Photosensitive glass

Abstract

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

Description

Technical Field

[0001] This invention relates to photosensitive glass, and more particularly to photosensitive glass with good dielectric properties in high-frequency bands such as 5G, which can be micro-processed through crystallization and etching based on exposure and heat treatment. Background Technology

[0002] In recent years, wireless transmission using high-frequency bands such as micrometer and millimeter waves has attracted attention as a high-capacity transmission technology. However, it is known that the dielectric loss during wireless transmission is directly proportional to the frequency and the dielectric loss tangent of the dielectric substrate. Therefore, as the frequency used increases, the signal frequency becomes higher, which in turn requires dielectric substrates with low dielectric loss tangents, especially in high-frequency bands.

[0003] On the other hand, assuming that high-frequency components are manufactured into devices, the substrates used require high dimensional accuracy and precise structural control. This is due to various reasons, including issues with the packaging processes of each component and the miniaturization of modules. Therefore, the microfabrication properties of the materials themselves are also required.

[0004] Previously, materials such as quartz, ceramics, and glass have been used as dielectric substrates. However, although these materials have good dielectric properties, most of them do not have sufficient microfabrication capabilities.

[0005] Here, photosensitive glass is also known as a type of glass with excellent microprocessability. Photosensitive glass can be microprocessed using very simple processing techniques, as disclosed in, for example, Patent Document 1.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: U.S. Patent Application Publication No. 2008 / 0248250 Summary of the Invention

[0009] However, previous photosensitive glass has not been studied for use as a material in high-frequency components, and therefore its dielectric properties were not considered, resulting in a relatively high dielectric loss tangent. Consequently, while previous photosensitive glass exhibited excellent microprocessability, it suffered from increased dielectric loss when used at high frequencies.

[0010] Therefore, the object of the present invention is to provide a photosensitive glass that improves the dielectric properties of the glass itself without compromising its microprocessability to solve the above-mentioned problems.

[0011] The inventors conducted in-depth research to solve the aforementioned problems. Their findings revealed that the above-mentioned problems can be solved through the following configuration.

[0012] [1] A photosensitive glass in which Li2SiO3 crystals are precipitated through exposure and heat treatment.

[0013] The value of the following formula (A) is 0.50 to 0.75.

[0014] The dielectric loss tangent at 20℃ and 10GHz is below 0.0090°.

[0015] [Li2O] / ([Li2O]+[Na2O]+[K2O]) Formula (A)

[0016] (In formula (A), [Li2O], [Na2O] and [K2O] represent the contents of Li2O, Na2O and K2O in the above-mentioned photosensitive glass, expressed as molar percentages based on oxides, respectively.)

[0017] [2] According to the photosensitive glass described in [1] above, the content of SiO2 is 65-78% by mass percentage based on oxides.

[0018] When a glass sample with a length of 30 mm × width of 20 mm and a thickness of 0.5 mm is immersed in 55 ml of an etching solution at 40 °C containing 5% HF and 0.7% HNO3 for 4 minutes, the etching rate of the glass portion, as determined by the following formula (1), is 2.75 or less.

[0019]

[0020] [3] The photosensitive glass according to [1] or [2] above contains, by mass percentage based on oxides, Al2O3: 0-5% (excluding 5%), Li2O: 5-15%, Na2O: 3-12%, K2O: 3-12%, ZnO: 0.3-8%, Sb2O3: 0.01-1% (excluding 1%), CeO2: 0.001-0.1%, and Ag2O: 0.05-1%.

[0021] [4] The photosensitive glass according to [1] or [2] above contains, by mass percentage based on oxides, Al2O3: 0-5% (excluding 5%), Li2O: 5-15%, Na2O: 3-12%, K2O: 3-12%, ZnO: 0-8%, Sb2O3: 0.01-1% (excluding 1%), CeO2: 0.001-0.1%, and Ag2O: 0.05-1%.

[0022] [5] The photosensitive glass according to any one of [1] to [4] above, wherein, expressed as a mass percentage based on oxides, contains B2O3: 0 to 8%.

[0023] [6] The photosensitive glass according to any one of [1] to [5] above, wherein the relative permittivity at 20°C and 10 GHz is 7.5 or less.

[0024] [7] A glass is obtained by exposing and heat-treating the photosensitive glass described in any one of [1] to [6] above to precipitate Li2SiO3 crystals.

[0025] [8] A glass is obtained by exposing, heat-treating and etching the photosensitive glass described in any one of [1] to [6] above to form a microstructure.

[0026] [9] A circuit board comprising an insulating substrate including the glass described above [8].

[0027]

[10] The circuit board according to [9] above is used in a high-frequency device.

[0028]

[11] The circuit board according to

[10] above includes a transmission line.

[0029]

[12] According to the circuit board described in

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

[0030]

[13] The circuit board described in

[11] above has a passive device function.

[0031]

[14] A high-frequency device comprising any one of the circuit boards described in any one of [9] to

[13] above.

[0032]

[15] A method for manufacturing glass having a fine structure includes:

[0033] The process of exposing the photosensitive glass described in any one of [1] to [6] above,

[0034] The process of heat-treating the exposed photosensitive glass to precipitate Li2SiO3 crystals.

[0035] The process of removing the above-mentioned precipitated Li2SiO3 crystals by etching.

[0036]

[16] According to the manufacturing method described in

[15] above, the heat treatment includes a step of holding in a first temperature region and a step of holding in a second temperature region.

[0037] The first temperature range mentioned above is 400℃ to 500℃, and the holding time within the first temperature range is more than 15 minutes.

[0038] The second temperature range is 500℃ to 700℃, and the holding time within the second temperature range is more than 15 minutes.

[0039]

[17] According to the manufacturing method described in

[15] above, the heat treatment includes a step of holding in a first temperature region and a step of holding in a second temperature region, wherein the first temperature region is 400°C to 600°C and the holding time in the first temperature region is more than 1 minute, and the second temperature region is the first temperature region +5°C to +300°C and the holding time in the second temperature region is more than 1 minute.

[0040]

[18] The photosensitive glass according to any one of [1] to [6] above, wherein the exposure amount is 0.5 J / cm 2 The transmittance (converted to 1 mmt) at 430 nm after exposure and heat treatment at 485 °C for 5 hours is above 4%.

[0041]

[19] The photosensitive glass according to any one of [1] to [6] above, wherein, for an exposure dose of 1 to 10 J / cm 2 The transmittance (converted to 1 mmt) at 430 nm was measured after exposure and heat treatment at 485°C for 5 hours. The exposure amount was used as the horizontal axis (J / cm). 2 When plotting the curve with the above transmittance as the vertical axis (%) on a coordinate plane, the transmittance at 430 nm (converted to 1 mmt) obtained by the following equation (4) is relative to the exposure amount of 1-10 J / cm. 2 The slope is below -0.12.

[0042]

[0043] X: Exposure (J / cm²) 2 Y: Transmittance at 430nm (converted to 1mmt)

[0044] According to the present invention, a photosensitive glass with low dielectric loss and excellent microprocessability in the high-frequency band is provided, as well as a method for manufacturing the same, a circuit board having the photosensitive glass, and a high-frequency device. Attached Figure Description

[0045] Figure 1 This is a cross-sectional view illustrating an example of a circuit board according to one embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram illustrating an example of a waveguide.

[0047] Figure 3 This is a diagram schematically illustrating the temperature changes during a two-step heat treatment of the photosensitive glass in the embodiment.

[0048] Figure 4 This is a graph showing the results of measuring the transmittance of glass A in the example.

[0049] Figure 5 This is a graph showing the results of the transmittance measurement of glass B in the example.

[0050] Figure 6 This is a graph showing the results of measuring the transmittance of glass C in the example.

[0051] Figure 7 This is a graph plotting the relationship between the exposure amount and the transmittance at 430nm for the glass A to C of the examples.

[0052] Figure 8 This is a graph plotting the relationship between the relative permittivity and transmission loss of the photosensitive glass in the embodiment.

[0053] Figure 9 This is a graph plotting the relationship between the dielectric loss tangent and transmission loss of the photosensitive glass in the embodiment.

[0054] Figure 10 This is a graph showing the transmittance of glass X when it is exposed and heat-treated under condition 1.

[0055] Figure 11 This is a graph showing the transmittance of glass X when it is exposed and heat-treated under condition 2. Detailed Implementation

[0056] In this manual, unless otherwise specified, the "~" sign indicating a range of values ​​shall be used to mean the lower limit and upper limit of the values ​​listed before and after it.

[0057] In this specification, unless otherwise specified, the glass composition is expressed as a mass percentage based on oxides, with mass % abbreviated as "%". It should be noted that in formula (A), [Li2O], [Na2O], and [K2O] are expressed as molar percentages based on oxides.

[0058] In this specification, "high frequency" refers to a frequency of 1 GHz or higher. Preferably, it is 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. Alternatively, it may be, for example, below 100 GHz.

[0059] In this specification, "photosensitive glass" refers to glass that can be micro-processed through a combination of crystallization and etching based on exposure and heat treatment. In particular, the photosensitive glass of the present invention is characterized by the precipitation of Li2SiO3 crystals through exposure and heat treatment, and the removal of the Li2SiO3 crystals by etching.

[0060] More specifically, "photosensitive glass" undergoes a chemical reaction through exposure, and the Ag contained in the photosensitive glass... + Ions accept electrons and become metal atoms. Then, the photosensitive glass is heat-treated to generate silver colloid. Further heat treatment at increasingly higher temperatures uses the silver colloid as a nucleus to form and precipitate Li₂SiO₃ crystals. These precipitated Li₂SiO₃ crystals have very high solubility in HF, allowing selectively exposed portions to be removed by HF etching.

[0061] Thus, because the glass undergoes a chemical reaction through exposure, it is called photosensitive glass.

[0062] The aforementioned Li₂SiO₃ crystals can be confirmed, for example, by X-ray diffraction (XRD). Specifically, when XRD is performed using CuKα rays at 2θ = 10–90°, if the peak with the highest intensity is observed in the range of 2θ = 26.5–27.5°, the crystallized glass contains Li₂SiO₃ crystals.

