JP2018010083A - Display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of halo in a display formed by laminating a plurality of display panels.SOLUTION: The present display is a display having a plurality of display panels each including a liquid crystal cell laminated and arranged and displaying images respectively on the display panels. The display comprises: a first display panel that is arranged at a position close to an observer; and a second display panel that is arranged at a position farther from the observer than the first display panel. A first phase difference plate is arranged between a first polarizer that is arranged on the observer side with respect to the first liquid crystal cell included in the first display panel and a second polarizer that is arranged between the first liquid crystal cell and the second liquid crystal cell included in the second display panel.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a display device.

  Conventionally, as a technique for improving the contrast of a liquid crystal display device, a technique has been proposed in which two display panels are overlapped and an image is displayed on each display panel based on an input video signal (for example, Patent Document 1). reference). Specifically, for example, a color image is displayed on the front (observer side) display panel among the two display panels arranged at the front and back, and a monochrome image is displayed on the rear (backlight side) display panel. Thus, the contrast is improved.

JP 2007-310161 A

  However, by using a plurality of panels, for example, there is a problem that light leakage (so-called halo) to a low luminance region around a high luminance region (white display region) occurs.

  The present invention has been made in view of the above circumstances, and a main object thereof is to suppress the occurrence of halos in a display device configured by overlapping a plurality of display panels.

  In order to solve the above problems, a display device according to the present invention is a display device in which a plurality of display panels each including a liquid crystal cell are arranged to overlap each other and displays an image on each of the display panels, and is close to an observer. A first display panel arranged at a position, and a second display panel arranged at a position farther from the observer than the first display panel, and an observer than the first liquid crystal cell included in the first display panel A first retardation plate disposed between a first polarizer disposed on the side and a second polarizer disposed between the first liquid crystal cell and a second liquid crystal cell included in the second display panel; Is arranged.

  In the display device according to the present invention, the first retardation plate may be disposed between the first polarizer and the first liquid crystal cell.

  In the display device according to the present invention, even if a second retardation plate is disposed between the second polarizer and the polarizer disposed on the side opposite to the observer side of the second liquid crystal cell. Good.

  In the display device according to the present invention, even if the second retardation plate is disposed between the second liquid crystal cell and a polarizer disposed on the opposite side of the observer side of the second liquid crystal cell. Good.

  In the display device according to the present invention, when an image having a first gradation of a predetermined gradation or higher is displayed in the first area of the display screen, the first display panel displays the first gradation in the first area. The second display panel may display an image corresponding to the first gradation in a second area obtained by enlarging the first area.

  In the display device according to the present invention, a light diffusion layer may be disposed between the first display panel and the second display panel.

  According to the present invention, it is possible to suppress the occurrence of halos in a display device configured by overlapping a plurality of display panels.

It is a top view which shows schematic structure of the liquid crystal display device which concerns on one Embodiment of this invention. FIG. 2 is a plan view illustrating a schematic configuration of a first display panel illustrated in FIG. 1. It is a top view which shows schematic structure of the 2nd display panel shown in FIG. It is AA 'sectional drawing of FIG.2 and FIG.3. It is a schematic sectional drawing of the liquid crystal display device which concerns on another embodiment of this invention. 6 is a graph showing the viewing angle characteristics of contrast of the liquid crystal display device of Sample 1. 5 is a graph showing the viewing angle characteristics of contrast of the liquid crystal display device of Sample 2. 10 is a graph showing the viewing angle characteristics of contrast of the liquid crystal display device of Sample 3. 10 is a graph showing the viewing angle characteristics of contrast of the liquid crystal display device of Sample 4. 10 is a graph showing the viewing angle characteristics of contrast of the liquid crystal display device of Sample 5. 14 is a graph showing the viewing angle characteristics of contrast of the liquid crystal display device of Sample 6.

  One embodiment of the present invention will be described below with reference to the drawings.

  The liquid crystal display device according to the present embodiment controls a plurality of display panels that display an image, a plurality of drive circuits (a plurality of source drivers and a plurality of gate drivers) that drive the respective display panels, and the respective drive circuits. A plurality of timing controllers, an image processing unit that performs image processing on input video signals input from the outside, and outputs image data to each timing controller, and a plurality of display panels are irradiated with light from the back side Including backlight. The number of display panels is not limited and may be two or more. The plurality of display panels are arranged so as to overlap each other in the front-rear direction as viewed from the observer side, and each displays an image. Hereinafter, the liquid crystal display device 10 including two display panels will be described as an example.

  FIG. 1 is a plan view showing a schematic configuration of a liquid crystal display device 10 according to the present embodiment. As shown in FIG. 1, the liquid crystal display device 10 is arranged at a first display panel 100 arranged at a position close to the observer (front side) and at a position farther from the observer than the first display panel 100 (rear side). The second display panel 200, the first timing controller 140 for controlling the first source driver 120 and the first gate driver 130 provided in the first display panel 100, and the second source provided in the second display panel 200. A second timing controller 240 that controls the driver 220 and the second gate driver 230 and an image processing unit 300 that outputs image data to the first timing controller 140 and the second timing controller 240 are included. The backlight (omitted in FIG. 1) is disposed on the back side of the second display panel 200.

  The first display panel 100 displays a color image corresponding to the input video signal in the first image display area 110, and the second display panel 200 displays a monochrome image corresponding to the input video signal in the second image display area 210. The image processing unit 300 receives an input video signal Data transmitted from an external system (not shown), executes image processing, outputs the first image data DAT1 to the first timing controller 140, and outputs the second image data DAT1. The second image data DAT2 is output to the timing controller 240. The image processing unit 300 outputs a control signal (not shown in FIG. 1) such as a synchronization signal to the first timing controller 140 and the second timing controller 240. The first image data DAT1 is image data for color display, and the second image data DAT2 is image data for monochrome display.

  The image processing unit 300 executes, for example, a maximum value filtering process included in the image processing. Specifically, for example, when displaying an image having a high gradation (first gradation) equal to or higher than a predetermined gradation in a predetermined area (first area) of the display screen, the image processing unit 300 includes the high gradation. The first image data DAT1 corresponding to the above is generated, a circular area of 11 pixels × 11 pixels is set as the filter size, and the gradation of the target pixel (for example, the central pixel) is replaced with the maximum gradation in the filter. Thus, the second image data DAT2 is generated. Accordingly, the first display panel displays an image corresponding to the high gradation in the first area, and the second display panel displays an image corresponding to the high gradation in the second area obtained by enlarging the first area. To do. According to the above processing, since the high-luminance area (for example, the white display area) can be enlarged with respect to the display image of the second display panel, for example, the diagonal depending on the distance between the first display panel and the second display panel. The problem of direction parallax is eliminated. On the other hand, the difference in the high luminance region between the first display panel and the second display panel can be one of the causes of the occurrence of halo. In such a form, the effect which suppresses generation | occurrence | production of a halo can be acquired more notably by arrange | positioning the 1st phase difference plate mentioned later.

  FIG. 2 is a plan view showing a schematic configuration of the first display panel 100, and FIG. 3 is a plan view showing a schematic configuration of the second display panel 200. FIG. 4 is a cross-sectional view taken along the line AA ′ of FIGS. 2 and 3.

  As shown in FIG. 4, the first display panel 100 includes a first liquid crystal cell 104, a first polarizing plate 105 disposed on the observer side of the first liquid crystal cell 104, and an observer side of the first liquid crystal cell 104. A second polarizing plate 106 disposed on the opposite side (backlight 400 side), and a first retardation plate 107 disposed between the first polarizing plate 105 and the first liquid crystal cell 104. Yes. The first liquid crystal cell 104 includes a thin film transistor substrate 101 (hereinafter referred to as a TFT substrate) disposed on the backlight 400 side, and a color filter substrate 102 (hereinafter referred to as a CF substrate) disposed on the viewer side and facing the TFT substrate 101. And a first liquid crystal layer 103 disposed between the TFT substrate 101 and the CF substrate 102.

  Any appropriate driving method can be adopted as the driving method of the first liquid crystal cell 104. As the driving method, for example, an IPS (In Plane Switching) method, a VA (Vertical alignment) method, or the like can be adopted. In the present invention, the liquid crystal driving method is not particularly limited, but in the present embodiment, the IPS method is adopted.

  The polarizing plate includes a polarizer. As the polarizer, a resin film (typically a polyvinyl alcohol-based resin film) in which a dichroic substance such as iodine is adsorbed and oriented is typically used. The polarizing plate usually includes a polarizer and protective layers respectively disposed on both sides of the polarizer. The 1st polarizing plate 105 and the 2nd polarizing plate 106 are arrange | positioned so that each absorption axis may orthogonally cross. Further, the absorption axis of the first polarizing plate 105 or the absorption axis of the second polarizing plate 106 and the alignment direction of the liquid crystal layer 103 are arranged in parallel.

  For example, the refractive index characteristic of the first retardation plate 107 is selected according to the driving method of the liquid crystal cell. For example, when the IPS method is adopted, it is preferable that the refractive index characteristics of the first retardation plate 107 satisfy the relationship of nx ≧ nz> ny. Here, “nx” is the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction), and “ny” is the direction orthogonal to the slow axis in the plane (that is, the fast phase). (Nz direction), and “nz” is the refractive index in the thickness direction. Typically, the first retardation plate 107 is arranged so that its slow axis is orthogonal to the absorption axis of the first polarizing plate 105 or the absorption axis of the second polarizing plate 106.

  The retardation plate may be a single layer or a laminate. The retardation plate is typically made of a resin film and can also function as a protective layer for the polarizer.

  By arranging the first retardation plate 107 between the first polarizing plate 105 and the second polarizing plate 106 (a third polarizing plate 205 described later), generation of halo can be effectively suppressed. Specifically, by arranging the first retardation plate 107, light that travels in an oblique direction among light incident on the first display panel 100 from the second display panel 200 in the low luminance region around the high luminance region. Transmission can be suppressed, and the occurrence of halo can be suppressed. Although the first retardation plate 107 can be disposed between the first polarizing plate 105 and the second polarizing plate 106, preferably, the first polarizing plate 105 and the first liquid crystal cell 104 are provided as in the illustrated example. Between. According to such a configuration, the first liquid crystal cell 104 and the second liquid crystal described later are compared with the case where the first retardation plate 107 is disposed between the first liquid crystal cell 104 and the second polarizing plate 106. The distance to the cell 204 can be made smaller to reduce the diagonal parallax.

  As shown in FIG. 2, the TFT substrate 101 has a plurality of data lines 111 extending in a first direction (for example, the column direction) and a second direction (for example, the row direction) different from the first direction. A plurality of gate lines 112 are formed, and thin film transistors 113 (hereinafter referred to as TFTs) are formed in the vicinity of the intersections of the plurality of data lines 111 and the plurality of gate lines 112. When the first display panel 100 is viewed in plan, a region surrounded by two adjacent data lines 111 and two adjacent gate lines 112 is defined as one pixel 114, and the pixel 114 is arranged in a matrix ( A plurality of rows and columns are arranged. The plurality of data lines 111 are arranged at equal intervals in the row direction, and the plurality of gate lines 112 are arranged at equal intervals in the column direction. On the TFT substrate 101, a pixel electrode 115 is formed for each pixel 114, and one common electrode (not shown) common to the plurality of pixels 114 is formed. The drain electrode constituting the TFT 113 is electrically connected to the data line 111, the source electrode is electrically connected to the pixel electrode 115, and the gate electrode is electrically connected to the gate line 112.

  As shown in FIG. 4, a plurality of colored portions 102 a are formed on the CF substrate 102 corresponding to each pixel 114. Each colored portion 102a is surrounded by a black matrix 102b that blocks light transmission, and is formed in a rectangular shape, for example. The plurality of colored portions 102a are formed of a red (R color) material and transmit a red portion that transmits red light, and a green portion that is formed of a green (G color) material and transmits green light. And a blue portion that is formed of a blue (B color) material and transmits blue light. The red portion, the green portion, and the blue portion are repeatedly arranged in this order in the row direction, the colored portions of the same color are arranged in the column direction, and the black matrix 102b is arranged at the boundary portion between the colored portions 102a adjacent in the row direction and the column direction. Is formed. As shown in FIG. 2, the plurality of pixels 114 corresponding to each coloring portion 102a includes a red pixel 114R corresponding to the red portion, a green pixel 114G corresponding to the green portion, and a blue pixel 114B corresponding to the blue portion. And.

  The first timing controller 140 has a known configuration. For example, the first timing controller 140 uses the first image data DA1 based on the first image data DAT1 output from the image processing unit 300 and the first control signal CS1 (clock signal, vertical synchronization signal, horizontal synchronization signal, etc.). And various timing signals (data start pulse DSP1, data clock DCK1, gate start pulse GSP1, and gate clock GCK1) for controlling driving of the first source driver 120 and the first gate driver 130 (see FIG. 2). ). The first timing controller 140 outputs the first image data DA1, the data start pulse DSP1, and the data clock DCK1 to the first source driver 120, and outputs the gate start pulse GSP1 and the gate clock GCK1 to the first gate driver 130. Output.

  The first source driver 120 outputs a data signal (data voltage) corresponding to the first image data DA1 to the data line 111 based on the data start pulse DSP1 and the data clock DCK1. The first gate driver 130 outputs a gate signal (gate voltage) to the gate line 112 based on the gate start pulse GSP1 and the gate clock GCK1.

  Each data line 111 is supplied with a data voltage from the first source driver 120, and each gate line 112 is supplied with a gate voltage from the first gate driver 130. A common voltage Vcom is supplied to the common electrode from a common driver (not shown). When the gate voltage (gate-on voltage) is supplied to the gate line 112, the TFT 113 connected to the gate line 112 is turned on, and the data voltage is supplied to the pixel electrode 115 via the data line 111 connected to the TFT 113. . An electric field is generated by the difference between the data voltage supplied to the pixel electrode 115 and the common voltage Vcom supplied to the common electrode. The liquid crystal is driven by this electric field to control the light transmittance of the backlight 400 to display an image. In the first display panel 100, color image display is performed by supplying a desired data voltage to the data lines 111 connected to the pixel electrodes 115 of the red pixel 114R, the green pixel 114G, and the blue pixel 114B.

  Next, the configuration of the second display panel 200 will be described with reference to FIGS. 3 and 4. As shown in FIG. 4, the second display panel 200 includes a second liquid crystal cell 204, a third polarizing plate 205 disposed on the viewer side of the second liquid crystal cell 204, and a backlight 400 of the second liquid crystal cell 204. 4th polarizing plate 206 arrange | positioned at the side. The second liquid crystal cell 204 is disposed between the TFT substrate 201 disposed on the backlight 400 side, the CF substrate 202 disposed on the viewer side and facing the TFT substrate 201, and between the TFT substrate 201 and the CF substrate 202. Second liquid crystal layer 203.

  The driving method of the second liquid crystal cell 204 corresponds to the driving method of the first liquid crystal cell 104, for example. Therefore, in this embodiment, the IPS system is adopted.

  The third polarizing plate 205 and the fourth polarizing plate 206 are arranged so that their absorption axes are orthogonal to each other. The absorption axis of the third polarizing plate 205 or the absorption axis of the fourth polarizing plate 206 and the alignment direction of the liquid crystal layer 203 are arranged in parallel. Further, the absorption axis of the second polarizing plate 106 and the absorption axis of the third polarizing plate 205 are parallel. Note that one of the second polarizing plate 106 and the third polarizing plate 205 may be omitted.

  As shown in FIG. 3, a plurality of data lines 211 extending in the column direction and a plurality of gate lines 212 extending in the row direction are formed on the TFT substrate 201, and the plurality of data lines 211 and the plurality of data lines 211 are formed. A TFT 213 is formed in the vicinity of each intersection with the gate line 212. When the second display panel 200 is viewed in plan, a region surrounded by two adjacent data lines 211 and two adjacent gate lines 212 is defined as one pixel 214, and the pixel 214 is arranged in a matrix ( A plurality of rows and columns are arranged. The plurality of data lines 211 are arranged at equal intervals in the row direction, and the plurality of gate lines 212 are arranged at equal intervals in the column direction. A pixel electrode 215 is formed for each pixel 214 on the TFT substrate 201, and one common electrode (not shown) common to the plurality of pixels 214 is formed. The drain electrode constituting the TFT 213 is electrically connected to the data line 211, the source electrode is electrically connected to the pixel electrode 215, and the gate electrode is electrically connected to the gate line 212.

  As shown in FIG. 4, a black matrix 202 b that blocks light transmission is formed on the CF substrate 202 at a position corresponding to the boundary portion of each pixel 214. In the region 202a surrounded by the black matrix 202b, no colored portion is formed, and for example, an overcoat film is formed.

  The second timing controller 240, based on the second image data DAT2 output from the image processing unit 300 and the second control signal CS2 (clock signal, vertical synchronization signal, horizontal synchronization signal, etc.), Various timing signals (data start pulse DSP2, data clock DCK2, gate start pulse GSP2, gate clock GCK2) for controlling the driving of the second source driver 220 and the second gate driver 230 are generated (see FIG. 3). . The second timing controller 240 outputs the second image data DA2, the data start pulse DSP2, and the data clock DCK2 to the second source driver 220, and outputs the gate start pulse GSP2 and the gate clock GCK2 to the second gate driver 230. Output.

  The second source driver 220 outputs a data voltage corresponding to the second image data DA2 to the data line 211 based on the data start pulse DSP2 and the data clock DCK2. The second gate driver 230 outputs a gate voltage to the gate line 212 based on the gate start pulse GSP2 and the gate clock GCK2.

  Each data line 211 is supplied with a data voltage from the second source driver 220, and each gate line 212 is supplied with a gate voltage from the second gate driver 230. A common voltage Vcom is supplied to the common electrode from a common driver. When the gate voltage (gate-on voltage) is supplied to the gate line 212, the TFT 213 connected to the gate line 212 is turned on, and the data voltage is supplied to the pixel electrode 215 via the data line 211 connected to the TFT 213. . An electric field is generated by the difference between the data voltage supplied to the pixel electrode 215 and the common voltage Vcom supplied to the common electrode. The liquid crystal is driven by this electric field to control the light transmittance of the backlight 400 to display an image. On the second display panel 200, monochrome image display is performed.

  Although not shown, a light diffusion layer may be disposed between the first display panel 100 and the second display panel 200. By arranging the light diffusion layer, it is possible to suppress the occurrence of moire due to the pattern of the black matrix 202b of the second liquid crystal cell 204 between the first liquid crystal cell 104 and the second liquid crystal cell 204, for example. Any appropriate configuration can be adopted as the light diffusion layer. The light diffusion layer is composed of, for example, a light diffusion adhesive including an adhesive (typically an acrylic adhesive) and light diffusing fine particles dispersed in the adhesive. When the light diffusing layer is composed of a light diffusing adhesive, typically, a laminate including a base film and a light diffusing layer formed on the base film is disposed between the panels.

  FIG. 5 is a schematic cross-sectional view of a liquid crystal display device according to another embodiment of the present invention. In the present embodiment, the second display panel 200 further includes a second retardation plate 207 disposed between the second liquid crystal cell 204 and the fourth polarizing plate 206, which is different from the above-described embodiment. Different.

  The refractive index characteristic of the second retardation plate 207 is selected according to, for example, the driving method of the liquid crystal cell. Specifically, when the IPS method is adopted as the driving method, it is preferable that the refractive index characteristics of the second retardation plate 207 satisfy the relationship of nx ≧ nz> ny. Typically, the second retardation plate 207 is arranged such that its slow axis is orthogonal to the absorption axis of the third polarizing plate 205 (second polarizing plate 106) or the absorption axis of the fourth polarizing plate 206. The

  By disposing the second retardation plate 207 between the third polarizing plate 205 (second polarizing plate 106) and the fourth polarizing plate 206, the third polarizing plate 205 (second polarizing plate 106) during white display. The amount of light that passes through the light increases, and white luminance (luminance during white display) can be improved. In addition, light passing through the second display panel 200 in an oblique direction can be reduced, and the amount of light when the second display panel 200 displays black can be reduced. As a result, the overall contrast can be improved. As described above, in the form in which the light diffusion layer is disposed between the first display panel 100 and the second display panel 200, a more remarkable effect can be obtained. The second retardation plate 207 can be disposed between the third polarizing plate 205 (second polarizing plate 106) and the fourth polarizing plate 206, but preferably, as shown in the illustrated example, the second liquid crystal cell. It arrange | positions between 204 and the 4th polarizing plate 206. FIG. According to such a configuration, the first liquid crystal cell 104 and the second phase described later are compared with the case where the second retardation plate 207 is disposed between the third polarizing plate 205 and the second liquid crystal cell 204. The distance between the liquid crystal cell 204 can be made smaller, and the parallax in the oblique direction can be reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said each embodiment, The form suitably changed by those skilled in the art from said each embodiment within the range which does not deviate from the meaning of this invention. Needless to say, it is included in the technical scope of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples. In this example, Samples 1 to 6 were produced by changing the arrangement of the phase difference plate in the display device.

[Sample 1]
Polarizing plate with retardation plate on the CF substrate side of the liquid crystal cell for color image display (refractive index characteristic of retardation plate: nx>nz> ny, angle formed between retardation axis of retardation plate and absorption axis of polarizer: 90 °) so that the retardation plate is positioned closer to the liquid crystal cell than the polarizer. Here, a liquid crystal having a positive dielectric anisotropy is adopted as the liquid crystal layer of the liquid crystal cell, and the absorption axis of the polarizing plate and the liquid crystal layer contained in the liquid crystal cell (liquid crystal molecules aligned in a homogeneous arrangement without applying an electric field) ) So as to be orthogonal to the major axis direction when no electric field is applied.
Next, a polarizing plate was bonded to the TFT substrate side of the liquid crystal cell for color image display so that the absorption axis thereof was orthogonal to the absorption axis of the polarizing plate on the CF substrate side. Thus, a first display panel was obtained.

  Polarizing plates were bonded to both sides of the liquid crystal cell for displaying black and white images so that their absorption axes were orthogonal to each other. Here, a liquid crystal having a positive dielectric anisotropy is adopted as the liquid crystal layer of the liquid crystal cell, and the absorption axis of one of the polarizing plates and the liquid crystal layer contained in the liquid crystal cell (aligned in a homogeneous arrangement without applying an electric field) The liquid crystal molecules were bonded so that the major axis direction when no electric field was applied was orthogonal. Thus, a second display panel was obtained.

  On the side where the TFT substrate is disposed with respect to the liquid crystal layer of the first display panel, the second display panel was laminated via a laminate including a light diffusion adhesive. Here, lamination was performed so that the absorption axis of the polarizing plate on the TFT substrate side of the first display panel and the absorption axis of the polarizing plate on the CF substrate side of the second display panel were parallel. Thus, the display device shown in FIGS. 1 to 4 was obtained. That is, in the display device according to Sample 1, only the polarizing plate on the CF substrate side of the liquid crystal cell for color image display is configured as a polarizing plate with a retardation plate.

[Sample 2]
In the production of the first display panel, a polarizing plate with no retardation plate laminated on the CF substrate side was bonded, and the polarizing plate with the retardation plate was bonded on the TFT substrate side in the same manner as Sample 1, A display device was obtained. That is, in the display device according to Sample 2, only the polarizing plate on the TFT substrate side of the liquid crystal cell for color image display is configured as a polarizing plate with a retardation plate.

[Sample 3]
In the production of the first display panel, a polarizing plate on which the retardation plate is not laminated is bonded to the CF substrate side, and in the production of the second display panel, the polarizing plate with the retardation plate is attached to the CF substrate side. A display device was obtained in the same manner as in Sample 1 except that they were combined. That is, in the display device according to Sample 3, only the polarizing plate on the CF substrate side of the liquid crystal cell for displaying black and white images is configured as a polarizing plate with a retardation plate.

[Sample 4]
In the production of the first display panel, a polarizing plate on which the retardation plate is not laminated is bonded to the CF substrate side, and in the production of the second display panel, the polarizing plate with the retardation plate is attached to the TFT substrate side. A display device was obtained in the same manner as in Sample 1 except that they were combined. That is, in the display device according to Sample 4, only the polarizing plate on the TFT substrate side of the liquid crystal cell for displaying black and white images is configured as a polarizing plate with a retardation plate.

[Sample 5]
A display device shown in FIG. 5 was obtained in the same manner as Sample 1 except that the second polarizing plate with the retardation plate was bonded to the TFT substrate when the second display panel was produced. That is, in the display device according to Sample 5, the polarizing plate on the CF substrate side of the liquid crystal cell for color image display and the polarizing plate on the TFT substrate side of the liquid crystal cell for monochrome image display are configured as a polarizing plate with a retardation plate. ing.

[Sample 6]
When producing the second display panel, a display device was obtained in the same manner as Sample 1 except that the polarizing plate with a retardation plate was bonded to the CF substrate side. That is, in the display device according to Sample 6, the polarizing plate on the CF substrate side of the liquid crystal cell for color image display and the polarizing plate on the CF substrate side of the liquid crystal cell for monochrome image display are configured as a polarizing plate with a retardation plate. ing.

[Evaluation of Samples 1 to 6]
The display devices according to Samples 1 to 6 were evaluated for halo generation, white luminance in the front direction, contrast in the front direction, and parallax in the oblique direction.

  Occurrence of halo occurs when a first master image in which a low-brightness area (black display area) is arranged around a high-brightness area (white display area) is leaked into a low-brightness area around the high-brightness area ( Evaluation was made by visually observing the presence (degree) of bright shadows (corresponding to high-luminance regions) that appeared in the black display region.

  The white luminance in the front direction is measured by measuring the luminance from the front direction of the display device by turning on the backlight with the maximum gradation signal input to the two display panels and maximizing the transmittance of the two display panels. It was evaluated by doing.

  The contrast in the front direction is determined by inputting the signal of the minimum gradation to the two display panels and turning on the backlight in a state where the transmittance of the two display panels is minimized. The black luminance) was measured, and this value was evaluated by dividing the white luminance in the front direction.

  The diagonal parallax is displayed on the image displayed on the first display panel and the second display panel when the display device displaying the second master image is viewed with the naked eye from an oblique direction with respect to the front direction. This was evaluated by observing the degree of deviation from the image.

  The evaluation results for samples 1 to 6 are shown in Table 1. 6 to 11 show the viewing angle characteristics of the contrast of the display devices according to Samples 1 to 6. FIG. 6 to 11, gradation is displayed from black to white as the contrast (white luminance / black luminance) increases.

  As shown in Table 1, in Samples 1, 2, 5, and 6, the occurrence of halo was satisfactorily suppressed, whereas in Samples 3 and 4, the occurrence of halo was confirmed. In Samples 1, 2, 5, and 6, the phase difference plate is arranged on the first display panel (color image display panel) on the viewer side, and when the first master image is displayed on the display device, It is considered that the phase difference of light entering from the second display panel in an oblique direction to the first display panel is compensated, and the light is favorably shielded by the polarizer on the CF substrate side of the first display panel. As a result, when the first master image is displayed, it is considered that no light leakage occurred in the low luminance area around the high luminance area.

  On the other hand, in Samples 3 and 4, since the retardation plate is not arranged on the first display panel, when the first master image is displayed on the display device, the second display panel is applied to the first display panel. Thus, it is considered that part of the light entering in the oblique direction is not shielded by the polarizer on the CF substrate side of the first display panel, but leaks into the low luminance region around the high luminance region, and halo is generated. In Samples 3 and 4, the contrast in the front direction was relatively large.

  Comparing sample 1 and sample 2, the sample 1 has a more suppressed oblique parallax. This is because Sample 2 has a CF substrate for the first display panel (specifically, a CF layer including the coloring portion 102a and the black matrix 102b) and a CF substrate for the second display panel (specifically, the black matrix). This is probably because the distance from the CF layer including 202b increases due to the arrangement of the retardation plate. When the distance is large, when the display device is viewed obliquely with respect to the front direction, the image displayed on the first display panel is easily shifted from the image displayed on the second display panel, and the parallax Is likely to occur.

  Compared to Sample 1, Samples 5 and 6 have significantly superior contrast in the front direction and improved viewing angle characteristics. In Samples 5 and 6, a phase difference plate is disposed on the second display panel on the backlight side (a panel for displaying monochrome images), and the phase difference of light transmitted through the second display panel in an oblique direction during black display is determined. It is considered that the light is well shielded by the polarizer on the CF substrate side of the second display panel after compensation. As a result, the amount of light transmitted through the second display panel and incident on the first display panel during black display is reduced, the black luminance in the front direction is lowered, and the contrast is remarkably increased as described above. It is done.

  Comparing the sample 5 and the sample 6, the sample 5 has a more suppressed oblique parallax. This is presumably because the distance between the first display panel CF layer and the CF layer of the second display panel is larger in Sample 6 due to the arrangement of the retardation plate, as described above.

  DESCRIPTION OF SYMBOLS 10 Liquid crystal display device, 100 1st display panel, 104 1st liquid crystal cell, 105 1st polarizing plate, 106 2nd polarizing plate, 107 1st phase difference plate, 110 1st image display area, 120 1st source driver, 130 First gate driver, 140 First timing controller, 200 Second display panel, 204 Second liquid crystal cell, 205 Third polarizing plate, 206 Fourth polarizing plate, 207 Second retardation plate, 210 Second image display region, 220 Second source driver, 230 Second gate driver, 240 Second timing controller, 300 Image processing unit.

Claims (6)

A plurality of display panels including liquid crystal cells are arranged to overlap each other, and each display panel displays an image.
A first display panel arranged at a position close to the observer, and a second display panel arranged at a position farther from the observer than the first display panel,
Arranged between the first polarizer disposed closer to the viewer than the first liquid crystal cell included in the first display panel, and the second liquid crystal cell included in the first liquid crystal cell and the second display panel. A first retardation plate is disposed between the second polarizer and the second polarizer;
A display device characterized by that. The first retardation plate is disposed between the first polarizer and the first liquid crystal cell;
The display device according to claim 1. A second retardation plate is disposed between the second polarizer and a polarizer disposed on the side opposite to the viewer side of the second liquid crystal cell;
The display device according to claim 1 or 2. The second retardation plate is disposed between the second liquid crystal cell and a polarizer disposed on the side opposite to the viewer side of the second liquid crystal cell;
The display device according to claim 3. When displaying an image of a first gradation of a predetermined gradation or higher in the first area of the display screen, the first display panel displays an image corresponding to the first gradation in the first area. The second display panel displays an image corresponding to the first gradation in a second area obtained by enlarging the first area.
The display device according to claim 1. A light diffusion layer is disposed between the first display panel and the second display panel;
The display device according to claim 1, wherein the display device is a display device.