JP2006003808A - Liquid crystal apparatus and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction of display quality, reduction of transmittance and the like due to vertical crosstalk to obtain display of high quality, in an active matrix liquid crystal apparatus. <P>SOLUTION: A plurality of scanning lines are formed on a color filter substrate, a plurality of data lines, TFD elements and pixel electrodes are formed on an element substrate and a liquid crystal is encapsulated in between the both substrates. The data lines 32 and the TFD elements 21 are covered with an over layer 25 and pixel electrodes 10 are connected to the TFD elements through contact holes 25a formed in the over layer and further connected to the data lines. A lower limit value of the thickness of the over layer formed on the upper side substrate is regulated based on the following formula 1 and formula 2. Formula 1 is Vc=äC'<SB>TFD</SB>/(C<SB>Lc</SB>+C'<SB>TFD</SB>)}×Vd<V(T50) and formula 2 is Cp=ε<SB>0</SB>×ε<SB>ovL</SB>(S/d). Thereby, reduction of display quality, reduction of transmittance and the like due to vertical crosstalk can be prevented and display of high quality can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal device and an electronic apparatus suitable for use in displaying various information.

  In a liquid crystal display device called a two-terminal element type active matrix or TFD (Thin Film Diode), since the distance between the pixel electrode and each signal line on both sides is generally narrow, the pixel electrode and the connection to the pixel electrode are particularly important. A so-called vertical crosstalk occurs due to the influence of the parasitic capacitance generated between adjacent signal lines that are not formed, and the display quality is degraded. Here, vertical crosstalk is a color such as cyan, magenta, yellow, etc., which is a single color such as red, blue, or green, or a complementary color relationship with each color of red, blue, and green, with gray as the background color. Is a phenomenon in which an area positioned in the vertical direction of the rectangular display area is displayed brighter than the background color to be displayed and is displayed in a slightly colored manner.

  Note that a transmissive liquid crystal display device excellent in visibility is known by using a TFT (thin film transistor) as an active element and defining the thickness of an interlayer insulating film to a predetermined thickness (for example, Patent Document 1). See).

Japanese Patent No. 3272212

  The present invention has been made in view of the above problems, and by defining the lower limit value of the thickness of the insulating layer to a predetermined thickness, it is possible to reduce display quality and transmittance due to vertical crosstalk. It is an object of the present invention to provide a liquid crystal device having an overlayer structure capable of preventing and obtaining a high-quality display and an electronic apparatus using the liquid crystal device.

In one aspect of the present invention, a liquid crystal device in which liquid crystal is sealed between a first substrate and a second substrate that are arranged to face each other, the first substrate is a transparent substrate having translucency, A data line formed on the transparent substrate, a two-terminal element formed on the transparent substrate and connected to the data line, a contact hole and formed on the transparent substrate, and the data line and the two An insulating film covering the terminal element; and a pixel electrode formed on the insulating film and connected to the two-terminal element through the contact hole; the second substrate includes a scanning line; The capacitance of the terminal element is C _TFD , the pixel capacitance of the liquid crystal sandwiched between the scanning line facing the pixel electrode is C _Lc , and the data line connected to the pixel electrode via the two-terminal element and the data line Parasitic capacitance generated between pixel electrodes C _p , the amplitude voltage of the data line is V _d , the sum of the capacitance C _TFD of the two-terminal element and the parasitic capacitance C _p is C ′ _TFD , and the transmittance in the voltage-transmittance characteristics of the liquid crystal is 50%. When the corresponding voltage is V (T50), the parasitic capacitance _Cp is inversely proportional to the thickness of the insulating film, and the thickness of the insulating film is {C ′ _TFD / (C _Lc + C ′ _TFD )} × It is set so as to satisfy V _d <V (T50).

  According to the above liquid crystal device, in the first substrate, a two-terminal element such as a thin film diode and a data line are formed on the transparent substrate. In addition, an insulating film (also referred to as an overlayer) is formed on the transparent substrate, and the data lines and the two-terminal elements are covered with the insulating film. A pixel electrode is formed on the insulating film. The pixel electrode is connected to the two-terminal element through an opening formed in the insulating film, that is, a contact hole. Thus, this liquid crystal device has a so-called overlayer structure.

In this liquid crystal device, when an insulating film is formed too thinly on the transparent substrate, so-called vertical crosstalk occurs due to the influence of parasitic capacitance generated between the pixel electrode and the data line connected thereto, Display quality deteriorates. Therefore, in this liquid crystal device, the capacitance of the two-terminal element is C _TFD , the pixel capacitance of the liquid crystal sandwiched between the scanning lines facing the pixel electrode is C _Lc , and the pixel electrode is interposed via the two-terminal element. C _{p is} the parasitic capacitance generated between the data line connected to the pixel electrode and the pixel electrode, V _{d is} the amplitude voltage of the data line, and the sum of the capacitance C _TFD of the two-terminal element and the parasitic capacitance C _p is C ′ _TFD , where the voltage corresponding to 50% transmittance in the voltage-transmittance characteristics of the liquid crystal is V (T50), the parasitic capacitance _Cp is inversely proportional to the thickness of the insulating film, The thickness is set so as to satisfy {C ′ _TFD / (C _Lc + C ′ _TFD )} × V _d <V (T 50). In a preferred example, the lower limit value of the thickness of the insulating film can be 0.5 μm or more. Thus, an insulating film is formed on the transparent substrate with a thickness equal to or greater than the calculated thickness of the insulating film. As a result, it is possible to prevent the display quality from being lowered and the transmittance from being lowered due to vertical crosstalk, and high-quality display can be obtained.

In one aspect of the liquid crystal device, the data line is formed at a position overlapping the pixel electrode on the transparent substrate, and a dielectric constant ε _{0 of} vacuum, a relative dielectric constant of the liquid crystal ε, and the pixel electrode The thickness d of the insulating film is defined on the basis of the following formula C _p = ε ₀ × ε × (S / d) where S is the area where the data lines overlap.

According to this aspect, in the above formula {C ′ _TFD / (C _Lc + C ′ _TFD )} × V _d <V (T50), the parasitic capacitance C _p that is less than V (T50) is calculated, and the parasitic capacitance is calculated. Substituting C _p into the above formula C _p = ε ₀ × ε × (S / d), the lower limit value of the thickness d of the insulating film is calculated. Thus, an insulating film is formed on the transparent substrate with a thickness equal to or greater than the calculated thickness of the insulating film. As a result, it is possible to prevent the display quality from being lowered and the transmittance from being lowered due to vertical crosstalk, and high-quality display can be obtained.

  In another aspect of the liquid crystal device, the data line may be formed on the transparent substrate at positions on both sides of the pixel electrode when the transparent substrate is viewed in plan. Thereby, since the distance between the pixel electrode and the data line is increased, the lower limit value of the thickness of the insulating film can be defined to a smaller value. Therefore, by setting the lower limit of the thickness of the insulating film formed on the transparent substrate to 0.5 μm or more, it is possible to prevent deterioration in display quality and transmittance due to vertical crosstalk, and so on. Display can be obtained.

  In addition, an electronic device including the above-described liquid crystal display device can be configured.

[First embodiment]
The best mode for carrying out the present invention will be described below with reference to the drawings. In the following first embodiment, the present invention is applied to a liquid crystal display device. In the first embodiment, the lower limit value of the thickness of the overlayer formed on the transparent substrate is defined to be a predetermined thickness, thereby preventing a reduction in display quality and a decrease in transmittance due to vertical crosstalk. To obtain a high-quality display image.

  First, the configuration of the liquid crystal display device according to the first embodiment of the present invention will be described. FIG. 1 is a plan view schematically showing a schematic configuration of a liquid crystal display device 100 of the present invention. In FIG. 1, the configuration of electrodes and wirings of the liquid crystal display device 100 is mainly shown as a plan view. Here, the liquid crystal display device 100 of the present invention is a liquid crystal display device having an overlayer structure. The liquid crystal display device 100 of the present invention is an active matrix driving method using a TFD element and is a transflective liquid crystal display device. The liquid crystal display device 100 of the present invention is also a liquid crystal display device having a normally white mode. FIG. 2 is a schematic cross-sectional view along the cutting line A-A ′ in the liquid crystal display device 100 of FIG. 1.

  First, the cross-sectional configuration of the liquid crystal display device 100 taken along the cutting line A-A ′ will be described with reference to FIG. 2, and then the configuration of electrodes and wirings of the liquid crystal display device 100 will be described.

  In FIG. 2, the liquid crystal display device 100 includes an element substrate 92 and a color filter substrate 91 disposed so as to be opposed to the element substrate 92 with a frame-shaped seal member 3 attached thereto, and TN (Twisted Nematic) inside. ) Type liquid crystal is sealed to form a liquid crystal layer 4. A conductive member 7 such as a plurality of gold particles is mixed in the frame-shaped seal member 3. The element substrate 92 includes a transparent substrate 1 (hereinafter, also referred to as “upper substrate”) such as a light-transmitting glass, and the color filter substrate 91 is also a transparent substrate 2 (hereinafter referred to as “transparent glass”). Also referred to as a “lower substrate”.

  On the inner surface of the lower substrate 2, a scattering layer 9 having fine irregularities formed on the surface is formed. On the inner surface of the scattering layer 9, a reflective layer 5 having a predetermined thickness is formed. A plurality of rectangular openings 20 (hereinafter also referred to as “transparent areas”) are formed in each reflective layer 5. Each reflective layer 5 can be formed of a thin film such as aluminum, an aluminum alloy, or a silver alloy. The opening 20 is formed so as to have an area of a predetermined ratio with respect to the total area of the sub-pixel SG for each sub-pixel SG arranged in a matrix in the vertical and horizontal directions on the inner surface of the color filter substrate 91.

  On the reflective layer 5 and between the sub-pixels SG, a black light-shielding layer BM is provided between the adjacent sub-pixels SG to prevent light from entering from one sub-pixel to the other sub-pixel. Is formed. The black light shielding layer BM can be made of a black resin material, for example, a black pigment dispersed in a resin. Instead of this, an overlapping light shielding layer (not shown) formed by overlapping R, G, and B colored layers may be used.

  On the reflective layer 5 and the opening 20, colored layers 6R, 6G, and 6B made of any of the three colors R, G, and B are formed for each subpixel SG. A color filter is constituted by the colored layers 6R, 6G, and 6B. A pixel G indicates a region for one color pixel composed of R, G, and B sub-pixels SG. In the following description, when referring to a colored layer regardless of color, it is simply referred to as “colored layer 6”, and when referring to a colored layer by distinguishing colors, it is referred to as “colored layer 6R” or the like. Further, as shown in FIG. 2, the thickness of the colored layer 6 formed on the opening 20 is formed to be thicker than the thickness of the colored layer 6 formed on the reflective layer 5. Thus, the colored layer 6 is designed to exhibit a desired hue and brightness in the reflective display mode and the transmissive display mode, respectively.

  A protective layer 18 made of a transparent resin or the like is formed on the colored layer 6 and the black light shielding layer BM. The protective layer 18 has a function of protecting the colored layer 6 from corrosion and contamination caused by chemicals used during the manufacturing process of the color filter substrate 91 and the liquid crystal display device 100. On the surface of the protective layer 18, a transparent electrode (scanning electrode) 8 (hereinafter also referred to as “scanning line of the lower substrate 2”) such as striped ITO (Indium-Tin Oxide) is formed. One end of the transparent electrode 8 extends into the seal member 3 and is electrically connected to the conducting member 7 in the seal member 3.

  On the other hand, a TFD element 21 and a data line 32 are formed on the inner surface of the upper substrate 1. On the inner surface of the upper substrate 1, a TFD element 21 is formed for each sub-pixel, and a plurality of TFD elements 21 arranged in the vertical direction are commonly connected to each data line 32. On the inner surface of the upper substrate 1, an insulating film made of transparent resin or the like and having an insulating property, that is, an overlayer 25 is formed. The TFD element 21 and the data line 32 are covered with the overlayer 25. The overlayer 25 has an opening, that is, a contact hole 25a for each subpixel. Each pixel electrode 10 is connected to each corresponding TFD element 21 and each data line 32 through each contact hole 25a. A protective layer 17 made of a transparent resin or the like is formed on each inner surface of the overlayer 25 and the pixel electrode 10. Scanning lines 31 are formed on the left and right peripheral edges on the inner surface of the upper substrate 1. One end of the scanning line 31 extends into the seal member 3, and the scanning line 31 is electrically connected to the conduction member 7 in the seal member 3.

  An alignment film (not shown) is formed on the inner surface of the transparent electrode 8 of the lower substrate 2 and the inner surface of the protective layer 17 of the upper substrate 1. In order to keep the thickness of the liquid crystal layer 4 uniform between these alignment films, particulate spacers (not shown) are randomly arranged. As a material for the spacer, a material mainly composed of silica or resin is preferable.

  A retardation plate (¼ wavelength plate) 11 and a polarizing plate 12 are arranged on the outer surface of the lower substrate 2, and a retardation plate (¼ wavelength plate) on the outer surface of the upper substrate 1. 13 and a polarizing plate 14 are arranged. A backlight 15 is disposed below the polarizing plate 12. The backlight 15 is preferably a point light source such as an LED (Light Emitting Diode) or a linear light source such as a cold cathode fluorescent tube.

  The transparent electrode 8 of the lower substrate 2, that is, the scanning line of the lower substrate 2, and the scanning line 31 of the upper substrate 1 are vertically connected via the conductive member 7 mixed in the seal member 3.

  When the reflective display is performed in the liquid crystal display device 100 of the first embodiment, the external light incident on the liquid crystal display device 100 travels along the path R shown in FIG. That is, the external light incident on the liquid crystal display device 100 is reflected by the reflective layer 5 and reaches the observer. In this case, the external light passes through the region where the colored layer 6 is formed, is reflected by the reflective layer 5 below the colored layer 6, and passes through the colored layer 6 again to have a predetermined hue. And brightness. Thus, a desired color display image is visually recognized by the observer.

  On the other hand, when transmissive display is performed, the illumination light emitted from the backlight 15 travels along the path T shown in FIG. 1 and is observed through the transmissive region, that is, the colored layer 6 on the opening 20. To the person. In this case, the illumination light has a predetermined hue and brightness by passing through the colored layer 6. Thus, a desired color display image is visually recognized by the observer.

  Next, with reference to FIG. 1, FIG. 3, and FIG. 4, the configuration of the electrodes and wirings of the element substrate 92 and the color filter substrate 91 of the present invention will be described. FIG. 3 is a plan view showing a configuration of electrodes, wirings, and the like of the element substrate 92 when the element substrate 92 is observed from the back direction (that is, the lower side in FIG. 2). FIG. 4 is a plan view showing the configuration of the electrodes of the color filter substrate 91 when the color filter substrate 91 is observed from the front direction (that is, the upper side in FIG. 2). In FIG. 3, the electrodes and wirings are formed on the back side in the observation direction, but are represented by solid lines for convenience of explanation. 3 and 4, other elements other than the electrodes and wiring are not shown for convenience of explanation.

  In FIG. 1, a region where the pixel electrode 10 of the element substrate 92 and the transparent electrode 8 of the color filter substrate 91 intersect constitute a sub-pixel SG which is the minimum unit of display. A region in which a plurality of the sub-pixels SG are arranged in a matrix in the vertical direction and the horizontal direction in the drawing is a display region V (region surrounded by a two-dot chain line). In the display area V, images such as letters, numbers, and figures are displayed. In FIG. 1, an area defined by the outer shape of the liquid crystal display device 100 and the display area V is a frame area 38 that does not contribute to image display.

  First, with reference to FIG. 3, the structure of the electrode and wiring of the element substrate 92 will be described. The element substrate 92 includes a TFD element 21, a pixel electrode 10, a plurality of scanning lines 31, a plurality of data lines 32, a Y driver IC 33, an X driver IC 34, and a plurality of external connection terminals 35.

  On the projecting region 36 of the element substrate 92, a Y driver IC 33 and an X driver IC 34 are mounted, for example, via an ACF (Anisotropic Conductive Film). In FIG. 3, the direction from the side 92a on the projecting region 36 side of the element substrate 92 to the side 92c on the opposite side is defined as the X direction, and the direction from the side 92d to the side 92b is defined as the Y direction.

  A plurality of external connection terminals 35 are formed on the overhang region 36. Each input terminal (not shown) of the Y driver IC 33 and the X driver IC 34 is connected to the plurality of external connection terminals 35 through conductive bumps. The external connection terminal 35 is connected to a wiring board (not shown) such as a flexible printed board via ACF or solder. Thereby, for example, signals and power are supplied to the liquid crystal display device 100 from an electronic device such as a mobile phone or an information terminal.

  The output terminal (not shown) of the X driver IC 34 is connected to the plurality of data lines 32 through conductive bumps. On the other hand, the output terminal (not shown) of each Y driver IC 33 is connected to the plurality of scanning lines 31 via conductive bumps. Accordingly, each Y driver IC 33 outputs a scanning signal to the plurality of scanning lines 31, and the X driver IC 34 outputs a data signal to the plurality of data lines 32.

  The plurality of data lines 32 are linear wirings extending in the vertical direction on the paper surface, and are formed in the X direction from the overhanging region 36 to the display region V. Each data line 32 is formed at a constant interval. Each data line 32 is connected to a plurality of TFD elements 21 at appropriate intervals, and each TFD element 21 is connected to a corresponding pixel electrode 10 through a contact hole 25a.

  The plurality of scanning lines 31 includes a main line portion 31a and a bent portion 31b that bends at substantially right angles to the main line portion 31a. Each main line portion 31 a is formed in the X direction from the overhanging region 36 in the frame region 38. Each main line portion 31a is formed substantially parallel to each data line 32 and at a predetermined interval. Each bent portion 31b extends in the Y direction to the inside of the seal member 3 located on the left and right in the frame region 38. The end portion of the bent portion 31 b is connected to the conductive member 7 in the seal member 3.

  Next, the configuration of the electrodes of the color filter substrate 91 will be described. The color filter substrate 91 has stripe-shaped transparent electrodes (scanning electrodes) 8 formed in the Y direction. As shown in FIGS. 1 and 4, the left end portion or the right end portion of each transparent electrode 8 extends into the seal member 3 and is connected to the conduction member 7 in the seal member 3.

  FIG. 1 shows a state where the color filter substrate 91 and the element substrate 92 are bonded together via the seal member 3 as described above. As shown in the figure, each transparent electrode 8 of the color filter substrate 91 is orthogonal to each data line 32 of the element substrate 92 and overlaps the plurality of pixel electrodes 10 in a row in a plane. Thus, the region where the transparent electrode 8 and the pixel electrode 10 overlap constitutes the sub-pixel SG.

  Further, the transparent electrode 8 (that is, the scanning line on the color filter substrate 91 side) of the color filter substrate 91 and the scanning line 31 of the element substrate 92 alternately overlap between the left side and the right side as shown in the figure. The transparent electrode 8 and the scanning line 31 are vertically connected via the conductive member 7 in the seal member 3. That is, conduction between each scanning line of the color filter substrate 91 as the transparent electrode 8 and each scanning line 31 of the element substrate 92 is alternately realized between the left side and the right side as shown in the figure. Thereby, the transparent electrode 8 of the color filter substrate 91 is electrically connected to the Y driver ICs 33 located on the left and right sides of the paper via the scanning lines 31 of the element substrate 92.

  Next, a gradation display method in the liquid crystal display device 100 will be described with reference to FIG. In this example, it is assumed that the liquid crystal panel is normally white. FIG. 5A shows a driving waveform of the scanning potential VA applied to the scanning electrode 8 from the Y driver IC 33 via the scanning line 31. FIG. 5B shows a drive waveform of the signal potential VB applied from the X driver IC 34 to the data line 32. FIG. 5C shows a driving waveform of the interelectrode voltage VAB of the scanning electrode 8 and the data line 32.

  The Y driver IC 33 applies a scanning potential VA to the scanning electrode 8 through the scanning line 31. On the other hand, the X driver IC 34 applies the signal potential VB to the data line 32. The potentials VA and VB will be described. First, a scanning potential VA as shown in FIG. 5A is applied to the scanning electrode 8. For each line selection period T, each scanning electrode 8 is sequentially selected via each scanning line 31, and a potential difference of ± Vsel with respect to a certain common potential VGND, that is, any potential having a voltage is applied. This voltage Vsel is called a selection voltage. Then, after the line selection period T, any potential having a voltage of ± Vhld with respect to the common potential VGND is applied. In the holding period Th, when the potential at the time of selection is VGND + Vsel, the potential of VGND + Vhld is applied, and when the potential at the time of selection is VGND-Vsel, the potential of VGND-Vhld is applied. This voltage Vhld is called a holding voltage. A period in which all the scan electrodes 8 are selected in a round is called a field period. In the next field period, the scan electrodes are sequentially selected using a selection voltage having a characteristic opposite to that of the previous field period. .

  On the other hand, as shown in FIG. 5B, any potential having a voltage of ± Vsig with respect to the common potential VGND is applied to the data line 32. Here, when the potential applied to the scan electrode 8 selected in a certain selection period is VGND + Vsel, VGND−Vsig is used as the ON potential Von, and VGND + Vsig is used as the OFF potential Voff. Further, when the potential applied to the scan electrode 8 selected in a certain selection period is VGND−Vsel, VGND + Vsig is used as the on potential Von and VGND−Vsig is used as the off potential Voff.

  That is, the waveform of the signal potential VB in each line selection period T is set according to the gradation of each pixel in the column related to the data line 32. First, the signal potential VB is set for each line selection period T. Are divided into an ON section and an OFF section, and are set to the ON potential Von in the ON section and to the OFF potential Voff in the OFF section. That is, the signal potential VB is pulse width modulated according to the gradation value. Then, the higher the gradation to be given to the pixel (the darker the normally white mode), the larger the proportion occupied by the ON section.

  Next, the interelectrode voltage VAB of the scan electrode 8 and the data line 32 is indicated by a solid line in FIG. This interelectrode potential VAB is applied to the liquid crystal layer 4. As shown in the figure, it can be seen that the absolute value of the interelectrode voltage VAB increases during the selection period of the pixel. Further, the liquid crystal layer voltage VLC applied to the liquid crystal layer 4 is indicated by hatching in FIG. When the liquid layer voltage VLC changes, the capacity formed by the liquid crystal layer 4 must be charged and discharged, so the liquid crystal layer voltage VLC changes in a transient response to the interelectrode voltage VAB. In FIG. 5C, the voltage VNL is the difference between the interelectrode voltage VAB and the liquid layer voltage VLC, that is, the terminal voltage of the TFD element 21. As described above, in the liquid crystal display device 100, gradation display is performed by pulse width modulation of the driving voltage applied to the liquid crystal layer 4.

(Overlayer structure)
First, an overlayer structure according to the liquid crystal display device 100 of the present invention will be described in detail with reference to FIGS. FIG. 6 is a plan view showing a layout of the plurality of pixel electrodes 10 and the like on the element substrate 92. FIG. 7A shows a cross-sectional view along the cutting line BB ′ of FIG. FIG. 7B shows an enlarged cross-sectional view of the region E1 in FIG. 7A, that is, the vicinity of the connection portion between the pixel electrode 10 and the TFD element 21 and the data line 32. Since FIG. 6 shows a configuration when the observation side is viewed from the back side, the front side in FIG. 6 and the upper side in FIG.

  The structure of the element substrate 92 in the liquid crystal display device 100 of the present invention, that is, the overlayer structure will be described. Although the protective layer 17 is formed so as to cover the pixel electrode 10 and the overlayer 25 (see FIG. 2), it is omitted in FIGS. 6 and 7 for convenience of explanation.

  A phase difference plate 13 and a polarizing plate 14 are disposed on the outer surface of the upper substrate 1. On the other hand, a TFD element 21 and a data line 32 are formed on the inner surface of the upper substrate 1.

  As shown in FIG. 7B, the TFD element 21 includes a first TFD element 21a and a second TFD element 21b. The first TFD element 21a and the second TFD element 21b include an island-shaped first metal film 322 made of tantalum tungsten or the like, and an insulating film 323 formed by anodizing the surface of the first metal film 322. And second metal films 316 and 336 formed on the surface and spaced apart from each other. Among these, the second metal films 316 and 336 are formed by patterning the same conductive film such as chromium, and the former second metal film 316 is branched from the data line 21 in a T shape, The latter second metal film 336 is used for connection to the connection portion 10z of the pixel electrode 10 such as ITO.

  Here, among the TFD elements 21, the first TFD element 21 a becomes the second metal film 316 / insulating film 323 / first metal film 322 in order when viewed from the data line 32 side. Due to the body / metal structure, the current-voltage characteristics are nonlinear in both positive and negative directions. On the other hand, when viewed from the data line 32 side, the second TFD element 21b becomes a first metal film 322 / insulating film 323 / second metal film 336 in the order opposite to the first TFD element 21a. The structure of For this reason, the current-voltage characteristics of the second TFD element 21b are obtained by making the current-voltage characteristics of the first TFD element 21a point-symmetric with respect to the origin. As a result, the TFD element 21 has a shape in which two TFDs are connected in series in opposite directions. Therefore, the current-voltage nonlinear characteristic is symmetric in both positive and negative directions compared to the case of using one element. become.

  As shown in FIG. 7B, a first metal film 312 and an insulating film 313 are formed from the upper substrate 1 below the data line 32. As shown in FIG. 6, the data lines 32a, 32b, and 32c are arranged at positions overlapping the pixel electrode 10 below the pixel electrodes 10a, 10b, and 10c, respectively.

  Further, an overlayer 25 is formed on the inner surface of the upper substrate 1, and the TFD element 21 and the data line 32 are covered with the overlayer 25. The overlayer 25 has a substantially circular opening, that is, a contact hole 25a in plan view. In particular, the thickness of the overlayer 25 sandwiched between the pixel electrode 10 and the upper substrate 1 is defined as D10 or more, which will be described later.

  Further, the pixel electrode 10 is formed on the inner surface of the overlayer 25. In FIG. 7A, the distance between the pixel electrode 10b and the data line 32b is D100.

  The pixel electrodes 10 are arranged in a matrix on the inner surface of the overlayer 25. The pixel electrodes 10a, 10b, and 10c are opposed to the colored layers 6 corresponding to B (blue), R (red), and G (green) colors, respectively. Each pixel electrode 10 has a connection portion 10 z that extends into the contact hole 25 a and is electrically connected to the TFD element 21. The connection portion 10z of each pixel electrode 10 is connected to the second metal film 336 of the corresponding TFD element 21 through the contact hole 25a. The pixel electrodes 10 belonging to the same column are commonly connected to one data line 32 via the TFD elements 21. In addition, the pixel electrodes 10 belonging to the same row face one transparent electrode 8 (scanning line).

(Method for defining the lower limit value of the thickness of the overlayer 25)
In a liquid crystal display device having an overlayer structure such as the liquid crystal display device 100 of the present invention, it is important how much the thickness of the overlayer 25 is defined. This is because if the overlayer 25 is formed too thick on the upper substrate 1, or conversely, if the overlayer 25 is formed too thin on the upper substrate 1, the display quality may be deteriorated. It is.

  Here, referring to Table 1 shown in FIG. 8A, the thickness of the overlayer 25 (see the thickness D10 of the overlayer 25 in FIG. 7A), the transmittance, and the hue (color). The relationship between contact hole processability and vertical crosstalk will be described. In Table 1, in order to roughly grasp the relationship between the thickness of the overlayer 25 and the transmittance, etc., when each of those elements is good, “◯” is indicated, and each of those elements is not good. In some cases, “x” is written.

  When the overlayer 25 is formed thick on the upper substrate 1, as shown in Table 1, the transmittance decreases, the hue (color) deteriorates, and the workability of the contact hole 25a decreases. , Vertical crosstalk is less likely to occur. That is, as the overlayer 25 becomes thicker, the proportion of the outside light and part of the light emitted from the backlight 15 being absorbed by the overlayer 25 increases accordingly. For this reason, since the amount of light passing through the pixel electrode 10 and the colored layer 6 is reduced, the transmittance is lowered and the hue is also deteriorated. Further, as the overlayer 25 becomes thicker, it becomes more difficult to form an opening having a desired size in the overlayer 25, so that the workability of the contact hole 25a is lowered. However, when the overlayer 25 is thick, the distance between the data line 32 and the pixel electrode 10 is increased, so that the parasitic capacitance generated between the data line 32 and the pixel electrode 10 is reduced. For this reason, vertical crosstalk hardly occurs. The vertical crosstalk will be described later.

  On the other hand, when the overlayer 25 is thinly formed on the upper substrate 1, as shown in Table 1, the transmittance is increased, the hue (color) is improved, and the workability of the contact hole 25a is improved. On the other hand, vertical crosstalk is likely to occur. That is, as the overlayer 25 becomes thinner, the proportion of external light and a part of the light emitted from the backlight 15 that is absorbed by the overlayer 25 decreases. For this reason, since the amount of light transmitted through the pixel electrode 10 and the colored layer 6 increases, the transmittance is increased and the hue is improved. Further, the thinner the overlayer 25 is, the easier it is to form an opening of a desired size in the overlayer 25, so that the workability of the contact hole 25a is improved. However, when the overlayer 25 is thinned, the distance between the data line 32 and the pixel electrode 10 becomes short, so that the parasitic capacitance generated between the data line 32 and the pixel electrode 10 increases. For this reason, vertical crosstalk is likely to occur.

  As described above, in the liquid crystal display device having the overlayer structure, if the overlayer 25 is formed too thick on the upper substrate 1 or the overlayer 25 is formed too thin on the upper substrate 1, the display quality is improved. Therefore, it is important to determine the thickness of the overlayer 25.

As described above, when the overlayer 25 is too thick, the transmittance decreases, the hue (color) deteriorates, and the workability of the contact hole 25 decreases. Therefore, the upper limit value of the thickness of the overlayer 25 formed on the upper substrate 1 is defined from the viewpoint of the aperture ratio of the pixel electrode and the brightness of the backlight 15, that is, from the viewpoint of the luminance of the desired display area V, etc. It is preferable to do this. For example, in the liquid crystal display device 100 of the present invention, the upper limit value of the thickness of the overlayer 25 formed on the upper substrate 1 is preferably about 4 μm or less. Here, the equation defining the relationship between the film thickness of the overlayer 25 and the transmittance is:
T / 100 = α × exp (−d) Formula (1)
It is represented by Here, “T” is the transmittance (%), “α” is the extinction coefficient, and “d” is the thickness of the overlayer 25 formed on the upper substrate 1.

  For example, an overlayer is formed on the upper substrate 1 using an insulating material having a relative dielectric constant of 3.4 and a transmittance of 94% (wavelength of 400 to 780 nm, when the thickness of the overlayer is 2 μm). When 25 is formed to a thickness of about 4 μm, the transmittance T is about 88 (%) from the above equation (1). Therefore, in this case, sufficient transmittance is obtained and the hue is improved. If the thickness of the overlayer 25 is 4 μm or less, the workability of the contact hole 25a is also improved.

  On the other hand, if the thickness of the overlayer 25 is too thin, vertical crosstalk tends to occur. Therefore, in the liquid crystal display device 100 of the present invention, in particular, the lower limit value of the thickness D10 (see FIG. 7A) of the overlayer 25 formed on the upper substrate 1 is defined from the viewpoint of reducing vertical crosstalk. To do. Here, prior to describing the method of defining the lower limit value of the thickness D10 of the overlayer 25, vertical crosstalk will be described.

(Generation principle of vertical crosstalk)
With reference to FIG. 9, vertical crosstalk will be described. In the following, for the convenience of explanation, the principle of occurrence of vertical crosstalk in a liquid crystal display device having no overlayer structure will be described. FIG. 9 is an enlarged plan view of only the display region V1 of the liquid crystal display device having no overlayer structure, and shows a state in which vertical crosstalk has occurred in the display region V1.

  For such a liquid crystal display device, the scanning line voltage and the data line voltage are applied so that the background area B and the area C have the same gray level. In the area A, the scanning line voltage and the data line voltage are applied so that a monochrome or complementary color rectangular display with a specified brightness is obtained. However, in practice, the gray level on the display image differs between Area B and Area C, which should have the same gradation level, due to the occurrence of vertical crosstalk. That is, the area C positioned in the vertical direction of the area A is displayed somewhat brighter than the area B, and is displayed in a slightly colored manner. Area A is displayed darker than the specified brightness. Such vertical crosstalk occurs when a monochrome or complementary color rectangle is displayed against a gray background.

  Next, the principle of occurrence of this vertical crosstalk will be described with reference to FIG. FIG. 10 is a partial plan view in which one pixel (RGB three subpixels) in the liquid crystal display device is enlarged.

  In such a liquid crystal display device, the pixel electrode 300 is usually formed at a substantially central position of the pair of data lines 302. This is due to a design reason that the aperture ratio of the pixel is increased within a range in which the pixel electrode 300 is not too close to the adjacent data lines 302. The data lines 302a, 302b, and 302c are connected to the pixel electrodes 300a, 300b, and 300c through the TFD element 301, respectively. For example, when attention is paid to the pixel electrode 300b, the data line 302a is adjacent to the pixel electrode 300b but is not connected to the pixel electrode 300b. Parasitic capacitances C1 and C2 exist between the pixel electrode 300b and two adjacent data lines 302b and 302a, respectively.

  In such a liquid crystal display device, in order to display a desired image, a desired voltage is applied to each of the pixel electrodes 300a to 300c in the line selection period T. In the example of FIG. 10, a desired voltage Vc is applied from the data line 302b to the pixel electrode 300b via the TFD element 301.

  However, since the parasitic capacitance C2 between the pixel electrode 300b and the adjacent data line 302a exists, a voltage corresponding to the parasitic capacitance C2 is applied from the data line 302a. The potential Vc of the electrode 300b changes from the desired potential. That is, the potential of a certain pixel electrode changes due to a parasitic capacitance between the pixel electrode and an adjacent data line. As a result, the transmittance of the pixel changes and vertical crosstalk occurs.

  Assume that blue is displayed in area A and gray is displayed in areas B and C as described above. In FIG. 10, the pixel electrode 300a corresponding to the data line 302a is a subpixel corresponding to blue, the pixel electrode 300b is a subpixel corresponding to red, and the rightmost pixel electrode 300c is a subpixel corresponding to green. Let it be a pixel.

  When these three color sub-pixels are present in area B in FIG. 9, the area is displayed in gray, so that the voltages applied to the three data lines 302a, 302b, and 302c are substantially equal, and the parasitic capacitance C2 is There is little influence on the pixel electrode 300b.

  On the other hand, since blue is displayed in the area A, only the data line 302a has a low potential (potential corresponding to white) in the area C, and the data lines 302b and 302c have a high potential (potential corresponding to black). Become. Therefore, in the area C, a potential difference is generated between the data line 302a and the pixel electrode 300b during the holding period, and the potential of the pixel electrode 300b is decreased by the parasitic capacitance C2. As a result, the transmittance of the red sub-pixel formed by the pixel electrode 300b is increased, and the area C becomes brighter and appears somewhat reddish. This is the principle of occurrence of vertical crosstalk. That is, vertical crosstalk occurs when the potential of an adjacent pixel electrode changes from a desired potential due to the influence of parasitic capacitance.

  On the other hand, the liquid crystal display device 100 of the present invention is a liquid crystal display device having an overlayer structure. However, this vertical crosstalk phenomenon can also occur in the liquid crystal display device 100 of the present invention. However, the principle of occurrence of vertical crosstalk is slightly different between the liquid crystal display device having no overlayer structure and the liquid crystal display device 100 of the present invention.

  Therefore, the principle of occurrence of vertical crosstalk in the liquid crystal display device 100 of the present invention will be briefly described. Returning to FIG. 7A, when attention is paid to one pixel electrode 10 b in the element substrate 92, the pixel electrode 10 b is connected to the data line 32 b through the TFD element 21. The data line 32b is disposed on the upper substrate 1 at a position substantially below the center of the pixel electrode 10b and overlapping the pixel electrode 10b. Further, the pixel electrode 10b and the data line 32b are insulated by the overlayer 25. For this reason, a parasitic capacitance Cp is generated between the pixel electrode 10 b and the data line 32 b via the overlayer 25.

  Therefore, in the liquid crystal display device 100 of the present invention, the potential of the pixel electrode 10b fluctuates during the holding period due to the influence of the parasitic capacitance Cp generated between one pixel electrode 10b and the data line 32b connected thereto. Vertical crosstalk occurs. In the liquid crystal display device 100 of the present invention, unlike the liquid crystal display device having no overlayer structure, the distance between the pixel electrode 10b and the adjacent data lines 32a and 32c that are not connected to the pixel electrode 10b is large. ing. Therefore, in the liquid crystal display device 100 of the present invention, the occurrence of vertical crosstalk is not a problem due to the influence of the adjacent data line 32 that is not connected to the pixel electrode 10b.

  Next, a method for defining the lower limit value of the thickness of the overlayer 25 capable of reducing the vertical crosstalk that characterizes the present invention will be described with reference to FIG. FIG. 11A shows, as an example, a layer cross-sectional view in which a local portion of a general transmissive liquid crystal panel is enlarged. FIG. 11B shows an example of a graph of voltage-transmittance characteristics of the liquid crystal panel.

  As described above, in the liquid crystal display device 100 of the present invention, the vertical crosstalk is caused by a change in the potential of the pixel electrode due to the influence of the parasitic capacitance Cp generated between the data line and the pixel electrode opposed via the overlayer 25. To occur.

  Here, the voltage applied to the liquid crystal from the data line connected to the pixel electrode during the holding period, that is, the voltage Vc caused by the parasitic capacitance Cp can be expressed as follows.

Vc = {C ′ _TFD / (C _Lc + C ′ _TFD )} × Vd (Formula 2)
Here, C ′ _TFD is the sum of the capacitance C _TFD of one TFD element and the parasitic capacitance Cp, C _Lc is the liquid crystal capacitance of one pixel electrode, and Vd is the amplitude of the data signal applied to the data line. Voltage. In order to reduce the vertical crosstalk, it is necessary to suppress the voltage Vc from the data line connected to the pixel electrode via the TFD element to a certain level due to the parasitic capacitance Cp.

  Therefore, in the present embodiment, the voltage Vc is defined to be a certain magnitude. Specifically, it is desirable to determine the upper limit value of the voltage Vc in relation to the applied voltage value in the voltage-transmittance characteristics as shown in FIG. Here, voltage-transmittance characteristics of a general transmissive liquid crystal panel will be described with reference to FIGS.

  The voltage-transmittance characteristics (so-called VT characteristics) of the liquid crystal layer 503 are expressed as in the graph of FIG. 11B, for example. In the graph shown in FIG. 11B, as shown in FIG. 11A, the light T1 is transmitted through the liquid crystal layer 503 sandwiched between the transparent electrodes 501 and 502, and the voltage V applied between the electrodes is changed. In this case, how the transmittance of the liquid crystal layer 503 changes is shown by way of an example of a normally white display mode. From this graph, it can be seen that the transmittance of the liquid crystal decreases as the voltage V applied to the liquid crystal layer 503 increases. In the graph, V (T10) indicates a voltage when the transmittance is 10%, and V (T50) indicates a voltage when the transmittance is 50%.

  In particular, in the liquid crystal display device 100 of the present embodiment, the upper limit value of the voltage Vc is set to be smaller than V (T50) as shown in the following equation.

That is, the voltage Vc is
Vc = {C ′ _TFD / (C _Lc + C ′ _TFD )} × Vd <V (T50) (Formula 3)
Set to be.

In the above description, the case where the voltage-transmittance characteristic of the liquid crystal layer 4 is used as a reference for defining the voltage Vc to be a certain magnitude has been described, but the voltage-transmittance characteristic here is voltage-reflectance. It is considered that the characteristic (so-called VR characteristic) is included. For example, as shown in FIG. 12, the voltage-reflectance characteristic supplies the light R1 reflected by the reflective film 504 to the liquid crystal layer 503 sandwiched between the transparent electrodes 501 and 502, and the voltage V applied between the electrodes. It shows how the reflectance of the reflected light changes when it is changed. For example, if the voltage corresponding to 50% reflectance is V (R50), the voltage Vc is
Vc = {C ′ _TFD / (C _Lc + C ′ _TFD )} × Vd <V (R50)
Can be set to Note that V (R50) and V (T50) are not necessarily the same value.

Next, the parasitic capacitance Cp that makes it possible to reduce vertical crosstalk in Equation 3 above is calculated. Specifically, the parasitic capacitance Cp is calculated as follows. In Formula 3 above, C _TFD , C _Lc , Vd, and V (T50) are constant. Therefore, by changing the value of the parasitic capacitance Cp in Formula 3 above, the parasitic capacitance Cp satisfying Formula 3 above is changed. Is calculated. Thereby, the parasitic capacitance Cp that can reduce the vertical crosstalk can be calculated.

  Next, in the first embodiment, the calculated parasitic capacitance Cp and the like are substituted into the following equation to calculate the lower limit value of the thickness of the overlayer 25 that can reduce the vertical crosstalk.

From the equation of capacitance of general substances, the parasitic capacitance Cp is
Cp = ε ₀ · ε _ovL (S / d) (Formula 4)
It is represented by “Ε ₀ ” is the dielectric constant of the vacuum, “ε _ovL ” is the relative dielectric constant of the _overlayer 25 (insulating layer), “S” is the area where the pixel electrode and the data line overlap, and “d” is the pixel electrode The distance from the upper substrate, that is, the thickness of the overlayer 25.

Therefore, in the above equation 4, the parasitic capacitance Cp calculated in the above equation 3 is substituted for the parasitic capacitance Cp, the vacuum permittivity is set to “ε ₀ ”, and the relative permittivity of the _overlayer 25 is set to “ε _ovL ”. Is substituted for “S” by the area S1 in FIG. 6 to calculate “d”. The value d thus obtained is the thickness D10 of the overlayer 25 that can reduce the vertical crosstalk.

  Here, an example of a design value that defines the lower limit value of the thickness of the overlayer 25 that can reduce the vertical crosstalk will be described with reference to Table 2 shown in FIG. In the following, Case 1 to Case 3 are taken as an example, and the lower limit value of the thickness of the overlayer 25 is calculated for each case.

In Case 1, first, the capacitance C _TFD of one TFD element is set to 4.0 × 10 ⁻¹⁴ (F), and the parasitic capacitance Cp is set to 3.5 × 10 ⁻¹⁴ (F). Since C ′ _TFD is the sum of C _TFD and Cp, C ′ _TFD is 7.5 × 10 ⁻¹⁴ (F). Next, in case 1, C ′ _{TFD is set} to 7.5 × 10 ⁻¹⁴ (F), C _{Lc is set} to 8.0 × 10 ⁻¹⁴ (F), Vd is set to 4.0 (V), and each parameter thereof is expressed by the above formula. Substituting into 3, voltage Vc is calculated. Thereby, the voltage Vc is calculated as 1.94 (V). Here, V (T50) is set to 2.0 (V) in the specification. Therefore, in Case 1, Vc = 1.94 (V) <V (T50) = 2.0 (V), which satisfies the above Equation 3. Therefore, in this case, it is possible to prevent the potential of the pixel electrode from fluctuating due to the parasitic capacitance Cp between the pixel electrode and the data line connected thereto during the holding period Th, and the transmittance of the liquid crystal layer 4 is set appropriately. Therefore, the vertical crosstalk can be reduced.

In Case 2, first, the capacitance C _TFD of one TFD element is set to 4.0 × 10 ⁻¹⁴ (F), and the parasitic capacitance Cp is set to 3.9 × 10 ⁻¹⁴ (F). Since C ′ _TFD is the sum of C _TFD and Cp, C ′ _TFD is 7.95 × 10 ⁻¹⁴ (F). Next, in case 2, C ′ _{TFD is set} to 7.9 × 10 ⁻¹⁴ (F), C _{Lc is set} to 8.0 × 10 ⁻¹⁴ (F), Vd is set to 4.0 (V), and each parameter thereof is expressed by the above formula. Substituting into 3, voltage Vc is calculated. Thereby, the voltage Vc is calculated as 1.99 (V). Here, V (T50) is set to 2.0 (V) in the specification. Therefore, in Case 2, Vc = 1.99 (V) <V (T50) = 2.0 (V), which satisfies the above Equation 3. Therefore, in this case, the vertical crosstalk can be reduced as in the case 1. However, since the value of Vc is almost the same as the value of V (T50), Vc may be equal to or higher than V (T50) depending on the accuracy of each parameter. Therefore, in this case, there is a possibility that reduction of vertical crosstalk is insufficient.

In Case 3, first, the capacitance C _TFD of one TFD element is set to 4.0 × 10 ⁻¹⁴ (F), and the parasitic capacitance Cp is set to 4.0 × 10 ⁻¹⁴ (F). Since C ′ _TFD is the sum of C _TFD and Cp, C ′ _TFD is 8.0 × 10 ⁻¹⁴ (F). Next, in case 3, C ′ _{TFD is set} to 8.0 × 10 ⁻¹⁴ (F), C _{Lc is set} to 8.0 × 10 ⁻¹⁴ (F), Vd is set to 4.0 (V), and each parameter thereof is expressed by the above formula. Substituting into 3, voltage Vc is calculated. Thereby, the voltage Vc is calculated as 2.00 (V). Here, V (T50) is set to 2.0 (V) in the specification. Therefore, in Case 3, Vc = 2.00 (V) <V (T50) = 2.0 (V), and the above Equation 3 is not satisfied. Therefore, in this case, the vertical crosstalk cannot be sufficiently reduced.

  Next, the parasitic capacitance Cp and the like calculated in the above cases 1 to 3 are substituted into the above equation 4, and the lower limit value of the thickness of the overlayer 25 is calculated.

In Case 1, the parasitic capacitance Cp is 3.5 × 10 ⁻¹⁴ (F), the vacuum dielectric constant ε ₀ is 8.854 × 10 ⁻¹² (F), and the relative dielectric constant ε _ovL of the _overlayer 25 (insulating layer) is 4.0. The overlapping area S of the pixel electrode and the data line (corresponding to the area S1 in FIG. 6) is set to 500 (μm ² ), and these parameters are substituted into the above equation 4 to obtain the thickness d of the overlayer 25. When (μm) (corresponding to the thickness D10 of the overlayer 25 in FIG. 7A) is calculated, the lower limit value of the thickness D10 of the overlayer 25 is 0.5 (μm).

In case 2, the parasitic capacitance Cp is set to 3.9 × 10 ⁻¹⁴ (F), and the parameters except for the thickness d (μm) of the overlayer 25 are the same as those in case 1, and these parameters are expressed by the above equation 4. When the thickness d (μm) of the overlayer 25 is calculated by substituting, the lower limit value of the thickness D10 of the overlayer 25 is 0.45 (μm).

In case 3, the parasitic capacitance Cp is set to 4.0 × 10 ⁻¹⁴ (F), and the parameters except for the thickness d (μm) of the overlayer 25 are the same as those in case 1, and these parameters are expressed by the above equation 4. When the thickness d (μm) of the overlayer 25 is calculated by substituting, the lower limit value of the thickness D10 of the overlayer 25 is 0.44 (μm).

  From the above results, it is understood that the lower limit value of the thickness D10 of the overlayer 25 is preferably specified to be 0.5 (μm) or more calculated in Case 1. In this case, when the transmittance T is calculated by substituting 0.5 (μm), which is the lower limit value of the thickness D10 of the overlayer 25, into the parameter d of Equation 1, the transmittance T is calculated to be 98%. The Therefore, in this case, sufficient transmittance can be obtained and the hue can be improved.

  Further, in the liquid crystal display device 100 of the present invention, if the thickness D10 of the overlayer 25 formed on the upper substrate 1 is specified to be 0.5 (μm) or more, the thickness of the overlayer 25 is reduced. It becomes easy to form the contact hole 25a. Therefore, the workability of the contact hole 25a is improved.

[Second Embodiment]
Next, a second embodiment will be described with reference to FIGS. 14 and 15. Note that the liquid crystal display device of the second embodiment has substantially the same configuration as that of the liquid crystal display device of the first embodiment, and the former only differs in the configuration of the element substrate from the latter. Therefore, only the configuration of the element substrate will be described below. FIG. 14 is a partial plan view of the element substrate corresponding to FIG. 6, and is a plan view in which the configuration of the element substrate 92 of the liquid crystal display device 100 is slightly changed. FIG. 15A is a cross-sectional view of the element substrate corresponding to FIG. 7A, and is a cross-sectional view taken along the cutting line CC ′ of FIG. FIG. 15B is an enlarged cross-sectional view of the vicinity of a connection portion between the pixel electrode 10 and the TFD element 21 and the data line 32 corresponding to FIG. 7B, and is a cross-sectional view of a region E2. . 14 shows a configuration when the observation side is viewed from the back side, so that the near side is the back side in FIG. 14 and the top side is the back side in FIG. In FIGS. 14 and 15, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The structure of the element substrate 93 in the second embodiment of the present invention, that is, the overlayer structure will be described. In addition, although the protective layer 17 is normally formed on each inner surface of the pixel electrode 10 and the overlayer 25, in FIG.14 and FIG.15, it abbreviate | omitted for convenience of explanation.

  A phase difference plate 13 and a polarizing plate 14 are disposed on the outer surface of the upper substrate 1. On the other hand, a TFD element 21 and a data line 32 are formed on the inner surface of the upper substrate 1.

  In the second embodiment, the arrangement of the TFD elements 21 on the upper substrate 1 is the same as in the first embodiment. The configuration of the TFD element 21 is the same as that of the first embodiment.

  In the second embodiment, the arrangement of the data lines 32 on the upper substrate 1 is different from that in the first embodiment. That is, in the first embodiment, the data lines 32a, 32b, and 32c are arranged at positions below and overlapping the pixel electrodes 10a, 10b, and 10c, respectively, as shown in FIG. On the other hand, in the second embodiment, the data lines 32a, 32b, and 32c do not overlap with the positions below the pixel electrodes 10a, 10b, and 10c, respectively, as shown in FIGS. 14 and 15A. Placed in position. In particular, one data line 32 is disposed between the pixel electrode connected to the data line 32 via the TFD element 21 and the adjacent pixel electrode 10 not connected to the one data line 32. This point is greatly different from the first embodiment in structure. The configuration of the data line 32 is the same as that of the first embodiment.

  Further, an overlayer 25 is formed on the inner surface of the upper substrate 1, and the TFD element 21 and the data line 32 are covered with the overlayer 25. The overlayer 25 has a substantially circular opening, that is, a contact hole 25a in plan view. Further, the pixel electrode 10 is formed on the inner surface of the overlayer 25 with the same layout as in the first embodiment.

  In the second embodiment having such a structure, as shown in FIG. 14, the data line 32 is formed at a position that does not overlap the pixel electrode 10. For this reason, in the second embodiment, the distance between the pixel electrode 10b and the data lines 32a and 32b is longer than that in the first embodiment. For example, in the second embodiment, as shown in FIG. 15A, the distance between the pixel electrode 10b and the data line 32b is D101, and the distance between the pixel electrode 10b and the data line 32a is D102. In the first embodiment, as shown in FIG. 7A, the distance between the pixel electrode 10b and the data line 32 is D100. Therefore, D100 <D101 and D100 <D102. For this reason, the parasitic capacitance Cp is reduced as the distance between the pixel electrode 10 and the data line 32 is increased. Therefore, in the second embodiment, the lower limit value of the thickness of the overlayer 25 can be defined smaller than in the first embodiment. Therefore, by setting the lower limit value of the thickness of the overlayer 25 to 0.5 μm as in the first embodiment, it is possible to obtain effects such as reduction in vertical crosstalk as in the first embodiment.

(Modification)
In the above embodiment, the present invention is applied to the transflective liquid crystal display device 100. However, the present invention is not limited to this, and the present invention can also be applied to a reflective or transmissive liquid crystal display device. In the above embodiment, the present invention is applied to the normally white liquid crystal display device 100. However, the present invention is not limited to this, and the present invention can also be applied to a normally black liquid crystal display device. In the above embodiment, the TN liquid crystal is applied to the liquid crystal display device 100. However, the liquid crystal display device 100 is not limited thereto, and the liquid crystal having negative dielectric anisotropy is applied to the liquid crystal display device 100. Also good.

[Electronics]
Next, an embodiment when the liquid crystal display device 100 according to the first embodiment of the present invention is used as a display device of an electronic apparatus will be described. The liquid crystal display device according to the second embodiment of the present invention can be similarly applied as a display device of such an electronic device.

  FIG. 16 is a schematic configuration diagram showing the overall configuration of the present embodiment. The electronic apparatus shown here includes the liquid crystal display device 100 and a control unit 410 that controls the liquid crystal display device 100. Here, the liquid crystal display device 100 is conceptually divided into a panel structure 403 and a drive circuit 402 composed of a semiconductor IC or the like. Further, the control means 410 includes a display information output source 411, a display information processing circuit 412, a power supply circuit 413, and a timing generator 414.

  The display information output source 411 includes a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a storage unit such as a magnetic recording disk or an optical recording disk, and a tuning circuit that tunes and outputs a digital image signal. The display information is supplied to the display information processing circuit 412 in the form of an image signal of a predetermined format based on various clock signals generated by the timing generator 414.

  The display information processing circuit 412 includes various well-known circuits such as a serial-parallel conversion circuit, an amplification / inversion circuit, a rotation circuit, a gamma correction circuit, and a clamp circuit, and executes processing of input display information to obtain image information. Are supplied to the drive circuit 402 together with the clock signal CLK. The driving circuit 402 includes a scanning line driving circuit, a data line driving circuit, and an inspection circuit. The power supply circuit 413 supplies a predetermined voltage to each of the above-described components.

  Next, specific examples of electronic devices to which the liquid crystal display device 100 according to the present invention can be applied will be described with reference to FIG.

  First, an example in which the liquid crystal display device 100 according to the present invention is applied to a display unit of a portable personal computer (so-called notebook personal computer) will be described. FIG. 17A is a perspective view showing the configuration of this personal computer. As shown in the figure, the personal computer 710 includes a main body 712 having a keyboard 711 and a display 713 to which the liquid crystal display panel according to the present invention is applied.

  Next, an example in which the liquid crystal display device 100 according to the present invention is applied to a display unit of a mobile phone will be described. FIG. 17B is a perspective view showing the configuration of this mobile phone. As shown in the figure, the cellular phone 720 includes a plurality of operation buttons 721, a reception port 722, a transmission port 723, and a display unit 724 to which the liquid crystal display device 100 according to the present invention is applied.

  Electronic devices to which the liquid crystal display device 100 according to the present invention can be applied include a liquid crystal television and a viewfinder in addition to the personal computer shown in FIG. 17A and the mobile phone shown in FIG. Type / monitor direct-view type video tape recorder, car navigation device, pager, electronic notebook, calculator, word processor, workstation, videophone, POS terminal, digital still camera, etc.

FIG. 3 is a plan view showing a configuration of electrodes and wirings of the liquid crystal display device according to the first embodiment. 1 shows a cross-sectional configuration of a liquid crystal display device according to a first embodiment. The top view which shows the structure of the electrode, wiring, etc. of the element substrate which concern on 1st Embodiment. 1 shows a configuration of electrodes of a color filter substrate according to a first embodiment. It is a wave form diagram of signal potential VA, VB, and VAB concerning a 1st embodiment. 1 is a partial plan view of an element substrate according to a first embodiment. The fragmentary sectional view of the element substrate etc. concerning a 1st embodiment is shown. It is a graph which shows the relationship between the thickness of an overlayer, and the transmittance | permeability. It is a figure explaining longitudinal crosstalk. It is a figure explaining longitudinal crosstalk. It is a figure explaining the method which prescribes | regulates the lower limit of the thickness of an overlayer. It is a figure explaining the method which prescribes | regulates the lower limit of the thickness of an overlayer. It is a figure explaining an example of the prescription | regulation method of the lower limit of the thickness of an overlayer. It is a figure explaining the method of prescribing the lower limit of the thickness of the overlayer concerning a 2nd embodiment. It is a figure explaining the method of prescribing the lower limit of the thickness of the overlayer concerning a 2nd embodiment. 1 is a circuit block diagram of an electronic apparatus to which a liquid crystal display device of the present invention is applied. 6 shows examples of electronic devices to which the liquid crystal display device of the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper substrate, 2 Lower substrate, 3 Seal member, 6 Colored layer, 7 Conductive member, 8 Scan electrode, 10 Pixel electrode, 31 Scan line, 32 Data line, 21 TFD element, 25 Overlayer, 25a Contact hole, 91 Color filter substrate, 92 element substrate, 100 liquid crystal display device

Claims (5)

A liquid crystal device in which liquid crystal is sealed between a first substrate and a second substrate that are arranged to face each other,
The first substrate includes a transparent substrate having translucency, a data line formed on the transparent substrate, a two-terminal element formed on the transparent substrate and connected to the data line, and a contact hole. And an insulating film formed on the transparent substrate and covering the data line and the two-terminal element, and a pixel electrode formed on the insulating film and connected to the two-terminal element through the contact hole. ,
The second substrate has scanning lines;
The capacitance of the two-terminal element is C _TFD , the pixel capacitance of the liquid crystal sandwiched between the scanning lines facing the pixel electrode is C _Lc , and the data line is connected to the pixel electrode via the two-terminal element C _{p is} the parasitic capacitance generated between the pixel electrode and the pixel electrode, the amplitude voltage of the data line is V _d , the sum of the capacitance C _TFD of the two-terminal element and the parasitic capacitance C _p is C ′ _TFD , When the voltage corresponding to the transmittance of 50% in the voltage-transmittance characteristic is V (T50), the parasitic capacitance _Cp is inversely proportional to the thickness of the insulating film,
The thickness of the insulating film is
{C ′ _TFD / (C _Lc + C ′ _TFD )} × V _d <V (T50)
A liquid crystal device set to satisfy the above. The data line is formed at a position overlapping the pixel electrode on the transparent substrate,
When the dielectric constant ε _{0 of} vacuum, the relative dielectric constant of the liquid crystal is ε, and the area where the pixel electrode and the data line overlap is S, the thickness d of the insulating film is expressed by the following formula: C _p = ε ₀ × ε × (S / d)
The liquid crystal device according to claim 1, wherein the liquid crystal device is defined based on:   The liquid crystal device according to claim 1, wherein the data line is formed on the transparent substrate at positions on both sides of the pixel electrode when the transparent substrate is viewed in plan.   The liquid crystal device according to claim 1, wherein a lower limit value of the thickness of the insulating film is 0.5 μm or more. An electronic apparatus comprising the liquid crystal device according to claim 1.

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