JPH03165861A - Overroll coater - Google Patents

Abstract

PURPOSE:To form a uniformly coated film on a long-sized base plate even by the coating liquid having a low viscosity by narrowing the width of the recording layer transferring part of a transfer roll narrower than the width of the base plate to which recording coating liquid is applied and forming an overroll coater. CONSTITUTION:A base plate 2 is passed while it is sent between a transfer roll 1 and a backing-up roll 3 by a carrier roll 4. A coated film is formed on the base plate 2. Coating liquid is ridden on the transfer roll 1 from a liquid reservoir part 5 provided between a doctor bar 6 and the transfer roll 1 and transferred on the base plate 2. The width of the transfer roll 1 is made narrower than the base plate 2 and therefore the transfer roll 1 is driven by the shaft 1' thereof. The guide grooves 10 of an optical disk are provided on the base plate 2 and the coated film 7 is formed thereon. At this time, a noncoated part 11 is formed on the base plate 2. After the transfer roll 1 transfers the coating liquid, it is rotated to the liquid reservoir part 5 in a state wherein the coating liquid is not present in the transfer part 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a roll coater which is one type of coating apparatus, and more particularly to an over-roll coater for forming a recording layer of an optical recording medium.

[Conventional technology] There are various types of conventional coating equipment, including many types of roll coaters, and their purposes range from printing to painting, adhesive coating, formation of special functional layers, and photolithography technology fields. etc. over a wide range of areas.

On the other hand, various methods have been proposed for forming the recording layer of an optical recording medium. For example, Te-TeOz, TeC. Te
A recording layer made of an inorganic thin film such as -Se, Sb-Se/Bi-Te, etc. is formed by vacuum evaporation, sputtering, etc., but in this case, the manufacturing cost is high, the setting of manufacturing conditions is complicated, and the toxicity of the material etc. There is also the problem of

On the other hand, optical recording media manufactured by coating have many advantages such as not only easy manufacture but also low equipment and running costs. Especially dyes,
It is advantageous for forming thin films made of organic substances such as pigments and resins. For this reason, the subinner method, dip coating method, etc. are often used.

However, in the Sviner method, the amount of coating liquid removed to areas other than the substrate is greater than the amount of coating liquid used to form a thin film, resulting in waste of the coating liquid. Further, the film thickness tends to be thicker at the outer peripheral part of the substrate than at the inner peripheral part, making it difficult to obtain a uniform film thickness. Furthermore, if dust or foreign matter adheres to the substrate, radial streaks will occur from that area to the outer periphery, and film thickness unevenness will occur at the concave and convex portions of the light guide groove provided on the substrate. The disadvantage is that it is easy to occur. Furthermore, this method is not suitable for cases where the guide grooves are not concentric or spiral, such as in an optical card.

In the dip coating method, the substrate is immersed in the coating solution for forming a thin film and then pulled up to apply the coating, so it requires a much larger amount of coating solution than is actually applied, and it requires repeated application of the same coating solution. For use, the pot life of the coating solution must be long.

Therefore, large-scale equipment is required to keep the composition of a large amount of coating liquid constant at all times. Furthermore, since the pulling speed of the substrate must be slowed down to obtain a uniform film thickness, there is a drawback that the working efficiency is extremely low.

In order to solve these problems, a method for forming an optical recording layer using a roll coater has been proposed in JP-A-63-44337. This is a method in which a coating liquid is supplied to a cylindrical roll and brought into contact with the substrate to form a uniform film thickness of 1 μm or less.The equipment used is a single-bar roll coater like the one used for resist coating. The principle is the same.

[Problem to be solved by the invention]

However, in the above proposal, since the substrate to be coated is not a long sheet, uneven film thickness occurs on each substrate at the initial stage of coating and dripping of the coating liquid occurs at the end of coating. This becomes more noticeable as the viscosity of the coating liquid decreases.

Therefore, the substrate needs to be larger than the effective recording area for the optical recording medium, and the area other than the effective recording area is wasted. To solve this problem, continuous groove formation and continuous recording layer formation using a long sheet can be considered, but in the over-roll coater as proposed above, a transfer roll for coating the substrate and a conveyor belt or backup roll are used. When the spacing (gap or clearance) is narrow and a low viscosity coating liquid is used, there are problems such as the coating liquid flowing into the conveyor belt or backup roll and staining the substrate.

[Means to solve the problem]

The present invention is an over-roll coater for coating and forming a recording layer on the upper surface of a substrate for an optical recording medium, in which the width of the recording layer transfer portion of the transfer roll is narrower than the width of the substrate to which a recording layer coating liquid is applied. This is an over-roll coater that is characterized by:

Representative embodiments of the invention are shown in FIGS. As shown in FIG. 1, a coating film 7 is formed on the substrate 2 by passing the substrate 2 between a transfer roll 1 and a backup roll 3 while being fed by a conveyance roll 4. The coating liquid is transferred onto the transfer roll 1 from a liquid reservoir 5 located between the doctor blade 6 and the transfer roll 1, and is transferred onto the substrate 2.

As shown in FIG. 2, since the transfer roll 1 is narrower than the substrate 2, it is driven by the transfer roll shaft 1'. A guide groove 10 for the optical disc is provided on the substrate, and a coating film 7 is formed on the guide groove 10 for the optical disc.
is formed on the substrate. A non-coated area 11 is formed. After transferring the coating liquid, the transfer roll 1 rotates to the liquid reservoir 5 with no coating liquid in the transfer section 9. In the liquid reservoir 5, a leakage prevention valve 8 prevents the coating liquid from leaking. Third
The figure shows the transfer roll 1 and the backup roll 3 with their backs facing the conveyance direction. For comparison, FIG. 5 shows a conventional over-roll coater viewed from the same direction as FIG. 3. As shown in FIG. 5, in the conventional device, a transfer part 9 and a non-transfer part 12 are formed on the transfer roll l, and the non-transfer part l
The coating liquid remaining on the roller 2 becomes a liquid drip 13 and flows into the backup roll 3, causing liquid stains 14. This also causes the substrate 2 to become dirty. On the other hand, in the apparatus of the present invention shown in FIG. 3, no liquid drips or liquid stains occur.

In this way, the present invention makes the transfer portion of the transfer roll of the over-roll coater narrower than the coating substrate, thereby preventing the coating liquid from flowing into the backup roll and staining the substrate, thereby obtaining a stable coating film without staining the substrate. possible.

Although a roll coater using a doctor bar is shown here, a doctor roll type one may also be used.

Further, the direction in which the substrate is conveyed may be such that the transfer roll rotates in the normal direction as shown by the solid arrow in FIG.
It is also possible to perform reverse coating as indicated by the broken line arrow. In addition, the coating liquid is circulated through the circulation system,
It is also possible to keep the concentration constant.

The term "coating liquid for forming an organic thin film" as used herein means a coating liquid for forming a thin film (recording layer) containing an organic substance (including organic metals, etc., but not completely inorganic substances) as one of its components. However, this coating liquid may contain the above-mentioned organic substance, solvent, binder, and other components.

Although there is a coating method in which a binder or the like is added to the coating solution, the coating solution for forming the recording layer of an optical recording medium is sometimes coated with a low viscosity without adding a binder. It is particularly suitable when using an organic thin film forming coating liquid with a viscosity of 10% or less and a viscosity of 20 cps or less at 20°C.

A coating liquid suitable for forming the recording layer of an optical recording medium using the apparatus of the present invention contains a material that forms the recording layer of the optical recording medium. Examples of organic dyes that can be used as materials include those that have appropriate solubility in organic solvents, such as cyanine dyes, merocyanine dyes, naphthoquinone dyes, anthraquinone dyes, triphenylmethane dyes, and squarylium dyes. , phthalocyanine dyes, naphthalocyanine dyes, amine dyes, polymethine dyes, azulene dyes, metal complex dyes, and the like. In addition, inorganic water-soluble materials, alkoxides, etc. can also be used.

These may be used alone or in combination, and other additives may be added. Examples of additives include polymeric binders such as vinyl resins such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, and ethylene-vinyl acetate copolymers, acrylic resins, polyester resins, polyurethane resins, and polycarbonates. Or cellulose resins such as nitrocellulose or cellulose acetate, olefin resins such as polyethylene and polypropylene, thermoplastic resins such as polybutyral resin, and thermosetting resins such as epoxy resins, acrylic polyol urethane resins, and unsaturated polyesters. Can be mentioned.

