JP4838618B2 - Panel heater for liquid crystal display - Google Patents

Description

  The present invention relates to a panel heater for a liquid crystal display device, and more particularly to a panel heater for a liquid crystal display device using a transparent conductive layer as a heating element.

  In recent years, portable communication terminals equipped with liquid crystal display devices, in-vehicle navigation systems, and the like have been widely used. A liquid crystal display device used for in-vehicle audio and in-vehicle navigation systems is expected to be used in a wide range from a low temperature range (for example, −30 ° C.) to a high temperature range (for example, + 80 ° C.). It is required to operate normally in the temperature range.

  In the liquid crystal display device, the response speed of the liquid crystal is temperature-dependent, the response is slow at low temperatures, and the response is fast at high temperatures. In particular, since the slow response speed at low temperatures is a problem in display quality, a panel heater that warms the liquid crystal display device is generally used in a liquid crystal display device that is expected to be used at low temperatures. is there.

  FIG. 3 is an explanatory view showing an example of a general panel heater (ITO heater) for a liquid crystal display device. In the example shown in FIG. 3, the transparent conductive film 13 is formed on almost the entire one surface of the glass substrate 11. For the transparent conductive film 13, for example, ITO (Indium Tin Oxide) is used.

  A pair of electrodes 12-1 and 12-2 for applying a voltage to the transparent conductive film 13 are provided on two opposing sides of the glass substrate 11. As the electrodes 12-1 and 12-2, for example, an FPC (flexible printed wiring board) is used. In the FPC, wiring is formed on the surface or inside of a deformable sheet-like substrate, and the electrical resistance of the wiring (forming a substantial electrode) is sufficiently low. The electrodes 12-1 and 12-2 are each crimped and electrically connected to the transparent conductive film 13 via an anisotropic conductive film, for example.

  The electrodes 12-1 and 12-2 are formed in a single band shape having a certain width. The electrode 12-1 and the electrode 12-2 are disposed substantially in parallel along two opposing sides of the glass substrate 11, respectively. In the electrodes 12-1 and 12-2, the electrodes 12-1 and 12-2 are opposed to the non-display area of the liquid crystal display panel, and the area between the electrodes 12-1 and 12-2 is the liquid crystal display panel. It is installed so as to face the display area.

  The electrodes 12-1 and 12-2 are connected to a panel heater power supply device mounted on a main board (not shown) and energized. Since the electrodes 12-1 and 12-2 are installed substantially in parallel and a voltage is applied thereto, a current flows uniformly through the transparent conductive film 13, and the panel heater and the liquid crystal display device can be heated substantially uniformly.

  The main board is a board on which an MPU for driving a liquid crystal display panel and a panel heater, a power supply device, and the like are mounted. When the panel heater is used in an in-vehicle liquid crystal display device, the main substrate and the panel heater are connected by, for example, a conductive clip pin in consideration of an impact such as vibration.

  In addition, a liquid crystal display device has been proposed that can reduce the size of the device by efficiently disposing the drive elements of the display liquid crystal cell and the electrodes of the panel heater (see, for example, Patent Document 1). In the liquid crystal display device described in Patent Document 1, driving elements are provided at both ends on the front surface side of the display liquid crystal cell, and electrodes are provided at both ends on the back surface side of the panel heater. The area on the front surface side of the liquid crystal cell for display and the area on the back surface side of the panel heater can be used effectively without contact between the drive element and the electrode of the panel heater, and the liquid crystal display device can be miniaturized. .

JP 2003-131247 A (paragraphs 0013-0014)

  However, in the method described in Patent Document 1, since the drive element of the liquid crystal cell for display and the electrode of the panel heater are arranged at close positions, there is a risk of contact. In addition, each wiring is concentrated and there is a problem that free design is not possible.

  It may be necessary to dispose two electrodes on one side of the liquid crystal display panel due to mounting restrictions on the substrate. For example, in some cases, it is required to arrange a terminal part of the liquid crystal display panel on one side of the liquid crystal display panel and to arrange an electrode of the panel heater on one side opposite to the side on which the terminal part is arranged. In that case, it is necessary to arrange two electrodes on one side of the panel heater.

  When two electrodes are arranged on one side on the glass substrate, the entire surface of the glass substrate can be heated by arranging the transparent conductive film in a U shape. FIG. 4 is an explanatory view showing an arrangement example of the transparent conductive film in the case where two electrodes are arranged on one side of a glass substrate of a panel heater (ITO heater) for a liquid crystal display device. As shown in FIG. 4, the transparent conductive film 23 is disposed in a U shape on substantially the entire one surface of the glass substrate 11. As the transparent conductive film 23, ITO is generally used.

  Electrodes 22-1 and 22-2 are connected to the two upper sides of the U-shaped transparent conductive film 23, respectively. As the electrodes 22-1 and 22-2, for example, FPC is used. The electrodes 22-1 and 22-2 are, for example, crimped and electrically connected to the transparent conductive film 23 via an anisotropic conductive film, for example.

  FIG. 5 is an explanatory diagram showing a current distribution (a result of simulation) when two electrodes are arranged on one side of a glass substrate of a panel heater for a liquid crystal display device. In FIG. 5, the example of the electric current which flows into the transparent conductive film 22 is represented by the broken line. As shown in FIG. 5, the current concentrates inside the folded portion of the transparent conductive film 22 (the portion where the overall current traveling direction can be changed).

Joule heat is generated when current flows through the resistor. Joule heat P is proportional to the square of the current and resistance, and is represented by P = I ² R. The transparent conductive film 22 generally has a surface resistance value of about 10Ω / □. For this reason, heat generation at a portion where current is concentrated increases, and display unevenness may occur, fusing, and peripheral components may be affected. Therefore, it is substantially difficult to dispose two electrodes on one side of the panel heater. Since it is difficult to dispose the electrode of the panel heater on one side of the liquid crystal display panel that faces the side where the terminal portion is disposed, the degree of freedom in designing the liquid crystal display device is reduced.

  Therefore, an object of the present invention is to provide a panel heater for a liquid crystal display device that has a high degree of design freedom and can generate heat uniformly.

The panel heater for a liquid crystal display device according to the present invention is a panel heater for a liquid crystal display device that uses a transparent conductive layer as a heating element, and one side of each of two transparent conductive layers arranged side by side (for example, a plane of the panel heater) When the shape is rectangular, an electrode is connected to one side), current flows from one of the two electrodes to the other through the transparent conductive layer, and the other side of the two transparent conductive layers ( For example, when the planar shape of the panel heater is rectangular, the plate conductor having a resistance value lower than the resistance value of the transparent conductive layer is electrically It is connected.

  When the shape of the surface of two transparent conductive layers is a rectangle, it is preferable that the length and width of each rectangle are equal. According to such a configuration, the heat generation amount can be made uniform over the entire surface.

  The plate-like conductor may be disposed in a non-display portion in the liquid crystal display device. According to such a configuration, heat generation in the non-display portion can be suppressed.

  In addition, it is preferable that overlapping portions overlapping with the respective transparent conductive layers are formed on the plate-like conductor, and the overlapping portions have a width substantially the same as the width of the transparent conductive layer. According to such a configuration, the heat generation amount can be made more uniform.

  According to the present invention, since it is possible to arrange an electrode on one side of the panel heater, the degree of freedom in design can be increased. In the case where the electrodes are arranged on one side, the wiring can be concentrated on one side, and the wiring can be simplified. In addition, there is an effect of preventing color unevenness caused by the amount of heat generation depending on the position, and an effect of preventing the folded portion of the current path from locally generating heat and affecting peripheral components.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an arrangement example of transparent conductive films and conductors of a panel heater (ITO heater) for a liquid crystal display device according to the present invention. As shown in FIG. 1, the panel heater for a liquid crystal display device includes a glass substrate 11, an electrode 22-1, an electrode 22-2, a transparent conductive film 103-1 as one plate-like transparent conductive layer, A transparent conductive film 103-2 as the other plate-like transparent conductive layer and a conductor 104 as a plate-like conductor are provided. Components similar to those of the panel heater for the liquid crystal display device shown in FIG. 4 are denoted by the same reference numerals as those in FIG.

  The shapes of the surfaces of the transparent conductive film 103-1 and the transparent conductive film 103-2 are each rectangular, and the length and width of each rectangle are equal. For example, ITO is used as the transparent conductive films 103-1 and 103-2. ITO is widely used as a transparent conductive film because of its high light transmittance and easy pattern formation.

  As the conductor 104, for example, an FPC provided with a copper foil having a sufficiently low electric resistance is used. As the base material for FPC, for example, resins such as polyimide and polyethylene terephthalate are used. The electrical resistance of the copper foil portion of the conductor 104 is sufficiently small, for example, about 0.001 Ω / □ compared to about 10 Ω / □ of the transparent conductive films 103-1 and 103-2.

  In the panel heater for a liquid crystal display device, a transparent conductive film 103-1 and a transparent conductive film 103-2 are disposed so that almost the entire surface of one side of the glass substrate 11 is divided into two. Note that the transparent conductive film 103-1 and the transparent conductive film 103-2 are not in contact with each other.

  Moreover, the conductor 104 is arrange | positioned in the part corresponding to the non-display area | region (inactive area) where an image is not displayed among the one surfaces of the glass substrate 11. FIG. The conductor 104 is provided so as to bridge one end of the transparent conductive film 103-1 and one end of the transparent conductive film 103-2. That is, the transparent conductive film 103-1, the conductor 104, and the transparent conductive film 103-2 are connected in this order and are arranged in a U shape.

  The overlapping portion where the transparent conductive films 103-1 and 103-2 and the conductor 104 overlap is the same width as the width of the transparent conductive film, and the entire surface of the overlapping portion is crimped via the anisotropic conductive film, Electrically connected. In the case of using an anisotropic conductive film, it is necessary to consider about 0.005Ω as the contact resistance. The electrical resistance of the copper foil portion of the conductor 104 including the contact resistance is sufficiently smaller than the resistance values of the transparent conductive films 103-1 and 103-2. Thus, the conductor 104 covers the entire surface in the width direction of the transparent conductive film, whereby the current density flowing in the length direction of the transparent conductive film can be made constant, and a uniform heat generation amount can be obtained.

  The electrode 22-1 is connected to the side of the transparent conductive film 103-1 where the conductor 104 is not connected, and the electrode 22-2 is connected to the side of the transparent conductive film 103-2 where the conductor 104 is not connected. Is done. As the electrodes 22-1 and 22-2, for example, FPC is used. For example, the electrodes 22-1 and 22-2 are pressure-bonded and electrically connected to the transparent conductive films 103-1 and 103-2 through an anisotropic conductive film, for example.

  FIG. 2 is an explanatory diagram showing a current distribution (result of simulation) of the panel heater for a liquid crystal display device according to the present invention. In FIG. 2, an example of current flowing through the transparent conductive film 103-1, the conductor 104, and the transparent conductive film 103-2 is represented by a broken line. As shown in FIG. 2, the current flowing from the electrode 22-1 flows uniformly over the entire surface of the transparent conductive film 103-1. The current flowing from the transparent conductive film 103-1 to the conductor 104 flows substantially uniformly over the entire surface of the conductor 104. The current flowing from the conductor 104 to the transparent conductive film 103-2 flows uniformly over the entire surface of the transparent conductive film 103-2.

  The current flowing through the conductor 104 and the current flowing through the transparent conductive films 103-1 and 103-2 are the same. However, since the electrical resistance of the conductor 104 is sufficiently smaller than the resistance values of the transparent conductive films 103-1 and 103-2, the heat generation amount in the conductor 104 is the heat generation amount in the transparent conductive films 103-1 and 103-2. Smaller than. In addition, since the conductor 104 is arrange | positioned in a non-display area | region, the one where the emitted-heat amount is smaller is preferable.

  When the folded portion of the transparent conductive film 22 shown in FIG. 5 is compared with the corresponding conductor 104 shown in FIG. 2, the current is concentrated inside the folded portion in the folded portion of the transparent conductive film 22 shown in FIG. On the other hand, in the conductor 104 shown in FIG. 2, the current flows uniformly over the entire surface of the conductor 104. Since the current flowing through the conductor 104 is substantially uniform, a large amount of current does not flow partially, and the amount of heat generated in the conductor 104 is also approximately uniform, thereby reducing adverse effects on the display area such as color unevenness. Can do.

  In the present embodiment, the case where two electrodes are arranged on one side of the panel heater has been described as an example. However, if the current path is folded, the shape of the panel heater and the arrangement of the electrodes are used. Can be applied. For example, the present invention can also be applied to a case where the panel heater is not rectangular but has a polygonal shape or a shape having a curved peripheral portion. In addition, the two transparent conductive films 103-1 and 103-2 are connected by the conductor 104, but the transparent conductive films 103-1 and 103-2 are supplementarily connected by the transparent conductive film material, and the conductor 104 You may connect.

  As described above, according to the present embodiment, since the current does not concentrate inside the folded portion of the current path, a panel heater in which two electrodes are arranged on one side can be practically used. That is, the degree of freedom in design can be increased. In addition, the wiring of the liquid crystal display panel and the panel heater can be simplified. In addition, it is possible to prevent color unevenness caused by the amount of heat generation depending on the position, and local current generation at the folded portion of the current path and affecting peripheral components.

  The present invention can be applied to a panel heater for a liquid crystal display device, and in particular, can be effectively applied to a panel heater for a liquid crystal display device that needs to return a current path.

Explanatory drawing which shows the example of arrangement | positioning of the transparent conductive film and conductor of the panel heater for liquid crystal display devices by this invention. Explanatory drawing which shows the electric current distribution (result of simulation) of the panel heater for liquid crystal display devices by this invention. Explanatory drawing which shows the example of the panel heater for common liquid crystal display devices. Explanatory drawing which shows the example of arrangement | positioning of the transparent conductive film in the case of arrange | positioning two electrodes on one side of the panel heater for liquid crystal display devices. Explanatory drawing which shows electric current distribution (result of simulation) in the case of arrange | positioning two electrodes to one side of the panel heater for liquid crystal display devices.

Explanation of symbols

11 Glass substrate 22-1 to 22-2 Electrode 103-1 to 103-2 Transparent conductive film 104 Conductor

Claims (4)

In a panel heater for a liquid crystal display device using a transparent conductive layer as a heating element,
An electrode is connected to one side of each of the two transparent conductive layers arranged side by side,
A current flows from one electrode of the two electrodes to the other electrode through the transparent conductive layer,
A panel heater for a liquid crystal display device, wherein the other side of the two transparent conductive layers is electrically connected by a plate-like conductor having a resistance value lower than the resistance value of the transparent conductive layer. The shape of the surface of the two transparent conductive layers is rectangular,
The panel heater for a liquid crystal display device according to claim 1, wherein each rectangle has the same length and width. The panel heater for a liquid crystal display device according to claim 1, wherein the plate-like conductor is disposed in a non-display portion of the liquid crystal display device. 4. The plate-like conductor has an overlapping portion that overlaps with each transparent conductive layer, and the overlapping portion has a width that is substantially the same as the width of the transparent conductive layer. 5. Panel heater for liquid crystal display devices.

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