JP3071076B2 - Liquid crystal display cell manufacturing method - Google Patents

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 display cell for maintaining a uniform distance between a pair of substrates constituting a large-screen liquid crystal display cell, and more particularly to a ferroelectric material having high-speed response and memory properties. The present invention relates to a method for manufacturing a liquid crystal display cell using liquid crystal.

[0002]

2. Description of the Related Art Ferroelectric liquid crystals have a very fast response speed.
In addition, since it has a memory property even after the electric field is removed due to the bistability of the orientation, its application as an optical modulation element is expected, and research and development are being actively conducted.

The structure and manufacturing method of a display cell using a conventional ferroelectric liquid crystal are described below.

Normally, in a liquid crystal cell, an insulating film and an alignment film are provided on a glass substrate with an ITO transparent electrode, and alignment treatment is performed by rubbing. Then, spacers are randomly dispersed on one of the substrates to secure a cell interval. Then, the two substrates are bonded to each other by the edge seal.

[0005] Then, the thickness 1.5 secured between the two substrates.
A ferroelectric liquid crystal is injected into an isotropic liquid state by heating into a space of ２2 μm, and then slowly cooled.

In the ferroelectric liquid crystal display cell manufactured by this method, the cell interval is controlled only by the spacer, so that the cell interval tends to depend on the density of the spacer. Is difficult to control with high accuracy.

As described above, the high-speed response of the ferroelectric liquid crystal,
In order for bistability of orientation and orientation to be realized effectively,
A cell interval of about 1.5 to 2 μm is desirable.

As a result of measuring the cell spacing of the liquid crystal display cell manufactured by the above-mentioned manufacturing method using the spacer of 1.5 μm by the applicant of the present invention, the result was 1.24 to 1.6 in the same cell.
It was confirmed that there was a variation of 4 μm, and the cell spacing was reduced in places where the spacer density was low. That is,
It can be said that it is difficult to precisely and uniformly control the cell interval over the entire cell area by using only the spacer.

Further, a ferroelectric liquid crystal display cell manufactured by a conventional manufacturing method has no special countermeasure against impact.
In fact, the present applicant has confirmed that when the polarizer is attached to both sides of the liquid crystal display cell by pressure bonding, the orientation of the ferroelectric liquid crystal is partially disturbed. That is, it can be said that the ferroelectric liquid crystal display cell manufactured by this manufacturing method does not have sufficient cell strength against mechanical shock from the outside.

In order to prevent this, there has been proposed a method of arranging protrusions in a strip shape and thereby maintaining a space between two substrates (Japanese Patent Publication No. 17007/1990).

FIG. 10 is a sectional view of a ferroelectric liquid crystal display cell in which strip-shaped projections are provided on a black matrix (hereinafter referred to as BM).

In FIG. 10, a band-shaped projection having a hardness smaller than the hardness of the substrate is provided on the BM of at least one of the pair of substrates.

Further, a ferroelectric liquid crystal is sandwiched between the pair of parallel substrates which have been subjected to the rubbing process in parallel with the extending direction of the band-shaped projection.

As shown in FIG. 10, transparent strip-shaped Y electrodes 2 parallel to each other are provided on a glass substrate 1, and an opaque BM3 is formed as a grid-like light-shielding pattern surrounding pixels to improve display performance. Is formed.

An insulating film 4 made of SiO _{2 and} an alignment film 5 made of polyimide are laminated on the Y electrode 2 through which light passes.

The opposing glass substrate 7 faces the glass substrate 1.
Are provided, and Y on the glass substrate 1 is
A transparent X electrode 8 is formed in a direction crossing the electrode 2.

An insulating film 4 made of SiO ₂ and an orientation film 5 made of polyimide in contact with a projection 6 made of epoxy resin or polyimide resin are provided so as to cover the X electrode.

As a method for forming the strip-shaped projections, a photo-curable negative resist-based polyimide is applied, and then photolithography using hydrazine or O ₂ plasma using SiO ₂ on the photo-curable polyimide film as a mask. A method of patterning in a process is known (Maung)
S. Htoo, "Microelectronic P
oligomers ", pp45-47, 1989, pub
flushed by Marcel Dekker I
nc. ).

However, the conventional method of forming a strip-shaped projection requires an expensive and high-precision photomask, and when a pattern shift occurs, the display quality is reduced as shown in FIG. Therefore, there is a disadvantage that a considerable number of man-hours are required for mask pattern alignment.

According to the above-mentioned document, p. 47, lines 16 to 17, no photodegradable positive resist polyimide has been known.

FIG. 11 is a plan view of one pixel of a ferroelectric liquid crystal display cell in which a pixel formed by a pair of electrodes and a projection overlap each other to reduce the effective area of the pixel.

In FIG. 11, a pixel 10 that transmits light indicated by a hatched portion corresponding to the intersection of a horizontally extending X electrode 8 and a vertically extending Y electrode 2 has a low light transmittance of 2 μm. The projection 6 partially overlaps with the projection 6 indicated by the oblique right portion.

For example, when the length of one side of a pixel is 50 μm, even if the overlap between the projection and the pixel is 5 μm, 10% of the area of each pixel is completely lost.

[0024]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has been made to improve the accuracy of cell interval control and the strength of a liquid crystal cell with respect to impact, and yet to achieve a simple method. This is for the purpose of simplifying the production of a projection which is improved in one orientation (monodomain property) and is self-aligned with the BM.

[0025]

SUMMARY OF THE INVENTION The present invention relates to a grid-shaped BM.
Forming a photo-decomposable film above a substrate having island-shaped pixels that are planarly filled in the substrate, and the light-transmitting island-shaped existing in a gap between the lattice-shaped BMs that are light-shielding from the substrate side. Anisotropically exposing the photodegradable film with linear light having different light traveling directions depending on directions through a pixel, and developing the exposed photodegradable film to project in one direction above the BM. Forming an inorganic insulating film over the entire surface of the substrate including the protrusions, forming an organic alignment film on the inorganic insulating film, and forming a counter substrate facing the substrate and the substrate. The method includes a step of forming an empty cell by bonding, and a step of injecting liquid crystal into the empty cell and sealing the empty cell.

That is, the present invention omits a photomask and a pattern matching process at the time of exposure by using an anisotropic backside exposure method using a photodegradable resin and linear light.
The protrusion is formed only in a specific direction on the BM of the substrate.

[0027]

According to the present invention, a continuous strip-shaped projection is formed on the BM in a self-aligning manner by using a lattice-shaped BM arranged for the purpose of improving the display contrast as a mask. By using the body as a space support between a pair of substrates, the cell gap is controlled with high precision over the entire surface of the cell.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Therefore, according to FIG. 1, the ferroelectric liquid crystal display cell uses the BM pattern on the substrate as a mask, and anisotropically different in angle distribution of light in a direction parallel to the electrode crossing between the pair of substrates. An example will be described with respect to a manufacturing method of forming a projection by exposure patterning with a neutral light source.

FIG. 1 shows the Y of the ferroelectric liquid crystal display cell of the present invention.
It is sectional process drawing of the manufacturing method of the board | substrate of an electrode side.

(1) Of a pair of substrates, Cr on a glass substrate 1 vertically insulated by a separation film 11 made of SiO ₂
A glass substrate 1 having a BM 3 made of ITO and a Y electrode 2 made of ITO on a separation film is prepared on a spinner (FIG. 1a).

(2) A positive photosensitive polyimide (for example, RN-901 manufactured by Nissan Chemical Industries, Ltd.) is spin-coated on the glass substrate 1 on which the BM 3 and the Y electrode 2 are formed, to a thickness equal to a desired cell gap thickness (for example, 1.5 μm) to produce a photodegradable film 12 (FIG. 1b).

(3) After pre-baking, so-called back exposure, in which light is irradiated from the glass substrate side, is performed. In this case, an anisotropic light source is used in which the light becomes parallel light in the direction in which the Y electrode extends and becomes non-parallel light in the radial direction in the direction in which the X electrode extends. Then, the light 13 passes perpendicularly to the Y electrode (FIG. 1).
c). The back exposure will be described later in detail.

(4) The photodegradable film 12 in the portion where light is transmitted
Is decomposed into a state easily dissolved in a developer. Upon development, the photodegradable film on the Y electrode that has been decomposed is removed, while
The photodegradable film above the BM 3 remains and protrudes above the separation film 11 to form a Y projection 14 parallel to the Y electrode.
d).

(5) Then, in order to prevent a short circuit due to foreign matter between the substrates over the entire surface of the substrate, 800 ° C. by sputtering.
Forming a SiO ₂ made of an insulating film 4 (FIG. 1e).

(6) Subsequently, a polyamic acid employing N-methylpyrrolidone as a diluent and dialkyl ether as a flattening agent is applied on the insulating film 4 and heated to 350 ° C. to obtain an orientation having a thickness of about 100 °. A film 5 is formed (FIG. 1f).

Next, FIG. 2 is a sectional view of a ferroelectric liquid crystal display cell having a projection according to the present invention.

As shown in FIG. 2, a Y projection 14 extending in parallel to the extending direction of the Y electrode 2 within the range of the BM 3 for blocking light on the glass substrate 1 faces the glass substrate 1 and the glass substrate. It is formed so as to support between the glass substrate 7 and the counter glass substrate 7.

On a transparent glass substrate 1, the surface is made of SiO ₂
An opaque BM 3 made of metal Cr covered with a separation film 11 of, for example, acrylic resin or a transparent resin, and a transparent strip-shaped Y electrode 2 made of ITO are further laminated on the separation film.

The Y projection 14 parallel to the Y electrode is provided above BM3.
Are in contact with the ferroelectric liquid crystal 9 and are in contact with the alignment film 5 on the opposing glass substrate 7.

An insulating film 4 made of SiO ₂ by sputtering and an alignment film 5 made of an aromatic polyimide film (for example, SP-710 manufactured by Toray) are formed on the Y electrode 2 and the X electrode 8 orthogonal to each other by sputtering. Is formed.

Although not shown, rubbing for alignment, sealing of a pair of substrates, injection of liquid crystal, and sealing of a liquid crystal injection port are performed as follows. Rubbing is performed on the surface of the alignment film as an alignment treatment. The rubbing direction at this time is parallel rubbing parallel to the Y protrusion.

Next, a thermosetting resin (for example, XN-21-F manufactured by Mitsui Toatsu Chemicals) or an ultraviolet curable resin is applied to the edge portion by printing, and the two substrates are sealed by heating or irradiation with ultraviolet rays. Inject liquid crystal.

Since the ferroelectric liquid crystal to be injected exhibits a high viscosity smectic phase at room temperature and is difficult to be injected in a thin cell gap, the liquid crystal is injected into the cell by heating in an isotropic liquid state.

After the injection, the liquid crystal cell is gradually cooled,
A monodomain ferroelectric liquid crystal display cell is formed, and the injection port is closed and sealed with epoxy resin.

The projection of the present invention is characterized in that it is formed in a self-aligned manner on the BM in parallel with one of the pair of electrodes sandwiching the ferroelectric liquid crystal by back exposure.
The path of the linear light from the light source to be exposed will be described below.

FIG. 3 shows that radial light is converted into Y light by a semi-cylindrical lens.
FIG. 5 is a layout diagram of an exposure light source that converts light into radial light parallel to the X direction and transmits through a photodegradable film on the BM, and a substrate having the BM.

As shown in FIG. 3, a point-like exposure light source 1
Radial light is radiated from 5 in all directions.

A semi-cylindrical lens 16 is arranged between one substrate having a lattice-shaped BM 3 that does not transmit light and pixels 10 arranged in a matrix that transmits light, and a light source in parallel with the Y electrode. Are arranged perpendicular to the YY ′ direction.

Radial light 13 from a point exposure light source 15
Is incident on the semi-cylindrical lens 16 so that Y−
The light is emitted in the form of radial light parallel to the Y ′ direction and radial in the XX ′ direction. That is, the light becomes anisotropic light in which the traveling direction of the light differs depending on the direction.

Therefore, the BM adjacent to the pixel 10 in the XX ′ direction is generated by the radial light incident from one substrate side.
Although the upper photodegradable film is almost decomposed, the photodegradable film on the BM adjacent to the pixel in the YY ′ direction is not decomposed by the parallel light incident from the other substrate side, and is not decomposed on the substrate at the time of development. It will remain.

Here, a more detailed position of the Y projection will be described below.

FIG. 4 shows B of the ferroelectric liquid crystal display cell of the present invention.
FIG. 3 shows a plan view of M and a Y protrusion disposed on the BM.

As shown in FIG. 4, the plane of the ferroelectric liquid crystal display cell has a grid-shaped light-impermeable BM3,
It is occupied by pixels 10 that are surrounded by a BM and pass light arranged in a matrix at the intersection of the Y electrode and the X electrode.

The Y projection 14 which is a feature of the present invention is formed on the BM by self-alignment and in parallel between the Y electrodes and between rows.

In some cases, the X projection 17 having a smaller height and a smaller width than the Y projection parallel to the X electrode remains on the substrate.

FIG. 5 is a cross-sectional view of one substrate along the line VV of FIG. 4, and FIG. 6 is a cross-sectional view of one substrate along the line VI-VI of FIG.

As shown in FIG. 5, the Y projection 14 is formed in parallel with the Y electrode, and has a width roughly equal to the width of the BM 3.

On the other hand, as shown in FIG.
Is extremely low and does not remain on the separation membrane 11 in some cases.

Whether or not the X projection remains remains not depending on the relative position between the exposure light source and the substrate, but is often determined by the exposure time and the development time. Therefore, it is not always necessary that the light be parallel in one direction. .

That is, in order to form such a projection, for example, a linear light source in which the width of the light from the light source is made extremely narrower than the length by a slit may be used.

As a light source for back exposure used for a substrate having a BM, a linear light source having a sufficiently large length with respect to the lattice pitch of the BM is used. At this time, as shown in FIG. 7, light irradiation is performed while the length direction of the light source and one direction of the BM match.

FIG. 7 is a perspective view showing the arrangement of a glass substrate of the present invention and a linear light source which form a projection on the BM in a self-aligned manner using a BM by using a linear light source.

As shown in FIG. 7, X parallel to the Y electrode
The linear exposure light source 15 is arranged in the −X ′ direction,
A positive photosensitive resist (RN-901 manufactured by Nissan Chemical Industries, Ltd.) laminated on a glass substrate in the direction is irradiated with light from the substrate side.

In the following description, the gist of the exposure state of the photodegradable film of the present invention is exaggerated so as to be easily grasped, but the protrusion of the present invention is formed in the BM region.

FIG. 8 is a sectional view of the photosensitive resist exposed on the glass substrate in the YY ′ direction.

FIG. 8 shows a BM in which the exposure light source is regarded as a point light source.
FIG. 4 shows an operation sectional view of a positive photosensitive resist in the YY ′ direction above.

In FIG. 8, the light 13 from the exposure light source 15
Is irradiated radially onto a positive photosensitive resist and becomes light passing through a transparent Y electrode 2 to photodecompose the positive photosensitive resist into a photodecomposer 18.

On the other hand, since the light 13 is blocked by the opaque BM 3, the heat treatment after exposure turns the positive photosensitive resist into a Y-projection 14 that supports between the two glass substrates.

By lengthening the development time and exposure time of the positive photosensitive resist, the Y projections 14 will fit within the BM 3.

Next, FIG. 9 shows a cross-sectional view of the photosensitive resist exposed on the glass substrate of FIG. 7 in the XX ′ direction.

FIG. 9 is a sectional view showing the operation of a positive photosensitive resist in the XX 'direction on a pixel where the exposure light source is regarded as a linear light source.

Although the light 13 from one point of the exposure light source 15 is blocked by the opaque BM 3, it becomes linear light according to the exposure light source of FIG. Would.

For this reason, the X projections 17 formed in parallel with the X electrodes by linear light have extremely small heights or do not exist at all.

As described above, the BM of the ferroelectric liquid crystal display cell
Utilizing, it is possible to easily form a protrusion of about 5 μm or less on a glass substrate in a self-aligned manner.

The ferroelectric liquid crystal display cell manufactured as described above was measured for cell intervals at 15 locations in the cell.
It was 1.52 μm, and it was found that the cell interval control could be performed with higher accuracy than the conventional cell.

A polarizer was attached in a crossed Nicols state on both sides of the ferroelectric liquid crystal display cell produced by the process of the present invention. Was not seen.

In general, spacers present in an effective display area often serve as a starting point of generation of a non-uniform alignment portion, and often lower the display contrast.

However, according to the structure of the present invention, no spacer is arranged in the effective display area, so that it is effective for improving the contrast.

The insulating film used here may be formed of SiO ₂ , silicon nitride, silicon carbide or the like by means of sputtering, vapor deposition or CVD.

Further, as the alignment film, polyvinyl alcohol, polyimide, polyamide, nylon or the like may be used.

The liquid crystal of this embodiment is not limited to a ferroelectric liquid crystal, but may be a nematic liquid crystal having a lower viscosity Δn · d.

As described above, according to the method of manufacturing a liquid crystal display cell of the present invention, a liquid crystal display cell having a uniform gap without damaging pixels is formed even when the size of the cell is within or outside 10 inches.

[0084]

According to the present invention, a photomask and a pattern matching process at the time of exposure can be omitted by using an anisotropic backside exposure method using a photodegradable resin and linear light, and the BM of the substrate can be reduced. The protrusion can be easily formed only in the specific direction above.

Alternatively, according to the present invention, a projection having a function as a spacer is formed in a self-aligned manner to produce a ferroelectric liquid crystal display cell, thereby improving the accuracy of cell spacing control and improving the single alignment property. This is effective for improving the improvement, preventing the aperture ratio from being lowered due to the pattern shift, and improving the resistance to mechanical shock such as external pressing of the panel after the panel is completed.

Further, since there is no spacer in the effective display pixel, it is effective for improving the display contrast.

Further, in the present invention, in producing a ferroelectric liquid crystal cell, the BM formed on a glass substrate is used, so that the alignment can be performed with high accuracy without a mask separate from the substrate. It is possible to easily form a continuous projection having a function as a spacer. Further, since the spacers are formed at a high density, it is effective for improving the uniformity of the cell gap and the impact resistance after the cell is completed.

Since the spacer particles are not scattered in the effective display pixels, it is effective for improving the display contrast.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a self-aligned projection according to the present invention.

FIG. 2 is a cross-sectional view of a ferroelectric liquid crystal display cell on which a projection of the present invention is arranged.

FIG. 3 is a perspective view showing the arrangement of a light source, a lens, and a substrate for manufacturing a projection according to the present invention.

FIG. 4 is a plan view of a substrate on which a projection of the present invention is formed.

FIG. 5 is a cross-sectional view taken on a plane parallel to an X electrode of a substrate on which a protrusion of the present invention is formed.

FIG. 6 is a cross-sectional view taken on a plane parallel to a Y electrode of the substrate on which the protrusions of the present invention are formed.

FIG. 7 is an arrangement perspective view of a linear light and a substrate for manufacturing the projection of the present invention.

FIG. 8 is an operation sectional view of a light source and a substrate for manufacturing a Y projection according to the present invention.

FIG. 9 is an operation sectional view of a light source and a substrate for manufacturing the X projection according to the present invention.

FIG. 10 is a sectional view of a conventional ferroelectric liquid crystal display cell having continuous projections.

FIG. 11 is a plan view in a case where a pixel is shifted from a conventional projection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Y electrode 3 BM 4 Insulating film 5 Alignment film 6 Projection 7 Counter glass substrate 8 X electrode 9 Ferroelectric liquid crystal 10 Pixel 11 Separation film 12 Photodegradable film 13 Light 14 Y projection 15 Exposure light source 16 Lens 17 X protrusion 18 Photodecomposition

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-2833 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13 101 G02F 1/1333 500 G02F 1/1334 G02F 1/1339 500

Claims (1)

(57) [Claims] 1. A method for manufacturing a liquid crystal display cell having a projection between a pair of parallel substrates, wherein the projection is formed by back exposure patterning with linear light using a black matrix pattern on the substrate as a mask. A method for manufacturing a liquid crystal display cell, comprising: