JP2718992B2 - Dual type grating - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual grating in which a diffraction grating is duplicated on both front and back surfaces of a substrate.

2. Description of the Related Art Conventionally, as a method of forming a grating on the surface of an optical information recording medium such as an optical disk, for example, Japanese Patent Application Laid-Open No.
There is one disclosed in Japanese Patent No. 16105. A method of producing this by a well-known ultraviolet curing method (2P method) using an optical disk as an example will be described with reference to FIGS. 5 to 7.

First, a stamper (die) 3 is fixed on a support plate 2 placed under the U-shaped arm 1, and an ultraviolet curable resin 4 is poured into the surface of the stamper 3. On the other hand,
The acrylic plate 7 is vacuum-chucked at the peripheral end of the holder 6 fixed to the upper cylinder 5, and air is introduced between the holder 6 and the acrylic plate 7 to make the acrylic plate 7 convex. Then, as shown in FIG. 6, the acrylic plate 7 is lowered in this state, pressed from above the ultraviolet curable resin 4 to bring the acrylic plate 7 into close contact with the stamper 3, and then the holder 6 is detached. Then, in a state where the acrylic plate 7 and the stamper 3 are brought into close contact with each other, as shown in FIG. 7, ultraviolet rays (UV) are exposed from the acrylic plate 7 side to be cured, and then the stamper 3 is peeled off. Thus, a desired optical disk can be obtained.

Problems to be Solved by the Invention In addition to forming a diffraction grating on one side of a substrate (corresponding to the acrylic plate 7 in the above-described example) using the above-described ultraviolet curing method, diffraction gratings are formed on both front and back surfaces of the substrate. There is a dual type grating to be formed. Also in this case, after forming the diffraction grating on the front surface side of the substrate by the ultraviolet curing method, the diffraction grating can be similarly formed on the back surface side. In this case, the substrate is made of a flexible plastic resin (corresponding to the acrylic plate 7 described above), has a large expansion coefficient due to the influence of temperature and humidity, and has a thickness and a thickness of the substrate due to the influence of the surrounding environment. The grating pitch fluctuates and its application range is rather limited.

In the process of manufacturing a dual-type grating in which diffraction gratings are formed on the front and back surfaces of the same substrate, there are the following problems. First, since the substrate itself has good transparency, it is not possible to separately expose the front and back surfaces after applying the photoresist on both the front and back surfaces of the substrate at the same time.
Second, since the shape of the diffraction grating itself is very fragile, it is not possible to duplicate the diffraction grating on one side by the conventional process as shown in FIGS. Can not. Thirdly, the method of duplicating a dual type grating by such a method is very poor in mass productivity.

On the other hand, when such a dual-type grating is used as an optical path separating means of a signal detection optical system to detect a focus error signal, a track error signal, and a magneto-optical signal (the details will be described later with reference to FIG. 4). ), It is necessary to improve the diffraction efficiency of these diffraction gratings in order to increase the efficiency of signal detection. In order to improve the diffraction efficiency, it is necessary to make the grating groove depth of the diffraction grating two to three times the grating pitch. Since the direction must be completely coincident with the lattice direction so that the lattice does not collapse, there is a restriction that the peeling operation is very difficult. In this case, since the force required at the time of peeling increases in proportion to the depth of the lattice groove, usually,
Either a separation margin is provided on the substrate, or the outer portion must be cut after the separation. For this reason, when a separation margin is provided, an extra space is required even after the separation, and the configuration of the entire optical element becomes large. In addition, the post-cut method has problems such as accuracy of external dimensions and chip processing. There is.

Means for Solving the Problems According to the invention as set forth in claim 1, a substrate is adhered to the surface of the stamper via an ultraviolet curable resin to perform ultraviolet exposure, and thereafter,
In a dual-type grating created by an ultraviolet curing method of duplicating a linear diffraction grating on both the front and back surfaces of the substrate by peeling the stamper from the substrate,
An end face forms a substrate made of a glass member having a predetermined angle of inclination with respect to the linear diffraction grating, and a precoat adhesive layer is provided on both front and back surfaces of the substrate formed of the glass member, and the ultraviolet light is applied to the surface of the precoat adhesive layer. A cured resin is applied.

According to a second aspect of the present invention, the shape of both end faces located in the grating direction of the linear diffraction grating replicated on the substrate is formed as inclined surfaces which are parallel to each other and have a constant inclination angle.

