JP2013068834A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal device capable of displaying a good image having high luminance and an excellent field angle characteristic.SOLUTION: A display device 1 includes: an LCD panel 11; and a surface light source device 10. The surface light source device 10 includes: a light guide plate 13 arranged with a plurality of light emergent side unit lenses 131 which are shaped like a part of approximately cylindrical shape or a part of approximately elliptic cylindrical shape; light source parts 12A, 12B provided along side faces 13a, 13b which are located in a direction orthogonal to a ridge direction of the light emergent side unit lens 131 and provided at positions facing the side faces 13a, 13b; and a lens sheet 14 provided between the light guide plate 13 and the LCD panel 11 and arranged with a plurality of unit lenses 141 at the light emergent side which are shaped like a part of approximately cylindrical shape or a part of approximately elliptic cylindrical shape, while a transmission axis of a lower polarization plate 112 of the LCD panel 11 is approximately parallel to an array direction of the unit lenses 141 when viewed from a direction orthogonal to an observation screen of the display device 1.

Description

  The present invention relates to a liquid crystal display device.

In recent years, there has been a remarkable spread of liquid crystal display devices that display images by illuminating an LCD panel from the back side with a surface light source device. As the surface light source device used in this liquid crystal display device, an edge light type, a direct type, and the like are known.
The edge light type surface light source device is a form in which a light source is disposed at a position facing at least one end surface of the light guide plate, and compared to a direct type surface light source device in which a light source is disposed on the back side of various optical sheets, There is an advantage that the thickness of the surface light source device can be reduced. Therefore, a liquid crystal display device using an edge light type surface light source device is used for various purposes, and development relating to its optical characteristics and the like has been actively performed (for example, Patent Document 1).

JP 2009-265613 A

With the widespread use of liquid crystal display devices, there is an increasing demand for further thinning of liquid crystal display devices. In addition, as a display device, it is always required to display an image having high luminance and good viewing angle characteristics. However, simply reducing the number of optical sheets and the like used for the surface light source device for the purpose of reducing the thickness has a problem of causing brightness unevenness in addition to lowering the front brightness and viewing angle.
In addition, from the viewpoint of weight reduction and design improvement, the width of the bezel (a frame-shaped member provided on the observation side of the liquid crystal transmission type display unit) has been reduced, and accordingly, light leakage from the light source unit, etc. There has been a problem that hot spots caused by the phenomenon are easily observed. This hot spot is more likely to occur due to the reduction in the number of optical sheets and the like due to the reduction in thickness.
Furthermore, there has been a problem that the dot pattern and the like formed on the back surface of the light guide plate are easily visible due to the reduction of the optical sheet accompanying the reduction in thickness.

  An object of the present invention is to provide a liquid crystal display device that has high luminance, good viewing angle characteristics, and can display a good image.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.
According to the first aspect of the present invention, a liquid crystal transmissive display unit (1) includes a liquid crystal layer (111) between a first polarizing plate (112) provided on the back side and a second polarizing plate (113) provided on the viewer side. 11) and a surface light source device (10) for illuminating the liquid crystal transmission display unit from the back side, wherein the surface light source device has a substantially cylindrical shape on the light exit surface (13c) side. A light guide plate (13) in which a plurality of light exit side unit lenses (131) having a partial shape or a partial shape of a substantially elliptic cylinder are arranged, and the light guide plate (13) positioned in a direction perpendicular to the ridge line direction of the light output side unit lens A light source part (12A, 12B) provided at a position along at least one of the side surfaces (13a, 13b) of the light guide plate and facing the side surface, the light guide plate, and the liquid crystal transmission display unit The liquid crystal transmission type table A lens sheet (14) in which a plurality of unit lenses (141) each having a substantially cylindrical partial shape or an elliptical cylindrical partial shape are arranged on the surface of the portion side, and the transmission axis of the first polarizing plate Is a liquid crystal display device (1, 2) characterized by being substantially parallel to the arrangement direction of the unit lenses as viewed from a direction orthogonal to the observation screen of the liquid crystal display device.
According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, when viewed from a direction orthogonal to the observation screen of the liquid crystal display device, the arrangement direction of the light exit side unit lenses (131) and the unit lens ( 141) The liquid crystal display device (1, 2) is characterized by being orthogonal to the arrangement direction of 141).

According to a third aspect of the present invention, in the liquid crystal display device according to the first or second aspect, the light source unit (12A, 12B) is provided on at least one of both end portions in the horizontal direction of the screen of the liquid crystal display device in a use state. The liquid crystal display device (1, 2) is characterized by being provided.
According to a fourth aspect of the present invention, in the liquid crystal display device according to any one of the first to third aspects, the transmission axis of the first polarizing plate (112) is a screen of the liquid crystal display device in use. A liquid crystal display device (1, 2) characterized by being parallel or substantially parallel to the left-right direction.

According to a fifth aspect of the present invention, in the liquid crystal display device according to any one of the first to fourth aspects, the second lens sheet is closer to the light guide plate (13) than the lens sheet (14). (26), and a unit lens (261) having a partial shape of a substantially cylindrical shape or a partial shape of a substantially elliptical column shape is provided on a surface of the second lens sheet on the liquid crystal transmission display unit side. A liquid crystal display device (2), wherein a plurality of the liquid crystal display devices are arranged, and the arrangement direction thereof is orthogonal to the arrangement direction of the unit lenses (141).
The invention according to claim 6 is the liquid crystal display device according to any one of claims 1 to 5, further comprising a light diffusion sheet having a function of diffusing light. Device.
The invention according to claim 7 is the liquid crystal display device according to any one of claims 1 to 6, wherein the polarization selective reflection sheet (15) that transmits predetermined polarized light and reflects other polarized light is provided. The liquid crystal display device (1, 2) is provided on the light guide plate side of the liquid crystal transmissive display unit.

  According to the present invention, an image having high luminance and good viewing angle characteristics can be displayed, and display defects such as hot spots, luminance unevenness, and a printed pattern on the back surface of the light guide plate are significantly reduced, and further A liquid crystal display device capable of being thinned can be provided.

It is a figure explaining the structure of the display apparatus 1 of 1st Embodiment. It is a figure which shows the relationship between the light-guide plate 13, the lens sheet 14, and the lower polarizing plate 112 in the display apparatus 1 of 1st Embodiment. It is a figure explaining the shape of the light emission side unit lens. It is a figure explaining the unit lens 141 of the lens sheet. It is a figure which shows the relationship between an incident angle and the reflectance by a polarization state. It is a figure which shows the mode of the light radiate | emitted in the front direction in a lens sheet 14, an incident angle, and a polarization state. It is a figure which shows the mode of the light radiate | emitted to the front direction, the incident angle, and the polarization state in the prism sheet 57 used as a comparative example. It is a graph which shows the viewing angle characteristic in the screen up-down direction of the measurement examples 1 and 2, and a screen left-right direction. It is a graph which shows the viewing angle characteristic in the screen up-down direction of the measurement examples 3 and 4, and a screen left-right direction. It is a graph which shows the viewing angle characteristic in the screen up-down direction of the measurement examples 5 and 6, and a screen left-right direction. It is a graph which shows the viewing angle characteristic in the screen up-down direction of the measurement example 7, and a screen left-right direction. It is a figure which shows the display apparatus 2 of 2nd Embodiment. It is a figure which shows the display apparatus 3 of a deformation | transformation form.

Embodiments of the present invention will be described below with reference to the drawings. In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding.
In addition, the terms “plate”, “sheet”, “film” and the like are used, but these are generally used in the order of thickness, “plate”, “sheet”, “film”. I am using it. However, there is no technical meaning for such use. Accordingly, the terms “sheet”, “plate”, and “film” can be appropriately replaced.
Furthermore, numerical values such as dimensions and material names of each member described in the present specification are examples of the embodiment, and the present invention is not limited thereto, and may be appropriately selected and used.

(First embodiment)
FIG. 1 is a diagram illustrating the configuration of the display device 1 according to the first embodiment.
FIG. 2 is a diagram illustrating a relationship among the light guide plate 13, the lens sheet 14, and the lower polarizing plate 112 in the display device 1 according to the first embodiment.
The display device 1 includes an LCD (Liquid Crystal Display) panel 11 and a surface light source device 10 that illuminates the LCD panel 11 from the back side. In addition, although description etc. are abbreviate | omitted, the display apparatus 1 is equipped with the normal apparatus required in order to operate | move as a display apparatus. The display device 1 is used as, for example, a liquid crystal television.
The surface light source device 10 is an edge light type surface light source device (backlight) including light source units 12A and 12B, a light guide plate 13, a lens sheet 14, a polarization selective reflection sheet 15, and the like.

In the drawings and the following description, for easy understanding, the screen vertical direction (screen vertical direction) when the observer views the LCD panel 11 from the front in the use state of the display device 1 is the Y direction. The horizontal direction of the screen (horizontal direction of the screen) is the X direction, and the thickness direction (depth direction, the direction orthogonal to the observation screen) is the Z direction. The observer visually recognizes the display on the screen of the LCD panel 11 from the Z2 side as the observer side toward the Z1 side as the back side. Further, in the thickness direction (Z direction) of the lens sheet 14 and the LCD panel 11, the Z1 side is a light incident side (light incident side), and the Z2 side is a light emission side (light output side).
Unless otherwise specified, in the following description, the screen horizontal direction and screen vertical direction are the screen horizontal direction (X direction) and screen vertical direction (Y direction) in the usage state of the display device 1.

The LCD panel 11 is a transmissive image display unit, and is disposed on the surface light source device 10 side (incident side, Z1 side) and the lower polarizing plate 112 and on the viewer side (exit side, Z2 side). An upper polarizing plate 113 and a liquid crystal layer 111 disposed between the lower polarizing plate 112 and the upper polarizing plate 113 are provided.
The liquid crystal layer 111 has two glass substrates (not shown) and a plurality of liquid crystal cells sealed between the glass substrates and arranged in a matrix. In this liquid crystal cell, an electric field is applied to each region where one pixel is formed, and the alignment direction of the liquid crystal cell is changed by the application of the electric field.
The lower polarizing plate 112 and the upper polarizing plate 113 are polarizing plates disposed on the incident side and the outgoing side of the glass substrate of the liquid crystal layer 111, respectively.
The lower polarizing plate 112 and the upper polarizing plate 113 decompose 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) (this embodiment) Then, it has a function of transmitting a P wave) and absorbing a polarization component (in this embodiment, an S wave) in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

In the present embodiment, the transmission axis (polarization axis) of the lower polarizing plate 112 and the transmission axis (polarization axis) of the upper polarizing plate 113 are perpendicular to the surface of the LCD panel 11 (the front direction of the observation screen of the display device 1). From the perspective, they are orthogonal. As shown by an arrow in FIG. 2C, the transmission axis of the lower polarizing plate 112 when viewed from the direction orthogonal to the observation screen of the display device 1 (front direction, Z direction) is the screen horizontal direction (X direction). Parallel to Further, the transmission axis of the upper polarizing plate 113 is parallel to the vertical direction of the screen (Y direction). In this specification, “parallel” and “orthogonal” include not only strictly parallel or orthogonal states but also states that can be regarded as parallel or orthogonal (substantially parallel or approximately orthogonal).
Further, as shown in FIG. 2, the transmission axis of the lower polarizing plate 112 is parallel to the arrangement direction of unit lenses 141 of a lens sheet 14 to be described later when viewed from a direction (Z direction) orthogonal to the surface of the LCD panel 11. Yes (see FIG. 2).

A polarization component (P wave in this embodiment) emitted from the surface light source device 10 and transmitted through the lower polarizing plate 112 is rotated by 90 ° when passing through the liquid crystal cell to which an electric field is applied. The polarization direction is maintained when passing through a liquid crystal cell to which no electric field is applied. Therefore, depending on whether or not an electric field is applied to the liquid crystal cell, the polarization component (P wave) in a specific direction transmitted through the lower polarizing plate 112 is transmitted through the upper polarizing plate 113 or absorbed by the upper polarizing plate 113 and blocked. You can control what is done. Then, by applying an electric field to such a liquid crystal cell, the LCD panel 11 controls transmission or blocking of light from the surface light source device 10 for each pixel, thereby enabling display of an image.
The LCD panel 11 of the present embodiment is described as an IPS system as an example, but is not limited thereto, and for example, an VA system LCD panel may be used.

The light sources 12A and 12B are portions that emit light that illuminates the LCD panel 11 from the back. The light source unit 12A of the present embodiment is provided at a position facing the light incident surface 13a which is one end surface (X1 side) of the light guide plate 13 in the horizontal direction of the screen, and the light source unit 12B is disposed on the light incident surface 13a. It is provided at a position facing the light incident surface 13b which is an opposing end surface (one end surface (X2 side end surface) of the light guide plate 13 in the left-right direction of the screen).
In the light source units 12A and 12B of the present embodiment, a plurality of LEDs that are point light sources 121 as light emitting sources are arranged at equal intervals in the vertical direction of the screen along the light incident surfaces 13a and 13b.

The light guide plate 13 is a substantially flat member that guides light. The light guide plate 13 causes the light emitted from the light source units 12A and 12B to enter from the light incident surfaces 13a and 13b and totally reflect the light from the light exit surface 13c and the back surface 13d, and to the opposite surfaces 13b and 13a in the horizontal direction of the screen. While being guided, the light is appropriately emitted from the light exit surface 13c to the lens sheet 14 side.
The light guide plate 13 of the present embodiment has a lenticular lens shape in which a plurality of light output side unit lenses 131 are arranged on the light output surface 13c side.

FIG. 3 is a diagram illustrating the shape of the light exit side unit lens 131. FIG. 3 shows a part of a cross section in a cross section (YZ plane) parallel to the arrangement direction of the light output side unit lenses 131 and parallel to the thickness direction of the light guide plate 13.
The light exit side unit lens 131 is a columnar lens that is convex on the LCD panel 11 side (Z2 side). The light output side unit lens 131 of the present embodiment is a partial shape of an elliptic cylinder whose major axis is orthogonal to the sheet surface of the light guide plate 13, and a plurality of them are arranged in the screen vertical direction (Y direction). The light exit side unit lens 131 may have a substantially cylindrical partial shape, or may have a shape formed by combining curved surfaces such as a plurality of types of elliptic cylinder shapes. In addition, for example, a substantially isosceles triangular prism shape with a base angle of about 55 to 65 °, and a top portion formed with a curved surface having a relatively large radius of curvature (that is, a substantially isosceles shape with a shaping rate of about 60%) It may be a shape approximated to a triangular prism shape).
In the cross section shown in FIG. 3, the arrangement pitch of the light output side unit lenses 131 is P1, and the lens height is H1 (the valley between the vertex t of the light output side unit lenses 131 in the thickness direction of the lens sheet 14 and the light output side unit lenses 131). To the point v that becomes the bottom of the valley). In the light guide plate 13 of the present embodiment, the light exit side unit lens 131 arrangement pitch P1 is equal to the lens width W1 in the arrangement direction.
Since the light exit side unit lenses 131 are formed on the light exit surface 13c and are arranged in a direction orthogonal to the light guide direction of the light from the light guide plate 13, light beams such as light collection and diffusion in the direction orthogonal to the light guide direction. Has control action.

In addition to the lenticular lens shape of the light output side unit lens 131, the light guide plate 13 may have the following configuration.
For example, the light guide plate 13 may have a form in which dots (not shown) or the like are formed on the back surface 13d that is the back surface side (Z1 side) by printing or the like.
The light guide plate 13 has a back side optical shape in which a plurality of unit prisms or unit lenses arranged in a direction orthogonal to the above-described light exit side unit lens are arranged on the back side (Z1 side) when viewed from the front direction. It is good.
The light guide plate 13 may be configured such that the thickness thereof decreases as the distance from the light incident surface increases along the light guide direction.
The light guide plate 13 may include a diffusing material that diffuses light therein.
The light guide plate 13 may include a diffusing material, and may have a configuration in which a configuration such as a rear-side optical shape and a change in thickness is appropriately combined.
The light guide plate 13 may have only a lenticular lens shape by the light exit side unit lens 131, no back side optical shape, no diffusing material, and no thickness change.
The light guide plate 13 is manufactured using, for example, an acrylic resin, a PC (polycarbonate) resin, a COP (cycloolefin polymer) resin, or the like. The light guide plate 13 can be produced by, for example, extrusion molding or injection molding. In the light guide plate, a lenticular lens shape may be formed by a UV molding method or the like with an ultraviolet curable resin or the like on the light exit surface of a plate-like member made of thermoplastic resin or the like serving as a substrate.

On the back side (Z1 side) of the light guide plate 13, a reflection plate (not shown) which is a plate-like member capable of reflecting light is provided. The reflecting plate has a function of reflecting light traveling toward the back side and directing it toward the light guide plate 13. As the reflector, one having specular reflectivity (regular reflectivity) or one having diffuse reflectivity such as a white sheet can be appropriately selected and used.
The reflection plate is a so-called specular reflection such as a sheet formed of a material having a high reflectance such as metal, or a sheet including a thin film (for example, a metal thin film) formed of a material having a high reflectance as a surface layer. It is preferable to use a reflecting plate that enables the light emission from the viewpoint of improving the light condensing performance and the light utilization efficiency.

The lens sheet 14 is an optical member that is disposed between the light guide plate 13 and the LCD panel 11 and has an action of controlling the direction of light emitted from the light guide plate 13.
FIG. 4 is a diagram illustrating the unit lens 141 of the lens sheet 14. In FIG. 4, the lens sheet 14 is shown by enlarging a part of a cross section (XZ plane) orthogonal to the sheet surface and parallel to the arrangement direction of the unit lenses 141.
Here, the sheet surface indicates a surface in the planar direction of the sheet when viewed as the entire sheet, and is used as the same definition in this specification. For example, the sheet surface of the lens sheet 14 is a surface in the planar direction of the lens sheet 14 when viewed as the entire lens sheet 14, and is a surface parallel to the observation screen of the LCD panel 11 in the present embodiment. .

The lens sheet 14 includes a plurality of columnar unit lenses 141 that are convex on the LCD panel 11 side on the LCD panel 11 side (light emission side, Z2 side). As shown in FIG. 4, the unit lens 141 of the present embodiment is a partial shape of a substantially elliptical column shape whose major axis is orthogonal to the sheet surface, and the screen vertical direction (Y direction) is the longitudinal direction, and the screen left and right They are arranged in the direction (X direction).
The unit lens 141 may have a substantially cylindrical shape, or may have a shape formed by combining curved surfaces such as a plurality of types of elliptic cylinder shapes. In addition, for example, a substantially isosceles triangular prism shape with a base angle of about 55 to 65 °, and a top portion formed with a curved surface having a relatively large radius of curvature (that is, a substantially isosceles shape with a shaping rate of about 60%) It may be a shape approximated to a triangular prism shape).
As shown in FIG. 1 and FIG. 2, the arrangement direction of the unit lenses 141 is orthogonal to the arrangement direction of the light output side unit lenses 131 of the light guide plate 13 as viewed from the direction orthogonal to the sheet surface (Z direction). It is parallel to the transmission axis of the lower polarizing plate 112.

The unit lens 141 has an arrangement pitch (distance between vertices t) of P2, and is a lens height (a bottom of a valley portion between the vertex t of the unit lenses 141 and the unit lens 141 in a direction orthogonal to the sheet surface). The dimension up to v) is H2. In the unit lens 141 of the present embodiment, the arrangement pitch P2 is equal to the lens width W2 in the arrangement direction.
The lens sheet 14 is used for liquid crystal television applications such as acrylic resin, PC resin, MBS (methyl methacrylate / butadiene / styrene copolymer) resin, PET (polyethylene terephthalate) resin, COP resin, and PS (polystyrene) resin. It is formed by extruding a thermoplastic resin having heat resistance that can be used. It is also possible to form the lens sheet 14 by forming the unit lens 141 by a UV molding method or the like on a sheet-like base material made of PET resin or PC resin with an ultraviolet curable resin or the like.

The polarization selective reflection sheet 15 is an optical member having a function of transmitting light in a specific polarization state and reflecting light in other polarization states.
The polarization axis of the polarized light transmitted through the polarization selective reflection sheet 15 is parallel to the transmission axis of the lower polarizing plate 112 when viewed from the normal direction (Z direction) of the observation screen of the display device 1.
As this polarization selective reflection sheet 15, for example, DBEF (manufactured by 3M) can be used.

FIG. 5 is a diagram showing the relationship between the incident angle and the reflectance depending on the polarization state (P wave, S wave).
FIG. 6 is a diagram illustrating a state of light emitted in the front direction, an incident angle, and a polarization state in the lens sheet 14. FIG. 6A schematically shows an optical path of light incident on the lens sheet 14 and emitted from the lens sheet 14 in a direction orthogonal to the sheet surface (front direction) in the arrangement direction of the unit lenses 141. FIG. 6B is a graph showing the transmittance according to the incident angle and the polarization state (P wave, S wave) in the lens sheet 14.
FIG. 7 is a diagram illustrating a state of light emitted in the front direction, an incident angle, and a polarization state in the prism sheet 57 as a comparative example. FIG. 7A schematically shows an optical path of light incident on the prism sheet 57 and emitted from the prism sheet 57 in a direction perpendicular to the sheet surface (front direction) in the arrangement direction of the unit prisms 571. FIG. 7B is a graph showing the transmittance according to the incident angle and the polarization state (P wave, S wave) in the prism sheet 57.
Here, the prism sheet 57 is an optical member in which a plurality of unit prisms 571 having an isosceles triangular prism shape that is convex toward the light exit surface side and whose apex angle is 90 ° is arranged. It is assumed that the refractive index is the same as that of the lens sheet 14 of the embodiment.

As shown in FIG. 5, the reflectivity differs between the P wave and the S wave depending on the incident angle. Therefore, the transmittance of the P wave and S wave transmitted through the optical sheet or the like varies depending on the incident angle.
Further, as shown in FIGS. 7A and 7B, in the prism sheet 57, light incident on the prism sheet 57 at an incident angle of about 20 to 25 ° is emitted in the front direction.
Therefore, in the prism sheet 57, as shown in FIG. 7B, there is little difference in the ratio of the P wave and the S wave in the light transmitted through the prism sheet 57 and emitted in the front direction. Since the lower polarizing plate 112 of the LCD panel 11 absorbs the S wave and transmits only the P wave, the display device 1 according to this embodiment has a prism sheet 57 instead of the lens sheet 14. In the figure), the luminance drop is increased by absorbing the S wave.

On the other hand, in the lens sheet 14, as shown in FIGS. 6A and 6B, light incident on the lens sheet 14 at an incident angle of about 0 to 50 ° is emitted in the front direction. The Therefore, the range of the incident angle of the light emitted in the front direction with respect to the lens sheet is wider than that of the prism sheet 57.
Therefore, in the lens sheet 14, as shown in FIG. 6B, the ratio of the P wave and the S wave in the light transmitted through the lens sheet 14 and emitted in the front direction is higher in the P wave than in the S wave. Many. Therefore, even when the S wave is absorbed by the lower polarizing plate 112, the influence of the decrease in luminance is smaller than that of the prism sheet 57. Therefore, by disposing the lens sheet 14 as in the display device 1 of the present embodiment, the above-described light loss is small, and high luminance and wide viewing angle can be expected.

Therefore, according to the present embodiment, the unit lenses 141 of the lens sheet 14 are arranged along the left-right direction of the screen, and pass through the lens sheet 14 when viewed from the normal direction (Z direction) of the LCD panel 11. Since the polarization axis of the P wave in the light and the transmission axis of the lower polarizing plate 112 are parallel, the amount of light transmitted through the lower polarizing plate 112 is increased, and the front luminance can be increased.
According to the present embodiment, the unit lenses 141 of the lens sheet 14 are arranged along the horizontal direction of the screen, and thus have a light beam control function in the horizontal direction of the screen. Therefore, in addition to the luminance increase in the front direction as described above, a good wide viewing angle in the left-right direction of the screen can be realized. In particular, the display device 1 used as a liquid crystal television as in the present embodiment preferably has a wide viewing angle in the left-right direction of the screen, and thus can be a high-quality display device.
According to the present embodiment, the light output side unit lenses 131 are arranged in the vertical direction of the screen, which is a direction orthogonal to the light guide direction of the light guide plate 13, so that the viewing angle in the vertical direction of the screen can be suitably controlled.

  According to the present embodiment, the arrangement direction of the light exit side unit lenses 131 of the light guide plate 13 is the screen vertical direction (Y direction), and the arrangement direction of the unit lenses 141 of the lens sheet 14 is the horizontal direction of the screen (X direction). Since they are orthogonal to each other, the light beam direction can be controlled in the vertical direction of the screen and the horizontal direction of the screen, and good viewing angle characteristics can be realized. Further, the light output side unit lens 131 of the light guide plate 13 and the unit lens 141 of the lens sheet 14 can be expected to reduce hot spots and luminance unevenness. In addition, when a printed pattern or the like having a diffusing action is provided on the back surface of the light guide plate 13, there is a problem that a printed pattern image is visually recognized. The unit lens 141 of the sheet 14 can greatly reduce the appearance of such a printed pattern image.

Here, the display devices of Measurement Examples 1 to 7 corresponding to the examples and comparative examples of the display device 1 of the present embodiment are manufactured, and whether or not display defects such as front luminance, viewing angle, and hot spot occur. evaluated.
In the display device of each measurement example, as shown in FIG. 1, the light source units 12 </ b> A and 12 </ b> B are arranged at both ends of each light guide plate in the left-right direction of the screen, and both use LEDs as the point light sources 121. In the display device of each measurement example, the LCD panel 11 has a screen size (size of the display area of the LCD panel 11) of 32 inches diagonal (706 mm × 398 mm) and a resolution of 1920 × 1080 dots. Moreover, in the display apparatus of each measurement example, the reflective plate is a mirror reflective one.
In the display device of each measurement example, the shape of the light guide plate, the shape and the number of optical sheets such as lens sheets, and the like are different, and the light guide plate and the optical sheet provided in the display device of each measurement example will be described below. To do.

The display device of Measurement Example 1 has a substantially flat plate shape, and has a printed dot pattern on the back surface but does not have a lenticular lens shape on the light exit surface (hereinafter, such a light guide plate is referred to as a printed light guide plate), A diffusion sheet having a directional diffusion action and a prism sheet (a plurality of unit prisms having an isosceles triangular prism shape with an apex angle of 90 ° are arranged on the light-emitting surface side. Unit prisms are arranged in the vertical direction of the screen (the ridge line of the unit prism is the screen) Parallel to the left-right direction)) and a polarization selective reflection sheet 15.
The display device of Measurement Example 2 includes the same printed light guide plate as that of Measurement Example 1, a lens sheet 14, and a polarization selective reflection sheet 15.
The display device of Measurement Example 3 is an example of the display device of this embodiment, and includes a light guide plate 13, a lens sheet 14, and a polarization selective reflection sheet 15.

The display device of Measurement Example 4 includes a printed light guide plate and a prism sheet (a plurality of unit prisms having an isosceles triangular prism shape with an apex angle of 90 ° on the light output surface side. The unit prisms are arranged in the horizontal direction of the screen (the ridge line of the unit prism). Is parallel to the vertical direction of the screen)), and a polarization selective reflection sheet 15.
The display device of Measurement Example 5 includes a light guide plate 13 and a prism sheet (a plurality of unit prisms having an isosceles triangular prism shape with an apex angle of 90 ° on the light-emitting surface side. The unit prisms are arranged in the horizontal direction of the screen (the ridge lines of the unit prisms). Is parallel to the vertical direction of the screen)), and a polarization selective reflection sheet 15.
The display device of Measurement Example 6 includes a printed light guide plate, a diffusion sheet having an omnidirectional diffusion action, and a polarization selective reflection sheet 15.
The display device of Measurement Example 7 includes a light guide plate 13, a diffusion sheet having a non-directional diffusion action, and a polarization selective reflection sheet 15.

Here, the light guide plate 13 of the embodiment has an arrangement pitch P1 of the light output side unit prisms of 93 μm, a lens height H1 of 38 μm, is made of acrylic resin, and has a thickness of 4 mm.
The printed light guide plate is made of acrylic resin, has a thickness of 4 mm, and has a dot-like print pattern having a light diffusion action on the back surface side.
Further, the lens sheet 14 is made of a PC resin with an arrangement pitch P2 of the unit lenses 141 = 64 μm, a lens height H2 = 28 μm, and a thickness of 0.3 mm.
In the prism sheet, a plurality of unit prisms made of urethane-based ultraviolet curable resin are arranged on one side of a sheet-like base material made of PET resin by a UV molding method. The unit prism of this prism sheet has an isosceles triangular prism shape, and the arrangement pitch is 50 μm and the prism height is 25 μm regardless of the arrangement direction. The thickness of the prism sheet is 285 μm.
The diffusion sheet is an omnidirectional light diffusion sheet (SK273, CH273) having a haze value of 94.8%.
The polarization selective reflection sheet 15 is DBEF manufactured by 3M.

  8 to 11 are graphs showing viewing angle characteristics in the screen vertical direction and screen horizontal direction of each measurement example. 8 to 11, the vertical axis represents relative luminance, and the horizontal axis represents the emission angle with respect to the observation screen of the LCD panel 11.

Table 1 is a table showing the results of evaluation of the configuration of each measurement example and the front luminance, half-value angle, presence / absence of side lobes, hot spots, and the like.
Regarding the front luminance, in a dark room environment, the luminance meter (Konica Minolta Co., Ltd.) was passed from the position of the normal direction (Z2 side) 800 mm of the observation surface side surface through the geometric center of the observation screen of the display device of each measurement example. Using a spectral radiance meter CS-1000), the luminance at the geometric center of the observation screen (display region) when the display device of each measurement example displayed white was measured. Then, the relative luminance of the front luminance of the display device of each measurement example was calculated using the front luminance of the display device of Measurement Example 1 as a reference (100%). The evaluation of front luminance is good when the relative luminance is 100% or more (◯ in Table 1), acceptable from 95% to less than 100% (not applicable in Table 1), and less than 95% is inappropriate (in Table 1). X).

The viewing angle is displayed in white on the display device of each measurement example in a dark room environment, and the luminance at each emission angle in the screen vertical direction and screen horizontal direction passing through the geometric center of the observation screen (display area) Measured using an angle characteristic evaluation apparatus (ELDIM viewing angle characteristic evaluation apparatus EZContrast), and as shown in FIGS. The vertical axis represents the relative luminance and the horizontal axis represents the emission angle.
The viewing angle is evaluated by calculating 1/2 angle (half-value angle, αV, αH) and 1/3 angle (βV, βH) from the graph of viewing angle characteristics of the display device of each measurement example. A ½ angle αV of 31 ° or more and a ½ angle αH of 31 ° or more in the left-right direction of the screen was judged good (◯ in Table 1), and those not satisfying this were judged unsuitable (x in Table 1). .

  Furthermore, the presence or absence of the occurrence of side lobes was evaluated from the visual observation on the display device of each measurement example and the luminance distribution state in the graph of the viewing angle characteristics of the display device of each measurement example. In the evaluation of side lobes, those with no side lobes are judged as good (◯ in Table 1), and those that are available but usable are acceptable (△ in Table 1). Those not present were regarded as unsuitable (in Table 1, x).

The hot spot passes through the geometric center of the display area of the display device of each measurement example in a dark room environment, and is observed from the position of the normal direction (Z2 side) 2 m of the surface on the observation surface. It was visually evaluated whether or not a hot spot was observed in the vicinity of 12A and 12B. In addition, from this front position, the display area of each transmissive display device is observed obliquely from the point moved ± 45 ° with respect to the normal direction of the surface on the observation surface in the vertical direction of the screen, and hot spots are observed. Whether or not it was visually evaluated.
In the evaluation of the hot spot, in the front direction and in the oblique direction, the hot spot is not observed (good in Table 1), the hot spot is observed but usable is acceptable (△ in Table 1), A hot spot was observed and it was not suitable for use.

  Furthermore, it was evaluated whether or not the dot-like printed pattern image formed on the back surface of the light guide plate was visually recognized. Regarding the evaluation of the printed pattern image, when the display device of each measurement example is displayed in white in a dark room environment and observed from the position of 500 mm in the front direction of the observation screen, the printed pattern image is not observed (in Table 1) ○), a sample that was slightly observed but could be used was acceptable (Δ in Table 1), and a sample that was not suitable for use when a printed pattern image was observed was regarded as unsuitable (× in Table 1). In the evaluation of the printed pattern image, the display devices of Measurement Examples 3, 5, and 7 are also used in the evaluation in which a printed pattern similar to the printed light guide plate is formed on the back side of the light guide plate 13.

As shown in Table 1, the shape of the lenticular lens on the light-emitting surface side is larger than that of Measurement Example 3 (Example) including the light guide plate 13 having a lenticular lens shape in which a plurality of light-emitting side unit lenses 131 are arranged on the light-emitting surface 13c. In the measurement example 2 including the printed light guide plate that does not have a low brightness, the hot spot is not eliminated. Furthermore, in measurement example 2, the printed pattern image on the back surface of the printed light guide plate is observed, and the masking of the printed pattern image due to the diffusion action or the like is insufficient.
Moreover, the measurement example 4 provided with the prism sheet | seat provided with the printing light guide plate and the unit prism arranged in the screen left-right direction has a low brightness | luminance compared with the measurement example 3, and the side lobe has arisen in the screen left-right direction. . Moreover, the hot spot has arisen, the concealment of the printing pattern of a printing light-guide plate is also insufficient, and is not suitable for use. In order to improve hot spots and the like, in measurement example 4, when a diffusion sheet was arranged instead of the polarization selective reflection sheet 15, side lobes were further observed.
The measurement example 5 including the light guide plate 13 but including the prism sheet including the unit prisms arranged in the left-right direction of the screen instead of the lens sheet 14 has good luminance and viewing angle, but is side in the left-right direction of the screen. Lobes are generated. Moreover, although it was in the usable range, the hot spot was also confirmed. Here, in order to improve hot spots and the like, in the measurement example 5, when the diffusion sheet was arranged in place of the polarization selective reflection sheet 15, the side lobe was further observed, and the viewing angle was insufficient. Furthermore, in the display device of Measurement Example 5, when the light guide plate 13 having the print pattern on the back surface was used, the print pattern image was visually recognized.

The display device of Measurement Example 6 including a printed light guide plate and a diffusion sheet, and the display device of Measurement Example 7 including a light guide plate 13 but a diffusion sheet instead of an optical sheet have a reduced viewing angle, hot spot, and side lobe. However, the brightness was extremely low and it was not suitable for use.
In the display device of Measurement Example 6, in the display device of Measurement Example 1 in which a prism sheet (the ridge line direction of the unit prism is the horizontal direction of the screen) is further disposed between the diffusion sheet and the polarization selective reflection sheet 15. The brightness is improved and the viewing angle is also improved, the hot spot is reduced, the printed pattern image of the printed light guide plate is improved, and the like, which can be used. However, in measurement example 1, although it is within the usable range, side lobes are generated in the vertical direction of the screen. Moreover, since the number of optical sheets increases, it is not preferable from the viewpoint of thinning.

  On the other hand, the display device of Measurement Example 3 (Example) has higher luminance than the display device of Measurement Example 1, and also has a 1/2 angle αV in the screen vertical direction and a 1/2 angle αH in the screen horizontal direction. The 1/3 angle βV in the vertical direction of the screen and the 1/3 angle β in the horizontal direction of the screen are large, and the viewing angle is wide and good. Further, no side lobe is generated, and the hot spot is good. Furthermore, the number of members is small and the thickness can be reduced while having the above-described good optical characteristics. In addition, when the light guide plate 13 having the print pattern on the back surface was used, the print pattern image was not visually recognized, and good results were obtained with respect to the concealment of the print pattern image.

From the above, according to the display device of the example which is measurement example 3, it has high brightness, has a good wide viewing angle (particularly, viewing angle in the horizontal direction of the screen), hot spots, side lobes, etc. Display defects can be reduced as much as possible.
Even when the back surface of the light guide plate 13 has a print pattern, the print pattern image is concealed by the diffusion action of the light exit side unit lens 131 of the light guide plate 13 or the unit lens 141 of the lens sheet 14 and is not visually recognized. Good video can be displayed.
Further, the number of optical sheets constituting the surface light source device 10 can be reduced, and the display device can be made thinner and the production cost can be reduced.

(Second Embodiment)
FIG. 12 is a diagram illustrating the display device 2 according to the second embodiment.
As shown in FIG. 12, the display device 2 of the second embodiment is that the surface light source device 20 includes a second lens sheet 26 on the light guide plate 13 side of the lens sheet 14. Except for this display device, the shape is substantially the same as that of the first embodiment. Therefore, in the second embodiment, parts that perform the same functions as those in the first embodiment described above are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate.
The display device 2 includes a second lens sheet 26 between the lens sheet 14 of the surface light source device 20 and the light guide plate 13. The second lens sheet 26 is formed by arranging a plurality of unit lenses 261 on the surface on the emission side (Z2 side).
The unit lenses 261 of the present embodiment have a substantially elliptic cylinder shape whose major axis is orthogonal to the sheet surface, and a plurality of unit lenses 261 are arranged in a direction orthogonal to the arrangement direction of the unit lenses 141 of the lens sheet 14. That is, the arrangement direction of the unit lenses 261 in the second lens sheet 26 is parallel to the arrangement direction of the light output side unit lenses 131 of the light guide plate 13. Even in such a form, the number of members increases, but the brightness is high and a good viewing angle can be realized. In particular, the front luminance can be improved.
Note that the pitch of the unit lenses 261 is desirably set to a size that does not cause moiré with the arrangement pitch of the light output side unit lenses 131 of the light guide plate. Further, the unit lens 261 may have a substantially cylindrical partial shape, or may have a plurality of curved surfaces.

(Deformation)
Without being limited to the embodiments described above, various modifications and changes are possible, and these are also within the scope of the present invention.
(1) In each embodiment, the light guide plate 13 may have a printed dot pattern having a diffusing action on the back surface, may include a diffusing material, or may have a prism shape or a lens shape on the back surface. The back surface may be flat.
Moreover, in each embodiment, although the example which is a substantially flat light-guide plate 13 was shown, it is not restricted to this, For example, when setting it as the form which is provided with only the light source part 12A as a light source, and is not provided with the light source part 12B. The light incident surface 13a side may be thick and the thickness may be reduced toward the side surface 13b side facing the light incident surface 13a.
The light guide plate 13 may appropriately combine the above-described shapes and the like.

(2) In each embodiment, the example in which the polarization selective reflection sheet 15 is provided between the lens sheet 14 and the LCD panel 11 has been described. However, the present invention is not limited thereto, and for example, a diffusion sheet having an action of diffusing light is provided. Alternatively, a configuration in which such an optical sheet is not provided (that is, a configuration in which various optical sheets are not provided between the lens sheet 14 and the LCD panel 11) may be employed. Note that the diffusion sheet may be disposed between the lens sheet 14 and the light guide plate 13. Further, an optical sheet may be provided as appropriate depending on the desired optical characteristics.
As such a diffusion sheet, a resin sheet-like member containing a diffusion material, a member coated with a binder containing a diffusion material of a resin sheet-like member serving as a base material, or a base material A microlens sheet or the like in which a microlens array is formed on one surface or the like of a resin sheet-like member can be used.

(3) In each embodiment, although light source part 12A, 12B showed the example provided in a screen left-right direction both ends, it is good not only as this but a form provided only with light source part 12A, for example.
Moreover, although light source part 12A, 12B showed the example in which both LED which is the point light source 121 was arranged in multiple numbers, not only this but a point light source is a thing of light source types other than LED, for example. You may use, and you may use not only a point light source but linear light sources, such as a cold cathode tube.

(4) In each of the embodiments, the light source units 12A and 12B are arranged at both ends in the left-right direction of the screen. However, the present invention is not limited to this, and the light source units 12A and 12B are arranged at both ends in the vertical direction of the screen. It is good also as a form.
FIG. 13 is a diagram showing a display device 3 in a modified form.
In the modified display device 3 shown in FIG. 13, the light source units 12 </ b> A and 12 </ b> B of the surface light source device 30 are arranged at both ends in the vertical direction of the screen.
At this time, the ridge line direction of the light output side unit lens 131 of the light guide plate 13 is the vertical direction of the screen. The ridge line direction of the unit lens 141 of the lens sheet 14 is the vertical direction of the screen. Then, between the lens sheet 14 and the light guide plate 13, a second lens sheet 36 in which unit lenses 361 are arranged in a direction in which the ridge line direction is the horizontal direction of the screen may be disposed.
Even in such a form, a display device with high luminance and a favorable viewing angle can be obtained. Here, in the display device 3 as shown in FIG. 13, since the light output side unit lens 131 of the light guide plate 13 and the unit lens 141 of the lens sheet 14 are subjected to the light beam control action in the horizontal direction of the screen, the viewing angle is Compared to the display device 1 of the first embodiment shown in FIG. 1 and the like and the display device 2 of the second embodiment shown in FIG. 12, the viewing angle in the horizontal direction of the screen tends to be narrowed. However, it can be used as a liquid crystal television, and can be suitably used for other display devices that do not require a wide viewing angle in the horizontal direction of the screen, such as a monitor of a personal computer.

  In addition, although this embodiment and modification can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited by the embodiments described above.

DESCRIPTION OF SYMBOLS 1, 2 Display apparatus 10 Surface light source device 11 LCD panel 111 Liquid crystal cell 112 Lower polarizing plate 113 Upper polarizing plate 12A, 12B Light source part 121 Point light source 13 Light guide plate 131 Light emission side unit lens 14 Optical sheet 141 Unit lens 15 Polarization selection reflection sheet 26 Second lens sheet 261 Unit lens

Claims (7)

A liquid crystal transmissive display unit comprising a liquid crystal layer between a first polarizing plate provided on the back side and a second polarizing plate provided on the viewer side;
A surface light source device for illuminating the liquid crystal transmission display unit from the back side;
A liquid crystal display device comprising:
The surface light source device is
A light guide plate in which a plurality of light exit side unit lenses having a substantially cylindrical partial shape or a substantially elliptic cylindrical partial shape are arranged on the light exit surface side;
A light source provided at a position along at least one of the two side surfaces of the light guide plate located in a direction perpendicular to the ridge line direction of the light exit side unit lens and facing the side surface;
A plurality of unit lenses that are provided between the light guide plate and the liquid crystal transmissive display unit and that have a part of a substantially cylindrical shape or a part of an elliptic cylinder are arranged on the surface of the liquid crystal transmissive display unit. Lens sheet,
With
The transmission axis of the first polarizing plate is substantially parallel to the arrangement direction of the unit lenses as viewed from the direction orthogonal to the observation screen of the liquid crystal display device,
A liquid crystal display device. The liquid crystal display device according to claim 1.
When viewed from a direction orthogonal to the observation screen of this liquid crystal display device, the arrangement direction of the light exit side unit lenses and the arrangement direction of the unit lenses are orthogonal to each other,
A liquid crystal display device. The liquid crystal display device according to claim 1 or 2,
The light source unit is provided in at least one of both end portions of the liquid crystal display device in a left-right direction of the liquid crystal display device in use;
A liquid crystal display device. In the liquid crystal display device according to any one of claims 1 to 3,
The transmission axis of the first polarizing plate is parallel or substantially parallel to the horizontal direction of the screen of the liquid crystal display device in use;
A liquid crystal display device. In the liquid crystal display device according to any one of claims 1 to 4,
A second lens sheet is provided on the light guide plate side of the lens sheet,
A plurality of unit lenses having a substantially cylindrical partial shape or a substantially elliptical columnar partial shape are arranged on the surface of the second lens sheet on the liquid crystal transmissive display unit side. Is orthogonal to the arrangement direction of the unit lenses,
A liquid crystal display device. In the liquid crystal display device according to any one of claims 1 to 5,
Having a light diffusing sheet having a function of diffusing light;
A liquid crystal display device. The liquid crystal display device according to any one of claims 1 to 6,
A polarization selective reflection sheet that transmits predetermined polarized light and reflects other polarized light is provided on the light guide plate side of the liquid crystal transmissive display unit,
A liquid crystal display device.

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