JP7228135B2 - Method for manufacturing glass substrate laminate, glass substrate, glass substrate laminate, and head mounted display - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a glass substrate laminate, a glass substrate, a glass substrate laminate, and a head mounted display.

2. Description of the Related Art In recent years, various forms of head-mounted displays have been developed, such as hat-type devices and eyeglass-type devices. Hat-type devices cover the user's field of vision and are often used as a system for experiencing virtual reality (VR). It is often used as a system for experiencing

A head-mounted display may use a transparent light guide plate. In this case, for example, an image displayed on the light guide plate can be seen while looking at the scenery of the outside (see-through device). In addition, for example, 3D display is realized by displaying different images on the light guide plates corresponding to the left and right eyes of the user, and images are projected directly onto the retina of the user by using the crystalline lens of the pupil to combine with the retina. You can also

As an image display method using a light guide plate, collimated light is incident from the end surface of the light guide plate, and the incident light is totally reflected inside the light guide plate and extracted outside by a diffraction phenomenon, and enters the user's pupil. There is something that makes

In this case, the light guide plate may be composed of a glass substrate laminate obtained by laminating a plurality of glass substrates having an uneven structure on one main surface (see Patent Documents 1 and 2, for example). Here, the concave-convex structure of the glass substrate is for, for example, facilitating the occurrence of a diffraction phenomenon. The purpose of this is to give a sense of depth to the image, and to obtain advantages such as facilitating the realization of 3D display with a sense of realism.

Japanese Patent Publication No. 2018-506068 Chinese Patent Application Publication No. 106324847

When general-purpose low-refractive glass (for example, one with a refractive index nd of about 1.49) is used as the glass substrate that constitutes the light guide plate of the head-mounted display, the minimum incident angle that causes total reflection increases. Therefore, it is difficult for light to propagate inside the light guide plate while repeating total reflection. As a result, it is difficult to increase the degree of freedom in optical design.

In addition, the head mounted display may also have a problem of being unable to display a desired image. The causes of this problem are roughly divided into those originating from the uneven structure of the glass substrate in the light guide plate of the head-mounted display and the adhesion between other members, and those originating from the roughness of the main surface of the glass substrate.

First, factors originating in the uneven structure of the glass substrate and the adhesion of other members will be described. A plurality of glass substrates forming a light guide plate of a head mounted display may be adhered to each other by a resin film which is another member. However, when the uneven structure is formed on the main surface, the adhesion between the glass substrate and the resin film becomes insufficient, and a gap is likely to be formed between the uneven structure of the glass substrate and the resin film. If such a gap occurs, when collimated light is propagated while repeating total reflection inside the glass substrate, scattering occurs due to the gap, which may cause a problem that a desired image cannot be displayed. .

Next, factors derived from the roughness of the main surface of the glass substrate will be described. A glass substrate that constitutes a light guide plate of a head-mounted display may have an uneven structure formed on its main surface by using, for example, a photolithography method. In the photolithography method, first, a thin film is formed on the main surface of a glass substrate by sputtering or the like. Next, a photoresist is applied to the thin film to form a resist layer, and the resist layer is covered with a photomask and irradiated with light (for example, ultraviolet rays). After that, the exposed portions of the resist layer are removed with a developing solution, and unnecessary portions of the thin film (portions corresponding to the removed resist film) are removed by etching. Then, by removing the non-exposed portion of the resist film, an uneven structure is formed on the glass substrate.

In these steps of photolithography, various chemicals such as acids, alkalis and developers are used. However, in order to increase the degree of freedom in optical design, general high-refractive-index glass used for optical lenses and the like tends to have weak chemical resistance. As a result, as shown in FIG. 7, the chemical not only removes the thin film 101, but also corrodes and roughens the main surface 102a of the glass substrate 102 together. When such a glass substrate is used to manufacture a light guide plate for a head-mounted display, the collimated light is scattered without being totally reflected inside the glass substrate, and there is a possibility that the light may leak outside in areas not intended for design. be. As a result, there may arise a problem that the desired image cannot be displayed.

An object of the present invention is to provide a glass substrate and a glass plate laminate that can improve the degree of freedom in optical design and improve the image display performance.

The present invention, which has been devised to solve the above problems, is a method for manufacturing a glass substrate laminate formed by laminating a plurality of glass substrates via a resin layer, wherein the refractive index nd is 1.55 to 2. 30, a step of forming a concave-convex structure on the first main surface of the glass substrate, a step of applying a liquid resin to the concave-convex structure, and a liquid resin or a cured product of the liquid resin; and laminating a plurality of glass substrates having an uneven structure. According to such a configuration, since the liquid resin is applied to the concave-convex structure formed on the first main surface of the glass substrate, the liquid resin enters the recesses of the concave-convex structure. Therefore, the adhesion between the uneven structure of the glass substrate and the liquid resin is improved, and a gap is less likely to be formed between the uneven structure of the glass substrate and the liquid resin (resin layer). Therefore, when used as a light guide plate for a head-mounted display, it is possible to prevent the situation in which the light propagating while repeating total reflection inside the glass substrate is scattered in the gaps, thereby improving the image display accuracy. . Each glass substrate constituting the glass substrate laminate has a refractive index nd of 1.55 to 2.30, and is a high refractive index glass. Therefore, when used as a light guide plate for a head-mounted display, total reflection of light is likely to occur inside the glass substrate utilizing the characteristics of the high-refractive-index glass, improving the degree of freedom in optical design. Here, "refractive index nd" refers to a value measured using a commercially available refractive index measuring instrument (for example, refractive index measuring instrument KPR-2000 manufactured by Shimadzu Corporation).

In the above configuration, the liquid resin is cured by applying light energy, and after the step of laminating the glass substrates having the uneven structure, the liquid resin is cured by light energy to obtain the glass substrate having the uneven structure. It is preferable to include a step of adhering them together. In this way, the liquid resin is uncured in the step of laminating the glass substrates. Therefore, when the glass substrates are laminated, the liquid resin can flow between the glass substrates, so that the gaps between the glass substrates can be more reliably filled. Moreover, when forming an uneven structure on the main surface of the glass substrate using the photolithography method, the liquid resin can be cured as part of the photolithography process.

