KR100474131B1 - Optical member and manufacturing method thereof - Google Patents

Abstract

The optical member of the present invention is a liquid crystal display device comprising a substrate, a cell made of two substrates spaced apart, at least one orientation layer on the substrate, and a cross-linked liquid crystal monomer or oligomer having locally different orientation of liquid crystal molecules And at least one anisotropic layer. The surface of the alignment layer adjacent to the liquid crystal layer contains an alignment pattern having a line structure that is parallel or fan-like defined within a locally limited area. The average spacing between the lines is less than the thickness of the liquid crystal layer and the angle between adjacent lines is less than 3 degrees.

Description

Optical member and manufacturing method thereof

The present invention relates to a liquid crystal display device comprising a substrate, a cell made up of two substrates spaced apart, at least one orientation layer on each substrate, and a liquid crystal layer disposed on the substrate or between the substrates, wherein the orientation of the liquid crystal molecules is locally different, And an optical member comprising at least one anisotropic layer composed of a monomer or an oligomer. The present invention also relates to a method of production and use of said member.

Anisotropic transparent or colored polymer network layers in which stereoscopic orientation high resolution optical axes are pre-installed are very important for display technology, integrated optics and anti-counterfeiting.

EP-A-545 234 discloses a liquid crystal cell having a fine structure in which the orientation is limited so that the region includes regions having different refractive indices. This kind of refractive index pattern of the liquid crystal can be obtained by using a stylus which moves correspondingly to a scanning pen of a scanning force microscope (scanning probe or atomic force microscope (AFM)), Lt; RTI ID = 0.0 > mechanically < / RTI > Depending on the pressure provided by the stylet, the line may consist of relatively sharp grooves or only uniformly aligned molecular rows. Hereinafter, the term "scratching" is used to indicate how to create line structures using stylets. In a plate cell structured in this manner, the pattern on the alignment layer constitutes an alignment pattern that is transferred to the liquid crystal. Optical nonlinear liquid crystal structures or any fixed optical waveguide structures are important applications.

EP-A-611 981 discloses a substance stabilizing the alignment structure of a monomeric liquid crystal by cross-linking and a stabilization method. The orientation structure of the liquid crystal is induced by the orientation layer (PPN layer) of the photo-orientable polymer network. For this purpose, in the first step, a desired pattern is formed in the PPN alignment layer by using the polarization, and in a second step, it is transferred to the liquid crystal layer deposited on the alignment layer by spin coating (PPN method). Then, the liquid crystal structure is stabilized by crosslinking. This type of crosslinked liquid crystal layer is hereinafter simply referred to as LCP (liquid crystal polymer).

European Patent Application No. 689 084 discloses an optical member whose layer structure is composed of an anisotropic layer of a liquid crystal monomer crosslinked with a plurality of PPN alignment layers, all of which are limited in the PPN process, i.e., limited resolution, And limited tilt angle adjustment).

Unpublished Swiss Patent Application No. 2036/95 discloses, for example, a method of manufacturing an optical member used as a mask for transferring a polarization pattern to a polarized light sensitive layer and its use.

European Patent Application No. 689 065 discloses an optical PPN member having a layered structure suitable for use in preventing forgery of a patent and a method of manufacturing the same.

It has been found herein that by using a cross-linkable liquid crystal with a micromechanically scratched orientation layer, features can be much better or even entirely new structures can be created.

According to the present invention, the above-described member has an alignment pattern having a line structure in which the surface of the alignment layer adjacent to the liquid crystal layer is limited within a locally limited area, and the average interval between the lines is equal to or less than the thickness of the liquid crystal layer The angle between adjacent lines is characterized by less than 3 degrees.

For example, smaller structures can be fabricated in contrast to the PPN process in this manner. In addition to the preferred orientation, the tilt angle of the molecules can be controlled and varied, and the preferred orientation can be continuously localized. This member requires only one substrate as opposed to the liquid crystal cell described in EP 545 234. Further, a three-dimensional structure (multi-layer) can also be constituted.

As shown in Fig. 1, the alignment layer 2 is arranged on the substrate 1 (e.g. glass). The layer is preferably made of polyimide and is preferably spin-coated by methods known to those skilled in the art. In the first step, the orientation layer is rubbed by conventional means parallel to the y-direction of Fig. As is well known, the purpose of this is to obtain a substantially uniformly oriented adjacent liquid crystal layer parallel to the direction of friction. The desired alignment pattern is then scratched using a micro-mechanical stylet. The method of adjusting the stylus is known from scanning probe microscopy techniques. The stylet is moved parallel to the x-axis to create the microstructure shown in Fig. A suitable liquid crystal monomer mixture of the desired thickness is then applied by spin coating. In the unscratched region 5 the liquid crystal layer is oriented parallel to the original rubbing direction y and in the scratched region 4 the liquid crystal layer is oriented parallel to the scratch direction x. The orientation pattern can be recorded with a single stylus or with multiple parallel stylus.

The liquid crystal layer is then stabilized by chemical or photochemical cross-linking. In the case of photochemical cross-linking, if it is not necessary to fix each part of the layer, it can be exposed through a suitable mask in the last stage mentioned above. Thus, in this case, the final LCP layer comprises a region 7 in which the liquid crystal molecules are oriented parallel to the direction of friction y and a region 6 in which the molecules are oriented parallel to the direction of friction x.

In addition, it is possible to adjust and adjust the inclination angle of the liquid crystal molecules by adjusting the stylus. As is well known, the liquid crystal molecules are not necessarily parallel to the surface but are inclined at an angle to the plane depending on the polymer of the orientation layer. The direction of friction or scratching is determined by whether the molecule is an angular negative value or a negative value that is inclined with respect to the x direction. A method which can be used according to the present invention is shown in Fig. 5; Scratching movements can always occur in the same direction, and are recorded again in the track already recorded, respectively, while the stylus is raised in the case of Fig. 5A or returned in the case of Fig. 5B. Therefore, in the latter case, the scratching in the y direction must always occur at the same time. Both of these scratching methods result in polymer-specific maximum tilt angles. The scratch pattern of Fig. 5c has a tilt angle of 0, while a tilt angle of less than the maximum possible value of the pattern of Fig. 5d or Fig. 5e results. Therefore, the tilt angle can be adjusted and adjusted by selecting a scratching method.

Because the crosslinked polymer is mechanically stable, the above method can be used repeatedly, with or without the buffer polymer layer. This is shown in Fig. Layers 21, 22 and 23 correspond to layers 1, 2 and 3 of FIG. After crosslinking layer 23, it is rubbed again and micro-mechanically scrunched. Alternatively, additional layers can be applied before friction and scratching to improve, for example, optical or orientation properties. Layer 24 is spin coated and then cross-linked to produce additional orientation patterns 25 and 26. The method can be repeated as often as necessary to obtain a structured three dimensional refractive index pattern in the z direction.

The present invention is used at any time when a power failure, that is, a high-resolution refractive index pattern in which no current flows, is required. Also, the scope of application includes all fields in which members manufactured by the PPN method can be used. However, the present invention is also capable of controlling the fine structure, the continuous change of the director direction and the addition of the inclination angle, so that it can be used for completely new possibilities in addition to the already known PPN applications.

Such possibilities include, for example, optical waveguide structures of integrated optics such as couplers, coupling-in structures (e.g. lattices), delay lines or polarization-influencing structures . This optical waveguide structure can also be used as a connection network in a simple manner in combination with an active or NLO active member. Stereo networks can be used for crossing, especially where there is no coupling between layers or optical waveguide interaction. One possible example in the present invention is the 180 ° optical waveguide bend of FIG. Light 32 is transmitted to waveguide 33 and is bent 180 degrees to reach point 32. In order to produce this kind of waveguide structure, the scratch direction must be changed continuously locally in both the inside bend region 34 and outside bend region 35, that is, the waveguide 33 itself. This is not possible with any method already known.

In addition, the electrostatic refractive index pattern can be used, for example, to produce a high resolution mask for PPN exposure. By using the present invention, it is possible to produce masks having higher resolution and higher complexity than the photolithography method described in Swiss Patent Application No. 2036/95.

The electrostatic refractive index pattern is also very important to prevent counterfeiting of all kinds of identification and documents. Due to the high resolution of the scratch pattern in accordance with the present invention, the diffraction effect can be used as an additional security element. That is, the refractive index pattern can operate as a polarization-dependent hologram. When a three-dimensional structure (volume hologram) is produced as described above, the scattering efficiency can be greatly improved.

The present invention is also very important in combination with the PPN method. The area having a large area can be optically structured by the PPN method, and then the microstructure can be applied by the method according to the present invention. In this case, for example, the orientation layer 2 of FIG. 1 or the layer 22 of FIG. 2 does not consist of a rubbed polymer layer, or a possible intermediate layer between the layers 23 and 24 is a layer of scratched polymer And an additional pattern is scratched after cross-linking. The same applies to all embodiments described hereinafter.

[Example]

Preparation of a member according to the invention

Diacrylate components (monomers 1, 2 and 3, respectively) of the following formulas 1, 2 and 3 are used as cross-linking monomers.

[Chemical Formula 1]

(2)

(3)

The above ingredients are used to develop supercooled nematic mixture MLCP, especially at low temperature (about 35 ° C), which can be prepared at room temperature. The ratio of Monomers 1, 2 and 3 in the mixture is 80: 15: 5. 2% of the photoinitiator IRGACURE 369 from Ciba-Geigy is also added to the mixture.

A polyimide layer having a thickness of about 100 nm is spin-coated on a test plate, which is ITO (indium-titanium oxide) coated glass, by a known method. The layer is rubbed with a conventional friction mechanism. Then, the grating structure whose lattice constant is variable and which forms an angle of 45 DEG with respect to the original rubbing direction is scratched using a piezo-driven stylus. This is shown schematically in Figure 4; The coated sample 41 is fixed to a table which is mechanically moved in the direction 45 (v = 3.6 mm / s). The stylet 43 is fixed to the small rod 44 and moves piezo-electricly in both directions 46 and 47. A constant frequency of 240 Hz is applied in direction 46, corresponding to an average spacing of 7.5 nm of the scratch lines and a line length of 10 μm. The grating period is determined by stopping and periodically stopping. Alternatively, the stylus can be raised or lowered periodically in the direction 47.

Then, LCP is applied by spin coating (parameter: 2000 rpm for 2 minutes). The layer thickness can be varied widely by selecting the MLCP concentration in the anisole solvent. For example, when the concentration is 5%, a layer about 65 nm thick is produced. The layer is then photocrosslinked in a vacuum (Hg arc lamp, 30 minutes). The cross-linked structure is examined with a polarizing microscope and an atomic force microscope (AFM). With a polarization microscope, the lattice is clearly observed up to the resolution limit of the microscope (i.e., up to the grating period of 720 nm). That is, the strip 42 of Figure 4 has a double refraction that is oriented differently than other portions of the sample. Observation under AFM revealed a lattice period of 240 nm. It can be seen from these measurements that an extremely fine refractive index pattern can be generated in the crosslinked anisotropic polymer.

The optical member of the present invention is effectively used for a mask, an optical waveguide or an optical waveguide network, a security device of an identification card, or a document by enabling fine structure, continuous change of a director direction, and addition of an inclination angle.

1 is a schematic cross-sectional view of one embodiment of a member according to the invention,

Figure 2 is a schematic cross-sectional view of another embodiment of a member according to the invention,

Figure 3 is a schematic top perspective view of another embodiment of a member according to the present invention,

4 is a view showing an arrangement for manufacturing a member according to the present invention,

Figure 5 illustrates various methods of guiding a stylus.

Claims (12)

A liquid crystal display device comprising a substrate, at least one orientation layer, and at least one anisotropic layer composed of a crosslinked liquid crystal monomer or oligomer having locally different orientation of liquid crystal molecules, wherein the surface of the orientation layer adjacent to the liquid crystal layer is in a locally limited region Wherein an average interval between lines is equal to or less than a thickness of the liquid crystal layer and an angle between adjacent lines is equal to or less than 3 占 with an alignment pattern having a limited parallel or fan-like line structure. A cell comprising two substrates spaced apart, at least one orientation layer on each substrate, and at least one anisotropic layer comprising a cross-linked liquid crystal monomer or oligomer disposed between the layers and having a locally different orientation of the liquid crystal molecules Wherein the liquid crystal layer has an alignment pattern having a line structure in which the surface of the alignment layer adjacent to the liquid crystal layer is confined within a locally limited region and an average interval between the lines is equal to or less than a thickness of the liquid crystal layer, Is not more than 3 DEG. 3. The optical member according to claim 1 or 2, wherein the alignment layer comprises a polymer network having a light-tuned structure. 3. The optical member according to claim 1 or 2, wherein the line structure is made of a groove-like structured element made by micromachining. A method for producing an optical member according to any one of claims 1 to 3, comprising micromachining the microstructure on the surface of the alignment layer, applying a liquid crystal oligomer or a monomer layer, and then cross-linking the liquid crystal layer. The method according to claim 5, wherein the direction of the optical axis changes along the direction of the scratched line. 7. The method of claim 6, wherein one of the two substrates in the cell is removed after crosslinking. The optical member according to claim 1 or 2, used as a mask for generating a limited polarization pattern, that is, a light beam whose locally polarized light can be changed. 3. Optical element according to claim 1 or 2, used to create a light-induced alignment pattern in the polarization-sensitive light layer. 3. Optical element according to claim 1 or 2, used as an optical waveguide or optical waveguide network. The optical member according to claim 1 or 2, used as a security element of an identification card or document. The optical member according to claim 1 or 2, wherein the optical member is used as a photorefractive element.