Liquid crystal display device

Abstract

A liquid crystal display device is provided, which can prevent light leakage caused by a black display of a projected image of the liquid crystal display device due to a high temperature of a light source, and can display a high-quality image without losing the sense of reality. The device comprises: a light-transmitting liquid crystal display element (4) having two glass substrates (2a, 2b) and a liquid crystal layer (3) sealed between the two glass substrates (2a, 2b); a backlight device (5) emitting light toward one glass substrate (2a) of the liquid crystal display element (4); an emitting-side polarizing plate (6) located on the other glass substrate (2b); an incident-side polarizing plate (7) located on one glass substrate (2a); and a plate-shaped polarizing element (10) having a base layer (8) including a glass substrate and a metal layer (9) having a polarization function and stacked on the base layer (8). The polarizing element (10) is configured such that the base layer (8) and the incident-side polarizing plate (7) are opposed to each other, and the thickness of the base layer (8) is set to be thicker than the thickness of each of the two glass substrates (2a, 2b).

Description

Technical Field

[0001] The present disclosure relates to a liquid crystal display device that can be used for projection display of image light or the like. Background Art

[0002] An example of the prior art is described in Patent Document 1, for example.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-228442 Summary of the invention

[0006] The liquid crystal display device disclosed in the present invention comprises: a light-transmitting liquid crystal display element, having two transparent substrates and a liquid crystal layer sealed between the two transparent substrates; an incident-side polarizing plate, located on one of the transparent substrates of the liquid crystal display element; a light source, emitting light toward one of the transparent substrates of the liquid crystal display element; and a plate-shaped polarizing element, having a base layer formed of glass and a metal layer with a polarizing function stacked on the base layer, wherein the polarizing element is arranged between the light source and the liquid crystal display element, with the metal layer being opposite to the light source, and the thickness of the base layer being set to a structure thicker than the thickness of each of the two transparent substrates.

[0007] Effects of the Invention

[0008] According to the liquid crystal display device disclosed in the present invention, it is possible to prevent the leakage of the black display of the projected image caused by the high temperature of the light source called the backlight, and to display a high-quality image without damaging the sense of reality. That is, the metal layer constituting the polarizing element also functions as a good thermal conductive component and a good heat dissipation component that receives the light radiated from the backlight and thus receives the radiant heat and transfers and diffuses heat to the surrounding area. Furthermore, the base layer constituting the polarizing element has a thickness thicker than the thickness of each of the two transparent substrates, so the heat capacity increases. As a result, it also functions as a heat insulating component that receives the light radiated from the backlight and thus receives the radiant heat to effectively reduce the radiant heat transmitted to the liquid crystal display element side. Therefore, it is possible to prevent the leakage of the black display in the liquid crystal display element accompanying the high temperature of the backlight, and it is possible to prevent the leakage of the black display of the projected image using the liquid crystal display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The objects, features and advantages of the present invention will become more apparent from the following detailed description and accompanying drawings.

[0010] Figure 1 This is a cross-sectional view schematically showing the structure of a liquid crystal display device according to an example of an embodiment of the present disclosure.

[0011] Figure 2This is a conceptual diagram for explaining the polarization function of a polarization element.

[0012] Figure 3A This is a diagram showing the stacked structure of a design model A of a liquid crystal display device used in a light leakage test.

[0013] Figure 3B It means looking from above Figure 3A A diagram showing a display state of a display surface of a liquid crystal display device.

[0014] Figure 4A This is a diagram showing the stacked structure of design model B of a liquid crystal display device used in a light leakage test.

[0015] Figure 4B It means looking from above Figure 4A A diagram showing a display state of a display surface of a liquid crystal display device.

[0016] Figure 5 This is a graph showing the temperature measurement results indicating the effect of suppressing the temperature rise of the metal layer.

[0017] Figure 6 It is a cross-sectional view schematically showing the structure of a liquid crystal display device according to another example of the embodiment of the present disclosure.

[0018] Figure 7 It is a cross-sectional view schematically showing the structure of a liquid crystal display device according to another example of the embodiment of the present disclosure.

[0019] Figure 8 yes Figure 6 Schematic top view of a liquid crystal display device.

[0020] Fig.9A This is a partially enlarged cross-sectional view showing an enlarged side surface of a polarizing element in a liquid crystal display device according to another example of an embodiment of the present disclosure.

[0021] Fig. 9B This is a partially enlarged cross-sectional view showing an enlarged side surface of a polarizing element in a liquid crystal display device according to another example of an embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the liquid crystal display device of the present disclosure will be described with reference to the drawings.

[0023] The structure of a liquid crystal display device based on the liquid crystal display device of the present disclosure will be described.

[0024] In recent years, due to the popularity of augmented reality-head-up display (AR-HUD), the display size has been enlarged, and with this, the temperature of the backlight has been increased. As a prior art for suppressing the temperature rise of a liquid crystal display device accompanying the temperature rise of the backlight, for example, Patent Document 1 describes reducing the brightness of the backlight by a given degree.

[0025] In the prior art described in the above-mentioned patent document 1, since no technology is proposed to prevent light leakage in a black display state in a liquid crystal display device accompanied by a high temperature of a backlight, if light leakage occurs locally in a projection image based on a black display, the reality of the projection image will be greatly impaired. Therefore, a technology that can solve such a problem has been sought in the past.

[0026] Figure 1 : is a cross-sectional view schematically showing the structure of a liquid crystal display device 1 according to an example of an embodiment of the present disclosure. Figure 1 In order to facilitate the illustration, the liquid crystal display device 1 of this embodiment is shown in a state of being exploded in the thickness direction. The liquid crystal display device 1 of this embodiment includes: a light-transmitting liquid crystal display element 4, which has two glass substrates 2a and 2b as transparent substrates, and a liquid crystal layer 3 sealed between the two glass substrates 2a and 2b; a backlight device 5 as a light source for emitting light to one glass substrate 2a of the liquid crystal display element 4; an emitting-side polarizing plate 6, which is located on the other glass substrate 2b of the liquid crystal display element 4; an incident-side polarizing plate 7, which is located on one glass substrate 2a of the liquid crystal display element 4; and a plate-shaped polarizing element 10, which has a base layer 8 formed of glass and a metal layer 9 laminated on the base layer 8 and having a polarization function. In addition, the polarizing element 10 is arranged between the backlight device 5 and the liquid crystal display element 4 so that the metal layer 9 faces the backlight device 5, and the thickness of the base layer 8 is thicker than the thickness of each of the two glass substrates 2a and 2b.

[0027] The above structure has the following effects. The metal layer 9 constituting the polarizing element 10 also functions as a good thermal conductive component and a good heat dissipation component that receives light radiated from the backlight device 5 and receives radiant heat, and transfers and diffuses heat to the surrounding area. Furthermore, since the base layer 8 constituting the polarizing element 10 has an increased heat capacity, it also functions as a heat insulating component that receives light radiated from the backlight device 5 and receives radiant heat, and effectively reduces the radiant heat transmitted to the liquid crystal display element 4 side. As a result, it is possible to prevent light leakage of the black display in the liquid crystal display element 4 accompanying the high temperature of the backlight device 5, and it is possible to prevent light leakage of the black display of the projected image in an image projection device such as an AR-HUD (Augmented Reality-Head-Up Display) that uses the liquid crystal display device 1.

[0028] The transparent substrate constituting the liquid crystal display element 4 may be a glass substrate, a transparent resin substrate, a translucent ceramic substrate, etc. In addition, the transparent substrate may be a composite substrate in which a plurality of substrates including a glass substrate, a transparent resin substrate, and a translucent ceramic substrate are stacked. For example, in the case where the transparent substrate is a composite substrate in which a glass substrate and a transparent resin substrate are stacked, the thermal conductivity of the glass is 0.55 to 0.75 (W / mK), which is higher than the 0.12 to 0.29 (W / mK) of the resin material, and therefore, the glass substrate may be configured to be located on the backlight device 5 and the metal layer 9 side. In this case, the heat can be dissipated more effectively by the metal layer 9 which also functions as a good thermal conductive component and a good heat dissipation component and the glass substrate connected to the metal layer 9. The glass substrate is suitable for reasons such as easy processing, low cost, and high transmittance. In the following description of the embodiment of the liquid crystal display device 1 disclosed in the present invention, the case where the transparent substrate is a glass substrate is described.

[0029] Furthermore, since the base layer 8 constituting the polarizing element 10 has an increased heat capacity, the thermal influence on the liquid crystal display element 4 can be reduced, and as a result, the thickness of the two glass substrates 2a and 2b constituting the liquid crystal display element 4 can be reduced.

[0030] The polarizing element 10 is disposed so that the metal layer 9 faces the backlight device 5. Thus, the metal layer 9, which is also a good heat conductor and heat dissipator, can effectively receive light radiated from the backlight device 5 and effectively receive radiant heat.

[0031] In addition, in the polarizing element 10, the thickness T3 of the base layer 8 is thicker than the thickness T1 and T2 of each of the two glass substrates 2a and 2b. As a result, the heat capacity of the base layer 8, which is also a heat insulating member, is increased, and the light radiated from the backlight device 5 can be received, thereby effectively storing heat and insulating the radiant heat. Among them, in this embodiment, the so-called heat insulation does not mean a complete blocking of heat transfer, but refers to a heat insulation effect to the extent that the purpose of preventing light leakage of the black display in the liquid crystal display element 4 can be achieved. The thickness T1 and T2 of each glass substrate 2a and 2b are, for example, about 200μm to 1000μm. The thickness T1 and T2 of these glass substrates 2a and 2b can be the same or different. The thickness T3 of the base layer 8 is selected to be more than 1 times and less than about 5 times the thickness of any thicker thickness T1 and T2 or the thickness of one of the same thicknesses T1 and T2, and preferably more than about 2 times and less than about 5 times. If it exceeds 5 times, there is a tendency for the device to be large-scale and heavy. In addition, "~" means "to", and the same applies to the following.

[0032] The thickness T3 of the base layer 8 may be thicker than the thickness (T1+T2) of the two glass substrates 2a and 2b respectively. In this case, the heat capacity of the base layer 8, which is also a heat insulating member, is further increased, and the light radiated from the backlight device 5 can be received to more effectively store and insulate the radiant heat. In addition, in the case of a structure in which the polarizing element 10 and the liquid crystal display element 4 are stacked, the mechanical strength of the liquid crystal display element 4 is significantly improved.

[0033] When the thicknesses T1 and T2 of the two glass substrates 2a and 2b are different, the thickness T1 of the glass substrate 2a on the side close to the backlight device 5 may be thicker than the thickness T2 of the glass substrate 2b on the side far from the backlight device 5. In this case, since the heat capacity of the glass substrate 2a increases, the glass substrate 2a also functions as a heat insulating member, and the heat insulating member receives the light radiated from the backlight device 5 and thus receives the radiant heat, thereby effectively reducing the radiant heat transmitted to the liquid crystal. T1 may be more than 1 times and less than about 2 times of T2, but is not limited to this range.

[0034] In the polarizing element 10, the base layer 8 is formed of glass, but it can be a glass substrate, for example. In this case, since the glass is light-transmitting, the light of the backlight device 5 can be appropriately transmitted to the liquid crystal display element 4 side. In addition, since the glass contains various chemically stable oxides such as silicon dioxide (SiO2), aluminum oxide (Al2O3), boric acid (B2O3), sodium oxide (Na2O), potassium oxide (K2O), and calcium oxide (CaO), there is almost no degradation caused by heat, and heat storage and heat insulation can be effectively performed for a long time. Furthermore, since the thermal conductivity of glass is 0.55~0.75 (W / mK), which is higher than 0.12~0.29 (W / mK) of resin materials, the thermal influence of glass on the liquid crystal display element 4 is smaller than that of resin materials, and it is easy to form an overall uniform heat distribution.

[0035] When the base layer 8 of the polarizing element 10 is a glass substrate, it may include blue plate glass (soda glass) whose main components are silicon dioxide (SiO2), sodium oxide (Na2O), and calcium oxide (CaO). Blue plate glass has the lowest melting point among glasses, is easy to process, and is cheap. In addition, when the base layer 8 is a glass substrate, it may also include white plate glass (alkali-free glass) whose main components are silicon dioxide (SiO2), boric acid (B2O3), and aluminum oxide (Al2O3). White plate glass is cheap, has a high transmittance in the wavelength range of visible light, ultraviolet light, and infrared light, and the upper limit of the general common use temperature is 120°C to 130°C, which is the same as blue plate glass. In addition, when the base layer 8 is a glass substrate, it may also include quartz glass whose main component is silicon dioxide (SiO2). Quartz glass is a high-purity glass with few impurities, has a high transmittance to ultraviolet light and infrared light, and has a high heat resistance temperature. The upper limit of the common use temperature of quartz glass is about 900°C. In addition, quartz glass has excellent chemical resistance and is easy to process by drilling and cutting.

[0036] The base layer 8 of the polarizing element 10 may also be a sapphire glass (Al2O3 single crystal) substrate (also called a sapphire crystal substrate). Sapphire glass has a Mohs hardness of 9, a heat-resistant temperature of about 2000°C, and a thermal conductivity of 42W / mK (20°C), which is several dozen times higher than the thermal conductivity of glass, 1.4W / mK (20°C).

[0037] Alternatively, the polarizing element 10 may be disposed at a distance from the backlight device 5. In this case, since the polarizing element 10 is not in contact with the backlight device 5, the polarizing element 10 does not directly receive heat from the backlight device 5 itself through heat conduction. As a result, the polarizing element 10 can be prevented from abnormally heating up.

[0038] When there is a gap (set as the gap g1) between the polarizing element 10 and the backlight device 5, the gap g1 can be, for example, about 0.1 mm to 10 mm. However, the gap g1 is not limited to this range. In this case, since the volume of the air layer existing in the gap g1 is large, the heat insulation effect of the air layer becomes larger, and it becomes difficult for the polarizing element 10 to receive the heat of the backlight device 5 itself through radiant heat. In addition, the air layer existing in the gap g1 becomes easy to convect and is easy to generate heat transfer caused by convection. If the gap g1 exceeds, for example, 10 mm, the liquid crystal display device 1 tends to be large. In addition, when the gap g1 is less than 0.1 mm, for example, the heat insulation effect of the air layer becomes small due to the small volume of the air layer existing in the gap g1, and there is a tendency that the polarizing element 10 becomes easy to receive the heat of the backlight device 5 itself through radiant heat. Furthermore, the gap g1 can be about 1 mm to 5 mm.

[0039] In addition, the polarizing element 10 may be arranged at a distance from the liquid crystal display element 4. In this case, since the polarizing element 10 is not in contact with the liquid crystal display element 4, the liquid crystal display element 4 does not directly receive heat from the polarizing element 10 itself through heat conduction. As a result, the abnormal temperature rise of the liquid crystal display element 4 can be suppressed.

[0040] When there is a gap (set as gap g2) between the polarizing element 10 and the liquid crystal display element 4, the gap g2 can be, for example, about 0.1 mm to 10 mm. However, the gap g2 is not limited to this range. In this case, since the volume of the air layer existing in the gap g2 is large, the heat insulation effect of the air layer becomes larger, and the air layer existing in the gap g2 becomes easy to convect, and becomes easy to produce heat transfer caused by convection. If the gap g2 exceeds 10 mm, for example, the liquid crystal display device 1 tends to be large. In addition, when the gap g2 is less than 0.1 mm, for example, since the volume of the air layer existing in the gap g2 is small, there is a tendency for the heat insulation effect of the air layer to decrease. Furthermore, the gap g2 can be about 1 mm to 5 mm.

[0041] A light diffusing member 11 having light diffusivity may also be provided between the backlight device 5 and the incident side polarizing plate 7. The light diffusing member 11 makes the light radiated from the backlight device 5 uniform and emits it toward the liquid crystal display element 4 side. The light diffusing member 11 is formed by mixing a granular light diffusing agent including acrylic resin, silicone resin, etc. in a plate-shaped substrate including a light-transmitting resin such as styrene-methyl methacrylate copolymer resin (MS resin), polystyrene resin (PS resin), polycarbonate resin (PC resin), and cycloolefin resin (COP resin). As an example, there is a light diffusing member 11 containing 85% by weight of MS resin, 10% by weight of PC resin, 2% by weight of COP resin, and 3% by weight of a light diffusing agent including acrylic resin.

[0042] The light diffusion member 11 also functions as a heat equalization member that receives light radiated from the backlight device 5 and uniformly receives radiant heat as a whole. This is based on the fact that it uniformizes the light radiated from the backlight device 5. In addition, the light diffusion member 11 also receives the light radiated from the backlight device 5 to store and insulate the radiant heat. That is, it is believed that this is caused by the increase in the average optical path length in the light diffusion member 11 due to repeated scattering of the light radiated from the backlight device 5 in the light diffusion member 11. Microscopically, since in the light diffusion member 11, photons collide with the molecules of the resin material constituting the substrate and the molecules of the light diffusion agent and repeatedly elastically scatter, a part of the kinetic energy caused by the collision of the photons is given to the molecules of the resin material and the molecules of the light diffusion agent, and the amplitude and vibration frequency of the lattice vibration of the lattice (atoms) constituting the molecules are increased. As a result, it is believed that in the resin material and the light diffusion agent, the probability of a part of the kinetic energy of the photons being converted into thermal energy as a whole is increased.

[0043] In addition, the light diffusion member 11 may be disposed between the backlight device 5 and the polarizing element 10. In this case, the base layer 8 of the polarizing element 10, which includes a glass substrate having a higher thermal conductivity and a larger heat capacity than the resin material, is closer to the liquid crystal display element 4 than the light diffusion member 11 whose substrate includes a resin material, and therefore, the thermal influence on the liquid crystal display element 4 can be further reduced, and the overall heat distribution can be easily uniform. As a result, the heat distribution of the liquid crystal display element 4 can also be easily uniform.

[0044] In addition, the light diffusion member 11 may be disposed between the backlight device 5 and the polarizing element 10, and spaced apart from the polarizing element 10. In this case, since the light diffusion member 11 and the polarizing element 10 are not in contact, the polarizing element 10 does not directly receive heat from the light diffusion member 11 itself through heat conduction. As a result, the polarizing element 10 can be prevented from abnormally heating up.

[0045] When there is a gap (set as gap g3) between the polarizing element 10 and the light diffusion member 11, the gap g3 can be about 0.1mm to 10mm. However, the gap g3 is not limited to this range. In this case, since the volume of the air layer existing in the gap g3 is large, the heat insulation effect of the air layer becomes larger, and the air layer existing in the gap g3 becomes easy to convect and becomes easy to generate heat transfer caused by convection. If the gap g3 exceeds 10mm, for example, the liquid crystal display device 1 tends to be large. In addition, if the gap g3 is less than 0.1mm, for example, the volume of the air layer existing in the gap g3 is small, so there is a tendency for the heat insulation effect of the air layer to decrease. Furthermore, the gap g3 can be about 1mm to 5mm.

[0046] In addition, the light diffusion component 11 can be disposed between the backlight device 5 and the polarizing element 10, in contact with the polarizing element 10. In this case, the light diffusion component 11 and the polarizing element 10 are integrated, and the effect of becoming a composite heat-insulating component with a larger heat capacity is achieved. In addition, the light diffusion component 11 can also be connected to the polarizing element 10 via a light-transmitting sheet, a light-transmitting film, a light-transmitting resin adhesive, etc. In this case, the light diffusion component 11 and the polarizing element 10 are integrated, and the composite heat-insulating component with a larger heat capacity is achieved.

[0047] The polarization axis of the metal layer 9 of the polarizing element 10 is parallel to the polarization axis of the incident-side polarizing plate 7. A conductive tape 12 is attached to the peripheral region of the metal layer 9 to improve heat dissipation. The metal layer 9 includes a plurality of metal fine wires (also called wire grids) 13 arranged in parallel at intervals.

[0048] Figure 2 : is a conceptual diagram for explaining the polarization function of the polarization element 10. The polarization element 10 has a base layer 8 and a metal layer 9 as described above. The surface portion of the base layer 8 on the backlight device 5 side may have a concave-convex pattern, which alternately repeats concave portions and convex portions along a direction X on a plane and extends in another direction Y perpendicular to the one direction X on a plane, and the surface portion of the base layer 8 on the backlight device 5 side is formed by joining one or more of the above-mentioned metal fine wires 13 in each concave portion. That is, the metal layer 9 may be the metal fine wire 13.

[0049] The metal fine wire 13 may include at least one of Al, Ag, Cu, Ni and Cr. That is, the metal fine wire 13 may be a structure in which one of Al, Ag, Cu, Ni and Cr (suitably non-magnetic metals) or a composition containing them as a main component or an alloy of Al, Ag, Cu and Cr (suitably non-magnetic metals) is used as a material, and fine metal wires with a diameter or thickness of about 100nm to about 500nm, for example, a diameter or thickness of about 250nm, are arranged in parallel on a plane at a spacing of about 100nm to about 200nm, for example, at a spacing of about 130nm.

[0050] The metal fine wire 13 can be an Al alloy with Al as the main component, and the Al alloy can be hard aluminum (Al-Cu alloy, Al-Cu-Mg alloy, Al-Zn-Mg-Cu alloy). The metal fine wire 13 can be an Ag alloy with Ag as the main component (Ag-Cu alloy). The metal fine wire 13 can be a Cu alloy with Cu as the main component (Cu-Zn alloy, Cu-Zn-Ni alloy, Cu-Sn alloy, Cu-Sn-Zn alloy). The metal fine wire 13 can be an alloy containing Ni and Cr (Ni-Cr alloy, Ni-Cr-Fe alloy, Ni-Cr-Mo alloy). The metal fine wire 13 can be an Fe alloy with Fe as the main component (Fe-Ni alloy, Fe-Ni36% alloy (Invar alloy), Fe-Ni-Co alloy (Kovar alloy), Fe-Cr alloy, Fe-Cr-Ni alloy).

[0051] The metal wire 13 may be a structure including a non-magnetic metal. In the case where the metal wire 13 includes a magnetic metal such as a ferromagnetic body that is easily magnetized by an external magnetic field, if the metal wire 13 is magnetized by the external magnetic field, the polarization plane of the linear polarization rotates together with the intensity of the magnetic field through the magnetic field generated by the metal wire 13. That is, a Faraday effect, which is a type of magneto-optical effect, is generated. If the polarization plane of the linear polarization passing through the polarization element 10 rotates, a mismatch with the cross Nicol condition of the liquid crystal display element 4 occurs. As a result, degradation of the display quality such as reduced contrast is likely to occur in the liquid crystal display element 4.

[0052] The metal fine wire 13 may be a structure including a paramagnetic metal as a non-magnetic metal. Examples of paramagnetic metals include aluminum (Al), chromium (Cr), molybdenum (Mo), titanium (Ti), zirconium (Zr), etc. The metal fine wire 13 may be a structure including a diamagnetic metal as a non-magnetic metal. Examples of diamagnetic metals include gold (Au), silver (Ag), copper (Cu), zinc (Zn), etc. The metal fine wire 13 may be a structure including non-magnetic stainless steel that is difficult to be magnetized by an external magnetic field. The metal fine wire 13 may also be a structure including completely non-magnetic brass (Cu-Zn alloy) that is not magnetized by an external magnetic field, etc.

[0053] The metal fine wire 13 may be a laminated structure in which multiple layers of the above-mentioned various metal layers, various alloy layers, and various non-magnetic metal layers are laminated. For example, it may be a structure in which a Mo layer, a Ti layer, etc. having high hardness are laminated on the lower side and / or upper side of an Al layer having high thermal conductivity but low hardness.

[0054] When the inventors of the present application proposed the liquid crystal display device 1 of the present disclosure that can prevent or suppress light leakage, they found out that the light leakage is caused by the following reasons. That is, they found out that the light leakage is caused by the contraction of the polarizing plate due to the in-plane distribution of the surface temperature of the polarizing plate on the light source side, the birefringence caused by the photoelastic effect of the glass, and the driving method of the liquid crystal display element 4 is unique to the IPS mode.

[0055] In the IPS (In-Plane Switching) method, the amount of backlight is controlled by rotating the liquid crystal molecules that are horizontal to the surfaces facing each other of the glass substrates 2a and 2b. Therefore, since there is no vertical tilt of the liquid crystal molecules, although the brightness changes and color changes based on the viewing angle are small, it is difficult to improve the contrast ratio, brightness, and response speed. Regarding the contrast ratio, since the leakage of the backlight is also large when the screen is black, a tight black cannot be obtained, and the brightness value of the black state becomes high, so the contrast ratio (brightness ratio of black to white) is also low. The reason why it is difficult to increase the brightness is the low numerical aperture, and the reason why it is difficult to respond at a high speed is the rotation method of the liquid crystal molecules. When the liquid crystal is driven in the IPS method, the deviation of the response speed in the entire grayscale range is small, and high-quality color rendering characteristics and viewing angle characteristics can be obtained.

[0056] Therefore, it is considered that cooling the incident side polarizing plate 7 and reducing the surface temperature distribution are effective for shrinking the incident side polarizing plate 7, and the material of the polarizing element 10 is studied. Table 1 shows the thermal conductivity of the base layer 8 including the glass substrate of the polarizing element 10, and the metal layer A (ITO) and the metal layer B (Al) including the material which are considered not to have a significant influence on the optical characteristics.

[0057] [Table 1]

[0058] (Unit: W / mK)

[0059] Base layer (glass substrate) ＜1 Metal layer A (ITO) 5～10 Metal layer B (Al) 236

[0060] The metal layer B made of aluminum (Al) has the highest thermal conductivity. A metal layer 9 including fine metal wires made of Al is produced by wire grid processing to impart polarization characteristics, and a polarizing element 10 having the same polarization direction as the incident-side polarizing plate 7 located on the backlight device 5 side is disposed between the incident-side polarizing plate 7 and the backlight device 5. This can reduce the influence on the distribution of light transmittance of the liquid crystal display element 4. In addition, regarding the base layer 8, a glass substrate tends to be significantly thicker than a thin film made of a resin material, and it is considered advantageous from the viewpoint of heat insulation, so a glass substrate is used for the base layer 8.

[0061] When the liquid crystal display device 1 of this embodiment is used in a head-up display device (abbreviated as; HUD), the backlight device 5 is mounted in a stacked state directly below a self-luminous light-emitting element such as an LED (Light Emitting Diode) and an EL (Electro Luminescence) element because of less thickness restrictions and priority to brightness efficiency. For this reason, a diffusion film may be provided between the polarizing element 10 and the backlight device 5 to prevent the light-emitting element from being exposed.

[0062] Figure 3A 1 is a diagram showing the stacked structure of a design model A of a liquid crystal display device used in a light leakage test. Figure 3B It means looking from above Figure 3A A diagram showing a display state of a display surface of a liquid crystal display device. Figure 4A 1 is a diagram showing the stacked structure of a design model B of a liquid crystal display device used in a light leakage test. Figure 4B It means looking from above Figure 4A A diagram showing a display state of a display surface of a liquid crystal display device.

[0063] In order to confirm the presence or absence of light leakage, the inventors of the present application conducted the following light transmission test of two types of test bodies, A and B. If, as in type A, a polarizing element 10 having a base layer 8 including a glass substrate and a metal layer 9 facing the backlight device 5 is placed between the diffusion film 11 as a light diffusion member and the backlight device 5, light leakage is still visible although the surface temperature of the light-emitting side of the liquid crystal display element 4 decreases. It is believed that the reason is that the diffusion film 11 becomes locally hot, especially the central part becomes hotter than the peripheral part (the four corners).

[0064] By inserting a polarizing element 10 having a base layer 8 including a glass substrate and a metal layer 9 facing the backlight device 5 between the incident side polarizing plate 7 and the diffusion film 11 as in type B, the surface temperature of the exit side of the liquid crystal display element 4 is reduced and light leakage can be improved. Since the thermal conductivity (0.55 to 0.75 (W / mK)) of the glass substrate constituting the polarizing element 10 is greater than the thermal conductivity (0.12 to 0.29 (W / mK)) of the resin material constituting the diffusion film 11, and the polarizing element 10 is located on the side closer to the liquid crystal display element 4 than the diffusion film 11, local high temperature of the incident side polarizing plate 7 is prevented.

[0065] Figure 5: is a graph showing the results of temperature measurement indicating the effect of suppressing the temperature rise of the metal layer 9. In order to confirm the effect of suppressing the temperature rise of the liquid crystal display element 4 caused by the metal layer 9, the liquid crystal display element 4 is irradiated with backlight light by the backlight device 5, and the temperature of the exit side surface of the liquid crystal display element 4, i.e., the center and corner of the display surface, is measured for the case where the metal layer 9 is present and the case where the metal layer 9 is not present, to confirm the presence or absence of temperature reduction and the degree of temperature reduction. In addition, Figure 5 In , δ1 represents the difference between the temperature of the center and the temperature of the corner of the display surface when there is no metal layer 9 , and δ2 represents the difference between the temperature of the center and the temperature of the corner of the display surface when there is the metal layer 9 .

[0066] As from Figure 5 As is clear from the graph of , the structure of the polarizing element 10 including the base layer 8 and the metal layer 9 is highly effective in suppressing the occurrence of in-plane temperature distribution on the display surface with respect to a temperature rise.

[0067] By applying the liquid crystal display device 1 of this embodiment to a head-up display device, display light is projected onto a windshield, which is an example of a projection member attached to the front windshield of a vehicle. A visual observer such as a driver can visually recognize the display light projected onto the windshield by overlapping the real scene ahead that can be seen through the windshield.

[0068] The polarizing element 10 and the incident-side polarizing plate 7 together change the ratio of light from the backlight device 5 that passes through the liquid crystal display device 1. As described above, the polarizing element 10 is formed with a base layer 8 based on a glass substrate, and a metal fine wire 13, also called a metal nanowire grid, is arranged on the surface portion of the base layer 8 on the backlight device 5 side to form fine metal slits on the surface portion. The polarizing element 10 transmits the light component that vibrates in the direction along the light transmission axis, and reflects the light component that vibrates in the direction along the light reflection axis that is perpendicular to the light transmission axis. That is, the polarizing element 10 is as described above. Figure 2 As shown, the light component vibrating in the direction perpendicular to the slit (grating) is transmitted, and the light component vibrating in the direction parallel to the slit (grating) is reflected.

[0069] The base layer 8 includes a glass substrate in the present embodiment, but in other embodiments, it may be a transparent resin substrate, a transparent resin sheet, etc. The so-called transparent resin refers to a resin having a total light transmittance of 70% or more measured by a 2 mm thick plate with smooth both sides based on JIS K 7361-1. For example, polyethylene, propylene-ethylene copolymer, polypropylene, polystyrene, copolymers of aromatic vinyl monomers and (meth) alkyl acrylates having lower alkyl groups, polyethylene terephthalate, terephthalic acid-ethylene glycol-cyclohexanedimethanol copolymer, polycarbonate, acrylic resin, and resins having an alicyclic structure, etc. can be cited.

[0070] Among these, as transparent resins, resins with a water absorption rate of less than 0.25%, such as polycarbonate, polystyrene, copolymers of aromatic vinyl monomers containing more than 10% of aromatic vinyl monomers and (meth) alkyl acrylates having low alkyl groups, and resins having alicyclic structures, are less deformed by moisture absorption, and thus the base layer 8 can obtain the same function as a large light diffusion layer 11 with less warping.

[0071] When the base layer 8 includes a transparent resin substrate, a transparent resin sheet, etc., a granular light diffuser may be mixed in the base layer 8. The light diffuser is a particle having the property of diffusing light, and can be roughly divided into an inorganic filler and an organic filler. As the inorganic filler, silicon oxide, aluminum oxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, and mixtures thereof can be cited. As the organic filler, acrylic resin, polyurethane, polyvinyl chloride, polystyrene resin, polyacrylonitrile, polyamide, polysiloxane resin, melamine resin, and benzoguanamine resin can be cited.

[0072] The shape of the light diffuser includes, for example, spherical, cubic, needle-shaped, rod-shaped, spindle-shaped, plate-shaped, flaky, and fibrous shapes, among which spherical is preferred because it can make the light diffusion direction isotropic. The diffusion film is prepared in a state where such a light diffuser is uniformly dispersed in a transparent resin.

[0073] In the case of the structure of type B, the light emitted from the backlight device 5 passes through the diffusion film (scatterer) 11 and reaches the polarizing element 10. Among the light that has arrived, the light component that vibrates in the direction along the light transmission axis of the polarizing element 10 passes through the polarizing element 10, passes through the incident-side polarizing plate 7, and is incident on the liquid crystal display element 4.

[0074] On the other hand, the light component vibrating in the direction along the light reflection axis of the polarization element 10 is reflected by the polarization element 10 .

[0075] Even if light emitted from the backlight device 5 is reflected by the polarizing element 10, the light diffusing member 11 is provided between the polarizing element 10 and the backlight device 5, so that the light is diffused in the vibration direction and returns to the polarizing element 10. As a result, the reflected light from the polarizing element 10 is reused, and the light quantity is increased.

[0076] The polarizing element 10 may be connected to a heat-conducting member such as a metal frame, a metal outer frame, or a metal container that conducts and diffuses heat to the outside. For example, a conductive tape 12 may be attached to the peripheral portion of the polarizing element 10, that is, the area outside the effective display area M. The conductive tape is formed into a rectangular flat plate by coating or vapor-depositing a metal film having excellent electrical and thermal conductivity such as Cu on one side of a resin film with a conductive adhesive.

[0077] The conductive tape 12 is made by forming a metal film with high thermal conductivity such as silver (Ag), copper (Cu), or aluminum (Al) on the surface of a resin sheet with a thickness of about 100 μm to 500 μm made of a resin material such as acrylic resin by vapor deposition. That is, the conductive tape 12 can be a metal sheet that is a type of heat dissipation sheet. The thermal conductivity of the metal sheet is about 230 to 400 W / (m·K).

[0078] The conductive tape 12 may be a graphite sheet having a thickness of about 25 μm to 100 μm, which is one type of heat dissipation sheet. The thermal conductivity of the graphite sheet is about 1500 W / (m·K).

[0079] The conductive tape 12 may be Figure 1 As shown, the polarizing element 10 is attached to the metal layer 9 at the peripheral portion. In this case, the conductive tape 12 can effectively receive heat from the metal layer 9 having high thermal conductivity.

[0080] The conductive tape 12 may be Figure 6 As shown, the conductive tape 12 is attached to the metal layer 9 and the side surface of the base layer 8 at the peripheral portion of the polarizing element 10. In this case, the conductive tape 12 is attached to the polarizing element 10 over a larger area, and can receive heat from the polarizing element 10 more effectively.

[0081] The conductive tape 12 may also be attached to the peripheral portion of the polarizing element 10 over the entire circumference. In this case, the heat generated in the polarizing element 10 can be uniformly dissipated to the surroundings. In addition, the conductive tape 12 may also be in contact with the heat-conducting member over the entire circumference. In this case, the effect of uniformly dissipating the heat generated in the polarizing element 10 to the surroundings is improved.

[0082] The conductive tape 12 may be light-transmitting. In this case, the conductive tape 12 can be prevented from affecting the display of the liquid crystal display element 4. That is, it can be prevented that: the light transmittance of the peripheral portion of the display portion of the liquid crystal display element 4 is reduced, the brightness of the image in the peripheral portion of the display portion is reduced; and the contrast of the image at the peripheral portion of the display portion is reduced. The light-transmitting conductive tape 12 can be produced by making the thickness of the metal film about 30nm or less when a metal film is formed on one side of a resin film by a vapor deposition method or the like. That is, by reducing the thickness of the metal film, the absorption of light in the metal film can be suppressed. In order to achieve this purpose more effectively, the thickness of the metal film can be about 20nm or less, or it can be about 3nm to 15nm.

[0083] When the conductive tape 12 has light transmittance, the light transmittance of the conductive tape 12 may not be 100%, but may be approximately 10% to 90%, or may be approximately 30% to 70%.

[0084] In the case where the polarizing element 10 is in contact with the heat-conducting member, the structure in which the end of the metal layer of the polarizing element 10 is in contact with the heat-conducting member can be adopted. In this case, since the metal layer with high thermal conductivity is in contact with the heat-conducting member, the heat can be efficiently transferred to the heat-conducting member. In addition, since the end of the metal layer is in contact with the heat-conducting member, the influence of the heat-conducting member on the display of the liquid crystal display element 4 can be suppressed. In addition, it can also be a structure in which an extension portion formed in a band shape in the peripheral direction of the metal layer is provided at the end of the metal layer, and the extension portion is in contact with the heat-conducting member. In this case, by increasing the contact area between the metal layer and the heat-conducting member, heat can be more efficiently transferred to the heat-conducting member. In order to achieve this purpose more effectively, a band-shaped extension portion can also be provided at the end of the metal layer throughout the entire circumference. In addition, it can also be a structure in which the end of the base layer of the polarizing element 10 and the end of the metal layer are in contact with the heat-conducting member.

[0085] When the metal layer is the metal thin wires 13, the width of the metal thin wires 13 in contact with the thermally conductive member may be greater than the width of the remaining portion. In this case, the contact area between the metal layer and the thermally conductive member increases, and heat can be transferred to the thermally conductive member more efficiently.

[0086] The polarizing element 10 may also be Figure 7 , Figure 8 As shown in FIG. 1 , the size of the polarizing element 10 is larger than that of the liquid crystal display element 4 when viewed from above. In this case, the heat capacity of the polarizing element 10 increases, and the polarizing element 10 can receive the light radiated from the backlight device 5 and store the radiant heat more effectively to insulate the heat. Figure 8As shown in FIG. 1 , the size of the polarizing element 10 when viewed from above is larger than the size of the liquid crystal display element 4, that is, the polarizing element 10 contains the liquid crystal display element 4 when viewed from above. In this case, it is easy to uniformize the thermal influence of the polarizing element 10 on the liquid crystal display element 4 without bias. The size (area) of the polarizing element 10 when viewed from above may be more than 1 times and less than about 1.5 times the size (area) of the liquid crystal display element 4 when viewed from above, and may be more than 1 times and less than about 1.3 times.

[0087] In addition, the polarizing element 10 may also be a structure whose size is smaller than that of the liquid crystal display element 4 when viewed from above and has a size equal to or greater than that of the effective display area of ​​the display portion of the liquid crystal display element 4. In this case, since the polarizing element 10 is miniaturized and lightweight, the liquid crystal display device 1 is lightweight and becomes cheap. In addition, when the heat-conducting member is in contact with the polarizing element 10, the size of the heat-conducting member when viewed from above can be relatively increased by the amount by which the size of the polarizing element 10 when viewed from above becomes smaller. As a result, the heat dissipation of the polarizing element 10 can be improved. In addition, in this case, the conductive tape 12 can be attached only to the side of the base layer of the polarizing element 10. Through this structure, the conductive tape 12 can be suppressed from affecting the display image of the liquid crystal display element 4. The size (area) of the polarizing element 10 when viewed from above can be about 0.8 times or more and less than 1 times the size (area) of the liquid crystal display element 4 when viewed from above, and can also be about 0.9 times or more and less than 1 times.

[0088] The polarizing element 10 may also be Fig.9A As shown, the surface roughness (arithmetic mean roughness) of the side of the base layer 8 is larger than the surface roughness (arithmetic mean roughness) of one main surface (e.g., upper surface) and the other main surface (e.g., lower surface) of the base layer 8. In this case, the surface area of ​​the side of the base layer 8 is increased, and the heat can be dissipated more efficiently. In addition, when the side of the base layer 8 is in contact with the heat-conducting member, the heat can be transferred to the heat-conducting member more efficiently. In addition, in this case, the side of the base layer 8 can also be joined to the heat-conducting member via a joining member of a type that is coated and hardened with an adhesive. The joining member enters into the fine concave-convex of the side of the base layer 8, and the joining member can efficiently receive heat from the side of the base layer 8. The joining member can include a heat-conducting member with high thermal conductivity such as metal particles.

[0089] The polarizing element 10 may be Fig. 9BAs shown in FIG. 1 , the arithmetic mean roughness of the side of the base layer 8 is larger than the arithmetic mean roughness of one main surface and the other main surface of the base layer 8, that is, the conductive tape 12 may be contacted or bonded to the side of the metal layer 9 and the base layer 8. In this case, the contact area or bonding area between the side of the base layer 8 and the conductive tape 12 is increased, and the heat of the polarizing element 10 can be effectively transferred to the conductive tape 12. When the conductive tape 12 is bonded to the side of the base layer 8, it can also be bonded via a bonding agent such as an adhesive or a bonding agent. In addition, the bonding agent may contain a thermally conductive member with high thermal conductivity such as metal particles.

[0090] For example, the arithmetic mean roughness of each of the one main surface and the other main surface of the base layer 8 may be about 1 nm to 100 nm, and the arithmetic mean roughness of the side surface of the base layer 8 may be about 100 nm to 500 nm. The arithmetic mean roughness can be adjusted by adjusting the particle size (average particle size) of a grinding tool such as an alumina grinding tool or a diamond grinding tool when grinding the surface to be ground.

[0091] The light diffusion member 11 may also be in contact with a heat conductive member such as a metal frame, a metal outer frame, or a metal container that conducts and diffuses heat to the outside.

[0092] In the case where the light diffusion member 11 is in contact with the heat conductive member, the structure may be such that the end of the light diffusion member 11 is in contact with the heat conductive member. In this case, the heat conductive member can be prevented from affecting the display of the liquid crystal display element 4. In addition, the structure may be such that an extension portion formed in a band shape in the peripheral direction of the light diffusion member 11 is provided at the end of the light diffusion member 11, and the extension portion is in contact with the heat conductive member. In this case, by increasing the contact area between the light diffusion member 11 and the heat conductive member, heat can be more efficiently transferred to the heat conductive member. In order to achieve this purpose more effectively, a band-shaped extension portion can be provided over the entire circumference of the end of the light diffusion member 11.

[0093] The aforementioned exit-side polarizing plate 6 is bonded to the exit-side surface of the liquid crystal display element 4 by a transparent adhesive, and the aforementioned incident-side polarizing plate 7 is bonded to the incident-side surface of the liquid crystal display element 4 by a transparent adhesive. In addition, the aforementioned light diffusion member 11 can be bonded to the incident-side polarizing plate 7 by a transparent adhesive, and the polarizing element 10 can be bonded to the light diffusion member 11 by a transparent adhesive. These bondings are optical bonding (Optical Bonding) using an optical elastic resin. As the transparent adhesive, a transparent optical adhesive, such as an OCA functional film (OCA; Optical Clear Adhesive), an adhesive (OCR; Optical Clear Resin), etc. can be used.

[0094] The adhesive can contain a diffusant as needed. As the material of the diffusant, there is no particular limitation, and inorganic and organic diffusants can be appropriately selected. As inorganic diffusants, diffusants containing glass, silicon oxide, aluminum oxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, etc. can be cited; as organic diffusants, diffusants containing fluororesins, polystyrene resins, acrylic resins, polycarbonate resins, silicone resins, polyethylene resins, ethylene-vinyl acetate copolymers, acrylonitrile, polyurethane, polyvinyl chloride, polyacrylonitrile, polyamide, polysiloxane resins, melamine resins, benzoguanamine resins or their crosslinked products can be cited. As the shape of the diffusant, there is no particular limitation, and spherical, ellipsoidal, cubic, needle-shaped, rod-shaped, spindle-shaped, plate-shaped, flaky, fibrous, etc. can be cited. Among them, spherical or ellipsoidal shapes close to spherical are preferred because the diffusion direction of light can be isotropic.

[0095] The refractive index of the diffusing agent is preferably different from the refractive index of the main polymer used as the base material of the adhesive composition, and the refractive index difference is preferably 0.05 or more and 0.15 or less. When the refractive index difference is less than 0.05, the light diffusion effect becomes insufficient. In addition, when the refractive index difference exceeds 0.15, although the light diffusion effect is improved, the transmittance of oblique incident light to the diffusion adhesive layer is reduced, and it becomes dark as a whole, which is not preferred.

[0096] According to this embodiment, the temperature rise of the liquid crystal display element 4 caused by the high temperature of the backlight device 5 can be suppressed, and the light leakage of the black display based on the projection image of the liquid crystal display device 1 can be prevented, so that a high-quality image without losing the realism can be displayed.

[0097] The embodiments of the present disclosure are described in detail above, but the present disclosure is not limited to the above embodiments, and various changes and improvements can be made within the scope of the present disclosure. It goes without saying that all or part of the above embodiments can be appropriately combined within the scope of no contradiction.

[0098] Industrial Applicability

[0099] The liquid crystal display device disclosed in the present invention can be applied to various electronic devices. As the electronic device, there can be cited a head-up display device such as AR-HUD, a digital display watch such as a smart watch, a car route guidance system (navigation system), a ship route guidance system, an aircraft route guidance system, a smart phone terminal, a mobile phone, a tablet terminal, a personal digital assistant (PDA), a video camera, a digital still camera, an electronic notepad, an electronic book, an electronic dictionary, a personal computer, a copier, a terminal device of a game device, a television, a product display label, a price display label, an industrial programmable display device, a car audio, a digital audio player, a fax machine, a printer, an automatic cash deposit and withdrawal machine (ATM), a vending machine, a head mounted image display device (Head Mounted Display device; HM), an advertising display device in a vehicle such as a bus or a train, a guidance display device installed at a station and an airport, etc.

[0100] Explanation of symbols

[0101] 1Liquid crystal display device

[0102] 2a, 2b glass substrate

[0103] 3 Liquid crystal layer

[0104] 4Liquid crystal display element

[0105] 5 Backlight device

[0106] 6 Polarizing plate on the output side

[0107] 7 Polarizing plate on the incident side

[0108] 8. Base

[0109] 9 Metal Layers

[0110] 10 Polarization elements

[0111] 11Light diffusion component

[0112] 12 Conductive tape

[0113] 13. Fine metal wire.

Claims

1. A liquid crystal display device comprising: A light-transmitting liquid crystal display element comprises two transparent substrates and a liquid crystal layer sealed between the two transparent substrates; An incident-side polarizing plate, located on one of the transparent substrates of the liquid crystal display element; a light source for emitting light toward one of the transparent substrates of the liquid crystal display element; and A plate-shaped polarizing element having a base layer formed of glass and a metal layer having a polarizing function stacked on the base layer; The polarizing element is disposed between the light source and the liquid crystal display element so that the metal layer faces the light source, and a conductive tape is attached to the peripheral region of the metal layer. The thickness of the base layer is thicker than the thickness of each of the two transparent substrates.

2. The liquid crystal display device according to claim 1, wherein: The thickness of the base layer is thicker than the total thickness of each of the two transparent substrates.

3. The liquid crystal display device according to claim 1 or 2, wherein: The base layer is a glass substrate.

4. The liquid crystal display device according to claim 1 or 2, wherein: The base layer includes a transparent resin, and the transparent resin includes a particulate light diffusing agent.

5. The liquid crystal display device according to claim 1 or 2, wherein: The polarization element is disposed at a distance from the light source.

6. The liquid crystal display device according to claim 1 or 2, wherein: The polarizing element is disposed at a distance from the liquid crystal display element.

7. The liquid crystal display device according to claim 1 or 2, wherein: The polarizing element is connected to the thermally conductive component.

8. The liquid crystal display device according to claim 1 or 2, wherein: The size of the polarizing element in a plan view is larger than that of the liquid crystal display element.

9. The liquid crystal display device according to claim 1 or 2, wherein: A light diffusing member having light diffusivity exists between the light source and the incident-side polarizing plate.

10. The liquid crystal display device according to claim 9, wherein: The light diffusion member is disposed between the light source and the polarization element.

11. The liquid crystal display device according to claim 10, wherein: The light diffusion member is disposed between the light source and the polarization element at a distance from the polarization element.

12. The liquid crystal display device according to claim 9, wherein: The light diffusion member is in contact with the heat conduction member.

13. The liquid crystal display device according to claim 9, wherein: The light diffusion member is bonded to the incident-side polarizing plate via a transparent adhesive containing a diffusing agent.

14. The liquid crystal display device according to claim 1 or 2, wherein: The polarization axis of the metal layer is parallel to the polarization axis of the incident-side polarizing plate.

15. The liquid crystal display device according to claim 1, wherein: The conductive tape has light transmittance.

16. The liquid crystal display device according to claim 1 or 2, wherein: The metal layer includes a plurality of metal thin wires that are spaced apart from each other and arranged in parallel.

17. The liquid crystal display device according to claim 1 or 2, wherein: The metal layer includes at least one of Al, Ag, Cu, Ni and Cr.

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