JPH0740098B2 - Method for manufacturing chiral smectic liquid crystal device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a chiral smectic liquid crystal device such as a liquid crystal display device and a liquid crystal-optical shutter array, and more specifically, to improve the initial alignment state of liquid crystal molecules. The present invention relates to a method for producing a ferroelectric chiral smectic liquid crystal device having a color filter having a uniform monodomain liquid crystal phase having no alignment defect and having improved display and driving characteristics.

[Prior Art] Examples of conventional liquid crystal elements include M.Sc.
hadt) and W. Helfrich's "Applied Physics Letters"("Applied
Physics Letters ") Volume 4, Issue 4 (Published February 15, 1971), pages 127-128," Voltage Dependant Optical Activity of a Twisted Nematic Liquid Crystal " “Voltag
e Dependent Optical Activity of a Twisted Nematic
Liquid crystal ") is known, which uses twisted nematic liquid crystal. This TN liquid crystal is a crosstalk during time-division driving using a matrix electrode structure with high pixel density. However, the number of pixels is limited because of the problem of occurrence of.

In addition, a display element of a type in which a switching element using a thin film transistor is connected to each pixel and switching is performed for each pixel is known, but a step of forming a thin film transistor on a substrate is extremely complicated, and a large area display element is used. There are problems that are difficult to create.

To solve these problems, Clar (Clar
Ferroelectric liquid crystal devices have been proposed in U.S. Pat. No. 4,367,924 by K) et al.

FIG. 2 schematically shows an example of a cell for explaining the operation of the ferroelectric liquid crystal. 21a and 21b are In ₂ O ₃ and SnO ₂
A substrate (glass plate) covered with a transparent electrode made of a thin film such as ITO or Indium Tin Oxide (SmC) in which a plurality of liquid crystal molecular layers 22 are aligned so as to be perpendicular to the glass surface.
^* Phase or SmH ^* phase liquid crystal is enclosed. The thick line 23 represents a liquid crystal molecule.
_{Has a} dipole moment (P _⊥ ) 24 in a direction orthogonal to its molecule. When a voltage above a certain threshold is applied between the electrodes on the substrates 21a and 21b, the helical structure of the liquid crystal molecules 23 is unraveled, and all the dipole moments (P _⊥ ) 24 are oriented in the electric field direction. Can be changed. The liquid crystal molecules 23 have an elongated shape and exhibit refractive index anisotropy in the major axis direction and the minor axis direction thereof. Therefore, for example, if polarizers arranged in a crossed Nicols positional relationship are placed above and below a glass surface, respectively. It is easily understood that the liquid crystal optical modulation element has optical characteristics that change depending on the polarity of voltage application.

The liquid crystal cell preferably used in the ferroelectric liquid crystal device in the present invention has a sufficiently thin thickness (for example, 10 μm or less).
can do. As the liquid crystal phase becomes thinner in this way, as shown in FIG. 3, even when no electric field is applied, the helical structure of the liquid crystal molecules unwinds and becomes a non-helical structure, and the dipole moment Pa or Pb thereof is directed upward (34a ) Or downward (34b). When electric fields Ea or Eb with different polarities equal to or more than a certain threshold value are applied to such a cell as shown in FIG. 3, the dipole moment becomes
Depending on the electric field vector of the electric field Ea or Eb, the direction is changed to the upward direction 34a or the downward direction 34b, and the liquid crystal molecules are aligned in either the first stable state 33a or the second stable state 33b accordingly.

As described above, there are two advantages of using such a ferroelectric liquid crystal as an optical modulation element. The first is that the response speed is extremely fast, and the second is that the alignment of the liquid crystal molecules has bistability. The second point is, for example, the third
Explaining further by the figure, when the electric field Ea is applied, the liquid crystal molecules are aligned in the first stable state 33a, but this state is stable even when the electric field is cut off. When a reverse electric field Eb is applied, the liquid crystal molecules are oriented in the second stable state 33b and the orientation of the molecules is changed. However, even when the electric field is cut off, the liquid crystal molecules remain in this state. Further, as long as the applied electric field Ea does not exceed a certain threshold value, the respective alignment states are maintained.
In order to effectively realize such a high response speed and bistability, it is preferable that the cell is as thin as possible.

