JPH04360121A - Light control material and light control element containing this material - Google Patents

Abstract

PURPOSE:To obtain the light control element with which the good uniformity of films is obtainable and which has the excellent difference in transmittance between the time when impressed with an electric field and the time when not impressed with the electric field and repetitive responsiveness by incorporating a high polymer combined with a specific triacrylate compd. and a monacrylate compd. into this element. CONSTITUTION:The high polymer of the light control material which is constituted to include a liquid crystal and the high polymer and controls the transmission and scattering of light according to the presence or absence of the impression of the electric field is obtd. by copolymerizing a polymerizable compd. consisting of the triacrylate compd. expressed by formula I and the monoacrylate compd. expressed by formula II. In the formula I, R<1> denotes a hydrogen atom, methyl group. In the formula II, R<2> denotes a hydrogen atom, methyl group; R<3> denotes 1 to 18C alkyl group, cyclohexyl group, tetrahydrofurfuryl group, etc. The above-mentioned light control material is crimped between a pair of substrates, one of which has electrodes on the transparent inside surface, by which the light control element is constituted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control material and a light control element containing the same.

0002

[Prior Art and Problems to be Solved by the Invention] A light control material made of a liquid crystal and a polymer holding it has a problem in that when no electric field is applied, the incident light is affected by the difference between the refractive index of the polymer and the refractive index of the liquid crystal. Due to scattering, it becomes cloudy, and when an electric field is applied, the liquid crystal aligns in the direction of the electric field, so the refractive index of the polymer and the refractive index of the liquid crystal become close to each other, etc. becomes transparent. Moreover, when the electric field is removed, the original cloudy state is restored.

[0003] Light control elements utilizing such properties are disclosed in, for example, ■Japanese Unexamined Patent Publication No. 64-62615 and ■Japanese Patent Publication No. 2-502.
This method is disclosed in Japanese Patent Publication No. 929 and Japanese Patent Application Laid-Open No. 1-252689. However, none of the above (1), (2) and (2) disclose the combination of the triacrylate compound represented by the general formula (I) and the monoacrylate compound represented by the general formula (II) of the present invention.

A light control element is required to have a desired transmittance, repeated response, voltage sensitivity, response speed, film uniformity, and durability such as light resistance, heat resistance, and water resistance. , ■
and (2) could not be said to have characteristics that could satisfy these requirements.

[0005]

[Means for Solving the Problems] The present invention is intended to solve the above-mentioned problems, and in particular, to solve problems such as membrane uniformity, transmittance, and repeatability. That is,
The present invention provides a light control material comprising a liquid crystal and a polymer, which controls the transmission and scattering of light depending on the presence or absence of an electric field, wherein the polymer is a triacrylate represented by the general formula (I) according to claim 1. A light control material characterized by being a polymer obtained by copolymerizing a polymerizable composition comprising a monoacrylate compound and a monoacrylate compound represented by general formula (II), and at least one of which is transparent. The gist of this invention is a light control element that is constructed by being sandwiched between a pair of substrates having electrodes on their inner surfaces.

The present invention will be explained in detail below. R1 in the general formula (I) and R2 in the general formula (II), which are the monomers forming the polymer, represent a hydrogen atom or a methyl group, and in the general formula (II), R3 represents a methyl group, an ethyl group, a propyl group. straight-chain or branched alkyl having 1 to 18 carbon atoms, such as butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, tridecyl group, pentadecyl group, stearyl group, etc. Base;
-{[CH(R4)]m -O}n -R5 (R4
represents a hydrogen atom or a methyl group, R5 is a methyl group,
Represents a straight or branched alkyl group having 1 to 5 carbon atoms such as an ethyl group, a propyl group, a butyl group, a pentyl group,
m represents an integer of 1 to 3, and n represents an integer of 1 to 10. ); represents a cyclohexyl group or a tetrahydrofurfuryl group.

Specifically, examples of the general formula (I) include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, etc.
Examples of I) include methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, iso-amyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, n-
Dodecyl acrylate, tridecyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, iso-propyl methacrylate, n-
Butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-
dodecyl methacrylate, tridecyl methacrylate,
Alkyl acrylate or alkyl methacrylate such as stearyl methacrylate; 2-methoxyethyl acrylate, ethoxypolyethylene glycol (n=2
) acrylate, methoxypolyethylene glycol (n
= 2, 4 or 9) acrylate, 1-methyl-2-methoxyethyl acrylate, 1-methyl-2-butoxy acrylate, 3-methoxypropyl acrylate, 2-
Examples include methoxyethyl methacrylate, ethoxypolyethylene glycol (n=2) methacrylate, methoxypolyethylene glycol (n=2, 4 or 9) methacrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, cyclohexyl methacrylate, and tetrahydrofurfuryl methacrylate.

As the liquid crystal, any of nematic liquid crystal, cholesteric liquid crystal, and smectic liquid crystal can be used. The nematic liquid crystal used in the present invention can be selected from a wide range as long as it exhibits a nematic state within the operating temperature range. Further, by adding an optically active substance to be described later to such a nematic liquid crystal, it can be made to take a cholesteric state. Examples of nematic liquid crystals include the substances shown in Table 1 below, or derivatives thereof.

