JP2523921B2 - How to make an optical disc master - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an optical disc master.

2. Description of the Related Art Optical disc masters are coated with a photoresist on a substrate such as glass whose surface is polished or glass with a V-shaped groove formed on the surface and which is intensity-modulated according to an information signal to be recorded. It is made to be sensitive to the laser light, and signal pits corresponding to the photosensitivity are formed. V on the surface
The reason for forming the V-shaped groove is to prevent the pits of the adjacent tracks from being read when the signal is read.

FIGS. 6 (a) and 6 (b) show the structure of a conventional optical disk master making apparatus, mainly the structure for irradiating a laser beam.

Substrate 1 coated with photoresist in FIG.
Are rotatably driven by the spindle 2 and transferred in the radial direction of the substrate 1 by the uniaxial moving table 3. The laser light 27 emitted from the argon laser oscillator 4 passes through the mirrors 5 and 6 and the intensity modulator 7 utilizing the electro-optical effect or the like.
Is subjected to intensity modulation according to the signal to be recorded, and the beam diameter is expanded by the beam expander 8 in which two lenses having different focal lengths are arranged so as to share the focus, and then the dichroic mirror 9 and the mirror 10 are set. After that, the substrate 1 is narrowed down by the lens actuator 11 to be irradiated.

The laser light from the helium neon laser 12 is used for focus and tracking control, passes through the polarization beam splitter 13, the quarter-wave plate 14, the dichroic mirror 9, and the mirror 10, and is focused by the lens actuator 11 to be applied to the substrate 1. . The reflected light from the substrate 1 of the helium neon laser light is separated from the incident light by the polarization beam splitter 13 through the mirror 10, the dichroic mirror 9, and the 1/4 wavelength plate 14, and is guided to the light receiving element 15 for focus and tracking detection. As a result, focus control and tracking adjustment of the laser light 27 on the substrate 1 are performed. In the figure, the photodetectors capable of focus control are collectively shown as a light receiving element for focus detection. For example, in the knife edge method, a lens, a knife edge between the focal plane of the lens, and a split light beam are used. It includes a detector, a cylindrical lens for the astigmatism method, and a quadrant photodetector. In the tracking servo system, for example, in the push-pull method, a system including a lens and a photodetector divided into two is represented as a light receiving element for tracking detection.

FIG. 6B is a side view of a portion of the substrate 1 shown in FIG. The lens actuator 11 is driven according to the signal obtained by the light receiving element 15,
The focus of the laser light 27 is controlled by the argon laser 4, and the substrate 1 is always irradiated with the focused light.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention A groove having a V-shaped cross section (hereinafter abbreviated as V groove) has a spiral shape,
Alternatively, when a photoresist is applied to a substrate formed in a concentric shape, if a spin coating method is used as is generally performed, the photoresist can be formed on two slopes, i.e., a circumferential side slope and a center side slope forming a V groove. The thickness is rarely the same, and in most cases, the thickness of the photoresist is different on both slopes as shown in the cross section in FIG. However, when the same laser beam is applied to two slopes with different film thickness,
For example, when the intensity of the laser light is adjusted to the thinner one, the laser light is narrowed down at the time of signal recording, and the depth of focus is shallow, so it is difficult to record on a thick slope. When the intensity of the laser light is adjusted to the slope having a large film thickness, the laser light is too strong for the slope having a small film thickness, so that there is a problem that the width of the signal pit is widened and a good signal cannot be obtained.

Means for Solving the Problems In order to solve these problems, the present invention measures the thickness of a photoresist previously coated on an optical disk substrate, and two linearly polarized laser beams whose polarization planes differ from each other by 90 degrees. Based on the above measurement results, a signal is recorded by irradiating the slope of the photoresist having a large film thickness with the P wave and irradiating the slope of the thin film with the S wave among the two laser beams.

Alternatively, two laser beams having different intensities are used, and one of the two laser beams having the higher intensity is irradiated on the slope having a large thickness of the photoresist and the one having the weak intensity is irradiated on the slope having the smaller thickness. To record the signal.

Operation In the first aspect of the invention, when recording a signal on the optical disk substrate, two laser lights of P wave and S wave having polarization planes different from each other by 90 degrees are used. The P-wave and the S-wave have different reflectances at the interface between the photoresist and air, and the P-wave has a smaller reflectance than the S-wave. Therefore, the P-wave is applied to a slope having a thick photoresist film. By irradiating and irradiating the S-wave on the slopes having a small film thickness, similarly good signals can be recorded on both slopes forming the V groove.

In addition, in the second invention, when recording a signal on the optical disk substrate, two laser beams having different intensities are used, and a strong laser beam is irradiated onto the thick slope of the photoresist to obtain a film thickness. By irradiating the thin inclined surface with a laser having a weak intensity, it is possible to similarly record a signal on either inclined surface forming the V groove.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 (a) is a diagram showing the configuration of an optical disk master forming apparatus according to an embodiment of the first invention.

The substrate 1 having the V groove formed by applying the photoresist is
The substrate 1 is rotationally driven by the spindle 2 and is transferred in the radial direction of the substrate 1 by the uniaxial moving table 3. The laser beam 22a emitted by the argon laser oscillator 4a has a plane of polarization perpendicular to the paper surface, undergoes intensity modulation according to the signal to be recorded by the intensity modulator 7a via the mirrors 5a and 6a, and the beam diameter is changed by the beam expander 8a. After being magnified, it is reflected by the polarization beam splitter 18 via the mirror 17. Laser light 22b emitted from argon laser oscillator 4b
Has a plane of polarization parallel to the plane of the paper, undergoes intensity modulation according to the signal to be recorded by the intensity modulator 7b via the mirrors 5b and 6b, and the beam diameter is expanded by the beam expander 8b, and then the polarization beam splitter 18 Through. The two laser lights having 90 ° different planes of polarization are combined by being reflected or transmitted by the polarization beam splitter 18. The combined laser light passes through the dichroic mirror 9 and the galvano mirror 16 and is narrowed down to the substrate 1 by the lens actuator 11. Focus on the position.

FIG. 2B is a side view of a portion where the substrate 1 is irradiated with the laser beams 22a and 22b.

The laser beams 22a and 22b are respectively focused on two slopes of the V groove by controlling the galvanometer mirror 16 and the lens actuator 11 by the focus and tracking servo system using the helium neon laser 12.
The laser light 22a from the argon laser oscillator 4a whose polarization plane is perpendicular to the paper surface is incident as a P wave on the slope of the V groove, while the laser light 22b from the argon laser oscillator 4b whose polarization surface is parallel to the paper surface. Enters as an S wave on the slope of the V groove.

Since the reflectance at the interface between the photoresist and the air is different between the P wave and the S wave, and the reflectance of the P wave is smaller than that of the S wave,
By irradiating the thick slope of the photoresist with the P wave and irradiating the thin slope of the photoresist with the S wave, a good signal is similarly obtained for both slopes forming the V groove. You can record.

2 (a), (b) and (c) show the principle of the method for measuring the film thickness of the photoresist.

An enlarged view of a part PQRS of the optical disk substrate shown in FIG. 3A is shown in FIG. 3B, and a cross-sectional view taken along the line AA in FIG. 3B is shown in FIG. Arrows e, f, g in FIG.
The broken lines indicated by indicate the peaks, valleys, and peaks of the V groove, respectively. When measuring the film thickness, for example, by irradiating a portion of the photoresist indicated by VWXY with a laser beam and exposing this portion to remove the photoresist, the film thickness t shown in FIG.
Is measured by STM (tunnel microscope). Control the output of the argon laser oscillator 4a, 4b based on this measurement result,
A signal is recorded by irradiating the slope having a large film thickness with a P wave or a strong laser beam and irradiating the slope having a small film thickness with an S wave or a weak laser beam.

