JP4586197B2 - Optical glass substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a glass material substrate having a fine surface shape that is useful as a substrate for a micro optical element, an optical instrument, or the like.

Conventionally, as a method for forming an optical element (lens element) having a refractive index distribution, (1) a minute semi-convex lens or a spherical lens having a refractive index different from that of a glass material substrate is manufactured in advance, and this is used as a glass material substrate. (2) Method of forming a refractive index distribution by ion diffusion to a glass material substrate, (3) Method of forming a refractive index distribution on a glass material substrate by light-induced absorption, (4) CVD A method of forming a film on a glass material substrate by a vapor phase method such as vapor deposition or a liquid phase method such as sol-gel method is known. However, these methods include (a)
By distributing induced defect structures with different chemical components or electronic states, when giving different refractive indexes to the glass material substrate, obtain uniform light transmission characteristics and wavelength dispersion at the desired location of the lens element. (B) The optical properties of the glass material are likely to deteriorate due to light irradiation, (c) The durability at the joint between the half-convex lens or the spherical lens and the glass material substrate is insufficient. ) There are problems such as low durability of the glass material in the usage environment.

  The inventors of the present invention stated that "the operation of heating the heated portion at a temperature higher than the previous time after partially heating the glass material substrate surface to a temperature at which the density change does not occur by laser beam irradiation. The technique of heating the same part to a temperature at which the density change occurs or more by repeating the process was developed (Patent Document 1, Patent Document 2, and Non-Patent Document 1). According to this technique, a refractive index distribution can be formed in a glass material having the same chemical composition by utilizing the density change of the heated portion on the surface of the glass material substrate. The obtained glass material can be changed under the condition that the shape and / or refractive index of the heated portion is controlled, so that it can be applied to micro optical elements in microlenses, microlens arrays, liquid crystal displays, plasma displays, etc. is there.

  The above-described method of irradiating a predetermined portion of a glass material substrate with a laser beam has a great advantage that an element can be precisely formed in a minute region.

Furthermore, laser irradiation is performed on the crystallized glass, and a raised structure (on the crystallized glass substrate (
There are a method (Patent Document 3) for forming a convex portion) and a method (Patent Document 4) for manufacturing a periodic raised shape by causing laser light to interfere.

However, the known method is a shape manipulation technique for one side of the substrate material to be processed, and it is difficult to simultaneously perform the same manipulation on the opposite side. When a glass material having such a single-sided raised structure is applied to a microlens, the numerical aperture is small and the light collecting property is low. If it becomes possible to produce a desired raised structure on both sides of the substrate, the performance as a micro optical element will be significantly improved. In the above methods (2) and (4), it is possible to process both the front and back surfaces simultaneously by performing patterning at the time of manufacturing the substrate, but practically it is formed on the front and back surfaces. There is a problem that it is difficult to align the elements.
JP 2002-255579 A Japanese Patent Laid-Open No. 2003-207605 N. Kitamura, K. Fukumi, J. Nishii, T. Kinoshita, N. Ohno, Jpn. J. Appl. Phys. 42 (2003) L712-L714. JP2005-62832 JP-A-11-216578

  A main object of the present invention is to provide a glass substrate provided with at least a pair of raised portions on both surfaces of a substrate made of a thin glass material plate in a direction coaxial with a vertical direction of the substrate surface, and a manufacturing method thereof.

As a result of intensive research in view of the current state of the above-mentioned technology, the present inventor has found that between the absorption coefficient α [cm ⁻¹ ] of the glass material for the laser beam in the specific wavelength region and the thickness t [cm] of the thin glass material sheet. And when a certain condition was satisfy | filled, it discovered that the surface and back surface of a glass material thin plate were heated effectively. As a result of further research based on such knowledge, the present inventor has found that a double-sided bulge structure or a single-sided bulge / single-sided depression structure at the same position on one surface of the thin plate and the other surface along the laser beam irradiation axis. Succeeded in forming.

More specifically, a minute region is thermally expanded by irradiating a laser beam to a thin plate of glass material that exhibits volume expansion by heating and maintains the volume expansion state as it is after the heating is completed. “Double-sided bulge structure” or bulge consisting of at least a pair of bulges (convex parts) and bulges (convex parts) that are aligned in the vertical axis direction on both sides of the laser beam irradiation surface side and back side of the glass substrate A "single-sided ridge / single-sided depression structure" consisting of at least a pair of a part (convex part) and a depressed part (concave part) was successfully formed at the same time.
The present invention has been completed based on such new findings.
That is, the present invention provides a glass material having the following raised structure and a novel manufacturing method thereof.
1. (1) It consists of a thin plate of glass material whose volume increases by heat treatment,
(2) A glass substrate provided with at least a pair of convex portions on the same axis in a direction perpendicular to both surfaces,
(3) density of the glass material ([rho ₁₎ and the density ([rho ₂₎ of the convex portion _{is, 0.01 ≦ Δρ / ρ 2 ≦} 0.2 ( however, Δρ = ρ ₁ -ρ ₂₎ that the relationship indicated by A glass substrate characterized by.
2. Item 2. The glass substrate according to Item 1, wherein the thickness of the thin plate is in the range of 10 to 150 µm .
3. 3. A micro optical element comprising the glass substrate according to item 1 or 2.
4). (1) It consists of a thin plate of glass material whose volume increases by heat treatment,
(2) A glass substrate provided with at least a pair of convex portions and concave portions on the same axis in a direction perpendicular to both surfaces thereof,
(3) density of the glass material ([rho ₁₎ and the density ([rho ₂₎ of the convex portion _{is, 0.01 ≦ Δρ / ρ 2 ≦} 0.2 ( however, Δρ = ρ ₁ -ρ ₂₎ that the relationship indicated by A glass substrate characterized by.
5). Item 5. The glass substrate according to Item 4, wherein the thickness of the thin plate is in the range of 10 to 150 µm .
6). 6. A micro optical element comprising the glass substrate according to item 4 or 5.
7). (1) It consists of a thin plate of glass material whose volume increases by heat treatment,
(2) At least a pair of convex portions (one surface side) and a concave portion (the other one surface side) and at least a pair of concave portions (one surface side) and a convex portion (the other one surface side) are provided on the same axis in the direction perpendicular to both surfaces. A glass substrate,
(3) density of the glass material ([rho ₁₎ and the density ([rho ₂₎ of the convex portion _{is, 0.01 ≦ Δρ / ρ 2 ≦} 0.2 ( however, Δρ = ρ ₁ -ρ ₂₎ that the relationship indicated by A glass substrate characterized by.
8). Item 8. The glass substrate according to Item 7, wherein the thin plate has a thickness in the range of 10 to 150 µm .
9. Item 9. A micro optical element comprising the glass substrate according to Item 7 or 8.
10. (1) It consists of a thin plate of glass material whose volume increases by heat treatment,
(2) At least a pair of convex portions (one surface side) and a convex portion (other one surface side) and at least a pair of concave portions (one surface side) and a convex portion (other one surface side) are coaxially arranged in a direction perpendicular to both surfaces. A glass substrate comprising:
(3) density of the glass material ([rho ₁₎ and the density ([rho ₂₎ of the convex portion _{is, 0.01 ≦ Δρ / ρ 2 ≦} 0.2 ( however, Δρ = ρ ₁ -ρ ₂₎ that the relationship indicated by A glass substrate characterized by.
11. Item 11. The glass substrate according to Item 10, wherein the thickness of the thin plate is in the range of 10 to 150 μm .
12 Item 12. A micro optical element comprising the glass substrate according to Item 10 or 11.
13. By irradiating a thin plate of glass material whose volume increases by heat treatment with a laser beam, a convex portion is formed on each side of one side and the other side of the thin plate, or a convex portion is formed on one side and on the other side. A method of manufacturing a glass substrate, comprising forming a recess. 14 A method of manufacturing a glass substrate according to item 13, the absorption coefficient for laser light of wavelength ^{1~25 μ m [α: cm -1} ] is using thin glass material is 100～400Cm ^-1 as substrate The condition that the product (α × t) of the absorption coefficient [α: cm ⁻¹ ] of the glass material and the thickness [t: cm] of the glass substrate at a predetermined laser beam wavelength is in the range of 0.01 to 1.5. Method of performing laser irradiation below (however, when the internal transmittance of the glass material is T, α and t satisfy the relational expression represented by T = e ^{−α · t} )
15. Item 15. The method for producing a glass substrate according to Item 13 or 14, wherein the thin plate has a thickness in the range of 10 to 150 µm .

  The starting material in the method for producing a glass substrate of the present invention is a glass material that undergoes a volume change by irradiating light rays from a heat ray laser and maintains the volume change even in a cooled state after the irradiation is stopped.

  Such a glass material is a high-density glass material compared to a glass material having the same composition obtained by slowly cooling a molten raw material under atmospheric pressure (hereinafter sometimes referred to as “normal glass”). Become. Such a high-density glass material decreases in density when heated above a certain temperature determined according to the type of glass, approaches the normal glass density, and maintains a changed density state even after cooling. It has the property to do.

  The above-mentioned high-density glass material can be prepared by various techniques. For example, a high-density glass material obtained by pressurizing ordinary glass at a high temperature, a high-density glass material obtained by rapidly cooling a molten ordinary glass from a high temperature, and the like can be mentioned.

  The density itself of the glass material used in the method of the present invention is not particularly limited, but in order to produce a raised structure suitable as an optical element, generally a glass material having a density of about 1% or more higher than that of ordinary glass. Is preferred. As described above, normal glass is obtained by slowly cooling a molten glass raw material under atmospheric pressure, and the density does not change by heating.

Dense glass material used as starting material in the method of the present invention, the absorption coefficient for laser light of wavelength 1~25μm for heating small area (α: cm ^-1) is, it is about 100 to 400 cm ^-1 Is preferred. The material of the glass material is not particularly limited, but a glass containing 20 mol% or more of silicon dioxide (SiO ₂ ), B ₂ O ₃ in order to realize a large density change (ie, volume change) by laser beam irradiation. A glass containing about 20 mol% or more of a component (glass network former) that forms a glass network structure, such as glass containing 20 mol% or more, or glass containing 20 mol% or more of P ₂ O ₅ is more preferable.

The thickness of the glass material substrate, the absorption coefficient for laser light having a wavelength of about ^{1~25 μ m [α: cm -1} ] is the glass material is about 100～400Cm ^-1, absorption of the glass material at a given laser wavelength The product (α × t) of the coefficient [α: cm ⁻¹ ] and the thickness [t: cm] of the glass substrate may be selected to be 1.5 or less.

More practically, the thickness of the glass material substrate is preferably about 10 to 150 μm. When the thickness of the high-density glass material substrate used in the present invention is within this range, the raised portions (convex portions) having substantially the same shape are formed on both surfaces of the thin plate by irradiation with a laser beam described later. On the other hand, a substrate of less than 10 μm is extremely difficult to process, and the increase in volume due to heat treatment is as small as about a submicron, so that the optical effect due to the formation of convex portions or concave portions is not sufficiently exhibited.

  As described above, the wavelength of the laser beam applied to the glass material substrate is preferably about 1 to 25 μm.

As the laser beam source to be used, a carbon dioxide gas laser (9.6-10.6 μm) or a carbon monoxide gas laser (5.2-5.8 μm) that emits heat rays in the 10 μm band with high light absorption efficiency in many glass materials is suitable. is there. In particular, when the starting material is silica glass, the absorption coefficient is 129 cm ⁻¹ , and thus the substrate thickness (t) obtained from α × t = 1.5 is about 116 μm, which is suitable as a fine optical element. Glass substrate. Although the reports of optical constants in the infrared region for other glasses are unclear, if the conditions for the laser light to reach the back surface are met, α × t ≦ 1.5 is a condition that can sufficiently heat the back surface. Become.

  As the glass material substrate is irradiated with the laser beam, the refractive index of the glass material changes as the density of the glass material changes. However, as long as the various conditions of the present invention are satisfied, in the laser beam irradiation region, sufficient heating is performed from the front surface to the back surface of the glass material substrate. It is so small that it does not substantially affect the optical properties.

In the glass material substrate according to the present invention, the density (ρ ₁ ) of the glass material and the density of the projections (
ρ ₂ ) is preferably in a relationship represented by 0.01 ≦ Δρ / ρ ₂ ≦ 0.2 (where Δρ = ρ ₁ −ρ ₂ ). When the density change rate (= volume change rate) indicated by Δρ / ρ ₂ is within this range, it is possible to form convex portions or concave portions having a desired shape.

FIG. 1 is a schematic view showing an outline of heating of a substrate when a laser beam is irradiated on one surface of a glass material thin plate (hereinafter, one surface of a thin plate irradiated with a laser beam is referred to as a “surface”. The other side is sometimes called the "back side"). The product (α × t) of the glass material absorption coefficient [α: cm ⁻¹ ] and its substrate thickness [t: cm] is 1.5 or less, and when the internal transmittance of the glass material is T, α and t satisfy the relational expression represented by T = e ^{−α · t} . The lower limit value of α × t ≦ 1.5 is preferably about 0.01. When the lower limit value is less than 0.01, the laser beam is not sufficiently absorbed, so that no lens is formed.

Since the laser beam intensity (heat input amount) decreases exponentially with respect to the depth direction from the glass substrate surface (right direction in FIG. 1), the laser intensity on the back surface of the glass substrate is expressed by the above relational expression. As is apparent from FIG. 4, it decreases in proportion to an exponential function of absorption coefficient × thickness t. Although the amount of laser energy on the back of the glass substrate has decreased, under the conditions of α × t ≦ 1.5, the laser energy absorbed in the path up to that heat is transferred as heat, and the temperature rises on the back. It is thought to help. If a sufficient temperature rise is obtained, as is apparent from FIG. 1, volume expansion occurs on the back surface of the glass substrate, and a biconvex lens is formed on the substrate.

The ridge shape depends on the intensity distribution of the laser beam, but all of the thermal properties such as the internal transmittance of the glass material (indicating the degree of light absorption of the glass material), the thermal diffusion coefficient, and the specific heat are all inside the glass substrate. The temperature distribution at is determined, thereby determining the degree of volume expansion, ie the raised shape. For example, as apparent from Example 1 and FIG. 2 below, both the convex portions on the front surface and the back surface may have substantially the same cross-sectional shape, or, as apparent from Example 2 and FIG. The portion may have a larger cross-sectional shape than the convex portion on the back surface.

When the intensity of the laser beam against the glass material is large, the surface becomes overheated, and a recessed structure is formed instead of a raised structure due to ablation or evaporation, whereas a raised structure is formed on the back surface by heat transfer. (See Example 3 and FIG. 4 below). In this case, a meniscus lens, not a biconvex lens, is formed as an optical element that is coaxial on both the front and back surfaces. The embodiment in this case is also useful as an optical element.
The glass substrate according to the present invention may be in the form of a microlens having one minute raised area (biconvex microlens or meniscus microlens), or a minute raised area (biconvex or meniscus microlens). A lens array having two or more lenses) may be used. That is, for example, the glass substrate of the present invention can have a configuration in which a large number of single microlenses having the shape shown in any of FIGS. In this case, if necessary, it is also possible to form a microlens array in which microlenses having different shapes are combined.
Alternatively, a structure including a biconvex microlens and a meniscus microlens can be formed by appropriately reversing the direction of laser irradiation on the glass material thin plate.
The glass substrate according to the present invention is useful as a micro optical element in a liquid crystal display, a plasma display or the like.

The glass substrate according to the present invention further collimates a surface emitting laser beam such as VCSEL in optical communication or optical information processing; optical fiber collimator that converts signal light spreading from the end of the optical fiber into parallel light; Or a photo-junction element that focuses light on the end of an optical fiber placed close to a microlens; it is placed on the surface of a micro-light-receiving element such as a photodiode or CCD in a sensor component that uses image processing or light and receives light An optical junction element for increasing efficiency; it is also useful as a fine light-emitting element that is disposed in front of a single element of a liquid crystal display or a plasma display and used for improving luminance and adjusting directivity.

  Furthermore, the glass substrate according to the present invention is also useful as a non-glare-treated substrate that reduces reflections such as illumination on the display surface.

  According to the present invention, the raised structure is formed on both the front surface and the back surface of the glass substrate along the region where the laser beam is transmitted, so that the effect as a lens is increased and a biconvex lens having a high numerical aperture is obtained. be able to. At this time, since the laser beam and the axis of the raised structure coincide with each other, the laser beam is irradiated one side at a time, and the alignment for axis alignment necessary for manufacturing the biconvex lens becomes unnecessary, and the number of processes is reduced. Therefore, a highly accurate micro optical element can be manufactured by a simple operation and at a low cost.

  Further, when the laser beam intensity is high, a depressed structure by ablation (evaporation) is formed on the irradiated surface of the glass substrate, and a raised structure by heat transfer is formed on the back surface. The obtained meniscus lens is useful as a lens for aberration correction.

Furthermore, since the shape of the lens can be manipulated by adjusting the intensity distribution in the radial direction of the laser beam, it is possible to manufacture a biconvex aspheric lens with higher performance.
Furthermore, the energy of the laser beam that is transmitted without being absorbed by the substrate is very small, and even after the glass substrate is placed on the target object in the specified equipment, the laser beam is irradiated and the laser beam is placed. Elements can be formed at the locations.

Hereinafter, examples will be shown to further clarify the features of the present invention.
[Example 1]
A CO gas laser (wavelength of about 99.99%, silica purity 99.99%, thickness t = 40μm, density 2.279g / cm ³ , densification rate 3.59%) is pre-densified by ultra-high pressure HIP treatment. 5.5 μm) was condensed into a circular beam spot with a diameter of 40 μm and irradiated (irradiation time 10 ms). The laser power was 0.6W. The shapes of the front and back surfaces of the thin plate after irradiation were measured with an atomic force microscope. The absorption coefficient α of silica glass at a laser wavelength of 5.5 μm is 129 cm ⁻¹ and α × t = 0.516.

FIG. 2 shows the shapes of the front surface (upper side in the figure) and the back surface (lower side in the figure) of the obtained glass substrate. It is clear that a 40 μm substrate has a raised structure with almost the same shape on the front and back surfaces by 0.6 W-10 ms laser irradiation.
[Example 2]
A CO gas laser (wavelength of about 99.99%, silica purity 99.99%, thickness t = 70μm, density 2.279g / cm ³ , densification rate 3.59%) is pre-densified by ultra-high pressure HIP treatment. 5.5μm)
Was condensed into a circular beam spot with a diameter of 70 μm and irradiated (irradiation time 10 ms). The laser power was 0.6W. The shapes of the front and back surfaces of the thin plate after irradiation were measured with an atomic force microscope. The absorption coefficient α of silica glass at a laser wavelength of 5.5 μm is 129 cm ⁻¹ and α × t = 0.903.

FIG. 3 shows the shapes of the front surface (upper side of the figure) and the back surface (lower side of the figure) of the obtained glass substrate. The raised structure on the back surface is about half that of the front surface.
[Example 3]
Silica glass densified in advance by ultra-high pressure HIP treatment (silica purity 99.99%, thickness t = 50μm
, Density 2.279g / cm ³ , densification rate 3.59%), CO gas laser (wavelength approx. 5.5μm) light was condensed into a 50μm diameter circular beam spot and irradiated (irradiation time 50ms) . The laser power was 0.6W. The shape of the front and back surfaces of the thin plate after irradiation was measured with an atomic force microscope. The absorption coefficient α of silica glass at a laser wavelength of 5.5 μm is 129 cm ⁻¹ and α × t = 0.645.

  FIG. 4 shows the shapes of the front surface (upper side of the figure) and the back surface (lower side of the figure) of the obtained glass substrate. Due to the increase in irradiation time, the substrate surface was overheated, and evaporation and ablation occurred on the surface. As a result, the irradiated surface was depressed. However, the back surface did not rise enough to cause ablation or evaporation, and a raised structure was formed.

  In this embodiment, an optical element substrate in which a lens having a negative focal length is formed on the substrate surface, a lens having a positive focal length is formed on the back surface of the substrate, and a meniscus lens is formed coaxially as a whole. Obtained.

When a glass substrate is irradiated with a heat ray laser beam under the condition of α × t ≦ 1.5 and under a sufficient thickness, the state of laser energy reduction in the glass material It is a schematic diagram which shows the outline | summary of the mechanism in which a protruding structure is formed in the surface and back surface. It is sectional drawing which shows the protruding structure of the surface of a glass substrate obtained in Example 1, and a back surface. It is sectional drawing which shows the protruding structure of the surface of the glass substrate obtained in Example 2, and a back surface. It is sectional drawing which shows the depression structure of the surface of the glass substrate obtained in Example 3, and the protruding structure of a back surface.

Claims (1)

By irradiating a thin plate of glass material whose volume increases by heat treatment with a thickness of 10 to 150 μm, a convex portion is formed on one side of the thin plate and both sides of the other side, or a convex portion is formed on one side. is, and a glass substrate manufacturing method, characterized by forming a recess in the other one side, the absorption coefficient for laser light of wavelength 1 to 25 m: thickness [alpha ^{cm -1]} is 100～400Cm ^-1 A thin plate of glass material having a thickness of 10 to 150 μm is used as a substrate, and the product of the absorption coefficient [α: cm ⁻¹ ] of the glass material at a predetermined laser beam wavelength and the thickness [t: cm] of the glass substrate (α × t) is a method of performing laser irradiation conditions to be within the range of 0.01 to 1.5 (provided that when the internal transmittance of the glass material was T, alpha and t, T = ^e-.alpha. It satisfies the relational expression represented by ^t.)

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