[0009]

[Table 1]

0010

[Table 2]

[0011]

[Table 3]

In Table 1 above, R' is an alkyl group or an alkoxy group, R is an alkyl group, and X' is an alkyl group, an alkoxy group, a nitro group, a cyano group, a trifluoromethyl group, a trifluoromethoxy group, or Represents a halogen atom. Furthermore, the benzene ring in Table 1 above may be further substituted with a fluorine atom.

The liquid crystal used in the present invention may be any of the liquid crystals shown in Table 1 or mixtures containing them.
For example, ZLI-1132, ZLI-184 from Merck & Co.
0 or ZLI-1565, or sold by British Drug House under the product names E-7, E-8, E-37, E-44, E-46 or BL001 to BL020. Liquid crystal etc. are used.

Furthermore, by adding the following optically active substance to such a nematic liquid crystal, it can be made to take a cholesteric state. As the optically active substance used in the liquid crystal composition of the present invention, chiral nematic compounds such as 2-methylbutyl group, 3-methylbutoxy group, 3-methylpentyl group, 3-methylpentoxy group, 4-methylhexyl group, There are compounds in which an optically active group such as a 4-methylhextoxy group is introduced into a nematic liquid crystal. In addition, alcohol derivatives such as l-menthol and d-borneol, d-camphor, 3-
Optical activities such as ketone derivatives such as methylcyclohexane, carboxylic acid derivatives such as d-citronellaic acid and l-camphoric acid, aldehyde derivatives such as d-citronellal, alkene derivatives such as d-linonene, and other amine, amide, and nitrile derivatives. Substances can be used.

Furthermore, as the smectic liquid crystal used in the present invention, smectic A liquid crystal, smectic chiral C
An example is liquid crystal. The above liquid crystal, the above general formula (I) and (
A polymerizable composition consisting of the monomer II) and a photopolymerization initiator are mixed, optionally heated to form a homogeneous solution, and exposed to light. As a result, the copolymer and the liquid crystal enter a phase-separated state, and a light control material can be obtained.

At this time, the compound of general formula (I) and the compound of general formula (I
The ratio of compound I) to be used is preferably 10/1 to 1/10 (compound (I)/compound (II); weight ratio), more preferably 1/1 to 1/10. Further, the compound of general formula (I) and the compound of general formula (II) each have 1
You may mix more than one species.

[0017] Furthermore, the proportion of liquid crystal in the homogeneous solution is
It can be used in an amount of 40 to 90% by weight, preferably 65 to 85% by weight. Examples of the photopolymerization initiator include 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-2-methyl-1-phenylpropan-1-one.

[0018] Furthermore, surfactants, photostabilizers, dyes, chain transfer agents, photosensitizers, crosslinking agents, etc. can be used in combination, if necessary. On the other hand, transparent electrodes such as ITO are used as the electrodes of the light control element of the present invention, and examples of the electrode substrate include transparent substrates such as glass or plastic plates such as polyester.

When a pair of transparent electrode substrates is used, it can be used as a transmission type dimming element, and when one electrode substrate is transparent and the other is opaque, a reflective element can be used after the opaque electrode substrate. By placing layers, it can be used as a reflective dimming device. The light control element of the present invention can be produced by, for example, forming a homogeneous solution containing the above-mentioned liquid crystal, a polymerizable composition, a photopolymerization initiator, and optionally various additives, sandwiching it between substrates having the above-mentioned electrodes, and exposing it to light. It can be produced by polymerizing the polymerizable composition.

[0020]

[Examples] Next, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to the following Examples. Example 1 Triacrylate compound Ia (R1 in general formula (I)
= H) 0.1 g, monoacrylate compound IIa (in general formula (II), R2 = H, R3 = C4 H9 (n)
)0.2g, 2,2-dimethoxy-2 as a polymerization initiator
- Phenylacetophenone 0.006g, E as liquid crystal
-8 (manufactured by BDH) to obtain a homogeneous solution, and 0.006 g of a plastic (divinylbenzene copolymer) spacer with a diameter of 10 μm was added to this solution.
This mixed solution was inserted between ITO-coated plastic (polyethylene terephthalate) with a size of 6 cm x 9 cm,
A uniform light control element without cracks etc. was obtained by exposure with an ultraviolet irradiation device. The energy given is 800
Corresponds to mJ.

FIG. 1 shows the transmittance spectra of the obtained dimming device when no electric field is applied (b) and when 100 V alternating current (60 Hz, sine wave) is applied (a). Note that when the electric field was removed, the spectrum returned to the original without applying the electric field. As shown in FIG. 1, a good transmittance difference was exhibited over a wide wavelength range. When viewed at a wavelength of 600 nm, it showed a transmittance difference of 64%. Example 2 Triacrylate compound Ia used in Example 1
0.1 g, monoacrylate compound IIb (general formula (
II) with R2 = H, R3 = C12H25(n))
Using 0.2 g, the other processes were carried out in the same manner as in Example 1 to produce a uniform light control element with no cracks or the like.

FIG. 2 shows the transmittance spectra of the obtained light control element when no electric field is applied (b) and when 100 V alternating current (60 Hz, sine wave) is applied (a). Furthermore, when the electric field was removed, the spectrum returned to the original without applying the electric field. As shown in FIG. 2, a good transmittance difference was exhibited over a wide wavelength range. A transmittance difference of 66% was observed at a wavelength of 600 nm. Example 3 Triacrylate compound Ia used in Example 1
0.1 g, monoacrylate compound IIc (general formula (
II), R2 = CH3 , R3 = -(CH2 CH
Using 0.2 g of 2O)2-CH3) and otherwise treating in the same manner as in Example 1, a uniform light control element with no cracks or the like was produced.

FIG. 3 shows the transmittance spectra of the obtained light control element when no electric field is applied (b) and when 100 V alternating current (60 Hz, sine wave) is applied (a). Furthermore, when the electric field was removed, the spectrum returned to the original without applying the electric field. As shown in FIG. 3, a good transmittance difference was exhibited over a wide wavelength range. When viewed at a wavelength of 600 nm, the transmittance difference was 64%. Examples 4 to 10 Compounds of general formula (I) and general formula (II) shown in Table 2 below and liquid crystals were used, and other treatments were carried out in the same manner as in Example 1.
We created a uniform light control element with no cracks, etc., and applied 100V AC (
Changes in transmittance were measured when a 60 Hz, sine wave) was applied and when no voltage was applied. The results are shown in Table 2 below.

[0024]

[Table 4]

Comparative Example 1 Triacrylate compound Ia (R1 in general formula (I)
=H) 0.3g, 0.006g of 2,2-dimethoxy-2-phenylacetophenone as a polymerization initiator, and 0.7g of E-8 (manufactured by BDH) as a liquid crystal to obtain a homogeneous solution, and in this solution Add 0.006 g of a spacer made of plastic (divinylbenzene copolymer) with a diameter of 10 μm to the sample, insert the mixed solution between 6 cm x 9 cm of ITO-coated plastic (polyethylene terephthalate), and expose to ultraviolet light using an ultraviolet irradiation device. As a result, a uniform light control element without cracks etc. was obtained. The energy given is 80
Corresponds to 0 mJ.

FIG. 4 shows the transmittance spectra of the obtained light control element when no electric field is applied (b) and when 100 V alternating current (60 Hz, sine wave) is applied (a). As shown in FIG. 4, no good transmittance difference was obtained. 600
When viewed at a wavelength of nm, the transmittance difference was 14%.

Comparative Example 2 Monoacrylate compound IIa (R in general formula (II)
2 = H, R3 = C4 H9 (n)), 0.3 g of 2,2-dimethoxy-2-phenylacetophenone as a polymerization initiator, and 0.7 g of E-8 (manufactured by BDH) as a liquid crystal. A light control element was produced by performing the same treatment as in Example 1, but phase separation did not occur at all, and a uniform light control film could not be obtained.

[0028]

Effects of the Invention: The light control material obtained by the present invention has good film uniformity, and the light control element using the light control material has good transmittance difference between when an electric field is applied and when no electric field is applied, repeat response, etc. It is useful for display devices, light control windows, etc.

[Brief explanation of drawings]

FIG. 1 is a transmittance spectrum diagram of the light control element of Example 1 when an electric field is applied and when no electric field is applied.

FIG. 2 is a transmittance spectrum diagram of the light control element of Example 2 when an electric field is applied and when no electric field is applied.

FIG. 3 is a transmittance spectrum diagram of the light control element of Example 3 when an electric field is applied and when no electric field is applied.

FIG. 4 is a transmittance spectrum diagram of the light control element of Comparative Example 1 when an electric field is applied and when no electric field is applied.

[Explanation of symbols]

In FIGS. 1 to 4, the vertical axis represents the transmittance, the horizontal axis represents the wavelength, and a represents the electric field (100 V AC,
500 Hz, sine wave) is applied, and b represents the transmittance spectrum when no electric field is applied.

Claims (2)

[Claims] 1. A light control material comprising a liquid crystal and a polymer and controlling the transmission and scattering of light depending on the presence or absence of an electric field, wherein the polymer has the following general formula (I) CH3 CH2 C[CH2 OCO(R
1) Triacrylate compounds represented by C=CH2]3 (I) (wherein R1 represents a hydrogen atom or a methyl group) and the following general formula (II)
CH2=C(R2)COOR3

(II) [In the formula, R2 represents a hydrogen atom or a methyl group, R3 represents an alkyl group having 1 to 18 carbon atoms, -{[
C(R4)H]m-O}n-R5 (R4 represents a hydrogen atom or a methyl group, R5 represents an alkyl group having 1 to 5 carbon atoms, m represents an integer of 1 to 3, and n represents 1 ~10
indicates an integer. ), cyclohexyl group or tetrahydrofurfuryl group. A light control material characterized in that it is a polymer obtained by copolymerizing a polymerizable composition comprising a monoacrylate compound represented by the following. 2. A light control element characterized in that the light control material according to claim 1 is sandwiched between a pair of substrates, at least one of which is transparent and which has an electrode on its inner surface.