JPH09227454A - Photopolymerizable compound and polymer-dispersion type liquid crystal display element produced by using the compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject new compound capable of keeping the specific resistance even by the irradiation with ultraviolet rays, having high compatibility with other liquid crystals and giving a display element produced by the phase- dispersion of a polymer of the compound, drivable at a low voltage and having high brightness and reflectivity. SOLUTION: This photopolymerizable compound is expressed by formula I (A and B are each a photopolymerizable functional group; X is CH2 or CO), e.g. the compound of formula II. The compound of formula II can be produced by reacting a compound of formula III with a compound of formula IV in chloroform in the presence of triethylamine. A display element containing at least a part of the constituent element of formula V in the polymer can be produced by using at least one component of the photopolymerizable compound of formula I as a precursor for forming a polymer in a display element containing a liquid crystal and the polymer in an oriented and mutually dispersed state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel organic compound, and further, to form a liquid crystal composition used as an electro-optical display element, a photopolymerizable compound which is one of the materials and a compound using the same. The present invention relates to a molecular dispersion type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, as a bright display element which does not use a polarizing plate, a display element in which a liquid crystal and a polymer are dispersed is drawing attention. The principle of operation of this display element utilizes the difference in the refractive index between the liquid crystal and the polymer.When the refractive index of the liquid crystal and that of the polymer match when an electric field is applied, a transmissive state is shown, and when the electric field is removed, the refractive index differs. In that case, the scattering state is indicated (Tokukaisho Sho 58-501631, which is called NCAP).
In addition, a display element of the opposite mode has been developed, which transmits when no electric field is applied and scatters when an electric field is applied (Mol.Cryst.Liq.Crys
t., 198, 357, (1991), which is called the reverse type).
For these modes, a method of improving visibility by mixing a dye has also been proposed. The polymers used in these display devices have already been used as mesogen groups such as biphenyl derivatives, phenylbenzoate derivatives, benzene rings and benzene rings bonded with a Schiff base, compounds having tolan derivatives, etc. (JP-A-4-22768).
4, JP-A-5-224187, WO 93/08497) are known.

[0003]

However, liquid crystal display devices using these polymers have the drawbacks of poor specific resistance, high driving voltage, and insufficient reflectance during scattering. Further, there were some kinds of compounds in which the polymer precursor was difficult to dissolve in the liquid crystal composition.

The present invention has responded to the above-mentioned demand in the actual situation, and its purpose is not to reduce the specific resistance value even when irradiated with ultraviolet rays, and the precursor of the polymer may be another type or two. It is an object of the present invention to provide a novel compound which has good compatibility with at least one kind of liquid crystal and can be driven by a low voltage in a display element which is polymerized and phase-dispersed and which is suitable for obtaining a display element which is bright and has excellent reflectance.

[0005]

According to the present invention, there is provided a compound of the general formula

[0006]

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(In the above formula, A and B represent a photopolymerizable functional group, and X represents CH 2 or CO). Further, the display element of the present invention is a display element in which a liquid crystal and a polymer are aligned and dispersed with each other,

[0008]

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(In the above formula, X represents CH2 or CO)
The component represented by is present in at least a part of the polymer. In a display element in which liquid crystal and polymer are aligned and dispersed with each other, the phase-separated liquid crystal and polymer may be aligned by shearing. Further, in the display device in which the liquid crystal and the polymer are aligned and dispersed with each other, the liquid crystal and the polymer may be phase-separated in a gel network form. Further, a display element in which a liquid crystal and a polymer are oriented and dispersed to each other is characterized by containing 0.1 to 15% of a photopolymerizable compound as a precursor for forming the polymer. In a display element in which liquid crystal and polymer are oriented and dispersed with each other,
It is characterized by containing a dichroic dye.

Next, the photopolymerizable compound (1-a) of the present invention
And the manufacturing method of (1-b) will be described.

[0011]

[Table 1]

Step A) Compound (2) and compound (3) are reacted in chloroform in the presence of triethylamine to obtain compound (1-a).

Step B) The compound (2) and the compound (4) are reacted in chloroform in the presence of triethylamine to obtain a compound (1-b).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 [Synthesis of Compound (1-a)] Production of diphenylmethane-4,4'-diyl dimethacrylate.

Step A) 60 ml of chloroform, 4,4'-dihydroxydiphenylmethane in a nitrogen purged flask.
4.6 g and triethylamine 9.7 ml were added and stirred. 5.5 g of distilled and purified methacryloyl chloride was slowly added dropwise thereto, and stirring was continued for 5 hours. The reaction solution is poured into water, extracted with chloroform, washed with dil.HClaq., Saturated NaHCO ₃ aq., And water, and then chloroform is distilled off. The residue was purified by silica gel-chloroform column chromatography, recrystallized from methanol, and diphenylmethane-4,4 '.
-1.3 g of diyl dimethacrylate were obtained. The melting point of this compound was 87.7 ° C.

(Example 2) [Synthesis of compound (1-b)] Production of benzophenone-4,4'-diyl dimethacrylate.

