JPH0356931A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the hue of a color filter from being deteriorated and to uniformize the thickness of a protective film by providing an inorganic transparent film between the color filter and the protective film. CONSTITUTION:In a color liquid crystal display device in which the color filter FIL is coated with the protective film PSV2 consisting of organic substance, the inorganic transparent film ITF is provided between the color filter FIL and the protective film PSV2. Therefore, the inorganic transparent film ITF prevents the transmission of O2 and H2O and wettability obtained in the case of forming the protective film PSV2 is made uniform by the inorganic transparent film ITF. Thus, the hue of the color filter FIL is not deteriorated and the thickness of the protective film PSV2 is made uniform.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a color liquid crystal display device, and more particularly to an active matrix type color liquid crystal display device using thin film transistors and the like.

[Conventional technology]

The active matrix color liquid crystal display device is
A nonlinear element (switching element) is provided corresponding to each of a plurality of pixel electrodes arranged in a matrix. Theoretically, the liquid crystal in each pixel is constantly moving (duty ratio 1.0), so compared to the so-called simple matrix method that uses a time-division drive method, the active method has better contrast, especially in color. It is becoming an indispensable technology. A typical switching element is a thin film transistor (TPT). In conventional active matrix color liquid crystal display devices, the color filters are coated with a protective film made of an organic material such as epoxy resin or acrylic resin to prevent dyes from the color filters from leaking into the liquid crystal. Note that an active matrix liquid crystal display device using thin film transistors is described in, for example, "12.5-inch active matrix color liquid crystal display employing redundant configuration," Nikkei Electronics, pp. 193-
210, February 15, 1986, published by Nikkei McGraw-Hill.

[Problem M that the invention attempts to solve]

However, in such a color liquid crystal display device, 0
2. Since H20 easily permeates through the protective film, the color tone of the color filter is likely to deteriorate, and color filters of different colors have different surface wettability to the protective film, so the protective film provided on the color filters of different colors Since the thickness of the protective film differs, the thickness of the protective film becomes non-uniform. The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a color liquid crystal display device in which the color tone of the color filter does not deteriorate and the thickness of the protective film is uniform.

[Means to solve the problem]

To achieve this object, in the present invention, in a color liquid crystal display device in which a color filter is covered with a protective film made of an organic substance, a transparent film is provided between the color filter and the protective film. [Function] In this color liquid crystal display device, the inorganic transparent film is ○.
, H. It prevents O 2 from permeating, and the inorganic transparent film provides uniform wettability when forming a protective film. [Embodiments] Hereinafter, the structure of the present invention will be explained together with an embodiment in which the present invention is applied to an active matrix type color liquid crystal display device. Note that throughout the description of the embodiments, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted. FIG. 2A is a plan view showing one pixel and its surroundings of an active matrix color liquid crystal display 'xi to which the present invention is applied, and FIG. 2B is a cross section taken along the IrB-IIB cutting line in FIG. 2A and a seal on the display panel. FIG. 2C is a cross-sectional view taken along the nc-trc line in FIG. 2A. Moreover, FIG. 3 (main part plan view) shows a plan view when the number of pixels shown in FIG. 2A is arranged. <Pixel Arrangement> As shown in Figure 2A, each pixel is connected to two adjacent scanning signal lines (gate signal line or horizontal signal line) OL and two adjacent video signal lines (drain signal line or vertical signal line). line) DL (in the area surrounded by four signal lines). Each pixel has a thin film transistor TPT, transparent pixel electrode IT○
1 and a storage capacitor element C add. Scanning signal line G
L extends in the column direction, and a plurality of L's are arranged in the row direction. The video signal lines DL extend in the row direction, and a plurality of video signal lines DL are arranged in the column direction. <<Overall cross-sectional structure of display section>> As shown in FIG. 2B, a thin film transistor TPT and a transparent pixel electrode IT○1 are formed on the lower transparent glass substrate SUBI side with respect to the liquid crystal LC, and the upper transparent glass substrate S
Color filter FIL. on the UBZ side. A light-shielding film BM having a light-shielding black matrix pattern is formed. The lower transparent glass substrate SUB 1 is, for example, 1.
The thickness is approximately 1 mm. The central part of Figure 2B shows a cross section of one pixel,
The left side shows the cross section of the left edge of the transparent glass substrates SUBI and SUB2 where external lead wiring exists, and the right side shows the cross section of the right edge of the transparent glass substrates SUB1 and SUB2 where no external lead wiring exists. It shows. Seal material SL shown on the left and right sides of Fig. 2B
is configured to seal the liquid crystal LC, and includes a transparent glass substrate StJB1 excluding the liquid crystal sealing port (not shown).
, is shaped along the entire forest periphery of SUB2. The sealing material SL is made of, for example, epoxy resin. Common transparent pixel electrode IT on the upper transparent glass substrate SUB2 side
O2 is supplied to the silver paste material SI at least in one place.
L is connected to an external lead wiring formed on the lower transparent glass substrate SUBI side. This external lead wiring includes a gate electrode GT, a source electrode SDI, and a drain electrode SD2.
are formed in the same manufacturing process as each. Alignment film ○RII, ORI2, transparent pixel electrode IT○2, common transparent pixel electrode IT○2, protective film PSV1, PSV2.
Each layer of the insulating film GI is formed inside the sealing material SL. The polarizing plates POLI and POL2 are formed on the outer surfaces of the lower transparent glass substrate SUBI and the upper transparent glass substrate SUB2, respectively. The liquid crystal LC has a lower alignment film ORI that sets the direction of the liquid crystal molecules.
It is sealed between I and the upper alignment film ○RI2, and the seal part S
It is sealed by L. The lower alignment film ○RII is formed on the upper part of the protective film PSVI on the side of the lower transparent glass substrate SUB1. A light shielding film BM, a color filter FIL. Protective film P
SV2, a common transparent pixel electrode ITO2 (COM), and an upper alignment film ORI2 are sequentially stacked. In this liquid crystal display device, the layers on the lower transparent glass substrate SUB1 side and the upper transparent glass substrate SUB2 side are formed separately, and then the upper and lower transparent glass substrates SOB↓ and SUB2 are stacked, and a liquid product LC is sealed between them. It is assembled by <Thin Film Transistor TPT> The thin film transistor TPT operates such that when a positive bias is applied to the gate electrode GT, the channel resistance between the source and drain becomes small, and when the bias is reduced to zero, the channel resistance becomes large. The thin film transistor TPT of each pixel has three
It is divided into two (plurality) of film transistors (split film transistors) TFTI, TPT2, and TFT3. Each of the thin film transistors TPTI to TFT3 is designed to have substantially the same size (channel length and radius are the same). Each of the divided thin film transistors TPTI to TFT3 mainly has a gate electrode GT.
, gate insulating film CI, i-type (intrinsic)
, a pair of source electrode SD1 and drain electrode SD2. Note that the source train is originally determined by the bias polarity therebetween, and in the circuit of this liquid crystal display device, the polarity is reversed during operation, so it should be understood that the source and drain are interchanged during operation. However, in the following description, for convenience, one side is fixed as a source and the other side is fixed as a drain. <Gate electrode GT> The gate electrode GT is the first conductive film g1 in FIG. 4 (FIG. 2A,
As shown in detail in the plan view depicting only the second conductive film g2 and the i-type semiconductor layer AS, the structure has a shape that protrudes vertically from the scanning signal line GL (upward in FIGS. 2A and 4). (branched into a T-shape). Gate electrode GT is thin film transistor TPTI~TFT3
The shape of each of the parts is designed to protrude to a certain area. The respective gate electrodes GT of the thin film transistors TPTI to TFT3 are integrated (as a common gate electrode) and are formed continuously to the scanning signal line OL. The gate electrode GT is made of a single-layer first layer so as not to create a large step in a certain region of the thin film transistor TPT.
It is composed of a conductive film g1. The first conductive film g1 is, for example, a chromium (Cr) film formed by sputtering. 1000
It is formed with a film thickness of about [A]. As shown in FIGS. 2A, 2B, and 4, the gate electrode GT is made thicker than the i-type semiconductor layer AS (as viewed from below) so as to completely cover the i-type semiconductor layer AS. Therefore, when a backlight BL such as a fluorescent lamp is attached below the lower transparent glass substrate SUBI, the gate electrode GT made of opaque chrome forms a shadow, and the backlight light does not shine on the i-type semiconductor layer AS. , a conductive phenomenon caused by light irradiation, that is, deterioration of the off-characteristics of the thin film transistor TPT, becomes less likely to occur. Note that the original size of the gate electrode 1-ffGT is the source electrode SDI and the drain electrode SD2.
(including the alignment margin between the gate electrode GT, the source electrode SDI, and the drain electrode SD2), and the depth length that determines the channel width W is the minimum width required to straddle between the source electrode SDI and the drain electrode SD2. It is determined by the ratio of the distance (channel length) L to the drain electrode SD2, that is, the factor W/L that determines the mutual conductance gm. The size of the gate electrode GT in this liquid crystal display device is of course made larger than the original size mentioned above. Note that if we consider only from the gate and light shielding functions of the gate electrode GT, the gate electrode GT and the scanning signal line OL
may be integrally formed in a single layer, in which case silicon-containing aluminum (Al) is used as the opaque conductive material.
). Pure aluminum, aluminum containing palladium (Pd), etc. can be selected. <<Scanning Signal Line GL>> The scanning signal line OL is composed of a composite film including a first conductive film g1 and a second conductive film g2 provided on the first conductive film g1. The first conductive film g1 of this scanning signal line GL is the gate electrode G
It is formed in the same manufacturing process as the first conductive film g1 of T, and is configured integrally. The second conductive film g2 is formed using, for example, an aluminum film formed by sputtering, and has a thickness of about 1,000 to 5,500 [people]. The second conductive film g2 is configured to reduce the resistance value of the scanning signal line GL and increase the signal transmission speed (improve the writing characteristics of pixel information). Furthermore, the scanning signal line GL is configured such that the width dimension of the second conductive film g2 is smaller than the convergence dimension of the first conductive film g1. That is, the side wall of the scanning signal line GL has a gradual step shape. <Insulating film GI> The insulating film GI is used as a gate pure film of each of the thin film transistors TPTI to TFT3. The insulating film GI is formed in the upper layer of the gate electrode GT and the scanning signal line GL. For example, the membrane GI is plasma C.
Using a silicon nitride film formed by VD,
The thickness of the film is approximately the same as that of a person. <<I-type semiconductor layer AS> As shown in FIG. 4, the i-type semiconductor RAS is used as a channel forming region for each of the thin film transistors TPTI to TFT3 divided into a plurality of parts. The i-type semiconductor layer AS is formed of a non-quality silicon film or a polycrystalline silicon film, and is formed with a film thickness of about 1800 mm. This i-type semiconductor layer AS is made of Si by changing the amount of supplied gas.
,N. An insulating film G used as a gate insulating film consisting of
Subsequently to the formation of I, it is formed in the same plasma CVD apparatus without being exposed to the outside from the plasma CVD apparatus. Also, P-doped N+ type semiconductor for ohmic contact! do (Fig. 2B) is similarly formed continuously to a thickness of about 400 [A]. Thereafter, the lower transparent glass substrate SUBI was taken out from the CVD apparatus, and the N" type semiconductor layer do and the i type semiconductor IAs were separated by photo processing technology as shown in FIGS. 2A, 2B, and 4. The i-type semiconductor layer AS is patterned in an island shape.As shown in detail in FIG. 2A and FIG. The i-type semiconductor layer AS at this intersection is designed to reduce short circuits between the scanning signal line GL and the video signal @DL at the intersection. <Source electrode SDI, drain electrode SD2> The source electrode SDI and drain@pole SD2 of each of the thin film transistors TPTI to TFT3 divided into a plurality of parts are connected to the second A
As shown in detail in FIGS. 2B, 2B, and 5 (a plan view depicting only the first to third conductive films d1 to d3 in FIG. 2A), they are provided separately on the i-type semiconductor layer AS. It is being Each of the source electrode SDI and drain electrode SD2 is
The first conductive film di. Second conductive film d2. The third conductive film d3 is sequentially stacked on top of each other. The first conductive film d of the source electrode SDI
1. The second conductive film d2 and the third conductive film d3 are formed in the same manufacturing process as the first conductive film di, second conductive film d2, and third conductive film d3 of the drain electrode SD2. The first conductive film d1 is a chromium film formed by sputtering,
The film thickness is about 500 to 1000 [A] (in this liquid crystal display device, the film thickness is about 600 [A]). The thicker the chromium film is, the greater the stress will be.
The shape is within the range of a film thickness of about 000 [persons]. The chromium film has good contact with the N+ type semiconductor layer do. In the chromium film, the aluminum of the second conductive film d2, which will be described later, is N+.
A so-called barrier layer is provided to prevent damage from spreading to the type semiconductor layer do. As the first conductive film di, in addition to the chromium film, a high melting point metal (
Mo, Ti. Ta. W) film, high melting point metal silicide (M
It may also be formed using a film (oSi, TiSi2, TaSi2, WSi2). After patterning the first conductive film d1 by photo processing, the N+ type semiconductor layer dO is removed using the same photo processing mask or using the first conductive film d1 as a mask. In other words, the N+ type semiconductor layer d remaining on the i type semiconductor layer AS
o, the portion other than the first conductive film d1 is removed by self-alignment. At this time, since the N+ type semiconductor H3do is etched so that its entire thickness is removed, the i-type semiconductor layer AS is also slightly etched at its surface, but the extent can be controlled by the etching time. Thereafter, the second conductive film d2 is formed by aluminum sputtering to a thickness of 3,000 to 5,500 [in this liquid crystal display device, about 3,500]. Aluminum film has less stress than chrome film,
It is possible to form a thick film, and the source electrode SDI,
It is configured to reduce the resistance values of the drain electrode SD2 and the video signal line DL. The second conductive film d2 may be formed of an aluminum film containing silicon or copper (Cu) as an additive instead of an aluminum film. After patterning the second conductive film d2 by photo processing technology,
A third conductive film d3 is formed. This third conductive film d3 is a transparent conductive film (Induim-
Tin-Oxide ITO: Nesa film). The film thickness is about 1000 to 2000 [λ] (in this liquid crystal display device, the film thickness is about 1200 [λ]). This third conductive film d3 constitutes the source electrode SDI, drain electrode SD2, and video signal line DL, and also constitutes the transparent pixel electrode IT○1. First conductive film d1 of source electrode SDI, drain electrode SD
Each of the two first conductive films d1 has an upper second conductive film d1.
Compared to the second and third conductive films d3, the first conductor Rl pattern d1 in these parts has nothing to do with the second conductive film d2 and the third conductive film d3. The source electrode SDI is connected to the transparent pixel electrode IT○1.The source electrode SDI is connected to the step shape of the i-type semiconductor layer AS (the first It is configured along a step corresponding to the sum of the thickness of the conductive film g1, the thickness of the N+ type semiconductor layer do, and the thickness of the i type semiconductor layer AS.Specifically, the source electrode SDI The first conductive film d1 is formed along the step shape of the i-type semiconductor layer AS, and the side connected to the transparent pixel electrode ITOI is formed in a smaller size on the upper part of the first conductive film d1. A third conductive film d2 connected to a second conductive film d2 and a third conductive film d1 exposed from the second conductive film d2.
It is composed of a conductive film d3. The second conductive film d2 of the source electrode SDI cannot overcome the step shape of the i-type semiconductor layer AS because the chromium film of the first conductive film d1 cannot be formed thickly due to increased stress. It is organized for the purpose of In other words, the second conductive film d2
The thicker shape improves the stepping force barrier. Since the second conductive film d2 can be formed thickly, it contributes to the resistance value of the source electrode SDI (drain electrode SD2). Therefore, by reducing the size of the second conductive film d2, the second conductive film d2 is connected to the exposed first conductive film d1.What are the first conductive film di and the third conductive film d3? Not only is the adhesive property good, but the step shape of the connecting portion between the two is small, so the source electrode SDI and the transparent pixel electrode IT○1 can be reliably connected. <Transparent pixel electrode ITOI> Transparent pixel electrode The ITOI is provided for each pixel and constitutes one of the pixel electrodes of the liquid crystal display section.The transparent pixel electrode ITOI has three transparent pixel electrodes corresponding to each of the thin film transistors TFTI-TFT3 divided into a plurality of pixels.
Two divided transparent pixel electrodes E1. It is divided into E2 and E3. The divided transparent pixel voltages tmE1 to E3 are each connected to the source ffllSDI of the thin film transistor TPT. Each of the divided transparent pixel electrodes E1 to E3 is patterned to have substantially the same area. In this way, the thin film transistor TPT of one pixel is divided into a plurality of thin film transistors TFTI to TFT3, and each of the divided transparent pixel electrodes E1 to E3 is connected to each of the divided thin film transistors TPT1 to TFT3. Even if a part of the pixel (for example, the thin film transistor TFTI) becomes a point defect, it is no longer a point defect when looking at the entire pixel (the thin film transistor TPT2
and thin film transistor TFT3 are not defective), so
The probability of point defects can be reduced, and defects can be made difficult to see. Moreover, by configuring each of the divided transparent pixel electrodes E1 to E3 with substantially the same area, the divided transparent pixel electrode E
It is possible to make the respective liquid crystal volumes itCpix formed by each of the pixels 1 to E3 and the common transparent pixel electrode IT○2 uniform. <<Protective Film PSVI> A protective film PSVI is provided over the thin film transistor TPT and the transparent pixel electrode ITOI. The protective film PSVI is mainly used to protect the thin film transistor TPT from moisture, etc., and a film having high transparency and good moisture resistance is used. The protective film PSv↓ is made of, for example, a silicon oxide film or a silicon nitride film formed by a plasma CVD apparatus, and is formed to a film thickness of about 8000 mm. <<Light-shielding film BM>> A shielding film is provided on the upper transparent glass substrate SUBZ side to prevent external light (light from above in FIG. 2B) from entering the i-type semiconductor 1'JAS used as a channel formation region. A BM is provided, and the shielding film BM has a pattern as shown by hatching in FIG. Note that FIG. 6 is a plan view depicting only the third conductive film d3 made of the IT◯ film, the color filter FIL, and the light shielding film BM in FIG. 2A. The light shielding film BM is formed of a film having a high light shielding property, such as an aluminum film or a chromium film, and in this liquid crystal display device, the chromium film is formed by sputtering to a thickness of about 1300 [λ]. Therefore, i of thin film transistors TPTl to TFT3
The type semiconductor layer As is sandwiched between the upper and lower light shielding films BM and the thick gate electrode GT, and this portion is not exposed to external natural light or backlight light. The light shielding film BM is formed around the pixel as shown by the hatched area in FIG. It is being Therefore, the outline of each pixel becomes clear due to the light shielding film BM, and the contrast is improved. In other words, the light shielding film BM has two functions: shielding light for the i-type semiconductor RAS and serving as a black matrix. Note that the backlight can be attached to the upper transparent glass substrate SUB2 side, and the lower transparent glass substrate SUBI can be set as the observation side (externally exposed side). <<Common transparent pixel electrode IT○2>> The common transparent pixel electrode IT○2 is connected to the lower transparent glass substrate SU
Opposing the transparent pixel electrode ITOI provided for each pixel on the BI side, the optical state of the liquid crystal LC responds to the potential difference (electric field) between each pixel electrode IT○1 and the common transparent pixel electrode IT○2. and change. A common voltage V com is applied to this common transparent pixel electrode ITO2. The common voltage Vcom is an intermediate potential between the low level open voltage V d min and the high level dynamic voltage Vdmax applied to the video signal line DL. <<Color Filter FIL>> The color filter FIL is constructed by coloring a dyed base material made of a resin material such as an acrylic resin with a dye. The color filter FIL is shaped like a dot for each pixel at a position facing the pixel (Fig. 7), and is dyed differently (
Figure 7 shows the third conductive film layer d3 and color filter F in Figure 3.
It depicts only IL, R. G. Each color filter FI Li; 45", 135'.
') 0 (1') hatched. The color filter FIL has a transparent pixel electrode ITOI as shown in FIG.
It is thickly shaped to cover all of (El to E3),
The light shielding film BM is attached to the transparent pixel electrode ETO so that it overlaps the color filter FIL and the edge part of the transparent pixel electrode T○1.
It is formed inside the periphery of I. The color filter FIL can be shaped as follows. First, a dyed base material is formed on the surface of the upper transparent glass substrate SUB2, and the dyed base material other than the red filter-shaped area is removed using photolithography technology. Thereafter, the dyed base material is dyed with a red dye and subjected to a fixing treatment to form a red filter R. Next, a green filter G and a blue filter B are sequentially formed by performing similar steps. <<Protective Film PSV2)> The protective film PSV2 is provided to prevent the dyes used to dye the color filters FIL into different colors from leaking into the liquid crystal LC. The protective film PSV2 is made of a transparent resin material such as acrylic resin or epoxy resin. <<Inorganic Transparent Film ITF>> As shown in the drawing, an inorganic transparent film ITF is provided between the color filter FIL and the protective film PSV2. The inorganic transparent film ITF is made of ITO@ or a silicon oxide film, and the ITO film is provided by sputtering, and the silicon oxide film is provided by dipping. Since the inorganic transparent film ITF prevents the transmission of 02 and H20, the color tone of the color filter FIL does not deteriorate. Furthermore, when the Kumamoto transparent film ITF is provided by sputtering or dipping, the film thickness of the inorganic transparent film ITF becomes uniform, and furthermore, the wettability when forming the protective film PS2 is uniform due to the inorganic transparent film ITF. Therefore, the thickness of the protective film PSV2 becomes uniform. <<Pixel Arrangement>> As shown in FIGS. 3 and 7, a plurality of pixels of the liquid crystal display section are arranged in the same column direction as the direction in which the scanning signal line OL extends, and are divided into pixel columns Xi, X2, X3, X4. ...is in charge of each of them. Each pixel column Xi, X2, X3, X
Each pixel of 4,... is a thin film transistor TF.
The arrangement positions of TI to TFT3 and divided transparent pixel electrodes E1 to E3 are configured to be the same. In other words, odd pixel row Xi
, X3, · each pixel is a thin film transistor TP
The arrangement position of T1 to TFT3 is on the left side, divided transparent pixel electrode E
1 to E3 are arranged on the right side. Each pixel in even numbered pixel columns X2, X4, . . . adjacent to each odd numbered pixel row Xi, X3, . . . receives a video signal from each pixel in odd numbered pixel columns Xi, X3, . It is composed of pixels that are line-symmetrically turned upside down with reference to the extending direction of the aDL. That is, pixel rows X2,
Each pixel of 4, . . . is a thin film transistor TP.
The arrangement positions of T1 to TFT3 are on the right side, and the transparent pixel electrodes E1 to
E3 is arranged on the left side. Then, each pixel of the pixel rows X2, X4-,...
, X3, . . . are shifted (shifted) by half a pixel in the column direction. In other words, each pixel interval of pixel row X is 1.0 (1.0 pitch)
Then, in the next pixel column X, each pixel interval is 1.0, and with respect to the previous pixel column
．． 5 pitches) is off. The video signal line DL extending in the row direction between each pixel is configured to extend in the column direction by a half pixel interval (0.5 pitch) between each pixel column X. As a result, as shown in FIG. 7, a pixel on which a predetermined color filter is applied in the previous pixel row Pixels on which filters of the same color are formed (for example, pixel row X
4 (pixels in which the red filter R is formed) are spaced apart by 1.5 pixel intervals (l.5 pitch), and the RGB color filters FIL are arranged in a triangular arrangement. Color filter F
The RGB triangular arrangement structure of IL can improve the mixing of each color, and therefore can improve the color and image resolution. Moreover, since the video signal line DL extends in the column direction by only half a pixel interval between each pixel column X, it does not intersect with the adjacent video signal line DL. Therefore, the video signal MD
It is possible to eliminate the routing of L and reduce its occupied area, and it is also possible to eliminate detours of the video signal line DL and eliminate the multilayer wiring structure. <<Equivalent circuit of the entire display device>> The equivalent circuit of the liquid crystal display device is shown in FIG. XiG, Xi+IG, . . . are video signal lines DL connected to pixels in which the green filter G is formed. XiB, Xi+IB, . . . are video signal lines DL connected to the pixels in which the blue filter B is formed. Xi+IR, Xi+2R, . . . are video signal lines DL connected to pixels in which the red filter R is formed. These video signal lines DL are selected by a video signal driving circuit. Yi is a scanning signal line OL that selects the pixel column X1 shown in FIGS. 3 and 7. Similarly, Yi+1, Yi+
Each of 2, . . . is a scanning signal line GL that selects each of the pixel columns X2, X3, . These scanning signal lines GL are connected to a vertical scanning circuit. <<Structure of storage capacitor element C add>> Each of the divided transparent pixel electrodes E1 to E3 is arranged in an L-shape so as to overlap with the adjacent scanning signal line GL at the end opposite to the end connected to the thin film transistor TPT. It is shaped by refraction. As is clear from FIG. 2C, this superposition is achieved by holding each of the divided transparent pixel electrodes E1 to E3 as one electrode PLI and the adjacent scanning signal line GL as the other electrode PLI. A capacitive element (electrostatic capacitive element) Cadd is configured. This storage capacitor C
The dielectric film add is made of the same layer as the edge film GI used as the gate i color edge film of the thin film transistor TPT. As is clear from FIG. 4, the storage capacitor element C add is formed in the widened portion of the first conductive film g1 of the gate line GL. Note that the first conductive film g1 at the portion intersecting with the video signal line DL is made thin in order to reduce the probability of short circuit with the video signal line DL. Each of the divided transparent pixel electrodes E1 to E3 and the electrode PLI are overlapped to form the storage capacitor element Cadd.
Similarly to the source electrode SDI, an island region is formed between the first conductive film d1 and the second conductive film d2 in order to prevent the transparent pixel electrode ITOI from being disconnected when going over the step shape. is provided. This island region is designed to be as small as possible so as not to reduce the area (aperture ratio) of the transparent pixel electrode IT○1. <<Equivalent circuit of storage capacitor element C add and its operation>> 2nd
FIG. 9 shows an equivalent circuit of the pixel shown in FIG. In FIG. 9, Cgs is a parasitic capacitance formed between the gate electrode GT and source electrode SDI of the thin film transistor TPT. The dielectric film of the parasitic capacitance Cgs is an insulating film GI. C pix is a liquid crystal capacitor formed between the transparent pixel electrode ITOI (PIX) and the common transparent pixel electrode IT02 (COM). The dielectric film of the liquid crystal capacitor C pix is the liquid crystal LC. Protective film PSVI and alignment film ORII, ORI
There is 21F. vlc is the midpoint potential. The storage capacitance element Cadd is . When the gI membrane transistor TPT switches, the midpoint potential (pixel electrode potential) Vi
It works to reduce the influence of gate potential change ΔVg on a. This situation can be expressed as the following formula. Δ Vlc== (Cgs/(Cgs+Cadd+Cp
ix))X ΔVg Here, Δv1c represents the change in midpoint potential due to ΔVg. This change ΔVlc causes the DC power applied to the liquid crystal LC, but the holding capacitance Ca
The larger dd is, the smaller its value can be. Further, the storage capacitor element C add also has the effect of lengthening the discharge time, so that video information is stored for a long time after the thin film transistor TPT is turned off. Reducing the DC component applied to the liquid crystal LC can improve the life of the liquid crystal LC and reduce so-called burn-in, in which the previous image remains when switching between liquid crystal display screens. As mentioned above, since the gate electrode GT is made large enough to completely cover the i-type semiconductor MAS, the source electrode SDI
, the overlap area with the drain electrode SD2 increases, the parasitic capacitance Cgs increases, and the midpoint potential vlc
has the opposite effect of becoming susceptible to the influence of the gate (scan> is 4 to 8 times the liquid crystal capacitance C pix (4・Cp
ix<Cadd<8・Cpix). 8 to 32 times the superposition capacitance Cgs (8 ・Cgs<C
add<32・Cgs). <Connection method of holding capacitor element C add electrode line> The final stage scanning signal line OL (or first stage scanning signal line GL) used only as a capacitor electrode line is connected to the common transparent pixel ffi as shown in FIG. Connect to the terminal ITO2 (Vcom). The common transparent pixel electrode IT○2 is, as shown in FIG. 2B,
The peripheral portion of the liquid crystal display device is connected to external lead wiring by a silver paste material SL. Moreover, some of the conductive layers (gl and g2) of this external lead wiring are formed in the same manufacturing process as the scanning signal line GL. As a result, the final stage scanning signal line (capacitive WA line) GL can be easily connected to the common transparent pixel electrode IT○2. can be connected to. Alternatively, as shown by the dotted line in FIG. 8, the final stage (first stage) scanning signal line (capacitive electrode line) GL may be connected to the first stage (final stage) scanning signal line GL. Note that this connection can be made by internal wiring within the liquid crystal display section or external wiring. <DC cancellation by scanning signal of storage capacitance element Cadd> This liquid crystal display device is based on the DC cancellation method (DC cancellation method) described in Japanese Patent Application No. 62-95125 previously filed by the applicant of the present application. As shown in FIG. 10 (time chart), by controlling the gap voltage of the scanning signal line GL, it is possible to further reduce the direct current applied to the liquid crystal LC. In FIG. 10, Vi is the operating voltage of an arbitrary scanning signal line GL, and V i +1 is the operating voltage of the scanning signal line GL at the next stage. Vee is a low-level pulse voltage Vdmin applied to the video signal line DL;
Vdd is a high-level dynamic voltage V d wax applied to the video signal line DL. Each time t = t. 1~
The voltage change amount Δv4 to ΔV4 of the midpoint potential vlc (see FIG. 9) at t4 is the total capacitance of the pixel C=Cgs+C
When pix + C add, it is expressed by the following formula. ΔV. = (Cgs/C)・V2 ΔV. =+(Cgs/C)・(Vl+V2)−(Cad
d/C)・v2 b. V. = − (Cgs/C)・V 1+(C
add/C)・(V1+V2) △V4=-(Cadd/C)・V 1 Here, if the dynamic voltage applied to the scanning signal line GL is sufficient (see Note 1 below), the liquid crystal LC The applied DC voltage is expressed by the following formula: ΔV, +ΔV, = (Cadd-V 2 - Cgs
-V 1 )/C Therefore, Cadd-V 2 =
When Cgs-V is 1, the DC voltage applied to the liquid crystal LC is O. (Note 1 At times t1 and t2, the change in the tremor voltage Vi affects the midpoint potential Vlc, but during the period from t2 to t3, the midpoint potential Via is made the same potential as the video signal potential through the signal line Xi. (Sufficient writing of video signals). The potential applied to the liquid crystal LC is almost determined by the potential immediately after the thin film transistor TPT is turned off (the off period of the thin film transistor TPT is overwhelmingly longer than the on period). Therefore, the liquid crystal L
In calculation of the DC component applied to C, the period t↓ to t3 can be almost ignored, and the potential immediately after the thin film transistor TPT is turned off, that is, time t3. It is only necessary to consider the influence during the transition at t4. Note that the polarity of the video signal is inverted for each frame or line, and the DC component due to the video signal itself is zero. In other words, in the DC cancellation method, the reduction due to the pull-in of the midpoint potential Vlc by the parasitic capacitance Cgs is compensated for by the storage capacitance element C.
add and the scanning signal line (capacitive electrode line) GL of the next stage to push it up and make it possible to extremely reduce the DC component applied to the liquid crystal LC. As a result,
The liquid crystal display device can improve the lifespan of the liquid crystal LC. Of course, if the gate electrode GT is made larger to increase the light shielding effect, the storage capacitor element C add
It is only necessary to increase the holding capacity of . As above, the invention made by the present inventor has been specifically explained based on the above embodiments, but this invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist thereof. Of course. For example, in the above embodiment, an inverted staggered structure of gate electrode type → gate insulating film formation → semiconductor layer formation → source/train electrode type was shown, but a staggered structure in which the vertical relationship or the order of formation is reversed is shown. This invention is also effective for Iffi. Further, in the above-mentioned embodiments, the case where the inorganic transparent film ITF is made of an ITO film or a silicon oxide film has been described, but other inorganic transparent films may be used. [Effect of the invention 1 As explained above, in the color liquid crystal display device according to the present invention, since the inorganic transparent film prevents the transmission of 02 and H20, the color tone of the color filter does not deteriorate, and the inorganic transparent film prevents the transmission of 02 and H20. Since the film provides uniform wettability when forming the protective film, the thickness of the protective film is uniform. As described above, the effects of this invention are remarkable.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a part of the liquid crystal display unit of the color liquid crystal display device shown in FIG. Figure 2B is a plan view of the main part showing one pixel of the liquid crystal display. Figure 2B is a partial view of the area cut along the section line B-IIB in Figure 2A and the area around the seal. II
C-II C cut llO? Sectional view along the line, 3rd
The figure is a plan view of a main part of a liquid crystal display section in which a plurality of pixels shown in FIG. 2A are arranged, FIGS. 4 to 6 are plan views depicting only a predetermined layer of pixels shown in FIG. 2A, and FIG. A plan view of the main parts depicting only the pixel electrode layer and color filter layer shown in FIG. 8.
The figure is an equivalent circuit diagram showing the liquid crystal display section of an active matrix color liquid display device, Figure 9 is an equivalent circuit diagram of the pixel shown in Figure 2A, and LO diagram is a scanning signal line using the DC cancellation method. This is a time chart 1 showing the dynamic voltage of . SUB: Transparent glass substrate GL: Scanning signal line DL: Video signal line GI: Edge film GT: Gate's clear A S-i type semiconductor layer SD: Source electrode or train fft hpsv
・Protective film BM...Light shielding film LC...Liquid crystal TPT...Thin film transistor ITO...Transparent pixel electrode gt d...Conductive film C add...Holding capacitor element Cgs...Parasitic capacitance Cpix...Liquid Product capacity■TF...Inorganic transparent film FIL--- ηRafzurg PSV2-. - I'm dumbfounded... The heat priest's elbow expense

Claims (1)

[Claims] 1. A color liquid crystal display device in which a color filter is covered with a protective film made of an organic substance, characterized in that an inorganic transparent film is provided between the color filter and the protective film.