JP6944654B2 - Optical member, liquid crystal display device - Google Patents

Description

The present invention relates to an optical member used in a display device or the like, and a liquid crystal display device provided with the optical member.

The liquid crystal display device includes an image source such as a liquid crystal panel that emits image light to be displayed, and also includes an optical sheet that enhances the quality of the image light from the image source and transmits the image light to the observer side. In order to provide the observer with a higher quality image, the optical sheet is often laminated with layers having various functions.

Patent Document 1 discloses that a prism sheet and an optical control sheet are used in combination in a liquid crystal display device. The optical control sheet has a base film layer and an optical functional sheet layer laminated on the base film layer. The optical functional sheet layer has prism portions and light absorbing portions alternately arranged on one surface of the base film layer. A rough surface is formed on the surface of the base film layer opposite to the surface on which the optical functional sheet layer is laminated.

Japanese Unexamined Patent Publication No. 2010-217871

By the way, in the liquid crystal display device of Patent Document 1, the arrangement direction of the prisms of the prism sheet and the arrangement direction of the prism portion and the light absorbing portion of the optical functional sheet layer are orthogonal to each other. However, depending on the optical characteristics required for the optical member, it may be necessary to match the arrangement direction of the prisms of the prism sheet with the arrangement direction of the light transmitting portion and the light absorbing portion of the optical functional sheet layer. However, when the arrangement direction of the prisms of the prism sheet and the arrangement direction of the prism portion and the light absorbing portion of the optical function sheet layer are substantially the same direction, the periodic structures interfere with each other, resulting in moire (interference fringes). Will occur, which will cause new problems. The present invention has been made in consideration of such a point, and an object of the present invention is to make moire inconspicuous.

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 a first direction and each extending linearly in a direction intersecting the first direction.
Each has a light absorbing portion and a light transmitting portion linearly extending in a direction intersecting the second direction, and the light absorbing portion and the light transmitting portion are arranged along the second direction. With alternating louver layers,
The optical element layer and the louver layer are arranged in this order from the incoming light side to the outgoing light side of the transmitted light.
The width of the light absorbing portion is smaller on the light emitting side than on the incoming light side.
The interface between the light absorbing portion and the light transmitting portion forms a reflecting surface, and the light absorbing portion and the light transmitting portion form a reflective surface.
The smaller angle α of the angles formed by the first direction and the second direction is 10 ° or less.
The angle α [°] and the distance D [μm] between the optical element layer and the louver layer are (200-20 × α) ≦ D ≦ 500.
Satisfy the relationship.

In the optical member of the present invention, the unit optical elements are arranged at a constant pitch in the first direction, and the distance between the optical element layer and the louver layer is twice the pitch of the unit optical element. It may be the above.

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

In the liquid crystal display device of the present invention, the smallest angle between the pixel arrangement direction of the liquid crystal panel and the second direction may be 10 ° or less.

According to the present invention, moire can be made inconspicuous.

FIG. 1 is a diagram for explaining an embodiment of the present invention, and is a cross-sectional view showing an example of a liquid crystal display device having an optical member. FIG. 2 is a perspective view showing an example of an optical sheet. FIG. 3 is a perspective view showing an example of a louver film. FIG. 4 is a top view of the optical sheet and the louver film superposed on each other. FIG. 5 is a diagram illustrating the action of light incident on the louver layer from the optical element layer. FIG. 6 is a diagram for explaining the louver layer. FIG. 7 is a diagram illustrating a method for measuring the 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, the scale, aspect ratio, etc. are appropriately changed from those of the actual product and exaggerated for the convenience of illustration and comprehension.

In addition, in this specification, the terms "board", "sheet", and "film" are not distinguished from each other based only on the difference in designation. 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 called an "optical film" or the like only by a difference in name. No.

Further, the "sheet surface (plate surface, film surface)" is a target sheet-like member (plate-like) when the target sheet-like (plate-like, film-like) member is viewed as a whole and from a broad perspective. A surface that coincides with the plane direction of a member or film-like member).

In addition, as used in the present specification, the terms such as "parallel", "orthogonal", and "identical" and the values of length and angle that specify the shape and geometric conditions and their degrees are strictly used. Without being bound by meaning, we will interpret it including the range in which similar functions can be expected.

1 to 6 are diagrams for explaining one embodiment according to the present invention. Of these, FIG. 1 is a cross-sectional view showing a schematic configuration of a liquid crystal display device including an optical member. FIG. 2 is a perspective view showing an optical sheet included in the optical member, and FIG. 3 is a perspective view showing a louver film included in the optical member. FIG. 4 is a top view of the optical sheet and the louver film superposed on each other. FIG. 5 is a diagram for explaining the action of the louver film. FIG. 6 is a diagram for explaining the louver layer of the louver film.

FIG. 1 shows an example of the liquid crystal display device 1 according to the present embodiment. 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 by a light source 10 and transmitted through an optical member 30 through a liquid crystal panel 20 in a predetermined pattern.

The light source 10 is arranged 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, a device capable of irradiating light with a certain degree of uniform illuminance can be used. As such a light source 10, in the present embodiment, a direct type device having a reflector and a plurality of point-shaped light emitters two-dimensionally arranged on the reflector is used. However, as the light source 10, an edge light type device having a light guide plate and a light emitting body arranged so as to face the side end faces of the light guide plate may 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 arranged on the light emitting side, a lower polarizing plate 23 arranged on the light entering side, and a liquid crystal layer 22 arranged 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 has a function of absorbing a linearly polarized light component (for example, an S wave) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction.

An electric field can be applied to the liquid crystal layer 22 for each region forming one pixel. Then, the orientation direction of the liquid crystal molecules in the liquid crystal layer 22 changes depending on the presence or absence of the electric field application. As an example, the polarization component in a specific direction transmitted through the lower polarizing plate 23 arranged on the light entry side rotates its polarization direction by 90 ° when passing through the liquid crystal layer 22 to which no electric field is applied, while rotating the polarization direction by 90 °. The polarization direction is maintained as it passes 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 polarizing component that vibrates in a specific direction that has passed through the lower polarizing plate 23 further transmits through the upper polarizing plate 21 arranged on the light emitting side of the lower polarizing plate 23. Alternatively, it can be controlled whether it is absorbed by the upper polarizing plate 21 and blocked.

In this way, the liquid crystal panel (liquid crystal display unit) 20 can control the transmission or blocking of the 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 publicly known documents (for example, "Flat Panel Display Dictionary (supervised by Tatsuo Uchida and Hiraki Uchiike)" published by Kogyo Chosakai in 2001). The detailed description of is omitted.

Next, the optical member 30 will be described. The optical member 30 has an optical sheet 40 and a louver film 60 in this order from the side closer to the light source 10 (light entry side). The optical member 30 collects the light from the light source 10 in the direction perpendicular to the display surface 25 and transmits it.

The optical sheet 40 has an optical element layer 41 including a plurality of unit optical elements 41a, and a flat plate-shaped base material layer 42. The optical sheet 40 is a member having a function of changing the traveling direction of the incoming light and transmitting the light. The optical element layer 41 is formed by a plurality of unit optical elements 41a arranged on one main surface of the base material layer 42. Each unit optical element 41a is formed as a columnar prism, arranged in the D1 direction in FIG. 2, and linearly extending in the D2 direction intersecting the D1 direction. In particular, in the illustrated example, each unit optical element 41a extends linearly in the D2 direction. Further, in the illustrated example, the D2 direction, which is the longitudinal direction of the unit optical element 41a, and the D1 direction, which 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 the required function. In the illustrated example, each unit optical element 41a has a triangular cross-sectional shape. Further, 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 without gaps on the base material layer 42 along the direction orthogonal to the longitudinal direction thereof. Therefore, one main surface of the optical sheet 40 is formed by the surface (prism surface) of the unit optical elements 41a arranged without gaps on the base material layer 42.

The optical sheet 40 can be appropriately designed depending on the type of the light source 10 or the like, whether the unit optical element 41a is on the light emitting side or the light entering side (the side of the light source 10). In the present embodiment, the unit optical element 41a is provided on the light emitting side as shown in FIG. 1 in combination with a direct type light source. Further, depending on the optical function required for the optical sheet 40, a diffusion layer may be further provided on the surface of the base material layer 42 opposite to the side on which the optical element layer 41 is provided. Further, the configuration of the optical element layer 41 such as the cross-sectional shape of the unit optical element 41a can be appropriately changed according to the optical function required for the optical sheet 40.

The material of the optical element layer 41 is not particularly limited, but it is desirable that it is an ultraviolet curable resin. Further, the refractive index of the optical element layer 41 and the base material layer 42 is preferably 1.55 or more and 1.61 or less, and more preferably 1.58, in consideration of the vulnerability of the material and the optical performance. preferable.

The base material layer 42 is a flat plate-like member capable of appropriately supporting the optical element layer 41. As the material forming the base material layer 42, various materials such as polyethylene terephthalate (PET), triacetyl cellulose (TAC), an acrylic resin, and polycarbonate can be used. Of these, PET is preferable as the material for the base material layer 42 in consideration of cost and rigidity.

The arrangement pitch of the unit optical elements 41a in the optical element layer 41 is not particularly limited, but is preferably 30 μm or more and 100 μm or less from the viewpoint of effectively exerting the functions of the optical element layer 41. The height (thickness) of the optical element layer 41 is preferably 15 μm or more and 50 μm or less. Further, the apex angle of the unit optical element 41a is preferably 90 °.

The optical element layer 41 and the base material layer 42 are preferably formed from materials having the same or similar refractive index so as not to cause a difference in refractive index at the interface and cause an optical action. It is more preferably formed from the material of.

The louver film 60 has a louver layer 61 having a light absorbing portion 61a and a light transmitting portion 61b, and a base material 62. The louver film 60 has a function of changing the traveling direction of the incoming light and emitting it from the light emitting side. Specifically, the louver film 60 can have a function of intensively improving the brightness in the front direction (normal direction of the display surface 25). 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 arranged alternately in a certain direction. As shown in FIG. 3, the light absorbing portion 61a and the light transmitting portion 61b are arranged in the D3 direction (second direction) and extend linearly in the D4 direction intersecting the D3 direction. In particular, in the illustrated example, the D3 and D4 directions are orthogonal to each other.

Here, the smaller of the angles formed by the D1 direction, which is the arrangement direction of the unit optical elements 41a of the optical element layer 41, and the D3 direction, which is the arrangement direction of the light absorbing portion 61a and the light transmitting portion 61b of the louver layer 61. The angle α is typically 0 °. On the other hand, as shown in FIG. 4, for the purpose of making moire invisible, the D1 direction, which is the arrangement direction of the unit optical element 41a, and the D3 direction, which is the arrangement direction of the light absorbing portion 61a and the light transmitting portion 61b, are set. It may be tilted. Even in such a case, from the viewpoint of expecting the effect of the combination of the optical action on the optical element layer 41 and the optical action on the louver layer 61, the D1 direction, which is the arrangement direction of the unit optical element 41a, and the light The smaller angle α formed by the D3 direction, which is the arrangement direction of the absorbing portion 61a and the light transmitting portion 61b, is limited to 10 ° or less. However, when the smaller angle α of the angles formed by the D1 direction and the D3 direction is approximately 0 °, the light absorbing portion is used when punching is performed using a punching blade to adjust the outer shape of the louver film 60. Since the punching blade is inserted along the D3 direction, which is the arrangement direction of the 61a and the light transmitting portion 61b, cracks and linear slags may occur. Therefore, the smaller angle α of the angles formed by the D1 direction and the D3 direction is preferably larger than 1 °. Further, from the viewpoint of controlling the viewing angle characteristic, the smaller angle α of the angles formed by the D1 direction and the D3 direction is preferably 5 ° or less.

The light absorbing portion 61a is a portion that absorbs light, for example, a portion containing light absorbing particles in the binder resin. Examples of the light absorbing particles include acrylic beads containing carbon black. Further, the light transmitting portion 61b is a portion that transmits light, and is made of, for example, a resin that transmits visible light. The light absorbing portion 61a and the light transmitting portion 61b are arranged alternately along the D3 direction.

As the cross-sectional shape of the light absorbing portion 61a, various shapes can be adopted 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 other base, and the cross-sectional shape of the light transmitting portion 61b is , The other base has a trapezoidal shape that is sufficiently smaller than the one base.

The materials of the light absorbing portion 61a and the light transmitting portion 61b are not particularly limited, but it is desirable that they are ultraviolet curable resins made of different materials. The light absorbing portion 61a and the light transmitting portion 61b are formed of materials having different refractive indexes from the viewpoint of forming a reflective interface at the interface. In particular, from the viewpoint of expecting total reflection at the interface between the light absorbing portion 61a and the light transmitting portion 61b, it is preferable that the refractive index of the light absorbing portion 61a is smaller than the refractive index of the light transmitting portion 61b. , Total reflection can be expected at the interface between the light absorbing portion 61a and the light transmitting portion 61b.

Specifically, the refractive index of the light absorbing portion 61a and the light transmitting portion 61b takes into consideration the brittleness and availability of the material and the reflection of light at the interface between the light absorbing portion 61a and the light transmitting portion 61b. The refractive index of the light absorbing portion 61a is 1.47 or more and 1.50 or less, the refractive index of the light transmitting portion 61b is 1.55 or more and 1.61 or less, and the difference in refractive index between the light absorbing portion 61a and the light transmitting portion 61b is It can be 0.05 or more and 0.14 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 having such a refractive index, the interface between the light absorbing portion 61a and the light transmitting portion 61b can form a total reflection surface. In particular, 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. Most of the light incident on the light absorbing unit 61a without being reflected at the interface between the light absorbing unit 61a and the light transmitting unit 61b is absorbed by the light absorbing unit 61a.

The base material 62 is a flat plate-like member capable of appropriately supporting the louver layer 61. As the material forming the base material 62, various materials can be used. However, considering that it is incorporated in the liquid crystal display device 1, it is preferable that the material of the louver film 60 has excellent mechanical properties, optical properties, stability, processability, etc., and can be obtained at low cost. .. Examples of such a material include polyethylene terephthalate (PET), triacetyl cellulose (TAC), an acrylic resin, and polycarbonate. Further, since the louver layer 61 is used between the light source 10 and the lower polarizing plate 23 of the liquid crystal panel 20, the base material 62 is birefringent in order to avoid disturbing the polarization state by the base material 62. Less is preferable. Further, in applications requiring high heat resistance such as in-vehicle applications, polycarbonate having a high glass transition point is preferable.

The louver film 60 may be laminated in the order of the louver layer 61 and the base material 62 from the light receiving side, or may be laminated in the order of the base material 62 and the louver layer 61. Further, in the louver layer 61, the width of the light absorbing portion 61a is smaller on the light emitting side than on the light entering side.

One slope 61a1 and the other slope 61a2 of the light absorbing portion 61a may be inclined from a direction perpendicular to the surface of the base material 62. This inclination angle is preferably larger than 0 ° and 10 ° or less. Further, the slopes 61a1 and 61a2 may be a straight line, a curved line, or a polygonal line forming a step. Further, the slopes 61a1 and 61a2 may have different shapes for each light absorbing portion 61a. In the present embodiment, as shown in FIG. 6, the slopes 61a1 and 61a2 are straight lines and are inclined by _{angles θ 1} and θ _{2 from the direction perpendicular to the surface of the base material 62, respectively. The inclination angles θ 1} and θ ₂ of the slopes 61a1 and 61a2 may be different from each other. In this case, the brightness can be concentrated or the viewing angle can be widened in a direction inclined with respect to the front direction (the 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 reflected by the windshield of the automobile or the like is selectively reduced to prevent deterioration of the driver's visibility. can do.

In the louver layer 61, the pitch p of the arrangement of the light absorbing portion 61a and the light transmitting portion 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. It is more preferably 30 μm or more and 100 μm or less. 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.

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

Here, the optical element layer 41 and the louver layer 61 are arranged at a predetermined distance. The distance between the optical element layer 41 and the louver layer 61 is, as shown in FIG. 5, the end of the optical element layer 41 on the light receiving side, that is, the top of the unit optical element 41a and the light entering of the louver film 60. The distance along the thickness direction between the side edge. The distance D may be provided by a spacer or the like, or may be provided by arranging another layer as described above between them. The distance D is preferably 280 μm or more and 500 μm or less. If this distance is too small, the light emitted from the optical member 30 may be glaring, and if it is too large, the optical member 30 becomes thick. Further, the distance D is preferably twice or more the pitch of the unit optical element 41a.

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

First, the light emitted from the light source 10 is incident on the optical sheet 40 of the optical member 30. The optical sheet 40 exerts a condensing function, and in the plane along the arrangement direction of the unit optical elements, the angle formed by the emitting 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 be smaller. In the optical sheet 40 of the present embodiment shown in FIG. 1, light traveling in a direction inclined with respect to the front direction is refracted by the optical element layer 41, whereby a light collecting function in the front direction is exhibited. NS. That is, the optical sheet 40 can collect the emitted direction of the transmitted light in a narrow angle range centered on the direction perpendicular to the display surface 25.