Step A) 60 ml of chloroform, 4,4'-dihydroxybenzophenone in a nitrogen purged flask 4.
9 g and triethylamine 9.7 ml were added and stirred. 5.5 g of distilled and purified methacryloyl chloride was slowly added dropwise thereto, and stirring was continued for 5 hours. The reaction solution is poured into water, extracted with chloroform, washed with dil.HClaq., Saturated NaHCO ₃ aq., And water, and then chloroform is distilled off. The residue was purified by silica gel-chloroform column chromatography and recrystallized from methanol to give benzophenone-4,4'-.
2.9 g of diyl dimethacrylate was obtained. The melting point of this compound was 114.8 ° C.

Example 3 [Display Element] As shown in FIG. 1, an electrode 3 made of a transparent electrode film (for example, an ITO film) is formed on glass substrates 1 and 2, and an alignment made of polyimide or the like is formed thereon. Apply the film. Next, rubbing is performed to form the orientation control layer 4, and the glass substrates 1 and 2 are further formed.
Were opposed to each other with the sealant 5 interposed therebetween, and the following composition was injected between the glass substrates to prepare a liquid crystal display cell. The cell gap was 5 μm.

In this embodiment, TL202 and MJ91261 are used as the liquid crystal.
(Both manufactured by Merck), S-1011 (manufactured by Merck) as a chiral component, S-344 (manufactured by Mitsui Toatsu Dye Co.) as a dichroic dye, and Examples 1 and 2 of the present invention as polymer precursors. The compounds diphenylmethane-4,4'-diyl dimethacrylate, benzophenone-4,4'-diyl dimethacrylate and the existing compound biphenyl-4-yl methacrylate were used.

The ratio of the composition used is that of TL202 and MJ91261.
A mixture of 90.9% of the mixture of 8: 2, 0.5% of S-1011 and 3.6% of S-344 was used as a base liquid crystal, and the base liquid crystal was used as a polymer precursor, and the compound diphenylmethane of Example 1 of the present invention was used. -4,4'-diyl dimethacrylate 5%
A mixed liquid crystal composition a, a liquid crystal composition b in which 5% of the compound of Example 2 benzophenone-4,4′-diyldimethacrylate were mixed, and a liquid crystal composition c in which 5% of the existing compound, biphenyl-4-yl methacrylate, were mixed were prepared. It was adjusted.

The liquid crystal compositions a, b, and c are enclosed in the above-described empty panel, and the polymer precursor is photopolymerized by ultraviolet irradiation to phase-separate the liquid crystal and the polymer. A display element A used, a display element B using the liquid crystal composition b, and a display element B using the liquid crystal composition c were prepared.

The display element thus manufactured is arranged in an optical system as shown in FIG. 2, a signal with a peak value changed by a 1 KHz rectangular wave is applied, and the reflectance is measured while changing the voltage. , Minimum reflectance, maximum reflectance, threshold voltage (voltage value when 5% change from minimum reflectance to maximum reflectance, hereinafter referred to as Vth), saturation voltage (from minimum reflectance to maximum reflectance)
The voltage value when 95% changed, hereinafter referred to as Vsat) was measured. The reflectance was 100% when white fine paper was placed instead of the element. By the way, it has already been investigated that the reflectance of the element has a viewing angle dependency due to the rotation of the element that the value of the reflectance changes depending on the incident direction of light even if the incident angle to the panel is constant. Therefore, in order to match the measurement conditions, the reflectance shown here is a value obtained when the panel is fixed at an incident angle at which the reflectance becomes the largest. In this way, the display element measurement results shown in the following table were obtained. The measurement was carried out at a cell temperature of 20 ° C.

[0024]

[Table 2]

From the results of this measurement, it can be seen that the use of the compound of the present invention makes it possible to compare Vth and Vsa with the use of the existing compound.
Although t increased a little, the maximum reflectance could be increased by 20 to 30%. The increase of the maximum reflectance is an important characteristic when manufacturing a display element, and the fact that it can be increased is significant.

As described above, by using the liquid crystal composition of the present invention, the maximum reflectance is larger than that of the conventional display device,
It was possible to obtain a liquid crystal display element whose display was bright and easy to see. Further, the compatibility of the compound of the present invention with liquid crystal,
It was found that there was no problem in formulating the compositions of the examples, and sufficient solubility was obtained at the content of the practical polymer precursor. Furthermore, the specific resistance of the liquid crystal composition containing the polymer precursor as a display element was 1.0 × 10 ¹¹ Ωcm or more, and the voltage holding ratio was 97% or more, which was a value that causes no problem in operation.

Although the TN type liquid crystal display cell is used in the above-mentioned embodiment, the same effect can be obtained when the MIM element, the TFT element or the like is used.

Here, the mixing ratio of the liquid crystal is not limited to the above example. Even if this liquid crystal composition is mixed with another liquid crystal at an arbitrary ratio, it functions as a display element.

The chiral component can be used without being limited to those shown here. As the chiral component, a polymer precursor having a chiral center can also be used. Also, the mixing ratio is not limited to the amount shown here, but if too much is added, the hysteresis tends to increase.

The dichroic dye can be used without being limited to the ones shown here, but if possible, a dye that absorbs little in the ultraviolet region is preferable. Of course, it is more preferable if the two-color ratio is high. The color of the dye can be arbitrarily selected according to the application. The content of the dye is not limited to the amount shown here, but if it is too large, the dye crystallizes or the display becomes dark.

Although the polymerization initiator was not used here, a photosensitizer can also be used. However,
Use with caution because the specific resistance tends to decrease.

The polymer precursor to be used may be a mixture of other photopolymerizable polymer precursors. The content of the polymer precursor may not be the amount shown here, but if it is too small, the scattering degree becomes weak, and if it is too large, the driving voltage becomes high.

As the polymerization conditions, ultraviolet rays having a length of 300 nm or longer were used here, but the polymerization can be performed by using light shorter than this. However, the specific resistance is likely to decrease, so care must be taken in polymerization. The light intensity was set to 3 mW / cm ² , but it is not limited to this. If the light intensity is weak, the polymerization time is lengthened, and if the light intensity is strong, the polymerization time is shortened. However, if the light intensity is too high, the specific resistance tends to decrease. Slight heating during photopolymerization (20-50
Polymerization is easy when (° C.).

For the reflective electrode, aluminum, silver,
Any electrode that reflects light, such as nickel or chromium, can be used. Alternatively, the electrodes may be transparent and a reflective background plate may be used on the back side of the device.

Any method can be used for the alignment treatment as long as the liquid crystal is aligned.

[0036]

As described above, by using the compound of the present invention, it becomes possible to manufacture a reflective display device having a higher reflectance than a display device using a conventional compound or composition. Further, the compound of the present invention had good compatibility when mixed with any conventional liquid crystal composition. By using the compound of the present invention, a bright power-saving man-machine interface such as a large-capacity display can be easily manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a display element according to a second embodiment of the present invention.

FIG. 2 is a diagram showing an optical system when measuring electro-optical characteristics of a display element in Example 2 of the present invention.

[Explanation of symbols]

 1, 2 Glass substrate 3 Electrode 4 Alignment control layer 5 Sealant 6 Dye 7 Liquid crystal 8 Polymer (9 Reflective background plate when not using reflective electrode) 10 Display element 11 Light source 12 Imaging lens 13 Photoelectron multiplication tube

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G02F 1/137 500 G02F 1/137 500

Claims (9)

[Claims] 1. A compound of the general formula (In the above formula, A and B represent a photopolymerizable functional group,
X represents CH2 or CO). ## STR2 ## The photopolymerizable compound according to claim 1, which is represented by: (3) The photopolymerizable compound according to claim 1, which is represented by: 4. In a display device in which a liquid crystal and a polymer are aligned and dispersed with each other, a compound represented by the general formula: (In the above formula, A and B represent a photopolymerizable functional group,
X represents CH2 or CO), and at least one component of a photopolymerizable compound represented by the general formula: A polymer-dispersed liquid crystal display device using a photopolymerizable compound, wherein a constituent element represented by the formula (X represents CH2 or CO) is present at least partially in the polymer. 5. In a display device in which a liquid crystal and a polymer are aligned and dispersed with each other, the polymer is used as a precursor for forming the polymer. By using a photopolymerizable compound represented by: The polymer-dispersed liquid crystal display device using the photopolymerizable compound according to claim 4, wherein the constituent element represented by the formula (1) is present at least partially in the polymer. 6. In a display device in which a liquid crystal and a polymer are aligned and dispersed with each other, as a precursor for forming the polymer: By using a photopolymerizable compound represented by: The polymer-dispersed liquid crystal display device using the photopolymerizable compound according to claim 4, wherein the constituent element represented by the formula (1) is present at least partially in the polymer. 7. A display device having a liquid crystal and a polymer aligned and dispersed with each other as a precursor for forming a polymer, represented by the general formula: (In the above formula, A represents a photopolymerizable functional group, and X represents C
A composition containing 0.1 to 15% of at least one component of a photopolymerizable compound represented by H 2 or CO) is used. Polymer dispersed liquid crystal display device. 8. A display device in which a liquid crystal and a polymer are oriented and dispersed to each other, wherein the liquid crystal contains a dichroic dye, and the compound represented by the general formula: The polymer-dispersed liquid crystal using photopolymerizability according to claim 4, wherein the constituent element represented by the formula (wherein X represents CH 2 or CO) is present at least partially in the polymer. Display element. 9. A display device in which a liquid crystal and a polymer are oriented and dispersed to each other, wherein at least one of the liquid crystal and the polymer contains or exists a chiral component, and a compound represented by the general formula: The polymer-dispersed type using a photopolymerizable compound according to claim 4, wherein the constituent element represented by the formula (wherein X represents CH 2 or CO) is present at least partially in the polymer. Liquid crystal display device.