JPS61153854A - Method for forming optical information recording medium - Google Patents

Abstract

PURPOSE:To reduce the cost of a medium by performing exposure which uses the 1st mask where an information pattern is formed to size corresponding to a unit information area and the 2nd mask where a grating pattern is formed uniformly and irrelevantly to the information pattern. CONSTITUTION:The 2nd mask 22 is arranged on an optical information recording medium 2 in contact. The 1st mask 21 is arranged above the 2nd mask 22 across a lens 26. The top of the 1st mask 21 is lighted with illumination light 27 and then light images of the information patterns 23 and 24 are projected on the medium 2 by a lens 26 through the 2nd mask to life size. Therefore, the part of the medium 2 where recording pits are formed is exposed to the information pattern of recording pits consisting of a grating and a developing process is carried out according to a normal process of lithography to manufacture the optical information recording medium 2 having recording pits consisting of the grating. This manufacturing method reduces the manufacture cost of the optical information recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for producing an optical information recording medium applicable to optical discs, optical cards, optical tapes, and the like.

[Prior art]

2. Description of the Related Art Conventionally, various types of media such as optical disks, optical cards, and optical tapes have been known as media for recording and reading information using light. The principles of recording or reading information on these media vary depending on the type of media material used, the optical system used for recording or reading, and the type of system, and several methods have been put into practical use. A typical example is a magnetic recording medium that uses light to change the direction of magnetization of the medium, and detects a signal by changing the intensity of the Kerr rotation angle that occurs when irradiated with read light. Recording method, or by changing the light transmittance, reflectance, and absorption spectrum of the medium only for the portion corresponding to the information.

The method of reproduction and the refractive index of the information recording part of the medium.

There is a method of detecting a change in light intensity corresponding to a signal by utilizing phenomena such as diffraction and interference of reproduction light irradiated onto the recording section by changing its shape.

For example, it is known that a unit recording area is recorded in the form of pits, which has a relatively simple configuration and can obtain a good S/C ratio of a reproduced signal.

In addition, by eliminating the need for auto-tracking (AT) and auto-focus (AP) technology for pit recording, it is possible to expand the range of applications and reduce the cost of media and devices for recording information. The applicant of the present invention has already proposed an optical information recording medium in which the unit information area to be processed is configured as a grid.

[Summary of the invention]

An object of the present invention is to provide a method for manufacturing a novel optical information recording medium in which the unit information area is structured in a lattice at a low cost.

The above-mentioned object of the present invention is to uniformly record an optical information recording medium in which the unit information area is constituted by a lattice with a first mask on which an information pattern is formed in a size corresponding to the unit information area, regardless of the information pattern. This is achieved by exposure using a second mask on which a lattice pattern is formed.

〔Example〕

First, with reference to FIG. 4, the basic structure of the lattice in the optical information recording medium manufactured according to the present invention will be explained.

In Figure 4, 11 is an optical information recording medium, 12 is a unit information area (hereinafter referred to as a recording bit) which is the smallest unit for recording information, 13 is a transparent protective layer, 14 is a light reflective film,
15 will hail the board. Here, the recording bits 12 are not simply uneven steps as in the conventional case, but have a periodic grating within the bits 12. Such a lattice structure can be formed not only by embossing but also by various means described below. The information reproducing light 17 is assumed to be light from a wide light source such as an LED, and the reproducing light illuminates the bit 12 and its surrounding area almost uniformly through the lens 16.

Due to the diffraction effect of the grating within the bit, the light that illuminates the bit is intensified and reflected in a specific direction determined by the pitch of the grating and the wavelength of the illumination light.

