JP4688143B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display (LCD).

FIGS. 9A and 9B are schematic exploded perspective views showing an example of the internal configuration of a liquid crystal display element that performs color display.
Reference is made to FIG. The liquid crystal display element includes an upper substrate 31 and a lower substrate 32 that are arranged to face each other, and a liquid crystal layer 39 that is sandwiched therebetween. The upper substrate 31 and the lower substrate 32 include, for example, a flat glass substrate, and an electrode having a predetermined pattern, which is formed of a transparent conductive material such as ITO (indium tin oxide) on its opposing surface. The liquid crystal layer 39 is a nematic liquid crystal layer formed of, for example, a nematic liquid crystal 39a having a negative dielectric anisotropy (Δε <0).

  On the outside of the upper substrate 31 and the lower substrate 32, a pair of upper and lower polarizing plates 41 and 42 are arranged in a crossed Nicols state. The upper and lower polarizing plates 41 and 42 each have a transmission axis in the in-plane direction, and transmit only light polarized in the direction of the transmission axis.

  A white backlight 52 is disposed outside the lower polarizing plate 42. The white backlight 52 is configured using, for example, a cold cathode fluorescent lamp (CCFL). In some cases, an inorganic white LED (light emitting diode), an organic LED, or the like is used.

  By applying a voltage to the liquid crystal layer 39 by voltage applying means connected between the electrodes of the upper and lower substrates 31 and 32, the alignment state of the liquid crystal molecules 39a changes. A change in the alignment state of the liquid crystal molecules 39a also changes the polarization state of the transmitted light. Light emitted from the white backlight 52 and passed through the liquid crystal layer 39 is displayed as “bright” when transmitted through the upper polarizing plate 41, and “dark” is displayed when shielded by the upper polarizing plate 41.

In order to perform color display, an area color filter 49 and a black mask 51 are disposed between the upper and lower substrates 31 and 32.
The area color filter 49 includes, for example, a red part 49r, a green part 49g, a blue part 49b, and a white part 49w. In the illustrated liquid crystal display element, light emitted from the white backlight 52 passes through different color regions (each color portion 49r, g, b, w) of the area color filter 49, so that a plurality of colors are provided for each region. Can be displayed.

The black mask 51 is disposed in order to increase contrast and color purity.
A drive circuit 53 is connected to perform a predetermined display.
With the structure shown in FIG. 9A, color segment display, display using a combination of segments and dots, and full dot display are possible.

The liquid crystal display element having a transmissive structure illuminated with a white light source as shown in the figure is not suitable for complicated color expression.
In order to improve color display quality, a liquid crystal display element employing a micro color filter method has been proposed.

  The micro color filter system is particularly introduced in a full-dot display type liquid crystal display element. For example, fine dots are color-coded into red (R), green (G), and blue (B), and one set of three dots (one pixel). ) Is displayed in color.

  However, even in this method, when the dots are large, it may be recognized that one pixel is composed of a plurality of dots due to the spatial resolution of the human eye, and high display quality may not be realized. Further, since one pixel is composed of a plurality of dots, the light use efficiency is lowered. For this reason, it is necessary to improve the brightness of the white backlight 52, and power consumption increases.

FIG. 9B illustrates another example of the internal structure of a liquid crystal display element that performs color display.
In the liquid crystal display element shown in FIG. 9A, an area color filter and a black mask are arranged in the liquid crystal cell, but in the liquid crystal display element shown in FIG. 9B, they are not arranged in the liquid crystal cell. . In order to perform color display, a multi-color backlight 55 is used instead of the white backlight 52.

  The multi-color backlight 55 is a backlight capable of emitting a plurality of colors, and uses, for example, an RGB multi-color LED light source. When the light emitted from the multi-color backlight 55 passes through the upper polarizing plate 41, “bright” is displayed depending on the color of the emitted light. The backlight synchronization drive circuit 54 synchronizes the light emitted from the multi-color backlight 55 and the alignment state of the liquid crystal molecules 39 a of the liquid crystal layer 39.

  A field sequential (FS) driving method is known as a method for driving a liquid crystal display element that does not include a color filter as shown in FIG. 9B.

  The field sequential driving method is a driving method in which image data of R, G, and B is time-resolved and displayed, and the image data is switched at such a high speed that an afterimage cannot be recognized, thereby allowing an observer to recognize the mixed color image. .

  FIG. 10 shows an example of a driving timing chart of the FS driving method. In this timing chart, the liquid crystal display element has a display section 1, a display section 2,..., A display section n defined as n display areas, and a voltage is applied between the upper and lower substrates (in the figure). Is displayed as “ON”.) Is assumed to be a normally black type that performs “bright” display.

  According to the FS driving method, one image is displayed in one frame period, for example, 16.7 ms. One frame period is composed of three subframe periods (here, called subframe periods 1, 2, and 3 along the time axis) SB. In each subframe period, one of R, G, and B One color data is displayed.

  In the display unit 1, a voltage is applied between the upper and lower substrates in the subframe periods 1 and 2 to be in a “bright” state (a state in which incident light is transmitted), and in the subframe period 3, a voltage is not applied. It becomes a “dark” state (a state in which incident light is not transmitted). On the other hand, the multi-color backlight emits red (R) in subframe period 1 and green (G) and blue (B) in subframe periods 2 and 3, respectively. Therefore, in the display unit 1, red (R) and green (G) light is transmitted during one frame period, and yellow, which is a mixed color of both colors, is recognized by the observer's eyes.

Similarly, on the display unit 2, magenta is displayed by red (R) transmitted in the subframe period 1 and blue (B) transmitted in the subframe period 3.
In the display unit n, green (G) transmitted in the subframe period 2 is directly recognized by the observer's eyes.

  The reason why the multi-color backlight does not emit light at the beginning of each subframe period is that the response of the liquid crystal layer to the applied voltage is slower than that of the backlight. The purpose is to provide a blank period and to adjust the period during which the liquid crystal layer transmits light and the light emission period of the backlight.

  In the normally white mode liquid crystal display element, the FS driving method is used, and in the positive display state in which the background is displayed in white, the segment display portion can be expressed in color. This is impossible with the color display liquid crystal display element shown in FIG.

  However, in this FS driving method, when an observer changes his / her line of sight when observing in a dark place or when the liquid crystal display element vibrates, a color break phenomenon occurs in which the monochrome display of each subframe is recognized by the human eye. In particular, the white display area may be recognized as a rainbow. When the color break phenomenon occurs, the display appearance is poor, and the display is difficult for human psychology.

The inventors of the present application have found that a color break phenomenon occurs when a light source is turned on in a plurality of subframes when forming an image in one frame. A proposal has been made that the backlight that has been made to emit light should emit light in a desired color within one subframe and be reflected in the display. (For example, see Patent Document 1.)
FIG. 11 shows an example of a driving timing chart of the FS driving method proposed previously.

  In the FS driving method shown in this timing chart, red (R) light is emitted from the multi-color backlight in the sub-frame period 1, and yellow (Y) is emitted from the multi-color backlight in the sub-frame periods 2 and 3, respectively. And cyan (C) light. Yellow (Y) light is formed by adding red (R) and green (G) light, and cyan (C) light is formed by adding green (G) and blue (B) light.

  In the display unit 1, a voltage is applied between the upper and lower substrates only in the subframe period 1 to enter a “bright” state (a state in which incident light is transmitted) and display in red (R). Similarly, in the display units 2 and n, a voltage is applied between the upper and lower substrates only in the subframe periods 3 and 2, respectively, so that a “bright” state is obtained, and display in cyan (C) and yellow (Y) is performed.

  According to the driving method of the liquid crystal display element according to the previous application, one color display is completed in one subframe, and the light emission color of the backlight is not limited to the primary colors of R, G, B, but also Y and C By including color mixture such as the above, a color break can be prevented and a good display can be realized.

  In this liquid crystal display element driving method, the emission color of the backlight can be changed for each frame, so that any color display can be easily realized, while the mixed color of the three sub-frames is Since it does not become white and may always change, it is necessary to shield the light other than the display portion as much as possible. Therefore, it is difficult to realize only a display whose background is black.

JP-A-2005-070440

An object of the present invention is to provide a liquid crystal display device with good display quality.

According to one aspect of the present invention, a light source capable of emitting a plurality of colors, a first substrate pair on which light emitted from the light source is incident, and a surface facing the first substrate pair are formed. A light transmitting state and a light shielding state are maintained between a first electrode having a first pattern and an opposing surface of the first substrate pair, and a voltage is applied using the first electrode. A first liquid crystal layer capable of selectively controlling the second substrate pair, a second substrate pair on which light emitted from the first substrate pair is incident, and a surface opposite to the second substrate pair; A voltage is applied between the second electrode having the second pattern, which is an inverted pattern of the first pattern, and the opposing surface of the second substrate pair, and using the second electrode. And a second liquid crystal layer capable of selectively controlling a light transmitting state and a light shielding state, and disposed on the light incident surface side of the first substrate pair. 1 polarizing plate, a second polarizing plate disposed on the light emitting surface side of the second substrate pair, a third polarizing plate disposed on the light emitting surface side of the first substrate pair, A fourth polarizing plate disposed on the light incident surface side of the second substrate pair, and one frame period is time-divided into a plurality of subframe periods, and the light source emits light within each subframe period, and the light emission In synchronization with the first liquid crystal layer and a control device that controls the light transmission state and the light shielding state of the second liquid crystal layer, and the first liquid crystal display element includes the first pair of substrates, The first electrode, the first liquid crystal layer, the first polarizing plate, and the third polarizing plate are included, and the second liquid crystal display element includes the second substrate pair and the second liquid crystal display device. Electrode, the second liquid crystal layer, the second polarizing plate, and the fourth polarizing plate, and the first and second liquid crystal display elements. But both a liquid crystal display element of normally white liquid crystal display device of normally white in which the display portion and the background portion is defined is provided.
According to another aspect of the present invention, a light source capable of emitting a plurality of colors, a first substrate pair on which light emitted from the light source is incident, and a surface facing the first substrate pair are formed. The light transmission state and the light-shielding state are maintained between the first electrode having the first pattern and the opposing surface of the first substrate pair, and a voltage is applied using the first electrode. A first liquid crystal layer capable of selectively controlling the second substrate pair, a second substrate pair on which light emitted from the first substrate pair is incident, and an opposing surface of the second substrate pair, A voltage is applied between the second electrode having the second pattern, which is the reverse pattern of the first pattern, and the opposing surface of the second substrate pair, and using the second electrode. A second liquid crystal layer capable of selectively controlling a light transmitting state and a light shielding state, and a light incident surface side of the first pair of substrates. A first polarizing plate, a second polarizing plate disposed on the light emitting surface side of the second substrate pair, and a first polarizing plate disposed between the first substrate pair and the second substrate pair. 3 polarizing plates, one frame period is time-divided into a plurality of subframe periods, the light source emits light within each subframe period, and the first liquid crystal layer and the second liquid crystal are synchronized with the light emission. A first liquid crystal display element having the first substrate pair, the first electrode, the first liquid crystal layer, and the first liquid crystal display element. The second liquid crystal display element includes the polarizing plate and the third polarizing plate, and the second liquid crystal display element includes the second substrate pair, the second electrode, the second liquid crystal layer, and the second polarizing plate. And the third polarizing plate, and the first and second liquid crystal display elements are both normally white liquid crystal display elements. There, a liquid crystal display apparatus is provided in which the display portion and the background portion is defined.
According to another aspect of the present invention, a light source capable of emitting a plurality of colors, a first liquid crystal cell, a first substrate pair on which light emitted from the light source is incident, and the first Between the first electrode having the first pattern and the opposing surface of the first substrate pair, and a voltage is generated using the first electrode. An ECB-type first liquid crystal cell and a second liquid crystal cell , each including a first liquid crystal layer capable of selectively controlling a light-transmitting state and a light-shielding state by being applied. A second substrate pair that is formed on the opposing surface of the second substrate pair and the second pattern that is an inversion pattern of the first pattern. And the surface of the second substrate pair facing each other, and a voltage is applied using the second electrode to transmit light. On purpose comprises a second liquid crystal layer capable of selectively controlling the light shielding state, and a ECB-type second liquid crystal cell, a first polarizing disposed on the light incident side of the first substrate pair A plate, a second polarizing plate disposed on the light emitting surface side of the second substrate pair, and one frame period is time-divided into a plurality of subframe periods, and the light source emits light within each subframe period. And a control device for controlling the light transmitting state and the light blocking state of the first liquid crystal layer and the second liquid crystal layer in synchronization with the light emission, and the first liquid crystal layer and the second liquid crystal The orientation directions of the central molecules of the layer are orthogonal, and the first polarizing plate and the second polarizing plate are arranged so as to be normally black as a whole, and a display portion and a background portion are defined. A liquid crystal display device is provided.
Furthermore, according to another aspect of the present invention, a light source capable of emitting a plurality of colors, a first substrate pair on which light emitted from the light source is incident, and a surface opposite to the first substrate pair Formed between the first electrode having the first pattern and the opposing surface of the first pair of substrates, and applying a voltage using the first electrode, A first liquid crystal layer capable of selectively controlling a light shielding state; a second substrate pair on which light emitted from the light source is incident; and a surface of the second substrate pair opposed to each other. A voltage is applied between the second electrode having the second pattern, which is an inverted pattern of the second pattern, and the opposing surface of the second substrate pair, and applying a voltage using the second electrode. a second liquid crystal layer capable of selectively controlling the light-shielding state and light-transmitting state, distribution in the first and the light incident surface side of the second substrate pairs A first polarizing plate, the second polarizing plate arranged on the first and the light emitting surface side of the second substrate pairs, and time-dividing one frame period into a plurality of subframe periods, each sub A control device for causing the light source to emit light within a frame period and controlling the light transmitting state and the light shielding state of the first liquid crystal layer and the second liquid crystal layer in synchronization with the light emission ; Formed on one opposing surface of the pair of substrates, formed on the opposing other surface of the first substrate pair, and a third electrode constituting a part of the first electrode having the first pattern. The second electrode including the second pattern, which is formed on one surface facing the fourth electrode constituting the other part of the first electrode including the first pattern and the second substrate pair. A fifth electrode constituting a part of the electrode of the second substrate, and on the other surface of the second pair of substrates facing each other, And a sixth electrode which constitutes the other portion of the second electrode with a second pattern, wherein the first substrate pair is a second board-to-the same substrate pairs, the first liquid crystal The third liquid crystal layer and the second liquid crystal layer are the same liquid crystal layer, and the third electrode and the fifth electrode are multilayered through an insulating film, and the first substrate pair and the first liquid crystal layer are made the same . The second substrate pair is formed on one side of the substrate, and the fourth electrode and the sixth electrode are multi-layered via an insulating film so that the first substrate pair and the second substrate are the same. A liquid crystal display device is provided which is formed on the other one-side substrate of the pair of substrates and has a display portion and a background portion defined.

  According to the present invention, a liquid crystal display device with good display quality can be provided.

FIG. 1 shows a schematic configuration of a liquid crystal display device according to an embodiment.
The liquid crystal display element according to the embodiment includes an upper liquid crystal display element (background display element) 30, a lower liquid crystal display element (display unit display element) 40, a multi-color backlight 50, an LCD driver 61, a backlight driver 62, and a synchronous controller. 63 is comprised.

  The two-layer structure panel 20 includes an upper liquid crystal display element 30 and a lower liquid crystal display element 40. The multi-color backlight 50 is disposed below the two-layer structure panel 20 (lower liquid crystal display element 40). The multi-color backlight 50 is a backlight that can emit light of a plurality of colors, for example, red (R), green (G), and blue (B). For example, CCFL, inorganic LED, organic LED, etc. can be used as a light source.

  The LCD driver 61 drives the upper liquid crystal display element 30 and the lower liquid crystal display element 40. The backlight driver 62 drives the multi-color backlight 50. The synchronization controller 63 provides a synchronization signal so that the LCD driver 61 and the backlight driver 62 are driven in synchronization.

The upper liquid crystal display element 30 and the lower liquid crystal display element 40 are both normally white liquid crystal display elements, for example.
FIG. 2 is a schematic exploded perspective view showing an example of the two-layer structure panel 20. This figure shows a configuration example in which both the upper liquid crystal display element 30 and the lower liquid crystal display element 40 are normally white liquid crystal display elements. The upper and lower liquid crystal display elements 30 and 40 are, for example, twisted nematic (TN) mode liquid crystal display elements in which the retardation of the liquid crystal layer when no voltage is applied is set to the first minimum value of Gooch & Tarry. It is.

  The upper liquid crystal display element 30 includes an upper substrate 11, a lower substrate 12 disposed to face the upper substrate 11 substantially in parallel, a liquid crystal layer 15 held between the upper substrate 11 and the lower substrate 12, and a polarizing plate 16. , 17. The liquid crystal layer 15 is filled with liquid crystal molecules 15a which are TN liquid crystals having a twist angle of 90 °.

  The upper substrate 11 includes, for example, a transparent substrate 11a that is a flat glass substrate, an electrode 11b that is formed of a transparent conductive material such as ITO (indium tin oxide) on the transparent substrate 11a, and an alignment film that is formed on the electrode 11b. 11c is included.

  The lower substrate 12 includes a transparent substrate 12a, an electrode 12b formed on the transparent substrate 12a, and an alignment film 12c formed on the electrode 12b. The material for forming the transparent substrate 12 a, the electrode 12 b, and the alignment film 12 c may be the same as that of the upper substrate 11.

The upper substrate 11 and the lower substrate 12 are arranged to face each other so that the alignment films 11c and 12c face each other.
2 is defined as an angle coordinate that represents the orientation direction (major axis direction) of liquid crystal molecules with an azimuth angle θ rotated counterclockwise in a plane parallel to the lower substrate 12 with the right direction as a reference (0 °). To do.

  The alignment films 11c and 12c of the upper substrate 11 and the lower substrate 12 are rubbed. The rubbing direction applied to the alignment film 11c of the upper substrate 11 is the direction of 45 ° azimuth, and the rubbing direction applied to the alignment film 12c of the lower substrate 12 is the azimuth angle of 315 ° (−45 °). Direction. The liquid crystal molecules 15a in contact with the alignment films 11c and 12c are aligned parallel to the rubbing direction and tilted so that the end portion on the tip side of the arrow indicating the rubbing direction is lifted from the substrate. Since the alignment films are arranged to face each other, the end of the liquid crystal molecules 15a on the lower substrate 12 side that is lifted from the substrate corresponds to the end of the liquid crystal molecules 15a on the upper substrate 11 side that contacts the substrate. Tilt so that.

  The liquid crystal molecules 15a in the liquid crystal layer 15 are twisted in the azimuth direction to form a helical structure. This helical structure turns counterclockwise, the twist angle (twist angle, turn angle) is 90 °, and the azimuth angle θ in the alignment direction of the liquid crystal molecules located at the center in the thickness direction is 270 °.

  The polarizing plate 16 is in close contact with the outer surface of the upper substrate 11, and the polarizing plate 17 is in close contact with the outer surface of the lower substrate 12. The azimuth angle of the transmission axis (indicated by an arrow) of the polarizing plate 16 is 45 °, and the azimuth angle of the transmission axis (indicated by an arrow) of the polarizing plate 17 is 135 °. The polarizing plates 16 and 17 are arranged in crossed Nicols.

  In a state where no voltage is applied, the liquid crystal molecules 15a are TN aligned. The light transmitted through the polarizing plate 17 and incident on the lower substrate 12 travels in the liquid crystal layer 15 while rotating the polarization direction along the director of the liquid crystal molecules 15a, and is emitted from the upper substrate 11 when rotated 90 °. Therefore, the light passes through the polarizing plate 16 on the upper substrate 11 side. For this reason, “bright” display is realized.

  When a voltage is applied, the liquid crystal molecules 15a stand perpendicular to the substrates (the upper substrate 11 and the lower substrate 12), so that the light transmitted through the polarizing plate 17 and incident on the lower substrate 12 passes through the liquid crystal layer 15 as it is. Proceeds and is blocked by the polarizing plate 16. In this case, “dark (black)” display is realized. Thus, the upper liquid crystal display element 30 is a normally white type liquid crystal display element.

In addition, a favorable black level can be obtained at the time of voltage application by setting the retardation of the liquid crystal layer 15 when no voltage is applied to the first minimum value of Gooch & Tarry.
The upper liquid crystal display element 30 and the lower liquid crystal display element 40 have, for example, a similar structure, but are different in the electrode structure. This will be described in detail later. Moreover, the directions of the transmission axes of the upper and lower polarizing plates 16 and 17 are different. For the lower liquid crystal display element 40, the direction of the transmission axis of the upper polarizing plate 16 is a 135 ° direction, and the direction of the transmission axis of the lower polarizing plate 17 is a 45 ° direction.

  Since the transmission axis of the lower polarizing plate 17 of the upper liquid crystal display element 30 and the transmission axis of the upper polarizing plate 16 of the lower liquid crystal display element 40 are parallel, one of the two polarizing plates is omitted. Is also possible. For example, when the polarizing plate 16 of the lower liquid crystal display element 40 is omitted, the polarizing plate 17 of the upper liquid crystal display element 30 is a constituent element of the upper liquid crystal display element 30 and a constituent element of the lower liquid crystal display element 40. I think that there is.

The illustrated two-layer structure panel 20 is a normally white type as a whole.
The upper and lower liquid crystal display elements 30 and 40 of the two-layer structure panel 20 can be configured by a combination of various types of elements.

A combination of the upper and lower liquid crystal display elements 30 and 40 of the two-layer structure panel 20 will be described with reference to FIGS.
FIG. 3A shows a two-layer structure panel 20 having a four-polarizing plate structure in which the upper and lower liquid crystal display elements 30 and 40 each include two polarizing plates 16 and 17, and FIG. 3A, the polarizing plate 16 of the lower liquid crystal display element 40 is omitted, and the polarizing plate 17 of the upper liquid crystal display element 30 is a component of the upper liquid crystal display element 30 and the lower liquid crystal. The two-layer structure panel 20 having a configuration of three polarizing plates, which is a constituent element of the display element 40, is shown.

  3A and 3B, the angle coordinates are defined in a plane parallel to the lower substrate 12, as in FIG. In the figure, the right direction is the 0 ° direction, the left direction is the 180 ° direction, the back direction of the paper is 90 °, and the front side of the paper is the 270 ° direction.

Hereinafter, a case where the observer observes from a 270 ° azimuth will be described.
Reference is made to FIG. FIG. 3A shows a form in which two normally white TN liquid crystal display elements are stacked as shown in FIG. The arrangement of the upper and lower liquid crystal display elements 30 and 40 is arbitrary, but the light use efficiency is advantageous when the directions of the transmission axes of the polarizing plates 16 and 17 arranged on the surface where the upper and lower elements overlap are parallel. Therefore, the preferred setting of the transmission axis orientation of the polarizing plates 16 and 17 and the preferred orientation direction of the central molecules of the liquid crystal layer 15 of the upper and lower liquid crystal display elements 30 and 40 are determined. The orientation directions of the central molecules of the liquid crystal layer 15 of the upper and lower liquid crystal display elements 30 and 40 are preferably both 215 ° to 315 °, and it is best to make both equal to 270 °.

  Reference is made to FIG. FIG. 3B shows one polarizing plate disposed on the surface where the upper and lower elements overlap when the orientation directions of the central molecules of the liquid crystal layer 15 of the upper and lower liquid crystal display elements 30 and 40 are equal to 270 °. This is the mode.

  The twist angles of the liquid crystal molecules of the TN liquid crystal layer 15 of the upper and lower liquid crystal display elements 30 and 40 in the two-layer structure panel 20 shown in FIGS. 3A and 3B are, for example, 70 ° to 130 °. For example, both are equally 90 °. Although it is not necessary to match the twist angles of the liquid crystal molecules of the upper and lower liquid crystal display elements 30 and 40, it is convenient to operate them when they are equal. However, it is not necessary to align the twist direction.

  The upper and lower liquid crystal display elements 30 and 40 are not limited to the TN type, and may be, for example, a combination of birefringence controlled (ECB) liquid crystal display elements capable of normally white display.

  4A and 4B are schematic plan views showing a part of electrode patterns of the lower liquid crystal display element (display unit display element) 40 and the upper liquid crystal display element (background display element) 30, respectively. . Since the electrode pattern corresponds to the display pattern, each electrode unit corresponds to each display unit. In this figure, the electrode portions are shown with diagonal lines.

  Reference is made to FIG. The lower liquid crystal display element 40 is used to display a display part (character part). For this reason, the electrode pattern is also formed corresponding to the character pattern. The electrodes of the lower liquid crystal display element 40 have 7-segment electrode electrode portions 21 to 27 that can display, for example, 10 characters “0” to “9”.

  Reference is made to FIG. The upper liquid crystal display element 30 is used for displaying the background. For this reason, the electrode pattern is also formed corresponding to the background pattern (character pattern reversal pattern). The electrodes of the upper liquid crystal display element 30 have an electrode structure that is wired so that, for example, the inversion patterns of the electrode portions 21 to 27 of the 7-segment electrode that can display 10 characters “0” to “9” can be driven. . In the drawing, an electrode portion 28 is shown as a part thereof.

  As shown in FIG. 2 and FIGS. 3A and 3B, the two-layer structure panel 20 uses a liquid crystal display element having a two-layer structure even if it is not composed of two liquid crystal display elements on the upper side and the lower side. It can also be configured. In this case, a normally black liquid crystal cell having a two-layer cell structure is used.

  FIG. 5 is a schematic view showing a two-layer structure panel 20 configured using a liquid crystal display element having a two-layer cell structure. In this figure as well, angular coordinates are defined as in FIGS. 3 (A) and 3 (B). Hereinafter, as in the case described with reference to FIGS. 3A and 3B, a case where the observer observes from a 270 ° azimuth will be described.

The two-layer structure panel 20 includes an upper liquid crystal cell 30a, a lower liquid crystal cell 40a, a polarizing plate 16 on the upper liquid crystal cell 30a side, and a polarizing plate 17 on the lower liquid crystal cell 40a side.
The upper and lower liquid crystal cells 30a and 40a are both TN type liquid crystal cells, for example. The liquid crystal molecules of the liquid crystal layer 15 of both the cells 30a and 40a have the same size and a reverse twist angle. The twist angle is, for example, 70 ° to 130 °. The liquid crystal molecules of the liquid crystal layer 15 of the upper liquid crystal cell 30a have a twist angle of 90 ° clockwise, for example, and that of the lower liquid crystal cell 40a has a twist angle of 90 ° counterclockwise, for example.

  The orientation directions of the central molecules of the liquid crystal layer 15 of the upper and lower liquid crystal cells 30a and 40a are orthogonal to each other. The orientation direction of the center molecule of the liquid crystal layer 15 of the upper liquid crystal cell 30a is 180 ° to 360 °, for example, 315 °, and that of the lower liquid crystal cell 40a is 215 ° to 315 °, for example, 225 °.

  The lower substrate 12 of the upper liquid crystal cell 30a is in contact with the upper substrate 11 of the lower liquid crystal cell 40a. Further, the polarizing plate 16 is in close contact with the outer surface of the upper substrate 11 of the upper liquid crystal cell 30a, and the polarizing plate 17 is in close contact with the outer surface of the lower substrate 12 of the lower liquid crystal cell 40a.

In this way, the two-layer structure panel 20 can be configured using a liquid crystal display element having a two-layer cell structure.
Both the upper and lower liquid crystal cells 30a and 40a can be formed of ECB type liquid crystal cells, for example, vertical alignment type liquid crystal cells. In this case, the orientation direction of the center molecule of the liquid crystal layer 15 of the upper and lower liquid crystal cells 30a and 40a can be set to the same orientation as 90 °, for example. Moreover, you may make both orthogonal. When the two are orthogonal to each other, the liquid crystal molecules function in the same manner even when the alignment of the liquid crystal molecules when no voltage is applied is a horizontal alignment.

  If a multilayer electrode structure with an insulating layer is formed on one side substrate in the liquid crystal cell, the liquid crystal according to the embodiment shown in FIG. 1 can be obtained by using one liquid crystal cell without adopting the two-layer cell structure. Operation similar to that of the display element can be realized.

Hereinafter, a method of driving the liquid crystal display element according to the embodiment actually performed by the inventors will be described.
In the driving method, the upper liquid crystal display element (background display element) 30 and the lower liquid crystal display element (display unit display element) 40 are controlled to transmit light, block light, and emit light from the multi-color backlight 55. Display in synchronization.

  In one frame, a background display subframe is provided. In the background display subframe, in addition to displaying the background portion, a portion of the display portion (character portion) that is not used for display (for example, FIG. When “0” is displayed using the display units 21 to 27 shown in A), the display unit 24 displays a part that is not used for the display. Then, in the other subframes, the character areas to be actually displayed (in the above example, the display units 21 to 23 and 25 to 27 displaying “0”) are displayed.

  With such a driving method, it is possible to perform color display with the background arbitrarily changed while maintaining multicolor display performance in the display unit, and it is possible to achieve good display quality. This driving method can be combined with the driving method of the liquid crystal display element according to the previous proposal of the present inventors (Japanese Patent Laid-Open No. 2005-070440).

  In the following two driving examples, the two-layer structure panel 20 is configured such that (i) the upper liquid crystal display element (background display element) 30 and the lower liquid crystal display element (display unit display element) 40 are both normally white liquid crystals. This is an example of driving in two cases: a display element; and (ii) a case of a liquid crystal display element having a two-layer cell structure and a normally black type as a whole.

  The lower liquid crystal display element (display unit display element) 40 and the upper liquid crystal display element (background display element) 30 each have a 7-segment display electrode pattern and its inverted pattern shown in FIGS. 4 (A) and 4 (B), respectively. I used something. Further, static driving was adopted as a liquid crystal driving method.

  FIG. 6 shows a display realized by the following driving example. An area displayed in red is represented by “R”, an area displayed in yellow is represented by “Y”, and an area displayed in blue is represented by “B”. That is, the display units 22, 25, and 27 shown in FIGS. 4A and 4B are displayed in red (R), the display units 21, 23, and 26 are displayed in yellow (Y), and the display Parts 24 and 28 are displayed in blue (B).

  In the driving example, one frame period of 16.5 ms is divided into three subframe periods of 5.5 ms, and blue light is emitted from the backlight in the first subframe period (subframe period 1). . Further, red light was emitted in the second subframe period (subframe period 2), and yellow light was emitted in the third subframe period (subframe period 3).

  The time of one frame period is not limited to 16.5 ms, and it can be set so as to realize a display that does not flicker in human eyes. In addition, each subframe period is divided so as to be equal time, but is not limited thereto.

  In each display region (for example, a segment such as the display unit 21), the number of subframes that transmit light is at most one. For this reason, three-color display using red (R), yellow (Y), and blue (B) is performed, but the display color can be increased by increasing the number of subframe periods.

  The difference (blank time) between the drive voltage application start time to the liquid crystal display element and the backlight lighting start time was 2.5 ms. The blanking time can be longer than this. However, in that case, in order to ensure the same display quality, it is necessary to improve the light emission luminance of the backlight.

  In the table showing the following driving examples, “on” in the column of LCD indicates that a driving voltage of 5 V is applied to the liquid crystal layer. “Off” indicates a voltage non-application state (0 V). Therefore, for example, in a normally white mode liquid crystal display element, light is transmitted when “off” and light is not transmitted when “on”.

  FIG. 7 is a table showing a first driving example. In the first driving example, the upper liquid crystal display element 30 and the lower liquid crystal display element 40 are both normally white TN mode liquid crystal display elements, and the liquid crystal display element shown in FIG. It was. The manufactured two-layer structure panel 20 of the liquid crystal display element has a configuration shown in FIG. The rise and fall response speeds of the liquid crystal layer 15 of the upper and lower liquid crystal display elements 30 and 40 are both 2 ms.

Reference is made to the column of the lower liquid crystal display element for displaying the display section.
For the display unit 21, only the subframe period 3 is “off (transmission)”. For this reason, “yellow” which is the backlight lighting color in the subframe period 3 is displayed.

For the display unit 22, only the subframe period 2 is “off (transmission)”. For this reason, “red” which is the backlight lighting color in the subframe period 2 is displayed.
Regarding the display units 23, 24, 25, 26, and 27, since only the subframe periods 3, 1, 2, 3, and 2 are “off (transmission)” in order, “yellow”, “blue”, “red” ","yellow"
“Red” is displayed.

Reference is made to the column of the upper liquid crystal display element for displaying the background.
For the display unit 28, only the subframe period 1 is “off (transmission)”. Therefore, “blue” which is the backlight lighting color in the subframe period 1 is displayed.

As a result, the color display including the background portion of the embodiment shown in FIG. 6 was successfully performed.
FIG. 8 is a table showing a second driving example. In the second driving example, the liquid crystal display element shown in FIG. 1 was manufactured using the normally black type liquid crystal display element operating in the two-layer structure shown in FIG.

  A vertical alignment mode liquid crystal cell was used for both the upper and lower liquid crystal cells. The upper and lower two cells were directly overlapped, and a polarizing plate was attached on the upper and lower sides (so that the two overlapped cells were sandwiched). The direction of the transmission axis of the polarizing plate attached on the upper side of the cell was 45 ° direction, the direction of the transmission axis of the polarizing plate attached on the lower side of the cell was 135 ° direction, and a crossed Nicol arrangement was adopted.

In the case of a normally black mode liquid crystal display element, light is transmitted when “on”, and light is not transmitted when “off”.
Accordingly, for the display unit 21 of the lower liquid crystal display element, for example, “on (transmission)” is displayed only in the subframe period 3, and “yellow” that is the backlight lighting color in the subframe period 3 is displayed.

  Further, since the display unit 28 of the upper liquid crystal display element is “on (transmission)” only in the subframe period 1, “blue” that is the backlight lighting color in the subframe period 1 is displayed.

Even when a liquid crystal display element having a two-layer structure was used, the color display including the background portion of the embodiment shown in FIG. 6 could be satisfactorily performed.
The inventors of the present invention adopted two TN-mode liquid crystal cells having the same twist angle and opposite twist directions as upper and lower cells, and stacked them so that the liquid crystal layer center molecules were orthogonal to each other. A TN normally black mode two-layer structure liquid crystal display element was manufactured and a driving experiment was conducted in the same manner. In this case as well, the color display including the background portion as shown in FIG. did it.

  The inventors of the present application confirmed that color display is possible if the response speed of the liquid crystal cell is a panel of 20 ms or less, both rising and falling. This indicates that color display is possible even when the transmittance of light emitted from the backlight is approximately 30% or less.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these. For example, in the embodiments, normally black mode and normally white mode liquid crystal cells are used, but other operation modes may be used as long as they are operation modes capable of high-speed response. It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  It can be used for all liquid crystal display elements that perform FS driving.

It is a figure which shows schematic structure of the liquid crystal display element by an Example. 2 is a schematic exploded perspective view showing an example of a two-layer structure panel 20. FIG. (A) And (B) is a figure for demonstrating the combination of the upper side and lower side liquid crystal display elements 30 and 40 of the two-layer structure panel 20. FIG. (A) And (B) is a schematic top view which shows a part of electrode pattern of the lower side liquid crystal display element (display part display element) 40 and the upper side liquid crystal display element (background display element) 30, respectively. It is the schematic which shows the two-layer structure panel 20 comprised using the liquid crystal display element of a two-layer cell structure. It is a figure which shows the display implement | achieved by the example of a drive. It is a table | surface which shows the 1st drive example. It is a table | surface which shows the 2nd drive example. (A) And (B) is a schematic disassembled perspective view which shows the example of an internal structure of the liquid crystal display element which performs a color display, respectively. It is a figure which shows an example of the drive timing chart of FS drive method. It is a figure which shows an example of the drive timing chart of the FS drive method by a previous proposal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Upper substrate 12 Lower substrate 11a, 12a Transparent substrate 11b, 12b Electrode 11c, 12c Alignment film 15 Liquid crystal layer 15a Liquid crystal molecule 16, 17 Polarizing plate 20 Two-layer structure panel 21-28 Electrode part (display part)
30 Upper LCD display element (background display element)
30a Upper liquid crystal cell 31 Upper substrate 32 Lower substrate 39 Liquid crystal layer 39a Liquid crystal molecule 40 Lower liquid crystal display element (display unit display element)
40a Lower liquid crystal cell 41 Upper polarizing plate 42 Lower polarizing plate 49 Area color filter 49r Red portion 49g Green portion 49b Blue portion 49w White portion 50 Multi-color backlight 51 Black mask 52 White backlight 53 Drive circuit 54 Backlight synchronous drive Circuit 55 Multi-color backlight 61 LCD driver 62 Backlight driver 63 Synchronous controller

Claims (7)

A light source capable of emitting multiple colors;
A first pair of substrates on which light emitted from the light source is incident;
A first electrode formed on opposing surfaces of the first pair of substrates and comprising a first pattern;
A first liquid crystal layer that is held between opposing surfaces of the first pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the first electrode; ,
A second substrate pair on which the light emitted from the first substrate pair enters;
A second electrode comprising a second pattern formed on opposite surfaces of the second pair of substrates, the second pattern being an inverted pattern of the first pattern;
A second liquid crystal layer that is held between opposing surfaces of the second pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the second electrode; ,
A first polarizing plate disposed on the light incident surface side of the first substrate pair;
A second polarizing plate disposed on the light exit surface side of the second substrate pair;
A third polarizing plate disposed on the light exit surface side of the first substrate pair;
A fourth polarizing plate disposed on the light incident surface side of the second substrate pair;
One frame period is time-divided into a plurality of subframe periods, the light source is caused to emit light within each subframe period, and the light transmission states of the first liquid crystal layer and the second liquid crystal layer are synchronized with the light emission. A control device for controlling the light shielding state,
A first liquid crystal display element including the first substrate pair, the first electrode, the first liquid crystal layer, the first polarizing plate, and the third polarizing plate;
A second liquid crystal display element including the second substrate pair, the second electrode, the second liquid crystal layer, the second polarizing plate, and the fourth polarizing plate;
The first and second liquid crystal display elements are both normally white liquid crystal display elements,
A normally white liquid crystal display device in which a display portion and a background portion are defined. A light source capable of emitting multiple colors;
A first pair of substrates on which light emitted from the light source is incident;
A first electrode formed on opposing surfaces of the first pair of substrates and comprising a first pattern;
A first liquid crystal layer that is held between opposing surfaces of the first pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the first electrode; ,
A second substrate pair on which the light emitted from the first substrate pair enters;
A second electrode comprising a second pattern formed on opposite surfaces of the second pair of substrates, the second pattern being an inverted pattern of the first pattern;
A second liquid crystal layer that is held between opposing surfaces of the second pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the second electrode; ,
A first polarizing plate disposed on the light incident surface side of the first substrate pair;
A second polarizing plate disposed on the light exit surface side of the second substrate pair;
A third polarizing plate disposed between the first substrate pair and the second substrate pair;
One frame period is time-divided into a plurality of subframe periods, the light source is caused to emit light within each subframe period, and the light transmission states of the first liquid crystal layer and the second liquid crystal layer are synchronized with the light emission. A control device for controlling the light shielding state,
A first liquid crystal display element including the first substrate pair, the first electrode, the first liquid crystal layer, the first polarizing plate, and the third polarizing plate;
A second liquid crystal display element including the second substrate pair, the second electrode, the second liquid crystal layer, the second polarizing plate, and the third polarizing plate;
The first and second liquid crystal display elements are both normally white liquid crystal display elements,
A liquid crystal display device in which a display portion and a background portion are defined. A light source capable of emitting multiple colors;
A first liquid crystal cell,
A first pair of substrates on which light emitted from the light source is incident;
A first electrode formed on opposing surfaces of the first pair of substrates and comprising a first pattern;
A first liquid crystal layer that is held between opposing surfaces of the first pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the first electrode; ,
An ECB-type first liquid crystal cell including:
A second liquid crystal cell,
A second substrate pair on which the light emitted from the first substrate pair enters;
A second electrode comprising a second pattern formed on opposite surfaces of the second pair of substrates, the second pattern being an inverted pattern of the first pattern;
A second liquid crystal layer that is held between opposing surfaces of the second pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the second electrode; ,
An ECB-type second liquid crystal cell including:
A first polarizing plate disposed on the light incident surface side of the first substrate pair;
A second polarizing plate disposed on the light exit surface side of the second substrate pair;
One frame period is time-divided into a plurality of subframe periods, the light source is caused to emit light within each subframe period, and the light transmission states of the first liquid crystal layer and the second liquid crystal layer are synchronized with the light emission. A control device for controlling the light shielding state,
The first liquid crystal layer and the second liquid crystal layer have orthogonal orientations of central molecules, and the first polarizing plate and the second polarizing plate are normally black as a whole. Placed in
A liquid crystal display device in which a display portion and a background portion are defined. A light source capable of emitting multiple colors;
A first pair of substrates on which light emitted from the light source is incident;
A first electrode formed on opposing surfaces of the first pair of substrates and comprising a first pattern;
A first liquid crystal layer that is held between opposing surfaces of the first pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the first electrode; ,
A second substrate pair on which light emitted from the light source is incident;
A second electrode comprising a second pattern formed on opposite surfaces of the second pair of substrates, the second pattern being an inverted pattern of the first pattern;
A second liquid crystal layer that is held between opposing surfaces of the second pair of substrates and that can selectively control a light-transmitting state and a light-blocking state by applying a voltage using the second electrode; ,
A first polarizing plate disposed on the light incident surface side of the first and second substrate pairs;
A second polarizing plate disposed on the light exit surface side of the first and second substrate pairs;
One frame period is time-divided into a plurality of subframe periods, the light source is caused to emit light within each subframe period, and the light transmission states of the first liquid crystal layer and the second liquid crystal layer are synchronized with the light emission. A control device for controlling the light shielding state,
A third electrode that is formed on one opposing surface of the first substrate pair and that constitutes a part of the first electrode comprising the first pattern;
A fourth electrode forming the other part of the first electrode, which is formed on the other opposite surface of the first substrate pair, and includes the first pattern;
A fifth electrode that is formed on one opposing surface of the second substrate pair and forms a part of the second electrode including the second pattern;
A sixth electrode which is formed on the other opposing surface of the second substrate pair and which constitutes the other part of the second electrode provided with the second pattern;
Including
The first substrate pair and the second substrate pair are the same substrate pair;
The first liquid crystal layer and the second liquid crystal layer are the same liquid crystal layer;
The third electrode and the fifth electrode are multilayered via an insulating film, and are formed on one side substrate of the first substrate pair and the second substrate pair that are the same,
The fourth electrode and the sixth electrode are multilayered via an insulating film, and are formed on the other one-side substrate of the first substrate pair and the second substrate pair,
A liquid crystal display device in which a display portion and a background portion are defined.   The control device performs display control of the display unit by controlling the first liquid crystal layer, and performs display control of the background unit by controlling the second liquid crystal layer. 5. The liquid crystal display device according to any one of 4 above.   The display unit is formed of a plurality of display units, and the control device displays each of the plurality of display units with light transmitted in at most one subframe period of the plurality of time-divided subframe periods. The liquid crystal display device according to claim 5, wherein the first liquid crystal layer is controlled in such a manner.   Among the plurality of display units, the control device includes the first liquid crystal layer and the display unit that is not used for display expressed in the display unit and the background unit is displayed in the same color. The liquid crystal display device according to claim 6, wherein the second liquid crystal layer is controlled.

Images