The light emitted from the optical sheet 40 is incident on the louver layer 61 of the louver film 60. Of the light incident on the louver layer 61 shown in FIG. 5, the light L41 traveling in a direction substantially parallel to the front direction passes through the louver layer 61 as it is without reaching the interface between the light absorbing portion 61a and the light transmitting portion 61b. be able to. The light L42 inclined with respect to the front direction is incident on the slope 61a1 or the slope 61a2 of the light absorbing portion 61a in the louver layer 61, and is reflected, ideally totally reflected. Further, at least a part of the light L42 inclined with respect to the front direction travels in the front direction by reflection on the slope 61a1 or the slope 61a2 of the light absorbing portion 61a. On the other hand, the light L43 that is greatly inclined with respect to the front direction is not totally reflected on the slope 61a1 or the slope 61a2 of the light absorbing portion 61a, and is partially reflected, but partly incident on the light absorbing portion 61a. Then, it is absorbed by the light absorption unit 61a.

The light transmitted through the louver layer 61 and emitted from the louver film 60 is incident on the lower polarizing plate 23 of the liquid crystal panel 20. The lower polarizing plate 23 transmits one of the polarized light components of the incident light and absorbs the other polarized light components. The light transmitted through the lower polarizing plate 23 selectively transmits through the upper polarizing plate 21 according to the state of electrolysis applied to each pixel. In this way, the liquid crystal panel 20 selectively transmits light for each pixel, and the image is displayed on the display surface 25.

By the way, as described above, in a display device such as Patent Document 1 in which the arrangement direction of the prism portion of the optical function sheet layer and the arrangement direction of the light absorption portion are aligned, a striped pattern called moire is observed on the display surface. Will be done. It is presumed that this moire is caused by the interference between the periodicity of the optical element layer and the periodicity of the louver layer. As a means for making moiré inconspicuous, it is known to provide a diffusion layer and to incline the direction in which the optical element layer exhibits periodicity and the direction in which the louver layer exhibits periodicity.

However, providing a strong diffusion layer disturbs the traveling direction of the light prepared by the optical element layer and the louver layer. In particular, since it is necessary to align the incident directions of the incident light on the liquid crystal display panel to some extent, it is not preferable to install a strong diffusion on the incoming light side of the liquid crystal display panel. Further, the optical element layer and the louver layer are members or elements that are related to each other and change the traveling direction of light. Therefore, it is contrary to the purpose of installing the optical element layer and the louver layer to incline the direction indicating the periodicity of the optical element layer and the direction indicating the periodicity of the louver layer in a disorderly manner. From this point, as described above, the smaller angle α between the D1 direction, which is the arrangement direction of the unit optical elements 41a, and the D3 direction, which is the arrangement direction of the light absorbing portion 61a and the light transmitting portion 61b, is It is restricted to 10 ° or less, preferably more than 1 ° and 5 ° or less.

On the other hand, the present inventor has made extensive studies on the arrangement direction of the unit optical element 41a of the optical element layer 41 (D1 direction) and the arrangement direction of the light absorbing portion 61a and the light transmitting portion 61b of the louver layer 61 (D3 direction). However, when the smaller angle α of the angles formed by the substantially same direction, more specifically, the D1 direction and the D3 direction is 10 ° or less, the width of the light absorbing portion 61a is on the light emitting side from the light entering side. It is small, and the interface between the light absorbing portion 61a and the light transmitting portion 61b forms a reflecting surface, and the smaller angle α [°] between the D1 direction and the D3 direction, the optical element layer 41 of the optical sheet 40, and the louver. The distance D [μm] between the film 60 and the louver layer 61 is
(200-20 × α) ≦ D ≦ 500
It was found that the moire generated by the optical element layer 41 and the louver layer 61 can be made invisible extremely effectively by satisfying the relationship between the above. The detailed mechanism by which such a phenomenon occurs is unknown, but the following matters are presumed to be one of the main causes.

First, as shown in FIG. 5, the light emitted from the optical element layer 41 and entering the louver layer 61 is the light L41 traveling in a direction substantially parallel to the front direction, and is inclined relatively small with respect to the front direction. It can be considered that there are three types of light L42, which is present, and light L43, which is relatively greatly inclined with respect to the front direction. Of these, the light L41 traveling in a direction substantially parallel to the front direction is so-called “blank light” that does not enter the light absorbing portion 61a and passes through the louver layer 61 as it is. On the other hand, a part of the light L42 that is inclined relatively small with respect to the front direction and a part of the light L43 that is inclined relatively large with respect to the front direction are incident on the slope 61a1 or the slope 61a2 and reflected. It becomes "reflected light" that passes through the louver layer 61.

