JP2016038517A - Optical sheet, video source unit, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet that can effectively prevent unnecessary emission of light with a simpler configuration and improve the brightness of light transmitted through a liquid crystal panel.SOLUTION: An optical sheet includes: a light transmission part that is arranged between a light source 25 and a liquid crystal panel 15 and has an optical functional layer 32 and a polarization sheet 27, where the optical functional layer has light transmission parts extending in one direction along a sheet surface with a predetermined cross section and arranged in plurality in a direction different from the direction of extension at predetermined intervals, and light absorption parts formed in the intervals of the adjacent light transmission parts. The polarization sheet includes a rugged layer extending in one direction along the sheet surface with a predetermined cross section and including unit projections arranged in plurality at a cycle of 1 μm or less in a direction different from the extension, and a metal thin film laminated on the rugged layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical sheet disposed in a display device, an image source unit including the optical sheet, and a display device.

  A liquid crystal display device such as a liquid crystal television illuminates a liquid crystal panel having video information with a surface light source device from the back side. As a result, part of the illumination light is transmitted through the liquid crystal panel to obtain video information and emitted to the viewer side, so that the viewer can view the video. On the other hand, the liquid crystal panel is limited in the light that can be effectively used due to its properties, and a device for efficiently using the light from the light source is necessary.

  For example, Patent Document 1 discloses an optical laminate in which a louver film and a reflective polarizing film are laminated. According to this optical laminate, it is described that by arranging this between the backlight and the liquid crystal panel, it is possible to effectively prevent the emission of unnecessary light and to improve the luminance of the light transmitted through the liquid crystal panel. Yes.

Japanese Patent No. 4856805

  However, the optical laminate described in Patent Document 1 has a configuration in which two different polymer materials are alternately laminated as described in the specification, and the number of polymer layers reaches several thousand, The process is complicated because there are so many.

  In view of the above problems, an object of the present invention is to provide an optical sheet that can effectively prevent unnecessary light from being emitted with a simpler structure and improve the luminance of light transmitted through a liquid crystal panel. In addition, an image source unit and a display device including the optical sheet are provided.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

  The invention described in claim 1 is an optical sheet (26) disposed between the light source (25) and the liquid crystal panel (15), and has an optical functional layer (32) and a polarizing sheet (27). The optical functional layer has a predetermined cross section, extends in one direction along the sheet surface, and is adjacent to a plurality of light transmission portions (33) arranged at predetermined intervals in a direction different from the extending direction. The polarizing sheet has a predetermined cross section and extends in one direction along the sheet surface, and 1 μm in a direction different from the extending direction. It is an optical sheet provided with the uneven | corrugated layer (29) which comprises the unit convex part (29a) arranged in multiple numbers with the following periods, and the metal thin film (30) laminated | stacked on the uneven | corrugated layer.

  According to a second aspect of the present invention, in the optical sheet (26) according to the first aspect, the direction in which the light transmitting portion (33) extends and the direction in which the uneven layer (29) extends are orthogonal to each other when viewed from the front.

  According to a third aspect of the present invention, in the optical sheet (26) according to the first or second aspect, a gap is formed between the optical functional layer (32) and the polarizing sheet (27), or the like. Layers are arranged.

  The invention according to claim 4 is a liquid crystal panel (15) having a lower polarizing plate (14), an upper polarizing plate (13), and a liquid crystal layer (12) disposed between the lower polarizing plate and the upper polarizing plate. And an optical sheet (26) according to any one of claims 1 to 3 disposed on the lower polarizing plate side of the liquid crystal panel.

  According to a fifth aspect of the present invention, in the video source unit (10) according to the fourth aspect, an angle formed by the direction in which the transmission axis of the lower polarizing plate (14) extends and the direction in which the light transmission portion (33) extends is formed. It is 0 degree or more and 10 degrees or less by the front view of a liquid crystal panel (15).

  The invention according to claim 6 is a display device in which the video source unit (10) according to any one of claims 1 to 5 is housed in a housing.

  According to the present invention, it is possible to efficiently provide light that can pass through the lower polarizing plate with a simple configuration, and to improve the light utilization efficiency.

It is a disassembled perspective view explaining the image source unit 10 concerning one form. 4 is an exploded cross-sectional view showing a cross section of the video source unit 10. FIG. 4 is an exploded cross-sectional view showing a different cross section of the video source unit 10. FIG. FIG. 4 is an enlarged view paying attention to a polarizing sheet 27 in FIG. 3. FIG. 3 is an enlarged view paying attention to a base material layer 31 and an optical function layer 32 in FIG. 2. It is a figure explaining the angle | corner which the direction where the light transmission part 33 extends and the direction where the transmission axis of the lower polarizing plate 14 extends is formed. FIG. 7A illustrates the optical sheet 126, and FIG. 7B illustrates the optical sheet 226. 4 is an exploded cross-sectional view showing a cross section of the video source unit 310. FIG.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these forms. Further, in the drawings shown, a configuration having a size that cannot be actually observed with the naked eye is shown in an easy-to-understand manner by exaggerating or deforming it.

  FIG. 1 is a diagram illustrating one embodiment, and is an exploded perspective view showing a video source unit 10 included in a display device. 2 is a part of an exploded sectional view of the image source unit 10 taken along the line II-II in FIG. 1, and FIG. 3 is a line indicated by III-III in FIG. A part of the exploded cross-sectional view of the image source unit 10 when cut along the line is shown. In addition to the image source unit 10, the description of the display device is omitted, but the display device operates as a display device, such as a housing for housing the image source unit, a power source for operating the image source unit, and an electronic circuit for controlling the image source unit. It is equipped with the usual equipment required for. Hereinafter, the video source unit 10 will be described.

