JP3269308B2 - Method for manufacturing resin substrate for optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a large-capacity optical information recording medium, in particular, to use an objective lens having a short wavelength of less than 700 nm and an NA = 0.55 or more, which is considered to become the mainstream, and having a track pitch of 1.0. The present invention relates to a method for producing a resin substrate suitable for an optical disk for recording / reproducing at a recording density of less than 3 μm by injection compression molding.

[0002]

2. Description of the Related Art More than ten years have passed since the emergence of a perforated medium as a recordable optical disk. During this time, magneto-optical media capable of recording and erasing, phase change media capable of overwriting by one beam, and the like have been put to practical use. Except for the very beginning, a semiconductor laser is used as a recording / reproducing light source.
m, and recently around 780 nm.

[0003] Since the spot diameter of the convergent light beam can be reduced if the wavelength is short, it is desired to shorten the wavelength. At present, however, the wavelength of a reliable and practical semiconductor laser is up to 780 nm. . Such an optical recording medium has a recording layer, a protective layer, and the like formed on a transparent resin substrate from the viewpoint of cost and mass productivity, and mainly uses a polycarbonate resin. In the case of a resin substrate, particularly, a polycarbonate resin substrate, the optical anisotropy of the substrate, that is, birefringence, and the warpage of the substrate, that is, the tilt, become problems. Particularly, in a magneto-optical medium, since a small Kerr rotation angle of about 0.5 degrees is detected, the influence of birefringence is large.

[0004] However, optimization of the molecular weight of the resin, etc.
By the improvement of the molding technique, the in-plane birefringence is suppressed to less than 20 × 10 ⁻⁶ , which is a practically ^acceptable level. On the other hand, the absolute value of the vertical birefringence, that is, the absolute value of the difference between the refractive index in the direction parallel to the substrate surface and the refractive index in the direction perpendicular to the substrate surface is particularly large in a polycarbonate resin substrate, and reaches 500 × 10 ⁻⁶ or more. With the development of the working optical head, the influence has been reduced to a level at which there is no practical problem.

[0005]

However, with the demand for higher density optical discs, semiconductor lasers having a wavelength of about 680 nm have been put to practical use, and it is expected that inexpensive and high-output ones will be provided in the near future. . Also, 800
Techniques for obtaining a wavelength of about 500 nm by combining a high-power semiconductor laser of about 1000 nm and a non-linear element have also been advanced, and a head combining a laser and a non-linear element has also been reduced in size.

Further, it has been reported that a semiconductor laser having a wavelength of about 500 nm has been successfully developed at a laboratory level. As described above, high-density optical discs using a semiconductor laser with a shorter wavelength are being mass-produced in the near future, beginning with a wavelength of about 680 nm. Further, in order to obtain a smaller spot diameter, it has been studied to increase the numerical aperture NA of the objective lens for convergence to 0.55 or more. At the time of the above-described high density, there is a concern that the optical anisotropy and tilt of the resin substrate once considered to be solved will become a serious problem again.

First, the optical anisotropy (birefringence) of the resin substrate
The following two points can be cited as problems relating to. 1) A phase difference generated when a light beam passes through a substrate.
(WA Challenger and TA Ri
nehart, Appl. Opt. , 31 (199
2), page 1853) For a medium that records and reproduces information using the polarization of light and rotation of its direction, such as a magneto-optical medium, ellipticity occurs with the rotation of linear polarization in a specific direction. This results in a lower carrier level and an increase in common mode noise in the working head.

An ordinary polycarbonate resin substrate has biaxial or uniaxial optical anisotropy, which means that the phase difference varies depending on the direction of incident light. In a convergent light beam, since there are various directions of incident light beams, light beams having innumerable phase differences are gathered, and a complicated wavefront which cannot be easily corrected by a phase difference plate or the like is formed. The phase difference is the birefringence of the substrate, which is determined by the incident direction of the light beam, is Δ
n, the substrate thickness is d, and the wavelength is λ,

[0009]

## EQU1 ## Δn · d / λ

Therefore, the phase difference substantially increases as the wavelength used for recording / reproducing becomes shorter. Accordingly, the problem of phase difference due to birefringence of the substrate becomes serious in the case of shortening the wavelength, especially in a magneto-optical medium used below 700 nm.

