JPH09185073A - Liquid crystal element and manufacturing method thereof - Google Patents

Abstract

(57) An object of the present invention is to suppress alignment disorder of liquid crystal which causes an inappropriate electric field strength which is generated in a taper region at an edge portion of a transparent electrode. SOLUTION: When the width of a taper region 7b at an edge portion 7a of a transparent electrode 7 is w and the film thickness thereof is d, 0 ≦ w / d
The transparent electrode 7 is made of amorphous I so that ≦ 2/3.
By forming the TO film by etching with a weak acid etching solution, a transparent electrode 7 having a steep taper region 7b satisfying 0 ≦ w / d ≦ 2/3 is formed, resulting in an inappropriate electric field strength. Distortion of the liquid crystal orientation that causes the occurrence of light is suppressed.

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 and a method for manufacturing the liquid crystal device, and more particularly, to a liquid crystal device and a liquid crystal device which are capable of improving the display quality by improving the shape of the edge portion of the transparent electrode. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal element of a system in which a transmitted light beam is controlled in combination with a deflection display device by utilizing a refractive index anisotropy of ferroelectric liquid crystal molecules has been known as Clarke (Clar
k), and Lagerwall et al. (for example, JP-A-56-107216 and US Pat. No. 4,367,924).

Ferroelectric liquid crystals generally have a chiral mectic C phase (SmC ^* ) or an H phase (SmH ^* ) in a specific temperature range, and in this state, they have a first phase in response to an applied electric field. Has an optical stable state and a second optical stable state, and has the property of maintaining that state when no electric field is applied, that is, bistability, and also responds to changes in the electric field. It is expected to be used quickly and widely as a high speed and memory type display element.

[0004]

By the way, the above-mentioned liquid crystal element using the ferroelectric liquid crystal has a structure very similar to that of the STN type liquid crystal element, but the major difference is that the transparent electrodes are opposed to each other. Gap between a pair of substrates (cell gap)
Is about 1 μm, which is extremely narrow.

Further, at present, the driving voltage between the transparent electrodes is about 20V, which is higher than the conventional driving voltage in the direction of increasing the response speed, and as a result, the electric field strength higher by one digit is applied to the liquid crystal molecules.

Therefore, the display quality is affected by the shape of the edge portion of the transparent electrode, which has not been a big problem in the past.

That is, as shown in FIG. 5, the ferroelectric liquid crystal 1
00 is injected between the pair of glass substrates 101, 1
02, the ITO film formed by the sputtering method is etched by the photolithography method to form the transparent electrodes 103, 104.
In the prior art, the width w of the tapered region 104b at the edge portion 104a of the transparent electrode 103 is generally the same as or larger than the film thickness d by using a strong acid etching solution. For example, the film thickness d is 100
When it is about 0 to 1500Å, the width w of the tapered region 104b is about 2000 to 3000Å. The transparent electrode 1
Although not shown on the 03 side, the transparent electrode 103 also has similar edge portions and tapered regions.

Therefore, when an electric field is applied between the transparent electrodes 103 and 104, there is a region where the electric field strength gradually decreases from the display region of the pixel formed by the transparent electrodes 103 and 104, and the electric field intensity is nonuniformly applied. . This area part is, when proper electric field strength is applied to the original display part,
The electric field strength is inappropriate.

For example, in FIG. 5, the transparent electrodes 103,
When the gap G between 104 is 1 μm and the film thickness d of the transparent electrode 104 is 0.1 μm, the electric field strength is 20 to 18 v / μm when the driving voltage is 20 V in the range of the taper region 104 b of the edge portion 104 a. Is about 10 with respect to the electric field strength required for driving the ferroelectric liquid crystal 100.
It is a portion to which only an electric field of not more than% is applied.

In this case, among the bistable directions of the alignment state of the liquid crystal molecules between the pixels of the transparent electrodes 103 and 104, there is a region in which each stable direction is held in an unspecified region,
In appearance, black and white regions are shown through a polarizing plate (not shown).

Then, when the driving voltage is increased in the two orientation states between the pixels, as shown in FIG. 6, the black regions 105 of the transparent electrodes 103 and 104 arranged in a matrix form the inside of the pixel 106. Then, the non-inversion region 107 synchronized with the scanning signal grows, effectively degrading the display quality. The drive margin is up to the limit voltage value at which the display quality is not lost, which is important as a large characteristic in actual use.

That is, the partially oriented regions between the pixels 106 are easily retracted into the pixels 106 during driving from the regions extended by the tapered regions of the transparent electrodes 103 and 104, and as a result, the above-mentioned driving margin is obtained. There was a problem of becoming narrow.

Therefore, it is an object of the present invention to provide a liquid crystal element and a method for manufacturing the liquid crystal element, which can improve a display quality by widening a driving margin.