In order for this ferroelectric liquid crystal element to exhibit a predetermined driving characteristic, the ferroelectric liquid crystal disposed between the pair of parallel substrates must be
Regardless of the applied state of the electric field, it is necessary that the molecular arrangement is such that conversion between the two stable states described above effectively occurs. For example, regarding a ferroelectric liquid crystal having a chiral smectic phase, a liquid crystal molecular layer of the chiral smectic phase is perpendicular to the substrate surface, and thus a region (monodomain) in which the liquid crystal molecular axes are aligned substantially parallel to the substrate surface is formed. Need to However, in the conventional ferroelectric liquid crystal device, the alignment state of the liquid crystal having such a monodomain structure was not always formed satisfactorily, and therefore, the actual condition was that sufficient characteristics were not obtained.

FIG. 4 shows a cross-sectional view of a conventional ferroelectric liquid crystal element, and FIG. 5 is a schematic explanatory view showing a state of alignment defects appearing in the conventional ferroelectric liquid crystal element.

That is, the conventional ferroelectric liquid crystal element 40 shown in FIG.
It has a pair of parallel substrates 41 and 42, and stripe-shaped transparent electrodes 43 and 44 having a matrix electrode structure are provided on the substrates 41 and 42, respectively.

Generally, a color filter is composed of red (R), green (G), and blue (B) dyes or a layer containing the dyes. However, since the film thickness of each dye layer is different regardless of the forming method, 2000Å A step A of about 1 μm is formed. As a result, when the alignment control is performed by utilizing the temperature lowering process, the above-mentioned step A causes the alignment defect in the ferroelectric liquid crystal 47 with the step A as a boundary. Also, this step A
On the substrates 41 and 42 on which the alignment control films 45 and 46 are present, respectively.
By providing the step, a step C formed corresponding to the step A also occurs in this alignment control film in the thickness of almost the pixel, and an alignment defect occurs in the ferroelectric liquid crystal 47 in the same manner as described above.

FIG. 5 is a sketch of the ferroelectric liquid crystal device observed with a crossed Nicols polarization microscope. White lines 51 in the drawing correspond to the lines of the spacer (not shown) used for the liquid crystal device, and the line 52 And 53 are observed corresponding to the step C on the substrate 41 in FIG. Further, a portion 54 in the figure is a ferroelectric liquid crystal sandwiched between opposed electrodes. A large number of blade lines 55 appearing in the polarization microscope represent alignment defects of the ferroelectric liquid crystal.

If there is a step of 1000 Å or more on the surface in contact with the ferroelectric liquid crystal as described above, an alignment defect is generated from the step and the monomain formation of the ferroelectric liquid crystal is hindered.

[Problems to be Solved by the Invention] The inventors of the present invention have found that such a step on the substrate, in particular, a step between the pixels of the color filter causes an alignment defect with respect to the ferroelectric liquid crystal. It became clear by the experiment that it has become.

An object of the present invention is to provide a ferroelectric chiral smectic liquid crystal element capable of preventing the occurrence of the above-mentioned alignment defects and sufficiently exhibiting the high-speed response and the memory effect characteristic originally possessed by the ferroelectric liquid crystal element. Especially.

[Means for Solving Problems] The inventors of the present invention have focused on the initial orientation in the temperature decreasing process in which the ferroelectric liquid crystal transitions from the isotropic phase (high temperature state) to the liquid crystal phase (low temperature state). The present inventors have found a ferroelectric chiral smectic liquid crystal device having a structure capable of satisfying both the operating characteristics of the device based on the bistability of the dielectric liquid crystal and the monodomain property of the liquid crystal layer.

The present invention is based on such knowledge, and more specifically, there is no step on the surface in contact with the liquid crystal layer, that is, by preventing abrupt changes in the film thickness of the liquid crystal layer, the initial alignment in the temperature lowering process. It is characterized in that it has a good property and forms a monodomain without alignment defects.

That is, the present invention relates to a liquid crystal device having a pair of substrates and a chiral smectic liquid crystal, and setting a gap between the pair of substrates small enough to suppress formation of a helical alignment structure of the chiral smectic liquid crystal. In the manufacturing method, a color filter unit is formed by arranging a plurality of color filter units on at least one substrate, and after applying a heat-meltable resin melted on the color filter layer,
By heating and pressurizing, the gap between the adjacent color filter units is filled with the heat-melting resin layer and the surface of the color filter layer is covered, and then the heat-melting resin layer is cured by cooling, and the cured heat-melting resin A method for producing a chiral smectic liquid crystal device, which comprises providing a transparent electrode and an orientation control film on the layer.

Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the basic structure of a ferroelectric liquid crystal device using the color filter substrate of the present invention. In FIG. 1, a ferroelectric liquid crystal element 1 has substrates 2 and 3 using transparent plates such as glass plates or plastic plates, and a ferroelectric liquid crystal 4 is sandwiched between them. Striped pattern-shaped transparent electrodes 5 and 6 forming a matrix electrode structure are arranged on each of the substrates 2 and 3, and alignment control films 7 and 8 are formed on the transparent electrodes. R (red), G
A heat-melting resin layer 10 is formed so that the (green) and B (blue) color filters are almost bound to each other, and a protective film or a flattening film 9 is further formed thereon. One pixel is composed of three color filter units consisting of R, G, and B.

In the substrate having the above structure, the step due to the thickness of the color filter and the depression between the pixels is corrected by the heat-meltable resin layer. Therefore, even if the transparent electrode and the alignment control film are sequentially formed on the pixel, the substrate surface Can be kept almost flat.

In the present invention, the step of the color filter substrate can be set to 1000 Å or less by the above-mentioned flattening, but it is preferably set to 500 Å or less. If the step exceeds 1000 Å, the liquid crystal element using the non-planarizing layer formed to have a thickness of 1200 Å or more, in particular, will have the edge line alignment defect shown in FIG.

Examples of the material of the alignment control film used in the present invention include polyvinyl alcohol, polyimide, polyamideimide, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea resin. , Resins such as acrylic resin, photosensitive polyimide, photosensitive polyamide, cyclic rubber photoresist, phenol novolac photoresist or electron beam photoresist (polymethylmethacrylate, epoxidized-1,4-polybutadiene, etc.) It can be formed selectively. Although the orientation control film 7 depends on the film thickness of the ferroelectric liquid crystal, it is generally set in the range of 10Å to 1 μm, preferably 100Å to 3000Å.

The color filter used in the present invention is not particularly limited as long as it does not cause problems such as discoloration and fading, pattern collapse, and cracks in the heating step (150 ° C. or less) of the heat-meltable resin, for example, , Azo, anthraquinone, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, pyrocholine, fluororubin,
A color filter made by forming a thin film of a quinophthalone-based coloring material by a vacuum deposition method, the coloring material, and, for example, natural proteins such as gelatin and casein,
Alternatively, polyvinyl alcohol, polyimide, polyamideimide, polyester, polycarbonate, polyvinyl acetal, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, acrylic resin, urethane resin, epoxy resin, or other resin, or photosensitive polyimide, photosensitive polyamide , A ring rubber type photoresist, a phenol novolac type photoresist, an electron beam photoresist and the like, and a color filter formed from a binder of a photosensitive resin. Although the layer thickness of the color filter is determined from the desired spectral characteristics, it is usually 0.
About 3 to 3 μm is desirable.

Examples of the heat-melting resin forming the heat-melting resin layer used in the present invention include polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl chloride acetate, polyamide, phenoxy resin, ethyl cellulose, polyisobutylene. , Polyester, terpene resin, rosin and its derivatives, petroleum resin, etc., either alone or in combination. Further, it is effective to use a resin having high transparency.

As a method for forming the heat-melting resin layer, after forming a color filter pattern on the substrate, a coating method such as spin coating, roll coating or dipping using a heat-melting resin solution is used to form a film having a thickness of about 0.5 to 5 μm. A thick resin layer is formed. Next, at the melting temperature of the heat-meltable resin, the melted resin was embedded in the gaps of the color filter pattern and the surface layer was flattened by a method utilizing heat treatment, heat press treatment, air blow, or the like. Then, return to room temperature and fix.

In some cases, a light-shielding layer may be provided between the color filter patterns for each color to improve the display characteristics.
A metal film having a light-shielding ability such as aluminum is deposited by a vapor deposition method or carbon black in a photosensitive polyamino resin,
A light-shielding resin layer in which a material having a light-shielding ability such as a complex oxide black pigment and metal powder is dispersed can be formed by a coating method.

Furthermore, when it is necessary to further increase the adhesiveness between the heat-fusible resin or color filter layer and the underlying substrate, the heat-fusible resin or color filter layer is first applied thinly on the substrate with a silane coupling agent. It is more effective to form the above or use a heat-meltable resin or a color filter layer in which a small amount of a silane coupling agent or the like is added in advance.

In addition, in order to protect the color filter layer and the heat-melting resin layer from various environmental conditions and to further flatten the surface, polyamide, polyimide are added to the heat-melting resin layer and the color filter layer surface. , Polyurethane, polycarbonate, silicon-based organic resin film is usually applied by spin coating or roll coating.
It can be provided as a protective film or a flattening film in a film thickness range of about 0.5 to 5 μm.

A particularly suitable liquid crystal material for use in the present invention is a liquid crystal having bistability and having ferroelectricity. Specifically, the chiral smectic C phase (Sm
Use C ^* ), H phase (SmH ^* ), I phase (SmI ^* ), J phase (SmJ ^* ), K phase (SmK ^* ), G phase (SmG ^* ) or F phase (SmF ^* ) liquid crystal You can

About this ferroelectric liquid crystal, "LE JOURNAL DE PHYSIQUE
LETTRES ") 1975, 36 (L-69)," Ferroelectric Liquid Crystals "(" Ferroelectri
c Liquid Crystals ");" Applied Physics Letters "1980,
No. 36 (11), “Submicro Second Bistable Electro-Optic Switching In Liquid Crystals” (“Submicro Second Bistable Ele
ctrooptic Switching in Liquid Crystals ");" Solid State Physics ", 1981 16 (141)," Liquid Crystals ", etc., and the ferroelectric liquid crystals disclosed therein can be used in the present invention. .

Specific examples of the ferroelectric liquid crystal include, for example, desiloxybenzylidene-p′-amino-2-methylbutylcinnamate (DOBAMBC), hexyloxybenzylidene-p ′.
-Amino-2-chloropropyl cinnamate (HOBACP
C), 4-o- (2-methyl) -butylresorcylidene-4'-octylaniline (MBRA8).

When an element is formed using these materials, since the liquid crystal compound is maintained in a temperature state in which it becomes a chiral smectic phase, the element can be supported by a block or the like in which a heater is embedded, if necessary.

[Operation] In the ferroelectric chiral smectic liquid crystal element of the present invention, since the thermofusible resin layer is provided at least in each gap of the color filter, the flatness of the substrate is improved, so that the surface in contact with the liquid crystal phase is provided. The liquid crystal phase sandwiched between the substrates having no step and having good flatness is gradually changed into a liquid crystal phase region from an isotropic phase to a liquid crystal phase. To form.

For example, the above-mentioned DOBAMB which shows a ferroelectric liquid crystal phase as a liquid crystal.
Explaining with C as an example, when gradually cooling from the isotropic phase of DOBAMBC, it undergoes a phase transition to a smectic A phase (SmA phase) at about 115 ° C. At this time, when the substrate is subjected to an alignment treatment such as rubbing or SiO ₂ oblique vapor deposition, a monodomain in which the molecular axes of liquid crystal molecules are parallel to the substrate and aligned in one direction is formed. Further, as the cooling proceeds, a phase transition to a chiral smectic C phase (SmC ^* phase) occurs at a specific temperature of about 90 to 75 ° C. depending on the thickness of the liquid crystal layer. If the thickness of the liquid crystal layer is about 2 μm or less, SmC ^*
The phase spiral unravels and exhibits bistability.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples.

Example 1 FIGS. 6 (a) to 6 (f) are process diagrams showing a second forming process including a color filter layer of R, G, B3 colors and a heat-fusible resin layer.

First, on a Corning # 7059 glass substrate 71, a blue colored resin material [Heliogen Blue L7080 (trade name, manufactured by BASF, CI No. 74160) that can obtain desired spectral characteristics is PA-1000C. (Commercial name, Ube Industries, Ltd., polymer content = 10%, solvent: N-methyl-2-pyrrolidone, pigment: polymer = 1: 2 blended) to produce a photosensitive colored resin material] spinner coating method Due to 1.5μ
The colored resin film 72 was formed by applying the resin to a thickness of m. (See FIG. 6 (a)) Next, the colored resin film 72 was prebaked at 80 ° C. for 30 minutes, and then exposed with a high pressure mercury lamp through a photomask 73 corresponding to the pattern shape to be formed. . (See FIG. 6 (b)) After the exposure, as shown in FIG. 6 (c), a dedicated developer (N-methyl-2-) that dissolves only the unexposed portion of the colored resin layer 72 having the photo-cured portion 72a. A developing solution containing pyrrolidone as a main component is developed using ultrasonic waves, and a dedicated rinse liquid (for example, a rinse liquid containing isopropyl alcohol as a main component) is used.
Then, post-baking was performed at 150 ° C. for 30 minutes to form a blue colored colored resin layer 74 made of a blue colored resin film having a pattern shape. (Fig. 6 (d)
Next, on the glass substrate on which the blue coloring pattern is formed, as the second color, a green coloring resin material [Lionol Green 6YK (trade name, manufactured by Toyo Ink Co., C.
I.No.74265) was dispersed in PA-1000 C (trade name, manufactured by Ube Industries, Ltd., polymer content = 10%, solvent: N-methyl-2-pyrrolidone, pigment: polymer = 1: 2 blend). A green patterned resin layer 75 was formed at a predetermined position on the substrate in the same manner as above except that a photosensitive colored resin material was used.

Further, as a third color, a red colored resin material [Irgazin Red BPT (trade name, manufactured by Ciba-Geigy, CINo. .71127) to PA-1000
C (Product name, Ube Industries, Polymer content = 10%, Solvent: N
-Methyl-2-pyrrolidone, pigment: polymer = 1: 2 blended) and prepared in the same manner as described above except that a photosensitive colored resin material is prepared. It is formed at the specified position of R, red, G
A colored pattern of three-color stripes of (green) and B (blue) was obtained. (See FIG. 6 (e)) Next, a methyl acetate solution of ethylene-vinyl acetate copolymer resin was applied on the obtained color filter with a spinner to a layer thickness of 1.5 μm, and heat-pressed at about 150 ° C. Then, the gap between the color filter pixels was filled with the heat-melting resin 77, and then the temperature was returned to room temperature to form a layer to which the color filter was bound (see FIG. 6 (f)).

On the color filter pattern obtained in this way,
A transparent resin material similar to that used for the colored resin material as the protective film or the flattening film 78 [PA-1000 C (trade name, manufactured by Ube Industries, Polymer content = 10%, solvent: N-methyl-2-pyrrolidone )] Was formed by a spinner coating method to a film thickness of about 0.5 μm. (See FIG. 6 (f)) As described above, it was possible to form the coplanarized color filter substrate.

Next, as shown in FIG. 1, ITO was formed into a film with a thickness of 500 Å by a sputtering method to form a transparent electrode 5. A polyimide forming solution (Hitachi Chemical Industries "PIQ") was applied as an orientation control film 7 on this with a spinner rotating at 3000 rpm.
Heating was performed at 0 ° C. for 30 minutes to form a 2000 Å polyimide film. Then, the surface of this polyimide coating film was rubbed.

The color filter substrate thus formed and the opposing substrate 3 were attached to each other to form a cell set, and a ferroelectric liquid crystal was injected and sealed to obtain a liquid crystal element. When this liquid crystal element was observed with a crossed Nicols polarization microscope, it was confirmed that the liquid crystal molecules inside did not have alignment defects.

[Effects of the Invention] As described above, according to the present invention, a large step is generated by filling the difference in film thickness of the color filter layer on the substrate and the gap between the color filter pixels with the heat-melting resin. In addition, by providing a protective film / planarizing film as needed, it is possible to eliminate minute steps between the color filter pixels and prevent the occurrence of alignment defects. It is possible to provide a chiral smectic liquid crystal element having a color filter that can sufficiently exhibit the characteristics of a ferroelectric liquid crystal.

[Brief description of drawings]

FIG. 1 is a sectional view showing the basic constitution of a ferroelectric liquid crystal device according to the present invention, FIGS. 2 and 3 are perspective views schematically showing the ferroelectric liquid crystal according to the present invention, and FIG. Is a cross-sectional view of a conventional ferroelectric liquid crystal element, and FIG. 5 is a schematic explanatory view showing the state of alignment defects appearing in the conventional ferroelectric liquid crystal element.
6 (a) to 6 (f) are process diagrams showing the process of forming the color pixel of the present invention. 1,40 …… Ferroelectric liquid crystal element 2,3,41,42,61,71 …… Substrate 4,47 …… Ferroelectric liquid crystal 5,6,43,44 …… Transparent electrode 7,8,45, 46 …… Orientation control film 9,48,78 …… Protective film (flattening film) 10 …… Heat-melting resin layer 77 …… Heat-melting resin

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Miki Tamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tatsuo Murata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Nobuyuki Sekimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshiki Kikuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 56) References JP-A-61-16624 (JP, A) JP-A-61-100728 (JP, A) JP-A-61-166523 (JP, A)

Claims (2)

[Claims] 1. A liquid crystal device comprising a pair of substrates and a chiral smectic liquid crystal, wherein the distance between the pair of substrates is set small enough to suppress the formation of a helical arrangement structure of the chiral smectic liquid crystals. In the method, a plurality of color filter units are arranged on at least one substrate to form a color filter layer, and a heat-melted resin which is melted by heat is applied onto the color filter layer, and then heat and pressure are applied to the adjacent colors. The gap between the filter units is filled with a heat-meltable resin layer and the surface of the color filter layer is covered, and then the heat-meltable resin layer is cured by cooling,
A method for producing a chiral smectic liquid crystal device, comprising providing a transparent electrode and an orientation control film on the cured heat-meltable resin layer. 2. The method for producing a chiral smectic liquid crystal device according to claim 1, wherein a transparent electrode is provided after forming an organic resin film on the cured heat-meltable resin layer.