WO2021192695A1

WO2021192695A1 - Optical member

Info

Publication number: WO2021192695A1
Application number: PCT/JP2021/005057
Authority: WO
Inventors: 朋一梅澤
Original assignee: 富士フイルム株式会社
Priority date: 2020-03-25
Filing date: 2021-02-10
Publication date: 2021-09-30
Also published as: JPWO2021192695A1; CN115244430A

Abstract

This optical member comprises: a single-layer substrate having a plurality of through holes that transmit light; and an anti-reflection structure that is formed on at least part of the inner wall surfaces of the through holes and includes a plurality of stripe-like grooves.

Description

Optical member

The present disclosure relates to an optical member having a plurality of through holes that emit incident light as parallel light.

An optical member having a plurality of through holes that emits incident light as parallel light is known. The optical member is a member in which a plurality of through holes penetrating the flat plate-shaped substrate in the thickness direction of the substrate are provided, and is also called a perforated plate or the like. In the optical member, a plurality of through holes are arranged two-dimensionally at equal intervals as an example, and one of the arrangement surfaces on which the through holes are arranged is an incident surface and the other is an exit surface.

Japanese Unexamined Patent Publication No. 2004-133308 describes a transfer device having the above optical member and transferring an image displayed on a liquid crystal display to a photosensitive recording medium using light from a light source. In the transfer device, the optical member is arranged between the liquid crystal display and the light source in a posture in which the incident surface, which is one of the array surfaces of the through holes, and the image display surface of the liquid crystal display face each other, and the light from the light source. Is incident on the optical member. The optical member emits the incident light as substantially parallel light by collimating the incident light through the through holes. The parallel light emitted from the optical member is incident on the liquid crystal display, photomodulated by the image of the liquid crystal display, irradiated to the photosensitive recording medium, and the photosensitive recording medium is surface-exposed. As a result, the image displayed on the liquid crystal display is transferred to the photosensitive recording medium.

The optical member described in JP-A-2004-133308 is produced by laminating a plurality of thin plates having a plurality of holes formed so that the positions of the holes are aligned. By stacking the holes of the thin plates, a through hole is formed through the optical member having a laminated structure in which the thin plates are laminated.

The inner wall surface of the through hole of the optical member is painted black, and most of the light incident on the through hole of the optical member that travels diagonally and is incident on the inner wall surface is absorbed, and the depth of the through hole is deep. The straight-ahead component that goes straight in the longitudinal direction (corresponding to the thickness direction of the flat plate-shaped substrate) is emitted through the through hole.

Further, Japanese Patent Application Laid-Open No. 2011-85512 discloses a plate-shaped optical member called a microluber that limits the range of the emitted direction of transmitted light with respect to an image display device having a limited viewing angle. The micro louver is a member that emits light from a liquid crystal display device in substantially parallel light, and has the same function as the above optical member. The micro louver includes a plurality of transparent portions and a light absorbing layer provided so as to surround each transparent portion. Of the light incident on the transparent portion, a part of the oblique light component that travels diagonally and is incident on the light absorption layer is absorbed, and the straight-moving component that travels straight in the thickness direction of the transmitting portion is transmitted through the transmitting portion and emitted.

When producing the micro louvers described in JP-A-2011-85612, first, a transparent photosensitive resin formed in a thin plate shape was exposed to a pattern, and the exposed patterns were developed to arrange them at intervals. Form a plurality of transparent parts. Then, a light absorption layer is formed by filling the gaps between the transparent portions with a black curable resin. As a result, a micro louver in which a plurality of transparent portions are arranged at intervals is produced.

In the micro louver described in Japanese Patent Application Laid-Open No. 2011-85612, a part of the oblique light component of the light incident on the transparent portion is absorbed by the light absorption layer, but antireflection between the transparent portion and the light absorption layer. No structure has been formed. When the oblique light component is reflected at the interface between the transparent portion and the light absorbing layer, the oblique light component cannot be absorbed by the light absorbing layer as a matter of course, so that the oblique light component is emitted from the transparent portion. Since the oblique light component is a negative factor for parallelizing the incident light, there is a demand to reduce it as much as possible. In particular, as the pixel size and pixel pitch become smaller as the number of pixels in an image increases, the influence of the oblique light component on the image quality increases, so that it is highly necessary to suppress the oblique light component.

On the other hand, as described above, the through holes of the optical member described in Japanese Patent Application Laid-Open No. 2004-133308 are formed by laminating a plurality of thin plates in which a plurality of holes are formed by photoetching. When holes are formed in each thin plate by photo-etching, a tapered protrusion is formed on the inner wall surface of the holes in each thin plate due to the side etching phenomenon. Therefore, in an optical member having a laminated structure obtained by laminating a plurality of thin plates so that the positions of the holes are matched, tapered protrusions are generated on the inner wall surface of the through holes by the number of each thin plate. Unevenness is formed. This unevenness has an effect of preventing reflection of an oblique light component on the inner wall surface of the through hole.

However, in a laminated structure such as the optical member of Japanese Patent Application Laid-Open No. 2004-133308, the effect of preventing the reflection of the oblique light component can be obtained by the unevenness formed on the inner wall surface, but the position of the hole of each thin plate is determined in the manufacturing process. Need to match. Therefore, as the pixel size and pixel pitch become smaller, alignment becomes more difficult and there is a concern that the yield decreases.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an optical member capable of emitting parallel light having a higher yield and suppressed oblique light components than before. ..

The optical member of the present disclosure includes a single-layer substrate having a plurality of through holes that transmit light, and a single-layer substrate.
It is an antireflection structure formed on at least a part of the inner wall surface of the through hole, and is an optical member having an antireflection structure including a plurality of streaky grooves.

In the optical member of the present disclosure, it is preferable that the groove includes at least a plurality of streaky first grooves along the depth direction of the through hole.

Alternatively, in the optical member of the present disclosure, it is preferable that the groove includes at least a plurality of streaky second grooves along the direction intersecting the depth direction of the through hole.

In the optical member of the present disclosure, it is more preferable that the groove further includes, in addition to the first groove, a plurality of streaky second grooves along the direction intersecting the depth direction of the through hole.

In the optical member of the present disclosure, it is preferable that the average period of the plurality of first grooves and the average period of the plurality of second grooves are different.

In the optical member of the present disclosure, the substrate is preferably an opaque material.

In the optical member of the present disclosure, it is preferable that the through hole has an aspect ratio larger than 20 which is a ratio of the depth to the size of the opening.

In the optical member of the present disclosure, it is preferable that the size of the opening of the through hole is larger than the average period of the groove.

In the optical member of the present disclosure, the size of the opening of the through hole is preferably 5 to 100 μm.

It is preferable that the optical member of the present disclosure is provided with a plurality of through holes, and the arrangement of the plurality of holes is a square arrangement.

