JPH07118100B2 - Information recording medium and manufacturing method thereof - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to improved optically readable recording media and methods for making such media. The recording medium of the present invention is well suited for use as a video disc or an audio disc.

[Conventional technology]

Conventionally, various methods have been used to manufacture optically readable recording media, including mechanical and photo-etching techniques. Conventional video and audio discs (e.g. compact discs) are typically performed by mechanical pressing operations in which quarter-wave pits are physically stamped into the recording medium. U.S. Pat. No. 4,423,137, assigned to the present applicant, discloses a method of making a recording medium by photoetching. This photo-etching method eliminates the significant drawbacks found in conventional stamping techniques.

While the photoetching method described in US Pat. No. 4,423,137 is well suited for various applications, it produces a recording medium that does not rely on destructive interference during the reading operation. This is because the recording medium described in this patent includes transmissive holes that allow the read beam to pass through rather than reflect it at the proper displaced phase. There are readers, such as some compact disc players, that use the phase difference between the read beams reflected from each portion of the recording medium for control purposes.

[Problems to be solved by the invention]

The present invention provides a recording medium that relies on a dephasing technique for the reading process, while providing an improved recording medium that retains the significant advantages of photo-etching processing.

[Means for solving problems]

According to the present invention there is provided an information recording medium adapted for use with a read beam, the information recording medium comprising a support having first and second surfaces. A layer of photoresist is deposited on a first side of the support, the photoresist layer comprising first and second photoresist regions having different thicknesses.
Defining an array of recesses therein to be divided into regions. In the preferred embodiment, the first region is an array of openings formed in the photoresist layer such that the first surface of the support is actually exposed in the openings. The first and second areas are distributed in a pattern indicating selected and stored information, such as audio information, video information, or both. A reflective layer is deposited over the photoresist layer and, if the recess forms an opening in the photoresist, on the first surface of the support at the opening. In both the first area with the recess and the second area between the recesses, the second part of the support
Both the support and the photoresist layer are adapted to transmit the read beam so that a portion of the read beam incident on the surface of the substrate is reflected by the reflective layer to the outside of the support. The spacing difference between the reflective layers in the first and second regions is selected to provide destructive interference between the portions of the read beam that are reflected outside the support by the reflective layers in the first and second regions.

According to the method of the present invention, information to be subsequently read by the read beam is recorded by first providing a support having first and second surfaces adapted to transmit the read beam. It The first side of the support is then coated with a photoresist layer adapted to transmit the read beam. Next, portions of the photoresist layer are exposed to create first and second areas of different exposure. At least part of the thickness of the photoresist
Removed in the first region to create a photoresist differential thickness between the first and second regions. In the preferred embodiment, a full thickness of photoresist is removed in the first region to expose a portion of the first surface of the support disposed below the first region. The remaining photoresist (and the exposed portion of the first side of the support) is then covered with a reflective layer adapted to reflect the read beam.
The selected differential thickness of the photoresist layer between the first and second regions is determined by the second surface of the support between the read beams reflected from the reflective layer disposed on the first and second regions. It is designed to create destructive interference above.

[Action]

The method of the present invention is adaptable for use with either modulated laser or contact exposure techniques. This method retains the important advantages of photo-etching and completely avoids the problems associated with stamping and pressing. In addition, the preferred embodiment described below is read through the support and through the remaining photoresist. This backside reading technique offers the important advantage that the active surface of the reflective layer is never exposed to contamination once it is applied.
The reason for this is that it is the lower surface of the reflective layer (the surface close to the photoresist) that is the active reflective surface. Once the deposition is made on this side of the reflective layer, it is never exposed during subsequent processing operations. Furthermore, the preferred embodiment described below can be carried out with a relatively small number of processing steps, which makes it well suited as an economical production technique for both replica discs and single plates made with modulated lasers.

The invention itself, as well as other attendant advantages, will be more fully understood in the following detailed description in conjunction with the accompanying drawings.

〔Example〕

Referring to the drawings, FIGS. 1a to 1f relate to a first embodiment of the method and recording medium of the present invention, and FIGS.
Figure 2f relates to a second embodiment of the method and recording medium of the invention.

First Embodiment The method of FIG. 1 uses a contact exposure technique by a master to form a recording medium such as a video disc or an audio disc. The first step in the method of Figure 1 is to inspect the support used as the recording medium. In this embodiment, the support 10 is, for example, PMMA.
/ Optical grade plastic support that can be formed of polycarbonate or cast epoxy. If the support 10 is intended to be used as a video disc,
It preferably has a thickness of 1.2 mm, an outer diameter of either 200 or 300 mm (depending on the application), and an inner diameter of 35 mm. If the support 10 is intended for use as a compact disc, it has a thickness of 1.2 mm and an outer diameter of 120 mm.
mm, as well as an inner diameter of 15 mm is preferred. In a first inspection step, the support 10 is inspected for optical surface properties and flatness.

The support 10 is then washed with a mild soap solution to remove particulate contamination, followed by a series of deionized water baths. The washed support is then visually inspected for contamination.

The photoresist, storage, solution preparation, and processing steps labeled Viscosity Test relate to the preparation of a suitable photoresist, and the photoresist in this example is a positive-type photoresist such as those commercially available as the Shipley 1400 series. Is. Preferably, the photoresist should be diluted to 3% solids. If obtained directly from Shipley, a suitable product is Shipley photoresist 1400-3. The viscosity of this photoresist is preferably 1.37 centistokes at 25 ° C.

The processing step 80 is a photoresist coating step in which the support 10 is coated with a layer of photoresist 20 to form the structure shown in Figure 1a. In this example, coating step 80 is performed at a temperature of about 20 ° C. and 50% relative humidity. Spin-coating techniques can be used in which a moving arm is used to dispense photoresist onto a substrate 10 rotating at a low speed of about 100 rpm. The rotational speed of support 10 is then accelerated to about 350 rpm to spin off the photoresist to form a layer of the desired thickness. The final thickness of the photoresist 20 in this example is approximately 1200Å. Subsequent to the coating step 80, the support 10
And photoresist 20 at 70 ° C for about 30 minutes in a HEPA filtration convection oven.
After baking at a temperature of 100 ° C, the resulting product is visually inspected for particulate contamination. Periodically, the thickness of the baked photoresist is inspected so that it is the desired 1200Å thickness.

The coated support of FIG. 1a is then, as shown in FIG. 1b,
It is exposed in the contact exposure step 82. This exposure step 82
In it, the photoresist layer 20 is contacted with the chrome master. The formation of the master does not form a part of the present invention and is therefore not detailed here. A suitable master can be formed by the process described in commonly assigned US Pat. No. 4,423,137. In this example, the exposing step is performed with exposing radiation having a wavelength of 400 nanometers. The exposure time is about 1.5 seconds and the UV source is about 4
Generates 00mw / cm ² . This exposing step 82 creates first and second regions of photoresist 20, which first and second regions differ in their degree of exposure. Especially the Master 70
Includes a transparent support 72 and a metal layer 74 defining an array of openings 76 therein. Areas of the photoresist 20 aligned with the openings 76 are exposed to ultraviolet radiation, but areas of the photoresist 20 aligned with the metal layer 74 are not exposed.

The exposed photoresist 20 is then removed in a developing bath at a developing step 84. Preferably, the concentration .27 to .29
A photoresist developer commercially available from Shipley is used as a microposit 351 with N, temperature of 20 ° C., and time of 25 seconds. In this example, the exposed photoresist is attacked in a tank in which the developer is agitated. Upon completion of developing step 84, the resulting developed photoresist forms the pattern shown in Figure 1c. This pattern is the first area exposed and removed by the action of the developer.
22 and a second region in which the unexposed photoresist 20 remains. The first region 22 of this embodiment is actually the support 10.
Is an opening in the photoresist layer 20 where is exposed.

A thin reflective layer 30 of metal such as aluminum is then deposited 86 to create the structure shown in Figure 1d.
At the top of the developed photoresist. The reflective layer 30 extends over both the first and second regions 22, 24 and covers the exposed portions of the support 10 formed in the openings in the photoresist layer 20. After the reflective layer 30 is formed, the structure is visually inspected for pinholes. In this embodiment, the reflective layer 30 is made of aluminum,
Has a reflectance of 75-85%. Other metals such as copper and gold may also be used in other embodiments. In this example, the reflective layer 30 is deposited on the support 10. For example, 48
A Stokes vacuum evaporator model 426-6 with an inch diameter chamber can be used.

In processing step 88, a protective coating 40 is provided on the reflective layer 30 to form the structure shown in Figure 1e. For example,
This protective coating 40 may be spin coated or roller coated.
It may be a UV curable polymer coated by any of the coating techniques. A suitable polymer is commercially available from Dainippon Ink and Chemicals as "Polymer-SD / 17". Preferably, the thickness of protective coating 40 is controlled at 10 microns. Preferably, the polymer is UV cured with a UV light source commercially available from, for example, American Altra Violet, having an intensity of 200 watts per meter, an arc length of 25 inches, and a position 6 inches above the support 10. Preferably, the support 10 is passed under this light source on a conveyor having a linear speed of 240 inches per minute.

The structure shown in FIG. 1e is a completed recording medium 50 readable through the support 10. An incident read beam directed at the support 10 is reflected by the reflective layer 30 in both the first area 22 and the second area 24. The difference in optical path length in these two regions is selected to provide a covering interference of the read beam when reflected from these two portions of reflective layer 30. Following the coating step 88,
The recording medium is inspected by reading the recorded information to match the accuracy of the recording operation.

In this example, the completed recording medium 50 of Figure 1e is adhered to a second completed recording medium 50 'by an adhesive layer 60 to form a completed disc. This is accomplished in step 90 of FIG. In this embodiment, the adhesive layer 60 may be an adhesive commercially available from 3M under the trade name No. 4696. In this way, a double-sided recording medium is obtained.

Following the gluing step 90, a suitable adhesive tape is applied to the finished disc to confirm the recorded program,
The finished package is shrink-wrapped, inserted into a sleeve or jacket to protect the disc from contamination and scratches.

Second Embodiment Referring to FIGS. 2a-2f, the second embodiment shown in FIG. 2 is similar in many respects to the first embodiment of FIG.
However, the embodiment of FIG. 2 uses a modulated light source and a different type of support to expose the photoresist.

As shown in FIG. 2, the first step is to inspect the incoming support 110. In this example, the support 110 is an optical grade glass disc having the same physical dimensions as the support 10 described above. After the acceptance test, the support 110 is washed in a series of wash solutions, deionized water, alcohol, and a Freon bath.

The support 110 is then visually inspected for contamination, and a 1200Å thick photoresist layer 120 is deposited on the support 10 in a coating step 180. The same photoresist and coating techniques described above can be used. The coating step 180 produces the structure shown in Figure 2a. This structure is HE at 90 ℃ for about 30 minutes
It is baked in a PA filtration convection oven and then visually inspected for particulate contamination. In addition, the thickness of photoresist 120 is examined.

In this embodiment, the baked photoresist 120 is
It is exposed in a laser recording step 182 as shown in Figure 2b. In this step 182, a time modulated laser writing beam 170 is used to expose selected areas 122 of photoresist 120. In this example, the modulated laser beam 170 has a rated power of 350 milliwatts, 75 to
It is generated by an argon ion laser operating at a wavelength of 457.9 nanometers with an operating power of 250 milliwatts. In this example, the exposure spot size with a radius dimension of .5 microns and a tangential dimension of .35 microns is .95.
Generated through a lens such as the Olympus eyepiece 1990 which has a release number of. Laser beam modulation can be obtained, for example, using a modulator of the type marketed by Coffeelent as model 3050.

The exposed area 122 of the photoresist 120 is removed and the photoresist is removed.
The exposed photoresist is then developed in step 184 to create the structure shown in 2c where the 120 unexposed areas 124 remain. This developing step 184 can be accomplished with a developer commercially available from Shipley as a microposit used at a concentration of .27 to .29 N, a temperature of 20 ° C. and a time of 13 seconds. In this embodiment, it is preferable to use the spraying method for development.

In a next processing step 186, a thin layer of aluminum (thickness about 1200Å) is deposited over the photoresist 120 to create the structure shown in Figure 2d. In this example, the same evaporation technique as described above can be used,
The reflectance of the reflective layer 130 is selected to be 75 to 85%. The structure of Figure 2d is then visually inspected for pinholes. If excessive pinholes are found, the glass support pair 110 is recirculated. If not, step 1
88 A protective coating 140 is provided. In this example, spin coating techniques are preferably used, and the same UV curable polymers and UV curing techniques described above are preferably used. At this point, the structure shown in FIG. 2e has developed, which is the finished recording medium 50 readable from the exposed surface of the support pair 110. Preferably, the recording medium 50 is inspected by optically reading the stored information to confirm the accuracy of the recording process.

In processing step 190, recording medium 50 is adhered to plastic support pair 165 to provide a finished disc having the desired thickness, strength and weight. In this example, the gluing step 190 can be performed using a gluing layer 160 such as that marketed as Adhesive No. 4693 by 3M Company. As mentioned above, the completed disc is displayed,
After packaging and wrapping, the process shown in FIG. 2 is completed.

It will be apparent from the above description that two embodiments have been described, both of which utilize the technique of photo-etching to produce an optically readable recording medium with significant advantages. The present invention is based on the specific materials and processes described above.
It should be understood that the parameters are not limited. Furthermore, in all applications it is not essential to remove the entire thickness of exposed photoresist. If desired, a negative type photoresist can be substituted for the positive type photoresist described above, and only a portion of the photoresist exposed area is exposed to create a recess that creates the desired difference in optical path length of the read beam. Photoresist can be used to remove. Further, various materials can be used for the photoresist layer. As used herein and in the claims below, the term "photoresist" refers to a type of precursor that is developable after an exposure operation to create first and second regions of different thickness. It is intended to be broadly construed to incorporate timber volume.

Accordingly, the above detailed description is to be regarded as illustrative rather than restrictive, and it is understood that the following claims, including all equivalents, define the scope of the invention. Is intended.

[Brief description of drawings]

FIG. 1 is a flow system diagram of the first embodiment of the production process of the present invention. 1a to 1f are sectional views of the recording medium taken at each stage of the production process of FIG. FIG. 2 is a flow system diagram of the second embodiment of the production process of the present invention. 2a to 2f are sectional views of the recording medium taken at each stage of the production process of FIG. 10,110 …… Support, 20,120 …… Photoresist 22,122 …… First area, 24,124 …… Second area 30,130 …… Reflective layer, 40,140 …… Protective layer

Front Page Continuation (72) Inventor Vinay Kumar Samara Parry United States Anaheim El 204 North Crisden Street 1275 (72) Inventor Thomas M Whiteworth United States Huntington Beach California Twelve's Street 416 (72) Inventor Lamb Chandler Lady Nomura United States Arvin Columbus, California 32 (56) References JP 62-110636 (JP, A)

Claims (21)

[Claims] 1. An information recording medium adapted to be used together with a reading beam, comprising: a support having first and second surfaces; and a support provided on the first surface of the support. A photoresist layer, and a reflective layer deposited on the photoresist layer, the photoresist layer defining an array of recesses therein, the recesses having a selected depth, And readings incident on the second surface of the support both in a first region containing the recesses and in a second region between the recesses, the readings being distributed in a pattern indicative of selected information. Both the support and the photoresist layer are configured to transmit the read beam so that a part of the beam is reflected to the outside of the support by the reflective layer, and (a) the first beam. In the area the support by the reflective layer The recess to provide destructive interference between the portion of the read beam that is reflected to the outside and (b) the portion of the read beam that is reflected to the outside of the support by the reflective layer in the second region. An information recording medium, characterized in that the selected depth is selected. 2. The information recording medium according to claim 1, wherein the selected recording information includes audio information, and the recording medium includes an audio disc. 3. The information recording medium according to claim 1, wherein the selected storage information includes video information, and the recording medium includes a video disc. 4. The information recording medium according to claim 1, wherein the reflective layer contains a reflective metal. 5. An information recording medium according to claim 1, wherein the selected depth of the recess of the photoresist layer is about .12 microns. 6. The information recording medium according to claim 1, wherein the reflective layer has a reflectance of 75% or more. 7. The information recording medium according to claim 1, further comprising a protective layer deposited on the reflective layer to protect the reflective layer from physical damage. 8. Further comprising at least one additional layer provided on the reflective layer and effective to inhibit reading of the selected stored information from the first side of the support. The information recording medium according to claim 1, wherein 9. The claim, wherein the recess extends completely through the photogist layer and the reflective layer is attached to the first surface of the support in the recess. The information recording medium according to item 1. 10. The information recording medium according to claim 1, wherein the photoresist layer is directly attached to the first surface of the support. 11. A method of manufacturing an information recording medium in which information is recorded for subsequent reading by a read beam, comprising: (a) a support having first and second surfaces for transmitting the read beam. B) coating said first surface of said support with a photoresist layer adapted to transmit said read beam; and c) said photoresist layer to create first and second areas of different exposure. Exposing at least a portion of the photoresist layer in the first region to create a recess having a selected depth, and e) removing the recess of the photoresist layer and the first region of the photoresist layer. A reflective layer adapted to reflect the read beam on both the first and second areas, the reflective layer being provided on the recess. To create destructive interference in the second surface of the support between the read beam and the read beam reflected from the reflective layer overlying the second region of the photoresist layer. A method for manufacturing an information recording medium, characterized in that the selected depth of the recess is formed. 12. The method according to claim 11, wherein the exposing step includes a step of contact-exposing the photoresist layer through a master. 13. The method of claim 11 wherein said exposing step comprises the step of sequentially exposing said photoresist layer with a time modulated light source. 14. The method of claim 11 wherein the reflective layer comprises a metal layer. 15. The first and second regions define a pattern of stored audio information, and the coated substrate formed in step (e) comprises an audio disc. The method according to claim 11, wherein: 16. A method according to claim 1, wherein the first and second areas define a pattern of stored video information, and the coated substrate of step (e) comprises a video disc. Scope The method according to clause 11. 17. The method of claim 11 wherein the selected thickness of the photoresist layer is about .12 microns. 18. The method according to claim 11, wherein the reflective layer has a reflectivity of 75% or more. 19. The method of claim 11 further comprising the step of coating the reflective layer with a protective layer to protect the reflective layer from physical damage. 20. The method further comprises the steps of defining a pattern of stored information in the first and second regions and providing at least one additional layer on the reflective layer, the at least one additional layer supporting the support. A method according to claim 11, characterized in that it is effective in suppressing the reading of information from the first side of the body. 21. The recess created in step (d) extends completely through the photoresist layer, and the reflective layer in the first region of the first surface of the support. The method according to claim 11, characterized in that it is attached to