JP2790076B2 - Glass substrate with minute recess and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate having minute concave portions suitable for manufacturing a flat microlens in which concave portions of a flat glass substrate are filled with a transparent resin or the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A projector television (hereinafter, PTV) using a transmission type liquid crystal display device has been put to practical use. Currently, in the development of this PTV, the focus is on how to achieve high brightness on the screen.
The development of high-power light valves and optical devices, and the application of flat microlenses are being studied energetically.

If a flat microlens is used for the PTV, light that is incident on the black matrix or the pixel electrode portion of the liquid crystal display element and does not contribute to the illumination of the pixel opening can be greatly reduced. The brightness on the screen can be improved without increasing the brightness, and as a result, it is possible to solve the problem of deterioration of characteristics of the display element due to light and heat.

In this case, the flat microlens is disposed on the light incident side of the liquid crystal display element, and condenses the light incident on the black matrix and the pixel electrode portion to the pixel opening to effectively use the light. It has the function of improving the target aperture efficiency.

Conventionally, as a flat plate microlens, a soda lime glass has a corrosion-resistant protective film (mask film) of Ti or the like.
By using a well-known photolithography technique, a circular or linear slit-shaped opening is provided, and the cross-section is substantially formed by a so-called ion exchange method in which this is immersed in a molten salt and ion-exchanged from the opening. Flat microlens array having a semicircular refractive index distribution (Japanese Patent Laid-Open No. 57-537)
No. 02), and a flat microlens in which a hemispherical concave portion is formed on the surface of a glass substrate by chemical etching and filled with a transparent resin or the like and used as a lens is known (Japanese Patent Application Laid-Open No. 5-45624). Furthermore, a method of forming a concave portion on the surface of a semiconductor substrate by dry etching is disclosed (JP-A-1-219702).

[0006]

In particular, a hemispherical surface obtained by performing chemical etching on a flat glass substrate with a mask film having a large number of fine openings formed on the surface thereof, and performing isotropic etching from the fine openings. In the production of a flat microlens having a lens formed by filling a transparent resin or the like into a concave portion, a defect sometimes occurs during chemical etching. Specifically, a portion that should originally become a hemispherical concave portion may become an irregular elliptical spherical (rugby ball-shaped) concave portion, or a mask film may be peeled off from a glass substrate during chemical etching.

Further, a concave portion obtained by performing dry etching on a glass substrate provided with a mask film having a large number of fine openings formed on the surface thereof cannot be formed into a completely spherical shape due to its etching mechanism.

An object of the present invention is to provide a flat microlens glass substrate in which the contours of minute recesses formed by etching and arranged one-dimensionally or two-dimensionally are circular, and the cross-section of the minute recesses is formed from an arc. An object of the present invention is to provide a glass substrate for a formed flat microlens. Further, a flat microlens using the same is provided.

[0009]

According to the present invention, there is provided a glass substrate provided with a corrosion resistant film, which is immersed in an etchant to form micro hemispherical concave portions of microlenses. Surface polishing degree,
In particular, it has been made based on the finding that it is governed by the surface roughness.

In general, a glass substrate is subjected to lapping and polishing after cutting to create a smooth surface. However, the scratch once generated in the lapping or polishing step remains in the form of a latent scratch near the surface of the glass substrate even if the polish advances so that it cannot be apparently determined.

When the latent scratch remaining near the surface of the glass substrate comes in contact with the glass etchant, the etchant penetrates into the deep scratch and the latent scratch is etched. by this,
Latent scratches that could not be determined before etching become apparent.

A hemispherical surface is formed by forming a corrosion-resistant protective film on a glass substrate having latent scratches, for example, by forming a fine opening corresponding to the arrangement of the lens array in the corrosion-resistant film, and performing isotropic etching from the fine opening. When attempting to form minute recesses, latent scratches become apparent, and the etching proceeds in an elliptical sphere, or etching proceeds rapidly in a specific direction, so that the corrosion-resistant film may peel off from the glass substrate. is there.