According to the first aspect of the present invention, when the substrate is formed of a glass member, the shape of the substrate is greatly changed under the influence of temperature, humidity, and the like as in the case where the substrate is formed of a plastic resin as in the related art. In particular, since the end face of the substrate has a certain angle of inclination with respect to the linear diffraction grating, when the separation is performed by using the inclination of the end face, the separation direction is the grating of the linear diffraction grating. Since it can be easily performed in a state in which the direction is completely coincident with the direction, it is possible to obtain a good linear diffraction grating with very little lattice collapse.

According to the second aspect of the present invention, the shape of the both end faces located in the grating direction of the linear diffraction grating replicated on the substrate is formed as an inclined surface which is parallel to each other and has a constant inclination angle, so that the inclined surface is formed. The substrate can be peeled off by using this, and when performing peeling of each surface,
Since the peeling directions can be easily performed in a state where they completely match the grating direction of the linear diffraction grating, it is possible to obtain a good linear diffraction grating with very little lattice collapse, and to obtain a highly efficient double-sided diffraction grating. A grating can be obtained.

Embodiment An embodiment of the present invention will be described with reference to FIGS.

The substrate 8 is formed of glass as a glass member. The linear expansion coefficient of the glass is 1 × 10 ^-5 /
° C (about one-seventh of the conventional acrylic plate), so that temperature expansion hardly occurs.
Also, the humidity expansion is similarly small. Among the glasses, those near BK3, in particular, are close to the refractive index of an unillustrated ultraviolet curable resin, are excellent in transmittance and surface accuracy, and are inexpensive. A pre-coat adhesive layer 9 is formed on both front and back surfaces of the substrate 8 made of glass as described above.

In addition, the shape of both end faces of the substrate 8 is formed as an inclined surface 10 which is parallel to each other and has a constant inclination angle. Further, a linear diffraction grating 11 as a diffraction grating is duplicated on the surface of the precoat adhesive layer 9 by a known ultraviolet curing method.

In such a configuration, when duplicating the linear diffraction grating 11 on the front and back surfaces of the substrate 8 to produce a dual-type grating, a well-known ultraviolet curing method (2P method) can be used. The description will be omitted here, focusing on the portion of the substrate 8 of the dual type grating according to the present invention.

FIG. 2 shows an apparatus for producing and peeling a dual type grating. Recess 13 of stamper fixing base 12
A stamper (for the surface) 14 is placed on the surface. On this stamper 14, inclined surfaces 10 are formed at both ends via an ultraviolet-curing resin (not shown), and a pre-coat adhesive layer 9 is formed on the front and back surfaces.
The substrate 8 made of glass having the above is bonded.
After curing by exposure to ultraviolet light in this state, one end has the same inclination angle as the peeling portion 17 by turning a screw 16 attached to the other end of the flat plate 15 whose one end rotates about the rotation fulcrum A. By pushing up the inclined surface 10 in the contact state (see FIG. 3), the substrate 8 having the linear diffraction grating 11 formed on the surface can be peeled off. In addition, a linear diffraction grating 11 is provided on the back surface opposite to the linear diffraction grating 11 on the front surface.
Can be duplicated by turning over the linear diffraction grating 11 on the duplicated surface and performing the same operation.

As described above, when the substrate 8 is made of a glass material, expansion such as temperature and humidity can be reduced as compared with the conventional case where the substrate 8 is made of a plastic resin (acrylic plate). Does not change the thickness of the substrate 8 itself or the lattice pitch. In addition, since the separation after exposure is performed using the inclined surface 10 formed on the end surface of the substrate 8, when the linear diffraction grating 11 is duplicated,
The separation can be performed in a state where the peeling direction is completely matched with the lattice direction, whereby a highly efficient double-sided grating free from lattice collapse can be manufactured.

Next, as described above, a linear diffraction grating
An application example in which signal detection is performed using a duplicated grating of 11 (hereinafter, referred to as a front surface linear diffraction grating 11a and a back surface linear diffraction grating 11b) will be described in a simplified manner.
FIG. 4 shows the state of a magneto-optical pickup signal detection optical system. Light reflected from a magneto-optical disk (not shown) (having a polarization direction of 45 ° with respect to the paper surface) is condensed by passing through a condensing lens 17, and is a surface linear diffraction grating formed on one surface of the substrate 8. 11a and a black angle θb. The incident light on the surface linear diffraction grating 11a is separated into transmitted light T and diffracted light K. The transmitted light T is not affected by the surface linear diffraction grating 11a,
In addition, the light is transmitted as it is without being affected by the back-side linear diffraction grating 11b and is incident on the four-division light receiving element 18. In this case, the transmitted light T has astigmatism due to the shape of the substrate of the dual grating. Therefore, a focus error signal can be detected by utilizing the effect of the astigmatism.

On the other hand, the diffracted light K diffracted by the surface linear diffraction grating 11a is further diffracted even backside linear diffraction grating 11b and the transmitted light T emitted in a state inclined by separation angle theta _0, the light receiving device 19 It is focused on the surface. Note that the diffracted light K also has astigmatism due to the substrate shape. This can be achieved by making the grating pitch of either (or both) the front surface linear diffraction grating 11a and the back surface linear diffraction grating 11b unequal. Can be corrected. In this case, the track error signal can be detected by receiving the diffracted light K by the two-divided light receiving element 19. The intensity ratio between the transmitted light T and the diffracted light K detected by the four-divided light receiving element 18 and the two-divided light receiving element 19 has a one-to-one relationship when the polarization direction is 45 ° with respect to the plane of the paper. If the polarization direction deviates even slightly from 45 ° by a magneto-optical disk (not shown), the intensity ratio changes, so that a magneto-optical signal can be detected.

Thus, in the magneto-optical pickup signal detection optical system,
By disposing the dual type grating having the substrate 8 made of the glass material according to the present invention, the volume of the substrate 8 itself does not expand and contract even under the influence of the surrounding environment such as temperature and humidity. Thereby, it is possible to eliminate a change in the spot shape of the transmitted light T and the diffracted light K passing through the substrate 8 and a change in the irradiation position.

Effects of the Invention The invention according to claim 1 adheres a substrate to the surface of a stamper via an ultraviolet curable resin and performs ultraviolet exposure, and thereafter,
In a dual-type grating created by an ultraviolet curing method of duplicating a linear diffraction grating on both the front and back surfaces of the substrate by peeling the stamper from the substrate,
An end face forms a substrate made of a glass member having a predetermined angle of inclination with respect to the linear diffraction grating, and a precoat adhesive layer is provided on both front and back surfaces of the substrate formed of the glass member, and the ultraviolet light is applied to the surface of the precoat adhesive layer. Since the cured resin is applied, the substrate shape does not significantly change under the influence of temperature, humidity, etc., as in the case where the substrate is formed of plastic resin as in the past,
In particular, since the end face of the substrate has a certain angle of inclination with respect to the linear diffraction grating, when peeling is performed using the inclination of the end face, the peeling direction is completely matched with the grating direction of the linear diffraction grating. Since it can be easily performed in a state where the grating is tilted, there is an effect that it is possible to obtain a good linear diffraction grating with very little grating collapse.

According to the second aspect of the present invention, since the shape of both end faces located in the grating direction of the linear diffraction grating replicated on the substrate is formed as an inclined surface which is parallel to each other and has a constant inclination angle, this inclined surface is formed. The substrate can be peeled off by utilizing this, and when peeling off the respective surfaces, the peeling directions can be easily performed in a state in which the grating directions of the linear diffraction grating completely coincide with each other. Therefore, it is possible to obtain a good linear diffraction grating with very little lattice tilt, and to obtain a highly efficient double-sided grating.

[Brief description of the drawings]

1 (a) is a plan view showing an embodiment of the present invention, FIG. 1 (b) is a longitudinal side view when cut along the lattice direction, and FIG. 2 is a peeling device of a dual type grating. FIG. 3 is a side view showing the state, FIG.
FIG. 4 is an optical path diagram showing a state of a magneto-optical pickup signal detecting optical system, and FIGS. 5 to 7 are process diagrams showing a conventional method of duplicating a grating on one surface of a substrate. 8 ... substrate, 9 ... pre-coat adhesive layer, 10 ... inclined surface,
11 ... Diffraction grating (linear diffraction grating), 14 ... Stamper

Claims (2)

(57) [Claims] An ultraviolet light for bonding a substrate to the surface of a stamper via an ultraviolet-curing resin, exposing the substrate to ultraviolet light, and then peeling the stamper from the substrate to replicate a linear diffraction grating on both front and back surfaces of the substrate. In a dual-type grating prepared by a curing method, an end face forms a substrate made of a glass member having an inclination of a certain angle with respect to the linear diffraction grating, and a precoat adhesive layer is formed on both front and back surfaces of the substrate formed by the glass member. A dual type grading, wherein the ultraviolet curable resin is applied to a surface of the precoat adhesive layer. 2. A linear diffraction grating replicated on a substrate, wherein both end surfaces located in the grating direction of the linear diffraction grating are formed as inclined surfaces which are parallel to each other and have a constant inclination angle. Dual type grading.