JPH04330652A - Exposure method for optical master disk - Google Patents

Abstract

PURPOSE:To prevent work exposing an optical master disk from becoming complicated, to always obtain an appropriate pit and to prevent the pit from becoming shallow. CONSTITUTION:The optical master disk 10 is divided into a light quantity decision area A and an information recording area B. The light quantity decision area A is irradiated with exposure light obtained by changing light quantity stepwise so as to form latent images 11, 12 and 13. The latent images 12 and 13 are developed, and the pit and the like are formed. The light quantity of appropriate exposure light is judged and the information recording area B is exposed by the exposure light of judged appropriate light quantity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exposing an optical disk master used in the manufacture of optical disks.

0002

2. Description of the Related Art A method for manufacturing an optical disc will be explained. An adhesive layer is formed on the surface of a glass disk, and a photoresist film is further formed on this adhesive layer. Next, the surface on which the photoresist film is formed is exposed to laser light to form a latent image. This latent image is then developed to form pits or grooves to produce an optical disc master. Next, this optical disk master is subjected to nickel plating, etc., and a stamper is manufactured by transferring the pits and the like of the optical disk master. Then, using this stamper, a plastic replica is manufactured by injection press molding or the 2P method, and this replica is subjected to disk processing to manufacture an optical disk.

However, variations occur in the shapes of pits and grooves on the master optical disc, which may cause the signal level of the optical disc to change from its original level. The causes of variations in the shape of pits and the like on an optical disc master are as follows. This is because there is some variation in the sensitivity of the photoresist film. This is because the photoresist liquid used varies slightly from product rod to product rod, or because the resist film is affected by the adhesive, resulting in deterioration of the resist film. Another reason is that the prebaking temperature (drying temperature of the resist film) and time during the photolithography process are not uniform. Furthermore, this is because the concentration and temperature of the developer used to develop the latent image formed on the photoresist film are not uniform.

Since it is almost impossible to manage the photoresist solution etc. so that there is no variation in the shape of the pits, etc., development is carried out so that the pits etc. have the most appropriate shape by detecting the diffracted light of the optical disk master. A developing device equipped with a device for detecting the end point of the process is used. That is, development is performed while the optical disc master is irradiated with laser light, and the diffracted light is measured. A developing device is used that stops development when it detects diffracted light that is obtained when preset appropriate pits and the like are formed.

[0005]

[Problems to be Solved by the Invention] However, measuring the diffracted light while performing development is complicated. Furthermore, since the way the developer flows on the surface of the photoresist film also affects the measured diffracted light, there is also the problem that it is difficult to select the measurement position. Furthermore, there is a possibility that the measured value of the diffracted light may change due to variations in the amount of developer and the way it flows. Therefore, there is a possibility that pits etc. of appropriate shape cannot always be obtained. Furthermore, if the sensitivity of the photoresist film is low, development must be carried out for a long time, and the entire photoresist film becomes thinner, causing pits and the like to become shallower, which may adversely affect the signal level. The present invention has been made by focusing on the above-mentioned conventional problems, and provides an optical disc master that does not make the work complicated, can always produce appropriate pits, etc., and does not have the risk of the pits becoming shallow. The purpose is to provide an exposure method.

[0006]

[Means for Solving the Problems] The present invention changes the light amount in stages in a light amount determining area that is a portion of the surface of the master disc on which the photoresist film is formed, other than the information recording area where information is recorded. A step of irradiating exposure light to form a plurality of latent images and developing the latent images to form a reference recess, determining an appropriate amount of exposure light from the reference recess, and exposing with the determined appropriate amount of light. This is a method for exposing an optical disc master, which includes the step of exposing the information recording area to light.

[0007]

According to the present invention, a plurality of latent images are formed by irradiating the light amount determining area with exposure light whose light amount is changed stepwise. This latent image is then developed to form a reference recess, and the appropriate amount of exposure light is determined from this reference recess. Then, the information recording area is exposed with the determined appropriate amount of exposure light.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Reference numeral 10 indicates an optical disc master. As shown in FIG. 2, this optical disc master 10 is constructed by forming an adhesive layer 2 on a glass substrate 1, and further forming a resist film 3 on the adhesive layer 2. The optical disc master 10 is shown in Figure 1.
It is divided into an outer light amount determining area A and an inner recording area B with a dashed-dotted line α as a boundary. Necessary information is written in the recording area B, and no information is written in the light amount determining area A.

