JP2002248395A - Die type coater for offset coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a die type coater for offset coating into a structure for preventing the generation of streak phenomenon. SOLUTION: A color roll 3 having large surface roughness is used and as a result, the generation of the streak phenomenon caused by accumulating foreign substance in a coating liquid 7 in the inside of a die coater head 5 to disturb the uniform flow-out of the coating liquid on the surface of the color roll from a lip is prevented and the foreign substance as well as the coating liquid is constantly discharged on the surface of color roll.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset coating die coater for applying a coating liquid to a traveling sheet-like material such as paper, film and metal foil.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3 or FIG. 4, a color roll 3 in an offset coating die coater is a roll obtained by further applying a chromium plating on a smooth metal roll surface. As shown in FIG. 4, the coating liquid 7 supplied from the die coater head 5 is applied to the surface of the color roll 3, and the coating liquid S on the surface of the roll 3 is a metal ring, which is a transfer target contacting the color roll 3. It is transferred to the sheet 6 after being transferred to the roll 4 or directly as shown in FIG.

In order to obtain a uniform coating surface on the web sheet 6, the surface of the color roll 3 is usually highly polished in order to keep the surface roughness of the color roll 3 low.

[0004] The coating method on the web sheet 6 by the die coater head 5 is roughly classified into two methods. One is called the direct die coating method.
As shown in FIGS. 7 and 8, the web sheet 6 is passed through a slight gap between the die coater head 5 and the backup roll 10 adjacent to the gap with a slight gap, and the coating liquid 7 is transferred from the die coater head 5 to the web sheet 6. It is a method of applying directly.

Another method is called an offset die coating method, and as shown in FIG. 3, a color roll 3 which is close to a die coater head 5 with a slight gap and is in circumferential contact with the color roll 3. The web sheet 6 is conducted between the backup roll 10 and the color roll 3.
Is transferred to the web sheet 6 running in contact with the backup roll 10.

Further, as shown in FIG.
Is transferred once to a metalling roll 4 in contact with the roll 3, and the coating liquid S on the metalling roll 4 is transferred to a backup roll 10 or a web sheet in contact with the metalling roll 4. 6 is also an offset die coating method.

[0007] Many die coaters have a die coater head 5 so that both types of coating can be performed with one facility.
And two or three rolls, such as the color roll 3, the metering roll 4, and the backup roll 10, which can be abutted and separated, in many cases.

The advantage of the direct die coater as shown in FIG. 5 is that the apparatus is composed of only the die coater head 5 and 101 backup rolls, and is a simple facility and the facility cost is low. In addition, since only one roll is driven, less power is consumed,
In addition, since the adjustment of the coating amount is only to adjust the gap between the die coater head 5 and the web sheet 6 surrounding the backup roll 10, the operation is simple, but on the other hand, the adjustment of the coating amount is disadvantageous. Since it relies on the adjustment of the gap between the die coater head 5 and the web sheet 6, the gap cannot be made too small, and is limited to about 30 μm, so that it is used only for products having a relatively large coating amount.

On the other hand, the die coater for offset coating is:
As shown in FIG. 5, it is not applied directly to the web sheet 6 from the die coater head 5, but as shown in FIG.
This is a method of transferring to the web sheet 6 via the color roll 3 or transferring from the color roll 3 to the web sheet 6 via the metering roll 4 as shown in FIG.
Even if the minimum gap between the die coater head 5 and the color roll 3 is the same, the coating liquid 7 can be extended around the color roll 3 by increasing the speed of the color roll 3 so that the web sheet 6 and the color By keeping the speed of the relationship with the roll 3 properly, it is possible to keep the coating amount low. That is, when the amount of liquid supplied to the die coater head 5 is the same, if the speed of the color roll 3 is doubled and the speed of the web sheet 6 is made appropriate, the coating amount can be reduced to half. In addition, even if the speed of the web sheet 6 is not changed, the coating amount can be adjusted by a doctor device described later in paragraph 0040.

[0010] As described above, increasing the speed is an important factor from the viewpoint of the purpose and economy of the coated product for the producer, but also finely adjusts the rotation speed of the plurality of driven rolls. When the foreign matter 8 is required in the coating liquid 7, the foreign matter 8 is gathered around the lip 1 of the die coater head 5 and the color roll 3 as in the case of the conventional offset coating shown in FIG. Then, it is caught between the lip 1 and the color roll 3 and becomes a pinching foreign matter 13, which causes a streaky uncoated portion.

[0011] The streaky uncoated portion is generally called a streak and is generated on the surface of the coating solution S of the color roll 3, and the streaky trace is transferred to the web sheet 6 as it is by the transfer. Becomes a defective product, which causes a problem that greatly affects the product yield.