  The video source unit 10 includes a liquid crystal panel 15, a surface light source device 20, an optical sheet 26, and a functional film 40. In FIG. 1, the upper side of the paper is the observer side.

  The liquid crystal panel 15 includes an upper polarizing plate 13 disposed on the functional film 40 side (observer side), a lower polarizing plate 14 disposed on the optical sheet 26 side, and the upper polarizing plate 13 and the lower polarizing plate 14. And a liquid crystal layer 12 disposed therebetween. The polarizing plates 13 and 14 decompose the incident light into two orthogonal polarization components (P wave and S wave) and transmit the polarization component (for example, P wave) in one direction (direction parallel to the transmission axis). And has a function of absorbing a polarization component (for example, S wave) in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

  In the liquid crystal layer 12, a plurality of pixels are arranged vertically and horizontally in a direction along the layer surface, and an electric field can be applied to each region where one pixel is formed. Then, the orientation of the pixel to which an electric field is applied changes. Thereby, the polarization component (for example, P wave) parallel to the transmission axis transmitted through the lower polarizing plate 14 disposed on the optical sheet 26 side (that is, the light incident side) is polarized when passing through the pixel to which an electric field is applied. The direction is rotated by 90 °, while maintaining the polarization direction as it passes through a pixel to which no electric field is applied. Therefore, depending on whether or not an electric field is applied to the pixel, the polarization component (for example, P wave) transmitted through the lower polarizing plate 14 further passes through the upper polarizing plate 13 disposed on the light output side, or the upper polarizing plate 13 It is possible to control whether or not it is absorbed and blocked.

  In this way, the liquid crystal panel 15 has a structure for expressing an image by controlling transmission or blocking of light from the surface light source device 20 for each pixel.

The liquid crystal panel is configured to be able to provide an image to the observer based on such a principle. Therefore, when illuminating from the back side of the liquid crystal panel, it is possible to transmit light having a polarization component parallel to the transmission axis of the lower polarizing plate so as to transmit the lower polarizing plate and increase the light use efficiency. .
Furthermore, the liquid crystal panel is excellent in the contrast and efficiency (transmittance) of the emitted light with respect to the incident light from the normal direction of the liquid crystal panel due to its properties. However, with respect to the incident light obliquely with respect to the normal direction of the liquid crystal panel and the observation by the observer from the oblique direction, there are problems of a decrease in contrast and a low efficiency (transmittance). That is, increasing the incident light from the normal direction of the liquid crystal panel is also effective in increasing the light utilization efficiency.

  The kind of liquid crystal panel is not particularly limited, and examples thereof include known types of liquid crystal panels. These include, for example, TN, STN, VA, MVA, IPS, OCB, and the like.

Next, the surface light source device 20 will be described.
The surface light source device 20 is an illuminating device that is disposed on the side opposite to the observer side with respect to the liquid crystal panel 15 and emits planar light to the liquid crystal panel 15. As can be seen from FIGS. 1 to 3, the surface light source device 20 of the present embodiment is configured as an edge light type surface light source device, and includes a light guide plate 21, a light source 25, and a reflection sheet 39.

  As can be seen from FIGS. 1 to 3, the light guide plate 21 includes a base portion 22 and a back optical element 23. The light guide plate 21 is a plate-like member as a whole formed of a light-transmitting material. In this embodiment, one plate surface side that is an observer side of the light guide plate 21 is a smooth surface, and the other plate surface side opposite to this is a back surface, and a plurality of back optical elements 23 are provided on the back surface. Are arranged.

  Various materials can be used as the material forming the base 22 and the back optical element 23. However, a material that is widely used as a material for an optical sheet incorporated in a display device and has excellent mechanical characteristics, optical characteristics, stability, workability, and the like, and can be obtained at low cost can be used. For example, a polymer resin having an alicyclic structure, a methacrylic resin, a polycarbonate, a polystyrene, an acrylonitrile-styrene copolymer, a methyl methacrylate-styrene copolymer, an ABS resin, a polyethersulfone, or a thermoplastic resin, Examples thereof include epoxy acrylate and urethane acrylate-based reactive resins (ionizing radiation curable resins and the like).

  The base portion 22 is a plate having a predetermined thickness at a portion that serves as a base of the back surface optical element 23 while light is guided therein.

The back surface optical element 23 is a protruding element formed on the back surface side of the base portion 22 (the side opposite to the side on which the optical sheet 26 is disposed), and has a triangular prism shape in this embodiment. The back optical element 23 has a columnar shape in which the protruding top ridge line extends in the left-right direction in FIG. 1, and a plurality of back optical elements 23 are arranged side by side at a predetermined pitch in a direction orthogonal to the extending direction. The back optical element 23 of this embodiment has a triangular cross section, but is not limited to this, and may be a cross section of any shape such as a polygon, a hemisphere, a part of a sphere, or a lens shape.
The arrangement direction of the plurality of back surface optical elements 23 is preferably the light guide direction. That is, the ridge lines of the respective back surface optical elements 23 extend in parallel to the direction in which the light sources 25 are arranged, or in the direction in which the light sources 25 extend if they are one long light source.