In the optical member of the present disclosure, it is preferable that the difference between the transmittance of the substrate with respect to light and the transmittance of the through hole is 70% or more.

In the optical member of the present disclosure, the through hole may be filled with a transparent material.

In the optical member of the present disclosure, it is preferable that the groove is provided at at least one open end of the through hole.

In the optical member of the present disclosure, it is preferable that the antireflection structure has an irregular structure.

In the optical member of the present disclosure, it is preferable that a fine concavo-convex structure is formed on at least one of the front and back surfaces of the substrate other than the opening of the through hole.

In the optical member of the present disclosure, it is preferable that the fine concavo-convex structure has an irregular structure.

In the optical member of the present disclosure, it is preferable that a protective layer is provided on the surface of the substrate on which the fine concavo-convex structure is formed.

In the optical member of the present disclosure, it is preferable that the depth of the groove of the antireflection structure is deeper than the depth of the recess of the fine concavo-convex structure.

In the optical member of the present disclosure, it is preferable that the substrate is silicon.

According to the present disclosure, it is possible to provide an optical member capable of producing a product having a good yield and emitting parallel light in which an oblique light component is suppressed.

It is a perspective view of the optical member of one Embodiment. FIG. 5 is a schematic cross-sectional view taken along line II-II of the optical member shown in FIG. It is an enlarged view of the inner wall surface of an example of a through hole. It is an enlarged view of the inner wall surface of another example of a through hole. It is an enlarged view of the inner wall surface of still another example of a through hole. It is explanatory drawing of an optical member. It is sectional drawing of the optical member of the design change example. It is sectional drawing of the optical member of another design change example. It is a figure for demonstrating the use example of an optical member. It is a figure which shows the process of the manufacturing method of an optical member. It is a figure which shows the manufacturing process of the substrate which has a fine concavo-convex structure. It is a figure which shows the process of the breakthrough treatment for the fine concavo-convex layer containing the hydrate of alumina. It is a figure which shows an example of a mask forming process. It is a figure which shows another example of a mask forming process. It is a figure which shows the inner wall surface of a recess. It is a figure for demonstrating the etching process. It is a figure for demonstrating the etching process. It is a figure which shows another example of the inner wall surface of a recess. It is a scanning micrograph which shows a part of the structure produced in the demonstration experiment. It is a scanning micrograph which enlarged a part of the structure shown in FIG. It is a scanning micrograph which further enlarged a part of the structure shown in FIG.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For easy visibility, the film thickness of each layer and their ratios are appropriately changed and drawn, and do not necessarily reflect the actual film thickness and ratio. In the present specification, the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.

The optical member of the present disclosure is a single-layer substrate having a plurality of through holes that transmit light, and an antireflection structure formed on at least a part of the inner wall surface of the through holes, and includes a plurality of streaky grooves. It has an anti-reflection structure.

FIG. 1 is a perspective view of the optical member 1 of one embodiment, and FIG. 2 is a diagram schematically showing a cross section of the optical member 1 shown in FIG. 1 in line II-II. The optical member 1 has a single-layer substrate 10 having a plurality of through holes 21 that transmit light, and an antireflection structure formed on at least a part of the inner wall surface 21b of the through holes 21, and has a plurality of streaky grooves. It is provided with an antireflection structure 25 including 24. The through hole 21 is provided so as to penetrate from one surface 10a of the substrate 10 to the other surface 10b, and the substrate 10 has an opening of the through hole 21 on the one surface 10a and the other surface 10b. The antireflection structure 25 is composed of a concavo-convex structure including a concave portion which is a plurality of streaky grooves 24 formed on the inner wall surface 21b and a convex portion between the grooves 24. In the optical member 1, one surface 1a and the other surface 1b of the optical member 1 coincide with the one surface 10a and the other surface 10b of the substrate 10.

The “single-layer substrate” means that the substrate 10 on which the through hole 21 is provided is a single layer, and the substrate 10 is not formed by laminating a plurality of layers. Naturally, the optical member 1 is a single layer. It does not mean that it is a layer. Therefore, it is not intended to exclude that the optical member 1 is composed of a plurality of layers as a whole by providing a protective layer or coating on the surface of the substrate 10. Since the substrate 10 on which the through holes 21 are provided is a single layer in the optical member 1, a thin plate having a plurality of holes formed by photoetching is formed like the optical member described in JP-A-2004-133308. It can be manufactured with a higher yield as compared with the case where it is formed by laminating a plurality of layers.

Further, the "streak-shaped groove" is a portion of the inner wall surface 21b that is recessed with respect to the most convex surface on the central axis side of the through hole 21 in one direction (in the example shown in FIG. 2, the depth direction Z). A groove that is continuously formed in a direction in which the length of the groove along one direction is three times or more the width of the groove in the direction orthogonal to one direction. The "most convex surface" on the central axis side of the through hole 21 is, for example, when a streak-shaped groove is formed by processing the inner wall surface 21b immediately after the through hole 21 is formed, the inside On the wall surface 21b, the unprocessed surface remaining adjacent to the streaky groove is the "most convex surface". Further, the groove 24 may be a groove whose width does not change in the length direction, or may be a groove whose width changes in the length direction. When the width of the groove 24 is changed, the width of the groove 24 used for comparison with the length of the groove 24 is the width at the widest portion.

The plurality of streaky grooves 24 constituting the antireflection structure 25 show, as an example, the streak-shaped grooves 24 along the depth direction Z of the through hole 21 in FIG. Examples of the shape of the streaky groove 24 are schematically shown in FIGS. 3 to 5. 3 to 5 are perspective views showing a part of the inner wall surface 21b of the through hole 21, and the vertical direction of the paper surface coincides with the depth direction Z of the through hole 21.

FIG. 3 is a schematic view showing an enlarged groove 24 shown in FIG. The grooves shown in FIG. 3 are a plurality of streaky first grooves 24a along the depth direction Z of the through hole 21. In the present specification, the "streak-shaped first groove 24a along the depth direction of the through hole 21" is not limited to the groove extending in the direction parallel to the depth direction as shown in FIG. , Includes a groove extending in a direction having an inclination in the range of ± 30 ° with respect to the depth direction. Further, the plurality of first grooves 24a may be parallel to each other, but may be non-parallel to each other. Further, the width of the first groove 24a may be changed so as to be narrowed or widened as it progresses in the depth direction. The distance P1 between the concave depth d1 of the first groove 24a and the adjacent first groove 24a may or may not be uniform. The average of the distances P1 between adjacent first grooves 24a is called the average period of the first grooves 24a.