Although this streak phenomenon is also observed in the direct die coating method as shown in FIG. 8, the web sheet 6 to be applied is like a paper not rolled by a calendar.
As shown in FIG. 7, in a sheet having a relatively uneven surface of the web sheet 6 and a rough surface, the foreign matter 8 is coated with the coating liquid S as shown in FIG.
Is discharged to the outside of the die coater head 5, and the streak phenomenon does not occur. However, a sheet having a small surface unevenness such as a film sheet has a problem that a streak phenomenon occurs in both the direct and offset coating methods.

[0013]

The prevention of the occurrence of the above-mentioned streak phenomenon is a major problem in the die coater system, and many improvement measures have been tried in the past. That is, as a cause, foreign matter 8 is mixed in the coating liquid 7 in the die coater head 5, and as shown in FIG.
8, it is clearly understood that the foreign matter 13 is sandwiched in the gap between the web sheet 6 supported by the backup roll 10 and the gap between the web sheet 6 supported by the backup roll 10 as shown in FIG. A filter for transmitting the foreign matter 8 in the coating liquid 7 has been provided.

However, the size of the foreign matter 8 is as wide as several μm to several hundred μm, and the foreign matter 8 cannot be removed if it is smaller than the size of the filter, and clogging of the filter may occur with time.
In reality, it is difficult to completely remove the foreign matter 8.

Another cause of the contamination of the foreign material 8 is that sand and other fine particles in the air are adsorbed by the web sheet 6 due to static electricity or the like of the web sheet 6 and are taken into the die coater head 5 from the running sheet 6. Is a phenomenon.

In the direct die coating method, the foreign matter 8 directly enters the coating liquid 7 in the die coater head 5 from the running web sheet 6 in the direct die coating method. The occurrence of foreign matter 8 in
This is due to mixing in the coating liquid 7 via the color roll 3 which comes into contact with the die coater head 5.

As a countermeasure for removing the foreign material 8 described above, for the purpose of removing the foreign material 8 on the web sheet 6, the static electricity of the web sheet 6 is removed, the foreign material 8 on the surface of the sheet 6 is removed by vacuum suction, or an adhesive roll is used. Various methods such as removal have been tried, but none of them has given satisfactory results at present.

As described above, the occurrence of the streak phenomenon has conventionally been caused not by the problem of the die coater head 5 but by the contamination of the foreign matter 8 by the coating liquid 7 and the web sheet 6, and appropriate measures have been taken. The occurrence of streaks is not reduced to nothing, but still has a great effect on product yield, and it is an issue to eliminate the streak phenomenon.

[0019]

In order to solve the above-mentioned problems, it is of course to eliminate the invasion of foreign matter from the outside into the die coater head as much as possible.
Consideration has been given to providing a function of preventing the occurrence of streak phenomena due to foreign substances mixed in the coating liquid. That is,
As can be seen in the case of direct coating in paragraph 0012 above, a streak phenomenon does not occur on a paper having large irregularities on the surface of a web sheet, and a phenomenon that occurs on a sheet with small irregularities such as a film sheet is considered. As a result, it has been found that the irregularities on the surface discharge the foreign matter out of the die coater head, and prevent the foreign matter from accumulating on the lip surface in the die coater head.

Based on the above findings, according to the first aspect of the present invention, a coating liquid is stored in a cavity of a die coater head which is surrounded by a lip and a back plate, and a color roll is provided near the die coater head. The coating liquid is applied to the surface of a rotating color roll through a slight gap between the coating liquid and the coating liquid on the surface of the rotating color roll. In the die coater for offset coating to be processed, a color roll having a large surface roughness is used.

According to the second aspect of the present invention, the coating amount of the coating liquid can be set by providing a gap adjusting device between the lip of the die coater head and the surface of the color roll and a rotating speed adjusting device for the color roll. 1 is added to the invention.

According to the third aspect of the present invention, the surface roughness of the color roll is set such that the cell depth is 10 to 200 microns.
A configuration in which the pitch in the surface length direction and the circumferential direction is set to 10 to 500 mesh is added to the invention of claim 1 or claim 2.

According to a fourth aspect of the present invention, the rotation speed of the color roll is variable within a range of 10 to 100% of the traveling speed of the transfer object. Was added to

According to the fifth aspect of the present invention, the material of the cell on the surface of the color roll is not limited to a metal material such as iron and stainless steel, but also a polymer material such as rubber and plastic, carbon and ceramic. The configuration that is selected from inorganic materials is added to the invention of claim 1, claim 2, claim 3, or claim 4.

[0025]

1 and 2 show an embodiment in which each of the first to fifth aspects of the present invention is applied, and FIGS.
FIG. 4 shows a configuration example of an offset coating type die coater. The coating liquid 7 is stored in the inner cavity 11 of the die coater head 5 which is surrounded by the lip 1 and the back plate 2, and a slight gap between the die coater head 5 and the color roll 3 adjacent to the coater head 5. The coating liquid 7 is applied to the surface of the color roll 3 rotating in the direction of the arrow through the gap,
The coating liquid S is further transferred to the transfer sheet 9 as the web sheet 6 which comes into contact with the surface of the color roll 3 and moves in the direction of the arrow.
Transfer coating.

The transfer object 9 is a web sheet 6 in FIG. 3, and is shown as a metering roll 4 in FIG. In the example of FIG. 4, the coating liquid S on the surface of the metalling roll 4 which is the transfer object 9 further
The image is transferred to the web sheet 6 which is the next transfer object.

In the first aspect of the present invention, a color roll 3 having a large surface roughness is used as shown in FIGS. In FIG. 1, the rough surface of the roll 3 is schematically shown, and in FIG. 2, it is shown as a schematic enlarged view, and the rough surface is represented as an aggregate of an infinite number of cells 12.

FIG. 2 is an enlarged view of a contact portion between the color roll 3 and the die coater head 5 in FIG. 1. The color roll 3 is rotated in the direction of the arrow, and is inserted into the inner cavity 11 of the die coater head 5. The coating liquid 7 is supplied from below, and the supplied coating liquid 7 is supplied to the surface of the color roll 3 from the gap between the roll 3 and the lip 1 with the rotation of the color roll 3 and is supplied to the surface of the color roll 3. It is applied to the surface, and is carried as a coating liquid S until it comes into contact with the transferred material 9 as the web sheet 6 shown in FIGS. 3 and 4, and is transferred to the moving transferred material 9 and carried away.

As shown in FIG. 2, since the peripheral surface of the color roll 3 is formed of an aggregate of an infinite number of cells 12,
The foreign matter 8 mixed in the coating liquid 7 enters the cell 12 without staying inside the lip 1, is carried away with the coating liquid 7, and is applied to the transfer-receiving body 9 without causing a streak phenomenon. It is applied as S.

The gap H between the lip 1 of the die coater head 5 and the surface of the color roll 3 is adjusted by adjusting the die coater head 5.
The coating amount on the color roll 3 can be adjusted according to the properties of the coating liquid, for example, the saccharides, concentration, viscosity, and temperature of the coating liquid, depending on the properties of the coating liquid. It is adjusted to be a predetermined value.

Similarly, when the rotation speed of the color roll 3 is adjusted, for example, when the rotation speed is increased, the thickness of the coating liquid S is reduced. Therefore, even if the rotation speed of the roll 3 is adjusted, a uniform predetermined value is obtained. Adjust the coating amount. If the rotation speed is excessively increased, there is a possibility that air existing in the cell 12 passes over the back plate 2 and mixes with the coating liquid 7 in the die coater head 5. It is important to adjust the rotation speed.

The surface roughness of the color roll 3 is selected so that the depth of the cells 12 is 10 to 200 microns and the pitch in the surface length direction and the circumferential direction is 10 to 500 mesh.

If the unevenness of the surface of the color roll 3 is too large, the air in the cells 12 on the surface of the roll 3 is brought into the coating liquid 7 in the die coater head 5. Also, the size of the cell 12 is limited. On the other hand, if the irregularities are too small, the foreign matter 8 in the coating liquid 7 will not easily be carried over the lip 1 to the coating liquid S of the die coater head 5, and a streak phenomenon will occur. There are restrictions.

When air particles are introduced into the coating liquid 7 in the die coater head 5, a part of the coating liquid S that is applied from the lip 1 to the surface of the color roll 3 is partially uncoated. The phenomenon of blurring may occur.

The method for processing the surface of the color roll 3 is as follows.
It can be obtained by any processing method such as gravure processing, hydrophilic chrome plating, shot blast processing, and etching. As long as the same surface roughness is obtained, the streak phenomenon prevention performance is not affected depending on the processing method. If the surface roughness of the color roll is within the above numerical range, the above-mentioned various conditions are satisfied.

The rotation speed of the color roll 3 is set to
It can be varied within the range of 10 to 100% of the running speed.

The material of the cell 12 on the surface of the color roll 3 is as follows.
Not only metal materials such as iron and stainless steel,
Rubber, selected from polymer materials represented by plastics, carbon, inorganic materials such as ceramics,
The surface may be further chromium plated.

5 and 7, in both cases, the web sheet 6 passes through the gap between the backup roll 10 and the die coater head 5 and is moved from the die coater head 5 to the web sheet 6.
This is an example of a direct coating method in which a coating liquid is applied directly to the color sheet 3 and the die coater head 5 in the embodiment of the present invention. .

However, FIG. 7 shows a case where the web sheet 6 has a rough surface, and as shown in an enlarged manner in FIG.
This shows a case in which the foreign matter 8 in the inside is led out of the lip 1 to the outside of the die coater head 5 by the rough surface of the web sheet 6 together with the coating liquid S, so that the streak phenomenon does not occur. FIG. 8 shows that the web sheet 6 is not rough,
The case where the foreign matter in the inside becomes the sandwiching foreign matter 13 and a streak phenomenon occurs is shown.

It is a known fact that, when an excessive amount of the coating liquid S is applied to the surface of the color roll 3, a doctor device for scraping the excessive amount of the coating liquid is mounted, which is a necessary fact in operation. If there is, the doctor device concerned, and the excess coating liquid scraped is returned to the storage tank or the like.

[0041]

According to the first aspect of the present invention, by using a color roll having a large surface roughness, foreign matters accumulate in the coating liquid in the inner cavity of the die coater head, and the coating liquid on the lip is applied to the surface of the color roll. This prevents the streak phenomenon from occurring by preventing the uniform outflow of foreign matter, makes it possible to always allow foreign matter to flow out along with the coating liquid into the rough surface of the color roll surface, and prevents foreign matter from accumulating in the inner cavity of the die coater head. It has an effect that can be achieved.

According to the second aspect of the present invention, the gap between the lip of the die coater head and the surface of the color roll and the rotation speed of the color roll can be adjusted, so that a predetermined coating amount can be set. The effect of improving the coater speed while preventing the occurrence of the coating can be realized, and in combination with the invention of claim 1, the product quality can be improved and the productivity can be improved by the offset coating die coater, and the cost can be reduced. To play.

According to the third aspect of the invention, by controlling the surface roughness of the color roll, further excellent effects can be obtained in combination with the first and second aspects of the invention.

According to the fourth aspect of the present invention, by causing the rotation speed of the color roll to be variable with respect to the traveling speed of the object to be transferred within a predetermined range, the occurrence of streaks and the occurrence of troubles in which air particles enter the coating liquid. In combination with the first, second, and third aspects of the present invention, various effects are brought about, such as an improvement in product quality, an improvement in productivity, and a reduction in cost.

According to the fifth aspect of the present invention, it is possible to select the material of the cell on the surface of the color roll corresponding to the service life, and in combination with the first to fourth aspects of the present invention, the die coater for offset coating is provided. It prevents various troubles and has various effects such as improvement of product quality, improvement of productivity and reduction of cost.

[Brief description of the drawings]

FIG. 1 is a partial side view of an embodiment in which a color roll is directly transferred to a web sheet.

FIG. 2 is an enlarged side view of a main part of the embodiment shown in FIG.

FIG. 3 is an overall side view of the embodiment of FIG. 1;

FIG. 4 is a side view of an embodiment in which a color roll is indirectly transferred to a web sheet via a metering roll.

FIG. 5 is a side view of the direct coating coater.

FIG. 6 is an enlarged side view of a main part of offset coating using a color roll having a smooth surface.

FIG. 7 is an enlarged side view of a main part of the rough web sheet direct coating.

FIG. 8 is an enlarged side view of a main part of web sheet direct coating that is not rough.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lip 2 back plate 3 color roll 4 metalling roll 5 die coater head 6 web sheet 7 coating liquid 8 foreign matter 9 transfer target 10 backup roll 11 lumen 12 cell 13 sandwiching foreign matter S coating coating liquid

Continued on the front page F term (reference) 4F040 AA22 AB04 BA14 BA26 CB03 CB06 CB27 CB37 DA12 DB10 4F041 AA02 AB01 BA05 CA03 CA12 CA21 4F042 AA22 BA05 BA08 BA12 DF23 4L055 BE08 CH10 EA15 FA22 FA30

Claims (5)

[Claims] 1. A coating liquid is stored in a cavity of a die coater head which is surrounded by a lip and a back plate through a small gap between the die coater head and a color roll adjacent to the coater head. In an offset coating die coater, the coating liquid is applied to the surface of a rotating color roll, and the coating liquid on the surface of the color roll is further transferred and coated on another running transfer body in contact with the surface of the color roll. A die coater for offset coating using a color roll having a large surface roughness. 2. The offset coating die coater according to claim 1, further comprising a gap adjusting device between the lip of the die coater head and the surface of the color roll and a rotating speed adjusting device for the color roll. 3. The surface roughness of the color roll is determined by the cell depth.
3. A die coater for offset coating according to claim 1, wherein the die coater has a pitch of 10 to 500 mesh in a surface length direction and a circumferential direction of 10 to 200 microns. 4. The die coater for offset coating according to claim 1, wherein the rotation speed of the color roll is variable within a range of 10 to 100% of the running speed of the transfer object. 5. The material of the cell on the surface of the color roll is selected from a metal material represented by iron, stainless steel, etc., a polymer material represented by rubber and plastic, and an inorganic material such as carbon and ceramic. Claim 1, Claim 2,
The offset coating die type coater according to claim 3 or 4.