JPS60252686A - Liquid crystal substance for heat addressing liquid crystal element - Google Patents

Abstract

PURPOSE:A liquid crystal substance for heat addressing liquid crystal elements, containing a mixture of specific biphenyl compounds, and having a wide liquid crystal phase temperature range and high performance. CONSTITUTION:A liquid crystal substance, containing (A)(i) a substance expressed by formula I and/or (ii) a substance expressed by formula II as main components and further (B)(i) a substance expressed by formula III and (ii) a substance expressed by formula IV as further main components. For example, the weight ratio between the components (i) and (ii) of the component (B) to be used is 77.2:22.8, 75:25, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to a liquid crystal material used in a thermal writing liquid crystal element that utilizes the thermo-optic effect of liquid crystal.

(2) Prior art and its problems When a thin layer of cholesteric liquid crystal or smectic liquid crystal exhibiting transparent liquid crystal composition i is partially heated and rapidly cooled,
The transition of the opaque liquid crystal group whose portion generally scatters light is known as the thermo-optic effect of the liquid crystal.

In addition, several liquid crystal devices have been proposed that take advantage of this phenomenon and write information by applying a temperature change to a portion of the liquid crystal cell and making that portion opaque. For example, a direct-view display element in which an image is written and viewed directly, a light valve element used for a projection display in which the written image is projected and viewed, and written information is displayed electrically or optically. It is a recording element etc. in a readable format. In addition, there are several methods for writing information, such as irradiating a laser beam to cause a temperature rise in the irradiated area, and using Joule heat generation in a resistor to raise the temperature. It is being For the sake of simplicity, we will explain below the details of a liquid crystal light valve element used in a projection display device in which an image is written by irradiating a liquid crystal cell with a laser beam, and the written image is enlarged and projected using a separate optical system. This will be explained using a case as an example.

Initially, the thermal writing liquid crystal light valve had the general formula 0nHt n
+1-@-N=He A so-called Schiff base-based liquid crystal material, represented by the symbol ON, was used.

This is because no liquid crystal material other than Schiff base-based materials has been found that exhibits a smectic phase at the operating temperature of a liquid crystal light valve, that is, around room temperature, and has an appropriate phase transition temperature. Here, the appropriate phase transition temperature is related to the temperature Tc at which the liquid crystal transitions to an isotropic liquid phase, and T
If c is too high, the temperature rise required for writing will increase,
Disadvantages arise in terms of power consumption and writing speed, and if Tc is too low, the liquid crystal molecular orientation order degree decreases due to the fact that the liquid crystal temperature in a steady state after writing is close to the phase transition temperature Tc. This causes the inconvenience of reduced contrast. Regarding such Schiff base-based liquid crystal materials, Taylor et al. of Bell Laboratories reported in the Journal of Applied
This is reported in Fix, Vol. 45, No. 10. However, it is widely known that Schiff base-based liquid crystal materials are prone to hydrolysis, and therefore thermal writing liquid crystal devices using this type of liquid crystal material have short lifespans and lack reliability, especially in terms of moisture resistance. There is. Therefore, subsequent attempts were made to improve liquid crystal materials, and chemical E was stable, with the general formula R-@-@-ON (R
A liquid crystal material of biphenyl threads, represented by an alkyl group or an alkoxy group, was created. Thank you for visiting International Business φ Machines Co., Ltd., R-@-@
219 of ``The Fixtures and Chemistry of Liquid Crystal Devices,'' published by Blenheim Publishing Co., Ltd., reports that a mixed liquid crystal consisting of the selected three components is optimal for use in thermal letter liquid crystal light valves. It is published on pages 239 to 239. Also, Thomson S.
Dubois of NIS-F, on pages 131 to 138 of Volume 3 of Anal de Physique (published in 1978), conducted a comparative study of mixed liquid crystals consisting of components selected from R-(Tobe0-ON'). So, R is 08 H1?, Co
It has been reported that a mixed liquid crystal consisting of three components, Hn, c, and HIo COO, is optimal for use in a thermal writing liquid crystal light valve. In this way, improvements in liquid crystal materials have been made, and they are no longer short-lived or short-lived, as in the case of early Schiff base liquid crystals.
Disadvantages such as low reliability have been overcome. However, all of the known liquid crystal materials mentioned above are unsatisfactory, particularly in terms of liquid crystal phase temperature range. For example, the 011 Ht recommended by Dewey mentioned above, (c dobe 0-ON and C5
Even in a mixed liquid crystal with ゜I(tt-itobe>'oN), the crystal transition temperature is about 12℃, and the recommended temperature by Devore is exactly 8℃.A liquid crystal light valve using such a liquid crystal material is During operation or storage, if the temperature drops below the crystal transition temperature of the liquid crystal material, that is, below about 10 degrees Celsius, the liquid crystal material will crystallize and become inoperable.Of course, even if the temperature recovers, the crystallization history will cause the liquid crystal molecules to change in alignment. There is an inconvenience that defects occur and the display quality deteriorates.It is extremely inconvenient for practical purposes that the lower limit of storage temperature is limited to about 10℃, and it is well known that a temperature of about -10℃ is required. Unfortunately, the reality is that a satisfactory liquid crystal light valve cannot be obtained by using existing liquid crystal materials.However, the present inventor has investigated in detail the relationship between the transition temperature of liquid crystal materials and display performance. As a result of many studies and experiments on many liquid crystal materials, we discovered a liquid crystal material that has a wide range of liquid crystal phase temperatures and can realize high-performance devices that were previously unobtainable, resulting in the present invention. be.

(3) Object of the Invention An object of the present invention is to provide a liquid crystal material for a thermal writing liquid crystal device having excellent performance.

(4) Structure of the Invention The liquid crystal material for a thermal writing liquid crystal element of the present invention is used for a thermal writing liquid crystal element of a type in which information is written by partially applying heat to the liquid crystal substance, and has the chemical formula: o, H1?
Contains a substance represented by -@-@-ON as a main component, a substance represented by the chemical formula C8゜H7, -o-8-CN, a substance represented by the chemical formula 08Hl 000-@-@-6N, and a chemical formula It is characterized by being a mixed liquid crystal containing both or either of the substances represented by 09H1°000-@-@-ON as a main component.

(5) Examples and effects Next, the present invention will be described in detail with reference to the drawings.

The figure shows a substance represented by the chemical formula C3H17-o-@-ON (hereinafter referred to as 00B) and a chemical formula 0. oH,, -@-@-
The substance represented by ON (hereinafter referred to as DOB) is mixed with a liquid crystal for two people (hereinafter referred to as N8P9) in a weight ratio of 77.2:22.8, and the chemical formula 0°H1 is added.
9000-@-@-ON (hereinafter referred to as NB)
FIG. 3 is a diagram showing the results of measuring the phase transition temperature of mixed liquid crystals prepared by mixing BP) in various proportions. In the figure, I, N, S, and 0 indicate the regions where the isotropic liquid crystal phase, nematic liquid crystal phase, smectic liquid crystal phase, and solid phase appear, respectively, and the solid line on the 8-0 boundary line is when the temperature increases, and the chain line is when the temperature decreases. indicates the value of As is clear from the figure, for example, N5P9 and N
The crystal transition temperature of a mixed liquid crystal (hereinafter referred to as N 8 P 10) prepared by mixing EBP and EBP at a weight ratio of 75:25 is -33.0°C1. Even when the temperature rises -
The temperature is extremely low at 12.0°C, and liquid crystal light valves using N8P10 do not cause any problems even at storage temperatures of -10°C. In addition, the liquid phase transition temperature Tc of N8P10 is 47.2
℃, the nematic phase temperature width is 3.4°C, and G) deviation is also optimal for writing when used in a liquid crystal light valve. T11 That is, as an example, an image written on a liquid crystal light valve using N 8 P 10 by irradiating an alkone laser beam with a light intensity of 300 mW for 1 μs per point,
Using a xenon lamp with a light intensity of lkw (G) and a gain of 6.4
When projected onto the screen, the brightness was 1QQft.
-L, a contrast of 10:1 was obtained. This is an excellent display performance compared to a conventional liquid crystal light valve using a liquid crystal material, which has a contrast of 7:1 under the same writing conditions. Note that, without being limited to N S P 10, extremely excellent performance similar to that of N 8 P 10 was observed in many mixed liquid crystals having different component ratios of OOB, DOB, and NEBP. Also, instead of NEBP, the chemical formula O8H
17000-=>◇)=Substance represented by ON (hereinafter referred to as 0
(denoted as EBF), further NgBP and UEBP are used.
A similar effect was observed when used in combination. On the other hand, as a comparative example, chemical formula 0. H8゜-◇X■
) using the substance represented by ON, and adding 00B and NEB to it.
When a mixed liquid crystal containing P was prepared, a crystal transition temperature of -25.2°C was obtained when the temperature was lowered, but was as high as 5.9°C when the temperature was increased, which was insufficient. Also, 2i mixed liquid crystal of OOB and NBBP that does not contain DOB or O
Both OB and 0EBF mixed liquid crystals have crystal transition temperatures as high as 16°C or 12°C, which is insufficient. C
A liquid crystal light valve using the liquid crystal material of these comparative examples was installed, and writing and display were performed under the same conditions as in the above-mentioned example in rows 7 and 7.
The contrast of i' was only as low as about 7:1.

The above example uses a liquid crystal light valve for a projection display device in which an image is written by irradiating a liquid crystal cell with a laser beam, and the written image is enlarged and projected using a separate optical system for viewing. Although the present invention has been described, it goes without saying that the liquid crystal material of the present invention has excellent performance when thermal writing is performed by other means, and when used as a direct-view display element, a memory element, or other elements. .

As explained above, according to the present invention, a liquid crystal material for a thermal writing liquid crystal element having excellent performance can be obtained.

[Brief explanation of drawings]

The figure is a diagram showing the relationship between the mixing ratio of mixed liquid crystals and the phase transition temperature for explaining the present invention. In the figure, I, N, S,
O indicates a region where an isotropic liquid phase, a nematic liquid crystal phase, a smectic liquid crystal phase, and a solid phase appear, respectively. 1 patent attorney Fu Uchiteru

Claims (1)

[Claims] Chemical formula 0. The substance represented by H,, γC00 (possible 8)-cN and the chemical formula 0. It contains as a main component either or both of the substances represented by H1, COO+ON, and furthermore, in addition to the above main components, it has a chemical formula of 0. H,t
X! The substance represented by door 10'N and the chemical formula C0oH21
A liquid crystal material for a thermal writing liquid crystal element, characterized in that it also contains a substance represented by BeiON as a main component.