Further, the plurality of streaky grooves 24 constituting the antireflection structure provided in the optical member 1 are not limited to the first groove 24a along the depth direction Z as described above. As shown in FIG. 4, there may be a plurality of streaky second grooves 24b along the direction intersecting the depth direction Z. The second groove 24b shown in FIG. 4 is a streak-like groove along a direction orthogonal to the depth direction Z, and is a groove extending in a direction parallel to one surface 10a of the substrate 10. However, the second groove 24b may be in a direction that intersects the depth direction Z, and is not limited to a groove that is orthogonal to the depth direction Z. Similar to the first groove 24a, the plurality of second grooves 24b may be parallel to each other, but may be non-parallel to each other. The width of the second groove 24b may also change in the direction in which the groove 24b extends. The average of the distance P2 between the second grooves 24b adjacent to the concave depth d2 of the second groove 24b is called the average period of the second groove 24b.

Further, as the plurality of streaky grooves 24 constituting the antireflection structure provided in the optical member 1, as shown in FIG. 5, the plurality of streaky first grooves 24a along the depth direction of the through hole 21 , And a groove in which a plurality of streaky second grooves 24b along the direction intersecting in the depth direction are combined in a grid shape may be included. In FIG. 5, the average period of the first groove 24a and the average period of the second groove 24b are substantially the same, but the average period of the first groove 24a and the second groove 24b may be different.

The distance P1 between the first grooves 24a and the distance P2 between the second grooves 24b may be regular or irregular. However, it is preferable that the distance between the grooves is irregular because the interference of light can be suppressed.

The streak-shaped groove 24 is a concept that collectively refers to a groove formed on an inner wall surface including the first groove 24a and the second groove 24b. Both the groove 24a and the second groove 24b are targeted.

For the average period of the streaky grooves 24, the substrate 10 is cut at a position where the inner wall surface 21b of the through hole 21 can be observed, and the inner wall surface 21b is observed from the front with a scanning electron microscope (SEM). measure. In the region where the streaky grooves 24 are observed in the SEM image, the distances between the grooves 24 at arbitrary 10 points are measured, and the average value of the measured distances is defined as the average period of the grooves 24. The average period of the streaky grooves 24 is, for example, several nm to 1 μm, but may be 10 nm to 800 nm, 10 nm to 400 nm, and further 10 nm to 200 nm. The preferable average period differs depending on the wavelength λ of the light to which the present member is applied, and the average period is preferably the wavelength λ or less used, and more preferably half or less (λ / 2 or less) of the wavelength used. For example, in order to obtain an antireflection effect in the visible light range of a wavelength of 380 nm to 780 nm, the average period of the streaky groove 24 is preferably the shortest wavelength of 380 nm or less, and further, 190 nm, which is half of the shortest wavelength of 380 mm. The following is more preferable. The concave depth of the groove 24 is, for example, several nm to 1 μm, but may be 10 nm to 800 nm, 10 nm to 400 nm, and further 10 nm to 200 nm. Further, from the viewpoint of more effectively obtaining antireflection, the concave depth of the groove 24 is preferably λ / 4 or more, more preferably λ / 2 or more, when the wavelength used is λ. For example, in order to obtain the antireflection effect in the range of visible light having a wavelength of 380 nm to 780 nm, the concave depth of the groove 24 is preferably 195 nm or more, which is λ / 4 with the longest wavelength of 780 nm, and 390 nm or more, which is λ / 2 or more. More preferred. Here, the concave depth of the groove 24 is the distance in the groove depth direction from the most recessed portion of the groove 24 to the position of the convex portion between the grooves 24.

The optical member 1 can be used, for example, as a collimator that emits incident light as parallel light. As schematically shown in FIG. 6, of the light incident from one surface 1a of the optical member 1, the straight component L1 that is incident on the through hole 21 and travels along the depth direction passes through the through hole 21 as it is and is optical. It is emitted from the other surface 1b of the member 1. On the other hand, the oblique light component L2 obliquely incident on the through hole 21 is incident on the inner wall surface 21b inside the through hole 21. Since the antireflection structure 25 in which a plurality of streaky grooves 24 are formed on the inner wall surface 21b is provided, the oblique light component L2 incident on the inner wall surface 21b is hardly reflected. When the inner wall surface 21b of the through hole 21 does not have the antireflection structure 25, at least a part of the oblique light component L2 is reflected once or multiple times by the inner wall surface 21b as shown by the broken line in FIG. It is emitted from the through hole 21. According to the optical member 1, the reflection of the light incident on the inner wall surface 21b can be suppressed, and as a result, the obliquely incident light incident on the inner wall surface 21b of the through hole 21 is emitted from the other surface 1b of the optical member 1. Can be suppressed. Therefore, according to the present optical member 1, it is possible to emit parallel light in which the oblique light component of the incident light is sufficiently suppressed.

It is preferable that the difference between the transmittance of the substrate 10 and the transmittance of the through hole 21 with respect to the light to be parallelized is 70% or more. The transmittance of the substrate 10 means the transmittance of light in a portion other than the through hole 21 of the substrate. When the difference between the transmittance of the substrate 10 and the transmittance of the through hole 21 is 70% or more, the emitted light that has become parallel light can be efficiently extracted.

It is preferable that the substrate 10 is an opaque material. If the substrate 10 is an opaque material, the light incident on one surface 10a and the other surface 10b of the substrate 10 and the light incident on the inner wall surface 21b of the through hole 21 are absorbed, so that the light is mixed between the through holes 21. It can be suppressed and the parallel lightening can be further improved. Here, opaque means that the transmittance for the light of the object to be parallelized is less than 30%. Visible light is mainly assumed as the target light, but infrared light or ultraviolet light may be used. Examples of materials that are opaque to visible light include silicon. A silicon wafer applicable to the substrate 10 is easily available and easy to handle.

If at least one surface 10a, the other surface 10b, and the inner wall surface 21b of the through hole 21 of the substrate 10 are painted black, the light incident on the one surface 10a, the other surface 10b, and the inner wall surface of the through hole 21 of the substrate 10 is absorbed. do. Therefore, even if the unpainted substrate itself is a transparent material, the substrate 10 has substantially the same transmittance as the opaque material by applying the black coating. Further, the through hole 21 may be hollow, but the through hole 21 may be filled with a transparent material.

As shown in the through holes 21 at both ends of the plurality of through holes 21 shown in FIG. 2, the streak-shaped grooves 24 may be provided over the entire area in the depth direction, but other through holes 24 may be provided. As shown in the through hole 21, it may be provided at least in a part. When the groove 24 is partially provided, it may be provided in the depth direction of the through hole 21, for example, in a region occupying 1% or more and 50% or less with respect to the depth D. Further, when the groove 24 is partially provided, it may be provided anywhere in the depth direction of the through hole 21. The groove 24 may be provided at the opening end of the through hole 21 in the depth direction, or may be provided inside the opening end. Further, the provided portion is not limited to one location, and may be provided at a plurality of discrete locations. Here, the opening end includes the opening of the through hole 21 located on one surface 10a or the other surface 10b of the substrate 10, and means a range of 1% with respect to the depth D from the opening. The average period of the streaky grooves 24 is measured in the region where the grooves 24 are formed.

If the groove 24 is provided on at least a part of the inner wall surface 21b of each through hole 21, the groove 24 is formed on the inner wall surface 21b of the oblique light component of the light incident into the through hole 21 from one end of each through hole 21. Reflection can be suppressed at least partially. The oblique light component traveling in a direction largely inclined with respect to the depth direction of the through hole 21 is incident on the inner wall surface 21b at the opening end of the through hole 21. Therefore, if the groove 24 is provided at least at the open end, the reflection of the oblique light component that is greatly inclined is suppressed, so that parallel light can be promoted, which is preferable.

The through hole 21 preferably has an aspect ratio D / A, which is the ratio of the depth D to the opening size A, to be larger than 20. If the through hole 21 has a tapered shape and the size of the opening on one surface 10a of the substrate 10 is different from the size of the opening on the other surface 10b, the size of the smaller opening is used as the size of the through hole 21. It is defined as the size A of the opening. The size of the opening shall be the diameter equivalent to the circle of the opening. If the aspect ratio of the through hole 21 is larger than 20, most of the oblique light component is incident on the inner wall surface 21b in the through hole 21 and absorbed, so that the parallelization of light can be sufficiently enhanced.

The size of the opening of the through hole 21 is preferably larger than the average period of the groove 24. The size of the opening of the through hole 21 is, for example, 5 μm to 1000 μm, preferably 5 μm to 500 μm, and even more preferably 5 μm to 100 μm.

Further, in the optical member 1, a fine concavo-convex structure 30 having an antireflection function is formed in a portion other than the opening of the through hole 21 on one surface 10a, which is one surface of the front and back surfaces of the substrate 10.

Since the fine concavo-convex structure 30 has an antireflection function, in the optical member 1 of this example, it is possible to suppress the reflection of light incident on a portion other than the opening of the through hole 21 on the one surface 10a. The fine concavo-convex structure 30 may include irregularities in a regular arrangement, but is preferably an irregular structure. If the fine concavo-convex structure is an irregular structure, light interference can be suppressed. Here, the term "irregular structure" means that, for example, the size or shape of the convex portions 32 is not uniform, or the arrangement pitch, which is the distance between a plurality of adjacent convex portions 32, is not uniform. In addition, at least one of the size, shape and arrangement pitch of the convex portion 32 means a structure in which the protrusions 32 are not regular. The average period of the fine concavo-convex structure 30 is approximately 1 μm or less. Here, the average period of the fine concavo-convex structure 30 is the average of the distances between the plurality of convex portions 32. The distance between the convex portions 32 is the distance from the convex portion located closest to the convex portion 32 when focusing on one convex portion 32, and is the distance between the vertices of the two convex portions. be. Specifically, in a scanning electron microscope (SEM) image on the surface of the fine concavo-convex structure 30, the distances between the convex portions 32 at arbitrary 10 points are measured, and the average value of the measured distances is calculated. The average period of the fine concavo-convex structure 30 is set. The average period of the fine concavo-convex structure 30 is, for example, several nm to 1 μm, but may be 10 nm to 800 nm, 10 nm to 400 nm, and further 10 nm to 200 nm. The preferable average period differs depending on the wavelength λ of the light to which the present member is applied, and the average period is preferably the wavelength λ or less used, and more preferably half or less (λ / 2 or less) of the wavelength used. For example, in order to obtain an antireflection effect in the visible light range of a wavelength of 380 nm to 780 nm, the average period of the streaky groove 24 is preferably the shortest wavelength of 380 nm or less, and further, 190 nm, which is half of the shortest wavelength of 380 mm. The following is more preferable. The unevenness difference e of the fine uneven structure 30 is, for example, several nm to 1 μm, but may be 10 nm to 800 nm, 10 nm to 400 nm, and further 10 nm to 200 nm. Further, from the viewpoint of more effectively obtaining antireflection, the unevenness difference e of the fine uneven structure 30 is preferably λ / 4 or more, and more preferably λ / 2 or more, when the wavelength used is λ. For example, in order to obtain the antireflection effect in the range of visible light having a wavelength of 380 nm to 780 nm, the concave depth of the groove 24 is preferably 195 nm or more, which is λ / 4 with the longest wavelength of 780 nm, and 390 nm or more, which is λ / 2 or more. More preferred.

When the fine concavo-convex structure 30 is provided as in the optical member 1, the recess depth d (d1, d2) of the groove 24 of the antireflection structure 25 provided on the inner wall surface 21b of the through hole 21 is the fine concavo-convex structure. It is preferably deeper than the unevenness difference e of 30. Of the light incident from one surface 10a of the optical member 1, the incident angle of the oblique light component incident on the inner wall surface 21b is larger than the incident angle of the light on the fine concavo-convex structure 30 as a whole. For light with a large incident angle, the larger the difference in unevenness, the higher the antireflection effect. Therefore, by making the depth of the streak-shaped recesses formed on the inner wall surface 21b of the through hole 21 deeper than the unevenness difference of the fine concave-convex structure 30, sufficient reflection prevention is provided for the oblique light component incident at a large incident angle. The effect is obtained.

In the optical member of the present disclosure, the fine concavo-convex structure 30 is not essential, but it is more preferable to provide the fine concavo-convex structure 30 on at least one of the front and back surfaces of the substrate. By providing the fine concavo-convex structure 30 on at least one of the front and back surfaces of the substrate, it is possible to suppress the reflection of light incident on a portion other than the through hole as described above. The reflected light on at least one of the front and back surfaces becomes a noise component with respect to the parallel light transmitted through the through hole 21. Therefore, by suppressing the reflected light by the fine concavo-convex structure 30, it is possible to reduce the mixing of noise components into the parallel light transmitted through the through hole 21.

7 and 8 show schematic cross-sectional views of the

optical members

2 and 3 of the other embodiments. The same elements as those of the optical member 1 of FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The optical member 2 has a fine concavo-convex structure 30 formed not only on one surface 10a of the substrate 10 but also on a portion other than the opening of the through hole 21 on the other surface 10b. By providing the fine concavo-convex structure 30 having an antireflection function on both the front and back surfaces of the substrate 10 in this way, the reflection of light incident on the portion other than the opening of the through hole 21 is suppressed on both the front and back surfaces of the substrate 10. be able to. Therefore, it is possible to further reduce the mixing of noise components into the parallel light transmitted through the through hole 21 as compared with the case where the fine concavo-convex structure 30 is provided on one of the front and back surfaces.

The optical member of the present disclosure may be further provided with a protective layer 35 on the surface of the fine concavo-convex structure 30, as shown in FIG. 8 as another example of the optical member 3. By providing the protective layer 35, it is possible to protect the fine uneven structure and improve the durability. As the protective layer 35, a transparent hard coat film is preferable, and for example, a PET (Polyethylene terephthalate) film or the like can be used.

