JPH0653262B2 - Method of applying flexible support - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coating method for a flexible support, and more particularly to a coating method effective for coating a magnetic recording material.

[Conventional technology]

Conventionally, as a thin-layer coating method for a high-viscosity liquid, an extrusion coating method (for example, a special coating method in which the extrusion port of the coating liquid is pressed against the flexible support to support the coating without supporting the back surface of the flexible support). JP-A-54-7306, JP-A-58
-189069 and JP-A-58-189070.
(See Japanese Patent Publication).

[Problems to be solved by the invention]

In this coating method, however, the coating liquid extrusion port (hereinafter referred to as the coating head) without supporting the back surface of the flexible support.
Since it is pressed against a flexible support (hereinafter referred to as a support), there is a problem that the thickness of the support is uneven, the rigidity is varied, the support is distorted, and the uniformity of the coating thickness is impaired. Especially in the manufacturing process of the flexible support, initially 6 to
When a substrate with a width of 8 m is cut to a width of 0.5 to 1.5 m and applied as a support, the uniformity of the coating thickness is extremely lost on the support including the edges of the fabric. I got it. Further, the above-mentioned strain of the support is generally greatly affected by the tension which increases as the transport speed of the support increases.

An object of the present invention is to provide a coating method which solves the above-mentioned problems and enables coating with a uniform coating thickness in an extrusion coating method in which a coating head is pressed against a support for coating.

[Means for solving problems]

As a result of earnest studies on the method for always maintaining the uniformity, the present inventors have confirmed that the coating thickness can be obtained by pre-heating the support to be coated.

That is, according to the present invention, a flexible support made of a relatively thin polyethylene terephthalate film is applied at a constant speed while applying a tension of 3 to 50 kg / m width, and at a speed of 50 to 14
After heating the support at a temperature of 0 ° C. for 0.3 to 5 seconds, one end of an extrusion type coating head is applied to one surface of the support stretched between the guide rollers and transported at a constant speed. Portions of the support to retreat to the other surface side of the support so as to be curved, and a coating liquid extrusion slot of the head is applied between one surface of the support and the head tip. By supplying the liquid under pressure, the heat-treated support maintains a uniform coating liquid application interval in the width direction with respect to the head tip portion,
The method for coating a flexible support is characterized in that a uniform coating film thickness is formed in the width direction of the support.

In the present invention, preferable effects are obtained when the coating liquid is a magnetic liquid. Further, the coating method in which the heat treatment step of the support and the coating step by the extrusion type coating head are continuously performed can obtain further excellent results. Further, the direction of the coating head is limited to the upward direction. It can also be applied to face down and sideways. The "coating liquid" may be any one that can be applied onto the support and can be applied by the extrusion coating method in which the coating head is pressed against the support for coating.

According to the present invention, performing heat treatment before coating means not only continuous treatment (online treatment) before coating head in the coating step but also treatment in another step before being supplied to the coating step. It also includes (offline processing).

Further, the method using a heating roll as the heat treatment is preferable because it is efficient, but it also includes the step of blowing heated air and performing the step before coating, for example, in a drying zone for coating the undercoat liquid.

[Work]

By carrying out the appropriate heat treatment of the present invention, the thickness unevenness of the support, the variation in rigidity, the strain of the support is made uniform, and the coating head is applied in the extrusion coating method in which the coating head is pressed against the support for coating. Since the gaps between the supports are kept uniform and the coating is carried out after the heat treatment, cracks in the coating layer due to the difference in mechanical elongation of the supports can be suppressed and uniform coating can be carried out.

As for the temperature condition of the heat treatment in this case, when the support is a polyethylene terephthalate film and the coating liquid is a magnetic liquid, a sufficient effect cannot be obtained at a temperature lower than 50 ° C., and when it exceeds 140 ° C., it depends on the thickness of the support. Deformation such as stretching becomes large, and good results cannot be obtained.

When the heating time was less than 0.3 seconds, no sufficient effect was obtained in the above temperature range. If it is 5 seconds or more, the deformation such as elongation becomes too large depending on the thickness of the support, and good results cannot be obtained.

When the tension of the support is less than 3 kg / m in the step of performing the heat treatment, it is not preferable for carrying the support, and when it exceeds 50 kg / m, deformation such as elongation of the support becomes large, which is not preferable.

〔Example〕

The present invention will be described with reference to examples. FIG. 1 shows an embodiment of the coating method according to the present invention. FIG. 2 shows an embodiment of the coating head portion in the present invention.

In FIG. 1, the support 4 is fed from a feeder 7 and heat-treated to a predetermined temperature by a plurality of heating rolls 1, which are heat treatment zones, before being coated by the coating head 2. Note that this heat treatment zone is not limited to the heating roll, and various configurations such as a heater or the like arranged in an appropriately partitioned room and a configuration for applying appropriate humidification can be adopted. The heat-treated support is a cooling roll 5.
Then, the tension cut roll 6 cuts off the relationship with the tension of the support 4 in the heating roll 1, and the coating is performed with the tension of the support 4 suitable for the coating head portion 2. Although the cooling roll 5 is provided in FIG. 1,
A configuration without this cooling roll may be used.

In FIG. 2, the coating head 2 is in contact with the support 4 when the coating liquid 3 is not sent out, but when coating is started, the coating head 2 is moved between the guide rollers 9, 9.
The support 4 is pushed up by the liquid pressure of the coating liquid 3 discharged from the coating liquid extruding slot 8, and the support 4 is in an appropriate tension state, and the support 4 and the coating head 2 have a predetermined tension. It will be maintained with a gap.

An experiment was conducted under the following conditions using the above coating apparatus, but the present invention is not limited to this.

Example 1-5, Comparative Example 3 A polyethylene terephthalate film having a thickness of 15 μm and a width of 500 mm was used as a support, and the coating solution was prepared by kneading and dispersing the magnetic layer coating solution of the following method to obtain a coating speed of 150 m. The coating was performed at a coating rate of 35 cc / m ² / min. The tension in the heating part was 20 kg / m.

Magnetic layer coating liquid CO-containing magnetic iron oxide (S _BET 35m ² / g) 10
0 parts Nitrocellulose 10〃 Polyurethane resin (trade name "Nitsuporan 2304" 8〃 (Nippon Polyurethane Industry Co., Ltd.) Polyisocyanate 8〃 Cr ₂ O ₃ 2〃 Carbon black (average particle size 20μm) 2〃 Stearic acid 1〃 Stearic acid Butyl 1〃 Methyl ethyl ketone 300〃 Heat treatment temperature… 40 _° , 50 _° , 70 _° , 100 _° , 1
40 _° , 150 ° C Heating time ... 0.3 seconds, 1 second, 3 seconds ... The heating time was changed by changing the wrap angle and the number of laps on the heating roll. The results are shown in Table 1. The coating thickness uniformity evaluation and the cross section are shown in FIG.

Examples 6 to 8 Comparative Example 4 A polyethylene terephthalate film support having a thickness of 15 μm was preliminarily heat-treated at 100 ° C. for 20 seconds at a tension of 20 kg in a step different from the coating step, and within 1 hour after the heat treatment,
After 1 day and 1 week, the coating was performed. Coating liquid,
The conditions of coating speed and coating amount are the same as in Example 1, and the results are shown in Table 2.
Shown in.

Effective up to about a week.

Examples 9 to 13 Comparative Examples 5 to 7 A stretched film of polyethylene terephthalate film was cut into a raw material, and a support at the end was used. The thickness of the support, the coating solution, the coating speed, and the coating amount in the heating section are the same as in Example 1. When the cutting support at the end of the raw material is used, one side is thin and the other side is thick as shown in FIG. The distribution is shown. The results are shown in Table 3.

It can be seen that the heat treatment at 50 ° C. or higher improves the thickness condition. However, different concavo-convex patterns occur at 150 ° C.
The same tendency was shown.

Examples 14 to 25 Comparative Examples 8 to 11 Support thickness of polyethylene terephthalate film, 7
As in the previous example, the end supports of μm, 18 μm, 38 μm, and 75 μm were used, and the heat treatment temperature was 70 ° C. for 1 to 4 seconds and 100 ° C.
The conditions of coating liquid, coating speed, and coating amount are set to 3 seconds and 1 second, respectively, and the results are shown in Table 4. The results are shown in Table 1. Also shows a thin coating on one side and a thick coating on the other side.

(2) When the support is as thin as 7 μm, it shows very fine unevenness. This is due to the winding wrinkles of the original roll itself.

(3) As the support becomes thicker at 18 μm, 38 μm, and 75 μm, large pattern unevenness occurs. This is considered to be the change in rigidity due to the difference in thickness of the material.

(4) The above thickness difference is 1 to 4 seconds at 70 ° C and 0.3 at 100 ° C.
It can be seen that the heat treatment for 2 seconds and 1 second becomes completely uniform, and is largely corrected.

Example 26 and Comparative Example 12 (Example 26) Each of the above embodiments was described on a polyethylene terephthalate support having a thickness of 10 μm and a width of 500 mm which was run at a transport speed of 100, 200 and 500 m / min. Based on the manufacturing process of the magnetic recording medium, tension: 5, 10,
After performing heat treatment at 12 kg / m, relative humidity when the heating zone is divided into a room: about 15%, temperature: 100 ° C.,
The above magnetic coating liquid was applied so that the dry thickness was 3 μm to form a magnetic layer, and calendering was performed to prepare a tape raw material.

However, the coating head used for coating the magnetic layer is disclosed in Japanese Patent Laid-Open No.
This is the same as the extrusion type coating head disclosed in Japanese Patent Application Laid-Open No. 0-238179, and the schematic configuration of the coating head portion is slot width: 0.6 mm, pocket portion diameter: 20 m.
m, radius of curvature of doctor edge surface: 15 mm, effective length of doctor edge surface: 6 mm, effective length of back edge surface: 7.5 mm, coating width: 450 mm.

