supplied
It is good to cool and store in advance at a predetermined temperature. The above-mentioned methods are employed independently.
Alternatively, a plurality of them may be used in combination. Solvent steam
The method of controlling the amount of emission is not limited to
From the position of the precoat device 14, the doctor blade 1
Along the application surface of the web 12, the application surface
A cover (not shown) may be provided. Install this cover
By evaporating from the coating solution on the web 12
The solvent becomes difficult to diffuse and the concentration of the solvent in the vicinity of the web 12
The degree rises. Therefore, the amount of solvent evaporation decreases.
The solid content concentration at the position of the doctor blade 16 is 80
% Or less. Alternatively,
Adjusts the components of the coating solution supplied to the precoater 14
May be. For example, a coating solution with a high boiling point of the lowest boiling solvent
Or adjust the coating solution with a low solid content concentration beforehand
Also good. As described above, the amount of solvent evaporation is controlled.
At the position of the doctor blade 16
The solid content concentration of the coating solution can be 80% or less.
When the solid content concentration of the coating liquid is 80% or less, the coating liquid is
Between the front end surface 32 of the doctor blade 16 and the web 12
Flow smoothly, and solid content can cause streaks
There is no. Therefore, according to the coating apparatus 10 of the present embodiment.
Can be applied with ultra-thin and uniform coating without streaks.
Yes. In the above-described embodiment, excessive application is performed.
Scraping member (application
Doctor blade 16 was used as the
Rod type scraping member (for example,
For example, flat rods and wires with a flat surface
Closely wound wire type rod, circumferential direction on the outer peripheral surface
Even if a grooved rod with grooves is used, etc.)
Good. [0029] EXAMPLES As a precoat, paint A is coated with methyl ethyl ketone.
Tons to adjust to the prescribed solids concentration, thickness 600m
It apply | coated using the die-coater on m PET base.
Then, with the doctor blade shown in FIG.
The final film thickness was wetted to 1 μm. In FIG.
The doctor blade shown has a radius of curvature of 4 mm at the tip surface,
The blade thickness is 1.5mm and the left side is the web running
It is arranged toward the upstream side in the row direction. The temperature of the coating solution is 35 ° C., and the temperature of the support is 2.
While adjusting to 5 ° C and changing various parameters
The measured results are shown in Table 1. In Table 1, the initial concentration and
Is a precoat prepared by adding methyl ketone to paint A
The solid concentration of the liquid. The intermediate concentration is the scraping position.
It is the solid content concentration of the paint. Also, distance is pleco
This is the distance from the starting position to the scraping position. further,
As the evaluation of the surface condition in Table 1, ◎ ... very good, ○ ... good
Favorable, x: Uneven scraping unevenness. Paint A
Will be described at the end of the embodiment. [0031] [Table 1]As can be seen from Table 1, coating is performed under the conditions of Comparative Example 1.
And the solid content concentration at the time of scraping becomes 81%, scraping off
Unevenness occurred. On the other hand, in the first embodiment, the doctor tube is used.
Reduce the distance between the raid and the precoat device to 20cm
The intermediate density is reduced to 75%
The shape was obtained. In Example 2, the coating speed is 240.
By increasing the speed to m / min, the solid content becomes 60%.
As a result, a good coated surface was obtained. These are considered in terms of evaporation time.
In comparison example 1, the evaporation time was 0.3s
On the other hand, 0.2 s in Example 1 and 0.075 in Example 2.
s. Therefore, the evaporation time is 0.2 s or less
If this is the case, the intermediate density will be as low as 80% or less, and good coating will be achieved.
It can be seen that a cloth surface is obtained. In Example 3, the precoat thickness is 30 μm.
To increase the intermediate concentration to 53%,
A very good coated surface could be obtained. This is
Solvent evaporation by increasing the thickness of the record
The relative proportion of
It is thought to be less. In Example 4, the first solid of the precoat liquid was used.
Since the initial concentration is as low as 20%, the intermediate concentration is also 51%
A good coated surface was obtained. In this way,
By setting the initial concentration of solids in the recording solution low
Even the intermediate density can be reduced and good coating
A planar shape can be obtained. In Example 5, the coating speed of Example 4 is used.
Was increased to 240m / min, so the solids concentration was 32%.
Furthermore, a very good coated surface was obtained. The sixth embodiment is different from the fourth embodiment in that
The initial concentration of solids in the salt solution was further reduced to 10%.
The intermediate density is as low as 24%, and a good coated surface is obtained.
It was. In addition, Example 7 is faster than Example 6 in coating speed.
Was increased to 240 m / min, so the intermediate concentration was 15%.
And a very good coated surface was obtained. From the results shown in Table 1, the evaporation time is shortened.
Increased precoat thickness, low solid content of precoat solution
The solid content concentration at the scraping part
The degree can be lowered and a good coated surface can be obtained.
it can. And to get a good coated surface,
It is preferable that the solid content concentration in the butt portion is 80% or less.
