TWI390020B - Polymerised lc films with varying thickness - Google Patents

Description

Polymeric liquid crystal film having different thicknesses

The present invention relates to a film of a polymeric liquid crystal (LC) material having at least two regions of differing thickness, for example, in the form of a surface grating. The invention further relates to a method of making the film, a polymerizable LC material for preparing the film, and the use of the film in an LC display or other optical or electro-optical component or device, decorative or security application.

Gratings are commonly used in the display industry, for example, to arrange LC molecules in a preferred orientation, such as the dual-amplitude display disclosed in WO 01/40853. Likewise, carefully fabricated protrusions (surface relief gratings) can be used to fabricate multi-domain vertical alignment (VA) displays, for example, as disclosed in U.S. Patent No. 6,188,457. Optical lithography steps are generally required to fabricate these gratings, and the complex structure can be established by only a consuming number of processing steps, for example, see EP 1 186 916 and US Pat. No. 6,188,457. The obvious disadvantage of this type of method involves cost. Therefore, efforts have been made to find alternative ways of fabricating optical and surface gratings.

One method has been to disperse small metal spheres into a matrix, and a high-intensity laser is used to cut the film into a hollow to produce a grating, as reported in JP 2001-311810. Unfortunately, this method is still time consuming and therefore expensive. An alternative approach is to use direct writing UV or Ar ⁺ laser technology. For example, a grating produced by photo-isomerisable azobenzene as a main molecule in this way is, for example, DYKim, SK Tripathy, L. Li, and J. Kumar, Applied Physics Letters 66 1166 (1995), P. Rochon It is known from E. Batalla and A. Natansohn, Applied Physics Letters 66 136 (1995). Irradiation of the azobenzene compound with linearly polarized visible light (usually from an Ar ⁺ laser) results in selective isomerization of the azo bond, resulting in a concomitant increase in height and, therefore, a surface relief grating. Unfortunately, azobenzene materials are thick and therefore not suitable for display applications.

An alternative method is slow photopolymerization of polymerizable LC molecules (referred to as reactive liquid crystals or RMs). It also has the advantage of not having to use polarized UV light. In one example of this system, which is disclosed in U.S. Patent 4,877,717, the acrylate-containing RMs are photopolymerized via a photomask. This reticle combines two different areas that allow all or no UV light to penetrate. This results in photopolymerization of the RM film in the UV exposed region, while the UV-protected region still does not polymerize. In an attempt to maintain thermodynamic equilibrium, the two zones (polymerization and non-polymerization) begin to spread. However, the rate of diffusion of the polymer is much slower than that of the monomer. This causes more monomer to be present in the UV exposed area. This monomer is then polymerized to create a grating structure where the film thickness is much greater than the area that has been exposed to UV. Unfortunately, the main disadvantage of commercializing this method is the slow rate at which diffusion processes occur.

Accordingly, there is a need for an advantageous method of fabricating a grating that does not have the disadvantages of the prior art methods described above. It is an object of the present invention to provide such a method and grating, in particular having the following advantageous properties of using a mercury lamp source that does not require polarization, using materials suitable for use in displays and providing rapid fabrication of the grating structure. Other objectives are apparent to the expert by the following description.

The inventors of the present invention have found that the above objects can be attained by using the methods disclosed below. In the process according to the invention, the mixture of polymerizable liquid crystal precursor compounds or reactive liquid crystal precursors (RM) undergoes a high degree of change upon exposure to unpolarized or polarized UV light. This RM mixture is relative to the prior art It is highly reduced when exposed to UV radiation.

The present invention relates to a polymer film obtained by polymerizing a polymerizable liquid crystal (LC) material containing at least one photosensitive compound, characterized in that the film comprises at least two regions of different thicknesses.

The invention further relates to a polymer film obtained by the method comprising: a) providing a layer of polymerizable LC material comprising at least one photosensitive compound on a substrate, b) optionally arranging the layer of LC material into a uniform orientation , c) exposing the LC material in the layer or in its selected region to light rays that cause isomerization of the isomerizable compound, preferably UV rays, d) exposing at least a portion of the material The LC material in the region polymerizes, thus orientationally fixed, and e) optionally removes the polymeric film from the substrate.

The invention further relates to a polymer film as described above and below, wherein the polymerizable liquid crystal (LC) material comprises a host material comprising one or more polymerizable liquid crystal precursor compounds, and at least one polymerizable photosensitive compound that is miscible with the host material And wherein the thickness of the polymerized LC film is controlled by varying the amount and/or type of the photosensitive compound and/or the amount and pattern of the polymerizable liquid crystal precursor compound of the host material.

The present invention relates to a polymerizable LC material comprising at least one of the photosensitive compounds described above and below.

The invention further relates to a polymer film as described above and below Uses of liquid crystal displays (LCDs) or other optical or electro-optical components or devices, decorative or security applications.

The invention further relates to the use of one or more of the polymer films described above as an alignment layer, an optical retardation film or an optical waveguide.

The invention further relates to an LCD comprising the polymer film described above and below.

Noun definition

The term "film" as used in this application includes self-supporting (ie, free standing) films that exhibit more or less significant mechanical stability and flexibility, and on a support substrate or on two substrates. A coating or layer between them.

The term "liquid crystal or liquid crystal material" or "liquid crystal or liquid crystal original compound" shall mean a material or compound containing one or more rod-shaped, plate-shaped or dish-shaped liquid crystal primaries (ie, groups having the ability to induce liquid crystal phase behavior). Liquid crystal (LC) compounds having a rod or plate shape are also known in the art as "rod" liquid crystals. Liquid crystal compounds having a dish-shaped basis are also known in the art as "disc-shaped" liquid crystals. The compound containing the liquid crystal or the material itself does not necessarily have a liquid crystal phase. It is also possible to exhibit liquid crystal phase behavior only when it is in a mixture with other compounds or when a liquid crystal original compound or material or a mixture thereof is polymerized.

For the sake of simplicity, the term "liquid crystal material" is used below for liquid crystal materials and liquid crystal materials.

The term "reactive mesogen" (RM) means a polymerizable liquid crystal original compound.

The term "director" is known in the art and represents the long molecular axis of the liquid crystal material in the liquid crystal material (in the case of rod-shaped compounds) or the short molecular axis (in The preferred orientation direction of the discotic compound).

The term "planar structure" or "planar orientation" refers to a film in which the optical axis is substantially parallel to the plane of the film.

The term "vertical structure" or "vertical orientation" refers to a film in which the optical axis is substantially perpendicular to the plane of the film, i.e., substantially parallel to the plane of the film.

The term "inclined structure" or "tilted orientation" refers to a film in which the optical axis is inclined at an angle θ between 0 and 90 degrees with respect to the plane of the film.

The term "beveled structure" or "beveled orientation" means an oblique orientation as defined above, wherein the angle of inclination is monotonically varied in the direction of the vertical film plane by a range of 0 to 90, preferably from a minimum to a maximum.

The inclination angle of the bevel film is shown below as the average inclination angle θ _ave unless otherwise stated.

The average tilt angle θ _{ave is} defined as follows

Where θ'(d') is the local inclination angle of the thickness d' in the film, and d is the total thickness of the film.

In a uniformly oriented planar, vertical, and oblique optical film comprising a uniaxial positive birefringence liquid crystal material, the optical axis of the film is represented by a director of liquid crystal material.

The term "photosensitive" refers to a compound that changes its structure or shape upon reaction by light, including but not limited to photoisomerization, photoinduced 2+2 cycloaddition, photo-fired alignment, or similar photodegradation processes. Further, the photosensitive compound may be polymerizable or photopolymerizable.

The method according to the invention is suitable for providing an LC film having a defined structure (for example, a thickness pattern or a surface relief grating). The original alignment of the LC material is maintained during polymerization, so that a film having a surface relief grating and a film having an increased birefringence can be produced.

The film according to the invention is preferably prepared by a process comprising the steps a) to e) above. Steps a) to e) can be carried out according to standard procedures known to the expert and described in the literature.

The polymerizable LC material comprises a photosensitive compound and a host material.

The photosensitive compound is preferably a liquid crystal or an LC compound, and further preferably a polymerizable compound containing one or more bond groups (optionally via a spacer) to a polymerizable group of the liquid crystal pronucleus.

The host material is a liquid crystal or liquid crystal material comprising one or more polymerizable liquid crystal compounds (RMs). Preferably, the host material exhibits a liquid crystal phase behavior prior to polymerization.

The LC material is provided as a thin film on a substrate, where it can be arranged in a uniform orientation by means of tools or methods known in the art, or where it can be spontaneously aligned. The LC material, or a selected region thereof, is then exposed to radiation at a specified wavelength that causes the isomerizable compound to change its shape (eg, due to E-Z isomerization), for example, UV radiation. The orientation of the LC material in the illuminated area or in all layers is then fixed by in situ polymerization. The isomerization and polymerization steps result in isomerization of the LC material and a dramatic reduction in thickness in the polymerization zone.

Since the optical retardation of the oriented LC layer is shown as the product of the layer thickness d of the LC material and the birefringence Δn. Δn, the change in thickness and birefringence can also cause a retardation change in the irradiated portion of the LC material. Initially, the retardation value of the LC material layer is determined by the layer thickness. Controlled by appropriate choice of the type and amount of individual components of the LC material.

The degree of isomerization and thickness range in the LC material layer can be controlled by varying the type and amount of individual components of the LC material, or by varying the radiation dose, intensity, time, and/or power. A film having a pattern of regions or pixels having a specified thickness value different from each other can also be prepared by applying a photomask between the radiation source and the LC layer. For example, a film containing two different thickness values can be fabricated using a simple, monochromatic mask. A more complex film with multiple regions of different thicknesses can be fabricated using a gray scale reticle. After the desired thickness value is obtained, the LC layer is polymerized. In this way, a polymer retardation film having a thickness value ranging from the initial LC layer to a small value can be produced.

Preferably, the host material is a polymerisable nematic or smectic LC material, particularly a nematic material, and preferably comprises at least one di- or poly-reactive non-pair RM and optionally one or more than one mono-reactive non-pair Palm RMs. Crosslinked films are obtained by using two or more reactive RMs which exhibit high mechanical stability against high external influences such as temperature or solvent and high optical stability. Films comprising crosslinked LC materials are therefore particularly preferred.

Polymerizable liquid crystal monomers, di- and poly-reactive compounds for use in the present invention can be prepared by methods known per se and described, for example, by standard methods of organic chemistry, for example, Methoden der organischen Chemie of Houben-Weyl, Thieme-Verlag, Stuttgart.

Examples of suitable polymerizable liquid crystal precursor compounds which may be used as monomers or comonomers in the polymerizable LC mixture together with the compounds according to the invention are disclosed, for example, in WO 93/22397, EP 0 261 712, DE 195 04 224, WO 95/22586, WO 97/00600, and GB 2 351 734. Of course However, the compounds disclosed in these documents are only considered as examples, and should not limit the scope of the invention.

Examples of particularly useful polymerizable liquid crystal precursor compounds (reactive liquid crystal precursors) are shown in the following table, however, they should be merely illustrative and are in no way intended to be limiting, but rather to explain the invention:

In the above formula, P is a polymerizable group, preferably a mercapto group, a methacryl group, a vinyl group, a vinyloxy group, a propenyl ether, an epoxy group, an oxycyclobutane, or a styryl group, and x and y. Is the same or different integer from 1 to 12, and A is a 1,4-phenylene group, which is optionally substituted by L ¹ mono-, di- or tri- or 1,4-cyclohexylene, and u and v are independently of each other. 0 or 1, Z ⁰ is -COO-, -OCO-, -CH ₂ CH ² -, -CH=CH-, -C≡C-, or a single bond, R ⁰ is a polar group or a non-polar group, and Ter is Quinone-like group, for example, a group, Chol is a cholesteryl group, and L, L ¹ and L ² are, independently of each other, H, F, Cl, CN, or optionally a halogenated alkyl group having 1 to 7 C atoms, an alkoxy group, an alkylcarbonyl group, An alkylcarboxy group, an alkoxycarbonyl group, or an alkoxycarbonyloxy group, and r is 0, 1, 2, 3, or 4. The benzene ring in the above formula is optionally substituted by 1, 2, 3, or 4 L groups.

In this regard, the term "polar group" means a fluorinated alkylcarbonyl group or alkoxycarbonyl group selected from the group consisting of F, Cl, CN, NO ₂ , OH, OCH ₃ , OCN, SCN, optionally having up to 4 C atoms. An alkylcarbonyloxy group, or an alkoxycarbonyloxy group, or a mono-, oligo or polyfluorinated alkyl or alkoxy group having 1 to 4 C atoms. The term "non-polar group" means, optionally, an alkyl group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylcarbonyloxy group having 1 or more, preferably 1 to 12, C atoms. Or alkoxycarbonyloxy, which is not covered by the definition of "polar group" above.

Preferably, the host material comprises from 0 to 97%, preferably from 25 to 70%, or a plurality of liquid crystal original compounds having a polymerizable group (single reactivity), from -3 to 100%, preferably from 5 to 75%, very preferably from 10 to 50%, or a plurality of liquid crystal original compounds having two or more polymerizable groups (di-reactive).

Particularly preferred are non-p-polymerizable liquid crystal original compounds, particularly the formulae R1 to R13 and R18, and very preferably R1 and R18.

As noted above, the thickness variation in the LC material layer can be controlled by varying the type and amount of compound in the host material.

Particularly preferred is a host material comprising no more than 75%, very preferably no more than 50% of the two reactive compounds.

Suitable photosensitive compounds are known in the art. For example, it is a compound which exhibits photoisomerization, photo-fired recombination or 2+2 cycloaddition, or other photodegradation process upon light irradiation. Particularly preferred are photoisomerizable compounds. Examples of such compounds include azobenzene, benzaldehyde oxime, azomethine, stilbene, spiropyran, spirulina, phlegonic anhydride, diarylethene, cinnamate. Further examples are 2-methyleneindole-1-ones, for example as described in EP 1 247 796, and (贰-)benzylidene-cycloalkanones, for example as described in EP 1 247 797 .

Particularly preferably, the photoisomerizable compound is selected from the group consisting of cinnamic acid esters, in particular polymerizable liquid crystal precursors or reactive liquid crystal precursors (RMs) comprising at least one cinnamate group, for example, as GB 2 314 839, EP 03007236.7, US 5,770,107, or GB 2 388 600 patent. Very preferably the LC material comprises one or more cinnamate RMs selected from the group consisting of

Wherein P, A, R ⁰ , Y, L ¹ , L ² and v have the meanings indicated above, and Sp is a spacer having 1 to 12 C atoms, for example, an alkyl group or an alkylene group.

The polymerizable or reactive group P is preferably selected from the group consisting of a vinyl group, an acryl group, a methacryl group, an oxabutyl group, or an epoxy group, and particularly preferably an acrylic group.

The spacer Sp is preferably an alkyl or alkylalkoxy group having up to 10 C atoms which is unsubstituted or mono- or polysubstituted by F, Cl, Br, I, or CN. Very preferred Sp groups are exoethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl.

Y is preferably CN or Cl or OCH ₃ .

R ^{0 is} preferably a linear alkyl or alkoxy group having 3 to 8 C atoms, particularly n-propyl, n-butyl, n-hexyl, n-heptyl or n-octyl.

As described above, the thickness variation in the LC material layer can be controlled by changing the type and amount of the photosensitive compound. Thus, it has been found that polymerizable LC materials containing the specified type and amount of photosensitive compound are particularly useful for the purposes of the present invention because these materials can be easily manipulated and adjusted for polymer film thickness.

Particularly preferred is a cinnamic acid ester RMs having a non-polar terminal group R ⁰ as defined above. Very preferred are the cinnamate RMs of formulae IIIa and IVa. Further preferred is a cinnamic acid ester comprising two or more polymerizable groups, in particular Formula V.

Preferably, the polymerizable LC material comprises from 5 to 90%, very preferably from 10 to 60%, most preferably from 15 to 35%, of one or more photosensitive compounds, preferably cinnamate RMs, most preferably selected from the group consisting of Formula IIIa, IVa and V. The light ray used to cause photoisomerization in the LC material depends on the type of photographic compound and can be readily selected by those skilled in the art. Compounds which exhibit UV-induced photoisomerization are generally preferred. For example, for cinnamate compounds of formulas III, IV and V, UV radiation having a wavelength in the UV-A range (320-400 nm) or a wavelength of 365 nm is generally used.

The optimum irradiation time and radiation dose depend on the type of LC material used, especially the type and amount of the photosensitive compound in the LC material.

The thickness of the film according to the present invention is preferably from 0.01 to 3 μm, very preferably from 0.02 to 0.2 μm.

The thickness variation, or height or surface grating within the film is preferably from 0.01 to 2 microns, very preferably from 0.02 to 0.2 microns.

The film according to the present invention can be used, for example, as a surface relief grating for aligning liquid crystal materials.

In order to prepare a polymerized LC film, it is preferred to apply the polymerizable LC mixture to a substrate, preferably in a planar orientation, and in situ polymerization, for example, by exposure to heat or actinic radiation to LC The orientation of the molecules is fixed. The alignment and curing are carried out in the LC phase of the mixture. This technique is known in the art and is described, for example, by Angew. Makromol of D.J. Broer et al. Chem. 183, (1990), 45-66.

The LC material can be arranged by, for example, shearing the material simultaneously or after coating, applying a magnetic or electric field to the coating material, or adding the surface active compound to the LC material, and processing the substrate on which the material is coated. . A review of alignment techniques is shown, for example, in "Thermotropic Liquid Crystals" by I. Sage, edited by GWGray, John Wiley & Sons, 1987, pp. 75-77, and "Liquid Crystals-Applications by T. Uchida and H. Seki". And Uses Vol. 3", edited by B. Bahadur, World Scientific Publishing, Singapore 1992, pp. 1-63. A review of the alignment materials and techniques is shown in J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), pp. 1-77.

In a preferred embodiment, the polymerisable LC material comprises an additive that induces or enhances the planar alignment of the LC molecules on the substrate. Preferably, the additive comprises one or more surfactants. Suitable surfactants are described, for example, in J. Cognard, Mol. Cryst. Liq. Cryst. 78 , Supplement 1, 1-77 (1981). Particularly preferred are nonionic surfactants, very preferably fluorocarbon surfactants such as the commercially available fluorocarbon surfactant Fluorad FC-171® (available from 3M Co.) or Zonyl FSN® (available from DuPont) And the surfactant described in the patent GB 0227108.8.

The polymerizable LC material is preferably dissolved or dispersed in a solvent, preferably an organic solvent. The solution or dispersion is then applied to the substrate, for example, by spin coating or other known techniques, and the solvent is evaporated prior to polymerization.

The polymerizable LC material may additionally comprise a polymeric binder or one or more monomers that form a polymeric binder and/or one or more dispersing adjuvants. Proper bonding Agents and dispersion aids are disclosed, for example, in WO 96/02597. However, it is particularly preferred to be an LC material that does not contain a binder or a dispersing adjuvant.

Polymerization occurs by exposure to heat or actinic radiation. The actinic ray means irradiation with light such as UV light, IR light or visible light, irradiation with X-rays or gamma rays, or irradiation with high energy particles such as ions or electrons. Preferably, the polymerization is carried out by UV irradiation at a non-absorption wavelength. As for the source of actinic rays, for example, a single UV lamp or a group of UV lamps can be used. Curing time can be reduced when using high lamp power. Another possible source of actinic radiation is a laser, such as a UV laser, an IR laser or a visible laser.

The polymerization is preferably carried out in the presence of an initiator which absorbs at the wavelength of the actinic ray. For example, when polymerizing by UV light, a photoinitiator which decomposes under UV irradiation to generate a radical or ion which initiates a polymerization reaction can be used. When curing an acrylic or methacrylic based polymerizable material, it is preferred to use a radical photoinitiator, preferably when curing a polymerizable material having a vinyl group, an epoxide and an oxytetraalkyl group. To use a cationic photoinitiator. It is also possible to use a polymerization initiator which generates a radical or an ion which initiates polymerization upon heating. As the photoinitiator for radical polymerization, for example, commercially available Irgacure 651, Irgacure 184, Darocure 1173, or Darocure 4205 (all available from Ciba Geigy AG) can be used, and in the case of cationic photopolymerization, commercially available UVI can be used. 6974 (Union Carbide). The photoinitiator concentration in the polymerisable LC material is preferably from 0.1 to 10%, very preferably from 0.5 to 5%.

The polymerisable LC material may additionally comprise one or more other suitable ingredients, for example, catalysts, sensitizers, stabilizers, inhibitors, chain transfer agents, co-reactive monomers, surface active compounds, lubricants, wetting agents, dispersants Hydrophobic Agents, adhesives, flow improvers, defoamers, deaerators, diluents, reactive diluents, adjuvants, colorants, dyes, or pigments.

Films in accordance with the present invention may also be used in optical or electro-optical devices other than those described above, for example, as alignment layers, optical filters or polarized beam splitters, or as decorative or security applications.

For example, it can be used as a birefringence mark, image or pattern in decorative or security applications. The method of the present invention produces a negative image in the film that is only visible between staggered polarizers. The preferred use of these films is as a security mark or security thread to identify and prevent the forgery of valuable documents, or to hide the identification of images, information or graphics. It can therefore be applied to consumer products or household objects, car bodies, foils, packaging materials, fabrics or textile fabrics, incorporated into plastics, or applied to valuable documents such as banknotes, credit cards or ID cards, national ID documents, licenses. Or any product of monetary value, such as stamps, tickets, stocks, checks, etc.

The use as a birefringent marking is particularly preferred as a patterned film provided on or directly on a reflective substrate, for example, a metal or metallized film or foil, as described in EP 02019792.7.

The following examples should describe the invention without limitation.

Example 1

The polymerizable LC host mixture H1 was formulated as follows.

H1:

(1) 39.40% (2) 24.60% (3) 24.60% (4) 9.72% Irgacure 651 1.00% Fluorad FC171 0.60% Irganox 1076 0.08%

The different polymerizable and photoisomerizable compounds P1 to P5 at a concentration of 20% by weight of the total solids were then added to the host mixture H1 to produce mixtures M1 to M5, as shown in Table 1.

By spin coating (3,000 RPM, 30 seconds) of each mixture of M1 to M5 (described in Tables 1 and 2) in a 50% by weight solution of xylene on a polishing polyimine (JSR AL1054) / glass slide And make a set of two films. In one case, the film was immediately photopolymerized (UV-A, 20 mW ^{- 2} , 60 sec, N ₂ ) without further processing. In another case, the spin-coated film was exposed to a photoisomerization step (365 nm, 20 mW ^- ₂ ) before photopolymerization (UV-A, 20 mW ^-2 , 60 sec, N2). 300 seconds).

The retardation of the polymeric film was determined by measuring the transmittance of the film between parallel polarizers, the orientation axis of the film being at an angle of 45 to the axis of the polarizer. The optical transmittance is measured by the Oriel Spectrograph in the wavelength range of 420-800 nm, which uses a tungsten lamp as a light source. Film retardation by measuring the intensity of the observation The quantity is substituted into the theory and calculated. The average tilt angle of the nematic director in the polymeric film is calculated by measuring the retardation of the film (as described above) as a function of the angle of incidence of the beam by rotating the sample from -60° to +60° (see O. Parri et al., Mol. Cryst. Liq. Cryst, Vol. 332, p. 273, 1999).

Figure 1 shows a retardation diagram of a film of mixture M1 which is (a) isomerized and (b) isomerized prior to photopolymerization. The other mixture, M2-5, produced a similar block diagram before and after isomerization.

Comparing the block diagrams of Figure 1, it is apparent that the isomerized and non-isomerized films are well-aligned planar films. The tilt angles calculated at the substrate and at the air interface are the same (within experimental error). Each film was measured to obtain an angle of inclination of about 1° at the substrate and 0° at the air interface. The important difference between the two block diagrams is the value of the normal incidence of 0°. The isomerized film has a lower value, i.e., isomerization of the film reduces retardation without changing the original alignment of the liquid crystal.

To demonstrate height variations, the isomerization of the various mixtures M1 to M5 and the thickness of the non-isomerized film were measured using a KLA-Tencor Alphastep 500 profiler. For these measurements, the thin film sheet was scraped off and a trajectory was measured through the scratch line to cause the height (thickness) of the film to be measured. The difference between the thickness (Δd), retardation (ΔR) and birefringence (Δn) of each mixture due to the isomerization step is shown in Table 2.

Example 2

An isomerized film was prepared from mixture M4 as described in Example 1. The film was isomerized via a reticle containing the symbol shown in Figure 2a. The film directly below the symbol is not exposed to UV light and is therefore not isomerized, while the remaining film is isomerized. After this isomerization step, the reticle was removed and the entire film was photopolymerized.

Figure 2b illustrates a film image produced by isomerization of the reticle of Figure 2a when viewed between crossed polarizers.

Figure 2c depicts a plot of the relative height difference as a function of the thickness of the different regions of the film. In addition, the KLA-Tencor Alphastep 500 machine and the attached software measurement were used, and as indicated by the line in Figure 2b, the length of the letter 'e' transferred to the film was crossed.

Figure 2c clearly shows that areas of different heights can be made using a reticle.

Further experiments have also shown that the degree of height difference produced in the film can be controlled by controlling the intensity of the UV light reaching the sample (e.g., using a gray scale mask). In this way, a more detailed structure can be constructed. For example, a gray scale reticle having a strip of 0%, 50%, and 100% incident UV light can be placed between the sample and the light source. The film is irradiated and then polymerized. The area of the film that receives the full UV dose is as thin as about twice that of the 50% UV recipient. Similarly, the area receiving the 50% dose is about twice as thin as the one who does not receive the UV. Since the UV dose directly affects the thickness of the film, a refractory grating can be fabricated in the RM film using a mask having a range of UV transmittance values (eg, instead of 0% and 100% or otherwise).

Example 3

The polymerizable LC host mixture H2 was formulated as follows.

H2:

(1) 60.00% (2) 11.70% (3) 11.70% (4) 15.00% Irgacure 651 1.00% Fluorad FC171 0.60%

The polymerizable LC mixture was obtained by dissolving the compounds P3, P4 and P6 in different concentrations in the main mixture H1 and H2.

A polymer film was prepared from these mixtures as described in Example 1 and the thickness thereof was measured. The results are shown in Fig. 3 (H1) and Fig. 4 (H2). It can be seen that the thickness variation depends on the host and the photoisomerizable compound, and the compound P4 having a non-polar terminal hexyl group produces the greatest thickness reduction, and the compound P6 having a polar terminal CN group produces a minimum thickness reduction.

Figures 1a and 1b show block diagrams of films from the isomerized (a) and unisomerized (b) polymerizable mixtures as described in Example 1 of the present invention.

Figure 2a shows a reticle for preparing a film according to Example 2 of the present invention.

Figure 2b shows a photograph of a film according to Example 2 of the present invention.

Figure 2c shows the thickness profile of a film according to Example 2 of the present invention.

Figures 3 and 4 show the thickness variation versus cinnamate concentration for different films prepared from polymerizable and photoisomerizable mixtures in accordance with the method of the present invention as described in Example 3.

(no component symbol description)

Claims (16)

A film of a polymeric liquid crystal (LC) material obtained by polymerizing a polymerizable liquid crystal (LC) material containing 5 to 40% by weight of at least one photosensitive compound and a host material, wherein the photosensitive compound is a polymerizable liquid crystal precursor compound And comprising one or more polymerizable groups directly bonded to the liquid crystal pronucleus or via a spacer to the liquid crystal pronucleus, wherein the polymerizable liquid crystal original compound is selected from the group consisting of polymerizable liquid crystal precursor compounds having at least one cinnamate group, And wherein the host material is a liquid crystal (LC) material comprising one or more polymerizable liquid crystal precursor compounds, characterized in that the film comprises at least two regions of different thicknesses. The film of claim 1, wherein the host material comprises 0 to 97% by weight of one or more liquid crystal original compounds having a polymerizable group (single reactivity), and 3 to 100% by weight of one or more Or a plurality of liquid crystal original compounds of a polymerizable group (di-reactive). The film of claim 1, wherein the host material comprises no more than 75% by weight of the two reactive compounds. The film of claim 1, wherein the photosensitive compound is selected from the group consisting of a nonpolar terminal alkyl group having 1 to 15 C atoms, a nonpolar terminal alkoxy group having 1 to 15 C atoms, or a di- or A plurality of polymerizable groups of polymerizable liquid crystal cinnamic acid ester. The film of claim 4, wherein the photosensitive compound is selected from the group consisting of: among them, Is 1,4-phenylene, L ^1, or by mono-, di- or tri-substituted phenyl group of 1,4 or 1,4-cyclohexylene group, P is a polymerizable group, Sp is a spacer group or a single bond , v is 0 or 1, Y is F, Cl, CN, NO ₂ , OH, OCH ₃ , OCN, SCN, or a fluorinated alkylcarbonyl group having at most 4 C atoms, an alkoxycarbonyl group, an alkylcarbonyloxy group Or alkoxycarbonyloxy, or a mono, oligo or polyfluorinated alkyl or alkoxy group having from 1 to 4 C atoms, R ⁰ being a nonpolar alkyl group having up to 15 C atoms or having up to 15 a non-polar alkoxy group of a C atom, and L ¹ and L ² are, independently of each other, H, F, Cl, CN, or a halogenated alkyl group having 1 to 7 C atoms, an alkane having 1 to 7 C atoms. An oxy group, an alkylcarbonyl group having 1 to 7 C atoms, an alkoxycarbonyl group having 1 to 7 C atoms or an alkoxycarbonyloxy group having 1 to 7 C atoms. A film according to claim 5, characterized in that Y is CN or Cl. The film of claim 5, characterized in that R ⁰ is a linear alkyl group having 3 to 8 C atoms or an alkoxy group having 3 to 8 C atoms. The film of claim 7, wherein the polymerizable group P in the photosensitive compound is selected from the group consisting of a mercapto group, a methacryl group, a vinyl group, a vinyloxy group, a propenyl ether, an oxocyclobutane, an epoxy group or Styryl. The film of claim 7, characterized in that the spacer Sp is an alkylene group having up to 10 C atoms or an alkoxy group having up to 10 C atoms, which is unsubstituted or F, Cl, Br , I or CN single- or multi-substituted. The film of claim 1, wherein the film is obtained by a method comprising the steps of: a) providing a layer of a polymerizable liquid crystal (LC) material comprising at least one photosensitive compound on the substrate, and b) liquid crystal (LC) The material layers are arranged in a uniform orientation, c) exposing the liquid crystal (LC) material in the layer or in its selected region to light rays causing isomerization of the isomerizable compound, d) at least one of the materials The liquid crystal (LC) material in the partially exposed areas is polymerized, thus orientationally fixed, and e) the polymeric film is removed from the substrate. The film of claim 10, wherein the light rays in step c) are UV rays. A method of preparing a film according to claim 1, comprising the steps of: a) providing a layer of a polymerizable liquid crystal (LC) material comprising at least one photosensitive compound on the substrate, and b) arranging the layers of the liquid crystal (LC) material to be uniform Orientation, c) exposing a liquid crystal (LC) material in the layer or in its selected region to a light ray that causes isomerization of the isomerizable compound, d) exposing at least a portion of the material to the region The liquid crystal (LC) material is polymerized, thus orientationally fixed, and e) the polymeric film is removed from the substrate. The method of claim 12, wherein the light ray in step c) is an ultraviolet ray. The film of claim 1, wherein the thickness of the film of the polymeric liquid crystal (LC) material is controlled by changing one or more factors selected from the group consisting of: the amount of the photosensitive compound and the polymerizable liquid crystal of the host material. The type of compound. A polymerizable liquid crystal (LC) material comprising 5 to 40% by weight of at least one photosensitive compound and a host material, wherein the photosensitive compound is a polymerizable liquid crystal precursor compound comprising one or more directly bonded to a liquid crystal pronucleus or a polymerizable group bonded to the pronucleus of the liquid crystal via a spacer, wherein the polymerizable liquid crystal original compound is selected from a polymerizable liquid crystal original compound having at least one cinnamate group, and wherein the host material comprises one or more polymerizable liquid crystals A liquid crystal (LC) material of the original compound. A use of a film according to any one of claims 1 to 11 and 14 for use in a liquid crystal display (LCD) or other optical or electro-optical component or device, or in a decorative or security application.