The magnetic layer is dried and solidified by vertical air flow drying at 80 ° C., and the calendering is performed with a diameter of 250 mm.
The calender linear pressure was 200 kgw / cm and the calender temperature was 80 ° C. by using two hard chromium plating rolls having a surface roughness of 0.01 μm.

When the tape raw fabric was manufactured in this manner, the presence or absence of cracks in the magnetic layer in the obtained tape raw fabric and the web conveyance state were observed. The results are shown in Table 5.

(Comparative Example 12) In the manufacturing process of the magnetic recording medium in Example 26, the heat treatment zone was arranged on the downstream side of the coating head, the relative humidity in the heat treatment zone was 15%, and the tensions were 2, 3, respectively. A tape raw material was prepared under the same conditions except that the amount was 5 kg / m, and the presence or absence of cracks in the magnetic layer in the tape raw material obtained in the same manner as in Example 1 and the state of web conveyance were observed. The results are shown in Table 5.

Example 27 and Comparative Example 13 (Example 27) The magnetic recording medium described in the above embodiment was placed on a polyethylene terephthalate support having a thickness of 10 μm and a width of 500 mm which were run at a transport speed of 200 and 500 m / min, respectively. Based on the manufacturing process of each temperature: 80, 90, 1
After heat treatment at 00,120 ° C. and tension of 5,12 kg / m, the above magnetic coating solution is applied so that the dry thickness becomes 3 μm to form a magnetic layer, and calendering is applied to the raw tape tape. It was created.

However, the other conditions were the same as in Example 1 above. The raw tape thus obtained was cut into 1/2 inch to prepare a video tape, which was left in an atmosphere at a temperature of 70 ° C. and a relative humidity of 5% for 48 hours, and then the heat shrinkage rate of the video tape was measured. Was measured. The results are shown in Table 6.

Comparative Example 13 In the manufacturing process of the magnetic recording medium in Comparative Example 12, the relative humidity in the heat treatment zone was 15%, the transport speed was 100,200 m / min, and the tension was 3.5 kg / m. A tape raw fabric was prepared under the conditions, and the tape raw fabric obtained in the same manner as in Example 2 was cut into 1/2 inch to produce a video tape, which was placed in an atmosphere at a temperature of 70 ° C. and a relative humidity of 5%. After standing for 48 hours, the heat shrinkage rate of the video tape was measured. The results are shown in Table 6.

As is clear from Tables 5 and 6, the method for manufacturing the magnetic recording medium according to this example makes it possible to increase the transport speed of the support as compared with the method of the comparative example. It can be seen that almost the same heat treatment effect can be obtained.

〔The invention's effect〕

As in the above example, by applying heat treatment to the support under a constant tension before coating, it is possible to apply a uniform coating thickness in the extrusion coating method in which the coating head is pressed against the support to perform coating. It has become possible and the product quality can be further improved. According to the method for manufacturing a magnetic recording medium of the present invention, even if a large tension acts on the support during heat treatment to cause elongation, the magnetic layer is not formed on the support at this point, The magnetic layer is not damaged by the difference in mechanical extension between the support and the magnetic layer. That is, since the tension of the strength required for high-speed transport of the support without meandering can be applied to the support, the magnetic layer can be applied at high speed.

Therefore, since the heat treatment can be performed while applying the magnetic layer at a high speed, it is possible to suppress deformation and curling of the flexible belt-like support due to thermal contraction in a high temperature environment, and to improve productivity.

[Brief description of drawings]

FIG. 1 is a schematic view of one embodiment of a coating method of the present invention in which heat treatment is performed immediately before coating. FIG. 2 is a side view of an embodiment of the coating head of the present invention. FIG. 3 is a chart showing the relationship between coating thickness uniformity evaluation and thickness distribution cross section. 1 ... Heating roll, 2 ... Coating head 3 ... Coating liquid, 4 ... Support 5 ... Cooling roll, 6 ... Tension cut roll 7 ... Feeder 8 ... Coating liquid extrusion slot, 9 ... … Guide rollers

Claims (3)

[Claims] 1. A flexible support made of a relatively thin polyethylene terephthalate film is transferred at a constant speed while applying a tension of 3 to 50 kg / m width, and is transported at a rate of 50 to 140.
After heating the support for 0.3-5 seconds at a temperature of ° C,
The tip of the extrusion type coating head is brought close to one surface of the support which is stretched between the guide rollers and is transported at a constant speed, and the support is retracted to the other surface side of the support, The heat-treated support is made to bend so that the coating liquid is pressure-supplied between one surface of the support and the tip of the head through the coating liquid extrusion slot of the head, so that the support after the heat treatment has the head end. A coating method for a flexible support, characterized in that a uniform coating film coating interval is maintained in the width direction of the portion to form a uniform coating film thickness in the width direction of the support. 2. The method for coating a flexible support according to claim 1, wherein the coating liquid is a magnetic liquid. 3. The method for coating a flexible support according to claim 1, wherein the heat treatment step of the support and the coating step by the extrusion type coating head are successively performed.