Light guide member

Abstract

The present invention provides a light guide member capable of guiding light of mutually different colors separately for each color. This light guide member has a first layer containing a first hologram, a second layer disposed below the first layer, and a third layer disposed below the second layer and containing a second hologram. The first hologram diffracts first light incident from above and also transmits second light incident from above and different in color from the first light. The second hologram diffracts the second light transmitted through the first hologram. The first layer guides the first light diffracted by the first hologram, and the third layer guides the second light diffracted by the second hologram. The refractive index of the second layer is lower than the respective refractive indices of the first layer and the third layer.

Description

Light guide member

[0001] The present invention relates to a light guide member.

[0002] For example, Patent Document 1 discloses a light guide member that includes a plurality of light guide layers each including a hologram such as a diffractive optical element and corresponding to light of different colors.

[0003] Japanese Patent Application Laid-Open No. 2020-177219

[0004] However, in the light-guiding member described in Patent Document 1, the light guided through the light-guiding layer is not totally reflected at the interface of the light-guiding layer, but passes through the interface, which may prevent light of different colors from being guided separately by color.

[0005] An object of the present invention is to provide a light guide member capable of separating light of different colors and guiding the light according to the colors.

[0006] A light-guiding member according to one aspect of the present invention comprises a first layer including a first hologram, a second layer disposed below the first layer, and a third layer disposed below the second layer and including a second hologram, wherein the first hologram diffracts first light incident from above and transmits second light incident from above and having a different color from the first light, the second hologram diffracts the second light that has transmitted through the first hologram, the first layer guides the first light diffracted by the first hologram, and the third layer guides the second light diffracted by the second hologram, and the refractive index of the second layer is lower than the refractive indexes of the first layer and the third layer.

[0007] According to the present invention, it is possible to provide a light guide member that can guide light of different colors separately according to the colors.

[0008] 1 is a schematic cross-sectional view showing the overall configuration of a light-guiding member according to a first embodiment; FIG. 2 is a schematic cross-sectional view of a light-guiding member according to a first modified example; FIG. 3 is a schematic cross-sectional view of a light-guiding member according to a second modified example; FIG. 4 is a diagram showing a method for producing a hologram provided in a light-guiding member according to an example and a comparative example; FIG. 5 is a diagram showing state changes of a monomer and a binder in response to exposure of interference fringes; FIG. 6 is a diagram showing the light-guiding result by a light-guiding member according to Example 1; FIG. 7 is a diagram showing the light-guiding result by a light-guiding member according to a comparative example; FIG. 8 is a schematic top view showing a first layer provided in a light-guiding member according to a second embodiment; and FIG. 9 is a schematic perspective view showing the first and third layers provided in a light-guiding member according to the second embodiment.

[0009] A light-guiding member according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the following embodiments are merely examples of the light-guiding member according to the embodiment of the present invention, and the present invention is not limited to the following.

[0010] Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of components described in the embodiments of the present invention are not intended to limit the scope of the embodiments of the present invention, but are merely illustrative examples. The sizes, positional relationships, etc. of components shown in each drawing may be exaggerated for clarity. In the following description, the same names and symbols indicate the same or similar components, and detailed descriptions will be omitted as appropriate.

[0011] In the following, for ease of understanding, the arrangement and configuration of each part may be described using an XYZ Cartesian coordinate system. The three axes in the XYZ Cartesian coordinate system are mutually orthogonal. In the XYZ Cartesian coordinate system, the direction in which the X axis extends is referred to as the "X direction," the direction in which the Y axis extends is referred to as the "Y direction," and the direction in which the Z axis extends is referred to as the "Z direction." The direction in which the arrow indicating the X axis points is referred to as the +X direction, and the direction opposite to the +X direction is referred to as the -X direction. The direction in which the arrow indicating the Y axis points is referred to as the +Y direction, and the direction opposite to the +Y direction is referred to as the -Y direction. The direction in which the arrow indicating the Z axis points is referred to as the +Z direction, and the direction opposite to the +Z direction is referred to as the -Z direction. In this specification, the +Z direction is referred to as "up" and the -Z direction is referred to as "down." However, these directional expressions merely describe the relationship between relative positions, orientations, directions, etc., and do not necessarily correspond to the relationship during use. These directions are unrelated to the direction of gravity. "Placing" does not necessarily mean direct contact, but also includes indirect placement, for example, via another member. In this specification, "perpendicular" may include a deviation of ±10 degrees from 90 degrees. "Parallel" may include a deviation of ±10 degrees from 0 degrees.

[0012] [First embodiment] <Configuration example of light guiding member according to first embodiment> (Overall configuration) The overall configuration of the light guiding member according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of the overall configuration of a light guiding member 100 according to the first embodiment. Fig. 1 shows a cross section of the light guiding member 100 including each of a plurality of layers included in the light guiding member 100.

[0013] The light-guiding member 100 shown in FIG. 1 is a member that receives first light L1 and second light L2, which are different in color from each other, from above, guides each of the first light L1 and the second light L2 in the +X direction, and then emits them upward.

[0014] Light-guiding member 100 includes a first layer 1 including a first hologram 11, a second layer 2 disposed below first layer 1, and a third layer 3 disposed below second layer 2 and including a second hologram 31. In the example shown in FIG. 1 , light-guiding member 100 also includes a first light-transmitting layer 4 disposed above first layer 1 and a second light-transmitting layer 5 disposed below third layer 3. First hologram 11 diffracts first light L1 incident from above and transmits second light L2 incident from above and having a different color from first light L1. Second hologram 31 diffracts second light L2 transmitted through first hologram 11. First layer 1 guides first light L1 diffracted by first hologram 11. Third layer 3 guides second light L2 diffracted by second hologram 31. The refractive index of the second layer 2 is lower than the refractive index of each of the first layer 1 and the third layer 3 .

[0015] In the example shown in Fig. 1 , the outer edge shape of the light-guiding member 100 when viewed from above is substantially rectangular. The first layer 1, the second layer 2, the third layer 3, the first light-transmitting layer 4, and the second light-transmitting layer 5 are stacked in the Z direction. The first layer 1, the second layer 2, the third layer 3, the first light-transmitting layer 4, and the second light-transmitting layer 5 are layers that extend in two orthogonal axial directions in a plane parallel to an imaginary plane that is orthogonal to the Z direction. In the example shown in Fig. 1 , the first layer 1, the second layer 2, the third layer 3, the first light-transmitting layer 4, and the second light-transmitting layer 5 extend in the X direction and the Y direction in a plane parallel to the XY plane.

[0016] 1 , first hologram 11 diffracts first light L1 incident from above in the +X direction. First light L1 diffracted by first hologram 11 is guided in the +X direction while being totally reflected by upper surface 41 of first light-transmitting layer 4 and by first interface 21 between first layer 1 and second layer 2. Second hologram 31 diffracts second light L2 that has passed through first hologram 11 in the +X direction. Second light L2 diffracted by second hologram 31 is guided in the +X direction while being totally reflected by second interface 22 between second layer 2 and third layer 3 and by lower surface 51 of second light-transmitting layer 5.

[0017] Here, for example, in a light-guiding member 100 that does not include the second layer 2 and has the first layer 1 stacked on the third layer 3, the first light L1 guided in the X direction may not be totally reflected at the interface between the first layer 1 and the third layer 3, but may transmit through the interface and enter the third layer 3. Furthermore, the second light L2 guided in the X direction may not be totally reflected at the interface between the first layer 1 and the third layer 3, but may transmit through the interface and enter the first layer 1. As a result of the first light L1 entering the third layer 3 and the second light L2 entering the first layer 1, the first light L1 and the second light L2 cannot be guided separately by color. For example, in a color display device, when a light-guiding member is used to guide image light of each color that constitutes a color image, the image light of each color cannot be guided separately, and the colors of the image light may mix, making it impossible to display the color image in the appropriate colors.

[0018] Furthermore, for example, in a light-guiding member in which a layer having a refractive index equal to or greater than the refractive index of each of the first layer 1 and the third layer 3 is disposed between the first layer 1 and the third layer 3, the first light L1 and the second light L2 cannot be guided separately for each color, as a result of which the first light L1 enters the third layer 3 and the second light L2 enters the first layer 1. As a result, for example, when a light-guiding member is used to guide image light of each color that constitutes a color image, the image light of each color cannot be guided separately, and the colors of the image light may mix, making it impossible to display the color image in appropriate colors.

[0019] In this embodiment, the refractive index of the second layer 2 disposed between the first layer 1 and the third layer 3 is lower than the refractive indexes of the first layer 1 and the third layer 3. For example, if the refractive index of the first layer 1 is n1, the refractive index of the second layer 2 is n2, and the refractive index of the third layer 3 is n3, then n2 / n1≦0.9 and n2 / n3≦0.9. Because the refractive index n2 of the second layer 2 is lower than the refractive index n1 of the first layer 1, the first light L1 guided through the first layer 1 is totally reflected at the first interface 21, thereby reducing the first light L1 from entering the third layer 3. Furthermore, because the refractive index n2 of the second layer 2 is lower than the refractive index n3 of the third layer 3, the second light L2 guided through the second layer 2 is totally reflected at the second interface 22, thereby reducing the second light L2 from entering the first layer 1. As described above, the light-guiding member 100 can guide the first light L1 through the first layer 1 and the second light L2 through the third layer 3, and therefore can guide light of different colors separately for each color. In other words, this embodiment can provide a light-guiding member 100 that can guide light of different colors separately for each color. For example, in a color display device, when a light-guiding member is used to guide image light of each color that constitutes a color image, the color display device can display a color image in appropriate colors using the image light of each color guided by the light-guiding member 100.

[0020] In this embodiment, the above-described effect of being able to guide light of different colors separately by color can be obtained even if the light-guiding member 100 does not include at least one of the first light-transmitting layer 4 and the second light-transmitting layer 5. However, if the first layer 1 and the third layer 3 are thin film-like layers, the shapes of the thin film-like layers may not be maintained constant, which may result in unstable light guidance by the light-guiding member 100. By including the first light-transmitting layer 4 and the second light-transmitting layer 5 in the light-guiding member 100, the shapes of the first layer 1 and the third layer 3 can be maintained approximately constant, allowing stable light guidance by the light-guiding member 100.

[0021] The first layer 1 guiding the first light L1 includes guiding the first light L1 through a light guide path formed by the first layer 1 and a layer other than the first layer 1. For example, in the light-guiding member 100 shown in FIG. 1 , the first layer 1 can guide the first light L1 through a light guide path formed by the first layer 1 and the first light-transmitting layer 4. Similarly, the third layer 3 guiding the second light L2 includes guiding the second light L2 through a light guide path formed by the third layer 3 and a layer other than the third layer 3. For example, in the light-guiding member 100 shown in FIG. 1 , the third layer 3 can guide the second light L2 through a light guide path formed by the third layer 3 and the second light-transmitting layer 5.

[0022] The shape of the outer edge of light-guiding member 100 when viewed from above is not limited to a substantially rectangular shape, and may be a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, etc. The area of ​​light-guiding member 100 when viewed from above can be changed as appropriate depending on the intended use of light-guiding member 100. The shape and area of ​​the outer edge of each of first hologram 11 and second hologram 31 when viewed from above can also be changed as appropriate depending on the intended use of light-guiding member 100.

[0023] In the light-guiding member 100 shown in FIG. 1 , the first layer 1 includes a third hologram 12 located at a position spaced apart from the first hologram 11 in the direction in which the first light L1 is guided. The third layer 3 includes a fourth hologram 32 located at a position spaced apart from the second hologram 31 in the direction in which the second light L2 is guided. In the example shown in FIG. 1 , the direction in which the first light L1 is guided and the direction in which the second light L2 is guided are both the +X direction. The fourth hologram 32 diffracts the second light L2 guided by the third layer 3 upward. The third hologram 12 diffracts the first light L1 guided by the first layer 1 upward and transmits the second light L2 diffracted by the fourth hologram 32. First light L1 diffracted by third hologram 12 and second light L2 diffracted by fourth hologram 32 are each emitted upward from light-guiding member 100 and extracted therefrom. With this configuration, light-guiding member 100 can extract, from light-guiding member 100, light of different colors that is incident on light-guiding member 100 and guided by light-guiding member 100, light of each color. For example, in a color display device, when a light-guiding member is used to guide image light of each color that constitutes a color image, image light of different colors that is guided by light-guiding member 100 can be extracted therefrom for each color. The color display device can display a color image in appropriate colors using the image light of each color extracted from light-guiding member 100.

[0024] In the light-guiding member 100, the fourth hologram 32 may diffract the second light L2 guided by the third layer 3 downward, and the third hologram 12 may diffract the first light L1 guided by the first layer 1 downward. In this case, the fourth hologram 32 diffracts the second light L2 guided by the third layer 3 downward and transmits the first light L1 diffracted by the third hologram 12. The first light L1 and the second light L2 guided by the light-guiding member 100 are each emitted downward from the light-guiding member 100 and extracted from the light-guiding member 100. From another perspective, the light-guiding member 100 is not limited to the same direction as the direction in which the first light L1 and the second light L2 are incident, and the first light L1 and the second light L2 may be extracted in a direction different from the direction in which the first light L1 and the second light L2 are incident.

[0025] The structure of each layer in the light guide member 100 will be described in detail below.

[0026] (First Layer 1) The first layer 1 can be formed from a light-transmitting resin material, glass material, or the like. For example, Bayfol HX200 manufactured by Covestro can be used for the first layer 1. The light-transmitting property of the first layer 1 preferably has a transmittance of 60% or more for wavelengths of light in the visible light range. The first hologram 11 is provided in the first layer 1, for example, by forming a structure such as a diffraction grating in a part of the first layer 1, which is formed from a resin material. However, the first hologram 11 may also be prepared separately from the first layer 1. For example, the first hologram 11 may be formed from a resin material and provided on the first layer 1, which is formed from a resin material or a glass material.

[0027] 1 , the first hologram 11 is a reflection volume hologram. A reflection volume hologram can select and diffract light of a specific wavelength. Because the first hologram 11 is a reflection volume hologram, the first hologram 11 can select and diffract the first light L1 from the first light L1 and the second light L2 incident on the light-guiding member 100, thereby preferably separating the first light L1 from the second light L2.

[0028] (Second Layer 2) The second layer 2 has a refractive index lower than that of the first layer 1 and the third layer 3. When the first layer 1 and the third layer 3 are primarily composed of PMMA (Polymethyl methacrylate), the refractive index of each of the first layer 1 and the third layer 3 is approximately 1.49. In comparison, the refractive index of the second layer 2 is preferably 1.30 or less, and more preferably 1.20 or less. For example, the low refractive index layer having voids disclosed in International Publication No. WO 2019 / 146628 can be used for the second layer 2, the contents of which are incorporated herein by reference.

[0029] (Third Layer 3) The third layer 3 can be formed of a light-transmitting resin material, glass material, or the like. For example, Bayfol HX200 manufactured by Covestro can be used for the third layer 3. The light-transmitting property of the third layer 3 preferably has a transmittance of 60% or more for wavelengths of light in the visible light range. The second hologram 31 is provided in the third layer 3, for example, by forming a structure such as a diffraction grating in a part of the third layer 3, which is formed of a resin material. However, the second hologram 31 may also be prepared separately from the third layer 3. For example, the second hologram 31 may be formed of a resin material and provided in the third layer 3 by being applied to the third layer 3, which is formed of a resin material or a glass material.

[0030] (First Light-Transmitting Layer 4 and Second Light-Transmitting Layer 5) The first light-transmitting layer 4 and the second light-transmitting layer 5 can each be configured to include a light-transmitting resin material, glass material, etc. The light-transmitting properties of the first light-transmitting layer 4 and the second light-transmitting layer 5 preferably provide a transmittance of 60% or more for wavelengths of light in the visible light region.

[0031] Table 1 shows an example of the refractive index of each layer constituting the light-guiding member 100.

[0032]

[0033] [First Modification] Next, a light guide member according to a first modification will be described. Note that the same names and symbols as those in the already described embodiment indicate the same or similar members or configurations, and detailed descriptions will be omitted as appropriate. This also applies to the following embodiments, modifications, examples, and comparative examples.

[0034] 2 is a schematic cross-sectional view illustrating an example of a light guide member 100 according to a first modified example. FIG. 2 shows a cross section of the light guide member 100 including each of a plurality of layers included in the light guide member 100.

[0035] The first modified example differs from the first embodiment mainly in that it has a first adhesive layer 6 disposed between the first layer 1 and the second layer 2, and a second adhesive layer 7 disposed between the second layer 2 and the third layer 3. The refractive indexes of the first adhesive layer 6 and the second adhesive layer 7 are higher than the refractive index of the second layer 2.

[0036] 2 , first light L1 diffracted by first hologram 11 is guided in the +X direction while being totally reflected by both the upper surface 41 of first light-transmitting layer 4 and the third interface 23 between the first adhesive layer 6 and the second layer 2. Furthermore, second light L2 diffracted by second hologram 31 is guided in the +X direction while being totally reflected by both the fourth interface 24 between the second layer 2 and the second adhesive layer 7 and the lower surface 51 of the second light-transmitting layer 5. In this first modified example, the same effects as those of the first embodiment can be obtained.

[0037] [Second Modification] Next, a light guiding member according to a second modification will be described. Fig. 3 is a schematic cross-sectional view showing an example of a light guiding member 100 according to the second modification. Fig. 3 shows a cross section of the light guiding member 100 including each of a plurality of layers included in the light guiding member 100.

[0038] The second modified example differs from the first embodiment mainly in that the first light L1, the second light L2, and the third light L3, which are different in color from one another, can be guided separately by color.

[0039] A light-guiding member 100 according to the second modification includes a fourth layer 8 disposed below the third layer 3 and a fifth layer 9 disposed below the fourth layer 8 and including a fifth hologram 91. In the example shown in FIG. 3 , the light-guiding member 100 also includes a first light-transmitting layer 4 disposed above the first layer 1 and a third light-transmitting layer 10 disposed below the fifth layer 9. In the second modification, the first hologram 11 diffracts the first light L1 incident from above and transmits the second light L2 and the third light L3 incident from above, the second light L2 having a different color from the first light L1 and the second light L2. The second hologram 31 diffracts the second light L2 that has passed through the first hologram 11 and transmits the third light L3 that has passed through the second hologram 31. The fifth hologram 91 diffracts the third light L3 that has passed through the second hologram 31. The fifth layer 9 guides the third light L3 diffracted by the fifth hologram 91. The refractive index of the fourth layer 8 is lower than the refractive index of each of the third layer 3 and the fifth layer 9.

[0040] In the example shown in Figure 3, the outer edge shape of the light-guiding member 100 when viewed from above is approximately rectangular. The first layer 1, the second layer 2, the third layer 3, the first light-transmitting layer 4, the fourth layer 8, the fifth layer 9, and the third light-transmitting layer 10 are stacked in the Z direction. The first layer 1, the second layer 2, the third layer 3, the first light-transmitting layer 4, the fourth layer 8, the fifth layer 9, and the third light-transmitting layer 10 are layers that extend in two orthogonal axial directions in a plane parallel to an imaginary plane perpendicular to the Z direction. In the example shown in Figure 3, the first layer 1, the second layer 2, the third layer 3, the first light-transmitting layer 4, the fourth layer 8, the fifth layer 9, and the third light-transmitting layer 10 each extend in the X direction and the Y direction in a plane parallel to the XY plane.

[0041] In the example shown in Fig. 3, first hologram 11 diffracts first light L1 incident from above in the +X direction. The first light L1 diffracted by first hologram 11 is guided in the +X direction while being totally reflected at upper surface 41 of first light-transmitting layer 4 and at first interface 21 between first layer 1 and second layer 2. Second hologram 31 diffracts second light L2 that has passed through first hologram 11 in the +X direction. Second light L2 diffracted by second hologram 31 is guided in the +X direction while being totally reflected at second interface 22 between second layer 2 and third layer 3 and at fifth interface 25 between third layer 3 and fourth layer 8. Fifth hologram 91 diffracts third light L3 that has passed through first hologram 11 and second hologram 31 in the +X direction. The third light L3 diffracted by the fifth hologram 91 is guided in the +X direction while being totally reflected at the sixth interface 26 between the fourth layer 8 and the fifth layer 9 and at the lower surface 101 of the third light-transmitting layer 10.

