Liquid crystal display device

Abstract

To provide a transparent liquid crystal display device with high image quality.SOLUTION: A liquid crystal display device has liquid crystal held between a TFT substrate and a counter substrate. A display region is formed in a part where the TFT substrate and the counter substrate overlap with each other. A terminal region is formed in a part of the TFT substrate that does not overlap with the counter substrate. A cover glass is disposed on the TFT substrate or the counter substrate. A first side surface of the light guide plate is in contact with a side surface of the cover glass on the terminal side. A plurality of LEDs are disposed on a second side surface of the light guide plate that faces the first side surface. A first lens 31 is formed on the first side surface of the light guide plate. A round prism 32 is formed on the second side surface. A pitch p2 of the round prism in a first direction is larger than a width w2 of the round prism in the first direction.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a display device, and more particularly to a transparent display using a liquid crystal display device. [Background technology]

[0002] There is a demand for a transparent display that allows the background to be seen, like glass. When displaying an image, a transparent display can display the same screen on both the front and back sides. In areas where no image is displayed, the image of the background can be seen through the glass, and when an image is displayed, the image can be displayed superimposed on the background. Such a transparent display can be realized, for example, by using a liquid crystal display device.

[0003] Patent Document 1 describes an example of a transparent display using a liquid crystal display device. Patent Document 2 describes a light source device that homogenizes light from multiple light sources using a prism sheet with fine prisms arranged on the entrance and exit sides. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-219440 A [Patent Document 2] JP 2019-200358 A Summary of the Invention [Problem to be solved by the invention]

[0005] Direct backlights cannot be used with transparent LCD displays. Therefore, a sidelight type light source is used, in which the light source is placed on the side of the substrate. This sidelight must efficiently supply uniform light to the transparent LCD panel. LEDs are actually used as the light source, but white LEDs may be used, or LEDs that emit separate R (red), G (green), and B (blue) lights may be used in parallel.

[0006] An object of the present invention is to realize a transparent liquid crystal display device having a bright screen with little color unevenness and excellent contrast by improving the light utilization efficiency and supplying uniform light to the display area. [Means for solving the problem]

[0007] The present invention overcomes the above problems, and representative means for achieving this are as follows.

[0008] (1) A liquid crystal display device in which liquid crystal is sandwiched between a TFT substrate having pixel electrodes and an opposing substrate, a display area is formed in a portion where the TFT substrate and the opposing substrate overlap, a terminal area is formed in a portion of the TFT substrate that does not overlap with the opposing substrate, a cover glass is disposed on the TFT substrate or the opposing substrate, a first side surface of a light guide plate is in contact with a side surface of the cover glass facing the terminal, and a plurality of LEDs are disposed on a second side surface of the light guide plate facing the first side surface, the liquid crystal display device being characterized in that a first lens is formed on the first side surface of the light guide plate and a round prism is formed on the second side surface, and the pitch of the round prism in a first direction is greater than the width of the round prism in the first direction.

[0009] (2) The liquid crystal display device described in (1), wherein the width of the round prism in the first direction is 80% to 95% of the pitch of the round prism in the first direction.

[0010] (3) The liquid crystal display device according to (1), wherein the radius of curvature at the apex of the round prism is 0.01 mm or more, and a straight line exists on the hypotenuse of the round prism.

[0011] (4) The liquid crystal display device according to (1), wherein the surface of the first lens is rough. (5) The liquid crystal display device according to (4), wherein the rough surface has an Rz of 1.0 μm or more and an Sm of 0.5 μm or more.

[0012] (6) The liquid crystal display device according to (4), wherein the rough surface has an Rz / Sm ratio of 2 or more.

[0013] The liquid crystal display device of (7) is the liquid crystal display device according to (1), characterized in that a displayed image can be viewed both when viewed from the TFT substrate side and when viewed from the counter substrate side. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a front view of the transparent liquid crystal display device. [Diagram 2] FIG. 2 is a side view of a transparent liquid crystal display device. [Diagram 3] 5A to 5C are cross-sectional views showing the operation of the transparent liquid crystal display panel. [Figure 4] FIG. 2 is a cross-sectional view showing the details of a liquid crystal layer. [Diagram 5] FIG. 1 is a plan view of a transparent liquid crystal display device according to a first embodiment. [Figure 6] 6 is a cross-sectional view taken along line AA in FIG. 5. [Figure 7] FIG. [Figure 8] 4 is a cross-sectional view showing the function of a round prism on the incident surface of a light guide plate. [Figure 9] 10A and 10B are plan views showing examples of dimensions of lenses formed on a light guide plate. [Figure 10] 10 is a cross-sectional view showing a state in which a rough surface is formed on a lenticular lens formed on an exit surface of a light guide plate. FIG. [Figure 11]This is an example of a rough surface. [Figure 12] FIG. 2 is a plan view of a liquid crystal display panel on which luminance distribution was measured. [Figure 13] 10 is a graph showing the luminance distribution of a liquid crystal display panel in the configuration of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described in detail below with reference to examples. EXAMPLES

[0016] Fig. 1 is a front view of the transparent liquid crystal display device 4000, and Fig. 2 is a side view. In Fig. 1 and Fig. 2, there is no backlight behind the display area 1000, and the substrate is made of transparent glass, so that light normally passes through and the back of the transparent liquid crystal display device 4000 can be seen.

[0017] A driving unit 2000 including a light source as a side light and a driving circuit area is disposed in a lower housing 3000. An image displayed in a display area 1000 of the display panel can be viewed from either the front or back side. Also, an image displayed on a transparent liquid crystal display device can give the impression of floating in the background.

[0018] FIG. 3 is a cross-sectional view showing the operation of a transparent liquid crystal display device 4000. FIG. 3 shows a basic structure of a transparent liquid crystal display device, which is slightly different from the structure of the embodiment shown in FIG. 6 and the like. In FIG. 3, liquid crystal 300 is sandwiched between a TFT substrate 100 on which pixel electrodes 130, signal lines, TFTs, etc. are formed, and a counter substrate 200 on which a common electrode 140 is formed. Since FIG. 3 is driven in a so-called field sequential manner, no color filter is present. A display area is formed in the area where the TFT substrate 100 and the counter substrate 200 overlap, and a terminal area is formed in the TFT substrate 100 in the area not overlapping with the counter substrate 200.

[0019] In Fig. 3, the TFT substrate 100 and the counter substrate 200 are bonded with a sealant 150, and liquid crystal 300 is sealed inside. The sealant 150 is made of a transparent resin. The liquid crystal 300 in Fig. 3 is what is called a polymer dispersed liquid crystal, and its configuration is shown in Fig. 4. Fig. 4 is an enlarged cross-sectional view of the liquid crystal portion in Fig. 3. In Fig. 4, the liquid crystal 300 is sandwiched between the TFT substrate 100, which has a pixel electrode 130 and an alignment film 160 formed thereon, and the counter substrate 200, which has a common electrode 140 and an alignment film 160 formed thereon. In Fig. 4, a pixel Pix is ​​formed corresponding to the pixel electrode 130.

[0020] This liquid crystal 300 is called polymer-dispersed liquid crystal, and is composed of a bulk 301 formed by a polymer and fine particles 302 containing liquid crystal molecules. When a voltage is applied between the pixel electrode 130 and the common electrode 140, the fine particles 302 containing liquid crystal molecules rotate due to the electric field, scattering light. If no voltage is applied between the pixel electrode 130 and the common electrode 140, light is not scattered. Since the scattering of light is controlled for each pixel, an image is formed. This image can be viewed from both the front and back of the liquid crystal display panel.

[0021] Returning to Fig. 3, the TFT substrate 100 is formed to be larger than the counter substrate 200, and the portion where the TFT substrate 100 and the counter substrate 200 do not overlap is a terminal region. In the terminal region, LEDs 10 serving as light sources are arranged facing the side surface of the counter substrate 200. Light from the LEDs 10 enters the inside of the liquid crystal display panel through the side surface of the counter substrate 200 or through the sealant 150. The incident light collides with fine particles 302 containing liquid crystal molecules in the liquid crystal layer 300 while repeatedly being totally reflected.

[0022] When light collides with a particle 302 in a pixel where a voltage is applied between the pixel electrode 130 and the common electrode 140, the light is scattered as shown in Fig. 3. On the other hand, in a pixel where no voltage is applied between the pixel electrode 130 and the common electrode 140, the light travels in a straight line. As a result, the scattering of the light incident on the liquid crystal 300 is controlled for each pixel, and an image is formed.

[0023] In Fig. 3, a driver IC 40 is placed alongside the LED 10, which is the light source. The driver IC 40 drives the liquid crystal display panel and becomes very hot during operation. In particular, the liquid crystal display device in Fig. 3 is driven in a field sequential manner, so data processing is performed at three times the speed of a normal driving method, and the driver IC 40 also generates a lot of heat.

[0024] A flexible wiring board 50 is connected to an end of the TFT substrate 100 in order to supply signals and power to the driver IC 40. In an actual display device, an LED wiring board for supplying power to the LEDs 10, which are the light sources, exists, but is omitted in FIG.

[0025] The transparent liquid crystal display device having the configuration shown in Fig. 3 has the following problems. That is, it is difficult to make the opposing substrate 200 sufficiently thick, and therefore the light from the LEDs cannot be sufficiently taken into the liquid crystal display panel. In addition, when viewed in a plan view, the LEDs 10 are arranged on the side surface of the opposing substrate 200, but the difference in luminance between the portion corresponding to the LEDs 10 and the portion not corresponding to the LEDs 10 becomes large, making it difficult to provide a uniform light source. In addition, a configuration in which single-color LEDs 10 are arranged in parallel is prone to color unevenness.

[0026] The configuration of the present invention shown in FIG. 5 and subsequent figures can efficiently capture light from a light source and supply uniform light to a liquid crystal display panel. FIG. 5 is a plan view of a transparent liquid crystal display device 4000 according to a first embodiment. In FIG. 5, the transparent liquid crystal display device 4000 is composed of a cover glass 400 including a display area 1000, a light guide plate 30, and a side light including a plurality of LEDs 10. The plurality of LEDs 10 are arranged on an LED substrate 20 and attached to the side surface of the light guide plate 30, but in FIG. 5, the LED substrate 20 is omitted for clarity. In FIG. 5, the light guide plate 30 may be formed of, for example, a transparent resin such as acrylic or polycarbonate, or glass.

[0027] In FIG. 5, 10R denotes a red LED, 10G denotes a green LED, and 10B denotes a blue LED. The red, green, and blue lights are mixed in the light guide plate 30, and white light is supplied to the liquid crystal display panel. In FIG. 5, the LED 10 is disposed on the incident side of the light guide plate 30. Note that a white LED 10 may be used instead of the single-color LED 10. The exit side 31 of the light guide plate 30 is abutted against the side of the cover glass 400 of the liquid crystal display panel. As will be described later, in order to improve the efficiency of use of light from the LED 10 and to obtain uniform light, microlenses or microprisms are formed on the incident side and exit side of the light guide plate 30.

[0028] Fig. 6 is a cross-sectional view taken along the line AA in Fig. 5. In Fig. 6, the right side constitutes the display area of ​​the liquid crystal display panel, and the left side constitutes the terminal area and side light of the liquid crystal display panel. In Fig. 5, a TFT substrate 100 on which pixel electrodes, scanning lines, video signal lines, TFTs, etc. are formed, and a counter substrate 200 on which counter electrodes, etc. are formed, are bonded together by a sealant 150, and a liquid crystal layer 300 is enclosed inside. The sealant 150 is a transparent sealant.

[0029] A cover glass 400 is disposed on the counter substrate 200 to supply light from the side light to the display area. The cover glass 400 is formed thick so as to easily capture light from the LEDs 10. The cover glass 400 has a thickness of, for example, about 3 mm. Since both the TFT substrate 100 and the counter substrate 200 have a thickness of, for example, 0.5 mm or 0.7 mm, the cover glass 400 also serves to reinforce the mechanical strength of the liquid crystal display panel.

[0030] 6, the portion where the TFT substrate 100 and the counter substrate 200 overlap is the display area. The TFT substrate 100 is formed larger than the counter substrate 200. The portion where the TFT substrate 100 does not overlap with the counter substrate 200 is the terminal area. A driver IC 40 for driving the liquid crystal display panel is disposed in the terminal area. A flexible wiring substrate 50 for supplying power and signals to the liquid crystal display panel is connected to the end of the terminal area.

[0031] Meanwhile, the side of the light guide plate 30 is butted against and bonded to the side of the end of the cover glass 400. Optical clear resin (OCR) is used to bond the side of the cover glass 400 and the side of the light guide plate 30. In FIG. 6, LEDs 10 are arranged on the other side of the light guide plate 30. As shown in FIG. 5, a large number of LEDs 10 are arranged on the side of the light guide plate 30. The light guide plate 30 homogenizes the light from the multiple LEDs 10 and gives the light a predetermined directionality so that the light can be more effectively taken in by the cover glass 400.

[0032] 6, a space formed between the light guide plate 30 and the terminal region of the TFT substrate 100 is filled with a resin 110 to maintain the mechanical strength of the transparent liquid crystal display device. As the resin 110, for example, a silicone resin, a urethane resin, an acrylic resin, or the like can be used.

[0033] The thickness of the light guide plate 30 is 3 mm, the same as the thickness of the cover glass 400. The height of the LEDs 10 abutted against the incident surface of the light guide plate 30 is, for example, 2 mm, which is slightly smaller than the thickness of the light guide plate 30, taking into consideration installation tolerance. The multiple LEDs 10 are connected to an LED substrate 20, and the LED substrate 20 is connected to a flexible wiring substrate 50 or another flexible wiring substrate and receives a current supply.

[0034] In Fig. 6, the surface of the light guide plate 30 facing the cover glass 400 is called the exit surface, and the surface facing the LEDs 10 is called the entrance surface. As shown in Fig. 7, a large number of round prisms 32 with rounded ends are formed on the entrance surface, and a large number of lenticular lenses 31 are formed on the exit surface. This is to ensure that the light from the LEDs 10 is sufficiently mixed in the light guide plate 30, and that diffused light and straight light are included in a well-balanced manner, so that the light can be sufficiently taken into the liquid crystal display panel.

[0035] In FIG. 7, lenticular lenses 31 are formed without gaps on the exit surface side of light guide plate 30. Lenticular lenses 31 have a pitch p1, a lens width w1, a lens height h1, and a cross-sectional curvature radius rp. By the way, when lenticular lenses 31 are formed without gaps, it means that lens pitch p1 and lens width w1 are the same. However, in reality, due to requirements of the manufacturing process, lens pitch p1 is slightly larger than lens width w1. In other words, light guide plate 30 is formed by injection molding of resin, and in such a manufacturing method, pitch p1 is slightly larger than lens width w1.

[0036] Round prisms 31 are formed with gaps on the incident surface side of the light guide plate 30. The pitch of the round prisms 31 is p2, and the width is w2, where p2>w2. p2-w2 is the width of the flat surface 321. The height of the round prism is h2, and the radius of curvature of the tip is zr. The apex angle of the round prism is φ.

[0037] The length of the light guide plate 30 in FIG. 7 in the light path direction (y direction) is lgl. In FIG. 7, the horizontal straight lines drawn on the exit surface and the entrance surface are imaginary lines to clearly show the shape of the lens. The same applies to the following figures. In FIG. 7, the round prism 32 is an xy cross-sectional view, and the round prism 32 extends in the z direction. In other words, it extends along the entrance surface of the light guide plate 30. In FIG. 7, the apex angle φ of the round prism 32 is 75 degrees.

[0038] Fig. 8 is a cross-sectional view showing the function of the round prism 32 at the incident surface. In Fig. 8, the arrow indicates the direction of the light emitted from the LED 10. Of the light emitted from the LED, light sl that travels in the y direction and perpendicularly enters the flat surface 321 travels straight in the y direction and becomes straight light sl. Of the light emitted from the LED, light that enters the prism at a right angle travels straight and becomes diffuse light dl. Of the light emitted from the LED 10, light that enters the prism 32 at an angle is refracted in the y direction and becomes focused light cl.

[0039] By appropriately setting the shape of the round prism 32 on the entrance surface of the light guide plate 30 and the area of ​​the flat surface 321, it is possible to adjust the ratio of the straight light sl, the convergent light cl, and the diffused light dl. Therefore, in combination with the action of the lenticular lens 31 on the exit surface, it is possible to control the directivity of the light exiting from the diffusion plate 30. Also, the light from the multiple LEDs 10 can be mixed sufficiently within the light guide plate 30.

[0040] FIG. 9 is a cross-sectional view showing the specific shapes of the entrance surface and the exit surface of the light guide plate 30. On the entrance surface side, the pitch of the round prisms 32 is 0.1 mm and the width is 0.09 mm, so the width of the flat surface 321 is 0.01 mm. In order to obtain the effect of the flat surface 321 to a certain extent, it is desirable to direct about 5% to 20% of the pitch of the round prisms 32 to the flat surface 321. The height of the round prism 32 is 0.0458 mm. The radius of curvature near the apex of the round prism is 0.02 mm. The cross section of the prism formed in the conventional light guide plate 30 is often a sharp triangle, but in the present invention, the apex of the prism is rounded. In other words, by making the apex of the prism round, the balance between the convergent light cl and the diffused light dl can be changed. In this embodiment, the radius of curvature near the apex of the round prism 32 is, for example, 0.01 mm or more. However, if the radius of curvature is too large, it becomes difficult to distinguish it from a lenticular lens, so the radius of curvature must be kept below a level that maintains the straight slopes of the triangle in the round prism.

[0041] On the emission surface side of the light guide plate 30 in Fig. 9, the pitch of the lenticular lenses 31 is 0.0733 mm, and the width is 0.0693 mm. The lens pitch is 0.004 mm larger than the lens width, but this is due to the requirements of the manufacturing method. The radius of curvature of the lenticular lenses 31 is R0.04 mm, and the height is 0.02 mm.

[0042] 7 to 9, by using round prisms 32 on the incident surface of the light guide plate 30 and forming flat surfaces between the round prisms 32, it is possible to sufficiently mix the light from the LEDs 10 in the light guide plate 30. In addition, in combination with the lenticular lens 31 on the exit surface, it is possible to optimize the directivity of the light exiting from the light guide plate 30.

[0043] 7 to 9, the extending direction of the round prism 32 formed on the incident surface and the extending direction of the lenticular lens 31 formed on the exit surface are the same z direction. However, there may be cases where the extending direction of the round prism 31 formed on the incident surface and the extending direction of the round prism 32 formed on the exit surface are at right angles to each other. EXAMPLES

[0044] Fig. 10 is a plan view showing the shape of the light guide plate 30 in Example 2. Fig. 10 differs from Fig. 9 in Example 1 in that the light guide plate 30 in Fig. 10 has a roughened exit surface on which the lenticular lens 31 is formed. By roughening the exit surface, it is possible to further increase the amount of diffused light. This makes it possible to uniformize the light within the cover glass 400.

[0045] 10, the incident surface of the light guide plate 30 is not roughened. That is, on the incident surface, it is necessary to control the light by the ratio of the round prisms 32 to the flat surface 321, and the radius of curvature near the apex of the round prisms 32, etc. This is because such a design can be performed more easily without roughening the surface.

[0046] Fig. 11 shows an example of a rough surface formed on the exit surface of the light guide plate 30. That is, it is a diagram defining Rz and Sm, which represent the degree of roughness of the surface. In this diagram, irregularities with triangular cross sections are formed regularly, but this is only for the purpose of defining Rz and Sm, and an actual rough surface has a continuous series of irregular irregularities.

[0047] The graph in FIG. 11 is an example of the surface roughness of the actual light guide plate 30 on the emission surface. The unit is μm. The values ​​of Rz, Sm, and Rz / Sm that can be read from the graph are Rz=1.30 to 2.08 μm, Sm=0.60 to 1.0 μm, and Rz / Sm=2.2 to 2.1. In order to obtain a certain degree of roughening effect, it is preferable that Rz is, for example, 1.0 μm or more, Sm is, for example, 0.5 μm or more, and Rz / Sm is 2 or more. On the other hand, it is necessary to suppress the size of the rough surface to a level that does not affect the effect of the lenticular lens 31. Considering these conditions, it is preferable that Rz is 1 μm or more and 5 μm or less, and Sm is 0.5 μm or more and 4 μm or less.

[0048] Incidentally, when the light guide plate 30 is formed from acrylic or polycarbonate resin, for example, injection molding is used. In this case, if the mold used for injection molding is roughened, the surface of the light guide plate 30 can be roughened without adding an additional process.

[0049] 12 and 13 show the results of evaluating the luminance distribution in the cover glass 400 when the light guide plate 30 shown in FIG. 10 is used. The evaluation was performed by computer simulation. FIG. 12 is a plan view of a transparent display device used as a premise in the simulation. The shape in FIG. 12 is the same as that in FIG. 5. That is, a red LED 10R, a green LED 10G, and a blue LED 10B are arranged on the incident surface of the light guide plate 30 at a pitch p3 (e.g., 3.66 mm). The size of each LED 10 is, for example, 2 mm in the x direction.

[0050] 10 is formed on the incident surface of the light guide plate 30 shown in Fig. 12, and the lenticular lens 31 with a roughened surface shown in Fig. 10 is formed on the exit surface of the light guide plate 30. The length lgl of the light guide plate 30 in the y direction is 10 mm. The dotted line in Fig. 12 is an imaginary line indicating the portion of the cover glass 400 where the luminance distribution was measured. The position of the dotted line is a position on the cover glass 400 that is distant by rp (14 mm) in the y direction from the exit surface of the light guide plate 30.

[0051] In Fig. 12, angle θ with respect to the side of light guide plate 30 extending in the y-axis direction (hereinafter simply referred to as angle θ with respect to the y-axis direction) indicates the direction of light at the measurement position. At the measurement position in Fig. 12, the light taken into the liquid crystal display panel is light with θ in the range of +5 degrees to -5 degrees. Therefore, the integral value of the amount of light with θ in the range of +5 degrees to -5 degrees was evaluated at the measurement position indicated by the dotted line in Fig. 12.

[0052] The evaluation results are shown in Fig. 13. The horizontal axis in Fig. 13 is the position, i.e., the position in the x direction in Fig. 12, in mm. The vertical axis is the luminance Lv at each location, in cd / m 2 That is, the vertical axis represents the integral value of the amount of light in the range of θ from +5 degrees to −5 degrees shown in FIG.

[0053] In Fig. 13, the evaluation is performed for each of the colors white, green, red, and blue. The ripple of each color in Fig. 13 represents the fluctuation in luminance. For example, the ripple of white is 15%. In general, if the ripple is 20% or less, that is, if the luminance fluctuation is 20% or less, the luminance fluctuation is considered to be within the acceptable range.

[0054] For the single colors Green, Red, and Blue, the ripple is about 15%, which is within the allowable range. Therefore, the specifications of this embodiment shown in Figures 10 and 11 are ones that address luminance unevenness and color unevenness.

[0055] As described above, by using the configurations of the present invention shown in Examples 1 and 2, it is possible to suppress unevenness in brightness and color in a transparent liquid crystal display device, and to efficiently increase the amount of light in the liquid crystal display panel.

[0056] In the above description, the cover glass 400 and the light guide plate 30 are arranged on the counter substrate 200 side, but the same applies when they are arranged on the TFT substrate 100 side.

[0057] In addition, in the above explanation, the display device has been described as a liquid crystal display device, but the present invention is not limited to liquid crystal display devices and can also be applied to other transparent display devices that use side lights. [Explanation of symbols]

[0058] 10...LED, 20...LED substrate, 30...light guide plate, 31...lenticular lens, 32...round prism, 40...driver IC, 50...flexible wiring board wiring, 60...first heat sink, 100...TFT substrate, 110...resin, 130...pixel electrode, 140...common electrode, 150...sealing material, 160...alignment film, 200...opposite substrate, 301...bulk, 300...liquid crystal layer, 302...particles containing liquid crystal molecules, 400...cover glass, 1000...display area, 2000...driver unit, 3000...casing, 4000...transparent liquid crystal display device

Claims

1. A liquid crystal display device in which liquid crystal is sandwiched between a TFT substrate having pixel electrodes and an opposing substrate, a display area is formed in a portion where the TFT substrate and the counter substrate overlap, and a terminal area is formed in a portion of the TFT substrate that does not overlap with the counter substrate; A cover glass is disposed on the TFT substrate or the opposing substrate, a first side surface of a light guide plate contacts a side surface of the cover glass on the terminal side, and a plurality of LEDs are disposed on a second side surface of the light guide plate opposite to the first side surface, a first lens is formed on the first side surface of the light guide plate; A round prism is formed on the second side surface, A liquid crystal display device, characterized in that the pitch of the round prisms in a first direction is larger than the width of the round prisms in the first direction.

2. 2 . The liquid crystal display device according to claim 1 , wherein the width of the round prism in the first direction is 80% to 95% of the pitch of the round prism in the first direction.

3. 2. The liquid crystal display device according to claim 1, wherein the radius of curvature at the apex of the round prism is 0.01 mm or more, and a straight line exists on the hypotenuse of the round prism.

4. 2. The liquid crystal display device according to claim 1, wherein a plane is formed between the adjacent round prisms.

5. 2. The liquid crystal display device according to claim 1, wherein the first lens is a lenticular lens.

6. 2. The liquid crystal display device according to claim 1, wherein the pitch of the round prism is larger than the pitch of the first lens.

7. 2. The liquid crystal display device according to claim 1, wherein the extending direction of the first lens is the same as the extending direction of the round prism.

8. 2. The liquid crystal display device according to claim 1, wherein the extending direction of the first lens and the extending direction of the round prism are perpendicular to each other.

9. 2. The liquid crystal display device according to claim 1, wherein the surface of the first lens is rough.

10. 10. The liquid crystal display device according to claim 9, wherein the rough surface has an Rz of 1.0 [mu]m or more and an Sm of 0.5 [mu]m or more.

11. 10. The liquid crystal display device according to claim 9, wherein the rough surface has an Rz / Sm ratio of 2 or more.

12. 10. The liquid crystal display device according to claim 9, wherein the round prism on the first side surface of the light guide plate does not have a rough surface.

13. 2. The liquid crystal display device according to claim 1, wherein the cover glass is disposed on the side of the opposing substrate.

14. 2. The liquid crystal display device according to claim 1, wherein a display image can be viewed from both the TFT substrate and the counter substrate.

Images