JP2005350626A - Colored reflective material, colored reflective filler and application using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colored reflective material with a high light utilization efficiency, a design property, a high manufacturing efficiency and an excellent low cost productivity. <P>SOLUTION: The colored reflective material is characterized in composed of a cholesteric liquid crystal layer having at least two independent selective reflective wavelength zones in a single layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a colored reflective material and a colored reflective filler that is a pulverized product of the colored reflective material. The present invention also relates to a colored coating agent using the colored reflective filler. Since the colored coating agent contains cholesteric liquid crystal as a colored reflective filler, it can be used as a paint exhibiting a metallic color. The colored coating agent is a non-light-absorbing material that changes in color tone depending on the angle and can provide bright color development. A reflective film or a coating layer can be obtained from the colored coating agent, and these can be used in various applications.

  The present invention further relates to the use of the colored reflective material, colored reflective filler or colored coating agent in decorative applications, cosmetic or pharmaceutical composition applications, optical elements or crime prevention applications. The colored reflective filler can be used as an effective pigment in colored plastics for decorative use or cosmetics, and used in automobiles, active or passive optical elements, optical films such as polarizing films or compensation films, crime prevention, eg ID cards It can be used for security labels, markings or patterns to prove documents such as credit cards and tickets.

  Conventionally, metallic paints using metal thin film powder, vapor deposited thin film, mica filler, cholesteric liquid crystal and the like are known. These metallic paints are colored by reflecting only light of a specific wavelength mainly due to interference, and are highly designable paints. Various types of metallic paints using cholesteric liquid crystals have been proposed (Patent Literature 1, Patent Literature 2, Patent Literature 3, Patent Literature 4, Patent Literature 5, Patent Literature 6, Patent Literature 7, Patent Literature 8, Patent Document 9).

  Since the metallic paint using the vapor-deposited thin film, mica filler, cholesteric liquid crystal and the like is an optical film that functions only for a specific wavelength, the region having a high reflectance is limited to the vicinity of the designed wavelength. Therefore, in order to obtain brighter reflection, it is necessary to increase the number of vapor deposition layers or to apply a liquid crystal layer in multiple layers. However, these are not preferable in terms of increase in process and cost. For example, in Patent Document 1, a reflective layer is obtained by stacking right-twisted cholesteric liquid crystal and left-twisted cholesteric liquid crystal. This necessitates two types of chiral agents for imparting torsion, leading to an increase in process and price. In addition to the above, a three-layer structure in which cholesteric liquid crystals in the same twist direction are stacked with a retardation plate interposed therebetween has been proposed (Patent Document 10), but this is also complicated and expensive to manufacture.

  In addition, a reflector having a high reflectance due to interference reflection by a multilayer laminated film and a large color change due to an incident angle has been proposed (Patent Document 11, Patent Document 12, and Patent Document 13). However, these patent documents have a problem that, for example, the total number of stacked layers reaches several hundred layers, and thus a thin layer having a thickness of the order of the optical wavelength has to be controlled.

  On the other hand, attempts to broaden the reflection band have been widely made (Patent Document 14, Patent Document 15, Patent Document 16, Patent Document 17, Patent Document 18, Patent Document 19, Patent Document 20, Patent Document 21). If the visible light region is covered, bright reflection with high reflectivity can be obtained. However, these examinations are for obtaining neutral reflection, and there is no characteristic that causes a sharp change in color tone due to a change in incident angle.

  Moreover, the laminated body which combined the cholesteric liquid crystal layer and the light control layer is proposed (patent document 22). However, the laminate can only see a color close to that of the light control layer, and although it can provide a stable color tone, it cannot give a sudden color change.