[0042] In the second modification, the first light L1 can be guided by the first layer 1, the second light L2 can be guided by the third layer 3, and the third light L3 can be guided by the fifth layer 9. This allows three different color lights to be guided separately for each color. For example, in a color display device, when a light guide member is used to guide image light of the three primary colors that constitute a color image, the color display device can display a color image in appropriate colors using the image light of each of the three primary colors guided by the light guide member 100.

[0043] In the second modified example, the light-guiding member 100 has the first light-transmitting layer 4 and the third light-transmitting layer 10, so that the shapes of the first layer 1, the third layer 3, and the fifth layer 9 can be maintained almost constant, and light can be guided stably by the light-guiding member 100.

[0044] In the second modification, the fifth layer 9 includes a sixth hologram 92 located at a position spaced apart from the fifth hologram 91 in the direction in which the third light L3 is guided. The sixth hologram 92 diffracts the third light L3 guided by the fifth layer 9 upward. With this configuration, the light-guiding member 100 according to the second modification can extract three different colors of light that are incident on the light-guiding member 100 and guided by the light-guiding member 100, from the light-guiding member 100, for each color. For example, in a color display device, when a light-guiding member is used to guide image light of three primary colors that constitute a color image, the image light of the three different colors guided by the light-guiding member 100 can be extracted from the light-guiding member 100 for each primary color. The color display device can display a color image in appropriate colors using the image light of each of the three primary colors extracted from the light-guiding member 100.

[0045] In light-guiding member 100 according to the second modification, fourth hologram 32 may diffract second light L2 guided by third layer 3 downward, third hologram 12 may diffract first light L1 guided by first layer 1 downward, and sixth hologram 92 may diffract third light L3 guided by fifth layer 9 downward. In this case, fourth hologram 32 diffracts second light L2 guided by third layer 3 downward and transmits first light L1 diffracted by third hologram 12. Furthermore, sixth hologram 92 diffracts third light L3 guided by fifth layer 9 downward and transmits second light L2 diffracted by fourth hologram 32. The first light L1, second light L2, and third light L3 guided by light-guiding member 100 are each emitted downward from light-guiding member 100 and extracted from light-guiding member 100. From another perspective, the light-guiding member 100 is not limited to being incident in the same direction as the first light L1, the second light L2, and the third light L3, and can also extract the first light L1, the second light L2, and the third light L3 in a direction different from the direction in which the first light L1, the second light L2, and the third light L3 are incident.

[0046] Examples and Comparative Examples Examples and comparative examples will be described below, but the present invention is not limited to these examples.

[0047] <Method of manufacturing first hologram 11 and second hologram 31> First, a method of manufacturing holograms such as first hologram 11 and second hologram 31 included in light-guiding member 100 according to the example and comparative example will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a diagram showing an example of a method of manufacturing holograms included in light-guiding member 100 according to the example and comparative example. Fig. 5 is a diagram showing changes in the state of the monomer and binder in response to exposure to interference fringes.

[0048] As shown in Figures 4 and 5, in the examples and comparative examples, the first hologram 11 and the second hologram 31 were produced by exposing the first layer 1 or the third layer 3, which contained a photopolymer, to interference fringes fg.

[0049] 4 , in the method for producing first hologram 11, first layer 1 disposed on first light-transmitting layer 4 was irradiated from above with first laser light B1, which was one of the laser lights branched from laser light having a peak wavelength of 532 nm. Furthermore, first layer 1 disposed on first light-transmitting layer 4 was irradiated from below via lens 110 with second laser light B2, which was the other of the laser lights branched from the laser light having a peak wavelength of 532 nm. First layer 1 was exposed to light having an intensity distribution corresponding to interference fringes fg generated by interference between first laser light B1 and second laser light B2.

[0050] 5, a cross-sectional light intensity distribution fg1 represents a cross-sectional light intensity distribution along the arrangement direction fg0 of the interference fringes fg aligned in the arrangement direction fg0. A first layer 1' represents the state of the first layer before the interference fringes fg are exposed. A first layer 1 represents the state of the first layer after the interference fringes fg are exposed. The first layer 1' and the first layer 1 contain a binder 13 and a plurality of monomers 14.

[0051] When the interference fringes fg are exposed, the positions of the plurality of monomers 14 change according to the light intensity distribution of the interference fringes fg. In the example shown in Fig. 5, the density of the monomers 14 increases and they bond to each other at positions where the light intensity of the interference fringes fg is high, and the density of the monomers 14 decreases at positions where the light intensity of the interference fringes fg is high. The refractive index increases at positions where the density of the monomers 14 is high, and decreases at positions where the density of the monomers 14 is low. In areas of the first layer 1 exposed to light having an intensity distribution according to the interference fringes fg, a refractive index distribution according to the light intensity distribution of the interference fringes fg is formed.

[0052] In the examples and comparative examples, a refractive index distribution corresponding to the light intensity distribution of the interference fringes fg was formed in a portion of the first layer 1, and then the entire surface of the first layer 1 was irradiated with ultraviolet light from a xenon light source or the like to cure the monomer 14. By curing the monomer 14, the refractive index distribution corresponding to the light intensity distribution of the interference fringes fg was fixed in the first layer 1 as the first hologram 11. The refractive index distribution of the first hologram 11 can diffract the first light L1 incident on the first hologram 11.

[0053] A semiconductor laser emitting laser light with a peak wavelength of 532 nm was used for exposure of the interference fringes fg to form the first hologram 11. The amount of laser light emitted from the semiconductor laser was 20 mJ / cm. ２ The angle θ formed between the optical axis B1c of the first laser beam B1 and the optical axis B2c of the second laser beam B2 shown in FIG.

[0054] (Method of Fabricating Second Hologram 31) Differences from the method of fabricating first hologram 11 will be described. Other than these differences, the method of fabricating second hologram 31 is the same as that of first hologram 11. For exposure of interference fringes fg to fabricate second hologram 31, a semiconductor laser emitting laser light with a peak wavelength of 639 nm was used. The amount of laser light emitted from the semiconductor laser was 15 mJ / cm. ２ It was decided.

[0055] <Configuration of light guide members according to examples and comparative examples> Table 2 shows a list of the configuration of the light guide members according to each of Examples 1 to 6 and the comparative example. In Table 2, OCA (Opticaly Clear Adhesive) is an adhesive. TAC (Triacetylcellulose) is a base material. For the OCA, LUCIACS (registered trademark) CS9861UAS (25 μm) manufactured by Nitto Denko Corporation was used.

[0056]

[0057] <Order of bonding layers in light guide members according to Examples and Comparative Examples> Light guide members according to Examples 1 to 6 and Comparative Example were fabricated by bonding together the layers shown in Table 2. A hand roller was used to bond each layer. When bonding the OCA, the release liner was peeled off before bonding. In the light guide members according to Examples 1 to 6 and Comparative Example, the first and third layers were hologram layers, the second layer was a low refractive index layer, and the first and second light transmissive layers were each made of glass. The order of bonding layers in the light guide members according to Examples 1 to 6 and Comparative Example is shown below.

[0058] (Example 1) (1) TAC and the first layer were laminated onto the first light-transmitting layer. (2) TAC and the third layer were laminated onto the second light-transmitting layer. (3) OCA was laminated onto both sides of the acrylic and second layer. (4) (1) and (3) were laminated together. (5) (2) and (4) were laminated together.

[0059] (Example 2) (1) OCA was attached onto the first light-transmitting layer, and then it was laminated with TAC and the first layer. (2) OCA was attached to the second light-transmitting layer, and then it was laminated with TAC and the third layer. (3) OCA was attached to both sides of the acrylic and the second layer. (4) (1) and (3) were laminated together. (5) (2) and (4) were laminated together.

[0060] (Example 3) (1) OCA was attached onto the first light-transmitting layer, and then it was attached to TAC and the first layer. (2) OCA was attached onto the second light-transmitting layer, and then it was attached to TAC and the third layer. (3) The above (1) was attached to acrylic and the second layer. (4) The above (2) and the above (3) were attached to each other.

[0061] (Example 4) (1) TAC and the first layer were bonded onto the first light-transmitting layer. (2) TAC and the third layer were bonded onto the second light-transmitting layer. (3) (1) and the second layer were bonded together. (4) (2) and (3) were bonded together.

[0062] (Example 5) (1) An OCA was attached onto the first light-transmitting layer, and then it was bonded to the TAC and the first layer. (2) An OCA was attached onto the second light-transmitting layer, and then it was bonded to the TAC and the third layer. (3) The above (1) was bonded to the second layer. (4) The above (2) was bonded to the above (3).

[0063] (Example 6) (1) The first layer was bonded onto the first light-transmitting layer. (2) The third layer was bonded onto the second light-transmitting layer. (3) The above (1) and the second layer were bonded together. (4) The above (2) and the above (3) were bonded together.

[0064] (Comparative Examples) (1) TAC and the first layer were bonded onto the first light-transmitting layer. (2) TAC and the third layer were bonded onto the second light-transmitting layer. (3) (1) was bonded to OCA. (4) (2) and (3) were bonded to each other.

[0065] <Light Guidance Results> Fig. 6 is a diagram showing an example of a light guiding result by the light guiding member according to Example 1. Fig. 6 shows a captured image of irradiation light 220 that has been guided by the light guiding member according to Example 1 and then irradiated onto irradiation surface 210. Fig. 7 is a diagram showing an example of a light guiding result by a light guiding member according to a comparative example. Fig. 7 shows a captured image of irradiation light 230 that has been guided by the light guiding member according to the comparative example and then irradiated onto irradiation surface 210.

[0066] 6 , the irradiation light 220 includes a first irradiation light 221 of the first light L1 and a second irradiation light 222 of the second light L2, which are separated from each other. This shows that the light guiding member of Example 1 can guide the first light L1 and the second light L2 separately by color and extract the light from the light guiding member separately by color.

[0067] 7, the first light L1 and the second light L2 are mixed and not separated in the irradiation light 230. This shows that the light guiding member of the comparative example cannot guide the first light L1 and the second light L2 separately by color, and therefore cannot extract the light by color separately from the light guiding member.

[0068] Second Embodiment Next, a light guide member according to a second embodiment will be described with reference to FIGS. 8 and 9. FIG.

