JP3268264B2 - Spin coating method and optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a spin coating method,
In particular, the present invention relates to a spin coating method for applying a coating liquid having a viscosity of 17 cps or less at the temperature during application.

[0002]

2. Description of the Related Art In recent years, various types of optical recording disks of the write-once type and the rewritable type have been receiving attention as large-capacity information carrying media.

[0003] Some of such optical recording disks use a dye film mainly containing a dye as a recording layer. Conventionally, a so-called air sandwich structure in which an air layer is provided on a recording layer made of a dye film, which has been widely used, or a dye film that can be reproduced in compliance with the Compact Disc (CD) standard A structure in which a reflective layer is provided in close contact with a recording layer made of (Nikkei Electronics, January 23, 1989, N.
o. 465, P107, Kinki Chemical Association Functional Dye Subcommittee, March 3, 1989, Osaka Science and Technology Center,
PROCEEDINGS SPIE-THE INTERNATIONAL SOCIETY FOR OPT
ICAL ENGINEERING VOL.1078 PP80-87, "OPTICAL DATA S
TORAGE TOPICAL MEETING "17-19, JANUARY 1989 LOS AN
GELES, etc.).

As a dye used in such a recording layer, a cyanine dye, a phthalocyanine dye, an azo metal dye, and the like are used. Such a dye is usually dissolved in an organic solvent, and the recording film is formed by spin coating. Since the spin coating method is a method conventionally used when applying a resist solution or an ultraviolet curable resin, the discharge nozzle used at this time is used for a coating liquid having a relatively high viscosity. Are diverted.

However, in such a method, when the viscosity of the coating liquid is as low as a viscosity (temperature at the time of coating) of 17 cps or less, the liquid dripping (excessive liquid is generated even if the discharge is stopped) or the liquid Dropping (the coating liquid accumulated at the needle tip drops), etc., resulting in a decrease in yield and an increase in material loss cost.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spin coating method and an optical recording medium which are free from dripping or dripping of liquid, have a high yield, and reduce material loss.

[0007]

This and other objects are achieved by any one of the following constitutions (1) to (4). (1) The viscosity at the time of application is 17 cp on the resin substrate.
In the spin coating method of applying a coating liquid of 0.5 cps or more, the coating liquid comprises a solution in which a dye is dissolved, the nozzle inner diameter A is 0.1 to 0.35 mm, and the nozzle length is B. (Mm), wherein a nozzle satisfying 12.5 A ≦ B ≦ 6 / A and using B = 5 to 25 mm is used. (2) The discharge pressure of the coating liquid from the nozzle is x (kgf
Cm ⁻² ), wherein the viscosity of the coating liquid is y (cps), and the spin coating method of (1) satisfies 170x ≧ 2y + 17. (3) The discharge pressure of the coating liquid from the nozzle is x (kgf
Cm ⁻² ), wherein the viscosity of the coating liquid is y (cps), and the spin coating method of (1) satisfies 2y + 221 ≧ 170x ≧ 2y + 17. (4) An optical recording medium manufactured by the spin coating method according to any one of the above (1) to (3).

[0008]

According to the spin coating method of the present invention, since the inner diameter and length of the nozzle to be used are specified as described above, there is no dripping or dripping of the liquid as described above, and therefore the product yield And material loss is low.

Japanese Patent Application Laid-Open No. 5-89535 discloses a method for removing the dye from the outer peripheral portion of the disk. With respect to the nozzle used at this time, only the diameter of the nozzle is described as <0.3 mm, and there is no disclosure of the relationship between the length and the inner diameter of the nozzle.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail. FIG. 1 shows two examples of the structure of a nozzle used in the spin coating method of the present invention. A nozzle 10 shown in FIG.
The nozzle 20 shown in FIG. 2B has a structure in which a fine tubular nozzle body 22 projects from the liquid reservoir 24 in the same manner as described above, while the nozzle 20 protrudes from the liquid reservoir 14 containing the coating liquid. In this example, the nozzle body 22 is supported and reinforced by the flange 26.

In this specification, the inner diameter A of the nozzle is
The inside diameter of the tubular nozzle bodies 12 and 22 is meant, and the length B of the nozzle means the length of the nozzle body, that is, the length of a portion where the same inside diameter is continuous.

The inner diameter A of the nozzle is 0.1 to 0.35
Set to mm.

When the inner diameter A of the nozzle exceeds 0.35 mm,
Liquid dripping occurs due to the weight of the liquid accumulated inside the nozzle. Furthermore, a large amount of coating liquid is required at the time of coating, and the production efficiency deteriorates. If the thickness is less than 0.1 mm, the discharge pressure becomes high, and when coming into contact with the substrate, droplets fly, resulting in a poor yield.

The nozzle used in the present invention has a nozzle length B (mm) of 12.5 A or more and 6 / A or less. If the value of B is less than 12.5 A, dripping tends to occur, and if it exceeds 6 / A, the discharge pressure increases,
This is because the amount of the discharged liquid increases and the cost increases. The length B of the nozzle is set to 5 to 25 mm.

Examples of the coating liquid include a cleaning liquid for a resin substrate, a coating liquid for an underlayer for an optical disk, a coating liquid for a primary treatment, and the like. It is used when forming a dye film as a recording layer of a recording medium. At this time, the coating liquid is composed of a solution in which a dye is dissolved in an organic solvent as a coating solvent.

Specific examples of the dye include a cyanine dye, a phthalocyanine dye, an azo metal complex dye, a rhodamine dye, an azo dye, and a triphenylmethane dye. Examples of the quencher include an amine dye, a dithiobenzyl metal complex, and a benzenedithiol metal complex.

Organic solvents used as coating solvents include keto alcohols, ketones, alcohols, hydrocarbons,
It may be appropriately selected from an ester type, an ether type, a cellosolve type, an alkyl halide type and the like. In particular, keto alcohol (such as diacetone alcohol), cellosolve (such as methyl cellosolve and ethyl cellosolve), and hydrocarbon (such as ethylcyclohexane and dimethylcyclohexane) are preferably used. Fluorinated alcohols, especially fluorinated alcohols (2,2,2-trifluoroethanol, 2,2,3
3,3-pentafluoro-1-propanol, 2,2
It is also preferable to use 3,3,4,4,4-heptafluoro-1-butanol, 2,2,3,3-tetrafluoro-1-propanol, etc.).

The coating liquid containing the coating liquid used for forming the recording layer of the optical recording medium as described above contains a solvent, a solvent and the like so that the viscosity at the time of coating is 17 cps or less. The amount etc. is adjusted. The lower limit of the viscosity is
0.5 cps.

In spin coating, the coating liquid is discharged from the nozzle by applying gas (air or nitrogen gas) pressure to the liquid retaining portions 14 and 24. When the coating liquid is discharged from the nozzle, Discharge pressure x (kgf · c
m ⁻² ) is preferably set so as to satisfy 170x ≧ 2y + 17, particularly 2y + 17 ≦ 170x ≦ 2y + 221, where y (cps) is the viscosity of the coating liquid.

By setting the discharge pressure x of the coating liquid within the above range, spin coating can be performed more efficiently.

When x is smaller than the above-mentioned value, a shortage of the discharge amount occurs, causing problems such as lack of coating and a long coating time. On the other hand, when it is larger than the above range, an excessive pressure is applied, and the probability of generation of the spray of the coating liquid increases, and the waste of the coating liquid increases.

The spin coating method may be a conventional method except for the nozzle shape and the discharge pressure. The coating film is dried by controlling the number of rotations as necessary. However, when discharging the dye solution, the rotation speed is preferably set to 1500 rpm or less. The thickness of the recording layer formed in this way is appropriately set according to the target reflectance and the like, but is usually about 1000 to 3000 A.

The content of the pigment in the coating solution is 0.1.
The content is 5 to 10% by weight, preferably 0.5 to 8% by weight. Note that the coating liquid may appropriately contain a binder, a dispersant, a stabilizer and the like.

FIG. 2 shows an example of an optical recording disk having such a dye film as a recording layer on a substrate. FIG. 2 is a partial sectional view. The optical recording disk 1 shown in FIG. 2 is a contact-type optical recording disk having a reflective layer adhered on a recording layer and capable of reproducing data in compliance with the CD standard. As shown, the optical recording disk 1
The recording layer 3 containing the above-described dye as a main component on the surface of the substrate 2
And a reflective layer 4 and a protective film 5 in close contact with the recording layer 3.

The substrate 2 is in the form of a disk. To enable recording and reproduction from the back side of the substrate 2,
It is preferably formed using a resin or glass which is substantially transparent (preferably at least 88% transmittance) for recording light and reproducing light (semiconductor laser light having a wavelength of about 600 to 900 nm, particularly about 630 to 790 nm). Good. The size is about 64 to 200 mm in diameter and 0.6 to 1.2 in thickness.
mm.

A tracking groove 23 is formed on the surface of the substrate 2 on which the recording layer 3 is formed, as shown in FIG.
The groove 23 is preferably a spiral continuous groove, having a depth of 0.08 to 0.25 μm, a width of 0.20 to 0.60 μm, and a groove pitch of 0.7 to 0.25 μm.
It is preferably 1.7 μm. With such a configuration of the groove, a good tracking signal can be obtained without lowering the reflection level of the groove portion. These values can be appropriately selected depending on the wavelength of the laser for recording and reproducing. The substrate 2 is preferably made of a resin, and various thermoplastic resins such as a polycarbonate resin, an acrylic resin, an amorphous polyolefin, TPX, and a polystyrene resin are suitable. And it can manufacture according to well-known methods, such as injection molding, using such a resin. The groove 23 is preferably formed when the substrate 2 is formed. After the manufacture of the substrate 2, a resin layer having the groove 23 may be formed by a 2P method or the like. In some cases, a glass substrate may be used.

The recording layer 3 may be formed by a usual spin coating method using the nozzle of the present invention, and its thickness is preferably 500 to 3000 A (50 to 300 nm) in dry film thickness. preferable. Outside this range, the reflectivity decreases,
It becomes difficult to perform good reproduction.

The recording layer 3 thus formed preferably has an extinction coefficient (imaginary part of the complex refractive index) k of 0.02 to 0.2 at the wavelength of the recording light and the reproducing light. When k is less than 0.02, the absorptivity of the recording layer decreases, and it is difficult to perform recording with normal recording power.
On the other hand, if k exceeds 0.2, the reflectance becomes very low, and it is difficult to perform good reproduction. The refractive index (real part of the complex refractive index) n of the recording layer 3 is 1.8 to 2.6.
Becomes When n <1.8, the reflectivity tends to decrease, and the reproduction signal tends to be small, and good reproduction tends to be difficult.

As shown in FIG. 2, on the recording layer 3,
The reflection layer 4 is provided in close contact with the substrate. As the reflective layer 4, a high-reflectance metal or alloy such as Au, Ag, or Al is preferably used. The thickness of the reflective layer 4 is preferably 500 A or more, and may be provided by vapor deposition, sputtering, or the like. The upper limit of the thickness is not particularly limited, but is preferably about 1200 A or less in consideration of cost, production operation time and the like.

As shown in FIG. 2, on the reflection layer 4,
A protective film 5 is provided. The protective film 5 is made of, for example, various resin materials such as an ultraviolet curable resin, and is usually 0.5 to 100 μm.
It is sufficient to provide a layer having a thickness of about m. The protective film 5 may be in the form of a layer or a sheet. The protective film 5 may be formed by an ordinary method such as spin coating, gravure coating, spray coating, dipping, or the like. Alternatively, the two-sided disc may be bonded together as shown in FIG.

FIG. 3 shows an example of the configuration. FIG.
Is a partial sectional view.

As shown in FIG. 3, the optical recording disk 10
Is an optical recording disk conforming to the DVD standard. A disk having the same structure as the optical recording disk 1 is formed by bonding a protective film 15 and a protective film 25 together with an adhesive.
Here, a thermosetting resin or the like may be used as the adhesive, and the thickness of the adhesive layer 50 is about 10 to 200 μm. In this case, the thickness per substrate (usually, polycarbonate resin) is 0.6 mm, and the recording layer 13, the reflection layer 14,
A protective film 15 is sequentially formed, and a recording layer 23, a reflective layer 24, and a protective film
5 and formed by bonding as described above.

The substrate is the same as that of the above-mentioned CD, except that the depth of the groove is 600 to 2000 A and the width is 0.2 mm.
2 ~ 0.5μm, groove pitch 0.6 ~ 1.0μm
It is.

The thickness of the recording layer is 500-3000 A, and the complex refractive index at 635 nm is n = 1.8-2.
6, k = 0.02 to 0.20.

