JP2008262002A - Image quality controller and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image quality controller capable of preventing a display quality from degrading, even when an environmental condition is changed, and to provide a liquid crystal display. <P>SOLUTION: In the image quality controller for controlling the image quality of a display panel (liquid crystal panel) 10, having an optical film having moisture content dependence as an optical characteristic and attached to the display surface thereof or provided inside and performing image display, according to the inputted drive signal, there are provided moisture detection sensors 21 and 22 detecting moisture information related to a moisture content, a correction table (table data recorded part) 40 where the information showing corresponding relation of moisture information, detected by the moisture detection sensors and an image quality change generated in the display panel caused by the change of the moisture content or correction values for correcting the image quality change, is held in advance and a drive signal correction part (control part) 30 correcting the drive signal to be given to the display panel, based on the moisture information detected by the moisture detection sensors and the content held in the correction table. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image quality control device and a liquid crystal display device, and in particular, is a technique used for a liquid crystal display device including an optical film for the purpose of compensating display characteristics.

  For example, a liquid crystal display device is generally composed of a liquid crystal cell, a linear polarizing plate, an optical compensation film, and a drive circuit. In the case of a transmissive liquid crystal display device, two polarizing plates are arranged on both sides of the liquid crystal cell in a crossed Nicol state, and one or a plurality of optical compensation films are arranged between the liquid crystal cell and the polarizing plate. . In the case of a reflective liquid crystal display device, a reflector, a liquid crystal cell, one optical compensation film, and one polarizing plate are arranged in this order. A polarizing plate consists of a transparent protective film and a polarizing film. In some cases, an elliptically polarizing plate having an optical compensation film as the transparent protective film of the polarizing plate may be used. The liquid crystal cell includes a rod-like liquid crystalline molecule, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystalline molecule.

  There are various types of liquid crystal cells having different alignment states of rod-like liquid crystalline molecules. That is, for transmissive liquid crystal cells, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Luquid Crystal), OCB (Optically Compensatory Band), STN (Super Twisted Nematic), VA (Vertically Aligned) ECB (Electrically Controlled Birefringence), and reflective liquid crystal cells of a type (display mode) such as TN, HAN (Hybrid Aligned Nematic), and GH (Guest-Host) have been proposed.

  In the case of a transmissive liquid crystal display device, among the upper and lower polarizing plates of the liquid crystal cell, the polarizing plate on the backlight side partially absorbs light from the light source and converts light incident on the liquid crystal cell into linearly polarized light. The exit-side polarizing plate allows the polarized light component parallel to the transmission axis to pass through the light passing through the liquid crystal cell and absorbs the polarized light component in the absorption axis direction. The optical compensation film is disposed between the polarizing plate and the liquid crystal cell in order to eliminate unnecessary image coloring and widen the viewing angle, and converts linearly polarized light by the polarizing plate into elliptically polarized light. That is, the linearly polarizing plate and the optical compensation film become an elliptically polarizing plate. As the optical compensation film, an optical compensation film having an optically anisotropic layer formed from a discotic compound or a liquid crystalline molecule on a transparent support, such as a stretched birefringent polymer film, is generally used. The optical properties of the optical compensation film are determined according to the optical properties of the liquid crystal cell, specifically the difference in display mode as described above, and optical compensation films with various characteristics corresponding to various display modes are proposed. Has been.

Incidentally, various control techniques have been proposed for display devices such as liquid crystal display devices. For example, in Patent Document 1, in order to control contrast, which is one of display characteristics, an environmental temperature is detected using a temperature sensor, and a voltage applied to an electrode of a liquid crystal display according to the detected environmental temperature. Propose to adjust automatically. That is, the applied voltage is controlled so that the contrast does not change due to a temperature change in consideration of the fact that the applied voltage when the optimum contrast is obtained changes according to the environmental temperature.
JP-A-5-127609

However, there are many cases where desired display quality cannot be obtained only by controlling the applied voltage according to the detected environmental temperature as in Patent Document 1. Specific examples will be described below.
In recent years, liquid crystal display devices have become increasingly larger, and in particular, when black is displayed, regardless of the image signal for display, the top and bottom, the left and right edges, or the four corners of the display screen are displayed. The phenomenon of light leaking in the direction tends to become prominent. In other words, since light leaks in a specific viewing direction regardless of the display image, a large display quality may be significantly reduced in a large liquid crystal display device. In particular, in the case of an OCB display mode liquid crystal display device provided with an optical compensation film, a change in color occurs due to a difference in environmental conditions, or a change occurs in the value of an applied voltage necessary to obtain an optimal black color. It has been found. In reality, such deterioration in display quality cannot be solved only by controlling the applied voltage in accordance with the detected environmental temperature.
An object of the present invention is to provide an image quality control device and a liquid crystal display device capable of preventing a deterioration in display quality even when environmental conditions change.

The above object of the present invention is achieved by the following configuration.
(1) An image quality control apparatus for controlling the image quality of a display panel, in which an optical film having a water content dependency on optical characteristics is mounted on or incorporated in a display surface and displays an image according to an input drive signal,
A moisture detection sensor for detecting moisture information related to moisture content for at least one of the optical film and the surrounding environment of the display panel;
Information indicating a correspondence relationship between at least moisture information detected by the moisture detection sensor and an image quality change generated in the display panel due to a change in the water content or a correction value for correcting the image quality change is stored in advance. Correction table,
An image quality control apparatus comprising: a drive signal correction unit that corrects a drive signal applied to the display panel based on moisture information detected by the moisture detection sensor and contents held in the correction table.

  According to this image quality control apparatus, it is possible to prevent a decrease in display quality caused by a change in the use environment of the display panel. For example, it has been confirmed that the optical characteristics of the optical film (retardation film) used for the liquid crystal display panel in the OCB display mode change as the temperature and humidity change. Further, the light leakage phenomenon in the liquid crystal display device described above occurs when a liquid crystal display device stored in a high humidity state of, for example, a humidity of 60% or more is moved to a low humidity environment. In addition, it has been confirmed that the remarkable state of the light leakage phenomenon gradually recovers when a low humidity environment is changed to a high humidity environment again. From such a situation, the light leakage phenomenon is caused by photoelastic deformation accompanying moisture absorption and desorption of the film material constituting the polarizing plate sandwiched between two polarizing films arranged in crossed Nicols. Conceivable. Therefore, the optical characteristics of the optical film are controlled by canceling the change in the optical characteristics expected to occur according to the humidity in the environment where the display panel is used or the moisture content inside the optical film of the display panel. It is possible to compensate for the change in the display quality and prevent the display quality from deteriorating.

(2) The image quality control device according to (1), wherein the moisture detection sensor includes a humidity sensor that detects humidity related to an environment surrounding the display panel.

  According to this image quality control apparatus, since the humidity related to the surrounding environment of the display panel can be detected using the moisture detection sensor, the change in the optical characteristics of the optical compensation film that is expected to occur with the humidity change is compensated. , Display quality can be prevented from deteriorating.

(3) The image quality control device according to (1), wherein the moisture detection sensor includes a moisture content sensor that detects a moisture content inside an optical compensation film included in the display panel.

  According to this image quality control apparatus, since the moisture content inside the optical compensation film provided in the display panel can be detected using the moisture detection sensor, the optical compensation film expected to be generated in accordance with the change in the moisture content. It is possible to compensate for the change in the optical characteristics of the display and prevent deterioration of display quality.

(4) The image quality control apparatus according to any one of (1) to (3), wherein a plurality of the moisture detection sensors independent from each other are arranged at different locations on the display panel.

  According to this image quality control apparatus, moisture information can be detected for each of a plurality of regions on the display panel using a plurality of moisture detection sensors. Therefore, even when the humidity or moisture content is different for each area on the display panel, such as when using a large display panel, an appropriate correction value is calculated for each area. It is possible to prevent the display quality from deteriorating over the entire area.

(5) A liquid crystal display device comprising the image quality control device according to any one of (1) to (4).

  According to this liquid crystal display device, as described above, the change in optical characteristics expected to occur according to the humidity in the environment where the liquid crystal display panel is used or the moisture content inside the optical compensation film of the liquid crystal display panel is offset. By performing control in such a manner, it is possible to compensate for changes in optical characteristics and prevent display quality from being deteriorated.

(6) The liquid crystal display device according to (5), wherein an optical compensation retardation film is used as the optical film.

  According to this liquid crystal display device, the viewing angle characteristics and the like of the liquid crystal display panel can be improved by using the retardation film. Moreover, the change of the optical characteristic which generate | occur | produces with the change of the moisture content of a phase difference film can be compensated by the above-mentioned control.

(7) In the liquid crystal display device according to (5) or (6), the drive signal correction unit may generate a drive voltage signal that causes an electro-optic effect in at least the liquid crystal layer of the display panel. A liquid crystal display device that performs correction based on the detected moisture information and the content held in the correction table.

  According to this liquid crystal display device, it is possible to compensate for changes in the optical properties of the optical film that occur with changes in environmental humidity and the like. That is, by adjusting the voltage of the driving voltage signal applied between the electrodes of the liquid crystal display panel, the alignment state of the liquid crystal molecules is adjusted, and the transmittance of light passing through the liquid crystal layer changes. Changes in optical properties can be offset.

(8) The liquid crystal display device according to (5) or (6),
Including a backlight that emits illumination light from the back side opposite to the display side surface of the display panel;
The liquid crystal display device that corrects at least the light emission luminance of the backlight based on moisture information detected by the moisture detection sensor and contents held in the correction table.

  According to this liquid crystal display device, it is possible to compensate for changes in the optical properties of the optical film that occur with changes in environmental humidity and the like. That is, by adjusting the luminance of the illumination light that illuminates the liquid crystal display panel from the back side, the intensity of the light passing through the liquid crystal layer changes, so that the change in the optical characteristics of the optical film can be offset.

(9) The liquid crystal display device according to any one of (5) to (8),
The display panel includes a color filter unit for controlling transmission or reflection of light of each of a plurality of basic color components,
The drive signal correction unit includes a drive voltage signal that causes at least an electro-optic effect in the liquid crystal layer of the display panel, and the correction of the moisture information detected by the moisture detection sensor and the correction independently for each of the plurality of basic color components. A liquid crystal display device that performs correction based on the content held by the table.

  According to this liquid crystal display device, the drive voltage signal is independently corrected for each of a plurality of basic color components (R color, G color, B color, etc.), so that the balance of the drive voltage is adjusted among the plurality of basic color components. Can achieve higher quality display.

(10) The liquid crystal display device according to any one of (5) to (8), wherein the display panel is an OCB mode (Optically Compensated Bend mode) liquid crystal display panel.

  According to this liquid crystal display device, since an OCB mode liquid crystal display panel is used, an extremely high display response speed can be obtained. Moreover, in the OCB mode liquid crystal display panel, the bend alignment of the liquid crystal molecules is the upper and lower target structure, so the change in the amount of refraction of the liquid crystal layer due to the viewing angle of the screen is self-compensated and the viewing angle dependency of the display is reduced it can. In addition, for optical films that need to be used to draw out the viewing angle characteristics of such bend orientation and obtain uniform and high-quality viewing angle characteristics, the optical characteristics can change significantly due to changes in moisture content. However, by controlling to offset the change in optical characteristics that are expected to occur according to the humidity in the environment where the display panel is used or the moisture content inside the optical compensation film of the display panel, It is possible to compensate for changes in characteristics and prevent display quality from being deteriorated.

(11) A liquid crystal display device that divides the display panel into a plurality of blocks and independently applies drive signals to the blocks,
The moisture detection sensors are arranged at a plurality of locations on the display panel, and a moisture content map in the display panel is created based on moisture content detection values from the moisture detection sensors,
For each block, a representative water content at the corresponding block position is obtained from the water content map, correction value data corresponding to the representative water content is determined from the correction table, and the determined correction value data is determined for each block. A liquid crystal display device that displays and drives each of the blocks superimposed on a drive signal.

  According to this liquid crystal display device, since the drive signal can be corrected in an independent state for each area of the display panel, a higher quality display is possible. Therefore, even when the humidity or moisture content is different for each area on the display panel, especially when using a large display panel, an appropriate correction value is calculated for each area. By controlling the drive signal using an independent correction value, it is possible to prevent the display quality from deteriorating over the entire area of the display panel.

  As described above, according to the image quality control device and the liquid crystal display device of the present invention, the optical characteristics expected to be generated according to the humidity in the environment where the display panel is used or the moisture content inside the optical compensation film of the display panel. By performing the control so as to cancel out the change in the image quality, it is possible to compensate for the change in the optical characteristics and prevent the display quality from deteriorating.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an image quality control device and a liquid crystal display device according to the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a main part of the liquid crystal display device according to the first embodiment.
In the first embodiment, it is assumed that the present invention is applied to a liquid crystal display device having a configuration as shown in FIG. The liquid crystal display device 100 mainly includes a liquid crystal panel 10, a moisture content sensor 21, a humidity sensor 22, a temperature sensor 23, a control unit 30, a table data recording unit 40, a voltage control unit 50, and an LCD. And a driver 60.

  The optical film used in the liquid crystal display device has its optical characteristics particularly affected by humidity. Therefore, the use of the temperature sensor 23 may be selectively switched. In addition, the present invention can be carried out with only one of the moisture content sensor 21 and the humidity sensor 22, but it is more accurate to use only the moisture content sensor 21 than when only the humidity sensor 22 is used. Correction control becomes possible.

  The liquid crystal panel 10 is composed of a large number of liquid crystal cells (10a) arranged so as to be two-dimensionally arranged at regular intervals in the direction along the horizontal (X) and vertical (Y) axes. Each liquid crystal cell 10a has a structure as shown in FIG. In this example, a liquid crystal panel 10 including an OCB mode liquid crystal cell 10a is assumed. Of course, the present invention is applicable even when a liquid crystal panel composed of liquid crystal cells other than the OCB mode is used.

  FIG. 2 is a perspective view showing one configuration of many liquid crystal cells included in the liquid crystal panel shown in FIG. The liquid crystal cell 10 a includes a polarizing plate 11, a liquid crystal cell substrate 12, a liquid crystal layer 13, a liquid crystal cell substrate 15, an optical compensation film 16, and a polarizing plate 17 arranged side by side in the thickness direction.

  The liquid crystal cell 10a is a transmissive type, and a part of the light (illumination light) incident from the back side of the liquid crystal cell 10a is transmitted through and emitted to the display surface, which is seen by the human eye as one pixel. . The direction of the polarization axis of the polarizing plate 11 disposed on the back surface side and the direction of the polarization axis of the polarizing plate 17 disposed on the display surface side are in a crossed Nicols state orthogonal to each other as shown in FIG. .

  In addition, a color filter layer 12a is formed on the liquid crystal cell substrate 12 to enable display of a color image. That is, the color filter layer 12a includes three independent optical filter portions that transmit only light of wavelengths corresponding to the respective color components of red (R), green (G), and blue (B), which are the three primary colors. The light component incident from the back surface side is split into R, G, and B color components and then incident on the liquid crystal layer 13. Accordingly, it is possible to select a color component of light that appears as a pixel on the display surface side of each liquid crystal cell 10a, and it is possible to display a full color image.

  The liquid crystal layer 13 includes a large number of liquid crystal molecules 14. These liquid crystal molecules 14 are aligned in a bowed state (bend alignment) as shown in FIG. When a voltage is applied to the bend-aligned liquid crystal molecules 14, the degree of bow bending changes, so the transmittance of light passing through the liquid crystal layer 13 changes, and the amount of light that appears on the display surface side of the liquid crystal panel 10. That is, the brightness of the pixel changes. Actually, the display operation of the liquid crystal cell 10a in the OCB mode is normally white, and the light transmittance is high when no voltage is applied to the liquid crystal molecules 14, and when the voltage is applied, the light transmittance is reduced to black. Of course, the gradation of brightness can be expressed by adjusting the applied voltage, and the black display characteristics can be controlled. For example, in the case of a VA mode liquid crystal panel, black cannot be controlled because the operation is normally black.

  In the OCB mode liquid crystal cell 10a having such a structure, the liquid crystal molecules 14 are bend-aligned, and the movement of the liquid crystal molecules 14 resembling the bending of the bow produces an acceleration effect of the orientation change. A response speed much faster than that of the liquid crystal panel in the mode can be obtained. In addition, since the bend orientation has a vertically symmetrical structure, the change in the amount of refraction of the liquid crystal layer 13 according to the difference in the angle at which the viewer views the screen is self-compensated. The dependence on the viewing direction can be reduced. However, in order to sufficiently bring out the original display characteristics of the OCB mode liquid crystal cell 10a, it is necessary to compensate the optical characteristics using the optical compensation film 16 suitable for the liquid crystal cell 10a.

  The optical compensation film 16 is a retardation film and is provided to eliminate image coloring in the screen display of the liquid crystal panel 10 and to widen the viewing angle. Convert to elliptically polarized light.

  As a material constituting the optical compensation film 16, for example, a cellulose ester film is assumed to be used. The in-plane retardation value (Re) of the optical compensation film 16 is preferably 0 to 70 nm or less. More preferably, it is 0-30 nm or less, More preferably, it is 0-10 nm or less. The retardation value (Rth) in the film thickness direction is preferably 400 nm or less, preferably 10 to 200 nm, and more preferably 30 to 150 nm.

  The retardation values (Re) and (Rth) can be measured using an automatic birefringence meter. For example, it can be determined using KOBRA-21ADH (Oji Scientific Instruments) by the following method.

  The Re and Rth are retardations measured at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. The following explanation is in-plane retardation at a wavelength λ and retardation in the thickness direction Re (λ) , Represents a method of measuring Rth (λ).

  When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method. Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotating axis) (if there is no slow axis, any in-plane The direction of the axis of rotation is the rotation axis of the film) and the light of wavelength λnm is incident from each of the inclined directions in steps of 10 degrees from the normal direction to 50 degrees on one side. KOBRA 21ADH or WR calculates based on the measured retardation value, the assumed average refractive index, and the input film thickness value.

In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing the sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Rth can also be calculated from the following formula (1) and formula (2) based on the value, the assumed value of the average refractive index, and the input film thickness value.

---式（１）

--- Formula (1)

Note:
The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In formula (1), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. . d represents the film thickness

Rth = ((nx + ny) / 2-nz) × d --- Formula (2)

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optic axis, Rth (λ) is calculated by the following method.
Rth (λ) is from -50 ° to + 50 ° with respect to the normal direction of the film, with Re (λ) as the slow axis (determined by KOBRA 21ADH or WR) in the plane and the tilt axis (rotation axis). In each 10 degree step, light of wavelength λnm is incident from each tilted direction and measured at 11 points. Based on the measured retardation value, average refractive index assumption and input film thickness value, KOBRA 21ADH or Calculated by WR.

  In the above measurement, the assumed value of the average refractive index may be the value in the polymer handbook (JOHN WILEY & SONS, INC) and various optical film catalogs. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx-nz) / (nx-ny) is further calculated from the calculated nx, ny, and nz.

  The slow axis of the optical compensation film 16 is preferably in the width direction ± 1 ° of the film or in the longitudinal direction ± 1 °.

FIG. 3 is a perspective view showing an attachment state of a moisture content sensor provided in the liquid crystal display device shown in FIG.
The water content sensor 21 provided in the liquid crystal display device shown in FIG. 1 is a resistance-type water content meter that uses electrical resistance and is mounted on the surface of the liquid crystal panel 10 as shown in FIG. The moisture content sensor 21 has a needle-like electrode 18 and is attached so that the electrode 18 penetrates the polarizing plate and contacts the optical compensation film 16. Thereby, the moisture content (moisture content) of the moisture contained in the optical compensation film 16 inside the liquid crystal panel 10 is detected. As the moisture content sensor 21, in addition to the electric moisture meter (resistance moisture meter) as described above, various types such as a high frequency moisture meter, a heating type, a dielectric type, an electromagnetic wave type, and a heat conduction type are available. The sensors are available.

  By using such a moisture content sensor 21, it is possible to directly measure the moisture content of the optical compensation film 16 itself that cannot be grasped by the environmental humidity. Can be detected accurately without delay.

  The humidity sensor 22 provided in the liquid crystal display device shown in FIG. 1 is a sensor for detecting the humidity (environmental humidity) in the usage environment of the liquid crystal panel 10 and is installed inside or outside the casing of the liquid crystal panel 10. The However, the humidity in the environment where the optical compensation film 16 in the housing of the liquid crystal panel 10 is actually used is easily affected by the heat generated by a backlight (not shown) installed in the vicinity of the liquid crystal panel 10. Since there may be a large difference between the humidity at a location away from 10, it is desirable to install the humidity sensor 22 inside the casing of the liquid crystal panel 10.

  The control unit 30 is configured by various control elements such as a microprocessor, and performs various controls of the entire liquid crystal display device shown in FIG. For example, the control unit 30 periodically captures the detection values of the moisture content sensor 21, the humidity sensor 22, and the temperature sensor 23 to constantly grasp the moisture content, humidity, temperature, and the like, and displays the liquid crystal panel 10 according to the results. A correction value for controlling the characteristics is acquired, or the acquired correction value is given to the voltage control unit 50.

  The table data recording unit 40 is configured by a memory (ROM or RAM) that can be accessed by the control unit 30 and is a data group necessary for compensating for a change in optical characteristics accompanying a change in water content of the optical compensation film 16. A correction table to be configured is stored in advance.

  The voltage control unit 50 determines the voltage to be applied to the liquid crystal cell 10a of the R color pixel of the liquid crystal panel 10 and the G voltage to determine the voltage to be applied to the liquid crystal cell 10a of the G color pixel. A drive unit and a B voltage drive unit that determines a voltage to be applied to the liquid crystal cell 10a of the B color pixel are provided, and the drive is independently input from the control unit 30 for each of the R, G, and B color components. The voltage of each color component is determined according to the signal.

  The control unit 30 determines each of the R, G, and B color components according to the information on the amount of moisture obtained from the result detected by at least one of the moisture content sensor 21 and the humidity sensor 22 and the contents of the correction table of the table data recording unit 40. Independent correction values are obtained, and a drive signal based on these correction values is given to the voltage controller 50.

  The LCD driver 60 applies the R, G, and B colors to the respective electrodes of a number of liquid crystal cells 10a provided in the liquid crystal panel 10 according to the voltage determined by the voltage control unit 50 for each of the R, G, and B color components. An independent drive voltage is applied to each component.

  For example, when a characteristic change occurs in the optical compensation film 16 with a change in the water content, any light of R, G, and B appears on the display surface even when black is displayed on the liquid crystal panel 10, and purely There is a possibility that a different color from black will appear. However, by correcting the applied voltage independently for each of the R, G, and B color components, it becomes possible to always display black with no color.

  A specific example of the relationship between the drive voltage and the light transmittance in the liquid crystal panel 10 shown in FIG. 1 is shown in FIG. That is, each liquid crystal cell 10a of the liquid crystal panel 10 generates an electro-optic effect in the liquid crystal layer 13 by an electric field generated by applying a voltage between electrodes provided across the liquid crystal cell, thereby transmitting light. Is used to express gradation and to switch the transmittance.

  In this example, each liquid crystal cell 10a is an OCB mode, and is a normally white element that displays black when a voltage is applied. Therefore, it is necessary to adjust the drive voltage so that the transmittance is 0% for each of the R, G, and B colors during black display. When the transmittance is slightly higher than 0%, even in black display, the color becomes black.

  When the humidity changes, the optical characteristics (retardation) of the optical compensation film 16 change, and any of R, G, and B light is applied to the display surface of the liquid crystal panel 10 even under black display due to the influence. Appearance may appear different from pure black.

  However, as shown in FIG. 1, based on the information detected by the moisture content sensor 21 or the humidity sensor 22, the applied voltages of R, G, B are independently controlled, and the characteristics of the optical compensation film 16 are determined by “feedback control”. By performing the correction corresponding to the change, the black color can be eliminated.

  A specific example of the relationship between the optical characteristics of the optical compensation film 16 provided on the liquid crystal panel 10 shown in FIG. 1 and humidity is shown in FIG. That is, as shown in FIG. 5, the retardation value (Rth) in the film thickness direction, which is one of the optical characteristics of the optical compensation film 16, is set to the wavelength of light to be transmitted (difference in R, G, B, etc.). Depending on the humidity, it varies depending on the humidity. Accordingly, when the humidity or the like changes, the retardation value (Rth) of the optical compensation film 16 changes, and the phase difference that affects the light that is transmitted through the liquid crystal panel 10 changes for each wavelength, and appears on the display surface side. A change occurs in the amount of light. As a result, when displaying black, at least one light component of R, G, and B appears slightly on the display surface side, and the light quantity balance between R, G, and B is broken, so May appear, and for example, reddish black may be displayed instead of the original black. Therefore, it is necessary to compensate for the change in the optical characteristics that occurs according to the change in the moisture content of the optical compensation film 16.

  A specific configuration example of the correction table 45 provided on the table data recording unit 40 of the liquid crystal display device shown in FIG. 1 is shown in FIG. As shown in FIG. 6, the correction table 45 includes independent tables 45a, 45b for each material (TAC (triacetyl cellulose), PET (polyethylene terephthalate), etc.) of the optical compensation film (retardation film) 16.・ ・ Is prepared. Each table also includes an R color correction unit 451 that holds correction data for R color, a G color correction unit 452 that holds correction data for G color, and a B color correction unit that holds correction data for B color. 453 is provided.

  The R color correction unit 451 is a relationship between a value representing a proper voltage (black display setting voltage) to be applied to the electrode of the R color liquid crystal cell 10a and the water content when displaying the correct black color on the liquid crystal panel 10. Is stored in advance (a data group of black display set voltage associated with each of various water contents). Similarly, the G color correction unit 452 displays a value (black display setting voltage) representing a proper voltage to be applied to the electrode of the G color liquid crystal cell 10a when the liquid crystal panel 10 is to display a correct black color, a water content, A predetermined data group representing the relationship is held. The B color correction unit 453 is a relationship between a value representing a proper voltage (black display set voltage) to be applied to the electrode of the B color liquid crystal cell 10a and the water content when displaying the correct black color on the liquid crystal panel 10. Is stored in advance.

  Therefore, the control unit 30 shown in FIG. 1 uses the water content obtained from the value detected by at least one of the water content sensor 21 and the humidity sensor 22 to drive the R color drive voltage from the R color correction unit 451 of the correction table 45. VbR is obtained as a correction value, G color drive voltage VbG is obtained from G color correction unit 452 as a correction value, and B color drive voltage VbB is obtained from B color correction unit 453 as a correction value. By applying these drive voltages VbR, VbG, and VbB to the voltage control unit 50, it is possible to display the correct black color on the liquid crystal panel 10 regardless of humidity changes and the like.

  When an image or the like is actually displayed on the liquid crystal panel 10, the drive voltage VbR which is a correction value for the gradation data of each color of R, G and B corresponding to the color and brightness of each pixel of the image to be displayed. , VbG, and VbB are applied to the voltage control unit 50 in a superimposed or added form. As a result, an image or the like can be displayed with a correct hue.

  However, the relationship between the proper voltage to be applied to the electrodes of the liquid crystal cell 10a for each color and the water content when displaying the correct black color on the liquid crystal panel 10 is the characteristic of the optical compensation film 16 actually used, particularly that It changes greatly according to the material of the material which comprises. Therefore, the control unit 30 acquires in advance information on the material of the optical compensation film 16 actually mounted on the liquid crystal panel 10. For example, when the material is TAC, the control unit 30 stores the table 45 a in the correction table 45. If the material is PET, the table 45b in the correction table 45 is selected and used. Therefore, the correction regarding the water content can be correctly performed on the optical compensation film 16 having various characteristics.

  In the correction table 45 shown in FIG. 6, it is assumed that the relationship between the black display setting voltage and the water content shows a linear change. It can be handled as it is simply by changing the contents of the stored data.

  In order to confirm the performance of the compensation control with respect to the humidity change of the liquid crystal display device shown in FIG. 1, experiments as described below were conducted. The results are shown in FIG. FIG. 7 is a graph showing changes in display quality according to changes in humidity and on / off of compensation control in the liquid crystal display device shown in FIG.

First, the change in the optical properties of the retardation film when the environmental temperature was 25 ° C. and the environmental humidity was 10% changed from the first state to the environmental humidity of 60% was examined. As a result, it was found that the Re value, which is the optical characteristic of the retardation film, changed by 5 and the Rth value changed by about 23 with respect to the environmental change from the first state to the second state. Therefore, the change in the display performance of the liquid crystal display device shown in FIG. 1 was estimated by simulation based on the optical characteristic values obtained experimentally. Specifically, an LCD master manufactured by “Shintech Co., Ltd.” was used as the reference device, and the color change during black display was calculated as a value on the u′v ′ chromaticity diagram. The conversion from the CIE 1931xy chromaticity diagram to the u′v ′ chromaticity diagram can be performed by the following equation.
u ′ = 4x / (− 2x + 12y + 3)
v '= 9y / (-2x + 12y + 3)

  The black color change from the front at a polar angle of 60 degrees in the first state where the applied voltage to the electrodes of R, G, and B colors is constant and the environmental humidity is 10% is that of all azimuth angles of Δu′v ′. The sum was “0.118”. Moreover, it shifted from the first state to the second state where the environmental humidity is 60%. As a result, in the second state, the blackness change from the front at a polar angle of 60 degrees was “0.136” as the sum of all azimuth angles of Δu′v ′. That is, when the humidity changes and the optical characteristics of the retardation film change, the dependency of the blackness on the viewing angle increases, so the display quality decreases. Therefore, in order to reduce the dependency of the blackness on the viewing angle, compensation control for the water content as described above was performed as the third state under the same conditions as in the second state. Specifically, the voltage balance of the voltages applied to the R, G, B color electrodes was changed from “1: 1: 1” to the optimum “0.97: 1.00: 1.03”. As a result, the change in blackness from the front at a polar angle of 60 degrees resulted in the sum of all azimuth angles of Δu′v ′ being “0.062”. That is, it has been confirmed that the dependence on the viewing angle of blackness is reduced by shifting from the second state to the third state. Therefore, implementing compensation control so as to optimize the balance of the voltages applied to the R, G, and B electrodes in accordance with the moisture content parameter reduces the dependency of the blackness on the viewing angle. It is very effective.

(Second Embodiment)
Next, another embodiment relating to the image quality control device and the liquid crystal display device of the present invention will be described below with reference to FIGS.
FIG. 8 is a block diagram showing the configuration of the main part of the liquid crystal display device according to the second embodiment. FIG. 9 is a schematic diagram showing an example of the mapping of water content in the liquid crystal display device shown in FIG.
The basic structure and basic control contents of the second embodiment are the same as those of the first embodiment. The following description is omitted for parts having the same structure and operation.

  In the liquid crystal panel 10B of the liquid crystal display device shown in FIG. 8, the display area is divided into a plurality of areas in the horizontal (X) and vertical (Y) axial directions and can be controlled independently of each other. (A11, A12, A13, A14, A21, A22, A23, A24, A31, A32, A33, A34) are formed. These partitioned regions (blocks) have a structure in which the voltage applied to each electrode can be controlled independently for each region. Selection of each of these areas can be performed by control of a plurality of divided line selectors 70.

  Further, in the liquid crystal display device 200 shown in FIG. 8, a plurality of moisture content sensors 21 (1) to 21 (14) are provided at different locations on the liquid crystal panel 10B. The positions at which these moisture content sensors 21 are arranged are assigned to the edges around the liquid crystal panel 10B so as not to disturb the display as shown in FIG. The position where each moisture content sensor 21 is arranged is a place hidden by a decorative board in the final product of the liquid crystal display device. In addition, about the number of the moisture content sensors 21 provided in the liquid crystal panel 10B, you may increase / decrease as needed.

  For example, in the case of a large-sized liquid crystal display panel or the like, there is a possibility that the environmental humidity and water content of each of the large liquid crystal display panels will vary greatly depending on the location of the panel. For this reason, there is a case where a correct water content or the like cannot be detected only with a single sensor. Therefore, as in the liquid crystal display device shown in FIG. 8, by installing independent moisture content sensors 21 at a plurality of locations on the liquid crystal panel 10B, more accurate moisture content can be detected for each location, It becomes possible to detect the average water content. Further, even when the water content varies greatly from panel to panel, independent compensation control can be performed for each partitioned area, so that accurate compensation can be performed over the entire panel.

  A specific example of control contents in the liquid crystal display device shown in FIG. 8 is shown in FIG. That is, the control unit 30B in FIG. 8 includes a moisture content map 201 representing the distribution of moisture content in each region over the entire panel of the liquid crystal panel 10B based on the detected moisture content values detected by the plurality of moisture content sensors 21. Create For example, based on the water content detected by the plurality of water content sensors 21 and information on the position where each sensor is installed, the maximum value and the minimum value of the water content are detected, and appropriate analysis processing is performed. It is possible to grasp the distribution of water content on the panel. In the example shown in FIG. 9, the moisture content in the lower right corner of the panel is large, and the moisture content is reduced toward the upper left corner of the panel.

  Next, using this water content map 201, the control unit 30B performs compensation control of the applied voltage independently for each partitioned area. That is, for each independently controllable region (block), the correspondence between the position and the position on the moisture content map 201 (see the control example in the middle of FIG. 9) is examined, and the corresponding moisture content information is included. Obtained from the water amount map 201. When a plurality of locations having different moisture contents on the moisture content map 201 and the position of one area are in a correspondence relationship, select one moisture content with a large ratio of areas contained in the same area, or You may assign the average moisture content calculated | required by calculation based on the ratio of an area, and several water content to a applicable area | region.

  Then, the control unit 30B refers to the correction table stored in the table data recording unit 40B shown in FIG. 8, and acquires correction values for the applied voltages of R, G, and B colors corresponding to the water content. And the acquired correction value is given to the voltage control part 50B as a drive signal with the information which pinpoints the place of an applicable area | region.

In the control example shown in FIG. 9, a black correction value representing the applied voltage V1 is assigned to the partitioned area A11 on the liquid crystal panel 10B, and similarly a black correction value representing the applied voltage V2 is assigned to the area A22. It is assumed that a black correction value representing the applied voltage V3 is assigned to the area A23 and a black correction value representing the applied voltage V4 is assigned to the area A34.
Note that the number of regions on the liquid crystal panel 10B may be increased or decreased as necessary.

(Third embodiment)
Another embodiment relating to the image quality control device and the liquid crystal display device of the present invention will be described below with reference to FIG.
FIG. 10 is a graph showing the relationship between temperature and desired applied voltage.
The basic structure and basic control contents of the third embodiment are the same as those of the first embodiment. However, in the third embodiment, correction control according to the temperature of the environment in which the liquid crystal display device is used is added.

  That is, in order to compensate for the temperature dependence of the liquid crystal panel 10 and the optical compensation film 16, the temperature sensor 23 shown in FIG. 1 is used to detect the temperature inside or near the liquid crystal panel 10, and the control unit 30 performs correction control according to the temperature detected by the temperature sensor 23.

  Since the liquid crystal display device is easily affected by heat generated by a backlight or the like used as a lighting device, the location of the temperature sensor 23 is more inside the liquid crystal panel 10 than the peripheral portion of the liquid crystal panel 10. desirable.

  Actually, the optimum applied voltage (black display setting voltage) VbT for displaying black on the liquid crystal panel 10 tends to change according to the environmental temperature as shown in FIG. Therefore, parameters related to the temperature dependence of the liquid crystal panel 10 and the optical compensation film 16 as shown in FIG. 10 are grasped in advance, and are stored in the controller 30 as independent constants for each of R, G, and B colors. Keep it. Then, the control unit 30 calculates the following equation based on the difference ΔT between the current temperature T detected by the temperature sensor 23 and the reference temperature (for example, 25 ° C.) and the constant held by itself, and R The driving voltage (voltage applied between the electrodes of each liquid crystal cell 10a) is corrected for each of the colors G, B.

V _R = Vb _R + k _R ΔT
V _G = Vb _G + k _G ΔT
V _B = Vb _B + k _B ΔT
However,
Vb _R , Vb _G , Vb _B : applied voltage of each color before temperature compensation (after water content compensation) k _R , k _G , k _B : constant of each color (corresponding to the slope of the characteristic in FIG. 10)
V _R , V _G , V _B : Applied voltage of each color after temperature compensation

By applying the voltages V _R , V _G , and V _B thus temperature-compensated between the electrodes of each liquid crystal cell 10a, not only the correction according to the water content of the optical compensation film 16 but also the temperature difference. Corresponding corrections can also be made.

(Fourth embodiment)
Another embodiment relating to the image quality control device and the liquid crystal display device of the present invention will be described below with reference to FIG.
FIG. 11 is a cross-sectional view illustrating a configuration example of a backlight.

  The fourth embodiment assumes a case where the present invention is applied to a liquid crystal display device configured in the same manner as in FIG. However, in the first embodiment, the compensation of the optical characteristics according to the change in the water content is realized by controlling the voltage applied to the liquid crystal cell 10a, whereas in the fourth embodiment, the illumination device is used. The control unit 30 performs control so as to compensate for a change in water content by controlling the light emission intensity of a certain backlight 80.

  The backlight 80 is configured as shown in FIG. FIG. 11A shows a perspective view of a state in which the backlight 80 is disassembled in the thickness direction, FIG. 11B shows a cross section in the thickness direction of the backlight 80, and FIG. The layout of the light emitting diode 82 in a partial region of FIG.

  As shown in FIGS. 11A and 11B, the backlight 80 includes a circuit board 81 disposed below and a light diffusion plate 83 disposed above. A number of light emitting diodes 82 are arranged with the optical axis facing upward. These light emitting diodes 82 include an element that emits R color, an element that emits G color, and an element that emits B color. For example, as shown in FIG. The light emitting diodes 82 are laid out.

  The light emitting diodes 82 for R, G, and B colors are configured such that the light emission intensity can be independently controlled. Therefore, white illumination light can be emitted by combining R, G, and B colors, and the hue of the illumination light can be adjusted by adjusting the balance of the emission intensity of each color of R, G, and B.

  In addition, the entire circuit board 81 is divided into a plurality of regions in the horizontal (X) and vertical (Y) axial directions, and a plurality of regions 84 (1), 84 (2), 84 (3), 84 (4 ), ... are formed. As shown in FIG. 11C, each region 84 includes a plurality of light emitting diodes 82 including the R, G, and B colors (the same number for each RGB color). For a large number of light emitting diodes 82 of each color, the emission intensity can be controlled independently for each of the regions 84 (1), 84 (2), 84 (3), 84 (4),. In the fourth embodiment, each light emitting diode 82 is controlled for each color under the same conditions for all of the regions 84 (1), 84 (2), 84 (3), 84 (4),. About the magnitude | size of each area | region 84 (1), 84 (2), 84 (3), 84 (4), ..., it can determine suitably as needed.

  Since the backlight 80 has the above-described structure, it is applied between the electrodes of the liquid crystal panel 10 by independently controlling the emission intensity of the R, G, B light emitting diodes 82 that generate the illumination light of the backlight 80. The same result as that obtained when the driving voltage to be controlled independently of R, G, and B is obtained. Therefore, the control unit 30 of the fourth embodiment emits light of R, G, and B colors of the backlight 80 instead of independently controlling the driving voltage applied between the electrodes of the liquid crystal panel 10. The light emission intensity of the diode 82 is controlled independently. That is, R, G, and B color correction values are acquired from the correction table 45 based on the water content of the optical compensation film 16 specified by the detection result of at least one of the water content sensor 21 and the humidity sensor 22 shown in FIG. And according to this correction value, the light emission intensity of the light emitting diode 82 of each color of R, G, B of the backlight 80 is controlled independently.

  For this reason, in the fourth embodiment, compensation control related to the drive voltage applied between the electrodes of the liquid crystal panel 10 is omitted, but the same control result as in the first embodiment can be obtained. That is, even when the water content of the optical compensation film 16 changes, the amount corresponding to the change in the optical characteristics generated in the optical compensation film 16 due to the change in the water content is compensated by the control of the backlight 80. Display in black.

(Fifth embodiment)
Another embodiment relating to the image quality control device and the liquid crystal display device of the present invention will be described with reference to FIG.
FIG. 12 is a block diagram showing the configuration of the main part of the liquid crystal display device according to the fifth embodiment.
The basic configuration and operation of the liquid crystal display device of the fifth embodiment are the same as those of the second embodiment. Moreover, the backlight 80 similar to 4th Embodiment is utilized as an illuminating device.

  As in the second embodiment, a plurality of moisture content sensors 21 arranged at different positions are mounted on the side portions of the display surface of the liquid crystal panel 10B in the liquid crystal display device 300. Also, as shown in FIG. 12, a backlight 80 having the same configuration as that of the fourth embodiment is disposed as a lighting device below the liquid crystal panel 10B.

  Information on the moisture content detected by each of the plurality of moisture content sensors 21 is input to the control unit 30C. The control unit 30C creates a map (see FIG. 9) showing the distribution state of the moisture content as described above based on the moisture content detected by each moisture content sensor 21 and the respective positions, and for each region on the map In addition, based on the content of the correction table 45 held by the table data recording unit 40C, information for acquiring correction values for each color of R, G, and B from the water content, and specifying the position of the corresponding region using these correction values. At the same time, it is given to the backlight drive unit 92 as a drive signal. Therefore, the light-emitting diode 82 on the backlight 80 is set to the correction value independently for each of the R, G, and B colors for each of the divided regions 84 (1), 84 (2), 84 (3),. Is controlled accordingly.

  In the fifth embodiment, correction control is not performed on the drive voltage applied to the electrodes of the liquid crystal panel 10B, and only the light emission intensity of each light emitting diode 82 of the backlight 80 is controlled. The operation may be changed so that the correction control is performed on the driving voltage in the same manner as in the second embodiment, and the above-described correction control is performed on the backlight 80 at the same time. In that case, the control unit 30C may perform control so as to give both the LCD drive unit 91 and the backlight drive unit 92 a drive signal including a correction value obtained from the correction table 45 based on the water content.

  In the fifth embodiment, since the distribution of moisture content can be detected for each region on the liquid crystal panel 10B and correction control can be performed independently for each of the plurality of regions, for example, as in a large liquid crystal display device Even if the water content is not uniform for each region on the liquid crystal panel 10B, it is possible to perform appropriate compensation control by distinguishing each region having a different water content, and it is possible to always display a proper black color. .

  In addition, the size of each area (A11, A12, A13,...) Divided on the liquid crystal panel 10B and each area (84 (1), 84 (2), 84 ( 3),...)) Are formed in the same size, and the former region and the latter region have a one-to-one correspondence as shown in FIG. Each region may be formed so that both sizes are different.

  As described above, the present invention can compensate for changes in the optical characteristics generated in the optical compensation film due to changes in humidity, etc., so that the liquid crystal display device using the liquid crystal panel provided with the optical compensation film and the image quality thereof can be reduced. By applying the present invention to the image quality control apparatus for controlling, it is possible to always prevent the image quality from being deteriorated regardless of the difference in various use environments, and for example, the performance for displaying appropriate black color is improved.

It is a block diagram which shows the structure of the principal part of the liquid crystal display device in 1st Embodiment. It is a perspective view which shows one structure of many liquid crystal cells contained in the liquid crystal panel shown in FIG. It is a perspective view which shows the attachment state of the moisture content sensor provided in the liquid crystal display device shown in FIG. 3 is a graph showing the relationship between drive voltage and light transmittance in the liquid crystal panel shown in FIG. 1. It is a graph which shows the relationship between the phase difference and the humidity which generate | occur | produce for every wavelength of the light regarding the optical compensation film provided in the liquid crystal panel shown in FIG. It is a schematic diagram which shows the structural example of the correction table provided in the liquid crystal display device shown in FIG. 3 is a graph showing changes in display quality according to changes in humidity and on / off of compensation control in the liquid crystal display device shown in FIG. 1. It is a block diagram which shows the structure of the principal part of the liquid crystal display device in 2nd Embodiment. It is a schematic diagram which shows the example of the mapping of the moisture content in the liquid crystal display device shown in FIG. It is a graph which shows the relationship between temperature and a desirable applied voltage. It is sectional drawing which shows the structural example of a backlight. It is a block diagram which shows the structure of the principal part of the liquid crystal display device in 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,10B Liquid crystal panel 10a Liquid crystal cell 11 Polarizing plate 12 Liquid crystal cell substrate 12a Color filter layer 13 Liquid crystal layer 14 Liquid crystal molecule 15 Liquid crystal cell substrate 16 Optical compensation film 17 Polarizing plate 21 Moisture content sensor 22 Humidity sensor 23 Temperature sensor 30, 30B, 30C control unit 40, 40B, 40C table data recording unit 45 correction table 45a, 45b table 50, 50B voltage control unit 60, 60B LCD driver 70 line selector 80 backlight 81 circuit board 82 light emitting diode 83 light diffusion plate 84 divided Area 91 LCD drive unit 92 Backlight drive unit 100, 200, 300 Liquid crystal display device 201 Water content map 451 R color correction unit 452 G color correction unit 453 B color correction unit

Claims (10)

An image quality control device for controlling the image quality of a display panel, in which an optical film having a water content dependency on optical characteristics is attached to or built in a display surface, and performs image display according to an input drive signal,
A moisture detection sensor for detecting moisture information related to moisture content for at least one of the optical film and the surrounding environment of the display panel;
Information indicating a correspondence relationship between at least moisture information detected by the moisture detection sensor and an image quality change generated in the display panel due to a change in the water content or a correction value for correcting the image quality change is stored in advance. Correction table,
An image quality control apparatus comprising: a drive signal correction unit that corrects a drive signal applied to the display panel based on moisture information detected by the moisture detection sensor and contents held in the correction table.   The image quality control apparatus according to claim 1, wherein the moisture detection sensor includes a humidity sensor that detects humidity related to an environment surrounding the display panel.   The image quality control device according to claim 1, wherein the moisture detection sensor includes a moisture content sensor that detects a moisture content inside an optical compensation film included in the display panel.   4. The image quality control device according to claim 1, wherein a plurality of the moisture detection sensors independent of each other are arranged at different locations on the display panel. 5.   A liquid crystal display device comprising the image quality control device according to claim 1.   6. The liquid crystal display device according to claim 5, wherein a retardation film for optical compensation is used as the optical film.   7. The liquid crystal display device according to claim 5, wherein the drive signal correcting unit detects moisture detected by the moisture detection sensor at least in a drive voltage signal that causes an electro-optic effect in a liquid crystal layer of the display panel. A liquid crystal display device that performs correction based on information and content held in the correction table. A liquid crystal display device according to claim 5 or 6,
Including a backlight that emits illumination light from the back side opposite to the display side surface of the display panel;
The liquid crystal display device that corrects at least the light emission luminance of the backlight based on moisture information detected by the moisture detection sensor and contents held in the correction table. A liquid crystal display device according to any one of claims 5 to 8,
The display panel includes a color filter unit for controlling transmission or reflection of light of each of a plurality of basic color components,
The drive signal correction unit includes a drive voltage signal that causes at least an electro-optic effect in the liquid crystal layer of the display panel, and the correction of the moisture information detected by the moisture detection sensor and the correction independently for each of the plurality of basic color components. A liquid crystal display device that performs correction based on the content held by the table.   9. The liquid crystal display device according to claim 5, wherein the display panel is an OCB mode (Optically Compensated Bend mode) liquid crystal display panel. 10.

Images