Light guide plate unit and image display device

Abstract

A technique for reducing adverse effects caused by a structure formed near a diffraction grating is provided. The present disclosure provides a light guide plate unit including a light guide plate, a first diffraction grating on a first surface side of the light guide plate, a second diffraction grating on the first surface side of the light guide plate, and a transition region structure on the first surface side of the light guide plate. The transition region structure extends from a first endpoint at or adjacent to the first diffraction grating to an apex and from the apex to a second endpoint at or between the first endpoint and the second diffraction grating. The first end point and the second end point are closer to the first surface of the light guide plate than the vertex.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from Japanese Priority Patent Application JP 2022-118480 filed on Jul. 26, 2022, and Japanese Priority Patent Application JP 2023-116991 filed on Jul. 18, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a light guide plate unit and an image display device, and more particularly, to a light guide plate unit having a diffraction grating and an image display device including the light guide plate unit.

[0004] One device for displaying video includes a head mounted display device (also referred to as an HMD). HMDs have been used in various fields. Some HMDs use a technology that displays an image superimposed on an external scene. This technology is also referred to as augmented reality (AR) technology, and products using this technology include AR glasses. In addition, HMDs can also be used for video display based on virtual reality technology.

[0005] So far, various proposals have been made regarding augmented reality technology and virtual reality technology. For example, PTL 1 below discloses a method for forming an optical waveguide. The method includes forming a metasurface using a specific technology. In addition, PTL 2 below discloses a waveguide for a display system. The waveguide includes a first portion and a second portion that cause a specific phase change.

[0006] Citation list

[0007] Patent Literature

[0008] [PTL 1]:JP 2021-176016A

[0009] [PTL 2]: WO 2016 / 130358A Summary of the invention

[0010] Technical issues

[0011] In the case where a diffraction grating is provided on a light guide plate, a structure including a material for forming the diffraction grating may also appear near the diffraction grating. Such a structure may affect the travel of light guided in the light guide plate and adversely affect the presented image. Therefore, an object of the present disclosure is to provide a technology for reducing the adverse effects caused by a structure formed near a diffraction grating.

[0012] Solution to the problem

[0013] A light guide plate unit and an image display device including the light guide plate unit are provided. According to an embodiment of the present disclosure, the light guide plate unit includes a light guide plate, a first diffraction grating and a transition zone (TZ) structure. Some or all of the first diffraction grating, the second diffraction grating and the transition zone structure may be disposed on a first surface side of the light guide plate.

[0014] According to at least some embodiments of the present disclosure, a transition region structure extends from a first endpoint located at or adjacent to the first diffraction grating to a vertex, and from the vertex to a second endpoint located at or between the first endpoint and the second diffraction grating.

[0015] According to some embodiments of the present disclosure, the transition region structure is between the first diffraction grating and the second diffraction grating, both of which are arranged on the first surface side of the light guide plate. In addition, the light guide plate unit may include a coating on at least a portion of a side of the transition region structure opposite to a side of the transition region structure adjacent to the first surface side of the light guide plate.

[0016] According to still other embodiments of the present disclosure, a portion of the transition region structure is between the first diffraction grating and the second diffraction grating. In addition, a reflective coating is disposed on the first surface side of the light guide plate and between the transition region structure and the first surface side of the light guide plate.

[0017] According to a further embodiment, the present disclosure provides a light guide plate unit, comprising:

[0018] a light guide plate; and

[0019] A structure having a first diffraction grating provided on one surface of the light guide plate, a second diffraction grating that diffracts light diffracted by the first diffraction grating, and a mountain shape between the first diffraction grating and the second diffraction grating, wherein

[0020] When the spatial frequency is 10 cycles / degree, the MTF value before the light enters the mountain shape is X 10 , and the MTF value after the light passes through the mountain shape is Y 10 When , the light guide plate unit is configured to satisfy the following mathematical expression 1. Note that when used in the mathematical expressions contained herein, A', B', X 10 , Y 10 , X 20 and Y 20 Each of them is a percentage value in the range of 0 to 1.

[0021] [Mathematical formula 1]

[0022] .

[0023] In the case where the "width of the slope of the mountain shape" is smaller than the "total reflection interval of light in the light guide plate", the "slope" can be configured so that the "width of the slope" is equal to or smaller than the "threshold specified based on the total reflection interval", and in the case where the "width of the slope of the mountain shape" is equal to or greater than the "total reflection interval of light in the light guide plate", the "slope" can be configured so that the "height of the slope" is equal to or smaller than the "threshold specified based on the width of the slope and the inclination angle of the slope".

[0024] In the case where each of the width w1 of the inclined surface 1 on the first diffraction grating side of the mountain shape and the width w2 of the inclined surface 2 on the second diffraction grating side is equal to or larger than the total reflection interval d of light in the light guide plate, the mountain shape is configured so that the height h1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 2,

[0025] [Mathematical formula 2]

[0026]

[0027] Among them, in mathematical expression 2,

[0028] h1 = (the height from the reference surface of the first diffraction grating to the apex of the mountain shape)

[0029] w1=(width of slope 1)

[0030] h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0031] w2=(width of slope 2)

[0032] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0033] θ airin = (incident angle of light when it enters the light guide plate)

[0034] n2 = (refractive index of the material forming the structure of the mountain shape)

[0035] θ' TIR = (light guiding angle in the mountain-shaped structure).

[0036] In the case where the width w1 of the inclined surface 1 on one side of the mountain-shaped first diffraction grating is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on one side of the second diffraction grating is equal to or larger than the total reflection interval d of light in the light guide plate,

[0037] The mountain shape is configured so that the width w1 of the slope 1 and the height h2 of the slope 2 satisfy the following mathematical expression 3,

[0038] [Mathematical formula 3]

[0039]

[0040] Among them, in mathematical expression 3,

[0041] w1=(width of slope 1)

[0042] h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0043] w2=(width of slope 2)

[0044] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0045] θ airin = (incident angle of light when it enters the light guide plate)

[0046] n2 = (refractive index of the material forming the structure of the mountain shape)

[0047] θ' TIR = (light guide angle in the mountain-shaped structure),

[0048] and

[0049] In the case where each of the width w1 of the inclined surface 1 on the side of the first diffraction grating of the mountain shape and the width w2 of the inclined surface 2 on the side of the second diffraction grating is smaller than the total reflection interval d of light in the light guide plate,

[0050] The mountain shape may be configured such that the width w1 of the slope 1 and the width w2 of the slope 2 satisfy Mathematical Expression 4 below.

[0051] [Formula 4]

[0052]

[0053] Among them, in mathematical expression 4,

[0054] w1=(width of slope 1)

[0055] w2=(width of slope 2).

[0056] When the spatial frequency is 20 cycles / degree, the MTF value before the light enters the mountain shape is X 20 , and the MTF value after the light passes through the mountain shape is Y 20When , the light guide plate unit can be configured to satisfy the following mathematical expression 5.

[0057] [Formula 5]

[0058] .

[0059] In the case where each of the width w1 of the inclined surface 1 on the first diffraction grating side of the mountain shape and the width w2 of the inclined surface 2 on the second diffraction grating side is equal to or larger than the total reflection interval d of light in the light guide plate, the mountain shape is configured so that the height h1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 6,

[0060] [Mathematical formula 6]

[0061]

[0062] Among them, in mathematical expression 6,

[0063] h1 = (the height from the reference surface of the first diffraction grating to the apex of the mountain shape)

[0064] w1=(width of slope 1)

[0065] h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0066] w2=(width of slope 2)

[0067] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0068] θ airin = (the incident angle of light when it enters the light guide plate)

[0069] n2 = (refractive index of the material forming the structure of the mountain shape)

[0070] θ' TIR = (light guide angle in the mountain-shaped structure),

[0071] In the case where the width w1 of the inclined surface 1 on one side of the mountain-shaped first diffraction grating is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on one side of the second diffraction grating is equal to or larger than the total reflection interval d of light in the light guide plate,

[0072] The mountain shape is configured so that the width w1 of the slope 1 and the height h2 of the slope 2 satisfy the following mathematical expression 7,

[0073] [Formula 7]

[0074]

[0075] Among them, in mathematical expression 7,

[0076] w1=(width of slope 1)

[0077] h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0078] w2=(width of slope 2)

[0079] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0080] θ airin = (incident angle of light when it enters the light guide plate)

[0081] n2 = (refractive index of the material forming the structure of the mountain shape)

[0082] θ' TIR = (light guide angle in the mountain-shaped structure),

[0083] and

[0084] In the case where each of the width w1 of the inclined surface 1 on the side of the first diffraction grating of the mountain shape and the width w2 of the inclined surface 2 on the side of the second diffraction grating is smaller than the total reflection interval d of light in the light guide plate,

[0085] The mountain shape may be configured such that the width w1 of the slope 1 and the width w2 of the slope 2 satisfy the following mathematical expression 8,

[0086] [Mathematical formula 8]

[0087]

[0088] Among them, in mathematical expression 8,

[0089] w1=(width of slope 1)

[0090] w2=(width of slope 2).

[0091] The light guide plate unit may further include a second structure on one surface or the other surface of the light guide plate, the second structure having a mountain shape configured to offset the angle deviation of light caused by the above structure (hereinafter referred to as “first structure”).

[0092] The width w1 of the inclined surface 1 on one side of the first diffraction grating of the first structure may be configured to satisfy

[0093] w1 < 0.1 d

[0094] (where d is the total reflection interval of light in the light guide plate).

[0095] In the case where the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure is equal to or larger than the total reflection interval d of light, the mountain shape of the second structure is configured to satisfy any one of the following mathematical expressions 9-1, 9-2, and 9-3,

[0096] [Mathematical formula 9]

[0097]

[0098] Among them, in mathematical expressions 9-1, 9-2 and 9-3,

[0099] Δφ is the tolerance of the slope angle of the mountain shape of the second structure,

[0100] φ2 is the angle formed by the inclined surface 2 on one side of the second diffraction grating of the first structure and the first surface of the light guide plate,

[0101] Δw is the tolerance of the slope width of the mountain shape of the second structure,

[0102] d is the total reflection interval of light as above,

[0103] n is any integer,

[0104] Δx is the error of x, where x is ((half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam)),

[0105] w2 is the width w2 of the inclined surface 2 on one side of the second diffraction grating of the first structure,

[0106] and

[0107] In the case where the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure is smaller than the total reflection interval d of light, the mountain shape of the second structure can be configured to satisfy any one of the following mathematical expressions 10-1, 10-2, and 10-3,

[0108] [Formula 10]

[0109]

[0110] Among them, in mathematical expressions 10-1, 10-2 and 10-3,

[0111] Δφ is the tolerance of the slope angle of the mountain shape of the second structure,

[0112] φ2 is the angle formed by the inclined surface 2 on one side of the second diffraction grating of the first structure and the first surface of the light guide plate,

[0113] Δw is the tolerance of the slope width of the mountain shape of the second structure,

[0114] Δx is the error of x, where x is ((half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam)),

[0115] w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure.

[0116] The area where the structure is located may be provided with a reflective coating or a coating configured to prevent light from entering the structure, the coating being configured to prevent light that has entered the structure from causing angular deviation due to the slope of the mountain shape.

[0117] A reflective coating may be provided between the light guide and the structure.

[0118] The coating may comprise a material having substantially the same refractive index as the structure.

[0119] A structure having a plurality of mountain shapes may be included between the first diffraction grating and the second diffraction grating, wherein

[0120] The heights of all the mountain shapes of the plurality of mountain shapes may be equal to or less than 90 nm.

[0121] The first diffraction grating is any of: an incident diffraction grating configured to diffract light entering the light guide plate and cause the light to travel in the light guide plate, an expander configured to expand light that has traveled in the light guide plate, and an emission diffraction grating configured to emit light from the light guide plate, and

[0122] The second diffraction grating may be a recycler that diffracts the light that has passed through the first diffraction grating and travels toward one end of the light guide plate and causes the light to travel to the first diffraction grating again.

[0123] The first diffraction grating is an incident diffraction grating configured to diffract light entering the light guide plate and cause the light to travel in the light guide plate, and

[0124] The second diffraction grating may be an expander configured to expand the light that is diffracted by the first diffraction grating and has traveled in the light guide plate.

[0125] The first diffraction grating is an expander configured to expand light that has traveled in the light guide plate, and

[0126] The second diffraction grating may be a transmission diffraction grating configured to transmit the light expanded by the expander from the light guide plate.

[0127] The first diffraction grating is an incident diffraction grating configured to diffract light entering the light guide plate and cause the light to travel in the light guide plate, and

[0128] The second diffraction grating may be a transmission diffraction grating configured to transmit, from the light guide plate, the light having traveled in the light guide plate.

[0129] The emission diffraction grating may be an emission diffraction grating configured to expand light having traveled in the light guide plate and emit the light from the light guide plate.

[0130] The chevron-shaped structure may include a material used to form the first diffraction grating, the second diffraction grating, or both of these diffraction gratings.

[0131] The light guide plate unit can be used to manufacture an image display device.

[0132] In addition, the present disclosure also provides an image display device, including:

[0133] The light guide plate unit comprises:

[0134] a light guide plate; and

[0135] A structure having a first diffraction grating provided on one surface of a light guide plate, a second diffraction grating that diffracts light diffracted by the first diffraction grating, and a mountain shape between the first diffraction grating and the second diffraction grating, wherein

[0136] When the spatial frequency is 10 cycles / degree, the MTF value before the light enters the mountain shape is X 10 , and the MTF value after the light passes through the mountain shape is Y 10 When , the light guide plate unit is configured to satisfy the following mathematical expression 1.

[0137] [Mathematical formula 11]

[0138] . BRIEF DESCRIPTION OF THE DRAWINGS

[0139] [ Figure 1 ] Figure 1 is a schematic diagram of an example of a light guide plate including a diffraction grating.

[0140] [ Figure 2 ] Figure 2 A and Figure 2 B is a view for explaining the mechanism of TZ formation.

[0141] [ Figure 3 ] Figure 3 is a view for explaining image quality degradation due to TZ.

[0142] [ Figure 4A ] Figure 4A It is a view used to explain the incident beam and the transmitted beam to which the specified TZ refers.

[0143] [ Figure 4B ] Figure 4B is a view for explaining the position of TZ.

[0144] [ Figure 4C ] Figure 4C is a view for explaining the position of TZ.

[0145] [ Figure 5 ] Figure 5 A to Figure 5 E is a schematic diagram showing an example of a TZ shape.

[0146] [ Figure 6 ] Figure 6 This is a view for explaining the definition of the TZ shape.

[0147] [ Figure 7 ] Figure 7 is a view for explaining parameters used in the present disclosure.

[0148] [ Figure 8 ] Figure 8 is a schematic diagram of an example of a light guide plate unit of the present disclosure.

[0149] [ Fig. 9 ] Fig. 9 9A and 9B are schematic diagrams for explaining the relationship between the TZ shape, PSF, and MTF.

[0150] [ Fig.10 ] Fig.10 It is the distribution diagram of MTF value.

[0151] [ Fig.11 ] Fig.11 It is the distribution diagram of MTF value.

[0152] [ Fig.12 ] Fig.12 It is the distribution diagram of MTF value.

[0153] [ Fig.13 ] Fig.13 It is the distribution diagram of MTF value.

[0154] [ Fig.14 ] Fig.14 It is the distribution diagram of MTF value.

[0155] [ Fig.15 ] Fig.15 It is the distribution diagram of MTF value.

[0156] [ Fig.16 ] Fig.16 is a schematic diagram of an example of a light guide plate unit having TZ and TZc.

[0157] [ Fig.17 ] Fig.17 is a schematic diagram of an example of a light guide plate unit having TZ and TZc.

[0158] [ Fig.18 ] Fig.18 It is the distribution diagram of MTF value.

[0159] [ Fig.19 ] Fig.19 It is the distribution diagram of MTF value.

[0160] [ Fig. 20 ] Fig. 20 It is the distribution diagram of MTF value.

[0161] [ Fig.21 ] Fig.21 It is the distribution diagram of MTF value.

[0162] [ Fig. 22 ] Fig. 22 is a schematic diagram of an example of a light guide plate unit having TZ and TZc.

[0163] [ Fig.23 ] Fig.23 is a schematic diagram of an example of a light guide plate unit provided with a reflective coating.

[0164] [ Fig.24 ] Fig.24 is a schematic diagram of an example of a light guide plate unit having a coating layer.

