JP2017167506A - Image source unit and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image source unit capable of improving use efficiency of light from a light source and enhancing qualities of a screen while having a layer having a light-transmitting portion and an interval portion.SOLUTION: The image source unit includes: 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 30 disposed on the lower polarizing plate side of the liquid crystal panel. The optical sheet includes a base material layer 31, an optical functional layer 32 disposed on one surface of the base material layer, and an adhesive layer 35 disposed on the other surface of the base material layer. The optical functional layer includes: a light-transmitting portion 33 having a predetermined cross-section and extending in one direction along the surface of the base material layer, and arranged in a plurality of numbers at a predetermined interval in a direction different from the extending direction; and an interval portion 34 formed between adjoining light-transmitting portions. The lower polarizing plate of the liquid crystal panel is bonded to the optical sheet with the adhesive layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image source unit that provides an image to an observer, 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, 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.

Patent Document 1 discloses a video source unit in which a surface light source, a prism sheet, an optical functional layer (a layer in which light transmitting portions and light absorbing portions are alternately arranged), and a liquid crystal panel are stacked in this order. Yes. Thereby, the direction of the light incident on the liquid crystal panel is brought close to the normal direction of the panel surface of the liquid crystal panel, and the light use efficiency is increased.
Similarly, in Patent Document 2, a light source, a brightness enhancement film (a sheet in which a plurality of prisms whose tops face the viewer side), a reflective polarizing film, and an LCF (light transmission portions and light absorption portions are alternately arranged). An arrangement in which the arranged film) and the liquid crystal panel are arranged in this order is disclosed. Thereby, the direction of the light emitted from the light source can be brought close to the normal direction of the panel surface of the liquid crystal panel, and the light use efficiency is improved. In addition, light incident on the LCF at a large angle with respect to the panel surface of the liquid crystal panel is absorbed by the light absorbing portion provided here.

JP 2010-217871 A Special table 2011-501219 gazette

  However, the optical functional layer described in Patent Documents 1 and 2 (LCF in Patent Document 2) includes a light absorbing portion as an intermediate portion between the light transmitting portions, so that some of the effective light is absorbed. There is.

  In addition, since the optical functional layer forms a stripe pattern between the light transmitting portion and the light absorbing portion, moire interference fringes may occur due to the relationship with the pixels of the liquid crystal panel.

  Accordingly, in view of the above problems, the present invention provides a video source unit that can improve the use efficiency of light from a light source and improve the quality of a screen while having a layer having a light transmission part and an intermediate part. The task is to do. In addition, a display device including the video source unit is 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.

  One embodiment of the present invention includes a lower polarizing plate (14), an upper polarizing plate (13), and a liquid crystal panel (15) having a liquid crystal layer (12) disposed between the lower polarizing plate and the upper polarizing plate. An optical sheet (30) disposed on the lower polarizing plate side of the liquid crystal panel, and the optical sheet comprises a base material layer (31) and an optical functional layer (32) disposed on one surface of the base material layer. And the pressure-sensitive adhesive layer (35) disposed on the other surface of the base material layer, and the optical functional layer has a predetermined cross section and extends in one direction along the surface of the base material layer and extends. A plurality of light transmission portions (33) arranged in a direction different from the direction at a predetermined interval, and a space portion (34) formed between adjacent light transmission portions, and a lower polarizing plate of the liquid crystal panel, An image source unit (10) in which an optical sheet is attached with an adhesive layer.

  In the image source unit (10), the optical sheet (30) may be provided with light scattering means (31a, 35) between the optical functional layer (32) and the lower polarizing plate (14).

  Moreover, as said light-scattering means, the rough surface (31a) is provided in the surface which forms an interface with an adhesive layer (35) among base material layers (31), and a base material layer and an adhesive layer And have a refractive index difference.

  Further, as the light scattering means, light scattering particles may be dispersed in the pressure-sensitive adhesive layer.

  In the image source unit (10), the 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 part (33) extends is 1 ° or more 41 in front view of the liquid crystal panel (15). .7 ° or less.

  In the video source unit (10), the 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 part (33) extends is 1 ° or more and 20 ° or less in a front view of the liquid crystal panel. Also good.

  The video source unit (10) further includes a reflective polarizing plate (28), and an angle formed between a direction in which the transmission axis of the reflective polarizing plate extends and a direction in which the light transmission portion (33) extends is The liquid crystal panel (15) can be provided so as to be 1 ° or more and 41.7 ° or less when viewed from the front.

  Further, the reflection type polarizing plate (28) has an angle formed by the direction in which the transmission axis of the reflection type polarizing plate extends and the direction in which the light transmission part (33) extends is 1 in a front view of the liquid crystal panel (15). It may be not less than 20 ° and not more than 20 °.

  The optical sheet (30) and the reflective polarizing plate (28) may be directly laminated.

  Of the image source unit (10), the light transmission part (33) has a trapezoidal cross section, in which the long lower base is the liquid crystal panel (15) side and the short upper base is the liquid crystal panel (15). You may install so that it may face the other side.

  Further, a light absorbing material may be contained in the interspace (34).

  A display device housed in the video source unit housing can be provided.

  According to the present invention, it is possible to provide light efficiently and improve the light utilization efficiency.

FIG. 2 is a perspective view for explaining a video source unit 10. 3 is a cross-sectional view of the video source unit 10. FIG. 4 is another cross-sectional view of the video source unit 10. FIG. It is a figure explaining polarizing sheet 28 '. It is the figure which expanded the part paying attention to the optical sheet 30 among FIG. 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. 6 is an enlarged cross-sectional view of a part of the optical sheet 130. 4 is an enlarged cross-sectional view of a part of an optical sheet 230. FIG. 3 is a perspective view illustrating a video source unit 310. FIG. is a graph showing the relationship between theta _S and the transmittance ratio T _P.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these forms.

  FIG. 1 is a diagram for explaining the first embodiment, and is a perspective view showing a video source unit 10 included in a display device. 2 is a part of a cross-sectional view of the video source unit 10 taken along the line II-II in FIG. 1, and when cut along the line III-III in FIG. Part of a cross-sectional view of the image source unit 10 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, 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 that is a polarizing plate disposed on the functional film 40 side (observer side), a lower polarizing plate 14 that is a polarizing plate disposed on the surface light source device 20 side, and an upper polarizing plate. A liquid crystal layer 12 disposed between the plate 13 and the lower polarizing plate 14. The upper polarizing plate 13 and the lower polarizing plate 14 decompose the incident light into two orthogonal polarization components (P wave and S wave), and the polarization component in one direction (direction parallel to the transmission axis) (for example, P And has a function of absorbing a polarization component (for example, S wave) in the other direction (direction parallel to the absorption axis) orthogonal 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. As a result, the polarization component (for example, P wave) parallel to the transmission axis transmitted through the lower polarizing plate 14 disposed on the surface light source device 20 side (that is, the light incident side) The polarization direction is rotated by 90 °, while the polarization direction is maintained when passing 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 and 2, 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, a light diffusion layer 26, a prism layer 27, and a reflective polarizing plate. 28, an optical sheet 30 and a reflection sheet 39.

  As can be seen from FIGS. 1 and 2, the light guide plate 21 has 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 resin, a polystyrene resin, an acrylonitrile-styrene copolymer, a methyl methacrylate-styrene copolymer, an ABS resin, a polyethersulfone, or the like. And epoxy acrylate-based and urethane acrylate-based reactive resins (such as ionizing radiation curable resins).

  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 optical element 23 is a protruding element formed on the back side of the base 22 (the side opposite to the side on which the reflective polarizing plate 28 is disposed), and in this embodiment, has a triangular prism shape. 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 direction in which the plurality of back surface optical elements 23 are arranged 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.

Returning to FIGS. 1 and 2, the light source 25 will be described. The light source 25 is arrange | positioned among the side surfaces which the base 22 of the light-guide plate 21 has on the one side surface of the direction where the several back surface optical element 23 is arranged. 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.

Next, the light diffusion layer 26 will be described. The light diffusion layer 26 is a layer that is disposed on the light output side of the light guide plate 21 and has a function of diffusing and emitting light incident thereon. Thereby, the uniformity of the light radiate | emitted from the light-guide plate 21 can be improved, and the damage | wound which exists in the light-guide plate 21 can be made not conspicuous.
As a specific embodiment of the light diffusion layer, a known light diffusion layer can be used, and examples thereof include a form in which a light diffusion agent is dispersed in a base material.

As can be seen from FIGS. 1 to 3, the prism layer 27 is a layer provided with a unit prism 27 a that is provided closer to the liquid crystal panel 15 than the light diffusion layer 26 and is convex toward the liquid crystal panel 15. The unit prism 27 a has a predetermined cross section and extends in the light guide direction of the light guide plate 21. In this embodiment, the plurality of unit prisms 27a are arranged in a direction different from the light guide direction (in this embodiment, a direction orthogonal to the light guide direction in plan view).
As the cross-sectional shape of the unit prism of such a prism layer, a known shape can be applied according to a required function. Depending on the shape, light can be further diffused or condensed.

  Next, the reflective polarizing plate 28 will be described. The reflective polarizing plate 28 decomposes incident light into two orthogonal polarization components (P wave and S wave) and transmits a polarization component (for example, P wave) in one direction (direction parallel to the transmission axis). And has a function of reflecting a polarization component (for example, S wave) in the other direction (direction parallel to the reflection axis) orthogonal to the one direction. As the structure of such a reflective polarizing plate, a known structure can be applied.

Here, the direction in which the transmission axis of the reflective polarizing plate 28 extends is the same as the direction in which the transmission axis of the lower polarizing plate 14 extends, and a light transmission portion 33 and a light absorption portion 34 of the optical function layer 32 described later. Is preferably 1 ° or more and 41.7 ° or less in a front view of the image source unit 1 with respect to the direction in which the image source extends. More preferably, it is 1 ° or more and 20 ° or less. More preferably, it is 1 degree or more and 5 degrees or less. By setting the angle to 5 ° or less, the viewing angle characteristics (brightness and cutoff balance) are particularly favorable.
If this angle is 0 ° or more and less than 1 °, the possibility of occurrence of moire fringes increases. In particular, with respect to the optical function layer 32, the edge of the optical function layer 32 which is a quadrangle and the direction in which the light transmitting portion 33 and the light absorbing portion 34 extend are almost parallel to each other. It becomes easy.

  Here, instead of the reflective polarizing plate 28, the following polarizing sheet 28 'can be used. Similarly to the reflective polarizing plate 28, the polarizing sheet 28 ′ 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 the polarized light (for example, S wave) different from this. is there. The structure of the polarizing sheet 28 'is shown enlarged in FIG. As can be seen from FIG. 4, in the polarizing sheet 28 ', a transparent uneven layer 28'b is provided on a transparent substrate 28'a, and a metal thin film 28'c having a certain thickness is laminated on the surface of the transparent uneven layer 28'b. Being done.

The transparent substrate 28'a is a flat sheet-like member that supports the transparent uneven layer 28'b and the metal thin film 28'c.
Various materials can be used as the material forming the transparent substrate 28'a. 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 resin (PET), triacetyl cellulose resin (TAC), methacrylic resin, and polycarbonate resin. Among these, it is preferable to use TAC, methacrylic resin, and polycarbonate resin with little birefringence in consideration of the combination with the lower polarizing plate.

  The transparent concavo-convex layer 28′b has a unit projection 28′ba having a triangular cross section in the cross section shown in FIG. And a plurality of unit convex portions 28'ba are arranged in a direction (the left-right direction in FIG. 4) perpendicular to the predetermined direction (the direction in which the ridge line of the unit convex portion 28'ba extends). ing.

  Examples of materials constituting the transparent uneven layer 28'b include ionizing radiation curable resins including ultraviolet curable resins such as epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, and polythiol. Can do.

  The metal thin film 28'c is a layer formed of a thin film of metal such as aluminum laminated on the surface of the transparent uneven layer 28'b.

  Accordingly, the polarizing sheet 28 'is a concave and convex surface having a triangular wave cross section composed of a groove line 28'ca and a ridge line 28'cb that are continuously repeated at a constant period A in the left-right direction in FIG. In the direction orthogonal to the paper surface, a triangular triangular wave surface of metal that repeats continuously at a constant period A is provided.

  When randomly polarized light (naturally polarized light) LR is incident on the polarizing sheet 28 ′ having such a configuration substantially perpendicularly to the surface of the transparent substrate 28′a, the groove line 28′ca and the ridge line 28′cb extend in the extending direction. The component of linearly polarized light (S-polarized light) having an electric field vector oscillating in parallel (in a direction orthogonal to the paper surface of FIG. 4) is parallel to the groove line 28'ca and the ridgeline 28'cb in the metal thin film 28'c. In order to oscillate electrons, a polarized component in the same direction as the incident light is radiated in the opposite direction, and as a result, S-polarized light is reflected as reflected light LH (however, reflected light LH in the figure is an optical path example and is a conceptual diagram). .) On the other hand, linearly polarized light (P) having an electric field vector oscillating in a direction orthogonal to the direction in which the groove line 28'ca and the ridge line 28'cb extend (the arrangement direction of the unit protrusions 28'ba, the horizontal direction in FIG. 4). The component (polarized light) cannot enter such electron vibrations, and therefore enters the metal thin film 28'c, reaches the back surface, and is transmitted as transmitted light LT. When random polarized light, which is a combined light of S-polarized light and P-polarized light, is incident on the polarizing sheet 28 ', 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 28 ′ extends (that is, the direction orthogonal to the direction in which the groove line 28′ca and the ridge line 28′cb extend, the direction in which the groove line 28′ca and the ridge line 28′cb are alternately arranged) Is the same as the direction in which the transmission axis of the lower polarizing plate 14 extends, and is a front view of the video source unit 10 with respect to the direction in which the light transmission part 33 and the light absorption part 34 of the optical function layer 32 described later extend. It is preferable that it is 1 degree or more and 41.7 degrees or less. More preferably, it is 1 ° or more and 20 ° or less. More preferably, it is 1 degree or more and 5 degrees or less. By setting the angle to 5 ° or less, the viewing angle characteristics (brightness and cutoff balance) are particularly favorable.
If this angle is 0 ° or more and less than 1 °, the possibility of occurrence of moire fringes increases. In particular, with respect to the optical function layer 32, the edge of the optical function layer 32 which is a quadrangle and the direction in which the light transmitting portion 33 and the light absorbing portion 34 extend are almost parallel to each other. It becomes easy.

Here, the polarizing sheet 28 ′ preferably satisfies the following conditions. Thereby, S polarized light and P polarized light can be efficiently separated.
The distance (constant period) A (μm) between adjacent groove lines 28′ca 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 28′cb with respect to the groove line 28′ca is preferably 1 μm or less, more preferably 0.2 μm or more and 0.4 μm or less. Furthermore, the thickness of the metal thin film 28′c in the direction perpendicular to the transparent substrate 28′a (the thickness direction of the transparent substrate 28′a) is preferably 0.01 μm or more. When the thickness d of the metal thin film 28'c is smaller than 0.01 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 28'c is decreased, and the extinction ratio of S-polarized light and P-polarized light is decreased. Therefore, the upper limit cannot be set for the thickness of the metal thin film 28'c.

  As a metal material that can be used for the metal thin film 28'c, 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. .

  Further, here, an example has been described in which the cross section of the unit convex portion 28′ba is a triangle, and thus the metal thin film 28′c is also a cross-sectional triangle, but the cross-sectional shape is not limited to this and may be a rectangle, A form including a curve in a part or the whole, such as a semicircle or a semi-ellipse, may be used.

The polarizing sheet 28 ′ can be produced, for example, as follows. That is, first, an original plate is prepared. The original plate is a mold in which the unevenness corresponding to the transparent uneven layer 28'b is formed on the surface. The unevenness can be formed by nano / micro cutting, lithography, two-beam interference exposure method, or the like.
Next, a laminated body in which an uncured ultraviolet curable resin is applied to one surface of the transparent substrate 28'a is prepared, and the ultraviolet curable resin side is pressed against the obtained original plate to be ultraviolet cured and peeled from the original plate. To do.
Then, aluminum is vacuum-deposited on the cured ultraviolet curable resin.

  Thus, since the polarizing sheet 28 'has a simple structure, it is easier to manufacture than the conventional reflective polarizing plate.

  Next, the optical sheet 30 will be described. As can be seen from FIG. 1 to FIG. 3, the optical sheet 30 is provided on the base material layer 31 formed in a sheet shape and one surface of the base material layer 31 (the surface on the light guide plate 21 side in this embodiment). The optical functional layer 32 and the adhesive layer 35 provided on the other surface (surface on the liquid crystal panel 15 side) of the base material layer 31 are provided.

  As will be described later, the optical sheet 30 changes the traveling direction of the light incident from the light incident side and emits the light from the light outgoing side, thereby intensively improving the luminance in the front direction (normal direction) (light collection). 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.

As shown in FIGS. 1 to 3, the base material layer 31 is a flat sheet-like translucent member that supports the optical functional layer 32 and the pressure-sensitive adhesive layer 35. FIG. 5 is an enlarged view of a part of the optical sheet 30 in FIG.
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 resin (PET), triacetyl cellulose resin (TAC), methacrylic resin, and polycarbonate resin.

  The base material layer 31 preferably has a small retardation, and specifically, the front retardation at a wavelength of 590 nm is preferably 15 nm or less. Thereby, it can be made to permeate | transmit to a lower polarizing plate, without disturbing the polarization state arranged with the reflective polarizing plate, the light absorbed by a lower polarizing plate can be restrained low, and the utilization efficiency of light can be improved. From this viewpoint, among those described above, TAC, methacrylic resin, and polycarbonate resin are preferable for use in the base material layer 31. Furthermore, a polycarbonate resin having a high glass transition point is desirable in applications that require high heat resistance such as in-vehicle applications. Specifically, the glass transition point of the polycarbonate resin is 143 ° C., which is generally suitable for in-vehicle applications that require durability at 105 ° C.

  Although the thickness of the base material layer 31 is not specifically limited, It is preferable that they are 25 micrometers or more and 300 micrometers or less. If the thickness of the base material layer 31 is out of this range, there is a possibility of causing a problem in workability. For example, wrinkles tend to occur when the base material layer 31 is thinner than 25 μm. Moreover, when the base material layer 31 becomes thicker than 300 micrometers, there exists a possibility that winding of the optical sheet 30 may become difficult.

  As can be seen from FIGS. 2, 3, and 5, the surface of the base material layer 31 is opposite to the surface on which the optical functional layer 32 is laminated (that is, the surface on which the adhesive layer 35 is disposed). Has a rough surface 31a. As will be described later, the rough surface 31a functions as a light scattering means in combination with the refractive index difference between the pressure-sensitive adhesive layer 35 and the base material layer 31. Thereby, generation | occurrence | production of a moire interference fringe can be suppressed. The surface roughness of the rough surface 31a is not particularly limited, but is preferably 0.1 μm or more in terms of average roughness (Ra). This is because if the surface roughness is too small, the above-described effect of forming a rough surface is reduced. On the other hand, from the viewpoint of increasing the light diffusion and reducing the effect of controlling the light emission range, the Ra is preferably 1.5 μm or less.

  A known method can be adopted as a method of forming the rough surface 31a. Examples thereof include transfer by a roll on which embossing is formed, sand blasting, printing, and painting.

  The optical functional layer 32 is a layer laminated on one surface of the base material layer 31 (the surface on the light guide plate 21 side in this embodiment), and light transmitting portions 33 and light absorbing portions 34 are alternately arranged along the layer surface. ing.

The optical functional layer 32 has a cross section shown in FIG. 5 and a shape extending to the back / front side of the paper. That is, in the cross section shown in FIG. 5, the light transmission part 33 having a substantially trapezoidal shape and the light absorption part 34 having a substantially trapezoidal cross section formed between two adjacent light transmission parts 33 are provided.
Here, as conceptually shown in FIG. 6, when the image source unit 1 is viewed from the front side of the viewer, the direction in which the light transmitting part 33 and the light absorbing part 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 1 ° or more and 41.7 ° or less. Thereby, it is possible to suppress the polarization component from being changed due to reflection at the interface between the light transmission part 33 and the light absorption part 34 and to improve the transmittance.
θ _S is more preferably 1 ° or more and 20 ° or less. This change in transmittance is reduced due to a change in the theta _S According, the variations of theta _S in manufacturing can reduce the variation given to performance, it is possible to provide an optical functional layer of stable performance.
Most preferably, θs is 1 ° or more and 5 ° or less. By setting the angle to 5 ° or less, the viewing angle characteristics (brightness and cutoff balance) are particularly favorable.
Further, when θs is set to 0 ° or more and less than 1 °, the possibility of occurrence of moire fringes increases. Further, from the viewpoint of manufacturing, in the optical function layer 32, the edge side of the optical function layer 32 that is a quadrangle and the direction in which the light transmission part 33 and the light absorption part 34 extend are nearly parallel, so that a whisker-like shape is formed at the time of cutting. Cutting waste tends to occur.

If this angle θ _S is 90 °, the light reflected at the interface between the light transmitting portion and the light absorbing portion at this time is polarized light of the absorption axis of the lower polarizing plate, and there is a problem that it is absorbed.

  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. An interval having a substantially trapezoidal cross section is formed between the adjacent light transmission portions 33. Therefore, the interval has a trapezoidal cross section having a long lower base on the upper base side (light guide plate 21 side) of the light transmission part 33 and a short upper base on the lower base side (liquid crystal panel side) of the light transmission part 33. The light absorbing portion 34 is formed by filling a necessary material described later. In this embodiment, the adjacent light transmission parts 33 are connected by the base part 32a on the long bottom side.

  The light transmission part 33 has a refractive index of Nt. Such a light transmission part 33 can be formed by hardening the composition which comprises a transmission part. Details will be described later. Although the value of the refractive index Nt is not particularly limited, as will be described later, the refractive index is from the viewpoint of appropriately reflecting light (including total reflection) at the interface with the light absorbing portion 34 on the slope of the trapezoidal cross section. It is preferable that it is 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 functions as an intermediate part formed at the above-described interval formed between the adjacent light transmission parts 33 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 a refractive index may be Nr and it can absorb light. Specifically, light absorbing particles are dispersed in a binder having a refractive index of Nr. The refractive index Nr is a refractive index lower than the refractive index Nt of the light transmission part 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 34 shown by _Dk in FIG. 5 is 50 micrometers or more and 150 micrometers or less. By setting it within these ranges, the balance between light transmission and light absorption can be further improved.

  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, etc. 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.

The pressure-sensitive adhesive layer 35 is a layer for sticking the optical sheet 30 to the lower polarizing plate 14 and laminating both without forming an air interface between the optical sheet and the liquid crystal panel 15 (lower polarizing plate 14). . Thereby, the light transmittance can be improved and the light utilization efficiency can be increased. Further, by attaching, it is possible to prevent scratches between the layers without rubbing.
The material which comprises the adhesive layer 35 is not specifically limited, A well-known adhesive, an adhesive agent, a photocurable resin, a thermosetting resin etc. can be used. As a more specific example, for example, an acrylic pressure-sensitive adhesive can be used as the pressure-sensitive adhesive layer 35, and more specifically, a pressure-sensitive adhesive combining an acrylic copolymer and an isocyanate compound can be used. However, the material constituting the pressure-sensitive adhesive layer 35 is preferably made of a material excellent in translucency and weather resistance due to the properties of the optical sheet 30.

  Although the thickness of the adhesive layer 35 is not specifically limited, It is preferable that they are 25 micrometers or more and 50 micrometers or less. Moire tends to occur when the pressure-sensitive adhesive layer 35 is thinner than 25 μm. Further, when the pressure-sensitive adhesive layer 35 is thicker than 50 μm, it becomes difficult to wind the optical sheet 30, and contamination due to the pressure-sensitive adhesive protruding from the end portion is likely to occur.

  Here, the base material layer 31 and the pressure-sensitive adhesive layer 35 preferably have a refractive index difference. Thereby, the light scattering means can be constituted by the rough surface 31a and the refractive index difference, and the generation of moire interference fringes can be prevented. One of the causes of the moire interference fringes is an interference fringe due to the stripe pattern of the light absorbing portion 34 and the regular pattern of pixels of the liquid crystal panel 15. Therefore, according to this embodiment, it is possible to suppress the deterioration of the screen quality due to the occurrence of such moire interference fringes.

The degree of the refractive index difference is not particularly limited, but is preferably 0.02 or more and 0.2 or less. If the ratio is smaller than 0.02, the effect of preventing the generation of moire interference fringes is reduced. If the ratio is larger than 0.2, the effect of controlling light by the optical functional layer 32 is diminished, and it is difficult to obtain materials. To do. The refractive index difference may be large on the base material layer 31 side or on the pressure-sensitive adhesive layer 35 side.
According to the inventor's test, the substrate layer 31 is made of polycarbonate having a refractive index of 1.585 and a thickness of 130 μm, and the refractive index is 1.490 (acrylic adhesive, Panac Co., Ltd., Panaclean ( When a pressure-sensitive adhesive layer having a thickness of 25 μm was formed using (registered trademark) PD-S1), no moire interference fringes were generated. No peeling occurred even at 95 ° C. for 1000 hours.
On the other hand, a light diffuser (acrylic styrene particles having a refractive index of 1.520 and an average particle diameter of 4 μm) dispersed in a base material layer made of polycarbonate having a rough surface (thickness of 130 μm and a refractive index of 1.585) has a thickness of 25 μm. Moire interference fringes could also be reduced when an optical sheet with an adhesive layer (acrylic adhesive, Panac Corporation, Panaclean (registered trademark) PD-S1, refractive index 1.490) was created. Accordingly, the light scattering means is also constituted by the pressure-sensitive adhesive layer in which the light diffusing material is dispersed. Therefore, as a modification, an adhesive layer in which a light diffusing material is dispersed may be laminated on a base material layer having no rough surface.
However, in this example, the adhesive strength tends to decrease.

  Thus, in the present invention, the light scattering means is provided between the optical functional layer 32 and the lower polarizing plate 14 to which the optical sheet 30 is attached.

The optical sheet 30 can be manufactured as follows, for example.
First, the light transmission portion 33 is formed on the surface of the base material layer 31 on which the rough surface 31a is not formed. 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.

  Although the material used as a light absorption part is not specifically limited, For example, photocurable resins, such as urethane (meth) acrylate resin, polyester (meth) acrylate resin, epoxy (meth) acrylate resin, and butadiene (meth) acrylate resin, are used. Examples thereof include a composition in which colored 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.

  And the adhesive layer 35 is formed by application | coating etc. in the side in which the rough surface 31a was formed among the base material layers 31. FIG.

  As a result, the optical sheet 30 in which the optical functional layer 32 is formed on one surface of the base material layer 31 and the pressure-sensitive adhesive layer 35 is stacked on the other surface on which the rough surface 31a is formed is produced.

  Returning to FIGS. 1 to 3, the reflection sheet 39 of the surface light source device 20 will be described. 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 reflectance such as a metal, a sheet including a thin film (for example, a metal thin film) made of a material having a high reflectance as a surface layer, It can be preferably applied.

  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 are directed to the reflective polarizing plate 28 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 light diffusion layer 26 and the uniformity is improved. Then, the light diffused or condensed by the prism layer 27 as necessary and emitted from the prism layer 27 reaches the reflective polarizing plate 28 next. Here, the light in the polarization direction along the transmission axis of the reflective polarizing plate 28 passes through the reflective polarizing plate 28 and travels toward the optical sheet 30.
On the other hand, the light in the polarization direction along the reflection axis of the reflective polarizing plate 28 is reflected and returned to the light guide plate 21 side as shown by dotted arrows L21 ′ and L22 ′ in FIG. The returned light is reflected by the light guide plate 21, the back surface optical element 23, or the reflection sheet 39 and travels again toward the reflective polarizing plate 28. During this reflection, the polarization direction of a part of the light is changed, and a part of the light is transmitted through the reflective polarizing plate 28. Other light is returned to the light guide plate side again. Thus, the light reflected by the reflective polarizing plate 28 can be transmitted through the reflective polarizing plate 28 by repeating the reflection. Thereby, the utilization factor of the light from the light source 25 is increased.
Here, the light emitted from the reflective polarizing plate 28 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 reflective polarizing plate 28 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 transmission part 33 is transmitted without reaching the interface between the light transmission part 33 and the light absorption part 34. Alternatively, as indicated by L <b> 52 in FIG. 5, the light reaches the interface between the light transmission part 33 and the light absorption part 34 and is totally reflected and passes through the light transmission part 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, since the direction in which the light transmission part 33 and the light absorption part 34 extend is an angle of 1 ° or more and 41.7 ° or less in front view with respect to the direction in which the transmission axis of the lower polarizing plate 14 extends, total reflection and reflection at the interface In this case, it is possible to prevent the polarization direction from changing. Therefore, most of the light reflected and reflected at the interface can be transmitted through the lower polarizing plate 14 and the light use efficiency (light 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.

  With such an optical sheet 30, light from the light guide plate 21 is efficiently collected, and light that is not collected is absorbed by the light absorption unit, so that appropriate light can be efficiently provided to the liquid crystal panel. It is possible to greatly improve the light utilization efficiency. Further, according to the optical sheet 30, the polarization direction of the light transmitted through the lower polarizing plate 14 is maintained, the light is provided to the lower polarizing plate 14, and the light absorbed by the lower polarizing plate 14 is reduced. It is possible to improve the light use efficiency (transmittance).

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 light that has passed through the optical functional layer 32 passes through the pressure-sensitive adhesive layer 35 and enters the lower polarizing plate 14 of the liquid crystal panel 15 without passing through the air layer. Thus, in this embodiment, light can be directly incident on the liquid crystal panel 15 without going through the air interface by the pressure-sensitive adhesive layer 35, so that loss of light can be suppressed and utilization efficiency can be improved.
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 this embodiment, the base layer 31 of the optical functional layer 32 is provided with a rough surface 31a and has a refractive index difference with the pressure-sensitive adhesive layer 35 laminated thereon. Thereby, generation | occurrence | production of a moire interference fringe can be prevented and a quality screen can be obtained.

  In the above, the example in which the optical sheet 20 and the liquid crystal panel 15 are pasted with the adhesive layer 35 has been described. About another layer, you may arrange | position through an air layer as needed, may stick with an adhesive, and may arrange | position so that it may contact without passing through an adhesive.

  FIG. 7 is a diagram for explaining the second embodiment and corresponds to FIG. In this embodiment, an optical sheet 130 is applied instead of the optical sheet 30, and the other configurations are the same as those of the video source unit 10.

  The optical sheet 130 includes the base material layer 31 similarly to the optical sheet 30, but includes an optical functional layer 132 instead of the optical functional layer 32, and is different from the optical sheet 30 in this respect. Specifically, in this embodiment, the intermediate portion 134 disposed between the adjacent light transmission portions 33 has a light reflection layer 134 a at the interface with the light transmission portion 33. A light absorbing part 134b is formed between the light reflecting layers 134a of the intermediate part 134.

The light reflecting layer 134a is a layer for reflecting light using reflection from a metal surface or other material surface, and is formed at the interface with the light transmitting portion 33 in the intermediate portion 134. The light reflecting layer 134a can be formed of a deposited film of aluminum, copper, silver, or the like, for example.
The light absorption part 134b may be formed following the light absorption part 34 described above.

  According to such an optical function layer 132, for example, the light indicated by L 71 in FIG. 7 is transmitted through the light transmitting portion 33 without reaching the interface between the light transmitting portion 33 and the intermediate portion 134. Alternatively, the light indicated by L72 in FIG. 7 can be reflected by the light reflecting layer 134a even if it reaches the interface between the light transmitting portion 33 and the intermediate portion 134, and is reflected and transmitted through the light transmitting portion 33. In this embodiment, since the reflection is not the reflection using the total reflection, even the light that does not satisfy the total reflection condition can be reflected by the light reflection layer 134a to be emitted. Thereby, it is possible to emit light brighter.

  FIG. 8 is a diagram for explaining the third embodiment and corresponds to FIG. In this embodiment, an optical sheet 230 is applied instead of the optical sheet 30, and the other configurations are the same as those of the video source unit 10.

  The optical sheet 230 includes the base material layer 31 as in the optical sheet 30, but includes an optical functional layer 232 instead of the optical functional layer 32, and is different from the optical sheet 30 in this respect. Specifically, the intermediate part 234 disposed between the adjacent light transmission parts 33 has a light reflection layer 234 a at the interface with the light transmission part 33. A transparent portion 234b that is transparent is formed between the light reflection layers 234a in the space portion 234.

The light reflection layer 234a is a layer for reflecting light using reflection from a metal surface or other material surface, and is formed at the interface with the light transmission portion 33 in the intermediate portion 234. The light reflection layer 234a can be formed of, for example, a vapor deposition film of aluminum, copper, silver, or the like.
The transparent portion 234b may be formed so as to transmit light by being filled with a cavity or a transparent resin.

According to such an optical function layer 232, for example, the light indicated by L <b> 81 in FIG. 8 passes through the light transmission portion 33 without reaching the interface between the light transmission portion 33 and the intermediate portion 234. Alternatively, the light indicated by L82 in FIG. 8 can be reflected by the light reflecting layer 234a even if it reaches the interface between the light transmitting portion 33 and the intermediate portion 234, and is reflected and transmitted through the light transmitting portion 33. In this embodiment, since the reflection is not based on the total reflection, even the light that does not satisfy the total reflection condition can be reflected by the light reflection layer 234a to be emitted, and the light can be emitted more brightly.
Further, in the optical function layer 232, as indicated by L83, the light incident on the transparent portion 234b of the intermediate portion 234 from the light incident surface side (lower side of the paper surface in FIG. 8) is repeatedly reflected on the inner side of the intermediate portion 234 to enter the light. It is returned to the surface side. The returned light is reflected by another part and returned to the optical functional layer again, and this can be utilized, so that brighter light can be provided.

  FIG. 9 is a diagram for explaining the fourth embodiment, and is a perspective view of the video source unit 310. FIG. 9 corresponds to FIG. The video source unit 310 is different from the video source unit 10 in that a prism layer 327 is disposed instead of the prism layer 27 included in the video source unit 10. Other configurations are the same as described above.

As can be seen from FIG. 9, the prism layer 327 includes a unit prism 327 a that is provided on the liquid crystal panel 15 side of the light diffusion layer 26 and is convex toward the liquid crystal panel 15 side. The unit prism 327a has a predetermined cross section and has a form extending in parallel with the direction in which the light transmitting portion 33 and the light absorbing portion 34 of the optical functional layer 32 extend. The unit prisms 327a are arranged in the same direction as the direction in which the light transmission parts 33 are arranged.
As the cross-sectional shape of the unit prism of such a prism layer, a known shape can be applied according to a required function. Depending on the shape, light can be further diffused or condensed.

Due to the nature of the optical functional layer 32, the light traveling in the direction in which the light transmitting portions 33 and the light absorbing portions 34 are alternately arranged is easily absorbed by the light transmitting portion 33 and the light absorbing portion 34. For the light traveling in the extending direction, it is difficult to reach the interface between the light transmitting portion 33 and the light absorbing portion 34, so that much light is transmitted.
On the other hand, in the prism layer 327, the direction of light traveling in the direction in which the unit prisms 327a are arranged is greatly changed (in the case of condensing, it is directed toward the front).
Therefore, when the prism layer 327 is configured as an optical element that collects light, the direction in which the light transmitting portion 33 and the light absorbing portion 34 of the optical function layer 32 extend and the direction in which the unit prism 327 a extends are parallel. (The direction in which the light transmission portions 33 and the light absorption portions 34 are alternately arranged and the direction in which the unit prisms 327a are arranged in parallel are made parallel), so that the light emitted from the prism layer 327 enters the light absorption portion 34. The amount absorbed can be reduced, and the light utilization efficiency can be increased.

As a test example, the relationship between θ _S (°) and light transmittance (%) shown in FIG. 6 was obtained by simulation.
(Test Example 1)
One example of the form in which the simulation is performed by the form of the image source unit corresponding to the image source unit 10 shown and described in FIG. 1 as Test Example 1 is as follows.

<Base material layer>
・ Thickness: Thickness 130μm
<Optical function layer>
・ Pitch: 39 μm (P _{k in} FIG. 5)
・ Light absorption part upper base width: 4 μm (W _{a in} FIG. 5)
・ Light absorption part lower bottom width: 10 μm (W _{b in} FIG. 5)
-Thickness of the light absorbing part: 102 μm (D _{k in} FIG. 5)
-Optical functional layer thickness: 127 μm
-Refractive index of light transmitting part: Refractive index 1.56
-Refractive index of light absorbing part: Refractive index 1.49
<Liquid crystal panel, reflective polarizing plate, light guide plate, light source>
A liquid crystal panel, a reflective polarizing plate, a light guide plate, and a light source included in a 6.5 inch liquid crystal display device (LQ065T5GG03 manufactured by Sharp Corporation) were used.

The results are shown in Table 1 and FIG. In Table 1 and FIG. 10, the transmittance ratio _TP is defined as a percentage of the transmittance T ₁ at θ _{S as a} target when the transmittance T ₀ when θ _S = 90 ° is 100%. The calculated value is calculated as T _P = (T ₁ / T ₀ ) · 100 (%). Take theta _S on the horizontal axis in FIG. 10, showing the transmittance ratio T _P on the vertical axis.

Further, when an approximate expression is obtained by the least square method based on this result, Expression (1) is obtained.
T _P = (4 × 10 ⁻⁸ ) · θ _S ³ − (5 × 10 ⁻⁶ ) · θ _S ² + (3 × 10 ⁻⁵ ) · θ _S +1.0117 (1)

According to this, it is possible to increase the transmittance ratio T _P by making θ _S smaller than 90 °. However, from the viewpoint of more effectively increasing the transmittance ratio, it is preferable that 0 ° ≦ θ _S ≦ 41.7 °, which is θ _S smaller than the inflection point of Equation (1). Further, as can be seen from FIG. 9, in the range where θ _S is 20 ° or less, the change in the transmittance ratio T _P is small with respect to the change in θ _S , and the variation in the transmittance (performance) due to the manufacturing variation is observed. Can be suppressed. Therefore, more preferably, 0 ° ≦ θ _S ≦ 20 °. However, as described above, 1 ° ≦ θ _S ≦ 41.7 ° is more preferable from the viewpoint of the occurrence of moire fringes and a manufacturing viewpoint, and more preferably, θ _S is 1 ° ≦ θ _S ≦ 20 °. is there.

  In Test Example 1, the result in the form of one example was shown, but the same tendency is shown for image source units having other forms such as an optical functional layer having another form.

(Test Example 2-1)
As Test Example 2-1, an image source unit corresponding to the image source unit 10 shown and described in FIG. 1 was produced and evaluated. The specific shape is as follows.
<Base material layer>
・ Material, thickness: Polycarbonate, thickness 130μm
<Optical function layer>
・ Pitch: 39 μm (P _{k in} FIG. 5)
・ Light absorption part upper base width: 4 μm (W _{a in} FIG. 5)
・ Light absorption part lower bottom width: 10 μm (W _{b in} FIG. 5)
-Thickness of the light absorbing part: 102 μm (D _{k in} FIG. 5)
-Optical functional layer thickness: 127 μm
-Material and refractive index of light transmission part: UV curable urethane acrylate, refractive index 1.56
-Material and refractive index of light absorbing part: 25% by mass of acrylic beads containing carbon black in UV curable urethane acrylate having a refractive index of 1.49 <Liquid crystal panel, reflective polarizing plate, light guide plate, light source>
A liquid crystal panel, a reflective polarizing plate, a light guide plate, and a light source included in a 6.5 inch liquid crystal display device (LQ065T5GG03 manufactured by Sharp Corporation) were used.
<Arrangement>
The layers are arranged in the order of FIG. 1, and the direction in which the light transmission part and the light absorption part of the optical sheet extend coincides with the direction in which the transmission axes of the reflective polarizing plate and the lower polarizing plate extend (that is, θ _S = FIG. 6). 0 °).

(Test Example 2-2)
The theta _S except for using 10 ° is the same as in Test Example 2-1.

(Test Example 2-3)
The theta _S except for using 90 ° is the same as in Test Example 2-1.

(Test Example 2-4)
except that the 45 ° to theta _S is the same as in Test Example 2-1.

For each of the video units as described above, the light source was turned on, and the luminance was measured from the front (automatic variable angle photometer, manufactured by Murakami Color Research Laboratory, GP-500). Test Example 2-3 (θ _S = 90 °) The brightness of other cases was expressed as a percentage (brightness ratio) with the brightness of the case being 100%. This corresponds to the transmittance ratio T _P.
As a result, the luminance ratio in the case of Test Example 2-1 was 100.5%, the luminance ratio in the case of Test Example 2-2 was 100.4%, and the luminance ratio in the case of Test Example 2-4 was 100.3%. Met. Since the strict conditions differ from those of Test Example 1 and the absolute values thereof are different, the same tendency as Test Example 1 can be obtained from Test Examples 2-1 to 2-4.
However, Moire fringes were observed in Test Example 2-1.

DESCRIPTION OF SYMBOLS 10,310 Image source unit 15 Liquid crystal panel 20 Surface light source device 21 Light guide plate 25 Light source 26 Light diffusion layer 27, 327 Prism layer 28 Reflective polarizing plate 30, 130, 230 Optical sheet 32 Optical functional layer 33 Light transmission part 34 Light absorption 34 Part

Claims (12)

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 optical sheet disposed closer to the lower polarizing plate than the liquid crystal panel,
The optical sheet includes a base material layer, an optical functional layer disposed on one surface of the base material layer, and an adhesive layer disposed on the other surface of the base material layer,
The optical functional layer is
A light transmitting portion having a predetermined cross section and extending in one direction along the surface of the base material layer, and a plurality of light transmitting portions arranged at predetermined intervals in a direction different from the extending direction;
An intermediate portion formed between the adjacent light transmission portions, and
The image source unit, wherein the lower polarizing plate and the optical sheet of the liquid crystal panel are bonded with the adhesive layer.   The image source unit according to claim 1, wherein the optical sheet is provided with light scattering means between the optical functional layer and the lower polarizing plate.   As the light scattering means, a surface of the base material layer that forms an interface with the pressure-sensitive adhesive layer is provided with a rough surface, and the base material layer and the pressure-sensitive adhesive layer have a refractive index difference. The video source unit according to claim 2.   The image source unit according to claim 2 or 3, wherein light scattering particles are dispersed in the pressure-sensitive adhesive layer as the light scattering means.   The angle formed by the direction in which the transmission axis of the lower polarizing plate extends and the direction in which the light transmission portion extends is 1 ° or more and 41.7 ° or less as viewed from the front of the liquid crystal panel. The video source unit described in 1.   The angle formed by the direction in which the transmission axis of the lower polarizing plate extends and the direction in which the light transmission portion extends is 1 ° or more and 20 ° or less in a front view of the liquid crystal panel. Video source unit. Furthermore, a reflection type polarizing plate is provided,
The angle formed by the direction in which the transmission axis of the reflective polarizing plate extends and the direction in which the light transmission part extends is 1 ° or more and 41.7 ° or less in a front view of the liquid crystal panel. The video source unit according to any one of the above. Furthermore, a reflection type polarizing plate is provided,
The angle formed by the direction in which the transmission axis of the reflective polarizing plate extends and the direction in which the light transmission portion extends is 1 ° or more and 20 ° or less in a front view of the liquid crystal panel. The video source unit described in 1.   The video source unit according to claim 7 or 8, wherein the optical sheet and the reflective polarizing plate are directly laminated.   10. The light transmissive portion has a trapezoidal cross section, and in the cross section, a long lower base faces the liquid crystal panel side, and a short upper base faces the side opposite to the liquid crystal panel. Video source unit.   The video source unit according to claim 1, wherein a light-absorbing material is contained in the intermediate portion.   A display device in which the video source unit according to claim 1 is housed in a casing.

Images