JP3399459B2 - Method for manufacturing optical disk substrate and apparatus for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a CD-Audio,
CD-I, CD-ROM, Video-CD, LD, D
Read-only type such as VD-Video and DVD-ROM, write-once such as CD-R and DVD-R (additional)
The present invention relates to an optical disc medium used for various optical disc devices such as a mold, a rewritable type such as a DVD-RAM, a DVD-RW, an MO, etc., an optical disc substrate used for the optical disc medium, a manufacturing method thereof, and a manufacturing device thereof.

[0002]

2. Description of the Related Art In a conventional optical disk duplication method, a metal stamper is prepared by nickel plating from a master plate with a photoresist having a light spot guide groove and / or an uneven pattern consisting of address pits and embossed pits for recorded information. Then, when a plastic substrate material (for example, polycarbonate) that has been melted at a high temperature is injected at high pressure into a mold in which the stamper is installed and then cooled and taken out, a plastic substrate having a concave-convex pattern duplicated on the surface is completed. This method is based on the current CD-Audio, C
D-R, CD-ROM, DVD-ROM, DVD
-R, DVD-RAM, DVD-RW, MO and other general methods for producing plastic substrates (injection molding method)
Is.

[0003]

According to the above-mentioned prior art, a stamper is produced by transferring the unevenness by nickel plating from the unevenness formed on the photoresist layer of the master disk which is the glass substrate with the photoresist.

At this time, even the fine irregularities (average roughness of about 1 to 3 nm) that are unintentionally generated on the surface of the photoresist film, such as light spot guide grooves, and / or address pits, or recorded information are recorded. It is transferred to the surface of the stamper together with the concavo-convex pattern consisting of embossed pits.
The unevenness is transferred from the stamper to the surface of the substrate by the injection molding method described as the above-mentioned conventional technique. Further, a reflective layer or a recording layer is formed on this substrate.

Information on an optical disk is recorded by reproducing information on the surface of the substrate or by physically or chemically changing the information on the surface of the substrate depending on the intensity of the reflected light. Information is recorded / reproduced by forming a layer and irradiating the guide groove with light. That is, in the latter case, in recording / reproducing information, the recording layer formed on the surface of the substrate is irradiated with laser light to change the reflectance and the like, and the strength of the reflected light amount is used as the information bearer. At this time, since the shape of the recording layer formed on the surface of the substrate is a film shape that reflects the above-mentioned unintentional fine irregularities, there is a problem that it causes noise and deteriorates the recording / reproducing characteristics. .

An object of the present invention is to reduce the fine irregularities formed on the surface of the above-mentioned substrate unintentionally, reduce the noise of the recording media formed by laminating, and improve the recording / reproducing characteristics. To provide a substrate.

As will be described later, when the method for manufacturing an optical disk substrate of the present invention is used, the manufacturing apparatus is required to have various performances. Therefore, another object of the present invention is to provide a UV processing apparatus for manufacturing the above-mentioned low noise substrate at high speed and with good controllability.

[0008]

The above-mentioned object is achieved by irradiating a master with a photoresist having a concavo-convex pattern or an optical disk substrate on which the concavities and convexities are transferred with ultraviolet rays.

It is generally known that the surface of some plastics is modified by irradiating it with high energy, short wavelength ultraviolet light. This is because a stable chemical bond on the surface of the plastic is broken by the irradiation of ultraviolet rays, and oxygen in the air is bonded to this to change it.

Since the optical disk substrate manufactured by injection molding is made of a plastic material, the chemical bond is broken within a depth range of only a few μm from the surface of the substrate by irradiating it with ultraviolet rays having a high energy and a short wavelength. Therefore, the light absorptivity of the substrate in the ultraviolet region of wavelength 280 nm to 400 nm increases, and the substrate surface is scraped and smoothed.
At this time, if the main wavelength of the ultraviolet light source to be irradiated is 254 nm that does not generate ozone, decomposition near the substrate surface and smoothing of the substrate surface occur remarkably, but ultraviolet rays having a wavelength of 184 nm that generate ozone are used at the same time. Then, the ultraviolet rays generate ozone in the vicinity of the light source, and the ultraviolet rays having a wavelength of 254 nm are absorbed by the ozone decomposition reaction, so that the increase of light absorption near the surface of the substrate and the smoothing of the substrate surface are difficult to proceed.

When the optical disk substrate is polycarbonate, which is a plastic having oxygen atoms in the main chain, the effect of the ultraviolet irradiation becomes remarkable.

Therefore, according to the present invention, (1) a substrate for an optical disc which is made of polycarbonate and has a concavo-convex pattern of light spot guide grooves and / or address pits or embossed pits for recorded information on the surface thereof, Wavelength is 300nm or more and 375nm
The optical disk substrate is characterized in that it is 50% or less at any wavelength in the following range. Since the substrate without UV irradiation has a higher transmittance at this wavelength, it is possible to estimate whether UV irradiation is performed or the irradiation conditions by a simple optical measurement and use it as an index for surface smoothing. Other methods for surface smoothing have different changes in transmittance. The substrate thickness used is 0.6 mm and 1.2 m.
m.

(2) In the optical disk substrate described in (1), the wavelength dependency of the transmittance of the substrate starts to absorb from the wavelength of about 650 nm toward the short wavelength side, that is, the transmittance starts to decrease and the wavelength of about 260 nm. In the following, the optical disk substrate is characterized by having a transmittance of almost 0%.

(3) In the optical disk substrate described in (1), the hardness in the range from the surface of the substrate to about 0.5 μm is 50% to 50% of the remaining range except about 100 μm from both sides.
The optical disk substrate is characterized by being 85% higher.
It has been found that UV irradiation increases the hardness of the surface, so it can be used as an index of surface smoothness that is relatively difficult to measure in hardness measurement, and if the surface hardness is high, it deteriorates even if many times of record rewriting (overwriting) It is difficult to do.

(4) The hardness in the range from the surface of the optical disk substrate described in (3) to about 0.5 μm is 140 N / mm.
^The optical disk substrate is characterized in that the number is ² or more.

(5) In the optical disk substrate described in (1), the average surface roughness (Ra) of fine irregularities on the surface of the substrate is 0.8 nm or less. Use as a substrate.

(6) The polystyrene-converted value of the average molecular weight in the range of up to about 20 μm from the surface of the substrate for an optical disc having an uneven pattern of light spot guide grooves and / or address pits, embossed pits for recorded information, etc. The optical disk substrate is characterized by having a weight average molecular weight of 4% to 22% smaller than the remaining weight average molecular weight excluding about 100 μm from both sides. It was found that the chemical bond on the surface of the substrate was broken by the irradiation of high-energy short-wavelength ultraviolet light, and the average molecular weight was changed.
It can be used as an index of the surface smoothness by measuring the molecular weight distribution in the range up to m and the remaining range except about 100 μm from both sides.

(7) An optical disk substrate according to (6), characterized in that the polystyrene-converted value of the average molecular weight in the range from the surface of the optical disk substrate to about 20 μm is 3.0 or less.

(8) In the optical disc substrate of any one of (1) and (6), the substrate is mainly composed of plastic having oxygen atoms in the main chain. The substrate undergoes a photoreaction (photo-Fries dislocation) when irradiated with high-energy short-wavelength ultraviolet light. At this time, it was found that the main chain having oxygen atoms was cut and the surface of the substrate was modified, so that the surface became smooth. Therefore, the presence or absence of the effect can be understood to some extent from the main component of the plastic.

(9) Using the optical disk substrate of (1) or (6), directly on the substrate or through another layer,
An information recording medium is characterized in that a reflective film or a recording film that changes by laser light irradiation is formed.

In the present invention, the uneven shape on the optical disk substrate is called a light spot guide groove (so-called groove), and it is premised that information is recorded on the recording film on the light spot guide groove. The area in which information is recorded does not need to be a groove. The basis of the present invention is to flatten the minute irregularity of the surface shape, which causes a noise component, when the uneven shape is formed on the optical disk substrate, by irradiating with ultraviolet rays. Therefore, the area in which information is recorded may be, for example, an area between grooves (so-called land). In particular, in the method in which information is recorded on both the land and the groove (land-groove method), the groove depth (corresponding to the size of the step between the land and the groove) is λ /
6n (λ; wavelength of laser beam for reproducing information, n: refractive index at wavelength λ of substrate for optical disk), and the groove is deeper than the groove depth λ / 8n in the case of groove recording. When the groove is deep as described above, the noise component generally tends to increase. However, by using the present invention, it is possible to significantly reduce the noise of the optical disk substrate for land-groove recording.

By the method described in detail above, it is possible to reduce the noise of the optical disk substrate, but various problems have occurred when the optical disk substrate is actually mass-produced. For example, the time required to manufacture one optical disk substrate with a normal injection molding machine is about several seconds to 10 seconds. However, when the optical disk substrate manufacturing method of the present invention is adopted, the time for manufacturing one optical disk substrate is several hundred seconds, which is not practical. Also,
When tens of thousands of optical disk substrates are irradiated with ultraviolet rays, the output of the ultraviolet lamp gradually decreases, which causes a problem that a sufficient noise reduction effect cannot be obtained. In order to solve these problems, as a result of intensive studies by the inventors, the following method for manufacturing an optical disk substrate,
It has been clarified that the problem can be solved by using an optical disk substrate manufacturing apparatus.

(10) A gas containing oxygen is caused to flow through a substrate for an optical disc having a plastic material having oxygen atoms in the main chain, which has irregularities on the surface, so that light of about 185 nm is shielded on the substrate for the optical disc. A method for manufacturing a substrate for an optical disk, which comprises irradiating an ultraviolet ray having a wavelength of 254 nm to modify the surface of the polycarbonate.

(11) Approximately 185 nm in an optical disk substrate manufacturing apparatus for performing surface treatment of an optical disk substrate
For an optical disc, comprising: an ultraviolet light source that shields light having a wavelength of about 254 nm and emits a light having a wavelength of about 254 nm; and means for relatively changing the distance between the optical disc substrate and the ultraviolet light source. Substrate manufacturing equipment.

(12) Approximately 185 nm in an optical disk substrate manufacturing apparatus for performing surface treatment of the optical disk substrate
Of an ultraviolet light source that shields light having a wavelength of about 254 nm and irradiates a light having a wavelength of about 254 nm, and means for relatively moving the optical disk substrate and the ultraviolet light source. Manufacturing equipment.

(13) Approximately 185 nm in an optical disk substrate manufacturing apparatus for performing surface treatment of the optical disk substrate
For an optical disc, which comprises: an ultraviolet light source for irradiating a light having a wavelength of about 254 nm with which the light having the wavelength of 10 nm is shielded; and a means for controlling the ultraviolet irradiation time from the ultraviolet light source to the optical disc substrate. Substrate manufacturing equipment.

(14) Approximately 185 nm in an optical disk substrate manufacturing apparatus for performing surface treatment of the optical disk substrate
Of a plurality of ultraviolet light sources that shield light of a wavelength of about 254 nm and emit light of a wavelength of about 254 nm, and means for independently controlling the emission energy of each ultraviolet light source. apparatus.

Further, depending on the material and shape of the substrate holder for holding the optical disc substrate during the irradiation of ultraviolet rays, the optical disc substrate is heated, resulting in a problem that the optical disc substrate is significantly deformed. In order to solve this problem, the following optical disk substrate manufacturing apparatus may be used.

(15) In the optical disk substrate manufacturing apparatus described in (12), there is provided a substrate holder made of fluororesin for holding the optical disk substrate, which is an optical disk substrate manufacturing apparatus.

(16) The optical disk substrate manufacturing apparatus described in (15), wherein the fluororesin is polytetrafluoroethylene.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Example 1 In a die in which a metal stamper was prepared by nickel plating from a master plate with a photoresist having an optical head guide groove and an uneven pattern of pits representing addresses and the like, and the stamper was installed. When the polycarbonate is melted at a high temperature and poured into it, it is molded by applying pressure, cooled and hardened, and taken out to complete a polycarbonate optical disk substrate having a concavo-convex pattern formed on its surface. Further, when the surface of the concave-convex pattern of the substrate was irradiated with ultraviolet rays for 150 seconds, a substrate for an optical disk was obtained in which fine irregularities which were unintentionally generated on the surface were smoothed. The lamp used at this time is a low pressure mercury lamp C-200UF (manufactured by Chemitronics), and the main wavelength is 254 nm. The distance from the lower surface of the lamp to the substrate was 10 mm. Ultraviolet irradiation was performed while arranging eight lamps in parallel in the atmosphere in which oxygen gas was kept flowing at 10 l / min while rotating the substrate thereunder. The lamp was still lit in the device, and the time until the substrate was inserted under the lamp and came out was set by the timer as the processing time.

As a result of observing the above-mentioned substrate with a scanning electron microscope, it was possible to greatly reduce the fine irregularities that were unintentionally generated on the surface of the photoresist film. Similarly, as a result of measuring the surface shape with an atomic force microscope (AFM), the average surface roughness Ra was about 25% smaller than that before the ultraviolet irradiation. The plate thickness of the substrate was reduced by about 30 nm. On the other hand, the macroscopic shape of the concavo-convex pattern such as the optical head guide groove and the pit representing the address etc. does not change.

The relationship between the UV irradiation time and the average surface roughness by AFM is as follows. The relationship between the ultraviolet irradiation time and the ultraviolet irradiation energy density is shown below. Ultraviolet irradiation energy measurement, Topcon illuminance meter UVR1,
A light receiving unit UVR25 (for wavelength 254 nm) was used.

UV irradiation time (sec) Irradiation energy density (J / cm ² ) Average surface roughness (nm) 0 0 1.0 30 3.9 1.0 60 60 7.8 0.8 100 100 13.0 0. 7 150 19.5 0.6 300 39.0 0.5 450 58.5 0.5 600 600 78.0 0.6 900 117.0 1.3 As can be seen from the above results, the UV irradiation time is short and average. The change in surface roughness is small. The smoothing effect can be seen for 60 seconds or more, but if it is too long, the surface becomes rough and the average surface roughness becomes large.

Next, in order to investigate the relationship with the noise of the substrates having different average surface roughnesses by changing the UV irradiation time, RIN
(Relative Intencity Noise) was measured. RIN is noise standardized by reflectance. It is as follows.
As shown in FIG.

UV irradiation time (sec) Average surface roughness (nm) Noise level variation (dBm / Hz) 0 1.0 -123.0 30 1.0 -123.5 60 0.8 -125.2 100 0.7-126.4 150 0.6-127.3 300 0.5-127.1 450 0.5-128.8 600 0.6-125.6 900 1.3-123.7 The above results From this, it was found that when the fine surface roughness on the surface of the substrate is smoothed and the average surface roughness becomes small, the noise level also becomes low. From the two relations, the ultraviolet irradiation time for smoothing the fine surface roughness on the substrate surface and reducing the noise level is 60 seconds or more and 600 seconds or less, and the preferable average surface roughness is 0.8 nm or less. I knew it was. A more preferable range is 100 seconds or more and 450 seconds or less.

Similarly, a polyvinyl chloride substrate was examined for changes due to ultraviolet irradiation.

UV irradiation time (seconds) Average surface roughness (nm) Noise level change amount (dBm / Hz) 0 13.0 -118.0 30 13.0 -118.0 60 13.2 -117.9 100 13.3 -117.9 150 13.3 -117.9 300 13.3 -117.9 450 13.8 -117.0 600 14.1 -116.8 900 14.8 -116.4 The above results As can be seen from the figure, the polyvinyl chloride substrate did not change so that the substrate surface became smooth. Hereinafter, only the results for the polycarbonate substrate are shown.

It was found that the reaction due to the ultraviolet irradiation causes a change in the depth of the guide groove and also in the pit representing the address. An example of the relationship between the ultraviolet irradiation time, the depth of the guide groove, and the pit read error is shown below. The relationship between the ultraviolet irradiation time and the depth of the guide groove is shown in FIG.

UV irradiation time (sec) Guide groove depth (nm) Read error (%) 0 64.9 7.5 30 63.5 6.5 6.5 60 62.7 6.0 100 100 62.0 5.5 150 61.1 5.0 300 57.2 5.5 450 53.5 5.7 600 48.9 6.0 900 40.5 7.5 It was found that the read error increases as the UV irradiation time increases.

Next, the relationship between the atmospheric gas at the time of ultraviolet irradiation and the etching amount of polycarbonate was investigated. It was found that the change in the oxygen concentration and the reaction rate of the polycarbonate substrate corresponded to each other when the mixed gas of oxygen and nitrogen was kept flowing during the ultraviolet irradiation. The higher the oxygen concentration, the faster the reaction. It is considered that this is because the chemical bond on the surface of the polycarbonate substrate is broken by the irradiation of ultraviolet rays and bonds with oxygen in the atmosphere. The relationship between the oxygen concentration in the atmosphere and the etching amount of the polycarbonate substrate when the ultraviolet irradiation time is 300 seconds is shown.

[0042] The etching amount was 45 nm when the same 300 seconds of ultraviolet irradiation was continued to flow nitrogen at 10 l / min. Further, it was 48 nm when the atmosphere as it was or the dry air was continuously flowed at 10 l / min without flowing the gas. From these results, it is understood that oxygen is required to increase the reaction rate, but even if oxygen cannot flow due to the structure of the apparatus, there is no problem with the atmosphere as it is, dry air, or nitrogen.

Further, FIG. 3 shows a change in transmittance wavelength dependency of the above substrate with respect to the ultraviolet irradiation time. The transmittance changes with a positive correlation with the ultraviolet irradiation density. In the substrate before being irradiated with ultraviolet rays, the transmittance starts to decrease from around 650 nm toward the short wavelength side, the transmittance gradually decreases up to around 450 nm, and the transmittance decreases remarkably from around 400 nm around 260 nm. Below, the transmittance was almost 0%. . On the other hand, the substrate irradiated with ultraviolet rays has a wavelength of 2
The transmittance is similar in the vicinity of 60 nm or less, but the wavelength 4
A remarkable decrease in transmittance starts from around 40 nm,
A second curve of transmittance change appears near 320 nm.
This second curve changed as follows with respect to the ultraviolet irradiation time. The substrate transmittance at a wavelength of 300 nm is shown.

[0044] Further, the substrate transmittances at wavelengths of 450 nm and 300 nm are shown.

UV irradiation time (second) Substrate transmittance (%) at 450 nm 300% Substrate transmittance at 300 nm (%) 0 95 58 30 95 95 52 60 95 32 32 100 95 95 28 150 95 25 300 300 95 18 450 88 15 15 600 80 12 900 From these results, it was found that the above-mentioned noise level and pit read error rate were low when the transmittance of the substrate was 80% or more at a wavelength of 450 nm and 35% or less at 300 nm. By measuring the transmittance of the substrate, it is possible to estimate whether or not the ultraviolet treatment is performed, the treatment conditions, the state of the substrate surface, and the like.

A ZnS.SiO ₂ film having a thickness of 120 nm as a lower protective layer, a Ge-Sb-Te film having a thickness of 8 nm as a data recording layer, and a ZnS.SiO ₂ film having a thickness of 135 nm serving as an upper protective layer are laminated on the surface of the above-mentioned ultraviolet-treated substrate. Then, a Cr—O film having a thickness of 30 nm and an Al—Ti film having a thickness of 80 nm were stacked as the heat diffusion layer and the reflection layer. Recording / reproducing characteristics were evaluated using the above-mentioned disks.

The relationship between the ultraviolet irradiation time at this time and the data error rate and PID read error after overwriting 100,000 times on the disk is shown below.

UV irradiation time (seconds) of PID after 100,000 overwrites Error rate Read error 0 1 × 10 ⁻² None 60 1 × 10 ⁻³ None 100 1 × 10 ⁻⁴ None 150 1 × 10 ⁻⁵ None 300 5 × 10 ⁻⁵ None 450 1 × 10 ⁻⁴ None 500 5 × 10 ⁻³ None 600 1 × 10 ⁻³ None 900 1 × 10 ⁻² Occurrence From the above results, it is preferable that the UV irradiation time is 60 seconds or longer and 600 seconds or shorter. It was found that the more preferable range is 100 seconds or more and 450 seconds or less.

Further, a SiN film having a thickness of 70 nm as a lower protective layer, a TeFeCo film having a thickness of 80 nm as an information recording layer, and a Si having an upper protective layer of Si are formed on the surface of the above-mentioned ultraviolet-treated substrate.
An N film was laminated in a thickness of 70 nm. Using the above disc, the recording / reproducing characteristics at a mark width of 0.5 μm were evaluated. The relationship between the UV irradiation time and C / N at this time is shown below.

[0050] From the above results, it was found that the ultraviolet irradiation time is preferably 60 seconds or more and 600 seconds or less, and more preferably 100 seconds or more and 450 seconds or less.

Next, the change in hardness of the polycarbonate substrate due to ultraviolet irradiation was examined. As a measuring device, Fischer's Fisherscope H100 was used. Since a flat surface is required, the surface of the polycarbonate substrate opposite to the surface having the concavo-convex pattern was irradiated with ultraviolet rays, and the difference between the presence and absence of ultraviolet irradiation was compared. The hardness unit is N / mm ² .

Surface 0.5 μm Inside 20 μm Inside 100 μm Hardness Hardness Irradiation time 0 sec 139 104 80-100 Irradiation time 60 sec 141 106 80-100 Irradiation time 100 sec 150 110 80-100 Irradiation time 300 sec 162 116 80-100 Irradiation time 600 seconds 173 121 80-100 Irradiation time 900 seconds 175 122 80-100 From the above results, it was found that the surface of the polycarbonate substrate was hardened by the ultraviolet irradiation. This is probably because the material on the surface of the substrate was crosslinked by ultraviolet rays and became hard. It is considered that the hardened surface increases the durability against rewriting many times as shown by the error rate result after overwriting 100,000 times. When the irradiation time is 600 seconds or longer, the change in hardness becomes small.

The molecular weight distribution of the polycarbonate substrate depending on the ultraviolet irradiation time was examined. The GPC method (gel permeation chromatography) was used as the measuring method. Approximately 20 μm of the surface of the polycarbonate substrate that has been irradiated with ultraviolet rays and the surface of the polycarbonate substrate that has not been irradiated with ultraviolet rays
Each of the scraped pieces (about 0.5 g) was dissolved in 2 ml of a solvent (tetrahydrofuran), and ultrasonic waves were applied to dissolve it to obtain a measurement sample.

The values are converted into polystyrene, and the distribution of the molecular weight is estimated from the weight average molecular weight indicating the weight average value of molecules having various molecular weights. If there are Ni macromolecules having a molecular weight of Mi, the weight average molecular weight is ΣNiM.
It is represented by i ² / ΣNiMi. The smaller the value of the weight average molecular weight, the more the number of low molecular weight. An example of the relationship between the ultraviolet irradiation time and the weight average molecular weight is shown below.

[0055] The molecular weight distribution on the substrate surface is as shown in Fig. 4.
It was also found that the components having a particularly low molecular weight such as oligomers were scarcely generated and were rather reduced, so that the effect of reducing about 10 defects per 1 cm ^{2 in the} storage life test to 1 or less was observed. This also contributes to the reduction of the error rate. This effect is considered to be manifested by the improved adhesiveness at the interface. The polystyrene equivalent value of the weight average molecular weight in the range from the surface to about 20 μm is 4% to 22% from the remaining average molecular weight excluding about 100 μm from both sides.
When the ultraviolet irradiation time was small and was 60 seconds or longer and 600 seconds or shorter, good results with an error rate of 1 × 10 ⁻³ or less were obtained. When the ultraviolet irradiation time was 100 seconds or more and 450 seconds or less, the error rate was 1 × 10 ⁻⁴ or less, and more favorable results were obtained.

On the polycarbonate substrate, a ZnS.SiO ₂ film having a thickness of 100 nm was used as a lower protective layer, a Ge—Sb—Te film having a thickness of 6 nm was used as an information recording layer, and a Zn protective layer was used as an upper protective layer.
An S.SiO ₂ film is laminated in a thickness of 40 nm, a Cr-O film is 30 nm and an Al-Ti film is 80 nm as a heat diffusion layer and a reflection layer.
The non-destructive disc reflectance was measured using the laminated discs. The reflectance from the polycarbonate substrate side was measured with a spectroscope. A change in the reflectance depending on the ultraviolet irradiation time was observed between the wavelength of 330 nm and the wavelength of 360 nm. The reflectance starts to rise from the wavelength of 330 nm, and the reflectance decreases from the peak of the wavelength of 345 nm to the wavelength of 360 nm. 7 shows a change in disk spectral reflectance with ultraviolet irradiation time at a wavelength of 345 nm. From this result, by measuring the spectral reflectance of the disk, it is possible to almost infer whether or not the ultraviolet treatment has been performed, the condition thereof, the state of the substrate surface, and the like.

Further, the wavelength is from 500 nm to 800 nm
Even within the range, changes due to UV irradiation were observed. The reflectance starts to gradually increase from the wavelength of 500 nm to the wavelength of 800 nm regardless of the ultraviolet irradiation time. However, it was found that the longer the UV irradiation time, the higher the reflectance in the above wavelength range. The relationship between ultraviolet irradiation time at a wavelength of 700 nm and disk spectral reflectance is shown. From this result, by measuring the spectral reflectance of the disk, it is possible to almost infer whether or not the ultraviolet treatment has been performed, the condition thereof, the state of the substrate surface, and the like.

When the recording medium was removed from the above-mentioned disk whose recording characteristics were evaluated, the molecular weight distribution on the substrate surface was measured again, and the same result as before the recording medium was laminated was obtained.

The results of measuring the transmittance and the substrate hardness were the same as before the recording media were laminated. It is shown below.

UV irradiation time of wavelength 320 nm (second) Substrate transmittance (%) Hardness of surface 0.5 μm 0 60 139 30 52 52 60 32 141 141 100 28 28 150 150 25 300 300 17 162 450 450 15 600 600 12 173 900 10 175 The present invention According to the optical spot guide groove required for the optical disc,
And / or, it is possible to reduce the fine irregularities that are unintentionally generated on the surface of the optical disc substrate, without impairing the shape of the irregular pattern formed of the address pits.

The ozone concentration between the master and the substrate and the light source after 600 seconds of UV irradiation was measured and found to be 0.1.
It was below ppm.

Example 2 A metal stamper was prepared by nickel plating from a master plate with a photoresist having an information surface as an uneven pattern of embossed pits on the surface, and the polycarbonate was melted at a high temperature and poured into a mold in which the stamper was installed. After that, when pressure is applied, molding, cooling and curing, and taking out,
A polycarbonate optical disk substrate having an uneven pattern formed on the surface is completed. Further, when the surface of the concave-convex pattern of the substrate was irradiated with ultraviolet rays for 150 seconds, a substrate for an optical disk was obtained in which fine irregularities on the surface which were generated unintentionally were smoothed. Here, the relationship between the average surface roughness, the depth of the information concavo-convex pattern, and the reading error of the information surface when the ultraviolet irradiation time was changed was measured. The results were as follows.

UV irradiation time Average surface roughness Information unevenness pattern depth Information surface readout error (second) (nm) (nm) (%) 0 1.0 102.8 6.4 30 30 1.0 101.46 2.2 60 0.8 100.6 5.8 100 100 99.9 5.6 150 150 0.6 98.0 5.4 300 0.5 0.5 95.1 5.6 450 0.5 0.5 91.0 5 0.7 600 0.6 86.8 5.8 900 900 1.3 78.5 6.4 As can be seen from these results, the depth of the information uneven pattern,
It is necessary to determine the ultraviolet irradiation time so that the pit read error has a desired value.

Since the molecular structure of several μm changes in the depth direction from the entire substrate or the surface on which the information pattern is formed depending on the temperature condition and the pressure condition at the time of injection molding, the reaction due to the ultraviolet irradiation also occurs. Naturally different. Therefore, the optimum time is slightly different for each injection condition and each material.

Example 3 Similarly, a photoresist surface of a master plate with a photoresist having a light spot guide groove and / or an uneven pattern of address pits, sector marks, and embossed pits such as recording information on the surface of a photoresist master. Ultraviolet irradiation was performed. The results of measuring the master surface by AFM are shown below.

