JP2006162859A - Liquid crystal display and startup method of the liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display, with which successful display quality can be obtained, without displaying mottling island-shaped patterns on a display screen at startup, and to provide a startup method of the device. <P>SOLUTION: The liquid crystal display device A including a liquid crystal display panel 1 which is provided with a transmission display element operating in an OCB mode and a reflection display element operating in a R-OCB mode within a single pixel region, a backlight device 4 which is arranged on a rear surface 1b side of the liquid crystal display panel 1 and irradiates the transmission display element with a backlight beam, and a backlight controller 7 which sets the backlight device 4 in light-out state in a transition period, when the liquid crystal molecules in the transmission display element transfer from spray orientation to bend orientation is employed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device and a method for starting the liquid crystal display device, and in particular, a liquid crystal display including a multi-gap structure liquid crystal display panel in which a reflective display portion and a transmissive display portion are provided in one pixel. The present invention relates to a method for starting an apparatus.

  In the field of display devices, active matrix display devices that can obtain high display quality are widely used. In this display device, a switching element is provided for each of a large number of pixel electrodes, and characteristics such as enlargement and high definition can be easily obtained by reliable switching for each pixel electrode. ing.

In recent years, reduction of power consumption has been demanded, and it has been demanded to increase the brightness of display by making the pixel area as large as possible. For this reason, a structure in which a thick insulating film is formed on the entire surface of the active matrix substrate and a reflective pixel electrode is formed on the insulating film has been put into practical use. In such a structure in which the pixel electrode is placed on the insulating film, an electrical short circuit can be prevented between the scanning line, the signal line, and the like arranged in the lower layer of the insulating film and the pixel electrode arranged in the upper layer. Therefore, it is possible to form a pixel electrode with a wide area so as to overlap these wirings. As a result, almost all of the pixel area including a switching element such as a thin film transistor (hereinafter abbreviated as TFT), a scanning line, and a signal line can be used as a pixel area contributing to display. It is possible to increase the rate and obtain a bright display.
In addition, the liquid crystal display mode using a reflective pixel electrode alone cannot be used in a dark place, so that the reflective liquid crystal display device can be partially transmissively displayed with a backlight attached to the liquid crystal display device. The transflective liquid crystal display device is widely used.

Recently, a liquid crystal display device operating in the OCB mode has attracted attention. The OCB mode is a mode in which gradation display is performed by utilizing the fact that liquid crystal molecules are in a bent alignment state when a voltage is applied, and the pretilt angle on one alignment film side gradually changes as a voltage is further applied. This OCB mode is characterized in that it can respond at high speed and has a high viewing angle.
Recently, as described in Patent Document 1, among the liquid crystal layers sandwiched between a pair of alignment films, one alignment film is parallel alignment, and the other alignment film is vertical alignment. An R-OCB mode in which molecules are hybrid-oriented has also been proposed.

Therefore, in a transflective liquid crystal display device in which the reflective liquid crystal display device can be partially transmissively displayed, a liquid crystal display device in which the transmissive region is operated in the OCB mode and the reflective region is operated in the R-OCB mode is provided. When configured, it can be expected to realize a transflective liquid crystal display device excellent in both high-speed response and reflection display and transmission display.
JP-A-9-146086

  However, the above-described transflective liquid crystal display device has a problem that a mottled island pattern is generated on the display screen when the device is activated. This requires a period of several seconds for the liquid crystal molecules in the transmission region of the device to reach the bend alignment from the splay alignment before startup, while the liquid crystal molecules in the reflection region of the device are always before and after startup. This is because it is in a hybrid alignment state, and there are two alignment states, splay alignment and hybrid alignment, in the liquid crystal layer when the apparatus is activated. In the case where bend alignment and hybrid alignment exist at the same time, a mottled island pattern does not occur.

  The present invention has been made in view of the above-described problems. In a dual-gap type (multi-gap type) transflective liquid crystal display device in which the thickness of the liquid crystal layer is different between the reflective display unit and the transmissive display unit. It is an object of the present invention to provide a liquid crystal display device capable of obtaining good display quality without displaying a mottled island pattern on the display screen at the time, and a method for starting the device.

In order to achieve the above object, the present invention employs the following configuration.
The liquid crystal display device of the present invention includes a liquid crystal display panel in which a transmissive display unit operating in the OCB mode and a reflective display unit operating in the R-OCB mode are provided in one pixel region, and a back surface side of the liquid crystal display panel. A backlight device arranged to irradiate the transmissive display portion with backlight light, and a backlight device that turns off the backlight device during a transition period until liquid crystal molecules in the transmissive display portion transition from a splay alignment to a bend alignment. And a light control unit.

  According to the above configuration, since the backlight device is turned off during the transition period until the liquid crystal molecules in the transmissive display section transition from the splay alignment to the bend alignment, only the image by the reflective display section is displayed on the display screen. Will be displayed. Thereby, the mottled island-like pattern produced by the presence of two orientation states of splay orientation and hybrid orientation is not displayed at the time of activation, and the display quality can be improved.

  The liquid crystal display device of the present invention is the liquid crystal display device described above, and is characterized in that a startup display control unit that displays a startup screen on the reflective display unit during the transition period is provided.

  According to said structure, since a starting screen is displayed in the said reflective display part during a transition period, a clear starting screen can be displayed.

  The liquid crystal display device of the present invention is the liquid crystal display device described above, wherein the liquid crystal display panel includes a pair of transparent substrates facing each other with a liquid crystal layer interposed therebetween, and the inner surface side of one transparent substrate Are provided with a common electrode and a common alignment film in order from the one transparent substrate side, and on the inner surface side of the other transparent substrate are provided a plurality of switching elements and a plurality of pixel electrodes connected to each switching element. An alignment film is provided on the switching element and the pixel electrode, a part of the pixel electrode is a reflective electrode that reflects incident light from the one transparent substrate side, and a remaining part of the pixel electrode is The transmissive electrode transmits the backlight from the other transparent substrate side, the reflective electrode formation region is the reflective display portion, and the transmissive electrode formation region is the front. Characterized in that it is a transmission display unit.

  According to the above configuration, since the transmissive display unit and the reflective display unit are provided in the formation region of one pixel electrode, high-speed response of image display can be achieved, and both reflective display and transmissive display can be achieved. A transflective liquid crystal display device excellent in the above can be configured.

  Next, a method for starting a liquid crystal display device according to the present invention includes a liquid crystal display panel in which a transmissive display unit operating in the OCB mode and a reflective display unit operating in the R-OCB mode are provided in one pixel region, and the liquid crystal display. A startup method of a liquid crystal display device comprising a backlight device arranged on the back side of the panel and irradiating the transmissive display portion with backlight light, wherein the liquid crystal molecules in the transmissive display portion are changed from splay alignment to bend alignment. The backlight device is turned off during the transition period until the transition to.

  According to the above configuration, since the backlight device is turned off until the liquid crystal molecules in the transmissive display section transition from the splay alignment to the bend alignment, only the image by the reflective display section is displayed on the display screen. Thus, the mottled island pattern generated by the presence of two orientation states of splay orientation and hybrid orientation at the time of startup is not displayed, and the display quality can be improved.

  According to another aspect of the invention, there is provided a method for starting a liquid crystal display device, wherein the start screen is displayed on the reflective display unit during the transition period.

  According to said structure, since a starting screen is displayed in the said reflective display part during a transition period, a clear starting screen can be displayed.

  As described above, according to the liquid crystal display device and the activation method of the present invention, it is possible to obtain good display quality without displaying a mottled island pattern on the display screen at the time of activation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings below, the film thicknesses and dimensional ratios of the respective components are appropriately changed for easy understanding of the drawings.

1 and 2 show an example of a transflective liquid crystal display device (liquid crystal display device) according to the present invention. As shown in FIG. 1, a transflective liquid crystal display device A includes a liquid crystal display panel 1 as a main body, a backlight device 4 disposed on the back surface 1b side of the liquid crystal display panel 1, a backlight control unit 7, The activation display control unit 8 is provided.
The liquid crystal display panel 1 is formed with a plurality of pixel regions as will be described later, and each pixel region is provided with a transmissive display unit that operates in the OCB mode and a reflective display unit that operates in the R-OCB mode. Yes. The backlight control unit 7 controls the backlight device 4 so that the backlight device 4 is turned on or off according to the state of the liquid crystal display panel 1. That is, the backlight control unit 7 turns off the backlight device 4 during the transition period until the liquid crystal molecules in the transmissive display unit transition from the splay alignment to the bend alignment. Furthermore, the activation display control unit 8 controls the liquid crystal display panel 1 so that the activation screen is displayed on the reflective display unit. Hereinafter, the liquid crystal display panel 1, the backlight device 4, the backlight control unit 7, and the activation display control unit 8 will be sequentially described in detail.

"LCD panel"
As shown in FIGS. 1 and 2, the liquid crystal display panel 1 includes an active matrix substrate (one transparent substrate) 2 on the side where the switching element 10 is formed, and a counter substrate (the other transparent substrate) provided to face the active matrix substrate. Substrate) 3 and a liquid crystal layer 5 as a light modulation layer held between the substrates 2 and 3. Further, on the outer surface side of the counter substrate 3, a phase difference plate (not shown) and a polarizing plate are sequentially laminated. Furthermore, a retardation plate (not shown) and a polarizing plate are laminated on the outer surface side of the active matrix substrate 2.

  As shown in FIG. 2, the counter substrate 3 is configured by sequentially arranging a color filter 42, a common electrode 43, and a common alignment film 44 inside a substrate 41 (one transparent substrate) (on the liquid crystal layer 5 side). Yes. The active matrix substrate 2 includes a substrate 6 (the other transparent substrate), a TFT (switching element) 10 formed on the substrate 6, a pixel electrode 11 connected to the TFT 10, a reflector 20, and a pixel electrode. 11 and an alignment film 29 stacked on top of each other. The liquid crystal layer 5 is disposed between the alignment films 29 and 44. The outer surface side of the substrate 41 is the display surface 1a of the liquid crystal display panel.

  The pixel electrode 11 includes a transmissive electrode 11a laminated on the substrate 6 and a reflective electrode 11b that constitutes the reflector 20 together with the insulating film 20a. Each of the transmissive electrode 11a and the reflective electrode 11b is connected to the TFT 10. In the liquid crystal display device according to the present embodiment, the reflective electrode 11b is formed in the reflective display portion 35, and the transmissive electrode 11a is formed in the transmissive display portion 36.

  In addition, a plurality of scanning lines and signal lines (not shown) are formed on the substrate 6 so as to be electrically insulated along the row direction and the column direction, and a TFT 10 is formed in the vicinity of the intersection of each scanning line and signal line. Has been. In the present invention, a region where the pixel electrode 11 (11a, 11b) is formed on the substrate 6 is called a pixel region M, and a region where the TFT 10 is formed, a region where a scanning line and a signal are formed are respectively element regions. This is called a wiring area.

  The TFT 10 has an inverted staggered structure, and a gate electrode 13, a gate insulating film 15, an i-type semiconductor layer 14, a source electrode 17 and a drain electrode 18 are formed in this order from the bottom layer of the substrate 6. An etching stopper layer 9 is formed between the source electrode 17 and the drain electrode 18. That is, a part of the scanning line is extended to form the gate electrode 13, and the island-like semiconductor layer 14 is formed on the gate insulating film 15 covering the gate line 13 so as to straddle the gate electrode 13 in plan view. A source electrode 17 is formed on one end of the i-type semiconductor layer 14 via an n-type semiconductor layer 16, and a drain electrode 18 is formed on the other end via an n-type semiconductor layer 16.

  In addition, a transmissive electrode 11a (pixel electrode 11) made of a transparent electrode material such as ITO is formed directly on the substrate body 6 at the center of a rectangular region surrounded by the scanning lines and the signal lines. ing. Thus, the transmissive electrode 11a is formed in the same plane position as the previous gate electrode 13. These transmissive electrodes 11a are directly connected to the connecting portion 17a at one end of the source electrode 17 connected so as to ride on the one end 11c, and are formed in a rectangular shape in plan view.

  Further, an insulating film 20a made of an organic material is laminated on the substrate 6, and a reflective electrode 11b (pixel electrode 11) made of a highly reflective metal material such as Al or Ag is formed on the insulating film 20a. Yes. The reflector 20 is constituted by the insulating film 20a and the reflective electrode 11b. The reflective electrode 11b is formed on the insulating film 20a so as to have a rectangular shape in plan view that is slightly smaller than a region surrounded by the previous scanning line and signal line.

  The insulating film 20a is an organic insulating film made of acrylic resin, polyimide resin, benzocyclobutene polymer (BCB) or the like, and strengthens the protection function of the TFT 10. The insulating film 20a is laminated on the substrate 6 relatively thickly to ensure insulation between the transmissive electrode 11a, the TFT 10, and various wirings, and to prevent a large parasitic capacitance from being generated between the transmissive electrode 11a. The step structure on the substrate 6 formed by the TFT 10 and various wirings is flattened by the thick insulating film 20a.

  Next, a contact hole 21 is provided in the insulating film 20a so as to reach one end portion 17a of each source electrode 17, and a recess 22 is formed so as to be positioned on the previous transmissive electrode 11a. A portion of the reflective electrode 11b corresponding to the position where the recess 22 is formed is formed with a planar through hole 23 that matches the opening 22a of the recess 22. These recesses 22 are formed so that most of the insulating film 20a is removed in the depth direction and only a part of the insulating film 20a is left as a coating layer 20b on the bottom 22b side, and the planar shape of the recess 22 is the same as that of the transmissive electrode 11a. It is formed in a strip shape slightly shorter than the transmissive electrode 11a so as to correspond to the planar shape.

  As described above, in each pixel region, the formation region of the recess 22 is the transmissive display unit 30 that transmits the incident light (light emitted from the backlight 4) from the active matrix substrate 2 side, and the reflective electrode A non-perforated portion 11b (portion where the through-hole 23 is not formed) serves as a reflective display portion 35 that reflects incident light from the counter substrate 3 side.

  Further, one of the pixel electrodes 11 (11a, 11b) corresponds to approximately one pixel region, and the area of the through hole 23 corresponds to the light passage region in the transmissive display, so that the entire area of the previous pixel electrode 11 It is preferable that the area ratio of the through-holes 23 in the range of 20 to 70%, for example, 50%. Furthermore, in this embodiment, only one through hole 23 is formed in the pixel electrode 11, but a plurality of through holes may be formed in the pixel electrode 11. In this case, the total area of the plurality of through holes is set to a range of 20 to 60% of the entire area of the pixel electrode 11. Of course, in that case, a concave portion is provided under each through hole in accordance with the formation position of the plurality of through holes.

  In the contact hole 21 provided in the insulating film 20a, a conductive portion 25 made of a conductive material is formed. Through the conductive portion 25, the reflective electrode 11b and the source electrode 17 disposed on the lower layer side of the insulating film 20a are formed. And are electrically connected. Therefore, the source electrode 17 is electrically connected to both the transmissive electrode 11a and the reflective electrode 11b.

On the substrate 6 configured as described above, an alignment film 29 made of polyimide or the like subjected to a predetermined alignment process such as rubbing is further formed so as to cover the reflector 20 and the recess 22. The alignment film 29 includes a first alignment film 29 a stacked on the entire surface of the substrate 6 and a second alignment film 29 b stacked only in the recess 22. That is, only the first alignment film 29a is stacked on the reflective electrode 11b, while the second alignment film 29b is stacked on the transmissive electrode 11a in the recess 22. The pretilt angle of the liquid crystal molecules by the first alignment film 29a is set larger than the pretilt angle of the liquid crystal molecules by the second alignment film 29b. That is, the pre-tilt angle of the first alignment film 29a is set in the range of 40 ° to 90 °, and the pre-tilt angle of the second alignment film 29b is set in the range of 10 ° or less.

  The first alignment film 29a is preferably a polyimide-based alignment film that exhibits vertical alignment. Further, the second alignment film 29b is preferably made of polyimide and exhibiting parallel alignment properties, and in particular, a film whose pretilt angle can be set to 10 ° or less is preferable. Examples of the first and second alignment films 29a and 29b include PIA-5560 manufactured by Chisso Petrochemical Co., Ltd.

  Next, in the recess 22 formed in the insulating film 20a, a step portion 22c that is a side wall of the recess 22 corresponding to the thickness of the insulating film 20a is formed. In the present embodiment, the inclination angle of the step portion 22c is set in a range of 25 ° to 55 °. With this configuration, light can be reflected at the stepped portion 22c, the boundary between the transmitting portion 30 and the reflecting portion 35 is not conspicuous, and display unevenness can be prevented. In particular, it is desirable that the inclination angle of the stepped portion 22c matches the pretilt angle of the liquid crystal molecules on the second alignment film 29b. Thereby, the boundary between the transmissive display unit 30 and the reflective display unit 35 is not conspicuous, and display unevenness can be prevented.

Next, the counter substrate 3 is formed with a color filter layer 42 as shown in FIG. 2 on the surface of the translucent substrate 41 made of glass, plastic or the like on the liquid crystal layer 5 side.
The color filter layer 42 has a structure in which color filters that transmit light of wavelengths of red (R), green (G), and blue (B) are periodically arranged, and each color filter has a pixel electrode. 11 (11a, 11b). In the color filter layer 42, a light shielding layer such as a black matrix is formed in a lattice shape in a region where the color filter is not formed.

  In addition, the color filter layer 42 is disposed on the reflective portion 35, the reflective color filter layer 42a, the transparent resin layer 42b laminated on the reflective color filter layer 42a, and the transmissive portion 30 for reflection. The transmission color filter layer 42c is integral with the color filter layer 42a for transmission. The thickness of the reflective color filter layer 42a is half the thickness of the transmissive color filter layer 42c. Further, the total thickness of the reflective color filter layer 42a and the transparent resin layer 42b is substantially the same as the thickness of the transmissive color filter layer 42c. Thereby, the surface of the color filter layer 42 on the liquid crystal layer 5 side is a flat surface.

  Since the thickness of the color filter layer 42a is set to one half of the thickness of the color filter layer 42c, the occurrence of color unevenness in the transmissive display unit 30 and the reflective display unit 35 can be prevented, and the contrast can be made constant. Brightness can be improved. Further, since the surface of the color filter layer 42 on the liquid crystal layer 5 side is a flat surface, the cell gap of the liquid crystal display panel 1 can be easily controlled.

  A transparent counter electrode (common electrode) 43 such as ITO and a common alignment film 44 are formed on the liquid crystal layer side of the color filter layer 42 described above. The common alignment film 44 is made of polyimide or the like that has been subjected to a predetermined alignment process such as rubbing, and is set to a pretilt angle substantially equal to the pretilt angle of the second alignment film 29b. An example of the common alignment film 44 is PIA-5560 manufactured by Chisso Petrochemical Co., Ltd.

  The substrates 2 and 3 configured as described above are held in a state of being spaced apart from each other by a spacer (not shown) and are applied in a rectangular frame shape around the substrate as shown in FIG. The thermosetting sealing material 45 is bonded and integrated. Then, liquid crystal is sealed in a space sealed by the substrates 2 and 3 and the sealing material 45 to form a liquid crystal layer 5 as a light modulation layer, and the liquid crystal display panel 1 is configured.

In the transflective liquid crystal display device A of the present embodiment, the recess 22 is formed in the insulating film 20a as described above, and the liquid crystal is introduced into the recess 22 as well. The thickness d ₃ is larger than the thickness d ₄ of the liquid crystal layer 5 in the reflective portion 35, and preferably the thickness d ₃ of the liquid crystal layer 5 in the transmissive portion 30 is the thickness d ₄ of the liquid crystal layer 5 in the reflective portion 35. Is approximately twice as large as In other words, the sum of the thickness of the reflector 20 and the thickness d ₄ of the liquid crystal layer 5 in the reflection portion 35 is equal to the thickness d ₃ of the liquid crystal layer 5 in the transmission portion 30.
Since d ₄ is set to be approximately twice d ₃ , the optical path length of the light transmitted through the liquid crystal layer 5 in the reflective display section 35 and the optical path length of the light transmitted through the liquid crystal layer 5 in the transmissive display section 30 are set. Can be almost matched.

Next, the optical characteristics of the liquid crystal display panel 1 will be described.
The liquid crystal layer 5 is made of liquid crystal molecules that are in a nematic state at room temperature. For example, AP-5517XX manufactured by Chisso Petrochemical Co., Ltd. can be exemplified.
In the liquid crystal layer 5 in the transmissive display unit 30, when the liquid crystal display panel 1 is activated and a transition voltage (voltage for white display) is applied, the alignment state of the liquid crystal molecules transitions from the splay alignment to the vent alignment. Thereafter, when the voltage is gradually increased from the transition voltage, the pretilt angle of the liquid crystal molecules in the vicinity of the alignment films 44 and 29a gradually increases according to the applied voltage, and hierarchical display becomes possible. As described above, the liquid crystal display device of the present embodiment is configured to operate in the OCB mode in the transmissive display unit 30.

  Here, splay alignment is an alignment state in which most of the liquid crystal molecules contained in the liquid crystal layer are parallel alignment (pretilt angle is 4 ° to 8 °). On the other hand, the vent alignment means that the liquid crystal molecules in the vicinity of the common alignment film 44 and the second alignment film 29b are in parallel alignment (the pretilt angle is 4 ° to 8 °), and the liquid crystal molecules in the vicinity of the center of the liquid crystal layer 5 are in vertical alignment. The alignment state is arranged in an arcuate shape as a whole. In order to transition from the splay alignment to the bend alignment, it is necessary to apply a constant electric field to the liquid crystal layer 5, and to transfer all the liquid crystal molecules in the transmissive display unit 30 from the splay alignment to the bend alignment, A response time of several seconds is required after the voltage is applied, that is, after the liquid crystal display panel 1 is started. Hereinafter, in the present embodiment, this response time is referred to as a transition period. During the transition period, the transmissive display unit 30 is in a state where hierarchical display is impossible.

Next, in the liquid crystal layer 5 in the reflective display section 35, when a transition voltage (voltage for white display) is applied, the liquid crystal molecules of the common alignment film 44 are aligned in parallel (the pretilt angle is as shown in FIG. 2). 4 ° to 8 °), the liquid crystal molecules in the vicinity of the first alignment film 29a are vertically aligned (the pretilt angle is 88 ° to 90 °), and the liquid crystal molecules in the vicinity of the center of the liquid crystal layer 5 are vertically aligned. So-called hybrid orientation is adopted. As the voltage is gradually increased from the transition voltage, the pretilt angle of the liquid crystal molecules in the vicinity of the common alignment film 44 gradually increases according to the applied voltage, and hierarchical display is possible. As described above, in the liquid crystal display device of the present embodiment, the reflection unit 35 is configured to operate in the R-OCB mode.
Note that the liquid crystal layer 5 in the reflective display section 35 is in an alignment state close to hybrid alignment before applying a transition voltage to the liquid crystal layer, so there is no transition period of several seconds like the transmissive display section 30. At the same time, the liquid crystal display panel 1 is shifted to the hybrid orientation at the same time as the liquid crystal display panel 1 is started, and the hierarchical display is immediately possible.

"Backlight device"
As shown in FIGS. 1 and 2, the backlight device 4 is disposed on the back surface 1b side of the liquid crystal display panel 1, and includes a light guide plate 4a and a light source unit 4c joined to the end surface 4b of the light guide plate 4a. Has been. The surface of the light guide plate 4a facing the liquid crystal display panel 1 is an emission surface 4d from which backlight is emitted, and the surface opposite to the emission surface 4d is a prism surface 4e. The light source unit 4c has a built-in light source such as an LCD. In the backlight device 4, the light emitted from the light source unit 4c is introduced into the light guide plate 4a through the end surface 4b of the light guide plate 4a, and the introduced light is emitted from the inner surfaces of the emission surface 4d and the prism surface 4e. The light propagates through the inside of the light guide plate 4a while being reflected, and then is irradiated to the liquid crystal display panel 1 side as backlight light from the entire exit surface 4d.

"Backlight controller"
As shown in FIG. 2, the backlight control unit 7 is connected to the backlight device 4 and controls turning on / off of the backlight device 4. The backlight control unit 7 controls the lighting timing of the backlight device 4 when the liquid crystal display panel 1 is activated, and the backlight device is turned off when the liquid crystal display panel 1 is activated. The backlight control unit 7 stores the transition period in advance, and the backlight device 4 can be turned on after the transition time has elapsed since the liquid crystal display panel 1 was started. Note that it is not always necessary to turn on the backlight device 4 after the transition time has elapsed, and the backlight device 4 may remain off in a state where sufficient external light is obtained.

`` Startup display control unit ''
As shown in FIG. 2, the activation display control unit 8 is connected to the liquid crystal display panel 1 to control image display on the liquid crystal front panel 1, and is particularly activated in the reflective display unit 35 during the transition period. An image is displayed.

"How to start the LCD"
Next, the operation (starting method) at the time of starting of the liquid crystal display device A of the present embodiment will be described. FIG. 3 schematically shows the alignment state of liquid crystal molecules in the liquid crystal display panel 1. FIG. 4 shows a sequence when the liquid crystal display device A is activated.
As shown in FIG. 3A, the liquid crystal molecules in the transmissive display unit 30 of the liquid crystal display panel 1 before activation are in a so-called splay alignment state. On the other hand, the liquid crystal molecules in the reflective display portion 35 are in an alignment state close to hybrid alignment.

  Next, the liquid crystal display panel 4 is activated and a transition voltage is applied to the liquid crystal layer 5. As shown in FIG. 3B, the liquid crystal molecules in the transmissive display unit 30 at this time are in a transition period in which the splay alignment transitions to the bend alignment (step S11 in FIG. 4), and the hierarchical display becomes impossible. Yes. On the other hand, the liquid crystal molecules in the reflective display section 35 are in a state in which the hybrid display is immediately performed simultaneously with the application of the transition voltage and the hierarchical display is possible. In addition, the backlight device 4 is not turned on by the backlight control unit 7 (step S21 in FIG. 4) and is turned off.

  At this time, the liquid crystal layer 5 has three states of splay alignment, bend alignment, and hybrid alignment. In particular, the boundary between the splay alignment and the hybrid alignment is visible due to the difference in optical properties. However, at this time, since the backlight device 4 is turned off, only the reflective display unit 35 displays an image, and the transmissive display unit 30 does not contribute to the image display. Accordingly, the viewer of the liquid crystal display panel cannot visually recognize the boundary between the splay alignment and the hybrid alignment.

  During the transition period, the activation display control unit 8 may cause the reflection display unit 35 to display the activation image.

  Next, when the transition period of several seconds is finished, as shown in FIG. 3C, the liquid crystal molecules in the transmissive display unit 30 are completely shifted to the bend alignment (step S12 in FIG. 4), so that hierarchical display is possible. Become. In addition, the liquid crystal molecules in the reflective display portion are continuously in a hybrid orientation and are capable of hierarchical display. In addition, the backlight control unit 7 applies a current of, for example, about 15 mA to the light source unit 4c (step S22 in FIG. 4) and turns on the backlight device 4.

  At this time, the liquid crystal layer 5 has two states of bend alignment and hybrid alignment, but the optical properties are almost the same between the bend alignment and the hybrid alignment. Impossible. Therefore, even if the backlight device 4 is in the lighting state, the spotted island pattern is not visually recognized by the observer.

  The liquid crystal display device A having the above configuration operates in a reflection mode in which the backlight 4 is not turned on when sufficient external light is obtained, and is turned on in an environment where no external light is obtained. It is possible to operate in transmissive mode. Therefore, in a situation where sufficient external light is obtained, the backlight device 4 may be continuously turned off even after the transition period ends.

  As described above, according to the liquid crystal display device A and the starting method thereof, the backlight device 4 is turned off during the transition period until the liquid crystal molecules in the transmissive display unit 30 transition from the splay alignment to the bend alignment. Only the image by the reflection display unit 35 is displayed on the display screen. Thereby, the display quality can be improved without displaying a mottled island pattern generated by the presence of two alignment states of splay alignment and hybrid alignment at the time of activation.

FIG. 1 is a schematic cross-sectional view showing the overall configuration of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a main part of a liquid crystal display panel constituting the liquid crystal display device. FIG. 3 is a diagram showing an essential part of the liquid crystal display panel, and is an enlarged schematic cross-sectional view for explaining a method of starting the liquid crystal display device. FIG. 4 is a flowchart for explaining a starting method of the liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS A ... Liquid crystal display device, 1 ... Liquid crystal display panel, 1a ... Display surface, 1b ... Back surface, 4 ... Backlight device, 5 ... Liquid crystal layer, 6 ... Other transparent substrate, 7 ... Backlight control part, 8 ... Start-up display Control part, 10 ... TFT (switching element), 11 ... Pixel electrode, 11a ... Transparent electrode, 11b ... Reflective electrode, 29a ... First alignment film (alignment film), 29b ... Second alignment film (alignment film), DESCRIPTION OF SYMBOLS 30 ... Transmission display part, 35 ... Reflection display part, 41 ... One transparent substrate, 43 ... Common electrode, 44 ... Common alignment film

Claims (5)

A liquid crystal display panel in which a transmissive display unit operating in the OCB mode and a reflective display unit operating in the R-OCB mode are provided in one pixel region;
A backlight device arranged on the back side of the liquid crystal display panel and irradiating the transmissive display unit with backlight light;
A backlight control unit that turns off the backlight device during the transition period until the liquid crystal molecules in the transmissive display unit transition from splay alignment to bend alignment;
A liquid crystal display device comprising:   The liquid crystal display device according to claim 1, further comprising an activation display control unit that displays an activation screen on the reflective display unit during the transition period. The liquid crystal display panel includes a pair of transparent substrates facing each other with a liquid crystal layer interposed therebetween, and a common electrode and a common alignment film are sequentially provided on the inner surface side of one transparent substrate from the one transparent substrate side. In addition, a plurality of switching elements and a plurality of pixel electrodes connected to each switching element are provided on the inner surface side of the other transparent substrate, and an alignment film is provided on the switching elements and the pixel electrodes.
A part of the pixel electrode is a reflective electrode that reflects incident light from the one transparent substrate side, and a remaining part of the pixel electrode is a transmission that transmits the backlight light from the other transparent substrate side. Electrode,
3. The liquid crystal display according to claim 1, wherein the reflective electrode forming region is the reflective display portion, and the transmissive electrode forming region is the transmissive display portion. apparatus. A liquid crystal display panel in which a transmissive display unit that operates in the OCB mode and a reflective display unit that operates in the R-OCB mode are provided in one pixel region, and the transmissive display unit is disposed on the back side of the liquid crystal display panel. A method for starting a liquid crystal display device comprising a backlight device for irradiating backlight light,
A startup method of a liquid crystal display device, wherein the backlight device is turned off during a transition period until liquid crystal molecules in the transmissive display portion transition from a splay alignment to a bend alignment. 5. The method of starting a liquid crystal display device according to claim 4, wherein a startup screen is displayed on the reflective display unit during the transition period.

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