Photosensitive glass

Abstract

To provide a photosensitive glass capable of precisely processing a pattern by suppressing crystal deposition by diffraction light and stray light when exposing through a mask having apertures.SOLUTION: When performing heat treatment for generating a colloid at a glass transition temperature Tg+20 to +65°C by irradiating a photosensitive glass with ultraviolet light having a wave length of 300 to 330 nm, (a gradient of exposure amounts of ultraviolet light of 1 to 2 J / cm2) / (a gradient of exposure amounts of ultraviolet light of 0 to 1 J / cm2) is greater than 1.0 when plotting absorbances of the colloid on exposure amounts of ultraviolet light of 0 J / cm2, 1 J / cm2, and 2 J / cm2 on a coordinate system having an abscissa axis for indicating an exposure amount (J / cm2) of ultraviolet light, and an ordinate axis for indicating an absorbance (mm-1) of the colloid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to photosensitive glass. [Background technology]

[0002] Photosensitive glass is glass whose glass structure changes in light-exposed areas when exposed to light in combination with heat treatment, and can selectively crystallize only the light-exposed areas. Specifically, by applying heat to photosensitive glass exposed to short-wavelength radiation such as ultraviolet light, Ag colloids are formed in the exposed areas, and the Ag colloids then act as nuclei for the precipitation of fine crystals, thereby changing the color, refractive index, chemical durability, and glass strength of the exposed areas (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-36200 A Summary of the Invention [Problem to be solved by the invention]

[0004] When processing a photosensitive glass into a specific pattern, exposure may be performed through a mask 2 with apertures 4, as shown in Figure 1. In this case, diffracted light 5 and stray light 6 are generated when irradiated light 3 passes through the apertures 4. Although the diffracted light 5 and stray light 6 are small in terms of exposure amount, if the sensitivity due to exposure is high, crystals may precipitate in the photosensitive glass, and in such cases, crystals may precipitate in areas other than the target area. Furthermore, if the diameter of the apertures 4 in the mask 2 is small, the diffraction angle becomes larger, and the diameter of the crystal precipitates on the back side of the photosensitive glass 1, opposite the exposed surface, becomes even larger. Thus, when exposure is performed through a mask having openings in the photosensitive glass, there is a risk that diffracted light and stray light may cause crystals to precipitate in positions other than the intended, and when the crystals are dissolved by etching, the intended structure may not be obtained.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a photosensitive glass that can be patterned with high precision by suppressing crystal precipitation due to diffracted light and stray light when exposed through a mask having apertures. [Means for solving the problem]

[0006] One aspect of the present invention is a photosensitive glass, in which the photosensitive glass is irradiated with ultraviolet light having a wavelength of 300 to 330 nm, and heat treatment to generate colloids is performed at a glass transition temperature (Tg) +20 to +65°C. The horizontal axis represents the ultraviolet light exposure (J / cm2). 2 ) and the vertical axis is the colloid absorbance (mm -1 ), the ultraviolet exposure dose is 0 J / cm 2 , 1 J / cm 2 , and 2 J / cm 2 When the absorbance of the colloid is plotted at 1 to 2 J / cm 2 (slope at 0-1 J / cm) / (UV exposure dose 0-1 J / cm 2 The term "photosensitive glass" refers to a glass having a "gradient of ultraviolet light exposure of 1 to 2 J / cm" (slope at 1 to 2 J / cm) of more than 1.0. 2 (slope at 0-1 J / cm) / (UV exposure dose 0-1 J / cm 2 The "gradient at the time of the analysis" is sometimes referred to as "this indicator." [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a photosensitive glass that can be patterned with high precision by suppressing crystal precipitation due to diffracted light or stray light when exposed through a mask having apertures. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a conceptual diagram showing how diffracted light 5 and stray light 6 are generated when light 3 is irradiated onto photosensitive glass 1 through a mask 2 having openings 4. [Figure 2]FIG. 2 plots the photosensitive glasses of Examples 1 and 2 on a coordinate system with the ultraviolet exposure (J / cm2) on the horizontal axis and the colloid absorbance (mm-1) on the vertical axis. [Figure 3] FIG. 3 is a photomicrograph of the glass surface after patterning of the photosensitive glass of Examples 1 and 2. [Figure 4] FIG. 4 plots the photosensitive glasses of Examples 1 to 23 on a coordinate system with Sb2O3 / CeO2 on the horizontal axis and this index on the vertical axis. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented in any modified form without departing from the gist of the present invention. In this specification, unless otherwise specified, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] In this specification, "photosensitive glass" refers to glass in which metal colloids are generated in the glass by exposure to light and heat treatment, and further crystals are precipitated. More specifically, in "photosensitive glass," trivalent Ce ions release electrons upon exposure, which are then trapped by Ag ions, generating silver atoms, as shown in the following formula: Ce 3+ → Ce 4+ + e - Ag + + e - → Ag The photosensitive glass is then heat-treated to generate silver colloid, and by further increasing the temperature and heat-treating it, crystals are precipitated using the silver colloid as nuclei.

[0011] One embodiment of the photosensitive glass of the present invention is a photosensitive glass in which NaF crystals precipitate as the primary crystals upon exposure and heat treatment. Because the refractive index of the glass changes in the region where NaF crystals precipitate, such glass can be suitably used, for example, for volume holographic diffraction gratings. In this specification, the term "primary crystals" refers to the crystals that precipitate in the largest amount among the crystals precipitated upon exposure and heat treatment. In this specification, photosensitive glass in which NaF crystals are precipitated as the main crystals upon exposure and heat treatment may be referred to as "refractive index changing glass." In refractive index change glass, crystals precipitate in exposed areas due to optical interference, and the glass containing the precipitated crystals functions as a diffraction grating. If the crystal precipitation is uneven, the uniformity of light may be impaired, but if the crystals precipitate precisely, light can be extracted more uniformly, thereby increasing the uniformity of light. The photosensitive glass of the embodiment of the present invention can be patterned with precision, so it is also suitable for use in "refractive index change glass."

[0012] Another embodiment of the photosensitive glass of the present invention is a photosensitive glass in which lithium silicate crystals such as Li2SiO3 crystals and Li2Si2O5 crystals are precipitated as the main crystals by exposure to light and heat treatment. In photosensitive glass in which lithium silicate crystals are precipitated, the solubility of the crystals in HF is very high, so the exposed portions can be selectively removed by HF etching, thereby forming a fine pattern. In this specification, photosensitive glass in which lithium silicate crystals are precipitated as the main crystals by exposure and heat treatment is sometimes referred to as "microfabricated glass." The photosensitive glass according to the embodiment of the present invention can be patterned with high precision, and is therefore suitable for use in "microfabricated glass."

[0013] In this specification, the term "photosensitive glass of the present embodiment" includes both refractive index change glass and microfabricated glass.

[0014] The NaF crystals and lithium silicate crystals can be identified by, for example, X-ray diffraction (XRD) measurement. Specifically, they are measured by XRD using CuKα radiation at 2θ=10 to 90°, and the obtained diffraction peaks are compared with the Cambridge Structural Database (CSD) or the Inorganic Crystal Structure Database (ICSD).

[0015] <Photosensitive glass> The photosensitive glass of an embodiment of the present invention (hereinafter also referred to as the photosensitive glass of this embodiment) is irradiated with ultraviolet light having a wavelength of 300 to 330 nm, and heat treatment to generate colloids is performed at the glass transition temperature Tg +20 to +65°C. The horizontal axis shows the ultraviolet light exposure (J / cm 2 ) and the vertical axis is the colloid absorbance (mm -1 ), the ultraviolet exposure dose is 0 J / cm 2 , 1 J / cm 2 , and 2 J / cm 2 When the absorbance of the colloid is plotted at 1 to 2 J / cm 2 (slope at 0-1 J / cm) / (UV exposure dose 0-1 J / cm 2 The slope at (a) is greater than 1.0. Here, carrying out the heat treatment at the glass transition temperature Tg+20 to +65°C means that, when T is the heat treatment temperature, Tg+20°C≦T≦Tg+65°C.

[0016] As described above, the photosensitive glass of this embodiment is a glass having an ultraviolet exposure dose of 1 to 2 J / cm 2 (slope at 0-1 J / cm) / (UV exposure dose 0-1 J / cm 2 It is important that the slope at Here, the ultraviolet exposure dose is 1 to 2 J / cm 2 "Slope at" and "UV exposure 0-1J / cm 2The "slope in the graph" is the amount of UV exposure (J / cm2) plotted on the horizontal axis when photosensitive glass is irradiated with UV light of wavelength 300-330 nm and heat-treated at the glass transition temperature Tg +20 to +65°C to generate colloids. 2 ) and the vertical axis is the colloid absorbance (mm -1 ) on the coordinate system where the UV exposure is 0 J / cm 2 , 1 J / cm 2 , and 2 J / cm 2 When the absorbance of the above colloids is plotted, it can be expressed by the following equations: UV exposure 1-2J / cm 2 Slope at UV exposure 1 J / cm 2 Plot of colloid absorbance at 2 J / cm2 vs. UV exposure 2 The slope of the line connecting the plots of colloids at these times is (Abs2-Abs1) / (2J / cm 2 -1 J / cm 2 ) UV exposure: 0-1J / cm 2 Slope at UV exposure 0 J / cm 2 Plot of colloid absorbance at 1 J / cm and UV exposure 2 The slope of the line connecting the plots of colloids at these times is (Abs1-Abs0) / (1J / cm 2 -0J / cm 2 ) In the above formula, "Abs2" is the UV exposure dose of 2 J / cm 2 "Abs1" means the absorbance of the colloid when the UV exposure is 1 J / cm 2 "Abs0" means the absorbance of the colloid when the UV exposure is 0 J / cm 2 This means the absorbance of the colloid when

[0017] This index is greater than 1.0, which means that the UV exposure is low, 0-1 J / cm 2 The slope in the range of 1 to 2 J / cm 2This means that the slope is smaller than the slope in the range of 1.0. In other words, if this index is greater than 1.0, the absorbance is low at exposure levels below the threshold, and increases above that level, resulting in a photosensitive glass in which crystals do not form at low exposure levels. On the other hand, if the index is less than 1.0, the reaction at low exposure levels is large, which may cause crystals to form in locations other than the intended location.

[0018] This index is preferably 1.5 or more, more preferably 2.0 or more, even more preferably 2.3 or more, particularly preferably 2.5 or more, and most preferably 2.8 or more, and may also be 5.5 or less, 5.4 or less, 5.3 or less, or 5.2 or less. For example, this index may be greater than 1.0 and 5.5 or less.

[0019] In the photosensitive glass of this embodiment, in order to make this index exceed 1.0, the numerator of the index, "ultraviolet light exposure dose 1 to 2 J / cm 2 or increase the "slope at 0-1 J / cm2" which is the denominator of the above index. 2 One method is to reduce the "slope in

[0020] UV exposure: 1-2 J / cm 2 The large slope at the UV exposure of 1 J / cm 2 In the above, this means that the amount of colloid generated is large. The reason for the large amount of colloid generated is that there is a large reduction reaction to Ag, and one of the reasons for this is that there are many electrons released from Ce. And the fact that there are many electrons released from Ce means that the amount of Ce is large to a certain extent. Therefore, as will be described later, in the photosensitive glass of this embodiment, for example, by adjusting the lower limit of the Ce content, it is possible to achieve an ultraviolet exposure dose of 1 to 2 J / cm. 2 The "slope at" can be increased.

[0021] UV exposure: 0-1 J / cm 2 The small slope at + Sb occurs earlier than 5+ There are many reduction reactions of Sb 5+This is because the number of electrons that can be captured by Ce exceeds the number of electrons released from Ce. Ag + Sb occurs earlier than 5+ Regarding the frequent reduction reaction of Sb 5+ The amount of Sb2O3 depends on the input amount and melting conditions. Therefore, as will be described later, in the photosensitive glass of this embodiment, for example, by adjusting the content of Sb2O3, it is possible to achieve an ultraviolet exposure dose of 0 to 1 J / cm 2 This can reduce the "slope in Also, Sb 5+ The amount of electrons that can be captured by Ce is not too large, which means that the amount of Ce is not too large. Therefore, as will be described later, in the photosensitive glass of this embodiment, for example, by adjusting the upper limit of the Ce content, it is possible to achieve an ultraviolet exposure dose of 0 to 1 J / cm. 2 This can reduce the "slope in

[0022] To irradiate the photosensitive glass with ultraviolet light of wavelength 300 to 330 nm, for example, a mask aligner (Nanotec: ES20ag) can be used. The UV irradiance can be measured by attaching an ultraviolet integrating actinometer (Ushio Inc.: UIT-250) and a photodetector (Ushio Inc.: UVD-S313). Furthermore, the heat treatment for generating the colloid is set at glass transition temperature Tg +20 to +65°C, and the heat treatment time is set to 1 to 10 hours, for example, by setting the temperature and time of the heating furnace within the above ranges.

[0023] The photosensitive glass of this embodiment has the above index of "ultraviolet light exposure amount 0 to 1 J / cm 2 It is preferable that the gradient at the time of exposure is 0.001 to 1.0. When the gradient is 0.001 or more, colloids are sufficiently generated after exposure and heat treatment. Furthermore, when the gradient is 1.0 or less, the reaction at low exposure is not too strong, and crystals are less likely to be generated in positions other than the intended position. The above slope is more preferably 0.005 or more, even more preferably 0.01 or more, even more preferably 0.03 or more, even more preferably 0.05 or more, even more preferably 0.07 or more, and particularly preferably 0.115 or more, and is more preferably 0.7 or less, even more preferably 0.5 or less, even more preferably 0.3 or less, and particularly preferably 0.2 or less.

[0024] In the photosensitive glass of this embodiment, the ratio of the Sb2O3 content to the CeO2 content expressed in mole percentage on an oxide basis, ie, Sb2O3 / CeO2, is preferably 3.0-20. Sb2O3 is a thermally reducing component that reduces metal ions during heat treatment. In the photosensitive glass of this embodiment, Sb2O3 reduces Ag in the high temperature range. + It plays a role in reducing ions. In the photosensitive glass of this embodiment, CeO2 also plays a role as a photosensitizer. When the Sb2O3 / CeO2 ratio is 3.0 or more, the amount of Sb2O3 relative to CeO2 is sufficiently high, making it difficult to react with low light exposure. Also, when the Sb2O3 / CeO2 ratio is 20 or less, the amount of Ce, the electron donor, is not too low, making it difficult to form colloids after exposure and heat treatment. Furthermore, the amount of Sb2O3 relative to CeO2 is not too high, making it sufficiently sensitive to high light exposure. The Sb2O3 / CeO2 is more preferably 5.0 or more, even more preferably 5.1 or more, even more preferably 5.3 or more, still more preferably 5.5 or more, particularly preferably 5.8 or more, and is more preferably 18 or less, even more preferably 16 or less, still more preferably 14 or less, still more preferably 12 or less, particularly preferably 10 or less.

[0025] The photosensitive glass of this embodiment preferably contains 0.01 to 0.3% Sb2O3 in mole percentage based on oxides. By containing 0.01% or more Sb2O3, the photosensitive glass of this embodiment can stably reduce metal ions during heat treatment. Furthermore, by containing 0.3% or less Sb2O3, the photosensitive glass of this embodiment can suppress coloration of the glass. Furthermore, the photosensitive glass of this embodiment contains 0.01 to 0.3% of Sb2O3, and therefore satisfies the "ultraviolet light exposure of 0 to 1 J / cm2" in this index. 2 This makes it easy to make this index greater than 1.0. This is because by adjusting the Sb2O3 content, + Sb occurs earlier than 5+ This is because the reduction reaction can be increased.

[0026] The photosensitive glass of this embodiment preferably contains 0.04% or more of Sb2O3, expressed as a mole percentage based on oxide, even more preferably 0.06% or more, particularly preferably 0.08% or more, and even more preferably 0.2% or less.

[0027] The photosensitive glass of this embodiment preferably contains 0.002 to 0.04% CeO2 in mole percentage based on oxide. When the CeO2 content is in the above range, the "ultraviolet light exposure dose of 1 to 2 J / cm2" of this index is satisfied. 2 The "gradient at the UV exposure level of 0 to 1 J / cm" can be increased. 2 This makes it easier to make this indicator exceed 1.0 because it reduces the "slope in" UV exposure: 1-2 J / cm 2 The large slope at the UV exposure of 1 J / cm 2 In the above, this means that the amount of colloid generated is large. The large amount of colloid generated is due to the large reduction reaction to Ag, which is one of the reasons for the large amount of electrons released from Ce. The large number of electrons released from Ce means that the amount of Ce is large to a certain extent. Therefore, by setting the lower limit of the CeO2 content to 0.002% or more, it is possible to achieve an ultraviolet exposure of 1 to 2 J / cm 2 The "slope at" can be increased. UV exposure: 0-1 J / cm 2 One of the reasons for the small slope in Sb 5+ The reason is that the amount of electrons that can be captured by Ce is not too large, which means that the amount of Ce is not too large. Therefore, by setting the upper limit of the CeO2 content to 0.04% or less, it is possible to achieve a "ultraviolet light exposure of 0 to 1 J / cm2 This can reduce the "slope in

[0028] The photosensitive glass of this embodiment preferably contains 0.007% or more of CeO2, more preferably 0.008% or more, and particularly preferably 0.009% or more, expressed as mole percentage on an oxide basis, and more preferably 0.03% or less, and even more preferably 0.025% or less.

[0029] The photosensitive glass of this embodiment may contain B2O3. B2O3 is a component that forms a network structure within the glass. B2O3 also contributes to improving dielectric properties such as the relative permittivity and dielectric loss tangent in the high frequency range, and to improving solubility. By including B2O3, the photosensitive glass of this embodiment can be expected to achieve the above effects.

[0030] The photosensitive glass of the present embodiment has, in terms of oxide-based mole percentage, SiO2 59.0~81.0%, Li2O 8.0 to 26.0%, Na2O 1.0 to 10.0%, K2O 1.0 to 10.0%, Al2O3 0-5.0%, ZnO 0 to 6.0%, B2O3 0-8.0%, It is preferable that it contains The preferred composition ranges of each component in the photosensitive glass of this embodiment will be described below.

[0031] SiO2 is a component that forms the glass skeleton through a network structure, enhances acid resistance and water resistance, and stabilizes the glass. In microfabricated glass, it is a component that forms and precipitates Li2SiO3 crystals as a crystalline phase. In the photosensitive glass of this embodiment, the SiO2 content is preferably 59.0 to 81.0%. An SiO2 content of 59.0% or more stabilizes the glass, and the precipitated crystalline phase when the photosensitive glass is crystallized is likely to be stable. In the photosensitive glass of this embodiment, the SiO2 content is more preferably 61.0% or more, even more preferably 62.0% or more, even more preferably 63.0% or more, particularly preferably 64.0% or more, even more preferably 65.0% or more, and most preferably 66.0% or more. Furthermore, when the SiO2 content is 81.0% or less, the glass raw material is easily melted and formed. The SiO2 content is more preferably 78.0% or less, even more preferably 76.0% or less, even more preferably 75.0% or less, particularly preferably 74.0% or less, and most preferably 73.0% or less.

[0032] Li2O is a component that reduces the viscosity of glass and improves its meltability, but adding too much will excessively disrupt the silica network structure, reducing glass stability. In microfabrication glass, Li2O is a component that forms and precipitates lithium silicate crystals such as Li2SiO3 crystals and Li2Si2O5 crystals. The photosensitive glass of this embodiment preferably contains 8.0 to 26.0% of Li2O. The inclusion of Li2O in the photosensitive glass of this embodiment makes it easier to obtain lithium silicate crystals and stabilize the precipitated crystal phase. The Li2O content is more preferably 10.0% or more, even more preferably 11.0% or more, even more preferably 12.0% or more, and particularly preferably 13.0% or more. Furthermore, when the Li2O content is 26.0% or less, glass stability is maintained. The Li2O content is more preferably 24.0% or less, even more preferably 23.0% or less, even more preferably 22.0% or less, particularly preferably 21.0% or less, and even more preferably 20.0% or less.

[0033] Na2O is a component that reduces the viscosity of glass and improves meltability, but adding too much of it will excessively disrupt the silica network structure, reducing glass stability. It is also a component that contributes to reducing dielectric loss when added in combination with Li2O or K2O. In refractive index-changing glass, it is a component that forms and precipitates NaF crystals. In the photosensitive glass of this embodiment, the Na2O content is preferably 1.0 to 10.0%. The inclusion of Na2O in the photosensitive glass of this embodiment improves glass meltability, and in the presence of fluorine:F, NaF crystals are easily obtained, stabilizing the precipitated crystalline phase. The Na2O content is more preferably 2.0% or more, even more preferably 3.0% or more, even more preferably 4.0% or more, and particularly preferably 5.0% or more. Furthermore, if the Na2O content is 10.0% or less, glass stability is maintained and deterioration due to weathering can be suppressed. The Na2O content is more preferably 9.0% or less, even more preferably 8.0% or less, and even more preferably 7.0% or less.

[0034] K2O is a component that reduces the viscosity of glass and improves meltability, but adding too much of it excessively disrupts the silica network structure, reducing glass stability. It is also a component that contributes to reducing dielectric loss when added in combination with Li2O or Na2O. It is also a component that facilitates the precipitation of Li2SiO3 crystals in microfabrication-type photosensitive glass. In the photosensitive glass of this embodiment, the K2O content is preferably 1.0 to 10.0%. When the photosensitive glass of this embodiment contains 1.0% or more of K2O, the glass meltability is improved. The K2O content is more preferably 2.0% or more, even more preferably 3.0% or more, and even more preferably 4.0% or more. Furthermore, if the K2O content is 10.0% or less, glass stability is maintained and deterioration due to weathering can be suppressed. The K2O content is more preferably 9.0% or less, even more preferably 8.0% or less, and even more preferably 7.0% or less.

[0035] Al2O3 is a component that is effective in improving acid resistance, improving Young's modulus, suppressing phase separation of glass, and reducing the thermal expansion coefficient. In the photosensitive glass of this embodiment, the Al2O3 content is preferably 0 to 5.0%. The inclusion of Al2O3 increases the stability of the glass and suppresses deterioration due to weathering. The Al2O3 content is preferably 0% or more, more preferably 0.5% or more, and even more preferably 1.0% or more. Furthermore, the Al2O3 content is preferably 5.0% or less. If the Al2O3 content is 5.0% or less, crystal precipitation from the glass can be maintained. The Al2O3 content is more preferably 4.5% or less, even more preferably 4.0% or less, and even more preferably 3.5% or less.

[0036] ZnO is a component that increases the solubility of Ag2O. ZnO can also exhibit effects such as improving chemical durability and suppressing undesired reduction of silver. In the photosensitive glass of this embodiment, the ZnO content is preferably 0 to 6.0%. By including ZnO in the photosensitive glass of this embodiment, it is possible to dissolve enough silver to exhibit sufficient photosensitivity for selective crystal precipitation. The ZnO content is preferably 0% or more, more preferably 0.2% or more, particularly preferably 0.4% or more, even more preferably 0.6% or more, and most preferably 0.8% or more. Furthermore, if the ZnO content is 6.0% or less, a decrease in the crystallization tendency can be suppressed. The ZnO content is more preferably 5.5% or less, even more preferably 5.0% or less, even more preferably 4.5% or less, particularly preferably 4.0% or less, even more preferably 3.5% or less, and most preferably 3.0% or less.

[0037] B2O3 is a component that is effective in improving acid resistance and reducing the thermal expansion coefficient. In the photosensitive glass of this embodiment, the B2O3 content is preferably 0 to 8.0%. The inclusion of B2O3 in the photosensitive glass of this embodiment increases the stability of the glass and suppresses deterioration due to weathering. In micro-fabrication glass, B2O3 has the effect of suppressing etching of the glass and thereby improving the pattern shape accuracy due to etching. The B2O3 content is preferably 0% or more, more preferably 0.1% or more, even more preferably 0.2% or more, particularly preferably 0.3% or more, even more preferably 0.4% or more, and most preferably 0.5% or more. Furthermore, the B2O3 content is preferably 8.0% or less. If the B2O3 content is 8.0% or less, variations in crystal precipitation characteristics due to phase separation can be suppressed. The B2O3 content is more preferably 7.0% or less, even more preferably 6.5% or less, and even more preferably 6.0% or less.

[0038] The photosensitive glass of this embodiment may contain SnO2. Like Sb2O3, SnO2 is a thermally reducing component, and reduces metal ions during heat treatment. In this embodiment, Ag + It plays a role in reducing ions. The coexistence of Sb2O3 further enhances the thermal reduction effect. The photosensitive glass of this embodiment contains SnO2, which promotes the generation of Ag colloids by heat treatment after exposure. Furthermore, if the SnO2 content is 1.0% or less, the reducing effect of metal ions will not be excessive, and there will be no risk of impairing the function of the photosensitive glass, such as making it difficult for Ag colloids to form during dissolution. The SnO2 content is more preferably 0.8% or less, even more preferably 0.6% or less, particularly preferably 0.4% or less, even more preferably 0.3% or less, most preferably 0.2% or less, and most preferably 0.1% or less.

[0039] The photosensitive glass according to this embodiment preferably contains 0.01 to 1.0% of Ag2O. Ag2O is a photosensitizer component that serves as the starting point for crystal growth, i.e., the nucleus source, for selectively crystallizing the exposed portions. When the photosensitive glass of this embodiment contains 0.01% or more of Ag2O, the exposed portions can be selectively crystallized. The Ag2O content is more preferably 0.015% or more, even more preferably 0.02% or more, even more preferably 0.022% or more, particularly preferably 0.025% or more, even more preferably 0.027% or more, and most preferably 0.028% or more. Furthermore, in the photosensitive glass according to this embodiment, the Ag2O content is preferably 1.0% or less. By setting the Ag2O content to 1.0% or less, it is possible to prevent Ag2O from remaining undissolved in the glass. Furthermore, it is possible to reduce the burden on the melting equipment. The Ag2O content is more preferably 0.9% or less, even more preferably 0.8% or less, even more preferably 0.7% or less, even more preferably 0.6% or less, particularly preferably 0.5% or less, even more preferably 0.4% or less, even more preferably 0.35% or less, and most preferably 0.3% or less.

[0040] The photosensitive glass of this embodiment preferably contains substantially no Cr, Ni, V, Mn, or Co. That is, the contents of Cr, Ni, V, Mn, and Co may be 5 ppm or less. This is because Cr, Ni, V, Mn, and Co are coloring components, and they can cause problems, particularly in variable refractive index glass, by deteriorating transmittance. Furthermore, Cr, V, Mn, and Co are coloring components that absorb UV light, and can cause problems in generating Ag colloids.

[0041] The photosensitive glass of this embodiment may contain components other than those described above (hereinafter referred to as "other components") to the extent that the effects of the present invention are not impaired. Examples of other components include Rb2O, Cs2O, MgO, CaO, SrO, BaO, P2O5, GeO2, Sc2O3, Y2O3, La2O3, Pr2O3, Nd2O3, Pm2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, TiO2, Fe2O3, ZrO2, Nb2O5, MoO3, HfO2, Ta2O3, and WO3. The total content of these components is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, even more preferably 2% or less, particularly preferably 1% or less, even more preferably 0.5% or less, and most preferably 0.1% or less.

[0042] The photosensitive glass of this embodiment preferably contains an ultraviolet absorbing component. This is because the photosensitive glass of this embodiment contains an ultraviolet absorbing component, which inhibits ultraviolet absorption by Ce, thereby suppressing colloid generation. Examples of ultraviolet absorbing components include Fe2O3 and TiO2. The photosensitive glass of this embodiment preferably contains 0.001% by mass or more of an ultraviolet absorbing component, more preferably 0.002% by mass or more, and even more preferably 0.003% by mass or more. From the viewpoint of maintaining the photosensitivity of the photosensitive glass, the content is preferably 0.05% by mass or less, more preferably 0.04% by mass or less, even more preferably 0.03% by mass or less, and particularly preferably 0.02% by mass or less.

[0043] <Method for manufacturing photosensitive glass> The method for producing the photosensitive glass of this embodiment will be exemplified below. The method for producing the photosensitive glass of this embodiment may include heating a glass raw material containing a photosensitizer component to obtain molten glass (melting step), molding the molten glass into a desired shape (molding step), and slowly cooling the molded glass (annealing step). Each step will be described below.

[0044] The melting step is a step of heating a glass raw material containing a photosensitizer component to obtain molten glass. The photosensitizer component is a component capable of forming nuclei that serve as starting points for crystal growth, thereby selectively crystallizing exposed areas. Examples of the photosensitizer component include the aforementioned Ag2O and Au2O. Ag2O is preferred because it does not absorb light in the visible region, is easily dissolved in glass, and has lower raw material costs than Au2O.

[0045] Examples of glass raw materials include a homogeneous mixture of metal oxides, carbonates, sulfates, nitrates, glass cullet, etc., in the form of powder or granules of an appropriate particle size. Glass cullet is glass waste generated during glass manufacturing processes, etc.

[0046] The method for heating the glass raw materials is not particularly limited, but for example, a method in which the glass raw materials are placed in a platinum crucible and the platinum crucible is placed in an electric furnace to heat and melt them can be mentioned. The melting temperature may be any temperature that can melt the glass raw materials used, and may be, for example, 1400 to 1600° C., preferably 1450 to 1550° C. The melting time may be, for example, 1 to 120 hours, preferably 2 to 100 hours, depending on the melting scale (weight).

[0047] The molding step is a step of molding the molten glass obtained in the melting step into a desired shape. The glass can be molded, for example, by pouring the molten glass into a preheated mold and solidifying it into a desired shape. In this case, the glass can be molded into a plate, a tube, or the like by a down-draw method, a press method, or the like, or into a block, a column, or the like by billet molding, or into other desired shapes depending on the intended use using a molding die.

[0048] The slow cooling step is a step of slowly cooling the glass formed in the forming step to room temperature. In this embodiment, the slow cooling step is preferably performed so that the cooling rate from temperature T1 to temperature T2 is 1° C. / min or less, where T1 is the annealing point (Ap) and T2 is the strain point (Sp).

[0049] By performing slow cooling from temperature T1 to temperature T2 at a cooling rate of 1°C / min or less, thermal strain inside the glass can be eliminated and variations in crystal precipitation can be suppressed. The cooling rate from temperature T1 to temperature T2 is more preferably 0.9°C / min or less, even more preferably 0.7°C / min or less, and particularly preferably 0.5°C / min or less. From the viewpoint of suppressing glass devitrification during slow cooling, the cooling rate from temperature T1 to temperature T2 is preferably faster than 0.1°C / min, more preferably 0.15°C / min or higher, and even more preferably 0.2°C / min or higher.

[0050] In the manufacturing method of this embodiment, even when the temperature T1 is changed from the annealing point (Ap), it is preferable that the cooling rate from the temperature T1 to the temperature T2 satisfy the above range. In this case, the range of change of the temperature T1 may be from the annealing point (Ap) + 30°C to the annealing point (Ap) - 10°C. If the temperature is raised too high, the glass may crystallize. In the manufacturing method of this embodiment, even when the temperature T2 is changed from the strain point (Sp), it is preferable that the cooling rate from the temperature T1 to the temperature T2 satisfy the above range. In this case, the range in which the temperature T2 is changed may be any range lower than the strain point (Sp).

[0051] <Application> The photosensitive glass according to this embodiment can form a highly accurate pattern when exposed to light and heat treated, making it suitable for use in optical elements and substrates for microfabrication. Examples of optical elements include volume holographic diffraction gratings, and examples of substrates for microfabrication include circuit boards for high-frequency applications and substrates for microfluidic devices.

[0052] In particular, the refractive index-changing glass according to a specific embodiment of the photosensitive glass of this embodiment can periodically change the refractive index of exposed and unexposed areas by two-beam interference exposure, and is particularly suitable for use as a volume holographic diffraction grating.

[0053] Furthermore, in the microfabricated glass according to another specific aspect of the photosensitive glass of this embodiment, a micropattern such as a glass through-hole (TGV) or a cavity can be formed by drawing a micropattern all at once using mask exposure and then etching after crystal precipitation. Therefore, the microfabricated glass can be suitably used particularly for circuit boards for high-frequency applications and substrates for microfluidic devices.

[0054] As described above, the present specification discloses the following configurations. 1. Photosensitive glass, in which the photosensitive glass is irradiated with ultraviolet light having a wavelength of 300 to 330 nm and heat-treated at the glass transition temperature Tg +20 to +65°C to generate colloids, and the horizontal axis represents the ultraviolet light exposure (J / cm 2 ) and the vertical axis is the colloid absorbance (mm -1 ), the ultraviolet exposure dose is 0 J / cm 2 , 1 J / cm 2 , and 2 J / cm 2 When the absorbance of the colloid is plotted at 1 to 2 J / cm 2 (slope at 0-1 J / cm) / (UV exposure dose 0-1 J / cm 2 A photosensitive glass having a slope (slope at θ) of greater than 1.0. 2. The ultraviolet light exposure dose is 0 to 1 J / cm 2 2. The photosensitive glass according to 1 above, wherein the slope in the graph is 0.001 to 1.0. 3. The photosensitive glass according to 1 or 2 above, wherein the ratio of the contents of Sb2O3 and CeO2 expressed as mole percentages on an oxide basis: Sb2O3 / CeO2 is 3.0 to 20. 4. The photosensitive glass according to any one of 1 to 3 above, which contains 0.01 to 0.3% of Sb2O3 expressed as a mole percentage based on oxides. 5. The photosensitive glass according to any one of 1 to 4 above, containing 0.002 to 0.04% CeO2 in mole percentage on an oxide basis. 6. The photosensitive glass according to any one of the above 1 to 5, which contains B2O3. 7. The photosensitive glass according to any one of 1 to 5 above, containing, expressed in mole percentages on an oxide basis, 59.0 to 81.0% SiO2, 8.0 to 26.0% Li2O, 1.0 to 10.0% Na2O, 1.0 to 10.0% K2O, 0 to 5.0% Al2O3, 0 to 6.0% ZnO, and 0 to 8.0% B2O3. 8. The photosensitive glass according to any one of 1 to 7 above, which contains 0.01 to 1.0% Ag2O in terms of mole percentage based on oxides. 9. The photosensitive glass according to any one of the above 1 to 8, which contains an ultraviolet absorbing component. [Example]

[0055] Examples will be described below, but the present invention is not limited to these Examples 1, 3 to 7, 15, and 20 to 23 are Examples, and Examples 2, 8 to 14, and 16 to 19 are Comparative Examples.

[0056] <Preparation of photosensitive glass> (Examples 1 to 23) The raw materials, such as SiO2, Al(OH)3, Na2CO3, NaF, NaBr, K2CO3, ZnO, CeO2, SnO, Sb2O3, and Ag-containing glass cullet, were placed in a platinum crucible and heated to 1300-1550°C for 24 hours while stirring to melt them. The uniformly melted glass was poured into a cast iron mold, formed into a plate, and slowly cooled to obtain the photosensitive glass for each example. The content of each component in the photosensitive glass of each example is shown in Table 1 (mol %) and Table 2 (mass %).

[0057] <Exposure, heat treatment> For each photosensitive glass, a mask aligner (Nanotech: ES20ag) was used to expose the glass to ultraviolet light with a wavelength of 300 to 330 nm at a dose of 0.5 J / cm. 2 , 1 J / cm 2 , 2J / cm 2, and 4 J / cm 2 The UV irradiance was measured using an ultraviolet integrating actinometer (Ushio Inc.: UIT-250) and a photodetector (Ushio Inc.: UVD-S313). Thereafter, heat treatment was carried out at the heat treatment temperature and for the time shown in Table 1 using a heat treatment furnace (UTO-15CD manufactured by KOYO THERMO SYSTEMS).

[0058] <Absorbance measurement> Each of the above UV exposure doses (J / cm 2 The absorbance (mm -1 ) was measured using a spectrophotometer (JASCO Corporation: V-770). Specifically, the maximum absorbance in the absorption band (400-500 nm) of the silver colloid formed in the glass was calculated using the spectrophotometer in 1 mm equivalent. In addition, the photosensitive glass that had not been exposed to light or heat treated (ultraviolet light exposure amount 0 J / cm 2 ) was also measured for absorbance in the same manner. Next, the UV exposure is 0 J / cm 2 , 0.5J / cm 2 , 1 J / cm 2 , 2J / cm 2 , and 4 J / cm 2 The absorbance of the colloid at 1000 nm is plotted on the horizontal axis, and the ultraviolet exposure dose (J / cm 2 ) and the vertical axis is the colloid absorbance (mm -1 ) and plotted on a coordinate system. From the above plot, the UV exposure dose is 1 to 2 J / cm 2 Slope at UV exposure 1 J / cm 2 Plot of colloid absorbance at 2 J / cm2 vs. UV exposure 2 The slope of the line drawn when the plots of colloids at different times are connected by a straight line) and the UV exposure dose of 0-1 J / cm 2 Slope at UV exposure 0 J / cm 2 Plot of colloid absorbance at 1 J / cm and UV exposure 2The slope of the line drawn when the absorbance of the colloid at each point was plotted was determined, and the following indexes were calculated for each example. The results are shown in Table 1. (UV exposure 1-2J / cm 2 (slope at 0-1 J / cm) / (UV exposure dose 0-1 J / cm 2 (slope at The ultraviolet exposure dose is 1-2 J / cm 2 The slope at "(Abs2-Abs1) / (2J / cm 2 -1 J / cm 2 ) and "ultraviolet light exposure 0-1J / cm 2 The slope at "(Abs1-Abs0) / (1J / cm 2 -0J / cm 2 )" In the above formula, "Abs2" is the ultraviolet exposure dose of 2 J / cm 2 "Abs1" means the absorbance of the colloid when the UV exposure is 1 J / cm 2 "Abs0" means the absorbance of the colloid when the UV exposure is 0 J / cm 2 This means the absorbance of the colloid when In Figure 2, the horizontal axis shows the amount of ultraviolet light exposure (J / cm ) for Examples 1 and 2. 2 ) and the vertical axis is the colloid absorbance (mm -1 ) is plotted on the coordinate system. FIG. 4 shows plots of Examples 1 to 23 on a coordinate system with Sb2O3 / CeO2 on the horizontal axis and this index on the vertical axis.

[0059] <Glass transition temperature Tg (℃)> The Tg of each photosensitive glass example was determined according to JIS R3103-3 (2001) using a Thermoplus EVO2TMA8311 manufactured by RIGAKU Corp. The results are shown in Table 1.

[0060] [Table 1]

[0061] [Table 2]

[0062] <Patterning performance test> (Test Examples 1 to 5) The photosensitive glasses of Examples 1 to 4 were closely fitted with a mask (2.3 mm thick, consisting of a quartz substrate with a Cr film light-shielding layer formed on one side) containing 100 equally spaced holes (10 columns x 10 rows = 100 holes), each with a diameter of 100 μm. The mask was then exposed to UV light with a wavelength of 300 to 330 nm using a mask aligner (Nanotec Corporation: ES20ag) so that the exposure dose was as shown in Table 3. The UV irradiance was measured using an ultraviolet integrating actinometer (Ushio Inc.: UIT-250) and a photodetector (Ushio Inc.: UVD-S313). The glass was then heat-treated at 535 to 600°C for 3 to 15 hours in a heat treatment furnace (Koyo Thermo Systems: UTO-15CD) to perform patterning. The crystals precipitated in the photosensitive glass were measured on the front side (exposed surface) and the back side (opposite side to the exposed surface) using a laser microscope (Keyence: VK-X3000). Of the 100 patterns (10 columns x 10 rows), the crystal precipitate diameters of 9 crystals (3 columns x 3 rows) were measured. The average crystal precipitate diameters of the 9 crystals measured are shown in Table 3 below. Furthermore, FIG. 3 shows a micrograph of the photosensitive glass surface after etching the glasses of Examples 1 and 2 after crystal precipitation.

[0063] [Table 3]

[0064] As shown in Table 3, in Examples 1, 3, and 4 of the embodiment, in Test Examples 1, 4, and 5 of the patterning performance test, the difference in crystal precipitation diameter between the crystals formed on the front and back sides of the photosensitive glass was small. Also, as shown in Figure 3, almost no pits were formed on the photosensitive glass surface after patterning. From this, it was found that the photosensitive glass of the embodiment, in which this index exceeds 1.0, can suppress crystal precipitation due to diffracted light and stray light during exposure, and can be patterned with high precision. Furthermore, as shown in Table 1 and Figure 4, it was found that the photosensitive glasses of the examples in which this index exceeds 1.0 have an Sb2O3 / CeO2 ratio, expressed as mole percentage based on oxides, in the range of 3.0 to 20. This suggests that when the Sb2O3 / CeO2 ratio is 3.0 or more, the Sb2O3 content relative to CeO2 is sufficiently high, making it difficult to react with low exposure light, and that when the Sb2O3 / CeO2 ratio is 20 or less, the content of Ce, the electron donor, is not too low, making it difficult to form colloids after exposure and heat treatment, and that the Sb2O3 content relative to CeO2 is not too high, making it sufficiently photosensitive to high exposure doses. On the other hand, in Comparative Example 2, in Test Examples 2 and 3 of the patterning performance test, the difference in crystal precipitation diameter between the crystals formed on the front and back sides of the photosensitive glass was large, as shown in Table 3. Furthermore, as shown in Figure 3, numerous pits were formed on the surface of the photosensitive glass after patterning. From this, it was found that the photosensitive glass of the Comparative Example, in which this index is 1.0 or less, was unable to sufficiently suppress crystal precipitation due to diffracted light and stray light during exposure, making it difficult to process patterns with high precision.

[0065] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-031547) filed on March 1, 2024, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0066] 1. Photosensitive glass 2. Mask 3 light 4 hole 5 Diffracted light 6 Stray light

Claims

1. The photosensitive glass is irradiated with ultraviolet light having a wavelength of 300 to 330 nm, and heat treatment to generate colloids is performed at the glass transition temperature (Tg) +20 to +65°C. The horizontal axis represents the ultraviolet light exposure (J / cm ２ ) and the vertical axis is the colloid absorbance (mm －１ ) on the coordinate system, the ultraviolet exposure amount is 0 J / cm ２ , 1 J / cm ２ , and 2 J / cm ２ When the absorbance of the colloid is plotted at 1 to 2 J / cm ２ (slope at 0-1 J / cm) / (ultraviolet light exposure amount 0-1 J / cm ２ The photosensitive glass has a slope at .gamma.

2. The ultraviolet light exposure dose is 0 to 1 J / cm ２ 2. The photosensitive glass according to claim 1, wherein the slope of the graph is 0.001 to 1.

0.

3. Sb in mole percentage on an oxide basis ２ O ３ and CeO ２ Ratio of the content of: Sb ２ O ３ / CeO ２ 3. The photosensitive glass according to claim 1, wherein the refractive index is 3.0 to 20.

4. Sb in mole percentage based on oxide ２ O ３ 3. The photosensitive glass according to claim 1, wherein the content is 0.01 to 0.3%.

5. CeO in mole percentage based on oxide ２ 3. The photosensitive glass according to claim 1, containing 0.002 to 0.04% of

6. B ２ O ３ The photosensitive glass according to claim 1 or 2, comprising:

7. In terms of mole percentage based on oxide, SiO ２ 59.0 to 81.0%, Li ２ 8.0-26.0% O, Na ２ O 1.0 to 10.0%, K ２ 1.0 to 10.0% O, Al ２ O ３ 0 to 5.0%, ZnO 0 to 6.0%, and B ２ O ３ 3. The photosensitive glass according to claim 1, containing 0 to 8.0% of

8. Ag in mole percentage based on oxide ２ 3. The photosensitive glass according to claim 1, containing 0.01 to 1.0% O.

9. 3. The photosensitive glass according to claim 1, further comprising an ultraviolet absorbing component.

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