JP2007087647A - Light guide plate, backlight, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate excellent in light separation property separating light including a plurality of wavelength area into respective wavelength areas. <P>SOLUTION: The light guide plate 9 guiding the light emitted from a light source 31 emitting light including a plurality of wavelength areas has a high refractive index layer 5, low refractive index layers 6 having a refractive index lower than that of the high refractive index layer 5, and an optical deflection element 7 for refracting the light. The high refractive index layer 5 is interposed between the low refractive index layers 6. The optical deflection element 7 is formed so as to deflect a part of the light traveling through the high refractive index layer 5 toward the low refractive index layer 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light guide plate, a backlight, and a liquid crystal display device.

  A conventional color liquid crystal display device includes a plurality of pixels, and each pixel includes red, green, and blue picture elements (also referred to as sub-pixels). When these three color picture elements emit light, the color of one pixel is determined. Hereinafter, red is indicated as “R”, green is indicated as “G”, and blue is indicated as “B”. In a color liquid crystal panel, light from a white light source is incident on each picture element. White light is transmitted through a red, green or blue color filter to perform color display.

  In the conventional color liquid crystal display device, white light is transmitted through the color filters of the respective colors, so that about 1/3 of the white light is transmitted, but almost 2/3 of the light is absorbed. . That is, the light utilization efficiency is about 33%.

  In Japanese Patent Application Laid-Open No. 9-113903, light emitted from a light source is incident on a light guide plate through a reflecting mirror, reflected by a diffraction grating disposed inside the light guide plate, and emitted from the light guide plate. A liquid crystal display device formed in the above is disclosed. When light is reflected by the diffraction grating, the R, G, and B colors are reflected in different directions due to the dispersion effect of the diffraction grating.

The R, G and B colors are separated into light traveling in different directions. The light extracted from the light guide plate has its deflection direction aligned by the deflection plate, and is condensed on the pixel opening by the lens. The R, G, and B colors are collected on pixels of different colors. According to this liquid crystal display device, it is disclosed that light loss due to color separation can be reduced and a bright liquid crystal display device with low power consumption can be obtained.
JP-A-9-113903

  In the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 9-113903, a reflection hologram is used as a diffractive optical element. The reflection hologram reflects light propagating through the light guide plate and can extract light separated into R, G, and B from the light guide plate.

The light incident on the reflection hologram becomes light that is totally reflected in the light guide plate and propagates. Therefore, all light that satisfies the critical angle θ _c obtained from the refractive index of the light guide plate and the refractive index of air is all reflective. Incident on the hologram. The incident angle of light incident on the reflection hologram is in a wide range. For this reason, the light in the wavelength region of each color when emitted from the light guide plate has a problem that it has a wide range of emission angles and color mixing may occur.

  A diffractive optical element having a small wavelength selectivity or a diffractive optical element having a small incident angle selectivity has different diffraction angles depending on the wavelength or incident angle of each light. Even when a light source formed with a wavelength is used, if the incident angle is different, the emission position and the emission angle from the light guide plate are different. In a liquid crystal panel, light may be incident on a picture element different from the corresponding picture element. That is, there may be a problem that color mixing occurs when light of another color enters the picture element of one color. In particular, a liquid crystal panel including high-definition pixels has a problem that color mixing is likely to occur because the interval between picture elements is small.

  It is an object of the present invention to provide a light guide plate, a backlight, and a liquid crystal display device that are excellent in light separation properties for separating light of a plurality of wavelength regions into light of each wavelength region.

  A light guide plate according to the present invention is a light guide plate for guiding light from a light source that emits light including a plurality of wavelength regions, and a high refractive index layer and a low refractive index layer having a refractive index smaller than that of the high refractive index layer. With. A diffractive optical element for diffracting the light is provided. The low refractive index layer is disposed so as to sandwich the high refractive index layer. The diffractive optical element is formed to diffract a part of the light propagating through the high refractive index layer toward the low refractive index layer.

  In the above invention, the diffractive optical element is preferably disposed in the low refractive index layer. The diffractive optical element is disposed on a boundary surface between the low refractive index layer and the high refractive index layer.

In the above invention, the light source is preferably formed to emit light in the first wavelength region and light in the second wavelength region. The light source is formed such that the wavelength λ ₁ emits light in the first wavelength region where λ _1min <λ ₁ <λ _1max . The light source, the wavelength lambda ₂ is formed to emit λ _2min <λ ₂ <λ the light of the second wavelength region _2max. When the grating pitch of the diffractive optical element is Λ, the refractive index n ₁ of the high refractive index layer and the refractive index n ₂ of the low refractive index layer are formed so as to satisfy the following expression. sin ⁻¹ ((λ _1min / Λ) −1) <sin ⁻¹ ((λ _2max / Λ) −sin θ _c ). Here, θ _c = sin ⁻¹ (n ₂ / n ₁ ), λ ₁ > λ ₂ , and n ₁ > n ₂ .

  Preferably, in the above invention, a plurality of the diffractive optical elements are provided, and the plurality of diffractive optical elements are arranged apart from each other.

  Preferably, in the above invention, the diffractive optical element is formed such that the grating pitch is non-uniform.

  Preferably, in the above invention, the diffractive optical element is formed so as to have a light collecting action.

  In the above invention, preferably, an auxiliary optical element disposed on the outer surface of the low refractive index layer is provided. The auxiliary optical element is formed so as to emit the light substantially in the normal direction of the surface of the low refractive index layer.

  In the above invention, preferably, the auxiliary optical element includes a microprism or a micromirror.

The backlight based on this invention is equipped with the above-mentioned light-guide plate and the said light source.
In the invention described above, the light source is preferably configured to emit the light including a red wavelength region, a green wavelength region, and a blue wavelength region.

In the above invention, preferably, the light source includes a linear light source.
In the above invention, preferably, the light source includes a condensing unit for condensing the light traveling toward the high refractive index layer.

In the above invention, preferably, the light collecting means includes a lens or a parabolic mirror.
A liquid crystal display device according to the present invention includes the above-described backlight, a drive element substrate including a drive element for driving the liquid crystal of each pixel, and a counter substrate disposed so as to face the drive element substrate. Is provided. The counter substrate includes a black matrix layer having an opening corresponding to the picture element. The light in the wavelength region of one hue emitted from the light guide plate is formed to pass through the opening of the corresponding one hue.

  Preferably, in the above invention, the counter substrate includes a color filter disposed so as to correspond to the opening. The light in the wavelength region of one hue emitted from the light guide plate is formed to pass through the color filter of the corresponding one hue.

  Preferably in the said invention, it has the said pixel of 3 colors. The picture elements are formed in a stripe arrangement or a delta arrangement.

  Preferably, in the above invention, a microlens formed on the surface of the driving element substrate facing the light guide plate is provided. The microlens is formed so as to collect the light in each wavelength region toward the opening.

  ADVANTAGE OF THE INVENTION According to this invention, the light-guide plate, backlight, and liquid crystal display device which were excellent in the light-separation property which isolate | separates the light of a several wavelength region into the light of each wavelength region can be provided.

(Embodiment 1)
A light guide plate, a backlight, and a liquid crystal display device according to the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic cross-sectional view of a backlight including a light guide plate in the present embodiment. The light guide plate in the present embodiment is a light guide plate for guiding light from a light source emitting light in a plurality of hue regions in a plane. The backlight in this embodiment is provided in a liquid crystal display device and irradiates light on the liquid crystal panel in a plane. In addition, the light guide plate in the present embodiment has a color separation function that separates white light into light in the wavelength region of each hue.

  The light guide plate 9 in the present embodiment includes a light guide layer 4, a reflective layer 8 disposed on one surface of the light guide layer 4, and a microprism 10 disposed on the other surface of the light guide layer 4. Prepare. The light guide plate 9 in the present embodiment includes a light guide layer 4 for guiding light from the light emitting member 1. The light guide layer 4 includes two or more refractive index layers. In the present embodiment, the light guide layer 4 includes a high refractive index layer 5 and a low refractive index layer 6 having a refractive index smaller than that of the high refractive index layer 5. In the present invention, a layer having a relatively higher refractive index than the low refractive index layer is referred to as a high refractive index layer, and a layer having a relatively lower refractive index than the high refractive index layer is referred to as a low refractive index layer.

  The high refractive index layer 5 is formed in a plate shape. The low refractive index layer 6 is formed in a plate shape. The high refractive index layer 5 and the low refractive index layer 6 are formed of transparent members so that light from the light emitting member 1 can propagate. The low refractive index layers 6 are respectively disposed on the main surfaces of the front and back surfaces of the high refractive index layer 5. The low refractive index layer 6 is arranged so as to sandwich the high refractive index layer 5.

  Of the two low refractive index layers 6, one of the low refractive index layers 6 is provided with a diffractive optical element 7. The light guide plate 9 in the present embodiment includes a plurality of diffractive optical elements 7. The diffractive optical element 7 is disposed on the boundary surface between the low refractive index layer 6 and the high refractive index layer 5. Each diffractive optical element 7 is arranged away from each other. In the present embodiment, a plurality of diffractive optical elements 7 are arranged at equal intervals. Each diffractive optical element 7 is arranged so as to correspond to the position of a picture element of a liquid crystal panel described later. In the present embodiment, the diffractive optical element 7 is arranged directly below each picture element.

  Of the main surface of the low refractive index layer 6 on which the diffractive optical element 7 is disposed, the reflective layer 8 is disposed on the main surface opposite to the main surface on which the diffractive optical element 7 is disposed. In the present embodiment, the reflective layer 8 is disposed at the bottom of the light guide plate 9. The reflection layer 8 is formed so that the light diffracted by the diffractive optical element 7 is reflected on the surface.

  On the surface of the low refractive index layer 6 on the side where the diffractive optical element 7 is not disposed, the micro prism 10 is disposed as an auxiliary optical element. The microprism 10 in the present embodiment is formed so that the cross-sectional shape is substantially an arc shape.

  The microprism 10 is disposed at a position corresponding to a picture element of a liquid crystal panel described later. In the present embodiment, a microprism 10 is disposed directly above the diffractive optical element 7, and a picture element is disposed directly above the microprism 10. The light reflected by the reflective layer 8 travels toward the microprism 10. The microprism 10 is formed so that light reflected by the reflective layer 8 is emitted in a direction perpendicular to the surface of the light guide layer 4.

  The backlight in the present embodiment includes a light guide plate 9 and a light source 31. The light source 31 is disposed on the side of the end face of the light guide plate 9. The light source 31 includes the light emitting member 1 and the coupling lens 2. LED (light emitting diode) is arrange | positioned so that the light emitting member 1 in this Embodiment may emit white light containing the light of the color of R, G, and B. FIG. The light emitting member 1 in the present embodiment is disposed on an extension of the central surface in the thickness direction of the high refractive index layer 5 in the light guide layer 4.

  The light source 31 includes a coupling lens 2 disposed between the high refractive index layer 5 and the light emitting member 1. The coupling lens 2 is disposed as a condensing unit for condensing light from the light emitting member 1 toward the high refractive index layer 5. The coupling lens 2 is formed so as to collect the light from the light emitting member 1 toward the high refractive index layer 5.

In FIG. 2, the schematic cross section explaining the effect of the light guide layer 4 in this Embodiment is shown. White light from the light emitting member 1 is emitted at a radiation angle θ _l and travels toward the coupling lens 2. The light from the light emitting member 1 is collected by the coupling lens 2 and enters the high refractive index layer 5 in the light guide layer 4. In the present embodiment, the condensed light is incident on the center of the end surface of the high refractive index layer 5 in the thickness direction of the high refractive index layer 5. Light enters at an incident angle theta _w is the high refractive index layer 5. The incident light propagates linearly inside the high refractive index layer 5.

  Referring to FIGS. 1 and 2, the incident light is reflected in the interface between the high refractive index layer 5 and the low refractive index layer 6 while being reflected in the high refractive index layer 5 as indicated by an arrow 50. Propagate.

In the present embodiment, the high refractive index layer 5 has a refractive index n ₁ and the low refractive index layer 6 has a refractive index n ₂ . Here, the refractive index n ₁ is larger than the refractive index n ₂ . Therefore, total reflection occurs at the boundary surface between the high refractive index layer 5 and the low refractive index layer 6 at a predetermined critical angle θ _c . The critical angle θ _c is expressed by the following formula.

Referring to FIG. 2, the incident angle θ _i to the interface between high refractive index layer 5 and low refractive index layer 6 when total reflection occurs is the refractive index n ₁ of high refractive index layer 5 and the low refractive index layer. It is larger than the critical angle θ _c determined by the refractive index n _{2 of} 6. That is, the incident angle θ _{i at} which total reflection occurs satisfies the relationship θ _i > θ _c .

As indicated by the arrow 50, a part of the light from the traveling light source enters the diffractive optical element 7 disposed below the high refractive index layer 5 at an incident angle θ _i . In the diffractive optical element 7, each wavelength λ is diffracted at different diffraction angles and color-separated. The light incident on the diffractive optical element 7 includes light reflected by the diffractive optical element 7 and light incident on the low refractive index layer 6 while being diffracted through the diffractive optical element 7.

The light diffracted by the diffractive optical element 7 is reflected by the surface of the reflective layer 8 and travels toward the surface of the light guide layer 4 opposite to the side where the reflective layer 8 is disposed. For example, in FIG. 2, light (wave 1) having a wavelength λ ₁ is emitted at an emission angle θ _{o wave 1} as indicated by an arrow 51. Light having a wavelength λ ₂ (wave2) is emitted at an emission angle θ _{o wave2} as indicated by an arrow 52. Light (wave ₃ ) having a wavelength λ ₃ is emitted from the surface of the light guide layer 4 at an emission angle θ _o wave ₃ as indicated by an arrow 53. Thus, light including a plurality of wavelength regions can be separated into light of each wavelength region.

In the present embodiment, the critical angle θ _{c at} which total reflection occurs can be increased by reducing the refractive index difference Δn between the high refractive index layer 5 and the low refractive index layer 6. By increasing the critical angle θ _c , it is possible to limit the range of the incident angle θ _i of light from the light source propagating inside the light guide layer 4. Thus, the incident angle theta _i of the diffractive optical element 7, by adjusting the refractive index difference between the high refractive index layer 5 to form a light guide layer 4 and the low-refractive index layer 6, the incident angle theta _i Limits can be controlled.

FIG. 3 shows a schematic schematic cross-sectional view until the light emitted from the light source reaches the diffractive optical element. Theta _w (radiation angle into the interior of the high refractive index layer 5) the angle of incidence of having entered into the high refractive index layer 5, when the light incident to propagate inside the high-refractive index layer 5, a high refractive index layer 5 and the low refractive index layer 6 are preferably at an angle at which total reflection is performed. That is, the incident angle θ _w to the high refractive index layer 5 is preferably determined so that the incident angle θ _i to the diffractive optical element 7 is smaller than the critical angle θ _{c of} total reflection. By adopting this configuration, almost all light is totally reflected inside the high refractive index layer 5. A relationship of the following equation between the incident angle theta _w to the high refractive index layer 5 and the incident angle theta _i of the diffractive optical element 7.

For example, when n ₁ = 1.52 and n ₂ = 1.47, the critical angle θ _c = 75.3 °. The incident angle θ _i incident on the low refractive index layer 6 at this time is 75.3 ° <θ _i <90 °, and the radiation angle θ _w may satisfy θ _w <± 14.7 °. Since the air between the coupling lens 2 and the light guide layer 4 is air, the angle when entering the high refractive index layer 5 from the coupling lens 2 should satisfy the incident angle θ _{w (air)} <± 23.1 °. Good.

The coupling lens 2 preferably has a condensing function so that the absolute value of the incident angle of light from the light emitting member 1 is equal to or less than θ _{w (air)} . That is, in the high refractive index layer 5, it is preferable that the incident angle to the high refractive index layer 5 is adjusted so that all the incident light propagates while being totally reflected.

In the present embodiment, a transmission type binary hologram is used as the diffractive optical element 7. When the grating pitch of the diffractive optical element 7 is Λ and light having a wavelength λ is incident on the diffractive optical element 7 at an incident angle θ _i , the exit angle θ _o from the diffractive optical element 7 is expressed by the following equation.

Here, m is the order of the diffracted light, n ₁ is the refractive index of the entrance surface, and n ₂ is the refractive index of the exit surface. By making the light from the light source incident at an appropriate incident angle θ _i while keeping the grating pitch Λ constant, the angle of θ _{o wave} (representing the output angle θ _{o of} light having the wavelength λ) depends on the wavelength λ. The light can be emitted and light can be separated into the respective wavelength regions. For example, with reference to FIG. 2, the wavelength lambda _1, lambda _2, lambda ₃ of the light, emission angle theta _{o wave1} corresponding to each, theta _{o wave2,} it can be emitted in theta _{o wave3, and so.}

  In the present embodiment, the reflective layer 8 is disposed on the surface of the low refractive index layer 6 on which the diffractive optical element 7 is disposed, and the light travels in the direction of return, but is not limited to this form. Light may be emitted from the surface of the low refractive index layer 6 on which the optical element 7 is disposed.

The relationship between the incident angle θ _i to the diffractive optical element and the outgoing angle θ _o and the diffraction efficiency of the diffractive optical element will be described with reference to FIGS. The graphs shown below are all the results of analysis. In the analysis method, Rigorous Coupled Wave Analysis (RCWA), which is widely used in diffraction grating analysis, was used. The light including the red wavelength region has a wavelength of 630 ± 9 nm, the light including the green wavelength is 525 ± 18 nm, and the light including the blue wavelength is 465 ± 13 nm.

FIG. 4 is a graph showing the relationship between the incident angle θ _i and the outgoing angle θ _o when light in each wavelength region is incident on the diffractive optical element. In FIG. 4, the horizontal axis represents the incident angle θ _i , and the vertical axis represents the exit angle θ _o . In the present embodiment, the refractive index n ₁ of the high refractive index layer 5 is 1.52, and the refractive index n ₂ of the low refractive index layer 6 is 1.47. The incident angle θ _i to the diffractive optical element was set in the range of 75.3 ° <θ _i <90.0 °. As the diffractive optical element 7, one having a grating pitch Λ of 367 nm, a duty ratio of 1: 1, and a grating height h of Λ / 2 is used.

For example, when light in a green wavelength region having a wavelength of 525 nm is incident at an incident angle θ _i = 75.3 °, the exit angle of −1st order (m = −1) transmitted diffracted light from the diffractive optical element 7 Becomes θ _o = 2.0 °. Similarly, when incident at an incident angle θ _i = 90.0 °, θ _o = 4.9 °. Thus, the range of the emission angle is 2.0 ° <θ _o <4.9 °, whereas the range of the incident angle incident on the diffractive optical element 7 is 75.3 ° <θ _i <90.0 °. And become smaller.

In this way, the fact that the range of the emission angle is reduced is the same for light having other wavelengths and light in other wavelength regions. In each wavelength region, the range of the emission angle of light in the red wavelength region is approximately −16 ° <θ _o <−10 °, and the range of the emission angle θ _o of light in the green wavelength region is approximately 0 ° <θ ₀ < The outgoing angle θ _o of light in the 8 ° and blue wavelength region is approximately 10 ° <θ _o <17 °. Thus, the light in each wavelength region is emitted from the light guide plate in a state where the emission angles do not overlap each other.

FIG. 5 shows an analysis result of the light guide plate from which the low refractive index layers arranged on both sides of the high refractive index layer are excluded as a comparative example. That is, an analysis result when the portion of the low refractive index layer is replaced with air is shown. The refractive index of the high refractive index layer is 1.5. On the other hand, the refractive index of air as the low refractive index layer is 1. The critical angle θ _c at which total reflection occurs at this time is θ _c = 41.8 °. Therefore, light satisfying the incident angle θ _i > 41.8 ° is incident on the diffractive optical element.

In FIG. 5, the horizontal axis represents the incident angle θ _i , and the vertical axis represents the outgoing angle θ _o . Other analysis conditions are the same as those of the light guide plate shown in FIG. The incident angle θ _i is 41.8 ° <θ _i <90.0 °. The emission angle range of light in the red wavelength region is approximately −47 ° <θ _o <−10 °, and the emission angle range of the green wavelength region is approximately −28 ° <θ _o <8 °, and the blue wavelength. The range of the light emission angle of the region is approximately −17 ° <θ _o <17 °. As shown in FIG. 5, the light in the red wavelength region, the light in the green wavelength region, and the light in the blue wavelength region have overlapping portions in the range of the respective emission angles. As a result, it can be seen that each color is mixed.

  On the other hand, as shown in FIG. 4, in the present invention, color separation can be performed so that the emission angles of light in the respective wavelength regions do not overlap, and color mixing can be avoided.

  In the light guide plate in the present embodiment, the diffractive optical elements are arranged apart from each other. The diffractive optical element may be formed on the entire surface of the low refractive index layer, for example, but at each position of a pixel including R, G, and B picture elements as in the light guide plate in the present embodiment. Correspondingly, the diffractive optical elements may be arranged discretely. By disposing the diffractive optical elements discretely, light of a desired color can be emitted only at a desired position.

  The light source in the present embodiment is formed so as to emit light including a red wavelength region, a green wavelength region, and a blue wavelength region, and is separated into wavelength regions of three colors by a diffractive optical element. Yes. By adopting this configuration, for example, in a liquid crystal display device, full color display can be performed without using a color filter. In addition, light absorption in the color filter can be reduced, and light utilization efficiency can be improved.

In addition, the diffractive optical element in the present embodiment is disposed on the boundary surface between the low refractive index layer and the high refractive index layer. By adopting this configuration, light having an incident angle θ _i that satisfies the critical angle θ _c of the light guide layer can be incident on the diffractive optical element, so that it is easy to limit the angle of light incident on the diffractive optical element. It can be adjusted.

  Further, the grating pitch Λ of the diffractive optical element in the present embodiment is formed to have an equal period. The lattice pitch is not limited to this form, and may be formed so as to have an unequal period. By forming the grating pitch so as to have an unequal period, for example, the emission direction of light in each wavelength region can be controlled. Here, the grating pitch indicates the pitch of the irregularities on the surface of the diffraction grating. Alternatively, since the emission direction of the diffractive optical element can be finely controlled, color mixing can be prevented more reliably.

  6 to 8 are graphs showing the diffraction efficiencies of the light in the respective wavelength regions emitted from the diffractive optical element. In each graph, the horizontal axis represents the incident angle of the diffractive optical element, and the vertical axis represents the diffraction efficiency. The legend in each graph shows, in order, wavelength, deflection state (TE polarization or TM polarization), diffraction order, and transmission (T) or reflection (R). For example, in the legend, “525TE-1T” is a light having a wavelength of 525 nm and indicates a TE-polarized minus first-order transmitted diffraction light. FIG. 6 shows the diffraction efficiency of light in the red wavelength region. FIG. 7 shows the diffraction efficiency of light in the green wavelength region. FIG. 8 shows the diffraction efficiency of light in the blue wavelength region.

  Referring to FIGS. 6 to 8, the diffraction efficiency of TE deflection is about 7% for both the −1st order transmitted light and the −1st order reflected light in the light of all wavelength regions. By making the low refractive index layer thin, the −1st order transmitted light and the −1st order reflected light can be brought close to each other on the surface of the light guide plate. That is, the low refractive index layer is thin in order to make the first-order transmitted light that has been transmitted through the diffractive optical element and reflected by the reflective layer close to the first-order reflected light reflected by the diffractive optical element on the surface of the light guide. Is preferred. Most of the light that is not diffracted travels while totally reflecting the inside of the high refractive index layer as zero-order transmitted light, and is incident on another diffractive optical element and diffracted.

  The diffractive optical element according to the present embodiment includes a plurality of diffractive optical elements having the same shape. However, the diffractive optical element is not limited to this form, and each diffractive optical element may be formed to have different diffraction efficiencies. Absent. For example, the diffraction efficiency of the diffractive optical element may be increased as the distance from the light source increases. By adopting this configuration, light can be emitted with almost uniform brightness from the entire surface of the light guide plate. The diffraction efficiency of the diffractive optical element can be adjusted, for example, by changing the height of the irregularities on the surface of the diffractive optical element.

  FIG. 9 is a schematic exploded perspective view of the liquid crystal display device according to the present embodiment. FIG. 10 is a schematic cross-sectional view of the liquid crystal display device in this embodiment. Referring to FIG. 9, the direction in which the respective picture elements 14R, 14G, 14B of liquid crystal panel 16 are arranged is defined as the Z direction, and the direction perpendicular to the Z direction on the main surface of liquid crystal panel 16 is defined as the X direction. The direction perpendicular to the main surface is defined as the Y direction.

  The liquid crystal display device 17 in the present embodiment includes a backlight, and the backlight includes the light guide plate 9 and the light source 31 described above. The liquid crystal display device 17 includes a liquid crystal panel 16 disposed so as to face the surface of the light guide plate 9. The liquid crystal panel 16 is formed in a plate shape. The liquid crystal panel 16 includes a plurality of pixels. The pixel includes a plurality of picture elements having respective hues. Each pixel in this embodiment has a red picture element 14R, a green picture element 14G, and a blue picture element 14B.

  FIG. 11 is a schematic plan view for explaining the arrangement of the respective picture elements in the present embodiment. In the present embodiment, the picture elements are formed in a stripe arrangement. In each picture element, the picture element 14R, the picture element 14G, and the picture element 14B are linearly arranged in the order of R, G, and B. In each of the picture elements 14R, 14G, and 14B, a plurality of picture element groups arranged in a straight line are arranged in parallel. Thus, the liquid crystal display device according to the present embodiment is formed so that the picture elements are in a stripe arrangement. The picture element in the present embodiment is formed in a size of 153 μm × 51 μm.

  Referring to FIGS. 9 and 10, liquid crystal panel 16 includes drive element substrate 11 including a drive element for driving liquid crystal arranged in each picture element. In the present embodiment, a TFT (Thin Film Transistor) is disposed on the surface of the substrate as a driving element. The liquid crystal panel 16 includes a counter substrate 15 disposed to face the drive element substrate 11. The counter substrate 15 has a black matrix layer 13 formed so as not to transmit light. The black matrix layer 13 has openings formed so as to correspond to the respective picture elements. In the present embodiment, one opening is formed in one picture element. The liquid crystal panel 16 includes the liquid crystal layer 12. The liquid crystal layer 12 is disposed so as to be sandwiched between the drive element substrate 11 and the counter substrate 15.

  The coupling lens 2 has a longitudinal direction and is formed along one end face of the light guide plate 9. In the present embodiment, the light source 31 includes a plurality of light emitting members 1. Each light emitting member 1 is arranged away from each other. The coupling lens 2 may be a lens array in which a plurality of circular lenses are arranged in a straight line, or may be a cylindrical lens formed so as to have a condensing function only in the Y direction.

  In the light source 31, by using a condensing means that can reduce the radiation angle to the inside of the high refractive index layer 5 when the light from the light emitting member 1 enters the high refractive index layer 5, a high refractive index is obtained. Light having an incident angle that satisfies the critical angle of the layer 5 can be increased, and light use efficiency is improved.

  In the present embodiment, since the arrangement of picture elements is formed in a stripe arrangement, picture elements in a direction perpendicular to the direction in which R, B, and G are arranged (the X direction in FIGS. 9 and 11). Since the adjacent picture elements have the same color, position adjustment in the X direction is not necessary. That is, collimation of the XZ plane is not necessary.

  With reference to FIGS. 9 and 10, the light emitted from the light emitting member 1 is collected by the coupling lens 2 and enters the high refractive index layer 5. The light incident on the high refractive index layer 5 travels while totally reflecting the inside of the high refractive index layer 5 as indicated by an arrow 50. The light incident on the diffractive optical element 7 is diffracted according to the respective wavelengths, and enters the low refractive index layer 6 on which the diffractive optical element 7 is disposed. Light incident on the low refractive index layer 6 is reflected by the reflective layer 8 and travels toward the liquid crystal panel 16. The light in the respective wavelength regions is emitted toward the corresponding picture elements 14R, 14G, and 14B as indicated by arrows 54R, 54G, and 54B.

  In the liquid crystal panel 16 of the present embodiment, a deflection plate, a wavelength plate, and an optical compensation plate are disposed on the surface of the drive element substrate 11 (not shown). The light emitted from the light guide plate 9 is aligned by the microprism 10 in the direction substantially perpendicular to the main surface of the liquid crystal panel 16. The light emitted from the light guide plate 9 passes through the deflection plate, the wavelength plate, the optical compensation plate, and the like, and after the deflection direction is aligned, passes through the drive element substrate 11 and the liquid crystal layer 12, and then the opening of the black matrix layer 13 Is incident on.

  In the liquid crystal panel 16 of the present embodiment, an optical compensation plate, a wavelength plate, and a deflection plate are disposed on the surface of the counter substrate 15 (not shown). Light passing through the opening exits through these optical films. The user can view the image by viewing the light emitted from the counter substrate 15 side.

  FIG. 12 is a schematic cross-sectional view of one pixel portion. As described above, as indicated by the arrow 50, the light incident on the diffractive optical element 7 is diffracted according to each wavelength. At this time, it is separated into light of each wavelength region. The direction of the diffracted light is changed by being reflected by the reflection layer 8.

  In the present embodiment, a microprism 10 as an auxiliary optical element is disposed on the surface of the light guide layer 4. The microprism 10 is formed so that incident light travels toward the corresponding picture element. The microprism 10 in the present embodiment is formed so that light travels in a direction perpendicular to the surface of the light guide layer 4. The microprism 10 is formed so that light enters in the normal direction of the surface of the liquid crystal panel 16.

  The area 61R indicates the area of the red picture element 14R, the area 61G indicates the area of the green picture element 14G, and the area 61B indicates the area of the blue picture element 14B. As indicated by the arrow 54R, the light in the red wavelength region passes through the picture element 14R. As indicated by the arrow 54G, the light in the green wavelength region passes through the picture element 14G. As indicated by the arrow 54B, the light in the blue wavelength region passes through the picture element 14B. In this way, light of a corresponding color can be guided to each picture element.

  Since the liquid crystal display device according to the present invention can separate light of each wavelength region in the light guide plate, it can eliminate the color filter that has been necessary in the past. As a result, it is possible to prevent a part of light from being absorbed by the color filter and to improve the light use efficiency. For example, the light utilization efficiency is about three times that of an apparatus that makes white light incident on a color filter as in the conventional technique.

  The light guide plate 9 in the present embodiment includes a microprism 10 as an auxiliary optical element disposed on the outer surface of the low refractive index layer 6. By adopting this configuration, optical axis correction can be easily performed, and light in the wavelength region of the corresponding color can be easily guided to the light guide layer 4 for each picture element. Alternatively, the optical axis of the diffracted light in each wavelength region can be made perpendicular to the surface of the liquid crystal panel. Therefore, even when the light guide plate and the liquid crystal panel are separated from each other, light in a wavelength region corresponding to each picture element can be made incident.

  The microprism can be formed by 2P (Photo Polymer) molding or the like. For example, after potting a light curable resin transparent to the light to be used on the surface of the light guide layer, the stamper is pressed and pressurized. Next, light for curing the photocurable resin can be irradiated to form a microprism.

  In the present embodiment, the microprism is disposed as the auxiliary optical element. However, the present invention is not limited to this form, and any auxiliary optical element may be used as long as the direction of the optical axis can be changed. For example, the auxiliary optical element may include a micromirror that changes the traveling direction by reflecting light.

  In the liquid crystal display device, in order to prevent color mixing in each picture element, it is preferable that light in each wavelength region separated by the diffractive optical element is incident on the corresponding picture element. Next, the distance from the diffractive optical element to the upper surface of the light guide layer and the width of the diffractive optical element will be described.

FIG. 13 is an enlarged schematic cross-sectional view of the light guide layer in a portion where one optical element is disposed. Let L be the distance from the diffractive optical element 7 to the upper surface of the light guide layer 4. The width of the diffractive optical element 7 is W. The distance L is the optical path length from the diffractive optical element 7 to the upper surface of the light guide layer 4. It is assumed that the wavelength of light from the light source is configured from λ _1min <λ ₁ <λ _1max . If the emission angles from the diffractive optical element when the wavelength λ ₁ is incident at the critical angles θ _c and 90 ° are θ _{oc wave1} and θ _{o90 wave1} , respectively, the emission positions Q _{c wave1 on} the surface of the light guide layer 4 and The emission position Q _{90 wave1} is as follows.

  Furthermore, since the diffractive optical element has a width W, the emission range is widened with the same length as this width. In order to prevent color mixing, assuming that the length of the picture element in the direction in which the R, G, and B picture elements are arranged is Z, the R, G, and B picture elements are arranged so as to satisfy the following conditions: It is preferable to set the width W of the diffractive optical element in the direction.

  In the present embodiment, a liquid crystal panel having a picture element with a length Z = 60 μm is used. A light guide plate having a length L of 380 μm in the light guide layer and a width W of the diffractive optical element of 20 μm was used. Moreover, the light source which emits the light of the above-mentioned wavelength range was used.

  In a liquid crystal display device, light in a wavelength region of each hue emitted from a light source may not be a single wavelength. For example, the wavelength of light of each color emitted from the light emitting member 1 may have a wavelength width of about ± 20 nm. For this reason, due to the relationship between the wavelength and the emission angle in the diffractive optical element, color unevenness due to the wavelength width may occur in each picture element. In such a case, a scattering plate or the like for making the color distribution of the R, G, and B picture elements uniform may be arranged on the surface of the liquid crystal panel. With this configuration, color unevenness can be suppressed.

In the present embodiment, the refractive index n ₁ of the high refractive index layer is 1.52, the refractive index n ₂ of the low refractive index layer is 1.47, and the ratio of the refractive index difference Δn to n ₁ is 3.3%. I made it. The refractive index difference is not limited to this form, and any refractive index difference may be used as long as the light in the wavelength region of each hue is not mixed.

In order to prevent light in each wavelength region from interfering with each other and mixing colors, it is sufficient that the emission angles θ _o from the diffractive optical elements of the light in each wavelength region do not intersect with each other, and are derived from the above equation (3). It is preferable to have a refractive index n ₁ and a refractive index n ₂ that satisfy the following formula. The wavelength lambda ₁ of the range of the first wavelength region, as _{λ 1min <λ 1 <λ 1max} , the range of the wavelength lambda ₂ of the light in the second wavelength region, and _{λ 2min <λ 2 <λ 2max} . When the grating pitch of the diffractive optical element is Λ, the refractive index n ₁ of the high refractive index layer and the refractive index n ₂ of the low refractive index layer are preferably within a range satisfying the following formula.

For example, the wavelength λ _R of light in the red wavelength region is 620 nm ≦ λ _R ≦ 640 nm, the wavelength λ _G of light in the green wavelength region is 540 nm ≦ λ _G ≦ 560 nm, and the wavelength of light in the blue wavelength region When λ _B is 450 nm ≦ λ _B ≦ 470 nm, the refractive index n ₁ is 1.52, and the lattice pitch Λ is 367 nm, the refractive index is within a range satisfying 0.89 <(n ₂ / n ₁ ) <1. A material for the low refractive index layer having a refractive index n ₂ may be selected. In addition, the high refractive index layer is not limited to a layer having a refractive index n ₁ of 1.52, and a material that satisfies the above formulas (7) to (10) may be selected.

FIG. 14 shows a graph when (n ₂ / n ₁ ) is 0.97 and the refractive index n ₁ is 1.45. FIG. 15 is a graph in which (n ₂ / n ₁ ) is 0.97 and the refractive index n ₁ is 1.55. In FIG. 14 and FIG. 15, the horizontal axis indicates the incident angle when entering the diffractive optical element, and the vertical axis indicates the exit angle when exiting from the light guide layer.

Each R, G, or B light has the above-described wavelength width in the present embodiment. In this case, the critical angle θ _c is 75.3 °. The range of the incident angle θ _i of the diffractive optical element is 75.3 ° <θ _i <90.0 °. As shown in FIGS. 14 and 15, in any of the refractive index n _1, R, areas of intersection of the exit angle between G and B is not within the scope of this refractive index n ₁ is R, G and B It can be seen that light in the wavelength region can be separated.

In this way, color mixing can be avoided if the refractive index n ₁ of the high refractive index layer and the refractive index n ₂ of the low refractive index layer satisfy the condition of the above formula (7). As a result, color display can be performed without using a color filter.

  Further, the thickness of each layer in the light guide layer may be adjusted. For example, the thickness of the high refractive index layer may be adjusted. Even if the incident angle of light with respect to the high refractive index layer is the same, by adjusting the thickness of the high refractive index layer, the position where the incident light reaches the boundary surface between the high refractive index layer and the low refractive index layer Be changed. For this reason, light can be used more efficiently by arranging the diffractive optical element at a position where incident light reaches.

  In the present embodiment, a transmissive liquid crystal display device has been described as an example of the liquid crystal display device. However, the present invention is not limited to this embodiment. For example, the present invention is applied to a transflective liquid crystal display device. Can do. Alternatively, the present invention is not limited to a liquid crystal display device, and the present invention can be applied to an apparatus including a light source that needs to separate light into a predetermined wavelength region.

(Embodiment 2)
With reference to FIG. 16, a light guide plate, a backlight, and a liquid crystal display device according to Embodiment 2 of the present invention will be described.

  FIG. 16 is an enlarged schematic cross-sectional view of one pixel portion of the liquid crystal display device according to the present embodiment. The liquid crystal display device according to the present embodiment includes the liquid crystal panel 16 as in the first embodiment. In the present embodiment, the configuration of the diffractive optical element disposed on the light guide plate is different from that of the first embodiment.

  The diffractive optical element 20 in the present embodiment has a light condensing function. In the present embodiment, the diffractive optical element 20 is formed so as to have a light focus at the opening of the black matrix layer 13 of the liquid crystal panel 16.

  As indicated by an arrow 50, the light incident on the diffractive optical element 20 is diffracted toward the inside of the low refractive index layer 6 while having a diffraction angle in each wavelength region. Thereafter, the light is reflected by the reflective layer 8 and enters the liquid crystal panel 16 through the microprism 10.

  As indicated by the arrow 57R, the light in the red wavelength region enters the picture element 14R. As indicated by the arrow 57G, the light in the green wavelength region enters the picture element 14G. Further, as indicated by an arrow 57B, light in the blue wavelength region enters the picture element 14B. Since the diffractive optical element 20 has a condensing function, the light in each wavelength region becomes thin. As a result, the pitch between picture elements can be reduced, and a high-resolution liquid crystal display device can be provided.

  Since other configurations, operations, and effects are the same as those in the first embodiment, description thereof will not be repeated here.

(Embodiment 3)
With reference to FIG. 17 and FIG. 18, a light guide plate, a backlight, and a liquid crystal display device according to Embodiment 3 of the present invention will be described. The liquid crystal display device includes the liquid crystal panel 16 and the light guide plate 9 as in the first embodiment. In the liquid crystal display device according to the present embodiment, the condensing means for condensing the light from the light emitting member toward the high refractive index layer in the configuration of the light source of the backlight is different from that of the first embodiment.

  FIG. 17 is a schematic cross-sectional view of the liquid crystal display device in this embodiment. The light emitting member 1 is disposed on the side of the light guide plate 9. The light emitting member 1 is disposed so as to face the high refractive index layer 5. In the present embodiment, a parabolic mirror 21 is disposed as a light collecting means.

  The parabolic mirror 21 is formed so that the cross-sectional shape is a parabola. The inner surface of the parabolic mirror 21 is formed so as to reflect light from the light emitting member 1. The light emitted from the light emitting member 1 is reflected by the surface of the parabolic mirror 21 and then enters the high refractive index layer 5. Even if a parabolic mirror is used as the condensing means instead of the coupling lens, light can be incident on the high refractive index layer at a predetermined angle.

In FIG. 18, an LED having a half-value angle of ± 50 ° or a half-value angle of ± 70 ° is employed as the light emitting member, and the radiation angle θ _w inside the high refractive index layer is 23.1 ° (see FIG. 2). An example of coupling efficiency when entering the refractive index layer is shown. The ratio of the light incident on the high refractive index layer with respect to all the light emitted from the light emitting member is expressed as the coupling efficiency.

  When an LED having a half-value angle of ± 50 ° is used, the coupling efficiency of the coupling lens is 48%, whereas the coupling efficiency of the parabolic mirror is as large as 77%. Similarly, when an LED having a half-value angle of ± 70 ° is used, the coupling efficiency of the parabolic mirror is larger than the coupling efficiency of the coupling lens. Thus, the parabolic mirror can obtain a high coupling efficiency with a simpler configuration than the coupling lens.

  Since other configurations, operations, and effects are the same as those in the first embodiment, description thereof will not be repeated here.

(Embodiment 4)
A light guide plate, a backlight, and a liquid crystal display device according to a fourth embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the arrangement of picture elements arranged on the liquid crystal panel and the configuration of the light source of the backlight are different from those in the first embodiment.

  FIG. 19 is a schematic exploded perspective view of the liquid crystal display device according to the present embodiment. FIG. 20 is a schematic cross-sectional view of the liquid crystal display device in this embodiment. FIG. 21 shows a schematic plan view of the arrangement of picture elements of the liquid crystal panel in the present embodiment.

  Referring to FIG. 21, as indicated by virtual line 62, one pixel in the present embodiment includes three picture elements 22R, 22G, and 22B. The picture elements 22R, 22G, and 22B are arranged so as to be substantially triangular. That is, the respective picture elements 22R, 22G, and 22B have a delta arrangement, and the openings of the black matrix layer 13 of the liquid crystal panel 16 are formed to have a delta arrangement.

  Image quality can be improved by making the arrangement of picture elements a delta arrangement. In the delta arrangement, picture elements adjacent to each other in the X direction in FIG. 21 are arranged with different hues. Therefore, it is preferable to perform collimation also on the XZ plane of the light guide plate.

  Referring to FIGS. 19 and 20, the backlight of liquid crystal display device 18 in the present embodiment includes light guide plate 9 and linear light source 27. The linear light source 27 includes a light guide 23. In the present embodiment, the light guide 23 is formed in a rectangular parallelepiped shape.

  The light guide 23 has a longitudinal direction, and a parabolic mirror 21 is disposed on an end face in the longitudinal direction. The light emitting member 1 is disposed at the end of the parabolic mirror 21. A low refractive index body 25 is arranged on the surface of the linear light source 27 on the side facing the light guide plate 9. The low refractive index body 25 is formed so that the refractive index is smaller than that of the light guide body 23. A cylindrical lens 26 is disposed on the end surface of the light guide plate 9 facing the linear light source 27. The cylindrical lens 26 is formed so as to collimate light in the XZ direction.

  The low refractive index body 25 is formed so that light incident on the light guide body 23 is reflected at the boundary surface between the surface of the light guide body 23 and the low refractive index body 25. The light emitted from the light emitting member 1 is incident on the light guide 23 with the angle of incidence on the light guide 23 controlled by the surface of the parabolic mirror 21 as indicated by an arrow 50. In the light guide 23, the light travels while being totally reflected at the boundary surface between the low refractive index body 25 and the light guide 23.