FIG. 2 shows the surface roughness (Ra) of the glass substrate.
And forming a corrosion-resistant protective film on the substrate, forming a minute opening in the corrosion-resistant film, and forming a contour of the recess when the recess formed when isotropically etched from the minute opening is viewed in plan. Here is an example. In addition, a was defined as the length of the shortest diameter of the contour shape of the concave portion, and b was measured as the length of the longest diameter. Arrows in the figure indicate the directions of latent scratches on the glass substrate surface. In other words, if there is a latent scratch on the glass substrate surface,
The direction was particularly preferentially etched, and it was confirmed that the concave portion formed had a rugby ball shape as described above.

FIG. 3 is a graph showing this relationship. In this example, when Ra of the glass substrate is 0.55 nm or more, the contour shape b / a of the concave portion formed by etching becomes 1.5 or more, and the contour shape is also disturbed and is no longer circular. It can be seen that it is no longer possible. On the other hand, when the Ra of the substrate is less than 0.4 nm, the b / a is 1.1 or less, and it can be said that the contour shape is substantially circular.

Further, when the Ra is 0.24 nm or less, the b / a is almost 1, and it can be said that the contour shape is a perfect circle.

This is caused by the presence of the latent scratches in the minute recesses formed by etching, and not all the recesses have the above-mentioned rugby ball shape. When the Ra of the glass substrate is large (for example, Ra
> 0.7 nm), most of the recesses have the above-mentioned rugby ball shape. For example, 0.4 <Ra <0.5n
In the range of m, the probability of the existence of latent scratches on the surface of the glass substrate becomes a problem.Therefore, even if one concave portion has a good circular contour shape, another concave portion may have a rugby ball shape. .

In the present invention, the minute recesses are 1 to 1
It means a size of about 00 μm, especially about 20 to 40 μm. This is because if the size of the concave portion is large, even if uneven etching occurs due to the appearance of the latent scratches and polishing scratches described above, the influence thereof is small.

In the present invention, a corrosion-resistant film is formed in order to suppress the occurrence of non-uniform etching and the peeling of the corrosion-resistant film due to the manifestation of the latent scratch, and to make the contour of the minute concave portion circular when viewed from above. The surface roughness of the glass substrate to be formed is strictly controlled to a center line average roughness Ra of 0.4 nm or less.

If the center line average roughness Ra of the surface of the glass substrate exceeds 0.4 nm, uneven etching due to the appearance of latent scratches and polishing scratches and peeling of the corrosion resistant film are likely to occur.

Basically, the smaller the surface roughness of the glass substrate on which the corrosion-resistant film is formed, the better. However, in practice, it is extremely difficult to make the center line average roughness Ra less than 0.05 nm. It is difficult and it is difficult to secure its productivity.

Further, in consideration of technical and economical points after achieving the above-mentioned problems, Ra of the glass substrate is set to 0.1.
About 1 to 0.24 nm is particularly preferable.

The surface of the glass substrate whose center line average roughness Ra is controlled to 0.4 nm or less can be created by the following method or the like. (1) In a final polishing step using abrasive grains such as cerium oxide in a conventional polishing method, polishing is performed gently under low load and low speed conditions. (2) Cerium oxide having a small particle size in the final polishing step Polishing using abrasive grains (3) Polishing using abrasive grains of colloidal silica or the like having a spherical shape and relatively low hardness

For a substrate having a center line average roughness Ra exceeding 0.4 nm, a film having the same composition as the glass substrate is formed on the surface of the glass substrate by a coating film thermal decomposition method, a sol-gel method, or the like. By sintering and filling the latent wound,
The surface roughness of the glass substrate can be improved, and the center line average roughness can be reduced to 0.4 nm or less. In addition, the surface roughness of the glass substrate can be improved by using high-energy charged particles to collide with the glass substrate by ion implantation to achieve local high temperature and use viscous flow and sintering of the glass. The average roughness can be 0.4 nm or less.

By smoothing the surface of the glass substrate by the various methods described above, it is possible to eliminate the occurrence of uneven etching due to latent scratches on the glass substrate. further,
When a corrosion-resistant protective film having a desired pattern is formed on a glass substrate, etching can proceed isotropically from the minute opening of the desired pattern. When a transparent resin or the like is filled in the concave portion of the substrate to produce a flat microlens, a favorable microlens can be formed.

Examples of the glass substrate used in the present invention include quartz glass, soda lime glass, alkali aluminosilicate glass, alkali borosilicate glass, multi-component alkali-free glass, and low expansion crystallized glass.

The smoothness of the glass substrate referred to in the present invention is a polishing level conventionally called photomask polishing, and the smoothness of the glass substrate at this level has a high resolution such as that of an atomic force microscope. It can be evaluated by an analysis method.

As the corrosion-resistant protective film material used in the present invention, an appropriate material can be selected depending on the resistance to the etchant used, the workability of photolithographic patterning, and the film forming cost. The film thickness to be formed can be arbitrarily selected according to the purpose, and film materials having different compositions can be laminated in multiple layers.

For example, examples of the corrosion-resistant protective film material include metals such as chromium, nickel, tantalum, silicon, and gold, and oxides or nitrides thereof. These corrosion-resistant protective films can be formed by a sputtering method, an evaporation method, or the like.

When etching the above-described glass substrate with a corrosion-resistant film, the etchant composition is selected according to the composition of the glass substrate to be etched. For example, when etching a quartz glass substrate, an aqueous solution containing hydrogen fluoride and a surfactant such as sodium dodecylbenzenesulfonate can be used as an etchant. Further, when etching a soda lime glass substrate, a mineral acid such as sulfuric acid and an organic acid such as acetic acid are often added in addition to hydrogen fluoride, and if necessary, sodium dodecylbenzenesulfonate (hereinafter, DBS) Surfactants such as may be added.

[0030]

In the substrate with minute recesses according to the present invention, the boundary between the minute recesses and the surface of the glass substrate, that is, the contour shape is a perfect circle when viewed in plan. Therefore, a good flat microlens can be obtained by filling the minute concave portion with a resin or the like having a different refractive index from the substrate.

Further, in the manufacturing method of the present invention, the surface roughness of the glass substrate on which the corrosion-resistant film is formed is controlled by the various methods described above in order to suppress the occurrence of minute uneven etching and the peeling of the corrosion-resistant film having openings. Strictly, the center line average roughness Ra is 0.4 nm or less by the method, more preferably 0.1 to 0.
It is controlled to 24 nm. For this reason, it is possible to eliminate the occurrence of uneven etching due to latent scratches on the glass substrate surface.

Further, by further etching the above-mentioned glass substrate, a glass substrate in which minute concave portions are densely arranged can be obtained.

[0033]

【Example】

(Example 1) Cerium oxide abrasive grains having a small particle diameter (average particle diameter of primary particles: 0.05 μm, average particle diameter of secondary particles: about 0.5 μm)
m), the final polishing of the quartz glass substrate was performed at low load (30 gf / cm ² ) and low speed (50 rpm).
Atomic force microscope (Digital Instruments Co., Ltd.):
As a result of examining the surface roughness of the polished glass substrate by NanoScope (hereinafter referred to as “AFM”), the center line average roughness R
a was found to be 0.15 nm.

As a corrosion-resistant protective film against an etchant, the surface of the present quartz glass substrate was formed by sputtering.
A three-layer film of CrOx / Cr / CrOx was formed. As a result of ESCA analysis of the Cr film, 40
Cr ・ 60CrOx / 75Cr ・ 25CrOx / 45Cr
-It had a three-layer structure of 55CrOx (atomic%). Next, small openings were formed in the three-layer Cr film in a predetermined concave arrangement pattern by photolithography in which a photoresist was applied, exposed, and developed. The formed small aperture array has a hexagonal array (pitch 50 μm in x direction, pitch 40 μm in y direction).
m), whereby an array of minute recesses having a hexagonal arrangement is obtained. The diameter of the opening is desirably sufficiently smaller than the diameter of the concave portion to be finally obtained. In the first embodiment, the small opening diameter is set to 5 μm.

