This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-191174 filed on Sep. 19, 2014, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical component suitable for use, for example, in a diffuser plate or a fluorescent diffuser plate for a solid-state light source such as an LED (light-emitting diode) or an LD (laser diode), a support substrate in a surface plate or the like for supporting a material to be subjected to a surface treatment such as a grinding or polishing treatment, a wheel for a projector, etc.
2. Description of the Related Art
In general, the transmittance of a translucent substrate of an optical component can be improved, for example, by mirror-finishing a surface of the translucent substrate to reduce the reflectance. Meanwhile, in the case of forming a dichroic film or an AR (antireflection) film on the translucent substrate, a surface of the translucent substrate is mirror-finished in advance, and the dichroic film or the AR film is formed on the mirror surface (see Japanese Laid-Open Patent Publication Nos. 10-311907 and 2006-312579, for example). The surface of the translucent substrate can be mirror-finished by using a polishing process as described in Japanese Laid-Open Patent Publication Nos. 10-311907 and 2006-312579, etc.
However, after performing the polishing process, a material such as an abrasive material may remain on the translucent substrate, and a defect may be generated in the dichroic film or the AR film due to the remaining material. In addition, disadvantageously, the polishing process contains a complicated operation to increase the production cost.
In view of the above problems, an object of the present invention is to provide an optical component having the following advantageous effects:
(a) a mirror surface can be formed without polishing processes;
(b) the surface can be made suitable for easily forming a dichroic film, an AR film, or the like without cost increase; and
(c) the reflectance can be reduced at a boundary with air or with a material having a different refractive index to thereby improve the transmittance.
[1] An optical component according to the present invention contains a translucent substrate and a glass layer, wherein the glass layer is disposed in contact with the translucent substrate and has a refractive index equal to or less than that of the translucent substrate.
[2] In the present invention, it is preferred that the glass layer have a surface roughness smaller than that of the translucent substrate.
[3] In the present invention, it is preferred that the translucent substrate contain alumina as a main component.
[4] In the present invention, it is preferred that the translucent substrate have a thickness of 5 mm or less and the glass layer has a thickness of 0.1 mm or less.
[5] In the present invention, the optical component may further contain a dichroic film formed on the glass layer.
[6] In the present invention, the optical component may further contain an antireflection film formed on the glass layer.
[7] In the present invention, the glass layer may be formed on each of both surfaces of the translucent substrate.
[8] In the present invention, the translucent substrate may contain a fluorescent layer.
[9] In this case, the glass layer preferably should be formed on the fluorescent layer.
[10] In the present invention, the translucent substrate may have a lens shape on a surface thereof.
[11] In this case, the optical component may further contain a reflection film formed on a back surface of the translucent substrate.
[12] Alternatively, the optical component may further contain a reflection film formed on a back surface of the translucent substrate, the glass layer being interposed between the reflection film and the translucent substrate.
The optical component of the present invention has the following advantageous effects:
(a) a mirror surface can be formed without polishing processes;
(b) the surface can be made suitable for easily forming a dichroic film, an AR film, or the like without cost increase; and
(c) the reflectance can be reduced at a boundary with air or with a material having a different refractive index to thereby improve the transmittance.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.
Several embodiment examples of the optical component of the present invention will be described below with reference to
As shown in
As shown in
The ceramic substrate 12 is a substrate made of a translucent ceramic material. For example, the thickness of the ceramic substrate 12 is preferably 0.01 to 5 mm, more preferably 0.01 to 2 mm. The ceramic substrate 12 preferably has only a small number of pores. For example, the ceramic substrate 12 preferably contains 1 to 1000 ppm of pores by volume. A small number of the pores can act to improve light diffusion in the ceramic substrate 12 though the pores have an adverse effect on the light transmittance of the ceramic substrate 12. The translucent ceramic material is not particularly limited, and may be alumina, aluminum nitride, spinel, PLZT (lanthanum-doped lead zirconate titanate), YAG, Si3N4, quartz, sapphire, AlON, hard glass such as Pyrex (registered trademark), etc. The translucent ceramic material is preferably a translucent alumina material containing alumina as a main component. Specifically, the alumina content of the translucent ceramic material is preferably 90% or more, more preferably 99% or more. In this case, for example, the ceramic substrate 12 has a refractive index of about 1.73 to 1.77 and a thermal expansion coefficient of about 6×10−6/K. The translucent alumina crystals preferably have an average grain diameter of 0.5 to 50 μm. For example, the average grain diameter can be measured as follows. An arbitrary portion of a sample is observed at 200-fold magnification using an optical microscope. The number N of crystals located on a 0.7-mm line segment in an observed image is counted. The average grain diameter can be calculated using the formula of:
0.7×(4/π)/N.
The glass layer 14 may be formed by a fusion method, a vapor phase method (such as a PVD or CVD method), a sol-gel method, etc. For example, by using the fusion method, a surface 14a of the glass layer 14 can be formed as a mirror surface (flat surface) as shown in
An experiment example will be described below. In this experiment example, as shown in
As shown in
One, two, three, or more glass layers 14 may be formed. For example, an advantageous effect of the optical component having two glass layers will be described below with reference to
In the left side of
As shown in
As shown in
When the refractive index na of the ceramic substrate 12, the refractive index nb1 of the first glass layer 14A, the refractive index nb2 of the second glass layer 14B, and the refractive index n of the air layer 16 satisfy the relation of na≅nb1>nb2>n, the reflectance can be reduced at the boundary with the air layer 16, so that the transmittance can be further improved. In the above, explanation has been given on the assumption that the transmittance of the glass layer 14 or the like formed on the ceramic substrate 12 is 100%. Even in a case where the transmittance of the glass layer 14 or the like is not 100%, the glass layer 14 or the like hardly affect the transmittance of the entire structure as long as the glass layer 14 has a small thickness.
Several specific examples of the optical component 10 according to this embodiment will be described below with reference to
In an optical component according to a first specific example (hereinafter referred to as a first optical component 10A), the glass layer 14 is formed on the surface 12a of the ceramic substrate 12, and a dichroic film 20 is formed on the surface 14a of the glass layer 14.
The dichroic film 20 is a type of mirror capable of transmitting a light with a particular wavelength (such as an excitation light) and reflecting lights with different wavelengths (such as wavelength-converted lights and mixed color lights). In general, the dichroic film 20 is formed by thin film coating such as multi-layer coating of dielectric layers.
Thus, the dichroic film 20 has a structure provided by alternately stacking high refractive index layers and low refractive index layers. The material of the high refractive index layer may include TiO2 (having a refractive index of 2.2 to 2.5), Ta2O3 (having a refractive index of 2.0 to 2.3), or the like. The material of the low refractive index layer may include SiO2 (having a refractive index of 1.45 to 1.47), MgF2 (having a refractive index of 1.38), or the like. In the dichroic film 20, the number of the high refractive index layers and the number of the low refractive index layers are each 5 to 100. Each layer has a thickness of 50 to 500 nm.
The ceramic substrate 12 preferably has a flat plate shape having the surface 12a and a back surface 12b opposite to the surface 12a. For example, the ceramic substrate 12 has a thickness of 0.01 to 5 mm and an area of about 0.1 mm×0.1 mm or more (equivalent to a square). In the case of selecting a large area, the thickness is preferably increased accordingly in order to ensure sufficient strength.
The shape of the ceramic substrate 12 is not limited to the flat plate shape. The ceramic substrate 12 may have a three-dimensional shape on one main surface 12a, the other main surface 12b, or both thereof, for example. For example, the ceramic substrate 12 may have a curved surface shape (a concave-convex lens shape) or assembly of the shapes. The ceramic substrate 12 may have a cooling fin shape, a hole, or a protrusion for the purpose of heat release.
In the case of putting emphasis on the light transmittance, the front transmittance of the ceramic substrate 12 is preferably about 30% or more, more preferably about 70% or more. In the case of putting emphasis not on the light transmittance but on the light diffuseness, the front transmittance of the ceramic substrate 12 is preferably about 50% or more. The diffuseness is defined as follows:
Diffuseness=1−Linear Transmittance/Front Transmittance.
In the first optical component 10A, the dichroic film 20 is not formed directly on the ceramic substrate 12. The glass layer 14 is first formed on the ceramic substrate 12, for example, by the fusion method, and the dichroic film 20 is subsequently formed on the glass layer 14. Therefore, even when the one main surface 12a of the ceramic substrate 12 is an as-fired surface, the dichroic film 20 is formed on a surface (fused surface) of the glass layer 14, which has a surface roughness smaller than that of the as-fired surface. In the above experiment example, the surface 14a of the glass layer 14 is a mirror surface.
Thus, the dichroic film 20 can be formed on the surface (such as the mirror surface) having a surface roughness smaller than that of the as-fired surface of the ceramic substrate 12 without the processes of polishing the one main surface 12a of the ceramic substrate 12 to form the mirror surface. Similarly, an AR film 22 (see a second optical component 10B shown in
In general, in the case of performing the polishing process, a material such as an abrasive material may remain on the ceramic substrate 12, and such a residue material may cause generation of defect in the dichroic film 20 or the AR film 22 formed on the polished surface. In addition, disadvantageously, the polishing process contains a complicated operation to increase the production cost. In contrast, as described above, in this embodiment, the dichroic film 20 or the AR film 22 can be formed on the surface (such as the mirror surface) having a surface roughness smaller than that of the as-fired surface of the ceramic substrate 12 without the polishing processes. Therefore, the problems caused by the polishing process can be solved in the present invention.
Furthermore, since the refractive index na of the ceramic substrate 12, the refractive index nb of the glass layer 14, and the refractive index n of the air layer 16 satisfy the relation of na≧nb>n and preferably satisfy the relation of na>nb>n, the reflectance can be reduced at the boundary with the air layer 16 to improve the transmittance (such as the front transmittance).
In the case of putting emphasis on the transmittance, it is preferred that the glass layer 14 contain substantially no pores. This is because the pores may act to reduce the transmittance even when the glass layer 14 has a small thickness. In the case of putting emphasis on the diffuseness, it is preferred that the pores be appropriately utilized depending on balance with the transmittance.
The glass layer 14 is preferably colorless and transparent. The glass layer 14 may be colored as long as it has a high transmittance with respect to a wavelength of a light that is utilized in the optical component 10.
The refractive index of the glass layer 14 is preferably between those of the ceramic substrate 12 and air in order to reduce the reflection caused by the refractive index difference. Specifically, in a case where the ceramic substrate 12 is composed of Al2O3, the glass layer 14 preferably has a refractive index of 1.35 to 1.65. The refractive index of the glass layer 14 is preferably approximately equal to that of the ceramic substrate 12 in order to reduce the reflection caused by the surface shape.
The composition of the glass layer 14 is not particularly limited, and may contain SiO2—B2O3, SiO2—BaO—B2O3, ZnO—B2O3—SiO2, or the like as a main component.
The softening temperature of the glass layer 14 is preferably 500° C. or higher, more preferably 700° C. or higher. Although a glass layer 14 having a lower softening point can be handled at a lower fusion temperature, such a glass layer 14 contains an alkali metal oxide or the like for lowering the fusion temperature and consequently is poor in a corrosion resistance, e.g. in a high-temperature high-humidity environment. In the case of forming the glass by the fusion method, the grain diameter of the glass powder used in the paste or the like is preferably about 0.5 to 5 μm.
The glass layer 14 preferably has a surface roughness Ra of 0.1 μm or less. The glass layer 14 preferably has a mirror surface. The optical properties (such as a front transmittance) of the optical component can be improved by forming the dichroic film 20, the AR film 22, or the like on the mirror surface.
The ceramic substrate 12 may have a mirror-polished surface, an as-fired surface, a ground surface, or the like, and the surface roughness of the ceramic substrate 12 is not limited.
The dichroic film 20 may be formed on the surface of the glass layer 14 formed on the ceramic substrate 12. Alternatively, the dichroic film 20 may be formed on a surface of a glass layer formed on a light emitting layer such as a fluorescent layer as described later. Thus, the glass layer 14 can exhibit also an advantageous effect of modifying the surface shape of the light emitting layer.
An optical component according to a second specific example (hereinafter referred to as a second optical component 10B) will be described below with reference to
As shown in
Also in this case, without the polishing processes, the dichroic film 20 can be formed on the surface 14Aa (such as a mirror surface) of the first glass layer 14A, and the AR film 22 can be formed on the surface 14Ba (such as a mirror surface) of the second glass layer 14B. Therefore, a desired film such as the dichroic film 20 or the AR film 22 can be easily formed without cost increase, and thus the optical properties (such as the front transmittance) of the second optical component 10B can be improved.
In the second optical component 10B, it is preferred that the materials of the first glass layer 14A and the second glass layer 14B exhibit an excellent wettability on the material of the ceramic substrate 12 in the application process of the first and second glass layers 14A, 14B on the ceramic substrate 12.
An optical component according to a third specific example (hereinafter referred to as a third optical component 10C) will be described below with reference to
As shown in
Thus, the excitation light 26 (such as a blue light) is diffused in the ceramic substrate 12, transmitted through the glass layer 14 and the dichroic film 20, introduced into the fluorescent layer 24, and converted to a light having a different wavelength (such as a yellow light 26a) in the fluorescent layer 24. A part of the yellow light 26a is transmitted toward the ceramic substrate 12, reflected by the dichroic film 20, and returned to the fluorescent layer 24. Therefore, the reflected and returned part contributes to increase in the yellow light amount, so that the brightness is improved as compared with a structure not having the dichroic film 20.
The fluorescent layer 24 contains a fluorescent material (i.e. fluorescent particles) and a binder of a glass. For example, the excitation light 26 may be an excitation light from a solid-state light source such as an LED or a laser diode (LD), a lamp such as a halogen lamp, etc.
For example, the ceramic substrate 12 is preferably an alumina substrate (a translucent alumina substrate) having a thermal conductivity of 30 W/m·K or more. When the thermal conductivity is 30 W/w·K or more, heat generated in the fluorescent layer 24 can be released through the ceramic substrate 12 to prevent thermal quenching. Of course, the ceramic substrate 12 may be a sapphire substrate, an aluminum nitride substrate, or the like, as long as it has a thermal conductivity of 30 W/m·K or more.
The ceramic substrate 12 may be formed by an arbitrary method such as a doctor blade method, an extrusion method, a gel casting method, a powder pressing method, or an imprint method without particular restrictions. In the case of forming the ceramic substrate 12 with a complicated shape, a thick shape, or a complicated thick shape, the gel casting method is particularly preferably used. In a preferred embodiment, a slurry containing a ceramic powder, a dispersion medium, and a gelling agent is cast into a mold, the slurry is turned into a gel to obtain a molded body, and the molded body is sintered to prepare the ceramic substrate 12 (see Japanese Laid-Open Patent Publication No. 2001-335371). In the case of forming the ceramic substrate 12 with a simple or thin shape, a tape formation method such as the doctor blade method is preferably used.
The material of the ceramic substrate 12 is particularly preferably a material provided by adding 150 to 1000 ppm of an auxiliary agent to a highly-pure alumina powder having a purity of 99.9% or more (preferably 99.95% or more). Examples of such highly-pure alumina powders include a highly-pure alumina powder available from Taimei Chemicals Co., Ltd.
The auxiliary agent is preferably magnesium oxide (MgO), and may further include zirconium oxide (ZrO2), yttrium oxide (Y2O3), lanthanum oxide (La2O3), and scandium oxide (Sc2O3).
The gel casting methods include:
(1) a method containing the steps of dispersing a gelling agent of a prepolymer of a polyvinyl alcohol, an epoxy resin, a phenol resin, or the like, together with an inorganic powder and a dispersing agent, in a dispersion medium, to prepare a slurry, casting the slurry into a mold, using a cross-linker to three-dimensionally cross-link the gelling agent, thereby converting the slurry to a gel state, and solidifying the slurry; and
(2) a method containing the step of chemically bonding an organic dispersion medium having a reactive functional group to a gelling agent, thereby solidifying the slurry. The method of (2) is described in Japanese Laid-Open Patent Publication No. 2001-335371 filed by the present applicant.
The fluorescent layer 24 may be formed by a known method such as a screen printing method, a dip coating method, or an ink jet method, without particular restrictions.
Also in the third optical component 10C, the dichroic film 20 can be formed on the surface 14a of the glass layer 14 without the polishing processes. Therefore, the dichroic film 20 can be easily formed without cost increase, and thus the optical properties (such as the front transmittance) of the third optical component 10C can be improved.
An optical component according to a fourth specific example (hereinafter referred to as a fourth optical component 10D) will be described below with reference to
As shown in
The dichroic film 20 may be formed on the surface 14a of the glass layer 14 formed on the ceramic substrate 12 as in the first optical component 10A, and may be formed on the surface 14a of the glass layer 14 formed on the fluorescent layer 24 as in the fourth optical component 10D. By forming the glass layer 14 on the fluorescent layer 24, the surface shape of the fluorescent layer 24 can be modified, and the dichroic film 20 can exhibit a desired function.
For example, in the fourth optical component 10D, the fluorescent layer 24 is located on a side that is irradiated with the excitation light 26. For example, the excitation light 26 (such as the blue light) is transmitted through the dichroic film 20 and introduced into the fluorescent layer 24. A part of the excitation light 26 is converted to a light having a different wavelength (such as the yellow light 26a) in the fluorescent layer 24, and diffused in the ceramic substrate 12. Another part of the excitation light 26 is transmitted through the fluorescent layer 24 without conversion, and also diffused in the ceramic substrate 12. Therefore, the wavelength-converted yellow light 26a and the excitation light 26 is mixed in the ceramic substrate 12, so that a mixed color light 26b (such as a white light) is emitted from the other main surface 12b of the ceramic substrate 12 (light outlet surface). A part of the yellow light 26a is transmitted toward the light source, reflected by the dichroic film 20, and returned to the ceramic substrate 12. Therefore, the reflected and returned part contributes to increase in the white light amount, so that the brightness is improved.
Also, the glass layer 14 on the fluorescent layer 24 in the fourth optical component 10D has the following advantageous effects. That is, the glass layer 14 contributes to surface modification of the fluorescent layer 24 for forming the dichroic film 20. Further, in a case that the structure of the fluorescent layer 24 is comparatively porous, the glass layer 14 serves as a cap for preventing contamination of the fluorescent layer 24 from outside, infiltration of resin into the fluorescent layer 24 during the assembly process of the fourth optical component 10D, or the like.
From the viewpoint of improving the light diffusion, it is preferred that the surface 12a of the ceramic substrate 12 should not be an as-fired surface, but processed by printing, mechanical processing, etc. Several specific examples of the surface 12a will be described below with reference to
As shown in
When the excitation light 26 is introduced into the lens-shaped ceramic substrate 12L, the excitation light 26 is diffused in the lens-shaped ceramic substrate 12L, and is further diffused by the lenses 30 on the surface of the lens-shaped ceramic substrate 12L. The diffused excitation light 26 enters the fluorescent layer 24. Therefore, the light emission from the fluorescent layer 24 is made uniform, and the brightness is stabilized.
The surface may have a lens shape other than the above shape containing the continuously arranged lenses 30 having the arc-like cross-section. For example, as shown in
In any of the above shapes, the height is about 10 to 1000 μm, and the pitch is about 0.1 to 3 mm.
The materials of the lens 30 and the protrusion 32 are not particularly limited, and may be the same as the material of the ceramic substrate 12. In a case where the materials of the lens 30 and the protrusion 32 are different from the materials of the ceramic substrate 12 and the glass layer 14, it is preferred that the ceramic substrate 12 have the highest heat resistance, the lens 30 and the protrusion 32 have an intermediate heat resistance, and the glass layer 14 have the lowest heat resistance (heat resistance of the ceramic substrate 12> heat resistance of the lens 30 and the protrusion 32> heat resistance of the glass layer 14). In that case, the previously-formed portion is not adversely affected by heat in the subsequently-formed portion in a heat treatment.
In conventional methods, when an optical film such as the dichroic film 20 or the AR film 22 is formed directly on the substrate having such lens 30 or protrusion 32 (such as the lens-shaped ceramic substrate 12L), the optical film often fails to have a desired shape and a desired function due to the concavo-convex surface shape. In this embodiment, the optical film is formed on the flat surface of the glass layer 14, and thus such problems are not caused. The lens 30, the protrusion 32, or the like for improving the diffuseness may be formed on the back surface of the ceramic substrate 12. In that case also, the same advantageous effects are achieved.
Several specific examples of optical components having a reflection film (optical components 10F to 10H according to sixth to eighth specific examples) will be described below with reference to
As shown in
As shown in
As shown in
As shown in
In the sixth optical component 10F, the blue light is reflected at the boundaries between the fluorescent layer 24, the glass layer 14, the lens-shaped ceramic substrate 12L, and the reflection film 34. The yellow light is generated in the fluorescent layer 24, a part of the yellow light is directly emitted, and another part of the yellow light is reflected at the boundaries between the glass layer 14, the lens-shaped ceramic substrate 12L, and the reflection film 34. The lens-shaped ceramic substrate 12L, the reflection film 34, the glass layer 14, and the like are utilized to efficiently mix all the light components.
The materials of the layers other than the reflection film 34 may be selected in the above-described manner. The material of the reflection film 34 may include a metal such as Ag (silver), Cr (chromium), Cu (copper), W (tungsten), or Pt (platinum), and may be formed by a plating method, a physical vapor deposition method, etc.
The surface 12a of the lens-shaped ceramic substrate 12L having the reflection film 34 may be an as-fired surface, a mirror-polished surface, or a glass layer 14 surface. For the purpose of widely reflecting and diffusing the light, it is preferable to increase the surface roughness of the surface 12a (rough surface). For the purpose of forming a light path with high accuracy, it is preferable to lower the surface roughness of the surface 12a (smooth surface).
In the sixth optical component 10F, it is preferred that the sum of the refractive index difference between the glass layer 14 and the fluorescent layer 24 and the refractive index difference between the glass layer 14 and the lens-shaped ceramic substrate 12L should be minimized. In this case, the thickness of the fluorescent layer 24 can be easily controlled advantageously.
In, the seventh optical component 10G, when the refractive index of the glass layer 14 is smaller than that of the fluorescent layer 24, the reflectance of the emission surface is smaller than a case in which the glass layer 14 is not provided. This is suitable for improving the brightness.
In the eighth optical component 10H, in order to make an underlayer for the reflection film 34 into a mirror surface at low cost, the first glass layer 14A is formed.
In the sixth optical component 10F to the eighth optical, component 10H, the reflection film 34 may be formed on a side surface of the lens-shaped ceramic substrate 12L though not shown in the figures. In this case, when a part of the incident light reaches the side surface of the lens-shaped ceramic substrate 12L, the part can be guided to the reflection film 34 on the back surface 12b. Furthermore, when a part of the reflected light reaches the side surface of the lens-shaped ceramic substrate 12L, the part can be guided to the fluorescent layer 24. Consequently, the light intensity can be further increased.
The surface roughnesses of Examples 1 to 4 and Comparative Example 1 were measured, and the transmittances thereof were evaluated. Examples 1 to 4 had a structure containing a translucent substrate and a glass layer formed thereon as shown in
In each of the samples (Examples 1 to 4 and Comparative Example 1), the surface roughness of the glass layer 14 was measured at 500-fold magnification using a laser microscope (VK-9700 manufactured by Keyence Corporation).
The front transmittance was used for transmittance evaluation. Specifically, the transmittance at a measurement wavelength of 460 nm was used.
As shown in
A light having a wavelength of 460 nm was emitted from the light source 40 toward the incidence surface (the translucent substrate side) of the sample fixed to the shield 48. The light that was transmitted through the sample and emitted from the emission surface (the glass layer) was detected by the detector 42.
The front transmittance was calculated as a ratio I/I0 of the intensity (I) of the light transmitted through the sample to the light intensity (I0) measured without the sample.
A translucent alumina substrate having a purity of 99.98%, an average crystal grain diameter of 25 μm, an outer size of 30×30 mm, and a thickness of 0.5 mm was formed by a gel casting method described in Japanese Laid-Open Patent Publication No, 2001-335371.
A paste containing a glass was printed on the translucent alumina substrate by a screen printing method. The glass contained SiO2—B2O3 as the main component. The glass paste was printed into a pattern having an outer size of 28×28 mm and a thickness of 0.02 mm. The resultant was dried at 60° C. to 100° C. and fired at 900° C. for 10 minutes, whereby the glass layer was formed on the surface of the translucent alumina substrate so that the sample (optical component) of Example 1 was obtained.
Example 2 was produced in the same manner as Example 1 except for using a glass containing SiO2—B2O3—B2O3 as the main component.
Example 3 was produced in the same manner as Example 1 except for using a glass containing ZnO—B2O3—SiO2 as the main component and a firing temperature of 700° C.
Example 4 was produced in the same manner as Example 3 except for using a firing temperature of 900° C.
The translucent alumina substrate was prepared in the same manner as Example 1 and used as the measurement sample of Comparative Example 1. Thus, the glass layer was not formed on the surface of the translucent alumina substrate.
The evaluation results of Examples 1 to 4 and Comparative Example 1 are shown in Table 1. The evaluation criteria were as follows.
A: The sample had a surface roughness of 0.1 μm or less and a transmittance of 74% or more.
B: The sample had a surface roughness of 0.1 μm or less and a transmittance of 66% or more but less than 74%.
C: The sample had a surface roughness of 0.1 μm or less and a transmittance of less than 66%.
D: The sample had a surface roughness of more than 0.1 μm.
As shown in Table 1, in Examples 1 to 4, all the samples had the surface roughness Ra of 0.05 μm, and thus the emission surfaces of the optical components were mirror surfaces. As is clear from the evaluation results of Examples 1 to 4, the transmittance depended on the type of glass and the firing temperature. In Comparative Example 1, since the glass layer was not formed, the sample had the surface roughness of 0.2 μm, i.e., the as-fired surface, and was evaluated as D.
Transmittance changes with light wavelengths were observed in Examples 5 and 6 and Comparative Example 2.
As shown in
As shown in
As shown in
The front transmittances of Examples 5 and 6 and Comparative Example 2 were evaluated in the same manner as First Example. In Second Example, the front transmittance evaluation was performed by use of excitation light 26 of wavelength ranging from 380 to 780 nm. The evaluation results are shown in
As shown in
The results of Examples 5 and 6 were not so different from each other in the second wavelength region (380 to 460 nm). More specifically, the transmittance was increased by about 3 as compared with Comparative Example 2.
The optical component of the present invention is not limited to the aforementioned embodiments. Various changes and modifications may be made to the embodiments without departing from the scope of the invention.
Number | Date | Country | Kind |
---|---|---|---|
2014-191174 | Sep 2014 | JP | national |