JP2008111877A - Liquid crystal display apparatus and driving method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display apparatus which has realized enhancement in contrast and has high display quality while raising a dynamic image performance by suppressing fall-off of display response speed when piling up two sheets of liquid crystal panels. <P>SOLUTION: The liquid crystal display apparatus 100 of this invention is constituted by optically piling up two or more normally black mode liquid crystal panels, and each liquid crystal panel outputs an image based on its video source. A 1st liquid crystal panel and a 2nd liquid crystal panel of the liquid crystal display apparatus 100 are provided with a gradation conversion part (1) 402a and a gradation conversion part (2) 402b (gradation conversion means), respectively, which performs conversion to a gradation value not lower than a threshold value when a gradation value not higher than the threshold value is input. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device that improves contrast and has high-speed response.

  As a technique for improving the contrast of the liquid crystal display device, there are various techniques as disclosed in the following Patent Documents 1 to 7.

  Patent Document 1 discloses a technique for improving the contrast ratio by appropriately adjusting the content and specific surface area of the yellow pigment in the pigment component of the color filter. Accordingly, it is possible to improve the problem that the contrast ratio of the liquid crystal display device is lowered due to the pigment molecules of the color filter scattering and depolarizing the polarized light. According to the technique disclosed in Patent Document 1, the contrast ratio of the liquid crystal display device is improved from 280 to 420.

  Patent Document 2 discloses a technique for improving the contrast ratio by increasing the transmittance and polarization degree of a polarizing plate. According to the technique disclosed in Patent Document 2, the contrast ratio of the liquid crystal display device is improved from 200 to 250.

  Further, Patent Document 3 and Patent Document 4 disclose a technique for improving contrast in a guest-host system using the light absorption of a dichroic dye.

  Patent Document 3 describes a method for improving contrast by a structure in which a guest-host liquid crystal cell has two layers and a quarter-wave plate is sandwiched between the two layers of cells. Patent Document 3 discloses that no polarizing plate is used.

  Patent Document 4 discloses a liquid crystal display element of a type in which a dichroic dye is mixed with liquid crystal used in a dispersion type liquid crystal system. In this patent document 4, there is a description that the contrast ratio is 101.

  However, the techniques disclosed in Patent Document 3 and Patent Document 4 have a lower contrast than other methods, and in order to further improve the contrast, the light absorption of the dichroic dye is increased, the dye content is increased, Although it is necessary to increase the thickness of the guest host liquid crystal cell, there are new problems such as technical problems, reduced reliability, and poor response characteristics.

  Patent Document 5 and Patent Document 6 disclose a contrast improving method using an optical compensation method, in which a liquid crystal display panel and a liquid crystal panel for optical compensation are provided between a pair of polarizing plates.

  In Patent Document 5, in the STN method, the contrast ratio of the display cell, the liquid crystal cell for differential optical compensation, and the retardation is improved from 14 to 35.

  In Patent Document 6, a contrast ratio is improved from 8 to 100 by installing an optical compensation liquid crystal cell for compensating the wavelength dependency of a TN liquid crystal display cell during black display.

  However, with the techniques disclosed in the above patent documents, a contrast ratio improvement effect of 1.2 times to 10 times is obtained, but the absolute value of the contrast ratio is about 35 to 420.

As a technique for improving contrast, for example, Patent Document 7 discloses a composite liquid crystal display device in which two liquid crystal panels are overlapped so that each polarizing plate forms a crossed Nicol. Yes. Patent Document 7 describes that a contrast ratio of one panel is 100, and the contrast ratio can be expanded to about 3 to 4 digits by superimposing two panels.
JP 2001-188120 A (publication date: July 10, 2001) JP 2002-90536 A (publication date: March 27, 2002) JP 63-25629 A (publication date: February 3, 1988) Japanese Patent Laid-Open No. 5-2194 (publication date: January 8, 1993) JP-A-1-49021 (Publication date: February 23, 1989) Japanese Patent Laid-Open No. 2-23 (Publication date: January 5, 1990) Japanese Patent Laid-Open No. 5-88197 (Publication date: April 9, 1993)

  However, since Patent Document 7 is intended to increase the gradation without increasing the gradation of each liquid crystal panel by overlapping two liquid crystal panels, the display response speed is lowered. No measures are taken. For this reason, there is a possibility that the display quality is remarkably lowered. Further, a normally black mode transmissive liquid crystal display such as the MVA mode has a slow response speed particularly on the low gradation side, which causes a display problem.

  The present invention has been made in view of the above problems, and its purpose is to realize an improvement in contrast while suppressing a decrease in display response speed and improving moving image performance when a plurality of liquid crystal panels are stacked. The object is to realize a liquid crystal display device with high display quality.

  In order to solve the above problems, a liquid crystal display device of the present invention is configured by overlapping a plurality of normally black mode liquid crystal panels, and each of the liquid crystal panels outputs an image based on the same video source. In the display device, at least one liquid crystal panel among the plurality of liquid crystal panels has gradation conversion means for converting a gradation value equal to or higher than the threshold when a gradation value equal to or lower than the threshold is input. It is characterized by that.

  The liquid crystal display device of the present invention is configured by overlapping normally black mode liquid crystal panels. The normally black mode liquid crystal display device is a liquid crystal display device that is optically configured to display black when no voltage is applied or when only a voltage equal to or lower than a threshold voltage is applied. A normally black mode liquid crystal display device originally has a characteristic of low black luminance and high contrast.

  According to the configuration described above, when two or more liquid crystal panels are overlapped, the panel transmittance is reduced, so that the black luminance is extremely low and a high-contrast image can be displayed. Further, according to the above configuration, when a gradation value equal to or lower than the threshold value is input, the gradation value equal to or higher than the threshold value is converted to be excluded from the display image. it can. In other words, by converting the gradation value so that the gradation value exists in a high gradation region that is equal to or higher than the threshold value, the low gradation part having a slow display response is removed from the display image, so that the image having a fast response speed is obtained. Can be obtained. Thereby, a liquid crystal display device with high display quality can be realized.

  In the liquid crystal display device of the present invention, at least one of the plurality of liquid crystal panels constituting the device only needs to have the gradation converting means. In order to further increase the display response speed, the device It is preferable that all the liquid crystal panels constituting the above have the gradation converting means.

  The threshold value is preferably determined from the target contrast ratio of the display device.

  If the threshold value is determined as described above, a low gradation region equal to or lower than the threshold value becomes a gradation region that is not necessary for achieving a target contrast ratio. For this reason, the gradation conversion means excludes from the display image a low gradation area that is less than a threshold value that is not necessary because the contrast ratio obtained when two or more panels are stacked is the target contrast ratio, and the gradation value The tone value can be converted so that it consists only of a tone value equal to or higher than the minimum necessary threshold value for achieving the target contrast ratio.

  The threshold value may be determined from a display response speed desired for improving the moving image performance.

  In the liquid crystal display device of the present invention, the threshold value is preferably a gradation value at which the luminance is (1 / X) × 100 (%) when the contrast ratio of the liquid crystal display device is X: 1.

  According to the above configuration, the contrast ratio of the present liquid crystal display device configured by overlapping a plurality of liquid crystal panels can be set to a target value, and the threshold value can be determined based on the target value. Therefore, it is possible to prevent a decrease in display response speed while maintaining an appropriate contrast ratio.

  Here, the above-mentioned luminance is defined with the luminance at the time of white display being 100%.

  Specifically, the contrast ratio is preferably 2000: 1 or more.

  In the liquid crystal display device of the present invention, the threshold value is preferably a gradation value when the luminance is 0.05% or less.

  According to said structure, even if a low gradation part is removed from a display image, a contrast ratio can be maintained at 2000: 1 or more. Thus, if the contrast ratio is 2000: 1 or more, better display can be performed.

  For example, when a liquid crystal display device is used for a TV application, the black expressive power is a little inferior to that of a PDP (plasma display). Further, when the liquid crystal display device is used for in-vehicle use, there is an intention that the user does not want to be aware that there is a display during black display. Therefore, particularly in these fields, high contrast display is required. If the contrast ratio is 2000: 1 or more, reliable black display that satisfies the user can be performed for both TV and in-vehicle use.

  Here, the gradation value at which the luminance is 0.05% means that the output luminance (luminance output to the liquid crystal panel) with respect to the input gradation value to the driving unit of the liquid crystal panel is 0.05%. Means gradation value.

  In the liquid crystal display device of the present invention, it is preferable that the gradation converting means has a lookup table in which an input gradation value and an output gradation value are associated with each other.

  According to the above configuration, gradation conversion can be easily performed by using a lookup table. Accordingly, it is not necessary to provide a circuit for performing complicated arithmetic processing, so that the cost can be reduced.

  In addition to the above configuration, the liquid crystal display device of the present invention has a γ value of 2.0 or more indicating the gradation luminance characteristics of the combined gradation obtained by combining the gradation of the image output to each of the liquid crystal panels. It is preferable to further include gradation luminance ratio setting means for setting the γ value of each of the liquid crystal panels so as to be 3.0 or less.

  When a liquid crystal display device is configured by stacking two or more liquid crystal panels, the γ characteristic of the liquid crystal display device as a whole is deeper than the γ characteristic of a liquid crystal display device including a single liquid crystal panel. That is, the γ value of the combined gradation obtained by combining the gradations of the images output to each liquid crystal panel (that is, the γ value obtained when a plurality of liquid crystal panels are overlapped) is one liquid crystal panel. It becomes larger than the γ value.

  Specifically, the γ characteristic of a normal one-panel liquid crystal display is γ = 2.2, but when a structure in which two panels are superposed in this state is taken, γ = 4. 84 and the γ value become very large. That is, the γ characteristic becomes very deep (the γ curve becomes a deep shape).

  Usually, if the γ value is 2.0 to 3.0 (preferably γ = 2.2), it can be adapted to the γ characteristic of image data transmitted from a television station. Therefore, as described above, the γ value indicating the gradation luminance characteristic of the combined gradation obtained by combining the gradations of the images output to the respective liquid crystal panels is 2.0 or more and 3.0 or less. By setting the γ value of each liquid crystal panel, the γ characteristic of the entire liquid crystal display device can be set to a desired γ characteristic. In order to set the γ value indicating the gradation luminance characteristic of the composite gradation to 2.0 or more and 3.0 or less, the γ value of at least one liquid crystal panel is set to the target γ value (2.0 ~ 3.0).

  For example, if the γ value of each panel constituting the liquid crystal display device of the present invention is reduced to γ = 1.48, the γ characteristic of the liquid crystal display device as a whole can be made closer to γ = 2.2. It can be a γ characteristic.

  In the liquid crystal display device of the present invention, it is preferable that the gradation luminance ratio setting means sets the γ value of the at least one liquid crystal panel to 1.0 or more and 2.0 or less.

  According to the above configuration, the γ value of the liquid crystal display device as a whole (that is, the γ value of the combined gradation obtained by combining the gradation of the image output to each liquid crystal panel) is 2.0 or more. It can be 0 or less. Usually, if the γ value is 2.0 to 3.0 (preferably γ = 2.2), it can be adapted to the γ characteristic of the image data transmitted from the television station. It is preferable to set the γ value in the above range.

  The response speed of the liquid crystal increases as the voltage difference between the state transitions increases. That is, the voltage difference has a positive correlation with the luminance difference, and the response speed increases as the luminance difference between the state transitions increases.

Here, when calculating the luminance difference of gradation transition of 0-32 gradations (6 bits) in each liquid crystal display with γ = 2.2 and γ = 1.8,
When γ = 2.2: 22.5
When γ = 1.8: 29.5
Thus, a luminance difference of about 7 is generated. The liquid crystal display with γ = 1.8 has a larger voltage difference by a luminance difference of 7 compared to the display with γ = 2.2, which contributes to high-speed response. Become.

  Therefore, by setting the γ value of the at least one liquid crystal panel to 1.0 or more and 2.0 or less, the luminance difference in gradation transition in the intermediate gradation becomes large, and the response in the intermediate gradation. Speed can also be improved. Therefore, according to said structure, a response speed can be improved more.

  In order to solve the above problems, a driving method of a liquid crystal display device of the present invention is configured by overlapping a plurality of normally black mode liquid crystal panels, and each of the liquid crystal panels displays an image based on the same video source. A driving method of a liquid crystal display device for outputting, wherein when a gradation value less than a threshold value is input to at least one liquid crystal panel among the plurality of liquid crystal panels, the gradation value is converted to a gradation value greater than the threshold value. It is characterized by performing key conversion.

  According to the above method, by constructing two or more normally black mode liquid crystal panels in an overlapped manner, the panel transmittance is lowered, so that the black luminance is extremely low and a high-contrast image can be displayed. . Furthermore, according to the above method, when a gradation value less than or equal to the threshold value is input, the gradation value is converted to a gradation value that is greater than or equal to the threshold value. The tone value can be excluded from the display image. Therefore, an image with a fast response speed can be obtained. Thereby, a liquid crystal display device with high display quality can be realized.

  In order to solve the above problems, a liquid crystal display device of the present invention is configured by overlapping a plurality of normally black mode liquid crystal panels, and each of the liquid crystal panels outputs an image based on the same video source. In the display device, each of the above values is set so that a γ value indicating a gradation luminance characteristic of a combined gradation obtained by combining the gradations of the image output to each of the liquid crystal panels is 2.0 or more and 3.0 or less. It is characterized by having gradation luminance ratio setting means for setting each γ value of the liquid crystal panel.

  When a liquid crystal display device is configured by stacking two or more liquid crystal panels, the γ characteristic of the liquid crystal display device as a whole is deeper than the γ characteristic of a liquid crystal display device including a single liquid crystal panel. That is, the γ value of the combined gradation obtained by combining the gradations of the images output to the respective liquid crystal panels is larger than the γ value of one liquid crystal panel.

  Specifically, the γ characteristic of a normal one-panel liquid crystal display is γ = 2.2, but when a structure in which two panels are superposed in this state is taken, γ = 4. 84 and the γ value become very large. That is, the γ characteristic becomes very deep (the γ curve becomes a deep shape).

  Usually, if the γ value is 2.0 to 3.0 (preferably γ = 2.2), it can be adapted to the γ characteristic of image data transmitted from a television station. Therefore, as described above, the γ value indicating the gradation luminance characteristic of the combined gradation obtained by combining the gradations of the images output to the respective liquid crystal panels is 2.0 or more and 3.0 or less. By setting the γ value of each liquid crystal panel, the γ characteristic of the entire liquid crystal display device can be set to a desired γ characteristic. In order to set the γ value indicating the gradation luminance characteristic of the composite gradation to 2.0 or more and 3.0 or less, the γ value of at least one liquid crystal panel is set to the target γ value (2.0 ~ 3.0).

  Furthermore, according to the above-described configuration, when two or more liquid crystal panels are stacked, the panel transmittance is reduced, so that the black luminance is extremely low and a high-contrast image can be displayed. Thereby, a liquid crystal display device with high display quality can be realized.

  In the liquid crystal display device of the present invention, it is preferable that the gradation luminance ratio setting means sets the γ value of the at least one liquid crystal panel to 1.0 or more and 2.0 or less.

  According to the above configuration, the γ value of the liquid crystal display device as a whole (that is, the γ value of the combined gradation obtained by combining the gradation of the image output to each liquid crystal panel) is 2.0 or more. It can be 0 or less. Usually, if the γ value is 2.0 to 3.0 (preferably γ = 2.2), it can be adapted to the γ characteristic of the image data transmitted from the television station. It is preferable to set the γ value in the above range. Further, by setting the γ value as described above, the shape of the γ curve becomes shallow, so that the response speed at the intermediate gradation can be improved. Here, that the shape of the γ curve becomes shallow means that the shape of the curve is close to a straight line, that is, the γ value is close to 1.

  Further, it is preferable that the liquid crystal display device is composed of two liquid crystal panels, and the gradation luminance ratio setting means sets both the γ values of the two liquid crystal panels to 1.48.

  According to the above configuration, the γ characteristic of the entire liquid crystal display device can be made closer to γ = 2.2.

  As described above, the liquid crystal display device of the present invention converts at least one of the plurality of liquid crystal panels to a gradation value equal to or higher than the threshold value when a gradation value equal to or lower than the threshold value is input. It is characterized by having gradation conversion means.

  As described above, the driving method of the liquid crystal display device according to the present invention provides a gradation value equal to or higher than the threshold value when a gradation value equal to or lower than the threshold value is input to at least one of the plurality of liquid crystal panels. It is characterized in that gradation conversion is performed to convert to.

  Therefore, according to the present invention, when two or more liquid crystal panels are stacked, the panel transmittance is lowered, so that the black luminance is extremely low, and a high-contrast image can be displayed. Furthermore, according to the present invention, by excluding the gradation value below the threshold value from the display image, the low gradation part having a slow display response is removed from the display image, so that an image with a high response speed can be obtained. . Thereby, a liquid crystal display device with high display quality can be realized.

  As described above, in the liquid crystal display device of the present invention, the γ value indicating the gradation luminance characteristic of the combined gradation obtained by combining the gradation of the image output to each of the liquid crystal panels is 2.0 or more. It is characterized by having gradation luminance ratio setting means for setting the γ value of each liquid crystal panel so as to be 0 or less.

  According to the present invention, each of the above values is set so that the γ value indicating the gradation luminance characteristic of the combined gradation obtained by combining the gradations of the images output to the respective liquid crystal panels is 2.0 or more and 3.0 or less. By setting each γ value of the liquid crystal panel, the γ characteristic of the entire liquid crystal display device can be set to a desired γ characteristic. Furthermore, according to the present invention, by arranging two or more liquid crystal panels so as to overlap each other, the panel transmittance is lowered, so that the black luminance is extremely low and a high-contrast image can be displayed. Thereby, a liquid crystal display device with high display quality can be realized.

  An embodiment of the present invention will be described as follows.

  As shown in FIG. 8, a general liquid crystal display device is configured by attaching polarizing plates A and B to a liquid crystal panel including a color filter and a driving substrate. Here, an MVA (Multidomain Vertical Alignment) type liquid crystal display device will be described.

  As shown in FIG. 9, the polarization axes of the polarizing plates A and B are orthogonal to each other, and when the threshold voltage is applied to the pixel electrode 8 (FIG. 8), the direction in which the liquid crystal is tilted is aligned with the polarizing plates A and B. The polarization axis of B and the azimuth angle are set to 45 degrees. At this time, since the polarization axis rotates when the incident polarized light passing through the polarizing plate A passes through the liquid crystal layer of the liquid crystal panel, light is emitted from the polarizing plate B. In addition, when only a voltage equal to or lower than the threshold voltage is applied to the pixel electrode, the liquid crystal is aligned perpendicular to the substrate, and the deflection angle of incident polarized light does not change, so that black display is obtained. That is, the liquid crystal display device illustrated in FIG. 8 is a normally black mode liquid crystal display device. In the MVA method, a high viewing angle is realized by dividing the direction in which the liquid crystal tilts when a voltage is applied into four (multidomain).

  However, in the case of the two polarizing plate configuration, there is a limit to the improvement in contrast. Accordingly, the inventors of the present application have found that the shutter performance is improved in both the front and oblique directions by adopting a configuration with three polarizing plates (each set in crossed Nicols) with respect to two liquid crystal display panels.

  The principle of contrast improvement will be described below.

Specifically, the inventors of this application
(1) About the front direction Leaked light was generated from the transmission axis direction of crossed Nicol due to depolarization in the panel (scattering of CF, etc.). It was found that the leakage light can be cut by matching the third polarizing plate absorption axis with respect to the leakage light in the transmission axis direction of the polarizing plate.

(2) Diagonal direction It has been found that the change in the amount of leakage light is insensitive to the collapse of the polarizing plate Nicol angle φ, that is, it is difficult for black to float with respect to the spread of Nicol angle φ at an oblique viewing angle.

  From the above, the present inventors have found that the contrast is greatly improved in the liquid crystal display device. In the following, the principle of contrast improvement will be described below with reference to FIGS. Here, the description will be made assuming that the two-polarizing plate configuration is the configuration (1) and the three-polarizing plate configuration is the configuration (2). The improvement in the contrast in the oblique direction is essentially caused by the configuration of the polarizing plate. Therefore, here, the description is modeled only by the polarizing plate without using the liquid crystal panel.

  FIG. 10A assumes the case where there is one liquid crystal display panel in the configuration (1), and shows an example in which two polarizing plates 101a and 101b are arranged in crossed Nicols. b) is a diagram showing an example in which three polarizing plates 101a, 101b, and 101c are arranged in crossed Nicols in the configuration (2). That is, in the configuration (2), since it is assumed that there are two liquid crystal display panels, there are two pairs of polarizing plates arranged in crossed Nicols. FIG. 10C is a diagram showing an example in which the polarizing plates 101a and 101b facing each other are arranged in crossed Nicols, and polarizing plates having the same polarization direction are overlapped on the outer sides of the respective polarizing plates. FIG. 10C shows the configuration of four polarizing plates, but the polarizing plates in a crossed Nicol relationship are a pair that assumes a case where one liquid crystal display panel is sandwiched. .

  The transmittance when the liquid crystal display panel performs black display is modeled as the transmittance when the polarizing plate without the liquid crystal display panel is arranged in crossed Nicols, that is, the cross transmittance, and is referred to as black display. The transmittance when white display is modeled as the transmittance when the polarizing plate without the liquid crystal display panel is arranged in parallel Nicol, that is, the parallel transmittance, is called white display when viewed from the front. FIGS. 11A to 11D show examples of the relationship between the wavelength of the transmission spectrum and the transmittance and the relationship between the wavelength of the transmission spectrum and the transmittance when the polarizing plate is viewed obliquely. It is a graph. The modeled transmittance corresponds to the ideal value of the transmittance for white display and black display in a system in which polarizing plates are arranged in a crossed Nicol manner and the liquid crystal display panel is held.

  FIG. 11A is a graph when the relationship between the wavelength of the transmission spectrum and the cross transmittance when the polarizing plate is viewed from the front is compared between the configuration (1) and the configuration (2). From this graph, it can be seen that the transmittance characteristics in the front of the black display tend to be similar between the configuration (1) and the configuration (2).

  FIG. 11B is a graph when the relationship between the wavelength of the transmission spectrum and the parallel transmittance when the polarizing plate is viewed from the front is compared between the configuration (1) and the configuration (2). From this graph, it can be seen that the transmittance characteristics in the front of white display tend to be similar between the configuration (1) and the configuration (2).

  FIG. 11C shows the relationship between the wavelength of the transmission spectrum and the cross transmittance when the polarizing plate is viewed obliquely (azimuth angle 45 ° −polar angle 60 °), and the above configurations (1) and (2). It is a graph at the time of comparing by. From this graph, the transmittance characteristics in the oblique black display show that the transmittance is almost 0 in the most wavelength range in the configuration (2), and a little light is transmitted in the most wavelength region in the configuration (1). It can be seen that In other words, it can be seen that light leakage occurs at an oblique viewing angle when black is displayed in the two-polarizer configuration (a worsening of black tightening), and conversely, an oblique viewing angle is displayed when black is displayed in the three-polarizer configuration. It can be seen that light leakage (deterioration of black tightening) is suppressed.

  FIG. 11 (d) shows the relationship between the wavelength of the transmission spectrum and the parallel transmittance when the polarizing plate is viewed obliquely (azimuth angle 45 ° −polar angle 60 °), and the above configurations (1) and (2). It is a graph at the time of comparing by. From this graph, it can be seen that the transmittance characteristics of the white display in the oblique direction tend to be similar between the configuration (1) and the configuration (2).

  From the above, at the time of white display, as shown in FIG. 11 (b) and FIG. 11 (d), there is almost no difference depending on the number of polarizing plates, that is, the number of Nicol cross pairs of polarizing plates, As can be seen from FIG.

  However, at the time of black display, as shown in FIG. 11C, in the case of the configuration (1) in which the crossed Nicols pair is 1, the black tightening deteriorates at an oblique viewing angle, and the configuration in which the crossed Nicols pair is 2 In the case of (2), it can be seen that deterioration of black tightening at an oblique viewing angle is suppressed.

  For example, when the wavelength of the transmission spectrum is 550 nm, the relationship of transmittance when viewed from the front and obliquely (azimuth angle 45 ° −polar angle 60 °) is as shown in Table 1 below.

  Here, in Table 1, “parallel” indicates parallel transmittance, and indicates the transmittance during white display. Further, the cross indicates a cross transmittance, and indicates a transmittance during black display. Therefore, parallel / cross indicates contrast.

  From Table 1, the front contrast in configuration (2) is about twice that in configuration (1), and the diagonal contrast in configuration (2) is about 22 times that in configuration (1). It can be seen that the contrast is greatly improved.

  The viewing angle characteristics during white display and black display will be described below with reference to FIGS. 12 (a) to 12 (c). Here, the case where the azimuth angle with respect to the polarizing plate is 45 ° and the wavelength of the transmission spectrum is 550 nm will be described.

  FIG. 12A is a graph showing the relationship between polar angle and transmittance during white display. From this graph, the transmittance of the configuration (2) is generally lower than that of the configuration (1), but the viewing angle characteristics (parallel viewing angle characteristics) in this case are the configurations (2) and configurations. It can be seen that (1) has a similar tendency.

  FIG. 12B is a graph showing the relationship between polar angle and transmittance during black display. From this graph, it can be seen that, in the case of the configuration (2), the transmittance at an oblique viewing angle (around polar angle ± 80 °) is suppressed. On the contrary, in the case of the configuration (1), it can be seen that the transmittance at an oblique viewing angle is increased. That is, the configuration (1) is more markedly worse in black tightening at an oblique viewing angle than the configuration (2).

  FIG. 12C is a graph showing the relationship between polar angle and contrast. From this graph, it can be seen that the contrast of the configuration (2) is much better than that of the configuration (1). The reason why the vicinity of 0 degree in the configuration 2 in FIG. 12C is flat is that the black transmittance is so small that the calculation is not possible due to the loss of digits, and the actual curve is smooth.

Next, the change in the amount of leakage light becomes insensitive to the collapse of the polarizing plate Nicol angle φ, that is, the deterioration of black tightening is less likely to occur with respect to the spread of the Nicol angle φ at an oblique viewing angle. This will be described below with reference to (a) and (b). Here, as shown in FIG. 13A, the polarizing plate Nicol angle φ is an angle in a state where the polarization axes of the polarizing plates facing each other are in a twisted relationship. FIG. 13A is a perspective view of a polarizing plate in which crossed Nicols are arranged, and the Nicol angle φ changes from 90 °. (Corresponding to the collapse of the Nicol angle)
FIG. 13B is a graph showing the relationship between the Nicol angle φ and the cross transmittance. Calculation is performed using an ideal polarizer (parallel Nicol transmittance 50%, crossed Nicol transmittance 0%). From this graph, it can be seen that the degree of change in the transmittance with respect to the change in the Nicol angle φ is smaller in the configuration (2) than in the configuration (1) during black display. That is, it can be understood that the three-polarizing plate configuration is less susceptible to the change in the Nicol angle φ than the two-polarizing plate configuration.

  Next, the thickness dependency of the polarizing plate will be described below with reference to FIGS. 14 (a) to 14 (c). Here, as shown in FIG. 10C, the thickness of the polarizing plate is adjusted by superposing polarizing plates with the same polarization axis one by one on the polarizing plates arranged in a pair of crossed Nicols (3 ). FIG. 10C shows an example in which the polarizing plates 101a and 101b having the polarization axis in the same polarization direction are superimposed on the pair of polarizing plates 101a and 101b arranged in crossed Nicols. In this case, in addition to the two polarizing plates arranged in a pair of crossed Nicols, the structure has two polarizing plates. Similarly, if the number of polarizing plates to be superimposed increases, the cross pair is −3, −4,. In the graphs shown in FIGS. 14A to 14C, each value is measured at an azimuth angle of 45 ° and a polar angle of 60 °.

  FIG. 14A is a graph showing the relationship between the polarizing plate thickness and the transmittance (cross transmittance) of a pair of polarizing plates arranged in crossed Nicols during black display. For comparison, this graph shows the transmittance in the case of having two pairs of polarizing plates arranged in crossed Nicols.

  FIG. 14B is a graph showing the relationship between the thickness and the transmittance (parallel transmittance) of the polarizing plates arranged in a pair of crossed Nicols during white display. For comparison, this graph shows the transmittance in the case of having two pairs of polarizing plates arranged in crossed Nicols.

  From the graph shown in FIG. 14 (a), it can be seen that if the polarizing plates are superimposed, the transmittance during black display can be reduced, but from the graph shown in FIG. 14 (b), if the polarizing plates are superimposed, It turns out that the transmittance | permeability at the time of white display becomes small. That is, in order to suppress the deterioration of black tightening at the time of black display, the transmittance at the time of white display is lowered only by overlapping the polarizing plates.

  Moreover, the graph which shows the relationship between the thickness of the polarizing plate arrange | positioned at a pair of crossed Nicols, and contrast becomes as shown in FIG.14 (c). For comparison, this graph shows the contrast when two pairs of crossed Nicols polarizing plates are provided.

  As described above, from the graphs shown in FIGS. 14A to 14C, the configuration of the polarizing plates arranged in two pairs of crossed Nicols suppresses the deterioration of black tightening at the time of black display and at the time of white display. It can be seen that a decrease in transmittance can be prevented. Moreover, since the two pairs of crossed Nicols polarizing plates are composed of a total of three polarizing plates, it can be seen that the thickness of the entire liquid crystal display device is not increased and the contrast can be greatly improved.

  FIGS. 15A and 15B specifically show the viewing angle characteristics of the crossed Nicols transmittance. FIG. 15A is a diagram showing the crossed Nicols viewing angle characteristics of the configuration (1), that is, the configuration of two crossed Nicol pairs of polarizing plates, and FIG. 15B is the configuration (2). That is, it is a view showing the crossed Nicols viewing angle characteristics of the two pairs of crossed Nicols polarizing plates.

From the diagrams shown in FIGS. 15 (a) and 15 (b), it can be seen that in the configuration of two crossed Nicols, the deterioration of black tightening (corresponding to the increase in transmittance during black display) is hardly observed. (Especially 45 °, 135 °, 225 °, 315 ° direction)
Further, FIGS. 16A and 16B specifically show the contrast viewing angle characteristics (parallel / cross luminance). FIG. 16A is a diagram showing the contrast viewing angle characteristics of the configuration (1), that is, the configuration of two crossed Nicol polarizing plates, and FIG. 16B is the configuration (2). That is, it is a diagram showing the contrast viewing angle characteristics of the three crossed Nicols polarizing plate three-piece configuration.

  From the diagrams shown in FIGS. 16A and 16B, it can be seen that the contrast of the two pairs of crossed Nicols is improved as compared with the structure of the pair of crossed Nicols.

Here, a liquid crystal display device using the above-described principle of improving contrast will be described below with reference to FIGS.
Here, for simplicity, the case where two liquid crystal panels are used will be described.

  FIG. 1 is a diagram showing a schematic cross section of a liquid crystal display device 100 according to the present embodiment.

  As shown in FIG. 1, the liquid crystal display device 100 is configured by alternately bonding a first panel, a second panel, and polarizing plates A, B, and C.

  FIG. 2 is a view showing the arrangement of the polarizing plate, the liquid crystal panel and the liquid crystal display device 100 shown in FIG. In FIG. 2, polarizing plates A and B and polarizing plates B and C are configured so that their polarization axes are orthogonal to each other. That is, the polarizing plates A and B and the polarizing plates B and C are arranged in crossed Nicols.

  Each of the first panel and the second panel includes a liquid crystal sealed between a pair of transparent substrates (the color filter substrate 220 and the active matrix substrate 230), and electrically changes the orientation of the liquid crystal to thereby provide a light source. And a means for arbitrarily changing a state where the polarized light incident on the polarizing plate A is rotated by about 90 degrees, a state where the polarized light is not rotated, and an intermediate state thereof.

Each of the first panel and the second panel includes a color filter and has a function of displaying an image with a plurality of pixels. Display methods having such functions include TN (TwistedNematic) method, VA (Vertical Alignment) method, IPS (InPlainSwitching).
) Method, FFS (Fringe Field Switching) method, or a method using a combination thereof, but a VA method having high contrast is suitable. Here, the description will be made using the MVA (Multidomain Vertical Alignment) method, but since the IPS method and the FFS method are also normally black methods, there are sufficient effects. The driving method uses active matrix driving by TFT (ThinFilmTransistor). Details of the manufacturing method of MVA are disclosed in Japanese Patent Laid-Open No. 2001-83523.

  The first and second panels in the liquid crystal display device 100 have the same structure, and have the color filter substrate 220 and the active matrix substrate 230 facing each other as described above, and plastic beads or color filter substrates. A columnar resin structure provided on 220 or the like is used as a spacer (not shown) to keep the substrate interval constant. Liquid crystal is sealed between a pair of substrates (color filter substrate 220 and active matrix substrate 230), and a vertical alignment film 225 is formed on the surface of each substrate in contact with the liquid crystal. As the liquid crystal, a nematic liquid crystal having negative dielectric anisotropy is used.

  The color filter substrate 220 is obtained by forming a color filter 221, a black matrix 224, and the like on a transparent substrate 210. An alignment control protrusion 222 that defines the alignment direction of the liquid crystal is formed.

  As shown in FIG. 3, the active matrix substrate 230 includes a TFT element 203, a pixel electrode 208, and the like formed on a transparent substrate 210, and further has an alignment control slit pattern 211 that defines the alignment direction of the liquid crystal. The black matrix 224 for shielding the alignment regulating protrusions 222 and unnecessary light for reducing the display quality shown in FIG. 3 is a diagram in which a pattern formed on the color filter substrate 220 is projected onto the active matrix substrate 230. When a voltage equal to or higher than the threshold is applied to the pixel electrode 208, the liquid crystal molecules are tilted in a direction perpendicular to the protrusions 222 and the slit pattern 211. In the present embodiment, the protrusion 222 and the slit pattern 211 are formed so that the liquid crystal is oriented in the direction of 45 ° azimuth with respect to the polarization axis of the polarizing plate.

  As described above, the positions of the red (R), green (G), and blue (B) pixels of the respective color filters 221 in the first panel and the second panel coincide with each other when viewed from the vertical direction. It is configured. Specifically, the R pixel of the first panel is the R pixel of the second panel, the G pixel of the first panel is the G pixel of the second panel, and the B pixel of the first panel is the second pixel. Each of the B pixels of the second panel is configured so that the position seen from the vertical direction is the same.

  FIG. 4 shows an outline of a drive system of the liquid crystal display device 100 having the above configuration.

  The driving system includes a display controller 400 necessary for displaying an image on the liquid crystal display device 100. As a result, appropriate image data based on the input signal is output to the liquid crystal display device 100.

  The display controller 400 includes first and second panel drive circuits (1) and (2) for driving the first panel and the second panel with predetermined signals, respectively. The display controller 400 includes a signal distribution unit 401 that distributes video source signals to the first and second panel drive circuits (1) and (2). Details of the display controller 400 will be described later.

Here, the input signal represents not only a video signal from a TV receiver, VTR, DVD, etc., but also a signal obtained by processing these signals. Therefore, the display controller 400 can display an image suitable for the liquid crystal display device 100. A signal that can be displayed is transmitted to each panel.

  FIG. 5 shows the connection relationship between the first and second panels and the respective panel drive circuits. In FIG. 5, the polarizing plate is omitted.

  The first panel drive circuit (1) is connected to a terminal (1) provided on a circuit board (1) of the first panel via a driver (TCP) (1). In other words, the driver (TCP) (1) is connected to the first panel, connected by the circuit board (1), and connected to the panel drive circuit (1).

  Since the connection of the second panel drive circuit (2) in the second panel is the same as that in the first panel, the description thereof is omitted.

  Next, the operation of the liquid crystal display device 100 having the above configuration will be described.

  The pixels of the first panel are driven based on the display signal, and the corresponding pixels of the second panel corresponding to the positions of the pixels of the first panel and the positions viewed from the vertical direction of the panel are the first panel. It is driven in response to In the case where the part (constituent part 1) composed of the polarizing plate A, the first panel, and the polarizing plate B is in a transmissive state, the part composed of the polarizing plate B, the second panel, and the polarizing plate C (constituent part) 2) is also in a transmissive state, and when the component 1 is in a non-transmissive state, the component 2 is also driven in a non-transmissive state.

  The same image signal may be input to the first and second panels, or separate signals associated with each other may be input to the first and second panels.

  Here, a method for manufacturing the active matrix substrate 230 and the color filter substrate 220 will be described.

  First, a method for manufacturing the active matrix substrate 230 will be described.

  First, as shown in FIG. 3, in order to form a scanning signal wiring (gate wiring, gate line, gate voltage line or gate bus line) 201 and auxiliary capacitance wiring 202 on the transparent substrate 10 by sputtering, Ti / A metal such as an Al / Ti laminated film is formed, a resist pattern is formed by photolithography, dry etching is performed using an etching gas such as a chlorine-based gas, and the resist is peeled off. As a result, the scanning signal wiring 201 and the auxiliary capacitance wiring 202 are simultaneously formed on the transparent substrate 210.

  Thereafter, a gate insulating film made of silicon nitride (SiNx) or the like, an active semiconductor layer made of amorphous silicon or the like, a low-resistance semiconductor layer made of amorphous silicon or the like doped with phosphorus or the like is formed by CVD, and then a data signal wiring (Source wiring, source line, source voltage line or source bus line) 204, drain lead-out wiring 205, auxiliary capacitance forming electrode 206 are formed by depositing a metal such as Al / Ti by sputtering, and by photolithography A resist pattern is formed, dry etching is performed using an etching gas such as a chlorine-based gas, and the resist is peeled off. As a result, the data signal wiring 204, the drain lead wiring 205, and the auxiliary capacitance forming electrode 206 are formed at the same time.

  The auxiliary capacitance is formed between the auxiliary capacitance wiring 202 and the auxiliary capacitance forming electrode 206 with a gate insulating film of about 4000 mm sandwiched therebetween.

  Thereafter, the TFT element 203 is formed by dry etching the low resistance semiconductor layer using chlorine gas or the like for source / drain separation.

  Next, an interlayer insulating film 207 made of acrylic photosensitive resin or the like is applied by spin coating, and a contact hole (not shown) for electrically contacting the drain lead-out wiring 205 and the pixel electrode 208 is formed by photolithography. Form. The film thickness of the interlayer insulating film 207 is about 3 μm.

  Further, the pixel electrode 208 and a vertical alignment film (not shown) are formed in this order.

  As described above, the present embodiment is an MVA type liquid crystal display device, and the slit pattern 211 is provided in the pixel electrode 208 made of ITO or the like. Specifically, a film is formed by sputtering, a resist pattern is formed by photolithography, and etching is performed with an etchant such as ferric chloride to obtain a pixel electrode pattern as shown in FIG.

  Thus, the active matrix substrate 230 is obtained.

  Note that reference numerals 212 a, 212 b, 212 c, 212 d, 212 e, and 212 f shown in FIG. 3 indicate electrical connection portions of slits formed in the pixel electrode 8. At the electrical connection portion in the slit, the orientation is disturbed and an orientation abnormality occurs. However, for the slits 212a to 212d, the time during which the positive potential supplied to the gate wiring is applied to operate the TFT element 203 in the on state is usually on the order of microseconds, and the TFT element 203 is operated in the off state. For this reason, since the time during which the negative potential supplied to the gate wiring is applied is usually on the order of milliseconds, the time during which the negative potential is applied is dominant. For this reason, when the slits 212a to 212d are positioned on the gate wiring, in addition to the alignment abnormality, impurity ions contained in the liquid crystal gather due to the gate minus DC application component, so that it may be visually recognized as display unevenness. Therefore, since it is necessary to provide the slits 212a to 212d in a region that does not overlap with the gate wiring in a plan view, it is preferable to hide the slits 212a to 212d with the black matrix 224 as shown in FIG.

  Next, a method for manufacturing the color filter substrate 220 will be described.

  The color filter substrate 220 includes a color filter layer composed of three primary colors (red, green, blue), a color filter 221 and a black matrix (BM) 224, a counter electrode 223, a vertical alignment film 225, and a transparent substrate 210. A protrusion 222 for controlling the orientation is provided.

  First, a negative acrylic photosensitive resin liquid in which carbon fine particles are dispersed is applied onto the transparent substrate 210 by spin coating, and then dried to form a black photosensitive resin layer. Subsequently, the black photosensitive resin layer is exposed through a photomask and then developed to form a black matrix (BM) 224. At this time, in the regions where the first colored layer (for example, red layer), the second colored layer (for example, green layer), and the third colored layer (for example, blue layer) are formed, the first colored layer opening, The BM is formed so that an opening for the second colored layer and an opening for the third colored layer (each opening corresponds to each pixel electrode) are formed. More specifically, as shown in FIG. 3, a BM pattern that shields an abnormal alignment region generated in the slits 212a to 212d of the electrical connection portions of the slits 212a to 212f formed in the pixel electrode 208 is formed in an island shape. In addition, a light shielding portion (BM) is formed on the TFT element 203 in order to prevent an increase in leakage current that is photoexcited when external light enters the TFT element 203.

  Next, after applying a negative acrylic photosensitive resin liquid in which a pigment is dispersed by spin coating, drying is performed, and exposure and development are performed using a photomask to form a red layer.

  Thereafter, the second color layer (for example, the green layer) and the third color layer (for example, the blue layer) are similarly formed, and the color filter 221 is completed.

  Further, a counter electrode 223 made of a transparent electrode such as ITO is formed by sputtering, and then a positive type phenol novolac photosensitive resin solution is applied by spin coating, followed by drying, and exposure and development using a photomask. To form a protrusion 222 for controlling vertical alignment. Further, columnar spacers (not shown) for defining the cell gap of the liquid crystal panel are formed by applying an acrylic photosensitive resin liquid, exposing, developing and curing with a photomask.

  Thus, the color filter substrate 220 is formed.

  In the present embodiment, the case of a BM made of resin is shown, but a BM made of metal may be used. The colored layers of the three primary colors are not limited to red, green, and blue, and may include colored layers such as cyan, magenta, and yellow, and may include a white layer.

  A method for manufacturing a liquid crystal panel (first panel, second panel) using the color filter substrate 220 and the active matrix substrate 230 manufactured as described above will be described below.

  First, the vertical alignment film 225 is formed on the surface of the color filter substrate 220 and the active matrix substrate 230 that are in contact with the liquid crystal. Specifically, baking is performed as a degassing process before the alignment film is applied, and then substrate cleaning and alignment film application are performed. After the alignment film is applied, alignment film baking is performed. After the alignment film is applied and washed, further baking is performed as a degassing process. The vertical alignment film 225 defines the alignment direction of the liquid crystal 226.

  Next, a method for sealing liquid crystal between the active matrix substrate 230 and the color filter substrate 220 will be described.

  As for the liquid crystal sealing method, for example, an injection port is provided for injecting a part of the thermosetting sealing resin around the substrate, the liquid injection is performed by immersing the injection port in a liquid crystal in a vacuum, and opening to the atmosphere, and then UV curing is performed. You may carry out by methods, such as a vacuum injection method, which seals an injection port with resin etc. However, the vertical alignment liquid crystal panel has a drawback that the injection time is very long as compared with the horizontal alignment panel. Here, explanation will be given by the liquid crystal dropping bonding method.

  A UV curable seal resin is applied around the active matrix substrate side, and liquid crystal is dropped onto the color filter substrate by a dropping method. An optimum amount of liquid crystal is regularly dropped on the inner part of the seal so as to obtain a desired cell gap by liquid crystal by a liquid crystal dropping method.

Further, in order to bond the active filter substrate and the color filter substrate on which the seal drawing and liquid crystal dropping were performed as described above, the atmosphere in the bonding apparatus was reduced to 1 Pa, and the substrates were bonded under this reduced pressure. After that, the atmosphere is set to atmospheric pressure, the seal portion is crushed, and a desired gap of the seal portion is obtained.

  Next, with respect to the structure having a desired cell gap in the seal portion, UV irradiation is performed with a UV curing device to temporarily cure the seal resin. Further, baking is performed to finally cure the sealing resin. At this time, the liquid crystal spreads inside the sealing resin and the liquid crystal is filled in the cell. A liquid crystal panel is completed by dividing the structure into liquid crystal panel units after baking is completed.

  In the present embodiment, the first panel and the second panel are manufactured by the same process.

  Subsequently, a mounting method of the first panel and the second panel manufactured by the above-described manufacturing method will be described.

  Here, after cleaning the first panel and the second panel, a polarizing plate is attached to each panel. Specifically, as shown in FIG. 4, polarizing plates A and B are attached to the front and back surfaces of the first panel, respectively. Moreover, the polarizing plate C is affixed on the back surface of the second panel. In addition, you may laminate | stack an optical compensation sheet etc. on a polarizing plate as needed.

  Next, a driver (liquid crystal driving LSI) is connected. Here, the connection of the driver by the TCP (Tape Career Package) method will be described.

For example, as shown in FIG. 5, after temporarily crimping an ACF (ArisotoropiConduktiveFilm) to the terminal portion (1) of the first panel, the TCP (1) on which the driver is placed is punched from the carrier tape and positioned on the panel terminal electrode. Combine, heat, and press-fit. Thereafter, the circuit board (1) for connecting the drivers TCP (1) and the input terminal (1) of the TCP (1) are connected by ACF.

  Next, the two panels are bonded together. The polarizing plate B is provided with an adhesive layer on both sides. The surface of the second panel is washed, the laminate of the adhesive layer of the polarizing plate B attached to the first panel is peeled off, precisely aligned, and the first panel and the second panel are bonded together. At this time, since bubbles may remain between the panel and the adhesive layer, it is desirable to bond them under vacuum.

  As another bonding method, an adhesive that cures at room temperature or below the heat resistance temperature of the panel, such as an epoxy adhesive, is applied to the periphery of the panel, a plastic spacer is sprayed, and fluorine oil is sealed, for example. Also good. A liquid that is optically isotropic, has a refractive index comparable to that of a glass substrate, and is as stable as liquid crystal is desirable.

  In addition, in this embodiment, as described in FIG. 4 and FIG. 5, the present invention can be applied to the case where the terminal surface of the first panel and the terminal surface of the second panel are at the same position. Moreover, the direction of the terminal with respect to the panel and the bonding method are not particularly limited. For example, a mechanical fixing method may be used regardless of adhesion.

  In order to reduce parallax due to the thickness of the inner glass, it is better to make the inner substrates facing each other of the two panels as thin as possible.

  When a glass substrate is used, a thin substrate can be used from the beginning. The possible substrate thickness varies depending on the production line and the size of the liquid crystal panel, but 0.4 mm glass can be used as the inner substrate.

There are also methods for polishing and etching glass. There are known techniques for etching glass (Patent Publications such as Japanese Patent Nos. 3524540 and 3523239). For example, a chemical working solution such as a 15% hydrofluoric acid aqueous solution is used. Portions that are not to be etched such as terminal surfaces are coated with an acid-resistant protective material, soaked in the chemical working solution and etched into the glass, and then the protective material is removed. The glass is thinned to about 0.1 mm to 0.4 mm by etching.
After the two panels are bonded together, the liquid crystal display device 100 is obtained by integrating with a lighting device called a backlight.

  Here, the specific example of the illuminating device suitable for this invention is demonstrated below. However, this invention is not restricted to the form of the illuminating device given below, It can change suitably.

  In the liquid crystal display device 100 of the present invention, the backlight is required to have an ability to provide a larger amount of light than a conventional panel according to the display principle. Moreover, since short wavelength absorption becomes more prominent even in the wavelength region, it is necessary to use a blue light source having a shorter wavelength on the illuminating device side. An example of a lighting device that satisfies these conditions is shown in FIG.

  In the liquid crystal display device 100 according to the present invention, a hot cathode lamp is used this time in order to obtain the same luminance as the conventional one. The hot cathode lamp is characterized in that the amount of light can be output about six times that of a cold cathode lamp used in general specifications.

  Taking a 37 inch diagonal WXGA as an example of a standard liquid crystal display device, 18 lamps having an outer diameter of 15 mm are arranged on a housing made of aluminum. In this housing, a white reflective sheet using a foamed resin is disposed in order to efficiently use the light emitted from the lamp in the back direction. A driving power source for the lamp is disposed on the rear surface of the housing, and the lamp is driven by power supplied from a household power source.

Next, a milky white resin plate is required for erasing the lamp image in the direct type backlight in which a plurality of lamps are arranged in the housing. This time, a plate member based on polycarbonate, which is 2mm thick and absorbs warp and heat deformation, is placed in the housing on the lamp, and the optical sheet to obtain the predetermined optical effect on its upper surface, specifically this time Arranges a diffusion sheet, a lens sheet, a lens sheet, and a polarization reflection sheet from the bottom. With this specification, it is possible to obtain a backlight luminance of about 10 times that of a general specification of 18 cold-cathode lamps of φ4 mm, two diffusion sheets and a polarizing reflection sheet. Thereby, the 37-inch liquid crystal display device of the present invention can obtain a luminance of about 400 cd / m ² .

  However, since the amount of heat generated by this backlight is five times that of the conventional one, fins for radiating heat to the air and a fan for forcing the air flow are installed on the back of the back chassis.

  The mechanism member of the present lighting device also serves as a main mechanism member of the entire module, and the mounted panel is disposed in the backlight, and a liquid crystal display controller including a panel drive circuit and a signal distributor, a light source power source, In some cases, a household general power supply is attached to complete the liquid crystal module. The liquid crystal display device of the present invention is obtained by disposing the mounted panel on the backlight and installing a frame body for pressing the panel.

  In the present embodiment, a direct illumination device using a hot cathode tube is shown, but a projection method or an edge light method may be used according to the application, and the light source is a cold cathode tube, LED, OEL, electron beam fluorescent tube. Or a combination of optical sheets can be selected as appropriate.

  Furthermore, as another embodiment, as a method for controlling the alignment direction of the vertically aligned liquid crystal molecules of the liquid crystal, in the embodiment described above, a slit is provided in the pixel electrode of the active matrix substrate, and a protrusion for alignment control on the color filter substrate side. However, they may be reversed, or a structure in which slits are provided on the electrodes of both substrates, or an MVA type liquid crystal panel in which alignment control protrusions are provided on the electrode surfaces of both substrates. I do not care.

  In addition, instead of the MVA type, a method using a vertical alignment film in which pretilt directions (alignment processing directions) defined by a pair of alignment films are orthogonal to each other may be used. In addition, a VA mode in which liquid crystal molecules are twisted alignment may be used, which may be referred to as a VATN (Vertical Alignment Twisted Nematic) mode. The VATN method is more preferable in the present invention because there is no decrease in contrast due to light leakage at the alignment control projection. The pretilt is formed by optical alignment or the like.

  Here, a specific example of a driving method in the display controller of the liquid crystal display device 100 having the above configuration will be described below with reference to FIG. Here, the case of input 8 bits (256 gradations) and liquid crystal driver 8 bits will be described.

  In the panel drive circuit (1) of the display controller unit, the input signal (video source) is subjected to drive signal processing such as γ conversion and overshoot to the 8-bit floor for the source driver (source drive means) of the first panel. Output key data.

  On the other hand, the panel drive circuit (2) performs signal processing such as γ conversion and overshoot, and outputs 8-bit grayscale data to the source driver (source drive means) of the second panel.

  The first panel, the second panel, and the output image that is output as a result are 8 bits, correspond one-to-one with the input signal, and are faithful to the input image.

  By the way, normally black mode liquid crystal display devices such as the MVA mode can realize image display with low black luminance and high contrast, but on the other hand, when the response speed is low on the low gradation side, particularly when displaying moving images. However, the display quality deteriorates. Therefore, in the present invention, the contrast is improved and the display response speed is improved by printing with a configuration in which two or more liquid crystal panels in a modally black mode are stacked. A configuration for realizing this will be described in the following embodiment.

[Embodiment 1]
In the first embodiment, in order to improve the display response speed, in each liquid crystal panel, when a gradation value equal to or lower than the threshold value is input, the gradation value of the entire image is converted by converting the gradation value to a value equal to or higher than the threshold value. The tone value is shifted to the high gradation region side above the threshold value, and the gradation value on the low gradation region side below the threshold value is excluded from the display image.

  As shown in FIG. 1, the liquid crystal display device of the present embodiment is configured by alternately bonding a first panel, a second panel, and polarizing plates A, B, and C. Then, as shown in FIG. 19, the present liquid crystal display device has a display controller 400 for independently driving two liquid crystal panels (first panel 420a and second panel 420b). .

  The display controller 400 includes a signal distribution unit 401 that distributes the same video source signal to the first panel 420a and the second panel 420b. Further, as a block for processing the video source signal distributed for the first panel 420a, a gradation conversion unit (1) (gradation conversion unit) 402a, a pseudo multi-gradation unit (1) 403a, A panel drive circuit (1) 404a is provided. Further, as a block for processing the video source signal distributed for the second panel 420b, a gradation conversion unit (2) (gradation conversion unit) 402b, a pseudo multi-gradation unit (2) 403b, A panel drive circuit (2) 404b is provided.

  The panel drive circuit (1) 404a and the panel drive circuit (2) 404b are arranged in the liquid crystal controller 410.

  The tone conversion unit (1) 402a and the tone conversion unit (2) 402b perform tone conversion so that the input tone value is equal to or greater than a preset threshold value. As a result, the gradation value of the entire image is shifted to the high gradation region side where the threshold value is greater than or equal to the threshold value. The pseudo multi-gradation unit (1) 403a and the pseudo multi-gray scale unit (2) 403b perform the above-described gradation conversion using a multi-gradation technique such as frame rate control (FRC). The video source signal is pseudo-multi-gradation so that the resulting gradation collapse does not occur.

Here, the principle of the pseudo multi-gradation processing will be described with reference to FIG.
FIG. 22 (a) shows a case where an image of 32 gradations is displayed with 6 bits gradations in an area of 2 × 2 pixels with 1 square pixel. Further, FIG. 22B shows a case where an image of 33 gradations with 6-bit gradations is displayed as in FIG. In the 6-bit gradation, it is naturally impossible to express a gradation between the 32 gradation and the 33 gradation.

  Therefore, as shown in FIG. 22 (c), a noise pattern having a 6-bit gradation and a gradation of 1 gradation is applied. The display state when the above noise pattern is superimposed during 32 gradation display is as shown in FIG. The average gray level of these one pixel in 4 frames is (32 × 3 + 33) /4=32.25, and it is possible to express gray levels between 32 gray levels and 33 gray levels that cannot be expressed originally. It will be.

  In this way, the pseudo multi-gradation processing is expressed as if the human eye is limited in the number of gradations using the property that the human eye recognizes the luminance by averaging time and space. This is a process that looks as if the number of gradations that can be increased. In the pseudo multi-gradation processing, how large is the pixel area as a unit, or how the noise pattern is designed (that is, the noise pattern in each frame, the number of periodic frames, etc.) ), There are various methods such as FRC.

  When actually performing pseudo multi-gradation processing, for example, as shown in FIG. 23, an 8-bit input signal (input data) is separated into upper 6 bits and lower 2 bits using a 6-bit driver, A 1-bit noise pattern is created based on the information of the lower 2 bits, and this noise pattern is superimposed on each pixel (upper 6 bits + 1 bit noise pattern).

  As described above, the panel drive circuit (1) 404a and the panel drive circuit (2) 404b are circuits for driving the first panel and the second panel with predetermined signals, respectively.

  Further, the display controller 400 serves as a gradation reference voltage generation circuit (1) as gradation luminance ratio setting means for setting γ characteristics of the first liquid crystal panel 420a and the second liquid crystal panel 420b to γ = 1.48, respectively. ) 405a and a gradation reference voltage generation circuit (2) 405b.

  These gradation reference voltage generation circuits are provided with a liquid crystal driver in which a ladder resistor is designed so as to match a desired γ characteristic. By using this driver and adjusting the reference voltage based on a normal γ setting method, the γ characteristic can be set to the above value.

  Further, it is possible to obtain a desired γ characteristic by performing digital processing by gradation conversion using an LUT without changing the ladder resistance of the driver. In this case, it is preferable to perform a pseudo multi-gradation process together to prevent gradation collapse.

Next, a method for driving the liquid crystal display device 100 by the display controller 400 will be described.
The video source signal input to the display controller 400 is first distributed to the video source signal for the first panel 420a and the video source signal for the second panel 420b in the signal distribution unit 401, respectively. Thereafter, the video source signal is sent to the gradation conversion unit (1) 402a or the gradation conversion unit (2) 402b, where gradation conversion processing is performed. Then, the gradation value of the input video source signal is converted into a gradation value equal to or greater than a preset threshold value.

  Here, the preset threshold value can be appropriately determined for each liquid crystal display device, but is preferably determined from a target contrast ratio (contrast ratio required for an image obtained from the liquid crystal display device). .

  Specifically, the threshold value is a level at which the luminance is (1 / X) × 100 (%) when the contrast ratio of the liquid crystal display device 100 configured by overlapping two liquid crystal panels is X: 1. It is a key value.

  As a result, the low gradation region below the threshold value becomes a gradation region that is not necessary for achieving the target contrast ratio. The gradation converters (1) and (2) exclude the low gradation area below the unnecessary threshold from the display image, and the minimum gradation area necessary for the gradation value to be the target contrast ratio. The gradation value can be shifted to the high gradation region side so that only the gradation value is included.

  The video source signal thus subjected to gradation conversion is subjected to pseudo multi-gradation processing in the pseudo multi-gradation unit (1) 403a or pseudo multi-gradation unit (2) 403b, respectively, and the panel drive circuit (1 ) 404a or panel drive circuit (2) 404b. In the panel drive circuits (1) and (2), a drive signal for displaying an image on the first panel 420a and the second panel 420b is generated based on the video source signal, and the source drivers 421a and 421b and the gate driver are generated. It transmits to 422a * 422b.

  Hereinafter, the principle that the display response speed can be improved while appropriately maintaining the contrast in the liquid crystal display device of the present embodiment will be described.

  FIG. 17 shows a liquid crystal display device having one normally black mode liquid crystal panel (γ value is 2.2) and two liquid crystal panels having a normally black mode (both γ values are 1.4). In a liquid crystal display device, a relationship between gradation and transmittance in a low gradation region is shown. FIG. 18 shows the relationship between gradation and transmittance in all gradation regions in a liquid crystal display device having a single liquid crystal panel configuration and a liquid crystal display device having a two liquid crystal panel configuration. In these figures, the luminance at the time of white display is represented by the transmittance (%) defined as 100%.

  As shown in FIG. 18, the liquid crystal display device including two liquid crystal panels as in the present invention has a luminance particularly in a low luminance (black luminance) region as compared with the liquid crystal display device including one liquid crystal panel. Can be very low.

  This is because the normally black mode liquid crystal panel originally has a characteristic that the black luminance is low and the contrast is high, but by overlapping two of them, the panel transmittance is lowered and the black luminance is extremely low. Then, by optimizing the panel structure, polarizing plate configuration, etc., and increasing the backlight luminance, the liquid crystal display device with extremely high contrast (for example, a contrast ratio of 1,000,000: 1) that reduces only the black luminance while maintaining the luminance. Is obtained.

  Here, when the contrast ratio (target contrast ratio) required for the liquid crystal display device is, for example, 1000: 1, the liquid crystal display device including two or more liquid crystal panels as in the present invention is extremely low. The luminance area (for example, an area of less than 4 gradations out of 63 gradations) is not required. This region is a region in which the response speed is a problem in the normally black mode. Therefore, the response speed of the entire liquid crystal display device can be improved by excluding this region from the display image.

  For example, in a liquid crystal display device having two liquid crystal panels having gradation luminance characteristics as shown in FIGS. 17 and 18, an area less than 4 gradations in 64 gradations (area indicated by A in the figure) is displayed from the display image. Even if it is eliminated, a contrast equivalent to that of a single-panel liquid crystal panel can be obtained. The response speed before excluding the area of less than 4 gradations from the display image is, for example, 70 ms when the gradation changes from 0 to 16 gradations. On the other hand, the response speed after removing an area of less than 4 gradations from the display image is 45 ms when the gradation changes from 4 to 16 gradations, for example. Thus, the response speed can be improved by excluding the low gradation region from the display image.

  As described above, the high gradation region shifted in the gradation conversion units (1) and (2) has a luminance of (1 / X) × when the contrast ratio required for the present liquid crystal display device is X: 1. Any gradation region that is 100 (%) or more is acceptable.

  Therefore, in the liquid crystal display device having gradation luminance characteristics shown in FIG. 18, for example, when the target contrast ratio is 1000: 1, the transmittance (luminance) is (1/1000) × 100 = 0.1 (%). The above gradation area is a high gradation area. That is, the gradation value when the transmittance (luminance) is (1/1000) × 100 = 0.1 (%) is the threshold value. According to FIG. 17, since the gradation area where the transmittance is 0.1% or more is an area having two or more gradations, an area having less than two gradations can be excluded. Therefore, the gradation conversion units (1) and (2) perform gradation conversion for shifting the input gradation value to the high gradation region side of two or more gradations.

  By the way, when the liquid crystal display device of the present invention is applied to a television receiver, a movie monitor or a broadcast monitor, the target contrast ratio is 2000: 1. If a contrast ratio higher than this contrast ratio is obtained, good display can be performed. Therefore, for example, if the target contrast ratio is 2000: 1, the gradation region where the luminance is (1/2000) × 100 = 0.05% or more may be set as the high gradation region.

  For example, in the case of a liquid crystal panel having gradation luminance characteristics as shown in FIG. 17, in order to set the contrast ratio to 2000: 1, two or more gradations may be set as a high gradation region. However, FIG. 17 shows a case of 6-bit gradation, and if the 8-bit gradation is corrected, 8 gradations or more become a high gradation region.

  Further, the gradation conversion processing in the liquid crystal display device 100 according to the present embodiment is performed using a lookup table (LUT) or the like, for example, 0 gradation → 32 gradation, 1 gradation → 35 gradation, and so on. This is performed by rereading the gradation value of each signal. That is, the gradation conversion unit (1) 402a and the gradation conversion unit (2) 402b have a lookup table in which input gradation values are associated with output gradation values. Thus, it is not necessary to provide a circuit for performing complicated arithmetic processing, and gradation conversion can be easily performed.

  FIG. 24 shows an example of a look-up table used when a gradation value of 8 gradations or less is excluded from a low gradation area. The 8-bit data output in this figure is finally output as 6-bit data by the pseudo multi-gradation processing.

  As described above, the γ value of the video source signal subjected to the gradation conversion process may be changed in the gradation reference voltage generation circuit as the gradation luminance ratio setting means. In this case, the first panel video source signal and the second panel video source signal that have been subjected to the gradation conversion processing are not only the liquid crystal controller 410 but also the gradation reference voltage generation circuit provided in the display controller 400. (1) 405a and the gradation reference voltage generation circuit (2) 405b are also transmitted. If gradation conversion is performed using the LUT, each process of eliminating the low gradation area and changing the γ value can be performed simultaneously.

  The gradation reference voltage generation circuit (1) 405a and the gradation reference voltage generation circuit (2) 405b combine the gradations of images output to the respective liquid crystal panels (first panel and second panel). The γ value of each of the liquid crystal panels is set so that the γ value of the obtained composite gradation (that is, the γ value obtained when two liquid crystal panels are overlapped) is 2.0 or more and 3.0 or less. It is to set. Specifically, the γ value of the liquid crystal panel is set to a value smaller than the target γ value so that the γ value of the combined gradation is 2.0 or more and 3.0 or less.

Here, the γ value is a value serving as an index of gradation luminance characteristics indicating the relationship between input gradation and output luminance. The γ value is determined by L = KE ^γ (K is a constant) where L is the display luminance and E is the input signal value.

  The principle of changing the γ value performed in the gradation reference voltage generation circuit will be described below.

  By overlapping a plurality of liquid crystal panels as in the liquid crystal display device of the present invention, the γ characteristic as a liquid crystal display becomes deeper than the original. Here, the deep γ characteristic means that the γ curve has a deep shape, but the γ value becomes a very large value. Therefore, the γ characteristic of at least one liquid crystal panel of the plurality of liquid crystal panels is made shallower than the desired γ characteristic (that is, one liquid crystal panel γ value is set to a value smaller than the target γ value). Thus, it is possible to compensate for the γ characteristic of a liquid crystal display device configured by overlapping a plurality of liquid crystal panels.

  To give a specific example, the γ characteristic of a liquid crystal display device composed of one liquid crystal panel is usually γ = 2.2, but when taking a structure in which two panels are superposed in this state, γ = 4.84 and the γ value becomes very large.

  FIG. 20 shows the relationship between the gradation and the transmittance before changing the γ characteristic by the gradation reference voltage generation circuit (gradation luminance ratio setting means) in the liquid crystal display device according to the present embodiment. In this figure, the relationship between the gradation and the transmittance (that is, the gradation luminance characteristic) in the case where the liquid crystal display device is constituted by one liquid crystal panel with γ = 2.2 is shown by a solid line, and γ = 2.2. The gradation luminance characteristics when a liquid crystal display device is configured using two liquid crystal panels are indicated by broken lines. As shown in FIG. 20, when two liquid crystal panels with γ = 2.2 are used to form a liquid crystal display device, γ sinks.

  Accordingly, the γ characteristics of each of the liquid crystal panels constituting the liquid crystal display device are both reduced to γ = 1.48. As a result, the γ characteristic of the entire liquid crystal display device constructed by superposing two liquid crystal panels is a value close to γ = 2.2, and a desired γ characteristic can be obtained.

  FIG. 21 shows the relationship between the gradation and the transmittance after the γ characteristic is changed by the gradation reference voltage generation circuit (gradation luminance ratio setting means) in the liquid crystal display device according to the present embodiment. In this figure, the solid line represents the relationship between the gradation and the transmittance (that is, the gradation luminance characteristic) in the case where the liquid crystal display device is constituted by one liquid crystal panel converted to γ = 1.48 by the gradation reference voltage generation circuit. The broken line shows the gradation luminance characteristics when a liquid crystal display device is configured using two liquid crystal panels converted to γ = 1.48 by the gradation reference voltage generation circuit. As shown in FIG. 21, when the γ characteristic of each liquid crystal panel is changed to γ = 1.48, the γ characteristic obtained when two sheets are stacked (that is, the gradation of the image output to each liquid crystal panel is synthesized). The obtained composite gradation γ value) can be made close to the target γ value γ = 2.2.

  In the above example, the γ characteristics of the two liquid crystal panels are set to the same value. For example, the γ characteristic of the first liquid crystal panel is set to γ = 2.2, and the γ characteristics of the second liquid crystal panel are set. The characteristic may be γ = 1, and the γ characteristic obtained when two sheets are stacked may be γ = about 2.2. In this way, the γ characteristics of the two liquid crystal panels may be set to different values so that the γ characteristics obtained in a state where the two liquid crystal panels are stacked become the desired γ characteristics.

  Thus, in this embodiment, the γ value of the combined gradation obtained by the gradation reference voltage generation circuit provided in each of the two liquid crystal panels is combined with the gradation of the image output to each liquid crystal panel. Γ value of each liquid crystal panel is set so that is close to 2.2. In order to set the γ value of the combined gradation to about 2.2, the γ value of at least one liquid crystal panel is set to a value smaller than the target γ value. In this way, by setting the γ value of each liquid crystal panel to be smaller than the target γ value, it is possible to avoid gradation transition in a region where the response speed is slow. The transmission response characteristic is improved.

  For example, the response speed before changing the γ characteristic (indicated by a broken line in FIG. 20) is, for example, 70 ms when the gradation changes from 0 to 16 gradations. On the other hand, the response speed after changing the γ characteristic (indicated by the broken line in FIG. 21) is, for example, 40 ms when the gradation changes from 0 to 16 gradations.

  Normally, if the target γ value is around 2.2, it can be adapted to the γ characteristic of the image data transmitted from the television station, so that the γ value of the entire liquid crystal display device (that is, each liquid crystal panel) The γ value of the combined gradation obtained by combining the gradations of the output image is set to 2.0 or more and 3.0 or less. For this purpose, it is preferable to set the γ value of each liquid crystal panel to 1.0 or more and 2.0 or less.

  Furthermore, when the liquid crystal display device is composed of two liquid crystal panels, it is more preferable that the gradation luminance ratio setting means sets both the γ values of the two liquid crystal panels to 1.48. According to this, the target γ value can be made closer to 2.2.

  In the gradation reference voltage generation circuits (1) and (2), in order to set the γ value as described above, the ladder design of the driver is changed and the reference voltage is adjusted so as to achieve the desired γ characteristic.

  The γ value as described above may be set by digital data processing or a combination of gradation voltage setting and digital data processing. When the γ value is set by digital data processing, the data is converted so that the target γ value is obtained by the LUT, and the pseudo multi-gradation processing may be performed so that gradation collapse does not occur.

  In the present embodiment, the gradation reference voltage generation circuit sets the γ value of each liquid crystal panel so that the γ value of the combined gradation is about 2.2. However, the present invention is not limited to this, as long as the γ value of each liquid crystal panel is set so that the γ value of the combined gradation is 2.0 or more and 3.0 or less.

  According to the liquid crystal display device of the present embodiment, when two or more normally black mode liquid crystal panels are overlapped, the panel transmittance is reduced, so that the black luminance is extremely low and a high contrast image is displayed. Can be displayed. Furthermore, according to the liquid crystal display device of the present embodiment, by shifting the gradation value to the high gradation region side, the low gradation portion with a slow display response is removed from the display image, so that an image with a fast response speed is obtained. Can be obtained. Thereby, a liquid crystal display device with high display quality can be realized.

  In particular, if the driving method of the present invention is applied to a normally black mode transmissive liquid crystal display device such as an MVA mode, which has a problem in that the display response speed is slow on the low gradation region side and the moving image performance is deteriorated. Improvement of display quality can be realized. Further, when OS driving is applied to a VA-type normally black mode transmissive liquid crystal display device such as an MVA mode, occurrence of angular response can be suppressed.

  OS driving is a driving method generally called “overdrive”, “overshoot driving” or the like, and is a method of applying an excessive voltage to the liquid crystal in one frame period to speed up a slow response speed region. When this OS drive is performed on a normally black mode liquid crystal display, an abnormal response called an angular response occurs in a low gradation region.

  Here, the principle of generating an angular response will be described using an MVA liquid crystal panel, which is one of the VA systems. FIG. 25 schematically shows a pixel of an MVA liquid crystal panel. In the vertical alignment method such as the MVA method, the direction in which the liquid crystal is tilted when a voltage is applied is defined by a structure (D) such as a rib or an electrode slit.

  The order of response of the liquid crystal at this time is as follows. (1) When a voltage is applied, first, the liquid crystal molecules in the region I close to the structure D respond first, thereby defining the direction in which the liquid crystal falls. (2) Thereafter, the liquid crystal molecules in the other region II are tilted in the direction defined in (1) in the manner of domino tilting. In this order, the liquid crystal molecules fall and the response is completed.

  Thus, region I responds fast and region II responds late. When OS driving is performed in this state, the region I reacts sensitively, but the region II does not react very sensitively even though it is OS driven. As a result, the difference in response characteristics increases between the region I and the region II.

  Therefore, for example, when a voltage for 63 gradations is applied by OS driving and then a voltage for 24 gradations is applied to display gradation values in 24 gradations, the response waveform has an angle as shown in FIG. It will have a waveform. That is, in the first frame (the portion indicated by 1 in FIG. 26), the response to the voltage for 63 gradations starts. In the fast response area I, the response rises to 24 gradations or more, while in the slow response area II, 24 gradations are not reached. Therefore, the whole picture element appears to rise to 24 gradations. In the second frame (the portion indicated by 2 in FIG. 26), the OS driving is finished and the voltage is switched to the voltage corresponding to 24 gradations. In the fast response region I, the state returns from the 24th gradation or more to the 24th gradation. In the slow region II, it continues to rise toward 24 gradations. Therefore, the whole picture element is less than 24 gradations. In the third frame (the portion indicated by 3 in FIG. 26), voltages for 24 gradations are continuously applied, so that the entire picture element seems to slowly reach 24 gradations.

  The gradation transition that generates such an angular response is limited to the response at the luminance transition on the low luminance side. Therefore, in this embodiment, the gradation setting is performed so as not to use the luminance transition area as much as possible. The occurrence of angular response can be suppressed.

  In the present embodiment, the configuration provided with both the gradation converting means and the gradation luminance ratio setting means has been described as an example. However, the present invention is not limited to such a configuration, and any of the above is described. It is sufficient to have at least. Thereby, a display response speed can be improved and a liquid crystal display device with excellent moving image performance can be realized. In order to improve the response speed more effectively, it is preferable to include at least gradation conversion means. Further, if the γ characteristic is set by the gradation luminance ratio setting means so as not to use the region where the response speed is slow, the response speed can be further increased. Therefore, it can be expected that the response speed can be further increased by a synergistic effect by providing both the gradation converting means and the gradation luminance ratio setting means.

  In this embodiment, a liquid crystal display device configured by stacking two liquid crystal panels is described as an example. However, the present invention is not limited to this, and three or more liquid crystal panels are stacked. It may be configured together.

  Furthermore, in the liquid crystal display device of the present invention, it is sufficient that at least one of the plurality of liquid crystal panels constituting the device has gradation converting means, and both of the two liquid crystal panels as in the present embodiment are used. The configuration is not limited to that having gradation conversion means. However, in order to further increase the display response speed, it is preferable that all the liquid crystal panels constituting the apparatus have gradation conversion means.

  Further, in the liquid crystal display device of the present invention, it is sufficient that at least one of the plurality of liquid crystal panels constituting the device has gradation luminance ratio setting means, and two liquid crystal panels as in the present embodiment. Are not limited to the configuration having the gradation luminance ratio setting means. However, in order to bring the gradation luminance characteristics of the combined gradation obtained by combining the gradations of the images output to each liquid crystal panel closer to the desired value of 2.0 ≦ γ ≦ 3.0, the device is It is preferable that all the liquid crystal panels to be configured have gradation luminance ratio setting means.

[Embodiment 2]
A television receiver to which the liquid crystal display device of the present invention is applied will be described below with reference to FIGS.

  FIG. 27 shows a circuit block of a liquid crystal display device 601 for a television receiver.

As shown in FIG. 27, the liquid crystal display device 601 includes a Y / C separation circuit 500, a video chroma circuit 501, an A / D converter 502, a liquid crystal controller 503, a liquid crystal panel 504, a backlight drive circuit 505, a backlight 506, a microcomputer. 507 and a gradation circuit 508 are provided.

The liquid crystal panel 504 has a two-panel configuration including a first liquid crystal panel and a second liquid crystal panel, and may have any of the configurations described in the above-described embodiments.
In the liquid crystal display device 601 having the above configuration, first, an input video signal of a television signal is input to the Y / C separation circuit 500 and separated into a luminance signal and a color signal. The luminance signal and the color signal are converted into R, G, and B which are the three primary colors of light by the video chroma circuit 501, and the analog RGB signal is converted into a digital RGB signal by the A / D converter 502, and the liquid crystal Input to the controller 503.

  In the liquid crystal panel 504, RGB signals from the liquid crystal controller 503 are input at a predetermined timing, and RGB gradation voltages from the gradation circuit 508 are supplied to display an image. The microcomputer 507 controls the entire system including these processes.

  Video signals are displayed based on various video signals such as video signals based on television broadcasts, video signals captured by cameras, video signals supplied via the Internet, video signals recorded on DVDs, etc. Is possible.

  Further, the tuner unit 600 shown in FIG. 28 receives a television broadcast and outputs a video signal, and the liquid crystal display device 601 displays an image (video) based on the video signal output from the tuner unit 600.

  When the liquid crystal display device having the above configuration is a television receiver, for example, as shown in FIG. 29, the liquid crystal display device 601 is sandwiched between the first housing 301 and the second housing 306. It has a configuration.

  The first housing 301 is formed with an opening 301 a that transmits an image displayed on the liquid crystal display device 601.

  The second housing 306 covers the back side of the liquid crystal display device 601. An operation circuit 305 for operating the liquid crystal display device 601 is provided, and a support member 308 is attached below. ing.

  As described above, in the television receiver and the video monitor having the above-described configuration, by using the liquid crystal display device of the present invention as the display device, it is possible to display an image with high contrast, high response speed, and high display quality. It becomes possible.

  However, the use of the liquid crystal display device of the present invention is not limited to the television receiver as described above. The liquid crystal display device of the present invention can be used for display devices for all purposes where high contrast is desired.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The liquid crystal display device of the present invention can improve the contrast while suppressing the decrease in display response speed and improving the moving image performance, so that a high contrast display is desired. It can be suitably used for a vehicle-mounted liquid crystal display or the like used for a monitor, a car navigation system, a speedometer display, or the like.

1 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention. It is a figure which shows the arrangement | positioning relationship between the polarizing plate and panel in the liquid crystal display device shown in FIG. FIG. 2 is a plan view of the vicinity of a pixel electrode of the liquid crystal display device shown in FIG. 1. It is a schematic block diagram of the drive system which drives the liquid crystal display device shown in FIG. It is a figure which shows the connection relation of the driver and panel drive circuit of the liquid crystal display device shown in FIG. It is a schematic block diagram of the backlight with which the liquid crystal display device shown in FIG. 1 is provided. FIG. 2 is a block diagram of a display controller that is a drive circuit that drives the liquid crystal display device shown in FIG. 1. It is a schematic sectional drawing of the liquid crystal display device of 1 sheet of liquid crystal panels. It is a figure which shows the arrangement | positioning relationship between the polarizing plate and panel in the liquid crystal display device shown in FIG. (A)-(c) is a figure explaining the principle of contrast improvement. (A)-(d) is a figure explaining the principle of contrast improvement. (A)-(c) is a figure explaining the principle of contrast improvement. (A) (b) is a figure explaining the principle of contrast improvement. (A)-(c) is a figure explaining the principle of contrast improvement. (A) (b) is a figure explaining the principle of contrast improvement. (A) (b) is a figure explaining the principle of contrast improvement. 5 is a graph showing a relationship between a gray level and a transmittance in a low gray level region in a liquid crystal display device having a single liquid crystal panel configuration and a liquid crystal display device having a two liquid crystal panel configuration. 5 is a graph showing a relationship between gradation and transmittance in all gradation regions in a liquid crystal display device having a single liquid crystal panel configuration and a liquid crystal display device having a two liquid crystal panel configuration. It is a block diagram which shows the structure of the display controller of the liquid crystal display device concerning embodiment of this invention. 6 is a graph showing the relationship between the gradation and the transmittance before the change of the γ characteristic by the gradation luminance ratio setting means in the liquid crystal display device according to the embodiment of the present invention. 6 is a graph showing the relationship between the gradation and the transmittance after changing the γ characteristic by the gradation luminance ratio setting means in the liquid crystal display device according to the embodiment of the present invention. (A)-(d) is for demonstrating pseudo multi gradation processing, and is a schematic diagram which shows the gradation value of a unit pixel area. It is a schematic diagram which shows the procedure of pseudo multi-gradation processing. It is a figure which shows an example of the look-up table used for a gradation conversion process. It is a schematic diagram which shows the pixel of the liquid crystal panel of a MVA system. It is a figure which shows the example of the angular response in the liquid crystal panel of a MVA system. It is a schematic block diagram of the television receiver provided with the liquid crystal display device of this invention. It is a block diagram which shows the relationship between the tuner part and liquid crystal display device in the television receiver shown in FIG. It is a disassembled perspective view of the television receiver shown in FIG.

Explanation of symbols

201 Scanning signal wiring 202 Auxiliary capacitance wiring 203 TFT element 204 Data signal wiring 205 Drain lead wiring 206 Auxiliary capacitance forming electrode 207 Interlayer insulating film 208 Pixel electrode 210 Transparent substrate 211 Slit patterns 212a to 12f Slit 220 Color filter substrate 221 Color Filter 222 Protrusion 223 Counter electrode 224 Black matrix 225 Vertical alignment film 226 Liquid crystal 227 Transparent layer 228 Flattening film 230 Active matrix substrate 100 Liquid crystal display device 101a / 101b / 101c Polarizing plate 402a Gradation conversion section (1) (gradation conversion means )
402b Tone conversion unit (2) (tone conversion means)
405a gradation reference voltage generation circuit (1) (gradation luminance ratio setting means)
405b gradation reference voltage generation circuit (2) (gradation luminance ratio setting means)
600 tuner unit 601 liquid crystal display device

Claims (10)

In a liquid crystal display device configured by overlapping a plurality of normally black mode liquid crystal panels, each of which outputs an image based on the same video source,
At least one liquid crystal panel of the plurality of liquid crystal panels has gradation conversion means for converting a gradation value equal to or higher than a threshold value when a gradation value equal to or lower than the threshold value is input. Liquid crystal display device.   2. The liquid crystal display device according to claim 1, wherein the threshold value is a gradation value with a luminance of (1 / X) × 100 (%) when the contrast ratio of the liquid crystal display device is X: 1. .   The liquid crystal display device according to claim 1, wherein the threshold value is a gradation value when the luminance is 0.05% or less.   2. The liquid crystal display device according to claim 1, wherein the gradation converting means has a lookup table in which input gradation values and output gradation values are associated with each other.   The γ value of each liquid crystal panel is set so that the γ value indicating the gradation luminance characteristic of the combined gradation obtained by combining the gradations of the images output to the respective liquid crystal panels is 2.0 or more and 3.0 or less. The liquid crystal display device according to claim 1, further comprising gradation luminance ratio setting means for setting each value.   6. The liquid crystal display device according to claim 5, wherein the gradation luminance ratio setting means sets the γ value of the at least one liquid crystal panel to 1.0 or more and 2.0 or less. A driving method of a liquid crystal display device configured by overlapping a plurality of normally black mode liquid crystal panels, each of the liquid crystal panels outputting an image based on the same video source,
A liquid crystal display device that performs gradation conversion for converting a gradation value equal to or higher than a threshold value when a gradation value equal to or lower than the threshold value is input to at least one liquid crystal panel of the plurality of liquid crystal panels. Driving method. In a liquid crystal display device configured by overlapping a plurality of normally black mode liquid crystal panels, each of which outputs an image based on the same video source,
The γ value of each liquid crystal panel is set so that the γ value indicating the gradation luminance characteristic of the combined gradation obtained by combining the gradations of the image output to each liquid crystal panel is 2.0 or more and 3.0 or less. A liquid crystal display device comprising gradation luminance ratio setting means for setting each value.   9. The liquid crystal display device according to claim 8, wherein the gradation luminance ratio setting means sets the γ value of the at least one liquid crystal panel to 1.0 or more and 2.0 or less. The liquid crystal display device is composed of two liquid crystal panels,
9. The liquid crystal display device according to claim 8, wherein the gradation luminance ratio setting means sets both the γ values of the two liquid crystal panels to 1.48.