JPH03153A - Coating device - Google Patents

Abstract

PURPOSE:To obtain a good coating by retreating the front edge surface from a tangent at a separating terminal where the web on the back edge surface of a coating head is separated. CONSTITUTION:The upstream coating head 5A is so arranged as to press down a web 1 between a first support roll 2 and a second support roll 3, and the downstream coating head 5B is so arranged as to press up the web with the lower layer coated between the second support roll 3 and a third support roll 4. A lower layer coating soln. 10 is applied on the continuously traveling flexible web 1 with the rear, unsupported from the upstream first coating head 5A set between the first support roll 2 and the second support roll 3 to form the lower layer. An upper layer coating soln. 20 is then applied from the downstream second coating head 5B while the coating soln. 10 is not dried. A good coating is obtained in this way.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is applicable to a coating process in which a coating liquid is extruded from an extrusion type coating head onto a coating layer previously coated on a web to obtain a plurality of coating layers. Regarding equipment.

[Conventional technology]

When applying magnetic paint, photographic light-sensitive materials, heat-sensitive recording materials, etc. when manufacturing magnetic recording media, extrusion coating methods (extrusion coating methods) are used, in which the coating liquid is applied to the web while extruding it from a narrow slot in the coating head. coating method) is known to be used.

This extrusion coating method has advantages such as superior film thickness controllability compared to roll coating, gravure coating, slide coating, or methods including doctor coating.

In recent years, for example, in magnetic recording media, it has been practiced to form an undercoat layer and an intermediate layer, to form a magnetic layer thereon, and to form a plurality of magnetic layers.

When stacking multiple coating layers like this, the conventional general method is to apply the first layer and dry it, then apply the second layer and dry it, so-called wet-on-dry. It is a method.

However, with this wet-on-dry method, the line length becomes long, the solvent in the coating liquid for the upper layer may dissolve the lower layer, and good coating properties cannot be obtained. The so-called wet-on-wet method, in which the second layer coating liquid is applied before the -th layer coating liquid is dry, is becoming preferred.

In addition, there are several proposals regarding multilayer coating methods, especially those in which the upper layer is coated using an extrusion coating device, such as JP-A-62-124831 and JP-A-62-124831;
The technique described in Japanese Patent No. 3-164.023 can be mentioned.

Furthermore, there have been various proposals for single-layer coating, including JP-A No. 6
No. 2-117666, No. 57-84771, 58-10
No. 4666, No. 58-189070, No. 59-94657
No. 58-202075. JP-A-62-117666 discloses that it is preferable to maintain a pool of coating liquid between the end of the front edge surface and the web.

[Problem to be solved by the invention]

However, in each of these proposals, there is no disclosure regarding the shape of the extrusion coating head when coating the previously applied coating layer from the extrusion coating head.

For example, JP-A No. 62-117666 shows the conditions for single-layer coating as well as the shape of the coating head. The back edge surface is flush with the edge of the front edge surface on the tangent at the end of the back edge surface. are in agreement.

On the other hand, when applying the second layer by extrusion, the same coating head as the one used for the -th layer is usually used. In addition, the coating head for the -th layer is placed on the web in order to prevent air accompanying the support from entering the coating liquid and causing bubble failure, and to prevent the coating liquid from flowing out to the upstream side. The web is pressed strongly against the coating head so that it comes into contact with the front edge surface of the coating head. However, if this embodiment and a coating head of a known shape are applied to the second layer coating, the coating film of the -th layer will be scraped off. Dropping leads to deterioration in coating properties such as streak failures and uneven film thickness, and if this is to be prevented, the coating area is narrow and the degree of freedom in setting conditions is small.

Furthermore, in the above-mentioned Japanese Patent Application Laid-Open No. 62-117666, it is said that it is preferable to form a liquid pool between the web and the web near the slot. Due to slight fluctuations in tension during transport, web vibrations due to speed changes, vibrations of transport rolls, and slight fluctuations in the amount of coating liquid supplied,
It is difficult to retain the liquid pool and results in contact between the web and the front edge surface.

Therefore, the main purpose of the present invention is to enable a wet-on-wet coating method to achieve good coating properties without coating failures such as streak failures, to have a wide coating area, and to provide freedom in setting coating conditions. An object of the present invention is to provide a coating device with a high degree of accuracy.

[Means to solve the problem]

The above problem involves applying the next coating solution onto the previously applied coating layer onto a continuously running flexible web from an extrusion-type coating head placed between support rolls. In a method for coating a coating liquid in a layered manner from the coating head in a state where the web is not dried and the back surface of the web is not supported; This can be solved by

Further, it is particularly preferable that the front edge surface is arranged in a positional relationship such that it does not come into contact with the previously applied coating layer.

[Effect]

According to the present invention, as shown in FIG. 2, the tangent of the backing surface 51a of the coating head 5B for upper layer coating at the separation end Y where the web 1 leaves! Since the front edge surface 50a is further retreated, that is, located further away from the web 1, the coating head 5B is moved toward the web until the front edge surface 50a is just about to contact the lower layer coating liquid 10, as shown in FIG. Since the front edge surface 50a can be pushed into the lower layer coating liquid 10 within the pushing range and coating can be carried out without causing the front edge surface 50a to come into contact with the lower layer coating liquid 10, the lower layer coating liquid is not scraped off.

Further, since the lower layer coating liquid IO is undried, the upper layer coating liquid 20 has good wettability with the lower layer coating liquid 10, so that the front edge surface 50a is
Even if there is no contact with the air, air entrainment is eliminated.

In this way, there are almost no factors that worsen the applicability, so
The coating area is wide and there is a high degree of freedom in coating setting conditions.

[Specific structure of the invention]

The present invention will be explained in more detail below.

FIG. 1 is an overall view of a magnetic recording medium manufacturing facility, in which both the lower layer and the upper layer are coated using an extrusion type coating head.

A flexible support (web) °1 is unwound from an unwinding roll IA, guided on a first support roll 2, a second support roll 3 and a third support roll 4, passing through magnetic orientation means 5, After being dried by the dryer 7, it is calendered by the calender 8, and then the take-up roll I
It is wound up by B.

An upstream application head 5A is arranged to push the web 1 between the first support roll 2 and the second support roll 3, and a downstream application head 5A is arranged between the second support roll 3 and the third support roll 4. The side coating head 5B is arranged so as to push against the web of the lower layer coating stream.

Each application head 5A or 5B has a front edge member 5.
0 and a backing member 51, and has a slot 53 therebetween communicating with a liquid reservoir 52. The coating liquid is
The liquid is pumped into the reservoir 52 and applied through the slot 53 onto the web 1 whose back surface is not supported.

In the present invention, a continuously running flexible web 1 with no back support is first coated from an upstream first coating head 5A disposed between a first support roll 2 and a second support roll 3. A lower layer coating liquid IO is applied to coat the lower layer, and then, in an undried state, the lower layer coating liquid IO is applied to the downstream second coating head disposed between the second support roll 3 and the third support roll 4. A so-called wet-on-wet coating is performed in which the upper layer coating liquid 20 is applied starting from 5B and layered.

As shown in FIG. 2, the shape of the second coating head 5B is such that the front edge surface 50a is set back from the tangent 1 of the backing surface 51a at the end Y of separation from which the web 1 leaves.

Furthermore, as shown in FIG. 2, this means that the angle θ between the tangent line l and the tangent line drawn from the separation end Y to the front edge surface 50a is θ>0 degrees. The angle θ is more preferably 5 degrees or more. The upper limit of the angle θ is
If the front edge surface 50a is too far away from the lower layer coating liquid 10 during coating, when the upper layer coating liquid 20 is pushed out, it will accumulate on the upstream side or flow out, making it difficult to coat with the desired coating thickness. Therefore, the temperature is approximately 30 degrees.

Furthermore, as shown in FIG. 3, the front edge surface 50a is
In the coating state, it is preferable that there is no contact with the lower layer coating liquid 10. Under this condition, the coating liquid 10 is not scraped off.

When the coating head is shaped as shown in FIG. 4, the separation end Y according to the present invention is at the position shown in the figure.

In the above example, when coating the lower layer, the coating head 5A
However, other coating methods such as gravure coating may be used. When the extrusion coating method is used for both the lower layer and the upper layer, the upstream coating head, 5A
The edge surfaces of the downstream coating head 5B and the downstream coating head 5B may have the same shape, but as mentioned above, in the upstream coating head 5A, the front edge surface is shaped like a web in order to prevent air from being entrained. It is desirable that the contact point be in contact with the

The coating liquid for the lower layer and the coating liquid for the upper layer may be the same or different. For example, when obtaining a magnetic recording medium,
The lower layer is a subbing layer and the upper layer is a magnetic layer, or the lower layer is a magnetic layer and the upper layer is a protective layer. When both layers are magnetic layers, the properties of each magnetic paint may be different.

〔Example〕

Next, examples of the present invention will be shown to clarify the effects of the present invention.

Each of the following magnetic paints was coated on a support made of polyethylene terephthalate with a thickness of 14 μm at a coating speed of 200 m/min.
The dry film thickness is 3.5 μm for the lower layer and 1.0 μm for the upper layer.
The results shown in Table 1 were obtained when the scraping of the lower layer liquid at the second coating head, the streak failure and uneven coating after coating were investigated. In the composition, all parts are by weight.

<Upper layer> ★Co-containing magnetic iron oxide (Hc=9000e).

BET value 45 i/g> 150 parts *Polyurethane resin 10 parts *Vinyl chloride-vinyl acetate resin 20 parts *Alumina powder *Myristic acid *Butyl stearate *Polyisocyanate *Toluene *Methyl ethyl ketone *Carbon black lower layer> 7-Fe, O, powder (Hc=7000 e.

BET value 25rd/g) ★α-A l , = Os ★Carbon black★Vinyl chloride copolymer★Polyurethane resin★Butyl stearate★Myrstic acid★Stearic acid★Methyl ethyl ketone★Toluene★Oleic acid 10 parts 2 parts 1 part 10 Parts 200 parts 200 parts 10 parts 100 parts 8 parts 5 parts 20 parts 7 parts 1 part 0.65 parts 0.35 parts 150 parts 150 parts 0.65 parts★Polyisocyanate 10 parts [Effects of the invention] As described above, the present invention According to the invention, in the wet-on-wet coating method, it is possible to obtain good coating properties without coating failures such as streak failures, and it is possible to achieve coating with a wide coating area and a high degree of freedom in setting coating conditions. Equipment provided.

[Brief explanation of drawings]

Figure 1 is an overall view of the magnetic recording medium manufacturing apparatus, Figure 2 is a diagram of the shape of the downstream coating head, Figure 3 is a sectional view of the coating situation by the downstream coating head, and Figure 4 is a diagram of the shape of another coating head. It is. 1...Web 2...-1st support role 3...
・Second support roll 4...Third support rolls 5A, 5B...Coating head 10...Lower layer coating liquid 20...Upper layer coating liquid l...Tangential diagram

Claims (2)

[Claims] (1) The next coating liquid is applied onto the previously applied coating layer onto the continuously running flexible web from an extrusion type coating head placed between support rolls. In a method of applying a coating liquid in a layered manner from the coating head in an undried state and without supporting the back surface of the web; A coating device characterized by: (2) The coating device according to claim 1, wherein the front edge surface is in a positional relationship such that it does not contact the previously applied coating layer.