UV irradiation time (second) Irradiation energy density (J / cm ² ) Center line average surface roughness (nm) 0 0.0 0.6 30 30 3.9 0.6 60 7.8 0.5 100 100 13 0.0 0.5 15 19.5 0.4 30 30 39.0 0.4 50 58.5 0.4 600 78.0 0.5 900 117.0 0.6 As can be seen from the above results, The effect of smoothing is seen, but if it is too long, it becomes rather rough and the center line average surface roughness becomes large.

Example 4 An example of an optical disk substrate manufacturing apparatus in the case of applying the optical disk substrate manufacturing method of the present invention described in detail above to mass production is shown below. FIG. 5 is a diagram showing an example of an optical disk substrate manufacturing apparatus suitable for mass production of the present invention. This device consists of a lamp house part and a belt conveyor part for transferring substrates. Further, the lamp house part is composed of an ultraviolet lamp 5-1, an ultraviolet lamp power source 5-2, an ultraviolet shielding plate 5-3, a lamp height adjusting part 5-4, and a socket part 5-10. Consists of a conveyor-belt 5-5, a substrate holder 5-6, a motor 5-7, a motor rotation speed control circuit 5-8, and a belt conveyor holder 5-11. Further, as shown in the figure, the optical disc substrate 5-9 is mounted on the substrate holder so that the signal surface (the surface on which the concavo-convex shape is formed) faces the ultraviolet lamp side, and it passes under the lamp house. By doing so, the low-noise optical disk substrate of the present invention can be mass-produced.

The ultraviolet light source has a U-shaped ultraviolet light emitting portion that blocks light having a wavelength of 185 nm.
A low-pressure mercury lamp that emits ultraviolet light having a dominant wavelength of 254 nm is used. Further, in order to uniformly irradiate the optical disk substrate with ultraviolet rays, the ultraviolet lamps are arranged symmetrically with respect to the traveling direction of the optical disk substrate. In addition, an ultraviolet illuminometer was installed on the conveyor belt, and the integrated illuminance distribution was measured when the optical disc substrate was conveyed at the same speed as the result, and as a result, the length of the light emitting portion of each lamp was 75 mm. However, within the range of 65 mm, the illuminance distribution target was ± 5% or less. At this time, the heights of the measurement surface of the ultraviolet illuminometer and the signal surface of the optical disc substrate were adjusted to be the same. in this way,
When a U-shaped UV lamp is used, it is important to arrange the lamps symmetrically with respect to the optical disc substrate transport direction in order to improve the uniformity of the illuminance distribution.

This apparatus uses 15 of the above ultraviolet lamps. In addition, the power switch of each lamp is independent so that the lamp to emit light can be selected.
Further, each lamp is mounted on a socket portion 5-10 having sockets corresponding to the number of lamps.

Further, since ultraviolet rays have an adverse effect on the human body, an ultraviolet shielding plate 5-3 made of stainless steel for shielding the ultraviolet rays is provided. Further, the socket portion 5-10 is joined to the ultraviolet shielding plate 5-3 via the lamp height adjusting portion 5-4. Further, the ultraviolet shielding plate 5-3 is joined to the belt conveyor holding table 5-11. The lamp height adjusting unit 5-4 has a screw shape, and the lamp height adjusting unit 5 is
-4 by rotating the uppermost part of the socket part 5-
The height of 10 can be adjusted.

A large number of substrate holders 5-6 are fixed to the conveyor belt 5-5 at intervals corresponding to the size of the optical disc substrate 5-9. The substrate holder 5-6 has a protrusion having a size corresponding to the hole opened at the center of the optical disc substrate 5-9, and the robot arm allows the optical disc substrates 5-9 to be mounted at a time five at a time. ing. The conveyor-belt 5-5 is adapted to be rotated by a motor 5-7. The motor 5-7 is fixed to the belt conveyor-holding base 5-11. The rotation of the motor 5-7 is controlled by the motor rotation speed control circuit 5-8.

Further, the apparatus for producing an optical disk substrate of the present invention is provided with the gas inlet 5-12, and as described above, the gas containing oxygen can be introduced into the apparatus. ing. Further, the optical disk substrate manufacturing apparatus of the present invention is provided with the exhaust port 5-13, and is designed to efficiently exhaust the gas containing an organic substance generated by the irradiation of the optical disk substrate with ultraviolet rays. There is.

With such an apparatus, in the case of mass-production trial production, it was possible to make the production time per optical disk substrate to about 5 seconds. Further, as a result of measuring the radial direction dependency and the circumferential direction dependency of the noise reduction effect of the optical disk substrate, it was found that both were 0.5 dB or less, and there was no practical problem. As described above, the optical disk substrate manufacturing apparatus of the present invention is suitable for mass production.

However, it has been found that two problems occur when a mass production trial is performed for 10,000 hours or more with this apparatus. First, there is a problem in that the emission intensity of the ultraviolet lamp gradually decreases due to long-term ultraviolet irradiation, and therefore the ultraviolet lamp must be frequently replaced. Generally, the emission intensity of a mercury lamp is reduced to about 70% as compared with the initial emission intensity when it is emitted for about 10,000 hours. As a result, there arises a problem that the noise reduction effect on the optical disk substrate is weakened.
In order to solve these problems, we tried the following methods.

The number of ultraviolet lamps to emit light is changed in time series so that the integrated illuminance of the ultraviolet rays applied to the surface of the substrate becomes constant.

For example, at first, only 10 out of 15 are used, and the integrated illuminance per new UV lamp is 1
Then, the integrated illuminance by 10 ultraviolet rays becomes 10. In advance, the motor 5 of the belt conveyor should be able to obtain a sufficient noise reduction effect even with an integrated illuminance of 10.
The rotation speed of -7 and the distance between the optical disk substrate 5-9 and the ultraviolet lamp 5-1 are set to the motor rotation speed control circuit 5-8.
And the lamp height adjusting unit 5-4. In this way, the surface treatment of the optical disk substrate 5-9 is performed, and the number of ultraviolet lamps that emit light is controlled so that the integrated illuminance that decreases with the passage of time is always about 10. With this method, simply change the number of UV lamps that emit light by the UV lamp power supply 5-2.
This is an excellent method because a constant integrated illuminance can always be obtained.
By doing so, even after the light has been emitted for 10,000 hours, the integrated illuminance can be set to about 10 by setting the number of the ultraviolet lamps to emit 15 to 15. The weak point of this method is that the integrated illuminance changes abruptly by about several percent each time the number of ultraviolet lamps to emit light increases, and thus the controllability is somewhat inferior.

(2) The moving speed of the optical disk substrate 5-9 is slowed down so that the integrated illuminance of the ultraviolet rays applied to the substrate surface becomes constant.

For example, first, the moving speed of the optical disk substrate 5-9 is adjusted by the motor rotation speed control circuit 5-8 so that all 15 lamps are made to emit light and the integrated illuminance becomes about 10. The distance between the optical disk substrate 5-9 and the ultraviolet lamp 5-1 is adjusted by the lamp height adjusting unit 5-4. In this way, the optical disk substrate 5-
9 is performed, and the moving speed of the optical disk substrate 5-9 is controlled by the motor rotation speed control circuit 5- so that the integrated illuminance, which decreases with the passage of time, is always about 10.
It is changed by 8. By thus controlling the moving speed of the optical disk substrate 5-9 in time series, the integrated illuminance can be constantly controlled to about 10.
For example, even after irradiation of 10,000 times, the optical disk substrate 5
By reducing the moving speed of -9 to about 70%,
An integrated illuminance of about 10 can be obtained. The weak point of this method is that the production time (tact time) per optical disk substrate changes with the passage of time. There is no problem when the noise reduction processing by ultraviolet irradiation of the present invention is performed independently of other processes, but when the noise reduction processing is performed in cooperation with another process on the line, the processing time changes with time. Is not preferable.

(3) The distance between the optical disk substrate 5-9 and the ultraviolet lamp is changed so that the integrated illuminance of the ultraviolet light irradiated on the substrate surface becomes constant.

For example, first, all 15 lamps are made to emit light, and the distance between the optical disk substrate 5-9 and the ultraviolet lamp 5-1 is set to 10 m by the lamp height adjusting unit 5-4.
Adjust so that m. Further, the motor rotation speed control circuit 5-8 adjusts the moving speed of the optical disk substrate 5-9 so that the integrated illuminance becomes about 10. In this way, the surface treatment of the optical disk substrate 5-9 is performed, and the distance between the optical disk substrate 5-9 and the ultraviolet lamp 5-1 is adjusted so that the integrated illuminance that decreases with the passage of time is always about 10. It is adjusted by the lamp height adjusting unit 5-4. Thus, the optical disk substrate 5-9
By controlling the distance between the UV lamp 5-1 and the ultraviolet lamp 5-1 in time series, the integrated illuminance can be constantly controlled to about 10. For example, even after irradiation of 10,000 times, by reducing the distance between the optical disk substrate 5-9 and the ultraviolet lamp 5-1 to about 5 mm, an integrated illuminance of about 10 can be obtained. It has been found that this method is the most excellent method because it can be controlled with high accuracy without changing the production time (takt time) per optical disk substrate with the passage of time. .

Of course, if necessary, (1) and (2)
It is needless to say that it is possible to use (3) properly, and there is no problem even if each method is used in combination.

It has been described above that two problems occur when mass-production trial production is performed using the above-mentioned device. Another problem is that depending on the material and shape of the substrate holder, the substrate for the optical disk is used. However, there is a problem in that it is thermally deformed or the substrate holder itself is deteriorated by irradiation of ultraviolet rays.

Since the substrate holder 5-6 is exposed to strong ultraviolet rays, the material must be chemically and thermally stable and hardly generate heat even if it absorbs ultraviolet rays. The inventors have tried various plastics and metals as the material of the substrate holder, but as a result, the material of the substrate holder 5-6 is optimally fluororesin. Among fluoropolymers,
In particular, polytetrafluoroethylene (poly (difluoromethylene)) or poly (chlorotrifluoroethylene) is the most suitable material because of its chemical stability, resistance to thermoplastic deformation, and easy processing. all right. When a substrate holder is made of a metal such as Al or stainless steel, the portion irradiated with ultraviolet rays remarkably generates heat, which causes a problem that the optical disk substrate is deformed. Also, when using plastics such as polycarbonate and polyethylene, the surface of the substrate holder will crack if it is used continuously for several months, or the surface of the substrate holder will be scraped and the shape will change due to decomposition by ultraviolet irradiation. There has occurred. Such a problem did not occur when a fluororesin was used.

The shape of the substrate holder is preferably as small as possible so that the substrate can always be held horizontally. The mercury lamp used in the present invention also emits light having a visible light wavelength other than ultraviolet light. Since such visible light rays pass through the transparent substrate used as the optical disk substrate, the visible light rays eventually reach the substrate holder. At this time, heat is generated by the visible light rays absorbed by the substrate holder. Therefore, for example, DVD-RA
For the M substrate, when the central hole diameter is 15 mm, the substrate diameter is 120 mm, and the flat portion near the center has a diameter of 34 mm, the diameter of the protruding portion of the substrate holder is 7 mm ± 0.5.
mm, and the diameter of the substrate holder is preferably 30 to 33 mm. The diameter of the substrate holder is the diameter (44
(mm or more) is not preferable because when the substrate is deformed due to the heat generated by the substrate holder, the influence becomes remarkable. If the diameter of the substrate holder is 30 mm or less, it is difficult to stably hold the optical disc substrate, which is not preferable.

[0085]

As described above, according to the present invention, by post-processing without changing the manufacturing process of the conventional optical disk substrate, the adhesiveness is excellent, the number of defects is small, and the undesired fine pattern is generated. There is an effect that it is possible to manufacture a substrate for an optical disc having a smooth information surface having no irregularities. As a result, the recording / reproducing characteristics were improved, a low error rate was obtained, and the performance of the optical disk was improved.

As a lamp for irradiating ultraviolet rays, approximately 1
By using an ultraviolet light source that shields the light of the wavelength of 85 nm and irradiates the light of the wavelength of about 254 nm, it is possible to suppress the generation of ozone that hinders the effect of the present invention. It is possible to process the optical disk substrate of.

Further, by controlling the distance between the ultraviolet light source and the optical disk substrate, the effect of the present invention on the optical disk substrate can always be kept constant even if the emission intensity of ultraviolet rays changes. It will be possible.

Further, by relatively moving the ultraviolet light source and the optical disk substrate, it is possible to perform uniform processing on the entire surface of the optical disk substrate.

Further, by controlling the integrated illuminance of ultraviolet light from the ultraviolet light source onto the optical disk substrate,
Even if the emission intensity of ultraviolet rays changes in time series, the effect of the present invention on the optical disk substrate can be kept constant at all times.

As a method of controlling the integrated illuminance of ultraviolet rays,
A method of providing a plurality of the ultraviolet light sources and changing the number of the ultraviolet light sources that emit light so that the integrated illuminance is always constant, and the relative movement speed of the optical disk substrate,
A method of time-series control so that the integrated illuminance is always constant, and a method of time-sequentially changing the distance between the ultraviolet light source and the optical disk substrate are effective.

Further, in the apparatus for manufacturing an optical disk substrate, a substrate holder made of a fluororesin such as polytetrafluoroethylene is used to hold the optical disk substrate, thereby suppressing the deformation of the substrate during the irradiation of ultraviolet rays. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an ultraviolet irradiation time and a tracking groove depth in one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between ultraviolet irradiation time and noise in one example of the present invention.

FIG. 3 is a diagram showing the relationship between the ultraviolet irradiation time and the change in the spectral transmittance of the substrate in one example of the present invention.

FIG. 4 is a diagram showing the relationship between the irradiation time of ultraviolet light and the change in the molecular weight distribution of the substrate in one example of the present invention.

FIG. 5 is a diagram showing an outline of an optical disk substrate manufacturing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

5-1 UV lamp, 5-2 UV lamp light source, 5-3
UV shielding plate, 5-4 lamp height adjusting part, 5-5 conveyor belt, 5-6 substrate holder, 5-7 motor, 5
-8 Motor rotation speed control circuit, 5-9 optical disk substrate, 5-10 socket section, 5-11 belt conveyor holding stand, 5-12 gas inlet.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI // C08L 69:00 C08L 69:00 (72) Inventor Makoto Miyamoto 1-280, Higashi Koikekubo, Kokubunji City, Tokyo Inside Hitachi Central Research Laboratory (56) ) Reference JP 2000-207787 (JP, A) JP 10-36536 (JP, A) JP 2000-187888 (JP, A) JP 10-199054 (JP, A) JP 10- 188363 (JP, A) JP 1-107339 (JP, A) JP 2000-113512 (JP, A) JP 2001-28149 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 7/26 G11B 7/24 C08J 7/00

Claims (7)

(57) [Claims] 1. A gas containing oxygen is caused to flow through an optical disk substrate having a plastic material having an oxygen atom in the main chain and having a surface irregularity, and the main wavelength is 1 on the optical disk substrate.
A method for producing a substrate for an optical disk, which comprises shielding the light of 85 nm and irradiating with ultraviolet rays having a main wavelength of 254 nm to modify the surface of the polycarbonate. 2. An optical disk substrate manufacturing apparatus for performing surface treatment of an optical disk substrate, wherein light having a dominant wavelength of 185 nm is blocked and the dominant wavelength is 2.
An optical disk substrate manufacturing apparatus comprising: an ultraviolet light source that emits light having a wavelength of 54 nm; and means for relatively changing the distance between the optical disk substrate and the ultraviolet light source. 3. An optical disk substrate manufacturing apparatus for performing a surface treatment of an optical disk substrate, wherein light having a dominant wavelength of 185 nm is blocked and a dominant wavelength is 2 nm.
An optical disk substrate manufacturing apparatus comprising: an ultraviolet light source for irradiating light having a wavelength of 54 nm; and means for relatively moving the optical disk substrate and the ultraviolet light source. 4. An optical disk substrate manufacturing apparatus for performing a surface treatment of an optical disk substrate, wherein light having a dominant wavelength of 185 nm is blocked and the dominant wavelength is 2.
An optical disk substrate manufacturing apparatus comprising: an ultraviolet light source for irradiating light having a wavelength of 54 nm; and means for controlling an ultraviolet irradiation time from the ultraviolet light source to the optical disk substrate. 5. In an apparatus for producing an optical disc substrate, which performs a surface treatment of an optical disc substrate, light having a dominant wavelength of 185 nm is blocked and the dominant wavelength is 2
An optical disk substrate manufacturing apparatus comprising: a plurality of ultraviolet light sources for irradiating light having a wavelength of 54 nm; and means for independently controlling the emission energy of each ultraviolet light source. 6. The optical disk substrate manufacturing apparatus according to claim 3, further comprising a substrate holder made of fluororesin for holding the optical disk substrate. 7. The optical disk substrate manufacturing apparatus according to claim 6, wherein the fluororesin is polytetrafluoroethylene.