JP2003255372A - Liquid crystal display and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active matrix type liquid crystal display which is bright and which has a high contrast and its manufacturing method. <P>SOLUTION: The protruding part 14 of a third interlayer insulator film 10 is formed in a region including at least the gap region between pixel electrodes 11b, 11c which are driven with potentials whose polarities are different. The other region of the third interlayer insulator film 10 is flattened. As a result, in the region of the protruding pat 14, a cell gap is shorter than that in the other region of the insulator film 10 and a light slipping width due to a transverse electric field can be suppressed to the minimum. Then, the alignment failure of liquid crystal material which is to be generated by allowing a pixel electrode 11 to be formed to have steps is suppressed and light slips in the liquid crystal display are suppressed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device using a switching element such as a thin film transistor (hereinafter referred to as "TFT") and a manufacturing method thereof. INDUSTRIAL APPLICABILITY The liquid crystal display device of the present invention is used for a direct view type liquid crystal display such as a liquid crystal color television and a projection type liquid crystal display such as a liquid crystal projector.

[0002]

2. Description of the Related Art A conventional active matrix type liquid crystal display device includes an active matrix substrate having a plurality of pixel electrodes, which are units of pixel display, arranged in a matrix, and an opposite substrate having an opposite electrode facing the pixel electrodes. , And a liquid crystal layer sandwiched between both substrates.

An active matrix substrate is manufactured, for example, by first forming switching elements for each pixel on the substrate, then forming scan wirings and signal wirings, and finally forming pixel electrodes. In such an active matrix substrate, due to the presence of switching elements and wiring,
The surface of the pixel electrode in the display region becomes uneven, and a step is formed in the alignment film formed on the pixel electrode. In the rubbing process for aligning the liquid crystal material, the alignment process may not be performed uniformly due to a step difference, and the liquid crystal material in the step portion of the alignment film may have poor alignment. When the alignment failure occurs, the liquid crystal material cannot be driven well in that portion, and the contrast is lowered due to light leakage of the liquid crystal display device and the display quality is lowered.

A flattening technique for eliminating irregularities on the surface of the pixel electrode has been proposed, for example, in Japanese Patent Laid-Open No. 11-142870. In this conventional technique, a flattening film is provided on an active matrix substrate, and the surface thereof is flattened by polishing. In the active matrix substrate whose surface is flattened, it is possible to prevent light leakage due to defective alignment of the liquid crystal material, which is caused by the unevenness of the surface, and improve the deterioration of contrast.

On the other hand, as a method of driving the active matrix substrate, there are a method of driving adjacent pixel electrodes with the same polarity and a method of driving adjacent pixel electrodes with different polarities. In an active matrix type liquid crystal display device, an inversion driving method in which each row or column of picture element electrodes is inverted according to a predetermined rule is used in order to prevent deterioration of the liquid crystal material and crosstalk or flicker in display quality. Has been adopted. For example, in the method of performing inversion driving for each row, the pixel electrode groups adjacent in the row direction are
Each pixel electrode is driven with a potential of the same polarity, but it is driven with a potential of a different polarity with respect to other pixel electrode groups in the one row direction.

Between the electrodes driven with different polarities,
An electric field is generated laterally between the electrodes. Due to the influence of the lateral electric field, alignment failure occurs in the liquid crystal material, light leakage occurs in this portion, and there is a problem that the contrast decreases. Although this light-through region can be hidden by a light-shielding film or the like, the aperture area per pixel display unit is reduced and the brightness is reduced. The flattening technique disclosed in Japanese Patent Laid-Open No. 11-142870 or the like cannot eliminate the alignment defect of the liquid crystal material due to the influence of the lateral electric field.

By shortening the distance between the active matrix substrate and the counter substrate (hereinafter referred to as "cell gap"), it is possible to narrow the region of light leakage due to the influence of the lateral electric field. For example, in Japanese Unexamined Patent Application Publication No. 2001-142414, in a boundary region between pixel electrodes driven with different polarities, unevenness is formed on a base surface located below the pixel electrodes to form a cell with a counter electrode. It is disclosed that by making the gap shorter than other regions, alignment failure of the liquid crystal material due to a lateral electric field in a boundary region between pixel electrodes driven by potentials of different polarities is prevented. However, since the optimum cell gap is determined depending on the type of liquid crystal material, if the cell gap is narrowed, the transmittance of the liquid crystal display device is lowered and the brightness is lowered.

[0008]

The inventors of the present invention investigated the relationship between the cell gap and the light-exiting region due to the influence of the lateral electric field, and the results shown in FIG. 5 were obtained.
Generally, the cell gap is about 3.0 μm,
For example, when the cell gap in the region affected by the lateral electric field is shortened by 0.5 μm to 2.5 μm, the width of the light passing region (hereinafter also referred to as “light passing width”) due to the influence of the lateral electric field is 1. It can be seen from the result of FIG. 5 that the size is reduced by about 0 μm.

According to the method described in Japanese Patent Laid-Open No. 2001-142414, as shown in FIG. 6B, the convex portion 10 is formed on the TFT array substrate 1 in the formation region of the scanning wiring 5a and the capacitance line 5b.
1 to form the scanning line 5a and the capacitance line 5b.
By reflecting the convex portion 101 on the surface of the interlayer insulating film 8 covering the
The cell gap d2 in the region where the lateral electric field is generated is made shorter than the cell gap d1 in the other regions.

However, by forming the interlayer insulating films 6 and 8,
The width of the region of the convex portion 101 is widened on the surface of the interlayer insulating film 8. It is not easy to control the width of the convex portion on the surface of the interlayer insulating film 8. Further, the tapered surface 102 of the convex portion 101 is also reflected on the surface of the interlayer insulating film 8. The film thickness of the interlayer insulating films 6 and 8 is generally 1.0 μm or more, and the tapered surface 1 of the convex portion 101 generated at both ends of the scanning wiring 5a and the capacitance line 5b.
The region 02 (hereinafter also referred to as “step region”) has a width of about 1.0 μm or more on the surface of the interlayer insulating film 8. In the stepped region on the surface of the interlayer insulating film 8, alignment failure due to tilting occurs, so it is necessary to take some light shielding measures. As a light-shielding measure, for example, increasing the width of a light-shielding layer (not shown) provided above the scanning wiring 5a or the capacitance line 5b or the light-shielding layer 9 provided between the counter substrate and the counter electrode 12 Accompanied by a decrease in the opening area.

As shown in FIGS. 6 (a) and 6 (b), by shortening the cell gap d1 between the pixel electrode 11 and the counter electrode 12, the region 15 of light leakage caused by the influence of the lateral electric field is formed. The width becomes narrow. For example, when the cell gap of the region 15 affected by the lateral electric field is shortened by 0.5 μm, the light leakage width is reduced by about 1 μm. However, when the film thickness of the interlayer insulating films 6 and 8 is, for example, 1 μm, the width of the step region 16 on the surface of the interlayer insulating film 8 depends on the convex portion 10 of the TFT array substrate 1.
The width is 1 μm or more wider than the width of the stepped region in No. 1. In the step region 16 on the surface of the interlayer insulating film 8, light leakage occurs due to defective alignment. That is, the expansion of the light leakage width due to the expansion of the step region exceeds the reduction of the light leakage width due to the shortening of the cell gap.

Therefore, it is necessary to enlarge the light-shielding region as a measure for increasing the width of the light passage, but if the light-shielding region is enlarged, the aperture area is reduced, which is not sufficient. Alternatively, when priority is given to securing the opening area, it is necessary to make the wiring thin, but this is accompanied by an increase in wiring resistance and a decrease in storage capacitor area, and this has a considerable effect on display quality.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an active matrix type liquid crystal display device having a bright and high contrast and a manufacturing method thereof.

[0014]

A liquid crystal display device according to a first aspect of the present invention includes a plurality of scanning wirings extending in parallel with each other and a plurality of scanning wirings intersecting the plurality of scanning wirings and extending in parallel with each other. Signal wiring, a plurality of switching elements connected to the scanning wiring and the signal wiring and arranged in a matrix, and a plurality of pixel electrodes connected to each of the plurality of switching elements and arranged in a matrix. A liquid crystal display device comprising: an active matrix substrate having: a counter electrode having a counter electrode facing the pixel electrode; and a liquid crystal layer interposed between the active matrix substrate and the counter substrate. The electrodes are a first pixel electrode group driven by a potential of the same polarity and a second image electrode driven by a potential of a polarity different from that of the first pixel electrode group. Consists of a electrode group, the first pixel electrode group and the second pixel electrode group, the polarity is driven inverted every period of 1 frame or 1 field, the active matrix substrate, the scanning lines,
An interlayer insulating film having a flat surface on the liquid crystal layer side is provided between the signal line and the switching element and the pixel electrode, and the interlayer insulating film is a first pixel electrode belonging to the first pixel electrode group. In a region including at least a break region of a gap between the pixel electrode and the second pixel electrode which belongs to the second pixel electrode group and is adjacent to the first pixel electrode, there is a protrusion protruding toward the liquid crystal layer side. .