Therefore, for example, if the grooves of the grating are selected so that at least the first-order diffracted light 18 does not enter the lens 16, all the diffracted light will be deflected outside the lens, and the specularly reflected light from the part where the bit 12 does not exist will be reflected from the lens 16. There is a clear difference in the amount of light compared to when the light returns through 16. Therefore, a reproduced signal with a good S/N ratio can be obtained. FIG. 4(C) is a diagram showing the optical output corresponding to the recording bits shown in FIG. 4(G). As is clear from Figure 4 0, from the part where the bit 12 is present, the lens 1
The amount of light that returns to 6 is from the part where there is no bit to lens 1.
The amount of light is extremely small compared to the amount of light returned to 6, and the difference in the amount of light between the bit portion and the non-bit portion is also noticeable. Therefore, if there is no grating inside the bit as in the past, the amount of light reflected from inside the bit increases and the S/N ratio decreases, or in the case of modulation methods where signals are recorded depending on the length of the recording bit. , the amount of reproduction light may vary depending on the length of the bit,
On the other hand, in contrast to this type of optical information recording medium, where the light intensity changes only in the bit part and the edges, which makes it difficult to reproduce the signal, if the grating pitch is constant,
Since the diffraction angle of light is always constant regardless of the length or size of the l bit, stable signal reproduction is possible.

Next, a method for manufacturing the above-mentioned optical information recording medium using a conventional 7-otolithography (hereinafter referred to as photolithography) technique will be explained with reference to FIG. FIG. 5 is a schematic plan view of a mask and an optical information recording medium, and ■ is a perspective view during exposure. In the figure, 1 is a mask for printing a recording bead pattern on a recording medium, 2 is an optical information recording medium manufactured by exposure using mask 1, and 3 and 4 are E B
(Electron Beam) Shows a lattice glass formed by K light. Reference numerals 5 and 6 indicate recording bits formed by a development process after exposure using a mask 1, each of which is composed of a grid represented by a matte finish. Exposure is performed by bringing the mask 1 into close contact with the medium 2 as shown in FIG. 0, and by irradiating illumination light 7 from the mask 1 side. Normally, recording bits are minute, for example, about 10 μm x 10 Rn, and several megabytes or more of information can be recorded on a credit card-sized optical information recording medium, but for convenience of explanation, the medium size is not shown in the drawings. It is drawn large.

However, when producing an optical information recording medium using such a method, a mask 1 is required that has a recording bit pattern exactly similar to that of the medium to be produced.

Therefore, an EB exposure machine for producing such a mask must have a huge capacity of memory for storing recording pit patterns. Furthermore, due to the contrast between the medium size and the grating pitch, high accuracy is required over a long stroke. Such a requirement in manufacturing a mask increases the manufacturing cost of the mask, which in turn leads to an increase in the price of the optical information recording medium.

Therefore, in the present invention, an optical information recording medium is manufactured using two masks. FIG. 1 is a schematic plan view showing patterns formed on two masks used in the present invention. Reference numeral 21 denotes a first mask, which has an information pattern 23 having the same size as the recording pit (for example, 10 μm×10 μm).
．． 24 is formed. The shaded area indicates a transparent area. 22
A lattice pattern consisting of second squares 25 is formed.

This grid has, for example, a slit with a width of 1 to 2 μm,
They are arranged on the entire surface at a pitch of ~2 μm.

FIG. 2 is a schematic side view showing an example of a specific manufacturing method using the mask shown in FIG. The optical information recording medium 2 is coated with preparations such as photoresist for 7-otolithography, and the second mask 22 is superimposed on this in close contact. A first mask 21 is placed above the second mask 22 with a lens 26 in between. first mask 21
When the top is illuminated with illumination light 27, an optical image of information patterns 23 and 24 as shown in FIG. Therefore, the portion of the medium 2 where the recording bits are to be formed is exposed to the information pattern of the recording bits consisting of a lattice, and is developed according to the usual 7-otolithography process, as shown in Figure 5. An optical information recording medium 2 in which the recording pins ) 25 and 26 are composed of gratings is manufactured.

Here, the information patterns 23 and 24 of the first mask 21 were formed to have the same size as the recording bits, but this does not apply when the information patterns are enlarged or reduced and projected onto the medium during exposure. do not have. That is, it is sufficient that the information pattern is formed in a size corresponding to the recording pit so that the projected image has the size to be recorded. Furthermore, the second mask 22 must naturally have a lattice formed with a slit width and pitch smaller than the recording bits.

When manufacturing the first mask 21 used in the present invention,
Because it is only necessary to form as many information patterns as the number of recording pits,
For example, when manufacturing with an EB optical machine, the memory capacity within the device is much smaller than the example shown in FIG. Also, the second
The mask 22 must form a fine lattice, but since the entire surface has the same pattern, there is no need to store information patterns in memory, and manufacturing is easy. Even if the pattern of the second mask 22 has some variation in the density of the grating, the thickness of the grating, or the deformation of the grating, there is no problem in practical use. Furthermore, in the example of FIG. 5, the mask 1 must be remade each time an optical information recording medium with a different information pattern is manufactured, but according to the present invention, even if the information pattern changes, the second mask 22 remains unchanged. Only the first mask 21, which can be manufactured at low cost and can be made using the same mask, needs to be replaced. Therefore, when producing optical information recording media with various information patterns, the present invention can significantly reduce the overall manufacturing cost.

FIG. 3 is a diagram illustrating another embodiment of the manufacturing method according to the present invention. First, in the first step, as shown in (g), a second mask 22 similar to that shown in FIG. .

Next, in the second step, a first mask 21' having an information pattern formed thereon as shown in (2) is placed over the medium 2 on which the lattice pattern has been printed, and the medium 2 is exposed to illumination light 27 again. This first
The mask 21' is a negative/positive inversion of the first mask 21 in the SI diagram.

The optical information recording medium 2 that has been exposed twice in this way has a recording layer consisting of a lattice, although the pattern shown in FIG.

The information pattern of the sheet is printed in the form of unexposed areas. Media 2 is then processed using the normal 7 otolithography technique to produce #15v! Recording bits as shown in :I are formed. Furthermore, the method of this embodiment also provides the same effect as the method shown in FIG. 2.

The present invention is not limited to the above-described embodiments, and can be applied in various ways. For example, the grating constituting the unit information area can be formed not only by a relief structure but also by a change in the refractive index, reflectance, or transmittance of the medium. Specifically, a photosensitive layer that causes the above-mentioned changes when irradiated with light is provided on the medium, and a grating is formed by performing side lighting in the same manner as the method explained in FIG. 2 or 3. In this case, development processing is not necessary, but in order to prevent changes in the photosensitive layer during storage and readout, the light used during exposure should be differentiated from the light incident after fabrication by intensity, wavelength, etc. [Effects of the Invention] As explained above, the present invention provides an optical information recording medium in which the unit information area is a lattice, with a size corresponding to the unit information area. The manufacturing cost of the medium can be reduced by manufacturing it by exposure using a first mask on which an information pattern is formed and a second mask on which a lattice pattern is uniformly formed regardless of the information pattern. This has the effect of reducing

[Brief explanation of the drawing]

4. Fig. 1 is a schematic plan view showing the patterns of two masks used in the present invention, Fig. 2 is a schematic side view illustrating an embodiment of the manufacturing method of the present invention, and Fig. 3 is a schematic plan view showing the patterns of two masks used in the present invention. A schematic side view illustrating another embodiment of the manufacturing method of the invention, FIG.
＠ is a diagram explaining the basic structure of a lattice in an optical information recording medium produced using the present invention, Figure 5, and ＠ are diagrams illustrating the basic structure of a lattice in an optical information recording medium produced using the present invention, respectively. FIG. 2 is a schematic plan view illustrating a method of manufacturing a recording medium. 2... Optical information recording medium 5, 6... Recording bit,
21.21'...First mask, 22...Second mask, 23.24...Information pattern, 25...Slit, 26...Lens, 27...Illumination light.

Claims (1)

[Claims] (1) By exposure using a first mask on which an information pattern is formed in a size corresponding to the unit information area and a second mask on which a lattice pattern is uniformly formed regardless of the information pattern, the unit information area is A method for manufacturing an optical information recording medium in which the information area is composed of a grid.