[0014]

The present invention has been made in view of the above circumstances, and includes a pair of substrates arranged so as to face each other, a transparent electrode formed on each of the substrates, and the pair of substrates. In the liquid crystal element having a liquid crystal sandwiched between the substrates, 0 ≦ w / d, where w is the width of the tapered region at the edge of the transparent electrode and d is the film thickness.
It is characterized in that the tapered region of the transparent electrode is formed so that ≦ 2/3.

Further, the transparent electrode is formed by etching an amorphous ITO film formed on the substrate with a weak acid etching solution by a photolithography method.

Further, the ITO film is formed by a sputtering method.

The deposition temperature of the ITO film on the substrate by the sputtering method is 80 at the substrate temperature at the time of sputtering.
In order to obtain a uniform amorphous ITO film at a temperature of 0 ° C. or lower, it is preferable to set the substrate temperature to 0 ° C. or higher and 50 ° C. or lower.

Further, in a method of manufacturing a liquid crystal device having at least a step of forming transparent electrodes on a pair of substrates into which liquid crystal is injected, an ITO film made of an amorphous film is formed on the substrate, and the ITO film is formed on the ITO film. When the width of the tapered region at the edge of the transparent electrode is w and the film thickness is d, the transparent electrode is etched by a photolithography method with a weak acid etching solution, and 0 ≦ w / d ≦ 2 /
The feature is that the patterning is performed so as to be 3.

In the present invention, an insulating layer, an alignment film and the like are formed on the transparent electrode (ITO film) of the substrate obtained by the above-mentioned process, and the other electrode-bearing substrate formed in the same manner as this electrode-bearing substrate. A liquid crystal element is obtained by facing and bonding and injecting liquid crystal. Incidentally, the transparent electrode (ITO film) pattern described above may be subjected to an annealing treatment, if necessary, in the steps after the pattern formation so that the characteristics such as transparency can be optimized.

(Function) The inventors of the present application have studied the relationship between the width w of the tapered region at the edge portion of the transparent electrode and the film thickness d thereof. As a result, 0 ≦ w / d ≦ 2/3. By forming the tapered regions of the transparent electrodes so that the liquid crystal is driven by applying an electric field between the transparent electrodes, the inappropriate electric field strength generated in the tapered regions at the edges of the transparent electrodes is caused. We have experimentally found that the alignment disorder of the liquid crystal can be suppressed.

Therefore, according to the present invention, the relationship between the film thickness d of the transparent electrode, the width w of the tapered region formed at the edge of the transparent electrode, and the film thickness d is 0≤w / d≤2. By forming a steep taper region such as / 3, it is possible to improve the display quality by eliminating the liquid crystal alignment disorder.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing a liquid crystal element according to the first embodiment. The liquid crystal element 1 is composed of a pair of glass substrates 4 and 4 which are arranged to face each other between polarizing plates 2 and 3.
5, glass substrates 4 and 5 are provided with transparent electrodes 6 and 7, insulating films 8 and 9, and alignment films 10 and 11, respectively. Metal transparent electrodes 12 and 13 are formed on the transparent electrodes 6 and 7, respectively.

Spacers (not shown) having a uniform diameter are scattered between the alignment films 10 and 11, and the glass substrates 4 and 5 are attached to the alignment films 10 and 11, and a strong bistability against an electric field is provided therebetween. A chiral smectic liquid crystal (hereinafter, abbreviated as liquid crystal) 14 having a dielectric property is injected. As the liquid crystal, a nematic liquid crystal or other liquid crystal material according to another liquid crystal display mode can be used.

The transparent electrodes 6 and 7 are made of an amorphous ITO film so as to have low crystallinity and are arranged in a matrix. In the transparent electrodes 6 and 7, the relationship between the width w of the tapered region at the edge portion and the film thickness d is 0 ≦.
It is formed so that w / d ≦ 2/3 (details will be described later).

Next, the method of forming the transparent electrodes 6 and 7 in the method of manufacturing the liquid crystal element 1 described above will be described with reference to FIGS.
This will be described with reference to FIG. The transparent electrode 7 side is shown in the figure.

First, a glass substrate (thickness: 1.1 mm) 5
An amorphous ITO film 15 having a film thickness of about 1500 Å is formed thereon by a sputtering method (see FIG. 2A).

The film forming conditions of the ITO film 15 at this time are as follows: pressure: 0.23 Pa, O ₂ flow rate: 0.53 sccm, set film forming temperature: 20 ° C. (substrate temperature: 40 ° C.), power: 2 k
w, transport speed: 220 mm / min, and ILC3949 manufactured by Nichiden Anelva Co., Ltd. was used as the sputtering device. The film forming temperature (substrate temperature) at this time is 80 ° C. or lower, and more preferably 0 to 50 ° C.

Amorphous ITO film 15 formed
Is composed of particles showing an extremely fine particle size of 50 to 70Å,
X-ray diffraction showed an amorphous property in which no peaks were observed on the 222nd and 411st faces, which are characteristic of ITO crystals. The sheet resistance value was 50Ω / □.

Then, a photoresist 16 having a film thickness of about 2 μm is formed on the ITO film 15 by a spin coating method, and 110 mmJ / cm ² is used by using a pattern mask 17.
Exposure (see FIG. 2 (b)), and tetramethylammonium hydride (2.38 ± 0.01 wt)
%) To develop the photoresist 16 to form a photoresist pattern 18 (see FIG. 2C). The post bake temperature at this time was 120 ° C.

Then, the ITO film 15 having the photoresist pattern 18 formed thereon is subjected to an etching treatment with a weak acid etching solution to pattern the transparent electrode 7 (FIG. 2 (d)).
Then, the photoresist pattern 18 is peeled off (see FIG. 2E).

At this time, the etching solution used for the etching treatment of the ITO film 15 is a dilute hydroiodic acid solution which is a weak acid (mixing volume ratio is 57 wt% HI: H ₂ O = 1: 7).
With a liquid temperature of 35 ° C. and an etching time of 300 sec.
And

This transparent electrode 7 is made of amorphous ITO.
By using the film and a weak acid etching solution, side etching was performed to the inside covered with the photoresist pattern 18, and a tapered region 7b was formed at the edge portion 7a as shown in FIG. The transparent electrode 7 formed under the above conditions has a film thickness d of about 1500 Å,
The width w of the tapered region 7b was controlled to about 900 to 1000Å, and the above-described relationship of 0 ≦ w / d ≦ 2/3 was satisfied. The transparent electrode 6 is also manufactured in the same manner.

Then, as shown in FIG. 1, metal routing electrodes 12 and 13 made of MoTa.AlSiCu are formed on the transparent electrodes 6 and 7 by a photolithography method at 1600Å.
Film with a thickness of about 3
= 1: 1 mixed insulating films 8 and 9 and polyimide-based alignment films 10 and 11 (for example, L manufactured by Toray Industries, Inc.)
P-64) each with a film thickness of about 50 Å. Then, the liquid crystal 14 is injected between the alignment films 10 and 11 of the glass substrates 4 and 5 held in the gap of about 1 μm.

As described above, in the present embodiment, the relationship between the width w of the tapered region at each edge of the transparent electrodes 6 and 7 and the film thickness d thereof is 0 ≦ w / d ≦ 2/3. By forming such a steep taper region, when a drive voltage is applied between the transparent electrodes 6 and 7 to drive the liquid crystal 14, it occurs in the taper region at the edges of the transparent electrodes 6 and 7. The disordered alignment of the liquid crystal 14 which causes an unsuitable electric field strength is eliminated,
We were able to improve the display quality.

Then, in order to compare with the transparent electrodes 6 and 7 of the liquid crystal element 1 manufactured in the above-mentioned embodiment,
The transparent electrode 20 in the liquid crystal element for the comparative example as shown in FIG. 4 was produced.

In this comparative example, first, a crystalline ITO film was formed on a glass substrate by sputtering (the film thickness was 150).
0 Å). The film forming conditions of the ITO film at this time are: pressure: 0.23 Pa, O ₂ flow rate: 0.53 sccm, set film forming temperature: 300 ° C. (substrate temperature: 320 ° C.), power:
2 kW, transport speed: 220 mm / min, and the sputtering apparatus was ILC3949 manufactured by Nichiden Anelva Co., Ltd.
Was used. Then, a photoresist pattern is formed on the ITO film, and 57 wt% of a concentrated acid etching solution is used.
The transparent electrode 20 was patterned by performing an etching process using the concentrated hydroiodic acid described above at a liquid temperature of 40 ° C. and an etching time of 300 sec.

The transparent electrode 20 formed under the above conditions
As shown in FIG. 4, the film thickness d is about 1500 Å, while the taper region 2 at the edge portion 20a is
The width w of 0b is formed in the range of 2000 to 3000Å and does not satisfy the relationship of 0 ≦ w / d ≦ 2/3 described above. Therefore, when a drive voltage is applied to drive the liquid crystal, an inappropriate electric field strength is generated in the tapered region 20b at the edge portion 20a of the transparent electrode 20, causing alignment disorder of the liquid crystal, resulting in poor display quality. .

Next, a method of forming a transparent electrode in the method of manufacturing a liquid crystal element according to the second embodiment will be described.

In this embodiment, an amorphous ITO film is formed on a glass substrate (thickness is about 700Å) as in the first embodiment described above. The conditions for forming the ITO film at this time are as follows: pressure: 0.23 Pa, O ₂ flow rate: 0.53
sccm, set film forming temperature: 20 ° C. (substrate temperature: 40
℃), power: 2 kW, transport speed: 220 mm / min
Therefore, the sputtering equipment is I manufactured by Nichiden Anelva Co., Ltd.
LC3949 was used. Then, a photoresist pattern is formed on this ITO film.

Then, a dilute hydroiodic acid solution for weak acid etching (mixing volume ratio: 57 wt% HI: H ₂ O =
1: 7), liquid temperature 35 ° C., etching time 150 s
The transparent electrode was patterned by performing an etching process with ec. As described above, this embodiment is the same as the first embodiment except that the thickness of the ITO film is set to about 700 Å and the etching time is set to 150 sec. The width w of the tapered region at the edge of the transparent electrode formed under these conditions
Was formed to a thickness of about 450 Å with respect to the film thickness d (about 700 Å), and satisfied the relationship of 0 ≦ w / d ≦ 2/3.

As described above, also in the present embodiment, the relationship between the width w of the tapered region at the edge portion of the transparent electrode and the film thickness d thereof is such that 0 ≦ w / d ≦ 2/3. When a driving voltage is applied between the transparent electrodes to drive the liquid crystal by forming a small tapered region, the alignment of the liquid crystal that causes the inappropriate electric field strength generated in the tapered region at the edge of the transparent electrode. Disturbances have been eliminated and the display quality has been improved.

[0043]

As described above, according to the present invention,
Forming a transparent electrode having a steep taper region that satisfies 0 ≦ w / d ≦ 2/3, where w is the width of the taper region at the edge of the transparent electrode and d is the film thickness thereof. Thereby, the alignment disorder of the liquid crystal which causes the inappropriate electric field strength generated in the tapered region at the edge portion of the transparent electrode is suppressed, the driving margin is widened, and the display quality can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a liquid crystal element according to an embodiment of the present invention.

2A and 2B are views for explaining a method of manufacturing a liquid crystal element according to an embodiment of the present invention, in which FIG. 2A is a diagram showing a step of forming an ITO film, and FIG. 2B is a step of exposing a photoresist. The figure which shows, (c) the figure which shows the formation process of the photoresist pattern, (d) the figure which shows the etching treatment process of ITO film,
(E) is a figure which shows the formation process of a transparent electrode.

FIG. 3 is a vertical cross-sectional view showing a taper region at an edge portion of a transparent electrode formed by a manufacturing method according to an embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view showing a taper region at an edge portion of a transparent electrode formed as a comparative example with respect to the present invention.

FIG. 5 is a schematic cross-sectional view showing a liquid crystal element according to a conventional example.

FIG. 6 is a diagram for explaining disorder of alignment of liquid crystal in a liquid crystal element according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal element 4,5 Substrate (glass substrate) 6,7 Transparent electrode 7a Edge part 7b Tapered area 10,11 Alignment film 15 ITO film

Claims (10)

[Claims] 1. A liquid crystal element comprising a pair of substrates arranged so as to face each other, transparent electrodes formed on the substrates, and liquid crystal sandwiched between the pair of substrates. The liquid crystal element is characterized in that the taper region of the transparent electrode is formed so that 0 ≦ w / d ≦ 2/3 when the width of the taper region at the edge portion is w and the film thickness thereof is d. 2. The liquid crystal device according to claim 1, wherein the transparent electrode is formed by etching an amorphous ITO film formed on the substrate by a photolithography method. 3. The liquid crystal element according to claim 2, wherein the ITO film is formed by a sputtering method. 4. The liquid crystal device according to claim 3, wherein a film forming temperature of the ITO film on the substrate by a sputtering method is 80 ° C. or lower at a substrate temperature. 5. The liquid crystal device according to claim 2, wherein the etching solution for patterning the ITO film on the transparent electrode by a photolithography method is a weak acid. 6. The liquid crystal device according to claim 1, wherein the liquid crystal is a chiral smectic liquid crystal that exhibits at least two stable states in an aligned state. 7. A method of manufacturing a liquid crystal device, which comprises at least a step of forming transparent electrodes on a pair of substrates into which liquid crystal is injected, wherein an ITO film made of amorphous is formed on the substrates,
When the width of the tapered region at the edge of the transparent electrode is w and the film thickness is d, the transparent film is etched by etching the ITO film with a weak acid etching solution by photolithography, and 0 ≦ w / d ≦ A method for manufacturing a liquid crystal element, which comprises patterning so as to be ⅔. 8. The method for manufacturing a liquid crystal element according to claim 7, wherein the ITO film is formed by a sputtering method. 9. The method for manufacturing a liquid crystal element according to claim 8, wherein a film forming temperature of the ITO film on the substrate by a sputtering method is 80 ° C. or lower at a substrate temperature. 10. The method for manufacturing a liquid crystal element according to claim 7, wherein the liquid crystal is a chiral smectic liquid crystal that exhibits at least two stable states in an aligned state.