It has also been proposed to use cholesteric liquid crystals in the form of beads (Patent Document 23). However, in the above proposal, the orientation characteristics in the particles are not always good, and the reflectance is not high. Since the individual particles face the same direction, even though they are the same particle, the reflected color of each particle has different characteristics, but the degree of change due to the angle remains unchanged.
US Pat. No. 6,394,595 US Pat. No. 6,387,457 US Pat. No. 5,683,622 US Pat. No. 6,338,807 European Patent Application No. 0201260 European Patent Application No. 0685749 European Patent Application No. 96102263 WO99 / 02340 pamphlet JP 2002-201222 A JP 2001-315243 A US Pat. No. 6,515,785 US Pat. No. 6,506,480 US Pat. No. 6,534,158 Japanese Patent Laid-Open No. 2001-100045 JP 2001-56484 A JP 2000-95883 A US Pat. No. 6,071,438 European Patent Application No. 08894545 US Pat. No. 6,217,955 JP 2001-56409 A JP 2001-261739 A JP 2001-180200 A JP 2001-201222 A

  An object of the present invention is to provide a colored reflector having high light utilization efficiency, excellent design properties, high production efficiency, low cost and excellent mass productivity.

  Further, the present invention provides a colored reflective filler that is a pulverized product of the colored reflective material, and further a colored coating agent using the colored reflective filler, and further a reflective film or coating obtained from the colored coating agent. The purpose is to provide a layer. Moreover, it aims at using the said colored reflective material, a colored reflective filler, and a colored coating agent for various uses.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the following colored reflectors and the like, and have completed the present invention.

  That is, the present invention relates to a colored reflective material comprising a cholesteric liquid crystal layer having at least two independent selective reflection wavelength bands in a single layer.

  In the colored reflector, the cholesteric liquid crystal layer preferably has discontinuous cholesteric twist pitch lengths corresponding to independent selective reflection wavelength bands in the thickness direction.

  The case where the cholesteric twist pitch length continuously increases or decreases in the thickness direction is “continuous”, and in this case, all wavelengths between the selected wavelength bands exhibit substantially uniform reflection intensity. If there is a part with no pitch length in the middle of the thickness direction, and there is a break (when there is a part with low reflectivity in the middle), that is, when the increase or decrease in pitch change is reversed (for example, it has been reduced in the middle) Is “discontinuous”). When the cholesteric twist pitch length exists discontinuously, a suitable colored reflector can be obtained.

  In the colored reflective material, the cholesteric liquid crystal layer preferably has a color that can be obtained by a complementary color mode using at least two independent selective reflection wavelength bands.

  In the present invention, a cholesteric liquid crystal layer having at least two independent selective reflection wavelength bands in a single layer is used as the colored reflector. The cholesteric liquid crystal layer is an optical thin film having two or more independent selective reflection wavelength bands even in a single layer because the twist pitch of the cholesteric liquid crystal that determines the interference wavelength is discontinuous in the thickness direction. Since this optical thin film (interference film) has two or more independent selective reflection wavelength bands while maintaining the manufacturing method, the number of steps, and the material cost substantially the same as the conventional one, it is possible to obtain a color by the complementary color effect by the reflected light. . In the conventional colored reflector, interference reflection is colored only by reflection around a wavelength having a specific reflection peak. For this reason, the spectral range with high reflectivity is extremely narrow, and it is difficult to obtain high reflection luminance. On the other hand, since the colored reflective material of the present invention has two or more reflection peak wavelengths, it can simply exhibit twice or more brightness. This indicates that the same effect as that obtained by seeding two or more liquid crystal layers can be obtained by one layer. Thus, the cholesteric liquid crystal layer has high light utilization efficiency, excellent design properties, high manufacturing efficiency, low cost, and excellent mass productivity.

  FIG. 1 is a schematic diagram of an example of a twist pitch change seen from the thickness cross-sectional direction of the cholesteric liquid crystal layer C used in the colored reflector of the present invention. FIG. 2 is a conceptual diagram of a spectrum corresponding to FIG. 1 and showing the relationship between each wavelength and the reflectance (selective reflection wavelength band). In FIG. 1, since there are few regions having a pitch length that reflects the intermediate wavelength, as shown in FIG. 2, the reflection characteristics cannot be obtained, and the reflectance is lowered. 1 and 2 have two independent selective reflection wavelength bands.

  If the cholesteric liquid crystal polymer layer used for the colored reflective material of the present invention has two or more independent selective reflection wavelength bands, the two or more independent selective reflection wavelengths shown in FIGS. A region having an intermediate pitch may exist in a region other than the pitch length, and some of the intermediate pitch may remain. It is preferable that the number of pitches in the wavelength region that is unnecessary for reducing the reflectance and obtaining the color tone change is several pitches or less. Specifically, the number of pitches is preferably less than 4 and more preferably 2 or less. On the other hand, as shown in FIG. 1, the number of long pitches and short pitches having independent selective reflection wavelengths is preferably 4 or more, more preferably 8 or more. The number of pitches can be confirmed by a cross-sectional TEM (transmission electron microscope). In order to obtain coloring with high saturation, it is preferable that the pitch change in the thickness direction is discontinuous, and the cholesteric twist pitch length corresponding to the independent selective reflection wavelength band exists discontinuously.

  The independent selective reflection wavelength band of the cholesteric liquid crystal polymer layer is appropriately selected according to the purpose of use. It is preferable that the independent selective reflection wavelength bandwidth is about 20 nm or more. The selective reflection wavelength band is measured by the method described in the examples. The selective reflection wavelength band is a reflection band having a reflectance that is half of the maximum reflection reflectance in the measured reflection spectrum.

  Note that the twist pitch of the cross section of the conventional cholesteric liquid crystal layer that reflects only a general single wavelength is uniform as shown in the conceptual diagram of FIG. Therefore, the shape of the reflectance spectrum corresponding to FIG. 3 is as shown in FIG. On the other hand, the twist pitch of the cross-section of the conventional cholesteric liquid crystal that has been widened to increase the reflectance changes continuously, and has a reflection characteristic at a wide band wavelength because of this structure. However, these have little change in reflectance with respect to change in incident angle, and change in color tone is poor.

  The present invention also relates to a colored reflective filler characterized by containing a pulverized product of the colored reflective material.

  As the colored reflective filler, a pulverized product of one kind of colored reflector can be used, and a pulverized product of two or more kinds of colored reflectors can be used. For example, as the two or more kinds of colored reflectors, those in which only the cholesteric twist direction of the cholesteric liquid crystal polymer layer is different (right direction and left direction) can be used. In this way, when those having different twist directions are combined, a specific image or pattern can be formed under circularly polarized light. As the two or more kinds of colored reflectors, cholesteric liquid crystal polymer layers having different selective reflection wavelength bands can be used. In this case, the range of options for the combination of specific reflection peaks is widened, and a specific image or pattern can be formed.

  The present invention also relates to a colored coating agent, wherein the colored reflective filler is dispersed in a light transmissive resin. The colored coating agent can be used in paints, inks, and the like, and a reflective film or a coating layer can be obtained from the colored coating agent.

  The present invention also relates to the use of the colored reflective material, colored reflective filler or colored coating agent in decorative applications, cosmetic or pharmaceutical composition applications, optical elements or crime prevention applications. In the present invention, the colored reflective material, colored reflective filler, or colored coating agent can be used in various applications in which a colorant, a pigment, or the like is used.

  The colored reflector of the present invention uses a cholesteric liquid crystal layer having at least two independent selective reflection wavelength bands in a single layer. The cholesteric liquid crystal layer includes, for example, a polymerizable mesogenic compound (a) and a polymerizable chiral. A liquid crystal mixture containing the agent (b) is applied to an alignment substrate, and is obtained by ultraviolet irradiation.

  For example, the step of applying a liquid crystal mixture containing a polymerizable mesogenic compound (a) and a polymerizable chiral agent (b) to an alignment substrate, and the substrate in contact with a gas containing oxygen in the liquid crystal mixture A method (Japanese Patent Laid-Open No. 2000-139953) is used in which a step of polymerizing and curing by performing ultraviolet irradiation from the side is performed, and a difference in polymerization rate in the thickness direction due to inhibition of oxygen polymerization is increased by ultraviolet irradiation from the substrate side. And a method (Japanese Patent Application No. 2003-126998).

  In such a method, in the step of polymerizing and curing by irradiating with ultraviolet light, the irradiation temperature is 20 ° C. or higher, and the irradiation temperature is adjusted to be higher in the subsequent stage than in the previous stage, so that it is independent in a single layer. A cholesteric liquid crystal layer having at least two selective reflection wavelength bands is obtained.

  With respect to the method described in Japanese Patent Application Laid-Open No. 2000-139953, a cholesteric liquid crystal layer having a selective reflection wavelength bandwidth wider than 200 nm can be obtained by the following method. By controlling the manufacturing conditions of the following method, a cholesteric liquid crystal layer having at least two independent selective reflection wavelength bands in a single layer can be obtained.

