JP3134526B2 - Dimming material and dimming element using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming material comprising a liquid crystal and a polymer holding the liquid crystal, and a dimming element using the same. In particular, the present invention relates to a light modulating material and a light modulating element which have a large change in light transmittance between when an electric field is applied and when no electric field is applied, and have excellent voltage sensitivity and heat resistance.

[0002]

2. Description of the Related Art A light modulating material composed of a liquid crystal and a polymer holding the liquid crystal, for example, when no electric field is applied, the incident light is scattered due to a difference between the refractive index of the polymer and the refractive index of the liquid crystal. When an electric field is applied, the liquid crystal is aligned in the direction of the electric field, so that the liquid crystal becomes transparent.

[0003] This light modulating material is easy to increase in area as compared with ordinary liquid crystal display elements and has advantages such as high durability.
It is expected for many uses such as automobiles. Conventionally, as such a light control material, a liquid crystal in which a liquid crystal is microencapsulated with a polymer (Japanese Patent Application Laid-Open No. 58-501631) and a liquid crystal in which a liquid crystal is dispersed in an epoxy resin in the form of fine droplets (Japanese Patent Application Laid-Open No. 63-50
1512), in which a liquid crystal is held in a network polymer by photopolymerization using an acrylic oligomer (JP-A-63-27163)
133) have been proposed.

However, these light modulating materials are still practically satisfactory in light transmittance, voltage sensitivity, uniformity of film, durability, heat resistance, and low temperature dependence. Did not.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems,
In particular, it is an object of the present invention to provide a light modulating material having improved film uniformity, light transmittance, electric field sensitivity and heat resistance, and a light modulating element comprising the same.

[0006]

Means for Solving the Problems For the above purpose, the present inventors have conducted intensive studies on a polymer holding a liquid crystal, and as a result, obtained by copolymerizing a specific trimethylolpropane compound and an acrylate compound. The present inventors have found that a dimming material using the obtained polymer exhibits good characteristics, and have reached the present invention.

That is, the present invention comprises a liquid crystal material and a polymer, wherein the polymer is a light modulating material which controls the scattering state of light by the presence or absence of the application of an electric field, wherein the polymer is represented by the general formula (I) according to claim 1 A light modulating material characterized by being a polymer obtained by copolymerizing a polymerizable composition comprising a trimethylolpropane compound represented by and a acrylate compound represented by the general formula (II), and at least A light control element is characterized in that one is sandwiched between a pair of substrates having electrodes on a transparent inner surface. Hereinafter, the present invention will be described in detail.

A monomer represented by the general formula:
R of (I)¹And R of the general formula (II) ^ThreeIs a hydrogen atom or
A tyl group, and in the general formula (I),^TwoHas 2 carbon atoms
Or 3 linear or branched alkylene groups;
Represents an integer of 1 to 10, and in the general formula (II), R^FourIs
Methyl, ethyl, propyl, butyl, pentyl
Group, hexyl group, heptyl group, octyl group, nonyl group,
Decyl group, dodecyl group, tridecyl group, pentadecyl
Linear or straight-chain having 1 to 18 carbon atoms such as
Is a branched alkyl group; a cyclohexyl group;
Rofurfuryl group;-(-R^Five-O-)_n-R⁶[R^FiveIs
− (CH_Two)_k-(K represents an integer of 2 to 11),-
CH_TwoCH_TwoCH (CH_Three)-, -CH_TwoC (CH_Three)
_TwoCH_Two-, -CH (CH_Three) CH_Two-, -CH_TwoCH
(CH_Three)-, -CH (CH_Three)-(CH_Two)_Three−, −
CH (CH_Three) CH_TwoCH_Two-, -CH_TwoC (C
_FourH₉)_TwoCH_TwoA straight chain having 2 to 11 carbon atoms such as
Represents a branched alkylene group;⁶Is a methyl group, d
Tyl, propyl, butyl, pentyl, hexyl
, Heptyl, octyl, etc., linear chains having 1 to 8 carbon atoms
Alternatively, n represents a branched alkyl group and n is an integer of 1 to 10.
Indicates a number. ].

As a preferred example of the general formula (I), R ¹
Is a hydrogen atom or a methyl group, and R ² is -C ₂ H ₄ -or -C
₃ H ₆ -, m can be cited trimethylolpropane compounds of the combination of 1 or 2. Preferred examples of the general formula (II) include acrylate compounds shown in Table 1 below.

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

The polymer of the present invention is obtained by photopolymerizing a polymerizable composition prepared by a combination appropriately selected from the compounds of the general formulas (I) and (II). Therefore, when this is used as a light modulating material, the light modulating material has excellent heat resistance and low temperature dependency.

As the liquid crystal held by the polymer, any of a nematic liquid crystal, a cholesteric liquid crystal and a smectic liquid crystal can be used. The nematic liquid crystal used in the present invention can be selected in a fairly wide range as long as it exhibits a nematic state in an operating temperature range.
In addition, a cholesteric state can be obtained by adding an optical rotatory substance described later to such a nematic liquid crystal. Examples of the nematic liquid crystal include the substances shown in Table 2 below and derivatives thereof.

[0015]

[Table 4]

[0016]

[Table 5]

[0017]

[Table 6]

In Table 2, R 'is an alkyl group or an alkoxy group, R is an alkyl group, 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.
Further, the benzene ring in Table 2 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 2 or a mixture containing them.
For example, ZLI-1132, ZLI-184 from Merck
Liquid crystal sold under the trade name 0 or ZLI-1565 or sold under the trade name E-7, E-8, E-37, E-44, E-46 or BL001-BL020 from British Drug House. Liquid crystal or the like is used.

The cholesteric state can be obtained by adding the following optically active substance to such a nematic liquid crystal. As the optical rotatory substance used in the liquid crystal composition of the present invention, chiral nematic compounds such as 2-methylbutyl group, 3-methylbutoxy group,
There is a compound in which an optically active group such as -methylpentyl group, 3-methylpentoxy group, 4-methylhexyl group or 4-methylhexoxy group is introduced into a nematic liquid crystal. Also,
JP-A-51-45546 discloses 1-menthol and d-menthol.
Alcohol derivatives such as borneol, d-camphor,
Ketone derivatives such as 3-methylcyclohexane, carboxylic acid derivatives such as d-citronellic acid and 1-camphoric acid, d
Optically active substances such as aldehyde derivatives such as -citronellal, alkene derivatives such as d-linonene, and other amines, amides, and nitrile derivatives can be used.

The smectic liquid crystal used in the present invention includes a smectic A liquid crystal and a smectic chiral C liquid crystal. The method for producing the light control device is not particularly limited. For example, the liquid crystal, the polymerizable composition comprising the monomers represented by the general formulas (I) and (II), and a photopolymerization initiator are mixed. To make a uniform solution, and expose to a predetermined amount with ultraviolet rays or electron beams. as a result,
The compounds represented by the general formulas (I) and (II) are copolymerized, and the copolymer and the liquid crystal are in a phase-separated state, whereby a polymer-maintaining liquid crystal light modulating material can be obtained.

At this time, the compound of the general formula (I) and the compound of the general formula (II) are used in a ratio of 10/1 to 1/10 (compound (I) / compound (II); weight ratio). Is preferable, and 1/1 to 1/10 are more preferable. Further, the compound of the general formula (I) and the compound of the general formula (II) may be used alone or in combination.

The ratio of the liquid crystal in the homogeneous solution is as follows:
It can be used at 40 to 90% by weight, preferably at 65 to 85% by weight. Examples of the photopolymerization initiator include 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and the like.

If necessary, a surfactant, a light stabilizer, a dichroic or non-dichroic dye, a chain transfer agent, a photosensitizer, a crosslinking agent and the like can be used in combination. On the other hand, a transparent electrode such as ITO is used as an electrode of the light control element of the present invention, and a transparent substrate such as a plastic plate of glass or polyester is used as an electrode substrate.

In order to increase the area or obtain a more uniform film thickness, it is preferable to include a spacer in the light control material. The spacer is not particularly limited, but a glass or a polymer such as polyvinylbenzene polymethyl methacrylate having a spherical or rod shape can be used. Use of the spacer includes a method of spraying the polymerizable composition on a substrate and then applying the polymerizable composition or a method of uniformly dispersing the polymerizable composition in the polymerizable composition and then introducing the spacer between the substrates.

When a pair of transparent electrode substrates is used, it can be used as a transmission type dimming element. When one is transparent and the other is opaque, a reflective layer is placed behind the opaque electrode substrate. Thereby, it can be used as a reflection type light control element. The light modulating device of the present invention is, for example, the liquid crystal described above, a polymerizable composition and a photopolymerization initiator, and, if necessary, sandwiches it between substrates having the electrodes as a uniform solution containing various additives, and performs exposure. It can be produced by polymerizing the polymerizable composition. It is also possible to apply a uniform solution of the polymerizable composition on a substrate and stack the substrates after polymerization.

[0027]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples. Example 1 0.1 g of a trimethylolpropane compound Ia (R ¹ = H, R ² = C ₃ H ₆ , m = 1 in the general formula (I)), an acrylate compound IIa (R ^{3 in the} general formula (II)) = H, R ⁴ =
_{C 4 H 9 (n))} 0.2g, as a polymerization initiator 2,2-dimethoxy-2-phenyl acetophenone 0.006 g, manufactured by E-8 (BDH Ltd. as a liquid crystal) was mixed with 0.7 g, homogeneous solution And a 10 μm diameter plastic (divinylbenzene copolymer) spacer 0.015 μm in the solution.
g of the mixed solution, and the mixed solution was cooled to an IT having a size of 6 cm × 9 cm.
When inserted between plastics with O (polyethylene terephthalate) and exposed by an ultraviolet irradiation device, a uniform light control element without cracks was obtained. The energy given corresponds to 400 mj.

An AC electric field (60 Hz,
(Sine wave) was applied, and the voltage dependence of the parallel light transmittance change was measured by a digital turbidity meter (Nippon Denshoku Industries Co., Ltd .; NDH-20D type). T ₀ = 22.0% T ₁₀₀ = 80.5% V ₁₀ = 5 V V ₉₀ = 24 V Transmittance difference (T ₁₀₀ −T ₀ ) = 58.5% (T ₀ : light transmittance at 0 applied voltage, T ₁₀₀ : increasing applied voltage Light transmittance when outgoing light transmittance is completely constant, V ₀ : applied voltage at which transmittance becomes 10% when T ₀ is 0% and T ₁₀₀ is 100%, V ₉₀ : same as left (Applied voltage at which the light transmittance becomes 90%), and both the voltage sensitivity and the transmittance difference showed good characteristics. Example 2 When the acrylate compound is IIb

[0029]

Embedded image

[0030] Except that
As a result of measuring the prepared uniform light control device without cracks in exactly the same manner as in Example 1, T ₀ = 15.0% T ₁₀₀ = 80.0% V ₁₀ = 6V V ₉₀ = 25V Transmittance difference = 65. 0%, showing good characteristics in both voltage sensitivity and transmittance change.

Example 3 The acrylate compound is IIc

[0032]

Embedded image

[0033] Except that
A uniform light control element without cracks was obtained. As a result of measuring this light control device in the same manner as in Example 1, T ₀ = 17.0% T ₁₀₀ = 81.0% V ₁₀ = 8V V ₉₀ = 27V The transmittance difference was 64.0%, and the voltage sensitivity was Also, good characteristics were exhibited with respect to changes in transmittance.

Example 4 The acrylate compound is IId (R in the general formula (II))^Three= C
H_Three, R^Four=-(CH _TwoCH_TwoO)_TwoCH_Three)
Outside, exactly the same as in Example 1, with no cracks and uniform dimming
An element was obtained. This dimming device was manufactured in the same manner as in Example 1.
Measurement result T₀= 13.9% T₁₀₀= 75.8% V_Ten= 13V V₉₀= 29V Transmittance difference = 61.9%, showing good characteristics in both voltage sensitivity and transmittance change
Was.

COMPARATIVE EXAMPLE 1 0.3 g of a trimethylolpropane compound Ia (R ¹ = H, R ² = C ₃ H ₆ , m = 1 in the general formula (I)), and 2,2-dimethoxy- as a polymerization initiator 0.008 g of 2-phenylacetophenone, E-8 as liquid crystal (manufactured by BDH)
A homogeneous solution was obtained by mixing with 0.7 g, and a plastic (divinylbenzene copolymer) having a diameter of 10 μm was obtained in this solution.
0.015 g of a spacer made by adding the mixture,
It was inserted between plastics with ITO (polyethylene terephthalate) having a size of 9 cm and exposed by an ultraviolet irradiation device to obtain a uniform light control element without cracks or the like. The energy given corresponds to 400 mj.

The light control device was measured in the same manner as in Example 1. T ₀ = 10.5% T ₁₀₀ = 42.2% V ₁₀ = 36 V V ₉₀ = 115 V Transmittance difference = 31.7% It was also found that the transmittance change and the voltage sensitivity were poor, which was not preferable as a light control element.

Comparative Example 2 Monoacrylate Compound IIa (R ³ =
_{^{H, R 4 = C 4 H}} 9 (n)) 0.3g, as a polymerization initiator 2,2-dimethoxy-2-phenylacetophenone 0.
006 g and 0.7 g of E-8 (manufactured by BDH) as a liquid crystal were used to produce a dimming device in exactly the same manner as in Example 1. However, no phase separation occurred and a uniform dimming film could not be obtained. Was.

[0038]

The light modulating material obtained by the present invention has good film uniformity, and the light modulating element using the light modulating material has a difference in transmittance between when an electric field is applied and when no electric field is applied, voltage sensitivity, It has excellent repetition response and heat resistance, and is useful for display devices, light control windows, and the like.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09K 19/54 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. An electric field application device comprising a liquid crystal and a polymer.
In light control materials that control the transmission and scattering of light depending on the presence or absence,
The polymer is represented by the following formula (I): C_TwoH_FiveC [CH_TwoO- (R^TwoO)_m-CO-C (R¹) = CH_Two]_Three (I) (wherein, R¹Represents a hydrogen atom or a methyl group;^TwoIs
A linear or branched alkylene group having 2 or 3 carbon atoms
And m represents an integer of 1 to 10. )
Limethylolpropane compound and the following formula (II): CH_Two= C (R^Three) -COOR^Four (II) (wherein, R^ThreeRepresents a hydrogen atom or a methyl group;^FourIs
An alkyl group having 1 to 18 carbon atoms, a cycloalkyl group,
Trahydrofurfuryl group or-(-R^FiveO-) _n-R
⁶(R^FiveIs a linear or branched alkyl having 2 to 11 carbon atoms
A kill group; ⁶Represents an alkyl group having 1 to 8 carbon atoms
And n represents an integer of 1 to 10. Acryle shown with)
Be a polymer obtained by copolymerizing a salt compound
Light control material characterized by the above. 2. A light control device comprising a light control material according to claim 1 sandwiched between a pair of substrates having electrodes on at least one transparent inner surface.