JPH02207220A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To allow driving with a low voltage and to eliminate the use of polarizing plates by constituting a light control layer of a nematic liquid crystal material contg. specific compds. and a transparent solid material, which liquid crystal material forms a continuous phase and which transparent solid material is dispersed in the liquid crystal material. CONSTITUTION:This device has two sheets of the substrates which have electrode layers and at least one of which is transparent and the light control layer supported between the substrates. The light control layer consists of the nematic liquid crystal material contg. the compds. expressed by formulas I, II and the transparent solid material. The liquid crystal material forms the continuous phase and the transparent solid material is dispersed in the liquid crystal material. In formula I, R<1> denotes 1 to 10C straight chain alkyl group or straight chain alkoxy group. In formula II, R<2> denotes 1 to 12C straight chain alkyl group. The driving of the large-area thin-film liquid crystal device with the low voltage is possible in this way and the need for the polarizing plates is eliminated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thin film containing a liquid crystal that can be formed over a large area. , blocking, and transmitting can be controlled electrically, and are used as screens to block the view in building windows and show windows, as well as curtains for lighting control, as well as to display characters and figures, and to provide high-speed response. Therefore, by electrically switching the display,
Used as display devices such as advertising boards, information boards, decorative display boards, etc.

(Prior art) Liquid crystal display elements have conventionally been TN using nematic liquid crystal.
type and STN type are in practical use.

Also, devices using ferroelectric liquid crystals have been proposed. These require polarizing plates and also require alignment treatment. On the other hand, as a method for manufacturing large, inexpensive liquid crystal devices that are bright and have good contrast without requiring these devices, a method is known in which liquid crystal encapsulation is used to disperse liquid crystal droplets in a polymer and then turn the polymer into a film. It is being Here, gelatin, gum arabic, polyvinyl alcohol, etc. have been proposed as the encapsulating substance (Japanese Patent Publication No. 58-501631, USP, 44
No. 35047).

In the technology disclosed in the above specification, if the liquid crystal molecules encapsulated with polyvinyl alcohol have positive dielectric constant anisotropy in a thin layer, the liquid crystal molecules can be encapsulated in the presence of an electric field. are aligned in the direction of the electric field, and when the refractive index n0 of the liquid crystal and the refractive index np of the polymer are equal, transparency is exhibited. When the electric field is removed, the liquid crystal molecules return to their random alignment and the refractive index of the liquid crystal drop becomes n. As the liquid crystal droplets shift, light is scattered at the interface between the liquid crystal droplets and the transmission of light is blocked, so that the thin layer becomes cloudy. In addition to the techniques described in "2," there are several other known technologies for forming thin films of polymers containing dispersed encapsulated liquid crystals in this way. JP-A No. 62-2231 discloses a liquid crystal dispersed in a special ultraviolet curable polymer.

(Problems to be Solved by the Invention) Important characteristics required for the practical use of large liquid crystal devices such as those described above are (i) ability to drive at low voltage (11) sufficient contrast (iii)
) Time division driving may be possible.

In particular, (i) and (city) are extremely important characteristics in order to make the driving part of the device inexpensive.

However, to date, (i) to (iii)
) A liquid crystal device that does not require a polarizing plate has not been fabricated.

The inventors of the present invention have conducted extensive studies on the preferred combination of the structure of a liquid crystal device and the chemical structure of the liquid crystal material used in the device, and have found that it can be driven at a much lower voltage than conventional large liquid crystal devices, and that it can be driven with a polarizing plate. We have succeeded in creating a liquid crystal device that can be made larger without the need for the use of.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a liquid crystal device described below.

That is, the liquid crystal device according to the present invention has two substrates each having an electrode layer and at least one of which is transparent, and a light control layer supported between the substrates, and this light control layer has the following general formula (1). )
and a transparent solid substance, the liquid crystal material forming a continuous phase, and the transparent solid substance being dispersed in the liquid crystal material. It is a liquid crystal device characterized by:

A compound represented by the general formula (J) (wherein R1 represents a linear alkyl group or a linear alkoxyl group having 1 to 10 carbon atoms) (hereinafter referred to as the compound of 2(1)) General A compound represented by formula (II) (wherein R2 represents a linear alkyl group having 1 to 12 carbon atoms) (hereinafter referred to as a compound of formula (n)).

).

In this device, the substrate may be a rigid material such as glass, metal, etc., or a flexible material such as a plastic film. Two substrates can be placed facing each other with an appropriate distance between them. Also, at least one of them is transparent, and the second one is transparent.
The light control layer supported between the layers must be visible from the outside world. However, complete transparency is not required. If the liquid crystal device is used to act on light passing from one side of the device to the other, both substrates are provided with suitable transparency. Appropriate transparent or opaque electrodes may be disposed on the entire surface or part of the substrate depending on the purpose.

A liquid crystal material and a transparent solid component are interposed between the two substrates. Incidentally, it is desirable to interpose a spacer for maintaining the distance between the two substrates in a conventional manner, similar to well-known liquid crystal devices.

The ratio of the liquid crystal material forming a continuous phase between the two substrates is preferably 70% by weight or more, and even more preferably 70 to 90% by weight (hereinafter, % means % by weight). ).

The transparent solid component interposed in the continuous phase of this liquid crystal material is
It may be dispersed in the form of particles, but preferably has a three-dimensional network structure. In any case, it is essential to form an optical interface with the liquid crystal material and to cause light scattering to occur. Its transparency can be determined appropriately depending on the purpose of use of the device, and its solidity is not limited to being rigid, but must be flexible, pliable, and elastic as long as it can meet the purpose. Also good. In the case of particles, if the particles are too large or too small compared to the wavelength of light, light scattering properties cannot be expected, but particles of appropriate size and shape can be selected depending on the purpose.

Synthetic resins are suitable as these transparent solid components. Ultraviolet curable monomers or oligomers are preferred as those that provide a three-dimensional network structure.

These liquid crystal devices can preferably be manufactured as follows.

That is, between two substrates each having an electrode layer and at least one of which is transparent, the above-mentioned liquid crystal material and an ultraviolet curable polymer-forming monomer or oligomer are placed as essential components, and a polymerization initiator and a chain are placed as optional components. The liquid crystal material forms a continuous phase by irradiating ultraviolet light through a transparent substrate in the presence of a solution consisting of a transfer agent, photosensitizer, dye crosslinking agent, etc., thereby polymerizing the monomers or oligomers; This is a method for manufacturing a liquid crystal device in which a transparent solid synthetic resin component in the form of a dimensional network is dispersed in a continuous liquid crystal phase.

In this method, the ultraviolet curable polymer-forming monomer or oligomer that is an essential component may be one that forms a three-dimensional network in the continuous phase of the liquid crystal material by the irradiated ultraviolet rays. Good examples of molecule-forming monomers are trimethylolpropane 1-reacrylate, tricyclodecane dimethylol diacrylate.
1., polyethylene glycol diacrylate, polypropylene glycol diacrylate, hexanediol diacrylate-1., neopentyl glycol diacrylate, tris(acryloxyethyl) isocyanurate, and the like.

Similarly, a good example of a polymer-forming oligomer is caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate.

Optional components include polymerization initiators, chain transfer agents, photosensitizers, dyes, crosslinking agents, etc., and can be appropriately selected depending on the types of monomers, oligomers, etc. and the performance of the desired liquid crystal device. can.

In particular, the combined use of a chain transfer agent can be extremely effective depending on the type of monomer or oligomer, preventing the resin from becoming too cross-linked, thereby making the liquid crystal material more responsive to electric fields, and lowering voltages. Drivability is demonstrated. A good example of a chain transfer agent is butanedioldithiopropione.
1., pentaerythritol tetrakis (β-thiopropionate), triethylene glycol dimercaptan, and the like. The amount of chain transfer agent added varies depending on the type of monomer or oligomer used, but if it is too small, the effect will be weak, and if it is too large, the opacity of the device will decrease and the contrast of the display will deteriorate. The effective amount is believed to be 0.05-30%, based on monomer or oligomer, with 0.1-20% being preferred.

In order to support a solution containing each of these components between two substrates, this solution may be injected between the substrates, but it may be applied onto one substrate using a coater such as a spinner.
Then, the other substrate may be stacked.

Curing of the uncured solution can be accomplished by irradiating a suitable dose of ultraviolet light through the transparent substrate. Depending on the type of monomer or oligomer or optional components,
Heat or electron beams can also be used instead.