I understand that. Table 2 shows the effects of coating solution temperature and support temperature.
Show. In Table 2, the thickness is 4 μm and the width is 600 mm.
The paint D is applied to the ramid base by 2μm as a dry film.
On the PEN base with a width of 1000 mm, the support pressure type
It apply | coated by thickness 10 micrometers using the die-coater. That
A carbide flat blade of φ1.5 at a position 30 cm away from the downstream side.
Scrape off excess paint with a towbar and wet the final film thickness
To 2 μm. In Table 2, the meaning and surface state of intermediate concentration
The evaluation criteria are the same as in Table 1. In addition, coating liquid B, C,
D will be described at the end of the embodiment. [0039] [Table 2] As can be seen from Table 2, when paint B is used, the support temperature
By setting the temperature and coating solution temperature low, good coating
A cloth surface shape was obtained. That is, the support temperature is as high as 60 ° C.
In Comparative Example 3, scraping unevenness occurred,
Example 8 where the coating solution temperature is as low as 40 ° C., and the support temperature is 4
Good in Example 11 and Example 12, which are as low as 0 ° C. and 50 ° C.
A smooth coated surface was obtained. In addition, coating solution temperature and support temperature
In Example 10 where the temperature was both as low as 20 ° C., it was very good.
A favorable coated surface was obtained. As a result, the coating solution temperature and
By setting the holding temperature low, a good coated surface shape
It can be seen that On the other hand, when paint C is used, the same inclination is applied.
The temperature of the support and the coating solution should be set low.
As a result, a good coated surface was obtained. That is, paint
Comparative Example 2 in which the cloth liquid temperature is 30 ° C. and the support temperature is 30
In Comparative Example 4 at ℃, even though scraping unevenness occurred
In contrast, the coating solution temperature and the support temperature were lowered to 20 ° C.
In Example 10, a good coated surface was obtained. Also, the temperature of the coating solution at which a good coated surface is obtained.
Table 2 shows that the temperature and the support temperature differ depending on the paints B and C.
I understand. That is, in the case of paint B, the coating liquid temperature and
A good coated surface is obtained when the support temperature is 50 ° C or lower.
In contrast, in the case of paint C, when the temperature is 26 ° C. or lower
A good coated surface was obtained. This is included in paints B and C
This is thought to be due to the difference in the lowest boiling point solvent. Snow
That is, the lowest boiling point solvent of paint B is ethyl methyl ketone (boiling point).
About 80 ° C), and the lowest boiling solvent of paint C is acetone.
(Boiling point approximately 56 ° C.). Therefore, paint C is paint B
The solvent evaporates more easily, and the intermediate concentration of solids increases.
It is considered easy. From the above results, good coated surface
According to the boiling point of the lowest boiling solvent contained in the paint.
Set the coating solution temperature and the support temperature.
Is a value that is 30 ° C lower than the boiling point of the lowest boiling solvent of the paint.
If it makes it, it turns out that a favorable coating surface shape is obtained. Next, the paints A to D will be described. The coating materials A and D are the raw materials shown below.
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. Paint B
Add 180g of methyl ethyl ketone to paint A and stir
And adjusted. For paint C, 180 g of acetone is applied to paint A.
In addition, the mixture was adjusted by stirring. 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, cyclohexanone
180 parts. The raw material component of the paint D 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. [0046] As described above, the coating device according to the present invention.
According to the arrangement, the solvent of the coating liquid applied on the support is
Solvent that evaporates between the coater and scraping member
The position of the scraping member by controlling the evaporation amount
The solid content concentration of the coating solution on the support was 80% or less.
Therefore, it is a case where an ultra-thin coating layer of 2 μm or less is formed.
However, it is possible to perform uniform coating without coating stripes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram showing an overall configuration of a coating apparatus according to the present invention. FIG. 2 is a side view showing a tip of a doctor blade. FIG. 3 is a side view showing a doctor blade used in an example. DESCRIPTION OF SYMBOLS 10 ... Application | coating apparatus, 12 ... Web, 14 ... Precoat apparatus, 16 ... Doctor blade, 18 ... Support roller,
22 ... coating head, 24 ... lip surface, 26 ... backup roller, 28 ... pocket part, 30 ... slit, 32 ...
Doctor blade tip

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Norio Shibata             1-2-1 Ogimachi, Odawara-shi, Kanagawa Pref.             Shishi Photo Film Co., Ltd. F-term (reference) 4D075 AC02 AC53 AC72 AC84 AC91                       DA04 DB31 DC27 DC28 EA05                       EB01 EB15 EB38

Claims (1)

[Claims] [Claim 1] An application side 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 the coating method in which the scraping member is relatively pressed to scrape off the excessive amount of the coating solution, the solid content concentration of the coating solution coated on the support is 80 at the position of the scraping member.
%, The evaporation amount of the solvent that evaporates from the coating solution on the support is controlled between the precoat device and the scraping member so as not to exceed%.