In the present specification, the term "flat" means a surface condition that uniformly regulates the thickness of the liquid crystal layer to the extent that the deterioration of display quality due to the variation in the thickness of the liquid crystal layer does not occur. Specifically, when the roughness of the surface of a region (for example, the average value of the unevenness measured by a surface roughness meter) is 1/10 or less of the thickness of the liquid crystal layer in the region, the surface is It is said to be flat.

In a liquid crystal display device according to a second aspect of the present invention, a plurality of scanning wirings extending in parallel with each other, a plurality of signal wirings intersecting with the plurality of scanning wirings and extending in parallel with each other, An active matrix substrate having a plurality of switching elements connected to the scan wiring and the signal wiring and arranged in a matrix, and a plurality of pixel electrodes connected to each of the plurality of switching elements and arranged in a matrix. A liquid crystal display device comprising a counter substrate having a counter electrode facing the pixel electrode, and a liquid crystal layer interposed between the active matrix substrate and the counter substrate, wherein the plurality of pixel electrodes are
A first pixel electrode group driven with a potential of the same polarity and a second pixel electrode driven with a potential of a different polarity from the first pixel electrode group.
A pixel electrode group, and the first pixel electrode group and the second pixel electrode group are driven with their polarities being inverted at each one frame or one field cycle, and the active matrix substrate is driven by the scanning wiring, An interlayer insulating film having a flat surface on the liquid crystal layer side is provided between the signal line and the switching element and the pixel electrode, and belongs to the first pixel electrode group on the interlayer insulating film. First
A pixel electrode, which belongs to the second pixel electrode group, and which has the first
An insulating convex layer protruding toward the liquid crystal layer side is formed in a region including at least a gap region of a gap between the pixel electrode and the second pixel electrode.

In the liquid crystal display device according to the second aspect of the present invention, the convex layer may be a light shielding layer having a light shielding property.

In the liquid crystal display device according to the first or second aspect of the present invention, the convex portion or the convex layer overlaps any one or a plurality of the scanning wiring, the signal wiring and the switching element. It may be formed in a region further including the overlapping region.

A method of manufacturing a liquid crystal display device according to a first aspect of the present invention comprises a step of planarizing a surface of the interlayer insulating film formed on the active matrix substrate by chemical mechanical polishing, and a surface planarizing. Forming a resist film on the formed interlayer insulating film, patterning the resist film to form a resist layer covering a region including at least the cut region, and masking the patterned resist layer. As the interlayer insulating film is thinned by etching the interlayer insulating film in a region other than a region including at least the cut region, and a convex portion is formed in the interlayer insulating film in a region including at least the cut region. And a step of performing.

A method of manufacturing a liquid crystal display device according to a second aspect of the present invention comprises a step of flattening the surface of the interlayer insulating film formed on the active matrix substrate by chemical mechanical polishing, and a step of flattening the surface. A step of sequentially forming an insulating film and a resist film on the formed interlayer insulating film, and a step of patterning the resist film to form a resist layer covering a region including at least the cut region,
By using the patterned resist layer as a mask and etching the insulating film, the insulating film in a region other than a region including at least the cut region is removed, and the insulating film in a region including at least the cut region is formed. And a step of forming a convex shape.

[0021]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, a transmissive liquid crystal display device will be described, but the liquid crystal display device of the present invention can also be applied to a reflective liquid crystal display device and a reflective / transmissive liquid crystal display device.

(Embodiment 1) A liquid crystal display device according to Embodiment 1 of the present invention includes an active matrix substrate in which a plurality of pixel electrodes, which are display units at the time of displaying an image, are arranged in a matrix, a counter electrode, and the like. The counter substrate includes a counter substrate which is opposed to the active matrix substrate with a proper distance from the active matrix substrate, and a liquid crystal layer sandwiched between the two substrates.

FIG. 1 is a plan view schematically showing the active matrix substrate of this embodiment. 2 (a) to 2
3F and FIG. 3A to FIG. 3C are cross-sectional views showing the manufacturing process of the liquid crystal display device of the present embodiment, and the cross-sectional view taken along the line AA ′ in FIG. The cross-sectional view taken along the line BB 'in 1 is shown on the right side.

The active matrix substrate used in this embodiment will be described with reference to FIGS. 1 and 3B. A light shielding film 2 is formed on an insulating substrate 1 such as a glass substrate, and an insulating film 20 covering the light shielding film 2 is formed. The active layer 3 and the gate insulating film 4 covering the active layer 3 are formed on the insulating film 20. The scanning wiring 5a and the capacitance line 5b are formed on the gate insulating film 4, and the signal wiring 7 intersects with the scanning wiring 5a via the first interlayer insulating film 6.
Are formed. In the present embodiment, the plurality of scanning wirings 5a parallel to each other extend in the row direction and the plurality of signal wirings 7 parallel to each other extend in the column direction. However, the scanning wirings 5a extend in the column direction and the signal wirings 7 extend in the row direction. You may arrange | position so that it may extend in a direction.

The active layer 3 is formed in the vicinity of the intersection of each scanning wiring 5a and each signal wiring 7, and the active layer 3, the gate insulating film 4, the scanning wiring (including the gate electrode) 5a and the signal wiring ( A TFT, which is a switching element, is composed of the source electrode 7). The TFT is ON / OFF switched by a scanning signal applied to the scanning wiring 5a.

The capacitance line 5b has an extending portion extending downward in FIG. 1 from the intersection with the signal wiring 7 along the signal wiring 7. An auxiliary capacitance for assisting the pixel capacitance is accumulated between the extension of the capacitance line 5b and the signal line 7.

On the insulating substrate 1, these scanning wirings 5a,
In order to cover the capacitance line 5b, the signal line 7 and the TFT, in other words, in the overlapping region where these lines 5a, 5b and 7 and the TFT are overlapped with each other, the light shielding film is provided via the second interlayer insulating film 8 having a predetermined thickness 9 is formed. Further, a third interlayer insulating film 10 that covers the light shielding film 9 is formed. Third
The surface of the interlayer insulating film 10 is planarized by chemical mechanical polishing (hereinafter referred to as “CMP”).

CMP is a method of physically polishing the surface with an abrasive, and further chemically polishing with a chemical agent.
This is to polish the surface of the thin film to flatten it. That is, the surface of the thin film is polished and flattened by using an abrasive and a chemical together. Wiring 5a, 5b, 7 and TF
The presence of T causes unevenness on the surface of the third interlayer insulating film 10. When the interlayer insulating film 10 is flattened,
An interlayer insulating film 10 that is sufficiently thicker than the layer thickness (height) of the wirings 5a, 5b, 7 and the TFT is formed. The inter-layer insulating film 10 is chemically and chemically treated with a polishing cloth (pad) and an abrasive (slurry).
Mechanically polish (remove). By polishing, the convex portions on the surface are removed, so that the surface of the interlayer insulating film 10 is flattened. CMP is effective in that the entire surface of the insulating film can be planarized as compared with the conventional planarization method such as the SOG method and the flow method.

In the flattened third interlayer insulating film 10, a convex portion 14 protruding toward the liquid crystal layer is formed in a region including at least a cut region described later. Contact holes reaching the drain electrodes of the respective TFTs are formed in the third interlayer insulating film 10 at positions overlapping the respective drain electrodes. In addition, the third interlayer insulating film 10
Pixel electrodes 11 connected to the drain electrodes of the respective TFTs via contact holes are provided on the upper side.

It is preferable that the gap region between the pixel electrodes 11 adjacent to each other be overlapped with the bus wiring (scanning wiring 5a and signal wiring 7). As a result, the area of the region where the pixel electrode 11 and the bus wirings 5a and 7 overlap with each other is reduced, so that the pixel electrode 11 and the bus wirings 5a and 7 are reduced.
The capacitance value accumulated between and becomes smaller, and the display quality is improved.

A plurality of pixel electrodes formed on the active matrix substrate are driven by a potential of the same polarity.
The pixel electrode group and the second pixel electrode group driven by a potential having a polarity different from that of the first pixel electrode group. Each of the first pixel electrode group and the second pixel electrode group has one frame or one frame.
The polarity is inverted and driven for each field cycle. As a result, deterioration of the liquid crystal material due to application of a DC voltage is prevented, and crosstalk and flicker in the display image are prevented. For example, during a display period corresponding to an image signal of one frame or one field, the pixel electrode groups arranged in odd rows are driven with a positive potential with reference to the potential of the counter electrode and arranged in even rows. The pixel electrode group is driven with a negative potential with reference to the potential of the counter electrode. On the contrary, in the period in which the display corresponding to the image signal of the next frame or field is performed, the pixel electrode groups arranged in the even rows are driven by the positive potential, and the pixel electrode groups arranged in the odd rows are negative. Driven by electric potential. The inversion drive method is not limited to this row inversion drive method, and may be a column drive method in which the polarity of the electric potential is inverted for each column in a frame or field cycle while driving the pixel electrode groups in the same column with the electric potential of the same polarity. . In addition, a pixel electrode group arbitrarily combined among a plurality of pixel electrodes arranged in a matrix and another pixel electrode group are driven with potentials having different polarities, and the polarity of the potentials is inverted in a frame or field cycle. May be.

