JPS61275385A - Liquid crystal substance for thermal writing liquid crystal element - Google Patents

Abstract

PURPOSE:To provide the title compsn. which is wide in smectic liq. crystal temp. range, exhibits a high degree of dielectric anisotropy and enables erasion of written information at low voltage, which comprises specific three kinds of compds. CONSTITUTION:At least one substance selected from among compds. of the formula I (wherein R1 is an 8-10C straight-chain alkoxy) is mixed with at least one substance selected from among compds. of the formula II (wherein R2 is an 8-9C straight-chain alkyl) and at least one substance selected form among compds. of the formula III (wherein R3 is an 8-12C straight-chain alkyl or 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 Cholesteric materials exhibiting a transparent liquid crystal structure When a thin layer of liquid crystal or smectic liquid crystal 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 the image is viewed directly, a light pulp element used for a projection type display in which the written image is projected and viewed, and the written information is read electrically or optically. type of recording element, etc. In addition, there are several known methods for writing information, such as irradiating the laser source to cause a temperature rise in the irradiated area, and using gel heat generation in a resistor to cause a temperature rise. For the sake of simplicity, below 0 is a liquid crystal light used in a projection type display device, in which an image is written by irradiating the liquid crystal cell with a laser source, and the written image is enlarged and projected using a separate optical system for viewing. This will be explained by taking the case of a pulp element as an example.

Initially, liquid crystal materials based on the general formula % were used for thermal writing liquid crystal light pulp. This is because liquid crystal materials having a transition temperature have not been found other than those based on thick bases. Here, the appropriate phase transition temperature refers to the temperature Tc at which the liquid crystal transitions to an isotropic liquid phase; if Tc is too high, the temperature rise required for writing will be large, which will reduce power consumption and writing speed. If 'rc is too low, the liquid crystal temperature in the steady state after writing will be lower than the phase transition temperature T.
The decrease in the degree of orientation order of liquid crystal molecules due to the closeness to c causes the disadvantage of a decrease in contrast.

Regarding such thick base-based liquid crystal materials, Taylor et al. of Bell Laboratories reported in Volume 45, No. 10 of the Journal of Applied Fixtures. Therefore, it is widely known that thermal writing liquid crystal devices using this type of liquid crystal material have a short life and lack reliability, especially in terms of moisture resistance. Therefore, subsequent attempts were made to improve liquid crystal materials.
A chemically stable biphenyl-based liquid crystal material represented by the general formula RSo-+o-CN (R is an alkyl group or an alkoxy group) has been created. International Business Machines' Dewey has a structure of n%cN and R is CaHzt * CoHso t CtoHtt
* CttHta e CaHttO・Published on pages 219 to 239 of ``Fixtures and Chemistry of Liquid Crystal Devices'' 0 In addition, Thomson eSeichibannis LoF's DeEvoir is anal.
On pages 131 to 138 of Volume 3 of De Fuisique (published in 1978), ν
Hty e c9Hto e C5Hr Og
CmHtyO* Ca HsyCOO#CIIHII
A comparative study of mixed liquid crystals consisting of components selected from a group of liquid crystal substances that are ICOO shows that R is (4H1? eC,H
,,C,H,. It has been reported that COO, a three-component mixed liquid crystal, is optimal for use in thermally written liquid crystal light pulp.Thus, improvements in liquid crystal materials have been made, and improvements have been made in the case of early thick base liquid crystals. The shortcomings such as short life and low reliability have been overcome.

However, all of the known liquid crystal materials mentioned above are insufficient, especially in terms of the liquid crystal phase temperature range.For example, the C6H17-o-o-
The crystal-to-liquid crystal transition temperature Tm is about 12°C even in the CN to C1゜H□-o-o-CN mixed liquid crystal, and the above-mentioned C5Hty-G-Q-CN sc recommended by DeBoer
,H,,-□cN,c, )(t.

Even in a mixed liquid crystal consisting of the three components COO & and CN, T
m is 8 degrees Celsius. Of course, liquid crystal light pulp using such a liquid crystal substance will crystallize and stop working if the temperature drops below the Tm of the liquid crystal substance during operation or storage, that is, below about 10 degrees Celsius. Even if the temperature recovers thereafter, defects occur in the alignment of liquid crystal molecules due to the crystallization history, resulting in the disadvantage of deteriorating the display image quality. It is extremely inconvenient for practical purposes that the lower limit of storage temperature is limited to around lθ℃.
It is well known that a temperature of around -10°C is required.
The reality is that it is not possible to obtain a satisfactory liquid crystal light pulp by using existing liquid crystal materials.

The inventors of the present invention have investigated in detail the relationship between the transition temperature of liquid crystal materials and display performance, and as a result of conducting experimental studies on a large number of liquid crystal materials, the inventors have found that a device with a wide range of liquid crystal phase temperatures and high performance not previously available. The present invention was achieved by discovering a liquid crystal material that realizes the following. 4) Means for Solving the Problems The liquid crystal material for a thermal writing liquid crystal element of the present invention is used for a thermal writing liquid crystal element in which information is written by partially applying heat to the liquid crystal material. Chemical formula x-Q-coo
-Q-Ncs (R, is a linear alkoxy group with carbon number n, = 8, 9.10) and the chemical formula R, COO<n (FcN (horse has carbon number nz = 8.
Contains as a main component one to two of the substances represented by the linear alkyl group of formula % 11.12 as a main component; basis)
It is characterized in that it contains one or more of the substances represented by as a main component.

The mixed liquid crystal of the present invention has an extremely wide smectic liquid crystal phase affinity range by adopting the above-mentioned composition, and since the main component liquid crystal has large dielectric anisotropy, it can be used in a thermal writing liquid crystal element. This has the advantage that written information can be erased with a low voltage in some cases.

(5) Examples The present invention will be described in detail below with reference to Examples. Figure C shows the chemical formula C3H1,0-o-CO0-o-NCS (hereinafter referred to as 0BTP13) and the chemical formula C,H,
.

A mixed liquid crystal (hereinafter referred to as N8
PX), chemical formula caH4y-Q-Q-CN (hereinafter referred to as 8BP), Cto Hz s gCN (hereinafter referred to as 1osp), C1°H! , o((ΣGCN (hereinafter referred to as 100BP), C11H□0-o-o-CN(
(hereinafter referred to as 1208P) in a weight ratio of s s, 6: 31.4: 8.2: 1.8
Mixed liquid crystal mixed in the ratio of (hereinafter referred to as N8P36A)
FIG. 3 is a diagram showing the results of measuring the phase transition temperature of mixed liquid crystals prepared by mixing various ratios of . In the figure, I, N, and 8°C are the isotropic liquid phase and nematic liquid crystal phase, respectively.

It shows the region where smectic liquid crystal phase and solid phase appear. As is clear from the figure, the mixed liquid crystal containing N5px is
It does not have the advantage of an increase in lc, but has the desirable feature that the nematic liquid crystal phase does not spread.Furthermore, Tm is 0°C in a mixed liquid crystal in which the mixing ratio of N8PX is about 75% by weight or less. It is sufficiently low as below. In this way, a mixed liquid crystal containing preferably about 75 weight percent or less of N8PX has an extremely wide smectic liquid crystal phase temperature range and a sufficiently low Tm. Mixed liquid crystal (hereinafter referred to as N8P37B) consisting of
The Tm of N8F3 is extremely low at -32.7°C.
A liquid crystal light valve using 7B does not cause any problems even at a storage temperature of -10°C. Also, the Tc of N8P37B is 57.
3°C, and the nematic phase temperature range is 3.2°C, both of which are optimal for writing when used in a liquid crystal light valve. That is, as an example, an image written on a liquid crystal light valve using N5F37B by irradiating an argon laser source with an output light intensity of 300 mW for 1 μs per point was written, and an image was written using a xenon lamp with a light intensity of 1 kW. 6.4
When projected onto a screen, the brightness was 100ft-
A contrast of 10:1 was obtained with L (contrast) of 10:10. This image can also be erased by applying a voltage of 90V. 1), erase voltage is 10
It should be noted that N
Not limited to 5P37B, N8PX and N5P3
88P in many mixed liquid crystals with different mixing ratios of 6A
Extremely excellent performance similar to that of 37B was observed. 0 again
The chemical formula for BTPB is CoHt*08COO8NC8
Te! Wasarelumono'Jt (hereinafter NBTPB t above)
-t type ii: When using a substance represented by CtoHttO+COO+NC8 (hereinafter referred to as DBTPE), or instead of 9EBP, the chemical formula C, Hl, Coo
In addition, when a substance represented by CN (hereinafter referred to as 8EBP) is used, 0BTPE is obtained.

Top 3 of 1 type selected from NBTPE and DBTPE
A similar effect was observed when the seed substance and one or both of 8BBP and 9EBP were used together. Also, 8BP, 10B for N8P36A
F.

100 B P v 120 B P Oj-Hi chemical formula C++ Ht *-o-ocNtCN r CttHt
s (H)CI'L C1tH□(H)CN.

C, H1□0-@-@-CNf c, H,, o'3shiC
N.

Similar effects were observed when using a substance selected from the substances represented by C, thso%cN, or a mixed liquid crystal consisting of a plurality of substances selected from these substances. Examples of mixed liquid crystals and their Tc are shown in the table below.
The Tm of these mixed liquid crystals is all below -10° C. In the table, the numbers in parentheses are mole percentages indicating the mixing ratio.

Table Tc (℃) 8BP (80 near), 9EBP (101), 0BT
PE (92) 49.188PC83B)
, 9EBP (10,9), DBTPE (a5)
47288P (73,2), 1008P (10,
7), 9EBF (83), 0BTPE (7J3) 51
28BP (754), 100BP (11,2), 9B
BP (8fl), DBTPB (4,6) 50.98B
P(78,7), 1208P(3,0), 9E
BP (945), 0BTPFt(8,7) 50
．． 38BP (81,3), 120BP (3,3)
, 9EBP(10,3) , DBTPE(5,1)
4858BP(59,7), l0BP(29,4
), 9EBF(5,4), 0BTPE(5,5
) 4828BP(56,1), l0BF(27J
), 100BPC6B), 9EBF(4J3
).

0BTPE (4J3)
50.68BP(58,9), l0BP(
29,0), 1208P(1,6), 9BBP
(53).

0BTPE(52)
48.98BP (71B), 100BP (1
0,3), 1208F(25), 9EBP(8,
0).

0BTPE(74)
53288P (69,7), 100BP (9
J3), 1208F (23), 9BBP (7
>).

0BTPE(7,0), DBTPE(3B)
543 Also, in the above, the chemical formula R+
+COO+NC8f Represented substance and chemical formula R1C
Substance and chemical formula represented by 0O-o-o-CN, -o
Although we have described an example of a mixed liquid crystal consisting only of the substance represented by -o-CN, it is sufficient to use a mixed liquid crystal containing these substances as the main components, and it is also possible to include a small amount of liquid crystal substances with other structures. Needless to say, examples of liquid crystal substances with other structures include substances represented by the following chemical formula.
Here, 几 represents an alkyl group or an alkoxy group.
cu, ()-u, ROCH,o()a, R-0-
C00()n, R-o-cu=ca-coo-oPR
tR(t◎-G-CNI B(n◎((CH,OR.

R Beni and (Nbe ζ t CH However, OR, R<5=(=t←(
), 几.

R00koR, -0<o>R.

n, 3◎-caoGR, R%coo-4ΣCN.

R4coo(Fa, R(Σcoo%n,.

a()-coo(H)cN, R, pcoo-itoR-
Q-Q-Coo-Q-Rt R(A(Xoo-o-cN
, -u-Q-coo-o-o-R, R-Q()coo-
()n, .

R' to NC-o-CO,)R,<*C00QR.

R-Q-cHto(8)cN, u-Q-cH, o4u
.

R-0-coo-Q-coo-o-R.

R unit coolCOO-0-R,.

R-o-C00-o-CH6CHt-o-CN.

The above example uses a liquid crystal light valve for a projection shop display device in which an image is written by irradiating the liquid crystal cell with a laser source, 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.

(6) As described in detail of the invention, according to the present invention, a liquid crystal material for a thermal writing liquid crystal element can be obtained which has a wide liquid crystal phase temperature range, requires a low applied voltage, and has excellent performance.

[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.
8. C indicates a region where an isotropic liquid phase, a nematic liquid crystal phase, a smectic liquid crystal phase, and a solid phase appear, respectively.

Claims (1)

[Claims] Chemical formula R_1▲There are mathematical formulas, chemical formulas, tables, etc.▼(R_
1 is a straight chain alkoxy group with carbon number n_1 = 8, 9, 10)
There are one or more types of substances and chemical formulas ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (R_2 is the number of carbon atoms n
_2 = 1 of the substance represented by 8, 9 straight chain alkyl group)
In addition to the above main components, there are chemical formulas, mathematical formulas, chemical formulas, tables, etc.
R_3 is characterized by containing as a main component one or more of the substances represented by a straight-chain alkyl group or a straight-chain alkoxy group having n_3 = 8, 9, 10, 11, or 12 carbon atoms. Liquid crystal material for thermal writing liquid crystal elements.