Light guide plate

Abstract

To provide a light guide plate capable of increasing color reproducibility of an image when used as a light guide plate for a spectacles-type device such as an AR / MR wearable device.SOLUTION: A light guide plate 10 comprises a glass plate 1 and a resin layer 2 formed on a main surface of the glass plate 1, and in the light guide plate 10, a difference in Abbe number νd between the glass plate 1 and the resin layer 2 is less than 10 and refractive index nd of the glass plate 1 and the resin layer 2 is 1.7 or greater and the difference is 1.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light guide plate for use in glasses-type devices such as wearable devices for AR (augmented reality) / MR (mixed reality). [Background technology]

[0002] In recent years, glasses-type devices such as wearable devices for AR / MR have been developed. These glasses-type devices are see-through devices that allow users to see images displayed on a light guide plate in the glasses while looking at the outside scenery. In such see-through devices, it is possible to realize 3D display by displaying different images on the light guide plates corresponding to the left and right pupils of the user, or to project images directly onto the user's retina by combining the image with the retina using the crystalline lens of the pupil.

[0003] As a method of displaying images using a light guide plate, a diffraction grating formed on the entrance surface of the light guide plate is used to make collimated light or laser light emitted from an image display element enter the light guide plate, and the entered light is guided while being totally reflected inside the light guide plate, and the light is taken out by a diffraction grating formed on the exit surface and made to enter the user's pupil. A light guide plate has been proposed in which the surface of a glass plate with high refractive index and excellent rigidity is coated with resin, and then a high-definition diffraction grating is formed by nanoimprinting (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-8599 A Summary of the Invention [Problem to be solved by the invention]

[0005] When a light guide plate made of a resin-coated glass plate is used in glasses-type devices such as wearable devices for AR / MR, images may not be projected with good color reproducibility.

[0006] In view of the above, an object of the present invention is to provide a light guide plate capable of improving the color reproducibility of an image when used as a light guide plate for a glasses-type device such as an AR / MR wearable device. [Means for solving the problem]

[0007] The light guide plate of the present invention is a light guide plate comprising a glass plate and a resin layer formed on a main surface of the glass plate, characterized in that the difference in Abbe number vd between the glass plate and the resin layer is less than 10, and the refractive indexes nd of the glass plate and the resin layer are 1.7 or more and the difference is 1.0 or less.

[0008] The light guide plate of the present invention comprises a glass plate and a resin layer, each of which has a refractive index according to the material. Here, if the difference in refractive index between the glass plate and the resin layer is small, light scattering at the interface between the two can be suppressed. However, since the refractive index of each material is wavelength-dependent, the refractive index difference may vary depending on the wavelength. For example, even if the difference in refractive index between the glass plate and the resin layer is small at a certain wavelength and light scattering at the interface between the two can be suppressed, the difference in refractive index between the glass plate and the resin layer may be large at another wavelength and light scattering at the interface between the two may be large. Therefore, the present inventor has focused on the Abbe number νd, which is an index of refractive index wavelength dependency, and has found that the above problem can be solved by reducing the difference in Abbe number νd between the glass plate and the resin layer as described above. Specifically, if the difference in Abbe number νd between the glass plate and the resin layer is reduced, the difference in the slope of the refractive index wavelength dependency curve between the two is reduced, and the variation in the refractive index difference at each wavelength is reduced, and as a result, light scattering at the interface between the two at each wavelength can be suppressed. This can improve the color reproducibility of the image. In the light guide plate of the present invention, the difference in refractive index nd between the glass plate and the resin layer is 1.0 or less, so that the difference in refractive index between the glass plate and the resin layer is small, making it difficult for light scattering loss to occur at the interface between them.