[0063] In this specification, "glass section etching rate" refers to the etching rate of the unexposed glass section (glass section) (unexposed section etching rate).

[0064] In this specification, the "exposed / unexposed etch rate selection ratio" refers to the ratio obtained by dividing the etch rate of the exposed and crystallized portion (exposed etch rate) by the etch rate of the unexposed glass portion (glass portion) (unexposed etch rate). A higher exposed / unexposed etch rate selection ratio indicates that only the exposed portion can be selectively removed; conversely, a lower exposed / unexposed etch rate selection ratio indicates that the unexposed glass portion is also more easily etched.

[0065] Photosensitive glass

[0066] The photosensitive glass of one embodiment of the present invention is characterized in that it precipitates Li2SiO3 crystals by exposure and heat treatment, the value of the following formula (A) is 0.50 to 0.75, and the dielectric loss tangent at 20°C and 10 GHz is 0.0090 or less.

[0067] [Li2O] / ([Li2O]+[Na2O]+[K2O]) Formula (A)

[0068] (In formula (A), [Li2O], [Na2O] and [K2O] represent the contents of Li2O, Na2O and K2O in the above-mentioned photosensitive glass, expressed as molar percentages based on oxides, respectively.)

[0069] In the photosensitive glass of this embodiment, the above formula (A) is an indicator of the degree of mixing of alkali metal atoms. The smaller the value of formula (A), the more mixed the alkali metal atoms are. If the value of formula (A) is 0.75 or less, the dielectric loss tangent at 20°C and 10GHz is a good value.

[0070] The values ​​of formula (A) are preferably in the following order: 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.

[0071] On the other hand, if the value of formula (A) is too small, the proportion of Li2O in the glass will decrease, making it difficult for Li2SiO3 crystals to precipitate. Furthermore, if the value of formula (A) is too small, the etching rate of the glass calculated by formula (1) described later will increase, leading to a deterioration in the selectivity ratio of the etch rate of the exposed / unexposed portion. Therefore, the value of formula (A) is 0.50 or higher, and preferably in the following order: 0.51 or higher, 0.52 or higher, 0.53 or higher, 0.54 or higher, 0.55 or higher, and 0.56 or higher.

[0072] Furthermore, the photosensitive glass of this embodiment, by containing a variety of alkali metal atoms as described above, utilizes the alkali mixing effect to achieve excellent dielectric properties in the high-frequency region, with a dielectric loss tangent of 0.0090° or less at 20°C and 10GHz. Preferably, it is 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.

[0073] The dielectric loss tangent mentioned above was determined using the split dielectric resonator method (SPDR method).

[0074] (composition)

[0075] The glass composition of the photosensitive glass used to implement this embodiment will be described below.

[0076] The composition of the photosensitive glass in one embodiment of the present invention is not particularly limited as long as it satisfies the above formula (A) and the range of dielectric loss tangent. For example, expressed as a mass percentage based on oxides, it preferably contains SiO2: 65-78%, Li2O: 5-15%, and Ag2O: 0.05-1%. Here, SiO2 and Li2O are components constituting Li2SiO3 crystals, and Ag2O is a component forming the crystal nucleus.

[0077] Furthermore, the photosensitive glass of this embodiment, expressed as a mass percentage based on oxides, preferably contains Al2O3: 0-5% (excluding 5%), Na2O: 3-12%, K2O: 3-12%, ZnO: 0.3-8%, Sb2O3: 0.01-1% (excluding 1%), and CeO2: 0.001-0.1%.

[0078] Furthermore, the photosensitive glass of this embodiment, expressed as a mass percentage based on oxides, preferably contains Al2O3: 0-5% (excluding 5%), Na2O: 3-12%, K2O: 3-12%, ZnO: 0-8%, Sb2O3: 0.01-1% (excluding 1%), and CeO2: 0.001-0.1%.

[0079] Al2O3 is a component that improves acid resistance, increases Young's modulus, enhances the phase separation properties of glass, and reduces the coefficient of thermal expansion.

[0080] Na2O and K2O are components that exhibit the alkali mixing effect by being mixed with Li2O, resulting in a lower dielectric loss tangent.

[0081] ZnO is a component that increases the solubility of Ag2O.

[0082] Sb₂O₃ is a thermally reducing component, which is responsible for the reduction of metal ions during heat treatment.

[0083] CeO2 is an optical sensitizer, a component that allows materials sensitive only to high-energy rays such as X-rays to be exposed to ultraviolet light.

[0084] The following is a detailed description of each ingredient.

[0085] SiO2 is the component used to form Li2SiO3 crystals as a crystalline phase and to precipitate them. In the photosensitive glass of this embodiment, the SiO2 content is preferably 65% ​​or more. By ensuring that the SiO2 content is 65% or more, it is easier to stabilize the precipitated crystalline phase of the crystallized glass.

[0086] The SiO2 content is more preferably 67% or more, further 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.

[0087] Furthermore, in the photosensitive glass of this embodiment, the SiO2 content is preferably 78% or less. If the SiO2 content is 78% or less, the glass raw material is easy to melt and form. If the SiO2 content is too high, Li2Si2O5 crystals, which are other crystals, are easily precipitated and are not as easy to remove by etching as Li2SiO3 crystals, so this is not preferred. In addition, the heat treatment conditions are also an important factor in order to precipitate Li2SiO3 crystals as a crystalline phase, but by keeping the SiO2 content below the above-mentioned upper limit, a wider range of heat treatment conditions can be selected.

[0088] The SiO2 content is more preferably 76% or less, further preferably 75% or less, even more preferably 74% or less, particularly preferably 73.5% or less, and most preferably 73% or less.

[0089] Li2O is used to form and precipitate Li2SiO3 crystals. Furthermore, the photosensitive glass of this embodiment achieves a lower dielectric loss tangent at 10 GHz through an alkali mixing effect based on the mixing of various alkali metal atoms such as Na2O and K2O in addition to Li2O.

[0090] Furthermore, the photosensitive glass of this embodiment can reduce its conductivity through the aforementioned alkali mixing effect. For example, when wiring such as copper is laid on a glass substrate, the insulation between the substrate and the wiring is important, and the reduction in conductivity based on the alkali mixing effect can help improve the insulation of the glass substrate.

[0091] Specifically, in this embodiment, the photosensitive glass, together with Na2O and K2O described later, has its Li2O content adjusted so that the value of the following formula (A) is 0.50 to 0.75.

[0092] [Li2O] / ([Li2O]+[Na2O]+[K2O]) Formula (A)

[0093] (In formula (A), [Li2O], [Na2O] and [K2O] represent the contents of Li2O, Na2O and K2O in the above-mentioned photosensitive glass, expressed as molar percentages based on oxides, respectively.)

[0094] In the photosensitive glass of this embodiment, the content of Li₂O (expressed as a mass percentage based on oxides) is preferably 5% or more. If the content of Li₂O is 5% or more, the desired crystals are easily obtained, and the precipitated crystalline phase is easily stabilized.

[0095] The Li2O content is preferably 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.

[0096] On the other hand, if the Li₂O content is too high, the effect of the alkali mixing will be smaller. Therefore, the Li₂O content (expressed as a mass percentage based on oxides) is preferably 15% or less. If the Li₂O content is 15% or less, the desired crystals are easily obtained, and the precipitated crystalline phase is easily stabilized.

[0097] The Li2O content is preferably in the following order: less than 13%, less than 12%, less than 11.5%, less than 11%, less than 10.5%, less than 10%, less than 9.8%, less than 9.6%, less than 9.4%, less than 9.2%, less than 9.0%, less than 8.8%, less than 8.6%, less than 8.4%, less than 8.2%, and less than 8.0%.

[0098] In the photosensitive glass of this embodiment, the Na2O content (expressed as a mass percentage based on oxides) is preferably 3% or more. If the Na2O content is 3% or more, a good alkali mixing effect is obtained, which can reduce the dielectric loss tangent by 10 GHz.

[0099] The Na2O content is more preferably 3.1% or more, further preferably 3.2% or more, even 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.

[0100] Furthermore, the Na₂O content (expressed as a mass percentage based on oxides) is preferably 12% or less. Excessive Na₂O increases the likelihood of Na substitution at Li sites in the Li₂SiO₃ crystal. As a result, it is predicted that Li₂SiO₃ crystals will become less prone to precipitation.

[0101] The Na2O content is more preferably 11.8% or less, further 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.

[0102] In the photosensitive glass of this embodiment, the K2O content (expressed as a mass percentage based on oxides) is preferably 3% or more. If the K2O content is 3% or more, a good alkali mixing effect can be obtained, and the dielectric loss tangent at 20°C and 10GHz can be reduced. Furthermore, the tendency for devitrification during glass manufacturing can be reduced.

[0103] The K2O content is more preferably 3.1% or more, further preferably 3.2% or more, even 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.

[0104] Furthermore, the K₂O content (expressed as a mass percentage based on oxides) is preferably 12% or less. If the K₂O content is 12% or less, the increase in the etching rate of the glass portion can be suppressed, and the decrease in the etching rate selectivity ratio of the exposed / unexposed portion can be suppressed. As a result, selective HF etching can be performed, and the desired micro-processing can be achieved. However, when the amount of K₂O is excessive, the possibility of K replacing Li sites in the Li₂SiO₃ crystal increases. As a result, it is predicted that the Li₂SiO₃ crystal becomes less likely to precipitate.

[0105] The K2O content is more preferably 11.8% or less, further 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.

[0106] Al2O3 is a component that improves acid resistance, increases Young's modulus, enhances the phase separation properties of glass, and reduces the coefficient of thermal expansion. In this embodiment, when the photosensitive glass contains Al2O3, the Al2O3 content is more preferably 0.2% or more, further preferably 0.4% or more, even 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.

[0107] On the other hand, Al2O3 may worsen the dielectric loss tangent in the high-frequency region. If the Al2O3 content is less than 5%, the dielectric loss tangent in the high-frequency region 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.