[0165] [ Fig.25 ] Fig.25 25A and 25B are views for explaining suppression of MTF degradation in a structure having a plurality of mountain shapes.

[0166] [ Fig.26 ] Fig.26 is a flowchart of an example of a method of manufacturing a light guide plate unit according to the present disclosure.

[0167] [ Fig. 27 ] Fig. 27 27A and 27B are views for explaining deposition of a resist material.

[0168] [ Fig.28 ] Fig.28 is a schematic diagram showing an example of an image display device.

[0169] [ Fig.29A ] Fig.29A is a schematic diagram of a measurement system for measuring MTF.

[0170] [ Fig.29B ] Fig.29Bis a view for explaining detailed information of components included in a measurement system for measuring MTF.

[0171] [ Fig. 30A ] Fig. 30A It is a flow chart of the MTF measurement method.

[0172] [ Fig. 30B ] Fig. 30B It is a flow chart of the MTF measurement method.

[0173] [ Fig.31A ] Fig.31A is a view showing a configuration example of a diffraction grating provided on a light guide plate.

[0174] [ Fig.32B ] Fig.31B is a view showing a configuration example of a diffraction grating provided on a light guide plate.

[0175] [ Fig.32A ] Fig.32A is a view showing a configuration example of a diffraction grating provided on a light guide plate.

[0176] [ Fig.32B ] Fig.32B is a view showing a configuration example of a diffraction grating provided on a light guide plate.

[0177] [ Fig.32C ] Fig.32C is a view showing a configuration example of a diffraction grating provided on a light guide plate.

[0178] [ Fig.32D ] Fig.32D is a view showing a configuration example of a diffraction grating provided on a light guide plate.

[0179] [ Fig.32E ] Fig.32E is a view showing a configuration example of a diffraction grating provided on a light guide plate. DETAILED DESCRIPTION

[0180] Preferred embodiments for implementing the present disclosure will be described below. Note that the embodiments described below show representative embodiments of the present disclosure, and the scope of the present disclosure is not limited to these embodiments.

[0181] The present disclosure will be described in the following order.

[0182] 1. First Embodiment (Light Guide Plate Unit)

[0183] 1.1 Overview of this Disclosure

[0184] 1.2 Definition of TZ and various types of parameters

[0185] 1.3 Example 1 of the MTF condition

[0186] 1.3.1 Example of Slant Specification

[0187] 1.3.2 Deviation of the beam angle caused by an inclined surface

[0188] 1.3.3 The optical relationship between TZ shape, PSF and MTF

[0189] 1.4 Example 1 of inclined plane configuration

[0190] 1.4.1 Configuration Example 1-1 (When both slopes are large)

[0191] 1.4.2 Configuration Example 1-2 (One slope has a larger width and the other slope has a smaller width)

[0192] 1.4.3 Configuration Example 1-3 (When the widths of both slopes are small)

[0193] 1.5 Example 2 of the MTF condition

[0194] 1.6 Example 2 of inclined plane configuration

[0195] 1.6.1 Configuration Example 2-1 (When the widths of the two slopes are large)

[0196] 1.6.2 Configuration Example 2-2 (One slope has a larger width and the other slope has a smaller width)

[0197] 1.6.3 Configuration Example 2-3 (When the widths of the two slopes are small)

[0198] 1.7 TZc Configuration Example

[0199] 1.7.1 Example 1 of TZc on the surface opposite to the surface where TZ is located

[0200] 1.7.2 Example 2 of TZc on the surface opposite to the surface where TZ is located

[0201] 1.7.3 Example 1 of TZc on the surface where TZ is located

[0202] 1.7.4 Example 2 of TZc on the surface where TZ is located

[0203] 1.8 Coating

[0204] 1.8.1 Examples of reflective coatings

[0205] 1.8.2 Examples of coatings

[0206] 1.9 Example of a case including a structure having a plurality of mountain shapes

[0207] 1.10 Manufacturing method

[0208] 1.11 Usage

[0209] 2. Second Embodiment (Image Display Device)

[0210] 1. First Embodiment (Light Guide Plate Unit)

[0211] 1.1 Overview of this Disclosure

[0212] In eyeglass-type goggles, a light guide plate having a surface relief grating (SRG) structure may be used. The light guide plate is provided with a diffraction grating on the surface of the light guide plate. For example, the diffraction grating may be formed using nanoimprint technology, but depending on the formation method, a structure including a material forming the diffraction grating may be formed near the diffraction grating. In this specification, the region where the structure is located is also referred to as a transition zone (TZ). The thickness of the TZ in a vertical direction relative to the surface of the light guide plate is non-uniform across the TZ, which may affect the light beam guided in the light guide plate and may cause further image quality degradation. Such a TZ is particularly likely to occur, for example, in the case where the diffraction grating is formed by further combining the above-mentioned nanoimprint technology with an inkjet method.

[0213] The above-mentioned problem regarding TZ will be described in more detail below with reference to the accompanying drawings.

[0214] Figure 1 A schematic diagram of an example of a light guide plate including a diffraction grating is shown. For example, in order to allow a light beam L emitted from a drawing engine to reach the user's eyes via the light guide plate, the light guide plate P shown in the figure is provided with at least two or more diffraction gratings (input coupling grating (ICG)) for introducing the light beam into the light guide plate and a diffraction grating (output coupling grating (OCG)) for emitting the light beam from the light guide plate. The light reflected from the light guide plate P by the OCG reaches the observer (particularly, the observer's eyes E). In addition, a diffraction grating (expander) having the function of splitting the light beam is generally provided in the light guide plate.

[0215] When such a diffraction grating is formed on the surface of the light guide plate using a light guide plate manufacturing process in which nanoimprint technology and inkjet technology are combined, a zone (TZ) having a non-uniform thickness shape is formed around the diffraction grating. Figure 2 A and 2B describe the mechanism of TZ formation.

[0216] like Figure 2As shown in FIG. 1A , a resist material R applied to a substrate by inkjet printing is molded by using a stamper ST to form a diffraction grating. In the stamper ST, a plurality of grooves in the G1 region are grooves for obtaining the diffraction grating 1, and a plurality of grooves in the G2 region are grooves for obtaining the diffraction grating 2. For example, the depth of the grooves in the G1 region and the depth of the grooves in the G2 region are appropriately adjusted according to the desired diffraction characteristics, for example, the depth of the grooves in the G1 region and the depth of the grooves in the G2 region may be different from each other as shown in the figure.

[0217] Furthermore, at the same time, as shown in the figure, the amount of the resist material R applied onto the substrate SB also differs between the G1 region and the G2 region, and at the same time, the film thickness of the resist to be formed may also differ between the G1 region and the G2 region.

[0218] Note that the depth of the grooves in the G1 region corresponds to the height of the diffraction grating 1 and may be, for example, 10 nm or more, 20 nm or more, or 30 nm or more. In addition, the depth may be, for example, 500 nm or less, 400 nm or less, or 300 nm or less.

[0219] The depth of the grooves in the G2 region corresponds to the height of the diffraction grating 2 and may be, for example, 10 nm or more, 20 nm or more, or 30 nm or more. In addition, the depth may be, for example, 500 nm or less, 400 nm or less, or 300 nm or less.

[0220] As shown in the figure, the depth of the grooves in the G1 region (i.e., the height of the diffraction grating 1) can be different from the depth of the grooves in the G2 region (i.e., the height of the diffraction grating 2), but can also be the same. Those skilled in the art can appropriately adjust these values ​​according to the desired diffraction characteristics of each diffraction grating.

[0221] When molding is performed by the stamper ST as described above, the resist material R flows, and at the same time, a TZ is formed between the G1 region and the G2 region. Figure 2 B shows a schematic diagram of TZ residual film thickness, where the vertical axis is the residual film thickness (RLT) of the resist and the horizontal axis is the position. T1 is the thickness of the resist material required for the diffraction grating 1. T2 is the thickness of the resist material required for the diffraction grating 2. In the region A1, thickness non-uniformity may occur due to the flow of the resist material used to form the diffraction grating 1. In the region A2, thickness non-uniformity may occur due to the flow of the resist material used to form the diffraction grating 2.

[0222] like Figure 2As shown in FIG. 2B , in the case where the height of the diffraction grating is high (G1 region), the amount of resist material applied also increases, and the residual film thickness (RLT) of the resist in the TZ also tends to become high in the portion near the G1 region in the TZ. On the other hand, in the case where the height of the diffraction grating is low (G2 region), the amount of resist material applied decreases, and the residual film thickness (RLT) of the resist in the TZ decreases in the portion near the G2 region in the TZ.

[0223] exist Figure 2 In B, the line of Case 1 shows an ideal flat TZ shape. However, by the above-mentioned diffraction grating formation method, such a flat TZ is not formed due to the fluidity of the resist material and the required diffraction grating structure. For example, the TZ may have a high residual film thickness RLT, as shown by the line of Case 2.

[0224] The following will refer to Figure 3 Describes the degradation of image quality due to TZ. The figure is a schematic diagram of a light beam guided through the TZ. In the case where the shape in the TZ is not flat, the guiding angle of the light beam reaching the resist residual film in the TZ changes. As shown in the figure, the guiding angle changes by 2φ. Therefore, the geometric optics modulation transfer function (MTF) deteriorates. MTF is one of the indicators of image quality and represents the contrast at a certain spatial frequency. When the angle of inclination of the shape of the TZ (hereinafter also referred to as "inclined surface") is large, the change in the guiding angle of the light beam irradiating the inclined surface also becomes larger. In addition, the area and number of times the light beam irradiates the inclined surface change according to the width of the TZ, and the ratio of the light beam whose guiding angle deviates also changes. Here, Figure 2 Compared with Case 2 and Case 3 in B, the shape of the conventional Case 2 has a high TZ shape and a large slope angle, so that the MTF degradation tends to be large.

[0225] The present inventors have found that the above problems can be solved by satisfying predetermined conditions. For example, according to the present disclosure, it is found that by forming the TZ between the two diffraction gratings to have Figure 2 The mountain-shaped structure (also referred to as the transition zone structure in this article) shown by the line of case 3 in B, and controlled to meet the predetermined conditions, can prevent image quality degradation. It should be noted that the mountain-shaped shape shown in the figure is not an actual mountain-shaped shape, but is schematically shown for better understanding of the present disclosure.

[0226] Hereinafter, first, the definition of TZ and various types of parameters for defining a predetermined condition will be described. Next, an embodiment of the present disclosure will be described.

[0227] 1.2 Definition of TZ and various types of parameters

[0228] The location and shape of the TZ are described in more detail below.

[0229] First, refer to Figure 4A The incident beam and the emitted beam used to specify the TZ are described. As shown in the figure, for example, the beam entering the ICG is called the incident beam (the solid line indicated by the reference mark L1 in the figure), and the beam emitted from the OCG is also called the emitted beam (the solid line indicated by the reference mark L2 in the figure). The incident beam is a beam having an incident angle corresponding to the central viewing angle and having a peak wavelength. The emitted beam is a beam having a central viewing angle.

[0230] Next, the position of TZ will be described below. Figure 4B A schematic diagram of a light guide plate provided with a diffraction grating is shown. In the figure, the TZ exists in the circled area. The TZ exists between two diffraction gratings provided on the light guide plate, for example, it may be the area between the ICG and the expander as shown in the lower left of the figure, or it may be the area between the expander and the OCG as shown in the lower right of the figure. In addition, in addition to the ICG and the OCG, the light guide plate in the figure is provided with an expander, but in the case where the expander is not provided, the TZ may be the area between the ICG and the OCG.

[0231] In addition, there is a case where the light guide plate is provided with a diffraction grating (also called a recycler) for returning light traveling from each diffraction grating toward the end of the light guide plate to the corresponding diffraction grating. In this case, the TZ may be a region between each diffraction grating and the recycler.

[0232] Therefore, TZ exists between two diffraction gratings provided on the light guide plate.

[0233] As shown in the figure, in the TZ region where a beam having a central viewing angle and a peak wavelength to be used is guided, the TZ in a direction perpendicular to the grating boundary of the beam passing portion is defined as a TZ cross section.

[0234] Furthermore, there may be cases where the light does not enter the diffraction grating vertically but obliquely, e.g. Figure 4C The light shown enters the area of ​​the expander (circled area). In this case, TZ is cut into a cross section perpendicular to the diffraction grating, as shown by the line TZ in the circled area. Note that in this case, as shown in the circled area in the figure, the total reflection interval d described later is also redefined as d'.

[0235] Next, the shape of the transition zone structure (TZ) according to an embodiment of the present disclosure will be described.

[0236] Examples of TZ shapes are Figure 5 A to 5E. Figure 5 G1 and G2 shown in A to 5E are the first diffraction grating and the second diffraction grating, respectively, and TZ is a structure having a mountain shape existing between these diffraction gratings.

[0237] like Figure 5 As shown in A, TZ may have a shape in which the slope is a curve. Figure 5 As shown in B, TZ can be amorphous. Figure 5 As shown in C, TZ can be trapezoidal. In addition, Figure 5 As shown in D, a portion of the inclined surface of TZ may enter the first diffraction grating and / or the second diffraction grating. Figure 5 As shown in E, the distance between the first diffraction grating and the second diffraction grating can be longer, and one end of TZ can reach the light guide plate.

[0238] In this specification, the highest position of the TZ cross section (the position farthest from the light guide plate surface) is defined as the vertex of the TZ. Figure 5 A to Figure 5 In each of E, the vertices are represented by black circles.

[0239] In addition, in this specification, the position where the height of TZ becomes the height of the resist residual film thickness (RLT) of the diffraction grating or two positions where the height of TZ becomes zero are defined as the end points of TZ. The end points are indicated by white circles in the figure.

[0240] In this specification, a shape formed by the vertex of the TZ and the two end points of the TZ is referred to as a mountain shape.

[0241] Figure 6 This is a view for explaining the definition of a TZ shape. In this specification, two straight lines drawn from the black circle (vertices) to the white circle (endpoints) are defined as slope 1 and slope 2, respectively. These are in no particular order.

[0242] As shown in the figure, the direction parallel to the surface of the light guide plate P (particularly, the surface provided with the diffraction grating) is defined as the X axis, and the direction perpendicular to the surface is defined as the Y axis. Then, the lengths of the inclined surface 1 and the inclined surface 2 in the X axis direction are defined as the width w1 of the inclined surface 1 and the width w2 of the inclined surface 2, respectively.

[0243] The lengths of the inclined surface 1 and the inclined surface 2 in the Y-axis direction are defined as the height h1 of the inclined surface 1 and the height h2 of the inclined surface 2, respectively. In addition, the height of each inclined surface is the length from the reference surface of the adjacent diffraction grating to the vertex, not the length from the surface of the light guide plate to the vertex. In the figure, the height h1 of the inclined surface 1 is the length from the reference surface S1 to the black circle (vertex) of the first diffraction grating G1 in the Y-axis direction. The height h2 of the inclined surface 2 is the length from the reference surface S2 of the second diffraction grating G2 to the black circle (vertex) in the Y-axis direction.

[0244] Figure 7 as well as Figure 7Table 1 in FIG. 1 illustrates other parameters used in the present disclosure. It should be noted that the light beam for which these parameters are directed is a light beam that uses the peak wavelength of the light source and has a light guide angle closest to the critical angle among the viewing angle light beams. This light beam is a light beam with a viewing angle that is most susceptible to the influence of TZ. Therefore, in the case where the target MTF value described later can be obtained using this light beam, the target MTF value is also successfully achieved in the entire viewing angle.

[0245] 1.3 Example 1 of the MTF condition

[0246] In one embodiment, a light guide plate unit according to the present disclosure includes: a light guide plate; and a structure having a first diffraction grating provided on one surface of the light guide plate, a second diffraction grating diffracting light diffracted by the first diffraction grating, and a transition region structure (also referred to herein as a structure having a mountain shape or simply as a mountain shape, or a structure between the first diffraction grating and the second diffraction grating), wherein the MTF value before the light enters the mountain shape at a spatial frequency of 10 cycles / degree is X 10 , and the MTF value after the light passes through the mountain shape is Y 10 When the light guide plate unit is configured to satisfy the following mathematical expression 1. Here, the light before entering the mountain-shaped shape may refer to the light after being diffracted by the first diffraction grating and before entering the structure having the mountain-shaped shape. In addition, the light after passing through the mountain-shaped shape may refer to the light before having passed through the structure having the mountain-shaped shape and being diffracted by the second diffraction grating.

[0247] [Mathematical formula 12]

[0248]

[0249] Since the two MTF values ​​X 10 and Y 10 is controlled so as to satisfy Mathematical Expression 1, and thus degradation of image quality can be prevented.

[0250] Here, the light may be a light beam whose light guide angle in the light guide plate is closest to the critical angle among the used viewing angle light beams.

[0251] Furthermore, the second diffraction grating may be provided on the same surface as the surface on which the first diffraction grating is provided, among the two surfaces of the light guide plate, or may be provided on the surface on the opposite side to the surface on which the first diffraction grating is provided.

[0252] Will refer to Figure 8 This embodiment is described in more detail.

[0253] The light guide plate unit U1 of the present disclosure shown in the figure includes a light guide plate P, a first diffraction grating G1 arranged on one surface of the light guide plate, a second diffraction grating G2 that diffracts light diffracted by the first diffraction grating, and a structure TZ having a mountain shape and existing between the first diffraction grating and the second diffraction grating and configured to satisfy the above-mentioned mathematical expression 1.

[0254] For example, as shown in the figure, the total height H of the height of the first diffraction grating G1 (particularly, an incident diffraction grating configured to diffract light entering the light guide plate and allow the light to travel in the light guide plate) and the thickness of the resist T This embodiment is particularly suitable when the height H of the first diffraction grating G1 and the thickness of the resist is 150 nm or more. That is, in the present disclosure, the total height H of the first diffraction grating G1 and the thickness of the resist is T It may preferably be 150 nm or more.

[0255] For example, in a structure having a mountain shape, a first diffraction grating is formed around a diffraction grating produced by nanoimprinting using an inkjet method.

[0256] The mountain-shaped structure may include a material used to form the first diffraction grating, the second diffraction grating, or both of the diffraction gratings. That is, the structure may include the material of the diffraction gratings when the diffraction gratings are formed.

[0257] In the above mathematical expression 1, "1 - Y 10 / X 10 ” corresponds to the degradation rate of the MTF of the beam after reaching the TZ (transmitted beam L2) relative to the MTF of the beam before reaching the TZ (incident beam L1).

[0258] A spatial frequency of 10 cycles / degree corresponds to a visual acuity of about 0.3, which is generally the minimum standard for a person to live with the naked eye. Therefore, by satisfying the above-mentioned MTF conditions at a spatial frequency of 10 cycles / degree, image quality that allows even small characters to be clearly seen can be achieved.

[0259] (MTF measurement method)

[0260] The following will refer to Fig.29A and Fig.29B and Fig. 30A and Fig. 30B Describe how MTF is measured. Fig.29A The configuration of the measurement system is shown. Fig.29B A table describing detailed information of components included in the measurement system is shown.

[0261] like Fig.29AAs shown, the measurement system includes an illumination system 100 for causing a parallel light beam to enter a light guide plate, and an imaging system 110 for detecting light emitted from the light guide plate.

[0262] The illumination system 100 includes a light source (LED) 101, a collimating lens 102, and an aperture 103. The details of these components that make up the illumination system are as follows: Fig.29B Described in.

[0263] The imaging system 110 includes an aperture 113 for the pupil, a camera lens 112, and a camera 111. The details of these components that make up the imaging system are also shown in FIG. Fig.29B Described in.

[0264] Please note that Fig.29B In FIG. 1 , ICG is a diffraction grating for causing incident light to travel into the above-mentioned light guide plate P. OCG is a diffraction grating for emitting light that has traveled in the light guide plate P from the light guide plate.

[0265] Fig. 30A and 30B A flowchart showing a measurement method is shown. By executing the procedure shown in the flowchart, the MTF degradation rate of the TZ can be acquired.

[0266] Specifically, for the light guide plate unit used as the measurement target, by Fig. 30A The flowchart shown in the figure obtains the PSF image and performs Fourier transform on the PSF image to obtain the MTF value (A'). Next, for the light guide plate unit with the TZ (mountain-shaped structure) removed, the MTF value (A') is obtained by Fig. 30B The flowchart shown acquires a PSF image and performs Fourier transform on the PSF image to obtain an MTF value (B').

[0267] Here, in the case where the spatial frequency of the PSF image is 10 cycles / degree, (A' / B') is (Y 10 / X 10 ).

[0268] Furthermore, in the case where the spatial frequency of the PSF image is 20 cycles / degree, (A' / B') is (Y 20 / X 20 ).

[0269] Therefore, in the above-mentioned measurement method, two MTF value measurements are performed in which only the presence or absence of TZ is changed, and then only the MTF value of the final emitted light is focused on to obtain the ratio. Therefore, it is possible to measure light guide plate units of various patterns, for example, not only in the case where the first diffraction grating and the second diffraction grating are the incident diffraction grating and the emission diffraction grating, respectively, but also in the case where the first diffraction grating and the second diffraction grating are the expander and the OCG, respectively.

[0270] In addition to the presence or absence of TZ in the light guide plate unit used as a measurement target, Fig. 30A and Fig. 30B The flowchart shown in is the same. In the above flowchart, the main steps are as follows.

[0271] First, the parallel light beam generated by the illumination system 100 is made to enter the light guide plate P. The entered parallel light beam reaches the ICG, is diffracted, and travels in the light guide plate. In the case where a TZ exists on the light guide plate, the traveling direction of the light beam may be changed by the TZ (S11 to S14 and S21 to S24).

[0272] Next, the light beam that has traveled in the light guide plate is diffracted by the OCG and emitted from the light guide plate. The emitted light is imaged by the imaging system 110. The imaging system 110 converges the light beam emitted by the lens 112, and then obtains a point image distribution (PSF) image through the camera 110 (S15, S16, S25, and S26).

[0273] The analysis device (PC) obtains the MTF (S17, S18, S27, and S28) by performing a two-dimensional Fourier transform on the PSF image. That is, the point image distribution is converted into a spatial frequency distribution by Fourier transform, and the MTF at the desired frequency is obtained. The analysis device only needs to be any device capable of performing a two-dimensional Fourier transform on the PSF image, and an information processing device commonly used in the technical field (e.g., a general-purpose computer) can be used.

[0274] Python is used as software for performing Fourier transform. When the value of MTF of a light guide plate unit (a unit including a light guide plate, a diffraction grating, and a TZ (a mountain-shaped structure)) is A', and the value of MTF of the light guide plate unit with the TZ removed is B', the MTF degradation rate of the TZ can be found by 1-(A' / B').

[0275] (The surface where the first diffraction grating, the second diffraction grating and the mountain-shaped structure are located)

[0276] The first diffraction grating and the second diffraction grating may be two diffraction gratings located on the light guide plate and arranged to sandwich the TZ.

[0277] The first diffraction grating and the second diffraction grating may exist on the same surface of the light guide plate, or the first diffraction grating may exist on one surface of the light guide plate and the second diffraction grating may exist on the other surface of the light guide plate.

[0278] In any case, according to the present disclosure, MTF degradation can be suppressed. Fig.31A and Fig.31B Describe the surface on which these diffraction gratings are located.

[0279] like Fig.31A As shown, the first diffraction grating G1 and the second diffraction grating G2 may exist on one surface SF1 of the light guide plate P. Then, the zone TZ where the mountain-shaped structure is located may be between the two diffraction gratings. According to the present disclosure, the MTF degradation caused by the mountain-shaped structure may be suppressed.

[0280] In addition, if Fig.31B As shown, the first diffraction grating G1 may exist on one surface SF1 of the light guide plate P, and the second diffraction grating G2' may exist on the other surface SF2. Then, the area TZ2 where the mountain-shaped structure is located may be between the two diffraction gratings.

[0281] In addition, in the case where the second diffraction grating G2 further exists on the surface SF1, the zone TZ3 where the mountain-shaped structure is located may be between the second diffraction grating G2' and the second diffraction grating G2. In this case, either of the diffraction gratings G2 and G2' may be regarded as the first diffraction grating.

[0282] Furthermore, in this case, the region TZ1 where the mountain-shaped structure is located may be between the first diffraction grating G1 and the second diffraction grating G2 on the surface SF1. According to the present disclosure, it is possible to suppress the degradation of the MTF caused by at least one of these mountain-shaped structures.

[0283] Therefore, according to the present disclosure, it is possible to suppress the degradation of the MTF caused by the mountain-shaped structure between any two diffraction gratings provided on the light guide plate.

[0284] (Diffraction characteristics of the first diffraction grating and the second diffraction grating)

[0285] The first diffraction grating and the second diffraction grating may be any two of the above-mentioned ICG, expander, OCG, and recycler. That is, the first diffraction grating may have diffraction characteristics as an ICG, an expander, an OCG, or a recycler. In addition, the second diffraction grating may also have diffraction characteristics as an ICG, an expander, an OCG, or a recycler. For example, the light guide plate unit of the present disclosure may include two or more diffraction gratings, which include a first diffraction grating and a second diffraction grating, and those skilled in the art may appropriately select the diffraction characteristics of each diffraction grating.

[0286] Therefore, the light guide plate unit according to the present disclosure may be provided with two or more diffraction gratings including a first diffraction grating and a second diffraction grating, and those skilled in the art may appropriately select the diffraction characteristics and arrangement of these diffraction gratings. Then, according to the present disclosure, the MTF degradation caused by the TZ between the two diffraction gratings may be suppressed. In the following, reference will be made to FIG. 32A to FIG. 32EExamples of arrangement of these diffraction gratings are described. These drawings are views showing schematic examples of the surface of the light guide plate unit, and show configuration examples of the diffraction gratings.

[0287] exist Fig.32A In FIG. 4 , the light guide plate P is provided with an ICG as a first diffraction grating and with an OCG as a second diffraction grating. The mountain-shaped structure may be located in a gray area TZ between these diffraction gratings.

[0288] In the present disclosure, it is possible to suppress the degradation of MTF caused by the mountain-shaped structure in TZ1 between these incident gratings. Therefore, the first diffraction grating is an incident diffraction grating configured to diffract light entering the light guide plate and cause the light to travel in the light guide plate, and

[0289] The second diffraction grating may be a transmission diffraction grating configured to transmit, from the light guide plate, the light having traveled in the light guide plate.

[0290] Furthermore, the OCG may have a diffraction characteristic as an expander. That is, the emission diffraction grating may be an emission diffraction grating configured to expand light that has traveled in the light guide plate and emit the light from the light guide plate.

[0291] exist Fig.32B In the embodiment, the light guide plate P is provided with an ICG, an expander, and an OCG. A mountain shape structure may exist in a gray area TZ1 between the ICG and the expander, or a mountain shape structure may exist in a gray area TZ2 between the expander and the OCG, or a mountain shape structure may exist in both area TZ1 and area TZ2.

[0292] In the present disclosure, the ICG can be regarded as the first diffraction grating, and the expander can be regarded as the second diffraction grating. Then, according to the present disclosure, the MTF degradation caused by the mountain-shaped structure in the TZ1 between these diffraction gratings can be suppressed.

[0293] In the present disclosure, the expander can be regarded as the first diffraction grating, and the OCG can be regarded as the second diffraction grating. Then, according to the present disclosure, the MTF degradation caused by the mountain-shaped structure in the TZ2 between these diffraction gratings can be suppressed.

[0294] Therefore, in the present disclosure, the first diffraction grating is an incident diffraction grating configured to diffract light entering the light guide plate and cause the light to travel in the light guide plate, and

[0295] The second diffraction grating may be an expander configured to expand the light that is diffracted by the first diffraction grating and has traveled in the light guide plate.

[0296] Furthermore, the first diffraction grating is an expander configured to expand the light that has traveled in the light guide plate, and

[0297] The second diffraction grating may be a transmission diffraction grating configured to transmit the light expanded by the expander from the light guide plate.

[0298] exist Fig.32C In the embodiment, the light guide plate P is provided with an ICG as a first diffraction grating and an OCG as a second diffraction grating. The ICG also has diffraction characteristics as an expander. The mountain-shaped structure may be in the gray area TZ between these diffraction gratings. In this case, the area where the mountain-shaped structure is located may be larger than Fig.32A The situation is even greater.

[0299] In the present disclosure, it is possible to suppress the MTF degradation caused by the mountain-shaped structure in the TZ between these diffraction gratings.

[0300] That is, the first diffraction grating may be an incident diffraction grating configured to diffract light entering the light guide plate to allow the light to travel in the light guide plate, and to expand the light to allow the light to travel in the light guide plate.

[0301] Fig.32D The recycling device is shown in Fig.32B An example of a configuration around a diffraction grating in an example of a configuration. The light guide plate P is provided with an ICG, an expander, and an OCG. The light guide plate P is further provided with a recycler 1 for returning light traveling from the ICG to one end of the light guide plate (the left end in the figure) to the ICG, a recycler 2 for returning light traveling from the expander or the OCG to one end of the light guide plate (the upper end in the figure) to the expander or the OCG, a recycler 3 for returning light traveling from the OCG to one end of the light guide plate (the right end in the figure) to the OCG, and a recycler 4 for returning light traveling from the expander or the OCG to one end of the light guide plate (the lower end in the figure) to the expander or the OCG.

[0302] The mountain-shaped structure may be located in one or more gray areas TZ1 to TZ6 between two adjacent ones of the diffraction gratings.

[0303] In the present disclosure, it is possible to suppress the MTF degradation caused by the mountain-shaped structure in the TZ between these diffraction gratings.

[0304] Fig.32E The recycling device is shown in Fig.32CAn example of a configuration around a diffraction grating in a configuration example. The light guide plate P is provided with an ICG and an OCG. The ICG also has a diffraction characteristic as an expander. The light guide plate P is further provided with a recycler 1 for returning light traveling from the ICG to one end of the light guide plate (the left end in the figure) to the ICG, a recycler 2 for returning light traveling from the OCG to one end of the light guide plate (the upper end in the figure) to the OCG, a recycler 3 for returning light traveling from the OCG to one end of the light guide plate (the right end in the figure) to the OCG, and a recycler 4 for returning light traveling from the OCG to one end of the light guide plate (the lower end in the figure) to the OCG.

[0305] The mountain-shaped structure may be located in one or more gray areas TZ1 to TZ5 between two adjacent ones of the diffraction gratings.

[0306] In the present disclosure, it is possible to suppress the MTF degradation caused by the mountain-shaped structure in the TZ between these diffraction gratings.

[0307] like Fig.32D and Fig.32E As shown, the first diffraction grating is any one of an incident diffraction grating configured to diffract light entering the light guide plate and causing the light to travel in the light guide plate, an expander configured to expand the light that has traveled in the light guide plate, and an emission diffraction grating configured to emit light from the light guide plate, and the second diffraction grating can be a recycler that diffracts light that passes through the first diffraction grating and travels toward one end of the light guide plate and causes the light to travel to the first diffraction grating again.

[0308] 1.3.1 Example of Slant Specification

[0309] In a preferred embodiment, when the “width of the slope of the mountain shape” is smaller than the “total reflection interval of light in the light guide plate”, the “slope” can be configured so that the “width of the slope” is equal to or smaller than the “threshold specified based on the total reflection interval”, and

[0310] When the “width of the mountain-shaped slope” is equal to or greater than the “total reflection interval of light in the light guide plate”, the “slope” can be configured so that the “height of the slope” is equal to or less than the “threshold specified based on the width of the slope and the inclination angle of the slope”.

[0311] The mountain shape has two inclined surfaces. Preferably, in the case of focusing on one of the two inclined surfaces, the inclined surface is configured so that the width of the inclined surface or the height of the inclined surface is equal to or less than a predetermined threshold value according to the relationship between the width of one inclined surface and the total reflection interval of the light beam traveling in the light guide plate. Therefore, by changing the configuration of the inclined surface according to the width of the inclined surface and the total reflection interval, it is easy to satisfy the above-mentioned MTF and to prevent the degradation of the MTF.

[0312] In the present disclosure, the total reflection interval refers to the total reflection interval of the light beam with respect to the peak wavelength of the light source spectrum of the light entering the light guide plate. Figure 7 The specified distance is shown.

[0313] In order to make the embodiment easier to understand, the deviation of the beam angle caused by one inclined surface will be described below, and then the relationship between the TZ shape, PSF and MTG will be described. Thereafter, a more specific embodiment will be described.

[0314] 1.3.2 Deviation of the beam angle caused by an inclined surface

[0315] like Figure 7 As shown, with an angle θ airin The light beam enters the light guide plate from the air, and then the light beam is brought into the light guide plate by the ICG and propagates. At this time, it is assumed that the light beam irradiates TZ once, that is, the angle of the light beam emitted from the OCG to the pupil side becomes θ airin +Δpeak. Δpeak can be obtained from the following grating mathematical expression and Snell's law.

[0316] Δpeak = φ*(2*n2*cos(θ' TIR )) / cos(θ airin )

[0317] Here, φ is the angle between the substrate and the slope of the TZ. airin is the angle of incidence in air. n2 is the refractive index of TZ. θ' TIR is the light guide angle in TZ. In other words, the deviation of the beam angle is proportional to the angle of the inclined surface.

[0318] 1.3.3 Relationship between TZ shape, PSF, and MTF

[0319] Fig. 9 A and Fig. 9 B shows a schematic diagram in a one-dimensional direction for explaining the relationship between the TZ shape, PSF, and MTF.

[0320] Will refer to Fig. 9 A describes a case where the slope width of TZ can be reduced. That is, a case where the slope width w of TZ is smaller than the total reflection interval d of the light beam in the light guide plate will be described.

[0321] Since the width of the inclined surface is smaller than the total reflection interval, the beam surface has a portion where the beam irradiates the inclined surface and a portion where the beam does not irradiate the inclined surface, and the beam ratio of the beam irradiated to the inclined surface becomes a beam ratio where the angle is deviated. The width ratio corresponding to the inclined surface in the beam surface is represented by w / d. The number of times the beam irradiates the inclined surface of the beam surface is once. In addition, as described above, the angle of the inclined surface affects the amount of deviation of the beam angle.

[0322] Considering the point spread function (PSF), when the total light quantity is 1, the PSF image shows that the beam angle does not deviate for a light quantity of 1-w / d, but deviates for a light quantity of w / d. The geometrical optics MTF can be calculated from this PSF image. Therefore, in order to achieve the target MTF value at a selectable bevel angle, it is only necessary to control w / d.

[0323] Here, PSF is a point image distribution, and when there are light beams with different angles in the light beam when converging into one point, an image with multiple points instead of one point will be obtained, and the dispersion of the angle in the light beam can also be known by the dispersion of the points.

[0324] The case where the slope width of the TZ is large will be described with reference to the right side of the figure. That is, the case where the slope width w of the TZ is larger than the total reflection interval d of the light beam in the light guide plate will be described.

[0325] Since the bevel width is large, the beam hits the bevel on the entire beam surface, and the beam surface has a portion where the beam hits the bevel n (=1, 2, 3...) times and a portion where the beam hits the bevel n+1 times. Since the entire beam hits the bevel n times or more, the beam angle changes from the original beam angle, so there is image distortion. However, image blur (MTF) is affected by the angle difference in the beam surface, so it is an effect caused by a bevel.

[0326] Considering the PSF, the amount of angular deviation due to a bevel can be expressed by the above Δpeak, so in order to achieve the target MTF value at a selectable bevel width, only the amount of angular deviation (ie, Δpeak) needs to be controlled.

[0327] Based on the above, a specific slope configuration example for preventing MTF degradation will be described below.

[0328] 1.4 Example 1 of inclined plane configuration

[0329] The mountain shape of TZ has two inclined surfaces. Therefore, for example, in the light guide plate unit of the present disclosure, the inclined surface can be specified for each of the following three cases.

[0330] 1.4.1 Configuration Example 1-1 (When both slopes are large)

[0331] The case where the widths of both inclined surfaces are large will be described below. This case corresponds to the case where the widths w1 and w2 of the inclined surfaces of the TZ are both equal to or larger than the total reflection interval d of the light beam in the light guide plate.

[0332] in this case, Fig.10The distribution of MTF values ​​in the case where the beam angle deviation amount Δpeak caused by each of the two inclined planes is represented by the vertical axis and the horizontal axis is shown. The horizontal axis and the vertical axis represent the beam angle deviation amount Δpeak changed by the inclined plane 1 and the inclined plane 2, respectively.

[0333] In the figure, based on the range of Δpeak at which the degradation rate of MTF is 50% or less (ie, satisfies Mathematical Expression 1) at a spatial frequency of 10 cycles / degree, Fig.10 The preferred TZ shape is represented by the following mathematical expression 2.

[0334] [Mathematical formula 13]

[0335]

[0336] Among them, in mathematical expression 2,

[0337] h1 = (the height from the reference surface of the first diffraction grating to the apex of the mountain shape)

[0338] w1=(width of slope 1)

[0339] h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0340] w2=(width of slope 2)

[0341] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0342] θ airin = (incident angle of light when it enters the light guide plate)

[0343] n2 = (refractive index of the material forming the chevron shape structure)

[0344] θ' TIR = (light guiding angle in mountain-shaped structure).

[0345] Since the constraint of mathematical expression 2 on the TZ shape strongly restricts the above reference Figure 7 The h1 and h2 mentioned above are therefore allowed even if w1 and w2 are large. That is, even if w cannot be controlled, only h needs to be limited.

[0346] For example, suppose θ airin = 25 [degrees], n1 = 2.0, n2 = 1.5, Λ (ICG spacing) = 360 nm and λ (peak wavelength) = 530 nm, with w1 (or w2) = 0.5 mm, 0 ​

[0347] 1.4.2 Configuration Example 1-2 (One slope has a larger width and the other slope has a smaller width)

[0348] The following describes an example where one bevel width is smaller but the other bevel width is larger. This case corresponds to the case where the bevel width w1 of the TZ is smaller than the total reflection interval d of the light beam in the light guide plate, while the bevel width w2 of the TZ is equal to or larger than the total reflection interval d of the light beam in the light guide plate.

[0349] in this case, Fig.11 Distribution of MTF values ​​is shown in a case where the vertical axis represents the beam angle deviation amount Δpeak caused by one inclined surface, and the horizontal axis represents the beam ratio PS of the angle deviated caused by the other inclined surface.

[0350] In the figure, the range of PS and Δpeak ( Fig.11 The preferred TZ shape is represented by the following mathematical expression 3.

[0351] [Formula 14]

[0352]

[0353] Among them, in mathematical expression 3,

[0354] w1=(width of slope 1)

[0355] h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0356] w2=(width of slope 2)

[0357] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0358] θ airin = (incident angle of light when it enters the light guide plate)

[0359] n2 = (refractive index of the material forming the chevron shape structure)

[0360] θ' TIR = (light guiding angle in mountain-shaped structure).

[0361] The characteristic of this mathematical expression is that when Figure 7 It is a valid constraint when the width of the slope on one side can be strongly restricted.

[0362] For example, suppose θ airin = 25 [degrees], n1 = 2.0, n2 = 1.5, Λ (ICG spacing) = 360 nm, λ (peak wavelength) = 530 nm, and t = 0.5 mm, d = 0.6 mm and 0 < w1 ≦ 0.14 mm hold.

[0363] 1.4.3 Configuration Example 1-3 (When the widths of both slopes are small)

[0364] An example of a case where the widths of the two inclined surfaces are small will be described below. This case corresponds to a case where both the inclined surface widths w1 and w2 of the TZ are smaller than the total reflection interval d of the light beam in the light guide plate.

[0365] in this case, Fig.12 The distribution of MTF values ​​is shown in the case where the vertical axis and the horizontal axis represent the angle-deviant beam ratio PS caused by each of the two slopes. The horizontal axis and the vertical axis represent the angle-deviant beam ratio PS changed by slope 1 and slope 2, respectively.

[0366] In the figure, a preferred TZ shape is expressed by the following Mathematical Expression 4 based on the range of PS at which the degradation rate of MTF is 50% or less (ie, Mathematical Expression 1 is satisfied) at a spatial frequency of 10 cycles / degree.

[0367] [Mathematical formula 15]

[0368]

[0369] Among them, in mathematical expression 4,

[0370] w1=(width of slope 1)

[0371] w2=(width of slope 2).

[0372] The characteristic is that the constraints are Figure 7 This is effective when the bevel width on both sides can be strongly restricted.

[0373] For example, suppose θ airin = 25 [degrees], n1 = 2.0, n2 = 1.5, Λ (ICG spacing) = 360 nm, λ (peak wavelength) = 530 nm, and t = 0.5 mm, d = 0.6 mm, 0 < w1, and w2 ≦ 0.090 mm holds.

[0374] As described in the above configuration examples 1-1 to 1-3, by controlling the width or height of each slope according to the magnitude relationship between the slope width of the mountain-shaped structure of the TZ and the total reflection interval, it is possible to prevent the MTF from being deteriorated.

[0375] That is, in a preferred embodiment,

[0376] In the case where the “width of the slope of the mountain shape” is smaller than the “total reflection interval of light in the light guide plate”, the “slope” can be configured so that the “width of the slope” is equal to or smaller than the “threshold specified based on the total reflection interval”, and

[0377] When the “width of the mountain-shaped slope” is equal to or greater than the “total reflection interval of light in the light guide plate”, the “slope” can be configured so that the “height of the slope” is equal to or less than the “threshold specified based on the width of the slope and the inclination angle of the slope”.

[0378] More specifically, the light guide plate unit of the present disclosure may be configured such that the width or height of two slopes in the mountain shape satisfies any one of the above-mentioned mathematical expressions 2 to 4 according to the size relationship between the width of each slope and the total reflection interval.

[0379] 1.5 Example 2 of the MTF condition

[0380] In the above 1.3, Mathematical Expression 1 has been described regarding the case where the spatial frequency is 10 cycles / degree, and then, in the above 1.4, an example of a mountain-shaped structure (TZ) configured to satisfy Mathematical Expression 1 has been described.

[0381] In the present disclosure, more preferably, the light guide plate unit of the present disclosure may be configured such that the MTF value satisfies a predetermined condition when the spatial frequency is 20 cycles / degree.

[0382] That is, in a more preferred embodiment, the light guide plate unit according to the present disclosure includes: a light guide plate; and a structure having a first diffraction grating provided on one surface of the light guide plate, a second diffraction grating that diffracts light diffracted by the first diffraction grating, and a mountain shape between the first diffraction grating and the second diffraction grating, wherein the MTF value before the light enters the mountain shape when the spatial frequency is 20 cycles / degree is X 20 , and the MTF value after the light passes through the mountain shape is Y 20 When , the light guide plate unit is configured to satisfy the following mathematical expression 5.

[0383] [Formula 16]

[0384]

[0385] Since the two MTF values ​​X 20 and Y 20 It is controlled to satisfy Mathematical Expression 5, so that image quality degradation can be prevented.

[0386] Here, the light may be a light beam having a light guide angle in the light guide plate closest to a critical angle among light beams at a viewing angle used.

[0387] 1.6 Example 2 of inclined plane configuration

[0388] Similar to the case where the spatial frequency is 10 cycles / degree, also in the case where the spatial frequency is 20 cycles / degree, for example, in the light guide plate unit of the present disclosure, the slope can be specified for each of three cases as follows.

[0389] 1.6.1 Configuration Example 2-1 (When the widths of the two slopes are large)

[0390] The case where the widths of both inclined surfaces are large will be described below. This case corresponds to the case where the widths w1 and w2 of the inclined surfaces of the TZ are both equal to or larger than the total reflection interval d of the light beam in the light guide plate.

[0391] In this case, Fig.13 The distribution of MTF values ​​in the case where the beam angle deviation amount Δpeak caused by each of the two inclined planes is represented by the vertical axis and the horizontal axis is shown. The horizontal axis and the vertical axis represent the beam angle deviation amount Δpeak changed by the inclined plane 1 and the inclined plane 2, respectively.

[0392] In the figure, the TZ shape obtained from the range of Δpeak at which the degradation rate of MTF is 50% or less (ie, satisfies Mathematical Expression 5) at a spatial frequency of 20 cycles / degree is expressed by the following Mathematical Expression 6.

[0393] [Mathematical formula 17]

[0394]

[0395] Among them, in mathematical expression 6,

[0396] h1 = (the height from the reference surface of the first diffraction grating to the apex of the mountain shape)

[0397] w1=(width of slope 1)

[0398] h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0399] w2=(width of slope 2)

[0400] A = cos(θ airin ) / (2*n2*cos(θ'TIR ))

[0401] θ airin = (incident angle of light when it enters the light guide plate)

[0402] n2 = (refractive index of the material forming the chevron shape structure)

[0403] θ' TIR = (light guiding angle in mountain-shaped structure).

[0404] Since the constraint of mathematical expression 6 on the TZ shape strongly restricts the above reference Figure 7 The h1 and h2 mentioned above are therefore allowed even if w1 and w2 are large. That is, even if w cannot be controlled, only h needs to be limited.

[0405] For example, suppose θ airin = 25 [degrees], n1 = 2.0, n2 = 1.5, Λ (ICG spacing) = 360 nm and λ (peak wavelength) = 530 nm, with w1 (or w2) = 0.5 mm, 0

[0406] 1.6.2 Configuration Example 2-2 (One slope has a larger width and the other slope has a smaller width)

[0407] The following describes an example in which one bevel width is smaller but the other bevel width is larger. This case corresponds to the case in which the bevel width w1 of the TZ is smaller than the total reflection interval d of the light beam in the light guide plate, and the bevel width w2 of the TZ is equal to or larger than the total reflection interval d of the light beam in the light guide plate.

[0408] in this case, Fig.14 The distribution of MTF values ​​in the case where the vertical axis represents the beam angle deviation amount Δpeak caused by one inclined surface and the horizontal axis represents the beam ratio PS at which the angle is deviated caused by the other inclined surface is shown.

[0409] In the figure, the TZ shape obtained from the range of PS and Δpeak at which the degradation rate of MTF is 50% or less (ie, satisfies Mathematical Expression 5) at a spatial frequency of 20 cycles / degree is expressed by the following Mathematical Expression 7.

[0410] [Mathematical formula 18]

[0411]

[0412] Among them, in mathematical expression 7,

[0413] w1=(width of slope 1)

[0414] ​h2 = (the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0415] w2=(width of slope 2)

[0416] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0417] θ airin = (incident angle of light when it enters the light guide plate)

[0418] n2 = (refractive index of the material forming the chevron shape structure)

[0419] θ' TIR = (light guiding angle in mountain-shaped structure).

[0420] The characteristic of this mathematical expression is that when Figure 7 It is a valid constraint when the width of the slope on one side can be strongly restricted.

[0421] For example, suppose θ airin = 25 [degrees], n1 = 2.0, n2 = 1.5, Λ (ICG spacing) = 360 nm, λ (peak wavelength) = 530 nm, and t = 0.5 mm, d = 0.6 mm and 0 < w1 ≦ 0.12 mm hold.

[0422] 1.6.3 Configuration Example 2-3 (When the widths of the two slopes are small)

[0423] The following describes an example in which the widths of the two inclined surfaces are small. This case corresponds to the case in which the widths w1 and w2 of the inclined surfaces of the TZ are both smaller than the total reflection interval d of the light beam in the light guide plate.

[0424] in this case, Fig.15 The distribution of MTF values ​​is shown in which the vertical axis and the horizontal axis represent the angle-shifted beam ratio PS caused by each of the two slopes. The horizontal axis and the vertical axis represent the angle-shifted beam ratio PS changed by slope 1 and slope 2, respectively.

[0425] In the figure, the TZ shape obtained according to the range of PS at which the degradation rate of MTF at the spatial frequency of 20 cycles / degree is 50% or less (ie, satisfies Mathematical Expression 5) is expressed by the following Mathematical Expression 8.

[0426] [Mathematical formula 19]

[0427]

[0428] Among them, in mathematical expression 8,

[0429] w1=(width of slope 1)

[0430] w2=(width of slope 2).

[0431] The characteristic of this mathematical expression is that when Figure 7 It is a valid constraint when the width of the slope on both sides can be strongly constrained.

[0432] For example, suppose θ airin = 25 [degrees], n1 = 2.0, n2 = 1.5, Λ (ICG spacing) = 360 nm, λ (peak wavelength) = 530 nm, and t = 0.5 mm, d = 0.6 mm and 0 < w1 and w2 ≦ 0.090 mm hold.

[0433] As described in the above configuration examples 2-1 to 2-3, by controlling the width or height of each inclined surface according to the magnitude relationship between the width of the inclined surface of the mountain-shaped structure of the TZ and the total reflection interval, it is possible to prevent the MTF from being deteriorated.

[0434] That is, in a preferred embodiment,

[0435] In the case where the “width of the slope of the mountain shape” is smaller than the “total reflection interval of light in the light guide plate”, the “slope” may be configured so that the “width of the slope” is equal to or smaller than the “threshold specified based on the total reflection interval”, and

[0436] When the “width of the mountain-shaped slope” is equal to or greater than the “total reflection interval of light in the light guide plate”, the “slope” can be configured so that the “height of the slope” is equal to or less than the “threshold specified based on the width of the slope and the inclination angle of the slope”.

[0437] More specifically, the light guide plate unit of the present disclosure may be configured such that the width or height of two slopes in the mountain shape satisfies any one of the above-mentioned mathematical expressions 6 to 8 according to the size relationship between the width of each slope and the total reflection interval.

[0438] 1.7 TZc Configuration Example

[0439] In the light guide plate unit of the present disclosure, one of the two surfaces of the light guide plate, the surface on the opposite side or the same side as the surface provided with the mountain-shaped structure (hereinafter also referred to as the first structure or TZ) may be provided with a structure (hereinafter also referred to as the second structure or TZc) for offsetting the influence of the mountain-shaped structure.

[0440] That is, the light guide plate unit according to the present disclosure may be configured so that the light beam whose angle is changed by the TZ is irradiated onto the TZc. The angle deviation of the light beam is offset by the TZc. Various embodiments may be adopted according to the shape of the TZ and the installation position of the TZc.

[0441] The light guide plate unit having such a configuration can also eliminate the MTF degradation, can satisfy the condition of the above-mentioned Mathematical Expression 1, and further satisfy the condition of Mathematical Expression 5.

[0442] Hereinafter, an example of a light guide plate unit having these two structures will be described.

[0443] 1.7.1 Example 1 of TZc on the surface opposite to the surface where TZ is located

[0444] In one embodiment, a TZc may be provided on the surface opposite to the surface provided with the TZ among the two surfaces of the light guide plate. After the light beam traveling in the light guide plate is irradiated on the TZ and the beam angle is changed, the light beam is irradiated on the TZc, so that the beam angle returns to the beam angle before irradiating the TZ.

[0445] In this case, TZ and TZc may preferably comprise the same material. Thus, the angular deviation of the light beam is easily offset.

[0446] For example, Fig.16 As shown, the TZ may exist on one of the two surfaces of the light guide plate P, and the TZc may be disposed on the other surface. The TZc may have substantially the same shape as the TZ. The TZc may be arranged to be point-symmetrical with the TZ with respect to the substrate cross section.

[0447] The light guide plate unit U2 shown in the figure includes a light guide plate P, a first diffraction grating G1 provided on one surface of the light guide plate, a second diffraction grating G2 that diffracts the light diffracted by the first diffraction grating, and a first structure TZ having a mountain shape and between the first diffraction grating and the second diffraction grating. Moreover, one surface or the other surface of the light guide plate includes a second structure TZc having a mountain shape, and the mountain shape is configured to offset the angular deviation of the light caused by the first structure TZ.

[0448] With regard to this embodiment, the shapes of TZ and TZc will be described.

[0449] First, the shape of the TZ will be described. Regarding the shape of the TZ, preferably, the width w1 of the inclined surface 1 satisfies w1 < 0.1 * d, and the width w2 of the inclined surface 2 satisfies w2 ≧ d. Here, d is the total reflection interval of light in the light guide plate.

[0450] In order to offset the influence of TZ on the beam, it is necessary to arrange the inclined surface of TZc corresponding to each inclined surface of TZ. Fig.17 As shown, when the slope width is large, the shape of TZc may require a valley shape and vertical side surfaces, which is difficult to achieve. Therefore, by satisfying the above w1 < 0.1 * d, TZc is easily formed.

[0451] Furthermore, in the case where w1 < 0.1 * d is satisfied, the influence of one inclined surface (the inclined surface of w1) is small, and thus there is also an advantage in that only the influence of the other inclined surface needs to be canceled.

[0452] That is, the light guide plate unit may be configured such that the width w1 of the inclined surface 1 on the first diffraction grating side of the first structure satisfies w1<0.1d (where d is the total reflection interval of light in the light guide plate).

[0453] Next, the shape of TZc will be described.

[0454] To improve the MTF degradation, it is only necessary to reduce the MTF degradation, but not to completely cancel it. Therefore, the TZc does not need to have a shape that completely matches the shape of the TZ, that is, there are tolerances related to the shape of the TZc and tolerances related to the position. These tolerances will be described below.

[0455] The widths of the inclined surfaces in the shape of the TZc are defined as wc1 and wc2, and the angles formed by the inclined surfaces of the TZc and the substrate are defined as φc1 and φc2.

[0456] In this case, the shape of TZc is represented by the following four mathematical expressions.

[0457] wc1 < 0.1 * d,

[0458] wc2 = w2 + Δw,

[0459] φc2 = φ2 + Δφ, and

[0460] x = d / 2 + n * d + Δx.

[0461] Here, the parameters in these mathematical expressions are as follows.

[0462] x: The horizontal distance difference between the vertex of TZ and one end of TZc

[0463] Δw: Tolerance of the bevel width of TZc

[0464] Δφ: Tolerance of the slope angle of TZc

[0465] Δx: Tolerance of x

[0466] n:any integer.

[0467] For x, d / 2 + n*d represents the interval at which the light beam of the TZ irradiated on the front surface of the light guide plate is irradiated to the rear surface. x is the horizontal distance from the left end of the inclined surface 2 of the first structure to the left end of the inclined surface of the second structure having the effect of offsetting the influence of the inclined surface 2. Δx is (half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam), that is, the error from (d / 2 + n*d). Therefore, as described above, x is represented by x = d / 2 + n*d + Δx.

[0468] The ranges of Δw, Δφ, Δx, and n in the above mathematical expressions will be further described below.

[0469] In the case where the TZc is arranged at a position to correct the angle deviation of the light beam caused by the TZ, the width and position of the inclined surface of the TZc affect the beam ratio that can correct the angle deviation, and the angle of the inclined surface affects how much the angle of the deviation of the light beam can be restored. These parameters can be expressed by the shape of the PSF similar to that of the configuration example 1 of the inclined surface (particularly, configuration examples 1-1 to 1-3), that is, the MTF value can be derived. Since w2 ≧ d, the concept of PSF is as follows Fig. 9 As shown in B.

[0470] Fig.18 Shown is the MTF distribution when Δw (horizontal axis) and Δφ (vertical axis) are changed.

[0471] As can be seen from the figure, the range in which the MTF value becomes higher than the MTF value in the absence of TZc (ie, the range indicated by circled number 1) is represented by the relational expression shown below (Mathematical Expression 9-1).

[0472] also, Fig.19 The MTF distribution when Δx (horizontal axis) and Δφ (vertical axis) are changed is shown. As can be seen from the figure, the range in which the MTF value becomes higher than the MTF value in the absence of TZc (i.e., the range indicated by the circled number 2 and the range indicated by the circled number 3) are expressed by the following relational expressions of (Mathematical Expression 9-2) and (Mathematical Expression 9-3), respectively.

[0473] In these mathematical expressions, in the case of φc2 < 0, this means a structure in which the right and left sides of the inclined surface are reversed and the angle of the inclined surface is -φc2.

[0474] [Mathematical formula 20]

[0475]

[0476] Among them, in mathematical expressions 9-1, 9-2 and 9-3,

[0477] Δφ is the tolerance of the slope angle of the mountain shape of the second structure,

[0478] φ2 is the angle formed by the inclined surface 2 on one side of the second diffraction grating of the first structure and the first surface of the light guide plate,

[0479] Δw is the tolerance of the slope width of the mountain shape of the second structure,

[0480] d is the total reflection interval of the above light,

[0481] n is any integer,

[0482] Δx is the error of x, where x is (half of the total reflection interval of the light beam) + (an integer multiple of the total reflection interval of the light beam),

[0483] w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure.

[0484] Therefore, when any of the conditions of (Mathematical Expression 9-1), (Mathematical Expression 9-2), and (Mathematical Expression 9-3) is satisfied, the MTF degradation in the case where the spatial frequency is 10 cycles / degree can be improved.

[0485] 1.7.2 Example 2 of TZc on the surface opposite to the surface where TZ is located

[0486] In the above 1.7.1, regarding the shape of TZ, the case where the width of the inclined surface 2 is w2 ≥ d has been described. Hereinafter, the case where the width of the inclined surface 2 is w2 < d will be described.

[0487] The widths of the inclined surfaces in the shape of the TZc are defined as wc1 and wc2, and the angles formed by the inclined surfaces of the TZc and the substrate are defined as φc1 and φc2.

[0488] In this case, the shape of TZc is represented by the following four mathematical expressions. Wc1 < 0.1 * d, wc2 = w2 + Δw, φc2 = φ2 + Δφ, and x = d / 2 + n * d + Δx are satisfied.

[0489] Here, for x, d / 2 + n*d represents an interval at which the light beam of the TZ irradiated on the front surface of the light guide plate is irradiated to the rear surface.

[0490] The ranges of Δw, Δφ, Δx, and n in the above mathematical expressions are described below. Since w2 < d, the concept of PSF is as follows Fig. 9 As shown in A.

[0491] Fig. 20The MTF distribution when Δw (horizontal axis) and Δφ (vertical axis) are changed is shown. As can be seen from the figure, the range of MTF values ​​located higher than the case where TZc does not exist (i.e., the range indicated by the circled number 4 and the range indicated by the circled number 5) are expressed by the relational expressions of (Mathematical Expression 10-1) and (Mathematical Expression 10-2), respectively.

[0492] also, Fig.21 The MTF distribution when Δx (horizontal axis) and Δφ (vertical axis) are changed is shown. From the figure, the range in which the MTF value becomes higher than the MTF value in the absence of TZc (ie, the range indicated by the circled number 6) is expressed by the relational expression of (Mathematical Expression 10-3).

[0493] However, in the case of φc2 < 0, this means a structure in which the right and left sides of the inclined plane are reversed and the angle of the inclined plane is -φc2.

[0494] [Mathematical formula 21]

[0495]

[0496] Among them, in mathematical expressions 10-1, 10-2 and 10-3,

[0497] Δφ is the tolerance of the slope angle of the mountain shape of the second structure,

[0498] φ2 is the angle formed by the inclined surface 2 on one side of the second diffraction grating of the first structure and the first surface of the light guide plate,

[0499] Δw is the tolerance of the slope width of the mountain shape of the second structure,

[0500] Δx is the error of x, where x is (half of the total reflection interval of the light beam) + (an integer multiple of the total reflection interval of the light beam),

[0501] w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure.

[0502] Therefore, when any of the conditions of (Mathematical Expression 10-1), (Mathematical Expression 10-2), and (Mathematical Expression 10-3) is satisfied, the MTF degradation in the case where the spatial frequency is 10 cycles / degree can be improved.

[0503] 1.7.3 Example 1 of TZc on the surface where TZ is located

[0504] In the above 1.7.1, a configuration example has been described in which the TZc exists on the surface on the opposite side to the surface where the TZ exists. Hereinafter, a case in which the TZc exists on the same plane as the plane where the TZ exists will be described.

[0505] In this case, if Fig. 22 As shown, the TZc may have substantially the same shape as the TZ. The TZc may be arranged symmetrically with respect to an axis orthogonal to the substrate.

[0506] First, the shape of TZ will be described.

[0507] Regarding the shape of the TZ, similar to 1.7.1 above, preferably, the width w1 of the inclined surface 1 satisfies w1 < 0.1 * d, and the width w2 of the inclined surface 2 satisfies w2 ≧ d. Here, d is the total reflection interval of light in the light guide plate. By satisfying w1 < 0.1 * d, it is easy to form a TZc.

[0508] Furthermore, in this case, the influence of one inclined surface (the inclined surface of w1) is small, so there is also an advantage that only the influence of the other inclined surface needs to be canceled.

[0509] Next, the shape of TZc will be described.

[0510] To improve the MTF degradation, it is only necessary to reduce the MTF degradation, not to completely cancel it. Therefore, the TZc does not need to have a shape that completely matches the shape of the TZ, that is, there are tolerances related to the shape of the TZc and tolerances related to the position. These tolerances will be described below.

[0511] The width of the inclined surface in the shape of TZc is defined as wc1 and wc2, and the angle formed by the inclined surface of TZc and the substrate is defined as φc1 and φc2. In this case, the shape of TZc is represented by the following four mathematical expressions.

[0512] wc1 < 0.1 * d,

[0513] wc2 = w2 + Δw,

[0514] φc2 = φ2 + Δφ,

[0515] x = d + n * d + Δx.

[0516] Here, the parameters in these mathematical expressions are as follows.

[0517] x: The horizontal distance difference between the vertex of TZ and one end of TZc

[0518] Δw: Tolerance of the bevel width of TZc

[0519] Δφ: Tolerance of the bevel angle of Tzc

[0520] Δx: Tolerance of x

[0521] n:any integer.

[0522] For x, d+n*d represents an interval at which the light beam of TZ irradiated onto the front surface of the light guide plate irradiates the front surface again.

[0523] Regarding the above mathematical expressions, the ranges of Δw, Δφ, Δx, and n can be expressed by (Mathematical Expression 9-1), (Mathematical Expression 9-2), and (Mathematical Expression 9-3) described in 1.7.1 above. That is, regarding Δw, Δφ, Δx, and n, when any of the conditions of (Mathematical Expression 9-1), (Mathematical Expression 9-2), and (Mathematical Expression 9-3) are satisfied, the MTF degradation in the case where the spatial frequency is 10 cycles / degree can be improved.

[0524] 1.7.4 Example 2 of TZc on the surface where TZ is located

[0525] In the above 1.7.3, regarding the shape of TZ, the case where the width of the inclined surface 2 is w2 ≧ d has been described.

[0526] Hereinafter, a case where the width of the inclined surface 2 is w2<d will be described.

[0527] In this case, as described in 1.7.2 above, the TZc has a shape in which the widths of the inclined surfaces are wc1 and wc2, and the angles formed by the inclined surfaces of the TZc and the substrate are φc1 and φc2.

[0528] In this case, the shape of TZc is represented by the following four mathematical expressions.

[0529] wc1 < 0.1 * d,

[0530] wc2 = w2 + Δw,

[0531] φc2 = φ2 + Δφ,

[0532] x = d + n * d + Δx.

[0533] Here, for x, d+n*d represents an interval at which the light beam of TZ irradiated onto the front surface of the light guide plate irradiates the front surface again.

[0534] Regarding the above mathematical expressions, the ranges of Δw, Δφ, Δx, and n can be expressed by (Mathematical Expression 10-1), (Mathematical Expression 10-2), and (Mathematical Expression 10-3) described in 1.7.2 above. That is, regarding Δw, Δφ, Δx, and n, when any of the conditions of (Mathematical Expression 10-1), (Mathematical Expression 10-2), and (Mathematical Expression 10-3) are satisfied, the MTF degradation in the case where the spatial frequency is 10 cycles / degree can be improved.

[0535] 1.8 Coating

[0536] In one embodiment, the area where the structure is located may be provided with a reflective coating configured to prevent light from entering the structure, or a coating configured to prevent light that has entered the structure from causing an angle deviation due to the slope of the mountain shape. Such a reflective coating or coating may also suppress MTF degradation. Moreover, the light guide plate unit having such a configuration may eliminate MTF degradation, may satisfy the conditions of the above-mentioned mathematical expression 1, and may further satisfy the conditions of mathematical expression 5. These layers will be described in more detail below.

[0537] 1.8.1 Examples of reflective coatings

[0538] In the following, reference will be made to Fig.23 A configuration example of a light guide plate unit of the present disclosure provided with a reflective coating is described. This figure is a schematic diagram of the configuration example.

[0539] As shown on the left side of the figure, the reflective coating RL is laminated on the light guide plate P to obtain a laminate. Then, a diffraction grating is formed by inkjet and nanoimprinting on the laminate, and diffraction gratings G1 and G2 and a mountain-shaped structure TZ are formed as shown on the right side of the figure. This gives a light guide plate unit U31 including the light guide plate P, the reflective coating RL, the diffraction gratings G1 and G2, and the mountain-shaped structure TZ. Therefore, the reflective coating can be provided between the light guide plate and the structure.

[0540] Here, the diffraction gratings G1 and G2 are not formed in the region where the reflective coating RL is located, and are formed to contact the light guide plate P.

[0541] On the other hand, the chevron shape structure TZ is formed on the reflective coating layer RL. That is, in the region where the reflective coating layer CL is located, a laminated structure in which the light guide plate P, the reflective coating layer RL, and the chevron shape structure TZ are laminated in sequence is formed.

[0542] The region where the reflective coating RL is located may be formed to cover the entire region where the chevron-shaped structure TZ is located, and the region where the reflective coating RL is located may be wider than the region where the chevron-shaped structure TZ is located.

[0543] As described above, the light guide plate unit U31 has a reflective coating RL between the mountain-shaped structure TZ and the light guide plate P. Due to the reflective coating CL, the light traveling in the light guide plate is totally reflected by the flat surface of the light guide plate P without irradiating the TZ, so there is no MTF degradation. Therefore, the reflective coating can greatly alleviate the MTF degradation caused by the TZ.

[0544] Preferably, the reflective coating may include a metal coating, that is, it may be a metal reflective coating. The metal material may contain, for example, aluminum, silver, gold, aluminum alloy, copper, mercury, chromium, nickel, platinum or tin as a main component, preferably, aluminum, silver, gold or aluminum alloy as a main component.

[0545] For example, the film thickness of the reflective coating may be 10 nm or more, preferably 20 nm or more, more preferably 30 nm or more. For example, the film thickness may be 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less.

[0546] The reflective coating is not necessarily formed by coating processing, but can be formed by other methods. For example, the reflective coating can be formed by vapor deposition or sputtering. The reflective coating can be referred to as a reflective layer.

[0547] 1.8.2 Examples of coatings

[0548] In the following, reference will be made to Fig.24 The light guide plate unit of the present disclosure includes a coating configured so that light entering the structure does not cause angle deviation due to the slope of the mountain shape. The figure is a schematic diagram of the light guide plate unit.

[0549] As shown in the light guide plate unit U32, the diffraction gratings are formed by inkjet and nanoimprinting on the laminate, so the diffraction gratings G1 and G2 and the mountain-shaped structure TZ are formed on the light guide plate P. Then, moreover, the coating layer CL is formed to cover the area where the mountain-shaped structure TZ is located. That is, in the area where the mountain-shaped structure TZ is located, the laminated structure where the light guide plate P, the mountain-shaped structure TZ, and the coating layer CL are located are sequentially formed.

[0550] This gives a light guide plate unit U32 including the light guide plate P, the diffraction gratings G1 and G2, the chevron-shaped structure TZ, and the coating CL.

[0551] As shown, the coating layer CL may be provided to cover the mountain-shaped TZ and form a flat shape (flat surface S). The coating layer may include a material having substantially the same refractive index as that of the TZ, and preferably, may include a material having the same refractive index as that of the TZ.

[0552] Due to this coating, the TZ is close to flat, which reduces the influence on the beam and alleviates the MTF degradation.

[0553] Furthermore, in the present disclosure, the structure including the original TZ and the coating layer can be regarded as a new TZ. Then, any method described in 1.8.1 or earlier above can be applied to the new TZ.

[0554] 1.9 Example of a case including a structure having a plurality of mountain shapes

[0555] The light guide plate unit of the present disclosure may include a structure having a plurality of mountain shapes disposed between the first diffraction grating and the second diffraction grating. In this case, preferably, the height of all the plurality of mountain shapes is equal to or less than 90 nm. Therefore, MTF degradation can be suppressed. Moreover, the light guide plate unit having such a configuration can eliminate MTF degradation, can satisfy the condition of the above-mentioned mathematical expression 1, and further satisfy the condition of mathematical expression 5. Fig.25 A and 25B are described.

[0556] for Fig.25 In the light guide plate unit U41 shown in A, there is a case where two structures m1 and m2 having a mountain shape are formed during the formation of the diffraction grating. For example, when a resist material having a high refractive index is used to form the diffraction grating, and the distance between the two diffraction gratings is large, there is a case where a mountain-shaped structure m2 having a higher height is formed next to the mountain-shaped structure m1 closest to the diffraction grating G1. In such a light guide plate unit U41, in the case where the height of the structure m2 is too high, for example, in the case where the height exceeds 90 nm, in particular, the possibility of causing MTF degradation increases.

[0557] Therefore, in the light guide plate unit of the present disclosure, in the case where a plurality of mountain shapes are provided between two diffraction gratings, it is required that the height of any one of these mountain shapes is preferably 90 nm or less, more preferably 85 nm or less, and still more preferably 80 nm or less.

[0558] That is to say, Fig.25 In the light guide plate unit U42 shown in B, the mountain-shaped structures m3 and m4 can be formed next to the mountain-shaped structure m1 instead of next to the structure m1, and the heights of all these structures m1, m3 and m4 are preferably 90 nm or less, more preferably 85 nm or less, and even more preferably 80 nm or less.

[0559] Therefore, it is possible to prevent the MTF from being deteriorated. Therefore, the degradation rate of the MTF at a spatial frequency of 10 cycles / degree can be 50% or less.

[0560] 1.10 Manufacturing method

[0561] For example, the light guide plate unit according to the present disclosure may be manufactured by a manufacturing method using a nanoimprinting technique. In particular, the manufacturing method may include depositing a resist material on the light guide plate by an inkjet method, and depositing the resist material using the inkjet method results in a mountain-shaped structure being formed on the light guide plate. Fig.26The flowchart shown in Fig. 27 The schematic diagrams in A and 27B describe the fabrication method.

[0562] In step S1 shown in the figure, a resist material RM is deposited on a light guide plate P. For example, the resist material may be any photocurable resin composition, in particular, an ultraviolet curable resin composition. The resist material may include, for example, any one of acrylic resin, polyimide resin, melamine resin, polyester resin, polycarbonate resin, phenolic resin and epoxy resin or a combination of two or more thereof as a resin component. In addition, these photocurable resins may include nanoparticles. Any known nanoparticles may be used as nanoparticles, examples of which include titanium oxide, zirconium oxide, silicon dioxide, silicon and nanodiamonds. In addition, in the case of including nanoparticles, one or two or more types of nanoparticles may be included in the photocurable resin. The light guide plate P may include any material that can be used as a light guide plate material in the technical field, and the material of the light guide plate P may be, for example, an inorganic material, an organic material or a mixed material of these materials. Specific examples of inorganic materials include glass and silicon, and specific examples of organic materials include polycarbonate-based resins, acrylic resins, thiourea-based resins and epoxy-based resins.

[0563] For example, in step S1, a resist material is applied to the light guide plate by an inkjet method. In the application of the inkjet method, the above-mentioned mountain-shaped structure is easily formed, and the problem regarding the above-mentioned TZ is easily caused. In step S1, by adjusting the amount and position of the resist material dripped, the shape of the mountain-shaped structure included in the light guide plate unit can be adjusted. More specifically, by adjusting the amount of resist material dripped in the area where the TZ appears, the amount of resist material dripped in the surrounding area where the two diffraction gratings are formed, and the position of these resist material drips, the shape of the mountain-shaped structure can be adjusted to a desired shape (for example, a shape that suppresses MTF degradation).

[0564] For example, in Fig. 27 In the case where the light guide plate unit obtained in the case where the resist material shown in A is dropped does not have the characteristics regarding the MTF according to the present disclosure, for example, by Fig. 27 B, the amount and position of the resist material dropped can be adjusted, the slope and height can be adjusted, and a light guide plate unit having characteristics regarding the MTF according to the present disclosure can be obtained. For example, according to the required performance of the light guide plate unit and the type or characteristics of the resist material, those skilled in the art can appropriately adjust the amount and position of the resist material dropped.

[0565] Note that the thicknesses T1 and T2 of the resist material required for forming the first diffraction grating and the second diffraction grating are determined according to the structures of these diffraction gratings. Therefore, by adjusting the thickness distribution of the resist material in the TZ while satisfying these thicknesses in the region where each diffraction grating is formed, a TZ having each diffraction grating and a desired shape can be formed.

[0566] In step S2, the stamper ST is pressed onto the light guide plate. That is, the stamper and the light guide plate are pressed in such a way that they sandwich the resist material. Therefore, the resist material enters the pattern for forming the diffraction configuration set in advance in the stamper.

[0567] In step S3, the resist material is cured. Curing can also be referred to as transfer. For example, depending on the type of resin, a method for curing can be appropriately selected. In the case where the resin can be photocured, the resin can be irradiated with light. More specifically, in the case where the resin is an ultraviolet curable resin, the resin is irradiated with ultraviolet light. By curing, a first diffraction grating and a second diffraction grating are formed, and a mountain-shaped structure therebetween is also formed.

[0568] In step S4, the stamper is separated from the light guide plate. That is, the diffraction grating is demolded from the stamper mold. In this way, the light guide plate unit according to the present disclosure is manufactured.

[0569] 1.11 Usage

[0570] The light guide plate unit according to the present disclosure can be used to manufacture an image display device. Then, for example, in the image display device, the light guide plate unit can be used to guide the light (particularly, the image display light) emitted from the drawing engine to the user's eyes. Since the light guide plate unit can prevent the MTF from deteriorating, an image with better image quality can be presented to the user. The following will describe a configuration example of the image display light.

[0571] 2. Second Embodiment (Image Display Device)

[0572] The present disclosure also provides an image display device including a light guide plate unit as described in 1 above. Fig.28 An example of an image display device is described.

[0573] The image display device 100 shown in the figure includes a light guide plate unit 101 and a drawing system 102 .

[0574] The light guide plate unit 101 may be any one of the light guide plate units of the present disclosure described in 1 above.

[0575] The drawing system 102 forms image display light guided by the light guide plate unit 101. The light guide plate unit 101 guides the image display light to reach the eyes 103 of the user.

[0576] Although not shown in the figure, the image display device 100 may have one or more optical elements on the optical path between the drawing system 102 and the light guide plate unit 101. The optical element may include a light guide optical system, which may include, for example, one or more collimating lenses and / or one or more relay lenses.

[0577] The mapping system 102 may be stored in the housing. The housing may also store the light guiding optical system.

[0578] In addition, the image display device 100 may further include an instrument for holding the light guide plate unit 101 in front of the eyes. For example, the instrument may include a temple portion and a frame portion of glasses. The instrument may be a strap for fixing the image display device 100 to the head. The instrument may be attached to the housing.

[0579] For example, the image display device 100 may be configured as a head mounted display (hereinafter also referred to as HMD). For example, the head mounted display may be a transmissive HMD or a non-transmissive HMD.

[0580] For example, the transmissive HMD may be configured as a glasses-type display. In this case, the light guide plate unit 101 may transmit light from an external view to reach the eyes. The light guide plate unit 101 may be disposed in a portion corresponding to the lens of the glasses. The video presented by the image display device 100 may be superimposed on the external view by the transmissive HMD, for example, AR may be provided to the user. For example, the non-transmissive HMD may completely cover both eyes. In this case, the light from the external view does not reach the eyes.

[0581] The present disclosure may also adopt the following configurations.

[0582] <1>

[0583] A light guide plate unit, comprising:

[0584] a light guide plate; and

[0585] A structure having a first diffraction grating provided on one surface of the light guide plate, a second diffraction grating diffracting light diffracted by the first diffraction grating, and a mountain shape between the first diffraction grating and the second diffraction grating, wherein

[0586] When the spatial frequency is 10 cycles / degree, the MTF value of the light before entering the mountain shape is X 10 , and the MTF value after the light passes through the mountain shape is Y 10 When , the light guide plate unit is configured to satisfy the following mathematical expression 1.

[0587] [Mathematical formula 22]

[0588]

[0589] <2>

[0590] according to <1> The light guide plate unit, wherein

[0591] In the case where the width of the slope of the mountain shape is smaller than the total reflection interval of light in the light guide plate, the slope is configured so that the width of the slope is equal to or smaller than a threshold value specified based on the total reflection interval, and

[0592] When the width of the mountain-shaped slope is equal to or greater than the total reflection interval of light in the light guide plate, the slope is configured so that the height of the slope is equal to or less than a threshold specified based on the width of the slope and the inclination angle of the slope.

[0593] <3>

[0594] according to <1> or <2> The light guide plate unit, wherein

[0595] In the case where each of the width w1 of the inclined surface 1 on the first diffraction grating side and the width w2 of the inclined surface 2 on the second diffraction grating side of the mountain shape is equal to or larger than the total reflection interval d of light in the light guide plate, the mountain shape is configured so that the height h1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 2,

[0596] [Mathematical formula 23]

[0597]

[0598] Among them, in mathematical expression 2,

[0599] h1=(the height from the reference surface of the first diffraction grating to the apex of the mountain shape)

[0600] w1=(width of slope 1)

[0601] h2=(the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0602] w2=(width of slope 2)

[0603] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0604] θ airin = (incident angle of light when it enters the light guide plate)

[0605] n2 = (refractive index of the material forming the mountain-shaped structure)

[0606] θ' TIR = (the light guide angle in the mountain-shaped structure),

[0607] In the case where the width w1 of the inclined surface 1 on the first diffraction grating side of the mountain shape is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on the second diffraction grating side is equal to or larger than the total reflection interval d of light in the light guide plate, the mountain shape is configured so that the width w1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 3,

[0608] [Mathematical formula 24]

[0609]

[0610] Among them, in mathematical expression 3,

[0611] w1=(width of slope 1)

[0612] h2=(the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0613] w2=(width of slope 2)

[0614] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0615] θ airin = (incident angle of light when it enters the light guide plate)

[0616] n2 = (refractive index of the material forming the mountain-shaped structure)

[0617] θ' TIR = (the light guide angle in the mountain-shaped structure),

[0618] and,

[0619] In the case where each of the width w1 of the inclined surface 1 on the first diffraction grating side of the mountain shape and the width w2 of the inclined surface 2 on the second diffraction grating side is smaller than the total reflection interval d of light in the light guide plate,

[0620] The mountain shape may be configured such that the width w1 of the slope 1 and the width w2 of the slope 2 satisfy Mathematical Expression 4 below.

[0621] <Mathematical formula 25>

[0622]

[0623] Among them, in mathematical expression 4,

[0624] w1=(width of slope 1)

[0625] w2=(width of slope 2).

[0626] <4>

[0627] according to <1> to <3> The light guide plate unit as described in any one of the preceding claims, wherein

[0628] When the spatial frequency is 20 cycles / degree, the MTF value before the light enters the mountain shape is X 20 And the MTF value after the light passes through the mountain shape is Y 20 When , the light guide plate unit is configured to satisfy the following mathematical expression 5.

[0629] <Mathematical formula 26>

[0630]

[0631] <5>

[0632] according to <4> The light guide plate unit, wherein

[0633] In the case where each of the width w1 of the inclined surface 1 on the first diffraction grating side and the width w2 of the inclined surface 2 on the second diffraction grating side of the mountain shape is equal to or larger than the total reflection interval d of light in the light guide plate, the mountain shape is configured so that the height h1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 6,

[0634] [Mathematical formula 27]

[0635]

[0636] Among them, in mathematical expression 6,

[0637] h1=(the height from the reference surface of the first diffraction grating to the apex of the mountain shape)

[0638] w1=(width of slope 1)

[0639] h2=(the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0640] w2=(width of slope 2)

[0641] A = cos(θ airin) / (2*n2*cos(θ' TIR ))

[0642] θ airin = (incident angle of light when it enters the light guide plate)

[0643] n2 = (refractive index of the material forming the mountain-shaped structure)

[0644] θ' TIR = (the light guide angle in the mountain-shaped structure),

[0645] In the case where the width w1 of the inclined surface 1 on the first diffraction grating side is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on the second diffraction grating side of the mountain shape is equal to or larger than the total reflection interval d of light in the light guide plate, the mountain shape is configured so that the width w1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 7,

[0646] [Mathematical formula 28]

[0647]

[0648] Among them, in mathematical expression 7,

[0649] w1=(width of slope 1)

[0650] h2=(the height from the reference surface of the second diffraction grating to the apex of the mountain shape)

[0651] w2=(width of slope 2)

[0652] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0653] θ airin = (incident angle of light when it enters the light guide plate)

[0654] n2 = (refractive index of the material forming the mountain-shaped structure)

[0655] θ' TIR = (the light guide angle in the mountain-shaped structure),

[0656] and,

[0657] In the case where each of the width w1 of the inclined surface 1 on the first diffraction grating side and the width w2 of the inclined surface 2 on the second diffraction grating side of the mountain shape is smaller than the total reflection interval d of light in the light guide plate, the mountain shape may be configured such that the width w1 of the inclined surface 1 and the width w2 of the inclined surface 2 satisfy the following Mathematical Expression 8,

[0658] [Mathematical formula 29]

[0659]

[0660] Among them, in mathematical expression 8,

[0661] w1=(width of slope 1)

[0662] w2=(width of slope 2).

[0663] <6>

[0664] according to <1> to <5> The light guide plate unit as described in any one of the preceding claims, wherein

[0665] The light guide plate unit further includes a second structure on one surface or the other surface of the light guide plate, the second structure having a mountain shape configured to offset an angle deviation of light caused by the structure (hereinafter referred to as “first structure”).

[0666] <7>

[0667] according to <6> The light guide plate unit, wherein

[0668] The width w1 of the inclined surface 1 on the first diffraction grating side of the first structure is configured to satisfy

[0669] w1 < 0.1 d

[0670] (Here, d is the total reflection interval of light in the light guide plate).

[0671] <8>

[0672] according to <7> The light guide plate unit, wherein

[0673] In the case where the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure is equal to or larger than the total reflection interval d of light, the mountain shape of the second structure is configured to satisfy any one of the following mathematical expressions 9-1, 9-2, and 9-3,

[0674] [Math 30]

[0675]

[0676] Among them, in mathematical expressions 9-1, 9-2 and 9-3,

[0677] Δφ is the tolerance of the slope angle of the mountain shape of the second structure,

[0678] φ2 is an angle formed by the inclined surface 2 on the second diffraction grating side of the first structure and the first surface of the light guide plate,

[0679] Δw is the tolerance of the slope width of the mountain shape of the second structure,

[0680] d is the total reflection interval of light as described above,

[0681] n is any integer,

[0682] Δx is the error of x, where x is ((half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam)),

[0683] w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure,

[0684] and

[0685] In the case where the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure is smaller than the total reflection interval d of light, the mountain shape of the second structure is configured to satisfy any one of the following mathematical expressions 10-1, 10-2, and 10-3,

[0686] [Mathematical formula 31]

[0687]

[0688] Among them, in mathematical expressions 10-1, 10-2 and 10-3,

[0689] Δφ is the tolerance of the slope angle of the mountain shape of the second structure,

[0690] φ2 is an angle formed by the inclined surface 2 on the second diffraction grating side of the first structure and the first surface of the light guide plate,

[0691] Δw is the tolerance of the slope width of the mountain shape of the second structure,

[0692] Δx is the error of x, where x is ((half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam)),

[0693] w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first structure.

[0694] <9>

[0695] according to <1> to <8> The light guide plate unit as described in any one of the preceding claims, wherein

[0696] The region where the structure is located is provided with a reflective coating configured to prevent light from entering the structure, or a coating configured to prevent light that has entered the structure from causing an angular deviation due to the slope of the mountain shape.

[0697] <10>

[0698] according to <9> The light guide plate unit, wherein the reflective coating is arranged between the light guide plate and the structure.

[0699] <11>

[0700] according to <9> The light guide plate unit, wherein the coating layer includes a material having a refractive index substantially the same as a refractive index of the structure.

[0701] <12>

[0702] according to <1> The light guide plate unit comprises

[0703] having a plurality of mountain-shaped structures disposed between the first diffraction grating and the second diffraction grating, wherein

[0704] The heights of all of the plurality of mountain shapes are equal to or less than 90 nm.

[0705] <13>

[0706] according to <1> to <12> The light guide plate unit as described in any one of the preceding claims, wherein

[0707] The first diffraction grating is any one of an incident diffraction grating configured to diffract light entering the light guide plate and causing the light to travel in the light guide plate, an expander configured to expand light that has traveled in the light guide plate, and an emission diffraction grating configured to emit light from the light guide plate, and

[0708] The second diffraction grating is a recycling device that diffracts the light that has passed through the first diffraction grating and travels toward one end of the light guide plate and allows the light to travel to the first diffraction grating again.

[0709] <14>

[0710] according to <1> to <12> The light guide plate unit as described in any one of the preceding claims, wherein

[0711] The first diffraction grating is an incident diffraction grating configured to diffract light entering the light guide plate and cause the light to travel in the light guide plate, and

[0712] The second diffraction grating is an expander configured to expand the light that is diffracted by the first diffraction grating and has traveled in the light guide plate.

[0713] <15>

[0714] according to <1> to <12> The light guide plate unit as described in any one of the preceding claims, wherein:

[0715] The first diffraction grating is an expander configured to expand the light that has traveled in the light guide plate, and

[0716] The second diffraction grating is a transmission diffraction grating configured to transmit the light expanded by the expander from the light guide plate.

[0717] <16>

[0718] according to <1> to <12> The light guide plate unit as described in any one of the preceding claims, wherein

[0719] The first diffraction grating is an incident diffraction grating configured to diffract light entering the light guide plate and cause the light to travel in the light guide plate, and

[0720] The second diffraction grating is a transmission diffraction grating configured to transmit, from the light guide plate, light having traveled in the light guide plate.

[0721] <17>

[0722] according to <16> The light guide plate unit, wherein the emission diffraction grating is an emission diffraction grating configured to expand light that has traveled in the light guide plate and emit the light from the light guide plate.

[0723] <18>

[0724] according to <1> to <17> The light guide plate unit described in any one of the preceding claims, wherein the chevron-shaped structure includes a material for forming the first diffraction grating, the second diffraction grating, or both of these diffraction gratings.

[0725] <19>

[0726] according to <1> to <18> The light guide plate unit described in any one of the preceding claims, wherein the light guide plate unit is used to manufacture an image display device.

[0727] <20>

[0728] An image display device, comprising:

[0729] A light guide plate unit, the light guide plate unit comprising:

[0730] a light guide plate; and

[0731] a structure having a first diffraction grating provided on one surface of the light guide plate, a second diffraction grating diffracting light diffracted by the first diffraction grating, and a mountain shape between the first diffraction grating and the second diffraction grating, wherein

[0732] When the spatial frequency is 10 cycles / degree, the MTF value before the light enters the mountain shape is X 10 , and the MTF value after the light passes through the mountain shape is Y 10 When , the light guide plate unit is configured to satisfy the following mathematical expression 1.

[0733] [Math 32]

[0734]

[0735] <21>

[0736] A light guide plate unit, comprising:

[0737] Light guide plate;

[0738] a first diffraction grating on a first surface side of the light guide plate;

[0739] a second diffraction grating on the first surface side of the light guide plate;

[0740] a transition zone structure on the first surface side of the light guide plate, wherein the transition zone structure extends from a first endpoint at or adjacent to the first diffraction grating to a vertex, and extends from the vertex to a second endpoint at or between the first endpoint and the second diffraction grating, wherein the first endpoint and the second endpoint are closer to the first surface of the light guide plate than the vertex.

[0741] <22>

[0742] according to <21> The light guide plate unit, wherein

[0743] When the width of the first portion of the transition zone structure extending from the first end point to the vertex is smaller than the total reflection interval of light in the light guide plate, the width of the first portion of the transition zone structure is equal to or smaller than a threshold specified based on the total reflection interval.

[0744] <23>

[0745] according to <21> The light guide plate unit, wherein:

[0746] When the width of the first portion of the transition zone structure extending from the first endpoint to the vertex is equal to or greater than the total reflection interval of light in the light guide plate, the height of the first portion of the transition zone structure is equal to or less than a threshold specified based on the width of the first portion of the transition zone structure and the inclination angle of the first portion of the transition zone structure.

[0747] <24>

[0748] according to <21> to <23> The light guide plate unit as described in any one of the preceding claims, wherein

[0749] When the spatial frequency is 10 cycles / degree, the MTF value before the light enters the transition region structure is X 10 , and the MTF value of light after passing through the transition zone structure is Y 10 When the light guide plate unit is configured to satisfy the following mathematical expression 1,

[0750] [Mathematical formula 1]

[0751] .

[0752] <25> according to <21> to <24> The light guide plate unit as described in any one of the preceding claims, wherein

[0753] When each of the width w1 of the inclined surface 1 on the first diffraction grating side of the transition region structure and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition region structure is equal to or larger than the total reflection interval d of light in the light guide plate, the transition region structure has a height h1 of the inclined surface 1 and a height h2 of the inclined surface 2 satisfying the following mathematical expression 2,

[0754] [Mathematical formula 2]

[0755]

[0756] Among them, in mathematical expression 2,

[0757] h1=(the height from the reference surface of the first diffraction grating to the apex of the transition region structure)

[0758] w1=(width of slope 1)

[0759] h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure)

[0760] w2=(width of slope 2)

[0761] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0762] θ airin = (the incident angle of light when entering the light guide plate)

[0763] n2 = (refractive index of the material of the transition region structure)

[0764] θ' TIR = (light guide angle in the transition zone structure),

[0765] When the width w1 of the inclined surface 1 on the first diffraction grating side of the transition zone structure is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition zone structure is equal to or larger than the total reflection interval d of light in the light guide plate, the width w1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 3,

[0766] <Mathematical formula 3>

[0767]

[0768] Among them, in mathematical expression 3,

[0769] w1=(width of slope 1)

[0770] h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure)

[0771] w2=(width of slope 2)

[0772] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0773] θ airin = (incident angle of light when it enters the light guide plate)

[0774] n2 = (refractive index of the material forming the transition region structure)

[0775] θ' TIR = (light guide angle in the transition zone structure),

[0776] and,

[0777] When each of the width w1 of the inclined surface 1 on the first diffraction grating side of the transition region structure and the width w2 of the inclined surface 2 on the second diffraction grating side is smaller than the total reflection interval d of light in the light guide plate,

[0778] The width w1 of the inclined surface 1 and the width w2 of the inclined surface 2 satisfy the following mathematical expression 4,

[0779] <Mathematical formula 4>

[0780]

[0781] Among them, in mathematical expression 4,

[0782] w1=(width of slope 1)

[0783] w2=(width of slope 2).

[0784] <26>

[0785] according to <21> to <26> The light guide plate unit as described in any one of the preceding claims, wherein

[0786] When the spatial frequency is 20 cycles / degree, the MTF value before the light enters the transition region structure is X 20 , and the MTF value of light after passing through the transition zone structure is Y 20 When , the light guide plate unit is configured to satisfy the following mathematical expression 5,

[0787] [Formula 5]

[0788] .

[0789] <27>

[0790] according to <26> The light guide plate unit, wherein

[0791] When each of the width w1 of the inclined surface 1 on the first diffraction grating side and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition region structure is equal to or larger than the total reflection interval d of light in the light guide plate,

[0792] The transition region structure has a height h1 of the slope 1 and a height h2 of the slope 2 satisfying the following mathematical expression 6,

[0793] <Mathematical formula 6>

[0794]

[0795] Among them, in mathematical expression 6,

[0796] h1=(the height from the reference surface of the first diffraction grating to the apex of the transition region structure)

[0797] w1=(width of slope 1)

[0798] h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure)

[0799] w2=(width of slope 2)

[0800] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0801] θ airin = (incident angle of light when it enters the light guide plate)

[0802] n2 = (refractive index of the material forming the transition region structure)

[0803] θ' TIR = (light guide angle in the transition zone structure),

[0804] When the width w1 of the inclined surface 1 on the first diffraction grating side of the transition area structure is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition area structure is equal to or larger than the total reflection interval d of light in the light guide plate, the width w1 of the inclined surface 1 and the height h2 of the inclined surface 2 of the transition area structure satisfy the following mathematical expression 7,

[0805] <Mathematical formula 7>

[0806]

[0807] Among them, in mathematical expression 7,

[0808] w1=(width of slope 1)

[0809] h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure)

[0810] w2=(width of slope 2)

[0811] A = cos(θ airin ) / (2*n2*cos(θ' TIR ))

[0812] θ airin = (incident angle of light when it enters the light guide plate)

[0813] n2 = (refractive index of the material of the transition region structure)

[0814] θ' TIR = (light guide angle in the transition zone structure),

[0815] and

[0816] When each of the width w1 of the inclined surface 1 on the first diffraction grating side of the transition area structure and the width w2 of the inclined surface 2 on the second diffraction grating side is smaller than the total reflection interval d of light in the light guide plate, the width w1 of the inclined surface 1 and the width w2 of the inclined surface 2 of the transition area structure satisfy the following mathematical expression 8,

[0817] <Mathematical formula 8>

[0818]

[0819] Among them, in mathematical expression 8

[0820] w1=(width of slope 1)

[0821] w2=(width of slope 2).

[0822] <28>

[0823] according to <21> to <27> The light guide plate unit as described in any one of the preceding claims, wherein

[0824] The transition zone structure is a first transition zone structure, wherein the light guide plate unit further includes a second transition zone structure on the first surface or the other surface of the light guide plate, wherein the second transition zone structure extends from a third endpoint to the vertex of the second transition zone structure, and extends from the vertex of the second transition zone structure to a fourth endpoint, wherein the third endpoint and the fourth endpoint are closer to the first surface or the other surface of the light guide plate than the vertex.

[0825] <29>

[0826] according to <28> The light guide plate unit, wherein

[0827] The width w1 of the inclined surface 1 on one side of the first diffraction grating of the first transition region structure is configured to satisfy

[0828] w1 < 0.1 d

[0829] (where d is the total reflection interval of light in the light guide plate).

[0830] <30>

[0831] according to <29> The light guide plate unit, wherein

[0832] In the case where the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure is equal to or greater than the total reflection interval d of light, the second transition region structure is configured to satisfy any one of the following mathematical expressions 9-1, 9-2, and 9-3,

[0833] [Mathematical formula 9]

[0834]

[0835] Among them, in mathematical expressions 9-1, 9-2 and 9-3,

[0836] Δφ is the tolerance of the slope angle of the second transition zone structure,

[0837] φ2 is an angle formed by the inclined surface 2 on one side of the second diffraction grating of the first transition region structure and the first surface of the light guide plate,

[0838] Δw is the tolerance of the slope width of the second transition zone structure,

[0839] d is the total reflection interval of light as described above,

[0840] n is any integer,

[0841] Δx is the error of x, where x is (half of the total reflection interval of the light beam) + (an integer multiple of the total reflection interval of the light beam),

[0842] w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure,

[0843] and

[0844] When the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure is smaller than the total reflection interval d of light, the second transition region structure is configured to satisfy any one of the following mathematical expressions 10-1, 10-2 and 10-3,

[0845] [Formula 10]

[0846]

[0847] Among them, in mathematical expressions 10-1, 10-2 and 10-3,

[0848] Δφ is the tolerance of the slope angle of the second transition zone structure,

[0849] φ2 is an angle formed by the inclined surface 2 on one side of the second diffraction grating of the first transition region structure and the first surface of the light guide plate,

[0850] Δw is the tolerance of the slope width of the second transition zone structure,

[0851] Δx is the error of x, where x is ((half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam)),

[0852] w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure.

[0853] <31>

[0854] according to <21> to <30> The light guide plate unit as described in any one of the preceding claims, wherein

[0855] The area of ​​the light guide plate including the transition zone structure includes:

[0856] A reflective coating configured to prevent light from entering the transition region structure, or a coating configured to prevent light that has entered the structure from causing angular deviation due to the slope of the transition region structure.

[0857] <32>

[0858] according to <31> The light guide plate unit, wherein the reflective coating is between the light guide plate and the transition zone structure.

[0859] <33>

[0860] according to <31> The light guide plate unit, wherein the refractive index of the transition zone structure and the refractive index of the material included in the emissive coating are substantially the same.

[0861] <34>

[0862] according to <21> The light guide plate unit, wherein

[0863] The transition region structure includes a plurality of vertices between the first diffraction grating and the second diffraction grating, wherein

[0864] The heights of all the vertices are equal to or less than 90 nm.

[0865] <35>

[0866] according to <21> to <34> The light guide plate unit according to any one of the preceding claims, wherein

[0867] The first diffraction grating is used for at least one of: diffracting light entering the light guide plate and causing the light to travel in the light guide plate, expanding light that has traveled in the light guide plate, or emitting light from the light guide plate, and

[0868] The second diffraction grating diffracts light that has passed through the first diffraction grating and travels toward one end of the light guide plate, and causes the light to travel to the first diffraction grating again.

[0869] <36>

[0870] according to <21> to <34> The light guide plate unit as described in any one of the preceding claims, wherein

[0871] The first diffraction grating diffracts light entering the light guide plate and causes the light to travel in the light guide plate, and

[0872] The second diffraction grating expands the light that has been diffracted by the first diffraction grating and has traveled in the light guide plate.

[0873] <37> according to <21> to <34> The light guide plate unit as described in any one of the preceding claims, wherein:

[0874] The first diffraction grating is an expander that expands the light that has traveled in the light guide plate, and

[0875] The second diffraction grating emits the light expanded by the expander from the light guide plate.

[0876] <38>

[0877] according to <21> to <34> The light guide plate unit as described in any one of the preceding claims, wherein

[0878] The first diffraction grating diffracts light entering the light guide plate and causes the light to travel in the light guide plate, and

[0879] The second diffraction grating emits light, which has traveled in the light guide plate, from the light guide plate.

[0880] <39>

[0881] according to <38> The light guide plate unit, wherein the second diffraction grating expands light having traveled in the light guide plate and emits the light from the light guide plate.

[0882] <40>

[0883] according to <21> to <39> The light guide plate unit described in any one of the preceding claims, wherein the transition region structure includes a material that is also included in the first diffraction grating, the second diffraction grating, or both of the first diffraction grating and the second diffraction grating.

[0884] <41>

[0885] according to <21> to <40> The light guide plate unit described in any one of the preceding claims, wherein the light guide plate unit is included in an image display device.

[0886] <42>

[0887] according to <21> The light guide plate unit described in claim 1, wherein the transition zone structure includes a first vertex and a second vertex between the first endpoint and the second endpoint.

[0888] <43>

[0889] according to <21> The light guide plate unit described in claim 1, wherein at least one of the first endpoint and the second endpoint is within a region of a corresponding at least one of the first diffraction grating and the second diffraction grating.

[0890] <44>

[0891] An image display device, comprising:

[0892] The light guide plate unit comprises:

[0893] Light guide plate;

[0894] a first diffraction grating, wherein the first diffraction grating is disposed on a first surface of the light guide plate;

[0895] a second diffraction grating on the first surface side of the light guide plate; and

[0896] a transition zone structure on the first surface side of the light guide plate, wherein the transition zone structure extends from a first endpoint located at or adjacent to the first diffraction grating to a vertex, and extends from the vertex to a second endpoint located at or adjacent to the second diffraction grating, wherein the first endpoint and the second endpoint are closer to the first surface of the light guide plate than the vertex.

[0897] <45>

[0898] A light guide plate unit, comprising:

[0899] Light guide plate;

[0900] a first diffraction grating disposed on a first surface side of the light guide plate;

[0901] a second diffraction grating on the first surface side of the light guide plate;

[0902] a transition region structure on the first surface side of the light guide plate, wherein a portion of the transition region structure is between the first diffraction grating and the second diffraction grating; and

[0903] A coating is provided on at least a portion of a side of the transition region structure opposite to a side of the transition region structure adjacent to the first surface side of the light guide plate.

[0904] <46> A light guide plate unit, comprising:

[0905] Light guide plate;

[0906] a first diffraction grating disposed on a first surface side of the light guide plate;

[0907] a second diffraction grating on the first surface side of the light guide plate;

[0908] a transition region structure over the first surface side of the light guide plate, wherein a portion of the transition region structure is between the first diffraction grating and the second diffraction grating; and

[0909] An emissive coating is on the first surface side of the light guide plate, wherein the emissive coating is disposed between the transition region structure and the first surface side of the light guide plate.

[0910] Although the embodiments and examples of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments and examples, and various modifications may be made based on the technical idea of ​​the present disclosure.

[0911] For example, the configurations, methods, steps, shapes, materials, numerical values, etc. described in the above-mentioned embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, numerical values, etc. may be used when necessary. In addition, the configurations, methods, steps, shapes, materials, numerical values, etc. of the above-mentioned embodiments and examples may be combined with each other without departing from the gist of the present disclosure.

[0912] In addition, in the present specification, the numerical range indicated by using "to" means a range including the numerical values ​​described before and after "to" as the minimum value and the maximum value, respectively. In the numerical ranges described at each stage in the present specification, the upper limit value or the lower limit value of the numerical range at a certain stage may be replaced with the upper limit value or the lower limit value of the numerical range at another stage.

[0913] It should be easily understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

[0914] Reference numerals list

[0915] TZ A mountain-shaped structure or an area where such a structure exists

[0916] G1 First diffraction grating

[0917] G2 Second diffraction grating

[0918] P Light Guide Plate

Claims

1. A light guide plate unit, comprising: Light guide plate; a first diffraction grating on a first surface side of the light guide plate; a second diffraction grating on the first surface side of the light guide plate; as well as a transition region structure on the first surface side of the light guide plate, wherein the transition region structure extends from a first endpoint to a vertex and from the vertex to a second endpoint, the first endpoint being located at or adjacent to the first diffraction grating, the second endpoint being located at or between the first endpoint and the second diffraction grating, wherein the first endpoint and the second endpoint are closer to the first surface of the light guide plate than the vertex.

2. The light guide plate unit according to claim 1, wherein When the width of the first portion of the transition zone structure extending from the first end point to the vertex is smaller than the total reflection interval of light in the light guide plate, the width of the first portion of the transition zone structure is equal to or smaller than a threshold specified based on the total reflection interval.

3. The light guide plate unit according to claim 1, wherein: When the width of the first portion of the transition zone structure extending from the first endpoint to the vertex is equal to or greater than the total reflection interval of light in the light guide plate, the height of the first portion of the transition zone structure is equal to or less than a threshold specified based on the width of the first portion of the transition zone structure and the inclination angle of the first portion of the transition zone structure.

4. The light guide plate unit according to claim 1, wherein When the spatial frequency is 10 cycles / degree, the MTF value before the light enters the transition region structure is X 10 , and the MTF value of light after passing through the transition zone structure is Y 10 When the light guide plate unit is configured to satisfy the following mathematical expression 1 [Mathematical formula 1] 。 5. The light guide plate unit according to claim 1, wherein When each of the width w1 of the inclined surface 1 on the first diffraction grating side of the transition region structure and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition region structure is equal to or greater than the total reflection interval d of light in the light guide plate, The transition region structure has a height h1 of the slope 1 and a height h2 of the slope 2 satisfying the following mathematical expression 2, [Mathematical formula 2] in, In mathematical expression 2, h1=(the height from the reference surface of the first diffraction grating to the apex of the transition region structure) w1=(width of slope 1) h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure) w2=(width of slope 2) A= cos(θ airin ) / (2*n2*cos(θ' TIR )) θ airin = (incident angle of light when it enters the light guide plate) n2 = (refractive index of the material of the transition region structure) θ' TIR = (light guide angle in the structure of the transition zone structure), When the width w1 of the inclined surface 1 on the first diffraction grating side of the transition region structure is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition region structure is equal to or larger than the total reflection interval d of light in the light guide plate, The width w1 of the inclined surface 1 and the height h2 of the inclined surface 2 satisfy the following mathematical expression 3, [Mathematical formula 3] Among them, in mathematical expression 3, w1=(width of slope 1) h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure) w2=(width of slope 2) A= cos(θ airin ) / (2*n2*cos(θ' TIR )) θ airin = (incident angle of light when it enters the light guide plate) n2 = (refractive index of the material forming the transition region structure) θ' TIR = (light guide angle in the transition zone structure), and, When each of the width w1 of the inclined surface 1 on the first diffraction grating side of the transition region structure and the width w2 of the inclined surface 2 on the second diffraction grating side is smaller than the total reflection interval d of light in the light guide plate, The width w1 of the inclined surface 1 and the width w2 of the inclined surface 2 satisfy the following mathematical expression 4, [Formula 4] Among them, in mathematical expression 4, w1=(width of slope 1) w2=(width of slope 2).

6. The light guide plate unit according to claim 1, wherein When the spatial frequency is 20 cycles / degree, the MTF value before the light enters the transition region structure is X 20 , and the MTF value of the light after passing through the transition zone structure is Y 20 When the light guide plate unit is configured to satisfy the following mathematical expression 5 [Formula 5] 。 7. The light guide plate unit according to claim 6, wherein When each of the width w1 of the inclined surface 1 on the first diffraction grating side and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition region structure is equal to or larger than the total reflection interval d of light in the light guide plate, The transition region structure has a height h1 of the slope 1 and a height h2 of the slope 2 satisfying the following mathematical expression 6, [Mathematical formula 6] in, In mathematical expression 6, h1=(the height from the reference surface of the first diffraction grating to the apex of the transition region structure) w1=(width of slope 1) h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure) w2=(width of slope 2) A= cos(θ airin ) / (2*n2*cos(θ' TIR )) θ airin = (incident angle of light when it enters the light guide plate) n2 = (refractive index of the material forming the transition region structure) θ' TIR = (light guide angle in the transition zone structure), When the width w1 of the inclined surface 1 on the first diffraction grating side of the transition region structure is smaller than the total reflection interval d of light in the light guide plate, and the width w2 of the inclined surface 2 on the second diffraction grating side of the transition region structure is equal to or larger than the total reflection interval d of light in the light guide plate, The width w1 of the slope 1 and the height h2 of the slope 2 of the transition zone structure satisfy the following mathematical expression 7, [Formula 7] Among them, in mathematical expression 7, w1=(width of slope 1) h2=(the height from the reference surface of the second diffraction grating to the apex of the transition region structure) w2=(width of slope 2) A= cos(θ airin ) / (2*n2*cos(θ' TIR )) θ airin = (incident angle of light when it enters the light guide plate) n2 = (refractive index of the material of the transition region structure) θ' TIR = (light guide angle in the transition zone structure), and When each of the width w1 of the inclined surface 1 on the first diffraction grating side of the transition region structure and the width w2 of the inclined surface 2 on the second diffraction grating side is smaller than the total reflection interval d of light in the light guide plate, The width w1 of the inclined surface 1 and the width w2 of the inclined surface 2 of the transition zone structure satisfy the following mathematical expression 8, [Mathematical formula 8] Among them, in mathematical expression 8, w1=(width of slope 1) w2=(width of slope 2).

8. The light guide plate unit according to claim 1, wherein The transition zone structure is a first transition zone structure, wherein the light guide plate unit further includes a second transition zone structure located on the first surface or the other surface of the light guide plate, wherein the second transition zone structure extends from a third endpoint to the vertex of the second transition zone structure, and extends from the vertex of the second transition zone structure to a fourth endpoint, wherein the third endpoint and the fourth endpoint are closer to the first surface or the other surface of the light guide plate than the vertex.

9. The light guide plate unit according to claim 8, wherein The width w1 of the inclined surface 1 on one side of the first diffraction grating of the first transition region structure is configured to satisfy w1 < 0.1 d (where d is the total reflection interval of light in the light guide plate).

10. The light guide plate unit according to claim 9, wherein: In the case where the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure is equal to or larger than the total reflection interval d of light, the second transition region structure is configured to satisfy any one of the following mathematical expressions 9-1, 9-2, and 9-3, [Mathematical formula 9] Among them, in mathematical expressions 9-1, 9-2 and 9-3, Δφ is the tolerance of the slope angle of the second transition zone structure, φ2 is an angle formed by the inclined surface 2 on one side of the second diffraction grating of the first transition region structure and the first surface of the light guide plate, Δw is the tolerance of the slope width of the second transition zone structure, d is the total reflection interval of light as described above, n is any integer, Δx is the error of x, where x is ((half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam)), w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure, and When the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure is smaller than the total reflection interval d of light, the second transition region structure is configured to satisfy any one of the following mathematical expressions 10-1, 10-2 and 10-3, [Formula 10] Among them, in mathematical expressions 10-1, 10-2 and 10-3, Δφ is the tolerance of the slope angle of the second transition zone structure, φ2 is an angle formed by the inclined surface 2 on one side of the second diffraction grating of the first transition region structure and the first surface of the light guide plate, Δw is the tolerance of the slope width of the second transition zone structure, Δx is the error of x, where x is ((half of the total reflection interval of the light beam) + (integer multiple of the total reflection interval of the light beam)), w2 is the width w2 of the inclined surface 2 on the second diffraction grating side of the first transition region structure.

11. The light guide plate unit according to claim 1, wherein: The area of ​​the light guide plate including the transition zone structure includes: A reflective coating or coatings configured to prevent light from entering the transition region structure, the coating configured to prevent light that has entered the structure from being angularly deviated due to the slope of the transition region structure. 12 . The light guide plate unit according to claim 11 , wherein the reflective coating is between the light guide plate and the transition region structure. 13 . The light guide plate unit according to claim 11 , wherein a refractive index of the transition region structure and a refractive index of a material included in the reflective coating are substantially the same.

14. The light guide plate unit according to claim 1, wherein The transition region structure includes a plurality of vertices between the first diffraction grating and the second diffraction grating, wherein The heights of all vertices of the plurality of vertices are equal to or less than 90 nm.

15. The light guide plate unit according to claim 1, wherein The first diffraction grating performs one of the following operations: diffracts light entering the light guide plate and causes the light to travel in the light guide plate, expands light that has traveled in the light guide plate, or emits light from the light guide plate, and The second diffraction grating diffracts light that has passed through the first diffraction grating and travels toward one end of the light guide plate, and causes the light to travel to the first diffraction grating again.

16. The light guide plate unit according to claim 1, wherein The first diffraction grating diffracts the light entering the light guide plate and causes the light to travel in the light guide plate, and The second diffraction grating expands the light that has been diffracted by the first diffraction grating and has traveled in the light guide plate.

17. The light guide plate unit according to claim 1, wherein The first diffraction grating is an expander that expands the light that has traveled in the light guide plate, and The second diffraction grating emits the light expanded by the expander from the light guide plate.

18. The light guide plate unit according to claim 1, wherein The first diffraction grating diffracts the light entering the light guide plate and causes the light to travel in the light guide plate, and The second diffraction grating emits light, which has traveled in the light guide plate, from the light guide plate. 19 . The light guide plate unit according to claim 18 , wherein the second diffraction grating expands light having traveled in the light guide plate, and emits the light from the light guide plate.

20. The light guide plate unit according to claim 1, wherein the transition region structure includes a material also included in the first diffraction grating, included in the second diffraction grating, or included in both the first diffraction grating and the second diffraction grating.

21. The light guide plate unit according to claim 1, wherein the light guide plate unit is included in an image display device. 22 . The light guide plate unit according to claim 1 , wherein the transition region structure includes a first vertex and a second vertex between the first end point and the second end point.

23. The light guide plate unit according to claim 1, wherein at least one of the first endpoint and the second endpoint is within a region of a corresponding at least one of the first diffraction grating and the second diffraction grating.

24. An image display device, comprising: The light guide plate unit comprises: Light guide plate; a first diffraction grating, wherein the first diffraction grating is disposed on a first surface of the light guide plate; a second diffraction grating on the first surface side of the light guide plate; and a transition region structure on the first surface side of the light guide plate, wherein the transition region structure extends from a first endpoint to a vertex and from the vertex to a second endpoint, the first endpoint being located at or adjacent to the first diffraction grating, the second endpoint being located at or adjacent to the second diffraction grating, wherein the first endpoint and the second endpoint are closer to the first surface of the light guide plate than the vertex.

25. A light guide plate unit, comprising: Light guide plate; a first diffraction grating disposed on a first surface side of the light guide plate; a second diffraction grating on the first surface side of the light guide plate; a transition region structure on the first surface side of the light guide plate, wherein a portion of the transition region structure is between the first diffraction grating and the second diffraction grating; as well as A coating is provided on at least a portion of a side of the transition region structure opposite to a side of the transition region structure adjacent to the first surface side of the light guide plate.

26. A light guide plate unit, comprising: Light guide plate; a first diffraction grating disposed on a first surface side of the light guide plate; a second diffraction grating on the first surface side of the light guide plate; a transition region structure over the first surface side of the light guide plate, wherein a portion of the transition region structure is between the first diffraction grating and the second diffraction grating; as well as A reflective coating is on the first surface side of the light guide plate, wherein the reflective coating is disposed between the transition region structure and the first surface side of the light guide plate.

Images