[0009] In the light guide plate of the present invention, the thickness of the glass plate is preferably 0.1 to 1 mm, and the thickness of the resin layer is preferably 1 μm or less. The intensity of the light incident on the light guide plate is reduced mainly due to loss caused by light scattering caused by the difference in refractive index at the interface between the glass plate and the resin layer, and loss caused by absorption inside the glass plate and the resin layer. When the thickness of the glass plate or the resin layer is small, the absorption loss inside the glass plate or the resin layer is small, and the influence of the light scattering loss at the interface between the glass plate and the resin layer tends to be relatively large. Therefore, when the thickness of the glass plate or the resin layer is small as described above, it is easy to enjoy the effects of the present invention.

[0010] The light guide plate of the present invention preferably has an internal transmittance of 70% or more at a wavelength of 450 to 650 nm when the glass plate has a thickness of 10 mm, which reduces absorption loss when light is guided inside the glass plate and increases the intensity of the emitted light.

[0011] The light guide plate of the present invention preferably has a difference in external transmittance between wavelengths of 450 nm and 650 nm of 5% or less, which reduces the variation in light emission intensity from the light guide plate depending on the wavelength, and makes it easier to improve the color reproducibility of images.

[0012] In the light guide plate of the present invention, the main surfaces of the glass plates preferably have a surface roughness Ra of 5 nm or less, which can suppress light scattering loss on the main surfaces of the glass plates when light is reflected and guided between the main surfaces of the glass plates, thereby increasing the intensity of the emitted light.

[0013] In the light guide plate of the present invention, it is preferable that an uneven structure is formed on the surface of the resin layer, so that the resin layer functions as a diffraction grating, allowing external light to enter the inside of the glass plate and allowing light inside the glass plate to exit to the outside.

[0014] In the light guide plate of the present invention, the resin layer is preferably made of a photocurable resin, which makes it possible to easily obtain a concave-convex structure having a nano-order shape.

[0015] The wearable device for AR / MR of the present invention is characterized by including any one of the light guide plates described above. Effect of the Invention

[0016] According to the present invention, it is possible to provide a light guide plate that can improve the color reproducibility of an image when used as a light guide plate for a glasses-type device such as an AR / MR wearable device. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of a light guide plate of the present invention. [Diagram 2] 13 is a graph showing transmittance curves of the light guide plate and the glass plate of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the light guide plate of the present invention will be described with reference to the drawings.

[0019] 1 is a schematic cross-sectional view showing one embodiment of the light guide plate of the present invention. The light guide plate 10 includes a glass plate 1 and a resin layer 2. The resin layer 2 is composed of resin layers 2a and 2b, each of which is formed on one main surface of the glass plate 1. Specifically, the resin layer 2a is formed on the surface of the light input portion of the glass plate 1, and the resin layer 2b is formed on the surface of the light output portion of the glass plate 1. An uneven structure is formed on the surfaces of the resin layers 2a and 2b, which function as a diffraction grating.

[0020] The light emitted from the image display element (not shown) is incident light L 1 The incident light L 1 The incident light L is diffracted by the resin layer 2a and enters the glass plate 1. 1 The incident light L is guided through the glass plate 1 to the light exit portion while being totally reflected between the two main surfaces of the glass plate 1. 1 is diffracted by the resin layer 2b formed in the light emitting portion, and the emitted light L 2The light is emitted to the outside of the glass plate 1 as a light beam and enters the human eye. In this way, the image projected from the image display element can be seen. In addition, since the light guide plate 1 itself is transparent and a see-through type, the outside scenery can also be seen through the light guide plate 1 at the same time. 1 and emitted light L 2 is visible light, for example light with a wavelength in the range of 400 to 800 nm.

[0021] (Glass plate 1) The refractive index (nd) of the glass plate 1 is 1.7 or more, preferably 1.8 or more, 1.9 or more, 1.95 or more, and particularly preferably 1.98 or more. On the other hand, the upper limit of the refractive index of the glass plate 1 is preferably 2.1 or less, 2.05 or less, 2.03 or less, and particularly preferably 2.01 or less. If the refractive index of the glass plate 1 is too low, the field of view (FOV) tends to be narrow when used as a light guide plate for a wearable device for AR / MR, etc. On the other hand, if the refractive index is too high, defects such as devitrification and striae occur, and the internal transmittance is likely to decrease.

[0022] The Abbe number of the optical glass 1 is not particularly limited, but since many resins with a refractive index of 1.7 or more have an Abbe number of 30 or less, from the viewpoint of reducing the difference in Abbe number with the resin layer 2, it is preferable that the lower limit of the Abbe number of the optical glass 1 be 20 or more, 22 or more, and particularly 25 or more, and that the upper limit be 30 or less, and particularly 28 or less.

[0023] The thickness of the glass plate 1 is preferably 0.1 mm or more, 0.15 mm or more, particularly 0.2 mm or more, and is preferably 1 mm or less, 0.5 mm or less, 0.4 mm or less, particularly 0.3 mm or less. If the thickness of the glass plate 1 is too small, the mechanical strength is likely to decrease. On the other hand, if the thickness of the glass plate 1 is too large, the weight of the wearable device using the glass plate 1 increases, and the discomfort when wearing the device tends to increase.

[0024] The length of the major axis (diagonal in the case of a rectangle) of the main surface of the glass plate 1 is preferably 100 mm or less, 80 mm or less, and particularly preferably 50 mm or less. This allows the wearable device to be miniaturized. There is no particular lower limit, but in reality it is 10 mm or more, and particularly 300 mm or more.

[0025] In addition, the more compact the glass plate 1 is (the smaller the thickness and major axis), the shorter the optical path length when light is guided inside the glass plate 1, the smaller the internal absorption loss, and the larger the influence of the light scattering loss at the interface between the glass plate 1 and the resin layer 2 tends to be. Therefore, when the thickness of the glass plate 1 is small as described above, it is easier to enjoy the effects of the present invention.

[0026] The internal transmittance of the glass plate 1 at a wavelength of 450 to 650 nm when the glass plate 1 has a thickness of 10 mm is preferably 70% or more, 80% or more, 90% or more, and particularly preferably 95% or more. This can suppress absorption loss when light is guided inside the glass plate 1, and can increase the intensity of the emitted light.

[0027] The surface roughness Ra of the first main surface 1a and the second main surface 1b of the glass plate 1 is preferably 5 nm or less, 3 nm or less, and particularly 2 nm or less. If the surface roughness Ra of the first main surface 1a and the second main surface 1b of the glass plate 1 is too large, scattering loss is likely to occur when light incident on the inside of the glass plate 1 is guided by repeating total reflection, making it difficult to obtain a bright and clear image. The lower limit of the surface roughness Ra of the first main surface 1a and the second main surface 1b of the glass plate 1 is not particularly limited, but is practically 0.1 nm or more.

[0028] The difference between the maximum and minimum distances between the first and second main surfaces 1a and 1b of the glass plate 1 (TTV=Total Thickness Variation) is preferably 5 μm or less, 3 μm or less, and particularly preferably 1 μm or less. If the TTV is too large, it becomes difficult for the light of each wavelength incident on the inside of the glass plate 1 to be accurately guided inside the glass plate 1, and the clarity of the obtained image is likely to decrease.

[0029] The glass plate 1 has a glass composition containing SiO , which is a component that improves the stability of vitrification. 2 Or B 2 O 3 , La, a component that increases the refractive index 2 O 3 Or Nb 2 O 5 By containing these components, it becomes easier to obtain a glass having a high refractive index and excellent mass productivity.

[0030] The preferred range of each component will be described below. In the following description, "%" means "% by mass" unless otherwise specified.

[0031] SiO 2 is effective for vitrification, but it is a component that greatly reduces the refractive index. 2 The content is preferably 1 to 45%, particularly preferably 3 to 35%.

[0032] B 2 O 3 However, since B is a component that increases the Abbe number, if its content is too high, it becomes difficult to obtain the desired Abbe number (for example, 30 or less). 2 O 3 The content is preferably 10% or less, particularly preferably 9.5% or less. There is no particular lower limit, but in order to increase the stability of vitrification, it is preferably 1% or more, particularly preferably 2% or more.

[0033] In addition, SiO 2 +B 2 O 3 The content of is preferably 1 to 55%, particularly preferably 5 to 40%. In this specification, "x+y+···" means the total amount of each component.

[0034] La 2 O 3 La is a component that significantly increases the refractive index and improves the stability of vitrification. 2 O 3The content of La is preferably 0 to 60%, 10 to 55%, 20 to 52%, and particularly preferably 30 to 50%. 2 O 3 If the content is too high, the resistance to devitrification decreases, and mass productivity tends to be poor.

[0035] Nb 2 O 5 Nb is a component that significantly increases the refractive index. It also has the effect of lowering the Abbe number. 2 O 5 The content is preferably 0 to 40%, more preferably 3 to 40%, and particularly preferably 5 to 39%.

[0036] Furthermore, 2 O 3 +Nb 2 O 5 The content is preferably 20 to 70%, particularly preferably 30 to 65%.

[0037] Others, La 2 O 3 Or Nb 2 O 5 In addition to Gd, a component that increases the refractive index 2 O 3 , Y 2 O 3 or Yb 2 O 3 can be contained.

[0038] Gd 2 O 3 La 2 O 3 Similarly, it can be contained in a large amount in the glass, but if it is too much, the glass density increases and devitrification becomes easy. Therefore, Gd 2 O 3 The content is preferably 0 to 20%, particularly preferably 1 to 10%.

[0039] Y 2 O 3 and Yb 2 O 3 The content of each of these components is preferably 0 to 10%, particularly preferably 0.1 to 8%. If the content of these components is too high, devitrification tends to occur.

[0040] Ln 2 O 3 By increasing the content of (Ln is at least one selected from La, Gd, Y, and Yb), it becomes easier to achieve a desired high refractive index (for example, 1.7 or more, 1.8 or more, or even 1.9 or more). However, Ln 2 O 3 If the content of Ln is too high, it is easy to cause devitrification. 2 O 3 The content is preferably 40 to 65%, more preferably 45 to 63%, and particularly preferably 48 to 60%.

[0041] In addition to the above components, TiO, which contributes to improving the refractive index, is also included. 2 or ZrO 2 It is preferred that it contains

[0042] TiO 2 is a component that increases the refractive index and decreases the Abbe number. 2 The content of TiO is preferably 5 to 40%, particularly preferably 10 to 30%. 2 If the content of TiO is too low, it becomes difficult to obtain the above-mentioned effect. 2 If the content is too high, the transmittance decreases and the vitrification becomes unstable.

[0043] ZrO 2 is also a component that increases the refractive index and decreases the Abbe number. 2 The content of ZrO is preferably 1 to 10%, particularly preferably 3 to 8%. 2 If the content of ZrO is too small, it becomes difficult to obtain the above effects. 2 If the content is too high, the transmittance decreases and the vitrification becomes unstable.

[0044] In addition, alkali metal components (Li 2 O, Na 2 O or K 2The glass may contain 0 to 30% in total of an alkali metal component (MgO, CaO, SrO, or BaO), an alkaline earth metal component (MgO, CaO, SrO, or BaO), or ZnO. The alkali metal component may be contained for the purpose of adjusting the refractive index and Abbe number. Specifically, the alkali metal component tends to lower the refractive index and Abbe number. The content of the alkali component is preferably 0 to 20%.

[0045] Sb 2 O 3 For the purpose of improving clarity and transmittance, it can be contained in the range of 0.1% or less.

[0046] As component (As 2 O 3 etc.), Pb components (PbO etc.) and fluorine components (F 2 etc.) have a large environmental impact and are therefore preferably not contained substantially. 2 O 3 and TeO 2 is a coloring component, and since it tends to reduce the transmittance in the visible range, it is preferable that it is not substantially contained. Here, "substantially not contained" means that it is not intentionally contained as a raw material, and does not exclude the inclusion of unavoidable impurities. Objectively, it means that the content of each of the above components is less than 0.1%.

[0047] A plurality of glass plates 1 may be laminated and used as a laminate. In this way, when glass plate 1 is used as a light guide plate for a wearable device, it becomes possible to project images overlapping in the depth direction of the display screen, thereby obtaining a 3D image. The number of laminated sheets is preferably 3 or more, and more preferably 6 or more.

[0048] (Resin layer 2) The refractive index (nd) of the resin layer 2 is 1.7 or more, preferably 1.8 or more, 1.9 or more, 1.95 or more, and particularly preferably 1.98 or more. On the other hand, the upper limit of the refractive index of the resin layer 2 is preferably 2.1 or less, 2.05 or less, 2.03 or less, and particularly preferably 2.01 or less. In this way, the difference in refractive index with the glass plate 1 becomes small, and light scattering loss at the interface between the glass plate 1 and the resin layer 2 becomes less likely to occur.

[0049] The difference in refractive index (nd) between the glass plate 1 and the resin layer 2 is 1.0 or less, and preferably 0.5 or less, 0.3 or less, 0.2 or less, and particularly preferably 0.15 or less. In this way, the difference in refractive index with the glass plate 1 becomes small, and light scattering loss at the interface between the glass plate 1 and the resin layer 2 becomes less likely to occur.

[0050] Taking into consideration the difference in Abbe number between the resin layer 2 and the optical glass 1, the Abbe number of the resin layer 2 is, for example, preferably 10 or more, 15 or more, 20 or more, and particularly preferably 25 or more, and the upper limit is preferably 45 or less, 40 or less, 35 or less, and particularly preferably 30 or less.

[0051] The difference in Abbe number (νd) between the glass plate 1 and the resin layer 2 is less than 10, and is preferably 8 or less, 5 or less, and particularly preferably 3 or less. In this way, for the reasons described above, light scattering at the interface between the glass plate 1 and the resin layer 2 can be suppressed at each wavelength, and color reproducibility of the image can be improved.

[0052] An index of color reproducibility of an image is, for example, the difference in external transmittance (transmittance including reflection loss) at wavelengths of 450 nm and 650 nm of light guide plate 10, which is a laminate of glass plate 1 and resin layer 2. The difference in external transmittance at wavelengths of 450 nm and 650 nm of light guide plate 10 is preferably 5% or less, 4% or less, 3% or less, and particularly preferably 2.5% or less. In this way, the variation in light emission intensity from light guide plate 10 according to wavelength is reduced, and the color reproducibility of the image is likely to be improved.

[0053] The thickness of the resin layer 2 is preferably 5 μm or less, 1 μm or less, and particularly 0.5 μm or less. If the thickness of the resin layer 2 is too large, the light absorption increases, and the intensity of the light emitted from the light guide plate 10 tends to decrease. The lower limit of the thickness of the resin layer 2 is not particularly limited, but in order to form a desired uneven structure on the surface, it is preferable that the thickness is 0.01 μm or more, and particularly 0.1 μm or more. Note that the smaller the thickness of the resin layer 2, the smaller the absorption loss inside the resin layer 2, and the influence of the light scattering loss at the interface between the glass plate 1 and the resin layer 2 tends to be relatively large. Therefore, when the thickness of the resin layer 2 is small as described above, it is easier to enjoy the effects of the present invention.

[0054] When forming a concave-convex structure on the surface of the resin layer 2, the height of the concave-convex structure may be appropriately set so as to obtain a desired diffraction ability. For example, the height of the concave-convex structure may be 0.01 to 0.2 μm, or further 0.03 to 0.1 μm.

[0055] The resin layer 2 is preferably a photocurable resin, which makes it possible to easily obtain a concave-convex structure having a nano-order shape. EXAMPLES

[0056] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0057] Table 1 shows examples (Nos. 1 to 3) of the present invention and a comparative example (No. 4), and Table 2 shows the compositions of the glass plates used in the examples and comparative example.

[0058] [Table 1]

[0059] [Table 2]

[0060] In this example, the difference in external transmittance according to wavelength was evaluated for a light guide plate having the characteristics and composition shown in Tables 1 and 2, in which a resin layer was formed on the surface of a glass plate. Specifically, the difference in external transmittance of the light guide plate at wavelengths of 450 nm and 650 nm was measured. The glass plate was prepared by mixing raw materials to have the composition shown in Table 2, melting and casting the raw materials at 1250 to 1400°C in air using a platinum crucible to obtain a glass molded body, and then cutting and polishing the glass molded body. The resin used for the resin layer had a refractive index of 1.71 to 2.10, an Abbe number of 24 to 36, and an internal transmittance of 99%. FIG. 2 shows the external transmittance curve of the light guide plate of Example 2. FIG. 2 also shows the external transmittance curve of the glass plate used in Example 2 for reference.

[0061] The surface roughness Ra of the glass plate was measured using a Bruker AFM Dimension Icon with a scan size of 10 μm and a scan speed of 1 Hz.

[0062] The refractive index of the glass plate was measured as follows. A glass plate with a thickness of 0.3 mm was cut at a right angle or polished at a right angle, and the cut or polished surface was mirror-polished with #1000 polishing paper. Two of the above glass plates were then bonded together in a refractive index matching immersion liquid (Kalnew) with a refractive index of 1.78, and the refractive index was measured using a Shimadzu KPR-2000. The Abbe number was calculated from the refractive indexes of the obtained wavelengths of d-line, C-line, and F-line.

[0063] The internal transmittance of the glass plate was measured as follows. Glass plates with a size of 10×10 mm or more and a thickness of 10 mm and a thickness of 3 mm were prepared from the glass molded body produced by the above-mentioned method, and were mirror-polished with #1000 abrasive paper or cerium abrasive powder. The internal transmittance not including reflection loss was calculated from the transmittance obtained by measuring these glass plates using a UV-3100 made by Shimadzu Corporation.

[0064] The refractive index of the resin was measured using an ellipsometer EF-5000 manufactured by Otsuka Electronics Co., Ltd. The Abbe number was calculated from the refractive index at each wavelength of the d-line, C-line, and F-line obtained.

[0065] The transmittance of the light guide plate having a resin layer formed on the surface of a glass plate was measured using UV-3100 manufactured by Shimadzu Corporation.

[0066] As shown in Table 1, the light guide plates of Examples No. 1 to 3 have a small Abbe number difference between the glass plate and the resin layer of 8 or less, and a small difference in transmittance at wavelengths of 450 nm and 650 nm of 2%. Therefore, it is considered that the color reproducibility is high when used as a light guide plate for an AR / MR wearable device. On the other hand, the light guide plate of Comparative Example No. 4 has a large Abbe number difference between the glass plate and the resin layer of 11, and a large difference in transmittance at wavelengths of 450 nm and 650 nm of 7%. Therefore, it is considered that the color reproducibility is poor when used as a light guide plate for an AR / MR wearable device.

Claims

1. A light guide plate including a glass plate and a resin layer formed on a main surface of the glass plate, The difference in Abbe number νd between the glass plate and the resin layer is less than 10; A light guide plate, characterized in that the refractive indexes nd of a glass plate and a resin layer are 1.7 or more and the difference therebetween is 1.0 or less.

2. 2. The light guide plate according to claim 1, wherein the glass plate has a thickness of 0.1 to 1 mm, and the resin layer has a thickness of 1 μm or less.

3. 3. The light guide plate according to claim 1, wherein the internal transmittance at wavelengths of 450 to 650 nm is 70% or more when the glass plate has a thickness of 10 mm.

4. 4. The light guide plate according to claim 1, wherein the difference in external transmittance between wavelengths of 450 nm and 650 nm is 5% or less.

5. 5. The light guide plate according to claim 1, wherein the main surface of the glass plate has a surface roughness Ra of 5 nm or less.

6. 6. The light guide plate according to claim 1, wherein an uneven structure is formed on a surface of the resin layer.

7. 7. The light guide plate according to claim 1, wherein the resin layer is made of a photocurable resin.

8. A wearable device for AR / MR comprising the light guide plate according to any one of claims 1 to 7.

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