[0108] The photosensitive glass of this embodiment contains a photosensitizer component. The photosensitizer component is a component that selectively crystallizes the exposed portion, generating crystal nuclei that serve as the starting point for crystal growth. In other words, by containing the photosensitizer component, the glass can be selectively removed. Examples of photosensitizer components include, for instance, Ag. + Au + Cu + Among these, Ag is preferred due to its lack of absorption in the visible light region, its easy solubility in glass (high solubility), and its low raw material cost. + .

[0109] Ag₂O functions as a photosensitizer component as described above. The inventors discovered that the higher the silver content in the glass, the lower the exposure sensitivity resulting in the formation of silver colloids. At first glance, it seems that higher exposure sensitivity is always better, but excessively high exposure sensitivity can lead to problems such as unwanted components reacting during exposure and forming silver colloids. In other words, a specific amount of silver is needed to reduce exposure sensitivity.

[0110] In addition, Ag₂O is also a component that serves as a nucleation source for crystals. A higher concentration of nucleation sources in the glass results in a finer crystal arrangement due to the greater number of finely distributed nuclei compared to the smaller number of nuclei in the same glass volume. Consequently, the formed crystals are smaller and are etched at grain boundaries more quickly.

[0111] If the Ag₂O content is low, there is a tendency for the Li₂SiO₃ crystals to become larger. As a result, the predicted surface condition after etching becomes rougher. If the sample surface is rough, it will cause problems in the packaging process when used as a substrate.

[0112] For the reasons stated above, the Ag₂O content in the photosensitive glass of this embodiment is preferably 0.05% or more. The Ag₂O content is preferably 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.

[0113] On the other hand, the Ag₂O content is preferably 1% or less. If the Ag₂O content is 1% or less, the melting residue of Ag₂O in the glass can be suppressed. Furthermore, due to the adverse effects of introducing Ag₂O at high concentrations on melting equipment and the high cost of Ag₂O itself as a raw material, it is not preferable to have an excessive Ag₂O content. In addition, the formation of silver colloid is not only determined by the amount of Ag₂O but is also affected by other components; therefore, arbitrarily increasing the amount of Ag₂O is meaningless.

[0114] The content of Ag2O is preferably below 0.90%, below 0.80%, below 0.70%, below 0.60%, below 0.55%, below 0.50%, below 0.45%, below 0.40%, below 0.35%, and below 0.30%.

[0115] CeO2 acts as an optical sensitizer, enabling materials sensitive only to high-energy rays such as X-rays to be exposed to ultraviolet light. Furthermore, in the photosensitive glass of this embodiment, CeO2 absorbs ultraviolet light and releases electrons towards Ag. + The role of ion supply.

[0116] In the photosensitive glass of this embodiment, the CeO2 content is preferably 0.001% or more. If the CeO2 content is 0.001% or more, Ag can be stably expressed upon exposure. + The reducing effect of ions.

[0117] The content of CeO2 is more preferably 0.004% or more, further 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.

[0118] On the other hand, the CeO2 content is preferably 0.1% or less. If it is 0.1% or less, the sensitivity to exposure will not become too high, which can avoid problems such as exposing unwanted parts and can control the microprocessability.

[0119] The CeO2 content is more preferably 0.09% or less, further 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.

[0120] Sb₂O₃ is a thermally reducing component that reduces metal ions during heat treatment. In the photosensitive glass of this embodiment, it serves to reduce Ag in high-temperature regions. + The role of ions.

[0121] In the photosensitive glass of this embodiment, the content of Sb₂O₃ is preferably 0.01% or more. If the content of Sb₂O₃ is 0.01% or more, the reduction of metal ions during heat treatment can be stably achieved.

[0122] The content of Sb2O3 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.

[0123] On the other hand, the coloring rate of glass varies greatly depending on the Sb₂O₃ content; therefore, if the concentration is too high, the glass color will darken, which is undesirable. Furthermore, Sb₂O₃ is designated as a "Class 2 controlled substance" and a "specially controlled substance" under the Specific Chemical Substances Hazard Prevention Regulations (Special Chemicals Regulations). According to Article 2.2 of the Specific Chemical Substances Hazard Prevention Regulations (Special Chemicals Regulations), substances with an Sb₂O₃ content exceeding 1% are themselves restricted as Specific Chemical Substances. Therefore, the Sb₂O₃ content is preferably less than 1%.

[0124] The content of Sb2O3 is more preferably 0.9% or less, further 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.

[0125] When it is desired to improve the thermal expansion coefficient of glass, it is not necessarily necessary to contain ZnO. On the other hand, ZnO increases the solubility of Ag₂O. In addition, ZnO sometimes exhibits effects such as improving chemical durability and suppressing the undesirable reduction of silver. Therefore, in the photosensitive glass of this embodiment, the ZnO content is preferably 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.

[0126] On the other hand, if the ZnO content is high, the crystallization tendency is significantly reduced than expected. Therefore, the ZnO content is preferably 8% or less. More preferably, the ZnO content is 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.

[0127] Furthermore, the photosensitive glass of this embodiment may contain B2O3. B2O3 is a component that improves dielectric properties such as relative permittivity and dielectric loss tangent in the high-frequency region, and enhances solubility. It also functions as a nucleating agent.

[0128] When the photosensitive glass of this embodiment contains B2O3, the content of B2O3 is more preferably 0.1% or more, further preferably 0.2% or more, even more preferably 0.3% or more, particularly preferably 0.4% or more, and most preferably 0.5% or more.

[0129] On the other hand, if the B2O3 content is too high, it will cause problems such as deterioration of the chemical durability of the glass and difficulty in the precipitation of Li2SiO3 crystals. Therefore, the B2O3 content is preferably 8% or less, and preferably in the following order: 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, and 2% or less.

[0130] Other components may be included within a range that does not impair performance. Examples of such other components include 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.

[0131] Their content is preferably less than 5%, more preferably less than 4%, further preferably less than 3%, even more preferably less than 2%, particularly preferably less than 1%, more preferably less than 0.5%, and most preferably less than 0.1%.

[0132] (physical properties)

[0133] The photosensitive glass of this embodiment contains various alkali metal atoms as described above, thus exhibiting excellent dielectric properties in the high-frequency region due to the alkali mixing effect. Furthermore, the excellent dielectric properties in the high-frequency region are achieved by maintaining the Al₂O₃ content within a specified range. It is believed that in the photosensitive glass of this embodiment, if the dielectric loss tangent at 20°C and 10 GHz is within the aforementioned preferred range, then the dielectric properties are also excellent relative to frequency bands higher than 10 GHz.

[0134] As described above, from the viewpoint of improving dielectric properties, the dielectric loss tangent of the photosensitive glass of this embodiment at 20°C and 10GHz is 0.0090° or less. Preferably, it is 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. The lower limit is not particularly limited, but for example, it is preferably 0.0005° or more.

[0135] From the viewpoint of improving dielectric properties, the relative permittivity of the photosensitive glass in this embodiment at 20°C and 10GHz is preferably 7.5 or less, more preferably 7.4 or less, even more preferably 7.3 or less, even more preferably 7.2 or less, particularly preferably 7.1 or less, and most preferably 7.0 or less. The lower limit is not particularly limited; for example, 3 or more is preferred.

[0136] The dielectric loss tangent and relative permittivity mentioned above were determined using the split dielectric resonator method (SPDR method).

[0137] In the photosensitive glass of this embodiment, from the viewpoint of improving microprocessability, the glass etching rate is preferably 2.75 or less, more preferably 2.70 or less, further preferably 2.65 or less, even more preferably 2.60 or less, further 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. If the glass etching rate is too high, the glass portion will be cut beyond the desired depth during etching, making it difficult to control microprocessability. The lower limit is not particularly limited, but for example, 0.1 or more is preferred.

[0138] The glass etching rate is calculated as follows. A glass sample with a length of 30 mm × width of 20 mm and a thickness of 0.5 mmt is immersed in 55 ml of an etching solution containing HF: 5% by mass and HNO3: 0.7% by mass at 40°C for 4 minutes. The value obtained by the following formula (1) is the glass etching rate.

[0139]

[0140] Furthermore, in the photosensitive glass of this embodiment, the etching rate selection ratio of the exposed portion / unexposed portion, expressed by the following formula (2), is preferably a larger value. The etching rate selection ratio of the exposed portion / unexposed portion is calculated based on the following formula (2) by separately determining the etching rate (etching rate of the exposed portion) when etching the glass after exposure and heat treatment and the etching rate (etching rate of the unexposed portion) when etching the glass without exposure and heat treatment.

[0141] It should be noted that the etching rate of the unexposed portion (=glass portion) in the following formula (2) has the same meaning as the etching rate of the glass portion described above. The calculation method for the etching rate of the exposed portion will be described later.

[0142]

[0143] The etching rate of the exposed section in the above formula (2) is calculated by etching the glass sample with a length of 30 mm × width of 20 mm and a thickness of 0.5 mm after exposure treatment and heat treatment, and then by the above formula (1). The specific processing conditions are shown below.

[0144] (i) Exposure processing

[0145] Using an exposure device (e.g., the MA-1200 manufactured by Dai Nippon Research Co., Ltd.), an exposure of 15 J / cm is achieved. 2 The entire flat glass is exposed using this method.

[0146] (ii) Heat treatment

[0147] A two-step heat treatment process is performed. The first step involves heat treatment at 485°C for 5 hours. The conditions for the second step are determined as follows: First, the crystallization peak is confirmed using a differential thermal analysis (DTA) device (e.g., Rigaku Thermoplus TG8120). Heat treatment is then performed within a range of -50°C to 150°C from the temperature at which the crystallization peak is confirmed, for a duration of 1 to 3 hours. At the same time, a glass of the same composition that is not exposed to light is also heat-treated under the same conditions, and the conditions under which no crystal precipitation is confirmed are taken as the heat treatment conditions.

[0148] It should be noted that, for example, a method for confirming the precipitation of the aforementioned crystals is based on microscopic observation. When observing with a microscope using incident illumination, the precipitated crystals will scatter light, making the glassy portion appear darker, while the crystalline portion appears brighter. This difference in brightness allows for confirmation of the presence or absence of crystal precipitation.

[0149] (iii) Etching

[0150] The glass sample was immersed in 55 ml of an etching solution at 40 °C containing 5% HF and 0.7% HNO3 for 4 minutes.

[0151] After the above processing, the value obtained by the above formula (1) will be used as the etching rate of the exposed part.

[0152] If the ratio of the etching rate of the exposed part to the etching rate of the unexposed part (= glass part) calculated by the above method is 3 or more, it is easy to selectively cut only the exposed part by etching, thus improving the micro-machinability.

[0153] The lower limit of the etch rate selection ratio for the exposed / unexposed area is preferably set in the following order: 4 or higher, 5 or higher, 6 or higher, 7 or higher, 8 or higher, 9 or higher, 10 or higher, 11 or higher, 12 or higher, 13 or higher, 14 or higher, 15 or higher, 16 or higher, 17 or higher, 18 or higher, 19 or higher, and 20 or higher. The upper limit of the etch rate selection ratio for the exposed / unexposed area is not particularly limited, but is generally 50 or lower, 45 or lower, and especially 40 or lower.

[0154] Furthermore, the photosensitive glass of this embodiment preferably has an exposure dose of 0.5 J / cm. 2 After exposure and heat treatment at 485℃ for 5 hours, the transmittance at 430nm (converted to 1mmt) is above 4%. This high transmittance indicates a low amount of silver colloid formation in the glass, resulting in less exposure sensitivity. Therefore, by maintaining a transmittance of above 4%, the microstructure can be easily controlled.

[0155] The lower limit of the transmittance is preferably set in the following order: 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 specifically 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, and 90% or less.

[0156] The aforementioned exposure was performed, for example, using the MultiLight ML-251D / B (manufactured by Ushio Electric Co., Ltd.) exposure apparatus light source unit. Specifically, the ultraviolet intensity was measured by combining the UIT-250 ultraviolet cumulative photometer and the UVH-S313 photodetector, the time required to reach the desired exposure level was calculated, and the ultraviolet light was irradiated using the aforementioned exposure apparatus for that time.

[0157] In addition, the transmittance at 430nm (converted to 1mmt) can be obtained, for example, using a spectrophotometer V-570 (manufactured by Japan Spectrophotometer Co., Ltd., with a wavelength range of 200-800nm) by the following formula (3).

[0158]

[0159] T′: Transmittance (converted value per mmt), T: Measured transmittance, ρ: Reflectance, L: Glass thickness (mmt)

[0160] Furthermore, the photosensitive glass in this embodiment is preferably suitable for exposure amounts of 1 to 10 J / cm. 2 The transmittance (converted to 1 mmt) at 430 nm was measured after exposure and heat treatment at 485°C for 5 hours. The exposure amount was used as the horizontal axis (J / cm). 2 When plotting the above transmittance as the vertical axis (%) on a coordinate plane, the transmittance at 430 nm (converted to 1 mmt) obtained by the following formula (4) is relative to the exposure amount of 1-10 J / cm. 2 The slope is below -0.12.

[0161]

[0162] X: Exposure (J / cm²) 2 Transmittance at Y: 430nm (converted to 1mmt)

[0163] In the above formula (4), the exposure amount is 1 to 10 J / cm. 2 The range refers to the transmittance at 430nm (converted to 1mmt).

[0164] It should be noted that the methods for measuring exposure and transmittance are derived using the methods described above.

[0165] This slope refers to the change in transmittance relative to the change in exposure. Consequently, a large slope indicates that the formation of silver colloids is related to 1–10 J / cm². 2 This corresponds to an increase in exposure. Therefore, by using a slope below -0.12, it is possible to control the fine structure by adjusting the exposure.

[0166] The slope described above 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. Furthermore, if the slope is too small, it will affect the accuracy of the slope relative to 1-10 J / cm². 2 Increasing the exposure level leads to the rapid formation of silver colloids, making it difficult to control the fine structure. Therefore, the slope is preferably -10 or higher, more preferably -9 or higher, and even more preferably -8 or higher.

[0167] (shape)

[0168] The shape of the photosensitive glass in this embodiment is not particularly limited, and it can be formed into various shapes depending on the purpose and application. For example, the photosensitive glass in this embodiment can be a plate with two opposing main surfaces, or it can be a shape other than a plate, depending on the product or application. More specifically, the photosensitive glass in this embodiment can be, for example, a flat glass plate without bending, or it can be a curved glass plate with a curved surface. The shape of the main surfaces is also not particularly limited, and it can be formed into various shapes such as circles and quadrilaterals.

[0169] <Manufacturing Method of Photosensitive Glass>

[0170] Next, a method for manufacturing the photosensitive glass according to this embodiment (hereinafter also referred to as this manufacturing method) will be described. Hereinafter, a method for manufacturing sheet-shaped glass will be described, but the shape of the glass can be appropriately adjusted according to the purpose.

[0171] In this process, amorphous glass is produced by melting and shaping raw materials formulated to the desired glass composition. The melting and shaping method is not particularly limited; for example, the glass raw materials are placed in a platinum crucible and then placed in an electric furnace at 1350°C to melt the raw materials. Then, the furnace temperature is raised to 1450°C for degassing and homogenization. The initial melting temperature of 1350°C is to allow silver chloride, used as a raw material for Ag₂O, to decompose and dissolve into the glass. If the temperature is too low, silver chloride will not decompose or dissolve into the glass. On the other hand, if the temperature is too high, the thermal decomposition rate of silver chloride is too fast, making it difficult for it to dissolve into the glass.

[0172] Therefore, as described above, firstly, the raw material is melted at 1350°C and then heated to 1450°C. The resulting molten glass is poured into a metal mold (e.g., a SUS plate) at room temperature, and after being held at the glass transition point for approximately 1 to 2 hours, it is cooled to room temperature to obtain an amorphous glass block. Furthermore, the obtained glass block is processed as needed, such as cutting, grinding, and polishing, to form a desired shape.

[0173] In this way, amorphous glass can be molded from a molten state into the desired shape. Therefore, compared with processes such as ceramics, which use powder or slurry to form and calcine, and processes such as synthetic quartz, which cut ingots into the desired shape after manufacturing, it has advantages in terms of ease of forming, ease of large-area production, and affordability of manufacturing.

[0174] <Methods for manufacturing glass with fine structures>

[0175] As one embodiment of the present invention, a method for manufacturing glass with a microstructure includes a step of selective microfabrication based on photostructuring of the photosensitive glass of this embodiment. This microfabrication method includes exposure, heat treatment, and etching steps. That is, it includes: (1) an exposure step of the photosensitive glass; (2) a heat treatment step of the exposed photosensitive glass to precipitate Li2SiO3 crystals; and (3) an etching step to remove the precipitated Li2SiO3 crystals. It should be noted that other steps may also be included.

[0176] (1) The process of exposing the photosensitive glass.

[0177] The following is an illustrative description of the process of exposing photosensitive glass.

[0178] First, the photosensitive glass is processed to the desired dimensions. Grinding can be performed when high precision is required.

[0179] Next, an optical mask with a finely patterned design is prepared and superimposed on glass, then irradiated with ultraviolet light. As the optical mask, a mask commonly used in ultraviolet lithography can be used. Exposure conditions, for example, are 0.1–25 J / cm². 2 The energy density is determined by irradiating ultraviolet light with wavelengths of 200–380 nm at any energy density within the range specified in the UV illuminometer. The energy density is calculated using a wavelength-sensitive UV illuminometer. Measurements are taken by irradiating the light-receiving part of the illuminometer with ultraviolet light passing through a bandpass optical filter that transmits a specific wavelength range (e.g., 300–320 nm).

[0180] (2) The process of heat-treating the exposed photosensitive glass to precipitate Li2SiO3 crystals.

[0181] Next, the photosensitive glass exposed in (1) above is subjected to heat treatment to precipitate Li2SiO3 crystals. This process preferably includes two heat treatment steps. The purpose of the first heat treatment is to colloidalize the metallic silver in the glass, generating silver colloids that serve as crystal nuclei for crystallization. The purpose of the second heat treatment is to precipitate Li2SiO3 crystals.

[0182] In one aspect of the present invention, the temperature range of the first heat treatment, i.e., the first temperature region, is preferably a temperature region where the rate of crystal nucleation in the glass composition increases. Specifically, the first temperature region 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 region is preferably 500°C or lower, more preferably 495°C or lower.

[0183] In another aspect of the present invention, the temperature range of the first heat treatment, i.e., the first temperature region, is preferably a temperature region where the rate of crystal nucleation in the glass composition increases. To promote crystal nucleation, the temperature region can be set to a higher temperature. Specifically, the first temperature region is preferably 400°C or higher, and in the following preferred order: 410°C or higher, 420°C or higher, and 430°C or higher. Furthermore, the first temperature region is preferably 600°C or lower, and in the following preferred order: 590°C or lower, 580°C or lower, 570°C or lower, 560°C or lower, and 550°C or lower.

[0184] In one aspect of the present invention, the holding time within the first temperature region is preferably in the following order: 15 minutes or more, 30 minutes or more, 45 minutes or more, 1 hour or more, 1 hour and 15 minutes or more, 1 hour and 30 minutes or more, 1 hour and 45 minutes or more, 2 hours or more, 2 hours and 15 minutes or more, 2 hours and 30 minutes or more, 2 hours and 45 minutes or more, 3 hours or more, 3 hours and 15 minutes or more, 3 hours and 30 minutes or more, 3 hours and 45 minutes or more, and 4 hours or more. If the holding time is within the above range, crystal nucleation can easily and sufficiently occur. On the other hand, from a manufacturing point of view, the holding time within the first temperature region is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0185] In another aspect of the present invention, the holding time within the first temperature region is preferably in the following order: 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 and 15 minutes or more, 1 hour and 30 minutes or more, 1 hour and 45 minutes or more, 2 hours or more, 2 hours and 15 minutes or more, 2 hours and 30 minutes or more, 2 hours and 45 minutes or more, 3 hours or more, 3 hours and 15 minutes or more, 3 hours and 30 minutes or more, 3 hours and 45 minutes or more, and 4 hours or more. If the holding time is within the above range, crystal nucleation can easily and sufficiently occur. On the other hand, from a manufacturing point of view, the holding time within the first temperature region is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0186] In one aspect of the present invention, the second temperature region is preferably a temperature region where the crystal growth rate of the Li2SiO3 crystal increases. Specifically, the second temperature region is preferably 500°C or higher, more preferably 505°C or higher, and even more preferably 510°C or higher. If the heat treatment temperature is increased, the crystal becomes easier to grow, thus shortening the heat treatment time; however, on the other hand, the transmittance of the unexposed portion becomes more likely to decrease. Therefore, the second temperature region is preferably 700°C or lower, 690°C or lower, 680°C or lower, 670°C or lower, 660°C or lower, and 650°C or lower in that order.

[0187] In another embodiment of the present invention, the second temperature region is preferably a temperature region where the crystal growth rate of the Li2SiO3 crystal increases. Specifically, the second temperature region is preferably 5°C or higher than the first temperature region, and preferably in the following order: 10°C or higher, 20°C or higher, 30°C or higher, 40°C or higher, and 50°C or higher. If the temperature region is increased, the crystal becomes easier to grow, thus shortening the heat treatment time; however, on the other hand, the transmittance of the unexposed portion becomes more likely to decrease. Therefore, the second temperature region is preferably 300°C or lower than the first temperature region, and preferably in the following order: 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.

[0188] In one aspect of the present invention, the holding time in the second temperature region is preferably in the following order: 15 minutes or more, 30 minutes or more, 45 minutes or more, 1 hour or more, 1 hour and 15 minutes or more, 1 hour and 30 minutes or more, 1 hour and 45 minutes or more, 2 hours or more, 2 hours and 15 minutes or more, 2 hours and 30 minutes or more, 2 hours and 45 minutes or more, and 3 hours or more. If the holding time is within the above range, crystal growth can easily and sufficiently proceed. On the other hand, from a manufacturability point of view, the holding time is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0189] In another aspect of the present invention, the holding time in the second temperature region is preferably in the following order: 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 and 15 minutes or more, 1 hour and 30 minutes or more, 1 hour and 45 minutes or more, 2 hours or more, 2 hours and 15 minutes or more, 2 hours and 30 minutes or more, 2 hours and 45 minutes or more, and 3 hours or more. If the holding time is within the above range, crystal growth can easily and sufficiently proceed. On the other hand, from a manufacturability point of view, the holding time is preferably 15 hours or less, more preferably 14 hours or less, and particularly preferably 13 hours or less.

[0190] There is no particular limitation on the heating rate during heat treatment, but it is generally 5°C / min or higher, more preferably 15°C / min or higher, and even more preferably 30°C / min or higher.

[0191] 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, so that cracks caused by the difference in expansion rates between the glass phase and the crystalline phase generated during heating are suppressed.

[0192] 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. This suppresses cracks caused by warping of the crystallized glass during cooling and the difference in expansion rates between the amorphous and crystalline phases. 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.

[0193] (3) Process of removing precipitated Li2SiO3 crystals by etching.

[0194] Next, the glass body is structured by removing the precipitated Li₂SiO₃ crystals through etching. The etching process is preferably performed in an etching solution containing HF. If the concentration of HF in the etching solution is too low, the etching of the Li₂SiO₃ crystals is difficult. Therefore, the preferred HF concentration in the solution is 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.

[0195] On the other hand, if the concentration of HF in the etching solution is too high, not only the crystal portion but also the glass portion will be etched. Therefore, the HF concentration in the solution is preferably in the following order: 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.

[0196] In addition to HF, the etching solution may also contain HCl and HNO3. This increases the acidity of the etching solution, making it easier to dissolve residues generated during etching, thus facilitating the more stable realization of fine structures. The concentration of HCl or HNO3 is generally preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and particularly preferably 0.3% by mass or more. On the other hand, the concentration of HCl or HNO3 is preferably 5% by mass or less, more preferably 4% by mass or less, and particularly preferably 3% by mass or less.

[0197] <Circuit Board>

[0198] The circuit board of this embodiment includes an insulating substrate (hereinafter also referred to as a glass substrate) comprising the above-mentioned photosensitive glass or glass on which a fine structure is formed.

[0199] Figure 1 An example of the structure of the circuit board of this embodiment is shown. Figure 1 The circuit board 1 shown 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 constitutes a signal wiring, and the second wiring layer 4 constitutes a ground line.

[0200] However, the structures of the first wiring layer 3 and the second wiring layer 4 are not limited to the above-described cases. The wiring layers may be formed only on one main surface of the glass substrate 2, or they may be formed inside the glass substrate 2 instead of on its main surface. Furthermore, the circuit board of this embodiment may also include… Figure 1 Other components not shown (passive devices, active devices, circuit components, etc.).

[0201] Thus, the circuit board of this embodiment may also be a circuit board comprising a glass substrate and a wiring layer formed inside the glass substrate or on at least one main surface.

[0202] <Uses>

[0203] Considering the good dielectric properties and excellent microfabrication in the high-frequency region, the above-mentioned circuit board is preferably used in high-frequency equipment.

[0204] As shown above, this can be a high-frequency device with a transmission line. In addition to the microstrip line previously shown, other examples of transmission lines include striplines, coplanar lines, slot lines, waveguides, substrate integrated waveguides (SIW), and waveguides.

[0205] Waveguides are hollow structures. Figure 2 The diagram shows a schematic representation of an example of a waveguide. Figure 2 The waveguide 10 shown has a glass substrate 11 and a hollow portion 12 inside it. The waveguide 10, as a structure, has its internal walls covered with metal for transmitting electromagnetic waves. In this case, the interior is hollow, meaning the dielectric material, which causes dielectric loss, is air, resulting in low loss, thus enabling high-power transmission.

[0206] Furthermore, by applying appropriate design to the circuit board of this embodiment, the transmission line (wiring) function can also include passive device functions such as filters, antennas, demultiplexers, and duplexers. For example, in the form of filters, which are one type of high-frequency device, configurations utilizing waveguides, SIW (Self-Insulated Wave) systems, and microstrip lines are known. In addition, configurations that apply microstrip lines to antenna applications are also known.

[0207] As for other applications, since the circuit board of this embodiment can be microfabricated, it can also be used in microfluidic devices. Microfluidic devices refer to a general term for devices that fabricate micro-flow paths and reaction vessels and are applied in biological research and chemical engineering. A specific example is a biomimetic chip. A biomimetic chip is a technology that can reproduce biological systems that are difficult to achieve in traditional experimental systems by forming micro-flow paths on a chip that simulates human organs. The circuit board of this embodiment can also be applied to the biological field or other fields as described above.

[0208] Example

[0209] The following describes the embodiments, but the present invention is not limited to these embodiments.

[0210] Experimental Example 1: Dielectric Properties and Processability of Photosensitive Glass

[0211] Hereinafter, 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 composition of glasses 1 to 26 in molar percentage based on oxides. Tables 5 to 8 show the glass composition of glasses 1 to 26 in mass percentage based on oxides.

[0212] <The Production of Photosensitive Glass>

[0213] The glass raw materials were prepared according to the composition shown in Tables 1-4 as indicated by the molar percentage of oxides, and weighed to approximately 400g of glass. Next, the mixed raw materials were placed in a platinum crucible and stirred in an electric furnace at 1350°C for about 1 hour. Then, the temperature was raised to 1450°C, and the mixture was stirred again for about 4 hours, followed by standing for about 2 hours to degas and homogenize. The resulting molten glass was then 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.

[0214] The physical properties of the obtained glass are shown in Tables 1 to 4. It should be noted that blank columns “-” in Tables 1 to 4 indicate that the physical property was not measured.

[0215] <Exposure, heat treatment and etching of photosensitive glass>

[0216] For glass 1 and 6, exposure, heat treatment and etching were performed, and processability was studied.

[0217] [exposure]

[0218] First, the obtained glass was processed into a flat plate (30mm x 20mm, 0.5mm thick), and the surface was mirror-polished to create a sample. Then, the sample was exposed using an exposure device (manufactured by Dai Nippon Research Co., Ltd., product name "MA-1200"). In this study, a method of exposing the entire flat glass plate was used. The exposure amounts are shown in Table 9 below.

[0219] [Heat Treatment]

[0220] For the exposed glass 1 and 6 Figure 3 The temperature change shown indicates that heat treatment was used to crystallize it. Figure 3 This is a diagram schematically illustrating the temperature changes during the two-step heat treatment process. Specifically, Figure 3 The following information is shown: In the heat treatment, the amorphous glass is heated to temperature T1 and held for a certain time, then heated to temperature T2 and held for a certain time, and then cooled down. Figure 3 The specific temperature and other conditions for heat treatment are shown in Table 9 below.

[0221] The presence or absence of Li2SiO3 crystals was confirmed by microscopic observation, XRD measurement, and transmission spectroscopy of heat-treated glass 1 and 6.

[0222] During microscopic observation, if incident illumination is used, the precipitated crystals scatter light, making the glassy portion appear darker, while the crystalline portion appears brighter. The presence or absence of precipitated crystals can be determined by observing the difference in brightness.

[0223] During XRD analysis, it is necessary to confirm whether peaks of Li2SiO3 crystals are present.

[0224] Furthermore, in the case of crystal precipitation, a decrease in overall transmittance in the near-ultraviolet to near-infrared range was observed in the transmission spectrum. The precipitation of Li₂SiO₃ crystals in glasses 1 and 6 was confirmed using the above methods.

[0225] [Etching]

[0226] The glass with Li2SiO3 crystals obtained by the above method was subjected to an etching test (immersed in 55 ml of etching solution at 40 °C containing HF: 5 wt% and HNO3: 0.7 wt% for 4 minutes).

[0227] The methods for determining each property are shown below.

[0228] (XRD measurement)

[0229] Sample preparation conditions for XRD determination

[0230] The heat-treated crystallized glass plate was cut into 10mm x 10mm length and 0.5mm thickness to obtain the sample for XRD determination.

[0231] XRD measurement conditions

[0232] X-ray diffraction was performed under the following conditions to identify the precipitated crystals. Crystal types were identified using diffraction peak patterns from the ICSD Inorganic Crystal Structure Database and the ICDD Powder Diffraction Database.

[0233] Measurement apparatus: SmartLab manufactured by Rigaku Corporation

[0234] Measurement method: Centralized tube voltage: 45kV

[0235] Tube current: 200mA X-ray used: CuKα rays

[0236] Measurement range: 2θ = 10°~80°

[0237] Speed: 10° / minute

[0238] Step size: 0.02°

[0239] (Relative permittivity: Dk, dielectric loss tangent: Df)

[0240] The relative permittivity and dielectric loss tangent at 10 GHz were determined using a circuit network analyzer and the split dielectric resonator method (SPDR). The measurement temperature was 20 °C.

[0241] (Etching rate of glass section)

[0242] The glass was processed into a flat plate (30mm x 20mm, 0.5mm thick), and the surface was mirror-polished to form a sample. The sample was cleaned and dried, and after weighing, an etching test was performed (immersed in 55ml of an etching solution containing 5% HF and 0.7% HNO3 at 40°C for 4 minutes). After the test, the sample was cleaned and dried again, and the weight was measured. The etching rate of the glass part (unexposed part) was calculated using the following formula (1).

[0243]

[0244] (Etching rate selection ratio for exposed / unexposed areas)

[0245] Regarding glass 1 and 6, the etching rates (etching rate of the exposed part) when etching is performed after exposure and heat treatment, and the etching rates (etching rate of the unexposed part) when etching is performed without exposure and heat treatment, are calculated respectively. The selection ratio of the etching rate of the exposed part / unexposed part is calculated based on the following formula (2). Here, the etching rate of the unexposed part has the same meaning as the etching rate of the glass part. The calculation method of the etching rate of the exposed part will be described later.

[0246]

[0247] The etching rate of the exposed section in the above formula (2) is calculated by etching the glass sample with a length of 30mm × width of 20mm and a thickness of 0.5mm after exposure treatment and heat treatment, and then by the above formula (1). The specific treatment conditions are as follows.

[0248] (i) Exposure processing

[0249] An exposure device (manufactured by Dai Nippon Research Co., Ltd., product name "MA-1200") was used to achieve an exposure of 15 J / cm. 2 The entire flat glass is exposed using this method.

[0250] (ii) Heat treatment

[0251] A two-step heat treatment was performed. The first step involved heat treatment at 485°C for 5 hours. The conditions for the second step were determined using the following method. First, the crystallization peak was confirmed using a DTA apparatus (Thermoplus TG8120, Rigaku Corporation). The heat treatment was performed at a temperature between -150°C and -100°C for 1 or 3 hours, relative to the temperature at which the crystallization peak was confirmed. During this process, the same treatment was performed on unexposed glass of the same composition to confirm that no crystals had precipitated. It should be noted that the method for confirming crystal precipitation was based on microscopic observation. When observed under a microscope using epi-irradiation, the precipitated crystals scatter light, making the glass portion appear darker, while the crystalline portion appears brighter. The presence or absence of crystal precipitation was confirmed by observing the brightness of the precipitated crystals.

[0252] (iii) Etching

[0253] The glass sample was immersed in 55 ml of an etching solution at 40 °C containing 5% HF and 0.7% HNO3 for 4 minutes.

[0254] After the above processing, the value obtained by the above formula (1) will be used as the etching rate of the exposed part.

[0255] (density)

[0256] The density of a glass block of about 20g without air bubbles was determined using the Archimedes method.

[0257] (Tg)

[0258] The determination was performed using the thermal expansion method as specified in JIS R3103-3 (2001).

[0259] (Average coefficient of thermal expansion)

[0260] The measurements were performed using a differential thermal dilatometer, following the method specified in JIS R3102 (1995). The measurement temperature range was 50–350 °C, and the units were expressed as ×10⁻¹⁰. －7 / ℃.

[0261] [Table 1]

[0262]

[0263] In the table, formula (A) has the following meanings. [Li₂O], [Na₂O], and [K₂O] represent the concentrations of each component as molar percentages.

[0264] Formula (A):

[0265] [Table 2]

[0266]

[0267] [Table 3]

[0268]

[0269] [Table 4]

[0270]

[0271] [Table 5]

[0272] mass% Glass 1 Glass 2 Glass 3 Glass 4 Glass 5 Glass 6 Glass 7 <![CDATA[SiO2]]> 70.6 71.7 72.1 71.1 72.7 716 72.5 <![CDATA[Al2O3]]> 3.2 3.3 3.2 3.2 3.2 3.2 3.3 <![CDATA[B2O3]]> 0.7 0.7 0.7 0.7 0.7 0.7 0.7 <![CDATA[Li2O]]> 8.4 8.6 8.1 9.0 8.7 9.5 9.6 <![CDATA[Na2O]]> 5.8 9.2 5.6 5.3 5.1 4.9 7.2 <![CDATA[K2O]]> 8.9 4.1 8.5 8.1 7.8 7.5 4.3 ZnO 1.9 2.0 1.2 2.0 1.3 2.0 2.0 <![CDATA[Sb2O3]]> 0.291 0.296 0.291 0.294 0.293 0.296 0.299 <![CDATA[CeO2]]> 0.022 0.022 0.022 0.022 0.022 0.022 0.022 <![CDATA[Ag2O]]> 0.146 0.148 0.146 0.147 0.147 0.148 0.149 total 100 100 100 100 100 100 100

[0273] [Table 6]

[0274] mass% Glass 8 Glass 9 Glass 10 Glass 11 Glass 12 Glass 13 Glass 14 <![CDATA[SiO2]]> 73.2 74.0 72.8 68.7 71.5 73.7 74.0 <![CDATA[Al2O8]]> 3.2 3.3 5.9 6.1 6.0 6.2 2.4 <![CDATA[B2O3]]> 0.7 0.7 0.7 0.8 0.8 0.8 0.8 <![CDATA[Li2O]]> 9.2 9.3 9.6 132 12.4 13.9 11.5 <![CDATA[Na2O]]> 4.7 7.0 1.8 1.8 0.0 1.1 1.8 <![CDATA[K2O]]> 7.2 4.0 6.7 7.0 6.9 1.7 6.9 ZnO 1.3 1.3 2.0 2.0 2.0 2.1 2.0 <![CDATA[Sb2O3]]> 0.295 0.299 0.294 0.303 0.301 0.311 0.303 <![CDATA[CeO2]]> 0.022 0.022 0.022 0.023 0.023 0.023 0.023 <![CDATA[Ag2O]]> 0.148 0.149 0.147 0.152 0.151 0.155 0.152 total 100 100 100 100 100 100 100

[0275] [Table 7]

[0276] mass% Glass 16 Glass 16 Glass 17 Glass 18 Glass 19 Glass 20 Glass 21 <![CDATA[SiO2]]> 71.3 69.4 71.3 71.8 72.0 78.9 74.5 <![CDATA[Al2O3]]> 2.4 5.8 6.0 6.1 4.4 6.1 3.7 <![CDATA[B2O3]]> 0.8 4.3 0.8 0.8 6.0 0.8 0.0 <![CDATA[Li2O]]> 11.5 9.6 11.4 11.5 8.9 11.7 11.3 <![CDATA[Na2O]]> 1.8 1.8 3.2 4.6 1.4 0.0 5.6 <![CDATA[K2O]]> 6.9 6.7 4.8 2.8 5.4 0.0 1.7 ZnO 4.9 2.0 2.0 2.0 1.4 2.0 2.8 <![CDATA[Sb2O3]]> 0.301 0.293 0.301 0.303 0.294 0.306 0.306 <![CDATA[CeO2]]> 0.022 0.022 0.022 0.023 0.022 0.023 0.023 <![CDATA[Ag2O]]> 0.150 0.146 0.150 0.151 0.147 0.153 0.153 total 100 100 100 100 100 100 100

[0277] [Table 8]

[0278] mass% Glass 22 Glass 23 Glass 24 Glass 25 Glass 26 <![CDATA[SiO2]]> 75.7 64.4 66.8 68.3 69.3 <![CDATA[A12O3]]> 1.8 5.4 5.6 5.8 5.8 <![CDATA[B2O3]]> 0.0 0.7 0.7 0.7 0.7 <![CDATA[Li2O]]> 9.4 4.4 6.8 8.3 9.4 <![CDATA[Na2O]]> 2.2 9.1 7.0 5.8 4.9 <![CDATA[K2O]]> 3.3 13.8 10.7 8.8 7.4 ZnO 7.1 1.8 1.9 1.9 1.9 <![CDATA[Sb2O3]]> 0.298 0.272 0.282 0.288 0.292 <![CDATA[CeO2]]> 0.022 0.020 0.021 0.022 0.022 <![CDATA[Ag2O]]> 0.149 0.136 0.141 0.144 0.146 total 100 100 100 100 100

[0279] [Table 9]

[0280]

[0281] Since the value of Equation (A) for Glass 1 to 9 and Glass 25 to 27 is 0.50 to 0.75, the dielectric loss tangent at 20°C and 10GHz is below 0.0090, which is a good value.

[0282] In addition, the SiO2 content of glass 1 to 9 and glass 25 to 27 is 65% or more by mass percentage, and the etching rate of the amorphous glass portion, which is the unexposed part, is 2.75 or less.

[0283] In addition, regarding glasses 1 and 6, the precipitation of Li2SiO3 crystals was actually observed through exposure and heat treatment.

[0284] On the other hand, the values ​​of formula (A) for glasses 10 to 22 exceed 0.75, and the dielectric loss tangent at 20°C and 10GHz exceeds 0.0090, indicating poor dielectric properties compared to glasses 1 to 9 and glasses 25 to 27 in the embodiments.

[0285] In addition, the value of formula (A) for glass 23 also exceeds 0.75, and the relative permittivity at 20°C and 10GHz is higher than that of glasses 1 to 9 and glasses 25 to 27 in the examples, indicating poor dielectric properties.

[0286] Furthermore, the value of formula (A) for glass 24 is less than 0.50, and the SiO2 content, expressed as a mass percentage based on oxides, is less than 65%. Therefore, the etching rate of the glass portion is 5.94, which is relatively high. Consequently, poor microprocessability is predicted, and the Li2O content is very low compared to other embodiments, making it difficult for Li2SiO3 crystals to precipitate.

[0287] Next, examples based on the calculation results (Calculation Examples 1-7) are shown in Tables 10 and 11. Table 10 shows the glass composition expressed as molar percentage, and the relative permittivity, dielectric loss tangent, and glass etching rate predicted at 10 GHz based on this composition. Since the predicted trace components Sb₂O₃·CeO₂·Ag₂O have almost no effect on the aforementioned properties, the calculations were performed based on the composition excluding trace components. Table 11 expresses the components shown in Table 10 as mass percentages. Since the composition excluding trace components is converted to a total amount in Table 11, the total is 100%.

[0288] [Table 10]

[0289]

[0290] [Table 11]

[0291] mass% Calculation Example 1 Calculation Example 2 Calculation Example 3 Calculation Example 4 Calculation Example 5 Calculation Example 6 Calculation Example 7 <![CDATA[SiO2]]> 71.5 72.2 729 71.9 72.3 72.6 73.0 <![CDATA[Al2O3]]> 3.2 3.2 3.2 3.2 3.2 3.2 3.2 <![CDATA[B2O3]]> 0.7 0.7 0.7 0.7 0.7 0.7 0.7 <![CDATA[Li2O]]> 7.9 7.4 6.8 8.0 8.0 7.4 7.4 <![CDATA[Na2O]]> 5.8 5.8 5.8 6.9 8.0 6.9 8.0 <![CDATA[K2o]]> 8.9 8.8 8.8 7.3 5.7 7.2 5.7 ZnO 1.9 1.9 1.9 2.0 2.0 1.9 2.0 <![CDATA[Sb2O3]]> - - - - - - - <![CDATA[CeO2]]> - - - - - - - <![CDATA[Ag2O]]> - - - - - - - total 100 100 100 100 100 100 100

[0292] In calculation examples 1-7, the Al2O3 content (expressed as a mass percentage) was less than 5%, and the Li2O content was less than 15%, resulting in a value of 0.75 or less for Equation (A). Therefore, the predicted value for the dielectric loss tangent at 10 GHz was 0.0090 or less, which is a good value. Furthermore, since the SiO2 content (expressed as a mass percentage) was 65% or more, the predicted value for the etching rate of the amorphous glass portion (the unexposed area) was also 2.75 or less.

[0293] Experimental Example 2: The Influence of Differences in Silver Content

[0294] Next, the differences caused by the silver content in the photosensitive glass will be explained. Glasses A, B, and C each contain different amounts of silver. The transmittance data measured after exposure and heat treatment of each glass are shown below. Figures 4-6 The silver content, exposure amount, and heat treatment conditions of these glasses are shown in Table 12.

[0295] [Table 12]

[0296]

[0297] The exposure method and transmittance measurement method of this test example are shown below. The sample used for exposure and transmittance measurement was a flat plate measuring 10mm × 10mm with a thickness of 2mm.

[0298] (Exposure Method)

[0299] The sample is exposed using the following method.

[0300] <Device Name>

[0301] MultiLight ML-251D / B light source unit for exposure equipment (manufactured by Ushio Electric Co., Ltd.)

[0302] <Device Composition>

[0303] Lighting fixture: MPL-25131

[0304] Lamp: Ultra-high pressure mercury lamp USH-250BY

[0305] Lamp power supply: HB-25103BY-C

[0306] Illumination optical unit: PM25C-75

[0307] <Exposure Method>

[0308] The intensity of ultraviolet light was measured using a combination of a UIT-250 ultraviolet cumulative photometer and a UVH-S313 receiver. The time required to reach the desired exposure level was then calculated, and the ultraviolet light was irradiated using the aforementioned exposure device at that time.

[0309] (Transmittance Measurement)

[0310] Transmittance was measured under the following conditions.

[0311] Measurement apparatus: V-570 spectrophotometer (manufactured by Japan Spectrophotometer Co., Ltd.)

[0312] Measurement wavelength range: 200-800nm

[0313] It should be noted that a sample holder with a φ3mm opening is used during spectrophotometry.

[0314] Figures 4-6 This is a graph showing the transmittance (converted to 1 mmt) of glass A, B, and C according to the exposure amount. In addition, the transmittance shown here is the value obtained by converting the transmittance equivalent to a thickness of 1 mmt using the following formula (3).

[0315]

[0316] T′: Transmittance (converted to 1 mmt), T: Measured transmittance, ρ: Reflectance, L: Glass thickness (mmt)

[0317] Figures 4-6 As can be seen from the data, the region around 430 nm is the absorption peak area for silver colloids, and the transmittance at 430 nm decreases with increasing exposure. This indicates that increasing exposure promotes the formation of silver colloids, resulting in a decrease in transmittance around 430 nm.

[0318] The transmittance at 430 nm, converted to the equivalent of 1 mmt, is expressed as T. 430_1mmt Based on these results, the horizontal axis represents the exposure amount (J / cm²). 2 ) and with the vertical axis as T 430_1mmt The redrawn diagram is Figure 7 .according to Figure 7 The exposure dose of each glass is 0.5 J / cm. 2 T at the time 430_1mmt and T 430_1mmt Relative to exposure levels of 1–10 J / cm 2 The slope is shown in Table 13. At this point, T 430_1mmt The slope is obtained using the following formula (4).

[0319]

[0320] X: Exposure (J / cm²) 2 Y: Transmittance at 430nm (converted to 1mmt)

[0321] [Table 13]

[0322] Glass A Glass B Glass C <![CDATA[0.5J / cm 2 T at the time 430_1mmt (%) 25.29 50.90 77.12 <![CDATA[1~10J / cm 2 T at the time 430_1mmt slope -0.46 -0.98 -2.62

[0323] Focusing on an exposure of 0.5 J / cm 2 It can be seen that as the silver content in the glass increases, T 430_1mmt The concentration increases. In other words, even at the same exposure level, it shows a tendency to be less prone to forming silver colloids. 0.5 J / cm 2 T 430_1mmt When the exposure is below 4%, the exposure sensitivity is too high, making it difficult to control the fine structure.

[0324] In addition, focusing on exposure levels of 1–10 J / cm 2 T 430_1mmt From the slope, we can see that the absolute value of the slope increases with the increase of silver content in the glass. In other words, when the silver content is low, at 1 J / cm²... 2 At the following exposure levels, silver colloid formation is almost saturated. On the other hand, with higher silver concentrations, relative to 1 J / cm²... 2 At the above exposure levels, silver colloid formation exhibits a relatively linear response.

[0325] 1~10J / em2 T 430_1mmt When the slope is greater than -0.12 (close to zero), at 1 J / cm 2 At the following exposure levels, silver colloid formation becomes saturated, making it difficult to control the fine structure.

[0326] Next, the 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 as a percentage by mass and the 0.5 J / cm³ predicted by calculation based on this silver content. 2 T at the time 430_1mmt and 1~10J / cm 2 T at the time 430_1mmt The slope.

[0327] [Table 14]

[0328] Calculation Example A Calculation Example B Calculation example c Calculation Example D Calculation Example E Calculation example F Ag2O [wt%] 0.12 0.10 0.08 0.06 0.05 0.04 <![CDATA[T at 0.5 J / cm2 430_1mmt (%)]]> 20.88 13.57 8.50 5.20 4.25 3.13 <![CDATA[Slope of T when it is 1 to 10 J / cm2]]> 430_1mmt > -0.39 -0.28 -0.20 -0.14 -0.12 -0.10

[0329] According to Table 14, if the silver content is less than 0.05%, then 0.5 J / cm³ 2 T at the time 430_1mmt Below 4%, the predicted exposure sensitivity is too high, making it difficult to control the fine structure.

[0330] Additionally, if the silver content is below 0.05%, the exposure dose will be 1–10 J / cm. 2 T at the time 430—1mmt The slope is greater than -0.12 (close to zero), therefore it is predicted to be at 1 J / cm 2 At the following exposure levels, the formation of silver colloids becomes saturated, making it difficult to control the fine structure.

[0331] (Example of transmission loss calculation)

[0332] When the fabricated glass was actually used as a substrate for high-frequency equipment, the transmission loss of the transmission line was calculated to determine the extent to which the dielectric properties affected the transmission loss of high-frequency signals. The transmission line was a microstrip line (MSL). The analysis software used was TXLINE (Cadence Corporation). The analysis model is as follows.

[0333] A copper wiring layer formed on one main surface of a glass substrate was defined as a microstrip line with a characteristic impedance of 50Ω and a wiring width (shown in Tables 15-18), and the transmission loss at 10 GHz was calculated. The thickness of the glass as the dielectric layer was 0.125 mm, and the thickness of the copper wiring as the conductor layer was 18 μm. The surface roughness of the copper wiring layer was set to be sufficiently smooth to prevent the skin effect from being a problem. The relative permittivity and dielectric loss tangent of the glass at 20°C and 10 GHz were used in the calculation and analysis. The relative permittivity and dielectric loss tangent of the glass used in this study are measured values ​​obtained during actual fabrication. The calculated transmission loss is shown in Tables 15-18. Furthermore, the magnitude of the transmission loss relative to the relative permittivity and dielectric loss tangent of the glass is shown in... Figure 8 , 9 .

[0334] [Table 15]

[0335] Glass 1 Glass 2 Glass 3 Glass 4 Glass 5 Glass 6 Glass 7 Dk@10GHz 6.88 6.86 6.78 6.87 6.78 6.86 6.85 Df@10GHz 0.0071 0.0073 0.0075 0.0076 0.0081 0.0081 0.0079 Transmission loss @10GHz (dB / m) 25 25 26 26 27 27 27 Width of wiring (μm) 154 154 156 154 156 154 154

[0336] [Table 16]

[0337] Glass 8 Glass 9 Glass 10 Glass 11 Glass 12 Glass 13 Glass 14 Dk@10GHz 6.77 6.73 6.71 7.22 7.08 6.93 6.87 Df@10GHz 0.0083 0.0084 0.0110 0.0112 0.0149 0.0135 0.0107 Transmission loss @10GHz (dB / m) 27 27 32 33 40 37 32 Width of wiring (μm) 156 157 157 147 150 153 154

[0338] [Table 17]

[0339] Glass 15 Glass 16 Glass 17 Glass 18 Glass 19 Glass 20 Glass 21 Dk@10GHz 6.93 6.72 6.92 6.90 6.53 6.27 6.76 Df@10GHz 0.0097 0.0107 0.0102 0.0099 0.0118 0.0155 0.0093 Transmission loss @10GHz (dB / m) 30 31 31 30 33 38 29 Width of wiring (μm) 153 157 153 153 161 167 156

[0340] [Table 18]

[0341] Glass 22 Glass 23 Glass 24 Glass 25 Glass 26 Dk@10GHz 6.41 7.00 6.95 6.94 6.93 Df@10GHz 0.0094 0.0057 0.0065 0.0075 0.0082 Transmission loss @10GHz (dB / m) 28 23 24 26 27 Width of wiring (μm) 164 151 152 152 153

[0342] Figure 8 The graph is plotted with the relative permittivity of the glass as the horizontal axis and the transmission loss as the vertical axis. Figure 9 The graphs are plotted with the dielectric loss tangent of the glass as the horizontal axis and transmission loss as the vertical axis. According to these graphs, the dielectric loss tangent contributes more to the improvement of transmission loss than the relative permittivity of the glass used as the substrate. In other words, high-frequency devices with lower transmission loss can be fabricated by using a glass substrate with a lower dielectric loss tangent. Therefore, based on calculations and analysis compared to existing photosensitive glasses, it has been confirmed that dielectric loss is improved when using a photosensitive glass with an improved dielectric loss tangent as the substrate.

[0343] Experimental Example 3: The effect caused by the difference in the first temperature region [nucleation temperature]

[0344] The differences in the holding temperature in the first temperature region [nucleation temperature] after exposure of the photosensitive glass at 485°C and 520°C are explained. The composition of the glass X used is shown in Table 19 as molar percentage and mass percentage. In addition, the exposure conditions and heat treatment conditions are shown in Table 20.

[0345] [Table 19]

[0346] Glass mol% wt% <![CDATA[SiO2]]> 68.6 70.7 <![CDATA[Al2O3]]> 1.8 3.2 <![CDATA[B2O3]]> 0.6 0.7 <![CDATA[Li2O]]> 16.5 8.4 <![CDATA[Na2O]]> 5.5 5.8 <![CDATA[K2O]]> 5.5 8.9 ZnO 1.4 1.9 <![CDATA[Sb2O3]]> 0.037 0.187 <![CDATA[CeO2]]> 0.003 0.009 <![CDATA[Ag2O]]> 0.029 0.117

[0347] [Table 20]

[0348]

[0349] The exposure method and transmittance measurement were performed using the same method as in Test Example 2.

[0350] Figure 10 and Figure 11 It is a graph showing the transmittance (converted to 1 mmt) of glass X according to the exposure amount. Figure 10 The transmittance is shown under condition 1 in Table 20 when exposure and heat treatment are performed. Figure 11 The transmittance is shown under condition 2 in Table 20 when exposure and heat treatment are performed. It should be noted that the transmittance shown here is the value obtained by converting the transmittance of a thickness of 1 mmt according to the following formula (3).

[0351]

[0352] T′: Transmittance (converted to 1 mmt), T: Measured transmittance, ρ: Reflectance, L: Glass thickness (mmt)

[0353] Figure 10 and Figure 11 In the image, the region around 430 nm is the absorption peak area for silver colloids. Since the transmittance at 430 nm decreases after heat treatment, it can be concluded that silver colloids have formed. Furthermore, [the text abruptly ends here]. Figure 10 and Figure 11 When comparing, it can be seen that the temperature maintained in the first temperature region is relatively high. Figure 11 The transmittance at 430 nm becomes lower. This is because the formation of silver colloid is further promoted by setting the first temperature region to a higher temperature. In other words, by setting the first temperature region to a higher temperature, silver colloid can be precipitated in a shorter time.

[0354] Industrial availability

[0355] The photosensitive glass of one embodiment of the present invention not only has excellent microprocessability but also excellent dielectric loss characteristics for high-frequency signals. By using such photosensitive glass, it is possible to realize a high-frequency device having a circuit board with microprocessed circuitry and excellent transmission loss characteristics for high-frequency signals.

[0356] Such photosensitive glass is very useful as a component in all high-frequency electronic devices that process high-frequency signals above 10 GHz, especially high-frequency signals above 30 GHz, and even higher than 35 GHz, as well as in devices that are accompanied by microfabrication, such as substrate-integrated waveguides.

[0357] The various embodiments have been described above with reference to the accompanying drawings, but the present invention is certainly not limited to the examples described above. It is understood that those skilled in the art will obviously be able to conceive of various modifications or alterations within the scope of the patent claims, and these also fall within the technical scope of the present invention. Furthermore, the constituent elements in the above embodiments can be arbitrarily combined without departing from the spirit of the invention.

[0358] It should be noted that this application is based on Japanese patent application filed on June 3, 2021 (Japanese Patent Application No. 2021-093783), the contents of which are incorporated herein by reference.

[0359] Symbol Explanation

[0360] 1 Circuit board

[0361] 2 Glass substrate

[0362] 2a, 2b Main surfaces

[0363] 3rd and 4th wiring layers

[0364] 10 Waveguides

[0365] 11 Glass substrate

[0366] 12 Hollow sections

Claims

1. A photosensitive glass in which Li₂SiO₃ crystals are precipitated through exposure and heat treatment. The value of the following formula (A) is 0.50 to 0.

75. The dielectric loss tangent at 20℃ and 10GHz is below 0.0090°. [Li2O] / ([Li2O]+[Na2O]+[K2O]) Formula (A) In formula (A), [Li2O], [Na2O] and [K2O] represent the contents of Li2O, Na2O and K2O in the photosensitive glass, respectively, expressed as molar percentages based on oxides.

2. The photosensitive glass according to claim 1, wherein, Expressed as a mass percentage based on oxides, it contains 65–78% SiO2. When a glass sample with a length of 30 mm × width of 20 mm and a thickness of 0.5 mm is immersed in 55 ml of an etching solution containing 5% HF and 0.7% HNO3 at 40 °C for 4 minutes, the etching rate of the glass portion, calculated by the following formula (1), is less than 2.

75. 。 3. The photosensitive glass according to claim 1 or 2, wherein, Expressed as a percentage by mass based on oxides, containing Al2O3: 0% or more and less than 5% Li2O: 5-15% Na2O: 3-12% K2O: 3-12% ZnO: 0.3-8% Sb₂O₃: ≥0.01% and <1% CeO2: 0.001–0.1% Ag2O: 0.05–1%.

4. The photosensitive glass according to claim 1 or 2, wherein, Expressed as a percentage by mass based on oxides, containing Al2O3: 0% or more and less than 5% Li2O: 5-15% Na2O: 3-12% K2O: 3-12% ZnO: 0-8% Sb₂O₃: ≥0.01% and <1% CeO2: 0.001–0.1% Ag2O: 0.05–1%.

5. The photosensitive glass according to claim 1 or 2, wherein, It contains 0–8% B2O3, expressed as a mass percentage based on oxides.

6. The photosensitive glass according to claim 1 or 2, wherein, The relative permittivity at 20℃ and 10GHz is below 7.

5.

7. A glass obtained by exposing and heat-treating the photosensitive glass according to any one of claims 1 to 6 to precipitate Li2SiO3 crystals.

8. A glass obtained by exposing, heat-treating and etching the photosensitive glass according to any one of claims 1 to 6 to form a microstructure.

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

10. The circuit board according to claim 9, wherein it comprises transmission lines.

11. The circuit board according to claim 10, wherein, The transmission line is a waveguide, a substrate integrated waveguide (SIW), or a microstrip line.

12. The circuit board according to claim 10, which has the function of a passive device.

13. Use of the circuit board of claim 9 for use in high-frequency devices.

14. A high-frequency device comprising a circuit board according to any one of claims 9 to 12.

15. A method for manufacturing glass with a fine structure, comprising: The process of exposing the photosensitive glass according to any one of claims 1 to 6 The process of heat-treating the exposed photosensitive glass to precipitate Li2SiO3 crystals. The process of removing the precipitated Li2SiO3 crystals by etching.

16. The manufacturing method according to claim 15, wherein, The heat treatment includes a step of holding in a first temperature region and a step of holding in a second temperature region. The first temperature range is 400℃ to 500℃, and the holding time in the first temperature range is more than 15 minutes. The second temperature zone is 500℃~700℃, and the duration of the second temperature zone is more than 15 minutes.

17. The manufacturing method according to claim 15, wherein, The heat treatment includes a step of holding in a first temperature region and a step of holding in a second temperature region. The first temperature range is 400℃ to 600℃, and the holding time in the first temperature range is more than 1 minute. The second temperature zone is the first temperature zone +5℃ to +300℃, and the duration of the second temperature zone is more than 1 minute.

18. The photosensitive glass according to claim 1 or 2, wherein, With an exposure of 0.5 J / cm 2 The transmittance at 430nm after exposure and heat treatment at 485℃ for 5 hours is more than 4% when converted to a 1mm value.

19. The photosensitive glass according to claim 1 or 2, wherein, For exposure rates of 1–10 J / cm 2 The transmittance at 430 nm, measured after exposure and heat treatment at 485°C for 5 hours, is the transmittance at 430 nm calculated by the following equation (4) relative to the exposure amount of 1-10 J / cm² when plotting a curve on a coordinate plane with the exposure amount as the horizontal axis and the transmittance as the vertical axis. 2 The slope is below -0.12, and the unit of the horizontal axis is J / cm. 2 The vertical axis is in percentage, and transmittance is calculated in 1mm increments. X: Exposure, in J / cm² 2 Y: Transmittance at 430nm, converted to 1mm.

Images