JP2005208188A - Liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal projector having excellent display quality which is not affected by dust in cooling air. <P>SOLUTION: The liquid crystal projector which takes air sent by a fan as the cooling air so as to cool a liquid crystal panel etc. is equipped with the liquid crystal panel part constituted by forming a transparent conductive member 2 on the liquid crystal panel 1, and a voltage generator 5 applying prescribed AC voltage, and is constituted so that the prescribed AC voltage is applied to the member 2 from the generator 5. Thus, the dust is prevented from adhering to the liquid crystal panel part and further the adhering dust, particularly, non-conductive dust is removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal projector having a function of preventing display failure caused by dust or the like in forced cooling cooling air.

  In the liquid crystal projector, the blocking light is generated by the switching action of the liquid crystal and the rectifying action by the polarizing plate, and the blocking light is converted into heat. Accordingly, a liquid crystal light valve composed of a liquid crystal panel and a polarizing plate and the vicinity thereof are at a high temperature, and cooling is necessary to reduce deterioration of the liquid crystal panel and the like. Usually, cooling uses an air flow by a fan. However, there is a problem that dust of a size of several tens of microns existing in the air flow adheres to the surface of a liquid crystal panel or the like due to static electricity and causes deterioration in image quality. there were.

As a countermeasure, a transparent conductive member is formed on both outer surfaces of the liquid crystal panel, and the transparent conductive member is grounded to electrically neutralize the liquid crystal panel and prevent the adsorption of charged dust (for example, patents) A method of preventing dust from adhering by using an electric repulsion by flowing an air stream ionized by corona discharge using an ionizer and charging an object with the same potential (see, for example, Patent Document 2). See).
JP 2000-180816 A (page 2-4, FIG. 3) JP 2001-68293 A (page 2-3, FIG. 1)

  However, in the conventional configuration disclosed in Patent Document 1, transparent conductive members are formed on both outer surfaces of the liquid crystal panel, and the transparent conductive members are grounded. Therefore, conductive dust made of metal powder or the like does not adhere to the liquid crystal panel because the electric charge charged in the dust moves to the conductive material and becomes electrically neutral when it comes into contact with a grounded conductive material. . However, in the case of non-conductive materials such as cellulose and plastic that do not have conductivity, even if they come into contact with a grounded conductive material, the charge charged to the dust moves to the conductive material only by changing the distribution state. It will not adhere to the liquid crystal panel. Most of the dust generated during normal use is made of non-conductive materials such as cotton fibers and plastic pieces of clothing. Therefore, the invention of Patent Document 1 has a problem that the effect on such non-conductive dust is poor.

  Moreover, in the conventional structure currently disclosed by patent document 2, it is invention which flows the air flow ionized by corona discharge and charges dust and a target object to the same electric potential. In this case, since ions generated by the ionizer are remarkably reduced when they are separated from the electrodes, an ion source must be installed in the vicinity of the liquid crystal panel or the polarizing plate. Therefore, it is difficult to perform a compact design and the cost is increased. Furthermore, since ozone harmful to the human body is generated by the ionizer, there is a problem that it is necessary to take measures to prevent ozone.

  The present invention solves the above-described conventional problems, and can realize a good display quality in which dust in the cooling air is not attached to the liquid crystal panel with a simple configuration, and the attached dust can be either conductive or non-conductive. It is an object of the present invention to provide a liquid crystal projector that can be reliably removed to reproduce good display quality.

  In order to solve the conventional problems, the present invention provides a liquid crystal projector that projects light from a liquid crystal panel by a projection lens after guiding light from a light source to a liquid crystal panel for displaying an image. A liquid crystal projector comprising: a conductive layer made of a transparent conductive member on a surface of a liquid crystal panel; and a voltage generator for applying a predetermined alternating voltage to the conductive layer.

The liquid crystal projector according to claim 1, wherein the conductive layer is formed on both surfaces of the liquid crystal panel.
The liquid crystal projector according to claim 1, wherein the liquid crystal panel further comprises a transparent insulating layer disposed on both surfaces thereof, and a conductive layer disposed on the surface of the transparent insulating layer.

The liquid crystal projector according to claim 1, wherein the predetermined AC voltage is in a range of 100V to 3kV.
Furthermore, the present invention provides a liquid crystal projector in which light from a light source is guided to a liquid crystal panel for displaying an image, and then the light from the liquid crystal panel is projected by a projection lens. A voltage generator for applying a predetermined AC voltage to the transparent conductive layer, and a controller for sending a control signal instructing the voltage generator to apply or stop the predetermined AC voltage; The test image projected on the screen from the projection lens is photographed and converted into a binarized image, and the area ratio (dark part / bright part) of the dark part and the bright part of the binarized image is calculated and the control is performed. A control unit that outputs to the unit, and a control that applies the predetermined AC voltage if the area ratio is greater than a predetermined value, and stops the predetermined AC voltage if the area ratio is smaller than the predetermined value Part A liquid crystal projector, characterized in that the One.

The liquid crystal projector according to claim 5, wherein the conductive layer is formed on both surfaces of the liquid crystal panel.
The liquid crystal projector according to claim 5, wherein the display unit further comprises a transparent insulating layer disposed on both surfaces of the liquid crystal panel, and a conductive layer disposed on the surface of the transparent insulating layer.

The liquid crystal projector according to claim 5, wherein the predetermined AC voltage is in a range of 100V to 3kV.
6. The liquid crystal projector according to claim 5, wherein the test image has the same color and brightness value for all the images.

  According to the liquid crystal projector of the present invention, it is possible to prevent the dust in the cooling air from adhering to the liquid crystal panel, and to reliably remove dust adhering to the liquid crystal panel, particularly non-conductive dust. Therefore, it is possible to realize a high-definition liquid crystal projector that does not deteriorate the display quality due to dust.

  Embodiments of a liquid crystal projector according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a main part of a liquid crystal projector according to Embodiment 1 of the present invention.
In FIG. 1, a liquid crystal panel 1 provided with transparent conductive members 2 on both sides is installed in parallel with a prism 4 arranged at a predetermined position on the optical axis inside a housing of a liquid crystal projector, and a blower fin 6 and a filter are provided. A cooling fan 8 consisting of 7 is arranged at a position for sending cooling air to the liquid crystal panel 1. The transparent conductive member 2 is connected to a voltage generator 5 that applies a predetermined AC voltage at all times or as necessary.

  Most of the dust in the cooling air sent to the liquid crystal panel 1 is removed by the filter 7. However, in order to sufficiently cool the light valves such as the liquid crystal panel 1 and the polarizing plate, the air volume of a certain amount or more is required, and therefore the pores of the filter 7 cannot be extremely small. Therefore, dust having a size of several tens of microns that is the same as or slightly larger than the filter pores passes through. Dust carried through the filter pores to the vicinity of the liquid crystal panel is charged by friction with a filter, an air flow, etc., and is electrostatically adsorbed to the liquid crystal panel having a relatively potential difference. However, as shown in the present invention, when an alternating voltage whose potential changes at a constant cycle is applied to the transparent conductive member 2 from the voltage generator 5, the liquid crystal panel surface and dust alternately have electrical affinity and electrical repulsion. It is generated and is in an electrically neutralized state, so that dust is not actively adsorbed to the liquid crystal panel, and adhesion of dust can be prevented.

  Moreover, when an alternating voltage whose potential changes at a constant period is applied from the voltage generator 5 to the transparent conductive member 2 of the liquid crystal panel to which dust has already adhered, the surface of the liquid crystal panel and the dust have the same potential and the electric affinity is lost. A time zone occurs, and the dust is easily separated from the object by the wind pressure received from the cooling air. In this method, dust is made of non-conductive materials such as cotton fibers and plastic pieces, and even if it comes in contact with a grounded conductive material, the charge charged to the dust does not move to the conductive material, only the distribution state changes, This is particularly effective when it is difficult to remove static charges by grounding.

  FIG. 2 shows an enlarged cross-sectional view of the main part of the liquid crystal panel portion in Embodiment 1 of the present invention. (A) is a structure in which a transparent conductive member such as ITO is directly formed on both surfaces of the liquid crystal panel 1, and can be easily downsized and configured at low cost. On the other hand, (b) has a structure in which the transparent conductive member 2 is formed on the transparent insulating member 3 made of glass, plastic or the like bonded to both surfaces of the liquid crystal panel 1, and thus has high reliability against voltage application. Moreover, since the dust adhesion position can be moved away by disposing the transparent insulating member 3 from the liquid crystal panel in which the optical focus is reduced, a defocus function can be provided. In the present invention, either method (a) or (b) may be used depending on the purpose.

FIG. 3 is a schematic diagram of the liquid crystal projector according to the first embodiment of the present invention. In FIG. 3, a light source lamp 10, a liquid crystal panel unit 40, a prism 4, and a projection lens 12 are arranged in the projection optical unit 11 of the liquid crystal projector, and a screen 21 that projects an image is arranged at the tip of the projection lens 12. . The liquid crystal panel unit 40 has the configuration shown in FIG. 2A or 2B and is connected to a voltage generator 5 that applies an AC voltage.
When a predetermined alternating voltage is applied from the voltage generator 5 to the conductive layer 2 of the liquid crystal panel unit 40 when the liquid crystal projector is used, dust attached to the surface of the liquid crystal panel is electrically neutralized. Therefore, by blowing air to the liquid crystal panel unit 40 by the cooling fan 8, it is possible to easily prevent dust from adhering to the liquid crystal panel and remove dust that has already been electrostatically adsorbed.

  The AC voltage applied to the conductive layer 2 differs depending on the material of the dust, the humidity, the air volume of the cooling fan, the structure and material of the flow path through which the cooling air passes. In general, the higher the applied voltage, the better. As a result of various experiments, the inventor of the present invention has confirmed that a display failure or operation failure of the liquid crystal panel is observed at a voltage higher than the AC voltage of 3 kV, and electrostatic adsorption such as cotton fibers cannot be prevented at a voltage lower than 100 V. . Therefore, the voltage applied to the conductive layer 2 in the present invention is suitably an AC voltage of 100 V or more and 3 kV or less.

  Further, as a technique for generating an AC voltage for implementing the present invention, a multifunctional safety standard test analyzer is known, for example, POP200 manufactured by Matsusada Precision Co., Ltd. or PA-2002 manufactured by Measurement Technology Laboratory Co., Ltd. 7740 is known. Using these known techniques, the voltage generator 5 for carrying out the present invention can be easily realized.

  As described above, in the first embodiment, a conductive layer made of a transparent conductive member is formed on the liquid crystal panel, and an AC voltage of 100 V to 3 KV is applied to the conductive layer, thereby contacting the surface of the liquid crystal panel unit. Dust is electrically neutralized. Therefore, dust can be prevented from electrostatically adsorbing to the liquid crystal panel. Also, by applying a voltage to the liquid crystal panel that already has dust attached to it, the surface of the liquid crystal panel and the dust have the same potential. Dust can be removed. Therefore, a liquid crystal projector capable of maintaining good display quality can be realized.

  Further, in the embodiment of the present invention, the object on which the transparent conductive member is formed is effective for a member in which the display quality of an image projected on the screen is deteriorated due to dust adhesion. It can also be applied.

(Embodiment 2)
FIG. 4 is a schematic diagram of a dust detection and removal system for a liquid crystal projector according to Embodiment 2 of the present invention. In FIG. 4, a light source lamp 10, a liquid crystal panel unit 40, a prism 4, and a projection lens 12 are disposed in the projection optical unit 11 of the liquid crystal projector, and a screen 21 that projects an image is disposed at the tip of the projection lens 12. . In the liquid crystal panel section 40, a transparent conductive member made of ITO or the like is formed on both surfaces of the liquid crystal panel as in the configuration of the first embodiment. A video camera having an imaging lens 13 is disposed in the detection unit 14 that detects the image 20 on the screen 21 and detects adhesion of dust, and generates a signal according to the size of the shadow of the image captured by the detection unit. It connects with the voltage generator 5 which applies an alternating voltage to an electroconductive transparent member via the control part 15 to do.

  The dust detection and removal system is implemented as follows, for example. That is, a test pattern of white light is projected on the screen 21 and the adhesion state of dust is monitored as a shadow on the screen by the detection unit 14 provided at the lower part of the liquid crystal projector. The control unit 15 binarizes the obtained shadow and then calculates the area ratio (dark part / bright part) of the dark part and the bright part. Since this area ratio is proportional to the amount and size of dust adhering to the liquid crystal panel section 40, if this area ratio exceeds a preset threshold value that requires dust removal, the voltage generator 5 A signal is sent, and a predetermined voltage is applied to the transparent conductive member of the liquid crystal panel unit 40. As a result, as in the case of the first embodiment, dust adhering to the liquid crystal panel portion is reliably removed. Further, the information that the dust is removed and the shading on the screen is reduced is monitored by the detection unit 14, a signal is sent from the control unit 15 to the voltage generator 5, and the voltage application is stopped.

  As described above, in the second embodiment of the present invention, the test pattern made of white light is projected onto the screen, and the projected image is photographed by the detection unit 14 to detect the amount of dust in the liquid crystal panel unit 40. When the dust exceeds a predetermined amount, the voltage generator 5 applies an AC voltage of 100 V to 3 KV to the conductive layer 2 of the liquid crystal panel unit 40, thereby easily removing dust adhering to the liquid crystal panel unit 40. Can be done. Further, when the detection unit 14 determines that the amount of dust attached to the liquid crystal panel unit 40 is less than a predetermined value, the applied voltage of the voltage generator 5 is stopped, so that power consumption can be suppressed.

  In this embodiment, white light is used as a test pattern. However, all the pixels of the test pattern may have the same color and luminance value, and are not limited to white light.

  In addition, by applying this example to a self-test immediately after power-on or a maintenance test after a certain period of use, it is possible to automatically suppress the generation of dust adhering to the LCD panel. A high-quality, maintenance-free high-quality liquid crystal projector can be easily realized.

  The liquid crystal projector according to the present invention can prevent the dust in the cooling air from adhering to the liquid crystal panel, and can reliably remove the dust adhering to the liquid crystal panel, particularly the dust made of a non-conductive material. Therefore, it is useful as a technology that can realize a high-definition liquid crystal projector without deterioration of display quality due to dust.

  In addition, the liquid crystal projector according to the present invention can automatically inspect the display quality at an arbitrary timing and automatically remove the dust adhering to the liquid crystal panel. Therefore, it is possible to provide a highly reliable and maintenance-free product.

Sectional drawing of the principal part of the liquid crystal projector in Embodiment 1 of this invention The principal part expanded sectional view of the liquid crystal panel part in Embodiment 1 of this invention Schematic diagram of a liquid crystal projector according to the first embodiment of the present invention Schematic diagram of a dust detection and removal system for a liquid crystal projector in Embodiment 2 of the present invention Main section enlarged sectional view of the conventional liquid crystal panel

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Transparent electrically conductive member 3 Transparent insulating member 4 Prism 5 Voltage generator 8 Cooling fan

Claims (9)

In a liquid crystal projector in which light from a light source is guided to a liquid crystal panel for displaying an image, and then the light from the liquid crystal panel is projected by a projection lens, a conductive layer made of a transparent conductive member is disposed on the surface of the liquid crystal panel And a voltage generator for applying a predetermined AC voltage to the conductive layer. The liquid crystal projector according to claim 1, wherein the conductive layer is formed on both surfaces of the liquid crystal panel. 2. The liquid crystal projector according to claim 1, wherein the liquid crystal panel has a transparent insulating layer disposed on both sides thereof, and a conductive layer disposed on the surface of the transparent insulating layer. The liquid crystal projector according to claim 1, wherein the predetermined AC voltage is in a range of 100 V to 3 kV. In a liquid crystal projector in which light from a light source is guided to a liquid crystal panel for displaying an image and then projected from the liquid crystal panel by a projection lens, a conductive layer made of a transparent conductive member is disposed on the surface of the liquid crystal panel A voltage generator for applying a predetermined AC voltage to the transparent conductive layer, a control unit for sending a control signal for instructing the voltage generator to apply or stop the predetermined AC voltage, and the projection lens Detection of taking a test image projected on a screen and converting it to a binarized image, calculating the area ratio (dark part / bright part) of the dark part and the bright part of the binarized image and outputting it to the control part And a control unit that controls to apply the predetermined AC voltage if the area ratio is larger than a predetermined value, and to stop the predetermined AC voltage if the area ratio is smaller than the predetermined value. Features and A liquid crystal projector that. The liquid crystal projector according to claim 5, wherein the conductive layer is formed on both surfaces of the liquid crystal panel. The liquid crystal projector according to claim 5, wherein the display unit includes a transparent insulating layer disposed on both surfaces of the liquid crystal panel, and a conductive layer disposed on a surface of the transparent insulating layer. The liquid crystal projector according to claim 5, wherein the predetermined AC voltage is in a range of 100 V to 3 kV. The liquid crystal projector according to claim 5, wherein the test image has the same color and brightness value of all the images.

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