2) The problem of astigmatism due to birefringence. (B.
E. FIG. Bernacki and M.S. Mansurip
ur, Appl. Opt. , 32 (1993), 654.
When a light beam is incident on the substrate obliquely, not perpendicularly to the substrate, with a convergent light beam (refer to page 7 or the like), refraction occurs.
It is well known that the refractive index varies depending on the incident angle. For this reason, the diameter of the substrate should be 1 μm
Astigmatism occurs in the beam, which should converge within a certain plane.

When astigmatism occurs, the recording / reproducing characteristics vary due to differences in the optical head where the focal plane is adjusted. Further, when the beam is an elliptical beam having a major axis in the cross-track direction, crosstalk from an adjacent track becomes a problem. In a high-density optical disk using a short-wavelength light source, the track pitch becomes narrower.
The problem of crosstalk becomes even more severe.

Conventionally, an application for a substrate having a vertical birefringence of less than 400 × 10 ^-6 (Japanese Patent Laid-Open No. 62-204451)
However, the description of the manufacturing method is inadequate, and it is not always possible to provide a substrate that is excellent in optical and mechanical properties and balances various properties. Another application (Japanese Unexamined Patent Publication No.
2-121767) proposes to make the main axis horizontal to the substrate surface. However, it cannot be said that there is a sufficient description as a manufacturing method, and it cannot satisfy mechanical characteristics other than optical characteristics. Not exclusively.

[0014] These are concerned only with a medium having a relatively high recording density at a wavelength of about 800 nm, and only consider the reduction of the phase difference due to birefringence. Earlier application (Japanese Patent Application Laid-Open No. 62-2044)
No. 51) proposes that the injection molding process is controlled in three stages, and that the pressure is significantly reduced immediately after the pressurizing process for transfer. However, in this case, the resin tends to shrink relatively freely. , Easy to cause subtle deformation. Although there is a proposal from the material side to use a polyolefin resin with low optical anisotropy, it is expensive because of poor adhesion to a thin film formed thereon, a small amount of production, and a complicated process. For these reasons, it is not always suitable for practical use.

Further, the thickness of a commonly used substrate is 1.
Although it is 2 mm, when the thickness of the substrate is less than 1.0 mm, the above-mentioned problem relating to birefringence is reduced. However, such a thin substrate is easily warped by itself and has poor mechanical stability.

[0016]

Means for Solving the Problems The present inventors have reduced the birefringence, particularly vertical birefringence, of a polycarbonate resin substrate which has been widely used at present and is inexpensive and has a proven track record in reliability. Various studies have been made on the injection molding method so as to be applicable to the medium, and the present invention has been reached. That is, the gist of the present invention is a method for producing a polycarbonate resin substrate for an optical information recording medium having an outer diameter of 80 mmφ or more and 150 mmφ or less, which is formed by injection compression molding, wherein a mold is filled with a molten resin. A first step, a second step of compressing and transferring the fine pattern on the stamper, a third step of holding and cooling the resin in the mold, and a fourth step of opening the mold to find out a molded product. The mold temperature is maintained at a temperature lower by 10 to 40 ° C. than the glass transition point Tg of the resin, and the pressure P1 applied per unit area of the substrate in the first step is set to 0 ≦ P1 <220 kgf / cm ^2. , The pressure P2 in the second step is set to 220 ≦ P2 ≦ 430 kgf
/ Cm ^2, and the pressure is controlled in two stages in the third step, and the pressures P3 and P4 are P4 + 60 ≦ P3 ≦ P2-4
0 kgf / cm ² and 80 ≦ P3 <220 kgf /
cm ² , 0 ≦ P4 <80 kgf / cm ² , and the time required for the first and ^second steps,
That is, the application of the pressure P2 ends from the start of the resin filling,
The time until the start of application of the pressure P3 is less than 3 seconds, and the pressure P3
The present invention is directed to a method for manufacturing a resin substrate for an optical information recording medium, in which the pressure is changed from 3 to the pressure P4 at a time at which 3 seconds or more have elapsed since the resin was filled and 5 seconds did not elapse.