FIG. 9 shows an example of the use of the optical member of the present disclosure. As shown in FIG. 9, the optical member 3 of the present disclosure can be used in the transfer device 100 that transfers the image displayed on the liquid crystal display 101 to the photosensitive recording medium 102. Although the case where the optical member 3 is provided is shown in FIG. 9, the optical member 1 shown in FIG. 6 or the optical member 2 shown in FIG. 7 can also be used. In the transfer device 100, the optical member 3 is in a posture in which one surface 10a of the substrate 10 provided with the through hole 21 and the image display surface of the liquid crystal display 101 face each other, and the liquid crystal display 101 and the photosensitive recording medium It is arranged between the 102 and the light from the liquid crystal display 101. The optical member 3 emits light incident on the optical member 3 as substantially parallel light by collimating with each through hole 21. The photosensitive recording medium 102 is surface-exposed by the light emitted from each through hole 21. As a result, the image displayed on the liquid crystal display 101 is transferred to the photosensitive recording medium 102.

The size and arrangement pitch of the through holes 21 are preferably formed so as to correspond to the pixel size and pixel pitch of the liquid crystal display 101. Therefore, when the pixels of the liquid crystal display 101 are in a square arrangement, it is preferable that the arrangement of the through holes 21 in the substrate 10 is also in a square arrangement. In particular, if the pixels of the liquid crystal display 101 and the through holes 21 have a 1: 1 correspondence, it is possible to obtain a higher sharp exposure image without causing light mixing between the pixels.

Since the optical member 3 has a fine concavo-convex structure 30 on the surface 10a on which the light from the liquid crystal display 101 is incident, the light incident on the surface 10a other than the through hole 21 is suppressed from being reflected on the surface 10a and is incident. Most of the emitted light is absorbed by the substrate 10. On the other hand, of the light incident on the through hole 21 from one surface 10a of the substrate 10, the straight component is emitted from the other surface 10b as it is, passes through the protective layer 35, and is irradiated to the photosensitive recording medium 102. On the other hand, of the light incident on the through hole 21, the oblique light component is incident on the inner wall surface 21b inside the through hole 21. Since the optical member 3 is provided with the antireflection structure 25 on the inner wall surface 21b of the through hole 21, the oblique light component incident on the inner wall surface 21b is not reflected and most of it is absorbed by the substrate 10. Further, a part of the light emitted from the other surface 10b of the substrate 10 and irradiating the photosensitive recording medium 102 may be reflected by the photosensitive recording medium 102 and returned to the optical member 3 side. Since the other surface 10b of the substrate 10 is also provided with the fine concavo-convex structure 30, it is possible to prevent the light incident on the other surface 10b from being reflected, and to prevent the light from being reflected again and heading toward the photosensitive recording medium. Therefore, the optical member 3 can guide only the linear component of the light emitted from the liquid crystal display 101 to the photosensitive recording medium 102, and can obtain an image with less bleeding and high transfer accuracy.

Further, in the optical member 3, the protective layer 35 is provided on the other surface 10b of the substrate 10 facing the photosensitive recording medium 102 to protect the fine concavo-convex structure 30, so that the photosensitive recording medium 102 comes into contact with the optical member 3. It is possible to prevent damage to the fine concavo-convex structure 30 in such a case.

Next, the manufacturing method of the optical member of the present disclosure will be described. Here, an example of a manufacturing method for manufacturing the optical member 2 will be described with reference to FIGS. 10-18. As shown in FIG. 10, the manufacturing process includes a substrate preparation step (ST1), a mask forming step (ST2), a dry etching step (ST3), and a mask removing step (ST4).

<Board preparation process>
First, as shown in ST1 of FIG. 10, a substrate 10 having a fine concavo-convex structure 30 having an average period of 1 μm or less on one surface 10a is prepared. An example of the substrate preparation process is shown in FIG. An example of the substrate preparation step is a step of forming a thin film containing aluminum on one surface of the substrate 9 to be processed (ST12), and the thin film containing aluminum is treated with warm water to change it into a fine concavo-convex layer containing alumina hydrate. It includes a step (ST13), a step of etching one surface of the substrate 9 to be processed from the fine concavo-convex layer side (ST14), and a step of removing the fine concavo-convex layer (ST15).

First, as shown in ST12 of FIG. 11, a thin film 50 containing aluminum (hereinafter referred to as an Al-containing thin film 50) is formed on one surface of the substrate 9 to be processed.

The Al-containing thin film 50 is, for example, a thin film made of any one of aluminum, aluminum oxide, aluminum nitride, and an aluminum alloy, but is changed to a fine concavo-convex layer containing an alumina hydrate such as boehmite by hot water treatment in a subsequent step. It may be a material. The "aluminum alloy" refers to silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), zinc (Zn), chromium (Cr), titanium (Ti) and nickel. It contains at least one element such as (Ni) and means a compound or a solid solution containing aluminum as a main component. From the viewpoint of forming an uneven structure, the Al-containing thin film 50 preferably has an aluminum component ratio of 80 mol% or more with respect to all metal elements.

The thickness of the Al-containing thin film 50 may be set according to the desired thickness of the fine concavo-convex layer obtained in the subsequent step. For example, the thickness of the Al-containing thin film 50 is 0.5 to 60 nm, preferably 2 to 40 nm, and particularly preferably 5 to 20 nm.

The method for forming the Al-containing thin film 50 is not particularly limited. For example, general film forming methods such as a resistance heating vapor deposition method, an electron beam vapor deposition method, and a sputtering method can be used.

Next, as shown in ST13 of FIG. 11, in the hot water treatment step, the Al-containing thin film 50 is hot-water treated. For example, as shown in ST13 of FIG. 11, the entire substrate 9 on which the Al-containing thin film 50 is formed is immersed in hot water by heating the pure water 56 in the container 55 using the hot plate 58. By hot water treatment, as shown in ST14 of FIG. 11, the Al-containing thin film 50 can be changed into a fine concavo-convex layer 52 containing an alumina hydrate. The fine concavo-convex layer 52 has a plurality of convex portions and a plurality of concave portions formed in an irregular shape and arrangement. The size of the convex portions of the concave-convex structure layer and the average distance between the convex portions (that is, the average period of the irregularities) can be controlled by the material of the Al-containing thin film 50, the formation thickness, and the hot water treatment conditions. Its average period is approximately 1 μm or less.

Here, "hot water treatment" means a treatment in which hot water acts on a thin film containing aluminum. The hot water treatment includes, for example, a method of immersing the laminate in which the thin film 50 containing aluminum is formed in water at room temperature and then boiling the water, a method of immersing the laminate in warm water maintained at a high temperature, or a method of immersing the laminate in hot water maintained at a high temperature. It is a method of exposing to. As described above, in the present embodiment, the pure water 56 in the container 55 is heated using the hot plate 58 to make hot water, and the substrate 9 to be processed is immersed in the hot water. The time of immersion in warm water and the temperature of hot water are appropriately set according to the desired uneven structure. As a guide, the time is 1 minute or more, and 3 minutes or more and 15 minutes or less are particularly suitable. The temperature of the hot water is preferably 60 ° C. or higher, and particularly preferably higher than 90 ° C. The higher the temperature, the shorter the processing time tends to be. For example, when a thin film containing aluminum having a thickness of 10 nm is boiled in warm water at 100 ° C. for 3 minutes, an irregular uneven structure in which the distance between the convex portions is 50 nm to 300 nm and the height of the convex portions is 50 nm to 100 nm is obtained. Be done.

Further, as shown in ST15 of FIG. 11, the surface of the substrate 9 to be processed on which the fine concavo-convex layer 52 containing alumina hydrate is formed is etched from the fine concavo-convex layer 52 side using the etching gas G2. As a result, as shown in ST1, a substrate 10 having a fine concavo-convex structure 30 on one surface 10a can be obtained. When etching is performed from the surface of the fine concavo-convex layer 52, the concavo-convex shape of the surface of the fine concavo-convex layer 52 gradually recedes due to dissolution erosion due to etching, and the unevenness of the fine concavo-convex layer 52 is reflected on the surface of the substrate 9 to be processed. Dissolved erosion acts in this form. As a result, the fine concavo-convex structure 30 that reflects the morphology of the fine concavo-convex layer 52 is formed on the surface of the substrate 9 to be processed. It should be noted that the meaning that the uneven shape of the fine uneven layer 52 is "reflected" means that the convex portion or the concave portion of the concave-convex shape has a convex portion or a concave portion at a position corresponding to one-to-one. It is not necessary and means a state that has some similarity to undulations.

In this etching step, it is preferable to use, for example, reactive ion etching, reactive ion beam etching, or the like. It is preferable to perform etching under the condition that the etching rate of the substrate 10 is higher than the etching rate of the fine concavo-convex layer 52. Examples of the etching gas G2 having high etching efficiency with respect to the substrate 10 include a fluorine-based gas or a chlorine-based gas similar to the etching gas G1.

Before the etching step of the substrate 9 to be processed, it is preferable to perform a breakthrough process of etching the fine concavo-convex layer 52 until at least a part of the surface of the substrate 9 to be processed is exposed. Specifically, as shown in FIG. 12, after the fine concavo-convex layer 52 is formed (ST14), the fine concavo-convex layer 52 is etched (ST40), and the substrate to be processed is formed in at least a part of the recesses of the fine concavo-convex layer 52. The surface of 9 is exposed (ST41). In this breakthrough process, in order to efficiently etch the fine concavo-convex layer 52, an etching gas G3 having a high etching efficiency for alumina hydrate is used. As the etching gas G3, for example, _{a gas containing argon (Ar) and trifluoromethane (CHF 3} ) is used. After that, in order to form the fine concavo-convex structure 30 on the surface of the substrate 9 to be processed, as shown in ST42 of FIG. 12, etching is performed on the surface of the substrate 9 to be processed using the etching gas G2 from the fine concavo-convex layer 52 side. As a result, a substrate 10 having a fine concavo-convex structure 30 on one surface 10a is obtained (ST1). By performing the breakthrough process, the time required for the etching process of the substrate can be significantly shortened, so that the manufacturing efficiency of the entire manufacturing process can be improved.

The mask removing step preferably includes a washing step using sulfuric acid superwater which is a mixture of _{sulfuric acid H 2} SO ₄ and hydrogen peroxide H ₂ O _{2, for example, SH-303 manufactured by Kanto Chemical Co., Inc.} By using sulfuric acid hydrogen peroxide, the fine uneven layer 52 remaining after the etching step can be efficiently removed.

The method for producing a substrate having a fine concavo-convex structure on its surface is not limited to the above. A substrate having a fine concavo-convex structure on the surface may be produced by irregularly adhering fine particles such as Cr to a flat plate-shaped substrate to be processed and etching the substrate surface using the particles as a mask. Further, a resin layer is formed on the surface of the substrate to be processed, and the uneven pattern of the mold having the uneven pattern is pressed against the resin layer to transfer the uneven pattern to the resin layer to form a mask by the resin layer on the surface of the substrate. By etching the surface of the substrate to be processed using this resin layer as a mask, a substrate having a fine concavo-convex structure on the surface may be produced. However, as described above, according to the method of forming a fine concavo-convex structure containing alumina hydrate, irregular fine concavo-convex structure of 1 μm or less can be easily produced, so that a substrate having a fine concavo-convex structure can be efficiently produced. Can be made well.

<Mask forming process>
Next, as shown in ST2 of FIG. 10, in the mask forming step, a mask 42 having an opening pattern 41 is formed on the fine concavo-convex structure 30.

The method for forming the mask 42 and the mask material in the mask forming step are not particularly limited, but it is preferable that the mask 42 is made of an organic material. If an organic material is used, a mask 42 having a desired opening pattern can be easily formed. Hereinafter, a method of forming the mask 42 from an organic material will be briefly described.

An example mask forming step includes a photoresist coating step, a photoresist exposure step, and a photoresist developing step. As shown in ST21 of FIG. 13, a positive photoresist 40 is applied to one surface 10a of the substrate 10. As shown in ST22 of FIG. 13, an exposure mask 47 is arranged on the photoresist 40, and the portion 40a forming the opening of the photoresist 40 is exposed by irradiating the laser beam L. After that, by developing the photoresist 40, only the exposed portion 40a of the photoresist 40 can be dissolved to form an opening, and a mask 42 having an opening pattern 41 can be formed (ST2).

Alternatively, the mask forming step of another example may include a step of applying the resin layer and a step of transferring the uneven pattern to the resin layer. As shown in ST23 of FIG. 14, a resin layer 46 made of, for example, a photocurable resin composition is applied to one surface 10a of the substrate 10. Then, as shown in ST24 of FIG. 14, an imprinting die 48 having a concavo-convex pattern corresponding to the opening pattern 41 of the mask 42 to be formed is used, and the concavo-convex pattern surface is pressed against the resin layer 46 to press the resin layer. The uneven pattern is transferred to 46. Then, as shown in ST25 of FIG. 14, the resin layer 46 is cured by irradiating the resin layer 46 with ultraviolet light 49, and then the imprinting die 48 is peeled off to form an opening pattern on the substrate 10. A mask 42 having 41 can be obtained (ST2).

<Dry etching process>
After that, as shown in ST3 of FIG. 10, in the dry etching step, the mask 42 formed in the mask forming step is used to perform dry etching on one surface 10a of the substrate 10 with the etching gas G1. By this dry etching, a through hole 21 corresponding to the opening pattern of the mask 42 is formed on one surface 10a of the substrate 10.

In the dry etching step, reactive ion etching is preferable. In order to make the etching rate for the substrate 10 larger than the etching rate for the mask 42, it is preferable to use the etching gas G1 having high etching efficiency for the substrate 10. Specific examples thereof include a fluorine-based gas or a chlorine-based gas. As the fluorine-based gas, for example, trifluoromethane (CFH ₃ ) or sulfur hexafluoride (SF ₆ ) can be used, and as the chlorine-based gas, for example, chlorine gas (Cl ₂ ) can be used.

When the through hole 21 is formed by dry etching on the substrate 10 provided with the fine uneven structure 30 on one surface 10a, as shown in FIG. 15, the inner wall surface 21b of the through hole 21 corresponds to the unevenness of the fine uneven structure 30. A streaky groove 24 is formed. FIG. 15 is a cross-sectional view of a portion of the optical member 1 including one through hole 21. The inner wall surface 21b of the through hole 21 has a width substantially corresponding to the width of the convex portion 32 of the fine concavo-convex structure 30 or the distance between the convex portions 32, and has a streak-like groove along the depth direction of the through hole 21. 24 is formed. In FIG. 15, the gray hatched portion is a groove 24 that is concave with respect to the white portion. The width of the streaky grooves 24 has a width substantially corresponding to the width of the convex portions 32 or the spacing between the convex portions 32 on the surface layer side in the depth direction, but the width gradually narrows on the deep layer side.

The reason why the streaky groove 24 as shown in FIG. 15 is formed is, roughly speaking, the interaction between the plurality of convex portions 32 of the fine concavo-convex structure 30 and the mask 42. The principle of forming the streaky groove 24 as shown in the figure will be described with reference to FIGS. 16 and 17. In FIGS. 16 and 17, the left figure shows a state in which the mask 42 is formed on the fine uneven structure 30 on one surface of the substrate 10 before the dry etching process, and the right figure shows the mask removed after the dry etching process. Indicates the state. In each view, the upper view is a plan view of the structure viewed from above the convex portion 32, and the lower view is a side view.

First, in the example of FIG. 16, when the mask 42 is formed on the substrate 10, the entire plurality of convex portions 32 of the fine concavo-convex structure 30 are masked in the vicinity of the boundary B corresponding to the inner wall surface 42a of the opening portion of the mask 42. The case where it is not covered by 42 is shown. That is, in the left view of FIG. 16, the inner wall surface 42a of the opening portion of the mask 42 is formed so as to bypass the foot portion of the convex portion 32 formed in a substantially conical shape.

As shown in the upper part of the left figure of FIG. 16, the portion of the inner wall surface 42a of the mask 42 that bypasses the convex portion 32 is recessed toward the inside of the mask 42 rather than the portion between the adjacent convex portions 32. When etching is performed to form the through hole 21 in this state, the portion of the convex portion 32 where the mask 42 is not provided is scraped in the depth direction by etching in the vicinity of the boundary B. On the other hand, the portion protected by the mask 42 is not scraped. Therefore, in the vicinity of the boundary B, the portions corresponding to the plurality of convex portions 32 are etched in the depth direction, and the inner wall surface 21b of the through hole 21 has a width substantially corresponding to the width of the convex portions 32, and A streak-like groove 24 is formed along the depth direction. As described above, in the example of FIG. 16, since the inner wall surface 42a of the mask 42 is formed so as to bypass the plurality of convex portions 32, the portion covered by the mask 42 and the convex portion not covered by the mask 42. A groove 24 is formed on the inner wall surface 21b of the through hole 21 due to the difference in erosion rate from the portion where the 32 is located.

In the example of FIG. 17, when the mask 42 is formed on the substrate 10, half of the plurality of convex portions 32 of the fine concavo-convex structure 30 are formed by the mask 42 in the vicinity of the boundary B corresponding to the inner wall surface 42a of the opening portion of the mask 42. Indicates the case of being covered. That is, as shown at the boundary B in the left figure of FIG. 17, the inner wall surface 42a of the opening portion of the mask 42 is formed linearly in a plan view. In this case, a part of the conical convex portion 32, in this example, half of the convex portion 32 is covered with the mask 42. On the other hand, the remaining portion of the convex portion 32 is an exposed portion that is not covered by the mask 42. When etching is performed to form the through hole 21 in this state, the portion corresponding to the exposed portion of the convex portion 32 that is not covered by the mask 42 in the vicinity of the boundary B is first eroded from the convex portion 32 and then convex. After the portion 32 is eroded, erosion in the depth direction that contributes to the formation of the through hole 21 is started. On the other hand, the portion where the convex portion 32 is not provided starts erosion in the depth direction, which contributes to the formation of the through hole 21, immediately after the start of etching. As described above, in the vicinity of the boundary B, the portion where the convex portion 32 is not provided is eroded faster by etching as compared with the portion where the convex portion 32 is provided. Therefore, the portion having a high erosion rate becomes a streak-shaped groove 24 having a width substantially corresponding to the interval of the convex portions 32 on the inner wall surface 21b of the through hole 21 and along the depth direction. As described above, in the example of FIG. 17, in the vicinity of the boundary B corresponding to the inner wall surface 42a of the mask 42, a groove is formed in the inner wall surface 21b of the through hole 21 due to the difference in erosion rate between the portion with the convex portion 32 and the portion without the convex portion 32. 24 is formed.

As shown above, the reason why the streaky groove 24 as shown in FIG. 15 is formed on the inner wall surface 21b of the through hole 21 is due to the interaction between the plurality of convex portions 32 of the fine concavo-convex structure 30 and the mask 42. ..

In the boundary B corresponding to the inner wall surface 42a of the actual mask 42, a state in which the mask 42 is not formed on the convex portion 32 of the fine concavo-convex structure 30 as shown in FIG. 16 and a part of the convex portion 32 as shown in FIG. Is considered to be mixed with the state of being covered with the mask 42. In both the example of FIG. 16 and the example of FIG. 17, the inner wall surface 21b of the through hole 21 is formed along the depth direction by the interaction between the plurality of convex portions 32 of the fine concavo-convex structure 30 and the mask 42. A plurality of streaky grooves 24 will be formed. Therefore, in the present manufacturing process, the width of the streaky groove 24 formed on the inner wall surface 21b and the formation interval of the groove 24 are the width of the convex portion 32 of the fine concavo-convex structure 30 and the interval between the convex portions 32, as described above. It changes according to.

In the dry etching step, etching by a so-called Bosch process, in which etching gas and etching protection gas are alternately used, which is a general method for forming recesses having a high aspect ratio with respect to the substrate, may be performed. According to the Bosch process, through holes having a high aspect ratio can be efficiently formed. When a through hole is formed using the Bosch process, a structure called Scallops, which is a streak-like groove extending in a direction that intersects substantially perpendicular to the depth direction, repeats in the depth direction on the inner wall surface of the through hole. Is known to be formed.

By forming the through hole 21 on the surface having the fine concavo-convex structure 30 as described above by using the Bosch process, the streaky first groove 24a in the depth direction shown in FIG. 15 described above can be formed. In addition, a streak-like second groove 24b that intersects substantially perpendicular to the depth direction can be formed. That is, as shown in FIG. 18, the grid-like unevenness in which the first groove 24a shown by gray hatching and the streak-shaped second groove 24b shown by diagonally downward-sloping hatching are combined is the inner wall surface 21b of the through hole 21. Will be formed in. In this case, in FIG. 18, the portion where the gray hatching and the diagonally downward-sloping hatching overlap is a deeper groove in which the first groove 24a and the second groove 24b overlap and the depths of the respective grooves are added. The average period of the second groove 24b, in which the portion is formed and the unevenness having a complicated shape is formed, can be controlled by adjusting the switching time between the etching gas and the etching protection gas.

If a substrate having no fine uneven structure on the surface is used, the mask forming step and the dry etching step are performed, and the etching by the Bosch process is performed in the dry etching step, the streaky first groove 24a along the depth direction is performed. It is possible to form a through hole 21 having only a streak-shaped second groove 24b that intersects substantially perpendicularly to the depth direction as shown in FIG.

<Mask removal process>
Finally, as shown in ST4 of FIG. 10, in the mask removing step, the stripping liquid 60 is sprayed onto the substrate 10 to remove the mask 42 remaining after the dry etching step. The mask removal preferably includes a dry etching step or a cleaning step using sulfuric acid hydrogen peroxide.

The dry etching step for removing the mask is, for example, a step of switching to an etching gas having a high etching property for the mask and performing etching after the above-mentioned dry etching step for forming the recess. Mask removal by dry etching can be switched from the process of etching the substrate to the process of removing the mask only by switching the gas, and the work efficiency is good.

Further, if the cleaning step using sulfuric acid hydrogen peroxide is used, the mask 42 remaining after the dry etching step for forming the recess can be efficiently removed with high cleaning power.

Through the above steps, the optical member 1 shown in ST5 of FIG. 10 can be obtained.

Hereinafter, an experiment demonstrating that a recess is formed in the substrate by the above manufacturing method and a streak-like groove is formed in the wall surface of the recess, that is, the through hole will be described.

A silicon wafer was used as the substrate to be processed, and first, a substrate having a fine concavo-convex structure on the surface was produced. Specifically, first, an aluminum thin film was formed on the surface of the substrate to be processed by a sputtering method. The thickness of the aluminum thin film was 10 nm. Then, as a hot water treatment, the whole substrate was immersed in boiling pure water for 3 minutes to change the aluminum thin film into a fine concavo-convex layer containing alumina hydrate. After that, a breakthrough treatment is performed from the surface of the fine concavo-convex layer using a mixed gas of _{Ar gas and CHF 3} gas, and reactive ion etching is performed using a mixed gas of _{SF 6} gas and CHF _{3 gas to perform the substrate to be processed.} A fine uneven structure was formed on the surface of the. In this way, a substrate having a fine uneven structure on the surface was obtained.

Then, the photoresist was applied on the fine uneven structure of the substrate having the fine uneven structure on the surface, and an exposure mask having a predetermined opening was arranged on the photoresist to perform laser exposure of the photoresist. Further, a mask having an opening pattern was formed by performing a developing process. Then, using this mask, _{reactive ion etching was performed using a mixed gas of SF 6} gas and CHF ₃ gas as the etching gas to form recesses on the surface of the substrate.

Finally, the mask was removed by washing with sulfuric acid hydrogen peroxide.

FIG. 19 is an SEM image showing a part of the structure produced as described above. As shown in FIG. 19, the structure has a plurality of recesses on the surface of the substrate. The opening of the recess was a square shape with a side of 20 μm. Here, a recess having a depth of 10 μm was formed.

FIG. 20 is an enlarged SEM image of the inner wall surface portion of one of the recesses in FIG. 19, and FIG. 21 is a further enlarged SEM image of the upper part of the inner wall surface of FIG. From FIGS. 20 and 21, it can be seen that a fine uneven structure is formed on the surface of the substrate. Further, it can be seen from FIG. 21 that a streak-like groove (a portion observed in a relatively dark color in the image) formed according to the fine uneven structure of the surface is formed on the inner wall surface of the recess.

As described above, according to the above manufacturing method, it is possible to obtain an optical member having a streaky groove on the inner wall surface of the through hole.

The disclosure of Japanese Patent Application No. 2020-055018, filed on March 25, 2020, is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims

A single-layer substrate with multiple through-holes that transmit light,
An optical member having an antireflection structure formed on at least a part of the inner wall surface of the through hole, and having an antireflection structure including a plurality of streaky grooves.
The optical member according to claim 1, wherein the groove includes at least a plurality of streaky first grooves along the depth direction of the through hole.
The optical member according to claim 1, wherein the groove includes at least a plurality of streaky second grooves along a direction intersecting the depth direction of the through hole.
The optical member according to claim 2, wherein the groove further includes a plurality of streaky second grooves along a direction intersecting the depth direction of the through hole.
The optical member according to claim 4, wherein the average period of the plurality of first grooves and the average period of the plurality of second grooves are different.
The optical member according to any one of claims 1 to 5, wherein the substrate is an opaque material.
The optical member according to any one of claims 1 to 6, wherein the through hole has an aspect ratio of more than 20, which is a ratio of a depth to an opening size.
The optical member according to any one of claims 1 to 7, wherein the size of the opening of the through hole is larger than the average period of the groove.
The optical member according to any one of claims 1 to 8, wherein the size of the opening of the through hole is 5 to 100 μm.
The optical member according to any one of claims 1 to 9, which has a plurality of the through holes and the arrangement of the plurality of holes is a square array.
The optical member according to any one of claims 1 to 10, wherein the difference between the transmittance of the substrate with respect to the light and the transmittance of the through hole is 70% or more.
The optical member according to any one of claims 1 to 11, wherein the through hole is filled with a transparent material.
The optical member according to any one of claims 1 to 12, wherein the groove is provided at at least one open end of the through hole.
The optical member according to any one of claims 1 to 13, wherein the antireflection structure is an irregular structure.
The method according to any one of claims 1 to 14, wherein a fine concavo-convex structure having an antireflection function is formed on at least one of the front and back surfaces of the substrate other than the opening of the through hole. Optical member.
The optical member according to claim 15, wherein the fine concavo-convex structure is an irregular structure.
The optical member according to claim 15 or 16, wherein a protective layer is provided on the surface of the substrate on which the fine concavo-convex structure is formed.
The optical member according to any one of claims 15 to 17, wherein the depth of the groove of the antireflection structure is deeper than the depth of the recess of the fine concavo-convex structure.
The optical member according to any one of claims 1 to 18, wherein the substrate is silicon.