JPS58109581A - Color liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a color liquid crystal display element which does not have dependence on visual angles, and has good dynamic stability and a long life, by enclosing a nematic liquid crystal contg. a dichroic colorant and a quaternary ammonium salt in a space between substrates subjected to a vertical orientation treatment. CONSTITUTION:In a color liquid crystal display element in which a nematic liquid crystal having a negative dielectric anisotropy and contg. a dichroic colorant and an ionic substance of a quaternary ammonium salt is enclosed in a space between two substrates and either or both of these substrates is/are subjected to a vertical orientation treatment, a compd. of the formula (wherein R1-R4 are each alkyl, fluoroalkyl, at least one of R1-R4 is a 7-20C alkyl; X<-> is halogen anion, nitro-substd. benzoate anion) is used as said quaternary ammonium salt. By using a display mode of a dynamic scattering mode in this color liquid crystal display element, positive display with high display contrast can be obtd. without using a polarizing plate.

Description

[Detailed Description of the Invention] Conventionally, a color display mode using a liquid crystal has been used.
2. Various types are known. Parable I/, (, υr Zhao,
The White-Taylor type liquid crystal is a nematic liquid crystal containing an optically active substance and a dichroic dye and having positive vs.
It is formed by interposing a substrate IulK which has been subjected to a similar process.

The display mode of this liquid crystal is that when the pressure is off (no electric field), it is in a tinted state, and when the pressure is on ('[, daytime), the molecules are aligned perpendicular to the substrate surface. A blank negative display is displayed. This Ibumo 1 is capable of displaying bright colors without the need for Mitsuya Kai.

It has advantages such as a wide viewing angle, but because it is a negative display, the display is a little less glossy. It has disadvantages such as being somewhat disadvantageous in terms of display quality.

Other display modes include negative! containing dichroic dyes! There is a method in which a nematic liquid crystal having 8-tolerance anisotropy is aligned obliquely to the substrate surface, and a polarization root is distributed to the front curve of one substrate surface. In this case, when the voltage is 01''F, the molecule becomes basic and becomes a slightly slanted white 1 tari-like jI, and the slightly 7tr-colored white outline is 75: Pak-Kyo.

And when 'drunk1t-ON, VCItd, molecule or group 41+j
. . . Since it is horizontal to l, it becomes colored due to the polarizing action of the polarizing plate. This display mode has the advantage that the display is easy to see because it is a positive display, but it requires a polarizing plate, which makes it costly, and the reliability of the display element depends on the durability of the polarizing plate under high temperature and humidity conditions. There are drawbacks, such as the fact that when the voltage is turned off, the molecules are arranged at an angle with respect to the substrate surface, resulting in a slightly colored state, resulting in poor display contrast as a whole.

Alternatively, the above-mentioned White-Taylor m display mode may be reversed, that is, a mode in which a liquid crystal containing a dichroic dye and having negative β' anisotropy is vertically aligned between the substrates. It is also known that the display mode consists of a body-type tube (based on vinyl chloride tubes, etc.).
1! As long as a reflective sheet with a flat surface is used, in order to suppress coloring when the voltage is OFF, the dye concentration must be extremely low, and the display contrast when the voltage is ON cannot be obtained very high. This is considered to be correlated with the inability to maintain a large cholesteric pitch when the voltage is turned on.

The present invention has been made in view of the above points, and its purpose is to use a display mode that utilizes a change in the molecular arrangement of a dichroic dye induced by a dynamic scattering mode (DAM). To provide a color liquid crystal display element which can provide a positive display with high display contrast without using a polarizing plate, is free from viewing angle dependence, has good operational stability, and has a long life.

Regarding the display mode of the DAM of the present invention, as shown in FIG.
1. (4+ or cuffed. That's sweet, jackhammer; board (1
) and (2), the liquid crystal (5) is sealed. Liquid crystal (51 is a mother liquid crystal having negative dielectric anisotropy, an optically active substance is added thereto, and a dichroic dye and an ionic substance η are added to g5
It has been added. The opposing surfaces of both threads &fl+ (2) are subjected to vertical alignment treatment, so that when electricity is applied, the long axis of the liquid crystal molecules and 2
The colored dye is placed on the substrate il+, +21 in a semicircular manner - this increases the light transmittance, making the base bright and clean.
It becomes b-. In this state, the color of the dichroic dye does not appear. Therefore, by applying a voltage of tOh6 between the electrodes (3) and (4), the state of the liquid crystal (5) in the gap between the working electrodes is determined by the dipole moment of the liquid crystal molecules as shown in the same figure (bl). At the same time, the ionic pickup agent added to the liquid crystal causes an ion flow that causes the molecules to rotate, resulting in a disordered state.2.
Because color dyes also become disordered together with liquid crystal molecules,
The incident light is absorbed by the dichroic dye to produce a colored display. Since the dichroic dye is tilted at various angles in the above state, the colored display is easy to see from any direction, resulting in a positive display with high contrast.

Hereinafter, the present invention will be explained in more detail based on Examples.

〔Example〕

An indium oxide-based transparent electrode is formed in a predetermined shape on a glass substrate, and then a silane coupling agent is applied and a vertical alignment process is performed. Next, two glass substrates are pressed against each other with a gap of 10 μm maintained to produce a liquid gloss-6-crystalline cell. Next, a liquid crystal substance having the composition shown below was injected into the liquid crystal cell and sealed to produce a color liquid crystal display element.

Mother liquid crystal: 90.2 wt% Negative attraction cyclohexanecarboxylic acid ester derivative Optically active material: 9 v, t h Benzoic acid with an alkoxy group having an asymmetric carbon at the end, represented by the following structural formula Ester derivative OHs OOOHs (*marked is asymmetric carbon) Dichroic dye 0.5wt 1.4
- Naphthylene derivative: 1.4-Phenyline derivative: ionic substance: 3.3'wt% quaternary ammonium salt The optical changes of the obtained color liquid crystal display element are shown in FIG. In the same figure, the horizontal axis represents the voltage applied to the electrodes of the liquid crystal display element, and the vertical axis represents the brightness of the liquid crystal display element. This shows the case where the optically active substance was not added to the flow-out side. Note that the brightness # was detected by the voltage generated in the phototransistor. As is clear from the figure, by adding the optically active substance r 2 :yt, the threshold value can be made steeper at a lower voltage.

According to experiments, the quaternary ammonium group, which is an ionic substance, has a general formula of a loalkyl group, and
1 (at least one of 1 to R4 has 7 or more and 20 or less carbon atoms; X- is a halogen anion or a nitro-substituted benzoic acid anion); It was confirmed that the device has good operational stability and has a long shelf life. This is thought to be due to the fact that the molecules of the ionic substance are long to some extent (7 or more carbon atoms) and the core molecules have anisotropy, resulting in a stable current flow. However, if the number of carbon atoms exceeds 20, the resistance of the ionic substance increases and the display contrast deteriorates.

For example, the quaternary ammonium salt may have the following structural formula.

+11 In formulas (1)2 to (6), X Fi halokene anion or di) o-substituted benzoic acid anion, or (
Particularly good results were obtained with the quaternary ammonium salt of formula 7).

As described above, according to the present invention, by using the DSM display mode, a positive display with high display contrast can be obtained without using a polarizing plate. Because it is added,
This has the remarkable effect of providing a color liquid crystal display element with good operational stability and long life.

[Brief explanation of the drawing]

FIG. 1 relates to a color liquid crystal display element of the present invention.
l is a cross-sectional side view of the main part when no voltage is applied;
FIG. 2, which is a cross-sectional side view of a main part when an i voltage is applied, is an explanatory diagram illustrating optical changes in a color liquid crystal display element when an optically active substance is added and when an optically active substance is not added. Ill, (2+ glass substrate, (3), (4) transparent electrode, (5) liquid crystal material JP-A-58-109581 (4) Figure 1 (a) (1)) 1ζ catty (V)

Claims (1)

[Scope of Claims] At least one of the two substrates is subjected to vertical alignment treatment, and in the gap between the substrates, an ionic substance of a dichroic dye and a quaternary ammonium salt and Kanakura In a color liquid crystal display device in which a nematic liquid crystal is sealed, the general formula of the quaternary heptammonium salt is One is a color oil leakage indicator characterized by comprising a carbon number of 7 or more and 20 or less.