JPS61275384A - Liquid crystal substance for thermal writing liquid crystal element - Google Patents

Abstract

PURPOSE:To provide the title compsn. which is wide in smectic liquid crystal temp. range and exhibits a high degree of dielectric anisotropy and enables erasion of written information at low voltage when used in thermal writing liquid crystal elements, which comprises specific two kinds of substances. CONSTITUTION:At least one substance selected from among compds. of the formula I (wherein R1 is a 1-8C straight-chain alkoxy) is mixed with at least one compd. selected from among compds. of the formula II (wherein R2 is an 8-12C straight-chain alkyl or straight-chain alkoxy) to obtain the title compsn.

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 a transparent liquid crystal structure is partially heated and rapidly cooled,
The phenomenon in which that portion transitions to an opaque liquid crystal structure that generally scatters light is known as the thermo-optic effect of 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 to make 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 written information is displayed electrically or optically. It is a recording element etc. in a readable format. In addition, there are several known 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 cause a temperature rise. ing. 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 used the general formula % formula %. A so-called Schiff base-based liquid crystal material was used.

This is because no liquid crystal material other than Ship 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 occur in terms of power consumption and writing speed, and if Te 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 Physics, 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 a chemically stable biphenyl liquid crystal material represented by the general formula R-Q-G-ON (R is an alkyl group or an alkoxy group) was created. Internashi, Dewey of Null Business Machines, Inc. (R-Q-C)
-ON structure where R is O@R17t C@RBI,
010H21HCBB R23HC@R170HO,
A report was published in ``The Physics and Chemistry'' published by Plenum Publishing Co., Ltd. that a mixed liquid crystal consisting of three components selected from the group of liquid crystal materials R, , O is optimal for use in thermal writing liquid crystal light valves. "Of Liquid Crystal Devices", pages 219 to 239. In addition, Dubois of Thomson C.N.F., in the third volume of Anal de Physique (published in 1978), pages 131 to 138, describes the structure of R()(ΣON as CaEty, C!*Rte. , Ca
HyOl 0sHxyO-Os&7COOtCoHo+
000, R is O@k11. +0*Ht
It has been reported that a three-component mixed liquid crystal having the following properties: o, 0oH1oC00 is optimal for use in a thermal writing liquid crystal light valve. In this way, improvements in liquid crystal materials have been made,
The disadvantages of early Schiff base liquid crystals, such as short life and 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, caHtr<n(nC
The crystal-liquid crystal transition temperature Tm is about 12°C even in the mixed liquid crystal of N and 01° island-shaped ON.
Even in the case of a mixed liquid crystal consisting of the three components SO, H1°000-G-<SON, Tm is 8°C. When a liquid crystal light valve using such a liquid crystal substance is operated or stored, if the temperature drops below the Tm of the liquid crystal substance, that is, below about 10°C, the liquid crystal substance will crystallize and become inoperable, and even if the temperature recovers afterwards. Due to the crystallization history, defects occur in the alignment of liquid crystal molecules, resulting in the disadvantage of deteriorating the display image quality. It is well known that the lower limit of storage temperature is limited to about 10°C, which is extremely inconvenient in practice, and that about -10°C is required. The reality is that a satisfactory liquid crystal light valve cannot be obtained by using existing liquid crystal materials. However, the inventors of the present invention have investigated in detail the relationship between the transition temperature of liquid crystal materials and display performance, and have conducted experimental studies on numerous liquid crystal materials. The present invention was achieved by discovering a liquid crystal material that enables the device to be realized.

(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) Specific means for solving the problems The liquid crystal material for thermal writing liquid crystal elements of the present invention is used in thermal writing liquid crystal elements in which information is written by partially applying heat to the liquid crystal material. and the chemical formula R1◇coo
<> NC! SCR1 contains as a main component one or more substances represented by a straight chain alkoxy group with carbon number n = 8.9.10, and furthermore, in addition to the above main component, it contains a substance with the chemical formula nt 0N (Rz is carbon number n, = 13,9
It is characterized in that it is a mixed liquid crystal containing as a main component multiple types of substances represented by +10+11t12 linear alkyl groups or linear alkoxy groups.

By adopting the above-mentioned composition, the mixed liquid crystal of the present invention has an extremely wide smect and liquid crystal phase temperature range, and since the main component liquid crystal has large dielectric anisotropy, it can be used in thermal writing liquid crystal devices. This has the advantage that written information can be erased with a low voltage when

(5) Examples The present invention will be described in detail below with reference to Examples. The figure shows a substance represented by the chemical formula C8 island, 0(n (:!0O-GNO8) (hereinafter referred to as 0BTPE), and the chemical formula 〇5Htt-
o-o-ON (hereinafter 8BP above f), Os. 1
12゜() (defense ON (hereinafter referred to as 10BP), C1゜n
txoG-<n ON (hereinafter referred to as 100I3F), o
Four types of substances represented by tt &lI O()()ay (hereinafter referred to as 1201F) were mixed in a weight ratio of 58.6:3.
1.4 : 8.2 : 1.8 It is a figure showing the results of measuring the phase transition temperature of mixed liquid crystals prepared by mixing them in various ratios with carefully mixed liquid crystal C (hereinafter referred to as N5P36A). . In the diagram I, N, S, C! indicate the regions where the isotropic liquid phase, nematic liquid crystal phase, smectile liquid crystal phase, and solid phase appear, respectively.

As is clear from the figure, the mixed liquid crystal containing OB'i'PE not only has an advantageous increase in Tc, but also has the favorable characteristic that the nematic liquid crystal phase does not spread. Furthermore, 'Jam' has a mixing ratio of OB'l'PE of 60.
For mixed liquid crystals of about weight percent or less, the temperature is sufficiently low at 0° C. or less. As described above, a mixed liquid crystal containing preferably about 60% by weight or less of on'rpi has an extremely wide smectage and liquid crystal phase temperature range and a sufficiently low φTm. For example, the Tm of a mixed liquid crystal (hereinafter referred to as N8F35B) consisting of 75% by weight of N5P36A and 25% by weight of 0BTPE is extremely low at -43.5°C, and even at the storage temperature of -10°C by Liquid Crystal Light Valve using N5P35B. No hindrance. Also NSF
Tc of 35B is 51.5℃, nematic phase temperature range is 3
．． 1°C, which is optimal for writing when used in liquid crystal light valves. That is, as an example, N
An image written on a liquid crystal light valve using a 5P35E by irradiating an argon laser beam with an output light intensity of 300 mW for 1 μs per point was projected onto a screen with a gain of 6.4 using a xenon lamp with a light intensity of IKW. However,
A contrast of 10:1 was obtained at a brightness of 100 ft-L. Moreover, this image could be erased by applying a voltage of 90V. 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 and an erase voltage of 100 .ANG.

In addition, N5P36 is not limited to N8F35B.
Extremely excellent performance similar to that of N5F35B was observed in many mixed liquid crystals with different mixing ratios of A and 0BTPE. Also, instead of 0BTPE, chemical formula 0%) or C0゜&O<n cooGo N08 (hereinafter D
A similar effect was observed when a substance represented by PTPE (abbreviated as PTPE) was used, and when two or three selected from 0ETPE, NBTPFi, and DPTP'E were used in combination. Also, instead of N5P36A, 8BP, 10BP
.

100BF, 1201F and chemical formula 0oHt. -1o
-o-ON.

OX, H,, -Q-Q-ON + 012 H2S
-Q-Q-ON +C3H5?0-o-o-CN, C0
H1,1O-o-o-CN.

A similar effect was observed when using a liquid crystal mixture consisting of a substance selected from among the substances represented by CIl H2S 0 ( ) (〉ON or a plurality of substances selected from among these substances. Examples of effective mixed liquid crystals and warp T
c is shown in the table. The Tm of all these mixed liquid crystals is -10.
below ℃. In the table, the numbers in parentheses are mole percentages indicating the mixing ratio.

Table Tc (℃) ・8BPC78,9), 100BF (12,1), 0BT
PE(9,0) 50.28BP(82,1),
l00BPC12,9)iDBTPE(5,0)
48.68BP (62,8), l0EP (31,0)
, 0BTPE(6,2), 46.48BP(
63,2), l0BF (31,3), DBTPE (5,
5) 48.1 table (continued) 8BPC86,1), 120BF (3,7), 0BTP
E(10,2) 47.68BPC87,5), 1
201PC3,9), DBTPff(8,6)
49.78BP (58,5), l0EP (28,8
), 100BP(7,3).

OB'l'PE(5,4)
49.18BP(62,0), l0BP(30
,6), 120BF(1,7).

0BTPE(5,7)
47.38BP (76,9), 100BF (11,
6), 120BF (2,9).

0BTPE(8,6)
51.28BP (79,7), 100BF (12,
3), 120BP(3,1).

DB'i”P]fl(4,9)
49.88BPC75,9), 100BF
(11,3), 0BTPE(8,4).

1) B'L'PE (4,4)
51.78BP (82,1), t20BP (3
,3),0BTPli(9,3).

DBTPE(5,3)
49.38BP (53,6), 100BF (6,3
), 120BF (26,2).

OB'l'P (4,6), DB'l'PE (9,3
) 66.6 Also, in the above, the chemical formula R
We have given an example of a mixed liquid crystal consisting only of the substance represented by 1-Q-000'O' NOS and the substance represented by the chemical formula R2"O"O' ON, but any mixed liquid crystal containing these as the main components may be used. It goes without saying that there is no problem even if a certain amount of a liquid crystal material having a different structure is contained. Examples of liquid crystal substances with other structures include substances represented by the following chemical formula. Here, R represents an alkyl group or an alkoxy group. R i) i>0OOH, R-Q-Q-000R
I RIRI RQ:::)-RI Rbe revision Σ)J
rΣ RIRq R, R-Q-chch -Q-R,
R-OCh CH2-0-R,n-Q-cnto()-
R,R(>-Coo()R.

R-C-cI(=aH-coo-0)-R,R()
()(shicN.

R-0-GQ-01120R, R-0-G-Q-(H,
an.

OR, R-e@Pe＞　R,R-Q'P::'G　R.

R-Q-0-0-, n-0- ('4 ni □, Rl bar)
R, R-Q-Gooo-Gu, R-G-G-000-Q
-ON, R()Q-COo<nkaifan()Coo<su(ΣR,R-()Coo lΣON, R()O-c
oo-o-.

R-00-coo-'IDR,,R-0(IΣcoo
-Q-C! N.

R()coo-C-0-R, R-G-0-aao-0-
R.

R()coo-00-R,n-G-coo-GshinnR9
Nq<coo-Q(3R,R(3N(ΣC00(R9R()-CH20-Q-Q-C'N, R-Q-O
H=0-G-Q-a, R, ()COO-Q-C00
-G-R,R-Q-coo-Q-COO-Q-R,R+
o-cao-o-cmtcmt QON.

R()o-Coo-G() R,Tt-GO000
(b) 1 In the above, the case of use in a liquid crystal light valve for a projection type display device in which a liquid crystal cell is irradiated with a laser beam to write an image, and the written image is enlarged and projected using another optical system for viewing. Although the present invention has been explained using examples of the present invention, the liquid crystal material of the present invention has excellent performance also when thermal writing is performed by other means, and when used as a direct-view display element, a memory element, or other elements. Needless to say.

(6) Detailed Description of the Invention As described in detail, the present invention provides a liquid crystal material for a thermal writing liquid crystal element that has a wide liquid crystal phase temperature range, requires only a low applied voltage, and has excellent performance.

[Brief explanation of the drawing]

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 crystal phase, a nematic liquid crystal phase, a smectic liquid crystal phase, and a solid phase appear, respectively. ,・'--- 1' (=Jinbugo I-1 Hara Zen0BTPE0 20 40 60 8
0 100NSP36A100 80 60
40 20 0 Mixing ratio (wt%) Procedural amendment (voluntary) 61.6.25 Showa Year Month Day 2, Name of invention Liquid crystal material for thermal writing liquid crystal element 3, Relationship with the person making the amendment Case Applicant Tokyo 5-33-1 Shiba, Miyakominato-ku (423) NEC Corporation (Contact address: NEC Corporation Patent Department) 5. Detailed explanation of the invention in the specification to be amended 6. Contents of the amendment

Claims (1)

[Scope of Claims] Chemical formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (R_1 is a linear alkoxy group with carbon number n_1 = 8, 9, 10) as a main component of one or more substances In addition to the above main components, there are chemical formulas, formulas, tables, etc. (R_2 is a linear alkyl group or a linear alkoxy group with carbon number n_2 = 8, 9, 10, 11, 12). A liquid crystal material for a thermal writing liquid crystal element, characterized in that it contains as a main component one or more of the represented substances.