JP4198942B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device called a so-called lateral electric field method.
[0002]
[Prior art]
A so-called horizontal electric field type liquid crystal display device has an electric field applied between a pixel electrode and the pixel electrode in each pixel region on the liquid crystal side surface of one of the substrates opposed to each other via liquid crystal. A counter electrode to be generated is formed, and the light transmittance of the liquid crystal is controlled by a component of the electric field substantially parallel to the substrate.
[0003]
Further, assuming that such a liquid crystal display device is applied to an active matrix type, gate signal lines extending in the x direction and juxtaposed in the y direction are provided on the liquid crystal side surface of the one substrate. A region surrounded by drain signal lines extending in the y direction and juxtaposed in the x direction is defined as a pixel region, and each of these pixel regions is operated by a scanning signal from a gate signal line, and the switching device A pixel electrode to which a video signal from the drain signal line is supplied via the pixel electrode and a counter electrode spaced apart from the pixel electrode are formed.
[0004]
In the case of color display, a structure in which a color filter is formed on the one substrate side and the color filter is not formed on the other substrate side has been known. This is to reduce the influence of misalignment of the other substrate with respect to one substrate with the recent high definition.
[0005]
[Problems to be solved by the invention]
However, the liquid crystal display device having such a configuration has a configuration in which the layer thickness is not uniformly formed in each of the red (R), green (G), and blue (B) color filters. .
[0006]
In order to balance the transmittance and color purity of the color filters of R, G, and B, each layer thickness may be set independently, or each layer thickness may not be formed uniformly due to manufacturing variations. It is.
[0007]
In this case, when the pixel electrode and the counter electrode are formed on the upper layer of the color filter via an interlayer insulating film, the height of the interlayer insulating film with respect to one substrate surface is reflected in the layer thickness of the color filter. The pixel electrodes or the counter electrodes are formed with different heights (height from one substrate surface).
[0008]
This means that the liquid crystal layer thickness in each pixel is not uniform, and the same light transmittance cannot be obtained.
[0009]
In addition, when the interlayer insulating film interposed between the pixel electrode and the counter electrode is, for example, a resin material formed by coating, the thickness of the interlayer insulating film differs for each color filter pixel having a different color, Different voltage drop due to the interlayer insulating film between the pixel electrode and the counter electrode shifts the luminance-voltage characteristic, and the halftone color balance is lost.
[0010]
The present invention has been made based on such circumstances, and an object of the present invention is to provide a liquid crystal display device in which display quality is improved.
[0011]
[Means for Solving the Problems]
Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
[0036]
  means1.
  The liquid crystal display devices according to the present invention are, for example, opposed to each other.First and secondA liquid crystal layer sandwiched between the substrates,
  A region surrounded by a plurality of gate signal lines and drain signal lines formed on the first substrate;A plurality of pixel regions;
  SaidFirstHaving a pixel electrode and a counter electrode formed in each pixel region of the surface of the substrate on the liquid crystal layer side,
  A color filter is provided between the counter electrode and the first substrate, and the color filter is different in color and thickness between adjacent pixel regions,
  SaidFirstThe substrate ofBeforeRecordOppositeDistance between electrodesIs a long pixel areaSaidFirstThe substrate ofBeforeDistance between counter electrodesIs shortPixelShorten the distance between the counter electrodes in the pixel area relative to the areaIt is characterized by this.
  Mean 2.
  The liquid crystal display device according to the present invention includes, for example, a liquid crystal layer sandwiched between first and second substrates facing each other,
  A plurality of pixel regions that are regions surrounded by a plurality of gate signal lines and drain signal lines formed on the first substrate;
  Having a pixel electrode and a counter electrode formed in each pixel region on the liquid crystal layer side surface of the first substrate,
A color filter is provided between the counter electrode and the first substrate, and the color filter is different in color and thickness between adjacent pixel regions,
  The pixel region having a long distance between the first substrate and the counter electrode is different from the pixel region having a short distance between the first substrate and the counter electrode in the pixel region. The distance between the electrodes is shortened.
[0037]
  means3.
  The liquid crystal display device according to the present invention includes, for example, means.1 or 2In,The pixel electrodeFormed between the first substrate and the color filterIt is characterized by being.
[0038]
  means4.
  The liquid crystal display device according to the present invention includes, for example, means.1 or 2InThe pixel electrode is formed in the same layer as the counter electrode.It is characterized by this.
  Means 5.
  The liquid crystal display device according to the present invention is characterized in that, for example, in the means 4, an overcoat layer is formed between the color filter and the counter electrode.
[0039]
  means6.
  The liquid crystal display device according to the present invention includes, for example, means.1 or 2InThe pixel electrode is formed between the color filter and the counter electrode, and an overcoat layer is formed between the color filter and the counter electrode.It is characterized by being.
  Mean 7
  In the liquid crystal display device according to the present invention, for example, in the means 1 or 2, the color filter is one of red, green and blue, and the thickness of each color has a relationship of red>green> blue. It is characterized by this.
[0040]
Further means of the present invention will be apparent from the present specification or drawings.
[0041]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a liquid crystal display device according to the present invention will be described with reference to the drawings.
[0042]
  referenceExample 1.
  << Equivalent circuit >>
  FIG. 2 shows a liquid crystal display device according to the present invention.referenceIt is a whole equivalent circuit diagram which shows an example. This figure is an equivalent circuit, but is drawn corresponding to the actual geometric arrangement.
[0043]
In FIG. 2, there is a pair of transparent substrates SUB1 and SUB2 arranged to face each other via a liquid crystal, and the liquid crystal is sealed by a sealing material SL that also serves to fix the other transparent substrate SUB2 to one transparent substrate SUB1.
[0044]
On the liquid crystal side surface of the one transparent substrate SUB1 surrounded by the sealing material SL, the gate signal lines GL extending in the x direction and arranged in parallel in the y direction, and extending in the y direction and aligned in the y direction. A drain signal line DL is provided.
[0045]
A region surrounded by each gate signal line GL and each drain signal line DL constitutes a pixel region, and a matrix aggregate of these pixel regions constitutes a liquid crystal display unit AR.
[0046]
Further, a common counter voltage signal line CL running in each pixel region is formed in each pixel region arranged in parallel in the x direction. The counter voltage signal line CL serves as a signal line for supplying a reference voltage for a video signal to a counter electrode CT described later in each pixel region.
[0047]
In each pixel region, a thin film transistor TFT that is operated by a scanning signal from the gate signal line GL on one side and a pixel electrode PX to which a video signal from the drain signal line DL on one side is supplied via the thin film transistor TFT are formed. Has been.
[0048]
The pixel electrode PX generates an electric field with the counter electrode CT connected to the counter voltage signal line CL, and the light transmittance of the liquid crystal is controlled by the electric field.
[0049]
One end of each of the gate signal lines GL extends beyond the sealing material SL, and the extending end constitutes a terminal to which the output terminal of the vertical scanning drive circuit V is connected. The input terminal of the vertical scanning drive circuit V receives a signal from a printed circuit board disposed outside the liquid crystal display panel.
[0050]
The vertical scanning drive circuit V is composed of a plurality of semiconductor devices, and a plurality of gate signal lines GL adjacent to each other are grouped, and one semiconductor device is assigned to each group.
[0051]
Similarly, one end of each of the drain signal lines DL extends beyond the seal material SL, and the extending end constitutes a terminal to which the output terminal of the video signal driving circuit He is connected. . The input terminal of the video signal driving circuit He is adapted to receive a signal from a printed circuit board arranged outside the liquid crystal display panel.
[0052]
This video signal drive circuit He is also composed of a plurality of semiconductor devices, and a plurality of adjacent drain signal lines DL are grouped, and one semiconductor device is assigned to each group.
[0053]
Further, the counter voltage signal line CL common to the pixel regions arranged in the x direction is connected in common at an end portion on the right side in the drawing, and the connection line extends beyond the seal material SL, and the extension A terminal CTM is formed at the end. A voltage serving as a reference for the video signal is supplied from the terminal CTM.
[0054]
One of the gate signal lines GL is sequentially selected by a scanning signal from the vertical scanning circuit V.
[0055]
In addition, a video signal is supplied to each of the drain signal lines DL by the video signal driving circuit He in accordance with the selection timing of the gate signal line GL.
[0056]
<Pixel configuration>
FIG. 3 is a plan view showing a configuration in the pixel region, and FIG. 4 shows a cross-sectional view taken along line IV-IV in FIG.
[0057]
First, a pair (one not shown) of gate signal lines GL extending in the x direction and juxtaposed in the y direction is formed on the liquid crystal side surface of the transparent substrate SUB1.
[0058]
These gate signal lines GL surround a rectangular area together with a pair of drain signal lines D (one not shown) to be described later, and this area is configured as a pixel area.
[0059]
Further, a counter voltage signal line CL disposed in parallel with the gate signal line GL is formed in a region between the gate signal lines GL.
[0060]
Thus, an insulating film GI made of, for example, SiN is formed on the surface of the SUB1 of the transparent substrate where the gate signal line GL and the counter voltage signal line CL are formed so as to cover the gate signal line GL and the counter voltage signal line CL. Yes.
[0061]
This insulating film GI functions as an interlayer insulating film for the gate signal line GL and the counter voltage signal line CL in the formation region of the drain signal line DL described later, and the gate insulating film in the formation region of the thin film transistor TFT described later. In the formation region of the capacitor element Cstg described later, the function as a dielectric film is provided.
[0062]
A semiconductor layer AS made of, for example, amorphous Si is formed on the surface of the insulating film GI so as to overlap a part of the gate signal line GL.
[0063]
This semiconductor layer AS is that of the thin film transistor TFT, and by forming a drain electrode SD1 and a source electrode SD2 on the upper surface thereof, an MIS type transistor having an inverted stagger structure having a part of the gate signal line GL as a gate electrode is formed. can do.
[0064]
Here, the drain electrode SD1 and the source electrode SD2 are formed simultaneously with the formation of the drain signal line DL.
[0065]
That is, the drain signal line DL extending in the y direction is formed, and a part of the drain signal line DL extends to the upper surface of the semiconductor layer AS to form the drain electrode SD1, and the drain electrode SD1 and the thin film transistor TFT are also formed. A source electrode SD2 is formed separated by the channel length.
[0066]
The source electrode SD2 extends slightly from the semiconductor layer AS surface to the upper surface of the insulating film GI on the pixel region side, and a contact portion for connection with a pixel electrode PX described later is formed.
[0067]
A thin layer doped with high-concentration impurities is formed at the interface between the semiconductor layer AS, the drain electrode SD1, and the source electrode SD2, and this layer functions as a contact layer.
[0068]
For example, when the semiconductor AS layer is formed, the contact layer has a high-concentration impurity layer already formed on the surface thereof, and is exposed from the pattern of the drain electrode SD1 and the source electrode SD2 formed on the upper surface thereof as a mask. It can be formed by etching the impurity layer.
[0069]
A color filter FIL is formed on the surface of the transparent substrate on which the thin film transistor TFT, the drain signal line DL, the drain electrode SD1, and the source electrode SD2 are thus formed.
[0070]
The color filter FIL has a color different from that of other pixel areas adjacent in the x direction and has a common color with that of other pixel areas adjacent in the y direction.
[0071]
That is, the color filter of the pixel region group arranged in parallel in the y direction is formed of a common resin material layer containing the same color pigment, and other pixels arranged in parallel in the y direction on both sides of the pixel region group. It is formed separately from the color filter FIL formed of a resin material layer that is formed in common in the region group and includes pigments of different colors.
[0072]
In this case, the color filter FIL also serves as a protective film that prevents direct contact of the thin film transistor TFT with the liquid crystal and prevents characteristic deterioration of the thin film transistor TFT.
[0073]
  A pixel electrode PX is formed on the upper surface of the color filter FIL. The pixel electrode PX extends in the y direction, for example, and is arranged in parallel in the x direction (thisreferenceIn the example, it is composed of two electrode groups. These electrodes are connected in common at the portion overlapping the counter voltage signal line CL.WhenBoth are close to the thin film transistor TFTInThe color filter FIL is electrically connected to the contact portion of the source electrode SD2 of the thin film transistor TFT through a contact hole CH1.
[0074]
A flattening film OC made of, for example, a resin material layer is formed on the upper surface of the color filter FIL on which the pixel electrode PX is formed in this manner so as to cover the pixel electrode PX.
[0075]
  Further, a counter electrode CT is formed on the upper surface of the planarizing film OC layer. The counter electrode CT includes a plurality (this) that extends in the y direction and is arranged in parallel in the x direction.referenceIn the example, it is composed of three electrode groups.
[0076]
Each of these counter electrodes CT is positioned with the pixel electrode PX in between when viewed in plan. That is, the counter electrodes CT are arranged in the order of the counter electrode CT, the pixel electrode PX, the counter electrode CT, the pixel electrode PX, and the counter electrode CT from the drain signal line DL on one side to the drain signal line DL on the other side. It is arranged at equal intervals.
[0077]
In addition, the counter electrode CT composed of the electrode group in this way is electrically connected to each other at a portion where the counter voltage signal line CL is overlapped, and a part of the counter electrode CT is composed of the planarizing film OC and the color filter. The counter voltage signal line CL is electrically connected through a contact hole CH2 formed through the FIL.
[0078]
Here, in each counter electrode group, a pair of counter electrodes CT positioned on both sides, in other words, the counter electrode CT adjacent to the drain signal line DL is formed to be slightly wider than the other counter electrodes CT. Yes.
[0079]
The reason is that the electric lines of force from the drain signal line DL are easily terminated at the counter electrode CT adjacent thereto, and are prevented from terminating at the pixel electrode PX beyond the counter electrode CT. This is because when the electric lines of force terminate in the pixel electrode PX, it becomes noise.
[0080]
Further, the portion where these counter electrodes CT are electrically connected overlaps with the portion where each pixel electrode PX is electrically connected via the underlying planarization film OC. The electrically connected portion is overlapped with the counter voltage signal line CL via the color filter FIL and the insulating film GI, and the capacitive element Cstg is formed in each of these overlapping portions.
[0081]
The capacitive element Cstg has a function of, for example, accumulating a video signal supplied to the pixel electrode PX for a relatively long time.
[0082]
An alignment film ORI1 is formed on the upper surface of the transparent substrate SUB1 on which the counter electrode CT is formed in this manner so as to cover the counter electrode CT. This alignment film ORI1 is a film that is in direct contact with the liquid crystal and determines the initial alignment direction of the molecules of the liquid crystal by rubbing formed on the surface thereof.
[0083]
<Relationship with other adjacent pixels>
FIG. 1 is a diagram showing a cross section of each pixel region that is adjacent to each other and includes a red color filter FIL (R), a green color filter (G), and a blue color filter (B). Note that the pixel shown in FIG. 4 shows the case where there are two pixel electrodes PX and three counter electrodes CT. Here, for simplicity of explanation, one pixel electrode PX and one counter electrode CT are shown. Shows the case of two.
In FIG. 1, first, the red color filter FIL (R), the green color filter (G), and the blue color filter (B) are formed with different layer thicknesses. As described above, in order to balance the transmittance and color purity of each color filter FIL, the thickness of each layer may be set uniquely, or the thickness may not be uniform due to manufacturing variations. Because.
[0084]
For this reason, the difference in the layer thickness of each color filter FIL is reflected in the height from the surface of the transparent substrate SUB1 of the planarization film OC formed thereon, and the height of the planarization film OC is the color filter. If the layer thickness of the FIL is large, the layer is formed high, and if the layer thickness of the color filter FIL is small, the layer is formed low.
[0085]
  In addition, thisreferenceIn the example, the planarization film OC is composed of a resin film formed by coating, but as the name suggests, it is difficult to completely planarize, and even if complete planarization is desired, it is difficult to manufacture. The fact is that it is complicated.
[0086]
Therefore, the liquid crystal layer thickness (liquid crystal gap) is small in a pixel having a large color filter FIL layer thickness, and the liquid crystal layer thickness is large in a pixel having a small color filter FIL layer thickness.
[0087]
The liquid crystal is interposed between the transparent substrate SUB1 and the transparent substrate SUB2 disposed opposite to the transparent substrate SUB1, and at least the color filter FIL is not formed on the liquid crystal side surface of the transparent substrate 2. ing.
[0088]
Thus, in a pixel region where the layer thickness of the liquid crystal is small, if a constant liquid crystal light transmittance is to be obtained in that portion, the voltage applied between the pixel electrode PX and the counter electrode CT must be increased. In addition, in the pixel region where the liquid crystal layer thickness is large, the voltage applied between the pixel electrode PX and the counter electrode CT must be reduced.
[0089]
In other words, when the voltage between the pixel electrode PX and the counter electrode CT is made uniform, the light transmittance of the liquid crystal varies depending on the layer thickness of the color filter FIL.
[0090]
  Because of this, the bookreferenceIn the example, for example, when the layer thicknesses are reduced in the order of a red (R) color filter, a green (G) color filter, and a blue (B) color filter, the planarizing film superimposed on each color filter. The OC film thickness is set to increase sequentially.
[0091]
More specifically, the thickness of the planarization film OC is expressed by the following equation (1),
[0092]
[Expression 1]
        0 <Differential film thickness difference between pixel regions
          <Difference in color filter film thickness between pixel areas (1)
Set to satisfyThe
[0093]
The thicker pixel of the color filter FIL is set so as to satisfy the relationship that the planarization film OC is thicker.
[0094]
When using the same material as that of the conventional flattening film OC in terms of its viscosity, the coating is performed by spin coating, but by controlling the number of rotations of the spin to an appropriate value as described above. The thickness can be set. Of course, methods other than spin coating may be used.
[0095]
The liquid crystal display device configured as described above can avoid an increase in driving voltage due to the attenuation of the driving electric field due to the thick layer thickness of the planarizing film OC, and is caused by the birefringence mode due to the thick liquid crystal layer thickness. A decrease in drive voltage can be avoided.
[0096]
When these work in a complementary manner, variations in driving voltage for the liquid crystal can be suppressed.
[0097]
  In addition, otherreferenceAs an example, the following equation (2),
[0098]
[Expression 2]
1/4 x thickness of color filter between pixels
<Difference in film thickness of planarization film OC between pixels
<3/4 × Difference in color filter FIL film thickness between pixels
………… (2)
By satisfying the above, it is possible to further suppress the luminance unevenness.
[0099]
And when setting it as the structure mentioned above, since the surface will be planarized if the planarization film OC is too thick, the following formula (3),
[0100]
[Equation 3]
Film thickness of planarization film OC
<3/2 times the thickness of the thickest color filter FIL (3)
Is preferably satisfied.
[0101]
Furthermore, if it is too thin, the so-called step reduction effect will be reduced,
The following formula (4),
[0102]
[Expression 4]
1/4 of the film thickness of the thinnest color filter FIL
<Film thickness of planarization film OC
<3/2 times the film thickness of the thickest color filter FIL (4)
Is preferably satisfied.
[0103]
  referenceExample 2.
  FIG. 5 shows another example of the liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example, and is a figure corresponding to FIG.
[0104]
The configuration different from FIG. 1 is that the counter electrodes CT positioned on both sides of the drain signal line DL are connected to each other by covering the drain signal line DL.
[0105]
In this case, it is possible to sufficiently avoid the electric lines of force that are noise from the drain signal line DL being terminated at the counter electrode CT and terminating at the pixel electrode PX adjacent to the counter electrode CT.
[0106]
  referenceExample 3
  FIG. 6 shows another example of the liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example, and is a figure corresponding to FIG.
[0107]
The configuration different from FIG. 1 is that the counter electrode CT is formed over the entire area of each pixel region and is also connected to the adjacent counter electrode CT.
[0108]
In this case, as the material of the counter electrode CT, a translucent material such as ITO (Indium Tin Oxide) is used.
[0109]
In this case, there is no concern about the disconnection of the counter electrode CT, and the entire resistance value can be greatly reduced.
[0110]
  referenceExample 4
  FIG. 7 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example, and is a figure corresponding to FIG.
[0111]
In the configuration different from that in FIG. 5, the pixel electrode PX is provided in the lower layer of the planarizing film OC, and the counter electrode CT is provided in the upper layer.
[0112]
Also in this case, the counter electrodes CT positioned on both sides of the drain signal line DL are connected to each other over the drain signal line DL.
[0113]
Since the level difference due to the planarization film OC is smaller than the level difference due to the color filter FIL, the counter electrode CT formed at the level difference portion is formed on the leveling film OC.
[0114]
  referenceExample 5.
  FIG. 8 shows another example of the liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example, and is a figure corresponding to FIG.
[0115]
The configuration different from FIG. 1 is that the pixel electrode PX is provided in the upper layer of the planarizing film OC and the counter electrode CT is provided in the lower layer, and the layers of each electrode are replaced.
[0116]
Even in this case, the same effect can be obtained.
[0117]
  referenceExample 6
  FIG. 9 shows another example of the liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example, for example, is a figure corresponding to FIG.
[0118]
6 is different from FIG. 6 in that the spacer for forming a gap between the transparent substrate SUB2 and the transparent substrate SUB1 is formed on the surface of the transparent substrate SUB2 on the liquid crystal side by, for example, selective etching of a resin material by a photolithography technique. It is comprised by the support | pillar SUP.
[0119]
In order to apply the present invention, it is required to set the layer thickness of the liquid crystal accurately, so that the variation in the height can be reduced by the spacer by the support column SUP.
[0120]
In this case, the position where the spacer is formed is set so that the tip thereof is in contact with the color filter FIL having the largest film thickness. Since the flattening film OC formed on the color filter FIL having the largest film thickness is small and its variation is small, it is possible to ensure a uniform gap by the spacer.
[0121]
In addition, the spacer also has a large variation when the height itself is large, but by contacting the color filter FIL having the largest film thickness, the height can be reduced and the variation can be reduced. Uniformity can be ensured.
[0122]
  referenceExample 7.
  FIG. 10 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example, and is a figure corresponding to FIG.
[0123]
The structure different from FIG. 9 is that the spacer by the support SUP is formed on the liquid crystal side surface of the transparent substrate 1.
[0124]
  referenceExample 8
  FIG. 11 shows another pixel of the liquid crystal display device according to the present invention.referenceIt is a top view which shows an example. FIG. 12 is a cross-sectional view taken along line XII-XII in FIG.
[0125]
  The liquid crystal display device shown in FIG.referenceUnlike the liquid crystal display device shown in the example, the color filter FIL is formed on the transparent substrate SUB2 side, and the planarizing film OC is formed so as to cover the color filter FIL.
[0126]
In each pixel region on the surface of the transparent substrate SUB1 on the liquid crystal LC side, a pixel electrode PX is formed on the gate insulating film GI. A counter electrode CT is formed on the upper surface of the laminate of the protective film PSV2.
[0127]
The counter electrode CT is disposed adjacent to the drain signal line DL, and is formed so as to cover the drain signal line DL, with the drain signal line DL interposed therebetween. It is formed so as to be connected to another counter electrode CT adjacent to the drain signal line of another adjacent pixel region.
[0128]
Then, the thickness of each protective film PSV1, PSV2 on the pixel electrode PX is set to d.₃, D₂The thickness of each protective film PSV1, PSV2 of the protective film PSV1, PSV2 in the region between the counter electrode CT and the pixel electrode PX is d.₃’, D₂′ And the relationship between them is the following equation (5):
[0129]
[Equation 5]
d₃≒ d₃', D₂<D₂‘<D₂+ d₄       ...... (5)
When the film thickness d of the pixel electrode PX is satisfied.₄The thickness of the liquid crystal on the pixel electrode PX (liquid crystal gap) d₁And the liquid crystal gap d on the region between the counter electrode CT and the pixel electrode PX₁The relationship of ′ is the following equation (6),
[0130]
[Formula 6]
d₁≒ d₁’(However, d₁≦ d₁’) …… (6)
It has become.
[0131]
Where d₁≦ d₁‘Becomes to d in actual manufacturing.₁> D₁This is because it is difficult to manufacture so as to be '.
[0132]
Thereby, the concentration of the electric field due to the liquid crystal gap unevenness in each pixel is reduced.
[0133]
Note that the approximation in the above formulas (5) and (6) is desirably 100 nm or less.
[0134]
Further, the electric field generated between the counter electrode CT and the pixel electrode PX is weakened by the protective films PSV1 and PSV2 interposed between these electrodes.
[0135]
From the relationship of the above equation (5), the electric field applied to the protective films PSV1 and PSV2 on the pixel electrode PX is smaller than the electric field applied to the protective films PSV1 and PSV2 in the region between the counter electrode CT and the pixel electrode PX. Liquid crystal gap d₁An electric field is easily applied to the liquid crystal at the location.
[0136]
FIGS. 13A, 13B, and 13C are diagrams showing the thickness x of the protective film on the pixel electrode PX and the change in the electric field in the liquid crystal thereby, as will be apparent from FIG. As the protective film thickness x decreases, the electric field on the pixel electrode PX increases.
[0137]
For this reason, in this method, which is a lateral electric field drive, a uniform electric field can be formed between the counter electrode CT and the pixel electrode PX in each pixel region.
[0138]
Incidentally, in the conventional configuration, d₃≒ d₃’D₂≒ d₂′, And the film thickness d of the pixel electrode PX₄Affected by the liquid crystal gap d on the pixel electrode PX₁And a liquid crystal gap d in a region between the counter electrode CT and the pixel electrode PX₁The relationship of ‘₁+ d₄≒ d₁'.
[0139]
In a birefringence mode liquid crystal used for lateral electric field driving, the wider the liquid crystal gap, the lower the liquid crystal driving voltage. Therefore, the liquid crystal gap d₁The liquid crystal at ‘d’ is d₁It becomes easier to drive at a lower voltage than the liquid crystal at this point.
[0140]
The liquid crystal gap d₁The shortest length X between the counter electrode CT and the pixel electrode PX passing through the surface of the protective film PSV2 at₁Is the liquid crystal gap d₁The shortest length X between the counter electrode CT and the pixel electrode PX passing through the surface of the protective film PSV2 at '₁Longer than 'and the above formula d₃≒ d₃’D₂≒ d₂Therefore, the expression E = A × V / x (E: electric field, V: voltage applied to the counter electrode and the pixel electrode, x: the shortest length of the counter electrode and the pixel electrode passing through the surface of the protective film PSV2) , A: positive proportionality constant)₁The electric field applied to the position 'is the liquid crystal gap d₁The electric field in the pixel area near the pixel electrode PX becomes weak, causing a decrease in light transmittance.
[0141]
  referenceExample 9
  FIG. 14 shows the present invention.Reference exampleFIG. 15 shows a cross-sectional view of a pixel in another part of the liquid crystal display device, and FIG. 15 shows a cross-sectional view of the pixel in another part of the liquid crystal display device. For example, in the liquid crystal display portion AR of the liquid crystal display device shown in FIG. 16, a cross-sectional view of the pixel at the portion X in the drawing is shown in FIG. 14, and a cross-sectional view of the pixel at the portion Y in the drawing is shown in FIG. In this case, the cross-sectional location of the pixel is the same as that shown in FIG.
[0142]
Comparing FIG. 14 and FIG. 15, the first different configuration is that the protective film PSV1 is formed with a different thickness at the liquid crystal display portion AR. The film thickness of the protective film PSV1 in the case of FIG.₃On the other hand, the film thickness of the protective film PSV1 in the case of FIG.₃(<X₃).
[0143]
In the formation of the protective film PSV1, it is not uniformly formed over the entire area of the liquid crystal display portion AR, indicating that the film thickness varies.
[0144]
Here, the protective film PSV2 formed on the upper surface of the protective film PSV1 has a film thickness of x in the case of FIG.₂On the other hand, in the case of FIG.₂(≒ x₂) And they are almost equal.
[0145]
At this time, the electric field applied to the region between the counter electrode CT and the pixel electrode PX is caused by the liquid crystal gap x₁, Y₁Is x₁≒ y₁(Equal to the diameter of the beads contained in the liquid crystal), the thickness of the protective film PSV1 becomes high.
[0146]
  Because of this, the bookreferenceIn the example, the protective film PSV2 has a thickness of x so that the electric field is uniform in each pixel region.₂<Y₂It is set to become. X of each film thickness of the protective film PSV1₃> Y₃This is to supplement the relationship.
[0147]
As a result, the following equation (7)
[0148]
[Expression 7]
x2 + x3≈y2 + y3, x₃> Y₃, X₂<Y₂  ...... (7)
The relationship is established.
[0149]
  Each of the abovereferenceIn the example, the pixel electrode PX is formed in the lower layer and the counter electrode CT is formed in the upper layer with respect to the protective film PSV, but these are reversed, that is, the pixel electrode is positioned in the upper layer and the counter electrode is positioned in the lower layer. Needless to say, the present invention can be applied to any other configuration.
[0150]
  referenceExample 10
  FIG. 17 shows another liquid crystal display device according to the present invention.referenceIt is a block diagram which shows an example, and is a figure corresponding to FIG.
[0151]
If the distance from the transparent substrate SUB1 to the liquid crystal layer varies depending on the layer structure of each pixel to be compared on the transparent substrate SUB1, the thickness of the liquid crystal layer also varies. In the horizontal electric field method, the driving voltage depends on the thickness of the liquid crystal layer. The thicker the liquid crystal layer, the same luminance can be obtained at a lower voltage. In this case, as shown in FIG. 17, assuming that the distances between the electrodes are all equal in each pixel, the pixel in the X region in the figure has a higher drive voltage than the pixel in the Y region. This will be described with reference to FIG. FIG. 23 is a BV curve with the voltage V on the horizontal axis and the luminance B on the vertical axis. The curve A is a BV curve in the region X in FIG. 17, and the curve B is a BV curve in the Y region. is there. The curve A has a BV curve that is gentler than the curve B, and therefore, the gradation displayed for a certain voltage is different.
[0152]
  So bookreferenceIn the example, as shown in FIG. 17, the distance between the electrodes has a special configuration. The distance from the substrate SUB1 to the counter electrode CT is longer in the pixel corresponding to the X region than in the pixel corresponding to the Y region, and has a relationship of d10> d20.
[0153]
In this case, a plurality of counter electrodes CT, for example, two for each pixel are formed. When the distance between the counter electrodes CT is L3 for pixels corresponding to the X region and L6 for pixels corresponding to the Y region, the relationship of L6> L3 is satisfied. That is, the distance between the counter electrodes CT is shortened in the pixel corresponding to the X region.
[0154]
Thereby, when the same voltage is applied, the electric field strengths formed in the X region and the Y region can be made closer to each other, and the slopes of the BV curves in both regions can be made closer. Thereby, the shift of gradation can be improved.
[0155]
Further, the distance between the pixel electrode PX and the counter electrode CT in the pixel corresponding to the region X is L1 and L2. The distances between the pixel electrode PX and the counter electrode CT in the pixels corresponding to the Y region are L4 and L5. At this time, L4, L5> L1, L2, or at least one of L4> L1 or L4> L2, L5> L1 or L5> L2 is satisfied, so that the same voltage is applied to the X region and the Y region. The electric field strengths formed can be made closer to each other, and the slopes of the BV curves in both regions can be made closer. Thereby, the shift of gradation can be improved.
[0156]
In FIG. 17, for example, the protective film PSV1 is an inorganic film, and the protective film PSV2 is an organic film. In FIG. 17, the counter electrode CT is arranged on the video signal line DL via the protective film PSV2.
[0157]
  As a result, the leakage electric field from the drain signal line DL can be shielded while suppressing the parasitic capacitance between the drain signal line DL and the counter electrode CT. In order to sufficiently reduce the parasitic capacitance and sufficiently achieve the leakage electric field shielding effect, it is desirable that the protective film PSV2 has a certain thickness. For this purpose, the protective film PSV2 is preferably an organic film. However, the organic film has a drawback that film thickness unevenness inherent to the coating apparatus tends to occur. But bookreferenceThe concept of the example makes it possible to avoid the influence of the difference in film thickness on the BV curve, so that only the shielding effect can be sufficiently achieved.
[0158]
  referenceExample 11
  FIG. 18 shows another liquid crystal display device according to the present invention.referenceIt is a block diagram which shows an example, and is a figure corresponding to FIG.
[0159]
FIG. 18 is a further improvement on the configuration of FIG. 17, and is different in that the number of counter electrodes CT and the number of pixel electrodes PX are increased as compared with the case of FIG.
[0160]
Further, there is a difference in that the counter electrode CT and the pixel electrode PX are both formed in the upper layer of the protective film PSV2. Other than that, it is the same as the case of FIG. 17, and the same effect as the case of FIG. 17 can be obtained.
[0161]
In FIG. 18, the distance of the pixel electrode PX from the substrate SUB1 is d30> d31, which is larger in the X region than in the Y region. In this case, when the distance between the pixel electrodes PX is L7 in the X region and L8 in the Y region, the relationship L8> L7 is satisfied.
[0162]
Thus, as in the case of FIG. 17, it is possible to make the electric field strengths formed in the X region and the Y region closer to each other when the same voltage is applied, and the slope of the BV curve in both regions. Can be brought closer. Therefore, gradation shift can be improved.
[0163]
  Example1.
  FIG. 19 shows a liquid crystal display device according to the present invention.oneIt is a block diagram which shows an Example, and is a figure corresponding to FIG.
[0164]
The improvement in gradation shift described with reference to FIG. 17 is effective as a configuration that provides a difference in the thickness of the liquid crystal layer between adjacent pixels.
[0165]
That is, FIG. 19 shows a configuration in which the thickness of the liquid crystal layer is different between adjacent pixels. Here, a color filter FIL is formed instead of the protective film PSV2. FIG. 19 shows a cross-sectional structure of a plurality of pixels in the extending direction of the gate signal line GL. The color of the color filter FIL is formed by forming one of R, G, and B for each pixel to form three primary colors. Yes. The boundary of each color filter FIL is located on the drain signal line DL.
[0166]
Here, in the liquid crystal display device, it is necessary to realize a predetermined color, and it is difficult to make the thickness of the color filter FIL completely the same between colors. For this reason, as shown in FIG. 19, the distance from the transparent substrate SUB1 to the liquid crystal layer is different for each pixel according to the color filter FIL, and the thickness of the liquid crystal layer is different.
[0167]
In order to improve gradation shift with such a structure, it is effective to use at least the following configuration (1) or (2). That is,
(1) The longer the distance from the substrate surface SUB1 to the counter electrode CT, the shorter the distance between the counter electrodes CT.
(2) The longer the distance from the substrate surface SUB1 to the counter electrode CT, the shorter the distance between each counter electrode CT and the pixel electrode PX.
[0168]
In this embodiment, for example, both the above configurations (1) and (2) are applied to further improve the gradation shift.
[0169]
In addition, the order of the R, G, and B film thicknesses in this embodiment is for explanation, and is not necessarily in this order. This is because the color filter FIL is appropriately set in accordance with the characteristics of each color material used for the color filter FIL.
[0170]
Of course, it may be configured to satisfy at least one of the above (1) and (2).
[0171]
  Example2.
  20 is a block diagram showing another embodiment of the liquid crystal display device according to the present invention and corresponds to FIG.
[0172]
  A difference from the case of FIG. 19 is that the counter electrode CT and the pixel electrode PX are arranged on the color filter FIL. Even in this configuration, the embodiment1By applying at least one of the configurations (1) and (2) described in (1), it is possible to reduce gradation shift. In this embodiment, both the configurations (1) and (2) are applied to further improve the gradation shift.
[0173]
  Example3.
  FIG. 21 is a block diagram showing another embodiment of the liquid crystal display device according to the present invention and corresponds to FIG.
[0174]
A different configuration from that in FIG. 19 is that an overcoat film OC is formed on the color filter FIL. The counter electrode CT is formed in the upper layer of the overcoat film OC, and the pixel electrode PX is formed in the lower layer of the overcoat film OC.
[0175]
  This configuration is also an example1By applying at least one of the configuration (1) and the configuration (2) shown in (2), it is possible to reduce gradation shift.
[0176]
Furthermore, this embodiment is characterized by the relationship between the thickness of the overcoat film OC and the color filter FIL. That is, the overcoat film OC is thinned in the pixel with the thick color filter FIL, and the overcoat film OC is thickened in the pixel with the thin color filter FIL. Thereby, the difference in the thickness of the liquid crystal layer between pixels of different colors can be reduced as compared with the state without the overcoat film OC. As a result, gradation shift can be reduced.
[0177]
The overcoat film OC is coated with a liquid overcoat material having an appropriately set viscosity, and after standing for about several tens of seconds, the overcoat material is heated together with the transparent substrate SUB1, thereby realizing the configuration shown in FIG. be able to.
[0178]
  In this embodiment, the structural features that reduce the difference in thickness of the liquid crystal layer and the embodiment1By applying both the configuration of (1) and the configuration of (2) shown in (1), the gradation shift can be further improved.
[0179]
  Example4.
  FIG. 22 is a block diagram showing another embodiment of the liquid crystal display device according to the present invention and corresponds to FIG.
[0180]
A configuration different from the case of FIG. 19 is that the pixel electrode PX is also above the overcoat film OC.
[0181]
  This configuration is also an example1By applying at least one of the configuration (1) and the configuration (2) shown in FIG.
[0182]
Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically.
[0183]
【The invention's effect】
As will be apparent from the above description, according to the liquid crystal display device of the present invention, it is possible to improve display quality.
[Brief description of the drawings]
FIG. 1 shows a liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 2 shows a liquid crystal display device according to the present invention.referenceIt is a whole equivalent circuit diagram which shows an example.
FIG. 3 shows a pixel of a liquid crystal display device according to the present invention.referenceIt is a top view which shows an example.
4 is a cross-sectional view taken along line IV-IV in FIG.
FIG. 5 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 6 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 7 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 8 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 9 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 10 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 11 shows another pixel of the liquid crystal display device according to the present invention.referenceIt is a top view which shows an example.
12 is a cross-sectional view taken along line XII-XII in FIG.
FIG. 13 shows the present invention.Reference exampleIt is explanatory drawing explaining the effect by.
FIG. 14 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 15 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 16 is an explanatory diagram necessary for showing the location of each pixel shown in FIGS. 14 and 15;
FIG. 17 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 18 shows another liquid crystal display device according to the present invention.referenceIt is sectional drawing which shows an example.
FIG. 19 shows a liquid crystal display device according to the present invention.oneIt is sectional drawing which shows an Example.
FIG. 20 is a cross-sectional view showing another embodiment of the liquid crystal display device according to the present invention.
FIG. 21 is a cross-sectional view showing another embodiment of the liquid crystal display device according to the present invention.
FIG. 22 is a cross-sectional view showing another embodiment of the liquid crystal display device according to the present invention.
FIG. 23 is an explanatory diagram of a deviation of a BV curve.
[Explanation of symbols]
  SUB ... Transparent substrate, GL ... Gate signal line, DL ... Drain signal line, AS ... Semiconductor layer, TFT ... Thin film transistor, PX ... Pixel electrode, CT ... Counter electrode, GI ... Insulating film, PSV ... Protective film, ORI ... Alignment film LC ... Liquid crystal.

Claims (5)

A liquid crystal layer sandwiched between first and second substrates facing each other;
A plurality of pixel regions that are regions surrounded by a plurality of gate signal lines and drain signal lines formed on the first substrate;
Having a pixel electrode and a counter electrode formed in each pixel region on the liquid crystal layer side surface of the first substrate,
A color filter is provided between the counter electrode and the first substrate, and the pixel electrode is formed between the first substrate and the color filter;
The color filter is different in color and thickness between adjacent pixel regions,
The layer thickness of the liquid crystal layer differs for each color of the corresponding color filter,
The pixel region having a long distance between the first substrate and the counter electrode is a distance between the counter electrodes in the pixel region with respect to the pixel region having a short distance between the first substrate and the counter electrode. And a distance between the pixel electrode and the counter electrode is shortened. A liquid crystal layer sandwiched between first and second substrates facing each other;
A plurality of pixel regions that are regions surrounded by a plurality of gate signal lines and drain signal lines formed on the first substrate;
Having a pixel electrode and a counter electrode formed in each pixel region on the liquid crystal layer side surface of the first substrate,
A color filter is provided between the counter electrode and the first substrate, and the pixel electrode is formed between the first substrate and the color filter;
The color filter is different in color and thickness between adjacent pixel regions,
The layer thickness of the liquid crystal layer differs for each color of the corresponding color filter,
The pixel region having a long distance between the first substrate and the counter electrode is different from the pixel region having a short distance between the first substrate and the counter electrode in the pixel region. A liquid crystal display device characterized by shortening a distance between electrodes.   The liquid crystal display device according to claim 1, wherein the pixel electrode is formed in the same layer as the counter electrode. The liquid crystal display device according to claim 3 , wherein an overcoat film is formed between the color filter and the counter electrode.   3. The liquid crystal display device according to claim 1, wherein the color filter is one of red, green, and blue, and the thickness of each color has a relationship of red> green> blue. .

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