In FIG. 1, the polarity of each pixel electrode at a certain timing is indicated by + or −. Pixel electrode group 11 in the same column
The potentials a and 11b and the pixel electrode groups 11c and 11d have the same polarity, and no horizontal electric field is generated between the pixel electrodes adjacent to each other in the row direction, for example, between the pixel electrode 11a and the pixel electrode 11b. However, between the pixel electrodes adjacent in the column direction, for example, the pixel electrode 11b and the pixel electrode 11c.
A lateral electric field is generated in the cut region 15 of the gap between the and. Therefore, the influence of the lateral electric field causes alignment failure of the liquid crystal material, resulting in light leakage.

In this embodiment, the convex portion 14 is formed in the cut region 15 of the third interlayer insulating film 10 to make the cell gap in the cut region 15 shorter than the cell gaps in the other regions. As a result, the vertical electric field between the counter electrode 12 and the portion of the pixel electrode near the cut region 15 can be made relatively stronger than the vertical electric field in the other regions. Therefore, the influence of the lateral electric field on the liquid crystal material is reduced, and a region where alignment failure of the liquid crystal material occurs,
In other words, the width of light leakage is reduced.

In this embodiment, since the side surface of the convex portion 14 is a gentle tapered surface, the pixel electrode 11 due to the step between the upper surface of the convex portion 14 and the flat surface of the third interlayer insulating film 10 is formed.
Is unlikely to break.

In this embodiment, the scan wiring 5 is formed by performing the flattening process of the third interlayer insulating film 10, that is, the CMP process.
A region that is shielded by a and the signal wiring 7 and the other region (transmissive region) are determined. If the flattening process is not performed, unevenness is generated on the surface of the interlayer insulating film 10 in the regions where the wirings 5a, 5b, 7 and the TFT exist. Due to the surface irregularities, light leakage occurs even in the transmissive region in the vicinity of the region where the wiring and the like exist. Therefore, it is necessary to shield the region wider than the region where the wiring and the like exist by using the light shielding layer. In the present embodiment, the CMP process is performed to planarize the third interlayer insulating film 10, so that the surface irregularities are eliminated, so that there is no light leakage due to the irregularities and only the region where the wiring or the like exists is shielded by the light shielding layer. Good.

Since the entire surface of the third interlayer insulating film 10 is flat, there is no light leakage due to the influence of steps in all regions of the pixel electrode 11, and all regions other than the regions in which wirings and the like are present are open regions. Can be used for on the other hand,
By forming the convex portion 14, the light passage area is suppressed, but the light passage width cannot be made zero, so that a light shielding layer is required. Therefore, the scanning wiring (metal) 5a, the signal wiring (metal) 7, and the light-shielding film region are overlapped with the light leakage region due to the influence of the suppressed lateral electric field, in other words, wiring is performed in the suppressed light leakage region. It is possible to suppress the expansion of the light-shielding region by arranging or the like. Therefore, the aperture area can be increased by effectively utilizing each pixel display unit without requiring an extra light shielding layer.

In the method described in Japanese Patent Laid-Open No. 2001-142414, as shown in FIG. 6B, the interlayer insulating films 6 and 8 are formed so that the region of the convex portion 101 and the step region of the TFT array substrate 1 are insulated from each other. The width of the surface of the film 8 becomes wider, and the width of light leakage is increased. On the other hand, in the present embodiment, since the convex portion 14 is formed on the upper layer of the active matrix substrate, that is, the third interlayer insulating film 10 in contact with the pixel electrode 11, the width of the convex portion 14 does not increase, The light leakage width can be suppressed to the necessary minimum.

Next, a method of manufacturing the liquid crystal display device of this embodiment will be described with reference to FIGS. 2 (a) to 2 (f) and 3 (a) to 3
This will be described with reference to (c). As shown in FIG. 2A, a light-shielding film to be a lower light-shielding layer of a transistor is deposited on a transparent insulating substrate 1 such as glass or quartz by a CVD method, a sputtering method or the like, and patterned by photo / etching. Thus, the lower light shielding film 2 is formed. As the light-shielding film, a metal film (Al, Ta, Ti, W,
Mo, Cr, Ni), single layer film such as polysilicon, Al
Si, MoSi ₂ , TaSi ₂ , TiSi ₂ , WS
i ₂ , CoSi ₂ , NiSi ₂ , PtSi, Pd ₂ S,
HfN, ZrN, TiN, TaN, NbN, TiC, T
A material having a light blocking effect such as aC, TiB ₂ or a combination thereof is used.

As shown in FIG. 2B, SiO _{2 is formed} on the entire surface.
An insulating film 20 such as a film is deposited. The active layer 3 of the transistor is formed on the insulating film 20. The active layer 3 is made of Si, Ge, G
It is made of semiconductors such as aAs and GaP, and is amorphous, polycrystalline,
After depositing a semiconductor film such as a single crystal, patterning is performed. For example, when polycrystalline silicon is used, an amorphous silicon thin film is generally formed on the insulating film 20.
After being deposited to a film thickness of 0 nm to 150 nm, it is polycrystallized by heat treatment at high temperature or laser light irradiation. After that, patterning is performed by photo / etching to form the active layer 3 having a predetermined shape. After that, impurity ion implantation may be performed for controlling the threshold voltage.

As shown in FIG. 2C, the gate insulating film 4 is formed on the active layer 3. The gate insulating film 4 is CVD
It is formed by deposition by a method, oxidation, or both. Subsequently, a gate electrode, a scanning wiring 5a and a capacitance line 5b are formed on the gate insulating film 4. Then, impurity ions are implanted into the active layer 3 using the gate electrode as a mask to form a source region and a drain region. The region where the impurity ions are not implanted becomes the channel region.

As shown in FIG. 2D, an insulating film is deposited on the entire surface to form a first interlayer insulating film 6. Next, a contact hole for taking out an electrode is opened in the first interlayer insulating film 6 in the region overlapping with the source region and the drain region, and the signal wiring 7 and the drain electrode made of a metal material such as Al are formed.

As shown in FIG. 2E, a nitride film and an oxide film are deposited on the entire surface to form a passivation film (second interlayer insulating film 8), and a hydrogenation process is performed. Next, a light-shielding film 9 made of a metal material such as Ti is formed in each region which overlaps with the active layer 3, the scanning wiring 5a and the signal wiring 7. Further, a third interlayer insulating film 10 that covers the light shielding film 9 is formed. The surface 13 of the third interlayer insulating film 10 is flattened by CMP processing.

After forming a resist film on the surface 13 of the third interlayer insulating film 10, a resist layer 16 having a predetermined pattern is formed as shown in FIG. 2 (f). Specifically, the break region 15 between the pixel electrodes 11 driven by potentials of different polarities
The resist layer 16 is formed in a region including the region and overlapping the light shielding film 9.

Next, as shown in FIG. 3A, the surface 13 of the third interlayer insulating film 10 is wet-etched by HF or the like using the patterned resist layer 16 as a mask. Since the wet etching is isotropic etching, the etching is wider than the size of the opening of the resist layer 16, and the tapered convex portion 14 is formed in the region of the third interlayer insulating film 10 covered with the resist layer 16. It is formed. The region of the third interlayer insulating film 10 not covered with the resist layer 16 is thinned by etching. Instead of wet etching, CF ₄ or C
Etching may be performed by dry etching using a gas such as F ₄ + CHF ₃ .

Third interlayer insulating film 1 overlapping with the drain electrode
After forming a contact hole in the 0 region, a transparent conductive film such as ITO is sputtered. As a result, the transparent conductive film is electrically connected to the drain electrode.

As shown in FIG. 3B, the cut areas of the transparent conductive film are removed by photo / etching to form a plurality of pixel electrodes 11 arranged in a matrix. The active matrix substrate of the present embodiment is manufactured by forming an alignment film on the pixel electrode 11 by a known method and performing steps such as rubbing treatment. When manufacturing a reflection type liquid crystal display device, the pixel electrode 11 is formed of a material having a high reflectance such as Al.

The active matrix substrate manufactured through the above steps is bonded to the counter substrate 50 having the counter electrode 12 with an appropriate gap. By further performing necessary steps such as a step of injecting a liquid crystal material between both substrates to form the liquid crystal layer 40, further sealing the liquid crystal layer 40, and a step of attaching a deflection plate to the outside of both substrates, a desired liquid crystal layer 40 can be obtained. An active matrix type liquid crystal display device is manufactured (see FIG. 3).
(See (c)).

In the liquid crystal display device of the present embodiment, the convex portion 14 of the third interlayer insulating film 10 is formed in the active matrix substrate in a region including at least a break region between the pixel electrodes 11 driven by potentials of different polarities. Has been formed.
Therefore, since the region of the convex portion is formed higher than the other regions, the cell gap is shortened and the influence of the vertical electric field on the liquid crystal material is increased. As a result, the width of light leakage due to the lateral electric field can be minimized.

Further, other regions of the third interlayer insulating film 10 are
Since the flattening process is performed by CMP, the surface of the pixel electrode 11 on the third interlayer insulating film 10 is flat. Therefore, the defective alignment of the liquid crystal material due to the stepped shape of the pixel electrode 11 is suppressed, and the light leakage of the liquid crystal display device is suppressed.

The convex portion 14 is formed without increasing the minimum required area of the non-opening area (light-shielding area) by forming the wiring or the light-shielding film, in other words, within the range of the non-opening area (light-shielding area).
Since a light leakage region is formed due to the formation of, the opening area does not decrease. Therefore, a liquid crystal display device having a high brightness and a high contrast is provided by making the most of each pixel area.

(Embodiment 2) In Embodiment 1, the third interlayer insulating film 10 is etched to form the protrusions 14. However, an insulating layer different from the third interlayer insulating film 10 is formed,
It may be convex. In this embodiment, a case where a convex light-shielding layer is formed on an interlayer insulating film will be described.

The active matrix substrate shown in the present embodiment has the structure shown in FIG. 4C, and the light-shielding film has a convex shape. That is, the light-shielding film is formed in the region where the convex portion 14 of the first embodiment is formed. The point where it is formed and the surface of the second interlayer insulating film 8 is CMP.
This is different from the active matrix substrate of the first embodiment in that the flattening process is performed by. Since the active matrix substrate of this embodiment can form a TFT element in the same manner as in Embodiment 1, FIGS. 2A to 2D are used.
, And the description is omitted. The subsequent manufacturing process will be described with reference to FIGS. 4 (a) to 4 (c).

As shown in FIG. 4A, a nitride film and an oxide film are deposited on the entire surface of the active matrix substrate to form a passivation film (second interlayer insulating film 8), and a hydrogenation process is performed. Next, the surface 13 of the second interlayer insulating film 8 is C
It is flattened by MP processing.

After forming a light-shielding film made of a metal material such as Ti on the surface 13 of the second interlayer insulating film 8, a resist layer 16 having a predetermined pattern is formed as shown in FIG. 4B. Specifically, the resist layer 16 is formed in a region including the cut region 15 between the pixel electrodes 11 driven by potentials of different polarities and in a region overlapping the wirings 5a and 5b and the active layer 3. To do. Similar to the first embodiment, the light shielding film is etched by wet etching or dry etching to form the tapered convex light shielding layer 24.

Further, the third interlayer insulating film 10 covering the convex light shielding layer 24 is formed. Since the convex light shielding layer 24 is interposed between the second interlayer insulating film 8 and the third interlayer insulating film 10,
Third interlayer insulating film 10 in the formation region of the convex light shielding layer 24
Protrudes. Next, in the same manner as in the first embodiment, a contact hole is formed in the region of the third interlayer insulating film 10 and ITO is formed.
The pixel electrode 11 is formed of a transparent conductive film such as
(See (c)). After that, through the same steps as in the first embodiment,
A liquid crystal display device is manufactured.

The liquid crystal display device of this embodiment is the same as that of the first embodiment.
Similarly to the above, since the third interlayer insulating film 10 in the region of the convex light shielding layer 24 is projected, the cell gap is shorter than in other regions. Therefore, the width of light leakage due to the lateral electric field can be minimized.

The other regions of the third interlayer insulating film 10 are
Since the surface of the second interlayer insulating film 8 that has been planarized by CMP is reflected, the surface is flat. Therefore, the defective alignment of the liquid crystal material due to the stepped shape of the pixel electrode 11 is suppressed, and the light leakage of the liquid crystal display device is suppressed.

Also in the active matrix substrate shown in the present embodiment, as in the first embodiment, the minimum area of the non-opening region (light-shielding region) is not increased by forming the wiring and the light-shielding film, in other words, the non-opening region (light-shielding region) is not increased. The convex light-shielding layer 24 can be formed within the opening region (light-shielding region). Therefore, the reduction of the opening area does not occur, so that the liquid crystal display device having a bright and high contrast can be provided by making the most of each pixel area.

[0059]

According to the present invention, an active matrix type liquid crystal display device having a bright and high contrast can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view schematically showing an active matrix substrate according to a first embodiment.

FIG. 2 is a cross-sectional view showing a manufacturing process of the liquid crystal display device of the first embodiment.

FIG. 3 is a cross-sectional view showing a manufacturing process performed subsequent to the process shown in FIG.

FIG. 4 is a cross-sectional view showing a manufacturing process of the liquid crystal display device of the second embodiment.

FIG. 5 is a graph showing a relationship between a cell gap and a light leakage width due to an influence of a lateral electric field.

FIG. 6 is a diagram showing a problem of a conventional liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Lower light-shielding film 3 Active layer 4 Gate insulating film 5a Scanning wiring 5b Capacitance line 6 First interlayer insulating film 7 Signal wiring 8 Second interlayer insulating film 9 Light-shielding film 10 Third interlayer insulating film 11 Pixel electrode 12 Facing Electrode 13 Chemically mechanically polished surface 14 Convex portion 15 Region where alignment failure occurs due to influence of lateral electric field (break region) 16 Region where light leakage occurs due to step shape (step region) 20 Insulating film 40 Liquid crystal layer 50 Counter substrate

Claims (6)

[Claims] 1. A plurality of scanning wirings extending in parallel with each other, a plurality of signal wirings intersecting with the plurality of scanning wirings and extending in parallel with each other, and connected to the scanning wirings and the signal wirings, and a matrix. An active matrix substrate having a plurality of switching elements arranged in a matrix and a plurality of pixel electrodes connected to each of the plurality of switching elements and arranged in a matrix, and a counter electrode facing the pixel electrodes. A liquid crystal display device comprising a counter substrate and a liquid crystal layer interposed between the active matrix substrate and the counter substrate, wherein the plurality of pixel electrodes are driven by a potential of the same polarity. And a second pixel electrode group driven with a potential having a polarity different from that of the first pixel electrode group, the first pixel electrode group and the second pixel electrode group. The electrode group, respectively 1
The active matrix substrate is driven by inverting the polarity every frame or one field period, and the active matrix substrate has a flat surface on the liquid crystal layer side between the pixel electrode and the scanning wiring, the signal wiring, and the switching element. A second pixel electrode that belongs to the first pixel electrode group and the second pixel electrode group that is adjacent to the first pixel electrode. A liquid crystal display device having a convex portion protruding toward the liquid crystal layer side in a region including at least a gap region between the pixel electrode and the pixel electrode. 2. A plurality of scanning wirings extending in parallel with each other, a plurality of signal wirings intersecting with the plurality of scanning wirings and extending in parallel with each other, and connected to the scanning wirings and the signal wirings, and a matrix. An active matrix substrate having a plurality of switching elements arranged in a matrix and a plurality of pixel electrodes connected to each of the plurality of switching elements and arranged in a matrix, and a counter electrode facing the pixel electrodes. A liquid crystal display device comprising a counter substrate and a liquid crystal layer interposed between the active matrix substrate and the counter substrate, wherein the plurality of pixel electrodes are driven by a potential of the same polarity. And a second pixel electrode group driven with a potential having a polarity different from that of the first pixel electrode group, the first pixel electrode group and the second pixel electrode group. The electrode group, respectively 1
The active matrix substrate is driven by inverting the polarity every frame or one field period, and the active matrix substrate has a flat surface on the liquid crystal layer side between the pixel electrode and the scanning wiring, the signal wiring, and the switching element. A first pixel electrode belonging to the first pixel electrode group, and a second pixel electrode group belonging to the first pixel electrode group, and adjacent to the first pixel electrode on the interlayer insulating film. A liquid crystal display device, wherein an insulating convex layer projecting to the liquid crystal layer side is formed in a region including at least a gap region of a gap with the second pixel electrode. 3. The liquid crystal display device according to claim 2, wherein the convex layer is a light shielding layer having a light shielding property. 4. The convex portion or the convex layer is formed in an area further including an overlapping area overlapping with any one or more of the scanning wiring, the signal wiring, and the switching element. Item 3. The liquid crystal display device according to item 1 or 2. 5. The method for manufacturing the liquid crystal display device according to claim 1, wherein the step of planarizing the surface of the interlayer insulating film formed on the active matrix substrate by chemical mechanical polishing, A step of forming a resist film on the planarized interlayer insulating film; a step of patterning the resist film to form a resist layer covering a region including at least the cut region; and the patterned resist layer By using the as a mask to etch the interlayer insulating film to thin the interlayer insulating film in a region other than the region including at least the cut region, and to form a protrusion on the interlayer insulating film in the region including at least the cut region. And a step of forming a liquid crystal display device. 6. The method for manufacturing a liquid crystal display device according to claim 2, wherein the surface of the interlayer insulating film formed on the active matrix substrate is planarized by chemical mechanical polishing, A step of sequentially forming an insulating film and a resist film on the planarized interlayer insulating film; a step of patterning the resist film to form a resist layer covering a region including at least the cut region; By using the resist layer as a mask and etching the insulating film, the insulating film in the region other than the region including at least the cut region is removed, and the insulating film in the region including at least the cut region is convex. A method of manufacturing a liquid crystal display device, the method including: