JP2000310793A - Liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the short circuit between upper and lower substrates, to obtain high reliability and to improve shock resistance by forming an auxiliary capacitance electrode which has an almost the same area as that of a pixel electrode and which overlaps on the pixel electrode on the substrate side of the pixel electrode through an insulating layer or each pixel so as to form an auxiliary capacitance under the pixel electrode. SOLUTION: An auxiliary capacitance electrode 2 having an almost same area as a pixel electrode 3 and overlapped with the pixel electrode 3 is formed in the substrate side of the pixel electrode 3 through an insulating layer for each pixel to form an auxiliary capacitance under the pixel electrode 3. By forming the auxiliary capacitance electrode 2 having the almost same area as the pixel electrode 3, no difference in the surface level is formed in the pixel electrode 3 and the aligning property can be improved. By forming a partition wall 18 between adjacent pixel electrodes without using a spacer, damages of the pixel electrode 3 by a spacer, the short circuit with the auxiliary capacitance electrode 2, or the short circuit between upper and lower electrodes can be prevented. Moreover, the partition wall 18 itself does not collapse by the pressure of the upper and lower substrates so that the shock resistance of the device can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device used for a display of a personal computer and the like.
In particular, the present invention relates to an active matrix type liquid crystal element using a switching element.

[0002]

2. Description of the Related Art Various liquid crystal materials such as a nematic liquid crystal, a smectic liquid crystal, and a polymer-dispersed liquid crystal are used as a liquid crystal for a liquid crystal display device. Most of them use a TN (twisted nematic) mode using a nematic liquid crystal.

FIG. 8 is a sectional view schematically showing a configuration of one pixel of a conventional active matrix type TN type liquid crystal element. In the figure, 1a and 1b are substrates, 2 is an auxiliary capacitance electrode,
3 is a pixel electrode, 4 is a passivation film, 5a and 5b
Is an alignment film, 6 is a counter electrode, and 10 is a thin film transistor (T
FT), 101 is a TN liquid crystal, and 102 is a spacer.
The TFT 10 includes a gate electrode 11 and a gate insulating film 12.
, I-type semiconductor layer 13, blocking layer 14, ohmic contact layer 15, source electrode 16, and drain electrode 17.

The substrate 1a is an active matrix substrate in which a pixel electrode 3 and a TFT 10 are formed for each pixel arranged in a two-dimensional matrix. In addition, the storage capacitor electrode 2 partially opposes the pixel electrode 3 to form the gate insulating layer 1.
2 and an auxiliary capacitor is connected in parallel with the TN liquid crystal 101.

On the substrate 1b side is a counter substrate, on which a counter electrode 6 common to all pixels or common to each scanning line is formed.

[0006] The active matrix substrate and the opposing substrate are each provided with alignment films 5a and 5b on the opposing surfaces thereof, which are subjected to an alignment treatment such as rubbing. Is sealed with a sealing material (not shown). Further, a polarizing plate is arranged and used outside the liquid crystal element.

[0007] The TN mode has a problem in image quality due to its low response speed and narrow viewing angle characteristics. Therefore, a liquid crystal element driven by an active matrix has been studied by utilizing the high-speed and wide viewing angle characteristics of a smectic liquid crystal such as a ferroelectric or antiferroelectric liquid crystal.

[0008]

In the conventional active matrix type TN type liquid crystal element shown in FIG.
The auxiliary capacitance electrode 2 forming the auxiliary capacitance suppresses the level fluctuation caused by capacitive coupling when the gate electrode 11 of the TFT 10 is turned on / off to a range that does not affect the image, and reduces the charge due to the liquid crystal resistance to a level that does not actually cause a problem. Formed to reduce. Therefore, usually, the auxiliary capacitance is 4 times the liquid crystal capacitance.
Since it can be formed with an auxiliary capacitance electrode having an area of about 1/20 of the pixel area S, it is formed in a part of the pixel electrode 3 or a region which does not overlap with the electrode.

However, in the case of a ferroelectric liquid crystal or an antiferroelectric liquid crystal having a spontaneous polarization, an auxiliary capacitance corresponding to the spontaneous polarization value is required. In the case of a liquid crystal having spontaneous polarization,
The switching of the liquid crystal generates a reversal current due to the reversal of the spontaneous polarization, and the current consumes the charge supplied to the liquid crystal capacitance.

For example, assuming that the amount of charge Q required for switching the ferroelectric liquid crystal is V, the voltage applied to the liquid crystal is V, the pixel electrode area is S, and the spontaneous polarization of the liquid crystal is Ps, Q = V · C _lc + 2Ps · S. On the other hand, in the case of the TN liquid crystal, Q = V · C _lc , and therefore, in the case of the ferroelectric liquid crystal, an extra charge corresponding to the spontaneous polarization is required. In the case of driving by the active matrix method, a desired display cannot be performed if a necessary amount of charge is not supplied during the ON period of the TFT. Therefore, when the ferroelectric liquid crystal is driven by the active matrix method, a TFT having a large charging capability is required to store a large amount of electric charges in a short time.

Table 1 shows the area of the auxiliary capacitance electrode required for the TN liquid crystal and the ferroelectric liquid crystal. In Table 1, the TN liquid crystal and the ferroelectric liquid crystals 1 to 4 each have a relative dielectric constant ５ of 5, a maximum drive voltage applied to the liquid crystal of 5 V, and a pixel electrode area S = 100 μm ×
It is set to 300 μm, and shows how many times the auxiliary capacitance electrode is required for the pixel electrode area for auxiliary capacitances having different capacitances. .

[0012]

[Table 1]

In a ferroelectric liquid crystal, electric charge consumed by a reversal current generated by reversal of spontaneous polarization = 2Ps ·
S is stored in the storage capacitor together with S. Therefore,
When a liquid crystal having a large spontaneous polarization and an insulating film having ε of about 5 to 20 are used, as shown in Table 1, an auxiliary capacitance electrode having an area close to the pixel electrode area is formed, and an auxiliary capacitance is formed in the pixel electrode. Need to be formed. However, when a large auxiliary capacitance is formed in the pixel electrode, there are the following problems.

(1) Since the auxiliary capacitance electrode is formed below the pixel electrode, the planarity of the pixel electrode formed thereon is reduced, and the liquid crystal alignment is deteriorated. Specifically, when a step due to the auxiliary capacitance occurs in a part of the pixel electrode, depending on the method of forming the capacitance, a single ITO layer may have a thickness of 1,000 to 2,000.
{Circle around (2)} In the case of two layers, a step close to 4000 ° is generated, and alignment disorder is generated.

(2) Since a thin insulating film is used over a large area in order to produce a large capacitance, short-circuiting is likely to occur in the upper and lower parts.

(3) Since the optimum gap of the smectic liquid crystal is narrower than 1 μm to about 2 μm compared to about 6 μm of the TN liquid crystal, it is difficult to form a gap. In some cases, a short circuit or a leak may occur in the auxiliary capacitance.

(4) The TN liquid crystal 1 of the liquid crystal element having the structure shown in FIG.
When a smectic liquid crystal is used in place of 01, an attempt is made to form an optimum gap, which has no problem with the TN liquid crystal, since the TFT 10 is thickest and the height is higher than the pixel electrode 3, so that the TFT 10 has a gap. It becomes a deciding factor. To get the gap of the liquid crystal cell,
A spacer 102 is disposed in the cell. If too much force is applied to the substrates 1a and 1b to make a gap, the spacer 102 damages the TFT 10 and the IT of the pixel electrode 3
Problems such as damage to the O film and short-circuiting between upper and lower sides, occurrence of short-circuiting between upper and lower sides of the auxiliary capacitor, and occurrence of defective orientation due to cracking of the spacer 102 itself are caused. As a result, display unevenness and contrast reduction have been caused.

In order to solve the problem caused by such a narrow gap, a flattening film is formed on a TFT or a pixel electrode. Since the distance between the liquid crystal and the liquid crystal increases, and the voltage applied to the liquid crystal relatively decreases due to the voltage drop due to the flattening film, the driving voltage must be increased. It has also been reported that such a configuration causes a burn-in phenomenon.

An object of the present invention is to provide a liquid crystal device having a spontaneous polarization and driving a liquid crystal requiring a large auxiliary capacitance by an active matrix method, which has a good alignment property.
An object of the present invention is to provide a highly reliable element which prevents vertical shorts.

[0020]

According to the present invention, a liquid crystal having spontaneous polarization is sandwiched between a pair of substrates, and a switching element and a pixel electrode are arranged for each pixel arranged two-dimensionally. An active matrix type liquid crystal element that controls signal application to each pixel electrode by using an auxiliary capacitance electrode having an area substantially equal to the pixel electrode and overlapping the pixel electrode for each of the pixels via an insulating layer. A liquid crystal element which is formed on a substrate side of an electrode and an auxiliary capacitor is formed below the pixel electrode.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, by making a storage capacitor electrode substantially the same as a pixel electrode, a step in the pixel electrode is eliminated, and a large storage capacitor is formed without lowering the orientation. Can be. Further, in the present invention, by forming a flattening film under the pixel electrode,
Since the large-capacity auxiliary capacitance can be used as a barrier against external force, vertical short-circuit can be reduced. At the same time, the orientation can be improved by forming a pixel electrode after being smoothed by the flattening film.

Further, in the present invention, by forming a cell gap by the partition walls, it is possible to prevent vertical short-circuit and damage to the pixel electrodes due to the formation of a large auxiliary capacitance, and to firmly fix the upper and lower substrates. The impact resistance can be improved even for smectic liquid crystals having poor impact resistance.

Hereinafter, the present invention will be described in detail with reference to specific embodiments.

[Embodiment 1] FIG. 1 is a cross-sectional view schematically showing the structure of an embodiment of the liquid crystal element of the present invention. FIG. 1A is a cross-sectional view of one pixel, and FIG. 1B is a cross-sectional view in a direction perpendicular to the paper surface at the point indicated by an arrow A in FIG. In FIG. 1, the same members as those in FIG. 8 described above are denoted by the same reference numerals. In FIG. 1, 7 is a liquid crystal having spontaneous polarization, and 18 is a partition.

FIG. 2 is a diagram showing an electrical equivalent circuit of this embodiment, and illustrates 4 × 4 pixels for convenience. In FIG. 2, 21 is an auxiliary capacitance, 22 is a liquid crystal capacitance,
Reference numeral 23 denotes a scanning signal line, reference numeral 24 denotes an information signal line, and reference numeral 25 denotes a lead line for grounding an auxiliary capacitance electrode forming an auxiliary capacitance.

The liquid crystal device of the present invention is driven by an active matrix system. As shown in FIG. 1, a liquid crystal 7 is sandwiched between a pair of substrates 1a and 1b arranged in parallel. , A polarizing plate (not shown) is attached to each substrate 1a,
1b.

The substrates 1a and 1b are insulative substrates, and usually glass plates are used, but plastic substrates can be used as long as necessary transparency and strength can be obtained. Substrate 1a
On the (active matrix substrate), a plurality of pixels are arranged in a two-dimensional matrix, and a pixel electrode 3 made of a transparent conductive film material such as ITO and a drain electrode 17 are connected to each pixel for each pixel. The TFTs 10 are arranged and formed. The gate electrode 11 of the TFT 10 of each pixel is connected to the scanning signal line 23, and the source electrode 16 is connected to the information signal line 24, and are controlled from the outside.

As shown in FIG. 1, a passivation film 4 is formed on the TFT 10 and the pixel electrode 3. This film functions as a protective film in the present embodiment. It is formed as a flattening film that also serves as a layer.

In the present invention, an auxiliary capacitance electrode 2 having an area substantially equal to that of the pixel electrode 3 is formed for each pixel, thereby forming the auxiliary capacitance 2. The auxiliary capacitance 2 is connected in parallel with the liquid crystal capacitance 3. A layer made of SiN, SiO ₂ or the like is formed on the entire surface as a passivation film 17 thereon, and an alignment film 5 made of polyimide or the like and having its surface subjected to an alignment treatment such as a rubbing treatment is further formed thereon.
a is formed.

On the other hand, a transparent counter electrode 6 to which a fixed reference voltage is applied to the pixel electrode 3 is formed on the substrate 1b (opposite substrate), and an alignment whose surface is subjected to an alignment treatment is formed thereon. The film 5b is formed.

The active matrix substrate and the opposing substrate are bonded to each other via a frame-shaped sealing material (not shown) at the outer peripheral portion, and a liquid crystal 7 is sealed in a region surrounded by both substrates and the sealing material. As the liquid crystal 7, a liquid crystal having spontaneous polarization, such as a smectic liquid crystal exhibiting ferroelectricity or antiferroelectricity, is used. By encapsulating these liquid crystals with a cell gap smaller than the helical pitch,
Mono-stable, bistable, tri-stable, or so-called thresholdless electro-optical characteristics without hysteresis characteristics can be provided. The cell gap is kept constant by the partition 18. The partition wall 18 is formed in a stripe shape between the pixel electrodes along the scanning signal line, for example, as shown in FIG.

As shown in FIG. 1, in this embodiment, the auxiliary capacitance electrode 2 is formed in the same area as the pixel electrode 3, so that
There is no step in the pixel electrode 3 and the orientation is good. In addition, since the partition 18 is formed between the adjacent pixel electrodes without using the spacer, damage to the pixel electrode 3 due to the spacer, short circuit with the auxiliary capacitance electrode, and short circuit between the upper and lower electrodes are prevented. Further, the partition walls 18 themselves are not crushed by the pressure of the upper and lower substrates, and the impact resistance of the element is improved.

In this embodiment, since the auxiliary capacitance electrode 2 is formed on the entire surface below the pixel electrode 3, the passivation film 4 is not made thicker as a planarization film, but is formed in a thickness of 2000-4.
It is possible to reduce the difference in height between the TFT 10 and the pixel electrode 3 which is about 000 °, and as a result, it is possible to increase the stability of the cell gap.

Next, an example of a method for manufacturing the liquid crystal element of the present embodiment will be described.

First, Cr and A are entirely formed on the glass substrate 1a.
metal film such as 1 to 500 to 2000 mm by sputtering.
The gate electrode 11 and the scanning signal line 23 are formed by patterning this metal film by photolithography.

Next, ITO is deposited on the entire surface of the substrate at 1500 ° C.
The auxiliary capacitance electrode 2 is formed by forming a film by a sputtering method and patterning the film.

Further, a thickness of 2000 to 4
A gate insulating film 12 made of a silicon nitride film (SiN) of 000 ° is formed by CVD or the like. This gate insulating film 12 is formed in common for all TFTs. An i-type (intrinsic) semiconductor layer (for example, an i-type amorphous silicon layer or an i-type polysilicon layer) 13 is deposited on the gate insulating film 12 in a thickness of 300 to 700 ° and a thickness of 1
A silicon nitride film layer of 2,000 to 2,000 degrees is formed, and is patterned to form a blocking layer 14 for protecting the channel region of the i-type semiconductor layer 13 from etching. Next, an n-type high-concentration silicon layer having a thickness of 300 to 1000 ° is formed, and is patterned to form an ohmic contact layer 15.

Subsequently, an ITO film serving as the pixel electrode 3 is formed on the entire surface to a thickness of 700 ° by a sputtering method, and is patterned to form the pixel electrode 3. 300 thickness on the whole surface of the substrate
A Cr layer of about 700 ° and an Al layer of about 1500 to 2500 ° are sequentially deposited and patterned to form a source electrode 16, a drain electrode 17, and an information signal line 24 to which the source electrode 16 is connected.

Next, after forming the passivation film 4 by 5000 mm by CVD, polyimide or the like is applied to a thickness of about 400 mm by printing, baked at a temperature of 200 to 250 ° C., and subjected to an orientation treatment by rubbing or the like. An alignment film 5a is formed.

The height difference between the respective regions of the TFT 10 and the pixel electrode 3 is conventionally 500 to 2000 ° (gate electrode 11) +300 to 700 ° (i-type semiconductor layer) +
1000-2000 (blocking layer 14) +300
~ 1000Å (ohmic contact layer) + 1800 ~
3200 ° (source electrode 16, drain electrode 17) -7
Where 00 ° (pixel electrode 3) = 3200 to 8200 °, the finished dimensions can be reduced to about 800 to 1300 °.

After an organic material such as an acrylic photopolymer is applied on the entire surface of the substrate by spin coating, mask exposure and development are performed to form partitions 18 between pixels. still,
The partition wall 18 can be formed before forming the alignment film 5a. In addition, the inorganic or organic gap material is 1 to
The other glass substrate 1b, which is preferably mixed and used at about 10% by weight, also has a transparent conductive film such as ITO of 500 to 500%.
The counter electrode 6 is formed by patterning by depositing at a thickness of 1000 °, an alignment film 5b is formed thereon in the same manner as the alignment film 5a, and an alignment process such as rubbing is performed.

The two substrates are adhered and fixed via a partition 18 with a sealing material drawn on the outer periphery, and the liquid crystal 7 is formed by a vacuum injection method.
Inject.

In the present invention, the material and thickness of each member,
The shape and manufacturing method are not particularly limited to those described above, and the conventional liquid crystal element technology can be applied as it is within a range in which the effects of the present invention can be obtained. Further, in this embodiment and the embodiments described later, a configuration using a TFT as a switching element is shown; however, a device such as a channel-etch type TFT or an MIM can be used in addition to this configuration.

[Embodiment 2] FIG. 3 shows the configuration of another embodiment of the present invention. Since the counter substrate is the same as that of FIG. 1, only the active matrix substrate is shown.

[0045] In this embodiment, as the insulating film forming the storage capacitance is obtained by a composite film structure plus passivation film 4 formed of the high dielectric constant inorganic films such as TaO _x in the gate insulating film 12. This passivation film 4
After the source electrode 16 and the gate electrode 17 are formed, they are formed by sputtering or the like, and have a thickness of about 3000 °. T
Since the aO _x film has a relative dielectric constant ε of about 20, even if the film thickness becomes large, the decrease in the capacitance value is small. After the passivation film 4 is formed, a contact hole is formed by etching, ITO is formed to a thickness of 1500 ° by sputtering, and is patterned to form the pixel electrode 3. Subsequent formation of the alignment film 5a is the same as that of the first embodiment.

[Embodiment 3] FIG. 4 shows the structure of an active matrix substrate according to a third embodiment of the present invention. In the present embodiment, after forming the source electrode 16 and the drain electrode 17, the storage capacitor electrode 2 is
A passivation film 4 of TaO _x is deposited to a thickness of 3000 °, a contact hole is formed by dry etching using a photoresist, and the photoresist is removed to remove the ITO to a thickness of 1000 °.
The pixel electrode 3 is formed by depositing and patterning. After the formation of the alignment film 5a, it is the same as the first embodiment.

Fourth Embodiment FIG. 5 shows the structure of an active matrix substrate according to a fourth embodiment of the present invention. In the present embodiment, the ohmic contact layer 15
Is formed, an ITO film having a thickness of 700 ° is formed on the entire surface of the substrate, and then patterned to form a second auxiliary capacitance electrode 2b. Thereafter, a source electrode 16 and a drain electrode 17 of the TFT 10 are formed by sputtering and etching. Then, the drain electrode 17 is connected to the second auxiliary capacitance electrode 2b.
Subsequently, a Si (OH) ₄ solution is spin-coated, a passivation film 4 also serving as a flattening film is formed on the auxiliary capacitance electrode 2b to a thickness of 0.7 to 1 μm, and a contact hole is formed. The pixel electrode 3 made of ITO is formed. After the formation of the alignment film 5a, it is the same as the first embodiment.
Reference numeral 2a denotes a first auxiliary capacitance electrode, which is formed in the same manner as the auxiliary capacitance electrode 2 of the first embodiment.

[Fifth Embodiment] FIG. 6 shows the structure of an active matrix substrate according to a fifth embodiment of the present invention. In this embodiment, the first auxiliary capacitance electrode 2 a is formed on the gate insulating layer 12.
The after forming a thickness of 1000Å in ITO, a TaO _x as the insulating film of the storage capacitor forming the first passivation film 4a and 3000Å is deposited by sputtering, followed by I
A storage capacitor electrode 2b is formed by depositing and patterning TO at a thickness of 1000 °, a second passivation film 4a is formed by spin-coating a Si (OH) ₄ solution, a contact hole is formed, and a thickness of 1000 ° made of ITO is formed. Is formed. After the formation of the alignment film 5a, it is the same as the first embodiment.

[0049]

[Example 1] As a first example of the present invention, the liquid crystal element of the first embodiment was manufactured. The steps will be described below.

On the entire surface of a glass substrate 1a having a thickness of 1.1 mm,
Molybdenum was deposited to a thickness of 2000 ° by sputtering and patterned by photolithography to form a gate electrode 11 and a scanning signal line.

Next, an auxiliary capacitor electrode 2 was formed by depositing ITO on the entire surface of the substrate to a thickness of 1500 ° by sputtering and patterning.

A gate insulating film 12 made of SiN is deposited on the entire surface of the substrate by CVD so as to have a thickness of Å, and amorphous silicon is deposited to a thickness of 3000 を to form an i-type semiconductor layer 13. The film was deposited to a thickness of 3000 ° and patterned to form a blocking layer 14. Further, n-type high-concentration silicon was deposited at a thickness of 1000 ° and patterned to form an ohmic contact layer 15.

Next, ITO serving as the pixel electrode 3 was deposited on the entire surface of the substrate to a thickness of 700 ° by sputtering and patterned. Then, Cr was sequentially deposited at 1000 ° and Al was deposited at 3000 °, and patterning was performed to form a source electrode 16, a drain electrode 17, and an information signal line.

Subsequently, 3000 SiN was deposited by CVD.
{Passing was performed to form a passivation film 4, and polyimide was applied thereon by an offset printing machine so as to have a thickness of 400 °, baked at 200 ° C, and rubbed on the surface to form an alignment film 5a.

A partition 18 was formed in the gap between the pixel electrodes on the substrate by using an acrylic photopolymer. The partition walls are 1.2 μm in height, 12 μm in width, and 280 μm in pitch,
It was formed parallel to the scanning signal line.

On the other glass substrate 1b, ITO is deposited to a thickness of 1000.degree. And patterned to form a counter electrode 6, and then the alignment film 5b is formed in the same manner as the alignment film 5a.
Was formed.

After a sealing material was drawn on the outer periphery of the two substrates, they were bonded to each other so that the rubbing directions were substantially parallel, and a liquid crystal composition having the following composition was injected by vacuum injection.

[0058]

Embedded image

The cell gap deviation of the obtained liquid crystal element is
1.2 ± 0.02 μm on the entire surface of the substrate
There were no cracks due to the pressing of the electrode surface, and no short circuit or leak due to the auxiliary capacitance. In addition, a short circuit between the upper and lower substrates and an alignment defect were prevented, and the liquid crystal element was excellent in image quality with less threshold unevenness. The liquid crystal element of this embodiment is
By providing an auxiliary capacitor on the entire surface under the pixel electrode, the flatness of the substrate surface is high, and the alignment itself of the liquid crystal is improved.
Rubbing of a flat part prevents uneven rubbing.In addition, the cell gap is maintained by partition walls, and no spacers are used.Therefore, there is no damage to pixel electrodes and uniformity of liquid crystal injection is high. As a result, a good image having no vertical short-circuit was obtained. As a result, the contrast was about 60 in the conventional configuration, but was improved to 120 or more.

Since the insulating film forming the auxiliary capacitance of the liquid crystal element of this embodiment is an SiN film having a thickness of 3000 °, the capacitance value of the auxiliary capacitance is about 6.2 pF (relative permittivity ε = 7, S = 10
0 μm × 300 μm), driving at 5 V can accumulate about 30 pC of electric charge, and can drive well to a liquid crystal of Ps = 50 (corresponding to 100 μm × 280 μm in pixel size).

[Embodiment 2] As a second embodiment of the present invention,
A liquid crystal element of Embodiment 2 was manufactured.

In the same manner as in Example 1, up to the ohmic contact layer 15 is formed,
The source electrode 16, the drain electrode 17 and the information signal line were formed by depositing and etching at 00 °. Subsequently, a passivation film 4 is formed by depositing TaO _x at 3000 ° using a sputtering apparatus, and a contact hole is formed by dry etching.
Then, the pixel electrode 3 was formed by depositing and etching.
The subsequent steps are the same as in the first embodiment.

In the liquid crystal element of this embodiment, the passivation film 4 has TaO _x (ε = 20, S = 100 μm × 300 μm).
m), the capacitance value of the auxiliary capacitor is not reduced as compared with the first embodiment even if the thickness of the insulating film of the auxiliary capacitor is increased.

The contrast of the liquid crystal device of this example was 150. In the liquid crystal element of the present embodiment, the short-circuit occurrence rate is further reduced as compared with the first embodiment, and the leak that does not lead to a short-circuit is also reduced.
0) Even in a test longer than 100 sec,
The level fluctuation of white and black was small, and the unevenness due to pixels was small.

Example 3 As a third example of the present invention, a liquid crystal element of Example 3 was manufactured.

An ohmic contact layer 15 was formed in the same manner as in Example 1 except that the auxiliary capacitance electrode 2 was not formed. Cr was deposited at 1000 ° and Al was deposited at 3000 °, and etching was performed to form a source electrode 16, a drain electrode 17, and an information signal. After forming the lines, ITO was deposited at 1000 Å and patterned to form the auxiliary capacitance electrode 2 on the gate insulating film 12. Thereafter, TaO _x was deposited at 3000 ° by sputtering to form a passivation film 4, and a contact hole was formed by dry etching using a photoresist. On top of this, ITO was deposited at a thickness of 1000 ° and patterned by photolithography using a pixel pattern mask to form a pixel electrode 3. After forming an alignment film 5a in the same manner as in Example 1, spin coating, exposure, and development were performed using an acrylic polymer to which 1.5% by weight of silica beads having a diameter of 1.3 μm was added to form partition walls. The substrate was bonded to the counter substrate formed in the same manner as in Example 1, and liquid crystal was injected.

The height of the partition after spin coating is 1.45 μm.
However, it was 1.2 ± 0.02 μm after the cell assembly, and was an element having high gap uniformity. The contrast after liquid crystal injection was 150, and an extremely high contrast was obtained.

The auxiliary capacitance of the liquid crystal element of this embodiment is 18 pF
The charge amount at the time of charging at 5 V is 90 pC, and Ps =
It can drive up to 100 liquid crystals (corresponding to a pixel size of 100 μm × 280 μm).

Example 4 As a fourth example of the present invention, a liquid crystal element of the fourth example was manufactured.

After forming up to the ohmic contact layer 15 in the same manner as in the first embodiment, the surface of the substrate is
The second auxiliary capacitance electrode 2b was formed by depositing to a thickness of Å and patterning. Thereafter, the source electrode 16, the drain electrode 17, and the information signal line are formed by sputtering and etching in the same manner as in the first embodiment, and a Si (OH) ₄ solution is spin-coated to have a thickness of about The passivation film 4 was formed to have a thickness of 1 μm. Thereafter, a contact hole was formed by dry etching using a photoresist. The subsequent steps were performed in the same manner as in Example 1 to obtain a liquid crystal element.

The obtained liquid crystal element had almost no short circuit and excellent insulating properties. Also, the contrast was as high as 180. This is because the passivation film formed with the Si (OH) ₄ solution has a high flattening ability.
By filling the convex portion of the TFT and raising the lower portion of the pixel electrode to make it overall flat, the pixel electrode is not affected by the unevenness of the film surface of the auxiliary capacitance portion, so that an extremely flat surface shape is achieved. This is because Further, in addition to the presence of the partition walls, the external force is absorbed by the thick flattening film by the flattening film, so that mechanical stress can be prevented, and as a result, short-circuit is prevented. Conceivable.

The auxiliary capacitance of the liquid crystal element of this embodiment was about 6.2 pF (assuming that ε = 7 and S = 100 μm × 300 μm) because the insulating film was a 3000-nm-thick SiN film. This is because it is possible to accumulate about 30 pC of electric charge by 5V driving, and it is possible to drive liquid crystal of Ps = 50 (100 μm × 2 in pixel size).
80 μm).

Example 5 Paste ink of a mixture of TiO _x + SiO _x particles (“RF4A1” manufactured by Catalysis Chemical Co., Ltd.)
6)) was printed to a thickness of 3000 mm using an offset printing machine, and calcined on a hot plate at 250 ° C. to form TiO _x +
A passivation film 4 made of a SiO _x particle film was formed, and a liquid crystal device of a fifth embodiment of the present invention was manufactured in the same manner as in the second embodiment except that the partition wall of the first embodiment was used.

In the liquid crystal device of this embodiment, TiO _x
+ SiO _x passivation film is composed of CV
Since the flatness is higher than that obtained by a vacuum deposition method such as D or sputtering, the resulting film has extremely high flatness.
Therefore, the short-circuit occurrence rate was lower than in Example 1. In addition, since the leak that does not result in a short circuit is also reduced, even in a test in which the holding time is longer than (1/60) × 100 sec, white and black level fluctuations are small, and unevenness due to pixels is small.

[0075] insulating film of the storage capacitor of the liquid crystal element of this embodiment, TiO _x in SiN film and 3000Å thick 3000Å
Since it is a composite film of + SiO _x particle film, its capacitance value is about 4.7 pF (ε = 8.5, S = 100 μm × 300 μm
As). This is because it is possible to accumulate about 23 pC of electric charge in the 5V drive, and it is possible to drive up to a liquid crystal of Ps = 10 (100 μm × 280 μ in pixel size).
m).

Example 6 A printing paste of MoTa fine particles (manufactured by Catalyst Chemicals Co., Ltd.) was formed by offset printing to a thickness of 30
A liquid crystal element was formed in the same manner as in Example 3 except that the passivation film was formed by firing at 250 ° C. on a hot plate at 250 ° C., and using the same partition wall as in Example 1.

The contrast of the obtained liquid crystal element was 150.
Thus, the liquid crystal element was a practical liquid crystal element with few vertical shorts. Further, a capacitance of about 17 pF was obtained as the auxiliary capacitance, but the leakage level was relatively large. However, when one frame was driven for 1/60 sec, characteristics without any problem were obtained.

Since about 85 pC of electric charge can be stored in the auxiliary capacitor of the liquid crystal element of the present invention by driving 5 V, Ps
= 100 (equivalent to a pixel size of 100 μm × 280 μm).

Example 7 As a seventh example of the present invention, a liquid crystal element according to the fifth example was manufactured.

After forming the ohmic contact layer 15 in the same manner as in the third embodiment, the source electrode 16, the drain electrode 17, and the information signal line are formed. A capacitor electrode 2a is formed, and TaO _x is deposited at a thickness of 3000 ° to form a first passivation film 4a.
Was deposited and patterned to form a second auxiliary capacitance electrode 2b. A Si (OH) ₄ solution is spin-coated thereon, and a contact hole is formed by dry etching using a resist.
, And patterned to form a pixel electrode 3. The subsequent steps were performed in the same manner as in Example 1 to obtain a liquid crystal element.

The storage capacity of the obtained liquid crystal element was about 18 た め because the insulating film was a TaO _x film having a thickness of 3000 °.
pF (assuming ε = 20, S = 100 μm × 300 μm)
In 5V drive, about 90pC charge can be stored.
It is possible to drive a liquid crystal of Ps = 100 (corresponding to a pixel size of 100 μm × 280 μm).

Also in this example, the obtained liquid crystal element exhibited excellent orientation and was free from vertical shorts and gap defects, and had a very high yield. The contrast was as good as 160.

The liquid crystal device of this example was subjected to a high-temperature, high-humidity continuous energization test. As a result, there was no image deterioration due to corrosion, threshold value shift, and the like, and a high-quality image could be maintained even after durability.

FIG. 7 shows the storage capacitance and contrast of each of the liquid crystal elements of Examples 1 to 7. In each example, six devices were manufactured. The value of the contrast in the description of each embodiment described above is an average value of the results. Note that the conventional example shown here is a liquid crystal element manufactured in the same manner as in Example 1 except that no auxiliary capacitance is formed.

[0085]

As described above, according to the present invention,
There is no step in the pixel electrode due to the auxiliary capacitance, the orientation is improved, and a display with high contrast is realized.

In the present invention, by controlling the cell gap by using the partition walls, damage to the pixel electrode by the spacer and short-circuiting of the upper and lower substrates due to the damage can be prevented, and the orientation can be further improved. Further, in the present invention, by flattening the unevenness under the pixel electrode using a flattening film, while further improving the orientation,
The flattening film can absorb external force and prevent short circuit between the upper and lower substrates. As a result, it is possible to provide a liquid crystal element having higher contrast, high reliability, and high impact durability with good yield.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a configuration of a liquid crystal element according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an electrical equivalent circuit of the liquid crystal element according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view schematically illustrating a configuration of a liquid crystal element according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically illustrating a configuration of a liquid crystal element according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view schematically illustrating a configuration of a liquid crystal element according to a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view schematically illustrating a configuration of a liquid crystal element according to a fifth embodiment of the present invention.

FIG. 7 is a diagram showing storage capacitance and contrast of a liquid crystal element according to an example of the present invention.

FIG. 8 is a cross-sectional view schematically illustrating a configuration of an example of a conventional liquid crystal element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1a, 1b Substrate 2, 2a, 2b Auxiliary capacitance electrode 3 Pixel electrode 4, 4a, 4b Passivation film 5a, 5b Alignment film 7 Liquid crystal 10 TFT 11 Gate electrode 12 Gate insulating film 13 i-type semiconductor layer 14 Blocking layer 15 Ohmic contact layer Reference Signs List 16 source electrode 17 drain electrode 18 partition 21 auxiliary capacitance 22 liquid crystal capacitance 23 scanning signal line 24 information signal line 101 TN liquid crystal 102 spacer

Continued on the front page F term (reference) 2H092 JA26 JA29 JA33 JA35 JA36 JA38 JA42 JA44 JA46 JB13 JB23 JB32 JB33 JB51 JB57 JB63 JB69 KA05 KA12 KA16 KA18 KB23 MA05 MA08 MA14 MA15 MA16 MA18 MA19 MA20 MA22 MA27 MA35 MA37 PA02 QA14

Claims (7)

[Claims] 1. A liquid crystal having spontaneous polarization is sandwiched between a pair of substrates, and a switching element and a pixel electrode are arranged for each two-dimensionally arranged pixel, and a signal is applied to each pixel electrode by the switching element. An active matrix type liquid crystal element that controls an auxiliary capacitance electrode having an area substantially equal to the pixel electrode and overlapping the pixel electrode for each pixel on the substrate side of the pixel electrode via an insulating layer, A liquid crystal element, wherein an auxiliary capacitor is formed below the pixel electrode. 2. The liquid crystal device according to claim 1, further comprising a flattening film under the pixel electrode covering the entire substrate including the switching device. 3. The liquid crystal device according to claim 2, wherein the flattening film has a laminated structure of an organic film and an inorganic film. 4. The liquid crystal device according to claim 1, wherein said switching device is a thin film transistor. 5. The storage capacitor is formed by a second storage capacitor electrode connected to the switching element, and a first storage capacitor electrode opposed to the second storage capacitor electrode via an insulating layer. The liquid crystal element according to claim 1, wherein 6. The liquid crystal device according to claim 1, wherein said pair of substrates maintain a predetermined distance by a partition structure bonded to both substrates. 7. The liquid crystal device according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal or an antiferroelectric liquid crystal.