JP2010015030A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display in which display failure is prevented over the whole region where a segment electrode and a common electrode are not superimposed on each other. <P>SOLUTION: A second glass substrate 2 on which a common electrode 5 is disposed is provided with an outer ITO (Indium Tin Oxide) 9 on the surface on the side opposite from liquid crystal 3. A driving IC 15 sets potentials of the segment electrode 4 and the common electrode 5 to drive a liquid crystal display panel 30. Further, when the maximum value and the minimum value of respective set potential of the segment electrode 4 and the common electrode 5 are denoted as V<SB>max</SB>, V<SB>min</SB>, the driving IC 15 sets the potential of the outer ITO 9 to a potential in the range of a potential lower than and nearest to (V<SB>max</SB>+V<SB>min</SB>)/2 to a potential higher than and nearer to (V<SB>max</SB>+V<SB>min</SB>)/2. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of preventing display defects due to static electricity.

When static electricity is generated on the surface of the liquid crystal display panel, a voltage is applied to the liquid crystal due to the static electricity, resulting in a display defect. In order to prevent such display defects, a configuration is known in which an antistatic layer is provided on the upper surface of a liquid crystal display panel and static electricity generated in the antistatic layer is discharged (see, for example, Patent Document 1). In the liquid crystal display panel described in Patent Document 1, an antistatic layer of InTiO ₃ is provided on the upper polarizing plate. Further, the metal frame (metal frame) connected to the ground pad and the antistatic layer are electrically connected. As a result, static electricity generated on the upper surface of the liquid crystal display panel is discharged, and display defects due to static electricity can be suppressed.

  FIG. 9 is a schematic cross-sectional view showing an example of a configuration in which ITO is provided as an antistatic layer on the upper surface of the liquid crystal display panel. The liquid crystal display panel shown in FIG. 9 sandwiches a liquid crystal 53 between a first glass substrate 51 provided with a segment electrode 54 and a second glass substrate 52 provided with a common electrode 55. The segment electrode 54 and the common electrode 55 are ITO (Indium Tin Oxide) electrodes, respectively. A polarizing plate 56 and a diffusion plate 57 are provided on the outer surface of the first glass substrate 51, and pins 62 and 63 are attached to the first glass substrate 51. Further, an ITO electrode 59 is provided on the outer surface of the second glass substrate 52, and a polarizing plate 58 is provided on the upper layer of the ITO electrode 59. Hereinafter, the ITO electrode 59 is distinguished from the common electrode 55 and the segment electrode 54 and is referred to as an external ITO 59. The external ITO 59 is formed wider than the polarizing plate 58, and the conductive elastic body 60 is provided in at least a part of the region where the polarizing plate 58 does not exist. Further, a metal frame 61 is provided on the outer edge of the liquid crystal display panel. The metal frame 61 is grounded and is electrically connected to the external ITO 59 via the conductive elastic body 60.

  Even if static electricity is generated on the second glass substrate 52 side of the liquid crystal display panel, the static electricity is discharged from the external ITO 59 through the conductive elastic body 60 and the metal frame 61. The configuration illustrated in FIG. 9 is different from the configuration described in Patent Document 1 in the stacking order of the polarizing plate and the antistatic layer, but the metal frame is formed from the antistatic layer (external ITO 59 in the example shown in FIG. 9). This is the same in that the static electricity is discharged through.

  In the configuration illustrated in FIG. 9, discharging is performed from the external ITO 59 through the metal frame 61, but the display defect may not be improved only by the configuration illustrated in FIG. 9. FIG. 10 is an explanatory diagram showing an example of a state in which a display defect occurs even when external ITO is provided. The same elements as those in FIG. 9 are denoted by the same reference numerals as those in FIG. However, in FIG. 10, illustration of the conductive elastic body 60, the metal frame 61, the pins 62 and 63, and the diffusion plate 57 is omitted.

The voltage applied to the liquid crystal in the region 71 where the common electrode 55 and the segment electrode 54 overlap is controlled by setting the potentials of the common electrode 55 and the segment electrode 54. In the region 72 where the segment electrode 54 exists but the common electrode does not exist, it is preferable that the liquid crystal is kept in a certain state so that display other than the desired display in the region 71 is not performed. However, the potential of the segment electrode 54 is appropriately switched for image display. Then, a potential difference is generated between the segment electrode 54 and the external ITO 59 that is always at the ground potential. FIG. 11 is an explanatory diagram illustrating an example of a potential difference between the segment electrode 54 and the external ITO 59. For example, as shown in FIG. 11, when driving the liquid crystal display panel, a segment electrode 54 (referred to as GND.) Ground and, and is switched to the GND potential higher than (the _{V a.).} Then, the average potential of the segment electrode 54 becomes V _a / 2, and a potential difference is generated between the segment electrode 54 and the external ITO 58. Since the second glass substrate 52 exists between the segment electrode 54 and the external ITO 58, the voltage V _a / 2 is not directly applied to the liquid crystal in the region 72, but by applying a minute DC voltage. The liquid crystal in the region 72 becomes light transmissive as time passes. That is, a portion that should not be in a light transmission state is in a light transmission state.

  FIG. 12 is an explanatory diagram showing a configuration example of a liquid crystal display panel that prevents display defects caused by a voltage generated between the external ITO 59 and the segment electrode 54. The same elements as those in FIG. 9 are denoted by the same reference numerals as those in FIG. However, in FIG. 12, illustration of the conductive elastic body 60, the metal frame 61, the pins 62 and 63, and the diffusion plate 57 is omitted. In the configuration shown in FIG. 12, the ITO electrode 65 is provided on the liquid crystal side surface on the second glass substrate 55 in the region 72 where the segment electrode 54 exists but the common electrode does not exist. The ITO electrode 65 is formed so as to face the segment electrode 54 with the liquid crystal 53 interposed therebetween. Hereinafter, the ITO electrode 65 is distinguished from the common electrode 55, the segment electrode 54, and the external ITO 59, and is referred to as internal ITO.

  The internal ITO 65 is set to the same potential as the opposing segment electrode 54. Specifically, conductive beads are included in a sealing material (not shown) for sealing liquid crystal between the two glass substrates 51 and 52, and the internal ITO 65 and the segment electrode 54 are connected via the conductive beads. The transfer structure is electrically connected. Since the internal ITO 65 is electrically connected to the segment electrode 54, it always has the same potential as the segment electrode. As a result, no voltage is applied to the liquid crystal in the region 72, and the display defect described with reference to FIG. 10 can be prevented.

  Patent Document 2 describes a liquid crystal panel in which a signal line is provided on one substrate, a dummy electrode facing the signal line is provided on the other substrate, and the dummy electrode and the signal line are connected by a connection wiring. .

JP-A-5-188388 (paragraphs 0009-0021) JP 2003-161959 A (paragraphs 0013-0019)

  As shown in FIG. 12, by forming the internal ITO 65 on the second glass substrate 52, it is possible to prevent the occurrence of display defects in the region 72 where the common electrode does not exist. However, the internal ITO 65 connected to the segment electrode 54 in the transfer structure cannot always be formed. If the internal ITO 65 cannot be formed, a display defect may occur due to a potential difference between the external ITO 59 and the segment electrode 54.

  For example, since the segment electrode and the common electrode must not be electrically connected, if the segment electrode on one substrate intersects the common electrode on the other substrate at the location where the seal material is placed, Does not include conductive beads. As a result, the internal ITO 65 connected to the segment electrode 54 in the transfer structure may not be provided on the second glass substrate 52.

  Further, for example, even if the internal ITO 65 is disposed on the second glass substrate 52, the internal ITO 65 is surrounded by other internal ITO and the common electrode 55 and cannot be routed to the sealing material. In some cases, the segment electrode 54 cannot be connected.

  Specific examples are shown below. FIG. 13 is an explanatory diagram illustrating an example of a liquid crystal display screen. Each region 81 shown in FIG. 13 is a region where the common electrode and the segment electrode overlap each other, and performs display by controlling the state of the liquid crystal in each region 81.

FIG. 14 is an explanatory diagram showing an arrangement example of each electrode and the sealing material in the liquid crystal display panel illustrated in FIG. FIG. 14A shows the common electrode and the internal ITO formed on the second glass substrate 52. In FIG. 14 (a), the common electrodes ₅₅ a, _{55 b} and the internal ITO65 _a ~65 _f are arranged. In the example shown in FIG. 14 (a), 2 two common electrodes ₅₅ a, _{55 b} are sequentially selected. FIG. 14B shows the segment electrodes formed on the first glass substrate 51 and the terminals 54 _g and 54 _h connected to the common electrodes 55 _a and 55 _b . In the example shown in FIG. 14B, in addition to the segment electrodes 54 _{a to} 54 _f , a common electrode on the second glass substrate and a counter electrode 82 facing the internal ITO are provided.

  FIG. 14C shows the sealing material formed on the second glass substrate 52. A sealing material 83 shown in FIG. 14C includes conductive beads. FIG. 14D shows the sealing material formed on the first glass substrate 51. The sealing material 84 shown in FIG. 14D does not include conductive beads. The glass substrates 51 and 52 are opposed to each other, and the liquid crystal is sealed in a space surrounded by a sealing material 83 containing conductive beads and a sealing material 84 containing no conductive beads.

A common electrode 55 _b shown in FIG. 14 (a), so as not to conductive state and the segment electrode 54 _e shown in FIG. 14 (b), is included the conductive beads sealant 84 shown in FIG. 14 (d) I can't. Then, even if internal ITO is arrange | positioned in the area | region 91 shown to Fig.14 (a), it cannot connect with a segment electrode by a transfer structure.

Further, a region 92 shown in FIG. 14A is surrounded by the common electrodes 55 _a and 55 _b and the internal ITO 65 _a . Therefore, even if the internal ITO is disposed in the region 92, it cannot be connected to the segment electrode by the transfer structure.

  As described above, in the areas 91 and 92 shown in FIG. 14A, the internal ITO connected to the segment electrode cannot be arranged in the transfer structure, and therefore, a display defect may occur due to a potential difference between the external ITO and the segment electrode.

  Such a problem is that a segment electrode is formed on a viewer-side glass substrate (second glass substrate 52) for visually recognizing the display, and a common electrode is formed on the rear-side glass substrate (first glass substrate 51). The same occurs even when ITO is formed on the glass substrate on the person side.

  In view of the above, an object of the present invention is to provide a liquid crystal display device capable of preventing display defects over the entire region where the segment electrode and the common electrode do not overlap.

In the liquid crystal display device according to the present invention, a liquid crystal is provided between a transparent substrate (for example, the second glass substrate 2) provided with a common electrode and a transparent substrate (for example, the first glass substrate 1) provided with a segment electrode. The liquid crystal display panel (for example, the liquid crystal display panel 30) is sandwiched, and the transparent substrate (for example, the second glass substrate 2) on the viewing side of the liquid crystal display panel is a transparent electrode provided on the surface opposite to the liquid crystal side. Provided with a certain external transparent electrode (for example, external ITO 9), driving means (for example, driving IC 15) for setting the potential of the common electrode and the segment electrode, and each potential and driving means to be set to the common electrode by the driving means for the segment electrode the maximum potential of each potential setting and V _max, the minimum potential when the V _min, the potential and the drive means drive means for setting the common electrode Se Among the potential to set the instrument _electrodes, the potential of the external transparent electrode potential within a range of up to _{(V max + V min) /} 2 from the lower most recent potential _{(V max + V min) /} 2 last higher potential than An external transparent electrode potential setting means for setting (for example, the driving IC 15 in the first embodiment and the external ITO potential setting unit 27 in the second embodiment) is provided.

The external transparent electrode potential setting means preferably sets the potential of the external transparent electrode to (V _max + V _min ) / 2.

  In addition, it is preferable to include external transparent electrode potential adjusting means (for example, an ESD element 16) that reduces the potential of the external transparent electrode when the potential of the external transparent electrode becomes equal to or higher than a predetermined value.

According to the present invention, the transparent substrate on the viewing side of the liquid crystal display panel includes the external transparent electrode that is a transparent electrode provided on the surface opposite to the liquid crystal side, and the external transparent electrode potential setting means and the drive means are common. among the potential the potentials and the driving means for setting the electrode is set to the segment _{electrode, (V max + V min)} / range 2 from the lower immediate potential to _{(V max + V min) /} 2 last higher potential than Since the potential of the external transparent electrode is set to the internal potential, display defects can be prevented in the entire region where the segment electrode and the common electrode do not overlap.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the lighting state means a state where the backlight light is transmitted through the liquid crystal display panel, and the extinguishing state means a state where the backlight light is blocked by the liquid crystal display panel.

[First Embodiment] FIG. 1 is an explanatory diagram showing an example of a first embodiment of the present invention. The liquid crystal display device of the present invention includes a liquid crystal display panel 30, a drive IC 15, and an ESD (Electrostatic Discharge) element 16. The drive IC 15 is a driver IC (Integrated Circuit) that drives the liquid crystal display panel 30.

  The liquid crystal display panel 30 sandwiches the liquid crystal 3 between the first glass substrate 1 provided with the segment electrodes 4 and the second glass substrate 2 provided with the common electrodes 5. Hereinafter, a case where a plurality of common electrodes 4 and segment electrodes 5 are provided will be described as an example. The liquid crystal 3 is sealed by the glass substrates 1 and 2 and the sealing material, but the sealing material is not shown.

  The type of the liquid crystal display panel 30 is not particularly limited. For example, a TN (Twisted Nematic) mode or an STN (Super-Twisted Nematic) mode may be used. Further, a liquid crystal display panel using a liquid crystal having a negative dielectric anisotropy and provided with a vertical alignment film at the interface between the liquid crystal and the common electrode and the segment electrode may be used.

  Each of the glass substrates 1 and 2 is a transparent substrate. Hereinafter, the common electrode 5 is provided on the second glass substrate 2 which is the glass substrate on the side where the display is visually recognized (referred to as the viewing side), and the segment electrode 4 is provided on the first glass substrate 1 disposed on the back side. However, the second glass substrate 2 may be provided with a segment electrode, and the first glass substrate 1 may be provided with a common electrode.

  The common electrode 5 and the segment electrode 4 are both ITO electrodes, and a plurality of them are provided.

  The second glass substrate 2 arranged on the viewing side of the liquid crystal display panel 30 includes the ITO electrode 9 on the surface opposite to the surface on which the liquid crystal 3 is present. Hereinafter, the ITO electrode 9 is referred to as an external ITO 9. The external ITO 9 is provided, for example, on the entire surface on the viewing side of the second glass substrate 2.

  A polarizing plate 8 is provided in an upper layer of the external ITO 9 in a range narrower than the external ITO 9. The first glass substrate 1 includes a polarizing plate 6 on a surface opposite to the surface on which the liquid crystal 3 is present. Although illustration is omitted, a diffusion plate may be provided on the polarizing plate 6 on the back side as in the configuration illustrated in FIG. The diffuser diffuses and irradiates backlight light from the back side of the liquid crystal display panel 30.

  A non-conducting elastic body 10 is provided in a region of the external ITO 9 where the polarizing plate 8 does not exist. A metal frame 11 is provided on the outer edge of the liquid crystal display panel. The metal frame 11 may be grounded. However, since the non-conductive elastic body 10 exists between the external ITO 9 and the metal frame 11, the external ITO 9 and the metal frame 11 are not electrically connected.

  The drive IC 15 controls the state of the liquid crystal in the region where the common electrode 5 and the segment electrode 4 overlap by setting the potentials of the plurality of common electrodes 5 and the plurality of segment electrodes 4. The driving IC 15 selects the common electrode 5 in order, sets the selected common electrode to the selected potential, and sets the unselected common electrode to the non-selected potential. Further, the drive IC 15 sets each segment electrode that overlaps the selected common electrode to each potential determined according to the image data (data that defines the display state).

  The drive IC 15 applies a voltage to the liquid crystal between the common electrode and each segment electrode by setting the potential of the selected common electrode and each segment electrode. Then, by sequentially switching the common electrode to be selected, an image is displayed on the liquid crystal display panel.

The drive IC 15 sets the potentials of the segment electrodes 4 on the first glass substrate 1 and the common electrodes 5 on the second glass substrate 2, respectively. The potentials set on the common electrodes and the potentials set on the segment electrodes There are several types. In FIG. 1, there are five types of potentials V _{0 to} V ₄ , and there are five types of potentials that can be set to the electrodes by the driving IC 15. In this example, it is assumed that V ₀ <V ₁ <V ₂ <V ₃ <V ₄ . At this time, V ₂ = (V ₀ + V ₄ ) / 2 = (V ₁ + V ₃ ) / 2. Further, FIG. 1 illustrates the case where V ₀ is the ground potential (GND), but V ₀ may not be the ground potential.

The drive IC 15 sets the potential of the common electrode and the segment electrode so that the average value of the maximum value and the minimum value of the common electrode set potential matches the average value of the segment electrode set potential and the minimum value. To do. In this example, the maximum value and the minimum value of the set potential of the common electrode are V ₄ and V ₀ , respectively, and the average value is V ₂ . As for the set potential of the segment electrode, the maximum value and the minimum value are V ₄ and V ₀ , respectively, and the average value is V ₂ . Examples of potential changes (drive waveforms) of the common electrode and the segment electrode will be described later.

The driving IC 15 also sets the potential of the external ITO 9 and keeps the potential of the external ITO 9 constant. The potential that the drive IC 15 sets to the external ITO 9 will be described. Of all the potentials set by the drive IC 15 to the common electrode and all the potentials set to the segment electrodes, the maximum potential is set to V _max and the minimum potential is set to V _min . The drive IC 15 has a potential (V _near1 ) that is lower than (V _max + V _min ) / 2 and _{close to} (V _max + V _min ) / 2 among all the potentials set to the common electrode and each potential set to the segment electrode. The potential of the external ITO 9 is set to a potential within the range from (V _max + V _min ) / 2 to (V _max + V _min ) / 2 and the potential closest to (V _max + V _min ) / 2 ( _denoted as V _near2 ). To do. That is, the potential of the external ITO 9 is set to a potential in the range of V _{near1 to} V _near2 .

In the example shown in FIG. 1, the potentials set for the common electrode and the potentials set for the segment electrode are five types from V _{0 to} V ₄ . V _max = V ₄ , V _min = V ₀ , and (V _max + V _min ) / 2 = V ₂ . _{Therefore, V Near1} is _{V 1} is the most recent potential _{V 2} lower than _{V 2. Also, V Near2} is _{V 3} is the most recent potential higher _{V 2} than _{V 2.} Therefore, the driving IC 15 may set the potential of the external ITO 9 to a potential in the range of V _{1 to} V ₃ .

Among the potentials in the range of V _{near1 to} V _near2 , the most preferable potential is (V _max + V _min ) / 2. In the example illustrated in FIG. 1, the driving IC 15 sets the potential of the external ITO 9 to V ₂ corresponding to (V _max + V _min ) / 2. When the potentials set for the common electrode and the potentials set for the segment electrode are odd types, (V _max + V _min ) / 2 is included in the potential. In this case, the driving IC 15 preferably sets the potential of the external ITO 9 to (V _max + V _min ) / 2.

However, the drive IC 15 shown in FIG. 1 may set the potential of the external ITO 9 to V ₁ (= V _near1 ) or V ₃ (= V _near2 ).

In addition, when the potentials set for the common electrode and the potentials set for the segment electrode are even types, (V _max + V _min ) / 2 is not included in the even-type potentials. In that case, the driving IC 15 may set the potential of the external ITO 9 to V _near1 or V _near2 .

For example, the type of set potential for the common electrode and the segment electrode is a four _{V 0, V 1, V 2} , V 3, potential driving IC15 can be set also as the these four types. Further, it is assumed that V ₀ <V ₁ <V ₂ <V ₃ . If (V _max + V _min ) / 2 is a potential between V ₁ and V ₂ , the driving IC 15 cannot set the potential (V _max + V _min ) / 2. In this case, V _near1 = V ₁ and V _near2 = V ₂ , and the drive IC 15 may set the potential of the external ITO 9 to either V ₁ or V ₂ .

  Although the potential of the external ITO 9 is set by the driving IC 15, it may suddenly rise due to static electricity. The ESD element 16 reduces the potential of the external ITO 9 when the potential of the external ITO 9 becomes equal to or higher than a predetermined value. Even if static electricity occurs and the potential of the external ITO 9 suddenly increases, the potential of the external ITO 9 decreases due to the ESD element 16. As a result, the drive IC 15 is protected from high voltage breakdown caused by static electricity.

Here, a case where the ESD element 16 is a varistor will be described as an example. The varistor (ESD element) 16 connects the external ITO 9 and the ground potential point 17. The potential at the ground potential point 17 is always the ground potential. If the potential difference between the external ITO 9 and the ground potential point 17 does not reach a predetermined value, the varistor 16 has a high resistance and does not generate a current from the external ITO 9 to the ground potential point 17. When the external ITO 9 is set to a potential in the range of V _{near1 to} V _near2 , this state is established, and no current flows from the external ITO 9 to the ground potential point 17. On the other hand, when the potential of the external ITO 9 rises and the potential difference between the external ITO 9 and the ground potential point 17 becomes a predetermined value or more, the resistance of the varistor 16 decreases, and the external ITO 9 passes from the external ITO 9 to the ground potential point 17 via the varistor 16. Current flows. As a result, the potential of the external ITO 9 is lowered, so that the driving IC 15 is protected from a high voltage due to static electricity.

  Here, the case where the ESD element 16 is a varistor has been described as an example. However, the ESD element 16 is not limited to a varistor, and the potential of the external ITO 9 is lowered when the potential of the external ITO 9 becomes a predetermined value or more. Any element can be used. For example, a protective diode or thyristor may be used as the ESD element 16 other than the varistor.

Next, the operation will be described. Here, an example in which there are eight common electrodes and driving by IAPT (Improved Alto-Pleshko Technique) is taken as an example. As already described, in the example shown in FIG. 1, there are five types of potentials set to the common electrode and the segment electrode set by the drive IC 15 and the segment electrode, V _{0 to} V ₄ , and V ₂ = ( V ₀ + V ₄ ) / 2. Among V _{0 to} V ₄ , the driving IC 15 sets any potential of V ₀ , V ₁ , V ₃ , V ₄ for each common electrode, and V ₀ , V ₂ , to set one of V _4.

  The driving IC 15 switches between positive polarity driving and negative polarity driving during the selection period T of the common electrode. The positive drive means that the potential of the selected common electrode is driven to be higher than the potential of the segment electrode. The negative polarity driving is driving so that the potential of the selected common electrode is lower than the potential of the segment electrode. Hereinafter, a case where negative polarity driving is performed in the first half of the selection period T and positive polarity driving is performed in the second half will be described as an example.

  FIG. 2 is an explanatory diagram illustrating an example of a driving waveform of a common electrode, and FIG. 3 is an explanatory diagram illustrating an example of a driving waveform of a segment electrode.

The selection period of the first common electrode will be described as an example. The drive IC 15 sets the potential of the selected first common electrode to V ₀ in the first half of the selection period T, and sets the potential of the selected first common electrode to V ₄ in the second half of the selection period T. Set (see FIG. 2). Then, the drive IC 15 sets the potential of the unselected common electrode to V ₃ in the first half of the first common electrode selection period. Then, in the second half of the selection period, setting the potential of the common electrode is not selected to V _1.

Therefore, the average value of the set potential is V ₂ in any common electrode.

In addition, the drive IC 15 determines the potential of the segment electrode in the LCD segment to be lit in the region where the selected common electrode and each segment electrode intersect (referred to as an LCD segment). in the first half of the set to V _4, in the second half in the selection period is set to V ₀ (see FIG. 3). Then, during the selection period of the first common electrode, a voltage of | V ₀ −V ₄ | is applied to the liquid crystal of the LCD segment to be turned on. Specifically, a voltage of | V ₀ −V ₄ | is applied in the first half of the selection period, and a voltage of | V ₄ −V ₀ | is applied in the second half, but the magnitude of the voltage is constant. Further, the potential difference between these segment electrodes and the unselected common electrode is | V ₃ −V ₄ | in the first half of the selection period of the first common electrode, and | V ₁ −V ₀ | in the second half. The value is constant.

Further, the drive IC 15 sets the potential of the segment electrode in the LCD segment to be turned off in the region where the selected common electrode and each segment electrode intersect to V ₂ during the selection period of the first common electrode. . Then, during the selection period of the first common electrode, a voltage of | V ₀ −V ₂ | is applied to the liquid crystal of the LCD segment to be turned on. Specifically, a voltage of | V ₀ −V ₂ | is applied in the first half of the selection period and a voltage of | V ₄ −V ₂ | is applied in the second half, but the magnitude of the voltage is constant. Further, the potential difference between these segment electrodes and the non-selected common electrode is | V ₃ −V ₂ | in the first half of the selection period of the first common electrode, and | V ₁ −V ₂ | in the _second half. The value is constant.

  After the selection period of the first common electrode ends, the drive IC 15 selects the next common electrode and repeats the same operation. Further, after the selection period of the last common electrode (eighth common electrode) ends, the common electrodes are selected again sequentially from the first common electrode. As a result, the state of each LCD segment is controlled to be on or off, and a desired image is displayed.

Segment electrodes, when the intersection between the common electrode are determined by the image data when are all turned off will continue to be set to the potential V ₂ (see FIG. 3). In addition, when the segment electrode is determined by the image data that all the intersections with the common electrodes are in the lighting state, the set potential is alternately switched between V ₄ and V ₀ , and the average value is V ₂ (see FIG. 3).

Regardless of whether to set off state of each LCD segment are lit, the average potential of the segment electrode 4 becomes V _2. The average potential of this segment electrode is equal to (V _max + V _min ) / 2.

The driving IC15 is the potential of the external ITO _9, is set to a potential in the range from _{V near1 (V 1)} to _{V near2 (V 3).} Accordingly, in the region where the segment electrode 4 and the common electrode 5 shown in FIG. 1 do not overlap, the difference between the average potential of the segment electrode and the potential of the external ITO 9 is | V ₃ −V ₂ | (= | V ₁ − V ₂ |).

  In this manner, in the region where the segment electrode 4 and the common electrode 5 do not overlap, the difference between the average potential of the segment electrode 4 and the potential of the external ITO 9 can be suppressed. Can be prevented.

In particular, when the drive IC 15 sets the potential of the external electrode 9 to V ₂ , the difference between the average potential of the segment electrode 4 and the potential of the external ITO 9 is set to 0 in a region where the segment electrode 4 and the common electrode 5 do not overlap. This is particularly preferable.

  Therefore, in the present invention, display defects can be prevented without disposing an internal ITO electrode (for example, the internal ITO 65 illustrated in FIG. 12) that is electrically connected to the counter electrode by the transfer structure, and the segment electrode and the common electrode do not overlap. Display defects can be prevented in the entire area.

  In the present embodiment, an ESD element 16 is provided between the external ITO 9 and the ground potential point 17 as shown in FIG. Therefore, even if the potential of the external ITO 9 suddenly increases due to static electricity, the potential of the external ITO 9 can be decreased and the drive IC 15 can be prevented from being damaged by high voltage.

In the above example, the case where the number of duties is 8 (that is, the number of common electrodes is 8) has been described as an example, but the number of duties is not particularly limited. Type of each potential set to the potentials and segment electrode is a common electrode is not limited to five V ₀ ~V _5. Further, as already described, the number of types of each potential set to the common electrode and each potential set to the segment electrode may be an even number.

  In the above description, the case of IAPT driving is exemplified, but driving may be performed by other driving methods. For example, it may be driven by MLA (multiline addressing method). Hereinafter, the case of MLA driving will be described as an example.

  In MLA, a plurality of common electrodes are selected simultaneously. Let L be the number of common electrodes selected simultaneously. A matrix (selection matrix) of L rows and K columns that defines the set potential of each common electrode is determined in advance. The element of the selection matrix is 1 or −1, and each row of the selection matrix corresponds to each common electrode that is simultaneously selected. For example, the drive IC 15 switches and selects a column of the selection matrix every time selection of all the common electrodes is completed.

FIG. 4 is an explanatory diagram showing an example of each potential set to the common electrode and the segment electrode during MLA driving. The drive IC 15 sets the potential of the L common electrodes selected at the same time to either V _min or V _{max according} to the L elements of the selected column in the selection matrix and the positive polarity drive or the negative polarity drive. set, setting the potential of the common electrode is not selected to V _c. V _c = (V _max + V _min ) / 2.

Further, the display data of the L LCD segments, which are the overlaps between the selected common electrodes and the segment electrodes, are represented by “1 (lit)” or “0 (unlit)”. The driving IC 15 calculates the inner product of the vector composed of the L data and the column being selected in the selection matrix, and sets the potential of each segment electrode according to the inner product and positive polarity driving or negative polarity driving. . In general, in MLA, there are L + 1 types of set potentials for segment electrodes. In this example, it is assumed that L = 4 and the set potentials for the segment electrodes are five types of V ₁ , V ₂ , V _c , V ₃ , and V ₄ . _However, a _{V 1 <V 2 <V c} <V 3 <V 4, V c = (V 1 + V 4) / 2 = (V 2 + V 3) is / 2. Further, V _min ≦ V ₁ and V ₄ ≦ V _max .

In this case, each potential set to the common electrode and each potential set to the segment electrode by the drive IC 15 becomes V _min , V ₁ , V ₂ , V _c , V ₃ , V ₄ , V _{max in} ascending order. It is _{(V max + V min) /} 2 = V c. Therefore, the driving IC5 is from the last potential _{V 2} to lower _{V c} than _{V c,} the potential in the range to the nearest potential _{V 3} in higher _{V c} than _{V c,} the potential of the external ITO 9 (see FIG. 1) You only have to set it. In particular, it is preferable to set the potential of the external ITO9 to _{V c.} If the potential of the external ITO 9 is set in this way, display defects can be prevented in the entire region where the segment electrode and the common electrode do not overlap as in the case of IAPT.

In the MLA driving example, V ₁ and V ₄ set for the segment electrodes may be V ₁ = V _min and V ₄ = V _max , respectively. An example of each potential set for the common electrode and the segment electrode in this case is shown in FIG.

In the MLA, each potential may be determined so that V _c = 0V.

In general, in MLA, the set potential for the segment electrode is described as L + 1. However, when L = 3 and one virtual row is provided, the segment electrode is set according to the type of the sign of the inner product. The number of potentials can be reduced to two. The two types of potential and _V p, _{V q.} However, V _p <V _q and (V _p + V _q ) / 2 = V _c . An example of each potential set in the common electrode and the segment electrode in this case is shown in FIG. The potentials set for the common electrode and the segment electrode are five types of V _min , V _p , V _c , V _q , and V _max in ascending order. Among these, the most recent potentials lower _{V c} than _{V c} is _{V p,} the nearest potential higher _{V c} than _{V c} is _{V q.} Accordingly, the driving IC 5 may set the potential of the external ITO 9 (see FIG. 1) to a potential in the range of V _{p to} V _q . In particular, it is preferable to set the _{V c.}

[Embodiment 2] FIG. 7 is an explanatory view showing an example of the second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals as those in FIG. The liquid crystal display device according to the second embodiment includes a liquid crystal display panel 30, a drive IC 15, an ESD element 16, and an external ITO potential setting unit 27. The configuration of the liquid crystal display panel 30 is the same as that of the first embodiment.

  In the second embodiment, the potential setting for the external ITO 9 (see FIG. 7) is performed not by the driving IC 15 but by the external ITO potential setting unit 27 (hereinafter simply referred to as the potential setting unit 27). The potential setting unit 27 is an electrical component that reduces the voltage supplied from a power source (not shown) and sets the external ITO 9 to the potential after the decrease. For example, the potential setting unit 27 is supplied with a voltage of 13.5 V from the power supply, and lowers the voltage to set the potential of the external ITO 9 to 3 V or the like. 13.5V and 3V described here are examples, and are not limited to these values. For example, a Zener diode or a three-terminal regulator may be used as the potential setting unit 27.

The potential set by the potential setting unit 27 in the external ITO 9 may be in the same range as in the first embodiment. That is, of all the potentials set by the drive IC 15 to the common electrode and all the potentials set to the segment electrodes, the maximum potential is V _max and the minimum potential is V _min . The drive IC 15 has a potential (V _near1 ) that is lower than (V _max + V _min ) / 2 and _{close to} (V _max + V _min ) / 2 among all the potentials set to the common electrode and each potential set to the segment electrode. _{from), (higher} than _{V max + V min) / 2} , the potential in the range of up to _{(V max + V min) /} 2 in the immediate vicinity of the potential _{(V Near2),} may be set the potential of the external ITO 9. In particular, it is preferable to set the potential of the external ITO9 to _{(V max + V min) /} 2.

  As described above, the potential setting unit 27 determines the potential of the external ITO 9, so that the same effect as in the first embodiment can be obtained.

In the first embodiment, the potential that the drive IC 15 can set for the common electrode and the segment electrode is set in the external ITO 9. In that case, when the types of potentials set for the common electrode and the segment electrode are even types, (V _max + V _min ) / 2 is not included in the even-type potentials. The potential cannot be the most preferred potential (V _max + V _min ) / 2. On the other hand, in the second embodiment, the potential setting unit 27, which is an electrical component independent of the drive IC 15, determines the potential of the external ITO 9, so that the set potential of the external ITO 9 can be freely determined. Therefore, the set potential of the external ITO 9 can be set to an ideal value ((V _max + V _min ) / 2) regardless of the set potential of the common electrode and the segment electrode.

For example, when performing IAPT driving, it is assumed that the types of potentials set for the common electrode and the segment electrode are six types of V _{0 to} V ₅ as shown in FIG. _However, it assumed to be _{V 0 <V 1 <V 2} <V 3 <V 4 <V 5. In this case, (V _max + V _min ) / 2 = (V ₀ + V ₅ ) / 2, and V _near1 = V ₂ and V _near2 = V ₃ . The driving IC 15 cannot set (V ₀ + V ₅ ) / 2, which is the most preferable potential, but the potential setting unit 27 can freely set the setting potential of the external ITO 9, so that the potential of the external ITO 9 is (V ₀ + V). ₅ ) / 2.

  In each embodiment, external ITO may also be provided on the back side of the liquid crystal display panel 30. In that case, the potential of the external ITO (not shown) on the back side may be set to the same potential as the external ITO 9 on the viewing side (see FIGS. 1 and 7).

  The present invention can be suitably applied to a liquid crystal display device that is required to prevent display failure due to static electricity.

Explanatory drawing which shows the example of the 1st Embodiment of this invention. Explanatory drawing which shows the example of the drive waveform of a common electrode. Explanatory drawing which shows the example of the drive waveform of a segment electrode. Explanatory drawing which shows the example of each electric potential set to a common electrode and a segment electrode at the time of MLA drive. Explanatory drawing which shows the example of each electric potential set to a common electrode and a segment electrode at the time of MLA drive. Explanatory drawing which shows the other example of each electric potential set to a common electrode and a segment electrode. Explanatory drawing which shows the example of the 2nd Embodiment of this invention. Explanatory drawing which shows the example of each electric potential set to a common electrode and a segment electrode at the time of IAPT drive. The typical sectional view showing the example of the composition which provided ITO as an antistatic layer on the upper surface of a liquid crystal display panel. Explanatory drawing which shows the example of the state which a display defect produces even if external ITO is provided. Explanatory drawing which shows the example of the electrical potential difference between a segment electrode and external ITO. Explanatory drawing which shows the structural example of the liquid crystal display panel which prevents the display defect resulting from the voltage which arises between external ITO and a segment electrode. Explanatory drawing which shows the example of a liquid crystal display screen. Explanatory drawing which shows the example of arrangement | positioning of each electrode and sealing material in a liquid crystal display panel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st glass substrate 2 2nd glass substrate 3 Liquid crystal 4 Segment electrode 5 Common electrode 9 ITO electrode (external ITO)
15 Drive IC
16 ESD element 17 Ground potential point 27 External ITO potential setting section

Claims (3)

A liquid crystal display panel that sandwiches liquid crystal between a transparent substrate provided with a common electrode and a transparent substrate provided with a segment electrode,
The transparent substrate on the viewing side of the liquid crystal display panel includes an external transparent electrode that is a transparent electrode provided on the surface opposite to the liquid crystal side,
Driving means for setting potentials of the common electrode and the segment electrode;
Of the potentials set by the drive means for the common electrode and the potentials set by the drive means for the segment electrodes, the maximum potential is set to V _max and the minimum potential is set to V _min. among the potential the potentials and the drive means is set to the segment electrode is set _{to, (V max + V min)} / range 2 from the lower immediate potential to _{(V max + V min) /} 2 last higher potential than An external transparent electrode potential setting means for setting the potential of the external transparent electrode to an internal potential. A liquid crystal display device comprising: The liquid crystal display device according to claim 1, wherein the external transparent electrode potential setting means sets the potential of the external transparent electrode to (V _max + V _min ) / 2. The liquid crystal display device according to claim 1, further comprising an external transparent electrode potential adjusting unit that reduces the potential of the external transparent electrode when the potential of the external transparent electrode becomes equal to or higher than a predetermined value.

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