  The “triangular shape” in the present specification includes not only a triangular shape in a strict sense but also a substantially triangular shape including limitations in manufacturing technology, errors in molding, and the like. Similarly, terms used in the present specification to specify other shapes and geometric conditions, for example, terms such as “parallel”, “orthogonal”, “ellipse”, “circle”, etc. are bound to the strict meaning. Therefore, it should be interpreted including an error to the extent that a similar optical function can be expected.

  The light guide plate 21 having such a configuration can be manufactured by extrusion molding or by molding the back optical element 23 on the base 22. In the light guide plate 21 manufactured by extrusion molding, the base portion 22 and the back surface optical element 23 can be integrally formed. Moreover, when manufacturing the light-guide plate 21 by shaping | molding, the back surface optical element 23 may be the same resin material as the base 22, or a different material.

The light source 25 will be described. In this embodiment, the light source 25 is disposed on one side surface in the direction in which the plurality of back surface optical elements 23 are arranged among the side surfaces of the base portion 22 of the light guide plate 21. The type of the light source is not particularly limited, but can be configured in various forms such as a fluorescent lamp such as a linear cold cathode tube, a point LED (light emitting diode), or an incandescent bulb. In this embodiment, the light source 25 is composed of a plurality of LEDs, and is configured to be able to individually and independently adjust the lighting and extinction of each LED and / or the lighting brightness of each LED by a control device (not shown). Yes.
In this embodiment, the light source 25 is disposed on the side surface on one side as described above. However, the light source may be disposed on the side surface opposite to the side surface. In this case, the shape of the back optical element is also formed following a known example.

  The reflection sheet 39 is a member that reflects the light emitted from the back surface of the light guide plate 21 and makes the light enter the light guide plate 21 again. The reflection sheet 39 is a sheet that is capable of so-called specular reflection, such as a sheet made of a material having a high reflectivity such as a metal, or a sheet including a thin film (for example, a metal thin film) made of a material having a high reflectivity as a surface layer. It can be preferably applied.

  Next, the optical sheet 26 will be described. The optical sheet 26 is disposed between the surface light source device 20 and the liquid crystal panel 15, and controls the light emitted from the surface light source device 20 to be transmitted through the liquid crystal panel 15. In this embodiment, the optical sheet 26 includes a polarizing sheet 27, a base material layer 31 formed in a sheet shape, and an optical functional layer provided on one surface of the base material layer 31 (the surface on the polarizing sheet 27 side in this embodiment). 32. In this embodiment, the optical sheet 26 is arranged with a predetermined gap with respect to the surface light source device 20 and the liquid crystal panel 15.

  The polarizing sheet 27 is a sheet that transmits the same polarized light as the polarized light (for example, P wave) transmitted through the lower polarizing plate and reflects polarized light (for example, S wave) different from the polarized light. The structure of the polarizing sheet 27 is shown enlarged in FIG. FIG. 4 is a view from the same viewpoint as FIG. As can be seen from FIG. 4, the polarizing sheet 27 is provided with a transparent uneven layer 29 on a transparent substrate 28, and a metal thin film 30 having a certain thickness is laminated on the surface of the transparent uneven layer 29.

The transparent substrate 28 is a flat sheet-like member that supports the transparent uneven layer 29 and the metal thin film 30.
Various materials can be used as the material forming the transparent substrate 28. However, a material that is widely used as a material for an optical sheet incorporated in a display device and has excellent mechanical characteristics, optical characteristics, stability, workability, and the like, and can be obtained at low cost can be used. Examples thereof include polyethylene terephthalate (PET), triacetyl cellulose (TAC), methacrylic resin, polycarbonate and the like. Among these, it is preferable to use TAC, methacrylic resin, and polycarbonate with little birefringence in consideration of the combination with the lower polarizing plate 14.

  In the transparent concavo-convex layer 29, the unit convex portion 29 a having a triangular cross section in the cross section shown in FIG. 4 maintains the cross section in a predetermined direction (a direction orthogonal to the paper surface of FIG. 4) along the surface of the transparent substrate 28. A plurality of unit convex portions 29a are arranged in a direction (left and right direction in FIG. 4) perpendicular to the predetermined direction (the direction in which the ridge line of the unit convex portion 29a extends).

  Examples of the material constituting the transparent uneven layer 29 include ionizing radiation curable resins including ultraviolet curable resins such as epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, and polythiol. .

  The metal thin film 30 is a layer formed of a thin film of metal such as aluminum laminated on the surface of the transparent uneven layer 29.

  Accordingly, the polarizing sheet 27 is a concave and convex surface having a triangular wave cross section composed of a groove line 30a and a ridge line 30b that are continuously repeated at a constant period A in the left-right direction of FIG. 4 and is orthogonal to the paper surface of FIG. Includes a continuous triangular metal wave surface having a constant period A.

  When random polarized light (naturally polarized light) L41 is incident on the polarizing sheet 27 having such a configuration substantially perpendicularly to the surface of the transparent substrate 28, it is parallel to the direction in which the groove line 30a and the ridge line 30b extend (in the plane of FIG. 4). The component of linearly polarized light (S-polarized light) having an electric field vector that oscillates in an orthogonal direction) is a polarized light component in the same direction as incident light because electrons are vibrated in the metal thin film 30 in parallel with the groove line 30a and the ridge line 30b. Are reflected in the opposite direction, and as a result, the S-polarized light is reflected as reflected light L42 (however, the reflected light L42 in the figure is an optical path example and is a conceptual diagram). On the other hand, the component of linearly polarized light (P-polarized light) having an electric field vector that vibrates in a direction orthogonal to the direction in which the groove line 30a and the ridgeline 30b extend (the arrangement direction of the unit convex portions 29a, the left-right direction in FIG. 4), Since such electron vibration cannot be excited, it enters the metal thin film 30 and reaches the back surface and is transmitted as transmitted light L43. When random polarization, which is a combined light of S-polarized light and P-polarized light, is incident on the polarizing sheet 27, it can be separated into S-polarized light of reflected light and P-polarized light of transmitted light.

  Here, the direction in which the transmission axis of the polarizing sheet 27 extends (that is, the direction orthogonal to the direction in which the groove line 30a and the ridge line 30b extend, the direction in which the groove line 30a and the ridge line 30b are alternately arranged) is the direction of the lower polarizing plate 14 described above. It is the same as the direction in which the transmission axis extends, and is 0 ° or more and 10 ° or less in the front view of the image source unit 10 with respect to the direction in which the light transmission portion 33 and the light absorption portion 34 of the optical function layer 32 described later extend. It is preferable.

Here, the polarizing sheet 27 preferably satisfies the following conditions. Thereby, S polarized light and P polarized light can be efficiently separated.
The size of the interval (constant period) A (μm) between adjacent ridge lines 30a is preferably 1 μm or less, more preferably 0.1 μm or more and 0.2 μm or less. Further, the height h (μm) of the ridge line 30b with respect to the groove line 30a is preferably 1 μm or less, more preferably 0.2 μm or more and 0.4 μm or less. Furthermore, the thickness d (μm) of the metal thin film 30 in the direction perpendicular to the transparent substrate 28 (thickness direction of the transparent substrate 28) is preferably 0.01 μm or more. When the thickness d of the metal thin film 30 is less than 0.010 μm, the transmittance of S-polarized light increases and the extinction ratio decreases. Even if the thickness d is increased, if the height h with respect to the period A is increased, the thickness in the direction perpendicular to the slope of the protrusion of the metal thin film 30 is reduced, and the extinction ratio between S-polarized light and P-polarized light is improved. Therefore, the upper limit of the thickness d of the metal thin film 30 cannot be set.

  As a metal material that can be used for the metal thin film 30, aluminum (Al) having a refractive index close to 0 and an extinction coefficient of about 5 is preferable, and gold (Au) and silver (Ag) are suitable accordingly.

  In the present embodiment, the example in which the cross section of the unit convex portion 29a is a triangle and the metal thin film 30 is also a triangular cross section has been described. However, the cross sectional shape is not limited to this and may be a rectangle, a semicircle, A form including a curve in part or all, such as a semi-ellipse, may be used.

The polarizing sheet 27 can be manufactured as follows, for example. That is, first, an original plate is prepared. The original plate is a mold in which unevenness corresponding to the transparent uneven layer 29 is formed on the surface thereof. The unevenness can be formed by nano / micro cutting, lithography, two-beam interference exposure method, or the like.
Next, a laminate in which an uncured ultraviolet curable resin is applied to one surface of the transparent substrate 28 is prepared, pressed against the original obtained from the ultraviolet curable resin, and cured from the original by peeling off the original.
Then, aluminum vacuum deposition is performed on the cured ultraviolet curable resin.

  Thus, since the polarizing sheet 27 has a simple structure, it is easier to manufacture than the conventional reflective polarizing plate.

Returning to FIGS. 1 to 3, the base material layer 31 will be described. The base material layer 31 is a flat sheet-like member having translucency that supports the optical functional layer 32.
Various materials can be used as the material forming the base material layer 31. However, a material that is widely used as a material for an optical sheet incorporated in a display device and has excellent mechanical characteristics, optical characteristics, stability, workability, and the like, and can be obtained at low cost can be used. Examples thereof include polyethylene terephthalate (PET), triacetyl cellulose (TAC), methacrylic resin, polycarbonate and the like. Among these, considering the combination of the surface light source device 20 and the lower polarizing plate 14, it is preferable to use TAC, methacrylic resin, and polycarbonate having a low birefringence.

  The optical functional layer 32 is a layer laminated on one surface of the base material layer 31 (in this embodiment, the surface on the polarizing sheet 27 side), and the light transmitting portions 33 and the light absorbing portions 34 are alternately arranged along the layer surface. ing. FIG. 5 is an enlarged view showing a part of FIG. 2 while paying attention to the base material layer 31 and the optical function layer 32. In the present embodiment, the optical functional layer 32 and the polarizing sheet 27 are arranged apart from each other.

The optical functional layer 32 has a shape having the cross section shown in FIG. 5 and extending in a direction perpendicular to the paper surface. That is, the light transmission part 33 having a substantially trapezoidal shape in the cross section shown in FIG. 5 and the light absorption part 34 having a substantially trapezoidal cross section formed between two adjacent light transmission parts 33 are provided. ing.
Here, as conceptually shown in FIG. 6, when the image source unit 10 is viewed from the front side of the observer side, the direction in which the light transmitting portion 33 and the light absorbing portion 34 extend as indicated by the solid line VIa and the dotted line VIb are indicated. The angle θ _s formed by the direction in which the transmission axis of the lower polarizing plate 14 extends is preferably 0 ° or more and 10 ° or less. Thereby, it can suppress that a polarization component changes with the reflection in the interface of the light transmission part 33 and the light absorption part 34, and also becomes an optical sheet with further sufficient transmission efficiency.
That is, the relationship with the polarizing sheet 27 is the same as the direction in which the light transmitting portion 33 and the light absorbing portion 34 extend and the direction in which the transmission axis of the polarizing sheet 27 extends when the image source unit 10 is viewed from the front on the viewer side. It is preferable that the angle formed by is also 0 ° or more and 10 ° or less. Therefore, when the image source unit 10 is viewed from the front side of the viewer, the direction in which the light transmitting portion 33 and the light absorbing portion 34 extend intersects with the direction in which the groove line 30a and the ridge line 30b extend at 80 ° or more and 90 ° or less. Preferably it is.

  The light transmission part 33 is a part whose main function is to transmit light. In this embodiment, in the cross section shown in FIGS. 2 and 5, a long bottom on the base material layer 31 side, the opposite side (light guide plate side) ) Having a substantially trapezoidal cross-sectional shape having a short upper base. The light transmissive portions 33 maintain the cross section along the layer surface of the base material layer 31 and extend in the above-described direction, and are arranged at a predetermined interval in a direction different from the extending direction. And between the adjacent light transmission parts 33, the intermediate part which has a substantially trapezoidal cross section is formed. Accordingly, the intermediate portion has a trapezoid having a long lower base on the upper base side (surface light source device 20 side) of the light transmission portion 33 and a short upper base on the lower base side (liquid crystal panel 15 side) of the light transmission portion 33. The light absorption part 34 is formed by having a cross section and filling a necessary material described later. In this embodiment, the adjacent light transmission parts 33 are connected on the long bottom side.

The light transmission portion 33 has a refractive index is a N _t. Such a light transmission part 33 can be formed by hardening a transmission part constituent composition. Details will be described later. While not the value of the refractive index N _t is particularly limited, the refractive index from the viewpoint of (. Including total reflection) appropriately reflect light at the interface between the light absorbing portion 34 in the slope of a trapezoidal cross-section, as described below Is preferably 1.55 or more. However, since a material with a refractive index that is too high is likely to break, the refractive index is preferably 1.61 or less. More preferably, it is 1.56 or less.

The light absorption part 34 is an intermediate part arranged between the adjacent light transmission parts 33 and arranged at the above-described interval, and has a cross-sectional shape similar to the cross-sectional shape of the interval. Therefore, the short upper base faces the liquid crystal panel 15 side, and the long lower base becomes the light guide plate 21 side. And the light absorption part 34 is comprised so that light can be absorbed while a refractive index is set to _Nr . Specifically, light absorbing particles are dispersed in a binder having a refractive index of _Nr . Refractive index N _r is a refractive index lower than the refractive index N _t of the light transmitting portion 33. Thus, by making the refractive index of the light absorbing portion 34 smaller than the refractive index of the light transmitting portion 33, the light incident on the light transmitting portion 33 under a predetermined condition is appropriately totally reflected at the interface with the light absorbing portion 34. Can be made. Even when the total reflection condition is not satisfied, some light is reflected at the interface.
The value of the refractive index _Nr is not particularly limited, but is preferably 1.50 or less from the viewpoint of appropriately performing the total reflection, and more preferably 1.47 or more from the viewpoint of availability. More preferably, it is 1.49 or more.

The difference in refractive index between the refractive index _Nt of the light transmitting portion 33 and the refractive index _Nr of the light absorbing portion 34 is not particularly limited, but is preferably 0.05 or more and 0.14 or less. By increasing the refractive index difference, more light can be totally reflected.

The optical function layer 32 is not particularly limited, but for example, the light transmission part 33 and the light absorption part 34 are formed as follows. That is, it is preferable that the pitch of the light transmission part 33 and the light absorption part 34 represented by _Pk in FIG. 5 is 20 μm or more and 100 μm or less. Further, the angle formed by the interface on the hypotenuse between the light absorbing portion 34 and the light transmitting portion 33 indicated by θ _k in FIG. 5 and the normal of the layer surface of the optical functional layer 32 is 1 ° or more and 10 ° or less. Is preferred. And it is preferable that the thickness of the light absorption part 33 shown by _Dk in FIG. 5 is 50 micrometers or more and 150 micrometers or less. By being within these ranges, the balance between light transmission and light absorption is often appropriate.

  In this embodiment, an example in which the interface between the light transmitting portion 33 and the light absorbing portion 34 is straight in the cross section is shown. However, the present invention is not limited to this, and may be a polygonal line shape, a convex curved surface shape, a concave curved surface shape, or the like. Also good. Moreover, the cross-sectional shape may be the same in the some light transmissive part 33 and the light absorption part 34, and a different cross-sectional shape may have predetermined regularity.

  According to the optical function layer 32, as will be described later, the function of changing the traveling direction of light incident from the light incident side and emitting the light from the light output side to intensively improve the luminance in the front direction (normal direction) ( (Condensing function). In this case, the change of the polarization component is suppressed, and the light use efficiency can be enhanced by these functions. Furthermore, it has a function (light absorption function) for absorbing light traveling at a large angle with respect to the front direction.

The optical function layer 32 can be produced as follows, for example.
First, the light transmission part 33 is formed in the base material layer 31. This inserts the base material sheet used as the base material layer 31 between the mold roll which has the shape which can transfer the shape of the light transmission part 33 on the surface, and the nip roll arrange | positioned so as to oppose this. At this time, the mold roll and the nip roll are rotated while supplying the composition constituting the light transmitting portion between the base sheet and the mold roll. As a result, a groove corresponding to the light transmitting portion formed on the surface of the mold roll (a shape obtained by reversing the shape of the light transmitting portion) is filled with the composition that constitutes the light transmitting portion, and the composition becomes the surface of the mold roll. It will be along the shape.

  Here, examples of the composition constituting the light transmission part include ionizing radiation curable resins such as epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, and polythiol.

  Light for curing with a light irradiation device is irradiated from the substrate sheet side to the composition constituting the light transmission portion sandwiched between the mold roll and the substrate sheet and filled therein. Thereby, a composition can be hardened and the shape can be fixed. And the base material layer 31 and the shape | molded light transmission part 33 are released from a metal mold | die roll with a mold release roll.

  Next, the light absorption part 34 is formed. In order to form the light absorption part 34, first, the composition constituting the light absorption part is filled in the interval between the light transmission parts 33 formed above. Thereafter, the surplus composition is scraped off with a doctor blade or the like. Then, the remaining composition can be cured by irradiating with ultraviolet rays from the light transmitting portion 33 side to form the light absorbing portion 34.

  The material used as the light absorbing portion is not particularly limited, but is colored in a photocurable resin such as urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate. And a composition in which the light absorbing particles are dispersed.

Further, instead of dispersing the light absorbing particles, the entire light absorbing portion can be colored with a pigment or a dye.
When using light-absorbing particles, light-absorbing colored particles such as carbon black are preferably used. However, the present invention is not limited to these, and selectively absorbs a specific wavelength according to the characteristics of image light. Colored particles may be used. Specific examples include organic fine particles colored with metal salts such as carbon black, graphite, and black iron oxide, dyes, pigments, colored glass beads, and the like. In particular, colored organic fine particles are preferably used from the viewpoints of cost, quality, availability, and the like. The average particle diameter of the colored particles is preferably 1.0 μm or more and 20 μm or less.

  Thereby, the optical functional layer 32 can be laminated on one surface of the base material layer 31.

  Returning to FIGS. 1 to 3, the functional film 40 will be described. The functional film 40 is a layer that is disposed on the light output side of the liquid crystal panel 15 and has functions of improving the quality of the video light and protecting the video source unit 10. Examples thereof include an antireflection film, an antiglare film, a hard coat film, a color tone correction film, a light diffusion film, and the like, and these are constituted by combining them alone or in combination.

  Next, the operation of the display device having the above configuration will be described with an example of the optical path. However, the optical path example is conceptual for explanation, and does not strictly represent the degree of reflection or refraction.

  First, as shown in FIG. 2, the light emitted from the light source 25 enters the light guide plate 21 through the light incident surface on the side surface of the light guide plate 21. FIG. 2 shows an example of an optical path of the light L21 and L22 incident on the light guide plate 21 from the light source 25 as an example.

  As shown in FIG. 2, the light L21 and L22 incident on the light guide plate 21 repeats total reflection due to a difference in refractive index with air on the light exit side surface of the light guide plate 21 and the back surface on the opposite side, thereby guiding the light guide direction (FIG. Proceed to the right of page 2).

  However, the back optical element 23 is disposed on the back surface of the light guide plate 21. For this reason, as shown in FIG. 2, the light L21, L22 traveling in the light guide plate 21 has its traveling direction changed by the back surface optical element 23, and is incident on the light exit surface and the back surface at an incident angle less than the total reflection critical angle. There is also. In this case, the light can be emitted from the light exit surface of the light guide plate 21 and the back surface on the opposite side.

  Lights L21 and L22 emitted from the light exit surface travel to the optical sheet 26 disposed on the light exit side of the light guide plate 21. On the other hand, the light emitted from the back surface is reflected by the reflection sheet 39 disposed on the back surface of the light guide plate 21, enters the light guide plate 21 again, and travels through the light guide plate 21.

  The light traveling in the light guide plate 21 and the light whose direction is changed by the back surface optical element 23 and reaching the light exit surface at an incident angle less than the total reflection critical angle are in each area along the light guide direction in the light guide plate 21. Arise. For this reason, the light traveling in the light guide plate 21 is gradually emitted from the light exit surface. Thereby, the light quantity distribution along the light guide direction of the light emitted from the light exit surface of the light guide plate 21 can be made uniform.

The light emitted from the light guide plate 21 then reaches the polarizing sheet 27 of the optical sheet 26. Here, light in the polarization direction along the transmission axis of the polarizing sheet 27 passes through the polarizing sheet 27 and travels toward the optical function layer 32.
On the other hand, the light in the polarization direction along the reflection axis of the polarizing sheet 27 is reflected and returned to the light guide plate 21 side as indicated by dotted arrows L21 ′ and L22 ′ in FIG. The returned light is reflected by the light guide plate 21, the back optical element 23, or the reflection sheet 39 and travels again toward the optical sheet 26. During this reflection, the polarization direction of a part of the light is changed, and a part of the light is transmitted through the polarizing sheet 27. Other light is returned to the light guide plate side again. Thus, the light reflected by the polarizing sheet 27 can be transmitted through the reflecting sheet 27 by repeating the reflection. Thereby, the utilization factor of the light from the light source 25 is increased.
Here, the light emitted from the polarizing sheet 27 has a polarization direction in a direction along the transmission axis of the lower polarizing plate 14 and is polarized light transmitted through the lower polarizing plate 14.

The light emitted from the polarizing sheet 27 enters the optical function layer 32. The light incident on the optical functional layer 32 is polarized light that passes through the lower polarizing plate 14 and travels with the following optical path. That is, for example, as indicated by L51 in FIG. 5, the light is transmitted through the light transmitting portion 33 without reaching the interface with the light absorbing portion 34. Alternatively, as indicated by L52 in FIG. 5, the light reaches the interface with the light absorbing portion 34 and is totally reflected and passes through the light transmitting portion 33. At this time, in this embodiment, the light reflected by the interface is brought closer to the direction parallel to the normal line of the liquid crystal panel 15 by the action of the inclination angle (θ _k ) of the interface. In addition, since the angle is smaller than the total reflection critical angle, some of the light that does not totally reflect is reflected at the interface. Such light also passes through the light transmitting portion 33 in the same manner.
As a result, it is possible to effectively provide the liquid crystal panel 15 with light that does not cause problems such as a decrease in contrast and color inversion when transmitted through the liquid crystal panel 15. Furthermore, when the direction in which the light transmission part 33 and the light absorption part 34 extend is an angle of 0 ° or more and 10 ° or less in front view with respect to the direction in which the transmission axis of the lower polarizing plate 14 extends, It is possible to prevent the polarization direction from being changed during reflection and reflection. Therefore, most of the total reflected and reflected light at the interface can be transmitted through the lower polarizing plate 14 and the utilization efficiency (transmittance) can be improved.

  On the other hand, as indicated by L53 in FIG. 5, the light incident on the optical function layer 32 at a large angle with respect to the normal to the sheet surface is absorbed by the light absorbing portion 34 and is not provided to the liquid crystal panel 15. Accordingly, it is possible to absorb light that causes a problem such as a decrease in contrast and color inversion.

As described above, the optical sheet 26 in which the polarizing sheet 27 and the optical functional layer 32 are combined can effectively prevent unnecessary light from being emitted and improve the luminance of the light transmitted through the liquid crystal panel. The polarizing sheet 27 transmits light that passes through the lower polarizing plate 14, and other light is reflected to be reused to improve the light use efficiency. The optical function layer 32 efficiently collects and collects the light. Since the light that has not been emitted is absorbed by the light absorbing portion, appropriate light can be efficiently provided to the liquid crystal panel. Therefore, the light utilization efficiency can be greatly improved by the combination of both.
In addition, when the relationship between the direction in which the light transmission part 33 and the light absorption part 34 extend and the light transmission axis of the lower polarizing plate 14 is an angle of 0 ° or more and 10 ° or less in front view, total reflection and reflection at the interface. When doing, it can suppress that a polarization direction changes. According to this, the polarization direction of the light in the polarization direction transmitted through the lower polarizing plate 14 is maintained and provided to the lower polarizing plate 14, and the light absorbed by the lower polarizing plate 14 can be suppressed to a low level. It is possible to improve utilization efficiency (transmittance).

  In the present invention, since a polarizing sheet having a structure in which a metal thin film is formed on an uneven surface is used, a simpler structure than that of a conventional reflective polarizing plate can be achieved.

  Further, the optical path will be described. The light emitted from the surface light source device 20 as described above enters the lower polarizing plate 14 of the liquid crystal panel 15. The lower polarizing plate 14 transmits one polarization component of incident light and absorbs the other polarization component. The light transmitted through the lower polarizing plate 14 selectively passes through the upper polarizing plate 13 according to the state of electric field application to each pixel. In this way, the liquid crystal panel 15 selectively transmits light from the surface light source device 20 for each pixel, so that an observer of the liquid crystal display device can observe an image. At that time, the image light is provided to the observer through the functional film 40, and the quality of the image is improved.

  In the above-described form, the optical functional layer 32 has a direction in which the short upper base of the light transmitting portion 33 is on the light guide plate 21 side and the long lower base is on the liquid crystal panel 15 side, but this may be reversed. In other words, the short upper base of the light transmission part may be oriented toward the liquid crystal panel and the long lower base toward the light guide plate. In this case, it does not have a light condensing function, but it can provide light to the lower polarizing plate while maintaining the polarization direction transmitted through the lower polarizing plate, and can suppress the light absorbed by the lower polarizing plate, It is possible to improve the light utilization efficiency (transmittance).

FIG. 7A is a diagram illustrating the second embodiment, and a part of the optical sheet 126 is enlarged. FIG. 7B is a diagram for explaining the third embodiment, and a part of the optical sheet 226 is enlarged. FIGS. 7A and 7B are views from the same direction as FIG.
In the optical sheet 126 shown in FIG. 7A, the transparent base material 28 of the polarizing sheet 27 is adhered and pasted to the optical functional layer 32 by the adhesive layer 136. In this way, the components of the optical sheet may be integrated.
On the other hand, in the optical sheet 226 shown in FIG. 7B, a polarizing sheet 227 is laminated on the surface of the optical functional layer 32 opposite to the surface on which the base material layer 31 is disposed. The polarizing sheet 227 does not have a transparent base material, and is formed only from the uneven layer 29 and the metal thin film 30. In this embodiment, the concavo-convex layer 29 and the metal thin film 30 are formed directly on the surface of the optical functional layer 32. According to this, in addition to the components of the optical sheet being integrated, the transparent substrate can be omitted.

  Moreover, although the example which separated the liquid crystal panel and the optical sheet was shown in the said form, it is not restricted to this, An optical sheet may be laminated | stacked directly on a liquid crystal panel. In that case, the aspect of the optical sheet is not limited, and any of the above-described optical sheets 26, 126, and 226 may be used.

  FIG. 8 is a diagram for explaining the layer structure of the video source unit 310 according to the fourth embodiment. FIG. 8 corresponds to FIG. As can be seen from FIG. 8, the image source unit 310 includes an optical sheet 326 instead of the optical sheet 26, and the optical functional layer 32 is disposed on the light exit surface side of the surface light source device 20 in the optical sheet 326. A polarizing sheet 27 is provided closer to the liquid crystal panel 15 than 32. The video source unit 310 can also efficiently use light from the light source.

FIG. 8 shows light L81 and L82 which are examples of optical paths. Lights L81 and L82 emitted from the light guide plate 21 in the same manner as the lights L21 and L22 illustrated in FIG. 2 enter the light transmitting portion 33 of the optical sheet 326. The lights L81 and L82 reach the interface with the light absorbing portion 34, and are totally reflected and pass through the light transmitting portion 33. At this time, the light reflected at the interface is brought closer to a direction parallel to the normal line of the liquid crystal panel 15 by the action of the inclination angle (θ _k ) of the interface. In addition, since the angle is smaller than the total reflection critical angle, some of the light that does not totally reflect is reflected at the interface. Such light also passes through the light transmitting portion 33 in the same manner.
As a result, it is possible to effectively provide the liquid crystal panel 15 with light that does not cause problems such as a decrease in contrast and color inversion when transmitted through the liquid crystal panel 15. At this time, when the light transmitting portion 33 and the light absorbing portion 34 extend in an angle of 0 ° or more and 10 ° or less when viewed from the front with respect to the direction in which the transmission axis of the lower polarizing plate 14 extends, At the time of total reflection and reflection, it is possible to suppress at least the polarization component in the direction in which the transmission axis of the polarizing sheet 27 and the lower polarizing plate 14 extends. And most of the light reflected and reflected at the interface can be transmitted through the polarizing sheet 27 and the lower polarizing plate 14, and the light utilization efficiency (transmittance) can be improved.

Lights L <b> 81 and L <b> 82 emitted from the optical function layer 32 and the base material layer 31 reach the polarizing sheet 27. Here, light in the polarization direction along the transmission axis of the polarizing sheet 27 passes through the polarizing sheet 27 and travels toward the liquid crystal panel 15.
On the other hand, the light in the polarization direction along the reflection axis of the polarizing sheet 27 is reflected and returned to the optical functional layer 32 side as indicated by dotted arrows L81 ′ and L82 ′ in FIG. The returned light is reflected by the base material layer 31, the optical function layer 32, the light guide plate 21, the back surface optical element 23, or the reflection sheet 39 and travels again toward the polarizing sheet 27. During this reflection, the polarization direction of a part of the light is changed, and a part of the light is transmitted through the polarizing sheet 27. Other light is returned to the optical function layer 32 side again. Thus, the light reflected by the polarizing sheet 27 can be transmitted through the polarizing sheet 27 by repeating the reflection. Thereby, the utilization factor of the light from the light source 25 is increased.
Here, the light emitted from the polarizing sheet 27 has the polarization direction along the transmission axis of the lower polarizing plate 14 and is polarized light that passes through the lower polarizing plate 14.

  In the image source unit 310 having such a configuration, the components of the optical sheet 326 can be integrally formed according to the above example, or the optical sheet 326 can be directly laminated on the liquid crystal panel 15.

DESCRIPTION OF SYMBOLS 10 Image source unit 15 Liquid crystal panel 20 Surface light source device 21 Light guide plate 25 Light source 26 Optical sheet 27 Polarizing sheet 29 Concavity and convexity layer 30 Metal thin film 32 Optical functional layer 33 Light transmission part 34 Light absorption part

Claims (6)

An optical sheet disposed between a light source and a liquid crystal panel,
An optical functional layer and a polarizing sheet;
The optical functional layer is
A light transmissive portion having a predetermined cross section, extending in one direction along the sheet surface, and arranged in a direction different from the extending direction at a predetermined interval;
A light absorbing portion formed at the interval between the adjacent light transmitting portions, and
The polarizing sheet is
A concavo-convex layer having unit protrusions having a predetermined cross section and extending in one direction along the sheet surface and arranged in a direction different from the extending direction with a period of 1 μm or less,
A metal thin film laminated on the uneven layer,
Optical sheet.   The optical sheet according to claim 1, wherein the extending direction of the light transmission part and the extending direction of the uneven layer are orthogonal to each other in a front view.   The optical sheet according to claim 1, wherein a gap is formed between the optical functional layer and the polarizing sheet, or another layer is disposed. A lower polarizing plate, an upper polarizing plate, and a liquid crystal panel having a liquid crystal layer disposed between the lower polarizing plate and the upper polarizing plate;
An image source unit comprising: the optical sheet according to claim 1 disposed on the lower polarizing plate side of the liquid crystal panel.   5. The video source unit according to claim 4, wherein an angle formed by a direction in which a transmission axis of the lower polarizing plate extends and a direction in which the light transmission portion extends is 0 ° or more and 10 ° or less in a front view of the liquid crystal panel.   A display device in which the video source unit according to claim 1 is housed in a housing.

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