[0069] Fig. 8 is a schematic top view showing a first layer 1a included in the light-guiding member according to the second embodiment. Fig. 9 is a schematic perspective view showing a first layer 1a and a third layer 3a included in the light-guiding member according to the second embodiment. Note that, for ease of understanding, Fig. 8 shows only the first layer 1a of the light-guiding member according to the second embodiment. Also, for ease of understanding, Fig. 9 shows only the first layer 1a and the third layer 3a of the light-guiding member according to the second embodiment.

[0070] In the light-guiding member according to this embodiment, the first layer 1a has a seventh hologram 15 in addition to the first hologram 11 and the third hologram 12. The third layer 3a has an eighth hologram 33 in addition to the second hologram 31 and the fourth hologram 32. These are the main differences from the light-guiding member 100 according to the first embodiment.

[0071] 8 , first layer 1a has a substantially rectangular outer edge when viewed from above. First hologram 11 is disposed at one corner of first layer 1a. Third hologram 12 is disposed at a corner of first layer 1a diagonally opposite to the corner at which first hologram 11 is disposed. Seventh hologram 15 diffracts first light L1 incident from first hologram 11 after being diffracted by first hologram 11, and can guide the light to third hologram 12.

[0072] 9 , the third layer 3a has a generally rectangular outer edge shape that is substantially congruent with the first layer 1a when viewed from above. The second hologram 31 is disposed at a corner of the third layer 3a that corresponds to the corner where the first hologram 11 is disposed in the first layer 1a. The fourth hologram 32 is disposed at a corner of the third layer 3a that is diagonally opposite to the corner where the second hologram 31 is disposed. The eighth hologram 33 diffracts the second light L2 that is diffracted by the second hologram 31 and then incident from the second hologram 31, and guides the light to the fourth hologram 32.

[0073] In addition to the first hologram 11 and the third hologram 12, the first layer 1a includes a diffraction element such as the seventh hologram 15, which allows the first light L1 incident via the first hologram 11 to be guided to the third hologram 12 by the diffraction element. This increases the degree of freedom in determining the positions at which the first hologram 11 and the third hologram 12 are arranged in the first layer 1a. Furthermore, since the first light L1 incident via the first hologram 11 can be guided to the third hologram 12 by the diffraction element depending on the shape of the first layer 1a, the degree of freedom in the shape of the first layer 1a is also increased. Note that the number of diffraction gratings arranged in addition to the first hologram 11 and the third hologram 12 is not limited to one, and may be two or more.

[0074] In addition to the second hologram 31 and the fourth hologram 32, the third layer 3a includes a diffraction element such as the eighth hologram 33, so that the second light L2 incident via the second hologram 31 can be guided to the fourth hologram 32 by the diffraction element. This increases the degree of freedom in determining the positions at which the second hologram 31 and the fourth hologram 32 are disposed in the third layer 3a. Furthermore, because the second light L2 incident via the second hologram 31 can be guided to the fourth hologram 32 by the diffraction element depending on the shape of the third layer 3a, the degree of freedom in the shape of the third layer 3a also increases. Note that the number of diffraction gratings arranged in addition to the second hologram 31 and the fourth hologram 32 is not limited to one, and may be two or more.

[0075] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0076] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all provided as examples to specifically explain the technology of the present invention, and the present invention is not limited to the illustrated figures. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0077] The light-guiding member 100 according to the embodiment can guide light of different colors separately, and therefore can be suitably used in a color display device to guide image light of each color that constitutes a color image. The color display device can display a color image in an appropriate color using the image light of each color guided by the light-guiding member 100. The light-guiding member 100 can be manufactured in a compact size, and therefore can be suitably used in small display devices such as AR (Augmented Reality) glasses and HMDs (Head Mounted Displays).

[0078] The light guiding member 100 according to the embodiment is not limited to a display device, but can also be used in various optical devices such as a lighting device, etc. Furthermore, the light guiding member 100 according to the embodiment can provide new uses other than those described above.

[0079] For example, aspects of the present invention are as follows: <1> A light-guiding member including a first layer including a first hologram, a second layer disposed below the first layer, and a third layer disposed below the second layer and including a second hologram, wherein the first hologram diffracts first light incident from above and transmits second light incident from above and having a color different from that of the first light, the second hologram diffracts the second light that has transmitted through the first hologram, the first layer guides the first light diffracted by the first hologram, and the third layer guides the second light diffracted by the second hologram, and the refractive index of the second layer is lower than the refractive indexes of the first layer and the third layer. <2> The light-guiding member according to <1>, wherein n2 / n1≦0.9 and n2 / n3≦0.9, where n1 is the refractive index of the first layer, n2 is the refractive index of the second layer, and n3 is the refractive index of the third layer. <3> The light-guiding member according to <1> or <2>, comprising a first light-transmitting layer disposed above the first layer and a second light-transmitting layer disposed below the third layer. <4> The light-guiding member according to any one of <1> to <3>, comprising a first adhesive layer disposed between the first layer and the second layer and a second adhesive layer disposed between the second layer and the third layer, wherein the refractive indices of the first adhesive layer and the second adhesive layer are higher than the refractive index of the second layer. <5> The light-guiding member according to any one of <1> to <4>, wherein the first hologram is a reflection volume hologram. <6> The light-guiding member according to any one of <1> to <5>, wherein the first layer includes a third hologram at a position spaced apart from the first hologram in the direction in which the first light is guided, the third layer includes a fourth hologram at a position spaced apart from the second hologram in the direction in which the second light is guided, the fourth hologram diffracting the second light guided by the third layer upward, and the third hologram diffracting the first light guided by the first layer upward and transmitting the second light diffracted by the fourth hologram.<7> The light-guiding member according to any one of <1> to <7>, including a fourth layer disposed below the third layer, and a fifth layer disposed below the fourth layer and including a fifth hologram, wherein the first hologram diffracts the first light incident from above and transmits the second light and a third light incident from above, the second hologram diffracts the second light that has transmitted through the first hologram and transmits the third light that has transmitted through the second hologram, the fifth hologram diffracts the third light that has transmitted through the second hologram, the fifth layer guides the third light diffracted by the fifth hologram, and a refractive index of the fourth layer is lower than a refractive index of each of the third layer and the fifth layer. <8> The light-guiding member according to <7>, including a first light-transmissive layer disposed above the first layer and a third light-transmissive layer disposed below the fifth layer. <9> The light-guiding member according to <7> or <8>, wherein the fifth layer includes a sixth hologram at a position spaced apart from the fifth hologram in a direction in which the third light is guided, and the sixth hologram diffracts the third light guided by the fifth layer upward.

[0080] This application claims priority based on Japanese Patent Application No. 2024-071234 filed with the Japan Patent Office on April 25, 2024, and includes the entire contents of this Japanese patent application.

[0081] 1 First layer 11 First hologram 12 Third hologram 13 Binder 14 Monomer 15 Seventh hologram 2 Second layer 21 First interface 22 Second interface 23 Third interface 24 Fourth interface 25 Fifth interface 26 Sixth interface 3 Third layer 31 Second hologram 32 Fourth hologram 33 Eighth hologram 4 First light-transmitting layer 41 Upper surface 5 Second light-transmitting layer 51 Lower surface 6 First adhesive layer 7 Second adhesive layer 8 Fourth layer 9 Fifth layer 91 Fifth hologram 92 Sixth hologram 10 Third light-transmitting layer 101 Lower surface 100 Light-guiding member 110 Lens 210 Irradiation surface 220, 230 Irradiation light 221 First irradiation light 222 Second irradiation light B1 First laser light B1c Optical axis B2 Second laser light B2c Optical axis fg Interference fringes L1 First light L2 Second light L3 Third light θ Angle

Claims

1. A light-guiding member comprising: a first layer including a first hologram; a second layer disposed below the first layer; and a third layer disposed below the second layer and including a second hologram; the first hologram diffracts first light incident from above and transmits second light incident from above and having a different color from the first light; the second hologram diffracts the second light that has transmitted through the first hologram; the first layer guides the first light diffracted by the first hologram; and the third layer guides the second light diffracted by the second hologram; and the refractive index of the second layer is lower than the refractive indexes of the first layer and the third layer.

2. The light-guiding member according to claim 1, wherein n2 / n1≦0.9 and n2 / n3≦0.9, where n1 is the refractive index of the first layer, n2 is the refractive index of the second layer, and n3 is the refractive index of the third layer.

3. A light-guiding member according to claim 1 or claim 2, comprising: a first light-transmitting layer disposed above the first layer; and a second light-transmitting layer disposed below the third layer.

4. A light-guiding member as described in claim 1 or claim 2, comprising a first adhesive layer disposed between the first layer and the second layer, and a second adhesive layer disposed between the second layer and the third layer, wherein the refractive index of each of the first adhesive layer and the second adhesive layer is higher than the refractive index of the second layer.

5. A light-guiding member according to claim 1 or 2, wherein the first hologram is a reflection-type volume hologram.

6. A light-guiding element as described in claim 1 or claim 2, wherein the first layer includes a third hologram at a position spaced apart from the first hologram in the direction in which the first light is guided, the third layer includes a fourth hologram at a position spaced apart from the second hologram in the direction in which the second light is guided, the fourth hologram diffracts the second light guided by the third layer upward, and the third hologram diffracts the first light guided by the first layer upward and transmits the second light diffracted by the fourth hologram.

7. A light-guiding element according to claim 1 or claim 2, comprising: a fourth layer disposed below the third layer; and a fifth layer disposed below the fourth layer and including a fifth hologram, wherein the first hologram diffracts the first light incident from above and transmits the second light and a third light incident from above, the second hologram diffracts the second light that has passed through the first hologram and transmits the third light that has passed through the second hologram, the fifth hologram diffracts the third light that has passed through the second hologram, and the fifth layer guides the third light diffracted by the fifth hologram, and the refractive index of the fourth layer is lower than the refractive indexes of the third layer and the fifth layer.

8. The light-guiding member according to claim 7, comprising: a first light-transmitting layer disposed above the first layer; and a third light-transmitting layer disposed below the fifth layer.

9. The light-guiding member according to claim 7, wherein the fifth layer includes a sixth hologram located at a distance from the fifth hologram in the direction in which the third light is guided, and the sixth hologram diffracts the third light guided by the fifth layer upward.

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