FIGS. 3 (a) and 3 (b) show another embodiment of the first invention.

In FIG. 1, two argon laser oscillators were used to obtain two recording laser lights having different polarization planes. However, as shown in FIG. 3 (a), the light of one argon laser oscillator 4 is half-mirrored. You can divide it into two at 20.
The laser light 22 from the argon laser oscillator 4 whose polarization plane is perpendicular to the plane of the drawing is split into two by the half mirror 20 after passing through the mirror 5. The light 23b transmitted through the polarization beam splitter 18 has a polarization plane of 9 by placing a half-wave plate 21 between the half mirror 20 and the polarization beam splitter 18.
Rotate 0 degrees. In FIG. 3, the half-wave plate 21 is placed between the mirror 6b and the intensity modulator 7b, but if it is between the half mirror 20 and the polarization beam splitter 18, there is no problem in other places. In addition, using an argon laser whose polarization plane is parallel to the paper surface, the light reflected by the polarization beam splitter 18
There is no inconvenience even if a half-wave plate is provided on the other side.

FIG. 3B is a side view of a portion where the substrate 1 is irradiated with the laser lights 23a and 23b.

Laser light 23 synthesized by polarization beam splitter 18
a and 23b are dichroic mirror 9 and galvano mirror 16
After that, the lens actuator 11 narrows down the substrate 1. Since the laser beam 23a reflected by the polarization beam splitter 18 is incident as a P wave on the slope of the V groove, it is applied to the slope of the photoresist having a larger film thickness. On the other hand, the laser beam 23b that has passed through the polarization beam splitter 18 is incident as an S wave on the slope of the V groove, so that the slope of the photoresist having the smaller thickness is irradiated.

As a photoresist, AZ-1350 (Chipley Co., Ltd.) diluted with AZ thinner to a volume ratio of 20% was used, and a linear velocity of 10 m /
When a signal was recorded using a laser with a wavelength of 458 nm and 10 mW at s, the thin slope of the photoresist could record a P wave or an S wave, but the thick slope could record a P wave. Recording was insufficient with S waves. When the opening angle of the V groove is 160 degrees, the incident angle is 10 degrees, and the S-wave reflectance Rs and the P-wave reflectance Rp at the interface between the photoresist and air.
Is Rs = 4.2% when the refractive index of photoresist is 1.5,
Rp = 3.8%.

 FIG. 4 shows an embodiment of the second invention.

In the same figure, as in FIG. 1 (a), two laser beams 24a and 24b whose polarization planes are different by 90 degrees are polarized beam splitter 18
The composition is taken in. Further, the output of the argon laser oscillator 4a is set so that the laser light 24a becomes stronger than 24b, and the laser lights 24a and 24b combined by the polarization beam splitter 18 are circularly polarized by the 1/4 wavelength plate 25. And is narrowed down to a substrate having a V-groove coated with photoresist.

Of the two slopes forming the V groove, the thick slope of the photoresist is irradiated with the strong laser beam 24a, and the thin slope is irradiated with the weak laser beam 24b to form the V groove. Good signals can be recorded on the two slopes as well.

 FIG. 5 shows another embodiment of the second invention.

In this embodiment, the output from one argon laser oscillator 4 is divided into two laser beams 26a and 26b by the half mirror 20 as shown in FIG. 3 (a). To change the intensity of the two laser beams, the ratio of transmission and reflection of the half mirror that splits the two beams is 50 pairs.
Of the two slopes that are offset from 50 and form the V-groove, the one that is narrowed down to the thick slope of the photoresist may be stronger. Further, in this case as well as in the previous embodiment, the two combined laser beams are converted into circularly polarized light by the 1/4 wavelength plate 25.

As a photoresist, AZ-1350 (Chipley Co., Ltd.) diluted with AZ thinner to a volume ratio of 20% was used, and a linear velocity of 10 m /
When a symbol was recorded using a laser with a wavelength of 458 nm at s, a signal could be recorded even at 10 mW on the thin slope of the photoresist, but at 10 mW on the thick slope, recording was insufficient,
The signal could be recorded at 12mW.

In this way, even on the thick slope of the photoresist, by increasing the laser power, it is possible to record a signal like the thin slope of the photoresist. Specifically, if the power of the laser beam applied to the thick slope of the V groove is made stronger than the laser power applied to the thin slope by about 20%, the same signal can be recorded on both slopes of the V groove. .

Although the polarization beam splitter is used to combine the two laser beams in the above embodiments, a half mirror may be used instead of the polarization beam splitter to combine the two beams. However, since the intensity of the laser beam is halved in the half mirror, it is necessary to increase the intensity of the beam before combining.

EFFECTS OF THE INVENTION As described above, of the two slopes forming the V groove of the optical disk substrate, the slope having a thicker photoresist film has a P
By irradiating the wave and irradiating the S-wave on the slope having a small film thickness, a good signal can be simultaneously recorded on both slopes forming the V groove.

Similarly, a V-groove is also formed by irradiating the slope of the photoresist having a larger film thickness with a strong laser beam and irradiating the slope of the photoresist having a smaller film thickness with a weaker intensity. Good signals can be simultaneously recorded on the two slopes.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are configuration diagrams of an optical disk master forming apparatus according to an embodiment of the present invention, FIGS. 2 (a) to 2 (c) are principle diagrams of photoresist film thickness measurement, and FIG. (A)
(B), FIGS. 4 and 5 are configuration diagrams showing another embodiment of the present invention, FIGS. 6 (a) and 6 (b) are configuration diagrams of a conventional optical disk master making apparatus, and FIG. FIG. 3 is a cross-sectional view of an optical disc substrate coated with photoresist. 1 ... Optical disc substrate, 2 ... Spindle, 3 ... Uniaxial moving base, 4 ... Argon laser oscillator, 5, 6, 10, 16, 17 ... Mirror, 7 ... Intensity modulator, 8 ... Beamex Panda, 9 ... Dichroic mirror, 11 ... Lens actuator, 12 ... Helium neon laser, 13, 18 ... Polarization beam splitter, 14, 25 ... 1/4 wavelength plate, 15, 19 ... For focus and tracking detection Light receiving element, 20 …… Half mirror, 21 …… 1/2 wave plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Ogawa, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Within

Claims (2)

(57) [Claims] 1. A disk-shaped optical disk substrate has a V-shaped cross section on one surface.
A step of forming a V-shaped groove in a spiral shape or a concentric shape, a step of polishing the surface on the same surface, a step of applying a photoresist on the same surface, and a laser beam whose intensity is modulated according to an information signal. In the method for producing an optical disc master, which comprises the step of irradiating the V-shaped groove with a signal to record a signal, the film thickness of the photoresist is measured on each of the two slopes forming the V-shaped groove, Using two linearly polarized laser lights having different planes of polarization of 90 degrees, the S-wave of the two laser lights is applied to the slope having the smaller thickness,
A method for producing an optical disk master, characterized in that a signal is recorded on both slopes of the V-shaped groove by irradiating the slope having a larger film thickness with a P wave. 2. A disk-shaped optical disk substrate has a V-shaped cross section on one surface.
A step of forming a V-shaped groove in a spiral shape or a concentric shape, a step of polishing the surface on the same surface, a step of applying a photoresist on the same surface, and a laser beam whose intensity is modulated according to an information signal. In the method for producing an optical disc master, which comprises the step of irradiating a laser beam and recording a signal, the film thickness of the photoresist is measured on each of the two slopes forming the V-shaped groove, and two laser beams having different intensities are measured. Of the two laser beams, the strong laser is applied to the thick slope and the weak laser is applied to the thin slope to form the V-shaped groove. A method for producing an optical disk master, characterized by recording signals on both slopes.