The thickness of the light control layer is usually adjusted to a range of 5 microns to 30 microns.

A liquid crystal device configured in this manner enables time-division driving, which was not possible with conventional droplet dispersion type liquid crystal devices, and also has a lower driving voltage ( , the contrast is large, and the response speed is fast.For example, in contrast to conventional droplet dispersion type liquid crystal devices, which require a driving voltage of 60V or more in effective value, and in many cases 100V or more, the liquid crystal of the present invention The device achieves a rise response time of 3 to 4 msec and a fall response time of 4 to 30 msec at a driving voltage of approximately 20V.

(Example) Examples of the present invention will be shown below to further specifically explain the present invention. However, the present invention is not limited to these examples.

Example 1 19.8% by weight of trimethylolpantriacrylate as a polymer-forming monomer (the same applies hereinafter), 0.2% of 2-hydroxy-2-methyl-1-phenylpropan-1-one as a polymerization initiator Then, 80% of the liquid crystal (A) described below was mixed as a liquid crystal material, and a small amount of alumina powder with an average particle size of 10 μm was added as a spacer.
It was inserted between two ITO glass plates with a diameter of 1 cm, and irradiated with ultraviolet rays to harden (polymerize) the monomer. The curing conditions were as follows: The liquid crystal device was heated using a metal halide lamp (80W/c
m) at a speed of 3.5 m and 7 minutes, and was irradiated with ultraviolet rays. The energy given is 500mJ/cm2
corresponds to The electrode spacing of the device is 11 μm.

When a cross section of the light control layer formed between two glass plates was observed using a scanning electron microscope, a three-dimensional polymer network was observed.

The resulting liquid crystal device has a threshold voltage of V+o
= 8.7 V, Vqo = 19.2 V, contrast -1:17, rise response time 2.5 msec, fall response time 19 msec, time division line number Nm, X = 2.3.

(]) Liquid crystal (A) Composition transition temperature 63 °C (N-I point) 25 °
C (C-N point) Refractive index n8-1.712 n,, -1,514 Δn=0.199 Threshold voltage (Vt,,) 1.34 V Viscosity at 20°C 50.1 c, p.

(2) Number of time-division drive lines N, , X-[(α2+1)/(α2 x)), where α-V. /V+.

(3) The light transmittance of the device when no voltage is applied is 0%,
If the light transmittance when the light transmittance does not change as the applied voltage increases is 100%, then the applied voltage at which the light transmittance becomes 90% is V2O, and the applied voltage at which the light transmittance becomes 10%. Let be VIO.

(Effects of the Invention) As described above, the present invention is a large-area, thin-film liquid crystal device that can be driven at a low voltage of about 20 V and has a rise response time of 3 to 30 volts even at such a low voltage. 4m
The response speed is as fast as seconds, and the contrast between transparent and opaque is approximately 1
:17, has a threshold value, and is capable of time-division driving with a 1/2 duty. Therefore, it becomes extremely easy to adjust lighting, view, and display large-sized displays for advertisements, etc., and furthermore, manufacturing such a liquid crystal device is extremely easy and inexpensive.

Claims (1)

[Claims] 1. Two substrates each having an electrode layer, at least one of which is transparent, and a light control layer supported between the substrates, wherein the light control layer has a general formula ▲ mathematical formula, chemical formula, or table. ▼ (In the formula, R^1 represents a linear alkyl group or linear alkoxyl group having 1 to 10 carbon atoms.) Compounds and general formulas ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (In the formula, R^2 represents a linear alkyl group having 1 to 12 carbon atoms.) Consisting of a nematic liquid crystal material containing a compound represented by ▼ and a transparent solid substance, the liquid crystal material forms a continuous layer. A liquid crystal device formed of a liquid crystal material, wherein the transparent solid material is dispersed in the liquid crystal material. 2. The liquid crystal device according to claim 1, wherein the liquid crystal material accounts for 70% by weight or more of the components of the light control layer. 3. The liquid crystal device according to claim 1, wherein the transparent solid material is made of synthetic resin. 4. The liquid crystal device according to claim 1, wherein the transparent solid substance is dispersed in the liquid crystal material in the form of particles or a three-dimensional network. 5. The liquid crystal device according to claim 1, wherein the light control layer has a thickness of 5 to 30 microns.