Next, a method of exposing the optical disc master 10 will be explained. The optical disc master 10 is placed on the turntable 4.
The exposure device 15 irradiates the light amount determining area A with laser light to form latent images 11, 12, and 13. The laser beams that form these latent images 11, 12, and 13 are applied while changing the light intensity in stages. Then, an object containing a developer is placed on the exposed area to develop the latent images 12, 13, and 14, and the photoresist film 3 is depressed to form pits or grooves as reference depressions. Judgment is then made visually. In the case of visual inspection, since pits or the like of an appropriate shape are formed in a portion that emits a certain level of gloss, the amount of light used to expose that portion is an appropriate amount of light. Therefore, for example, if a part where pits etc. obtained by developing the latent image 12 are formed has a certain gloss,
Information is recorded in the recording area B using exposure light of an amount that forms the latent image 12.

[0010] After exposing the light amount determining section A, the optical disk master 10 is removed from the turntable 4, and the latent images 11, 12, 13 are formed by using a developing device or by dipping (spraying a developer). After development, the appropriate amount of exposure light may be determined by visual inspection.

[0011] As will be explained below, it may be inspected whether the pits or the like have a proper shape or not using a diffraction light detection device. As shown in FIGS. 3 and 4, an optical disc master 10
LDs 15, 16, 17 are arranged corresponding to the pits etc. obtained by developing the latent images 11, 12, 13 on the lower surface side, and CCD arrays 20, 21, 2 are arranged on the upper surface side of the optical disk master 10.
2, the detection light is emitted from the LDs 15, 16, and 17 toward the pits, etc. of the optical disc master 10, and the degree of diffraction of each pit, etc. is determined. The degree of diffraction that a properly shaped pit, etc. exhibits is determined experimentally in advance, so by detecting the degree of diffraction, it is possible to check whether the formed pit, etc. has an appropriate shape. It is possible to determine whether or not the exposure light is present, and the appropriate amount of exposure light can be determined. Then, in the same manner as in the above case, information is recorded in the recording area B using an appropriate amount of exposure light.

A second embodiment will be explained. As shown in FIG. 5, latent images 31, 32, and 33 are formed at regular intervals or more so that they can be detected. These latent images 31, 32, 3
3 is also formed by changing the amount of light in stages, latent images 31, 32,
33 is developed. In addition, as a diffraction light inspection device, LD1
One LD 18 and one CCD array 25 are arranged, and when a diffraction value indicating a proper pit or the like is detected by these LD 18 and CCD array 25, a means such as a buzzer is provided to display it. In this apparatus, it can be determined that the amount of exposure light used to form the pits etc. that was detected when the buzzer sounded is the most appropriate. Since the amount of exposure light for writing information in the recording area B is adjusted to an appropriate value in this way, there is no need to adjust the development time and the like in the latent image development stage. Therefore, the pit etc. will not become shallow.

[0013]

As described above, according to the present invention, proper pits and the like can always be formed with simple operations. Furthermore, since the development time and the like are kept constant, there is no fear that pits or the like will become shallow.

[Brief explanation of drawings]

FIG. 1 is a plan view of an optical disc master according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II of the optical disc master in FIG. 1;

FIG. 3 is a diagram showing the configuration of a diffraction light detection device for carrying out the method for exposing an optical disk master according to the first embodiment.

FIG. 4 is a diagram for explaining an inspection using the diffraction light detection device of FIG. 3;

FIG. 5 is a diagram showing the configuration of a diffraction light detection device for carrying out the method of exposing an optical disc master according to a second embodiment.

[Explanation of symbols]

1 Glass substrate 2 Adhesive layer 3 Resist film 10　　　Optical disc master A Light amount determination area B Information recording area

Claims (1)

[Claims] Claim 1: A light amount determining area, which is a part of the surface of the master disc on which the photoresist film is formed, other than the information recording area where information is recorded, is irradiated with exposure light whose light amount is changed stepwise to forming a latent image and developing the latent image to form a reference recess, determining an appropriate amount of exposure light from the reference recess, and exposing the information recording area with the determined appropriate amount of exposure light; A method for exposing an optical disc master, comprising the steps of: