CA1298728C - Optical memory element and manufacturing method thereof - Google Patents
Optical memory element and manufacturing method thereofInfo
- Publication number
- CA1298728C CA1298728C CA000516113A CA516113A CA1298728C CA 1298728 C CA1298728 C CA 1298728C CA 000516113 A CA000516113 A CA 000516113A CA 516113 A CA516113 A CA 516113A CA 1298728 C CA1298728 C CA 1298728C
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Abstract
ABSTRACT OF THE DISCLOSURE
A method is disclosed for manufacturing an optical memory element, comprising the steps of providing a substrate, disposing a resist film on the substrate, providing a photo-mask carrying a guide groove pattern on the resist film so as to position the photo-mask over a predetermined position of the substrate, forming a guide groove pattern latent image on the resist film, developing the guide groove pattern latent image formed on the resist film, conducting an etching operation through the developed guide groove pattern so as to form guide grooves in the substrate, removing the resist film from the substrate, and disposing a recording medium layer on the substrate having the guide grooves formed therein.
A method is disclosed for manufacturing an optical memory element, comprising the steps of providing a substrate, disposing a resist film on the substrate, providing a photo-mask carrying a guide groove pattern on the resist film so as to position the photo-mask over a predetermined position of the substrate, forming a guide groove pattern latent image on the resist film, developing the guide groove pattern latent image formed on the resist film, conducting an etching operation through the developed guide groove pattern so as to form guide grooves in the substrate, removing the resist film from the substrate, and disposing a recording medium layer on the substrate having the guide grooves formed therein.
Description
The present invention relates to an optical memory element capable of at least one operation selected from recording, reproducing and erasing by means of optical beam irradiation, and more specifically to an optical memory element substrate and a photo-mask for use in trans-scribing guide truck and truck address patterns onto an optical memory element substrate.
of late, demand for optical memory elements has increased year by year due to their high density and large capacity. Optical memory elements can be classified into three types in terms of their manner of use: read-only memory, add-on memory and erasable memory.
The optical memory elements ensure high density and large capacity because a bit (information recording unit), which is determined solely by the optical beam diameter, can be made as small as about l ~m in size.
This fact, however, places a number of restrictions on an optical memory system; optical beam positioning must be extremely accurate in order to record information precisely in a predetermined point or reproduce proper information recorded at a preselected point. In the case of a read-only type optical memory, in general, address data can be recorded together with data information so that it is possible to properly position the optical beam while recorded data information is being reproduced. For add-on memory or erasable memory type, on the other hand, it is difficult to record address data together with data information in the memory. Therefore, in an add-on memory or erasable memory, guide signals or guide addresses are normally recorded on the memory substrate.
For instance, an optical memory element to be used as an add-on or erasable memory normally has guide trucks in the substrate, to guide an information-recording or -reproducing beam spot to a specified position on the optical memory element. In many cases, truck address-indicating data is written in a part of each guide truck to locate the guide truck.
lZ987Z8 It is an object of the present invention to provide an optical memory element in which guide trucks and truck addresses are accurately formed on the substrate of an optical memory element.
Another object of the invention is to provide a method for manufacturing an optical memory element, which method ensures accurate formation of guide trucks and truck addresses.
Another object of the invention is to provide 10 a mask which facilitates coincidence between the guide truck center and the disc center hole when transcribing guide trucks and addresses on a resist film applied on an optical disc.
Still another object of the present invention 15 is to provide a photo-mask which prevents deficient close contact between a resist film and the photo-mask from being caused by a rise of the resist film on the peripheral portion of the disc glass.
A further object of the present invention is 20 to provide improvement in the configuration of a glass substrate so as to obtain guide trucks and address-indicating grooves of more accurate shape.
Accordingly, the invention provides a method for manufacturing an optical memory element, comprising 25 the steps of providing a substrate, disposing a resist film on the substrate, providing a photo-mask carrying a guide groove pattern on the resist film so as to position the photo-mask over a predetermined position of the substrate, forming a guide groove pattern latent image on the resist 30 film, developing the guide groove pattern latent image formed on the resist film, conducting an etching operation through the developed guide groove pattern so as to form guide grooves in the substrate, removing the resist film from the substrate, and disposing a recording medium layer 35 on the substrate having the guide grooves formed therein.
The substrate is of disc shape with a hole in rs its center. The photo-mask is provided with a marker .; ~, ~,.
lZ987Z8 of the shape corresponding to the center hole in the disc substrate and a pattern corresponding to guide trucks to be formed on the disc substrate.
The photo-mask may be cut away at a position corresponding to the rise of the resist film.
The peripheral portion of the substrate may be ground so as to be inclined such that the plane of the substrate with the grooves formed therein is higher than the rise of the resist film which can occur on the peripheral portion of the substrate when the resist film is applied on the substrate.
The present invention will be more fully under-stood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein:
Fig. 1 is a perspective view of the essential part of a conventional glass substrate of an add-on memory or erasable memory after grooves have been formed thereon;
Fig. 2 is a perspective view o a typical optical memory element (optical disc);
Fig. 3 is a sectional view showing part of an optical disc system;
Fig. 4 is a sectional view showing the manner of contact between the glass substrate and the photo-mask of a conventional optical memory element;
Fig. 5 is a sectional view explaining the manufac-turing steps of an optical memory element according to an embodiment of the present invention;
Fig. 6 is a plan view o an embodiment of an optical disc photo-mask of the present invention;
Fig. 7 is a plan view showing a part of another embodiment of optical disc photo-mask of the present invention;
Fig. 8 is a partially enlarged sectional view of another embodiment of an optical disc photo-mask of the present invention;
Fig. 9 is a sectional view showing the entire ~Z98~28 photo-mask of Fig. 8;
Figs. 10 (a) and 10 (b) are partially enlarged sectional views showing other embodiments of optical memory element photo-mask of the present invention;
Fig. 11 is also a partially enlarged sectional view showing still another embodiment of optical memory element photo-mask of the present invention;
Figs. 12 (a) and 12 ~b) are a plan view and a sectional view, respectively, of the glass substrate for an optical memory element;
Figs. 13 (a), 13 (b) and 13 (c) are partially enlarged sectional views of glass substrates for embodiments of optical memory elements of the present invention;
Figs. 14 (a), 14 (b) and 14(c) are partially enlarged sectional views of optical memory element glass substrates on which resist film is applied.
Fig. 1 shows the essential part of a memory substrate of an add-on or erasable memory in perspective view. As shown, stripe-shaped grooves are formed in the substrate, and information is recorded or reproduced along the grooves. Although not shown, the grooves are intermittent in the circumferential direction so as to provide address bit information for each groove. In a disc shaped optical memory element as shown in Fig. 2, in particular, guide trucks 3 and truck address portion 2 (together with sector address if the trucks are divided into many sectors) are formed concentrically or spirally in substrate 1. For the purpose of simplicity, only one truck 3 and only one address portion 2 are shown in Fig.
2.
A number of methods have been practiced for manufacturing a disc substrate provided with trucks and addresses as described above. A mask which carries guide trucks and addresses thereon may be placed in airtight manner on a resist film applied on a disc glass, to form the trucks and addresses in the form of grooves or pits directly on the disc glass. In this method, it is essential to form the guide trucks in such a manner that the guide truck center coincides as precisely as possible with the center hole of the disc glass. With poor concentricity between the guide trucks and the disc glass, when the disc glass is rotated for recording, reproduction or erasion with the center hole fixed on a rotary shaft 4, as shown in Fig. 3, the guide trucks vibrate significantly with respect to a recording, reproducing or erasing laser beam 5, hampering truck servo operation for controlling the lens position. For the above reason, it has been necessary to join the guide truck center and the disc glass center holeas precisely as possible (with eccentricity allowance preferably within 20 ~m), in the optical exposure for guide trucks.
The above manufacturing method can cause another problem in the guide truck and truck address pattern trans-cription process. Resist film 6, when applied, tends to have a partial rise 8 at the peripheral portion of the disc glass as shown in Fig. 4. This rise 8 often impairs close contact between the resist film 6 and photo-mask 7, although it is desirable that they be disposed in close contact with each other. The width of this deficient degree of close contact is usually 1 to 2 mm. In Fig.
4, the guide truck and address pattern on the photo mask 7 are omitted. The deficiency in degree of close contact prevents the guide trucks and truck addresses from being formed at proper positions.
Fig. 5 shows the manufacturing steps for a substrate of an optical memory element in accordance with an embodiment of the present invention. Referring now to Fig. 5, the manufacturing method of the optical memory element substrate will be described stepwise.
Step I
An optical memory element glass substrate which is highly reliable with respect to oxygen and moisture penetration (or which does not permit oxygen or moisture penetration) is cleaned. A photo resist film 6 is applied lZ987Z8 on the glass substrate l (See Fig. 5 (a)). The thickness of the photo resist film 6 is preferably about lO0 nm to 500 nm.
Step II
A mask plate 7 on which guide truck and address information have been patterned is placed in airtight manner over the photo resist film 6 on the glass substrate l. Then, the mask plate 7 is irradiated with ultraviolet ray A to transcribe the mask pattern of the mask plate 7 onto the photo resist film 6 (See Fig. 5 (b)). Since the optical memory element is disc shaped, it is desirable that the mask plate 7 is round.
Step III
The photo resist film 6 with the mask pattern thereon is developed so as to form grooves in the resist film 6 (See Fig. 5 (c)).
Step IV
The glass substrate 1 covered with the photo resist film 6 having grooves formed therein is subjected to a wet etching operation or a dry etching operation such as sputtering (reactive ion etching) in an etching gas atmosphere such as CF4 or CHF3. Grooves 8 are then ormed in the glass substrate l (See Fig. 5 (d)).
Step V
The developed resist film 6 is removed from the glass substrate 1 by means of sputtering in an 2 atmosphere, or dissolving in a solvent such as acetone.
In this way, the glass substrate 1 with the grooves 8 formed therein is produced (See Fig. 5 (e)).
Step VI
After step V, a recording medium layer is formed on the glass substrate l having the grooves 8 formed therein.
The glass substrate l having grooves for guide trucks and guide address information is completed through the above process. According to this process, the mask plate 7 with a pattern for guide trucks and guide address information thereon, prepared in advance, is placed in lZ987Z8 airtight manner over the glass substrate 1 coated with the photo resist film 6, so as to transcribe the mask pattern of the mask plate 7. Therefore, the time required for transcribing the guide pattern can be substantially reduced.
The optical disc mask 7 used in the above manufac-turing process will now be described.
Fig. 6 is a plan view of an embodiment of an optical disc mask of the present invention. The mask 7 has been produced by forming a Cr or CrO film over, say, a quartz glass disc plate and etching the film to produce the pattern shown in Fig. 6. Referring to Fig.
6, the shaded part indicates the areas where Cr or CrO
remains unremoved. "a" is an information area in a part lS of which are formed trucks 3 and addresses 2 spirally or concentrically. Cr or CrO is removed in the area "b"
of the mask 7. A positioning reference marker C is provided in the area "b". Concentricity with the trucks can be secured by recording the reference marker C and the guide trucks simultaneously by using the same recording device.
For Example, when the marker C has virtually the same diameter as the glass disc center hole, the marker C can be easily adjusted to the disc center hole when placing the mask on the glass disc for pattern transcription, so that it is easy to achieve concentricity of the trucks with the disc.
Tha marker need not be limited to the above embodiment. As shown in Fig. 7, two markers C may be recorded at an interval of about 10 to 20 ~m and with diameters such that the glass disc center hole is positioned between the two markers. Assuming the glass disc center hole is about 15 mm in diameter, for instance, the two markers may have the diameters of about 14.09 mm and 15.01 mm, respectively. With such markers, it is easy to position the mask with respect to the glass disc center hole. Gener-ally, the center hole of a glass disc has a high degree of roundness but often differs in diameter, for instance 1~98728 within the range of about 15 + 0.5 mm, depending upon the manufacturing process. To provide for various center hole diameters of the disc, a plurality of markers C with different diameters may be formed concentrically on a mask so that the same mask can be used for discs with different center hole diameters. Alternatively, instead of using the marker C of Fig. 6, it is possible to use the area "b" as a marker if the area "b" is made narrower.
In the above embodiment, Cr or CrO is used in the shaded area of Fig. 6. However, other metal film such as Ni, Ti or Ta may be used in place of Cr or Cro.
As will be understood from the above, by using the mask of the present invention, it is possible to improve theconcentricity of the memory disc guide truck with the memory disc center hole, thus minimizing vibration of the guide truck with respect to the optical beam in recording, reproducing or erasing information on the disc. Consequently, servo operation of an objective lens for condensing a laser beam becomes easy.
Another embodiment of mask 7 used in the manufactur-ing method of the present invention will now be described with reference to Fig. 8 which is a partially enlarged sectional view of another embodiment of an optical memory element photo-mask of the present invention. As shown, a groove 9 is formed in the photo-mask 7 at a position facing the peripheral portion of the glass disc 1, to accommodate the rise 8 of the resist film 6, thus eliminating deficient close contact between the glass disc 1 and the photo-mask 7.
For a glass disc of about 130 + 0.1 mm diameter, for instance, the groove desirably has a width "Y" (about 4 mm for example) with the inside diameter of a circle defined by the groove being "X" (127 mm for example) as - shown in Fig. 9. The depth "Z" of the groove should be about 0.2 to 0.5 mm. The sectional shape of the groove is not necessarily square as shown in Fig. 9. It may be triangular as shown in Fig. 10 (a) or semi-circular , lZ987Z8 as shown in Fig. 10 (b). In short, the groove provided in the photo-mask may be of any shape as long as it can absorb the rise 8 of the resist film 6 on the periphery of the glass disc 1. In this sense, instead of forming a groove, peripheral portion 10 of the photo-mask 7 may be made thinner than the central portion as shown in Fig.
ll, to absorb the rise 8 of the resist film 6.
By using the photo-mask of the present invention, the guide truck and truck address pattern for an optical memory element can be properly transcribed onto the resist film applied on the optical memory element substrate.
The sectional shape of the glass disc substrate will now be described with reference to the drawings.
Fig. 12 (a) i~ a plan view of the glass disc substrate 1 and Fig. 12 (b) is a sectional view of the glass disc substrate 1. Outer edges 15 of the glass disc substrate 1 are chamfered, as shown.
Fig. 13 is an enlarged sectional view of the chamfered edge 15. Fig. 13 (a) is a sectional view of the chamfered edge of a conventional glass disc substrate, and Figs. 13 (b) and 13 (c) are sectional views showing the chamfered edge configuration of glass disc substrates of the present invention. In both of Figs. 13 (b) and 13 (c), surface portion 17 without guide grooves is ground to be lower than glass disc substrate surface plane 18.
Figs. 14 (a), 14 (b) and 14 (c) are sectional views of the glass disc substrates having the edges shown in Figs. 13 (a), 13 (b) and 13 (c), respectively, on which resist film has been applied by the spin coat method.
At the edges of the glass disc substrates, the resist film has a rise 8 due to surface tension.
On the glass disc substrate of conventional shape shown in Fig. 14 (a), the rise 8 of the resist film 6 is higher than the resist film surface plane 11. When placing the mask plate 7 on the glass substrate 1 in manu-facturing step II, under this condition, the mask plate 7 will be positioned on plane 11', resulting in defective lZ987Z~
contact over a large area between the mask plate 7 and the resist film 6. On the glass disc substrate of the shape shown in Figs. 14 (b) or 14 (c), in contrast, the rise 8 of the resist film 6 is lower than the resist film surface plane 11 so that the mask plate 7 can be positioned on the resist film surface plane 11. Consequently, an adequate degree of contact can be obtained between the mask plate 7 and the resist film 6 over the area 16 with the guide grooves formed thereon.
As will be appreciated from the above, according to the present invention, the guide grooves formed in the optical memory element are entirely of proper shape, thus reducing noise in reproduced signals.
While only certain embodiments of the present invention have been described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as claimed.
of late, demand for optical memory elements has increased year by year due to their high density and large capacity. Optical memory elements can be classified into three types in terms of their manner of use: read-only memory, add-on memory and erasable memory.
The optical memory elements ensure high density and large capacity because a bit (information recording unit), which is determined solely by the optical beam diameter, can be made as small as about l ~m in size.
This fact, however, places a number of restrictions on an optical memory system; optical beam positioning must be extremely accurate in order to record information precisely in a predetermined point or reproduce proper information recorded at a preselected point. In the case of a read-only type optical memory, in general, address data can be recorded together with data information so that it is possible to properly position the optical beam while recorded data information is being reproduced. For add-on memory or erasable memory type, on the other hand, it is difficult to record address data together with data information in the memory. Therefore, in an add-on memory or erasable memory, guide signals or guide addresses are normally recorded on the memory substrate.
For instance, an optical memory element to be used as an add-on or erasable memory normally has guide trucks in the substrate, to guide an information-recording or -reproducing beam spot to a specified position on the optical memory element. In many cases, truck address-indicating data is written in a part of each guide truck to locate the guide truck.
lZ987Z8 It is an object of the present invention to provide an optical memory element in which guide trucks and truck addresses are accurately formed on the substrate of an optical memory element.
Another object of the invention is to provide a method for manufacturing an optical memory element, which method ensures accurate formation of guide trucks and truck addresses.
Another object of the invention is to provide 10 a mask which facilitates coincidence between the guide truck center and the disc center hole when transcribing guide trucks and addresses on a resist film applied on an optical disc.
Still another object of the present invention 15 is to provide a photo-mask which prevents deficient close contact between a resist film and the photo-mask from being caused by a rise of the resist film on the peripheral portion of the disc glass.
A further object of the present invention is 20 to provide improvement in the configuration of a glass substrate so as to obtain guide trucks and address-indicating grooves of more accurate shape.
Accordingly, the invention provides a method for manufacturing an optical memory element, comprising 25 the steps of providing a substrate, disposing a resist film on the substrate, providing a photo-mask carrying a guide groove pattern on the resist film so as to position the photo-mask over a predetermined position of the substrate, forming a guide groove pattern latent image on the resist 30 film, developing the guide groove pattern latent image formed on the resist film, conducting an etching operation through the developed guide groove pattern so as to form guide grooves in the substrate, removing the resist film from the substrate, and disposing a recording medium layer 35 on the substrate having the guide grooves formed therein.
The substrate is of disc shape with a hole in rs its center. The photo-mask is provided with a marker .; ~, ~,.
lZ987Z8 of the shape corresponding to the center hole in the disc substrate and a pattern corresponding to guide trucks to be formed on the disc substrate.
The photo-mask may be cut away at a position corresponding to the rise of the resist film.
The peripheral portion of the substrate may be ground so as to be inclined such that the plane of the substrate with the grooves formed therein is higher than the rise of the resist film which can occur on the peripheral portion of the substrate when the resist film is applied on the substrate.
The present invention will be more fully under-stood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein:
Fig. 1 is a perspective view of the essential part of a conventional glass substrate of an add-on memory or erasable memory after grooves have been formed thereon;
Fig. 2 is a perspective view o a typical optical memory element (optical disc);
Fig. 3 is a sectional view showing part of an optical disc system;
Fig. 4 is a sectional view showing the manner of contact between the glass substrate and the photo-mask of a conventional optical memory element;
Fig. 5 is a sectional view explaining the manufac-turing steps of an optical memory element according to an embodiment of the present invention;
Fig. 6 is a plan view o an embodiment of an optical disc photo-mask of the present invention;
Fig. 7 is a plan view showing a part of another embodiment of optical disc photo-mask of the present invention;
Fig. 8 is a partially enlarged sectional view of another embodiment of an optical disc photo-mask of the present invention;
Fig. 9 is a sectional view showing the entire ~Z98~28 photo-mask of Fig. 8;
Figs. 10 (a) and 10 (b) are partially enlarged sectional views showing other embodiments of optical memory element photo-mask of the present invention;
Fig. 11 is also a partially enlarged sectional view showing still another embodiment of optical memory element photo-mask of the present invention;
Figs. 12 (a) and 12 ~b) are a plan view and a sectional view, respectively, of the glass substrate for an optical memory element;
Figs. 13 (a), 13 (b) and 13 (c) are partially enlarged sectional views of glass substrates for embodiments of optical memory elements of the present invention;
Figs. 14 (a), 14 (b) and 14(c) are partially enlarged sectional views of optical memory element glass substrates on which resist film is applied.
Fig. 1 shows the essential part of a memory substrate of an add-on or erasable memory in perspective view. As shown, stripe-shaped grooves are formed in the substrate, and information is recorded or reproduced along the grooves. Although not shown, the grooves are intermittent in the circumferential direction so as to provide address bit information for each groove. In a disc shaped optical memory element as shown in Fig. 2, in particular, guide trucks 3 and truck address portion 2 (together with sector address if the trucks are divided into many sectors) are formed concentrically or spirally in substrate 1. For the purpose of simplicity, only one truck 3 and only one address portion 2 are shown in Fig.
2.
A number of methods have been practiced for manufacturing a disc substrate provided with trucks and addresses as described above. A mask which carries guide trucks and addresses thereon may be placed in airtight manner on a resist film applied on a disc glass, to form the trucks and addresses in the form of grooves or pits directly on the disc glass. In this method, it is essential to form the guide trucks in such a manner that the guide truck center coincides as precisely as possible with the center hole of the disc glass. With poor concentricity between the guide trucks and the disc glass, when the disc glass is rotated for recording, reproduction or erasion with the center hole fixed on a rotary shaft 4, as shown in Fig. 3, the guide trucks vibrate significantly with respect to a recording, reproducing or erasing laser beam 5, hampering truck servo operation for controlling the lens position. For the above reason, it has been necessary to join the guide truck center and the disc glass center holeas precisely as possible (with eccentricity allowance preferably within 20 ~m), in the optical exposure for guide trucks.
The above manufacturing method can cause another problem in the guide truck and truck address pattern trans-cription process. Resist film 6, when applied, tends to have a partial rise 8 at the peripheral portion of the disc glass as shown in Fig. 4. This rise 8 often impairs close contact between the resist film 6 and photo-mask 7, although it is desirable that they be disposed in close contact with each other. The width of this deficient degree of close contact is usually 1 to 2 mm. In Fig.
4, the guide truck and address pattern on the photo mask 7 are omitted. The deficiency in degree of close contact prevents the guide trucks and truck addresses from being formed at proper positions.
Fig. 5 shows the manufacturing steps for a substrate of an optical memory element in accordance with an embodiment of the present invention. Referring now to Fig. 5, the manufacturing method of the optical memory element substrate will be described stepwise.
Step I
An optical memory element glass substrate which is highly reliable with respect to oxygen and moisture penetration (or which does not permit oxygen or moisture penetration) is cleaned. A photo resist film 6 is applied lZ987Z8 on the glass substrate l (See Fig. 5 (a)). The thickness of the photo resist film 6 is preferably about lO0 nm to 500 nm.
Step II
A mask plate 7 on which guide truck and address information have been patterned is placed in airtight manner over the photo resist film 6 on the glass substrate l. Then, the mask plate 7 is irradiated with ultraviolet ray A to transcribe the mask pattern of the mask plate 7 onto the photo resist film 6 (See Fig. 5 (b)). Since the optical memory element is disc shaped, it is desirable that the mask plate 7 is round.
Step III
The photo resist film 6 with the mask pattern thereon is developed so as to form grooves in the resist film 6 (See Fig. 5 (c)).
Step IV
The glass substrate 1 covered with the photo resist film 6 having grooves formed therein is subjected to a wet etching operation or a dry etching operation such as sputtering (reactive ion etching) in an etching gas atmosphere such as CF4 or CHF3. Grooves 8 are then ormed in the glass substrate l (See Fig. 5 (d)).
Step V
The developed resist film 6 is removed from the glass substrate 1 by means of sputtering in an 2 atmosphere, or dissolving in a solvent such as acetone.
In this way, the glass substrate 1 with the grooves 8 formed therein is produced (See Fig. 5 (e)).
Step VI
After step V, a recording medium layer is formed on the glass substrate l having the grooves 8 formed therein.
The glass substrate l having grooves for guide trucks and guide address information is completed through the above process. According to this process, the mask plate 7 with a pattern for guide trucks and guide address information thereon, prepared in advance, is placed in lZ987Z8 airtight manner over the glass substrate 1 coated with the photo resist film 6, so as to transcribe the mask pattern of the mask plate 7. Therefore, the time required for transcribing the guide pattern can be substantially reduced.
The optical disc mask 7 used in the above manufac-turing process will now be described.
Fig. 6 is a plan view of an embodiment of an optical disc mask of the present invention. The mask 7 has been produced by forming a Cr or CrO film over, say, a quartz glass disc plate and etching the film to produce the pattern shown in Fig. 6. Referring to Fig.
6, the shaded part indicates the areas where Cr or CrO
remains unremoved. "a" is an information area in a part lS of which are formed trucks 3 and addresses 2 spirally or concentrically. Cr or CrO is removed in the area "b"
of the mask 7. A positioning reference marker C is provided in the area "b". Concentricity with the trucks can be secured by recording the reference marker C and the guide trucks simultaneously by using the same recording device.
For Example, when the marker C has virtually the same diameter as the glass disc center hole, the marker C can be easily adjusted to the disc center hole when placing the mask on the glass disc for pattern transcription, so that it is easy to achieve concentricity of the trucks with the disc.
Tha marker need not be limited to the above embodiment. As shown in Fig. 7, two markers C may be recorded at an interval of about 10 to 20 ~m and with diameters such that the glass disc center hole is positioned between the two markers. Assuming the glass disc center hole is about 15 mm in diameter, for instance, the two markers may have the diameters of about 14.09 mm and 15.01 mm, respectively. With such markers, it is easy to position the mask with respect to the glass disc center hole. Gener-ally, the center hole of a glass disc has a high degree of roundness but often differs in diameter, for instance 1~98728 within the range of about 15 + 0.5 mm, depending upon the manufacturing process. To provide for various center hole diameters of the disc, a plurality of markers C with different diameters may be formed concentrically on a mask so that the same mask can be used for discs with different center hole diameters. Alternatively, instead of using the marker C of Fig. 6, it is possible to use the area "b" as a marker if the area "b" is made narrower.
In the above embodiment, Cr or CrO is used in the shaded area of Fig. 6. However, other metal film such as Ni, Ti or Ta may be used in place of Cr or Cro.
As will be understood from the above, by using the mask of the present invention, it is possible to improve theconcentricity of the memory disc guide truck with the memory disc center hole, thus minimizing vibration of the guide truck with respect to the optical beam in recording, reproducing or erasing information on the disc. Consequently, servo operation of an objective lens for condensing a laser beam becomes easy.
Another embodiment of mask 7 used in the manufactur-ing method of the present invention will now be described with reference to Fig. 8 which is a partially enlarged sectional view of another embodiment of an optical memory element photo-mask of the present invention. As shown, a groove 9 is formed in the photo-mask 7 at a position facing the peripheral portion of the glass disc 1, to accommodate the rise 8 of the resist film 6, thus eliminating deficient close contact between the glass disc 1 and the photo-mask 7.
For a glass disc of about 130 + 0.1 mm diameter, for instance, the groove desirably has a width "Y" (about 4 mm for example) with the inside diameter of a circle defined by the groove being "X" (127 mm for example) as - shown in Fig. 9. The depth "Z" of the groove should be about 0.2 to 0.5 mm. The sectional shape of the groove is not necessarily square as shown in Fig. 9. It may be triangular as shown in Fig. 10 (a) or semi-circular , lZ987Z8 as shown in Fig. 10 (b). In short, the groove provided in the photo-mask may be of any shape as long as it can absorb the rise 8 of the resist film 6 on the periphery of the glass disc 1. In this sense, instead of forming a groove, peripheral portion 10 of the photo-mask 7 may be made thinner than the central portion as shown in Fig.
ll, to absorb the rise 8 of the resist film 6.
By using the photo-mask of the present invention, the guide truck and truck address pattern for an optical memory element can be properly transcribed onto the resist film applied on the optical memory element substrate.
The sectional shape of the glass disc substrate will now be described with reference to the drawings.
Fig. 12 (a) i~ a plan view of the glass disc substrate 1 and Fig. 12 (b) is a sectional view of the glass disc substrate 1. Outer edges 15 of the glass disc substrate 1 are chamfered, as shown.
Fig. 13 is an enlarged sectional view of the chamfered edge 15. Fig. 13 (a) is a sectional view of the chamfered edge of a conventional glass disc substrate, and Figs. 13 (b) and 13 (c) are sectional views showing the chamfered edge configuration of glass disc substrates of the present invention. In both of Figs. 13 (b) and 13 (c), surface portion 17 without guide grooves is ground to be lower than glass disc substrate surface plane 18.
Figs. 14 (a), 14 (b) and 14 (c) are sectional views of the glass disc substrates having the edges shown in Figs. 13 (a), 13 (b) and 13 (c), respectively, on which resist film has been applied by the spin coat method.
At the edges of the glass disc substrates, the resist film has a rise 8 due to surface tension.
On the glass disc substrate of conventional shape shown in Fig. 14 (a), the rise 8 of the resist film 6 is higher than the resist film surface plane 11. When placing the mask plate 7 on the glass substrate 1 in manu-facturing step II, under this condition, the mask plate 7 will be positioned on plane 11', resulting in defective lZ987Z~
contact over a large area between the mask plate 7 and the resist film 6. On the glass disc substrate of the shape shown in Figs. 14 (b) or 14 (c), in contrast, the rise 8 of the resist film 6 is lower than the resist film surface plane 11 so that the mask plate 7 can be positioned on the resist film surface plane 11. Consequently, an adequate degree of contact can be obtained between the mask plate 7 and the resist film 6 over the area 16 with the guide grooves formed thereon.
As will be appreciated from the above, according to the present invention, the guide grooves formed in the optical memory element are entirely of proper shape, thus reducing noise in reproduced signals.
While only certain embodiments of the present invention have been described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as claimed.
Claims (35)
1. A method for manufacturing an optical memory element having guide tracks and address tracks for storing information, which comprises the steps of:
applying a photo resist film onto a substrate which includes a centre hole to form a coated substrate;
preparing a photo mask plate by;
forming a mask pattern on said mask plate, said mask pattern comprising a guide track pattern and address track pattern, and forming a position reference marker on said mask plate with reference to said mask pattern for positioning said mask plate;
placing said mask plate on said coated substrate so as to position said position reference marker with reference to said centre hole of said coated substrate;
transcribing, from said mask plate, a latent image of said mask pattern onto said photo resist film;
developing said latent image on said photo resist film to form a developed photo resist film; and etching said substrate so as to form guide tracks and address tracks in said substrate in conformance with said mask pattern, whereby alignment between said centre hole of said substrate and said tracks is improved.
applying a photo resist film onto a substrate which includes a centre hole to form a coated substrate;
preparing a photo mask plate by;
forming a mask pattern on said mask plate, said mask pattern comprising a guide track pattern and address track pattern, and forming a position reference marker on said mask plate with reference to said mask pattern for positioning said mask plate;
placing said mask plate on said coated substrate so as to position said position reference marker with reference to said centre hole of said coated substrate;
transcribing, from said mask plate, a latent image of said mask pattern onto said photo resist film;
developing said latent image on said photo resist film to form a developed photo resist film; and etching said substrate so as to form guide tracks and address tracks in said substrate in conformance with said mask pattern, whereby alignment between said centre hole of said substrate and said tracks is improved.
2. The method of claim 1, wherein said substrate is disc shaped and wherein the shape of said position reference marker corresponds to the shape of said centre hole in said substrate.
3. The method of claim 1, wherein said mask plate includes a peripheral mask portion and wherein a part of said peripheral mask portion is removed before said mask plate is placed on said photo resist film so as to receive any resin portion of said photo resist film that is of improper thickness whereby contact between said mask plate and said substrate is improved.
4. The method of claim 1, wherein said substrate includes a peripheral substrate portion and wherein said peripheral substrate portion is removed before said photo resist film is applied to said substrate so as to receive any risen portion of said photo resist film that is of improper thickness, whereby contact between said mask plate and said substrate is improved.
5. The method of claim 2, wherein said mask plate is prepared by forming a metallic mask film on said mask plate, and etching said mask film to form said mask pattern and said position reference marker means on said mask plate.
6. The method of claim 5, wherein said substrate comprises glass, said mask plate comprises quartz glass, and said metallic mask film comprises Cr, CrO, Ni, Ti, or Ta.
7. The method of claim 6, wherein said photo resist film is applied on said substrate with a spin coating method, said mask plate is placed on said photo resist film in an airtight manner, said mask pattern is transcribed onto said photo resist film by irradiating said mask plate with ultraviolet rays, and said substrate is etched by wet etching or dry etching in a CR4 or CHF3 gas atmosphere.
8. The method of claim 1, further comprising removing said developed photo resist film from said substrate and forming a recording medium layer on said substrate.
9. The method of claim 7, wherein said photo resist film has a thickness of from about 100nm to 500nm.
10. The method of claim 5, wherein said position reference marker means comprises a mark of a similar size as said centre hole etched on said metallic mask film.
11. The method of claim 5, wherein said position reference marker comprises a plurality of marks of various sizes compared to said centre hole etched on said metallic mask film.
12. The method of claim 3, wherein said peripheral mask portion is removed to form a mask groove corresponding to the outer peripheral edge of said photo resist film.
13. The method of claim 12, wherein said mask groove is formed to be square-shaped, tapered, or curved.
14. The method of claim 12, wherein said mask groove is formed with a depth of from about 0.2 to 0.5 mm.
15. The method of claim 4, wherein said peripheral substrate portion is removed by grinding said substrate to form an outer inclined substrate edge which declines from the tracks plane of the portion of said substrate adjacent to where said tracks are to be etched to below said tracks plane at the outer edge of said substrate.
16. The method of claim 15, wherein said outer edge of said substrate comprises a chamfered edge.
17. A method for manufacturing an optical memory element having circular guide tracks and circular address tracks for storing information, which comprises the steps of:
applying a photo resist film onto a disc substrate;
placing a photo mask plate having a mask pattern on said photo resist film, wherein said mask plate has a diameter larger than said substrate, and wherein said mask plate includes a peripheral mask portion which extends beyond the periphery of said photo resist film so as to receive any risen portion of improper thickness of said photo resist film, wherein alignment between said mask plate and said disc substrate is improved;
transcribing said mask pattern from said mask plate onto said disc substrate so as to form circular guide tracks and circular address tracks thereon;
removing said photo resist film and said photo mask plate from said substrate; and disposing a recording medium on said substrate so as to form said optical memory element.
applying a photo resist film onto a disc substrate;
placing a photo mask plate having a mask pattern on said photo resist film, wherein said mask plate has a diameter larger than said substrate, and wherein said mask plate includes a peripheral mask portion which extends beyond the periphery of said photo resist film so as to receive any risen portion of improper thickness of said photo resist film, wherein alignment between said mask plate and said disc substrate is improved;
transcribing said mask pattern from said mask plate onto said disc substrate so as to form circular guide tracks and circular address tracks thereon;
removing said photo resist film and said photo mask plate from said substrate; and disposing a recording medium on said substrate so as to form said optical memory element.
18. The method of claim 17, wherein part of said peripheral mask portion is removed to form a mask groove which receives any risen portion of improper thickness of said photo resist film.
19. The method of claim 18, wherein said mask groove is formed to be square-shaped, tapered or curved.
20. The method of claim 17, wherein said peripheral mask portion is thinner than the central portion of said photo mask plate so as to receive any risen portion of improper thickness of said photo resist film.
21. The method of claim 17, wherein said mask groove is formed with a depth of from about 0.2 to 0.5 mm.
22. The method of claim 17, wherein said substrate has a peripheral substrate portion which is removed before said photo resist is applied to said substrate so as to receive any risen portion of improper thickness of said photo resist film.
23. The method of claim 22, wherein said peripheral substrate portion is removed to form an outer inclined substrate edge which declines from the tracks plane of the portion of said substrate adjacent to where said tracks are to be etched to below said tracks plane at the outer edge of said substrate.
24. The method of claim 23, wherein said outer edge of said substrate comprises a chamfered edge.
25. The method of claim 17, wherein said substrate includes a centre hole formed therein and said photo mask plate includes a position reference marker formed thereon so that when said mask plate is placed on said photo resist film said reference marker is positioned so as to properly align said mask plate over said substrate.
26. The method of claim 13, wherein said substrate has a peripheral substrate portion which is removed before said photo resist is applied to said substrate so as to receive any risen portion of improper thickness of said photo resist film.
27. A mask plate used to manufacture an optical memory element which comprises:
a mask pattern formed thereon, said mask pattern comprising guide track and address track patterns, and a position reference marker formed on said mask plate for positioning said mask plate in proper alignment with an optical memory element, wherein said mask plate includes a peripheral removed section which corresponds to the peripheral portion of the substrate coated with a resist film of said optical memory element for accommodating any rise in the peripheral portion of said resist film.
a mask pattern formed thereon, said mask pattern comprising guide track and address track patterns, and a position reference marker formed on said mask plate for positioning said mask plate in proper alignment with an optical memory element, wherein said mask plate includes a peripheral removed section which corresponds to the peripheral portion of the substrate coated with a resist film of said optical memory element for accommodating any rise in the peripheral portion of said resist film.
28. The mask plate as defined in claim 27, wherein said peripheral removed section is a groove which is square shaped.
29. The mask plate as defined in claim 27, wherein said peripheral removed section is a groove which is triangular shaped.
30. The mask plate as defined in claim 27, wherein said peripheral removed section is a groove which is semi-circular shaped.
31. The mask plate as defined in claim 27, wherein said peripheral removed section extends from a central portion to the peripheral edge of said mask plate.
32. The mask plate as defined in claim 27, wherein said position reference marker corresponds to the shape of a centre hole formed in the substrate of said optical memory element.
33. A mask plate used to manufacture an optical memory element having guide tracks and address tracks for storing information which comprises:
a disc shaped plate having a guide track pattern and address track pattern formed thereon, and a position reference marker formed near the centre of said plate for aligning said mask plate with the centre hole of a substrate of an optical memory element and aligning said guide and address track patterns for transcription onto said substrate.
a disc shaped plate having a guide track pattern and address track pattern formed thereon, and a position reference marker formed near the centre of said plate for aligning said mask plate with the centre hole of a substrate of an optical memory element and aligning said guide and address track patterns for transcription onto said substrate.
34. A substrate used to form an optical memory element which comprises a disc shaped plate having first and second faces and having first and second chamfered outer edges for accommodating any rise in the peripheral portion of a resist film formed thereon, wherein first and second inner peripheral portions adjacent to said chamfered outer edges are formed so as to taper from the surface planes of said first and second faces to said chamfered outer edges.
35. A substrate used to form an optical memory element which comprises a disc shaped plate having first and second faces and having first and second chamfered outer edges for accommodating any rise in the peripheral portion of a resist film formed thereon, wherein said chamfered outer edges taper from the surface planes of said first and second faces so as to form rounded, convex shaped edges.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000516113A CA1298728C (en) | 1985-08-30 | 1986-08-15 | Optical memory element and manufacturing method thereof |
| US08/074,272 US5470694A (en) | 1985-08-30 | 1993-06-10 | Optical memory element and manufacturing method thereof |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19293785A JPS6252741A (en) | 1985-08-30 | 1985-08-30 | Mask for optical memory disk |
| CA000516113A CA1298728C (en) | 1985-08-30 | 1986-08-15 | Optical memory element and manufacturing method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1298728C true CA1298728C (en) | 1992-04-14 |
Family
ID=42116049
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000516113A Expired - Lifetime CA1298728C (en) | 1985-08-30 | 1986-08-15 | Optical memory element and manufacturing method thereof |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS6252741A (en) |
| CA (1) | CA1298728C (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5814336A (en) * | 1981-07-20 | 1983-01-27 | Toshiba Corp | Information storage medium and its production |
-
1985
- 1985-08-30 JP JP19293785A patent/JPS6252741A/en active Granted
-
1986
- 1986-08-15 CA CA000516113A patent/CA1298728C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6252741A (en) | 1987-03-07 |
| JPH0447912B2 (en) | 1992-08-05 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |