JP2018045048A - Optical member and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress moire caused by a periodical structure of an optical element layer and a periodical structure of a louver layer.SOLUTION: An optical member 30 transmits light. The optical member 30 includes: an optical element layer 41 having a plurality of unit optical elements 41a arranged in a D1 direction and each linearly extending in a D2 direction intersecting the D1 direction; and a louver layer 61 having a light-absorbing part 61a and a light-transmitting part 61b arranged in the D1 direction and each extending in the D2 direction intersecting the D1 direction, in which the light-absorbing part 61a and the light-transmitting part 61b are alternately arranged along the D1 direction. At least three diffusion layers are disposed between the optical element layer 41 and the louver layer 61.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical member used for a display device and the like, and a liquid crystal display device including the optical member.

  The liquid crystal display device usually includes a liquid crystal display panel (liquid crystal panel) for displaying an image and a backlight (light source) for illuminating the liquid crystal panel. In such a liquid crystal display device, light from the backlight is emitted not only in the front direction of the display surface of the liquid crystal panel but also in various directions inclined from the front direction. Therefore, the light emitted from the liquid crystal display device is also emitted in various directions. For example, when the liquid crystal display device is mounted on an automobile, the emitted light emitted upward is reflected by the windshield of the automobile. The driver's view may be hindered.

  In order to solve this problem, as a conventional technique, for example, in Patent Document 1, an optical member having a prism sheet and a light control sheet is provided between a light source and a liquid crystal panel to limit the traveling direction of light. By providing the optical member, it is possible to limit the incident direction of light incident on the liquid crystal panel and limit the direction of light emitted from the liquid crystal display device.

JP 2010-217871 A

  However, in the liquid crystal display device described in Patent Document 1, moire (interference fringes) occurs in the displayed image. As a result of intensive studies by the present inventors, it has been found that this moire is caused by interference between the periodic structure of the prism sheet (optical element layer) and the periodic structure of the light control sheet (louver layer). It was. The present invention is an invention that solves such problems. That is, an object of the present invention is to provide an optical member that suppresses moire caused by the periodic structure of the optical element layer and the periodic structure of the louver layer.

The optical member of the present invention is an optical member that transmits light,
An optical element layer having a plurality of unit optical elements arranged in one direction and extending linearly in a direction crossing the one direction;
A light absorbing portion and a light transmitting portion arranged in the one direction and extending linearly in a direction crossing the one direction, and the light absorbing portion and the light transmitting portion alternately along the one direction; An array of louver layers,
With
At least three diffusion layers are provided between the optical element layer and the louver layer.

  The optical member of the present invention may further include a reflective polarization separation layer between the optical element layer and the louver layer.

  In the optical member of the present invention, at least one diffusion layer may be provided between the louver layer and the reflective polarization separation layer.

  In the optical member of the present invention, the diffuse reflectance in at least one diffusion layer provided between the louver layer and the reflective polarization separation layer is 1.0% or more and 7.0% or less. Also good.

  The liquid crystal display device of the present invention includes any one of the optical members described above, a light source, and a liquid crystal panel.

  According to the present invention, moire caused by the periodic structure of the optical element layer and the periodic structure of the louver layer can be suppressed.

FIG. 1 is an exploded sectional view showing an example of the configuration of a liquid crystal display device having an optical member of the present invention. FIG. 2 is an exploded sectional view showing another example of the configuration of the liquid crystal display device having the optical member of the present invention. FIG. 3 is a perspective view illustrating an example of an optical sheet. FIG. 4 is a perspective view showing an example of a louver film. FIG. 5 is a diagram for explaining the action of light incident on the louver layer. FIG. 6 is a diagram for explaining the action of light incident on the louver layer. FIG. 7 is a diagram illustrating a method for measuring diffuse reflectance.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual product.

  In the present specification, the terms “plate”, “sheet”, and “film” are not distinguished from each other only based on the difference in names. For example, an “optical sheet” is a concept that includes a member that can be called a plate or a film. Therefore, an “optical sheet” can be distinguished from a member that is called an “optical film” or the like only by a difference in name. Absent.

  In addition, “sheet surface (plate surface, film surface)” means a target sheet-like member (plate-like) when the target sheet-like (plate-like, film-like) member is viewed as a whole and globally. It refers to the surface that coincides with the plane direction of the member or film-like member.

  In addition, as used in the present specification, the shape and geometric conditions and the degree thereof are specified. For example, terms such as “parallel”, “orthogonal”, “identical”, and values of length and angle are strict. Without being bound by meaning, it should be interpreted including the extent to which similar functions can be expected.

  FIGS. 1-6 is a figure for demonstrating one Embodiment and modification by this invention. Among these, FIG. 1 and FIG. 2 are sectional views showing a schematic configuration of a liquid crystal display device including the optical member of the present invention. FIG. 3 is a perspective view showing an optical sheet included in the optical member, and FIG. 4 is a perspective view showing a louver film included in the optical member. 5 and 6 are diagrams for explaining the action of light incident on the louver film.

  1 and 2 show an example of the liquid crystal display device 1 in the present embodiment and another example, respectively. The liquid crystal display device 1 includes a light source 10, a liquid crystal panel 20, and an optical member 30 provided between the light source 10 and the liquid crystal panel 20. The liquid crystal display device 1 is a device that forms an image by transmitting planar light emitted from the light source 10 and transmitted through the optical member 30 through the liquid crystal panel 20 in a predetermined pattern.

  The light source 10 is disposed on the rearmost surface of the liquid crystal display device 1 (the surface farthest from the surface that emits light), and irradiates the optical member 30 with light. As the light source 10, an apparatus capable of irradiating light with a certain degree of uniform illuminance can be used. As such a light source 10, a direct type device having a reflecting plate and a plurality of point-like light emitters two-dimensionally arranged on the reflecting plate can be used. Further, as the light source 10, an edge light type device having a light guide plate and a light emitter disposed to face the side end face of the light guide plate can be used.

  The liquid crystal panel 20 functions as a shutter that controls transmission or blocking of light transmitted through the optical member 30 for each pixel, and is configured to display an image on the display surface 25. The liquid crystal panel 20 includes an upper polarizing plate 21 disposed on the light exit side, a lower polarizing plate 23 disposed on the light incident side, and a liquid crystal layer 22 disposed between the upper polarizing plate 21 and the lower polarizing plate 23. ,have. The polarizing plates 21 and 23 decompose the incident light into two orthogonal polarization components (P wave and S wave) and vibrate in one direction (direction parallel to the transmission axis) (for example, P wave) ) And absorbs a linearly polarized light component (for example, S wave) that vibrates in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

  An electric field can be applied to the liquid crystal layer 22 for each region where one pixel is formed. Then, the orientation direction of the liquid crystal molecules in the liquid crystal layer 22 changes depending on whether or not an electric field is applied. As an example, the polarization component in a specific direction transmitted through the lower polarizing plate 23 disposed on the light incident side rotates the polarization direction by 90 ° when passing through the liquid crystal layer 22 to which no electric field is applied, The polarization direction is maintained when passing through the liquid crystal layer 22 to which an electric field is applied. In this case, depending on whether or not an electric field is applied to the liquid crystal layer 22, the polarization component that vibrates in a specific direction transmitted through the lower polarizing plate 23 further transmits through the upper polarizing plate 21 disposed on the light output side of the lower polarizing plate 23. Alternatively, it is possible to control whether the light is absorbed and blocked by the upper polarizing plate 21.

  In this manner, the liquid crystal panel (liquid crystal display unit) 20 can control transmission or blocking of light transmitted from the light source 10 through the optical member 30 for each pixel. The details of the liquid crystal panel 20 are described in various known documents (for example, “Flat Panel Display Dictionary (supervised by Tatsuo Uchida, Hiraki Uchiike)” published by the Industrial Research Council in 2001). The detailed description of is omitted.

  Next, the optical member 30 will be described. The optical member 30 has the optical sheet 40, the reflective polarization separation sheet 50, and the louver film 60 in this order from the side close to the light source 10. The optical member 30 condenses and transmits light from the light source 10 in a direction perpendicular to the display surface 25.

  The optical sheet 40 includes an optical element layer 41 including a plurality of unit optical elements 41 a and a flat substrate layer 42. The optical sheet 40 is a member having a function of changing the traveling direction of incident light and transmitting it. The optical element layer 41 is formed by a plurality of unit optical elements 41 a arranged on one main surface of the base material layer 42. Each unit optical element 41a is formed in a columnar shape, and is configured as a prism arranged in the D1 direction in FIG. 3 and extending linearly in the D2 direction intersecting the D1 direction. In particular, in the illustrated example, each unit optical element 41a extends linearly in the direction D2. In the illustrated example, the direction D2 that is the longitudinal direction of the unit optical elements 41a and the direction D1 that is the arrangement direction of the unit optical elements 41a are orthogonal to each other.

  As the cross-sectional shape of the unit optical element 41a, a known shape can be applied according to a required function. In the illustrated example, each unit optical element 41a has a triangular cross-sectional shape. In the illustrated example, each unit optical element 41a is formed in a columnar shape and has the same cross-sectional shape along the longitudinal direction thereof. Further, the plurality of unit optical elements 41a are arranged on the base material layer 42 without a gap along a direction orthogonal to the longitudinal direction. Therefore, one main surface of the optical sheet 40 is formed by the surface (prism surface) of the unit optical elements 41 a arranged on the base material layer 42 without a gap.

  The optical sheet 40 is a light emitter in which the light source 10 is disposed facing the optical sheet 40, or a light guide plate disposed facing the optical sheet 40 and a light emission disposed facing the side surface of the light guide plate. The unit optical element 41a is on the light exit side as in the example of FIG. 1 or the unit optical element 41a is on the light incident side (on the side of the light source 10) as in the example of FIG. ) Can be designed as appropriate. Moreover, according to the optical function requested | required of the optical sheet 40, the diffused layer may further be provided on the surface on the opposite side to the side in which the optical element layer 41 of the base material layer 42 was provided. Further, the configuration of the optical element layer 41, such as the cross-sectional shape of the unit optical element 41a, can be changed as appropriate according to the optical function desired for the optical sheet 40.