The resin used in the present invention is a polycarbonate resin, which is produced by reacting one or more bisphenols with phosgene or a carbonate such as diphenyl carbonate. This is exemplified in Japanese Patent Publication No. Hei 6-20784 and Japanese Patent Publication No. Hei 6-20783. Among them, a typical one is a type of bisphenol A which is widely used at present.
FIG. 1 is a conceptual diagram of an apparatus used for injection compression molding in the present invention, and FIG. 2 is a schematic diagram of pressure control.

Hereinafter, the disk substrate forming method of the present invention will be described in detail. FIG. 1 shows an example of a molding apparatus for performing the substrate molding method of the present invention. The molding apparatus 10 includes a movable mold 11 and a fixed mold 12. A stamper 14 for transferring and forming a bit or a laser guide groove on the surface of the substrate 13 is formed on the movable mold 11 by inner and outer stamper holders 15 and 16. Fixed.

On the other hand, the fixed mold 12 is mounted on a fixed platen 17, and a sprue cylinder or sprue portion 18 is provided at the center. A resin inflow path 18a is formed at the center of the sprue part 18, and one end 18b of the resin inflow path 18a is
The other end 18c is connected to the injection nozzle 20 and opens into the cavity 19 formed between the two. The fixed mold 12 is fixed to the fixed board 17 by a mold presser 21 arranged on the outer peripheral portion and attached to the fixed board 17.

As shown in FIG. 1, the movable mold 11 and the fixed mold 12 are provided with temperature control channels 22a to 22d, 23.
a to 23d, each die 1
The temperature of the inner side (hereinafter, referred to as an inner peripheral portion) and the outer side (hereinafter, referred to as an outer peripheral portion) of the first and second temperatures are adjusted. Further, a cooling medium passage 24 is formed in the sprue portion 18 so as to surround the central resin inflow passage 18a.

The method of manufacturing a disk substrate according to the present invention is performed by such a molding apparatus 10. That is, in the molding apparatus 10, the movable mold 11 is closed by the fixed mold 12, and a molten resin such as polycarbonate is injected from the injection nozzle 20 to the resin inflow passage 18 a of the sprue portion 18.
Through the cavity 19. Before the step of injecting the molten resin into the cavity 19, the movable mold 11
Pressure in the direction.

The pressurization of the movable mold 11, that is, the mold clamping pressure is the pressure described in the present invention. The molten resin in the cavity 19 is press-molded into a disk having a desired thickness by the mold clamping pressure, and preformat information such as pits or grooves of the stamper 14 is transferred. After the press forming, the mold clamping pressure is maintained as it is or is changed stepwise. Thereafter, the molded disk substrate is placed in a mold 1
Take out from 1 and 12. That is, immediately before the mold is opened, air is introduced between the substrate and the fixed mold 12 from an air release mechanism attached to the fixed mold 12 to separate the disk substrate from the fixed mold 12 and open the mold.

The movable mold 11 separates the disk substrate from the stamper 14 by supplying air at the same time as opening the mold or during the period after the mold is opened until the mechanical projection mechanism operates. In FIG. 2, the pressure control is divided into at least three stages.

The first step of filling the molten resin into the mold is completed before the resin temperature decreases and the resin does not flow easily, so that the first step is shorter than 1 second. The second process for transferring the fine pattern of the stamper to the filled resin surface is as follows:
Usually, it is selected to be about 0.5 to 2 seconds. The third step of cooling the resin is determined in consideration of stability of mechanical properties, tact time and the like in a period of from several seconds to about 30 seconds. When the substrate is suddenly taken out, it is near the glass transition point Tg, so that it is easily deformed. For example, when the central portion of the substrate is removed from the mold by suction, the substrate warps due to slight catching (necessary to prevent the mold from dropping when opened).

The temperature of the molten resin is a temperature at which the fluidity of the resin can be sufficiently ensured and deterioration due to decomposition or the like can be prevented. For example, in the case of a polycarbonate resin comprising bisphenol A having a molecular weight of about 15,000, a temperature of about three hundred and several tens degrees Celsius to 400
℃ is selected. Of course, since it is determined based on the melting point, fluidity, and heat resistance of the resin, if the melting point of the resin changes, it does not always fall within this range.

The mold temperature Tmo is usually selected to be slightly lower than the glass transition point Tg of the resin. When the temperature is lower than Tg by several tens of degrees C. or more, formation of a skin layer on the surface of the mold is promoted, and particularly, in-plane birefringence increases. If it is higher than Tg, the substrate is taken out of the mold while being soft, which is not preferable in terms of mechanical properties.

For example, when the resin temperature at the time of filling is 350 ° C. and the Tg of the resin is 140 ° C., Tmo is 100 ° C. to 120 ° C.
And the cooling time is 5 seconds to 10 seconds. With at least these three steps, it is possible to manufacture an optical disk resin substrate having a current vertical birefringence of about 500 × 10 ⁻⁶ .

As for the in-plane birefringence of the polycarbonate resin substrate, the resin temperature and the mold temperature are set to a certain temperature or more to secure the fluidity of the resin, and the molecular weight of the resin itself is set to 14000 to 14,000. By lowering it to about 20,000, it can be lowered sufficiently. In addition, it can be reduced by annealing at a low temperature for a relatively short time. That is, it is easy to make it less than 20 × 10 ^-6 (Japanese Patent Publication No. 6-20784, Japanese Patent Application Laid-Open No. Sho 60-155424).

On the other hand, it is not easy to lower the vertical birefringence of a polycarbonate resin substrate, which is usually referred to as 500 to 600 × 10 ^-6 . It is already known that it is better to apply the pressure P2 in the second step to transfer the image and transfer it in the third step, and then to cool in the third step by reducing the pressure P3 as low as possible (Japanese Patent Publication No. 5-67878).

The present inventors have found that the larger the pressure difference from P2 to P3 and the lower P3, the more the vertical birefringence is reduced, and that the pressure is reduced from P2 to P3 within a specific time range. Was found to be effective. The timing of the pressure drop substantially coincides with the timing before and after passing through Tg when the temperature inside the resin filled in the mold rapidly decreases.

That is, the cause of the vertical birefringence is not due to the flow at the time of filling the resin as in the in-plane birefringence, but
At the time of cooling, it is determined by the balance between the pressure in the thickness direction near Tg and the pressure at which the resin tends to shrink. P2, P
If 3 is much higher, the substrate solidifies while being compressed in the thickness direction. Even if P3 is low, if the transition from P2 to P3 is fast, the resin shrinks too freely, so that the resin is still solidified in a high stress state.

In any case, anisotropy is generated in the stress in the plate thickness direction and the stress in the in-plane direction, and a large vertical birefringence as described above is left due to this and a large photoelastic constant peculiar to the polycarbonate resin. It is. Conventionally, vertical birefringence has been described only by the orientation that occurs when the resin flows, or has been described focusing only on residual strain during compression molding.
(For example, JP-A-4-83620). As far as the present inventors know, there is no example referring to the pressure balance in the resin during the solidification of the resin, particularly when the resin is cooled to around Tg.

It goes without saying that the above-mentioned new invention relating to the vertical birefringence generation mechanism by the present inventors supports the novelty of the present invention described below. The present inventors have concluded that, apart from considerations, it has been difficult to obtain a substrate applicable to optically and mechanically high-density media only by these three steps of control that have been proposed and used empirically in the past. did. That is, the pressure difference between P2 and P3 is large, and P
If it is attempted to reduce the value of 3 to one step from P2 to P3, the resin tends to be shrunk or warped.

This is because the resin temperature is not uniform in the radial direction of the mold, and the timing of passing the Tg varies by 2 to 3 seconds. Therefore, when pressure is applied at once, the effect is uniform in the radial direction. It is considered that, as a result, a stress difference occurs between the inner and outer circumferences. Further, since the temperature distribution also exists in the thickness direction, the stress distribution may be asymmetric on the front and back surfaces of the substrate.

Therefore, it is necessary to reduce the pressure in the cooling process stepwise by setting the pressure profile to four or more steps. Although there has been a proposal to gradually or gradually reduce the pressure drop, as described above, only a specific pressure difference and timing are particularly effective in reducing vertical birefringence. I have to say that the method is not enough.

In the present invention, a four-stage pressure profile as schematically shown in FIG. 2 is used. Mold temperature T
As for mo, from the same consideration as in the case of the three-step control, the glass transition point Tg of the resin is 10 ° C. to 40 ° C.
Keep at low temperature. Maintaining the mold temperature in such a range also has the effect of keeping the cooling rate of the resin in a substantially constant range.

That is, one of the features of the present invention in which the pressure is controlled in a specific time range is to change the pressure when the resin temperature is cooled to around Tg. Keeps the specific time range over which the pressure should be changed. The pressure P1 when filling the resin is 0
≦ P1 <220 kgf / cm ² . 220kgf /
When cm ² or more, the resistance at the time of resin filling is increased,
Since the shear stress increases and the orientation of the resin is promoted,
It is not preferable because in-plane birefringence becomes too large.

The pressure P2 for transferring the fine pattern is 2
20 ≦ P2 ≦ 430 kgf / cm ² . 220 kg
If it is less than f / cm ² , transfer of the fine pattern is insufficient. For example, a depth of 0.5 to 1 μm and a width of 0.3 to 0.6 μm
When a groove of about m is formed, there is a problem that the transfer rate of the convex shape of the stamper is poor, and only a shallow groove can be formed.

When it is larger than 430 kgf / cm ² , the residual stress strain in the substrate is increased, so that the birefringence is increased and the substrate is likely to be warped. In the present invention, the substrate is held in the mold for a fixed cooling time after the transfer, and during this time, the pressure is gradually reduced to P3 and P4. The timing of reducing the pressure from P2 to P3 is set to less than 3 seconds from the start of filling the resin into the mold.

Since about 0.5 seconds is usually sufficient for filling the resin into the mold, the remaining P2 application time is less than about 2.5 seconds. The pressure drop from P3 to P4 is defined as a time period when the temperature of the resin in the mold almost approaches Tg. That is, the timing of changing the pressure from P3 to P4 is
This is a time zone in which three seconds or more have elapsed since the resin was filled and no more than five seconds elapsed.

The pressures P3 and P4 are P4 + 60 ≦ P3 ≦ P2
-40kgf / cm^TwoAnd 80 ≦ P3 <220kgf
/ Cm^Two, 0 ≦ P4 <80kgf / cm^TwoSo that
Set. P2-P3 is 40kgf / cm^TwoLess than
And P3 is 220kgf / cm ^TwoAbove, P2
Has no effect of reducing the pressure from P3 to P3,
The pressure will fluctuate from 2 to P4 at once.
Is not preferred.

Finally, P4 is set to 0 ≦ P4 <80 kgf / c
set so that the m ^2. P4 is 80 kgf / cm ²
Above, there is no particular effect of reducing the vertical birefringence. In the case of the present invention, the time for applying any one of the pressures P1 to P4 is not zero. Setting P4 to 0 kg / cm ² is effective in reducing in-plane birefringence. P4 is 2
From 0 kgf / cm ² to 80 kgf / cm ² , relatively large negative birefringence tends to occur particularly in the outer peripheral portion.

This is a level that does not cause a problem in a medium such as a phase change medium that detects a change in reflectivity, but a level that causes a problem in a magneto-optical medium, from −20 × 10 ⁻⁶ to −50 × 1.
It is in the range of 0 ^-6. Here, the sign of in-plane birefringence is
A case where the refractive index of the radial main axis is larger than the refractive index of the circumferential main axis is defined as positive. According to the study of the present inventors, this negative birefringence is such that the resin substrate has a glass transition point Tg measured by a differential scanning calorimeter of the resin, Tg−40 ° C. ≦ Ta ≦
Annealing at a temperature Ta of Tg−10 ° C. can significantly reduce the temperature. In most cases, −
It can be smaller than 20 × 10 ^-6 . (The absolute value can be reduced).

It is known that the reduction in birefringence due to annealing is due to the relaxation of the orientation of the resin or thermal strain. To reduce the temperature, annealing for 30 minutes or more is required. Since the area with large in-plane birefringence in the outer periphery is limited to less than a few mm from the outermost periphery, if it is desired to reduce the birefringence in the outer periphery, the outer diameter of the mold should be 3 mm or more than the outer diameter of the resin substrate It is also effective to reduce the outer peripheral portion to a predetermined outer diameter after molding a resin substrate approximately equal to the above-mentioned mold diameter by making it larger by less than 10 mm.

Of course, annealing and outer periphery cutting may be combined. In the four-stage pressure control in the present invention, the steps P3 and P4 set the pressure range to the above P3 and P4.
The pressure may be reduced stepwise by dividing into multiple stages while maintaining the conditions imposed on the fourth. Hereinafter, the present invention will be described in detail with reference to examples. It goes without saying that the present invention does not depend on the molding machine having a specific structure used in the following examples. The invention is not limited to the specific polycarbonate resin used in the following examples.

[0046]

【Example】

Examples 1 to 14, Comparative Examples 1 to 16 Bisphenol A type polycarbonate resin having a molecular weight of 14300 was used as a molding resin. The glass transition point Tg measured by a differential scanning calorimeter is 140 ° C. The temperature of the resin in the cylinder of the molding machine was set to 350 ° C., and the mold was filled with the resin. Mold temperature is 110 ° C ~ 120
C varied. Resin substrate is 130mm, thickness is 1.2
mm.

The molding machine is a disk 5 manufactured by Sumitomo Heavy Industries, Ltd.
A MIII (trade name) was used. Table 1 summarizes the molding conditions and evaluation results of Examples and Table 2 of Comparative Examples. As the evaluation results, the maximum value and the minimum value of the in-plane birefringence and the vertical birefringence measured at four points were shown at 10 mm intervals from a radius of 30 mm to 60 mm. Furthermore, as a result of evaluating the mechanical properties of the substrate in accordance with the standard of the current optical disk (ISO / IEC13549), those that cleared with a sufficient margin were indicated by ○, those that cleared the marginally but clear were indicated by △, and those that did not meet the standard were indicated by ×. .

The quality of the transfer of the pits in the groove and the sector portion was also evaluated in accordance with the above-mentioned standards, and those which were cleared with a sufficient margin were evaluated as ○, those which were cleared slightly but cleared, and those which were out of the standard as ×. expressed. Example 1
0 and 11 are examples in which P3 and P4 are divided into two stages, and are effective in improving mechanical characteristics.

Example 15, Comparative Examples 17 and 18 The results of annealing the substrate of Example 1 at 120 ° C. for 1 hour are shown in Example 15 (Table 1). The mechanical properties were good. The annealing reduced the vertical birefringence by about 80 × 10 ⁻⁶ . In particular, the in-plane birefringence can reduce a large negative value at the outermost peripheral portion, falls within a range of + 10 × 10 ⁻⁶ to −10 × 10 ⁻⁶ , and obtains good optical characteristics as a whole. You can now use it.

The results of annealing the substrate of Example 1 at 90 ° C. are shown in Comparative Example 17 (Table 2), and the results of annealing at 130 ° C. are shown in Comparative Example 18 (Table 2). At 90 ° C., the in-plane birefringence could be reduced, but the vertical birefringence had little effect. At 130 ° C., the substrate was too close to the glass transition point and the substrate softened slightly, deteriorating the mechanical properties.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

[0054]

[Table 4]

[0055]

According to the method of the present invention, a substrate having a small optical anisotropy, that is, a small birefringence, and having excellent mechanical stability can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an example of an apparatus used in the method of the present invention.

FIG. 2 is a schematic diagram of pressure control in the method of the present invention.

[Description of Signs] 10 Molding apparatus 11 Movable mold 12 Fixed mold 13 Substrate 14 Stamper 18 Sprue part 19 Cavity

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI // B29K 69:00 B29K 69:00 B29L 17:00 B29L 17:00 (56) References JP-A-62-222812 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/64-45/78 B29K 69:00 B29L 17:00

Claims (5)

(57) [Claims] 1. A method for producing a polycarbonate resin substrate for an optical recording medium having a diameter of 80 mmφ or more and less than 150 mmφ and a thickness of 1.0 mm or more and 1.5 mm or less, which is formed by injection compression molding. A first step of filling the inside, a second step of compressing and transferring the fine pattern on the stamper, a third step of holding and cooling the resin in the mold, and opening the mold to know the molded product. And a fourth step of discharging the mold, wherein the mold temperature is set at 1 with respect to the glass transition point Tg of the resin.
The temperature is kept lower by 0 to 40 ° C., and the pressure P1 applied per unit area of the substrate in the first step is 0 ≦ P1 <22.
0 kgf / cm ^2, and the pressure P2 in the second step is 220 ≦
P2 ≦ 430 kgf / cm ² , the pressure is controlled in two stages in the third step, and the pressures P3 and P4 are set to P4 + 60
≦ P3 ≦ P2-40 kgf / cm ² and 80 ≦ P3
<220 kgf / cm ² , 0 ≦ P4 <80 kgf / cm
² and the time required for the first and second steps, ie, the pressure P2 from the start of resin filling.
Is completed, the time until the start of application of the pressure P3 is set to less than 3 seconds, and the timing at which the pressure is changed from the pressure P3 to the pressure P4 is set to a time after 3 seconds or more from the resin filling and 5 seconds or less. A method for manufacturing a resin substrate for an optical information recording medium. 2. The method for producing a resin substrate for an optical information recording medium according to claim 1, wherein the pressure P4 is set to 0. 3. The resin substrate after molding has a glass transition point Tg measured by a differential scanning calorimeter of a resin forming the substrate.
2. The method for producing a resin substrate for an optical information recording medium according to claim 1, wherein the annealing is performed at a temperature Ta satisfying Tg-40 ≦ Ta ≦ Tg−10 ° C. for at least 30 minutes. 4. An outer diameter of a mold cavity is set to be 3 mm or more and less than 10 mm larger than an outer diameter of a desired resin substrate, and after molding the resin substrate, an outer peripheral portion of the resin substrate is cut to a predetermined outer diameter. 4. The method according to claim 1, wherein:
The method for producing a resin substrate for an optical information recording medium according to any one of the above. 5. The optical information recording medium according to claim 1, wherein the application time of the pressure P3 and the pressure P4 is divided to decrease the pressure P3 and the pressure P4 with time. A method for manufacturing a resin substrate.