JP3068877B2 - Groove fabrication method for optical disc master - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a groove on an optical disk master.

[0002]

2. Description of the Related Art When a groove is formed in a photoresist film on a master disk of an optical disk such as an optical recording disk, a laser beam is irradiated while rotating the disk at a constant angular velocity (CAV). At this time, in order to form a groove having the same width over the entire circumference, a method of changing the laser power to be applied in accordance with the difference between the linear velocities of the inner circumference and the outer circumference has been adopted.

[0003] That is, when the rotation of the disk in CAV according toward the disc inner circumference to the outer circumference, but the linear velocity of the rotation is increased, the laser light irradiating unit relative to the innermost circumference of the linear velocity V _in in accordance with the ratio V / V _in the linear velocity V in, gradually accordance laser power _{P in (V / V i n} ) ( however, P _in the laser power at the innermost) so that, toward the outer periphery A method of increasing the laser power has been adopted.

[0004] By changing the laser power in this manner, the cutting rate P / V obtained by dividing the laser power by the linear velocity becomes the same over the entire circumference of the disk.

For example, on an optical recording disk for recording a CD signal, a groove for development monitoring and a groove for tracking a data area are formed. These grooves are cut under the conditions shown in Table 1. ing.

[0006]

[Table 1]

[0007]

As shown in Table 1, if the cutting rate P / V is set equal, theoretically, the same groove should be formed. However, in the experiments of the present inventors, the groove width of the data area on the inner peripheral side was actually 0.40 to 0.42 μm, while the developing groove width was 0.44 to 0.46 μm.
As a result, it was found that the groove width increased toward the outer periphery of the disk.

An object of the present invention is to provide a method capable of forming a groove having the same width over the entire circumference of a disk when irradiating a laser beam onto a photoresist film of an optical disk master to cut the groove. It is in.

[0009]

The above object is achieved by the present invention described in the following (1) and (2).

(1) When cutting a groove by irradiating a laser beam onto a photoresist film of an optical disk master, the ratio of laser power P to the linear velocity V of the optical disk master is set to a cutting rate P / V, The relationship between the cutting rate P _O / V _{O at} the outermost periphery of the master and the cutting rate P _i / V _i at the innermost periphery is represented by P _i / V _i.
= K (P _O / V _O ), and when k is k = 1−c × (Vo / Vi), c satisfies the condition of 0.01 ≦ c ≦ 0.08. Groove manufacturing method for the master optical disc.

(2) The method for producing a groove of an optical disk master according to (1), wherein the cutting rate is continuously reduced from the inner periphery to the outer periphery.

[0012]

The intensity I _(x) of the laser beam applied to the master optical disk ideally has a Gaussian distribution, and is expressed by the following equation when x is the distance from the center of the laser beam.

I _(x) = I _exp (-2x ² / W ² )

Here, I _O is the maximum intensity of the laser beam, and W is the beam radius of 1 / e ² of I _O. Therefore, ideally, the width W of the laser beam is constant even when the intensity _IO is changed. Therefore, conventionally, when the linear velocity differs between the inner circumference and the outer circumference of the disk, the laser power is set so that the cutting rate becomes equal according to the change. However, actually, when the laser power is increased on the outer peripheral side of the disk, the distribution of the laser beam changes, and therefore, it is considered that the groove width becomes wider toward the outer peripheral side of the disk.

The laser beam used for forming a pattern on the photoresist film is the Gaussian beam described above, and a laser beam having a certain level or more is effectively acting. Assuming that this level is equal to or greater than the half width of the Gaussian beam, the effective beam power Peff can be obtained by the following equation, where δ is the half width.

[0016]

(Equation 1) This equation, and substituting the measured value of the width of the data area and the groove for the development of effective laser power P _i and P _O at the inner periphery and the outer periphery becomes as follows.

[0017]

(Equation 2) From Table 1, since I _O = 3.57I _i ,

P _o / P _i = 1.15, and the outer circumference of the disk is over-irradiated by 15% compared to the inner circumference.

For this reason, in order to form the same groove over the entire circumference of the disk, it is necessary to lower the cutting rate of the laser applied to the outer circumference by about 13% from the inner circumference.

Therefore, in the present invention, the laser power P
The cutting rate is the ratio of the linear velocity V of the optical disk master
When P / V, the cutting rate P _O / V _O at the outermost circumference of the optical disc master is defined as (P _i / V _i ) = (P _O / V _O ) with respect to the cutting rate P _i / V _i at the innermost circumference. × [1-c × (Vo
/ Vi)] and set the coefficient c to 0.01
By setting ≦ c ≦ 0.08, the cutting rate on the outer circumference is made smaller than the cutting rate on the inner circumference.

[0021]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

The substrate of the optical disk master used in the present invention is usually a disk-shaped glass plate. This disk-shaped glass plate usually has, for example, an outer diameter of 350 mm or 178 mm.
mm and a thickness of about 6 to 10 mm.

After polishing the disk-shaped glass plate, it is washed and dried. Preferably, a primer film is applied to the polished surface of the washed glass plate. A photoresist layer is provided on the primer film surface by spin coating. In this case, the resist material may be a positive type or a negative type. OFPR has advantages such as high sensitivity, no peeling during development, and excellent dry etching resistance. -800 or OFPR-2HOECH
ST AZ-1300, KODAK KMPR-8
0P, AZ1300 manufactured by SHIPLAY, COPYLEXRP-50 manufactured by AGFA, or the like is preferably used. In this case, the photoresist layer is 500-5000 A, especially 8
The layer is formed to a thickness of 00 to 3000 A. This is in consideration of the desired pit or groove depth and the transfer rate.

The photoresist layer is irradiated with convergent light of a laser beam to expose a groove or pit pattern according to a known format such as CCF or SSF. As a laser light source to be used, an argon laser, a krypton laser, a helium-cadmium laser, or the like is used.

The rotation of the optical disk master during the laser beam irradiation is performed at a constant angle (CAV).

As described above, in the groove cutting, the cutting rate is gradually lowered toward the outer periphery of the disk so as to satisfy the following relationship in consideration of the beam radius which expands with an increase in the laser power.

P _i / V _i = P _{O /} V _O × [1-c × (Vo / Vi)]

0.01 ≦ c ≦ 0.08, more preferably 0.025 ≦ c ≦ 0.075

In order to lower the cutting plate P / V toward the outer periphery, it is usually necessary to lower Po. However, even if Vo is raised, Po. Vo may be changed.

By developing the photoresist layer exposed to the groove pattern under such conditions, a pattern in the data area and a development monitor pattern are formed.

As the developing solution to be used, microposits 351/450, 352/452, 3 manufactured by SHIPLEY are used.
53/453, 354/454, 355/455 developer, AZ manufactured by Hoechst, AZ312MIF,
A known organic alkali-based alkaline aqueous solution such as AZ351, AZ400K developer, OFPR developer manufactured by Tokyo Ohka Co., Ltd. is suitable. The development may be performed by a spin method or an immersion method in addition to the spray method.

The grooves on the photoresist film thus obtained have the same width over the entire circumference.
Incidentally, the method for producing a groove of an optical disc master according to the present invention includes:
As a matter of course, the present invention can be applied to the case where grooves of the same width are formed at different linear velocities on the same disk as described above, as well as the case where the optical disk master is rotated at CAV.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

A disc-shaped substrate using soda-lime glass was subjected to ordinary polishing, scrubbing, chemical etching, washing and drying steps, and then a primer film was formed. On top of this primer film, O
FPR-800 (trade name of Tokyo Ohka Co., Ltd.) was applied by spin coating to form a photoresist film. The thickness of the photoresist layer was 1000A.

Next, grooves were formed on the photoresist film by irradiating convergent light of a laser beam of an argon laser with a laser cutting device. The irradiation conditions and scanning conditions are as shown in Table 2.

[0036]

[Table 2]

As shown in Table 2, the cutting rate was set to 2.00 mJ / m at the innermost circumference, and to 1.9 mJ / m at the outermost circumference.

The photoresist film having the groove exposed in this manner was developed to remove the exposed portion. The development is carried out by a spray method.
An FPR developer was used.

Table 3 shows the width of the groove formed on the optical disk master.

[0040]

[Table 3]

As is apparent from Table 3, the width of the groove is uniform over the entire circumference of the disk.

[0042]

According to the method of manufacturing a groove on an optical disk master of the present invention, the cutting power is gradually reduced at a desired ratio from the inner circumference to the outer circumference during laser beam irradiation. Can be formed.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G11B 7/26 G11B 7/00

Claims (2)

(57) [Claims] 1. When cutting a groove by irradiating a laser beam onto a photoresist film of an optical disk master,
The ratio between the laser power P and the linear velocity V of the optical disk master is defined as a cutting rate P / V, and the cutting rate P _O / V _{O at} the outermost circumference of the optical disk master and the cutting rate P _i / V _i at the innermost circumference are determined. Let the relationship be P _i / V _i = k (P _O
/ V _O ), and when k is 1−c × (Vo / Vi), c satisfies the condition of 0.01 ≦ c ≦ 0.08. Method. 2. The method according to claim 1, wherein the cutting rate is continuously reduced from the inner circumference to the outer circumference.