In addition, durability-modifying additives such as various surfactants, dispersants, ultraviolet absorbers, visible light absorbers, and antioxidants may be added.

The solvent used in the coating solution is a roll coater, circulation system parts,
Anything that does not adversely affect the substrate, the recording layer formation, or its materials may be used. When using the above-mentioned organic dyes, ester solvents such as ethyl acetate and butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, acetone, and diacetone alcohol can be used. Ketone solvents such as methanol, ethanol, isobrobyl alcohol, ether solvents such as methyl ethyl ether and diethyl ether, aromatic solvents such as toluene and xylene, and halogenated carbon solvents such as dichloromethane and dichloroethane. Solvents and organic solvents such as furan solvents such as tetrahydrofuran can be used alone or in combination. Among these, those having a boiling point of 70° C. or higher, particularly 70 to 160° C., are preferred because they can easily form a uniform coating film with a diameter of about 0.1 μm. If a material with a boiling point of 70° C. or lower is used, unevenness tends to occur during the drying process.

In addition to inorganic materials such as glass and ceramics, the substrate is made of
In addition to various organic compound sheets, sheets whose surfaces have been modified with photocurable materials, thermosetting materials, etc., and sheets with light guide grooves formed therein can also be used.

[Example] Example A recording layer of an optical recording medium was formed using an over-roll coater having the configuration shown in FIGS. 1 to 3.

2.5 parts by weight of organic dye IR-820 (manufactured by Nippon Kayaku ■) was mixed with a 4/1 mixture of diacetone alcohol (boiling point 167.9°C)/methyl ethyl ketone (boiling point 79.6°C) 10
Dissolved in 0 parts by weight and filtered through a 0.2 μm diameter filter.
0 cps to prepare a coating solution (viscosity: 3.0 cps).

The substrate used was polycarbonate (Panlight, manufactured by Teijin Kasei ■) 4 on which guide grooves for optical cards were continuously molded with ultraviolet curing resin. The length of the board is 3m, the width is 25cm
m, and the thickness was 0.7 mm. Further, the effective transfer portion width of the transfer roll was 20 cm.

When the transfer roll was rotated forward at a speed of 2 m/min and the distance between the transfer roll and the backup roll was set to 0.6 mm, coating was performed, and 900 people ± 50 people achieved a uniform film thickness of 40 cm from the start of coating. I was able to obtain it within the following card patterns.

Comparative Example Coating was carried out under the same conditions as in the Examples using the conventional over-roll coater shown in FIGS. 4 and 5. In this device, the width of the recording layer transfer portion of the transfer roll is wider than the width of the substrate.

The coating liquid flowed from the transfer roll to the backup roll after 30 cm from the start of coating, and the substrate was stained after about 1 m of coating. Although the coated surface covered with ultraviolet curable resin was 11 solvent resistant to the coating solution, the opposite surface was eroded by the coating solution because it was made of polycarbonate.

[Effects of the Invention] According to the over-roll coater of the present invention, a uniform coating film can be continuously obtained on a long substrate even with a low-viscosity coating liquid, and continuous production can be suitably performed, resulting in an inexpensive optical recording medium. can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of an example of an over-roll coater of the present invention, Fig. 2 is a schematic plan view thereof, and Fig. 3 is a schematic diagram of the transfer roll and backup roll portion thereof facing away from the conveyance direction. FIG. 4 is a schematic side view of an example of a conventional overroll coater, and FIG. 5 is a schematic diagram showing the transfer roll and backup roll portion thereof with their backs facing the conveyance direction. l: Transfer roll l゜: Transfer roll shaft 2: Substrate
3: Backup roll 4: Conveyance roll
5.Liquid reservoir part 1 2 6: Curtain bar 7: Coating film 8: Leak prevention valve 9: Transfer part lO: Optical disc guide groove

Claims (1)

[Claims] 1. An over-roll coater for coating and forming a recording layer on the upper surface of a substrate for an optical recording medium, wherein the width of the recording layer transfer portion of the transfer roll is the substrate to which the recording layer coating liquid is applied. An overroll coater characterized by being narrower than the width of the . 2. The organic thin film forming coating liquid has a solid content concentration of 10
% or less, and the viscosity at 20° C. is 20 cps or less.