JPS6230222A - Production of smectic liquid crystal device - Google Patents

Abstract

PURPOSE:To decrease the number of dislocations of the liquid crystal material packed in a panel as far as possible by injecting the liquid crystal material into the panel then reheating up the liquid crystal material up to the smectic A phase then subjecting the same to slow cooling. CONSTITUTION:The liquid crystal material in the cell takes the smectic C phase while forming domains in the process when the liquid crystal material changes from the liquid phase to the smectic A phase if the liquid crystal material is slowly cooled by natural cooling after the liquid crystal cell is constituted by filling said material into the cell. An injection port 3 is hermetically closed by a sealing material to com plete the liquid crystal panel upon thorough cooling of the liquid crystal material injected into the panel. Such liquid crystal panel is contained into a thermostatic chamber and is again heated until the liquid crystal material packed into the cell attains the smectic A phase. The heating of the liquid crystal panel is stopped at the point of the time when all the liquid crystal molecules are arrayed in the smectic A phase. If the crystal panel is gradually cooled to the temp. at which the smectic phase is attained in succession thereto, the liquid crystal molecules in the panel begin to simultaneously tilt so as to have an angle theta with the normal of the layer and the liquid crystal molecules in the liquid crystal panel change to the smectic C phase. The dislocations generated in the stage of injection are mostly annihilated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for manufacturing a chiral smectic liquid crystal device.

(Prior art) In recent years, liquid crystal devices using chiral smectic C phase have been developed to have high-speed response and memory retention properties, so they are used for display devices, cameras, and printers. For example, P-decyloxybenzylidene-P-amino-2-methybutylcinnamate is widely known, and its liquid crystal molecules have a constant azimuthal angle θ as shown in Figure 6. Layer L1. L2. L3. They are arranged in a twisted spiral structure for each L4.

By the way, a liquid crystal compound having this chiral smectic C phase is injected between two substrates A and H having a gap (for example, about l#Lm) that is smaller than the interpolation period (usually used) to form a liquid crystal compound. When a cell is constructed (Fig. 7A), the liquid crystal molecules lose their helical structure and form domains with molecular axes parallel to substrates A and H, tilted at an angle θ clockwise from the normal direction of the layers, and a domain counterclockwise. It has a mixture of domains tilted by θ, or 10 degrees, around it (as shown in the figure), and it also has an electric dipole in a direction perpendicular to the 1-molecule axis.

Therefore, if one domain has an electric dipole pointing -L with respect to substrates A and H, the other domain will have an electric dipole pointing downward, thus creating an electric field between substrates A and B. When an electric field is applied, all the liquid crystal molecules are aligned at a position tilted either 10 or 10 from the normal direction of the layer, and when an opposite electric field is applied, the liquid crystal molecules are also reversed and tilted at 10 or 10. 〇 Arrange them in a tilted position all at once.

When polarizing plates are placed on both sides of this cell and an electric field is applied,
The movement of liquid crystal molecules creates bright and dark states, allowing it to function as a display panel or optical shutter (
(FIG. 8), the liquid crystal panel constructed in this manner has an extremely fast response speed of microseconds and an excellent property of retaining the pattern once displayed even after the electric field is removed.

This smectic liquid crystal panel is made by injecting a ferroelectric liquid crystal material into a liquid phase between substrates, forming monodomains in the smectic A phase while slowly cooling, and then cooling to the chiral smectic C phase to form domains. It is configured to grow and have uniform display characteristics.

However, since the surface of the panel substrate has various anisotropies due to its processing process, there is a problem in that a large number of dislocations occur during the formation of monodomains, which deteriorates the display quality of the liquid crystal panel.

(Objective) In view of these problems, an object of the present invention is to propose a method for manufacturing a smectic liquid crystal device that can reduce as much as possible the number of dislocations in a liquid crystal material filled in a panel.

(Means for Solving the Problem) That is, the present invention is characterized in that after the liquid crystal material is injected, the temperature is raised again to the smectic A phase, and then the temperature is slowly cooled.

(Structure) Therefore, details of the present invention will be described below based on illustrated embodiments.

FIG. 1 shows an embodiment of a cell constituting a smectic liquid crystal panel used in the present invention, and reference numeral 1 in the figure denotes one substrate constituting the liquid crystal display panel, which is made of a transparent conductive material. , segment electrodes 1a, 1a, 1a...
A thin film of polyimide is provided by printing or dipping on the surface of an electrically insulating transparent plate 1b such as glass on which... is formed to form a random horizontal alignment film layer IC having uniform orientation in all directions in the plane of the substrate 1. It is composed of

Reference numeral 2 denotes the other substrate constituting the liquid crystal display panel, which is an electrically insulating transparent plate on which common electrodes 2a, 2a, 2a, . . . are formed orthogonally to the segment electrodes 1a, la, la, . A polyimide thin film is provided on the surface of the polyimide film 2b, and the surface of this thin film is rubbed in one direction to form a uniaxially oriented film layer 2c which is oriented in only one direction. These two substrates 1.2 are arranged in parallel with the random horizontal alignment film layer IC and the uniaxial alignment film layer 2c facing each other with a gap smaller than the helical pitch of the liquid crystal compound, and have a liquid crystal injection port on the negative side. 3 are bonded together with a sealant 4 to form a cell.

After forming a liquid crystal cell by filling the cell thus formed with a liquid crystal material using a widely known method, when this cell is gradually cooled by natural cooling, the liquid crystal material in the cell 6 becomes
In the process of changing from the liquid phase to the smectic A phase, it becomes the smectic C phase while forming domains (second diagram),
When the injected liquid crystal substance has sufficiently cooled, the injection port 3 is sealed with a sealing material to complete the liquid crystal panel. The liquid crystal panel at this point contains a large number of dislocations between domains, so the display quality is very low (FIG. 5).

When this liquid crystal panel is placed in a constant temperature oven and heated again until the liquid crystal substance filled inside the cell reaches the smectic A phase (Fig. 2 ■), the liquid crystal substance in the cell is replaced by the liquid crystal substance formed during the panel construction described above. While maintaining the layered structure, all the liquid crystal molecules are aligned so that their long sleeves are parallel to the substrate while pulling the disordered liquid crystal molecules at the dislocation site into the molecular alignment of the domain (Fig. 3 ■). Needless to say, in this smectic A phase, the layers of liquid crystal molecules are aligned in the direction perpendicular to the substrate. When all the liquid crystal molecules are aligned in the smectic A phase, heating of the liquid crystal panel is stopped, and then the liquid crystal panel is gradually cooled down to the temperature at which it becomes the smectic C phase (Fig. 2 ■). The liquid crystal molecules all begin to tilt at an angle θ with respect to the layer normal.

Needless to say, the temperature drop rate during this cooling process is extremely low compared to the movement speed of the liquid crystal molecules, so the liquid crystal molecules in the liquid crystal panel enter the smectic C phase without disrupting the alignment relationship in the above-mentioned process. (FIG. 3I) As a result, most of the dislocations generated during implantation disappear when the smectic C phase is reached.

[Example] P-decyloxybenzylidene-P-amino-2-methybutylcinnamate, a strongly inductive liquid crystal substance, was heated to a temperature of 11
When we observed a liquid crystal panel produced by heating it to 7°C, injecting it into a liquid phase into a cell, and cooling it naturally using a polarizing microscope, we found that dislocations had occurred over the entire surface of the panel, as shown in Figure 7. The density reached as high as 1200 pieces per mrn'.

The liquid crystal panel described above was placed in a constant temperature bath, and the temperature was raised again to 93°C, the temperature at which 2-methylbutyl-P (P-n-decyloxybenzylibuamino) changes to the smectic A phase, and then slowly cooled. However, as shown in FIG. 5, most of the dislocations have disappeared, and the density has drastically decreased to about 250 dislocations per mrn'.

In the above-mentioned examples, P-decyloxybenzylidene-P-amino-2-methybutylcinnamate was explained, but pyrimidine-based liquid crystal compounds represented by the general formula % and 5-4-
(A ferroelectric chiral smectic liquid crystal compound made by mixing equal proportions of 2-methylbutyloxyresolcylidene-4-alkyl n-octylaniline and Pn-cutylphenyl-P'-6-methyloctyloxybenzoate. Even when used, after filling the cell,
Heating to a temperature at which each liquid crystal substance becomes smectic A phase,
Dislocations can then be eliminated by a step of slow cooling.

In addition, in the above embodiment, a substrate having a uniaxially oriented film layer and a random horizontally oriented film layer formed of polyimide on the surface was used, but the -axis oriented film was made of an organic material such as polyvinyl alcohol, fluororesin, or silane. Membrane and S i 02
Substrates formed by oblique vapor deposition, random horizontal alignment films, organic films such as epoxy, polyvinyl alcohol, fluorine resin, polyurethane, silane, phenol, urea, etc., inorganic films formed by vapor deposition of 5i02, MgF2, etc. It has been confirmed that the same effect can be obtained when using a substrate formed by the following methods.

(Effects) As explained above, in the present invention, after the liquid crystal substance is injected into the cell, the process of heating the liquid crystal substance again to the smectic A phase and then gradually cooling it is added.
A smectic liquid crystal device with high display quality can be realized by effectively eliminating dislocation that occurs when filling a liquid crystal material.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a perspective sectional view and a sectional view of an apparatus showing one embodiment of a liquid crystal cell used in the present invention, respectively, and FIG. 2 is a temperature cycle of a liquid crystal material in a manufacturing method according to the present invention. FIG. 3 is an explanatory diagram showing the state of molecular arrangement from above the substrate showing the phase transition during the reheat treatment process. FIG. 4 is an explanatory diagram showing the dislocation of the liquid crystal panel after the heat treatment according to the present invention. Figures 5 and 5 are explanatory diagrams showing dislocations in conventional devices, Figure 6 is a schematic diagram showing the molecular arrangement of chiral smectic liquid crystals, and Figures 7 (a) and (b) respectively define the cell gap between liquid crystal molecules. Figure 8 is a schematic diagram showing the arrangement of molecules when the helical pitch is lower than that of smectic A.
FIG. 2 is an explanatory diagram showing the relationship between phase domains and polarization. 1...Substrate 1a...Electrically insulating transparent plate IC...Random horizontal alignment film layer 2...Substrate 2a...Electrically insulating transparent plate 2C...-Axis alignment Membrane layer 3... Inlet 4... Seal material Figure 1 (a)? b (b) Fig. 2 I [■ Fig. 3 ■

Claims (1)

[Claims] A step of sealing a ferroelectric chiral smectic liquid crystal compound into a cell structure formed by opposing two substrates and cooling it to a smectic C phase, and converting the liquid crystal substance sealed in the cell structure into a smectic A phase. After heating to
A method for manufacturing a smectic liquid crystal device, which comprises a step of cooling to a smectic phase.