Method for manufacturing hologram substrate, hologram substrate, method for manufacturing replica hologram substrate, and method for manufacturing laminated hologram element

Abstract

The present invention provides, for example, a method for manufacturing a hologram substrate enabling easy and accurate reading of alignment marks provided on the hologram substrate. The present invention is a method for manufacturing a hologram substrate 100 comprising a hologram layer 20 and a plurality of alignment marks 31, 32 provided outside the hologram layer. The manufacturing method according to the present invention includes: a hologram layer formation step ST2 of forming a hologram layer by radiating light beams L1, L2 onto a photosensitive material 10 for interference from two different directions at least one of which is not the normal direction of the photosensitive material; and an alignment mark formation step ST3 of forming alignment marks composed of holograms by radiating light beams L1, L3 onto outside of the hologram layer-forming region of the photosensitive material for interference from one side and the other side in the normal direction of the photosensitive material.

Description

Method for manufacturing hologram substrate, method for manufacturing hologram substrate, method for manufacturing replica hologram substrate, and method for manufacturing laminated hologram element

[0001] The present invention relates to a method for manufacturing a hologram substrate, a method for manufacturing a hologram substrate, a replica hologram substrate, and a method for manufacturing a laminated hologram element. In particular, the present invention relates to a method for manufacturing a hologram substrate, a method for manufacturing a hologram substrate, a replica hologram substrate, and a method for manufacturing a laminated hologram element, which enable alignment marks provided on each hologram substrate to be easily and accurately read and each hologram substrate to be easily and accurately aligned when manufacturing a laminated hologram element by stacking multiple hologram substrates (including replica hologram substrates).

[0002] A method for manufacturing a laminated hologram element by laminating a red hologram layer, a green hologram layer, and a blue hologram layer has been proposed (see, for example, Patent Document 1). For example, when this laminated hologram element is used as a light guide plate, if the positions of the hologram layers are misaligned, misalignment occurs in the light guide directions of red wavelength light, green wavelength light, and blue wavelength light, resulting in a problem of reduced color reproducibility.

[0003] For this reason, the manufacturing method described in Patent Document 1 proposes providing alignment marks for positioning outside each hologram layer (in Patent Document 1, these are referred to as interference fringe formation regions). The alignment marks described in Patent Document 1 have the same interference fringes as the hologram layers (see, for example, paragraph 0097 of Patent Document 1). For this reason, when reading the alignment marks, it is necessary to apply illumination light to the end faces of the substrates (light guide plate 121 and support body 124 in Patent Document 1) that support each hologram layer, and then detect and capture the diffracted light (reflected diffracted light) generated by the alignment marks using an imaging device (see, for example, paragraph 0097 of Patent Document 1). In order to accurately read an alignment mark (to suppress distortion of the captured image of the alignment mark) and to image the alignment mark from its normal direction (the normal direction of the hologram layer) (so that the direction of the diffracted light generated by the alignment mark is normal to the alignment mark), the angle of incidence of the illumination light on the substrate must satisfy a specific condition (Bragg condition) that corresponds to the interference fringes of the alignment mark (in other words, the interference fringes of the hologram layer) (see, for example, paragraph

[0093] of Patent Document 1). Therefore, if the angle of incidence of the illumination light on the substrate deviates from this condition, the direction of the diffracted light generated by the alignment mark will deviate from the normal direction of the alignment mark, resulting in a problem of reduced accuracy in reading the alignment mark. On the other hand, satisfying this condition imposes many constraints on the position and angle of incidence of the illumination light, the shape of the substrate onto which the illumination light is incident, and so on.

[0004] Japanese Patent Application Laid-Open No. 2015-175967

[0005] The present invention has been made to solve the problems of the conventional technology as described above, and has an object to provide a method for manufacturing a hologram substrate, a method for manufacturing a hologram substrate, a method for manufacturing a replica hologram substrate, and a method for manufacturing a laminated hologram element, which enable alignment marks provided on each hologram substrate to be easily and accurately read when manufacturing a laminated hologram element by stacking multiple hologram substrates, and which enable each hologram substrate to be easily and accurately aligned.

[0006] In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a hologram substrate comprising a hologram layer and a plurality of alignment marks provided outside the hologram layer, the method comprising: a hologram layer forming step of forming the hologram layer by irradiating a photosensitive material with light from two different directions, at least one of which is not a normal direction to the photosensitive material, and causing interference; and an alignment mark forming step of forming the alignment mark consisting of a hologram by irradiating a region of the photosensitive material outside the region where the hologram layer is formed with light from one side and the other side in the normal direction of the photosensitive material, and causing interference.

[0007] According to the method for manufacturing a hologram substrate of the present invention, in the hologram layer formation step, a hologram layer is formed by irradiating a photosensitive material with light from two different directions (at least one of which is not the normal direction of the photosensitive material) and causing interference. Meanwhile, in the alignment mark formation step, an alignment mark made of a hologram is formed by irradiating an area of ​​the photosensitive material outside the region where the hologram layer is to be formed with light from one side and the other side of the normal direction of the photosensitive material (i.e., irradiating with light from the same normal direction but in opposite directions). That is, because the direction of light used when forming the hologram layer is different from that used when forming the alignment mark, the interference fringes that form the hologram layer and the interference fringes that form the alignment mark are not the same, but different, as in Patent Document 1. Since alignment marks are formed by irradiating light from one side and the other side in the normal direction of a photosensitive material and causing interference, for example, if illumination light is irradiated onto an alignment mark provided on a hologram substrate from one side in the normal direction of the hologram substrate, diffracted light (reflected diffracted light) generated by the alignment mark will travel in one direction in the normal direction of the hologram substrate. Therefore, by placing an imaging means on one side in the normal direction of the hologram substrate and using this imaging means to detect and image the diffracted light generated by the alignment mark from one side in the normal direction of the hologram substrate, it is possible to easily and accurately read the alignment marks provided on the hologram substrate. Therefore, multiple hologram substrates can be aligned easily and accurately. Furthermore, even if, when reading an alignment mark, illumination light is simultaneously irradiated onto both the alignment mark and the hologram layer from one side in the normal direction of the hologram substrate, the diffracted light (reflected diffracted light) generated by the hologram layer, unlike the diffracted light generated by the alignment mark, travels away from one side in the normal direction of the hologram substrate, making it difficult to detect by the imaging means, and it is possible to image only the alignment mark with relatively high contrast.

[0008]

[0013] In the hologram layer forming step of the present invention, as described above, the alignment mark is formed by causing light to interfere from two different directions, but as with the alignment mark forming step, if one of the two directions is set to the normal direction of the photosensitive material, it is efficient in that a common light source can be used in both steps. That is, the method for manufacturing a hologram substrate according to the present invention preferably includes, prior to the hologram layer forming step and the alignment mark forming step, a mask arrangement step of arranging a mask on the photosensitive material, the mask having a first opening provided in a position corresponding to the hologram layer and a second opening provided in a position corresponding to the alignment mark, so as to face one side in the normal direction of the photosensitive material, and blocking light at other positions, wherein in the hologram layer forming step, light is irradiated onto the photosensitive material from one side in the normal direction of the photosensitive material through the first opening of the mask, and in the alignment mark forming step, light is irradiated onto the photosensitive material from one side in the normal direction of the photosensitive material through the second opening of the mask.

[0009] According to the above-described preferred method, a common light source that irradiates light from one side in the normal direction of the photosensitive material can be used in both the hologram layer formation process and the alignment mark formation process, thereby enabling both processes to be performed efficiently. Furthermore, by blocking the second opening of the mask in the hologram layer formation process (allowing light to pass only through the first opening), and by blocking the first opening of the mask in the alignment mark formation process (allowing light to pass only through the second opening), a light source that irradiates a large amount of light that spreads over an area including both the first opening and the second opening can be used. Furthermore, since the positional relationship between the hologram layer and the alignment mark formed on the photosensitive material is determined by the positional relationship between the first opening and the second opening in the mask, forming the hologram layer and the alignment mark using the same mask allows for the manufacture of a hologram substrate with little variation in the positional relationship between the two.

[0010] Preferably, in the alignment mark forming process, a reflecting mirror is positioned facing the other side of the photosensitive material in the normal direction of the photosensitive material, and the alignment mark is formed by causing interference between light irradiated onto the photosensitive material from one side of the normal direction of the photosensitive material through the second opening of the mask and light that is reflected by the reflecting mirror and irradiated onto the photosensitive material from the other side of the normal direction of the photosensitive material.

[0011] According to the above-described preferred method, the alignment mark formation process can be carried out efficiently because light irradiated onto the photosensitive material from one side in the normal direction of the photosensitive material can be simply reflected by a reflecting mirror, and the reflected light can be used as light irradiated onto the photosensitive material from the other side in the normal direction of the photosensitive material.

[0012] In a hologram substrate manufactured by carrying out the method for manufacturing a hologram substrate according to the present invention, the direction of diffracted light generated when light is irradiated onto the hologram layer from one side in the normal direction of the hologram layer is not the normal direction of the hologram layer. This is because at least one of the two directions of light used to form the hologram layer is not the normal direction of the photosensitive material. On the other hand, the direction of diffracted light generated when light is irradiated onto an alignment mark from one side in the normal direction of the alignment mark is the normal direction of the alignment mark. This is because the light used to form the alignment mark is light irradiated from one side and the other side in the normal direction of the photosensitive material. Therefore, in order to solve the above problem, the present invention also provides a hologram substrate comprising a hologram layer and a plurality of alignment marks, wherein the alignment marks are formed from holograms, and the direction of diffracted light generated when light is irradiated onto the hologram layer from one side in the normal direction of the hologram layer is not the normal direction of the hologram layer, but the direction of diffracted light generated when light is irradiated onto the alignment marks from one side in the normal direction of the alignment marks is the normal direction of the alignment marks.

[0013] In order to solve the above-mentioned problems, the present invention also provides a method for producing a replica hologram substrate by preparing the hologram substrate as a master hologram substrate and replicating it, the method comprising: a photosensitive material arranging step of arranging a photosensitive material with respect to the master hologram substrate so that the photosensitive material faces one side in a normal direction of the master hologram substrate; and a duplication step of duplicating the hologram layer and the alignment marks of the master hologram substrate in the photosensitive material by causing interference between light irradiated onto the photosensitive material from one side in the normal direction of the photosensitive material and diffracted light generated when the light is irradiated onto the master hologram substrate.

[0014] According to the method for manufacturing a replica hologram substrate of the present invention, a replica hologram substrate can be easily manufactured (a master hologram substrate can be replicated) simply by arranging a photosensitive material so that it faces one side of the master hologram substrate in the normal direction and irradiating the photosensitive material with light from one side of the photosensitive material in the normal direction.

[0015] Furthermore, in order to solve the above-mentioned problems, the present invention provides a method for manufacturing a laminated hologram element by preparing, as the hologram substrate, a red hologram substrate having a red hologram layer that is the hologram layer and a red alignment mark that is the alignment mark, which are formed by irradiating it with light of a red wavelength; a green hologram substrate having a green hologram layer that is the hologram layer and a green alignment mark that is the alignment mark, which are formed by irradiating it with light of a green wavelength; and a blue hologram substrate having a blue hologram layer that is the hologram layer and a blue alignment mark that is the alignment mark, which are formed by irradiating it with light of a blue wavelength; and laminating the red hologram substrate, the green hologram substrate, and the blue hologram substrate together, the method comprising: irradiating the red alignment mark of the red hologram substrate with first illumination light having a wavelength that includes a red wavelength from one side in the normal direction of the red hologram substrate; capturing an image of the red alignment mark from one side in the normal direction of the red hologram substrate to obtain a first captured image; an image acquisition step of irradiating the green alignment mark of the green hologram substrate with second illumination light having a wavelength including a green wavelength from one side in the normal direction of the green hologram substrate and capturing an image of the green alignment mark from one side in the normal direction of the green hologram substrate to acquire a second captured image, and irradiating the blue alignment mark of the blue hologram substrate with third illumination light having a wavelength including a blue wavelength from one side in the normal direction of the blue hologram substrate and capturing an image of the blue alignment mark from one side in the normal direction of the blue hologram substrate to acquire a third captured image; a coordinate detection step of detecting coordinates of the red alignment mark, the green alignment mark, and the blue alignment mark by image processing the first captured image, the second captured image, and the third captured image, respectively; a position adjustment step of adjusting positions of the red hologram substrate, the green hologram substrate, and the blue hologram substrate so that the coordinates of the red alignment mark, the green alignment mark, and the blue alignment mark match; and the red hologram substrate after position adjustment.and a lamination step of laminating the green hologram substrate and the blue hologram substrate together.

[0016] In the manufacturing method of a laminated hologram element according to the present invention, the "red wavelength" refers to, for example, a wavelength of 600 to 700 nm, the "green wavelength" refers to, for example, a wavelength of 500 to 560 nm, and the "blue wavelength" refers to, for example, a wavelength of 430 to 500 nm. Furthermore, in the manufacturing method of a laminated hologram element according to the present invention, the "hologram substrate" may be a master hologram substrate manufactured by the manufacturing method of a hologram substrate according to the present invention, or a replica hologram substrate manufactured by the manufacturing method of a replica hologram substrate according to the present invention. According to the manufacturing method of a laminated hologram element according to the present invention, in the image acquisition step, the red alignment mark is irradiated with first illumination light having a wavelength including a red wavelength from one side in the normal direction of the red hologram substrate. This causes diffracted light (reflected diffracted light) generated by the red alignment mark to travel in one direction normal to the red hologram substrate. Therefore, in the first image acquired by imaging the red alignment mark from one side in the normal direction of the red hologram substrate, the red alignment mark is imaged with relatively high contrast. Similarly, in the second captured image, the green alignment mark is captured with a relatively high contrast, and in the third captured image, the blue alignment mark is captured with a relatively high contrast. Therefore, in the coordinate detection step, the coordinates of the red, green, and blue alignment marks can be detected with high accuracy by image processing the first, second, and third captured images. According to the present invention, in the position adjustment step, the positions of the red hologram substrate, the green hologram substrate, and the blue hologram substrate are adjusted so that the coordinates of the red, green, and blue alignment marks match, and in the bonding step, the hologram substrates after the adjustment are bonded together. Therefore, it is possible to manufacture a laminated hologram element in which the red hologram layer, the green hologram layer, and the blue hologram layer of each hologram substrate are aligned with high accuracy.

[0017] According to the present invention, by stacking multiple hologram substrates, when manufacturing a laminated hologram element, it is possible to easily and accurately read the alignment marks provided on each hologram substrate, and to manufacture hologram substrates that can easily and accurately align each hologram substrate.

[0018] Fig. 6 is a flow diagram showing the general steps of a method for manufacturing a hologram substrate according to one embodiment of the present invention. Fig. 7 is a schematic diagram explaining the general steps of a method for manufacturing a hologram substrate according to one embodiment of the present invention. Fig. 8 is a schematic diagram explaining a method for closing first opening 41 and second openings 42, 43 of mask 40 shown in Fig. 2 using an auxiliary mask. Fig. 9 is a flow diagram showing the general steps of a method for manufacturing a replica hologram substrate according to one embodiment of the present invention. Fig. 10 is a schematic diagram explaining the general steps of a method for manufacturing a replica hologram substrate according to one embodiment of the present invention. Fig. 11 is a flow diagram showing the general steps of a method for manufacturing a laminated hologram element according to one embodiment of the present invention. Fig. 12 is a schematic diagram explaining an image acquisition step ST32 shown in Fig. 6.

[0019] An embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the drawings are for reference purposes only, and the dimensions, scale, and shapes of the components shown in the drawings may differ from the actual ones.

[0020] [Method for manufacturing hologram substrate] Fig. 1 is a flow diagram showing the outline of the steps of the method for manufacturing a hologram substrate according to this embodiment. Fig. 2 is a schematic diagram explaining the outline of the steps of the method for manufacturing a hologram substrate according to this embodiment. As shown in Fig. 1, the manufacturing method according to this embodiment includes a mask placement step ST11, a hologram layer formation step ST12, and an alignment mark formation step ST13.

[0021] <Mask Placement Step ST11> Figure 2(a) is a plan view showing a schematic configuration of a mask prepared in the mask placement step ST11. In Figure 2(a), the Z direction indicates the thickness direction (corresponding to the thickness direction of the hologram substrate described below) that is the normal direction of the mask, the X direction indicates a direction perpendicular to the Z direction and parallel to one side of the hologram substrate described below, and the Y direction indicates a direction perpendicular to the Z direction and the X direction. This also applies to other figures. As shown in Figure 2(a), the mask 40 prepared in the mask placement step ST11 has a first opening 41 provided at a location corresponding to a hologram layer described below and second openings 42 and 43 provided at locations corresponding to multiple alignment marks (two in this embodiment) described below, and blocks light in other locations. The mask 40 is made of, for example, glass or a transparent resin such as polycarbonate, polyamide, or acrylic, and the first opening 41 and second openings 42 and 43 are formed, for example, by laser processing. The areas of the mask 40 other than the first opening 41 and the second openings 42, 43 are configured to block light by being printed with a color such as a black print. In this embodiment, since the alignment marks described below are rectangular in plan view, the corresponding second openings 42, 43 are also rectangular in plan view. However, the present invention is not limited to this. For example, if the alignment marks described below are circular in plan view, the corresponding second openings 42, 43 may also be circular in plan view. The second openings 42, 43 may have any shape corresponding to the shape of the alignment marks. The same applies to the first opening 41.

[0022] FIG. 2( b) is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing the mask placement step ST11. In FIG. 2( b), the mask 40 is shown as a cross-section along the line AA in FIG. 2( a). The cross-section of the mask 40 in other figures is also shown as a cross-section along the line AA. As shown in FIG. 2( b), in the mask placement step ST11, the mask 40 is placed on one side of the photosensitive material 10 in the normal direction (Z direction) of the photosensitive material 10 (the lower side in the example shown in FIG. 2( b)). In this embodiment, the photosensitive material 10 is supported by a light-transmitting plate 50, and the mask 40 is placed below this light-transmitting plate 50. The photosensitive material 10 may be, for example, a photosensitive resin such as a photopolymer or photoresist, or a laminate of a photosensitive resin and a substrate. For example, the photopolymer "Bayfol (registered trademark) HX200" manufactured by Covestro is used as the photosensitive resin. The substrate may be made of, for example, glass or triacetylcellulose (TAC).The light-transmitting plate 50 may be made of any material as long as it has a refractive index equivalent to that of the photosensitive material 10, and examples of the material that may be used include glass, triacetylcellulose (TAC), and resins such as polycarbonate.

[0023] <Hologram Layer Forming Step ST12> Figure 2(c) is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing the hologram layer forming step ST12. As shown in Figure 2(c), in the hologram layer forming step ST12, light beams L1 and L2 are irradiated onto photosensitive material 10 from two different directions (a direction forming an angle α with respect to the XY plane (hereinafter referred to as the "α direction") and a direction forming an angle β with respect to the XY plane (hereinafter referred to as the "β direction"), respectively, and interfere with each other to form hologram layer 20. Coherent light beams such as laser beams are used as light beams L1 and L2. In this embodiment, the α direction in which light L1 is irradiated is the normal direction (Z direction) of the photosensitive material 10 (i.e., α=90°), and the β direction in which light L2 is irradiated is not the normal direction (Z direction) of the photosensitive material 10 (i.e., β≠90°). Then, with the second openings 42 and 43 of the mask 40 closed (a state in which light can pass only through the first opening 41), light L1 is irradiated onto the photosensitive material 10 from one side in the normal direction (Z direction) of the photosensitive material 10 (the bottom side in the example shown in FIG. 2(c)) through the first opening 41 of the mask 40 and the light-transmitting plate 50. As a result, the photosensitive material 10 is irradiated with interference light of light L1 and light L2, and the photosensitive material 10 is irradiated with interference light of light L1 and light L2. The monomer component in the irradiated portion of the mask 40 diffuses, generating interference fringes with a refractive index distribution, thereby forming a hologram (volume hologram) layer 20. To maintain the coherence of the light L1 and the light L2, it is preferable to split the light emitted from the same laser light source into light L1 and light L2 using a polarizing beam splitter, rotate the polarization axis of the split light L2 using a half-wave plate to match the polarization axis of the light L1, and then magnify and flatten the light using a magnifying lens and a collimating lens, respectively, before irradiating the light from two directions (the α direction and the β direction). An example of a method for blocking the second openings 42 and 43 of the mask 40 will be described later.

[0024] <Alignment Mark Forming Process ST13> Figure 2(d) is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing the alignment mark forming process ST13. As shown in Figure 2(d), in the alignment mark forming process ST13, light L1 is irradiated from one side in the normal direction (Z direction) of the photosensitive material 10 (the bottom side in the example shown in Figure 2(d)) to the outside of the region where the hologram layer 20 is to be formed, as in the hologram layer forming process ST12, and light L3 is irradiated from the other side in the normal direction (Z direction) (the top side in the example shown in Figure 2(d)) to cause interference, thereby forming alignment marks 31 and 32 made of holograms. In this embodiment, with the first opening 41 of the mask 40 closed (a state in which light can pass only through the second openings 42 and 43), light L1 is irradiated onto the photosensitive material 10 from one side (bottom) in the normal direction (Z direction) of the photosensitive material 10 via the second openings 42 and 43 of the mask 40 and the light-transmitting plate 50. Also, in this embodiment, a reflecting mirror 60 is disposed so as to face the other side (top) in the normal direction (Z direction) of the photosensitive material 10. As a result, light L1 that passes through the second openings 42 and 43 of the mask 40 and is transmitted through the light-transmitting plate 50 and the photosensitive material 10 is reflected by the reflecting mirror 60 to become light L3 that is irradiated onto the photosensitive material 10 from the other side (top) in the normal direction (Z direction) of the photosensitive material 10. As a result, the photosensitive material 10 is irradiated with interference light of the light L1 and the light L3, the monomer component in the irradiated portion of the photosensitive material 10 is diffused, and interference fringes having a refractive index distribution are generated, thereby forming alignment marks 31 and 32 made of holograms (volume holograms). An example of a method for closing the first opening 41 of the mask 40 will be described later.

[0025] A hologram substrate can be manufactured by performing the mask placement process ST11, hologram layer formation process ST12, and alignment mark formation process ST13 described above. In this embodiment, the hologram layer formation process ST12 and the alignment mark formation process ST13 are performed in this order. However, the present invention is not limited to this. It is also possible to perform the alignment mark formation process ST13 first and then the hologram layer formation process ST12. FIG. 2( e) is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing an example of a hologram substrate manufactured by the manufacturing method of this embodiment. FIG. 2( f) is a plan view showing an example of a hologram substrate manufactured by the manufacturing method of this embodiment. In a preferred embodiment, the hologram substrate 100 shown in FIGS. 2( e) and 2( f) has a configuration in which substrates 70 are laminated on both sides of a photosensitive material 10 on which a hologram layer 20 and alignment marks 31 and 32 are formed, using an appropriate adhesive or a self-adhesive photosensitive material 10. The substrate 70 may be made of, for example, glass or a resin such as polycarbonate, polyamide, or acrylic. However, the present invention is not limited to this. The hologram substrate 100 may have a structure in which the substrate 70 is not laminated (a structure in which only the hologram layer 20 and the photosensitive material 10 on which the alignment marks 31 and 32 are formed) or a structure in which the substrate 70 is laminated on only one side. The hologram substrate 100 shown in FIGS. 2( e) and 2( f) includes a hologram layer 20 and a plurality of (two in this embodiment) alignment marks 31 and 32, and the alignment marks 31 and 32 are formed of holograms. The direction of diffracted light generated when light is irradiated onto the hologram layer 20 from one side in the normal direction (Z direction) of the hologram layer 20 is not the normal direction (Z direction) of the hologram layer 20. On the other hand, when light is irradiated onto the alignment marks 31 and 32 from one side in the normal direction (Z direction) of the alignment marks 31 and 32, the direction of the diffracted light generated is the normal direction (Z direction) of the alignment marks 31 and 32.

[0026] Hereinafter, an example of a method for closing the second openings 42 and 43 of the mask 40 in the hologram layer forming step ST12 and an example of a method for closing the first opening 41 of the mask 40 in the alignment mark forming step ST13 will be described. As a method for closing the first opening 41 and the second openings 42 and 43 of the mask 40, for example, a method using an auxiliary mask can be considered. FIG. 3 is a schematic diagram illustrating a method for closing the first opening 41 and the second openings 42 and 43 of the mask 40 using an auxiliary mask. FIG. 3(a) is a plan view (similar to FIG. 2(a)) showing the schematic configuration of the mask 40. FIG. 3(b) is a plan view showing the schematic configuration of the auxiliary mask. FIG. 3(c) is a plan view showing the second openings 42 and 43 of the mask 40 being closed using the auxiliary mask in the hologram layer forming step ST12. FIG. 3(d) is a plan view showing the first opening 41 of the mask 40 being closed using the auxiliary mask in the alignment mark forming step ST13. 3B, the auxiliary mask 40A, like the mask 40, has a first opening 41A and second openings 42A and 43A, and blocks light in other areas. Like the mask 40, the auxiliary mask 40A is made of a transparent resin such as glass, polycarbonate, polyamide, or acrylic, and the first opening 41A and second openings 42A and 43A are formed by laser processing, for example. The areas of the auxiliary mask 40A other than the first opening 41A and second openings 42A and 43A are printed with a color such as black, for example, to block light.

[0027] 3(a) and 3(b), the first opening 41A and the second openings 42A, 43A of the auxiliary mask 40A have dimensions equal to or larger than the first opening 41 and the second openings 42, 43 of the mask 40, respectively. Preferably, the first opening 41A and the second openings 42A, 43A of the auxiliary mask 40A have dimensions slightly larger than the first opening 41 and the second openings 42, 43 of the mask 40, respectively. The Y-direction separation distance between the first opening 41A and the second openings 42A, 43A of the auxiliary mask 40A is equal to the Y-direction separation distance between the first opening 41 and the second openings 42, 43 of the mask 40. The X-direction separation distance between the second openings 42A and 43A of the auxiliary mask 40A is equal to the X-direction separation distance between the second openings 42 and 43 of the mask 40. However, the positional relationship in the X direction between the first opening 41A and the second openings 42A and 43A of the auxiliary mask 40A is different from the positional relationship in the X direction between the first opening 41 and the second openings 42 and 43 of the mask 40.

[0028] The auxiliary mask 40A having the above configuration is arranged so as to overlap with the mask 40 in the Z direction (for convenience, it is not shown in the above-mentioned FIGS. 2(b) to 2(d)). In the above-mentioned FIGS. 2(b) to 2(d), the auxiliary mask 40A may be arranged above or below the mask 40. FIGS. 3(c) and 3(d) illustrate the case where the auxiliary mask 40A is arranged above the mask 40. The X-direction end of the auxiliary mask 40A is attached to, for example, a uniaxial stage (not shown) that is movable in the X direction, so that the auxiliary mask 40A can move in the X direction relative to the stationary mask 40.

[0029] In the hologram layer forming step ST12, the auxiliary mask 40A is positioned relative to the mask 40 as shown in FIG. 3( c). In the state shown in FIG. 3( c), the second openings 42 and 43 of the mask 40 are blocked by the auxiliary mask 40A, while the first opening 41 of the mask 40 overlaps with the second opening 41A of the auxiliary mask, resulting in a state in which light can pass through only the first opening 41. In the alignment mark forming step ST13, the auxiliary mask 40A is positioned relative to the mask 40 as shown in FIG. 3( d). In the state shown in FIG. 3( d), the first opening 41 of the mask 40 is blocked by the auxiliary mask 40A, while the second openings 42 and 43 of the mask 40 overlap with the second openings 42A and 43A of the auxiliary mask, resulting in a state in which light can pass through only the second openings 42 and 43. As described above, by using auxiliary mask 40A and adjusting the position of auxiliary mask 40A, it is possible to close second openings 42 and 43 of mask 40 in hologram layer forming step ST12, and to close first opening 41 of mask 40 in alignment mark forming step ST13. However, the present invention is not limited to this, and various embodiments can be adopted as long as it is possible to close second openings 42 and 43 of mask 40 in hologram layer forming step ST12, and to close first opening 41 of mask 40 in alignment mark forming step ST13.

[0030] [Method for Manufacturing Replica Hologram Substrate] When mass-producing the above-mentioned hologram substrate 100, the mask placement step ST11, hologram layer formation step ST12, and alignment mark formation step ST13 described with reference to Figures 1 and 2 may be repeated, but it is also possible to employ a mode in which hologram substrate 100 is used as a master hologram substrate and replica hologram substrates are manufactured (mass-produced) by duplicating this. A method for manufacturing this replica hologram substrate will be described below.

[0031] Fig. 4 is a flow diagram showing the outline of the steps of the method for manufacturing a replica hologram substrate according to this embodiment. Fig. 5 is a schematic diagram explaining the outline of the steps of the method for manufacturing a replica hologram substrate according to this embodiment. As shown in Fig. 4, the manufacturing method according to this embodiment includes a preparation step ST21, a photosensitive material placement step ST22, and a duplication step ST23.

[0032] <Preparation Step ST21> In preparation step ST21, the above-described hologram substrate 100 is prepared as a master hologram substrate. Specifically, the above-described mask placement step ST11, hologram layer formation step ST12, and alignment mark formation step ST13 are performed to manufacture master hologram substrate 100.

[0033] <Photosensitive Material Disposing Step ST22> Figure 5(a) is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing the photosensitive material disposing step ST22. As shown in Figure 5(a), in the photosensitive material disposing step ST22, a photosensitive material 10A is disposed with respect to master hologram substrate 100 so as to face one side (the lower side in the example shown in Figure 5(a)) in the normal direction (Z direction) of master hologram substrate 100. Unlike the photosensitive material 10 that constitutes master hologram substrate 100, this photosensitive material 10A does not yet have hologram layer 20 or alignment marks 31 and 32 formed thereon.

[0034] <Replication Process ST23> FIG. 5(b) is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing the replication process ST23. As shown in FIG. 5(b), in the replication process ST23, the photosensitive material 10A is irradiated with the same light L1 as used in manufacturing the master hologram substrate 100 described above, from one side (the bottom side in the example shown in FIG. 5(b)) in the normal direction (Z direction) of the photosensitive material 10A. That is, the angle α that the light L1 forms with respect to the XY plane is 90°. However, unlike in manufacturing the master hologram substrate 100 described above, the mask 40 is not used when irradiating the light L1 in the replication process ST23. Therefore, the entire light L1 is irradiated onto the photosensitive material 10A, and the light L1 transmitted through the photosensitive material 10A is simultaneously irradiated onto both the hologram layer 20 and the alignment marks 31 and 32 of the master hologram substrate 100. When light L1 is irradiated onto master hologram substrate 100, diffracted light (reflected diffracted light) R1 is generated at hologram layer 20, and diffracted light (reflected diffracted light) R2 and R3 are generated at alignment marks 31 and 32, respectively. Diffracted light R2 and R3 travel to one side (downward) of the normal direction (Z direction), and diffracted light R1 travels in a direction corresponding to the direction (β direction, see FIG. 2(c)) of light L2 used to form hologram layer 20 of master hologram substrate 100. These diffracted light R1 to R3 are then irradiated onto photosensitive material 10A.

[0035] Therefore, photosensitive material 10A is irradiated with the interference light of light L1 and diffracted light R1-R3, and the monomer component in the irradiated portion of photosensitive material 10A diffuses, generating interference fringes with a refractive index distribution, so that a hologram (volume hologram) layer 20A is formed in the portion irradiated with the interference light of light L1 and diffracted light R1, an alignment mark 31A made of a hologram (volume hologram) is formed in the portion irradiated with the interference light of light L1 and diffracted light R2, and an alignment mark 32A made of a hologram (volume hologram) is formed in the portion irradiated with the interference light of light L1 and diffracted light R3. The interference fringes that constitute hologram layer 20A and alignment marks 31A and 32A formed in this manner are the same as the interference fringes that constitute hologram layer 20 and alignment marks 31 and 32, respectively. That is, the hologram layer 20A and the alignment marks 31A and 32A formed on the photosensitive material 10A are copies of the hologram layer 20 and the alignment marks 31 and 32 of the master hologram substrate 100, respectively.

[0036] A replica hologram substrate can be manufactured by performing the preparation step ST21, photosensitive material placement step ST22, and replication step ST23 described above. Figure 5(c) is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing an example of a replica hologram substrate manufactured by the manufacturing method according to this embodiment. The replica hologram substrate 100A shown in Figure 5(c) has a configuration in which a photosensitive material 10A (see Figure 5(b)) on which a hologram layer 20A and alignment marks 31A and 32A have been formed is cut to an appropriate size (after cutting the outer edge of the photosensitive material 10A), and then, in a preferred embodiment, substrates 70 are laminated on both sides of the photosensitive material 10A on which the hologram layer 20A and alignment marks 31A and 32A have been formed, using an appropriate adhesive or a self-adhesive photosensitive material 10A, similar to the master hologram substrate 100 shown in Figure 2(e). The substrate 70 may be made of glass or a resin such as polycarbonate, polyamide, or acrylic, as in the master hologram substrate 100. However, the present invention is not limited to this. The replica hologram substrate 100A may be configured without the substrate 70 (i.e., with only the hologram layer 20A and the photosensitive material 10A on which the alignment marks 31A and 32A are formed) or with the substrate 70 laminated on only one side. The replica hologram substrate 100A shown in FIG. 5C also includes a hologram layer 20A and multiple (two in this embodiment) alignment marks 31A and 32A, as in the master hologram substrate 100. The direction of diffracted light generated when light is irradiated onto the hologram layer 20A from one side in the normal direction (Z direction) of the hologram layer 20A is not the normal direction (Z direction) of the hologram layer 20A. On the other hand, when light is irradiated onto the alignment marks 31A and 32A from one side in the normal direction (Z direction) of the alignment marks 31A and 32A, the direction of the diffracted light generated is the normal direction (Z direction) of the alignment marks 31A and 32A.

[0037] [Method for Manufacturing Laminated Hologram Element] A method for manufacturing a laminated hologram element by stacking a plurality of master hologram substrates 100 (or replica hologram substrates 100A) will be described below. In the following description, stacking of master hologram substrates 100 will be taken as an example, but the process is similar when stacking replica hologram substrates 100A. FIG. 6 is a flow chart showing the outline of the method for manufacturing a laminated hologram element according to this embodiment. As shown in FIG. 6, the manufacturing method according to this embodiment includes a preparation step ST31, an image acquisition step ST32, a coordinate detection step ST33, a position adjustment step ST34, and a bonding step ST35.

[0038] <Preparation Step ST31> In preparation step ST31, red hologram substrate 100R, green hologram substrate 100G, and blue hologram substrate 100B are prepared. Red hologram substrate 100R is a hologram substrate having red hologram layer 20R as hologram layer 20 and red alignment marks 31R and 32R as alignment marks 31 and 32, which are formed by performing mask placement step ST11, hologram layer formation step ST12, and alignment mark formation step ST13 using red wavelength light as light L1 to L3 shown in FIG. 2. Green hologram substrate 100G is a hologram substrate having green hologram layer 20G as hologram layer 20 and green alignment marks 31G and 32G as alignment marks 31 and 32, which are formed by performing mask placement step ST11, hologram layer formation step ST12, and alignment mark formation step ST13 using green wavelength light as light L1 to L3 shown in FIG. Blue hologram substrate 100B is a hologram substrate having blue hologram layer 20B, which is hologram layer 20, and blue alignment marks 31B and 32B, which are alignment marks 31 and 32, formed by performing mask positioning step ST11, hologram layer forming step ST12, and alignment mark forming step ST13 using light of a blue wavelength as light L1 to L3 shown in Fig. 2. In this embodiment, for each of red hologram substrate 100R, green hologram substrate 100G, and blue hologram substrate 100B, a substrate 70 is laminated on only one side of photosensitive material 10 on which hologram layers 20R to 20B and alignment marks 31R to 31B, 32R to 32B are formed.

[0039] <Captured Image Acquisition Step ST32> Figure 7 is a schematic diagram illustrating captured image acquisition step ST32 in the manufacturing method of the laminated hologram element according to this embodiment. In captured image acquisition step ST32, first, as shown in Figure 7(a), red hologram substrate 100R and blue hologram substrate 100B are arranged facing each other in the Z direction (the thickness direction of each substrate). Specifically, as shown in Figure 7(a), red hologram substrate 100R is adsorbed (vacuum adsorbed) by suction stage 81, and blue hologram substrate 100B is adsorbed (vacuum adsorbed) by suction stage 82, which is arranged opposite suction stage 81 in the Z direction.

[0040] Next, as shown in FIG. 7B , suction stages 81 and 82 are moved the same distance in the horizontal direction (e.g., the X direction) (accompanying this, red hologram substrate 100R and blue hologram substrate 100B also move horizontally), so that red alignment mark 32R of red hologram substrate 100R faces imaging unit 1a in the Z direction across half mirror 3a, and blue alignment mark 32B of blue hologram substrate 100B faces imaging unit 1b in the Z direction across half mirror 3b. Light source 2a is positioned so that its emitted light is reflected by half mirror 3a and irradiates the image within the field of view of imaging unit 1a. Light source 2b is positioned so that its emitted light is reflected by half mirror 3b and irradiates the image within the field of view of imaging unit 1b. In other words, the combination of imaging unit 1a, light source 2a, and half mirror 3a and the combination of imaging unit 1b, light source 2b, and half mirror 3b each constitute a coaxial epi-illumination optical system. However, the present invention is not limited to this. It is also possible to use ring illumination concentric with the imaging units 1a and 1b as the light sources 2a and 2b, respectively, without using the half mirrors 3a and 3b. The imaging units 1a and 1b may be, for example, a CCD area sensor or a CMOS area sensor (e.g., the "CA-H500MX" manufactured by Keyence Corporation). The light source 2a may be, for example, a red LED light source (e.g., the "HLV3-22RD-2" manufactured by CCS). The light source 2b may be, for example, a blue LED light source (e.g., the "HLV3-22BL-2" manufactured by CCS). However, as long as the light source 2a emits light with a wavelength including a red wavelength and the light source 2b emits light with a wavelength including a blue wavelength, it is also possible to use the same white LED light source as the light sources 2a and 2b.

[0041] Next, in the state shown in Figure 7(b), the light source 2a and the half mirror 3a irradiate the red alignment mark 32R of the red hologram substrate 100R with first illumination light having a wavelength that includes red wavelengths from one side (the bottom side in the example shown in Figure 7(b)) in the normal direction (Z direction) of the red hologram substrate 100R (angle α shown in Figure 7(b) = 90°), and the imaging unit 1a captures an image of the red alignment mark 32R from one side (the bottom side) in the normal direction (Z direction) of the red hologram substrate 100R, thereby obtaining a first captured image. Similarly, in the state shown in Figure 7(b), third illumination light having a wavelength including blue wavelengths is irradiated onto blue alignment mark 32B of blue hologram substrate 100B from one side (the upper side in the example shown in Figure 7(b)) in the normal direction (Z direction) of blue hologram substrate 100B by light source 2b and half mirror 3b, and blue alignment mark 32B is imaged from one side (the upper side) in the normal direction (Z direction) of blue hologram substrate 100B by imaging means 1b, thereby obtaining a third captured image.

[0042] In order to accurately detect the coordinates of the red alignment mark 32R and the blue alignment mark 32B in the coordinate detection step ST33 described below, it is preferable to increase the resolution of the first and third captured images. Therefore, it is preferable to capture the first captured image by limiting the field of view of the imaging unit 1a to the red alignment mark 32R and its vicinity, rather than the entire red hologram substrate 100R. After capturing the first captured image of the red alignment mark 32R and the third captured image of the blue alignment mark 32B, the first captured image of the red alignment mark 31R and the third captured image of the blue alignment mark 31B are captured in the same manner. Specifically, the suction stage 81 is moved in the horizontal direction (X direction) relative to the imaging unit 1a (and, accordingly, the red hologram substrate 100R is moved in the horizontal direction), thereby setting the field of view of the imaging unit 1a to the red alignment mark 31R and its vicinity, and capturing the first captured image. Alternatively, two imaging means 1a may be provided for respectively capturing images of the red alignment marks 31R and 32R. The same applies to the imaging means 1b.

[0043] <Coordinate Detection Step ST33> In the coordinate detection step ST33, the first captured image and the third captured image are each subjected to image processing to detect the coordinates (XY coordinates) of the red alignment marks 31R, 32R and the blue alignment marks 31B, 32B. The coordinates of the red alignment marks 31R, 32R and the blue alignment marks 31B, 32B can be, for example, the center coordinates of the pixel areas corresponding to the red alignment marks 31R, 32R and the blue alignment marks 31B, 32B extracted by performing binarization processing on the first captured image and the third captured image. Note that the coordinates of the red alignment marks 31R, 32R and the blue alignment marks 31B, 32B detected in the first captured image and the third captured image are directly relative coordinates in the respective fields of view of the imaging unit 1a and the imaging unit 1b. Since the positions of the image capturing units 1a and 1b relative to the same predetermined reference position can be known in advance, the relative coordinates of the red alignment marks 31R, 32R and the blue alignment marks 31B, 32B detected in the first and third captured images can be corrected using the positions of the image capturing units 1a and 1b, respectively, to calculate the absolute coordinates of the red alignment marks 31R, 32R and the blue alignment marks 31B, 32B relative to the same reference position. These absolute coordinates are used as the coordinates in the position adjustment step ST34 described below.

[0044] <Position Adjustment Step ST34> In position adjustment step ST34, the positions of red hologram substrate 100R and blue hologram substrate 100B are adjusted so that the coordinates of red alignment mark 31R and blue alignment mark 31B match and the coordinates of red alignment mark 32R and blue alignment mark 32B match. Specifically, the positions of red hologram substrate 100R and blue hologram substrate 100B are adjusted by moving at least one of suction stage 81 that suctions red hologram substrate 100R and suction stage 82 that suctions blue hologram substrate 100B in the X direction, the Y direction, or by rotating it around the Z direction.

[0045] <Bonding Step ST35> In the bonding step ST35, the red hologram substrate 100R and the blue hologram substrate 100B are bonded together after their positions have been adjusted. Specifically, for example, the suction stages 81 and 82 are moved the same distance in the horizontal direction (e.g., the X direction) (since they are moved the same distance, the adjusted positions of the red hologram substrate 100R and the blue hologram substrate 100B remain unchanged) to eliminate the imaging units 1a and 1b, the light sources 2a and 2b, and the half mirrors 3a and 3b from being present between the suction stages 81 and 82. Next, to bond the red hologram substrate 100R and the blue hologram substrate 100B together, for example, a UV-curable adhesive (not shown) is applied to the blue hologram substrate 100B. Then, the red hologram substrate 100R and the blue hologram substrate 100B are brought into contact with each other. Specifically, at least one of the suction stages 81 and 82 is moved in the Z direction to bring the red hologram substrate 100R and the blue hologram substrate 100B into contact with each other. Finally, ultraviolet light is irradiated from an ultraviolet light irradiation means (not shown) toward the adhesive to harden the adhesive, thereby bonding the red hologram substrate 100R and the blue hologram substrate 100B together. Note that the bonding step ST35 is preferably performed in a vacuum chamber (not shown) so that the red hologram substrate 100R and the blue hologram substrate 100B are bonded together while being precisely aligned. That is, it is preferable to carry the suction stages 81 and 82 into the vacuum chamber, and then apply the adhesive, move at least one of the suction stages 81 and 82 in the Z direction, and irradiate ultraviolet light.

[0046] Through the steps described above, red hologram substrate 100A and blue hologram substrate 100B are bonded together, resulting in a laminate of these substrates. However, because green hologram substrate 100G remains to be bonded (because step ST36 shown in FIG. 6 returns "No"), the manufacturing method according to this embodiment again performs image acquisition step ST32 through bonding step ST35. Although details will be omitted, in the second image acquisition step ST32 through bonding step ST35, green hologram substrate 100G and the laminate of red hologram substrate 100A and blue hologram substrate 100B are positioned opposite each other in the Z direction, and the same procedures as described above are performed. In the second captured image acquisition step ST32, green alignment marks 31G, 32G of green hologram substrate 100G are irradiated with second illumination light having a wavelength that includes a green wavelength from one side in the normal direction (Z direction) of green hologram substrate 100G, and green alignment marks 31G, 32G are captured from one side in the normal direction (Z direction) of green hologram substrate 100G to acquire a second captured image, and the light source that irradiates the second illumination light can be, for example, a green LED light source (for example, "HLV3-22GR-2" manufactured by CCS). However, as long as the light source emits light with a wavelength that includes a green wavelength, it is also possible to use, for example, a white LED light source.

[0047] By performing the image acquisition process ST32 twice as described above, the first, second, and third images are acquired as a whole in the image acquisition process ST32. Furthermore, by performing the coordinate detection process ST33 twice, the coordinates of red alignment marks 31R and 32R, green alignment marks 31G and 32G, and blue alignment marks 31B and 32B are detected as a whole in the coordinate detection process ST33. Furthermore, by performing the position adjustment process ST34 twice, the positions of red hologram substrate 100R, green hologram substrate 100G, and blue hologram substrate 100B are adjusted as a whole in the position adjustment process ST34 so that the coordinates of red alignment mark 31R, green alignment mark 31G, and blue alignment mark 31B match, and the coordinates of red alignment mark 32R, green alignment mark 32G, and blue alignment mark 32B match. Furthermore, by performing the bonding step ST35 twice in total, the position-adjusted red hologram substrate 100R, green hologram substrate 100G, and blue hologram substrate 100B are bonded together in the entire bonding step ST35.

[0048] Through the steps described above, all hologram substrates (red hologram substrate 100R, green hologram substrate 100G, and blue hologram substrate 100B) are bonded together ("Yes" in step ST36 shown in FIG. 6), allowing the laminated hologram element to be manufactured. FIG. 7C is a cross-sectional view (XZ cross-sectional view perpendicular to the Y direction) showing an example of a laminated hologram element manufactured by the manufacturing method according to this embodiment. In a preferred embodiment, the laminated hologram element 200 shown in FIG. 7C has a configuration in which a substrate 70 is laminated on the green hologram substrate 100G via an appropriate adhesive or using the self-adhesive photosensitive material 10 that constitutes the green hologram substrate 100G. Examples of materials that can be used as the substrate 70 include glass and resins such as polycarbonate, polyamide, and acrylic.

[0049] According to the manufacturing method of the hologram substrate 100 and the manufacturing method of the laminated hologram element 200 according to the present embodiment described above, an imaging unit (e.g., imaging unit 1a) is disposed on one side of the hologram substrate (e.g., red hologram substrate 100R) in the normal direction. This imaging unit detects and captures diffracted light generated by an alignment mark (e.g., red alignment mark 32R) from one side of the hologram substrate in the normal direction. This allows for easy and accurate reading of the alignment mark on the hologram substrate. Therefore, multiple hologram substrates (red hologram substrate 100R, green hologram substrate 100G, and blue hologram substrate 100B) can be easily and accurately aligned. Furthermore, by bonding the hologram substrates together after adjusting their positions, it is possible to manufacture the laminated hologram element 200 in which the red hologram layer 20R, green hologram layer 20G, and blue hologram layer 20B of each hologram substrate are accurately aligned.

[0050] DESCRIPTION OF SYMBOLS 10: Photosensitive material 20: Hologram layer 31, 32: Alignment mark 40: Mask 41: First opening 42, 43: Second opening 50: Light-transmitting plate 60: Reflection mirror 70: Substrate 100: Hologram substrate (master hologram substrate) 100A: Replica hologram substrate 200: Laminated hologram element L1, L2, L3: Light ST11: Mask placement step ST12: Hologram layer formation step ST13: Alignment mark formation step

Claims

1. A method for manufacturing a hologram substrate having a hologram layer and a plurality of alignment marks provided outside the hologram layer, comprising: a hologram layer forming step of forming the hologram layer by irradiating a photosensitive material with light from two different directions, at least one of which is not the normal direction of the photosensitive material, and causing interference; and an alignment mark forming step of forming the alignment marks consisting of holograms by irradiating a region of the photosensitive material outside the region where the hologram layer is formed with light from one side and the other side of the normal direction of the photosensitive material, and causing interference.

2. A method for manufacturing a hologram substrate as described in claim 1, further comprising, prior to the hologram layer forming process and the alignment mark forming process, a mask arranging process for arranging a mask on the photosensitive material, the mask having a first opening provided in a position corresponding to the hologram layer and a second opening provided in a position corresponding to the alignment mark, and blocking light at other positions, so as to face one side of the normal direction of the photosensitive material; in the hologram layer forming process, light is irradiated onto the photosensitive material from one side of the normal direction of the photosensitive material through the first opening of the mask; and in the alignment mark forming process, light is irradiated onto the photosensitive material from one side of the normal direction of the photosensitive material through the second opening of the mask.

3. A method for manufacturing a hologram substrate as described in claim 2, wherein in the alignment mark forming process, a reflecting mirror is positioned facing the other side of the photosensitive material in the normal direction of the photosensitive material, and the alignment mark is formed by causing interference between light irradiated onto the photosensitive material from one side of the normal direction of the photosensitive material through the second opening of the mask and light reflected by the reflecting mirror and irradiated onto the photosensitive material from the other side of the normal direction of the photosensitive material.

4. A hologram substrate comprising a hologram layer and a plurality of alignment marks, wherein the alignment marks are formed from holograms, and the direction of diffracted light generated when light is irradiated onto the hologram layer from one side in the normal direction of the hologram layer is not the normal direction of the hologram layer, and the direction of diffracted light generated when light is irradiated onto the alignment marks from one side in the normal direction of the alignment marks is the normal direction of the alignment marks.

5. A method for producing a replica hologram substrate by preparing the hologram substrate described in claim 4 as a master hologram substrate and replicating it, the method comprising: a photosensitive material arranging step of arranging a photosensitive material relative to the master hologram substrate so that the photosensitive material faces one side of the master hologram substrate in the normal direction; and a duplication step of duplicating the hologram layer and alignment marks of the master hologram substrate onto the photosensitive material by causing interference between light irradiated onto the photosensitive material from one side of the normal direction of the photosensitive material and diffracted light generated when the light is irradiated onto the master hologram substrate.

6. A method for manufacturing a laminated hologram element by preparing a red hologram substrate as claimed in claim 4, the red hologram substrate having a red hologram layer and red alignment marks formed by irradiating light of a red wavelength, a green hologram substrate having a green hologram layer and green alignment marks formed by irradiating light of a green wavelength, and a blue hologram substrate having a blue hologram layer and blue alignment marks formed by irradiating light of a blue wavelength, and laminating the red hologram substrate, the green hologram substrate, and the blue hologram substrate, an image acquisition step of irradiating the red alignment mark of the red hologram substrate with first illumination light having a wavelength including a red wavelength from one side in a normal direction of the red hologram substrate, and capturing an image of the red alignment mark from one side in the normal direction of the red hologram substrate, thereby acquiring a first captured image; irradiating the green alignment mark of the green hologram substrate with second illumination light having a wavelength including a green wavelength from one side in the normal direction of the green hologram substrate, and capturing an image of the green alignment mark from one side in the normal direction of the green hologram substrate, thereby acquiring a second captured image; and irradiating the blue alignment mark of the blue hologram substrate with third illumination light having a wavelength including a blue wavelength from one side in the normal direction of the blue hologram substrate, and capturing an image of the blue alignment mark from one side in the normal direction of the blue hologram substrate, thereby acquiring a third captured image; a coordinate detection step of detecting coordinates of the red alignment marks, the green alignment marks, and the blue alignment marks by image processing the first captured image, the second captured image, and the third captured image, respectively; a position adjustment step of adjusting positions of the red hologram substrate, the green hologram substrate, and the blue hologram substrate so that the coordinates of the red alignment marks, the green alignment marks, and the blue alignment marks match; and a bonding step of bonding the red hologram substrate, the green hologram substrate, and the blue hologram substrate after the position adjustment.A method for manufacturing a laminated hologram element having the above structure.

Images