JPH09185045A - Manufacturing method of liquid crystal element - Google Patents

Abstract

(57) Abstract: It is possible to prevent peeling of a planarization layer and generation of microrack by an etching solution used for patterning a transparent electrode made of an ITO film. SOLUTION: I containing an amorphous component on a planarizing layer 4
The TO film 5 is formed, a photoresist is applied, and patterning is performed using a weak acid etching solution, so that peeling of the planarization layer 4 and generation of microrack are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal element, and more particularly to a method for manufacturing a liquid crystal element having a step of etching a transparent electrode made of an ITO film.

[0002]

2. Description of the Related Art TN (Twisted Nematic) and STN (Sutured Nematic)
BACKGROUND ART In a liquid crystal element such as a per twisted nematic type, an ITO (Indium Tin Oxide) film has been generally used as a transparent electrode.

It is known that the ITO film has high crystallinity and has a peak in 222 plane or 400 plane in X-ray diffraction. As described above, since the transparent electrode is required to have high transparency and low sheet resistance regardless of vapor deposition / sputtering, an ITO film having high crystallinity is widely used.

In the etching process for patterning a transparent electrode made of an ITO film, conventionally, a strong acid etching solution such as hydrochloric acid-ferric chloride type, hydrobromic acid type, hydroiodic acid type is generally used. Is used for.

Further, in order to prevent uneven etching, an etching solution of hydroiodic acid mixed with ferric chloride is also used, but all of them belong to the category of strong acids.

[0006]

By the way, the above-mentioned I
When the pattern of the transparent electrode composed of the TO film is formed on the color filter substrate composed of the color filter composed of the resin material and the flattening layer provided thereon, the ITO described above is used.
Chlorine ions / bromine ions contained in the film etching solution easily pass through the flattening layer made of a resin material, and the transparent electrode (I
(TO film), a color filter, and a salt with Na contained in the glass substrate on which the flattening layer is formed.

The above-mentioned strong acids such as hydrochloric acid-ferric chloride (pH: -1.52 to -1.22) and hydrobromic acid (p:
H: -1.58 to -1.28), hydroiodic acid (57w)
At t%, an etching solution such as pH: −1.58 to −1.28), hydroiodic acid-ferric chloride system (pH: −1.39 to −1.09) is applied to the planarizing layer. As shown in FIG. 3, the peeled portion 1 reacts with the metal component added in a trace amount and is formed on the flattening layer 11 formed on the color filter 10 of the liquid crystal element.
2 and the occurrence of microrack 13 are triggered. In the figure,
14 is a glass substrate, 15 is a black matrix, 16
Is a transparent electrode made of an ITO film. The above-mentioned pH of the etching solution is a value obtained by subtracting 2 from the pH value measured by a pH meter of a sample obtained by diluting the etching solution 100 times. As described above, when the peeling portion 12 or the microrack 13 is generated in the flattening layer 11 due to the etching liquid for patterning the transparent electrode 16 made of the ITO film, the adhesion strength of the flattening layer 12 is lowered and the flattening layer 12 is heated in a later step. There is a problem that defects such as peeling of the planarization layer 11 occur over a wide range.

Therefore, according to the present invention, the transparent electrode (ITO film) is formed without causing peeling or microrack on the flattening layer.
It is an object of the present invention to provide a method for manufacturing a liquid crystal element capable of forming a film.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, in which a color filter and a surface of the color filter are provided on at least one of a pair of opposed substrates into which liquid crystal is injected. A planarization layer for planarizing
In a method of manufacturing a liquid crystal element, which comprises at least a step of forming a transparent electrode made of an ITO film, the ITO film containing an amorphous component is formed on the planarization layer, a photoresist is applied, and a weak acid etching solution is applied. The transparent electrode is patterned by using the etching process.

The ITO film has a film thickness of d (μm), a peak intensity of 222 surface of the ITO film is H ₁ , and 111 surface of a standard substance Si powder by X-ray diffraction at 3 ° incidence. Let H _{2 be} the peak intensity of 1 / d × (H
It is characterized by being an ITO film having low crystallinity that satisfies ₁ / H ₂ ) ≦ 1/5.

In the above-mentioned ITO film containing an amorphous component, the lower the peak intensity H _{1 on the} 222 surface, the higher the amorphous property. However, I containing an amorphous component
The peak intensity H _{1 on} the 222 surface of the TO film changes depending on the analytical sensitivity of X-ray diffraction and its film thickness.
Amorphousness is quantified by a value normalized by the peak intensity H ₂ of the 111 surface of the i powder and the film thickness d of the ITO film containing the amorphous component (1 / d × (H ₁ / H ₂ ) ≦ 1/5)
did.

Further, when 1 / d × (H ₁ / H ₂ ) becomes larger than 1/5, the "1/5" value is due to the presence of a crystal part in the above-mentioned ITO film, and therefore the value of "1/5" is weak acid etching. The upper limit value indicates that a residue is generated even if the solution is etched.

[0013]

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

FIG. 1 is a schematic sectional view showing a substrate of a liquid crystal element according to the first embodiment. As shown in this figure,
1 is a pair of glass substrates sandwiching a chiral smectic liquid crystal (not shown) showing ferroelectricity (only one substrate is shown in the figure), 2 is a black matrix which is a light shielding layer, 3 is a color filter, 4 is The flattening layers (overcoats) 5 are transparent electrodes (ITO film).

The color filter 3 is composed of red (R), green (G), blue (B), and white (W) pixels, and is controlled by the voltage applied between the pair of glass substrates 1. Color display is performed by color mixing.

The flattening layer 4 is formed so as to cover the color filter 3, and protects the color filter 3 and secures the flatness of the color filter 3.

The transparent electrode (ITO film) 5 contains an amorphous component so that the crystallinity becomes low, and the flattening layer 4 is formed.
It is patterned on the top (details will be described later).

An insulating film (not shown), an alignment film (not shown), etc. are formed on the transparent electrode (ITO film) 5 of the glass substrate 1 described above, and the pair of glass substrates 1 are bonded together. By injecting a chiral smectic liquid crystal (not shown) exhibiting ferroelectricity, a liquid crystal element capable of color display is manufactured. It should be noted that the other glass substrate was not formed with a black matrix, a color filter, or a flattening layer.

Next, a method of manufacturing the above-mentioned liquid crystal element will be described with reference to FIGS.

First, a glass substrate (thickness: 1.1 mm) 1
A metal film (Mo film) having a film thickness of about 1000 Å is formed on the surface of the metal film by, for example, a sputtering method.
(o film) is patterned as a black matrix 2 by a photolithography method. Then, a photosensitive coloring resin is applied onto the black matrix 2, and a color filter 3 composed of red (R), green (G), blue (B), and white (W) pixels is formed by photolithography. It is formed with a film thickness of about 0.5 μm (see FIG. 2A).

Then, a flattening layer 4 made of, for example, polyvinyl siloxane is applied on the color filter 3 by a spin coating method to a thickness of about 1.5 μm to form a color filter substrate (see FIG. 2B).

Then, an ITO film 5 containing an amorphous component, which will be a transparent electrode, is formed on the flattening layer 4, which is the color filter substrate, to a film thickness of about 700 Å by a sputtering method (see FIG. 2C). .

The film forming conditions of the ITO film 5 at this time are, for example, substrate temperature: 30 ° C., pressure: 3 mTorr, O ₂ flow rate: 3 sc.
cm, Ar flow rate: 200 sccm, power: 0.57 k
w, transport speed: 500 mm / min, and ILC705 manufactured by Nichiden Anelva was used as the sputtering device.

Then, a photoresist is applied on the ITO film 5 and exposed and developed to form a photoresist pattern 6 having a film thickness of about 2 μm (see FIG. 2D). Then, the ITO film 5 on which the photoresist pattern 6 is formed is etched with a weak acid etching solution, and then the photoresist pattern 6 is peeled off to pattern the transparent electrode 7 made of the ITO film (see FIG. 2E). .

At this time, the etching solution of the weak acid used for etching the ITO film 5 has a pH (value obtained by subtracting 2 from the pH value measured by a pH meter of the sample obtained by diluting the etching solution 100 times) with a value of -1. Higher than 1, and in the present embodiment −
1.0 diluted dihydroiodic acid (mixing volume ratio is HI (57
wt%): H ₂ O = 60: 40 to 10:90 is preferable, and in this embodiment, it is 50:50), and the liquid temperature is 25.
The etching rate at 0 ° C. is preferably 10 to 30 Å / sec, and in this embodiment, the etching rate is 5 Å / sec. still,
The above-mentioned diluted hydriodic acid of the etching solution does not contain chlorine ions or bromine ions which easily pass through the flattening layer 4 which is a resin film.

As for the etching time at this time, when over-etching was performed about twice as long as the appropriate etching time, the side edge amount of the ITO film 5 was small and the distance between the pixels of each ITO film 5 (about 10 μm). ),
It was about 1 μm.

Then, an insulating film (not shown), an alignment film (not shown), etc. are formed on the transparent electrode 7 and face the other glass substrate (which is not provided with a color filter etc.) which has been similarly treated. A liquid crystal element capable of color display is obtained by injecting a liquid crystal (not shown) after bonding.
As the liquid crystal to be injected, liquid crystal materials applicable to various liquid crystal display modes, such as nematic liquid crystal, smectic liquid crystal, chiral smectic liquid crystal (particularly liquid crystal exhibiting ferroelectricity), can be used. Further, the pattern of the transparent electrode 7 can be optimized in the characteristics such as the direction of the annealing treatment and the transparency, if necessary, in the steps after the pattern formation.

As described above, in the present embodiment, the substrate temperature is lowered at the time of sputtering and the gas pressure is lowered in a high vacuum.
By further reducing the O ₂ flow rate, the ITO film 5 containing an amorphous component is formed. Then, when the ITO film 5 containing the amorphous component is etched, the weak acid hydriodic acid diluted with water is used as the etching liquid so that it does not react with the metal component added to the flattening layer 4 in a trace amount. Therefore, it is possible to prevent peeling of the flattening layer 4 and generation of microrack.

Further, the ITO film 5 containing the amorphous component of the liquid crystal element according to the present embodiment has a smoother surface than the crystalline ITO film, so that the ITO film 5 is excellent in flatness, and the control of the orientation to the liquid crystal is improved.

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

This embodiment is the same up to the step of forming the black matrix 2, the color filter 3, and the flattening layer 4 (FIGS. 2A and 2B) in the above-described first embodiment. .

Then, as shown in FIG. 2C, an ITO film 5 containing an amorphous component is formed on the flattening layer 4, for example, substrate temperature: 30 ° C., pressure: 2 mTorr, O ₂ flow rate: 2 s.
ccm, Ar flow rate: 200 sccm, power: 0.75
A film having a thickness of about 700 Å was formed by a sputtering method under the film forming conditions of kW and a conveying speed of 500 mm / min. As the sputtering device, ILC705 manufactured by Nichiden Anelva was used.

At this time, in X-ray diffraction at 3 ° incidence, the peak intensity of the standard substance Si powder <111 plane> was 600.
When showing 00 cps, the ITO film 5 containing the above-mentioned amorphous component has a halo peak of 1000 to 2000 cps, and the peak intensity of the ITO film 5 <222 face> depends on the film thickness, but when the film thickness is 1000 Å 1000 cp
s or less.

Therefore, the thickness of the ITO film 5 is d (μm),
When the peak intensity of the 222 surface of the ITO film 5 is H ₁ , and the peak intensity of the 111 surface of the standard material Si powder by X-ray diffraction at 3 ° incidence is H ₂ , 1 / d × (H ₁ / H ₂ ) ≦ 1
Since the relationship of / 5 is satisfied, the ITO film 5 according to the present embodiment has low crystallinity.

Next, as in the case of the above-described first embodiment, a photoresist is applied on the ITO film 5, exposed and exposed.
After forming a photoresist pattern 6 having a film thickness of about 2 μm through development (see FIG. 2D), the photoresist pattern 6 is peeled off and the ITO film 5 is patterned (see FIG. 2E).

At this time, the acid used for etching the ITO film 5 was diluted hydroiodic acid having a pH of -1.0 (mixing volume ratio: HI (57 wt%): H ₂ O = 60: 40 to 10). :
90 is preferable, and is 50:50 in this embodiment).
The etching rate at a liquid temperature of 25 ° C is 10 to 30Å
/ Sec is preferable, and in this embodiment, 10Å / sec
I went in.

As described above, also in this embodiment, the ITO film 5 having a side edge amount of 1 μm or less is patterned, and hydroiodic acid diluted with water is used as the etching solution for the ITO film 5 containing an amorphous component. As a result, peeling of the flattening layer 4 and generation of the microrack 13 could be prevented.

Although hydroiodic acid is expensive, in the present embodiment, it is possible to reduce the manufacturing cost by diluting it and using it.

Oxalic acid (17 wt%) was used as the acid used for etching the ITO film 5 at a liquid temperature of 45 ° C. for 8 to 10.
It can also be performed at an etching rate of 11Å / sec.

Further, after forming the transparent electrode made of the ITO film obtained by the above-mentioned process, the liquid crystal element is obtained through the same steps as those in the first embodiment. At this time, if necessary, the pattern of the transparent electrode 7 made of the ITO film can be subjected to an annealing treatment.

[0041]

As described above, according to the present invention,
An ITO film containing an amorphous component is formed on the flattening layer, a photoresist is applied, and the transparent electrode is patterned by etching using a weak acid etching solution. Since it does not damage the color filter and the color filter, peeling of the planarization layer and generation of microrack can be prevented, and the manufacturing yield can be improved.

Further, by using a weak acid etching solution for patterning the transparent electrode, it is possible to reduce corrosion on the manufacturing apparatus.

[Brief description of the drawings]

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

2A and 2B are views for explaining a method for manufacturing a liquid crystal element according to an embodiment of the present invention, FIG. 2A is a diagram showing a black matrix and color filter forming process, and FIG. 2B is a flattening layer forming process. FIG. 4C is a diagram showing a process of forming an ITO film, FIG. 7D is a diagram showing a process of forming a photoresist pattern, and FIG. 8E is a diagram showing a process of forming a transparent electrode.

FIG. 3 is a diagram showing a substrate of a liquid crystal element manufactured by a manufacturing method according to a conventional example.

[Explanation of symbols]

 1 Glass Substrate (Substrate) 2 Black Matrix 3 Color Filter 4 Flattening Layer 5 ITO Film 6 Photoresist Pattern 7 Transparent Electrode

Claims (7)

[Claims] 1. A color filter, a flattening layer for flattening the surface of the color filter, and a transparent electrode made of an ITO film are formed on at least one of a pair of opposed substrates into which liquid crystal is injected. In the method for manufacturing a liquid crystal element having at least a step, the ITO film containing an amorphous component is formed on the planarization layer, a photoresist is applied, and an etching treatment is performed using a weak acid etching solution to form the transparent electrode. A method for manufacturing a liquid crystal element, which comprises patterning. 2. The ITO film has a thickness d of the ITO film.
(Μm), the peak intensity of the 222 surface of the ITO film is H
₁ , where the peak intensity on the 111 plane of the standard substance Si powder by X-ray diffraction at 3 ° incidence is H ₂ , the low crystallinity ITO film that satisfies 1 / d × (H ₁ / H ₂ ) ≦ 1/5 The method for manufacturing a liquid crystal element according to claim 1, wherein 3. The method for producing a liquid crystal element according to claim 1, wherein the etching solution is a dilute hydroiodic acid solution having a pH higher than −1.1. 4. The method for manufacturing a liquid crystal element according to claim 1, wherein the color filter is formed by a photolithography method. 5. The method of manufacturing a liquid crystal element according to claim 1, wherein the flattening layer is formed by a spin coating method. 6. The method of manufacturing a liquid crystal element according to claim 1, wherein the ITO film is formed by a sputtering method. 7. The method for manufacturing a liquid crystal element according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal.