Display device and its driving method

Abstract

To improve in-plane temperature distribution of a display panel in a display device including a mechanism for heating the display panel.SOLUTION: A display device comprises: a display panel including a liquid crystal layer provided between a pair of substrates; and a heater including a plurality of electrodes arranged apart from each other and disposed adjacent to the display panel. The plurality of electrodes includes a first electrode heated at a first temperature and a second electrode heated at a second temperature lower than the first temperature. Each of the plurality of electrodes may be a transparent electrode provided on a transparent substrate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] One embodiment of the present invention relates to a display device and a driving method thereof.

Background Art

[0002] Conventionally, liquid crystal display devices have been used as display interfaces for various electronic devices. A liquid crystal display device is a display device that controls on / off of a plurality of pixels by controlling a voltage applied to a liquid crystal layer interposed between a pair of substrates. The response characteristics of the liquid crystal greatly affect the display quality of the liquid crystal display device. For example, as the temperature of the external environment decreases, the viscosity of the liquid crystal increases, so the response characteristics of the liquid crystal deteriorate. Specifically, when using a liquid crystal display device at low temperature, there is a problem that the response speed of the liquid crystal molecules to a voltage change becomes slow, and the switching of the on / off operation of each pixel becomes slow.

[0003] In order to solve the above problems, attempts have been made to provide a heater as a mechanism for heating a display panel including liquid crystal, and to warm the display panel with the heater to maintain the response characteristics of the liquid crystal even at low temperature. For example, Patent Document 1 discloses a liquid crystal display device capable of heating a display panel to an appropriate temperature in a short time by providing a transparent heater combined with a transparent substrate and a transparent electrode in the display panel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional liquid crystal displays equipped with transparent heaters can quickly raise the overall temperature of the display panel because the panel is heated uniformly. However, actual display panels contain heat sources such as driver circuits located on the TFT substrate. Therefore, if the temperature is raised uniformly by a transparent heater, the temperature near the driver circuits may become higher than other areas. In this case, an uneven distribution of temperature occurs in the in-plane temperature distribution of the display panel, resulting in an uneven distribution of the liquid crystal response characteristics. As a result, conventional liquid crystal displays equipped with transparent heaters have the problem of variations in display quality within the display screen due to the uneven temperature distribution of the display panel.

[0006] One embodiment of the present invention has been made in view of the above problems, and one of its objectives is to improve the in-plane temperature distribution of a display panel in a display device equipped with a mechanism for heating the display panel. [Means for solving the problem]

[0007] A display device according to one embodiment of the present invention comprises a display panel including a liquid crystal layer provided between a pair of substrates, and a heater disposed adjacent to the display panel, the heater including a plurality of electrodes arranged spaced apart from each other, wherein the plurality of electrodes include a first electrode heated at a first temperature and a second electrode heated at a second temperature lower than the first temperature.

[0008] A method for driving a display device according to one embodiment of the present invention comprises a display panel including a liquid crystal layer provided between a pair of substrates, and a heater disposed adjacent to the display panel, the heater including a plurality of electrodes arranged spaced apart from each other, wherein the plurality of electrodes include a first electrode and a second electrode adjacent to the first electrode, and the voltage applied to the second electrode is made smaller than the voltage applied to the first electrode. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing the configuration of a display device relating to one embodiment of the present invention. [Figure 2]This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Figure 3] This is a rear view showing the configuration of a display device relating to one embodiment of the present invention. [Figure 4] This is a rear view showing the configuration of a display device relating to one embodiment of the present invention. [Figure 5] This is a rear view showing the configuration of a display device relating to one embodiment of the present invention. [Figure 6] This is a rear view showing the configuration of a display device relating to one embodiment of the present invention. [Figure 7] This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Figure 8] This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Figure 9] This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Figure 10] This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Figure 11] This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Figure 12] This is a rear view showing the configuration of a display device relating to one embodiment of the present invention. [Figure 13] This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Figure 14] This is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described below with reference to the drawings, etc. However, the present invention can be implemented in various forms without departing from its essence, and is not to be interpreted as being limited to the embodiments described below. Furthermore, in order to make the explanation clearer, the width, thickness, shape, etc. of each part may be schematically represented in the drawings compared to the actual embodiments, but these schematic figures are just examples and do not limit the interpretation of the present invention.

[0011] In this specification and its figures, elements identical or similar to those described in previously shown figures are denoted by the same reference numerals, and redundant explanations may be omitted. In this specification, ordinal numbers are assigned for convenience to distinguish parts, components, etc., and do not indicate priority or order. Furthermore, when multiple identical elements are arranged and it is necessary to distinguish between individual elements, different letters may be added after the reference numerals indicating the elements to distinguish them. However, if it is not necessary to distinguish between the elements, the letters may be omitted from the reference numerals indicating the elements in the explanation.

[0012] In the present invention, when a single film is processed to form multiple films, these multiple films may have different functions or roles. However, these multiple films originate from a film formed as the same layer in the same process, and have the same layer structure and the same material. Therefore, these multiple films are defined as existing in the same layer. Furthermore, when a single film is processed to form multiple patterns, in this specification, etc., each pattern may be distinguished by assigning an ordinal number.

[0013] In this specification, expressions such as "above" and "below" describe the relative positional relationship between the structure of interest and other structures. In this specification, in a side view, the direction from the array substrate described later toward the opposing substrate is defined as "above," and the opposite direction is defined as "below." In this specification and the claims, when describing a manner in which one structure is placed on top of another structure, unless otherwise specified, the expression "above" includes both cases in which the other structure is placed directly above the structure so as to be in contact with it, and cases in which the other structure is placed above the structure via yet another structure.

[0014] In each embodiment, expressions such as "α includes A, B, or C", "α includes any one of A, B, and C", and "α includes one selected from the group consisting of A, B, and C" do not exclude the case where α includes a plurality of combinations of A to C unless otherwise specified. Further, these expressions do not exclude the case where α includes other elements.

[0015] (First Embodiment) <Overview of Display Device> FIG. 1 is a perspective view showing an overview of a display device 10 according to an embodiment of the present invention. As shown in FIG. 1, the display device 10 includes a display panel 102, a light source 104, a protection substrate 151A, and a protection substrate 151B. In FIG. 1, one direction in the plane of the display panel 102 is defined as the D1 direction, a direction orthogonal to the D1 direction is defined as the D2 direction, and a direction orthogonal to the D1-D2 plane is defined as the D3 direction.

[0016] The display panel 102 includes an array substrate 150, a counter substrate 152, a liquid crystal layer 210 (see FIG. 2) between the array substrate 150 and the counter substrate 152, a gate driving circuit 28, and a data driving circuit 38. In the present embodiment, both the array substrate 150 and the counter substrate 152 have translucency. Specifically, the support substrates serving as the bases of the array substrate 150 and the counter substrate 152 are both transparent to visible light. The counter substrate 152 is arranged in the D3 direction so as to face the array substrate 150. The array substrate 150 and the counter substrate 152 are arranged to face each other with a gap therebetween and are bonded together by a sealing material 154. As described above, the liquid crystal layer 210 is provided in the gap between the array substrate 150 and the counter substrate 152.

[0017] The array substrate 150 has a display area 12 and a peripheral area 14 located outside the display area 12. Multiple gate lines 16 (also called scan signal lines) are arranged in the D1 direction of the display area 12, and multiple data lines 17 (also called video signal lines) are arranged in the D2 direction. The area enclosed by these gate lines 16 and data lines 17 functions as a pixel 15. Therefore, multiple pixels 15 are arranged in the row direction and the column direction. Here, the row direction refers to the direction parallel to the D1 direction, and the column direction refers to the direction parallel to the D2 direction. In the display area 12, m pixels 15 are arranged in the row direction, and n pixels 15 are arranged in the column direction. The values ​​of m and n are set appropriately according to the vertical display resolution and the horizontal display resolution.

[0018] Each of the multiple pixels 15 arranged in the display area 12 has a pixel circuit that includes a switching element formed by a thin-film transistor (TFT). The pixel circuit includes a switching element and a capacitive element to control the on / off operation of each pixel 15. The thin-film transistors are formed on a support substrate that constitutes the array substrate 150.

[0019] A gate drive circuit 28 and a data drive circuit 38 (sometimes collectively referred to as a driver circuit) are provided in the peripheral region 14 of the array substrate 150. Although not shown in the figure, a group of wirings connecting the gate wiring 16 to the gate drive circuit 28 and a group of wirings connecting the data wiring 17 to the data drive circuit 38 are also provided in the peripheral region 14. Figure 1 shows an embodiment in which the gate drive circuit 28 and the data drive circuit 38 are provided as integrated circuits (ICs) and mounted on the support substrate using the COG (Chip on Glass) method. However, the gate drive circuit 28 and the data drive circuit 38 are not limited to this example; they may also be mounted on the support substrate using the COF (Chip on Film) method, or they may be formed on the support substrate using thin-film transistors, similar to the pixel circuit described above.

[0020] The light source 104 is a long, elongated member extending along the D1 direction. The light source 104 is composed of, for example, a plurality of light-emitting diodes (LEDs) arranged along the D1 direction. In addition to light-emitting diodes, the light source 104 may also include optical components such as reflectors, diffusers, and lenses. In this embodiment, the timing of light emission of the light source 104 is controlled by a light emission control circuit 110 that is synchronized with the gate drive circuit 28 and the data drive circuit 38. Figure 1 shows an example in which the light emission control circuit 110 is mounted on the array substrate 150 in a COG (coordinate of grain) manner, but the embodiment is not limited to this example. For example, the light source 104 and the light emission control circuit 110 may be provided as separate members (light emission units) independent of the display panel 102. Alternatively, the light emission control circuit 110 may be incorporated into the gate drive circuit 28 or the data drive circuit 38.

[0021] The protective substrates 151A and 151B are components that protect the display panel 102. Protective substrate 151A is provided adjacent to the array substrate 150, and protective substrate 151B is provided adjacent to the opposing substrate 152. Protective substrates 151A and 151B are made of light-transmitting substrates (for example, glass substrates or plastic substrates). As shown in Figure 2, protective substrates 151A and 151B function as light guide plates that guide light emitted from the light source 104 to the display panel 102. Therefore, it is preferable that protective substrates 151A and 151B have the same refractive index as the array substrate 150 and the opposing substrate 152. The array substrate 150 and protective substrate 151A, and the opposing substrate 152 and protective substrate 151B are fixed together with a light-transmitting adhesive.

[0022] The display panel 102 is arranged with an array substrate 150 and a counter substrate 152 facing each other, with a liquid crystal layer 210 provided between them. The array substrate 150 is larger than the counter substrate 152, and is sized such that a portion of the peripheral region 14 is exposed from the counter substrate 152. Although not shown in the figures, terminals are provided on the periphery of the array substrate 150 for attaching a flexible printed circuit board for supplying external signals to the gate drive circuit 28 and the data drive circuit 38.

[0023] The light source 104 is positioned adjacent to one side of the protective substrate 151A or 151B. In this embodiment, the light source 104 is positioned on the array substrate 150 and adjacent to the side of the protective substrate 151B. Figure 2 shows a configuration in which the light source 104 is mounted on the array substrate 150, but is not limited to this example, and any configuration is acceptable as long as the mounting position can be fixed. For example, the light source 104 may be supported by a housing surrounding the display panel 102.

[0024] Figure 2 is a cross-sectional view showing the configuration of a display device according to one embodiment of the present invention. Specifically, Figure 2 is a schematic cross-sectional view showing the structure corresponding to the cross-section between A1 and A2 of the display device shown in Figure 1. As shown in Figure 2, most of the light L irradiated from the light source 104 is incident on the side surface 15C of the protective substrate 151B. The light L incident on the side surface 15C of the protective substrate 151B passes through the protective substrate 151A, the protective substrate 151B, and the display panel 102 to reach the outer surface 15B of the protective substrate 151B or the outer surface 15A of the protective substrate 151A (or the outer surface 16 of the transparent electrode 160).

[0025] On the outer surface 15A of the protective substrate 151A (or the outer surface 16 of the transparent electrode 160) and the outer surface 15B of the protective substrate 151B, light L travels from a medium with a higher refractive index to a medium with a lower refractive index. In this case, if the angle of incidence of light L incident on the outer surface 15A of the protective substrate 151A (or the outer surface 16 of the transparent electrode 160) and the outer surface 15B of the protective substrate 151B is greater than the critical angle, light L undergoes total internal reflection. In other words, light L that satisfies the total internal reflection condition travels in the direction D2 while repeatedly undergoing total internal reflection on the outer surface 15A of the protective substrate 151A (or the outer surface 16 of the transparent electrode 160) and the outer surface 15B of the protective substrate 151B.

[0026] The liquid crystal layer 210 is composed of polymer-dispersed liquid crystal. The liquid crystal layer 210, composed of polymer-dispersed liquid crystal, has its scattering state and non-scattering state controlled for each pixel 15. Here, the "scattering state" refers to a state in which the liquid crystal molecules are oriented so that incoming light is scattered, and the "non-scattering state" refers to a state in which the liquid crystal molecules are oriented so that incoming light passes through without being scattered.

[0027] Light L traveling in the D2 direction while passing through the display panel 102 is scattered at least partially when it passes through pixels where the liquid crystal layer 210 is in a scattering state. At this time, some of the scattered light is emitted to the outside as scattered light LA ​​and LB without satisfying the aforementioned total internal reflection condition and is observed by the user of the display device 10. Conversely, in pixels where the liquid crystal layer 210 is not in a scattering state, scattered light LA ​​and LB are not generated, so light entering from the outside passes through the pixel and exits directly to the back side (the side opposite to where the observer is located). In other words, the user can see the back side through the display device 10.

[0028] Thus, the display device 10 of this embodiment displays an image to the user by putting the liquid crystal layer 210 of a specific pixel into a scattering state (e.g., an ON state) and emitting scattered light LA ​​and LB. Pixels other than the specific pixel are in a non-scattering state (e.g., an OFF state), so scattered light LA ​​and LB are not generated, and they are perceived by the user as transparent pixels.

[0029] <Overview of the transparent heater> As shown in Figure 2, in this embodiment, the display device 10 has a plurality of transparent electrodes 160A to 160D arranged spaced apart from each other on the outer surface 15A of the protective substrate 151A. Although not shown in the figure, each of the plurality of transparent electrodes 160A to 160D is connected to a predetermined power supply and is configured so that a predetermined voltage can be applied (a predetermined amount of current can flow).

[0030] Each transparent electrode 160A to 160D is composed of a translucent metal oxide, such as ITO (Indium-Tin Oxide). Electrodes composed of metal oxides have a higher resistance than electrodes composed of metal, and therefore generate heat when current is passed through them. However, each transparent electrode 160A to 160D is not limited to electrodes composed of metal oxides; transparent electrodes using wire grids (metal nanowires) or carbon nanotubes may also be used.

[0031] In this embodiment, multiple transparent electrodes 160A to 160D can be used as heating elements to heat the display panel 102. Thus, the display device 10 of this embodiment includes a transparent heater 200 composed of a protective substrate 151A (transparent substrate) and multiple transparent electrodes 160A to 160D. The transparent heater 200 can heat the display panel 102 by generating heat from the multiple transparent electrodes 160A to 160D.

[0032] Figure 3 is a rear view showing the configuration of a display device 10 according to one embodiment of the present invention. Specifically, Figure 3 corresponds to a view of the display device 10 from the side where the multiple transparent electrodes 160A to 160D are arranged. The transparent heater 200 is composed of a protective substrate 151A and multiple transparent electrodes 160A to 160D. As shown in Figure 3, in this embodiment, multiple transparent electrodes 160A to 160D, with the D1 direction as the longitudinal direction, are arranged in a stripe pattern in the D2 direction. However, the number of transparent electrodes 160 is not limited to four, but can be any number of two or more.

[0033] Although not shown in the diagram, each transparent electrode 160A to 160D is connected to a wiring for applying voltage. Each transparent electrode 160A to 160D may be connected to an independent and different wiring, or some of the transparent electrodes 160A to 160D may be connected to a common wiring. For example, if each transparent electrode 160A to 160D is connected to a different power supply by different wiring, different voltages can be applied to each transparent electrode 160A to 160D independently. Also, if some of the transparent electrodes 160A to 160D are connected to a common wiring, the same voltage can be applied to the transparent electrode 160 connected to the common wiring.

[0034] In this embodiment, transparent electrodes 160B to 160D are connected by common wiring to a first power supply (not shown) capable of outputting a first voltage, while transparent electrode 160A is connected by separate wiring to a second power supply (not shown) capable of outputting a second voltage lower than the first voltage. That is, in this embodiment, the voltage applied to transparent electrode 160A can be lower than the voltage applied to transparent electrodes 160B to 160D. As a result, transparent electrode 160A is heated to a lower temperature than transparent electrodes 160B to 160D.

[0035] As shown in Figure 3, a light source 104, a gate drive circuit 28, a data drive circuit 38, and a light emission control circuit 110 are arranged on one side of the display device 10, and these elements behave as heat sources. Therefore, the temperature of the display panel 102 in the area near the heat sources is relatively higher than in other areas. In this embodiment, among the multiple transparent electrodes 160, the transparent electrode 160A, which is positioned closest to the heat sources such as the light source 104, the driver circuits (gate drive circuit 28, data drive circuit 38), and the light emission control circuit 110, is heated at a lower temperature than the other transparent electrodes 160B to 160D. By adopting this configuration, the display device 10 of this embodiment can prevent excessive heating near the heat sources and improve the in-plane temperature distribution of the display panel 102.

[0036] Furthermore, as mentioned above, there is a risk of excessive heating near heat sources such as the light source 104 and the gate drive circuit 28. Therefore, in this embodiment, transparent electrodes 160 are not provided in areas that overlap with the heat sources in a plan view. For example, as shown in Figure 3, the multiple transparent electrodes 160A to 160D are arranged in positions that do not overlap with the light source 104 or the driver circuit in a plan view.

[0037] In this embodiment, an example is shown in which a light source 104, a gate drive circuit 28, a data drive circuit 38, and a light emission control circuit 110 are arranged as a heat source, but the embodiment is not limited to this example. That is, in the display device 10 of this embodiment, the heating temperature of the transparent electrode placed closest to the heat source (at least one element of the light source 104, gate drive circuit 28, data drive circuit 38, and light emission control circuit 110) arranged on the array substrate 150 should be set lower than that of the other transparent electrodes.

[0038] In this embodiment, the display device 10 employs a field-sequential method for color display because the liquid crystal layer 210 is composed of polymer-dispersed liquid crystal. In the field-sequential method, the display panel needs to be driven at high speed because each RGB color of light is irradiated in a time-division manner. Therefore, when employing the field-sequential method, the deterioration of the liquid crystal response characteristics as the temperature decreases significantly affects the display image quality. However, in this embodiment, the display device 10 maintains the display panel 102 at an appropriate temperature using a transparent heater 200, while also reducing variations in the in-plane temperature distribution of the display panel 102. Therefore, when performing color display using the field-sequential method with the display device 10, it is possible to suppress the deterioration of the display image quality.

[0039] (Modified version of the first embodiment) In the first embodiment, an example was shown in which transparent electrodes 160B to 160D are heated at a first temperature, and transparent electrode 160A, which is closest to the heat source, is heated at a second temperature lower than the first temperature. However, the embodiment is not limited to this example. For example, transparent electrode 160 may be heated at three or more temperatures. Specifically, transparent electrodes 160C and 160D may be heated at a first temperature, transparent electrode 160B may be heated at a second temperature lower than the first temperature, and transparent electrode 160A may be heated at a third temperature lower than the second temperature.

[0040] Furthermore, in the first embodiment, an example was shown in which the transparent electrode 160A closest to the heat source, such as the light source 104, is heated at a lower temperature than the other transparent electrodes 160B to 160D, but the invention is not limited to this example. For example, the transparent electrodes 160C and 160D, which are relatively farther from the heat source, may be heated at a first temperature, and the transparent electrodes 160A and 160B, which are relatively closer to the heat source, may be heated at a second temperature lower than the first temperature.

[0041] Thus, the display device 10 of this embodiment may average the in-plane temperature distribution of the display panel 102 by setting the heating temperature of each transparent electrode 160A to 160D, taking into consideration the in-plane temperature distribution (for example, temperature gradient) of the display panel 102.

[0042] (Second Embodiment) In this embodiment, a display device 10A having a structure different from that of the first embodiment will be described. Specifically, in the display device 10A of this embodiment, a transparent heater 200A is arranged so as to overlap with the heat source in a plan view. In this embodiment, elements common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed explanations will be omitted.

[0043] Figure 4 is a rear view showing the configuration of a display device 10A according to one embodiment of the present invention. Specifically, Figure 4 corresponds to a view of the display device 10A from the side where the multiple transparent electrodes 160A to 160E are arranged. The transparent heater 200A is composed of a protective substrate 151A and the multiple transparent electrodes 160A to 160E.

[0044] As shown in Figure 4, the transparent heater 200A of this embodiment includes a transparent electrode 160E in addition to the transparent electrodes 160A to 160D described in the first embodiment. In a plan view, the transparent electrode 160E is arranged to overlap with heat sources such as the light source 104, the gate drive circuit 28, the data drive circuit 38, and the light emission control circuit 110.

[0045] In this embodiment, the transparent electrode 160E functions as a preliminary heating element. For example, the transparent electrode 160E may be heated at a lower temperature than the transparent electrode 160A. In other words, the transparent electrode 160E may be provided as an element for heating the area of ​​the display panel 102 where the heat source such as the light source 104 is located, in situations where the amount of heat emitted from the heat source such as the light source 104 is insufficient.

[0046] Furthermore, the transparent electrode 160E does not need to be heated. That is, the transparent electrode 160E does not need to have voltage applied to it when driving the transparent heater 200A. In this case, the transparent electrode 160E can function as an electromagnetic shield to protect circuits such as the gate drive circuit 28, the data drive circuit 38, and the light emission control circuit 110 from electromagnetic waves. Also, arranging the transparent electrodes 160 evenly on the protective substrate 151A is preferable in order to average out the stress and external temperature acting on the protective substrate 151A.

[0047] (Third embodiment) This embodiment describes a display device 10B having a structure different from that of the first embodiment. Specifically, the display device 10B of this embodiment includes a transparent heater 200B in which a plurality of transparent electrodes 160 are arranged in a matrix. In this embodiment, elements common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed explanations are omitted.

[0048] Figure 5 is a rear view showing the configuration of a display device 10B according to one embodiment of the present invention. Specifically, Figure 5 corresponds to a view of the display device 10B from the side where the multiple transparent electrodes 160A to 160L are arranged. The transparent heater 200B is composed of a protective substrate 151A and multiple transparent electrodes 160A to 160L.

[0049] As shown in Figure 5, in this embodiment, twelve transparent electrodes 160A to 160L are arranged in rows and columns. In this embodiment, transparent electrodes 160B to 160D, 160F to 160H, and 160J to 160L are heated at a first temperature, transparent electrodes 160A and 160I are heated at a second temperature lower than the first temperature, and transparent electrode 160E is heated at a third temperature lower than the second temperature. In other words, the temperature of transparent electrode 160E, which is located at the position where the temperature is highest within the surface of the display panel 102 (closest to the heat source and close to the center of the display panel 102), is set to the lowest temperature. Next, the temperatures of the transparent electrodes 160A and 160I, which are located in positions where the temperature is highest (closest to the heat source and closest to the edge of the display panel 102), are set higher than those of transparent electrode 160E, and lower than those of the other transparent electrodes 160B-160D, 160F-160H, and 160J-160L.

[0050] The display device 10B of this embodiment has more transparent electrodes 160 constituting the transparent heater 200B than the display device 10 of the first embodiment, so that the in-plane temperature distribution of the display panel 102 can be averaged more precisely and appropriately. For example, Figure 5 shows an example in which each transparent electrode 160 is heated at three temperatures, but even more temperatures may be set. Also, Figure 5 shows an example in which the temperatures of transparent electrodes 160B~160D, 160F~160H, and 160J~160L are set to the same temperature, but the invention is not limited to this example, and at least some of the temperatures may be set to different temperatures.

[0051] (Fourth Embodiment) In this embodiment, a display device 10C having a structure different from that of the first embodiment will be described. Specifically, in the display device 10C of this embodiment, a plurality of light sources 104 are arranged, and the temperature of the transparent electrode 160 is adjusted according to the positions of the plurality of light sources 104. In this embodiment, elements common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed explanations will be omitted.

[0052] Figure 6 is a rear view showing the configuration of a display device 10C according to one embodiment of the present invention. Specifically, Figure 6 corresponds to a view of the display device 10C from the side where the multiple transparent electrodes 160A to 160D are arranged. The transparent heater 200C is composed of a protective substrate 151A and the multiple transparent electrodes 160A to 160D.

[0053] As shown in Figure 6, the display device 10C of this embodiment has two light sources 104A and 104B arranged along two opposing sides of the array substrate 150. Specifically, the display device 10C comprises two light sources 104A and 104B that face each other across the display area 12. In other words, the light sources 104A and 104B are arranged adjacent to each of the two opposing sides of the opposing substrate 152.

[0054] Light sources 104A and 104B are elongated members with the D1 direction as their longitudinal direction, and are composed of multiple light-emitting diodes arranged along the D1 direction. Light sources 104A and 104B may be the same light source, or they may be light sources with different specifications.

[0055] In this embodiment, the temperature of the transparent electrode 160A closest to the light source 104A and the transparent electrode 160D closest to the light source 104B is set lower than that of the other transparent electrodes 160B and 160C. Specifically, in this embodiment, transparent electrodes 160B and 160C are heated to a first temperature, transparent electrode 160D is heated to a second temperature lower than the first temperature, and transparent electrode 160A is heated to a third temperature lower than the second temperature.

[0056] In the region where the transparent electrode 160A is located, the light source 104A, gate drive circuit 28, data drive circuit 38, and light emission control circuit 110 are located adjacent to it. Therefore, the region where the transparent electrode 160A is located will be relatively hotter than the other regions, so the temperature of the transparent electrode 160A is set to the lowest level. On the other hand, in the region where the transparent electrode 160D is located, only the light source 104B is located adjacent to it. In other words, the region where the transparent electrode 160D is located will be relatively hotter than the region where the transparent electrode A is located, so the temperature of the transparent electrode 160D is set to a higher level than that of the transparent electrode 160A.

[0057] As described above, in this embodiment, when multiple light sources 104 are provided, the temperature of multiple transparent electrodes 160 is appropriately set according to the position of each light source 104. With this configuration, the display device 10C of this embodiment can prevent excessive heating near the heat source and improve the in-plane temperature distribution of the display panel 102.

[0058] (Modification of the fourth embodiment) In the fourth embodiment, an example was shown in which two light sources 104A and 104B are arranged along two opposing sides of the array substrate 150, but the embodiment is not limited to this example. For example, the light sources 104 may be arranged along two mutually orthogonal sides of the array substrate 150 so that the two light sources 104 are orthogonal to each other. In this case, since it is necessary to selectively lower the temperature of the transparent electrodes 160 that are close to the light sources 104 in both the row and column directions, the multiple transparent electrodes 160 are arranged in a matrix, as shown in Figure 5. At this time, the temperature of the transparent electrodes 160 located in a region that is simultaneously affected by the heat of the two light sources may be set even lower than that of the transparent electrodes 160 located in other regions.

[0059] In this embodiment, an example in which two light sources 104 are arranged has been described, but it is not limited to this example; it is also possible to arrange three or four light sources 104.

[0060] (Fifth embodiment) In this embodiment, we will describe display devices 10D to 10H having a structure different from that of the first embodiment. Specifically, in the display devices 10D to 10H of this embodiment, the positions of the multiple transparent electrodes 160A to 160D constituting the transparent heater differ from those of the first embodiment. In this embodiment, elements common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed explanations are omitted.

[0061] Figure 7 is a cross-sectional view showing the configuration of a display device 10D according to one embodiment of the present invention. In this embodiment, the transparent heater 200D is composed of a protective substrate 151B and a plurality of transparent electrodes 160A to 160D. As shown in Figure 7, the plurality of transparent electrodes 160A to 160D are arranged on the outer surface 15B of the protective substrate 151B. In the example shown in Figure 7, the transparent heater 200D can be provided on the display panel 102 by a simple process of forming the transparent electrodes 160A to 160D on the protective substrate 151B and then bonding the protective substrate 151B to the opposing substrate 152.

[0062] Figure 8 is a cross-sectional view showing the configuration of a display device 10E according to one embodiment of the present invention. In this embodiment, the transparent heater 200E is composed of a protective substrate 151A and a plurality of transparent electrodes 160A to 160D. As shown in Figure 8, the plurality of transparent electrodes 160A to 160D are arranged on the inner surface 15D of the protective substrate 151A. In other words, the plurality of transparent electrodes 160A to 160D are arranged between the protective substrate 151A and the array substrate 150. The protective substrate 151A and the array substrate 150 are fixed together by an adhesive layer 165 containing resin. In the example shown in Figure 8, the transparent heater 200E can be provided on the display panel 102 by a simple process in which the transparent electrodes 160A to 160D are formed on the protective substrate 151A, and then the protective substrate 151A is bonded so that each transparent electrode 160 faces the array substrate 150.

[0063] Figure 9 is a cross-sectional view showing the configuration of a display device 10F according to one embodiment of the present invention. In this embodiment, the transparent heater 200F is composed of a protective substrate 151A and a plurality of transparent electrodes 160A to 160D. As shown in Figure 9, the plurality of transparent electrodes 160A to 160D are arranged on an array substrate 150. That is, the plurality of transparent electrodes 160A to 160D are arranged between the protective substrate 151A and the array substrate 150. The protective substrate 151A and the array substrate 150 are fixed together by an adhesive layer 165 containing resin. In the example shown in Figure 9, the transparent heater 200F can be provided on the display panel 102 by a simple process of bonding the protective substrate 151A to the array substrate 150 on which the transparent electrodes 160A to 160D are formed.

[0064] Figure 10 is a cross-sectional view showing the configuration of a display device 10G according to one embodiment of the present invention. In this embodiment, the transparent heater 200G is composed of a protective substrate 151B and a plurality of transparent electrodes 160A to 160D. As shown in Figure 10, the plurality of transparent electrodes 160A to 160D are arranged on the inner surface 15E of the protective substrate 151B. In other words, the plurality of transparent electrodes 160A to 160D are arranged between the protective substrate 151B and the opposing substrate 152. The protective substrate 151B and the opposing substrate 152 are fixed together by an adhesive layer 166 containing resin. In the example shown in Figure 10, the transparent heater 200G can be provided on the display panel 102 by a simple process in which the transparent electrodes 160A to 160D are formed on the protective substrate 151B, and then the protective substrate 151B is bonded so that each transparent electrode 160 faces the array substrate 150.

[0065] Figure 11 is a cross-sectional view showing the configuration of a display device 10H according to one embodiment of the present invention. In this embodiment, the transparent heater 200H is composed of a protective substrate 151B and a plurality of transparent electrodes 160A to 160D. As shown in Figure 11, the plurality of transparent electrodes 160A to 160D are arranged on a counter substrate 152. That is, the plurality of transparent electrodes 160A to 160D are arranged between the protective substrate 151A and the counter substrate 152. The protective substrate 151A and the counter substrate 152 are fixed together by an adhesive layer 166 containing resin. In the example shown in Figure 11, the transparent heater 200H can be provided on the display panel 102 by a simple process of bonding the protective substrate 151B to the counter substrate 152 on which the transparent electrodes 160A to 160D are formed.

[0066] As described above, the transparent heater can be constructed by arranging a plurality of transparent electrodes 160 on any of the array substrate 150, the opposing substrate 152, the protective substrate 151A, and the protective substrate 151B. The choice of which substrate to place the transparent electrodes 160 on can be determined appropriately in light of the manufacturing process of the display device.

[0067] (Sixth Embodiment) In this embodiment, a display device 10I having a different structure from the first embodiment will be described. Specifically, the display device 10I of this embodiment includes a feedback mechanism for controlling a plurality of transparent electrodes 160A to 160D. In this embodiment, elements common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed explanations will be omitted.

[0068] Figure 12 is a rear view showing the configuration of a display device 10I according to one embodiment of the present invention. Specifically, Figure 12 corresponds to a view of the display device 10I from the side where the multiple transparent electrodes 160A to 160D are arranged. Figure 13 is a cross-sectional view showing the configuration of a display device 10I according to one embodiment of the present invention. The transparent heater 200I is composed of a protective substrate 151A and multiple transparent electrodes 160A to 160D.

[0069] As shown in Figure 12, in this embodiment, sensors 170A to 170D are arranged corresponding to each of the multiple transparent electrodes 160A to 160D. Each sensor 170A to 170D is a temperature sensor and is arranged on the inner surface 15D of the protective substrate 151A, as shown in Figure 13. Thus, each sensor 170A to 170D has the role of measuring the in-plane temperature distribution of the display panel 102. In this embodiment, sensor 170 is arranged in the peripheral region 14. Thus, it is desirable to arrange sensor 170 in a position that does not overlap with the display region 12 so as not to interfere with image display. However, this is not the only example, and sensor 170 may be arranged in the display region 12.

[0070] Furthermore, as shown in Figure 13, each sensor 170A to 170D is placed between the array substrate 150 and the protective substrate 151A. However, this is not limited to this example; each sensor 170A to 170D may also be placed between the opposing substrate 152 and the protective substrate 151B. Moreover, although the example shown in Figure 13 shows sensor 170 being placed on the protective substrate 151A, this is not the only example. For example, each sensor 170A to 170D may be placed on the array substrate 150, the opposing substrate 152, the protective substrate 151A, or the protective substrate 151B.

[0071] Although not shown in the diagram, the display device 10I in this embodiment includes a temperature control circuit connected to each transparent electrode 160A to 160D and each sensor 170A to 170D. In this embodiment, the temperature of the display panel 102 is measured using each sensor 170A to 170D and transmitted to the temperature control circuit described above. The temperature control circuit controls the temperature of each transparent electrode 160A to 160D based on the measured temperature. That is, the display device 10H has a function to feed back the measurement results from each sensor 170A to 170D to the temperature control of the transparent heater 200I. The display device 10I can lower the temperature of the transparent electrode 160 corresponding to a particular area of ​​the display panel 102 if it is determined that the temperature in that area is high, or raise the temperature of the transparent electrode 160 corresponding to a particular area of ​​the display panel 102 if it is determined that the temperature in that area is low. In this way, the display device 10I can precisely control the in-plane temperature distribution of the display panel 102 by dynamically controlling the temperature of each transparent electrode 160A to 160D based on the temperature of the display panel 102 measured by each sensor 170A to 170D.

[0072] (Seventh Embodiment) This embodiment describes a display device 10J having a structure different from that of the first embodiment. Specifically, in this embodiment, the heating temperature of the multiple transparent electrodes 180A to 180D is varied according to the film thickness of each transparent electrode 180A to 180D. In this embodiment, elements common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed explanations are omitted.

[0073] Figure 14 is a cross-sectional view showing the configuration of a display device 10J according to one embodiment of the present invention. The transparent heater 200J is composed of a protective substrate 151A and a plurality of transparent electrodes 180A to 180D. In this embodiment, the film thickness of transparent electrode 180A is t1, and the film thickness of transparent electrodes 180B to 180D is t2. Here, there is a relationship t1 > t2 between film thickness t1 and film thickness t2, that is, the film thickness of transparent electrode 180A is thicker than the film thickness of transparent electrodes 180B to 180D.

[0074] In this embodiment, the same power supply (not shown) is connected to transparent electrodes 180A to 180D, and the same voltage is applied. At this time, transparent electrode 180A has a thicker film thickness than the other transparent electrodes 180B to 180D, so its resistance when current flows is relatively smaller than that of transparent electrodes 180B to 180D. In other words, when the same voltage is applied to transparent electrodes 180A to 180D, the Joule heat generated in transparent electrode 180A is relatively smaller than that of transparent electrodes 180B to 180D. Thus, in the display device 10J, the temperature of transparent electrode 180A is set relatively lower by making the film thickness of transparent electrode 180A, which is closest to the heat source such as the light source 104, thicker than that of the other transparent electrodes 180B to 180D.

[0075] As described above, in this embodiment, by controlling the film thickness of the transparent electrode 180 according to the set temperature, each transparent electrode 180A to 180D can be heated to a temperature corresponding to the location of the heat source. With this configuration, the display device 10J of this embodiment can prevent excessive heating near the heat source and improve the in-plane temperature distribution of the display panel 102.

[0076] (Eighth embodiment) In the embodiments described above, an example was given in which a transparent heater 200 is constructed using a protective substrate 151A and a transparent electrode 160. However, the heater is not limited to this example, and it does not have to be transparent. For example, an opaque substrate may be used as the protective substrate 151A, or an opaque electrode (such as an electrode made of a metal layer) may be used instead of the transparent electrode 160. However, when using an electrode made of a metal layer as the heating element of the heater, it is desirable to increase the resistance value by making the film thickness thin or the electrode width narrower to facilitate heating.

[0077] (Ninth Embodiment) In the embodiments described above, an example was given in which the temperature of the transparent electrode 160A, which is closer to the heat source, is lower than the temperatures of the other transparent electrodes 160B to 160D. However, the example is not limited to performing such temperature control from the time the transparent heater 200 is started. For example, during the first period after starting the transparent heater 200, the same voltage may be applied to the multiple transparent electrodes 160A to 160D. In this case, each transparent electrode 160A to 160D is heated to the same temperature. Next, in the second period following the first period, the voltage applied to transparent electrode 160A may be lower than the voltage applied to the other transparent electrodes 160B to 160D. In this case, the transparent electrode 160A, which is closer to the heat source, is heated to a relatively lower temperature than the other transparent electrodes 160B to 160D.

[0078] According to this embodiment, for a short period after starting the transparent heater 200, all transparent electrodes 160 can be heated evenly, quickly raising the overall temperature. This improves the temperature rise of the transparent heater 200 and allows for a rapid improvement in the display quality of the display device 10.

[0079] (Tenth embodiment) In each of the embodiments described above, the reference temperature of the transparent electrode 160 (the set temperature of the transparent electrode furthest from the heat source) may be set according to the temperature of the external environment. For example, a temperature control table may be provided that associates a reference temperature with each ambient temperature, and the reference temperature of the transparent electrode 160 may be set by referring to the temperature control table based on the temperature of the external environment obtained by a sensor or the like. In this case, the transparent electrode 160 closer to the heat source, such as the light source 104, should be set to a temperature lower than the reference temperature.

[0080] Furthermore, if the reference temperature changes, the overall temperature distribution of the transparent heater 200 may change. In that case, as in the sixth embodiment, multiple sensors may be provided to grasp the in-plane temperature distribution of the display panel 102, and the output of each sensor may be fed back to adjust the set temperature of each transparent electrode 160. This makes it possible to improve the in-plane temperature distribution of the display panel 102 by feedback control using each sensor, even if the reference temperature set for the transparent electrode 160 is changed according to the temperature of the external environment.

[0081] (11th embodiment) In the embodiments described above, a rectangular display panel was used as an example for the display panel 102, but the shape of the display panel is not limited to a rectangular shape. For example, the display panel 102 may be a polygonal display panel or a non-rectangular display panel such as a circle. Furthermore, when using a polygonal display panel or a non-rectangular display panel as the display panel 102, it is desirable to appropriately change the shape of each electrode constituting the transparent heater 200 to match the shape of the display panel 102. For example, when using a circular display panel as the display panel 102, the shape of each electrode should be designed so that when the electrodes constituting the transparent heater 200 are arranged side by side, the overall outer shape becomes circular.

[0082] The embodiments described above (including modifications below) of the present invention can be combined and implemented as appropriate, provided they do not contradict each other. Furthermore, any additions, deletions, or design changes made by those skilled in the art based on these embodiments, or additions, omissions, or changes in processes, are also included within the scope of the present invention, as long as they retain the essence of the present invention.

[0083] Any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to a person skilled in the art, are naturally considered to be brought about by the present invention. [Explanation of symbols]

[0084] 10, 10A~10J…Display device, 12…Display area, 14…Peripheral area, 15…Pixel, 15A, 15B…Outer surface, 15C…Side, 15D, 15E…Inner surface, 16…Gate wiring, 17…Data wiring, 28…Gate drive circuit, 38…Data drive circuit, 102…Display panel, 104, 104A, 104B…Light source, 110…Light emission control circuit, 150…Array substrate, 151A, 151B…Protective substrate, 152…Opposite substrate, 154…Sealing material, 160, 160A~160L…Transparent electrode, 165, 166…Adhesive layer, 170, 170A~170D…Sensor, 180, 180A~180D…Transparent electrode, 200, 200A~200J…Transparent heater, 210…Liquid crystal layer

Claims

1. A display panel including a liquid crystal layer provided between a pair of substrates, A heater comprising a plurality of electrodes arranged in a matrix at a distance from each other, and positioned adjacent to the display panel, A light source is disposed adjacent to at least one side surface of the pair of substrates, Equipped with, The plurality of electrodes include a first electrode heated at a first temperature and a second electrode heated at a second temperature lower than the first temperature. A display device in which, in a plan view, the second electrode is positioned closer to the light source than the first electrode.

2. The aforementioned plurality of electrodes are a plurality of transparent electrodes, The display device according to claim 1, wherein the heater is composed of a transparent substrate and the plurality of transparent electrodes.

3. The display device according to claim 1, wherein the liquid crystal layer includes a polymer-dispersed liquid crystal.

4. The display device according to claim 1, wherein the light source is arranged adjacent to each of two opposing sides of at least one of the pair of substrates.

5. The display device according to claim 1 or 4, wherein the plurality of electrodes are arranged in positions that do not overlap with the light source in a plan view.

6. A driver circuit is provided on at least one of the pair of substrates. The display device according to claim 1, wherein, in a plan view, the second electrode is positioned closer to the driver circuit than the first electrode.

7. The display device according to claim 6, wherein the plurality of electrodes are arranged in positions that do not overlap with the driver circuit in a plan view.

8. A first voltage is applied to the first electrode. The display device according to claim 1, wherein a second voltage lower than the first voltage is applied to the second electrode.

9. The film thickness of the second electrode is thicker than the film thickness of the first electrode. The display device according to claim 1, wherein a common voltage is applied to the first electrode and the second electrode.

10. The heater has a structure in which the plurality of electrodes are provided on a substrate, The display device according to claim 1, wherein the substrate is located between the display panel and the plurality of electrodes.

11. The heater has a structure in which the plurality of electrodes are provided on a substrate, The plurality of electrodes are located between the display panel and the substrate, as described in claim 1. display device.

12. In a plan view, multiple sensors are arranged in a position that overlaps with the display panel. The display device according to claim 1, wherein the plurality of sensors measure the in-plane temperature distribution of the display panel.

13. A method for driving a display device comprising: a display panel including a liquid crystal layer provided between a pair of substrates; a heater disposed adjacent to the display panel and including a plurality of electrodes arranged in a matrix at a distance from each other; and a light source disposed adjacent to at least one side of the pair of substrates, The plurality of electrodes include a first electrode and a second electrode adjacent to the first electrode. In a plan view, the second electrode is positioned closer to the light source than the first electrode. A method for driving a display device, wherein the voltage applied to the second electrode is made smaller than the voltage applied to the first electrode.

14. In a plan view, multiple sensors are arranged in a position that overlaps with the display panel. The method for driving a display device according to claim 13, wherein the plurality of sensors measure the in-plane temperature distribution of the display panel.

15. A method for driving a display device according to claim 13, wherein the same voltage is applied to each of the plurality of electrodes during a first period, and the voltage applied to the second electrode is made smaller than the voltage applied to the first electrode during a second period following the first period.

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