  The arrangement pitch of the unit optical elements 41 a in the optical element layer 41 is not particularly limited, but is preferably 20 μm or more and 100 μm or less from the viewpoint of effectively exhibiting the function of the optical element layer 41. The height (thickness) of the optical element layer 41 is preferably 10 μm or more and 50 μm or less.

  The optical element layer 41 and the base material layer 42 are preferably formed of materials having the same or similar refractive index so as not to cause an optical action by causing a difference in refractive index at the interface between them. More preferably, it is formed from the following materials.

  The reflective polarization separation sheet 50 includes a reflective polarization separation layer 51 and a diffusion layer 53 in the example shown in FIGS. 1 and 2. In particular, in the illustrated example, the reflection-type polarization separation sheet 50 is provided on the first diffusion layer 53a provided on the light incident surface side (the light source 10 side) of the reflection-type polarization separation layer 51 and on the light emission surface side. There are two diffusion layers 53, the second diffusion layer 53b. The reflective polarization separation layer 51 decomposes the incident light into two orthogonal polarization components (P wave and S wave), transmits the polarization component in one direction, and transmits the polarization component in the other direction orthogonal to the one direction. It has a function of reflecting the polarization component. A known structure can be applied to the structure of such a reflective polarization separation layer.

  The diffusion layer 53 diffuses the traveling direction of the incident light and emits the light. The diffusion layer 53 may be configured as a layer having an internal diffusion function (internal diffusion layer) having a base material and diffusion particles dispersed in the base material, or a surface diffusion having an uneven surface. A layer having a function (surface diffusion layer) may be used. When a large difference in refractive index between the base material and the diffusing particles cannot be ensured due to cost and other constraints, it is preferable to use a surface diffusion layer that can stably exhibit strong diffusion performance. In particular, when the first diffusion layer 53a and the second diffusion layer 53b are surface diffusion layers, the first diffusion layer 53a and the second diffusion layer 53b may be provided by processing the reflective polarization separation layer 51. Alternatively, the reflective polarization separation layer 51 may be provided as a different layer.

  The louver film 60 includes a louver layer 61 having a light absorption part 61 a and a light transmission part 61 b, a base material 62, and a third diffusion layer 63. The louver film 60 has a function of changing the traveling direction of the incident light and emitting it from the light exit side. Specifically, the louver film 60 having the configuration shown in FIG. 1 can have a function of intensively improving the luminance in the front direction (normal direction of the display surface 25), and the louver film having the configuration shown in FIG. 60 can have a function of changing the exit direction of the emitted light so that the viewing angle of the incident light is widened. Further, it has a function of absorbing light incident at a large angle with respect to the front direction.

  The louver layer 61 is formed by light absorbing portions 61a and light transmitting portions 61b that are alternately arranged in a certain direction. As shown in FIG. 4, the light absorption part 61 a and the light transmission part 61 b are arranged in the D1 direction and extend linearly in the D2 direction intersecting the D1 direction. In particular, in the illustrated example, the D1 direction and the D2 direction are orthogonal to each other. That is, the arrangement direction of the light absorption part 61a and the light transmission part 61b and the arrangement direction of the unit optical element 41a coincide with each other, and the extending direction (longitudinal direction) of the light absorption part 61a and the light transmission part 61b matches the unit optical. The extending direction (longitudinal direction) of the element 41a coincides.

  The light absorbing portion 61a is a portion that absorbs light, for example, a portion that includes light absorbing particles in a binder resin. Examples of the light absorbing particles include acrylic beads containing carbon black. Moreover, the light transmission part 61b is a part which permeate | transmits light, for example, consists of resin which can permeate | transmit visible light. The light absorption parts 61a and the light transmission parts 61b are alternately arranged along the direction D1.

  Various shapes can be adopted as the cross-sectional shape of the light absorbing portion 61a depending on the required function. In the present embodiment, as shown in FIG. 5, the cross-sectional shape of the light absorbing portion 61a is a trapezoidal shape in which one base is sufficiently smaller than the bottom of the other, and the cross-sectional shape of the light transmitting portion 61b is The other base has a trapezoidal shape that is sufficiently smaller than one base.

  The material of the light absorption part 61a and the light transmission part 61b is not particularly limited, but is preferably an ultraviolet curable resin. The refractive index of the light absorption part 61a and the light transmission part 61b is determined based on the fragility and availability of the material and reflection of light at the interface between the light absorption part 61a and the light transmission part 61b. The refractive index is 1.47 or more and 1.50 or less, the refractive index of the light transmission part 61b is 1.55 or more and 1.61 or less, and the refractive index difference between the light absorption part 61a and the light transmission part 61b is 0.05 or more and 0.00. It is preferable that it is 14 or less. The refractive index of the light absorbing portion 61a is more preferably 1.49, and the refractive index of the light transmitting portion 61b is more preferably 1.56. By increasing the difference in refractive index between the light absorbing portion 61a and the light transmitting portion 61b, more light can be totally reflected at the interface between the light absorbing portion 61a and the light transmitting portion 61b. Note that most of the light incident on the light absorbing portion 61a without being totally reflected at the interface between the light absorbing portion 61a and the light transmitting portion 61b is absorbed by the light absorbing portion 61a.

  The base material 62 is a flat member that can appropriately support the louver layer 61. Various materials can be used as the material forming the substrate 62. However, considering that it is incorporated in the liquid crystal display device 1, the material of the louver film 60 preferably has excellent mechanical properties, optical properties, stability, workability, and the like, and can be obtained at low cost. . Examples of such a material include polyethylene terephthalate (PET), triacetyl cellulose (TAC), acrylic resin, polycarbonate, and the like. Further, since the louver layer 61 is used between the reflective polarization separation layer 51 and the lower polarizing plate 23 of the liquid crystal panel 20, the polarization state adjusted by the reflective polarization separation layer 51 is disturbed by the base material 62. In order to avoid this, it is preferable that the base material 62 has little birefringence. Furthermore, in applications where high heat resistance is required, such as in-vehicle applications, polycarbonate having a high glass transition point is preferable.

  The third diffusion layer 63 diffuses the traveling direction of the incident light and emits the light. The third diffusion layer 63 may be configured as an internal diffusion layer having a base material and diffusion particles dispersed in the base material, or may be a surface diffusion layer having an uneven surface. When a large difference in refractive index between the base material and the diffusing particles cannot be ensured due to cost and other constraints, it is preferable to use a surface diffusion layer that can stably exhibit strong diffusion performance. In particular, when the third diffusion layer 63 is a surface diffusion layer, the third diffusion layer 63 may be provided by processing the louver layer 61 or the base material 62, or the louver layer 61 or the base material 62. May be provided as different layers.

  The configuration of the louver film 60 can be changed as appropriate according to the required function. For example, as shown in FIG. 1, the third diffusion layer 63, the louver layer 61, and the base material 62 may be laminated in this order from the light incident side. Or as shown in FIG. 2, you may laminate | stack in order of the 3rd diffused layer 63, the base material 62, and the louver layer 61 from the light-incidence side. Also in the louver layer 61, as shown in FIGS. 1 and 5, the width of the light absorbing portion 61a may be large on the light entrance side and small on the light exit side, or as shown in FIGS. Furthermore, it may be smaller on the light incident side and larger on the light exit side.

  One inclined surface 61 a 1 and the other inclined surface 61 a 2 of the light absorbing portion 61 a may be inclined from a direction perpendicular to the surface of the base material 62. This inclination angle is preferably larger than 0 ° and not larger than 10 °. Further, the slopes 61a1 and 61a2 may be straight lines, curved lines, or polygonal lines that form steps. Furthermore, the slopes 61a1 and 61a2 may have different shapes for each light absorbing portion 61a. In the example shown in FIGS. 5 and 6, the inclined surfaces 61a1 and 61a2 are straight lines, and one inclined surface 61a1 of the light absorbing portion 61a is perpendicular to the surface of the base material 62, and the light absorbing portion 61a. The other inclined surface 61 a 2 is inclined by an angle θ from a direction perpendicular to the surface of the base material 62. If the inclination angles of the inclined surfaces 61a1 and 61a2 are different, the luminance is concentrated and the viewing angle is widened in the direction inclined with respect to the front direction (normal direction of the display surface 25). In particular, when the liquid crystal display device 1 having such an optical member 30 is mounted on an automobile, the emitted light in the direction toward the windshield or the like of the automobile is selectively reduced to prevent the driver's visibility from deteriorating. be able to.

  In the louver layer 61, the pitch p of the arrangement of the light absorption part 61a and the light transmission part 61b is not particularly limited, but is preferably 20 μm or more and 100 μm or less from the viewpoint of effectively exerting the function of the louver layer 61. More preferably, it is 30 μm or more and 100 μm or less. Further, the height (thickness) d of the light absorbing portion 61a is preferably 50 μm or more and 150 μm or less, and more preferably 60 μm or more and 150 μm or less.

  Note that a diffusion layer different from the third diffusion layer 63 may also be provided on the light exit surface side of the louver film 60.

  Moreover, although the optical sheet 40 and the louver film 60 of the optical member 30 have been illustrated in FIGS. 1 and 2, respectively, these are not limited to the combinations of FIGS. For example, the optical member 30 may have the optical sheet 40 shown in FIG. 1 and the louver film 60 shown in FIG. 2, or the optical sheet 40 shown in FIG. 2 and the louver film 60 shown in FIG. May be.

  In the third diffusion layer 63 described above, the diffuse reflectance is more preferably 1.0% or more and 7.0% or less. If the diffuse reflectance is 1.0%, sufficient diffusion occurs with respect to incident light, and moire can be made invisible. However, when the diffuse reflectance is greater than 7.0%, the light is diffused by the optical sheet 40 even if the outgoing direction of the transmitted light is condensed in a narrow angle range centered on the direction perpendicular to the display surface 25. This is not preferable because the brightness in the front direction decreases because of too much.

  In addition, the reflective polarization separation sheet 50 and the louver film 60 are arranged with a predetermined interval, and an air layer exists at this interval. The air layer is preferably 0.5 mm or more and 5.0 mm or less. If the air layer is too thin, the light emitted from the optical member 30 may be glaring, and if it is too large, the optical member 30 will be thick.

  In addition to the optical sheet 40, the reflective polarization separation sheet 50, and the louver film 60, the optical member 30 can be additionally provided with a layer having an arbitrary function such as a protective layer for protecting these.

  Next, the operation of the liquid crystal display device 1, particularly the operation when light enters the optical member 30 from the light source 10 will be described.

  First, the light emitted from the light source 10 enters the optical sheet 40 of the optical member 30. The optical sheet 40 exhibits a condensing function, and in the plane along the arrangement direction of the unit optical elements, the angle formed by the emission direction with respect to the front direction is larger than the angle formed by the incident direction with respect to the front direction. The traveling direction of the transmitted light is changed so as to decrease. In the optical sheet 40 shown in FIG. 1, the light traveling in the direction inclined with respect to the front direction is refracted by the optical element layer 41, thereby exhibiting a condensing function in the front direction. On the other hand, when the light source 10 is a combination of an edge light and a light guide plate, the traveling direction of the light incident on the optical member 30 is greatly inclined with respect to the front direction. Therefore, as shown in FIG. Total reflection is performed by the unit optical element 41 a of the layer 41, and thereby a light collecting function in a direction perpendicular to the display surface 25 is exhibited. That is, the optical sheet 40 corresponding to the type of the light source 10 can condense the emission direction of the transmitted light in a narrow angle range with the direction perpendicular to the display surface 25 as the center.

  The light emitted from the optical sheet 40 is incident on the reflective polarization separation sheet 50. The light incident on the reflective polarization separation sheet 50 is diffused by the first diffusion layer 53a, and, for example, the brightness distribution according to the arrangement of the unit optical elements 41a of the optical sheet 40 transmitted immediately before is weakened. In-plane uniformity is improved. The light transmitted through the first diffusion layer 53 a is incident on the reflective polarization separation layer 51. The light of the polarization component that vibrates in the direction parallel to the transmission axis of the reflective polarization separation layer 51 passes through the reflective polarization separation layer 51, is diffused again by the second diffusion layer 53 b, and travels toward the louver film 60. The in-plane uniformity of brightness is further enhanced by diffusion in the second diffusion layer 53b. On the other hand, the light of the polarization component that vibrates in the direction parallel to the reflection axis of the reflective polarization separation layer 51 is reflected and travels toward the optical sheet 40. The reflected light is reflected again by a not-shown reflecting plate or the like provided on the back surface of the light source 10 and is incident on the reflective polarization separation layer 51 again. In this way, only light having a specific polarization component is transmitted through the reflection-type polarization separation sheet 50, and light reflected by the reflection-type polarization separation layer 51 is also reflected to be transmitted through the reflection-type polarization separation sheet 50. become.

  The light incident on the louver film 60 is first diffused by the third diffusion layer 63 and then incident on the louver layer 61 shown in FIG. 5 or FIG. Due to the diffusion in the third diffusion layer 63, the in-plane uniformity of brightness is further enhanced. Of the light incident on the louver layer 61 shown in FIG. 5, the light that is substantially parallel to the front direction can pass through the louver layer 61 as it is without reaching the interface between the light absorbing portion 61a and the light transmitting portion 61b. . The light inclined with respect to the front direction is incident on the inclined surface 61a1 or the inclined surface 61a2 of the light absorbing portion 61a in the louver layer 61, and is reflected and totally reflected at an ideal position. In addition, the light that is greatly inclined with respect to the front direction is not totally reflected by the inclined surface 61a1 or the inclined surface 61a2 of the light absorbing portion 61a, but partially reflected, but a part of the light is incident on the light absorbing portion 61a. And is absorbed by the light absorber 61a.

  The light totally reflected by the inclined surface 61a1 or the inclined surface 61a2 of the light absorbing portion 61a will be described in detail. In the example shown in FIG. 5 and FIG. 6, when the incident light is reflected by the inclined surface 61a1, the inclined surface 61a1 is parallel to the front direction, so that the incident angle and the reflection angle are equal even when viewed from the front direction. The function of diffusion is not demonstrated. On the other hand, when the incident light is reflected by the inclined surface 61a2, in the example shown in FIG. 5, as shown by the light L5, the light inclined from the front direction is reflected by the inclined surface 61a2 and becomes light parallel to the front direction. To Penetrate. In the example shown in FIG. 6, as indicated by light L <b> 6, light substantially parallel to the front direction is reflected by the inclined surface 61 a 2 to be transmitted as light inclined from the front direction. That is, the inclined surface 61a2 exhibits a light collecting and diffusing function.

  The light transmitted through the louver layer 61 and emitted from the louver film 60 enters the lower polarizing plate 23 of the liquid crystal panel 20. The lower polarizing plate 23 transmits one polarized component of incident light and absorbs the other polarized component. The light transmitted through the lower polarizing plate 23 is selectively transmitted through the upper polarizing plate 21 in accordance with the state of electrolytic application to each pixel. In this manner, the liquid crystal panel 20 selectively transmits light for each pixel and displays an image on the display surface 25.

  By the way, in the conventional display device, it is known that a striped pattern called moire is observed on the display surface. Moire is thought to be visualized by the interference of the periodicity of two different structures. Therefore, as a means for making such moire inconspicuous, providing a diffusion layer or inclining the direction of exhibiting the periodicity of the two structures has been implemented. However, in the liquid crystal display device, when the optical element layer and the louver layer are arranged between the light source and the liquid crystal display panel, a diffusion layer is simply provided, or the optical element layer and the liquid crystal display panel are arranged with respect to the pixel arrangement. Even if the direction indicating the periodicity of the louver layer is inclined, the moire may not be effectively made inconspicuous.

  The present inventor has conducted extensive research on this point, and until now, the pixel arrangement was considered to be moire, but in reality it was caused by interference between the periodicity of the optical element layer and the periodicity of the louver layer. It was confirmed that strong moire had occurred. The optical element layer and the louver layer are members that are related to each other and change the traveling direction of light. Therefore, it is contrary to the installation purpose of the optical element layer and the louver layer to randomly tilt the direction indicating the periodicity of the optical element layer and the direction indicating the periodicity of the louver layer. In addition, since it is necessary to align the incident direction of incident light to the liquid crystal display panel to some extent, and the traveling direction of the light arranged in the optical element layer and the louver layer is disturbed, the liquid crystal display panel is more It was impossible to install strong diffusion on the light entrance side. As a result, the moire caused by the interference of the periodicity of the optical element layer and the periodicity of the louver layer is more conspicuous and the generation process is extremely complicated due to the overlap with the pixel arrangement of the liquid crystal display panel. It was discovered that

  Then, the present inventor has further studied earnestly and by providing at least three diffusion layers between the optical element layer 41 and the louver layer 61, the moire generated by the optical element layer 41 and the louver layer 61 is extremely effective. It was found that it can be made invisible. Although the detailed mechanism by which such a phenomenon occurs is unknown, the following matters are presumed to be one of the main causes.

  First, it is considered that the plurality of diffusion layers provided by shifting the positions in the front direction between the optical element layer 41 and the louver layer 61 are not merely adding diffusion but exhibiting a synergistic diffusion function. . Even if a light / dark pattern is generated in the light incident on the first diffusion layer 53a located closest to the light incident side, the light / dark pattern is diffused by the first diffusion layer 53a and incident on the second diffusion layer 53b. become. When the first diffusion layer 53a and the second diffusion layer 53b are shifted in the front direction, the light emitted from the first diffusion layer 53a has a light / dark pattern when incident on the first diffusion layer 53a. Are diffused to such an extent that the light forming the two bright portions adjacent to each other overlaps and enters the second diffusion layer 53b. As a result, the diffusion in the second diffusion layer 53b is performed very efficiently in order to eliminate the light / dark pattern. Further, a third diffusion layer 63 is provided on the light output side of the second diffusion layer 53b. Therefore, the diffusion in the second diffusion layer 53b and the diffusion in the third diffusion layer 63 form a light / dark pattern, similar to the superposition of the diffusion in the first diffusion layer 53a and the diffusion in the second diffusion layer 53b. It is carried out very efficiently in disappearing. Even if a light / dark pattern is generated in the incident light to the second diffusion layer 53b, the light / dark pattern is incident on the third diffusion layer 63 in a state where the light / dark pattern is greatly weakened. It will be very effective.

  Such synergistic diffusion by at least three diffusion layers is performed between the optical element layer 41 and the louver layer 61. In other words, after the light and dark pattern generated in the optical element layer 41 has a synergistic diffusion effect, the light and dark pattern generated in the optical element layer 41 is sufficiently reduced and then enters the louver layer 61. That is, the three diffusion layers function not to make the moire once generated conspicuous, but to eliminate the periodicity of the light transmitted through the optical element layer 41 that causes moire. As a result, even if the pixel arrangement of the liquid crystal display panel provided on the light output side is further overlapped, it is predicted that it is possible to effectively avoid the phenomenon that moire suddenly occurs due to a complicated interference state. Is done.

  Diffusion by the three diffusion layers is extremely effective for the disappearance of the light / dark pattern, in other words, uniformity of the in-plane distribution of brightness. It does not exceed the range of addition. That is, it does not function to unnecessarily excessively diffuse the traveling direction of the light collected by the optical element layer 41, and the three diffusion layers are compatible with the optical element layer 41.

  One of the main causes is the interference between the periodicity of the optical element layer 41 and the periodicity of the louver layer 61 by the three diffusion layers provided between the optical element layer 41 and the louver layer 61. It is thought that moiré can be made extremely inconspicuous. However, the present invention is not limited to the above estimation.

  As described above, the optical member 30 of the present embodiment is an optical member that transmits light, and is a plurality of units that are arranged in the D1 direction and extend linearly in the D2 direction, each intersecting the D1 direction. An optical element layer 41 having an optical element 41a, and a light absorption part 61a and a light transmission part 61b arranged in the D1 direction and extending linearly in the D2 direction, each intersecting the D1 direction. And a louver layer 61 in which transmission parts 61b are alternately arranged along the direction D1, and at least three diffusion layers (first diffusion layer 53a, second diffusion) between the optical element layer 41 and the louver layer 61. A layer 53b and a third diffusion layer 63) are provided. According to such an optical member 30, since at least three diffusion layers are provided, the light is aggregated and diffused in each of them, and the light period due to the arrangement of the unit optical elements 41 a of the optical element layer 41. And the generation of moire caused by interference between the periodic structure of the optical element layer 41 and the periodic structure of the louver layer 61 can be suppressed. In particular, the light is transmitted through the optical element layer 41 more effectively by being diffused at a distance, for example, as in the first diffusion layer 53a and the third diffusion layer 63, by the three diffusion layers. Periodicity can be lost.

  Further, the optical member 30 of the present embodiment further includes a reflective polarization separation layer 51 between the optical element layer 41 and the louver layer 61. According to such an optical member 30, light reflected by the lower polarizing plate 23 of the liquid crystal panel 20 is reduced by making the light from the light source 10 only light of a specific polarization component by the reflective polarization separation layer 51. can do. That is, the light use efficiency can be improved. Also, the moire can be reduced by the reflective polarization separation layer 51.

  Further, in the optical member 30 of the present embodiment, at least one diffusion layer (second diffusion layer 53b or third diffusion layer 63) is provided between the louver layer 61 and the reflective polarization separation layer 51. . According to such an optical member 30, the louver film 60 having the louver layer 61 and the reflective polarization separation sheet 50 having the reflective polarization separation layer 51 are prevented from coming into direct contact to form an optical interface. be able to. In addition, by disposing the diffusion layers on both sides of the reflective polarization separation layer 51, it is possible to sufficiently secure the arrangement interval along the front direction of the diffusion layers. Thereby, the diffusion function in the diffusion layer is more effectively exhibited.

  Further, in the optical member 30 of the present embodiment, the diffuse reflectance of the diffusion layer (third diffusion layer 63) provided between the louver layer 61 and the reflective polarization separation layer 51 is 1.0% or more and 7 0.0% or less. According to such an optical member 30, the third diffusion layer 63 is sufficiently diffused with respect to incident light, and the effect of suppressing the occurrence of the moire described above can be further exhibited. On the other hand, it is possible to effectively avoid harming the optical path adjusting action (light collecting action in the illustrated example) in the optical element layer 41.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to this Example.

  As an example, the optical member 30 shown in FIG. 1 was created, the light source 10 was turned on, and the presence or absence of moire was confirmed from the light output side. In the observation, the liquid crystal panel 20 is not used in order to confirm moire due to interference between the optical element layer 41 of the optical sheet 40 and the louver layer 61 of the louver film 60.

  Specific materials and shapes of each layer in the examples will be described.

  As the light source 10, the one attached to the 6.5 inch liquid crystal panel (LQ065T5GG03, manufactured by Sharp Corporation) was used.

  As the optical sheet 40, polyethylene terephthalate (A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm is used, an ultraviolet curable urethane acrylate having a refractive index of 1.56 is used, and an optical element layer 41 having a pitch of 50 μm and an apex angle of 90 °. It was created.

  As the reflective polarization separation sheet 50, DBEF-D2-400 (manufactured by 3M) was used. DBEF-D2-400 has diffusion layers on both the light incident surface side and the light exit surface side. These diffusion layers correspond to the first diffusion layer 53a and the second diffusion layer 53b.

For the louver film 60, first, a light transmitting portion 61 b of an ultraviolet curable urethane acrylate having a refractive index of 1.56 was formed on a substrate 62 made of a polycarbonate film having a thickness of 130 μm. Then, between the light transmitting portions 61b, light absorbing portions 61a of a UV curable urethane acrylate having a refractive index of 1.49 containing 25% of acrylic beads containing carbon black are formed at intervals of a pitch p of 47 μm. did. The length W _a of the bottom side of the light absorbing part 61a on the light source side is 10 μm, the length W _b of the bottom side on the observation side is 4 μm, the height d is 120 μm, the slope angle of the slope 61a1 is 4.5 °, and the slope 61a2 The inclination angle was 4.5 °. Further, a mat surface was provided on the light incident surface side of the louver film 60. The diffuse reflectance on the light source side of the louver layer 61 is changed in Examples 1 to 4 and Comparative Examples 1 to 4 in Table 1 below by changing the processing conditions of the glass blast on the mat surface to change the roughness of the mat surface. It is changed like this.

  Comparative Examples 1 to 4 to be compared with Examples 1 to 4 were prepared. In Comparative Examples 1 to 4, the reflective polarization separation sheet 50 was not provided. Other configurations of Comparative Examples 1 to 4 are the same as those of Examples 1 to 4, respectively.

  Here, a method for measuring the diffuse reflectance will be described. The diffuse reflectance is defined by the omnidirectional diffuse reflectance obtained by excluding the light reflectance for the specular reflected light from the total light reflectance. The diffuse reflectance of each layer was measured using a haze meter (HR-100 Murakami Color Research Laboratory) shown in FIG.

  First, the diffusion layer of the sheet to be measured for diffuse reflectance is directed to the light incident side, and a black plate is disposed on the opposite side, and the irradiation light from a direction inclined by 45 ° with respect to the normal line of the sheet Was irradiated. D65 is used as a measurement light source. Then, the specular reflection light was excluded, and the omnidirectional light in the integrating sphere at that time was obtained with a detector. And the ratio of the obtained omnidirectional light and irradiation light was expressed in percentage, and the diffuse reflectance was calculated.

  Table 1 below shows the diffuse reflectance measured for each layer and the evaluation of moire for each example and comparative example. The diffuse reflectance on the light source side (the side on which the matte surface is provided) of the louver film 60 is such that the incident direction of light from the measurement light source to the louver film 60 is D1 in a plan view when the louver film 60 is viewed from above. The louver film 60 and the measurement light source were arranged so as to be substantially parallel. Here, as described above, the reflective polarization separation sheet 50 decomposes the incident light into two orthogonal polarization components, transmits the polarization component in one direction, and transmits the other direction orthogonal to the one direction. It has a function of reflecting the polarized light component. Here, since the light of the polarization component in the other direction is diffusely reflected, the diffuse reflectance of the reflected polarization separation sheet 50 observed is the first diffusion layer 53a provided on the reflection polarization separation sheet 50 and the first diffusion layer 53a. It is observed to be higher than the actual diffuse reflectance of the two diffusion layers 53b. In addition, about the evaluation of moire, it has confirmed visually. In the column of "Evaluation of moire" in Table 1, "A" is attached to the sample in which moire is not confirmed, and there is a problem when carefully observed. “B” was given to samples in which moiré was confirmed to be thin enough not to become “C”, and “C” was given to samples in which moiré was clearly confirmed.

  As shown in Table 1, although moire was not confirmed in Examples 1 to 3, it was confirmed that moire was generated in Comparative Examples 1 to 4. Moreover, as understood from the comparison between Examples 1 to 3 and Example 4, it is thin when the diffuse reflectance of the mat surface (third diffusion layer 63) of the louver film 60 is less than 1.0%. It was confirmed that moire occurs. Therefore, it was confirmed that the generation of moire can be suppressed by providing at least three diffusion layers between the optical sheet 40 and the louver film 60. In particular, when the diffuse reflectance of the mat surface (third diffusion layer 63) of the louver film 60 is 1.0% or more, the occurrence of moire is remarkably suppressed.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Light source 20 Liquid crystal panel 21 Upper polarizing plate 22 Liquid crystal layer 23 Lower polarizing plate 25 Display surface 30 Optical member 40 Optical sheet 41 Optical element layer 41a Unit optical element 42 Base material layer 50 Reflective polarization separation sheet 51 Reflective type Polarized light separating layer 53a First diffusion layer 53b Second diffusion layer 60 Louver film 61 Louver layer 61a Light absorption part 61b Light transmission part 62 Base material 63 Third diffusion layer

Claims (5)

An optical member that transmits light,
An optical element layer having a plurality of unit optical elements arranged in one direction and extending linearly in a direction crossing the one direction;
The light absorbing portions and the light transmitting portions are arranged in the one direction and each extend linearly in a direction intersecting the one direction, and the light absorbing portions and the light transmitting portions are alternately arranged along the one direction. An array of louver layers,
With
At least three diffusion layers are provided between the optical element layer and the louver layer,
Optical member.   The optical member according to claim 1, further comprising a reflective polarization separation layer between the optical element layer and the louver layer.   The optical member according to claim 2, wherein at least one diffusion layer is provided between the louver layer and the reflective polarization separation layer.   4. The optical according to claim 3, wherein a diffuse reflectance in at least one of the diffusion layers provided between the louver layer and the reflective polarization separation layer is 1.0% or more and 7.0% or less. Element. The optical member according to any one of claims 1 to 4,
A light source;
LCD panel,
A liquid crystal display device comprising:

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