The optical recording medium of the present invention is not limited to a contact-type optical recording medium as shown in the drawings, but may be any as long as it has a recording layer containing a dye. Examples of such a medium include a pit-formed optical recording medium having an air sandwich structure, and similar effects can be obtained by applying the present invention.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention. Examples 1-1 to 1-12 A dye layer was formed on a polycarbonate resin substrate having a diameter of 120 mm and a thickness of 1.2 mm by a spin coating method using a nozzle having the shape shown in Table 1 and a discharge pressure. In this case, a solvent in which a dye was dissolved was used to facilitate determination of dripping and uneven coating. The solvents used are shown in Table 1. The dyes used differed depending on the solubility in the solvent. In the test for the hydrocarbon-based solvent, the dye of Chemical Formula 2 was used, and the other dyes of Chemical Formula 1 were used. The yield of non-defective products when 10 sheets were continuously coated was evaluated and is shown in Table 1. The criteria for non-defective products were based on the absence of defects and unevenness in the area where the coating was performed by visual inspection.

[0037]

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[0038]

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[0039]

[Table 1]

Comparative Examples 1-1 to 1-5 A dye layer was formed in the same manner as in the example except for the nozzle shape and the discharge pressure. The yield of non-defective products when 10 sheets were continuously formed was evaluated and is shown in Table 1 at the same time. At this time, the dye of Chemical Formula 2 was used for the test of the hydrocarbon solvent, and
Were used.

From this table, it can be seen that the yield is good when the nozzle of the present invention is used. Further, it can be seen that the productivity is further improved by using the discharge pressure range of the present case.

Embodiment 2 The optical recording disk sample No. having the structure shown in FIG. 1
Was prepared. First, a recording layer containing a dye was formed on a polycarbonate resin substrate having a diameter of 120 mm and a thickness of 1.2 mm by a spin coating method. On this recording layer, a reflective layer was formed, and a protective film was further formed.

The nozzle used to form the recording layer 3 had an inner diameter (A) of 0.25 mm, a length of 10 mm, and a discharge pressure of 0.5 kgf · c.
m ^-2 . The coating solution contains a dye and an organic solvent. As the dye, the compound of the above formula 1 was used. The pigment content was 1.5 wt%.

As the organic solvent, 2,2,3,3-tetrafluoro-1-propanol was used. The viscosity of this solvent was 9.2 cps. The thickness of the recording layer is 2
00 nm. The reflective layer was made of Au, and was formed to a thickness of 85 nm by a sputtering method. Then, a UV-curable acrylic resin protective film (5 μm thick) was formed thereon.

The above sample No. 780 nm for 1
The variation of the reflectance in one round at a radius of 22 mm to 58 mm was measured. As a result, the change in the reflectance was within 1%, which proved to be good.

Comparative Example 2 The nozzle shape used in Example 2 was (A) 0.25 mm,
(B) A sample was prepared in the same manner, except that the thickness was 3 mm, and evaluated in the same manner. Under these conditions, dripping occurs and 2
2.5% change in reflectance in one round from 8mm to 35mm
Became.

[0047]

According to the present invention, the yield can be improved and the cost can be reduced in the spin coating process.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of a nozzle of the present invention. A represents the inner diameter of the nozzle, and B represents the length of the nozzle.

FIG. 2 is a partial sectional view showing an example of the optical recording disk of the present invention.

FIG. 3 is a partial sectional view showing an example of the optical recording disk of the present invention.

[Explanation of symbols]

 1, 10 Optical recording disk 2, 12, 22 Substrate 23, 123, 223 Groove 3, 13, 23 Recording layer 4, 14, 24 Reflective layer 5, 15, 25 Protective film 50 Adhesive layer

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 7/26 B05C 11/08 B05D 1/40

Claims (4)

(57) [Claims] In a spin coating method, a coating liquid having a viscosity of 17 cps or less and 0.5 cps or more at a coating temperature is applied on a resin substrate, wherein the coating liquid comprises a solution in which a dye is dissolved, Nozzle inner diameter A is 0.1 ~ 0.35mm and nozzle length is B
(Mm), 12.5A ≦ B ≦ 6 / A is satisfied,
A spin coating method using a nozzle set at B = 5 to 25 mm. 2. The discharge pressure of the coating liquid from the nozzle is x
The spin coating method according to claim 1, which satisfies 170x ≧ 2y + 17 when the viscosity of the coating liquid is y (cps), (kgf · cm ⁻² ). 3. The discharge pressure of the coating liquid from the nozzle is x
2. The spin coating method according to claim 1, wherein 2y + 221 ≧ 170x ≧ 2y + 17, where y (cps) is the viscosity of the coating liquid (kgf · cm ⁻² ). 4. An optical recording medium manufactured by the spin coating method according to claim 1.