JP2015014681A - Display system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display system for a vehicle capable of suppressing video light from being reflected in a windshield.SOLUTION: A display system for a vehicle includes: a windshield of an automobile; a liquid crystal display device installed with a predetermined interval from the windshield in the automobile; and a light control sheet arranged in the liquid crystal display device or on a surface for emitting video light of the liquid crystal display device. The liquid crystal display device includes: a light source; and a liquid crystal panel arranged at an observer side from the light source. The liquid crystal panel respectively includes a polarizer at the light source side and the observer side. The direction of the transmission axis of the polarizer arranged at the observer side is a direction through which light which oscillates in a horizontal direction passes, and the light control sheet includes: light transmission parts having light transmissivity arranged in parallel along a sheet surface; and light absorption parts having light absorptivity arranged between the adjacent light transmission parts.

Description

  The present invention relates to a display system for a vehicle including a display device installed in a car.

  A display device (vehicle display device) such as a car navigation may be installed in a car. At present, liquid crystal display devices are mainly used as in-vehicle display devices.

  A liquid crystal display device provides video light to an observer so that a viewer can visually recognize a liquid crystal panel including video information by using a surface light source device (backlight) disposed on the back side of the liquid crystal panel as illumination.

  Patent Document 1 discloses a light control sheet that can emit a high-quality image in a liquid crystal display device. There are various types of liquid crystal display devices. For example, Patent Document 2 discloses a TN (Twisted Nematic) type liquid crystal display device, and Patent Document 3 discloses a VA (Vertical Alignment) method or the like. An IPS (In-Plane Switching) type liquid crystal display device is disclosed. The TN method has an advantage that the manufacturing cost can be suppressed although the image quality is inferior to that of the VA method and the IPS method.

JP 2010-217871 A Japanese Patent No. 4063919 JP 2008-176059 A

  When a conventional liquid crystal display device is installed in a car, video light emitted from the liquid crystal display device may be reflected on the windshield, thereby obstructing the driver's view. That is, a part of the image light emitted from the conventional liquid crystal display device is directed upward to be irradiated on the windshield. Depending on the positional relationship between the liquid crystal display device, the windshield, and the observer, the image light applied to the windshield as described above is reflected and reflected on the windshield, thereby hindering the observer's view.

  In order to suppress the reflection of image light on the windshield as described above, as described in Patent Document 1, a light control sheet called a louver has been used. However, in all liquid crystal display devices, the image light is not reflected on the windshield as described above. The inventor of the present invention tends to cause the above-described image light to be reflected on the windshield in the TN liquid crystal display device as disclosed in Patent Document 2, and VA as disclosed in Patent Document 3 It has been found that the above-mentioned image light is hardly reflected on the windshield in the liquid crystal display device of the IPS method or the IPS method.

  Then, this invention makes it a subject to provide the vehicle display system which can utilize effectively the light control sheet called a louver based on the said knowledge, and can suppress that image light reflects in a windshield.

  The present invention will be described below.

  According to a first aspect of the present invention, there is provided a vehicle windshield, a liquid crystal display device installed at a predetermined distance from the windshield in the vehicle, and emitting image light in the liquid crystal display device or the liquid crystal display device. The liquid crystal display device includes a light source and a liquid crystal panel disposed closer to the viewer side than the light source, and the liquid crystal panel is polarized on the light source side and the viewer side, respectively. The direction of the transmission axis of the polarizing plate arranged on the viewer side is a direction through which the light vibrating in the horizontal direction passes, and the light control sheet is arranged in parallel along the sheet surface. It is a display system for vehicles provided with the light transmission part which has translucency, and the light absorption part which has the light absorption property arrange | positioned between adjacent light transmission parts.

  In the present invention, “having translucency” means that the material is formed without intentionally adding a material that absorbs or scatters visible light. That is, some absorption or scattering is inevitably caused when visible light is transmitted. Further, “having light absorption” means being configured to intentionally absorb part or all of incident visible light.

  According to a second aspect of the present invention, in the vehicle display system according to the first aspect, the light transmitting portion and the light absorbing portion extend in the horizontal direction.

  According to a third aspect of the present invention, in the vehicle display system according to the first or second aspect, the liquid crystal display device is a TN liquid crystal display device.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the image light radiate | emitted from the vehicle-mounted display apparatus reflects in a windshield.

2 is a cross-sectional view conceptually showing a positional relationship of members constituting the vehicle display system 100. FIG. It is a disassembled perspective view explaining the image source unit 10 concerning one form. 2 is an exploded perspective view illustrating a liquid crystal panel 15. FIG. FIG. 4 is an exploded view showing a cross section of the surface light source device 20 in the thickness direction (up and down direction in FIG. 2) along the line indicated by IV-IV in FIG. FIG. 5 is an exploded view showing a cross section of the surface light source device 20 in the thickness direction (vertical direction in FIG. 2) along the line indicated by VV in FIG. It is the figure which expanded a part of light-guide plate 21. FIG. 3 is an enlarged view of a part of the prism sheet 30. FIG. 3 is a view showing a cross section of a light control sheet 50. FIG. It is a figure explaining a part of manufacturing process of the light control sheet | seat 50. FIG. It is a figure explaining the other part of manufacturing process of the light control sheet | seat 50. FIG. FIG. 4 is a diagram illustrating an example of an optical path of image light emitted from a liquid crystal display device 101. It is a figure explaining the preferable form of the light control layer.

  The above-described operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these embodiments. In addition, each drawing shown below shows a structural member notionally, and does not show the magnitude | size and ratio of a member correctly. Moreover, in each drawing shown below, the code | symbol which becomes repeated may be abbreviate | omitted for legibility.

  FIG. 1 is a cross-sectional view conceptually showing the positional relationship of members constituting a vehicle display system 100 according to one embodiment (viewed from a horizontal direction orthogonal to the traveling direction of an automobile).

The vehicle display system 100 includes an automobile windshield 102 and a liquid crystal display device 101 installed in the automobile with a predetermined distance from the windshield 102. When the windshield 102 and the liquid crystal display device 101 are arranged in this manner, if the liquid crystal display device 101 is a conventional in-vehicle display device, a part of video light L1 and L2 emitted from the in-vehicle display device. When the windshield 102 is irradiated and reflected, it may be reflected on the windshield 102 and obstruct the driver's view.
Note that the image light reflected by the windshield 102 as described above is mainly a polarization component other than P-polarized light.
As will be described later, the liquid crystal display device 101 emits image light having a polarization component other than P-polarized light. However, the light control sheet 50 (see FIG. 2) is provided on the liquid crystal display device 101 or the surface of the liquid crystal display device 101 that emits image light. In this case, the reflection of the image light on the windshield 102 as described above can be suppressed.

  FIG. 2 is an exploded perspective view conceptually showing the video source unit 10 which is a part of the liquid crystal display device 101. In FIG. 2, the lower side of the paper is the light source side, and the upper side of the paper is the observer side.

  The liquid crystal display device 101 is a TN liquid crystal display device. The liquid crystal display device 101 has an image source unit 10, and observation is performed after white light source light emitted from the surface light source device 20 included in the image source unit 10 is transmitted through the liquid crystal panel 15 to obtain image information. Provided to the party. The liquid crystal display device 101 includes a housing (not shown), in which the video source unit 10 is built. The housing is a member that forms an outer shell of the liquid crystal display device 101 and accommodates most of the members constituting the liquid crystal display device 101 inside. Further, the housing has an opening so as to support the image source unit 10, and the image source unit 10 is fitted and attached to the opening. In addition, the liquid crystal display device 101 includes various known constituent members for functioning as a liquid crystal display device.

  The video source unit 10 includes a surface light source device 20, a liquid crystal panel 15, and a light control sheet 50. In the illustrated embodiment, the light control sheet 50 is disposed on the surface (outermost surface) of the image source unit 10 (liquid crystal display device 101) that emits image light to the viewer side.

The liquid crystal panel 15 includes a liquid crystal cell 12 having a liquid crystal sandwiched between two transparent substrates, an upper polarizing plate 13 disposed on the viewer side of the liquid crystal cell 12, and a surface light source device 20 of the liquid crystal cell 12. And a lower polarizing plate 14 disposed on the side.
FIG. 3 is an exploded perspective view illustrating the liquid crystal panel 15. In FIG. 3, the lower side of the paper is the light source side, and the upper side of the paper is the observer side.
The upper polarizing plate 13 and the lower polarizing plate 14 decompose the incident light into two orthogonal polarization components, transmit the polarization component in one direction (direction parallel to the transmission axis), and orthogonal to the one direction. It has a function of absorbing the polarization component in the other direction. The solid line 13 a shown in FIG. 3 is the transmission axis of the upper polarizing plate 13, and the solid line 14 a is the transmission axis of the lower polarizing plate 14. The transmission axis 13a and the transmission axis 14a are orthogonal to each other when viewed from the observer side. Further, in a posture in which the liquid crystal display device 101 is installed in a car, the direction of the transmission axis 13a of the upper polarizing plate 13 is a direction through which at least a part of the light vibrating in the horizontal direction passes.

In the liquid crystal cell 12, an electric field can be applied to each region where one pixel is formed. The orientation of the liquid crystal cell 12 to which an electric field is applied changes. The polarization component in a specific direction transmitted through the lower polarizing plate 14 disposed on the surface light source device 20 side (that is, the light incident side) rotates the polarization direction by 90 ° when passing through the liquid crystal cell 12 to which an electric field is applied. On the other hand, when passing through the liquid crystal cell 12 to which no electric field is applied, the polarization direction is maintained. For this reason, depending on whether or not an electric field is applied to the liquid crystal cell 12, the polarized light component in a specific direction transmitted through the lower polarizing plate 14 is further transmitted through the upper polarizing plate 13 disposed on the light output side of the lower polarizing plate 14, or It is possible to control whether the light is absorbed and blocked by the upper polarizing plate 13.
In this way, the liquid crystal panel 15 is configured to be able to express an image by controlling transmission or blocking of light from the surface light source device 20 for each pixel.

  Next, the surface light source device 20 will be described. FIG. 4 is an exploded view showing a cross section in the thickness direction (vertical direction in FIG. 2) of the surface light source device 20 along the line indicated by IV-IV in FIG. 2, and FIG. The exploded view which shows the cross section of the thickness direction (the paper surface up-down direction of FIG. 2) of the surface light source device 20 along the line shown by V was shown.

  The surface light source device 20 is an illuminating device that is disposed on the opposite side of the liquid crystal panel 15 from the observer side and emits planar light to the liquid crystal panel 15. As can be seen from FIGS. 2, 4, and 5, in this embodiment, the surface light source device 20 is configured as an edge light type surface light source device, and includes a light guide plate 21, a light source 25, a prism sheet 30, and a reflection sheet 40. And have.

  As can be seen from FIGS. 2, 4, and 5, the light guide plate 21 includes a base portion 22, a back prism 22 a, and a unit optical element portion 23. The light guide plate 21 is a plate-like member as a whole formed of a light-transmitting material, and a unit optical element portion 23 is disposed on one plate surface side to form a light exit surface. The other plate surface side is a back surface, and a back surface prism 22a is formed. That is, as will be described later, the light guide plate 21 is provided with an uneven shape on each of its front and back surfaces.

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

  The base portion 22 is a portion serving as a base for the back prism 22a and the unit optical element portion 23, and is a plate-like portion having a predetermined thickness.

  The back surface prism 22a has a concavo-convex shape formed on the back surface side of the base portion 22 (the plate surface opposite to the side where the unit optical element portion 23 is disposed), and a plurality of triangular prism-shaped back surface prisms 22a are arranged in parallel. Yes. The back prism 22a has a columnar shape in which the ridge line of the convex portion extends in the left-right direction in FIG. 2, and the plurality of back prisms 22a are arranged at a predetermined pitch in a direction orthogonal to the extending direction. The back prism 22a of this embodiment has a triangular cross section, but is not limited to this, and may be any shape such as a polygon, a hemisphere, a part of a sphere, or a lens shape.

The unit optical element portion 23 has a concavo-convex shape formed on the side of the base portion 22 opposite to the back prism 22a (the surface on the viewer side), and unit optical elements 23a that are a plurality of convex portions are arranged in parallel. The unit optical element 23a is a part that functions as a light exit surface when the light guide plate 21 is used in a surface light source device.
As shown in FIGS. 2 and 5, the unit optical element 23a is a columnar element that has a substantially triangular cross section and maintains the cross section, and its ridge line extends in one direction. The direction in which the unit optical elements 23a extend is a direction orthogonal to the direction in which the unit optical elements 23a are arranged in parallel and the direction in which the ridgeline of the back prism 22a extends. That is, the unit optical element 23a is configured such that its ridge line is orthogonal to the ridge line of the back prism 22a in plan view.

  FIG. 6 shows an enlarged view of a part of the light guide plate 21 in FIG. The unit optical element 23 a has a substantially triangular shape that has a base on one surface of the base portion 22 and is a convex portion protruding from the base portion 22. In the unit optical element 23a of this embodiment, the apex that faces the bottom of the cross section is curved.

Further, in this embodiment, the unit optical element 23a is an isosceles triangle in the cross section appearing in FIGS. 5 and 6 (the cross section along the direction in which the unit optical elements 23a are arranged in parallel). According to this, it is possible to effectively increase the luminance in the front direction and to impart symmetry to the angular distribution of the luminance in the plane along the parallel direction of the unit optical elements 23a.
However, although the cross section of this embodiment is an isosceles triangle, it is not necessarily limited to this, and other shapes such as a triangle (for example, an unequal triangle), a quadrilateral, a polygon such as a pentagon, a hemisphere, or a sphere. The shape may be any shape such as a part or a lens shape.

  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 dimensions of the light guide plate 21 having the above configuration can be set as follows as an example. First, as a specific example of the unit optical element 23a, the width Wa (see FIG. 6) along the plate surface of the light guide plate 21 can be 20 μm or more and 500 μm or less, and the normal direction nd to the plate surface of the light guide plate 21 is nd. The height Ha (see FIG. 6) of the unit optical element 23a along the line can be 4 μm or more and 250 μm or less. Further, when the cross-sectional shape of the unit optical element 23a is a triangular shape, the angle of the apex angle θ4 (see FIG. 6) can be set to 90 ° or more and 150 ° or less.
On the other hand, the thickness of the base 22 can be 0.35 mm or more and 6 mm or less.

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

  Returning to FIGS. 2, 4 and 5, the light source 25 will be described. The light source 25 is disposed on one or both of a pair of side surfaces which are both ends in the longitudinal direction in which the unit optical element 23 a extends, among the two sets of side surfaces of the base portion 22 of the light guide plate 21. The type of the light source is not particularly limited, but may 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 lamp. In this embodiment, the light source 25 is composed of a plurality of LEDs, and the output of each LED by a control device (not shown), that is, the brightness when each LED is turned on and off, and / or the brightness when each LED is turned on, is adjusted. It is configured so that it can be adjusted independently of the output.

  Next, the prism sheet 30 will be described. As can be seen from FIGS. 2, 4, and 5, the prism sheet 30 is formed on the surface facing the light guide plate 21 among the main body 31 formed in a sheet shape and the surface of the main body 31, that is, on the light incident side surface. The unit prism portion 32 provided and the light diffusion layer 33 provided on the surface of the main body portion 31 opposite to the unit prism portion 32, that is, the light exit side surface are provided.

  As will be described later, the prism sheet 30 changes the traveling direction of the light incident from the light incident side and emits the light from the light output side, thereby intensively improving the luminance in the front direction (normal direction) (condensing light). Function). This condensing function is mainly exhibited by the unit prism portion 32 of the prism sheet 30. In addition, the prism sheet 30 has a function of preventing interference fringes between the liquid crystal panel 15 and hiding defects such as scratches. This function is mainly exhibited by the light diffusion layer 33.

  As shown in FIGS. 2, 4, and 5, the main body 31 is a flat sheet-like member having a function of supporting the unit prism portion 32 and the light diffusion layer 33.

  The unit prism portion 32 is arranged such that a plurality of unit prisms 32 a are arranged along the light incident side surface of the main body portion 31 as well shown in FIGS. 2, 4, and 5. More specifically, the unit prism 32a is a columnar member formed so as to extend while maintaining the predetermined cross-sectional shape shown in FIG. 4 in a direction orthogonal to the arranged direction. The extending direction is perpendicular to the direction in which the unit prisms 32a are arranged, and is shifted by 90 degrees with respect to the direction in which the unit optical element 23a of the light guide plate 21 extends. Therefore, the extending direction of the unit prism 32a and the extending direction of the unit optical element 23a are orthogonal to each other when the display device is viewed from the front.

  Further, the longitudinal direction of the unit prism 32a intersects the transmission axis of the lower polarizing plate 14 of the liquid crystal panel 15 when observed from the front. Preferably, the longitudinal direction of the unit prism 32a of the prism sheet 30 is a surface parallel to the display surface of the display device with respect to the transmission axis of the lower polarizing plate 14 of the liquid crystal panel 15 (the sheet surface of the main body 31 of the prism sheet 30). Intersecting at an angle greater than 45 ° and less than 135 °. The angle here means the smaller one of the angles formed by the longitudinal direction of the unit prism 32a and the transmission axis of the lower polarizing plate 14, that is, an angle of 180 ° or less. . In particular, in the present embodiment, the longitudinal direction of the unit prism 32a of the prism sheet 30 is orthogonal to the transmission axis of the lower polarizing plate 14 of the liquid crystal panel 15, and the direction in which the unit prisms 32a of the prism sheet 30 are arranged is the liquid crystal The panel 15 is preferably parallel to the transmission axis of the lower polarizing plate 14.

  Next, the sectional shape of the unit prism 32a in the parallel direction will be described. FIG. 7 is an enlarged view of a part of the prism sheet 30 in FIG. Here, nd represents the normal direction of the sheet surface of the main body 31.

  As can be seen from FIG. 7, in this embodiment, the unit prism 32 a has an isosceles triangular cross section that protrudes toward the light guide plate 21 of the main body 31. That is, the width of the unit prism 32 a in the direction parallel to the sheet surface of the main body 31 decreases as the distance from the main body 31 increases along the normal direction nd of the main body 31.

  In this embodiment, the outer contour of the unit prism 32a is line symmetric with respect to an axis parallel to the normal direction nd of the main body 31, and the cross section is an isosceles triangle. As a result, the luminance on the light exit surface of the prism sheet 30 has a symmetrical angular distribution of luminance about the front direction on the surface parallel to the parallel direction of the unit prisms 32a. In particular, when the light sources are arranged in two rows (two sides), there are many line-symmetric shapes. However, when the light sources are arranged in one row (one side), they are not necessarily symmetrical.

  Here, the dimensions of the unit prism 32a are not particularly limited. However, when the apex angle θ5 (see FIG. 7) is 60 ° or more and 70 ° or less and the base width W is about 50 μm, an appropriate condensing characteristic is obtained. Can often be obtained.

  In the present embodiment, the unit prism having a triangular cross-sectional shape as described above has been described. However, the present invention is not limited to this, and a trapezoid in which the apex of the triangle is a short upper base may be used. Further, the shape of the slope may be a polygonal line or a curve.

  The light diffusion layer 33 is a layer in which a large number of light diffusion particles having a refractive index different from that of a resin are dispersed in a layer made of a light-transmitting resin. Since a part of the light diffusing particles protrudes from the surface of the light diffusion layer 33, unevenness is formed on the surface. The light-transmitting resin used for the light diffusion layer 33 is not particularly limited as long as it is a light-transmitting resin capable of dispersing the light diffusion particles and holding the light diffusion particles. . Examples of such resins include thermoplastic resins such as polyamide resins, polyurethane resins, polyester resins, and acrylic resins, thermosetting resins, and active energy ray curable resins (ionizing radiation curable resins). . On the other hand, as light diffusion particles, crosslinked organic fine particles such as acrylic-styrene copolymer, polymethyl methacrylate, polystyrene, polyurethane, benzoguanamine, and melamine, resin fine particles such as silicone, and inorganic fine particles such as silica, alumina, and glass Etc. can be used. The light diffusing particles may be used alone or in combination of two or more. The shape of the light diffusing particles may be spherical or indefinite. Furthermore, the particle size distribution may be either monodispersed or polydispersed, and suitable conditions may be selected as appropriate.

In the prism sheet 30 having the above-described configuration, the light diffusion layer 33 is first provided on one surface side of the base material serving as the main body, and the unit prism portion 32 is molded on the other surface side of the base material. Can be manufactured. The light diffusing layer 33 is formed by applying a light-transmitting resin before curing in which light diffusing particles are dispersed on one surface of a base material serving as a main body and curing the resin. Can do.
Various materials can be used as the material forming the main body 31 and the unit prism portion 32. However, it is widely used as a material for an optical sheet incorporated in a display device, and has excellent mechanical properties, optical properties, stability, workability, and the like, and can be obtained at low cost, such as acrylic, styrene, polycarbonate, Transparent resins mainly composed of one or more of polyethylene terephthalate, acrylonitrile and the like, and epoxy acrylate and urethane acrylate-based reactive resins (ionizing radiation curable resins and the like) can be suitably used.

  Returning to FIG. 2, FIG. 4 and FIG. 5, the reflection sheet 40 of the surface light source device 20 will be described. The reflection sheet 40 is a member that reflects 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 40 is a sheet that is capable of so-called specular reflection, such as a sheet made of a material having a high reflectivity such as a metal, or a sheet that includes a thin film (for example, a metal thin film) made of a material having a high reflectivity as a surface layer. It can be preferably applied. Thereby, it becomes possible to improve the usability of light and to improve energy utilization efficiency.

Next, the light control sheet 50 will be described. FIG. 8 is a view showing a cross section of the light control sheet 50. In FIG. 8, the lower side of the paper is the light source side, the upper side of the paper is the observer side, the left side of the paper is the lower side when the liquid crystal display device 101 is installed in the car, and the right side of the paper is the liquid crystal display device 101 inside the car. This is the upper side in the installed posture.
As shown in FIG. 8, the light control sheet 50 includes a base material layer 51 and a light control layer 52.

The base material layer 51 is a layer that becomes a base material for forming the light control layer 52 described in detail later. The base material layer 51 has translucency.
The main component of the material which comprises the base material layer 51 will not be specifically limited if it has translucency. The “main component” means a component that is contained in an amount of 50% by mass or more based on the entire material constituting the layer (the same applies hereinafter). Examples of the main component of the material constituting the base material layer 51 include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, terephthalic acid-cyclohexanedimethanol-ethylene. Polyester resins such as glycol copolymers, polyamide resins such as nylon 6, polyolefin resins such as polypropylene and polymethylpentene, acrylic resins such as polymethyl methacrylate, styrenes such as polystyrene and styrene-acrylonitrile copolymers Examples thereof include a resin, a cellulose resin such as triacetyl cellulose, an imide resin, and a polycarbonate resin. Among these, PET is preferable from the viewpoints of mass productivity, price, availability, etc. in addition to performance. In addition to the main components, other resins and various additives may be appropriately added to the resin constituting the base material layer 51. Examples of general additives include phenol-based antioxidants, lactone-based stabilizers, and the like. Moreover, you may add well-known additives, such as a ultraviolet absorber, a filler, a plasticizer, an antistatic agent, in these resins suitably as needed.

As will be described later, the light control sheet 50 may be disposed between the light source 25 and the liquid crystal panel 15. Further, between the prism sheet 30 and the liquid crystal panel 15, a reflective polarizing sheet (transmits a predetermined polarized light (for example, P wave) out of the light reaching from the light source side and reflects other polarized light (for example, S wave)). Sheet) may be provided. By using the reflective polarizing sheet, the brightness of the displayed image can be improved. In this case, when the light control sheet 50 is disposed closer to the observation side than the reflective polarizing sheet and closer to the light source 25 than the liquid crystal panel 15, it is desirable to use a polycarbonate having a low retardation for the base material layer 51. In this case, the retardation value is desirably 15 nm or less. This is to prevent the polarization of the reflective polarizing sheet from being disturbed by the retardation of the base material layer 51.
Further, in order to use the liquid crystal display device 101 for in-vehicle use, it is desirable to use polycarbonate having high heat resistance for the base material layer 51.
Furthermore, it is desirable that the surface of the base material layer 51 is provided with irregularities. This is to prevent Newton's ring caused by sticking between the base material layer 51 and a member that contacts the base material layer 51 such as the reflective polarizing sheet or the lower polarizing plate 14.

  The thickness of the base material layer 51 is not particularly limited, but is preferably 50 μm or more and 200 μm or less, and more preferably 75 μm or more and 125 μm or less.

  The light control layer 52 is a layer having a function capable of controlling the path of transmitted light. That is, as will be described below, light incident at an angle close to the perpendicular to the layer surface of the light control layer 52 can be transmitted, and light incident at an incident angle greater than a certain angle can be absorbed or reflected.

  In the cross section shown in FIG. 8, the light control layer 52 includes a light-transmitting portion 53 that is substantially trapezoidal, and a light-absorbing portion 54 in which a cross-section formed between the light-transmitting portions 53 is formed in a substantially trapezoidal recess It has. A plurality of light transmission parts 53 and light absorption parts 54 extend in the horizontal direction and are arranged in parallel in a direction orthogonal to the horizontal direction.

  The light transmission part 53 is a part that transmits light, and in the cross section shown in FIG. It is an element having a substantially trapezoidal cross section. The light transmission parts 53 are arranged in parallel at a predetermined interval in the direction along the sheet surface. Accordingly, a recess having a substantially trapezoidal cross section is formed therebetween. The concave portion is a groove having a trapezoidal cross section having a lower base on the upper base side of the light transmission portion 53 and an upper base on the lower bottom side of the light transmission portion 53, and a necessary material described later herein. The light absorption part 54 is formed by being filled.

  Note that the cross-sectional shapes of the light transmitting portion 53 and the light absorbing portion 54 are not limited to trapezoids, but may be triangles or rectangles. The shape or each side may be a polygonal line or a curved line. When the cross-sectional shapes of the light transmission part 53 and the light absorption part 54 are trapezoids or triangles, the angle θ (see FIG. 8) of the hypotenuse of the trapezoids or triangles with respect to the normal direction of the sheet surface is greater than 0 degrees and 20 degrees. The following is preferable.

  The period (pitch) in which the light transmission parts 53 are arranged in parallel is not particularly limited, but is preferably 30 μm to 200 μm, and more preferably 30 μm to 100 μm.

The light transmission portion 53 has a refractive index of N _p, having optical transparency. Such a light transmission part 53 can be formed by hardening the light transmission part structure composition demonstrated below, for example. The value of the refractive index N _p is not particularly limited, but is preferably from availability viewpoint, etc. apply material is 1.49 to 1.56.

  As a light transmissive part composition, the composition which mix | blended ultraviolet curable resin (P1) and the reactive dilution monomer (M1) can be used, for example.

  Examples of the ultraviolet curable resin (P1) include prepolymers such as epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, and polythiol.

  Examples of the reactive dilution monomer (M1) include vinyl pyrrolidone, 2-ethylhexyl acrylate, β-hydroxy acrylate, and tetrahydrofurfuryl acrylate.

  These ultraviolet curable resins (P1) and reactive diluent monomers (M1) can be used alone or in combination of two or more.

  Further, if necessary, a mold release agent and a polymerization initiator may be added to the light transmitting part constituting composition, and silicone is used as various additives in order to improve the coating film modification and coating suitability. It is also possible to add a system additive, a rheology control agent, a defoaming agent, an antistatic agent, an ultraviolet absorber and the like.

  From the viewpoint of productivity and the like when forming the light control layer 52 as described later, the elastic modulus of the light transmission portion 53 is preferably 10 MPa or more and 2000 MPa or less.

  Next, the light absorption unit 54 will be described. The light absorbing portion 54 is formed in a recess between the adjacent light transmitting portions 53 and has a light absorbing property (can absorb light as a whole). Therefore, the shape is generally along the recess.

Light absorbing portion 54 is the same as the refractive index N _p of the light transmitting portion 53, or composed of a predetermined material having smaller refractive index N _b which. When the refractive index N _b of the refractive index N _p and the light absorbing portion 54 of the light transmitting portion 53 was set to N _p> N _b is the interface between the light absorbing portion 54 and the light transmission section 53, the refractive index difference and the interface Based on the relationship with the angle of incidence of light, a portion of the image light can be appropriately reflected at this interface and emitted to the observer. Thereby, in addition to the image light (see L81 in FIG. 8) transmitted through the light transmitting portion 53 without being reflected at the interface, the image light (see L82 in FIG. 8) thus reflected at the interface is provided to the observer. , Can be a bright picture.

  In addition, by reflecting a part of the image light at the interface between the light absorption unit 54 and the light transmission unit 53 as described above, at least of the image light traveling upward in the posture in which the liquid crystal display device 101 is installed in the vehicle interior. A part of the light can be emitted downward from the original direction. That is, the image light emitted from the liquid crystal display device 101 and irradiated on the windshield can be reduced.

The difference in refractive index between N _p and N _b is not particularly limited, but is preferably 0 or more and 0.06 or less. The larger the refractive index difference, the more light is reflected at the interface.

  Further, the image light (see L83 in FIG. 8) incident at a small incident angle with respect to the interface between the light absorption unit 54 and the light transmission unit 53 is reflected at the interface between the light absorption unit 54 and the light transmission unit 53. Without being incident on the light absorbing portion 54, the light is absorbed. Also by this, the image light emitted from the liquid crystal display device 101 and irradiated on the windshield can be reduced.

In the present embodiment, the light absorption part 54 has light absorption performance by containing the light absorption particles 55. Such a light absorbing portion 54 can be formed by filling a concave portion between adjacent light transmitting portions 53 with a binder (light absorbing portion constituting composition) in which light absorbing particles 55 are dispersed. In such form the refractive index of the binder and N _b.

  Although what is used as a binder contained in a light absorption part structure composition is not specifically limited, For example, the composition which mix | blended ultraviolet curable resin (P2) and the reactive dilution monomer (M2) is used preferably.

  Examples of the ultraviolet curable resin (P2) include urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate.

  Moreover, as a reactive dilution monomer (M2), a vinyl monomer, a (meth) acrylic acid ester monomer, and a (meth) acrylamide derivative are mentioned as a monofunctional monomer, for example. Moreover, (meth) acrylate type thing is mentioned as a polyfunctional monomer.

  These ultraviolet curable resins (P2) and reactive dilution monomers (M2) can be used alone or in combination of two or more.

  In addition, you may further add various additives, such as a polymerization initiator, silicone, an antifoamer, a leveling agent, and a solvent, to a light absorption part structure composition as needed.

  As the light absorbing particles 55, light absorbing colored particles such as carbon black are preferably used. However, the light absorbing particles 55 are not limited to these, and colored particles that selectively absorb a specific wavelength in accordance with the characteristics of the image light may be used as the light absorbing particles. 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. More specifically, acrylic cross-linked fine particles containing carbon black, urethane cross-linked fine particles containing carbon black, and the like are preferably used. Such colored particles are usually contained in the binder in the range of 3% by mass to 30% by mass. The average particle diameter of the colored particles is preferably 1.0 μm or more and 20 μm or less. Here, the “average particle diameter” means that obtained by particle size measurement by a mass distribution method.

  In addition, the means for absorbing light in the light absorption part is not limited to the method using light absorption particles as in the present embodiment. Other examples include a method of coloring the entire light absorbing portion constituting composition constituting the light absorbing portion with a pigment or a dye to form an entirely colored light absorbing portion.

  The thickness of the light control layer 52 is not particularly limited, but is preferably 80 μm or more and 250 μm or less, and more preferably 95 μm or more and 150 μm or less.

  The light control sheet 50 as described above can be produced by forming the light control layer 52 on one surface side of the base material layer 51. Examples of the method of forming the light control layer 52 on one surface side of the base material layer 51 include the methods illustrated in FIGS. 9 and 10. FIG. 9 is a diagram for explaining a part of the process of forming the light control layer 52. FIG. 10 is a diagram for explaining another part of the process of forming the light control layer 52.

  First, a base sheet 51 ′ to be the base layer 51 is prepared. In order to mold the light transmission part 53, a mold roll 120 having a groove having a shape corresponding to the light transmission part 53 and the recess 53a is prepared at a predetermined pitch. Next, as shown in FIG. 9, the base material 51 ′ is fed between the mold roll 120 and the nip roll 121. The arrow IX shown in FIG. 9 is the direction in which the substrate 51 'is fed. In accordance with the feeding of the base material 51 ′, droplets of the light transmission part constituting composition 53 ′ are continuously supplied from the supply device between the mold roll 120 and the base material 51 ′. When supplying the light transmissive part constituting composition 53 ′ from the supply device onto the base material 51 ′, the bank 122 in which the light transmissive part constituting composition 53 ′ is accumulated between the mold roll 120 and the base material 51 ′. To be formed. In this bank 122, the light transmitting portion constituting composition 53 'spreads in the width direction of the base material 51' (back side / front side in FIG. 9).

  The light transmitting part constituting composition 53 ′ supplied between the mold roll 120 and the base material 51 ′ as described above is pressed by the pressing force between the mold roll 120 and the nip roll 121. It is filled between the mold rolls 120. Thereafter, the light transmissive part 53 can be formed by irradiating the light transmissive part constituting composition 53 ′ with ultraviolet rays by the light irradiation device 123 and curing the light transmissive part constituting composition 53 ′. The intermediate sheet 50 ′ having the light transmission part 53 formed on the base material layer 51 is pulled off from the mold roll 120 by being pulled through the peeling roll 124.

  Next, as shown in FIG. 10, a light absorbing portion 54 is formed between the light transmitting portions 53 of the intermediate sheet 50 ′ to obtain the light control layer 52. Specifically, the light absorbing portion constituting composition 125 is supplied onto the light transmitting portion 53, and the light absorbing portion constituting composition 125 is filled in the concave portions 53 a between the light transmitting portions 53 by the doctor blade 126. Thereafter, the excess light absorbing portion constituting composition 125 is scraped off, and the light absorbing portion constituting composition 125 remaining in the concave portion 53a between the light transmitting portions 53 is irradiated with ultraviolet rays and cured. Thereby, the light absorption part 54 can be formed. Note that the arrow X shown in FIG. 10 is the feeding direction of the intermediate sheet 50 '.

  The image source unit 10 may be provided with sheets having various functions used in a normal liquid crystal display device in addition to the light control sheet 50. Examples thereof include a sheet for correcting color tone, a sheet having an antiglare function, a sheet for preventing reflection, and a hard coat sheet.

  Next, the operation of the display device having the above configuration will be described with an example of the optical path.

  First, as shown in FIG. 4, 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. 4 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. 4, the light L21 and L22 incident on the light guide plate 21 is reflected from the total reflection due to the difference in refractive index with air on the surface of the unit optical element portion 23 of the light guide plate 21 and the back surface on the opposite side. The emitted light is repeatedly reflected by the reflection sheet 40 and proceeds in the direction in which the unit optical element 23a extends (light guide direction).

However, a back surface prism 22 a is formed on the back surface side of the base portion 22 of the light guide plate 21. For this reason, as shown in FIG. 4, the light L21 and L22 traveling in the light guide plate 21 are sequentially deflected by the back prism 22a and may enter the unit optical element unit 23 at an incident angle less than the total reflection critical angle. . In this case, the light can be emitted from the surface of the unit optical element portion 23 of the light guide plate 21. Lights L21 and L22 emitted from the unit optical element portion 23 travel to the prism sheet 30 disposed on the light output side of the light guide plate 21.
As a result, the light traveling in the light guide plate 21 is gradually emitted from the light exit surface, and the light quantity distribution along the light guide direction of the light emitted from the unit optical element portion 23 of the light guide plate 21 is made uniform. Can do.

  Here, the unit optical element portion 23 of the illustrated light guide plate 21 is constituted by a plurality of unit optical elements 23a, and the cross-sectional shape of each unit optical element 23a is a shape formed by chamfering a triangle or the apex angle of the triangle. Yes. That is, the unit optical element 23 a is configured to have an inclined surface with respect to the light guide direction of the light guide plate 21. Therefore, as shown in FIG. 6, the light L41 emitted from the light guide plate 21 via the unit optical element 23a is refracted when emitted from the light guide plate 21. This refraction is a refraction that approaches the sheet surface normal line nd (the angle formed with the normal line nd decreases) in the parallel direction of the unit optical elements 23a. By such an action, the unit optical element unit 23 can narrow the traveling direction of the transmitted light to the front direction side with respect to the light component along the direction orthogonal to the light guide direction. That is, the unit optical element part 23 exerts a condensing effect on the light component along the direction orthogonal to the light guide direction.

  As described above, the emission angle of the light emitted from the light guide plate 21 is narrowed down within a narrow angle range centering on the front direction on the plane parallel to the parallel direction of the unit optical elements 23a of the light guide plate 21.

  The light emitted from the light guide plate 21 then enters the prism sheet 30. Similar to the unit optical element 23a of the light guide plate 21, the unit prism 32a of the prism sheet 30 condenses the transmitted light by refraction and total reflection at the light incident surface of the unit prism 32a. However, the light whose traveling direction is changed by the prism sheet 30 is a component in a plane perpendicular to the parallel direction of the unit prisms 32 a in the prism sheet 30, and the component condensed by the light guide plate 21. Is different. That is, as indicated by L51 in FIG. 7, the light incident on the unit prism 32a is totally reflected at the interface based on the refractive index difference between the unit prism 32a and air. At this time, since the oblique side of the unit prism 32a is inclined by θ5 / 2 with respect to the sheet surface normal nd, the reflected light at the interface becomes an angle closer to the normal nd than the incident light.

  That is, the light guide plate 21 narrows the light traveling direction within a narrow angle range centering on the front direction on the surface parallel to the parallel direction of the unit optical elements 23a of the light guide plate 21. On the other hand, in the prism sheet 30, the light traveling direction is narrowed down to a narrow angle range centering on the front direction on the surface parallel to the parallel direction of the unit prisms 32 a of the prism sheet 30. Therefore, the front direction luminance can be further increased by the optical action of the prism sheet 30 without impairing the front direction luminance increased by the light guide plate 21.

  The light L51 totally reflected by the unit prism 32a passes through the main body 31, is diffused by the light diffusion layer 33, and is emitted from the prism sheet 30. At this time, since the decrease in luminance is suppressed in the present invention, the brightness of the light deflected by the unit prism 32a with high front luminance as described above can be efficiently emitted. Further, since the image definition is suppressed to a low level, the scratch concealment is sufficiently secured.

  The light emitted from the prism sheet 30 enters the lower polarizing plate 14 of the liquid crystal panel 15. The lower polarizing plate 14 transmits one polarization component of incident light and absorbs the other polarization component. The light transmitted through the lower polarizing plate 14 is selectively transmitted through the upper polarizing plate 13 in accordance with the state of electric field application to each pixel in the liquid crystal cell 12. In this manner, 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 10 can observe an image.

  When the light control sheet 50 is not provided, a part of the image light emitted to the observer side as described above is irradiated on the windshield by moving upward (see L1 and L2 in FIG. 1). Depending on the positional relationship between the liquid crystal display device, the windshield, and the observer, the image light applied to the windshield as described above may be reflected and reflected on the windshield, thereby hindering the observer's field of view.

  According to the vehicle display system 100, the light control sheet 50 includes the light control sheet 50, so that the light control sheet 50 absorbs or reflects the image light directed upward as described above, and the image light is irradiated onto the windshield. This can be suppressed. Therefore, reflection on the windshield can be suppressed. A preferred installation posture of the liquid crystal display device 101 and a preferred form of the light control layer 52 at this time will be described with reference to FIGS. FIG. 11 is a diagram for explaining an example of the optical path of the image light emitted from the liquid crystal display device 101, and is based on the same viewpoint as FIG. FIG. 12 is a diagram for explaining a preferred form of the light control layer 52, which is based on the same viewpoint as FIG.

As shown in FIG. 11, the angle of the windshield 102 with respect to the horizontal plane is θ _w , the angle of the image display surface of the liquid crystal display device 101 with respect to the horizontal plane is θ _d , of the image light emitted from the liquid crystal display device 101 above the horizontal plane The angle of the image light L _U having the largest angle with respect to the horizontal plane with respect to the normal direction of the image display surface is θ _O , and the angle of the reflected light traveling direction when the image light L _U is reflected by the windshield 102 with respect to the horizontal plane is θ e Then, it is preferable to determine the installation posture of the liquid crystal display device 101 and the form of the light control layer 52 so that the following formula is satisfied. However, in the following formula, θ _w , θ _O , θ _d , θe <90 °.
| Θ _e | = | θ _w − (90 ° + θ _O −θ _w −θ _d ) |> 20 °

Here, θ _O can be considered as follows (see FIG. 12).
The angle between the line connecting the lower end on the incident side of the light transmission part and the upper end on the output side of the light transmission part with respect to the normal direction of the image display surface is θ _i (where θ _i <90 °), and the refraction of the light transmission part If the rate is n,
n × sinθ _i = sinθ _O
∴θo ＝ asin (n × sinθ _i )
Therefore, it is preferable to determine the installation posture of the liquid crystal display device 101 and the form of the light control layer 52 so that the following formula is satisfied.
| Θ _e | = | θ _w − (90 ° + asin (n × sin θ _i ) −θ _w −θ _d ) |> 20 °

By using the light control layer 52 so that | θ _e |> 20 ° as described above, the image light (reflected light) emitted from the liquid crystal display device 101 and reflected by the windshield 102 is reflected on the ceiling or floor. Since the light travels in the direction, the reflected light hardly enters the observer's (driver's) field of view.

The image light reflected by the windshield as described above is mainly a polarization component other than P-polarized light. That is, light (P-polarized light) whose electric field vibration direction is parallel to the incident surface is likely to pass through the windshield, but image light is reflected on the windshield when other light is reflected by the windshield. .
In the VA mode and IPS mode liquid crystal display devices, only the light oscillating in the vertical direction is allowed to pass through the transmission axis of the polarizing plate provided on the viewer side of the liquid crystal panel (the light oscillating in the horizontal direction is allowed to pass). The direction other than P-polarized light can be suppressed. Video light emitted as P-polarized light from the display surface of the in-vehicle display device is likely to enter the windshield as P-polarized light. Therefore, when the VA liquid crystal display device and the IPS liquid crystal display device are used as the in-vehicle display device, the reflection of the image light on the windshield can be suppressed to some extent without using the light control sheet 50.
On the other hand, in the TN liquid crystal display device, the direction of the transmission axis of the polarizing plate provided on the viewer side of the liquid crystal panel is a direction through which at least a part of the light oscillating in the horizontal direction passes, Video light containing a large amount of other polarization components is emitted. Therefore, when a TN liquid crystal display device is used as an in-vehicle display device, image light is likely to be reflected on the windshield.
That is, light control is performed on a liquid crystal display device in which the direction of the transmission axis of a polarizing plate arranged on the viewer side passes through at least a part of the light oscillating in the horizontal direction as in a TN liquid crystal display device. By providing the sheet 50, the light control sheet 50 can be used effectively, and image light can be prevented from being reflected on the windshield. Therefore, according to the vehicle display system 100, the light control sheet 50 can be used effectively, and the image light emitted from the liquid crystal display device 101 can be suppressed from being reflected on the windshield 102.

  In the above description, the light control sheet 50 is disposed on the outermost surface of the liquid crystal display device 101 on the viewer side. However, the light control sheet 50 is installed on the viewer side from the light source 25. Good. For example, the light control sheet 50 may be disposed between the light source 25 and the liquid crystal panel 15.

Example 1
First, a mold roll used for the production of the light control layer was produced as follows. The columnar iron core was plated with copper, and the copper-plated portion was cut with a cutting tool to form a plurality of grooves corresponding to the light transmitting portion at a predetermined pitch in the roll axis direction. The cross-section (surface perpendicular to the direction in which the groove extends) of the groove is constant, the upper base (axis side of the mold roll) is 4 μm, the lower base (opening side of the groove) is 22 μm, the depth is 120 μm, The angle with respect to the upper base of both hypotenuses is 4.5 °. The pitch of the grooves in the roll axis direction was 47 μm. After forming such grooves, chrome plating was performed to produce a mold roll.

  Next, a light transmission part was molded on a base material (a polycarbonate film having a thickness of 130 μm) using the mold roll and a transparent ultraviolet curable resin (refractive index: 1.56). Next, a black ultraviolet curable resin (refractive index: 1.49) was filled in the recesses between the adjacent light transmission parts to form a light absorption part. Furthermore, a polycarbonate film having a thickness of 100 μm was bonded to the surface side on which the light transmitting part and the light absorbing part were formed as described above via an ultraviolet curable adhesive to produce a light control sheet. The thickness of the light control sheet was 400 μm.

  The light control sheet produced as described above is used for an existing TN liquid crystal display device (the direction of the transmission axis of the polarizing plate arranged on the viewer side of the liquid crystal panel passes light oscillating in the horizontal direction). The liquid crystal display device is placed between the backlight (light source) and the liquid crystal panel, and is placed under the windshield of the automobile. As a result, when the light control sheet was used, the reflection of the image light on the windshield could be clearly reduced as compared with the case where the light control sheet was not used.

(Comparative Example 1)
The light control sheet produced in the same manner as in Example 1 was placed between the backlight (light source) of the existing IPS liquid crystal display device and the liquid crystal panel, and was placed under the windshield of the automobile. As a result, it was possible to suppress the reflection of image light on the windshield, but even when the light control sheet was not used, there was little reflection of image light on the windshield. The effect was not clear.

DESCRIPTION OF SYMBOLS 10 Image source unit 12 Liquid crystal cell 13, 14 Polarizing plate 15 Liquid crystal panel 20 Surface light source device 21 Light guide plate 22 Base 22a Back surface prism 23 Unit optical element part 25 Light source 30 Prism sheet 31 Main body part 32 Unit prism part 32a Unit prism 50 Light control Sheet 51 Base material layer 52 Light control layer 53 Light transmission part 54 Light absorption part

Claims (3)

Car windshields,
A liquid crystal display device installed at a predetermined distance from the windshield in the automobile;
A light control sheet disposed in the liquid crystal display device or on a surface of the liquid crystal display device that emits image light, and
The liquid crystal display device includes a light source and a liquid crystal panel disposed on the viewer side from the light source,
The liquid crystal panel includes polarizing plates on the light source side and the observer side,
The direction of the transmission axis of the polarizing plate arranged on the observer side is a direction through which light oscillating in the horizontal direction passes.
The light control sheet includes a light transmissive part having translucency arranged in parallel along the sheet surface, and a light absorbing part having light absorptivity disposed between the adjacent light transmissive parts. Vehicle display system.   The vehicle display system according to claim 1, wherein the light transmission part and the light absorption part extend in a horizontal direction.   The vehicle display system according to claim 1, wherein the liquid crystal display device is a TN liquid crystal display device.

Images