JPH02504556A - liquid crystal elastomer element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] liquid crystal elastomer element The present invention relates to an optical element (optical component) consisting essentially of a liquid crystal elastomer. concerning their manufacturing methods and their use in integrated optics. Ru.

The rapid development of integrated optics has led to new optical elements such as switches, modules, etc. Development of polarizers, couplers, polarizers, etc. is required. Such an element are used in optical data transmission and optical sensor technology.

For their production, optical structures are made as easily as possible. Materials that can be manufactured are required.

In this context, liquid crystal materials have a wide variety of suitable physical and chemical properties. It is becoming more and more widely used industrially. Under the influence of an electric field, e.g. For example, light absorption, light scattering, birefringence, reflection or color can be changed.

A long time ago, the production of polymers that achieved the structural principles of liquid crystal compounds became possible. achieved success. Since linear and lateral ) Liquid crystal main chain type and side chain type polymers have been synthesized and studied (H, Finke l+++ann.

Angew, Chew, 99.840 (1987)).

Liquid crystal side-chain polymers are produced by subjecting the polymer to an alternating current electric field at a temperature higher than its glass transition temperature. (V, P, 5hibaev at al,, Polymer Communications 24.364 ( 1983)), resulting in orientation of the mesogenic groups.

This field-induced orientation is lower than the glass transition temperature when the electric field is applied to the polymer. Can be frozen by cooling to temperature. Then, the orientation is determined by the electric field. Remains stable even after being switched off.

Aligned liquid crystal polymer films exhibit improved optical clarity and different properties compared to non-aligned environments. It is outstanding in terms of birefringence.

M., Piskunov et al., Makromol, Chem. Rapid Communications 3, 443 (1982) , describes a method for aligning nematic liquid crystal side-chain polymers in a magnetic field.

H, Finkelmann et al-, Mol+Cryst, Liq+ Cryst.

92, 49 (1983), a nematic liquid crystal similar to the surface alignment of low molecular weight liquid crystals. The orientation of side chain polymers on the surface of thin films is described. This surface orientation is transparent It only works well at temperatures just below the point, and very long conditioning It takes time.

H, J, Coles and R, Simon (Polymer 26.1801 (1985)) described the use of liquid crystalline side-chain polymers as optical storage media. Ru.

equivalent to bipolarly oriented polymer liquid crystals to produce nonlinear optical elements. There is a lot of interest.

Meredith et al, (Macromolecules 15+1 385 (1982)'! C) N on a bipolarly oriented film of liquid crystal polymer A method for preparing doped with LO chromophore DANS is described.

Nonlinear optical elements are used for applications in optical data transmission and optical signal processing and storage. Special application for functional integration of optical fibers and optic structures There is a lot of interest in this. International Publication W087106.019 is for optical element manufacturing describes the use of smectic low molecular weight liquid crystals. Part of liquid crystal film By orienting the light, a refractive index pattern can be written on the liquid crystal. Used as waveguides and diffraction gratings.

When the polymer chains in a liquid crystal polymer are interconnected by difunctional molecules, the liquid crystal polymer Polymers with mesogenic side groups known as lastomers A rimmer network is obtained. The chain segments and mesogenic groups in these materials are Although movable at temperatures above the glass transition temperature, the material itself is a result of crosslinking. , maintain its shape stability. Special interest in these liquid crystal elastomers is that mechanical Their ability to orient due to the action of For example, liquids at temperatures above the glass transition temperature When tensile stress is applied to a crystalline elastomer film, the long axis of the mesogenic side groups is oriented parallel to the preferred direction. Cool the film to below the glass transition. When the stress is removed and the stress is removed, the orientation is permanently maintained (J, 5chatzle , H. Finkelmann, Mol.

Cryst, Liq, Cryst, 142.85 (1987)) That is, the effect of mechanical deformation of the elastomer on the alignment of liquid crystal molecules is determined by the electric field or Similar to the effect that a magnetic field has on the orientation of low molecular weight liquid crystals or non-crosslinked liquid crystal polymers. be.

Recently, liquid crystal elastomer can be selected (locally) in a limited area by mechanical action. We have discovered that it is also possible to selectively orient the material. This method allows locally modified A liquid crystal elastomer having a certain birefringence is obtained. Therefore, obtained in this way Because the materials used can selectively achieve birefringence changes in selectable regions, It is particularly suitable for the production of optical elements.

Here we will discuss the properties typical of such elastomers, namely anisotropic phase behavior. At the same time, shape stability and elasticity are important for applications.

Therefore, the present invention relates to liquid crystal elastomers with locally modified birefringence. Ru.

The invention also relates to optical elements containing liquid crystal elastomers.

The present invention further provides that the elastomer in the liquid crystal state is applied locally in these areas. Liquids suitable for use in optical elements, characterized in that they are subjected to local modification of birefringence. The present invention relates to a method for producing a crystalline elastomer.

Finally, the invention relates to the use of liquid crystal elastomers in optical elements and the use of such elements. Concerning use in integrated optics.

For clarity, formula 1 schematically shows the structure of liquid crystal elastomer: Mesogenic side groups (2) are connected to the polymer backbone ( 1) connected terminally or laterally (1atera-tty) to (The example shown is an example where it is attached at the end). (4) is two adjacent polygons. Represents a cross-linking unit of mer mirror opening.

Systems suitable for the present invention basically have mesogenic groups in the polymer network as side groups. and combine to produce the liquid crystal phase state of the elastomer. suitable Examples of suitable elastomers are polysiloxanes (H.

Finkelmann et al, Makromol, Chea+, Rapid Commun, 5°287 (1984) and J, ScbM tzle, H., Finkelmann, Mol.

Cryst, Liq, Cryst, 142.85 (1987)). deer However, it is also possible to use other liquid crystal elastomers known to those skilled in the art. So Besides, preferred copolymers further have a non-liquid crystalline chromophore as a side group. be.

Among the nidistomers that exist in a glassy state at room temperature, the polymer backing Bones derived from polymethacrylate, polychloroacrylate or polystyrene Particularly preferred is a body. A preferred spacer is an alkylene group + CH (n is preferably 1-6, especially 3-6). In general, shorten the spacer length. Shrinking stiffens the polymer backbone and therefore increases the glass transition temperature.

Among mesogenic groups, those that give a high clearing point, such as three aromatic rings, are preferred. .

Preferred elastomers that exist in a liquid crystalline state at room temperature are polyacrylates, Contains polysiloxane or polyphosphazene as the polymer backbone , and a copolymer containing a non-liquid crystalline chromophore that lowers the clearing point. This error In a group of stomas, the preferred spacer length n is 6 or more, and preferably n is 6 to 1. It is preferably in the range of 8. The preferred mesogenic group is on the long axis of the Mengen unit. long-chain radicals that lower the clearing point, e.g. alkyls with up to 15 chain members; alkyl, alkoxy and oxaalkyl groups.

Among elastomers with a smectic or nematic phase, its dilatation The vector is oriented perpendicular to the deformation axis during material elongation and parallel to the deformation axis during material compression. It is preferable that the Elastomers are commonly used in polymer chemistry by a method, e.g. by simple random copolymerization or by multifunctional crosslinker molecules. It is produced by a random polymer-like addition reaction with Another easy way is Mesogenic monomers are copolymerized with functional comonomers to form liquid crystal copolymers; This is a method of converting this into a network structure using a crosslinking agent in the second reaction step (R, Z entel, Liq, Cryst, 1, 589 (1986)).

Copolymers in which non-liquid crystalline chromophores are also attached as side groups may e.g. In order to reduce the refractive value, or to change other specific material properties, the application This is important.

Copolymers with side groups with nonlinear optical properties are materials for nonlinear optical properties It is suitable as As an alternative, a liquid crystal elastomer with low molecular weight NL It can be used as a matrix polymer in which an O chromophore is dissolved. Furthermore, pressure Elastomers doped with low molecular weight crystals are preferred for sensor fabrication.

In a preferred method according to the invention (1, c, elastomer film (ff , c, one liquid crystal), preferably macroscopically (tnacroscopically) The uniformly ordered film Jt, A is heated to a temperature higher than its glass transition temperature and its liquid crystal At temperatures below the aintropic phase transition temperature (Tac-z), stamp-like protuberances Applicable to bases with mechanical structure. The raised mechanical structure may be in the micron range. , and duplicate the waveguide contour. When the elastomer and base come into contact, The raised structure at the base of the elastomer is transferred into the originally planar surface of the elastomer. Elas The tomer deforms locally in those areas of the film and as such the elastomer – wall thickness changes occur. Depending on the orientation of the optical axis with respect to the bounding surface of the elastomer , the optical axis changes locally due to these local mechanical coating thickness changes, Therefore, the birefringence of the elastomer changes locally. These local changes in the optical axis are It is permanently retained at temperatures below tc-t, and the glass transition of the elastomer At temperatures below that, it freezes into a permanently and mechanically stable solid state. It will be done.

The macroscopic orientation of the optical axis (n) of the elastomer is determined by the mechanical deformation of the elastomer film. Obtaining birth through or voluntarily. to the boundary surface of the elastomer film. The orientation of the optical axis(s) depends on the direction of mechanical deformation of the film and the phase structure. determined by the structure (nematic, smectic) and the chemical structure of the elastomer. .

The base preferably has a raised structure on its surface necessary for local deformation of the elastomer. It may be made of different materials. Preferred base material is glass or polymer , such as polymethyl methacrylate, polystyrene or polycarbonate It is. However, other materials known to those skilled in the art may also be used as a base. It is possible.

Raised structures (or indentations) are generally in the micron range. , for example, 1 to 3 μm. However, they have larger dimensions It's okay. This depends in particular on the film thickness of the elastomer. Furthermore, non-conducting In the case of electroconductive bases, conventional methods may be more suitable.

Depending on the quality of the surface of the elastomer or base, the elastomer and base may be Sometimes they stick together when you touch them, and sometimes they don't. Those materials adhere If you do not want to introduce the structure of the base surface into the elastomer, and lowered its base to a temperature below the glass transition temperature. It can be removed afterwards. In that case, the surface structure is permanently retained in the elastomer. be done.

Examples of applications here are press molding, chip, sheet and film structures. It is.

Optical waveguides manufactured by the method described by the present invention are distinguished by low attenuation. There is. In some cases values of approximately 1 dBcm-” are achieved. They are therefore It can be advantageously used in product optics, such as polarizers.

Nonlinear optical elements with high second-order susceptibility and Optical waveguides made of non-centrosymmetrically oriented elastomers are used for optical data transmission and Optical insulators, modulators, couplers, optical switches and optics for information storage Suitable for use in valves.

Optical waveguides made of nonlinear optical elements and elastomers with high third-order sensitivity are It can be used in optical communication technology and information processing devices.

Furthermore, optical memories and holographic gratings can be applied to the method according to the invention. It can be manufactured more easily.

The following examples are intended to illustrate the invention and not to limit it. stomach. The spacer length shown indicates the number n of spacers + CHs, and the monomer ratio is the monomer ratio. It is given in le%.

Example l Elastomer used: Monomer ratio Polymer backbone: Polymethacrylate 7 groups: o-@Σcoo8oco, g3 crosslinking agent, OCN+CH teNCO'1 Glass transition degree: 45°C1 Clearing point: 120°C 50μm phi A macroscopically preoriented film of elastomer with a lumen wall thickness is heated to 70°C. Heat and insert a glass plate with a 3 μm raised mechanical structure that replicates the waveguide contour. apply to the base. The material is then cooled to room temperature.

Locally altered birefringence (more specifically at the boundaries of film thickness changes) An elastomer film having the following properties is obtained. In this way the structure is It is written specifically to a constant area. This material exhibits excellent properties as an optical waveguide.

Structures are written on the following elastomers in the same manner as in Example 1.

Example 2 Same as that described in Example 1 except that the spacer length is 7.8.10 and 12. 4 types of elastomers.

Example 3 Four types of epoxy backbones with spacer lengths of 6 and 11 with the following structures: Polymethacrylate/So)y' group: H-(CHt)m+ cOOcΣpage giantΣ(CHt)m-H93 crosslinking agent: OCN+CHxe NCO2m= 6.8 Example 4 Four types of elastomers m with the following structures with spacer links 6 and 11: Monomer ratio Polymer backbone: Polymethacrylate crosslinker: OCN+ C1h8NCO2m: 6.8 Example 5 Four types of polymer backbones with spacer lengths of 6 and 11 with the following structures: Polymethacrylate crosslinking agent: OCN C)+! (瀘N C0,2m: 6.8 Example 6 Four types of polymer backbones with spacer lengths of 63 and 11 with the following structures: Polymethacrylate crosslinking agent, 0CN-@-CHz%NCO2m : 6.8 Example 7 The spacer length is 3 (nematic, glass transition temperature: 12°C, clearing point: 59°C), 6 (smectic) glass transition temperature: 5°C, clearing point: 80°C), 8.10.12 Five types of elastomers have the following structures [monomer ratio is H, Finkelma nn et al, Makromol, Chew, RapidCo mmun-5, 287-293 (1984)].

Polymer backbone: Poly(hydrodienemethylsiloxane) mesogenic group :　　　　　　　-o8coo(φΣOCH.

The materials of Examples 2 to 7 also exhibit good to extremely excellent properties as optical waveguides. .

international search report , Yu1.1ao11.11@, PCr/EP 89100313 International Search Report S^　　　27550

Claims (5)

[Claims] 1. Liquid crystal elastomer characterized by having regions with locally altered birefringence Tomer. 2. Optical element containing liquid crystal elastomer. 3. By locally changing the film thickness of an elastomer in a liquid crystal state, birefringence can be reduced. Used in optical elements characterized by causing local modification in these regions A method for producing liquid crystal elastomer suitable for 4. Use of liquid crystal elastomer in optical elements. 5. Use of the optical element of claim 2 in integrated optics.