In the above configuration, the surface roughness Ra of the second main surface opposite to the first main surface of the glass substrate is preferably 10 nm or less. This makes it easier for total reflection to occur inside the glass substrate. Here, the "surface roughness Ra" refers to a value measured according to JIS B-0601 (1994) using a Surfcorder ET-4000AK manufactured by Kosaka Laboratory when it can be measured by physically contacting a needle. . On the other hand, when the measurement cannot be performed by physically contacting the needle, it refers to a value calculated using image analysis software from images observed using various optical microscopes.

In the above configuration, the glass substrate contains 10 to 60% by mass of SiO ₂ , 1 to 40% by mass of BaO, and 0.5 to 40% by mass of TiO ₂ +La ₂ O ₃ , and has a liquid phase. It is preferable that the viscosity is 10 ^3.0 dPa·s or more. By doing so, it becomes easier to produce a glass having high devitrification resistance and a high refractive index. Here, "TiO ₂ +La ₂ O ₃ " means the total amount of TiO ₂ and La ₂ O ₃ . "Liquidus viscosity" refers to a value obtained by measuring the viscosity of a glass at the liquidus temperature by a platinum ball pull-up method. The "liquidus temperature" is measured by placing the glass powder that passes through a 30-mesh standard sieve (opening: 500 µm) and remains in a 50-mesh standard sieve (opening: 300 µm) in a platinum boat and holds it in a temperature gradient furnace for 24 hours. refers to the measured value of the temperature at which crystals precipitate.

The present invention, which has been devised to solve the above problems, is a glass substrate laminate obtained by laminating a plurality of glass substrates via a resin layer, wherein the glass substrate has an uneven structure on its first main surface. and has a refractive index nd of 1.55 to 2.30, and the resin layer is a cured product of a photocurable resin. According to such a configuration, the cured product of the photocurable resin forming the resin layer is a liquid resin in an uncured state. Therefore, the cured product of the photo-curing resin is cured in a state of entering the recesses of the uneven structure due to fluidity in the uncured state. As a result, the adhesion between the concave-convex structure of the glass substrate and the resin layer is improved, and a gap is less likely to be formed between the concave-convex structure of the glass substrate and the resin layer. Therefore, when it is used as a light guide plate for a head-mounted display, it is possible to prevent a situation in which the light propagated while repeating total reflection inside the glass substrate is scattered in the gaps and the displayed image is disturbed. Each glass substrate constituting the glass substrate laminate has a refractive index nd of 1.55 to 2.30, and is a high refractive index glass. Therefore, when used as a light guide plate for a head-mounted display, total reflection of light is likely to occur inside the glass substrate utilizing the characteristics of the high-refractive-index glass, improving the degree of freedom in optical design.

The present invention, which has been devised to solve the above problems, is a head-mounted display comprising a light guide plate having the glass substrate laminate described above. According to such a configuration, it is possible to obtain the same effects as those described for the above-described glass substrate laminate.

The present invention, which has been devised to solve the above problems, is a glass substrate having an uneven structure on a first main surface, wherein the glass substrate has a refractive index nd of 1.55 to 2.30, and has an uneven structure. The bottom surface of the recess is made of glass, and the surface roughness Ra is 10 nm or less. According to such a configuration, the glass substrate has a refractive index nd of 1.55 to 2.30 and is a high refractive index glass. Therefore, when used as a light guide plate for a head-mounted display, total reflection of light is likely to occur inside the glass substrate utilizing the characteristics of the high-refractive-index glass, improving the degree of freedom in optical design. Furthermore, the bottom surface of the concave portion of the concave-convex structure is a smooth glass surface with a surface roughness Ra of 10 nm or less. Therefore, when used as a light guide plate for a head-mounted display, it is possible to prevent collimated light from scattering without being totally reflected in the glass substrate and leaking to the outside at unintended portions in terms of design. Incidentally, when forming the concave-convex structure by photolithography, adjusting the glass composition to enhance the chemical resistance makes it easier to regulate the surface roughness Ra of the bottom surface of the concave portion of the concave-convex structure to 10 nm or less. Here, "refractive index nd" refers to a value measured using a commercially available refractive index measuring instrument (for example, refractive index measuring instrument KPR-2000 manufactured by Shimadzu Corporation). In addition, "surface roughness Ra" refers to a value measured according to JIS B-0601 (1994) using a Surfcorder ET-4000AK manufactured by Kosaka Laboratory when the measurement can be made by physically contacting a needle. On the other hand, when the measurement cannot be performed by physically contacting the needle, it refers to a value calculated using image analysis software from images observed using various optical microscopes.

In the above configuration, the undulation of the bottom surface of the recess is preferably 20 nm or less. In this way, since the undulations of the bottom surface of the unevenness are reduced, scattering of light on the bottom surface of the concave portion can be more reliably prevented. Here, "undulation" is a value calculated using image analysis software from images observed using various optical microscopes.

In the above configuration, it is preferable that the convex portion of the concave-convex structure is made of a material different from that of the glass substrate, and that the difference in refractive index nd between the convex portion of the concave-convex structure and the glass substrate is 0.01 or more. In this way, the uneven structure can be easily formed on the glass substrate. Moreover, since the refractive index difference with the surrounding members becomes large, the diffraction phenomenon tends to occur.

In the above structure, the difference between the maximum thickness and the minimum thickness of the glass substrate is preferably 0.5 μm or less. In this way, when it is used as a light guide plate for a head-mounted display, it is possible to more reliably prevent a situation in which light leaks to the outside at a portion not intended in terms of design. Here, the "difference between the maximum thickness and the minimum thickness of the glass substrate" is calculated by excluding the portion where the concave-convex structure is formed.

In the above configuration, the surface roughness Ra of the second main surface opposite to the first main surface of the glass substrate is preferably 10 nm or less. This makes it easier for total reflection to occur inside the glass substrate.

In the above structure, the glass composition is SiO ₂ 10 to 60% by mass, BaO
It preferably contains 1-40% and TiO ₂ +La ₂ O ₃ 0.5-40%. By doing so, it becomes easier to produce a glass having high devitrification resistance and a high refractive index. Here, "TiO ₂ +La ₂ O ₃ " means the total amount of TiO ₂ and La ₂ O ₃ .

In the above structure, it is preferable that the ratio of (width at 5% height)/(width at 95% height) is 0.5 to 1.2. By doing so, it is possible to impart the designed diffraction performance to the glass substrate. Here, the “width at 5% height” refers to the width of the protrusion at the height obtained by multiplying the height of the protrusion of the uneven structure by 0.05. "Width at 95% of height" refers to the width of the protrusion at the height obtained by multiplying the height of the protrusion of the uneven structure by 0.95. "Width" refers to the diameter of the convex portion of the concavo-convex structure in the case of a columnar shape, and the length of the shortest side in the case of a polygonal shape.

The present invention, which has been devised to solve the above problems, is a head-mounted display, characterized by comprising a light guide plate having the aforementioned glass substrate. According to such a configuration, it is possible to enjoy the same effects as those described for the glass substrate described above.

ADVANTAGE OF THE INVENTION According to this invention, the glass substrate laminated body which can aim at the improvement of the flexibility of an optical design, and the improvement of the display performance of an image can be provided.

It is a sectional view showing a glass substrate concerning this embodiment. 1. It is sectional drawing which expands and shows the convex part periphery of the uneven|corrugated structure of the glass substrate of FIG. It is a sectional view showing a glass substrate layered product concerning this embodiment. FIG. 4 is a perspective view showing an example of a head mounted display including the glass substrate laminate of FIG. 3; It is sectional drawing which shows the liquid resin application process included in the manufacturing method of the glass substrate laminated body which concerns on this embodiment. It is sectional drawing which shows the lamination process included in the manufacturing method of the glass substrate laminated body which concerns on this embodiment. It is a cross-sectional view showing a problem of a conventional glass substrate having an uneven structure.

As shown in FIG. 1, a glass substrate 1 according to this embodiment has a first main surface 1a and a second main surface 1b facing each other in the thickness direction, and has an uneven structure 2 on the first main surface 1a. The glass substrate 1 can be suitably used as a light guide plate for a head-mounted display, but its application is not limited to this.

The concave-convex structure 2 is for extracting light propagating inside the glass substrate 1 by, for example, a diffraction phenomenon. The convex portions of the uneven structure 2 may be formed from the same material as the glass substrate 1 or may be formed from a material different from that of the glass substrate 1 . In the former case, for example, a method of directly processing the first main surface 1a of the glass substrate 1 by laser etching (laser engraving) can be used. In the latter case, for example, a photolithography method, a method of forming a predetermined structure by sputtering using a mask, a method of forming a uniform film and then laser-etching the film, an imprint method using a mold, and the like. can be used. In this embodiment, the projections of the uneven structure 2 are made of a material different from that of the glass substrate 1 in order to provide a fine and dense uneven structure. Further, the concave bottom surface 2 a of the concave-convex structure 2 is formed by the first main surface (glass surface) 1 a of the glass substrate 1 .

When the convex portions of the concave-convex structure 2 are formed of a material different from that of the glass substrate 1, the convex portions of the concave-convex structure 2 are preferably formed of a transparent material. Examples of transparent materials include TiO ₂ , SiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ and organic materials. Here, "transparent material" means a material having an internal transmittance of 70% or more at a wavelength of 550 nm in terms of an optical path length of 1 mm.

The height of the protrusions of the uneven structure 2, that is, the distance A from the bottom surface 2a of the protrusions to the apex 2b of the protrusions is preferably 10 nm to 1000 nm, 15 nm to 1000 nm, 50 nm to 800 nm, 100 nm to 700 nm, and 200 nm to 500 nm. By doing so, the diffraction phenomenon is likely to occur. It is preferable that the irregularities of the uneven structure 2 are formed periodically. Various shapes such as a columnar shape, a polygonal prismatic shape, and a tapered shape can be selected for the shape of the convex portions of the uneven structure 2 . The width B of the protrusions of the uneven structure 2 and the width (interval between protrusions) C of the recesses of the uneven structure 2 can be appropriately designed according to the wavelength of incident light.

The glass substrate 1 has a surface roughness Ra of 10 nm or less on the bottom surface 2a of the concave portion of the concave-convex structure 2 . In this way, when it is used as a light guide plate for a head-mounted display, the collimated light is scattered without being totally reflected inside the glass substrate 1, and the light leaks to the outside at a portion not intended in terms of design. can be prevented. The surface roughness Ra of the bottom surface 2a of the recess is preferably 5 nm or less, 2 nm or less, 1 nm or less, or 0.5 nm or less.

The surface roughness Ra of the second main surface 1b of the glass substrate 1 is preferably 10 nm or less, 5 nm or less, 2 nm or less, 1 nm or less, and 0.5 nm or less. This makes it easier for total reflection to occur inside the glass substrate 1 .

If the bottom surface 2a of the concave portion of the concave-convex structure 2 has a large undulation, there is a risk that light may leak to the outside at portions not intended in terms of design when used as a light guide plate for a head-mounted display. Therefore, the undulation of the bottom surface 2a of the concave portion of the concave-convex structure 2 is preferably 20 nm or less, 10 nm or less, 5 nm or less, and particularly preferably 1 nm or less.

As shown in FIG. 2, it is preferable that (width B1 at 5% height)/(width B2 at 95% height) be 0.5 to 1.2. By doing so, the glass substrate 1 can be provided with diffraction performance as designed. If the etching conditions for removing unnecessary portions of the thin film are strengthened when forming the uneven structure 2, (width B1 at a height of 5%)/(width B2 at a height of 95%) becomes smaller, but it is designed to be too strong. Diffraction performance may not be obtained. Therefore, (width B1 at 5% height)/(width B2 at 95% height) is preferably 0.7 or more, 0.8 or more, 0.9 or more, and 0.95 or more. On the other hand, if the etching conditions are weak, the main surface of the glass substrate 1 is less likely to be eroded, but if the etching conditions are too weak, (width B1 at 5% height)/(width B2 at 95% height) becomes large, and as designed. Diffraction performance is not obtained. Therefore, (width B1 at 5% height)/(width B2 at 95% height) is preferably 1.15 or less, 1.10 or less, 1.08 or less, 1.05 or less, or 1.02 or less.

The glass substrate 1 is a high refractive index glass with a refractive index nd of 1.55 to 2.30. If the refractive index nd of the glass substrate 1 is too low, it becomes difficult for total reflection to occur inside the glass substrate 1, and the degree of freedom in optical design decreases. Therefore, the refractive index nd of the glass substrate 1 is preferably 1.58 or more, 1.60 or more, 1.63 or more, 1.65 or more, 1.68 or more, and particularly preferably 1.70 or more. On the other hand, if the refractive index nd of the glass substrate 1 is too high, it becomes difficult to form the glass substrate 1 into a plate shape, and the production efficiency of the glass substrate 1 tends to decrease. Therefore, the refractive index nd of the glass substrate 1 is preferably 2.00 or less, 1.90 or less, or 1.85 or less, and particularly preferably 1.80 or less.

When the convex portions of the concave-convex structure 2 are formed of a material different from that of the glass substrate 1, the difference in refractive index nd between the convex portions of the concave-convex structure 2 and the glass substrate 1 is preferably 0.01 or more, 0.02 or more, or 0.02 or more. 03 or more, and particularly preferably 0.05 or more. By doing so, the refractive index difference with the surrounding members becomes large, so that the diffraction phenomenon is likely to occur.

If the difference between the maximum thickness and the minimum thickness of the glass substrate 1 becomes large, there is a possibility that light may leak outside at portions not intended in terms of design when the head mounted display is assembled. Therefore, the difference between the maximum thickness and the minimum thickness of the glass substrate 1 is preferably 0.5 μm or less, 0.2 μm or less, 0.1 μm or less, or 0.05 μm or less.

The glass substrate 1 contains SiO₂is preferably contained in an amount of 5 mass% or more, and the glass composition is SiO in mass%.₂ 10-60%, BaO 1-40%, TiO₂+La ₂O.₃ It is more preferable to contain 0.5 to 40%. The reasons for specifying the glass composition in this manner are as follows. In addition, in description of the content range of each component, % means the mass %.

The content of SiO ₂ is preferably 5% or more, particularly 10-60%. When the content of SiO ₂ decreases, it becomes difficult to form a glass network structure and vitrification becomes difficult. In addition, the high-temperature viscosity is too low, making it difficult to ensure a high liquidus viscosity. Furthermore, the chemical resistance tends to decrease. Therefore, the content of SiO ₂ is preferably 15% or more, 20% or more, 25% or more, 30% or more, particularly preferably 35% or more. On the other hand, when the content of SiO ₂ increases, the meltability and moldability tend to deteriorate, and the refractive index tends to decrease. The content of SiO ₂ is therefore preferably 55% or less, 51% or less, 48% or less, 45% or less, particularly preferably 42% or less.

Among alkaline earth metal oxides, BaO is a component that increases the refractive index without significantly lowering the high-temperature viscosity. The content of BaO is preferably 1 to 40%. When the content of BaO increases, the liquidus viscosity tends to decrease, and the refractive index, density, and coefficient of thermal expansion tend to increase. Therefore, the BaO content is preferably 35% or less, 32% or less, or 30% or less, and particularly preferably 28% or less. On the other hand, when the content of BaO is small, it becomes difficult to obtain a desired refractive index and to ensure a high liquidus viscosity. Therefore, the content of BaO is preferably 5% or more, 10% or more, 12% or more, 15% or more, 17% or more, 20% or more, 23% or more, and particularly preferably 25% or more.

TiO₂and La₂O.₃is a component that effectively increases the refractive index. Therefore, TiO₂and La ₂O.₃is preferably 0.5% or more, 1% or more, 3% or more, 5% or more, 8% or more, 11% or more, 15% or more, and particularly preferably 17% or more. On the other hand, TiO₂and La₂O.₃When the total amount of Therefore, TiO₂and La₂O. ₃is preferably 40% or less, 30% or less, or 25% or less, and particularly preferably 22% or less.

TiO ₂ is the component that increases the refractive index the most among common oxides, excluding heavy metal oxides such as rare earth oxides. However, when the content of TiO ₂ increases, the glass tends to be colored and the devitrification resistance tends to decrease. Therefore, the content of TiO ₂ is preferably 0-35%, 0.1-30%, 0.1-15%, 1-12%, 2-11%, 3-10%, particularly preferably 4-9%. When priority is given to increasing the refractive index over improving devitrification resistance, the content of TiO ₂ is preferably 7 to 35%, 15 to 32%, and particularly preferably 20 to 30%.

La ₂ O ₃ is a component that effectively increases the refractive index. However, when the content of La ₂ O ₃ increases, the liquidus temperature tends to decrease. Therefore, the content of La ₂ O ₃ is preferably 0-15%, 0-13%, 5-12%, particularly preferably 7-11%.

In addition to the above components, the following components, for example, can be added as optional components.

The content of Al ₂ O ₃ is preferably 0-8%. When the content of Al ₂ O ₃ increases, devitrified crystals tend to precipitate during molding, and the liquidus viscosity tends to decrease, and the refractive index tends to decrease. Therefore, the content of Al ₂ O ₃ is preferably 8% or less, 7% or less, and particularly preferably 6% or less. On the other hand, when the content of Al ₂ O ₃ decreases, the balance of the glass composition is lost and the glass tends to devitrify. Therefore, the content of Al ₂ O ₃ is preferably 0.1% or more, 0.5% or more, 1% or more, 3% or more, and particularly preferably 5% or more.

The content of B ₂ O ₃ is preferably 0-15%. As the content of B ₂ O ₃ increases, the refractive index and Young's modulus tend to decrease. Moreover, the chemical resistance tends to decrease. Therefore, the content of B ₂ O ₃ is preferably 9% or less, 8% or less, and particularly preferably 7% or less. On the other hand, when the content of B ₂ O ₃ decreases, the liquidus temperature tends to decrease. Therefore, the content of B ₂ O ₃ is preferably 1% or more, 3% or more, and particularly preferably 5% or more.

The content of MgO is preferably 0 to 12%. MgO is a component that increases the Young's modulus and lowers the viscosity at high temperatures. properties, or the density and coefficient of thermal expansion become too high. Therefore, the content of MgO is preferably 10% or less, 5% or less, 3% or less, 2% or less, 1.5% or less, 1% or less, and particularly preferably 0.5% or less.

The content of CaO is preferably 0 to 15%. When the content of CaO increases, the density and coefficient of thermal expansion tend to increase. Therefore, the CaO content is preferably 13% or less, 10% or less, 8% or less, and particularly preferably 7% or less. On the other hand, when the CaO content is low, the meltability tends to decrease, the Young's modulus tends to decrease, and the refractive index tends to decrease. Therefore, the content of CaO is preferably 0.5% or more, 1% or more, 3% or more, 4% or more, and particularly preferably 5% or more.

The content of SrO is preferably 0 to 15%. If the content of SrO increases, the refractive index, density, and coefficient of thermal expansion tend to increase. Therefore, the SrO content is preferably 13% or less, 12% or less, and particularly preferably 11% or less. On the other hand, when the content of SrO is small, the meltability tends to be lowered, and the refractive index tends to be lowered. Therefore, the SrO content is preferably 1% or more, 3% or more, 5% or more, 7% or more, and particularly preferably 10% or more.

The content of ZnO is preferably 0-15%. However, when the content of ZnO increases, the density and coefficient of thermal expansion increase. Therefore, the content of ZnO is preferably 15% or less, 12% or less, 10% or less, 8% or less, 6% or less, and particularly preferably 4% or less. On the other hand, when the ZnO content is low, it becomes difficult to ensure a high liquidus viscosity. Therefore, the content of ZnO is preferably 0.1% or more, 0.5% or more, more than 1%, 1.5% or more, 2% or more, 2.5% or more, and particularly preferably 3% or more is.

ZrO ₂ is a component that increases the refractive index, but when its content increases, the liquidus temperature tends to decrease. The content of ZrO ₂ is therefore preferably 0-10%, 0.1-7%, 0.5-6%, particularly preferably 1-5.5%.

Nb ₂ O ₅ is a component that increases the refractive index, but if its content increases, raw material costs tend to increase. Therefore, the content of Nb ₂ O ₅ is preferably 0-30%, 1-25%, 5-23%, 10-22%, particularly preferably 15-21%.

Li ₂ O, Na ₂ O and K ₂ O are components that lower the high-temperature viscosity and raise the coefficient of thermal expansion. , it becomes difficult to secure a high liquidus viscosity. Therefore, the total amount of Li ₂ O, Na ₂ O and K ₂ O is preferably 15% or less, 10% or less, 5% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably is 0.1% or less. Further, the content of each of Li ₂ O, Na ₂ O and K ₂ O is preferably 10% or less, 8% or less, 5% or less, 2% or less, 1% or less and 0.5% or less, Particularly preferably, it is 0.1% or less.

When lowering high-temperature viscosity is prioritized over increasing liquidus viscosity, the total amount of Li ₂ O, Na ₂ O and K ₂ O is preferably 0.1 to 25%, 5 to 23%, 10 to 20%. , in particular 12-18%. The content of Li ₂ O is preferably 10% or less, 8% or less, 5% or less, 2% or less, 1% or less, 0.5% or less, and particularly preferably 0.1% or less. . The content of Na ₂ O is preferably 1-22%, 3-20%, 5-15%, particularly preferably 8-12%. The content of K ₂ O is preferably 0.1-10%, 1-9%, 2-8%, particularly preferably 3-7%.

As a refining agent, As₂O.₃, Sb₂O.₃, CeO₂, SnO₂, F, Cl, SO₃One or two or more selected from the group of can be added in the range of 0 to 1%. However, As ₂O.₃, Sb₂O.₃and F, it is preferable to refrain from using them as much as possible from an environmental point of view, and the content of each is preferably less than 0.1%. CeO₂is preferably 0 to 1%, 0.01 to 0.5%, and particularly preferably 0.05 to 0.4%. In addition, SnO ₂is preferably 0 to 1%, 0.01 to 0.5%, and particularly preferably 0.05 to 0.4%. In addition, SnO₂, SO₃and Cl are preferably 0 to 1%, 0.001 to 1%, 0.01 to 0.5%, and particularly preferably 0.05 to 0.3%.

PbO is a component that lowers high-temperature viscosity, but from an environmental point of view, it is preferable to refrain from using it as much as possible. The content of PbO is preferably 0.5% or less, particularly preferably less than 0.1%.

Bi ₂ O ₃ , Gd ₂ O ₃ , Ta ₂ O ₅ and WO ₃ are components that increase the refractive index, but they are expensive and difficult to obtain in large quantities. The content of each of these components is preferably 1% or less, particularly preferably 0.5% or less.

Fe ₂ O ₃ and Cr ₂ O ₃ are components mixed as raw material impurities, and when these components are increased, the transmittance inside the glass substrate tends to decrease. Therefore, the content of Fe ₂ O ₃ is preferably 500 ppm (0.05%) or less, 200 ppm or less, 100 ppm or less, 50 ppm or less, and particularly preferably 30 ppm or less. The content of Cr ₂ O ₃ is preferably 5 ppm (0.0005%) or less, 3 ppm or less, 2 ppm or less, 1 ppm or less, and particularly preferably 0.5 ppm or less. It should be noted that the content of Fe ₂ O ₃ and Cr ₂ O ₃ can be reduced by using high-purity glass raw materials.

The density of the glass substrate 1 is preferably 5.0 g/cm ³ or less, 4.8 g/cm ³ or less, 4.5 g/cm ³ or less, 4.3 g/cm ³ or less, or 3.7 g/cm ³ or less. , particularly preferably 3.5 g/cm ³ or less. In this way, the weight of the device can be reduced. The "density" can be measured by the well-known Archimedes method.

The thermal expansion coefficient of the glass substrate 1 is preferably 30×10 ⁻⁷ to 100×10 ⁻⁷ /° C., 40×10 ⁻⁷ to 90×10 ⁻⁷ /° C., 60×10 ⁻⁷ to 85×10 ⁻⁷ /°C, and particularly preferably 65 × 10 ^-7 to 80 × 10 ^-7 /°C. If the thickness of the glass substrate 1 is small and a functional film such as a reflective film is formed on the main surface of the glass substrate 1, the glass substrate 1 tends to warp. Therefore, by setting the coefficient of thermal expansion within the above range, it becomes easier to prevent such a situation. The "thermal expansion coefficient" is a value measured with a dilatometer and refers to an average value in a temperature range of 30 to 380°C.

The strain point of the glass substrate 1 is preferably 500° C. or higher, 550° C. or higher, 600° C. or higher, 620° C. or higher, and particularly preferably 640° C. or higher. This makes it difficult for the glass substrate 1 to thermally shrink due to the high-temperature heat treatment in the device manufacturing process. In addition, "strain point" refers to the value measured based on the method of ASTM C336.

The temperature at which the glass substrate 1 has a high-temperature viscosity of 10 ^2.5 dPa·s is preferably 1400° C. or lower, 1300° C. or lower, 1200° C. or lower, and particularly preferably 1100° C. or lower. By doing so, the productivity of the glass substrate is improved because the meltability is improved.

The liquidus temperature of the glass substrate 1 is preferably 1200° C. or lower, 1150° C. or lower, 1130° C. or lower, 1100° C. or lower, 1050° C. or lower, 1030° C. or lower, 1000° C. or lower, 980° C. or lower, and particularly preferably 950° C. It is below. Also, the liquidus viscosity is preferably 10 ^{3. 0} dPa·s or more, 10 ^3.5 dPa·s or more, 10 ^4.0 dPa·s or more, 10 ^4.5 dPa·s or more, 10 ^4.8 dPa·s or more, 10 ^5.0 dPa·s or more , 10 ^5.2 dPa·s or more, and particularly preferably 10 ^5.3 dPa·s or more. This makes it difficult for the glass to devitrify during molding, and facilitates molding by the float method or the overflow down-draw method. Here, the "liquidus viscosity" refers to a value obtained by measuring the viscosity of the glass at the liquidus temperature by the platinum ball pull-up method. The "liquidus temperature" is measured by placing the glass powder that passes through a 30-mesh standard sieve (opening: 500 µm) and remains in a 50-mesh standard sieve (opening: 300 µm) in a platinum boat and holds it in a temperature gradient furnace for 24 hours. refers to the measured value of the temperature at which crystals precipitate.

The glass substrate 1 can be formed by an overflow downdraw method, a slot down method, a redraw method, a float method, or a rollout method. In this embodiment, the overflow down-draw method is adopted from the viewpoint of improving the surface smoothness of both surfaces of the glass substrate 1 .

The internal transmittance of the glass substrate 1 at a wavelength of 550 nm converted to an optical path length of 10 mm is preferably 80% or more, 85% or more, or 90% or more, and particularly preferably 95% or more. If the internal transmittance of the glass substrate 1 is too low, the loss of light from entering the glass substrate 1 to exiting becomes large.

The thickness D of the glass substrate 1 is preferably 3 mm or less, 2 mm or less, and particularly preferably 1 mm or less. If the thickness of the glass substrate 1 is too large, the mass of the glass substrate laminate 3 increases, making it difficult to apply to devices such as head-mounted displays. On the other hand, if the thickness of the glass substrate 1 is too small, it becomes difficult to handle when assembling the device. Therefore, the thickness D of the glass substrate 1 is preferably 0.01 mm or more, 0.03 mm or more, and particularly preferably 0.05 mm or more.

As shown in FIG. 3, the glass substrate 1 is, for example, in the state of a glass substrate laminate 3 when used as a light guide plate of a head-mounted display. The glass substrate laminate 3 includes a plurality of glass substrates 1 and resin layers 4 arranged between the glass substrates 1 . That is, the glass substrate 1 and the resin layer 4 are alternately laminated in the thickness direction.

Although the number of laminated glass substrates 1 is three in the illustrated example, it is not limited to this, and may be, for example, two or more, five or more, or ten or more.

The resin layer 4 is made of a cured product of a photocurable resin (for example, an ultraviolet curable resin). That is, the resin layer 4 is a liquid resin before curing. Therefore, the resin layer 4 is hardened in a state of entering into the recesses of the concave-convex structure 2 formed on the glass substrate 1 due to fluidity in the uncured state. As a result, the adhesion between the uneven structure 2 of the glass substrate 1 and the resin layer 4 is improved, and there is no gap between the uneven structure 2 of the glass substrate 1 and the resin layer 4 . The “gap” here means a gap that can cause scattering of light propagating inside the glass substrate 1 . The presence or absence of a gap at the interface between the glass substrate 1 and the resin layer 4 can be determined, for example, by using an electron microscope to determine whether there is a gap at the interface between the glass substrate 1 and the resin layer 4, particularly around the uneven structure 2. . Thus, when the resin layer 4 is composed of a cured product of a photocurable resin instead of a resin film, the surface roughness Ra of the bottom surface 2a of the concave portion is not set to 10 nm or less, and the resin layer 4 is used for the light guide plate of the head-mounted display. It is possible to improve the display accuracy of the actual image. In other words, from the viewpoint of improving the accuracy of image display, at least one of the following: the surface roughness Ra of the bottom surface 2 of the concave portion is set to 10 nm or less; is preferred.

The resin layer 4 is preferably made of a transparent material.

The thickness of the resin layer 4 (in this embodiment, from the first main surface 1a of one of the two glass substrates 1 adjacent in the thickness direction to the second main surface 1b of the other glass substrate 1 The distance) E is preferably 0.5 mm or less, 0.2 mm or less, and particularly preferably 0.1 mm or less. If the thickness of the resin layer 4 is too large, the mass of the resin layer 4 increases, leading to an increase in the mass of the glass substrate laminate 3 . On the other hand, if the thickness of the resin layer 4 is too small, there is a concern that the adhesive strength of the glass substrate 1 will be lowered. Therefore, the thickness E of the resin layer 4 is preferably 1 μm or more, 5 μm or more, and particularly preferably 10 μm or more.

As shown in FIG. 4 , the glass substrate laminate 3 can be used as a light guide plate for a head mounted display 5 . Thus, the head mounted display 5 having the glass substrate laminate 3 in the light guide plate (display section) has the following three advantages.

First, since the glass substrate laminate 3 is in a state where there is no gap between the concave-convex structure 2 of the glass substrate 1 and the resin layer 4 as described above, while repeating total reflection inside the glass substrate 1, It is possible to reliably prevent the occurrence of a situation in which the propagating light is scattered in the gap and the displayed image is disturbed.

Secondly, when the head mounted display 5 is a see-through device, it is possible to reliably prevent the occurrence of a situation in which it is difficult to visually recognize the external scenery due to the gap.

Thirdly, since each glass substrate 1 constituting the glass substrate laminate 3 is made of high-refractive-index glass, total reflection of light tends to occur inside the glass substrate 1 using the characteristics of the high-refractive-index glass. The degree of freedom in optical design is improved.

The head-mounted display 5 may project a different image onto each glass substrate 1 constituting the glass substrate laminate 3 and display the image (VR or AR) visually recognized by the user in 3D. Further, each glass substrate 1 of the glass substrate laminate 3 is used as a dedicated glass substrate for displaying a predetermined color, such as a glass substrate for displaying red, a glass substrate for displaying green, and a glass substrate for displaying blue. (See, for example, the form of FIG. 5 of Patent Document 2).

Next, a method for manufacturing the glass substrate laminate 3 configured as described above will be described. Among the methods for manufacturing the glass substrate laminate 3, the method for manufacturing the glass substrate 1 will also be described. Of course, the method for manufacturing the glass substrate 1 is not limited to the case where it is incorporated into the method for manufacturing the glass substrate laminate 3 , and can be implemented independently as a method for manufacturing the glass substrate 1 .

The method for manufacturing the glass substrate laminate 3 according to the present embodiment includes, in order, a glass substrate preparation step, an uneven structure formation step, a liquid resin application step, a lamination step, and a curing step. Among them, the glass substrate preparation step and the concave-convex structure forming step correspond to the manufacturing method of the glass substrate 1 .

The glass substrate preparation step is a step of preparing a glass substrate 1 having a refractive index nd of 1.55 to 2.30. In the glass substrate preparation step, for example, the glass substrate 1 is obtained by forming the glass raw material prepared so that the refractive index nd is within the above-described range into a plate shape by the overflow down-draw method.

The concave-convex structure forming step is a step of forming the concave-convex structure 2 on the first main surface 1a of the glass substrate 1, as shown in FIG. Examples of the method for forming the concave-convex structure 2 include a photolithography method, a method of forming a predetermined structure by sputtering using a mask, a method of forming a uniform film and then laser-etching the film, and a method of using a mold. A method such as an imprint method can be used.

Here, in the concave-convex structure forming step, when the concave-convex structure 2 is formed using a photolithography method, if the chemical resistance of the glass substrate 1 is low, the bottom surface 2a of the concave portion may be roughened. If the glass composition range of 1 (especially the content of SiO ₂ ) is regulated, the chemical resistance is improved, so the surface roughness Ra of the bottom surface 2a of the recess can be made 10 nm or less.

The liquid resin application step is a step of applying a liquid resin 6 to the concave-convex structure 2 formed on the first main surface 1a of the glass substrate 1, as shown in FIG. Examples of the method of applying the liquid resin 6 to the concave-convex structure 2 include a method of applying the liquid resin 6 by spraying, and a method of dropping the liquid resin 6 onto the first main surface 1a of the glass substrate 1 and applying the liquid resin 6 uniformly using a recoater or a roller. It is possible to use a method of applying to Moreover, as the liquid resin 6, thermosetting resin, etc. can be used in addition to the photo-curing resin as long as the liquid state can be maintained.

The stacking step is a step of stacking a plurality of glass substrates 1 via a liquid resin 6, as shown in FIG. The liquid resin 6 is applied to the concave-convex structure 2 formed on the first main surface 1a of one of the two glass substrates 1 adjacent in the thickness direction, and the second main surface 1b of the other glass substrate 1. sandwiched between As a result, the concave-convex structure 2 formed on one glass substrate 1 and the second main surface 1 b of the other glass substrate 1 are brought into direct contact with the liquid resin 6 .

The curing step is a step of curing the liquid resin 6 to bond the glass substrates 1 together. As a method for curing the liquid resin 6, a curing method according to the type of the liquid resin 6 is used. That is, for example, when a thermosetting resin is used as the liquid resin 6, the liquid resin 6 is hardened by applying heat energy to it, and when a photo-setting resin is used as the liquid resin 6, the liquid resin 6 is cured by light energy. to harden. In particular, when curing is performed using light energy, since there is no need to perform heating, it is possible to suppress the temperature rise of the peripheral members. Further, when the photolithography method is used to form the concave-convex structure 2, the liquid resin 6 can be cured as part of the process. As the light energy, for example, light having a wavelength in the ultraviolet region or the visible light region can be used.

The present invention will be described in detail below based on examples. However, the following examples are merely illustrative. The present invention is by no means limited to the following examples.

Table 1 shows sample no. 1 to 10 are shown. In addition, "N.A." in the table means unmeasured.

Each sample in the table was produced as follows. First, glass raw materials were prepared so as to have the glass composition shown in the table, and melted at 1400° C. for 24 hours using a platinum pot. Next, the obtained molten glass was poured onto a carbon plate and formed into a flat plate. The properties shown in the table were evaluated for the obtained glasses.

The refractive index nd is such that after preparing a rectangular parallelepiped sample of 25 mm × 25 mm × about 3 mm, the temperature range from (annealing point Ta + 30 ° C.) to (strain point Ps - 50 ° C.) is 0.1 ° C./min. It is a value measured using a refractive index measuring instrument KPR-2000 manufactured by Shimadzu Corporation while annealing at a cooling rate and then penetrating a refractive index matching immersion liquid between glasses.

The density ρ is a value measured by the well-known Archimedes method.

The coefficient of thermal expansion α is a value measured with a dilatometer and is an average value in the temperature range of 30 to 380°C.

The strain point Ps and annealing point Ta are values measured according to the method of ASTM C336.

The softening point Ts is a value measured according to the method of ASTM C338.

The temperatures at high temperature viscosities of 10 ^4.0 dPa·s, 10 ^3.0 dPa·s, 10 ^2.5 dPa·s and 10 ^2.0 dPa·s are values measured by the platinum ball pull-up method.

The liquidus temperature TL is the temperature at which crystals precipitate after passing through a standard sieve of 30 meshes (500 μm) and remaining in a standard sieve of 50 meshes (300 μm) by placing the glass powder in a platinum boat and holding it in a temperature gradient furnace for 24 hours. is the measured value. The liquidus viscosity logηTL is a value obtained by measuring the viscosity of the glass at the liquidus temperature by the platinum ball pull-up method.

In this example, the sample No. in Table 1 was used. Using the glass No. 4, a glass substrate laminate was produced as follows. Of course, sample no. A glass substrate laminate may be produced using glasses of 1 to 3 and 5 to 10.

First, sample no. The material of No. 4 was melted in a continuous melting furnace and formed into a plate having a thickness of 1 mm by an overflow down-draw method to obtain a glass substrate.

Next, using a photolithography method, a SiO ₂ film was patterned into a shape having a predetermined periodicity on the main surface of the manufactured glass substrate to form an uneven structure. Specifically, first, a 200 nm-thick SiO ₂ film was formed on a glass substrate by a sputtering method. Next, a photoresist was applied on the _SiO2 film to form a resist film, and the resist film was covered with a predetermined photomask and irradiated with ultraviolet rays. Further, the exposed portion of the resist film was removed with a developing solution, and unnecessary portions of the SiO ₂ film (portions corresponding to the removed resist film) were removed by etching using hydrochloric acid. After that, by removing the non-exposed portions of the resist film, a periodic concave-convex structure including cylindrical projections with a height of 200 nm and a diameter of 50 nm was formed on the glass substrate.

Regarding the bottom surface of the concave portion of the uneven structure of the obtained glass substrate, the surface shape was observed and analyzed using a laser microscope "VK-X/250/260" manufactured by Keyence Corporation. The waviness was 20 nm or less. Further, when the glass substrate was cut and its cross section was observed using an electron microscope, the difference between the maximum thickness and the minimum thickness of the glass substrate was 0.5 μm. Furthermore, the projections of the uneven structure have a diameter of 49 nm at a height of 10 nm from the main surface of the glass substrate, a diameter of 50 nm at a height of 190 nm from the main surface of the glass substrate, and a width at 5% of the height. /(width at 95% of height) was 0.98.

Furthermore, an appropriate amount of UV curable resin was dropped on the surface having the uneven structure of the glass substrate, and the thickness was made uniform with a recoater, and another glass substrate having the uneven structure was placed thereon. After that, the ultraviolet curable resin was cured by irradiating ultraviolet rays from above to obtain a glass substrate laminate.

When the thus produced glass substrate laminate was cut and the concave-convex structure included in the cut surface was confirmed with an electron microscope, a concave-convex structure having periodic convex portions with a height of 200 nm and a width of 50 nm was formed. No gap was observed at the interface between the glass substrate and the resin around the uneven structure. Further, when the surface roughness Ra of the surface facing the surface having the uneven structure was measured, it was 10 nm.

The present invention is not limited to the above embodiments, and can be embodied in various forms without departing from the scope of the present invention.

In the above embodiment, the liquid resin applied to the concave-convex structure is cured after laminating the glass substrates, but the liquid resin applied to the concave-convex structure may be cured before laminating the glass substrates. . In this case, the glass substrates can be glued together, for example, by another adhesive layer. At this time, due to the fluidity of the liquid resin, the surface of the resin layer (the surface opposite to the uneven structure) can be smoothed while removing the gap between the uneven structure and the resin layer in advance. Any material such as a thermosetting resin film can be selected in addition to the cured product of the curable resin.

1 Glass substrate 1a First main surface 1b Second main surface 2 Concavo-convex structure 2a Concave bottom surface 2b Convex apex 3 Glass substrate laminate 4 Resin layer 5 Head mounted display 6 Liquid resin

Claims (6)

A method for manufacturing a glass substrate laminate obtained by laminating a plurality of glass substrates via a resin layer,
preparing a glass substrate having a refractive index nd of 1.55 to 2.30;
forming an uneven structure on the first main surface of the glass substrate;
a step of applying a liquid resin to the uneven surface of the uneven structure and filling the recesses of the uneven structure with the liquid resin ;
A method for manufacturing a glass substrate laminate, comprising: laminating a plurality of glass substrates having an uneven structure through the liquid resin or a cured product thereof. The liquid resin is cured by applying light energy,
2. After the step of laminating the glass substrates having the concave-convex structure, the step of curing the liquid resin by the light energy to bond the glass substrates having the concave-convex structure to each other is provided. The method for producing the glass substrate laminate according to 1. 3. The method for manufacturing a glass substrate laminate according to claim 1, wherein the surface roughness Ra of the second main surface opposite to the first main surface of the glass substrate is 10 nm or less. 1 to 1, wherein the glass substrate contains 10 to 60% by mass of SiO ₂ , 1 to 40% by mass of BaO, and 0.5 to 40% by mass of TiO ₂ +La ₂ O ₃ as a glass composition. 4. The method for producing a glass substrate laminate according to any one of 3. A glass substrate laminate obtained by laminating a plurality of glass substrates via a resin layer,
The glass substrate has an uneven structure on the first main surface and has a refractive index nd of 1.55 to 2.30,
The resin layer is made of a cured product of a photocurable resin,
The glass substrate laminate, wherein the resin layer is formed on the concave-convex surface of the concave-convex structure and filled in the concave portions of the concave-convex structure. A head mount display comprising a light guide plate having the glass substrate laminate according to claim 5 .

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