Here, the light transmitted through each light transmitting portion 61b, for example, the region A shown in FIG. 5 will be examined. The plain light escapes from the central portion of each light transmitting portion 61b along the arrangement direction of the light transmitting portion 61b. More specifically, the light-through light L41 in FIG. 5 is emitted from a region that does not overlap with the light absorbing portion 61a when observed from the front direction. On the other hand, the reflected light escapes from both end portions of each light transmitting portion 61b along the arrangement direction of the light transmitting portion 61b. More specifically, the reflected light L42 in FIG. 5 is emitted from a region overlapping the light absorbing portion 61a, that is, a region above the inclined surface 61a1 when observed from the front direction. Similar light is emitted from the region above the inclined surface 61a2. That is, by increasing the width of the light transmitting portion 61b from the incoming light side to the outgoing light side, it is possible to widen the brightly observed region corresponding to each light transmitting portion 61b by utilizing the "reflected light". .. As a result, the light-dark pattern of the "non-existing light" consisting of the bright part corresponding to the light transmitting portion 61b and the dark part corresponding to the light absorbing portion 61a is blurred by the "reflected light", and the period of brightness caused by the louver layer 61 is blurred. It is presumed that it will be possible to effectively weaken the sex. The width of the light absorbing portion 61a of the louver layer 61 on the light emitting side is sufficiently narrow, and the light-dark pattern due to the light absorbing portion 61a being visually recognized as a dark portion is not observed.

Further, as shown in FIG. 5, among the light transmitted through one light transmitting portion 61b, the light forming the “blank light” and the light forming the “reflected light” are emitted from different unit optical elements 41a. Sometimes there is. In this case, the arrangement periodicity of the unit optical element 41a of the optical element layer 41 is eliminated by the louver layer 61. As a result, it is possible to effectively suppress the generation of moire caused by the periodicity of the optical element layer 41 and the periodicity of the louver layer 61.

As a result of further studies, the present inventor found that the smaller angle α between the D1 direction and the D3 direction and the distance D between the optical element layer 41 of the optical sheet 40 and the louver layer 61 of the louver film 60. However, it was found that by satisfying a certain relationship, moire caused by "blunt light" and "reflected light" can be suppressed.

The angle α affects the degree of interference between the periodicity of the optical element layer 41 and the periodicity of the louver layer 61. Specifically, as the angle α becomes larger, moire due to the periodicity of the optical element layer 41 and the periodicity of the louver layer 61 is less likely to occur. On the other hand, the distance D affects the degree of loss of the periodicity of the light transmitted through the optical element layer 41. Specifically, as the distance D becomes longer, the periodicity of the light transmitted through the optical element layer 41 disappears, and it becomes less likely to interfere with the periodicity of the louver layer 61. Therefore, when the angle α and / or the distance D becomes sufficiently large, moire due to the “blank light” and the “reflected light” is suppressed. As a result of the examination by the inventor of the present invention, the angle α [°] and the distance D [μm] have been determined.
(200-20 × α) ≦ D ≦ 500
It was found that by satisfying the relationship of, moire caused by "non-existing light" and "reflected light" is suppressed.

As a result of further diligent studies by the present inventor, when the distance between the optical element layer 41 and the louver layer 61 is twice or more the arrangement pitch of the unit optical elements 41a, the distance from the plurality of unit optical elements 41a is increased. It was possible to effectively promote the light entering the same light transmitting portion 61b.

It is considered that one of the main causes is that moire due to interference between the periodicity of the optical element layer 41 and the periodicity of the louver layer 61 can be made inconspicuous extremely effectively. However, the present invention is not bound by the above speculation.

As described above, in the present embodiment, the optical member 30 is an optical member that transmits light, and is a plurality of units that are arranged in the D1 direction and each of which extends linearly in a direction intersecting the D1 direction. It has an optical element layer 41 having an optical element 41a, a light absorbing portion 61a and a light transmitting portion 61b arranged in the D3 direction and extending linearly in a direction in which each intersects the D3 direction, and the light absorbing portion 61a and the light transmitting portion 61a. The louver layers 61 in which the portions 61b are alternately arranged along the D3 direction are provided, and the optical element layer 41 and the louver layer 61 are arranged in this order from the incoming light side to the outgoing light side of the transmitted light to absorb light. The width of the portion 61a is smaller on the light emitting side than on the incoming light side, the interface between the light absorbing portion 61a and the light transmitting portion 61b forms a reflecting surface, and the smaller angle α of the angles formed by the D1 direction and the D3 direction is It is 10 ° or less, and the relationship between the angle α and the distance D between the optical element layer 41 and the louver layer 61 is (200-20 × α) ≦ D ≦ 500 is satisfied. According to such an optical member 30, the periodicity caused by the louver layer 61 can be effectively weakened, whereby moire can be made inconspicuous.

Further, in the optical member 30 of the present embodiment, the unit optical elements 41a are arranged at a constant pitch in the D1 direction, and the distance between the optical element layer 41 and the louver layer 61 is the pitch of the unit optical element 41a. It is more than double. According to such an optical member 30, it is possible to promote the light from the plurality of unit optical elements 41a to enter the same light transmitting portion 61b. As a result, the periodicity of brightness caused by the optical element layer 41 can be effectively eliminated by the louver layer 61. As a result, the moire can be made inconspicuous more effectively.

It is possible to make various changes to the above-described embodiment. Hereinafter, an example of modification will be described.

For example, depending on the optical characteristics required for the liquid crystal display device 1, the pixel arrangement direction of the liquid crystal panel 20 may be aligned with the arrangement direction of the light absorbing portion 61a and the light transmitting portion 61b of the louver layer 61. In this case, in the conventional liquid crystal display device, moire occurs due to the periodicity in the pixel arrangement direction of the liquid crystal panel 20 and the periodicity in the arrangement direction between the light absorbing portion 61a and the light transmitting portion 61b of the louver layer 61. rice field. However, in the liquid crystal display device 1 provided with the above-mentioned optical member 30, since the periodicity is weakened by the light emitted from the louver layer 61, the pixel arrangement direction of the liquid crystal panel 20 and the light absorbing portion of the louver layer 61 are weakened. Even if the arrangement directions of the light transmitting portion 61b and the light transmitting portion 61a are aligned with each other, the occurrence of moire is suppressed. Therefore, the smallest angle formed by the pixel arrangement direction of the liquid crystal panel 20 and the arrangement direction (D3 direction) of the light absorbing portion 61a and the light transmitting portion 61b of the louver layer 61 can be set to 10 ° or less.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

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 emitting side.

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

As the light source 10 and the liquid crystal panel 20, those attached to the 6.5-inch liquid crystal panel (LQ065T5GG03, manufactured by Sharp Corporation) were used.

As the optical sheet 40, 100 μm thick polyethylene terephthalate (A4300, manufactured by Toyobo) is used, and an ultraviolet curable urethane acrylic rate having a refractive index of 1.58 is used, and an optical element layer 41 having a pitch of 50 μm and an apex angle of 90 ° is used. It was created.

Regarding the louver film 60, first, a light transmitting portion 61b of an ultraviolet curable urethane acrylic rate having a refractive index of 1.56 was formed on a base material 62 made of a polycarbonate film having a thickness of 130 μm. Then, between the light transmitting portions 61b, light absorbing portions 61a of an ultraviolet curable urethane acrylic rate having a refractive index of 1.49 containing 25% of acrylic beads containing carbon black are formed at intervals of 47 μm pitch p. bottom. _{The length W a} of the base of the light absorbing portion 61a on the light source side is 10 μm, the length W _b of the base on the observation side is 4 μm, the height d is 120 μm, the inclination angle of the slope 61a1 is 4.5 °, and the slope 61a2. The inclination angle was 4.5 °. The diffuse reflectance of the louver film 60 on the light emitting surface side is 3.4%. Further, a mat layer of an ultraviolet curable urethane acrylic rate having a diffuse reflectance of 4.0% was provided on the light receiving surface side of the louver film 60.

The smaller angle α between the arrangement direction (D1 direction) of the unit optical element 41a and the arrangement direction (D3 direction) of the light absorbing portion 61a and the light transmitting portion 61b is 0.5, 10 °. It is either. Further, an air layer provided by a spacer or the like is formed between the optical sheet 40 and the louver film 60. The thickness of the air layer, that is, the distance D between the optical sheet 40 and the louver film 60 is any of 0, 200, and 500 μm. Among these, those satisfying the relationship of (200-20 × α) ≦ D ≦ 500 were designated as Examples 1 to 7, and those not satisfying the relationship were designated as Comparative Examples 1 and 2 for comparison with Examples.

In the examples and comparative examples, the optical member 30 in which the optical sheet 40, the reflective polarizing separation sheet, and the louver film 60 are laminated in this order is installed on the surface of the light source 10, and the width of the light absorbing portion 61a of the louver layer 61 is wide. The side was arranged on the light source 10 side. When the D1 direction is used as a reference, in each of the Examples and Comparative Examples, the D3 direction is tilted to 0 °, 5 °, and 10 ° with respect to the D1 direction, and the angle α is set to 0 °, 5 °, and 10 °. Changed. Further, in the liquid crystal panel 20, the pixels are arranged in the D1 direction and the direction orthogonal to the D1 direction.

Further, 10 [mu] m as a reference example 1, the angle alpha 10 °, in the case where the distance D between 0 .mu.m, the light source side of the base of the light absorbing portion 61a length _{W a} a 4 [mu] m, the bottom of the viewing-side length _{W b} Changed to. That is, the width of the light absorbing portion 61a was made smaller on the incoming light side than on the outgoing light side. Further, as Reference Example 2, when the angle α is 10 ° and the distance D is 0 μm, the refractive index of the light absorbing portion 61a of the louver layer 61 is changed to 1.56. As a result, total reflection does not occur between the light absorbing portion 61a and the light transmitting portion 61b. That is, the louver film 60 in Reference Examples 1 and 2 cannot intensively improve the brightness in the front direction. In Reference Examples 1 and 2, other configurations are the same as those in Examples and Comparative Examples.

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

First, the layer of the target sheet is directed toward the incoming light side, the black plate is arranged on the opposite side, and the irradiation light is irradiated at an angle of 45 ° with respect to the normal line of the sheet. D65 is used as the measurement light source. Then, the specularly reflected light is excluded, and the omnidirectional light in the integrating sphere at that time is obtained by the detector. Then, the ratio of the obtained omnidirectional light to the irradiation light is expressed as a percentage, and the diffuse reflectance is calculated.

For Examples 1 to 7, Comparative Examples 1 and 2, and Reference Examples 1 and 2, the light source 10 was turned on and moire was confirmed. The results of Examples 1 to 7, Comparative Examples 1 and 2, and Reference Examples 1 and 2 are shown in Table 1 below.

Moire was not confirmed in Examples 1-7. This is because the periodic light generated in the optical element layer 41 is spread by the louver layer 61, so that the generated periodicity of light and darkness is alleviated in a wide range, and the occurrence of moire due to the periodicity is reduced. It is thought that this is because the moiré pattern was created. On the other hand, in Comparative Examples 1 and 2, the occurrence of moire was confirmed. In particular, moire was strongly generated on the entire surface of the observed liquid crystal panel. It is considered that this is because the moire caused by the above-mentioned "non-existing light" and "reflected light" could not be suppressed. Further, in Reference Example 1, since the wide side of the light absorbing portion 61a is the light emitting side, it is considered that moire did not occur because the “reflected light” acts to diffuse. In Reference Example 2, it is considered that "reflected light" did not occur and moire did not occur because the interface between the light absorbing portion 61a and the light transmitting portion 61b did not form a reflecting surface.

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 60 Louver film 61 Louver layer 61a Light absorption Part 61b Light transmitting part 62 Base material

Claims (4)

An optical member that transmits light
An optical element layer having a plurality of unit optical elements arranged in a first direction and each extending linearly in a direction intersecting the first direction.
Each has a light absorbing portion and a light transmitting portion linearly extending in a direction intersecting the second direction, and the light absorbing portion and the light transmitting portion are arranged along the second direction. With alternating louver layers,
The optical element layer and the louver layer are arranged in this order from the incoming light side to the outgoing light side of the transmitted light.
The width of the light absorbing portion is smaller on the light emitting side than on the incoming light side.
The interface between the light absorbing portion and the light transmitting portion forms a reflecting surface, and the light absorbing portion and the light transmitting portion form a reflective surface.
The smaller angle α of the angle formed by the first direction and the second direction is larger than 1 ° and 5 ° or less.
The angle α [°] and the distance D [μm] between the optical element layer and the louver layer are (200-20 × α) ≦ D ≦ 500.
I saw the relationship of
An air layer having a thickness of D [μm] exists between the optical element layer and the louver layer.
Optical member. The unit optical elements are arranged at a constant pitch in the first direction.
The optical member according to claim 1, wherein the distance between the optical element layer and the louver layer is at least twice the pitch of the unit optical element. The optical member according to claim 1 or 2,
Light source and
LCD panel and
A liquid crystal display device. The liquid crystal display device according to claim 3, wherein the smallest angle between the pixel arrangement direction of the liquid crystal panel and the second direction is 10 ° or less.

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