  A reflection part 24 is formed inside the light guide 23. The reflector 24 is formed so as to reflect light traveling inside the light guide 23 and guide the light to the light guide plate 9. In the present embodiment, the respective reflecting portions 24 are formed so as to have the same size, and are arranged at a predetermined interval.

  The reflection part is not limited to this form, and the reflection part may be increased as the distance from the light emitting member increases, or the distance between the light emission parts may be decreased as the distance from the light emission member. By adopting one of these configurations, the intensity of light emitted from the linear light source 27 can be made substantially uniform over the longitudinal direction of the linear light source.

  The light emitted from the linear light source 27 enters the cylindrical lens 26, and the light is aligned in the XZ direction. Moreover, each light is collimated regarding a YZ surface by reflecting a reflection part. The light incident on the light guide plate 9 travels through the inside of the high refractive index layer 5. A part of the light enters the diffractive optical element 7 and is diffracted while being separated into the respective wavelength regions, and then reflected by the reflective layer 8. After this, as shown by arrows 58R, 58G, and 58B, the light in the respective wavelength regions is directed to the picture elements 22R, 22G, and 22B of the same hue on the liquid crystal panel 16, as in the first embodiment.

  Since other configurations, operations, and effects are the same as those in the first embodiment, description thereof will not be repeated here.

(Embodiment 5)
With reference to FIG. 22, a light guide plate, a backlight, and a liquid crystal display device according to Embodiment 5 of the present invention will be described. The liquid crystal display device in this embodiment is different from that in Embodiment 1 in the configuration of the liquid crystal panel.

  FIG. 22 is a schematic cross-sectional view of the liquid crystal display device in this embodiment. The liquid crystal display device includes a backlight including the light source 31 and the light guide plate 9 as in the liquid crystal display device in the first embodiment.

  The liquid crystal display device in the present embodiment includes a liquid crystal panel 34. The liquid crystal panel 34 includes a black matrix layer 13 having an opening. In the openings of the black matrix layer 13, red color filters 28R, green color filters 28G, or blue color filters 28B are arranged so as to correspond to the colors of the respective picture elements.

  In the liquid crystal display device according to the present embodiment, as indicated by an arrow 54R, light in the red wavelength region passes through the red color filter 28R. Similarly, as indicated by an arrow 54G, light in the green wavelength region passes through the green color filter 28G. As indicated by an arrow 54B, the light in the blue wavelength region passes through the blue color filter 28B. For this reason, it is possible to prevent color mixing from occurring at the boundary portion of each picture element due to a manufacturing error or the like.

  Alternatively, depending on the wavelength of light emitted from the light source, the thickness of the light guide layer, or the pitch between the pixels of the liquid crystal panel, the emission angles of light in the respective wavelength regions may not be sufficiently separated. In such a case, light of different color wavelength regions may enter each picture element and color mixing may occur. Even in this case, the influence of the color mixture can be eliminated by passing the color filters of the respective colors.

  Since most of the light incident on the color filters 28R, 28G, and 28B is light in the wavelength region of the colors of the color filters 28R, 28G, and 28B, the light absorption in the color filters 28R, 28G, and 28B is Almost no light utilization efficiency can be achieved.

  Since other configurations, operations, and effects are the same as those in the first embodiment, description thereof will not be repeated here.

(Embodiment 6)
With reference to FIGS. 23 to 27, a light guide plate, a backlight, and a liquid crystal display device according to Embodiment 6 of the present invention will be described. The liquid crystal display device in the present embodiment includes a microlens arranged on the surface of the liquid crystal panel.

  FIG. 23 is a schematic cross-sectional view of the liquid crystal display device in this embodiment. The liquid crystal display device includes a backlight, and the backlight includes the light source 31 and the light guide plate 9 as in the first embodiment. The liquid crystal panel 16 includes the drive element substrate 11 and the counter substrate 15 as in the first embodiment.

  In the present embodiment, a microlens 29 is disposed on the surface of the drive element substrate 11 of the liquid crystal panel 16. The microlenses 29 are arranged so as to correspond to the respective picture elements. The microlens 29 is disposed at a position corresponding to the opening of the black matrix layer. In the present embodiment, a microlens 29 is disposed directly below the opening.

  FIG. 24 shows an enlarged schematic cross-sectional view of a portion corresponding to one pixel of the liquid crystal display device. The light emitted from the light guide plate 9 travels in the normal direction of the surface of the liquid crystal panel 16 as in the first embodiment. In the present embodiment, light is collected toward the respective openings of the black matrix layer 13 by the microlenses 29 formed on the surface of the drive element substrate 11. As indicated by arrows 59R, 59G, and 59B, the light in the wavelength region of each color is collected by the microlens 29. The light in the wavelength region of each color is emitted from the liquid crystal panel 16 with a predetermined inclination angle. For this reason, the viewing angle of the liquid crystal display device can be widened.

  Alternatively, even when the microprism 10 as an auxiliary optical element is disposed, the optical axis in each wavelength region cannot be completely corrected, and there is a case where each light has a slight spread. Even in such a case, light can be condensed by the microlens 29, and the influence of color mixing can be suppressed.

  Next, with reference to FIGS. 25 to 27, a method for manufacturing the microlens arranged on the liquid crystal panel will be described. 25 to 27 are schematic cross-sectional views in the respective manufacturing steps.

  First, with reference to FIG. 25, the photocurable resin 30 is arranged on the surface of the drive element substrate 11 which is the substrate on the backlight side of the liquid crystal panel 16 on the surface. Here, the photocurable resin 30 uses a transparent resin with respect to light from the light source. In the present embodiment, a negative dry film resist is used as the photocurable resin 30.

  Next, referring to FIG. 26, an exposure process is performed in which the photocurable resin 30 is exposed. In the exposure step, parallel light is irradiated from the side opposite to the side where the photocurable resin 30 is disposed. The irradiated light passes through a deflecting plate (not shown), the liquid crystal layer 12 and the like, and further passes through the opening of the black matrix layer 13 and is irradiated onto the photocurable resin.

  In the exposure step, irradiation is performed while changing the direction of the parallel light, as indicated by arrows 60a to 60c. That is, it is performed while changing the incident angle of the parallel light. The integrated exposure amount is adjusted by changing the intensity of the irradiated light and the moving speed of the parallel light. A lens portion 32 having a lens shape in cross section is formed. The lens portion 32 is a portion where the photocurable resin is cured by exposure. Around the lens portion 32, an uncured portion 33 that has not been irradiated with light remains.

  Next, as shown in FIG. 27, development is performed to remove the uncured portion and form the microlens 29. After the development process, an auxiliary exposure process for completely curing the photocurable resin by performing baking or the like as necessary may be performed.

  The manufacturing method of the microlens in the present embodiment uses the opening of the black matrix layer of the liquid crystal panel. That is, using the picture element of the liquid crystal panel, the light curable resin is exposed using light transmitted through the picture element. Therefore, it is not necessary to perform a complicated alignment process or use an expensive alignment device between the picture element and the microlens, and high-accuracy alignment can be easily performed. Further, the manufacturing time can be shortened.

  Furthermore, since the optical axis of the microlens and the center of the opening of the black matrix layer are completely coincident with each other, it is possible to provide a liquid crystal display device that has high light utilization efficiency and excellent front luminance and viewing angle characteristics. it can.

  Since other configurations, operations, and effects are the same as those in the first embodiment, description thereof will not be repeated here.

  In each drawing according to the above embodiment, the same or corresponding parts are denoted by the same reference numerals.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

3 is a cross-sectional view of a light guide plate in Embodiment 1. FIG. FIG. 5 is a first enlarged schematic cross-sectional view illustrating the operation of the light guide plate in the first embodiment. FIG. 6 is a second enlarged schematic cross-sectional view for explaining the operation of the light guide plate in the first embodiment. 4 is a graph for explaining an incident angle and an emission angle of the light guide plate in the first embodiment. 6 is a graph illustrating an incident angle and an emission angle of a light guide plate of a comparative example in the first embodiment. 6 is a graph illustrating the diffraction efficiency of light in the red wavelength region in the light guide plate of the first embodiment. 6 is a graph for explaining the diffraction efficiency of light in the green wavelength region in the light guide plate of the first embodiment. 6 is a graph for explaining the diffraction efficiency of light in a blue wavelength region in the light guide plate of the first embodiment. 2 is an exploded schematic perspective view of the liquid crystal display device in Embodiment 1. FIG. 1 is a schematic cross-sectional view of a liquid crystal display device in Embodiment 1. FIG. 3 is a schematic plan view illustrating the arrangement of picture elements in Embodiment 1. FIG. 3 is an enlarged schematic cross-sectional view of a portion of one pixel of the liquid crystal display device in Embodiment 1. FIG. FIG. 3 is an enlarged schematic cross-sectional view of a light guide layer in which the diffractive optical element according to Embodiment 1 is arranged. 6 is a first graph when the refractive index of the high refractive index layer in the first embodiment is changed. 6 is a second graph when the refractive index of the high refractive index layer in the first embodiment is changed. 6 is an enlarged schematic cross-sectional view of a pixel portion of a liquid crystal display device in a second embodiment. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device in Embodiment 3. FIG. 10 is a table showing the coupling efficiency in the third embodiment. 6 is a schematic exploded perspective view of a liquid crystal display device according to Embodiment 4. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device in Embodiment 4. FIG. FIG. 10 is a schematic plan view showing an arrangement of picture elements in a fourth embodiment. FIG. 10 is a schematic cross-sectional view of a liquid crystal display device in a fifth embodiment. FIG. 10 is a schematic cross-sectional view of a liquid crystal display device in a sixth embodiment. FIG. 10 is an enlarged schematic cross-sectional view of a pixel portion of a liquid crystal display device in a sixth embodiment. FIG. 16 is a first process explanatory diagram of the microlens manufacturing method according to Embodiment 6. FIG. 10 is a second process explanatory diagram of the microlens manufacturing method according to the sixth embodiment. FIG. 10 is an explanatory diagram of a third step of the method of manufacturing a microlens in the sixth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting member, 2 Coupling lens, 4 Light guide layer, 5 High refractive index layer, 6 Low refractive index layer, 7,20 Diffractive optical element, 8 Reflective layer, 9 Light guide plate, 10 Micro prism, 11 Drive element board | substrate, 12 Liquid crystal layer, 13 black matrix layer, 14R, 14G, 14B, 22R, 22G, 22B picture element, 15 counter substrate, 16, 34 liquid crystal panel, 17, 18 liquid crystal display device, 21 parabolic mirror, 23 light guide, 24 reflective portion, 25 low refractive index body, 26 cylindrical lens, 27 linear light source, 31 light source, 28R, 28G, 28B color filter, 29 microlens, 30 photocurable resin, 32 lens portion, 33 uncured portion, 50 Arrow (indicating optical path), 51-53, 54R, 54G, 54B, 57R, 57G, 57B, 58R, 58G, 58B, 59R, 59G, 59B Arrow, 6 a~60c arrow, 61R, 61G, 61B area, 62 virtual _{line, θ l, θ w, θ} w (air), θ i, θ o wave1, θ o wave2, θ o wave3, θ oc wave1, θ o90 wave1 Angle, Q _{c wave1} , Q _{90 wave1} position, W width, Z length.

Claims (17)

A light guide plate that guides light from a light source that emits light including a plurality of wavelength regions,
A high refractive index layer;
A low refractive index layer having a refractive index smaller than that of the high refractive index layer;
A diffractive optical element for diffracting the light,
The low refractive index layer is disposed so as to sandwich the high refractive index layer,
The diffractive optical element is a light guide plate formed to diffract part of the light propagating through the high refractive index layer toward the low refractive index layer. The diffractive optical element is disposed in the low refractive index layer,
The light guide plate according to claim 1, wherein the diffractive optical element is disposed on a boundary surface between the low refractive index layer and the high refractive index layer. The light source is formed to emit light in a first wavelength region and light in a second wavelength region;
The light source is formed such that a wavelength λ ₁ emits light in the first wavelength region of λ _1min <λ ₁ <λ _1max ,
The light source wavelength lambda ₂ is formed to emit light of said second wavelength region _{λ 2min <λ 2 <λ 2max} ,
The refractive index n ₁ of the high-refractive index layer and the refractive index n ₂ of the low-refractive index layer are formed so as to satisfy the following expression, where Λ is the grating pitch of the diffractive optical element: The light guide plate described.
sin ⁻¹ ((λ _1min / Λ) −1) <sin ⁻¹ ((λ _2max / Λ) −sin θ _c )
Here, θ _c = sin ⁻¹ (n ₂ / n ₁ ), λ ₁ > λ ₂ , and n ₁ > n ₂ . A plurality of the diffractive optical elements are provided,
The light guide plate according to claim 1, wherein the plurality of diffractive optical elements are arranged apart from each other.   The light guide plate according to claim 1, wherein the diffractive optical element is formed so that a grating pitch is non-uniform.   The light guide plate according to claim 1, wherein the diffractive optical element is formed to have a condensing function. An auxiliary optical element disposed on the outer surface of the low refractive index layer,
The light guide plate according to claim 1, wherein the auxiliary optical element is formed so as to emit the light in a substantially normal direction of a surface of the low refractive index layer.   The light guide plate according to claim 7, wherein the auxiliary optical element includes a microprism or a micromirror. The light guide plate according to claim 1;
A backlight comprising the light source.   The backlight according to claim 9, wherein the light source is formed to emit the light including a red wavelength region, a green wavelength region, and a blue wavelength region.   The backlight according to claim 9, wherein the light source includes a linear light source.   The backlight according to claim 9, further comprising a condensing unit for condensing the light from the light source toward the high refractive index layer.   The backlight according to claim 12, wherein the light collecting means includes a lens or a parabolic mirror. A backlight according to claim 9;
A drive element substrate including a drive element for driving the liquid crystal of each pixel;
A counter substrate disposed to face the drive element substrate,
The counter substrate includes a black matrix layer having an opening corresponding to the picture element,
A liquid crystal display device formed so that the light in the wavelength region of one hue emitted from the light guide plate passes through the opening of the corresponding one hue. The counter substrate includes a color filter disposed to correspond to the opening,
The liquid crystal display device according to claim 14, wherein the light in a wavelength region of one hue emitted from the light guide plate is formed to pass through the color filter of the corresponding one hue. It has the picture elements of three colors,
The liquid crystal display device according to claim 14, wherein the picture elements are formed in a stripe arrangement or a delta arrangement. Of the surface of the drive element substrate, comprising a microlens formed on the surface facing the light guide plate,
The liquid crystal display device according to claim 14, wherein the microlens is formed so as to collect the light in each wavelength region toward the opening.

Images