The substrate with the Cr film having the small openings is
Chemical etching was performed by immersion in an aqueous solution containing F and DBS as a surfactant. Where HF and DB
The concentration of S was 10% by weight and 0.1% by weight, respectively. Thus, the surface of the quartz glass substrate was etched starting from the small opening. The corrosion-resistant protective film,
Etching was performed with an aqueous solution containing cerium ammonium nitrate and perchloric acid, and this was completely removed.

As a result of observation of this substrate by an electron microscope (SEM), it was found that an isotropic concave portion having a radius of curvature of about 20 μm was obtained corresponding to the mask opening (FIG. 1). As a result of observing the entire hemispherical concave portion, no defect such as an elliptical spherical defect was observed at all. FIG. 4 (a) shows a trace of a single row of contours having minute recesses, and FIG. 4 (b) shows a partially enlarged cross-sectional view thereof.

By the above-described procedure, a substrate having minute concave portions, each of which is independent and whose contour is all circular, was obtained.

Further, a case where the minute concave portions are densely arranged on the entire surface of the substrate will be described below. The substrate was immersed again in the previous etchant to etch the entire substrate surface. The two-stage etching resulted in a completely dense arrangement in which each of the adjacent concave portions was in the same hexagonal shape in plan view and the adjacent concave portions were in close contact with each other.

After the above-described two-step etching, the concave portion was filled with an epoxy-based transparent resin material having a higher refractive index than the quartz glass substrate, and a quartz substrate was separately bonded thereon, and the resin was light-cured. As a result, a quartz plate-shaped microlens having no defect was obtained (see FIG. 5).

(Example 2) The final polishing of the quartz glass substrate was carried out under the same conditions as in Example 1 by using colloidal silica (average particle size: 0.05 µm) as abrasive grains. According to the AFM observation, the center line average roughness Ra of the polished glass substrate is:
It turned out to be 0.12 nm.

On the surface of the present quartz glass substrate, a Cr film was formed as a corrosion-resistant protective film against an etchant by a sputtering method. As a result of ESCA analysis of the Cr film, it was found to be 80Cr.20CrOx (atomic%) with a total film thickness of 120 nm. Next, in the same manner as in Example 1, a small opening pattern was formed in the corrosion-resistant protective film, an etching process was performed, and then the corrosion-resistant protective film was removed.

As a result of observing the substrate with an electron microscope (SEM), it was found that an isotropic recess having a radius of curvature of about 20 μm was obtained corresponding to the mask opening. As a result of observing the entire hemispherical concave portion, no defect such as an elliptical spherical defect was observed at all.

Next, the substrate was immersed again in the etchant to etch the entire surface of the substrate. The two-stage etching resulted in a completely dense arrangement in which each of the adjacent concave portions was in the same hexagonal shape in plan view and the adjacent concave portions were in close contact with each other.

After the two-step etching process, the concave portions were filled with an epoxy-based transparent resin material having a higher refractive index than that of the quartz glass substrate, and a quartz substrate was separately bonded thereon, and the resin was light-cured. As a result, a defect-free quartz flat plate microlens could be obtained.

Example 3 Tetraethoxysilane (Si
Dilute hydrochloric acid (1% by weight) was added to an ethanol solution of (OC ₂ H ₅ ) ₄ ), and the mixture was stirred at room temperature for 1 hour to carry out hydrolysis and condensation polymerization of tetraethoxysilane. Here, the molar ratio of ethanol and water to tetraethoxysilane was set to 5 and 6, respectively. This solution was further diluted with ethanol to control the thickness of the coating,
A sol-gel coating solution was used.

Using this coating solution, a quartz glass substrate (Ra = 0.6 nm) at a normal final polishing level
Was subjected to dip coating. After drying at room temperature for 1 hour, heat treatment is performed at 850 ° C. for 5 hours,
The sol-gel SiO ₂ film was sintered. After sintering, the thickness of the sol-gel SiO ₂ film was 200 nm. As a result of observation by AFM, Ra of the fired glass substrate was about 0.2 n.
m.

On the surface of the present quartz glass substrate, a Cr film was formed as a corrosion-resistant protective film against an etchant by a sputtering method. This Cr film was the same as in Example 2. Next, in the same manner as in Example 1, a small opening pattern was formed in the corrosion-resistant protective film, an etching process was performed, and then the corrosion-resistant protective film was removed.

As a result of observing the substrate with an electron microscope (SEM), it was found that an isotropic recess having a radius of curvature of about 20 μm was obtained corresponding to the mask opening. As a result of observing the entire hemispherical concave portion, no defect such as an elliptical spherical defect was observed at all.

Next, the substrate was immersed again in the above etchant to etch the entire surface of the substrate. The two-stage etching resulted in a completely dense arrangement in which each of the adjacent concave portions was in the same hexagonal shape in plan view and the adjacent concave portions were in close contact with each other.

After the two-step etching process, the concave portions were filled with an epoxy-based transparent resin material having a higher refractive index than that of the quartz glass substrate, and a quartz substrate was separately bonded thereon, and the resin was light-cured. As a result, a defect-free quartz flat plate microlens could be obtained.

Example 4 Low-weight (30 gf / c) cerium oxide abrasive grains (average primary particle diameter: 0.05 μm, average secondary particle diameter: about 0.5 μm) were used.
m ² ), the final polishing of the soda lime glass substrate was performed at a low speed (50 rpm). As a result of examining the surface roughness of the polished glass substrate by an atomic force microscope (AFM), it was found that the center line average roughness Ra was 0.20 nm.

A three-layer film of CrOx / Cr / CrOx was formed under the same conditions as in Example 1 of the present soda-lime glass substrate. Next, in the same manner as in Example 3, a small opening pattern was formed in the corrosion-resistant protective film, and an etching process was performed.
Subsequently, the corrosion-resistant protective film was removed.

As a result of observation of this substrate by an electron microscope (SEM), it was found that an isotropic concave portion having a curvature radius of about 20 μm was obtained corresponding to the mask opening. As a result of observing the entire hemispherical concave portion, no defect such as an elliptical spherical defect was observed at all.

Next, the substrate was immersed again in the above etchant to etch the entire surface of the substrate. The two-stage etching resulted in a completely dense arrangement in which each of the adjacent concave portions was in the same hexagonal shape in plan view and the adjacent concave portions were in close contact with each other.

After the two-step etching process, the concave portions were filled with an epoxy-based transparent resin material having a higher refractive index than that of the soda-lime glass substrate, and a quartz substrate was separately bonded thereon, and the resin was light-cured. As a result, a defect-free soda-lime glass flat microlens could be obtained.

Example 5 A soda lime glass substrate was finally polished under the same conditions as in Example 4 using colloidal silica (average particle size: 0.05 μm) as abrasive grains. AF
Observation of the center line average roughness Ra of the polished glass substrate by observation
Was found to be 0.14 nm.

A Cr film was formed on the surface of the present soda lime glass substrate under the same conditions as in Example 2. Next, a small opening pattern was formed on the corrosion-resistant protective film in the same manner as in Example 2.
Further, an etching treatment was performed, and then the corrosion-resistant protective film was removed.

As a result of observing the substrate with an electron microscope (SEM), it was found that an isotropic recess having a radius of curvature of about 20 μm was obtained corresponding to the mask opening. As a result of observing the entire hemispherical concave portion, no defect such as an elliptical spherical defect was observed at all.

Next, the substrate was immersed again in the above etchant to etch the entire surface of the substrate. The two-stage etching resulted in a completely dense arrangement in which each of the adjacent concave portions was in the same hexagonal shape in plan view and the adjacent concave portions were in close contact with each other.

After the two-step etching, the recess was filled with an epoxy resin material having a higher refractive index than that of the soda lime glass substrate, and a quartz substrate was separately bonded thereon, and the resin was light-cured. As a result, a defect-free soda-lime glass flat microlens could be obtained.

In each of the first to fifth embodiments described above, the minute concave portions are arranged hexagonally.
If the fine recesses are arranged in four directions according to the purpose and the above-described two-stage etching process is performed, the outline shape is square or rectangular in a plan view, and the glass with the fine recesses arranged on the substrate surface completely densely. Needless to say, a substrate is obtained.

Further, in the above-described first to fifth embodiments, all of the fine openings of the mask film are point openings (circles). The contour of the concave portion formed according to the opening can be an ellipse (oval shape) in plan view (see FIG. 6).

In the above-described first to fifth embodiments, the two-stage etching process described above obtains a glass substrate with minute recesses arranged on the substrate surface in a completely dense manner. Depending on the processing time,
Needless to say, a glass substrate with minute concave portions with a part of the initial substrate surface left can be obtained.

Comparative Example 1 The same three-layer film of CrOx / Cr / CrOx as in Example 1 and photolithographic patterning were performed on a quartz glass substrate (R = 0.45 nm) of a conventional polishing level. Further, the conventional polishing of the quartz substrate with the Cr film having the small opening was etched under the same conditions as in Example 1. Thus, the surface of the quartz glass substrate was etched starting from the small opening.

After removing the corrosion-resistant protective film, observation was performed with an optical microscope and an electron microscope (SEM). On a quartz glass substrate having a conventional polishing level of Ra of about 0.45 nm, latent scratches remain on the surface, which are evident by the etching process, and an isotropic hemispherical concave portion should be formed. An elliptical spherical distorted opening corresponding to the direction of the polishing scratch and the latent scratch was obtained. When trying to form a lens by filling this elliptical spherical recess with transparent resin or the like,
It was determined that this oval spherical concave portion would cause a lens defect.
FIG. 7 (a) shows a trace of a row of contours having minute recesses, and FIG. 7 (b) shows a partially enlarged sectional view thereof.

Comparative Example 2 The same three-layer CrOx / Cr / CrOx film as in Example 4 and photolithographic patterning were performed on a soda-lime glass substrate (R = 0.75 nm) of the conventional polishing level. . Further, etching of the conventional polished soda lime glass substrate with the Cr film having the small opening was performed under the same conditions as in Example 4. Thereby, the surface of the soda lime glass substrate was etched starting from the small opening.

After removing the corrosion-resistant protective film, observation was performed with an optical microscope and an electron microscope (SEM). A latent scratch on the surface of a soda lime glass substrate having a conventional polishing level of Ra of about 0.75 nm has been revealed by the etching process, and an isotropic hemispherical concave portion should be formed. In this case, the opening became an elliptical spherical irregular shape corresponding to the direction of the polishing scratch and the latent scratch. In addition, the Cr film was peeled off during the etching process, and there were places where minute concave portions were not formed. It was determined that the elliptical concave portion and the portion where the Cr film was peeled off became a defect that would cause a lens defect.

In this example, the results for the quartz glass substrate and the soda lime glass substrate were shown. However, the relationship between the glass surface roughness and the etching characteristics is the same for multi-component alkali-free glass and low expansion crystallized glass. showed that.

[0069]

According to the various methods described above, when a fine concave portion is formed on a glass substrate whose surface is smoothed to have a center line average roughness Ra of 0.4 nm or less by an etching method, latent scratches on the glass substrate can be obtained. It is possible to eliminate uneven etching caused by polishing scratches.

Further, in a glass substrate having a corrosion-resistant film having a small opening, etching progresses isotropically from the opening, and in addition, peeling of the corrosion-resistant film can be suppressed. If a minute opening corresponding to, for example, an arrangement of microlenses is formed in this corrosion resistant film, it becomes possible to form a hemispherical concave portion of a flat microlens array with a high yield.

[Brief description of the drawings]

FIG. 1 is a plan view of a glass substrate having minute concave portions formed by etching according to the present invention.

FIG. 2 is a schematic diagram illustrating a relationship between Ra of a glass substrate and a contour shape of a minute concave portion.

FIG. 3 is a graph showing a relationship between Ra of a glass substrate and a contour shape of a minute concave portion.

FIG. 4 is a schematic diagram illustrating a contour shape and a partially enlarged cross section of a minute concave portion when Ra = 0.15 nm of a glass substrate.

FIG. 5 is a cross-sectional view of a flat microlens.

FIG. 6 is a view showing a glass substrate having a fine concave portion whose contour is an ellipse in plan view.

FIG. 7 shows a conventional case where the polishing state is poor (Ra = 0.45n)
m) is a schematic view showing the outline shape and a partially enlarged cross section of an elliptical spherical (rugby ball-shaped) concave portion obtained from the glass substrate of FIG.

[Description of Signs] 1 glass substrate, 2 etched part, 3 contour shape of minute concave part, 4 transparent resin,

Continuation of the front page (72) Inventor Kenjiro Hamanaka 3-5-1-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka Inside Nippon Sheet Glass Co., Ltd. (56) References JP-A-3-214121 (JP, A) JP-A-7 -49403 (JP, A) JP-A-7-63904 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 3/00-3/14

Claims (9)

(57) [Claims] 1. A glass for a flat plate microlens in which a large number of fine concave portions formed by etching are regularly arranged one-dimensionally or two-dimensionally on a glass substrate surface having a center line average roughness Ra of 0.4 nm or less. A substrate, the contour shape of the minute concave portion when viewed in plan is substantially circular,
A ratio of the major axis to the minor axis of the contour shape is 1.1 or less, wherein the glass substrate with minute recesses is provided. However, the longest diameter of the contour shape is referred to as a long diameter, and the shortest diameter is referred to as a short diameter. 2. The glass substrate with minute recesses according to claim 1, wherein the contour is circular. 3. A glass substrate for a flat plate microlens in which a large number of minute concave portions formed by etching are regularly arranged two-dimensionally on a surface of a glass substrate having a center line average roughness Ra of 0.4 nm or less. The glass substrate with minute recesses, wherein the minute recesses have an arc-shaped cross section and are arranged almost densely in a plan view. 4. The glass substrate with minute recesses according to claim 3, wherein the minute recesses are arranged in a completely dense manner, and the contour shape is:
A glass substrate with minute recesses that is square, rectangular, regular hexagonal, or hexagonal. 5. A glass substrate for a flat microlens comprising a glass substrate having a center line average roughness Ra of 0.4 nm or less and a plurality of minute recesses formed by etching on a glass substrate surface. The minute recess is obtained by rotating the oval shape around its long axis.
The oval shape is a plan view
Two semicircles with the same radius and a straight line connecting them
Minute recesses glass substrate, characterized in that comprising a. 6. A method for producing a glass substrate having minute concave portions, comprising the following steps: (A) a step of forming a corrosion-resistant film on a flat glass substrate having a center line average roughness Ra controlled to 0.4 nm or less; (b) a step of forming small openings in the corrosion-resistant film in a predetermined arrangement; C) a step of immersing the substrate in an etchant; and (d) a step of removing the corrosion-resistant film. 7. The method for manufacturing a glass substrate with minute recesses according to claim 6, further comprising the following steps. (E) immersing the substrate from which the corrosion-resistant film has been removed in an etchant. 8. The method for manufacturing a glass substrate with minute recesses according to claim 6, wherein said glass is quartz glass, said corrosion-resistant film is made of metal chromium and its oxide or nitride, and said etchant is a fluorine-containing material. A method for producing a glass substrate having minute concave portions, which is an acid-based etchant. 9. A flat plate type micro-plate according to claim 1, wherein the concave portion of the glass substrate with minute concave portions is filled with a resin having a refractive index different from that of the glass substrate to have a lens function. lens.