Photosensitive glass

Abstract

The present invention relates to photosensitive glass in which Li2SiO3 crystals precipitate as a result of light exposure and heat treatment, wherein the value of expression (A): [Li2O] / ([Li2O]+[Na2O]+[K2O]) is 0.50 to 0.75, and the dielectric loss tangent at 20°C and 10 GHz is 0.0090 or less.

Description

[Technical Field]

[0001] The present invention relates to photosensitive glass, and in particular to photosensitive glass that has good dielectric properties in high frequency bands such as the 5G region, and that can be microfabricated by crystallization and etching through exposure and heat treatment. [Background technology]

[0002] In recent years, wireless transmission using high-frequency bands such as microwave and millimeter-wave bands has attracted attention as a large-capacity transmission technology. However, it is known that the dielectric loss during wireless transmission is proportional to the frequency and the dielectric loss tangent of the dielectric substrate. Therefore, as the signal frequency increases with the expansion of the frequency range used, there is a demand for dielectric substrates with a particularly low dielectric loss tangent in the high-frequency band.

[0003] On the other hand, when considering the creation of devices using high-frequency components, the substrates used also require high dimensional accuracy and precise structural control. There are various reasons for this, including issues with the packaging process for each component and the need to miniaturize modules. Therefore, the material itself also needs to be able to be micro-processed.

[0004] Conventionally, materials used for dielectric substrates include quartz, ceramics, and glass. However, although these materials have relatively good dielectric properties, many of them are not suitable for micromachining.

[0005] Among glasses, photosensitive glass is known as glass that is extremely suitable for microfabrication. Photosensitive glass can be microfabricated using a very simple processing process, and is disclosed in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2008 / 0248250 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional photosensitive glass had not been considered for use as a material for high-frequency components, and so its dielectric properties were not taken into consideration, resulting in a relatively high dielectric loss tangent. As a result, although conventional photosensitive glass is excellent in microfabrication, it has the problem of large dielectric loss when used in high-frequency bands.

[0008] SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a photosensitive glass that improves the dielectric properties of the glass itself while not impairing its microfabrication properties. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved by the following configuration. [1] A photosensitive glass in which Li2SiO3 crystals precipitate upon exposure to light and heat treatment, The value of the following formula (A) is 0.50 or more and 0.75 or less, Photosensitive glass having a dielectric loss tangent of 0.0090 or less at 20°C and 10 GHz. [Li2O] / ([Li2O]+[Na2O]+[K2O]) Formula (A) (In formula (A), [LiO], [NaO], and [KO] respectively represent the contents of LiO, NaO, and KO in the photosensitive glass expressed as mole percentages based on oxides.) [2] In terms of mass percentage based on oxide, it contains 65-78% SiO2. The photosensitive glass according to the above item [1], wherein when a glass sample having a length of 30 mm, a width of 20 mm, and a thickness of 0.5 mm is immersed for 4 minutes in 55 ml of an etching solution containing 5 mass % of HF and 0.7 mass % of HNO3 at 40°C, the glass portion etching rate calculated by the following formula (1) is 2.75 or less.

[0010]

number

[0011] [3] Mass percentage based on oxides, Al2O3: 0-5% (excluding 5%) Li2O: 5-15% Na2O: 3-12% K2O: 3-12% ZnO: 0.3 to 8% Sb2O3: 0.01 to 1% (excluding 1%) CeO2: 0.001-0.1% Ag2O: 0.05~1% The photosensitive glass according to the above [1] or [2], which contains: [4] Mass percentage based on oxides Al2O3: 0-5% (excluding 5%) Li2O: 5-15% Na2O: 3-12% K2O: 3-12% ZnO: 0 to 8% Sb2O3: 0.01 to 1% (excluding 1%) CeO2: 0.001-0.1% Ag2O: 0.05~1% The photosensitive glass according to the above [1] or [2], which contains: [5] The photosensitive glass according to any one of the above [1] to [4], containing 0 to 8% B2O3 in terms of mass percentage based on oxides. [6] The photosensitive glass according to any one of the above [1] to [5], which has a relative dielectric constant of 7.5 or less at 20° C. and 10 GHz. [7] A glass in which Li2SiO3 crystals are precipitated by exposing and heat-treating the photosensitive glass according to any one of the above [1] to [6]. [8] Glass having a microstructure formed by subjecting the photosensitive glass according to any one of the above [1] to [6] to exposure, heat treatment and etching. [9] A circuit board comprising an insulating substrate containing the glass described in [8] above.

[10] The circuit board according to [9] above, for use in a high-frequency device.

[11] The circuit board according to

[10] above, comprising a transmission line.

[12] The circuit board according to

[11] above, wherein the transmission line is a waveguide, a substrate integrated waveguide (SIW), or a microstrip line.

[13] The circuit board according to

[11] above, having a function of a passive device.

[14] A high-frequency device comprising the circuit board according to any one of [9] to

[13] above.

[15] A step of exposing the photosensitive glass according to any one of the above [1] to [6] to light. a step of heat-treating the exposed photosensitive glass to precipitate Li2SiO3 crystals; a step of removing the precipitated Li2SiO3 crystals by etching; A method for producing a microstructured glass, comprising:

[16] The heat treatment includes holding in a first temperature range and holding in a second temperature range; the first temperature range is 400°C or higher and 500°C or lower, and the holding time in the first temperature range is 15 minutes or longer; The manufacturing method according to

[15] above, wherein the second temperature range is 500°C or higher and 700°C or lower, and the holding time in the second temperature range is 15 minutes or longer.

[17] The manufacturing method described in

[15] above, wherein the heat treatment includes holding in a first temperature range and holding in a second temperature range, the first temperature range being 400°C or higher and 600°C or lower, and the holding time in the first temperature range being 1 minute or longer, and the second temperature range being the first temperature range +5°C or higher and +300°C or lower, and the holding time in the second temperature range being 1 minute or longer.

[18] Exposure 0.5J / cm 2 The photosensitive glass according to any one of the above [1] to [6], which has a transmittance (1 mmt equivalent) of 4% or more at 430 nm when exposed to light at 485° C. and then heat-treated at 485° C. for 5 hours.

[19] Exposure amount 1~10J / cm 2The transmittance at 430 nm (1 mm equivalent value) was measured when the sample was exposed to light at 485°C for 5 hours and then heat-treated at 485°C. The exposure dose was plotted on the horizontal axis (J / cm 2 ) and plotted on a coordinate plane with the transmittance (%) on the vertical axis, the exposure dose of 1 to 10 J / cm is calculated by the following formula (4): 2 The photosensitive glass according to any one of the above [1] to [6], wherein the slope of the transmittance (converted to 1 mmt) at 430 nm with respect to the wavelength is −0.12 or less.

[0012]

number

[0013] According to the present invention, there are provided a photosensitive glass that has small dielectric loss in the high frequency band and excellent micromachinability, a method for producing the same, and a circuit board and a high frequency device that include the photosensitive glass. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a circuit board according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of a waveguide. [Figure 3] FIG. 3 is a diagram showing a schematic diagram of temperature changes in a two-stage heat treatment performed on the photosensitive glass of the example. [Figure 4] FIG. 4 is a graph showing the results of measuring the transmittance of the glass A of the example. [Figure 5] FIG. 5 is a graph showing the measurement results of the transmittance of Glass B of the example. [Figure 6] FIG. 6 is a graph showing the results of measuring the transmittance of the glass C of the example. [Figure 7] FIG. 7 is a graph plotting the relationship between the exposure dose and the transmittance at 430 nm for Glasses A to C of the examples. [Figure 8]FIG. 8 is a graph plotting the relationship between the relative dielectric constant and transmission loss in the photosensitive glass of the example. [Figure 9] FIG. 9 is a graph plotting the relationship between the dielectric loss tangent and the transmission loss in the photosensitive glass of the example. [Figure 10] FIG. 10 is a graph showing the transmittance when glass X is exposed to light and heat treated under condition 1. [Figure 11] FIG. 11 is a graph showing the transmittance when glass X is subjected to exposure and heat treatment under condition 2. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] In this specification, unless otherwise specified, glass compositions are expressed in terms of mass percentage based on oxides, and mass % is simply expressed as "%." In formula (A), [LiO], [NaO], and [KO] are expressed in terms of mole percentage based on oxides.

[0017] In this specification, "high frequency" means a frequency of 1 GHz or higher, preferably 5 GHz or higher, more preferably 10 GHz or higher, even more preferably 20 GHz or higher, particularly preferably 28 GHz or higher, and most preferably 35 GHz or higher. Also, for example, it is 100 GHz or lower.

[0018] In this specification, "photosensitive glass" refers to glass that can be microfabricated by a combination of exposure to light, crystallization by heat treatment, and etching. In particular, the photosensitive glass of the present invention is characterized in that Li2SiO3 crystals are precipitated by exposure to light and heat treatment, and then removed by etching.

[0019] More specifically, "photosensitive glass" undergoes a chemical reaction upon exposure to light, and the Ag contained in the photosensitive glass +The ions become metal atoms by receiving electrons. The photosensitive glass is then heat-treated to generate silver colloids, and by further increasing the temperature and heat treatment, Li2SiO3 crystals are formed around the silver colloids and precipitate. Because the precipitated Li2SiO3 crystals have a very high solubility in HF, the exposed areas can be selectively removed by HF etching.

[0020] Since this glass undergoes a chemical reaction when exposed to light, the glass is called photosensitive glass.

[0021] The Li2SiO3 crystals can be identified by, for example, X-ray diffraction (XRD) measurement. Specifically, when XRD measurement is performed using CuKα radiation at 2θ=10 to 90°, if the strongest peak is confirmed in the range of 2θ=26.5 to 27.5°, the glass-ceramics contains Li2SiO3 crystals.

[0022] In this specification, the term "glass portion etching rate" refers to the etching rate of the glass portion (glass portion) that has not been exposed to light (etching rate of the unexposed portion).

[0023] In this specification, the "etching rate selectivity of exposed portion / unexposed portion" refers to the ratio of the etching rate of the exposed and crystallized portion (etching rate of exposed portion) divided by the etching rate of the unexposed glass portion (glass portion) (etching rate of unexposed portion). A higher etching rate selectivity of exposed portion / unexposed portion indicates that only the exposed portion can be selectively removed, and conversely, a lower etching rate selectivity of exposed portion / unexposed portion indicates that the unexposed glass portion is also more easily etched.

[0024] <Photosensitive glass> The photosensitive glass of one embodiment of the present invention is a photosensitive glass in which Li2SiO3 crystals precipitate upon exposure to light and heat treatment, characterized in that the value of the following formula (A) is 0.50 or more and 0.75 or less, and the dielectric loss tangent at 20°C and 10 GHz is 0.0090 or less: [Li2O] / ([Li2O]+[Na2O]+[K2O]) Formula (A) (In formula (A), [LiO], [NaO], and [KO] respectively represent the contents of LiO, NaO, and KO in the photosensitive glass expressed as mole percentages based on oxides.)

[0025] In the photosensitive glass of this embodiment, the above formula (A) is an index representing the degree of alkali metal atom mixing, and the smaller the value of formula (A), the more alkali metal atoms are mixed in. If the value of formula (A) is 0.75 or less, the dielectric loss tangent at 20°C and 10 GHz will be a good value.

[0026] The value of formula (A) is, in order of preference, 0.74 or less, 0.73 or less, 0.72 or less, 0.71 or less, 0.69 or less, 0.68 or less, 0.67 or less, 0.66 or less, 0.65 or less, 0.64 or less, 0.63 or less, 0.62 or less, 0.61 or less, and 0.60 or less.

[0027] On the other hand, if the value of formula (A) becomes too small, the proportion of Li2O in the glass decreases, making it difficult for Li2SiO3 crystals to precipitate. Furthermore, if the value of formula (A) becomes too small, the etching rate of the glass calculated by formula (1) described below increases, resulting in a problem of a deterioration in the etching rate selectivity ratio of the exposed area to the unexposed area. Therefore, the value of formula (A) is 0.50 or more, and is preferably 0.51 or more, 0.52 or more, 0.53 or more, 0.54 or more, 0.55 or more, and 0.56 or more.

[0028] Furthermore, as described above, the photosensitive glass of this embodiment contains multiple types of alkali metal atoms, and as a result of the alkali mixing effect, it has excellent dielectric properties in the high frequency range, with a dielectric loss tangent at 20°C and 10 GHz of 0.0090 or less, preferably 0.0089 or less, more preferably 0.0088 or less, even more preferably 0.0087 or less, even more preferably 0.0086 or less, and particularly preferably 0.0085 or less.

[0029] The dielectric loss tangent is measured by the split post dielectric resonance method (SPDR method).

[0030] (composition) The glass composition for realizing the photosensitive glass of this embodiment will be described below.

[0031] The composition of the photosensitive glass of one embodiment of the present invention is not particularly limited as long as it satisfies the above formula (A) and the range of the dielectric loss tangent, but for example, it preferably contains, expressed as mass percentages on an oxide basis, 65 to 78% SiO2, 5 to 15% Li2O, and 0.05 to 1% Ag2O. Here, SiO2 and Li2O are components that constitute Li2SiO3 crystals, and Ag2O is a component that forms the crystal nuclei.

[0032] Furthermore, the photosensitive glass of this embodiment preferably contains, expressed as mass percentages on an oxide basis, Al2O3: 0 to 5% (excluding 5%), Na2O: 3 to 12%, K2O: 3 to 12%, ZnO: 0.3 to 8%, Sb2O3: 0.01 to 1% (excluding 1%), and CeO2: 0.001 to 0.1%.

[0033] Furthermore, the photosensitive glass of this embodiment preferably contains, expressed as mass percentages based on oxides, Al2O3: 0 to 5% (excluding 5%), Na2O: 3 to 12%, K2O: 3 to 12%, ZnO: 0 to 8%, Sb2O3: 0.01 to 1% (excluding 1%), and CeO2: 0.001 to 0.1%.

[0034] Al2O3 is a component that is effective in improving acid resistance, Young's modulus, improving the phase separation characteristics of glass, and lowering the thermal expansion coefficient.

[0035] Na2O and K2O are components that, when mixed with Li2O, produce an alkali mixing effect and lower the dielectric loss tangent.

[0036] ZnO is a component that increases the solubility of Ag2O.

[0037] Sb2O3 is a thermally reducing component that reduces metal ions during heat treatment.

[0038] CeO2 is an optical sensitizer, a component that makes materials that are only sensitive to high-energy rays such as X-rays sensitive to ultraviolet rays as well.

[0039] Each component will be described in detail below.

[0040] SiO2 is a component for forming and precipitating Li2SiO3 crystals as a crystalline phase. In the photosensitive glass of this embodiment, the SiO2 content is preferably 65% ​​or more. When the SiO2 content is 65% or more, the precipitated crystalline phase of the crystallized glass is likely to be stable.

[0041] The SiO2 content is more preferably 67% or more, even more preferably 68% or more, even more preferably 69% or more, particularly preferably 69.5% or more, even more preferably 70% or more, and most preferably 70.5% or more.

[0042] Furthermore, in the photosensitive glass of this embodiment, the SiO2 content is preferably 78% or less. When the SiO2 content is 78% or less, the glass raw material is easily melted and formed. When the SiO2 content is too high, Li2Si2O5 crystals, which are a different type of crystal, tend to precipitate, which is undesirably difficult to remove by etching compared to Li2SiO3 crystals. Furthermore, the heat treatment conditions are also an important factor in precipitating Li2SiO3 crystals as a crystalline phase, and by keeping the SiO2 content below the above upper limit, a wider range of heat treatment conditions can be selected.

[0043] The SiO2 content is more preferably 76% or less, even more preferably 75% or less, even more preferably 74% or less, particularly preferably 73.5% or less, and most preferably 73% or less.

[0044] LiO is a component for forming and precipitating LiSiO crystals. In addition, the photosensitive glass of this embodiment can reduce the dielectric loss tangent at 10 GHz due to the alkali mixing effect achieved by mixing multiple types of alkali metal atoms, such as NaO and KO, in addition to LiO.

[0045] In addition, the photosensitive glass of this embodiment can reduce electrical conductivity due to the alkali mixing effect. For example, when wiring copper or the like on a glass substrate, insulation between the substrate and the wiring is important, and the reduction in electrical conductivity due to the alkali mixing effect can contribute to improving the insulation of the glass substrate.

[0046] Specifically, in the photosensitive glass of this embodiment, the content of Li2O, together with Na2O and K2O described below, is adjusted so that the value of the following formula (A) is 0.50 or more and 0.75 or less.

[0047] [Li2O] / ([Li2O]+[Na2O]+[K2O]) Formula (A) (In formula (A), [LiO], [NaO], and [KO] respectively represent the contents of LiO, NaO, and KO in the photosensitive glass expressed as mole percentages based on oxides.)

[0048] In the photosensitive glass of this embodiment, the Li2O content (expressed as a mass percentage based on oxides) is preferably 5% or more. When the Li2O content is 5% or more, the desired crystals are easily obtained and the precipitated crystal phase is easily stabilized.

[0049] The Li2O content is, in order of preference, 5.2% or more, 5.4% or more, 5.6% or more, 5.8% or more, 6.0% or more, 6.2% or more, 6.4% or more, 6.6% or more, 6.8% or more, and 7% or more.

[0050] On the other hand, if the Li2O content is too high, the alkali mixing effect will be reduced, so the Li2O content (expressed as a mass percentage based on the oxide) is preferably 15% or less. When the Li2O content is 15% or less, it is easy to obtain the desired crystals and the precipitated crystal phase is likely to be stable.

[0051] The LiO content is, in order of preference, 13% or less, 12% or less, 11.5% or less, 11% or less, 10.5% or less, 10% or less, 9.8% or less, 9.6% or less, 9.4% or less, 9.2% or less, 9.0% or less, 8.8% or less, 8.6% or less, 8.4% or less, 8.2% or less, and 8.0% or less.

[0052] In the photosensitive glass of this embodiment, the Na2O content (expressed as a mass percentage based on oxides) is preferably 3% or more. When Na2O is 3% or more, a good alkali mixing effect is obtained, and the dielectric loss tangent at 10 GHz can be reduced.

[0053] The Na2O content is more preferably 3.1% or more, even more preferably 3.2% or more, still more preferably 3.3% or more, particularly preferably 3.4% or more, even more preferably 3.5% or more, and most preferably 3.6% or more.

[0054] The Na2O content (mass percentage based on oxide) is preferably 12% or less. If the amount of Na2O is excessively large, there is a high possibility that Na will substitute for the Li site of the Li2SiO3 crystal. As a result, it is expected that the Li2SiO3 crystal will be less likely to precipitate.

[0055] The Na2O content is more preferably 11.8% or less, even more preferably 11.6% or less, even more preferably 11.4% or less, particularly preferably 11.2% or less, even more preferably 11% or less, and most preferably 10.8% or less.

[0056] In the photosensitive glass of this embodiment, the content of K2O (expressed as a mass percentage based on oxide) is preferably 3% or more. When K2O is 3% or more, a good alkali mixing effect is obtained, and the dielectric loss tangent at 20°C and 10 GHz can be reduced. Furthermore, the tendency for devitrification during glass production can be reduced.

[0057] The K2O content is more preferably 3.1% or more, even more preferably 3.2% or more, still more preferably 3.3% or more, particularly preferably 3.4% or more, even more preferably 3.5% or more, and most preferably 3.6% or more.

[0058] Furthermore, the K2O content (expressed as a mass percentage based on oxides) is preferably 12% or less. When the K2O content is 12% or less, an increase in the etching rate of the glass portion can be suppressed, and a decrease in the etching rate selectivity ratio between the exposed portion and the unexposed portion can be suppressed. As a result, selective HF etching becomes possible, and the desired fine processing can be achieved. Furthermore, if the amount of K2O is excessively large, there is a high possibility that K will substitute for the Li site of the Li2SiO3 crystal. As a result, it is expected that Li2SiO3 crystal will be less likely to precipitate.

[0059] The K2O content is more preferably 11.8% or less, even more preferably 11.6% or less, even more preferably 11.4% or less, particularly preferably 11.2% or less, even more preferably 11% or less, and most preferably 10.8% or less.

[0060] Al2O3 is a component that is effective in improving acid resistance, Young's modulus, improving the phase separation characteristics of glass, and reducing the thermal expansion coefficient, etc. When the photosensitive glass of this embodiment contains Al2O3, the Al2O3 content is more preferably 0.2% or more, even more preferably 0.4% or more, still more preferably 0.6% or more, particularly preferably 0.8% or more, even more preferably 1% or more, and most preferably 1.2% or more.

[0061] On the other hand, Al2O3 may deteriorate the dielectric loss tangent in the high frequency range. If the Al2O3 content is less than 5%, the dielectric loss tangent in the high frequency range can be further reduced. The Al2O3 content is preferably 4.5% or less, more preferably 4% or less, and even more preferably 3.5% or less.

[0062] The photosensitive glass of this embodiment contains a photosensitizer component. The photosensitizer component is a component that can generate nuclei that serve as starting points for crystal growth, in order to selectively crystallize exposed portions. In other words, the inclusion of the photosensitizer component makes it possible to selectively remove glass. Examples of the photosensitizer component include Ag + , Au + , Cu + Among these, Ag is the most popular because it has no absorption in the visible region, is easily dissolved in glass (high solubility), and has low raw material costs. + is preferred.

[0063] As mentioned above, Ag2O functions as a photosensitizer component. The inventors discovered that the higher the silver content in the glass, the lower the exposure sensitivity of silver colloid formation. At first glance, a higher exposure sensitivity seems preferable, but if the exposure sensitivity is too high, problems arise, such as silver colloid formation occurring in undesired areas due to exposure. In other words, it is necessary to lower the exposure sensitivity by including a certain amount of silver.

[0064] Ag2O is also a nucleating element for crystals. A relatively high amount of nucleating element in a glass results in a finer crystalline arrangement than a smaller number of finely distributed nuclei in the same glass volume. As a result, the crystals formed are smaller in size and etch faster at the grain boundaries.

[0065] When the Ag2O content is low, the size of the Li2SiO3 crystals tends to increase. As a result, it is expected that the surface condition after etching will be more rough. If the sample surface is rough, problems will arise in the packaging process when used as a substrate.

[0066] For the above reasons, the AgO content in the photosensitive glass of this embodiment is preferably 0.05% or more, and the AgO contents are, in order of preference, 0.055% or more, 0.06% or more, 0.065% or more, 0.07% or more, 0.075% or more, 0.08% or more, 0.085% or more, 0.09% or more, 0.095% or more, and 0.10% or more.

[0067] On the other hand, the Ag2O content is preferably 1% or less. A Ag2O content of 1% or less can prevent Ag2O from remaining undissolved in the glass. Furthermore, adding Ag2O at high concentrations can have a negative effect on melting equipment, and Ag2O itself is an expensive raw material, so it is not desirable to add too much Ag2O. Furthermore, the generation of silver colloid is not determined solely by the amount of Ag2O, but is also affected by other components, so simply increasing the amount of Ag2O is pointless.

[0068] The Ag2O content is, in order of preference, 0.90% or less, 0.80% or less, 0.70% or less, 0.60% or less, 0.55% or less, 0.50% or less, 0.45% or less, 0.40% or less, 0.35% or less, and 0.30% or less.

[0069] CeO2 is an optical sensitizer that makes glass that is only sensitive to high-energy rays such as X-rays sensitive to ultraviolet rays. In the photosensitive glass of this embodiment, CeO2 emits electrons upon receiving ultraviolet rays, and converts them into Ag + It plays a role in supplying ions.

[0070] In the photosensitive glass of this embodiment, the CeO2 content is preferably 0.001% or more. When the CeO2 content is 0.001% or more, Ag is stable against exposure to light. + The reduction effect of ions can be exerted.

[0071] The CeO2 content is more preferably 0.004% or more, even more preferably 0.006% or more, even more preferably 0.008% or more, particularly preferably 0.01% or more, even more preferably 0.012% or more, and most preferably 0.014% or more.

[0072] On the other hand, the CeO2 content is preferably 0.1% or less. If it is 0.1% or less, the sensitivity to light exposure will not be too high, and problems such as exposure to unnecessary areas can be avoided, making it possible to control fine processing.

[0073] The CeO2 content is more preferably 0.09% or less, even more preferably 0.085% or less, even more preferably 0.08% or less, even more preferably 0.075% or less, and most preferably 0.07% or less.

[0074] Sb2O3 is a thermally reducing component that reduces metal ions during heat treatment. In the photosensitive glass of this embodiment, Ag + It plays a role in reducing ions.

[0075] In the photosensitive glass of this embodiment, the Sb2O3 content is preferably 0.01% or more. When the Sb2O3 content is 0.01% or more, metal ion reduction can be stably carried out during heat treatment.

[0076] The Sb2O3 content is more preferably 0.05% or more, further preferably 0.07% or more, even more preferably 0.09% or more, particularly preferably 0.11% or more, even more preferably 0.13% or more, and most preferably 0.15% or more.

[0077] On the other hand, the rate at which glass changes color varies greatly depending on the Sb2O3 content, so if the concentration is too high, the glass will darken, which is undesirable. Furthermore, Sb2O3 is designated as a "Class 2 Controlled Substance" and a "Specially Controlled Substance" under the Specified Chemical Substances Hazard Prevention Regulations (Specified Chemical Substances Regulations), and according to Article 2-2 of the Specified Chemical Substances Hazard Prevention Regulations (Specified Chemical Substances Regulations), any substance with an Sb2O3 content of more than 1% is itself subject to regulation as a specified chemical substance. Therefore, it is preferable for the Sb2O3 content to be less than 1%.

[0078] The Sb2O3 content is more preferably 0.9% or less, even more preferably 0.85% or less, even more preferably 0.8% or less, even more preferably 0.75% or less, and most preferably 0.7% or less.

[0079] If the thermal expansion coefficient of the glass is to be increased, ZnO is not necessarily included. On the other hand, ZnO increases the solubility of Ag2O. ZnO may also exhibit effects such as improving chemical durability and suppressing undesired reduction of silver. Therefore, in the photosensitive glass of this embodiment, the ZnO content is, in descending order of preference, 0% or more, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.52% or more, 0.54% or more, 0.56% or more, 0.58% or more, 0.60% or more, 0.62% or more, 0.64% or more, 0.66% or more, 0.68% or more, and 0.7% or more.

[0080] On the other hand, if the ZnO content is too high, the crystallization tendency will be significantly lower than desired. Therefore, the ZnO content is preferably 8% or less. The ZnO content is more preferably 7.5% or less, even more preferably 7% or less, even more preferably 6.5% or less, particularly preferably 6% or less, even more preferably 5.5% or less, and most preferably 5% or less.

[0081] The photosensitive glass of this embodiment may also contain B2O3. B2O3 is a component that is effective in improving dielectric properties such as the relative permittivity and dielectric loss tangent in the high frequency range, and in improving solubility. It also acts as a nucleating agent.

[0082] When the photosensitive glass of this embodiment contains B2O3, the B2O3 content is more preferably 0.1% or more, even more preferably 0.2% or more, still more preferably 0.3% or more, particularly preferably 0.4% or more, and most preferably 0.5% or more.

[0083] On the other hand, a high B2O3 content can cause problems such as a deterioration in the chemical durability of the glass and difficulty in precipitating Li2SiO3 crystals, so the B2O3 content is preferably 8% or less, followed by 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, and 2% or less, in that order.

[0084] Other components may also be included to the extent that they do not impair performance, such as Rb2O, Cs2O, MgO, CaO, SrO, BaO, P2O5, GeO2, Sc2O3, Y2O3, La2O3, Pr2O3, Nd2O3, Pm2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, TiO2, V2O5, Cr2O3, MnO2, Fe2O3, CoO, NiO, ZrO2, Nb2O5, MoO3, HfO2, Ta2O3, and WO3.

[0085] The content of these is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, still more preferably 2% or less, particularly preferably 1% or less, even more preferably 0.5% or less, and most preferably 0.1% or less.

[0086] (Physical Properties) As described above, the photosensitive glass of this embodiment contains multiple alkali metal atoms, and as a result, the alkali mixing effect results in excellent dielectric properties in the high frequency range. Furthermore, by setting the Al2O3 content within a predetermined range, excellent dielectric properties in the high frequency range are achieved. In the photosensitive glass of this embodiment, if the dielectric loss tangent at 20°C and 10 GHz is within the above-mentioned preferred range, it is believed that the dielectric properties in the frequency range above 10 GHz will also be excellent.

[0087] As described above, the dielectric loss tangent of the photosensitive glass of this embodiment at 20°C and 10 GHz is 0.0090 or less from the viewpoint of improving the dielectric properties. It is preferably 0.0089 or less, more preferably 0.0088 or less, even more preferably 0.0087 or less, even more preferably 0.0086 or less, and particularly preferably 0.0085 or less. There is no particular lower limit, but for example, 0.0005 or more is preferred.

[0088] The photosensitive glass of this embodiment has a relative dielectric constant at 20°C and 10 GHz of preferably 7.5 or less, more preferably 7.4 or less, even more preferably 7.3 or less, still more preferably 7.2 or less, particularly preferably 7.1 or less, and most preferably 7.0 or less, from the viewpoint of improving dielectric properties. The lower limit is not particularly limited, but is preferably 3 or more, for example.

[0089] The dielectric loss tangent and relative dielectric constant are measured by the split post dielectric resonance method (SPDR method).

[0090] In the photosensitive glass of this embodiment, the glass portion etching rate is preferably 2.75 or less, more preferably 2.70 or less, even more preferably 2.65 or less, even more preferably 2.60 or less, even more preferably 2.55 or less, even more preferably 2.50 or less, particularly preferably 2.45 or less, and most preferably 2.40 or less, from the viewpoint of improving micro-processability. If the glass portion etching rate is too high, the glass portion will be cut more than necessary during etching, making it difficult to control micro-processability. The lower limit is not particularly limited, but for example, 0.1 or more is preferred.

[0091] The glass etching rate is calculated as follows: A glass sample measuring 30 mm long x 20 mm wide and 0.5 mm thick is immersed in 55 ml of an etching solution containing 5 mass % HF and 0.7 mass % HNO3 at 40°C for 4 minutes. The glass etching rate is calculated using the following formula (1):

[0092]

number

[0093] Furthermore, in the photosensitive glass of this embodiment, it is preferable that the etching rate selectivity ratio of exposed portion / unexposed portion, expressed by the following formula (2), is a larger value. The etching rate selectivity ratio of exposed portion / unexposed portion is calculated based on the following formula (2) by determining the etching rate when glass that has been exposed and heat-treated is etched (exposed portion etching rate) and the etching rate when glass that has not been exposed and heat-treated is etched (unexposed portion etching rate).

[0094] The etching rate of the unexposed portion (=glass portion) in the following formula (2) is synonymous with the etching rate of the glass portion described above. The method for calculating the etching rate of the exposed portion will be described later.

[0095]

number

[0096] The etching rate of the exposed area in the above formula (2) is calculated by subjecting a glass sample of 30 mm length x 20 mm width x 0.5 mm thickness to exposure treatment, heat treatment, and then etching, using the above formula (1). The specific treatment conditions are shown below.

[0097] (i) Exposure processing An exposure device (for example, manufactured by Dai Nippon Kaken Co., Ltd., product name "MA-1200") was used, and the exposure dose was 15 J / cm 2 The entire flat glass is exposed to light so that the

[0098] (ii) Heat treatment A two-stage heat treatment is carried out. The first stage heat treatment conditions are 485°C for 5 hours. The second stage heat treatment conditions can be determined by the following method. First, a crystallization peak is confirmed using a differential thermal analysis (DTA) device (e.g., Thermoplus TG8120 manufactured by Rigaku Corporation). Heat treatment is carried out for 1 to 3 hours at a temperature in the range of -50°C to 150°C from the temperature at which the crystallization peak is confirmed. At this time, heat treatment is carried out under the same conditions on glass of the same composition that has not been exposed to light, and the conditions under which it can be confirmed that no crystals are precipitated are determined as the heat treatment conditions.

[0099] The presence or absence of crystal precipitation can be confirmed, for example, by observation under a microscope. When observed under a microscope using epi-illumination, the area where crystals have precipitated will appear bright while the glass area will appear dark due to light scattering. The presence or absence of crystal precipitation can be confirmed by the difference in brightness.

[0100] (iii) Etching The glass sample is immersed in 55 ml of an etching solution containing 5 mass % of HF and 0.7 mass % of HNO3 at 40°C for 4 minutes. After the above process is performed, the value obtained by the above formula (1) is defined as the etching rate of the exposed portion.

[0101] If the etching rate selectivity ratio of the exposed portion to the unexposed portion (=glass portion) calculated from the etching rate of the exposed portion and the etching rate of the unexposed portion (=glass portion) obtained by the above method is 3 or more, it becomes easier to selectively remove only the exposed portion by etching, improving microfabrication properties.

[0102] The lower limit of the etching rate selectivity ratio of exposed portion / unexposed portion is, in order of preference, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, 19 or more, and 20 or more. The upper limit of the etching rate selectivity ratio of exposed portion / unexposed portion is not particularly limited, but is generally 50 or less, 45 or less, and particularly 40 or less.

[0103] In addition, the photosensitive glass of this embodiment has an exposure dose of 0.5 J / cm 2 It is preferable that the transmittance (1 mmt equivalent) at 430 nm when exposed to light at 400 K and heat-treated at 485°C for 5 hours is 4% or more. A high transmittance means that the amount of silver colloid generated in the glass is low and the exposure sensitivity is not too high. Therefore, a transmittance of 4% or more makes it easy to control the microstructure.

[0104] The lower limit of the transmittance is, in order of preference, 6% or more, 8% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, and 15% or more. The upper limit of the transmittance is not particularly limited, but is generally 98% or less, 97% or less, 96% or less, 95% or less, 94% or less, 93% or less, 92% or less, 91% or less, or 90% or less.

[0105] The exposure is performed using, for example, a light source unit for an exposure device, Multilight ML-251D / B (manufactured by Ushio Inc.) Specifically, a UV integrating actinometer UIT-250 and a photodetector UVH-S313 are combined to measure the UV intensity, calculate the time required for the desired exposure amount, and irradiate the UV light for that time using the exposure device.

[0106] The transmittance at 430 nm (1 mmt equivalent value) is calculated, for example, by using a spectrophotometer V-570 (manufactured by JASCO Corporation, measurement wavelength range: 200-800 nm) according to the following formula (3).

[0107]

number

[0108] In addition, the photosensitive glass of this embodiment has an exposure dose of 1 to 10 J / cm 2 The transmittance at 430 nm (1 mm equivalent value) was measured when the sample was exposed to light at 485°C for 5 hours and then heat-treated at 485°C. The exposure dose was plotted on the horizontal axis (J / cm 2 ) and plotted on a coordinate plane with the transmittance (%) on the vertical axis, the exposure dose of 1 to 10 J / cm is calculated by the following formula (4):2 It is preferable that the slope of the transmittance at 430 nm (converted to 1 mmt) with respect to the wavelength is −0.12 or less.

[0109]

number

[0110] In the above formula (4), the exposure dose is 1 to 10 J / cm 2 The transmittance is in the range of 430 nm (1 mmt equivalent value). The exposure amount and transmittance are measured by the methods described above.

[0111] The slope indicates the amount of change in transmittance relative to the amount of change in exposure dose. If the slope is large, the generation of silver colloid will be 1 to 10 J / cm 2 This means that the increase in the exposure dose corresponds to the increase in the exposure dose. Therefore, since the slope is −0.12 or less, it becomes possible to control the fine structure by adjusting the exposure dose.

[0112] The gradient is more preferably -0.14 or less, even more preferably -0.16 or less, even more preferably -0.18 or less, and particularly preferably -0.20 or less. If the gradient is too small, the gradient is 1 to 10 J / cm 2 As the exposure dose increases, silver colloid is rapidly generated, making it difficult to control the fine structure. Therefore, the slope is preferably −10 or more, more preferably −9 or more, and even more preferably −8 or more.

[0113] (shape) The shape of the photosensitive glass of this embodiment is not particularly limited, and can be formed into various shapes depending on the purpose and use. For example, the photosensitive glass of this embodiment may be a plate having two mutually opposing main surfaces, or may be a shape other than a plate depending on the product to which it is applied, the use, etc. More specifically, the photosensitive glass of this embodiment may be, for example, a flat glass plate without warping, or a curved glass plate having a curved surface. The shape of the main surface is also not particularly limited, and can be formed into various shapes such as a circle or a rectangle.

[0114] <Method for manufacturing photosensitive glass> Next, a method for producing the photosensitive glass of this embodiment (hereinafter also referred to as the present production method) will be described. Below, a method for producing a plate-shaped glass will be described, but the shape of the glass can be adjusted appropriately depending on the purpose.

[0115] In this process, raw materials prepared to achieve the desired glass composition are melted and formed into amorphous glass. The melt-forming method is not particularly limited; for example, the prepared glass raw materials are placed in a platinum crucible and then placed in an electric furnace at 1350°C to melt the raw materials. The temperature of the electric furnace is then increased to 1450°C, and the raw materials are degassed and homogenized. The initial melting temperature of 1350°C is set to decompose the silver chloride used as a raw material for AgO and dissolve it in the glass. If the temperature is too low, the silver chloride will not decompose and dissolve in the glass. On the other hand, if the temperature is too high, the thermal decomposition rate of the silver chloride will be too fast, making it difficult to dissolve in the glass.

[0116] Therefore, as described above, the raw materials are first melted at 1350°C and then heated to 1450°C. The resulting molten glass is poured into a metal mold (e.g., a SUS surface plate) at room temperature and held at the glass transition temperature for, for example, 1 to 2 hours, and then cooled to room temperature to obtain a glass block of amorphous glass. The resulting glass block is then cut, ground, polished, or otherwise processed as needed to form it into the desired shape.

[0117] As described above, amorphous glass can be formed into a desired shape from a molten state, and therefore has advantages over processes such as ceramics, which are formed from powder or slurry and then fired, or synthetic quartz, which are produced from an ingot and then cut into a desired shape, in that it is easier to form, can be made into a large-area product, and can be produced at low cost.

[0118] <Method for manufacturing glass with microstructure> One embodiment of the present invention relates to a method for manufacturing glass having a microstructure formed thereon, which includes selective microfabrication of the photosensitive glass by photostructuring. The microfabrication method includes the steps of exposure, heat treatment, and etching. Specifically, the method includes: (1) exposing the photosensitive glass to light; (2) heat treating the exposed photosensitive glass to precipitate Li2SiO3 crystals; and (3) removing the precipitated Li2SiO3 crystals by etching. Other steps may also be included.

[0119] (1) A process of exposing photosensitive glass The process of exposing the photosensitive glass will now be described by way of example.

[0120] First, the photosensitive glass is processed to the desired size. Surfaces that require high precision may be polished.

[0121] Next, an optical mask on which a fine pattern is formed is prepared, and placed on the glass and irradiated with ultraviolet light. The optical mask may be one used in ordinary ultraviolet exposure lithography. The exposure conditions are, for example, ultraviolet light with a wavelength of 200 to 380 nm at 0.1 to 25 J / cm. 2 The energy density is calculated using a wavelength-sensitive ultraviolet illuminance meter. The ultraviolet light is passed through a bandpass optical filter that transmits a specific wavelength range (for example, wavelengths of 300 to 320 nm) and incident on the light receiving part of the illuminance meter, and then measurement is performed.

[0122] (2) The exposed photosensitive glass is heat-treated to precipitate Li2SiO3 crystals. Next, the photosensitive glass exposed in (1) above is heat-treated to precipitate Li2SiO3 crystals. This process preferably includes two heat treatment stages. The first heat treatment stage is intended to colloidize the metallic silver in the glass and generate silver colloids that serve as nuclei for crystallization. The second heat treatment stage is intended to precipitate Li2SiO3 crystals.

[0123] In one embodiment of the present invention, the temperature range in the first heat treatment, i.e., the first temperature range, is preferably a temperature range in which the crystal nucleation rate is high for the glass composition. Specifically, the first temperature range is preferably 400°C or higher, more preferably 410°C or higher, even more preferably 420°C or higher, and particularly preferably 430°C or higher. Furthermore, the first temperature range is preferably 500°C or lower, more preferably 495°C or lower.

[0124] In one embodiment of the present invention, the temperature range in the first heat treatment, i.e., the first temperature range, is preferably a temperature range in which the rate of crystal nucleation is high for that glass composition. To promote crystal nucleation, the temperature range may be set higher. Specifically, the first temperature range is preferably 400°C or higher, followed by 410°C or higher, 420°C or higher, and 430°C or higher, in order of preference. The first temperature range is preferably 600°C or lower, followed by 590°C or lower, 580°C or lower, 570°C or lower, 560°C or lower, and 550°C or lower, in order of preference.

[0125] In one embodiment of the present invention, the holding time in the first temperature range is, in order of preference, 15 minutes or more, 30 minutes or more, 45 minutes or more, 1 hour or more, 1 hour 15 minutes or more, 1 hour 30 minutes or more, 1 hour 45 minutes or more, 2 hours or more, 2 hours 15 minutes or more, 2 hours 30 minutes or more, 2 hours 45 minutes or more, 3 hours or more, 3 hours 15 minutes or more, 3 hours 30 minutes or more, 3 hours 45 minutes or more, and 4 hours or more. When the holding time is within the above range, nucleation tends to proceed sufficiently. Meanwhile, from the viewpoint of manufacturability, the holding time in the first temperature range is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0126] In one embodiment of the present invention, the holding time in the first temperature range is, in order of preference, 1 minute or more, 5 minutes or more, 10 minutes or more, 15 minutes or more, 30 minutes or more, 45 minutes or more, 1 hour or more, 1 hour 15 minutes or more, 1 hour 30 minutes or more, 1 hour 45 minutes or more, 2 hours or more, 2 hours 15 minutes or more, 2 hours 30 minutes or more, 2 hours 45 minutes or more, 3 hours or more, 3 hours 15 minutes or more, 3 hours 30 minutes or more, 3 hours 45 minutes or more, and 4 hours or more. When the holding time is within the above range, nucleation tends to proceed sufficiently. Meanwhile, from the viewpoint of manufacturability, the holding time in the first temperature range is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0127] In one embodiment of the present invention, the second temperature range is preferably a temperature range in which the crystal growth rate of the Li2SiO3 crystal is high. Specifically, the second temperature range is preferably 500°C or higher, more preferably 505°C or higher, and even more preferably 510°C or higher. Increasing the heat treatment temperature facilitates crystal growth and allows for a shorter heat treatment time, but on the other hand, it tends to reduce the transmittance of the unexposed areas. Therefore, the second temperature range is preferably 700°C or lower, 690°C or lower, 680°C or lower, 670°C or lower, 660°C or lower, or 650°C or lower, in order of preference.

[0128] In one embodiment of the present invention, the second temperature range is preferably a temperature range where the crystal growth rate of the Li2SiO3 crystal is high. Specifically, the second temperature range is preferably at least 5°C higher than the first temperature range, with the following in order of preference: +10°C or higher, +20°C or higher, +30°C or higher, +40°C or higher, and +50°C or higher. Increasing the temperature range facilitates crystal growth and shortens the heat treatment time, but it also tends to reduce the transmittance of the unexposed areas. Therefore, the second temperature range is preferably at most 300°C higher than the first temperature range, with the following in order of preference: +290°C or lower, +280°C or lower, +270°C or lower, +260°C or lower, +250°C or lower, +240°C or lower, +230°C or lower, +220°C or lower, +210°C or lower, and +200°C or lower.

[0129] In one embodiment of the present invention, the retention time in the second temperature range is, in order of preference, 15 minutes or more, 30 minutes or more, 45 minutes or more, 1 hour or more, 1 hour 15 minutes or more, 1 hour 30 minutes or more, 1 hour 45 minutes or more, 2 hours or more, 2 hours 15 minutes or more, 2 hours 30 minutes or more, 2 hours 45 minutes or more, and 3 hours or more. When the retention time is within the above range, crystal growth tends to proceed sufficiently. From the viewpoint of manufacturability, the retention time is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0130] In one embodiment of the present invention, the retention time in the second temperature range is, in order of preference, 1 minute or more, 5 minutes or more, 10 minutes or more, 15 minutes or more, 30 minutes or more, 45 minutes or more, 1 hour or more, 1 hour 15 minutes or more, 1 hour 30 minutes or more, 1 hour 45 minutes or more, 2 hours or more, 2 hours 15 minutes or more, 2 hours 30 minutes or more, 2 hours 45 minutes or more, and 3 hours or more. When the retention time is within the above range, crystal growth is likely to proceed sufficiently. From the viewpoint of manufacturability, the retention time is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0131] The temperature rise rate in the heat treatment is not particularly limited, but is generally 5° C. / min or more, more preferably 15° C. / min or more, and even more preferably 30° C. / min or more.

[0132] On the other hand, the heating rate is preferably 300°C / min or less, more preferably 250°C / min or less, and even more preferably 200°C / min or less, which can suppress cracking caused by the difference in expansion coefficient between the glass phase and the crystalline phase during heating.

[0133] The cooling rate is not particularly limited, but is preferably 100°C / min or less, more preferably 90°C / min or less, and even more preferably 80°C / min or less, so that warping of the crystallized glass and cracking due to the difference in expansion coefficient between the amorphous phase and the crystalline phase can be suppressed during cooling. On the other hand, the cooling rate is generally 1°C / min or more, more preferably 5°C / min or more, and even more preferably 10°C / min or more.

[0134] (3) A process of removing the precipitated Li2SiO3 crystals by etching. Next, the precipitated Li2SiO3 crystals are removed by etching to structure the glass body. The etching is preferably performed using an etching solution containing HF. If the HF concentration in the etching solution is too low, etching of the Li2SiO3 crystals will be difficult. Therefore, the HF concentration in the solution is preferably 0.5% by mass or more, 1% by mass or more, 1.5% by mass or more, 2% by mass or more, 2.5% by mass or more, and 3% by mass or more, in order of preference.

[0135] On the other hand, if the HF concentration in the etching solution is too high, not only the crystalline portion but also the glass portion will be etched, so the HF concentration in the solution is preferably 20% by mass or less, 18% by mass or less, 16% by mass or less, 14% by mass or less, 12% by mass or less, 10% by mass or less, 8% by mass or less, and 6% by mass or less, in order of preference.

[0136] Furthermore, the etching solution may contain HCl or HNO3 in addition to the above-mentioned HF. This increases the acidity of the etching solution, making it easier to dissolve residues generated by etching, making it easier to achieve a microstructure more stably. The concentration of HCl or HNO3 is generally preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and particularly preferably 0.3 mass% or more. On the other hand, the concentration of HCl or HNO3 is preferably 5 mass% or less, more preferably 4 mass% or less, and particularly preferably 3 mass% or less.

[0137] <Circuit board> The circuit board of this embodiment includes an insulating substrate (hereinafter also referred to as a glass substrate) including the above-mentioned photosensitive glass or glass in which a microstructure is formed on the photosensitive glass.

[0138] Fig. 1 shows an example of the structure of a circuit board according to this embodiment. The circuit board 1 shown in Fig. 1 includes an insulating glass substrate 2, a first wiring layer 3 formed on a first main surface 2a of the glass substrate 2, and a second wiring layer 4 formed on a second main surface 2b of the glass substrate 2. The first wiring layer 3 and the second wiring layer 4 form a microstrip line as an example of a transmission line. The first wiring layer 3 forms a signal line, and the second wiring layer 4 forms a ground line.

[0139] However, the structures of the first wiring layer 3 and the second wiring layer 4 are not limited to those described above. The wiring layer may be formed on only one main surface of the glass substrate 2, or may be formed inside the glass substrate 2 rather than on the main surface of the glass substrate 2. The circuit board of this embodiment may also include other components (passive devices, active devices, circuit components, etc.) not shown in FIG.

[0140] As described above, the circuit board of this embodiment may be a circuit board including a glass substrate and a wiring layer formed inside or on at least one main surface of the glass substrate.

[0141] <Application> The above circuit board is preferably used for high frequency devices because it has good dielectric properties in the high frequency range and is excellent in micromachining ability.

[0142] As described above, the high-frequency device may include a transmission line, such as a microstrip line, a strip line, a coplanar line, a slot line, a waveguide, a substrate integrated waveguide (SIW), a waveguide, etc.

[0143] A waveguide has a hollow structure. An example of a waveguide is shown in Figure 2. The waveguide 10 shown in Figure 2 has a glass substrate 11 and a hollow portion 12 inside it. The waveguide 10 has a structure in which the inner wall surface of the tube is covered with metal, and is used to transmit electromagnetic waves. In this case, a feature of the waveguide is that it is hollow inside, meaning that the dielectric that causes dielectric loss is air, so there is low loss, and it is possible to transmit large amounts of power.

[0144] Furthermore, by applying an appropriate design to the circuit board of this embodiment, it is possible to impart the transmission line (wiring) function with the passive device function of a filter, antenna, duplexer, diplexer, etc. For example, known forms of filters, which are high-frequency devices, include configurations that use transmission lines such as waveguides, SIW, and microstrip lines. In addition, configurations that apply microstrip lines to antenna applications are also known.

[0145] As another application, the circuit board of this embodiment can be microfabricated and therefore may be used in a microfluidic device. A microfluidic device is a general term for devices that create microchannels and reaction vessels and are used in bioresearch and chemical engineering. A specific example is a biomimetic chip. A biomimetic chip is a technology that allows the reproduction of biological systems that were difficult to reproduce in conventional experimental systems by forming microchannels on a chip that mimics human organs. The circuit board of this embodiment may be applied to the bio field as described above and other fields. [Example]

[0146] Examples will be described below, but the present invention is not limited to these examples.

[0147] Test Example 1: Dielectric properties and processability of photosensitive glass In the following, Glasses 1 to 9 and Glasses 24 to 26 are Examples, and Glasses 10 to 23 are Comparative Examples. Tables 1 to 4 show the glass compositions of Glasses 1 to 26 in mole percentages based on oxides. Tables 5 to 8 show the glass compositions of Glasses 1 to 26 in mass percentages based on oxides.

[0148] <Preparation of photosensitive glass> Glass raw materials were mixed to obtain the compositions shown in Tables 1 to 4 in terms of oxide-based mole percentages, and weighed out to give approximately 400 g of glass. The mixed raw materials were then placed in a platinum crucible, placed in an electric furnace at 1350°C, and stirred for approximately 1 hour. The mixture was then heated to 1450°C, stirred again for approximately 4 hours, and then allowed to stand for approximately 2 hours to degas and homogenize. The resulting molten glass was poured into a metal mold, held at 470°C for 2 hours, and then cooled to 70°C over 8 hours to obtain a glass block.

[0149] The physical properties of the obtained glasses are shown in Tables 1 to 4. In Tables 1 to 4, a blank "-" indicates that the corresponding physical property was not measured.

[0150] <Photosensitive glass exposure, heat treatment, and etching> Glasses 1 and 6 were subjected to exposure, heat treatment and etching to examine their processability. [exposure] First, the obtained glass was processed into a flat plate (30 mm long x 20 mm wide, 0.5 mm thick) and the surface was polished to a mirror finish to prepare a sample. The sample was then exposed to light using an exposure device (manufactured by Dai-Nippon Kaken Co., Ltd., product name "MA-1200"). In this study, a method was used in which the entire flat glass was exposed to light. The exposure dose is shown in Table 9 below.

[0151] [Heat treatment] The exposed glasses 1 and 6 were crystallized by heat treatment at the temperature changes shown in Figure 3. Figure 3 is a diagram showing the temperature changes in the two-stage heat treatment. Specifically, Figure 3 shows that in the heat treatment, the amorphous glass is heated to temperature T1, held for a certain period of time, then heated to temperature T2, held for a certain period of time, and then cooled. The specific conditions, such as temperature, for the heat treatment in Figure 3 are shown in Table 9 below.

[0152] The presence or absence of Li2SiO3 crystal precipitation was confirmed for the heat-treated glasses 1 and 6 by microscopic observation, XRD measurement, and spectral transmittance spectroscopy. When observing under a microscope using epi-illumination, light scattering occurs in the areas where crystals have precipitated, making the glassy areas appear dark and the crystalline areas appear bright. The presence or absence of crystal precipitation can be confirmed by the difference in brightness. In the XRD measurement, it was confirmed whether the peak of Li2SiO3 crystal appeared. Furthermore, if crystals are precipitated, a decrease in the overall transmittance is confirmed in the near ultraviolet to near infrared range in the spectral transmission spectrum. By the above method, the precipitation of Li2SiO3 crystals was confirmed in Glasses 1 and 6.

[0153] [etching] The glass with Li2SiO3 crystals precipitated obtained by the above method was subjected to an etching test (immersion for 4 minutes in 55 ml of an etching solution containing 5 mass % HF and 0.7 mass % HNO3 at 40°C).

[0154] The methods for measuring each physical property are shown below.

[0155] (XRD measurement) XRD measurement sample preparation conditions The heat-treated crystallized glass plate was cut into a size of 10 mm length x 10 mm width and 0.5 mm thickness to obtain a sample for XRD measurement.

[0156] XRD measurement conditions X-ray diffraction was measured under the following conditions to identify the precipitated crystals. The crystal species were identified using the diffraction peak patterns recorded in the ICSD inorganic crystal structure database and the ICDD powder diffraction database. Measurement equipment: Rigaku SmartLab Measurement method: Focused method Tube voltage: 45 kV Tube current: 200mA X-ray used: CuKα ray Measurement range: 2θ=10°~80° Speed: 10° / min Step: 0.02°

[0157] (relative permittivity: Dk, dielectric loss tangent: Df) The dielectric constant and dielectric loss tangent at 10 GHz were measured by the split post dielectric resonance (SPDR) method using a network analyzer at a temperature of 20°C.

[0158] (Glass etching rate) The prepared glass was processed into a flat plate (30 mm long x 20 mm wide, 0.5 mm thick) and the surface was polished to a mirror finish to prepare a sample. The prepared sample was washed, dried, and weighed, and then subjected to an etching test (immersion for 4 minutes in 55 ml of an etching solution containing 5% HF and 0.7% HNO3 by mass at 40°C). After the test, the sample was washed and dried again, and its weight was measured. The etching rate of the glass portion (unexposed portion) was calculated using the following formula (1).

[0159]

number

[0160] (etching rate selectivity of exposed / unexposed areas) For Glasses 1 and 6, the etching rates when etching was performed after exposure and heat treatment (exposed area etching rate) and when etching was performed without exposure and heat treatment (unexposed area etching rate) were determined, and the exposed area / unexposed area etching rate selectivity was calculated based on the following formula (2). Here, the unexposed area etching rate and the glass area etching rate are synonymous. The method for calculating the exposed area etching rate in this case will be described later.

[0161]

number

[0162] The etching rate of the exposed area in the above formula (2) was calculated by subjecting the glass sample, which was 30 mm long x 20 mm wide and 0.5 mm thick, to an exposure treatment, a heat treatment, and then etching, using the above formula (1). The specific treatment conditions are shown below.

[0163] (i) Exposure processing An exposure device (manufactured by Dai Nippon Kaken Co., Ltd., product name "MA-1200") was used, and the exposure dose was 15 J / cm 2 The entire flat glass plate was exposed to light so that the

[0164] (ii) Heat treatment A two-stage heat treatment was performed. The first stage was heat-treated at 485°C for 5 hours. The second stage heat treatment conditions were determined as follows: First, the crystallization peak was confirmed using a DTA device (Rigaku Thermoplus TG8120). This time, heat treatment was performed for 1 hour or 3 hours at temperatures ranging from -150°C to -100°C, relative to the temperature at which the crystallization peak was confirmed. The same treatment was also performed on glass of the same composition that had not been exposed to light, and the absence of crystal precipitation was confirmed by microscopic observation. When observed under a microscope using epi-illumination, the areas where crystals had precipitated appear bright while the glass areas appear dark due to light scattering. The presence or absence of crystal precipitation was confirmed by the brightness of this contrast.

[0165] (iii) Etching The glass sample was immersed in 55 ml of an etching solution containing 5 mass % of HF and 0.7 mass % of HNO3 at 40°C for 4 minutes. After the above treatment, the value calculated by the above formula (1) was taken as the etching rate of the exposed portion.

[0166] (density) The density of a glass block of about 20 g containing no bubbles was measured by the Archimedes method.

[0167] (Tg) Measurement was carried out by the thermal expansion method according to the method specified in JIS R3103-3 (2001).

[0168] (average thermal expansion coefficient) Measurements were made using a differential thermal dilatometer in accordance with the method specified in JIS R3102 (1995). The measurement temperature range was 50 to 350°C, and the unit was ×10 -7 The temperature was expressed as / °C.

[0169] [Table 1]

[0170] [Table 2]

[0171] [Table 3]

[0172] [Table 4]

[0173] [Table 5]

[0174] [Table 6]

[0175] [Table 7]

[0176] [Table 8]

[0177] [Table 9]

[0178] Glasses 1 to 9 and glasses 25 to 27 have a value of formula (A) of 0.50 or more and 0.75 or less, and therefore have a dielectric loss tangent of 0.0090 or less at 20° C. and 10 GHz, which is a good value. Furthermore, glasses 1 to 9 and glasses 25 to 27 have an SiO2 content of 65% or more expressed in mass percentage, and the etching rate of the amorphous glass portion, which is the unexposed portion, is 2.75 or less. In addition, for glasses 1 and 6, the precipitation of Li2SiO3 crystals was actually confirmed by exposure and heat treatment.

[0179] On the other hand, Glasses 10 to 22 had values ​​of formula (A) exceeding 0.75, and dielectric loss tangents at 20° C. and 10 GHz exceeding 0.0090, and were inferior in dielectric properties to Glasses 1 to 9 and Glasses 25 to 27 of the Examples.

[0180] Glass 23 also had a value of formula (A) exceeding 0.75, and its relative dielectric constant at 20° C. and 10 GHz was higher than those of Glasses 1 to 9 and Glasses 25 to 27 of the Examples, indicating poor dielectric properties.

[0181] Glass 24 had a value of formula (A) of less than 0.50 and an SiO2 content of less than 65% expressed as a mass percentage based on oxides, so the glass etching rate was a high value of 5.94. Therefore, it is expected that fine processing is poor and the Li2O content is very low compared to the other examples, making it difficult for Li2SiO3 crystals to precipitate.

[0182] Next, Tables 10 and 11 show examples based on the calculation results (Calculation Examples 1 to 7). Table 10 shows the glass composition expressed in mole percentage, along with the relative permittivity, dielectric loss tangent, and glass etching rate at 10 GHz predicted by calculation based on that composition. Since the trace components Sb2O3, CeO2, and Ag2O are expected to have almost no effect on the aforementioned physical properties, calculations were performed based on a composition excluding these trace components. Table 11 also shows the components shown in Table 10 expressed in mass percentage. In Table 11, the composition excluding the trace components is converted into the total amount, so the total is 100%.

[0183] [Table 10]

[0184] [Table 11]

[0185] In calculation examples 1 to 7, the Al2O3 content is less than 5% in mass percentage, and the Li2O content is 15% or less, so the value of formula (A) is 0.75 or less. Therefore, the predicted value of the dielectric loss tangent at 10 GHz is expected to be a good value of 0.0090 or less. Furthermore, because the SiO2 content is 65% or more in mass percentage, the predicted value of the etching rate of the unexposed amorphous glass portion is expected to be 2.75 or less.

[0186] Test Example 2: Effect of different silver amounts Next, we will explain the differences in photosensitive glass depending on the silver content. Glasses A, B, and C each contain a different amount of silver. Figures 4 to 6 show the transmittance data measured for each glass after exposure and heat treatment. Table 12 shows the silver content, exposure dose, and heat treatment conditions for these glasses.

[0187] [Table 12]

[0188] The exposure method and transmittance measurement method used in this test example are as follows: The size of the sample used for exposure and transmittance measurement was a flat plate of 10 mm x 10 mm and 2 mm thick.

[0189] (Exposure method) The samples were exposed in the following manner. <Device name> Light source unit for exposure equipment: Multilight ML-251D / B (manufactured by Ushio Inc.) <Device configuration> Light fixture: MPL-25131 Lamp: Ultra-high pressure mercury lamp USH-250BY Lamp power supply: HB-25103BY-C Irradiation optical unit: PM25C-75 <Exposure method> The UV intensity was measured using a combination of a UV integrating actinometer UIT-250 and a UVH-S313 photodetector. The time required for the desired exposure was then calculated, and UV light was irradiated for that amount of time using the exposure device.

[0190] (Transmittance measurement) The transmittance was measured under the following conditions. Measuring device: Spectrophotometer V-570 (manufactured by JASCO Corporation) Measurement wavelength range: 200-800nm During the spectroscopic measurements, a sample holder with a φ3 mm opening was used.

[0191] Figures 4 to 6 are graphs showing the transmittance (converted to 1 mmt) of Glasses A, B, and C by exposure dose. The transmittance values ​​shown here are values ​​converted to transmittance equivalent to a thickness of 1 mmt using the following formula (3).

[0192]

number

[0193] 4 to 6, the area around 430 nm is where the absorption peak of silver colloid is located, and it can be seen that the transmittance at 430 nm decreases as the exposure dose increases. This indicates that the production of silver colloid is promoted as the exposure dose increases, resulting in a decrease in transmittance around 430 nm.

[0194] The transmittance at 430 nm converted to 1 mmt is T 430_1mmt Based on these results, the horizontal axis represents the exposure dose (J / cm 2 ) Vertical axis T 430_1mmt Based on Figure 7, the exposure dose of each glass was 0.5 J / cm 2 T in 430_1mmt and exposure dose of 1 to 10 J / cm 2 T for 430_1mmt The slope of is shown in Table 13. At this time, T 430_1mmt The slope was calculated using the following formula (4).

[0195]

number

[0196] [Table 13]

[0197] Exposure dose 0.5J / cm 2 As the silver content in the glass increases, T 430_1mmt In other words, even with the same exposure dose, it was found that silver colloid was less likely to be generated.2 T in 430_1mmt If the ratio is less than 4%, the exposure sensitivity becomes too high, making it difficult to control the fine structure.

[0198] In addition, the exposure dose is 1 to 10 J / cm 2 T in 430_1mmt When we look at the slope of the graph, we can see that the absolute value of the slope increases as the silver content in the glass increases. In other words, when the silver content is low, the absolute value of the slope becomes 1 J / cm 2 At exposure levels below 1 J / cm, the silver colloid generation is almost saturated. 2 The silver colloid formation shows a relatively linear response to the above exposure dose.

[0199] 1~10J / cm 2 T in 430_1mmt When the slope of becomes larger than -0.12 (approaching zero), 1 J / cm 2 Below this exposure level, the silver colloid generation becomes saturated, making it difficult to control the fine structure.

[0200] Next, examples based on the calculation results (Calculation Examples A to F) are shown in Table 14. Table 14 shows the silver content in the glass expressed as a mass percentage and the predicted value of 0.5 J / cm 2 calculated based on that content. 2 T in 430_1mmt and 1–10 J / cm 2 T in 430_1mmt The graph shows the slope of the

[0201] [Table 14]

[0202] From Table 14, when the silver content is lower than 0.05%, the 2 T in 430_1mmt It is expected that the value will be less than 4%, and the exposure sensitivity will be too high, making it difficult to control the fine structure.

[0203] Also, when the silver content is lower than 0.05%, the exposure dose is 1 to 10 J / cm 2T in 430_1mmt The slope of becomes greater than -0.12 (approaches zero), so 1J / cm 2 It is expected that at exposure doses below this level, the generation of silver colloids will be saturated, making it difficult to control the fine structure.

[0204] (Example of transmission loss calculation) When the fabricated glass was actually used as a substrate for high-frequency devices, the transmission loss of the transmission line was calculated to confirm the extent to which the dielectric properties would affect the transmission loss of high-frequency signals. The transmission line was a microstrip line (MSL). TXLINE (Cadence) was used as the analysis software. The analysis model is as follows:

[0205] The copper wiring layer formed on one main surface of the glass substrate was specified to have a wiring width (shown in Tables 15 to 18) that would result in a characteristic impedance of 50 Ω for the microstrip line, and the transmission loss at 10 GHz was calculated. The thickness of the glass, which serves as the dielectric layer, was set to 0.125 mm, and the thickness of the copper wiring, which serves as the conductor layer, was set to 18 μm. The surface roughness of the copper wiring layer was set to be sufficiently smooth so that the skin effect would not be an issue. The relative permittivity and dielectric loss tangent of the glass at 20°C and 10 GHz were used for the calculation analysis. The relative permittivity and dielectric loss tangent of the glass used in this study were measured using actual fabricated samples. The calculated transmission loss is shown in Tables 15 to 18. The magnitude of transmission loss versus the relative permittivity and dielectric loss tangent of the glass is shown in Figures 8 and 9.

[0206] [Table 15]

[0207] [Table 16]

[0208] [Table 17]

[0209] [Table 18]

[0210] Figure 8 is a plot of glass relative permittivity on the horizontal axis and transmission loss on the vertical axis. Figure 9 is a plot of glass dielectric loss tangent on the horizontal axis and transmission loss on the vertical axis. These figures show that the dielectric loss tangent of the glass used as a substrate contributes more to improving transmission loss than the relative permittivity of the glass. In other words, using a glass substrate with a low dielectric loss tangent makes it possible to fabricate high-frequency devices with even less transmission loss. Therefore, computational analysis confirmed that dielectric loss is improved when using photosensitive glass with an improved dielectric loss tangent as a substrate compared to existing photosensitive glass.

[0211] Test Example 3: Effects of differences in the first temperature range [nucleation temperature] This section explains the difference between exposing the photosensitive glass to light and then holding it at 485°C and 520°C in the first temperature range (nucleation temperature). The composition of Glass X used is shown in Table 19, expressed in mole percentage and mass percentage. The exposure conditions and heat treatment conditions are also shown in Table 20.

[0212] [Table 19]

[0213] [Table 20]

[0214] The exposure method and transmittance measurement were carried out in the same manner as in Test Example 2. Figures 10 and 11 are graphs showing the transmittance (converted to 1 mmt) of glass X by exposure dose. Figure 10 shows the transmittance when exposure and heat treatment were performed under condition 1 in Table 20, and Figure 11 shows the transmittance when exposure and heat treatment were performed under condition 2 in Table 20. The transmittances shown here are values ​​converted to transmittance equivalent to a thickness of 1 mmt using the following formula (3):

[0215]

number

[0216] In Figures 10 and 11, the region around 430 nm is where the absorption peak of silver colloid is located, and the transmittance at 430 nm decreases after heat treatment, indicating that silver colloid is being generated. Furthermore, comparing Figures 10 and 11, it can be seen that Figure 11, which has a higher holding temperature in the first temperature range, has a lower transmittance at 430 nm. This is because the generation of silver colloid is further promoted by setting the first temperature range to a higher temperature. In other words, setting the first temperature range to a higher temperature makes it possible to precipitate silver colloid in a shorter time. [Industrial Applicability]

[0217] The photosensitive glass of one embodiment of the present invention not only exhibits excellent microfabrication properties but also excellent dielectric loss properties for high-frequency signals. By using such photosensitive glass, it is possible to achieve a high-frequency device having a circuit board that has been subjected to microfabrication and that exhibits excellent transmission loss properties for high-frequency signals.

[0218] Such photosensitive glass is extremely useful as a component for high-frequency electronic devices in general that handle high-frequency signals exceeding 10 GHz, particularly high-frequency signals exceeding 30 GHz, and even high-frequency signals of 35 GHz or higher, as well as for devices that involve microfabrication, such as substrate integrated waveguides.

[0219] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0220] This application is based on a Japanese patent application (Patent Application No. 2021-093783) filed on June 3, 2021, the contents of which are incorporated by reference into this application. [Explanation of symbols]

[0221] 1 circuit board 2. Glass substrate 2a,2b Main surface 3,4 wiring layer 10 Waveguide 11 Glass substrate 12 Hollow part

Claims

1. Li by exposure and heat treatment ２ SiO ３ A photosensitive glass in which crystals are precipitated, The value of the following formula (A) is 0.50 or more and 0.75 or less, A photosensitive glass having a dielectric loss tangent of 0.0090 or less at 20°C and 10 GHz. [Li ２ O] / ([Li ２ O]+[Na ２ O]+[K ２ O]) Formula (A) (In formula (A), [Li ２ O], [Na ２ O] and [K ２ O] are the mole percentages of Li in the photosensitive glass based on oxides. ２ O, Na ２ O and K ２ indicates the content of O.)

2. In terms of mass percentage based on oxides, SiO ２ : Contains 65 to 78% A glass sample of 30 mm length x 20 mm width and 0.5 mm thickness was mixed with HF: 5 mass % and HNO ３ 2. The photosensitive glass according to claim 1, wherein the glass portion etching rate calculated by the following formula (1) is 2.75 or less when the photosensitive glass is immersed in 55 ml of an etching solution at 40° C. containing 0.7% by mass of ZnO. [Equation 1]

3. Mass percentage based on oxides Al ２ O ３ : 0 to 5% (excluding 5%) Li ２ O: 5~15% Na ２ O:3~12% K ２ O:3~12% ZnO: 0.3-8% Sb ２ O ３ : 0.01 to 1% (excluding 1%) CeO ２ :0.001~0.1% Aẹ ２ O: 0.05~1% 3. The photosensitive glass according to claim 1, further comprising:

4. Mass percentage based on oxides Al ２ O ３ : 0 to 5% (excluding 5%) Li ２ O: 5~15% Na ２ O:3~12% K ２ O:3~12% ZnO: 0 to 8% Sb ２ O ３ : 0.01 to 1% (excluding 1%) CeO ２ :0.001~0.1% Aẹ ２ O: 0.05~1% 3. The photosensitive glass according to claim 1, further comprising:

5. In terms of mass percentage based on oxides, B ２ O ３ 5. The photosensitive glass according to claim 1, wherein the content is 0 to 8%.

6. 6. The photosensitive glass according to claim 1, which has a relative dielectric constant of 7.5 or less at 20° C. and 10 GHz.

7. The photosensitive glass according to any one of claims 1 to 6 is exposed to light and heat treated to produce Li. ２ SiO ３ Crystallized glass.

8. 7. Glass having a microstructure formed by exposing, heat-treating and etching the photosensitive glass according to any one of claims 1 to 6.

9. A circuit board comprising an insulating substrate comprising the glass of claim 8.

10. 10. The circuit board of claim 9 for use in a high frequency device.

11. The circuit board of claim 10 comprising a transmission line.

12. The circuit board of claim 11 , wherein the transmission line is a waveguide, a substrate integrated waveguide (SIW), or a microstrip line.

13. The circuit board according to claim 11, having a function of a passive device.

14. A high frequency device comprising the circuit board according to any one of claims 9 to 13.

15. A step of exposing the photosensitive glass according to any one of claims 1 to 6 to light; The exposed photosensitive glass is heat treated to form Li ２ SiO ３ A step of precipitating crystals; The precipitated Li ２ SiO ３ removing the crystals by etching; A method for producing a microstructured glass, comprising:

16. the heat treatment includes holding in a first temperature range and holding in a second temperature range; the first temperature range is 400°C or higher and 500°C or lower, and the holding time in the first temperature range is 15 minutes or longer; The manufacturing method according to claim 15, wherein the second temperature range is 500° C. or more and 700° C. or less, and the holding time in the second temperature range is 15 minutes or more.

17. the heat treatment includes holding in a first temperature range and holding in a second temperature range; the first temperature range is 400°C or higher and 600°C or lower, and the holding time in the first temperature range is 1 minute or longer; The manufacturing method according to claim 15, wherein the second temperature range is from the first temperature range +5°C to +300°C, and the holding time in the second temperature range is 1 minute or longer.

18. Exposure dose 0.5 J / cm ２ 7. The photosensitive glass according to claim 1, wherein the transmittance at 430 nm (1 mmT equivalent) is 4% or more when the glass is exposed to light at 400 nm and then heat-treated at 485° C. for 5 hours.

19. Exposure amount 1-10J / cm ２ The transmittance at 430 nm (1 mm equivalent value) is measured when the film is exposed to light at 485° C. for 5 hours, and then heat-treated at 485° C. The exposure dose is plotted on the horizontal axis (J / cm ２ ) and plotted on a coordinate plane with the transmittance (%) on the vertical axis, the exposure dose of 1 to 10 J / cm is calculated by the following formula (4): ２ 7. The photosensitive glass according to claim 1, wherein the slope of transmittance (1 mmT equivalent value) at 430 nm versus wavelength is −0.12 or less. [Equation 2]

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