For example, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen at an ultraviolet irradiation intensity of 20 to 200 mW / cm ² at a temperature of 20 ° C. or higher for 0.2 to 5 seconds. The step (1) of irradiating ultraviolet rays from the alignment substrate side, the step (2) of heating the liquid crystal layer at 70 to 120 ° C. for 2 seconds or more in a state where the liquid crystal layer is in contact with the gas containing oxygen, and then In the state in which the liquid crystal layer is in contact with a gas containing oxygen, the step of irradiating with ultraviolet rays from the alignment substrate side at a temperature of 20 ° C. or higher and lower than the step (1) for 10 seconds or more. (3) Next, there is a method performed by the step (4) of irradiating ultraviolet rays in the absence of oxygen (Japanese Patent Application No. 2003-93963).

Further, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen, at a temperature of 20 ° C. or higher, an ultraviolet irradiation intensity of 1 to 200 mW / cm ² and a range of 0.2 to 30 seconds. Step (1) of irradiating ultraviolet rays from the orientation substrate side three times or more while lowering the ultraviolet irradiation intensity and increasing the ultraviolet irradiation time each time the number of times of ultraviolet irradiation increases, and then in the absence of oxygen Then, there is a method performed by the step (2) of irradiating with ultraviolet rays (Japanese Patent Application No. 2003-94307).

Further, the ultraviolet polymerization step is carried out for 0.2 to 5 seconds at an ultraviolet irradiation intensity of 20 to 200 mW / cm ² at a temperature of 20 ° C. or higher in a state where the liquid crystal mixture is in contact with a gas containing oxygen. Step (1) of irradiating ultraviolet rays from the alignment substrate side, and then in a state where the liquid crystal layer is in contact with a gas containing oxygen, until it reaches a temperature higher than Step (1) and 60 ° C. or higher, A step (2) of irradiating with ultraviolet rays from the alignment substrate side for 10 seconds or more at a temperature rising rate of 2 ° C./second or lower with an ultraviolet irradiation intensity lower than that in step (1), and then irradiating with ultraviolet rays in the absence of oxygen. An example is a method performed in the step (3) (Japanese Patent Application No. 2003-94605).

  Furthermore, the following method can be used. In the following method, a cholesteric liquid crystal layer having a wide reflection wavelength band and good heat resistance can be obtained. For example, there is a method in which a liquid crystal mixture containing a polymerizable mesogenic compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) is subjected to ultraviolet polymerization between two substrates (Japanese Patent Application 2003). No. 4346, Japanese Patent Application No. 2003-4101). Further, there is a method in which a polymerizable ultraviolet absorber (d) is further added to the liquid crystal mixture and ultraviolet polymerization is carried out between two substrates (Japanese Patent Application No. 2003-4298). In addition, a method of applying a liquid crystal mixture containing a polymerizable mesogenic compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) on an alignment substrate and performing ultraviolet polymerization in an inert gas atmosphere (Japanese Patent Application No. 2003-4406).

The ultraviolet polymerization step is performed for 0.1 to 5 seconds at a temperature of 70 ° C. or higher and an ultraviolet irradiation intensity of 10 to 200 mW / cm ^{2 in} a state where the liquid crystal mixture is in contact with a gas containing oxygen. , Ultraviolet ray irradiation (1), and then a step (2) of heat treatment at 70 ° C. or higher for 0.1 to 5 seconds in a state where the liquid crystal layer is in contact with a gas containing oxygen, After step (1) and step (2), the step can be performed by step (3) in which ultraviolet rays are irradiated in the absence of oxygen. Preferably, the step (1) and the step (2) are repeated a plurality of times, and then the step (3) of ultraviolet irradiation is performed (Japanese Patent Application No. 2004-71158).

Further, in the ultraviolet polymerization step, the liquid crystal mixture is in contact with a gas containing oxygen at an ultraviolet irradiation intensity of 10 to 200 mW / cm ² at a temperature of 70 ° C. or higher for 0.01 to 5 seconds. , Ultraviolet irradiation step (1), and then the step (2) of heat-treating at 70 ° C. or more for a time exceeding 5 seconds in a state where the liquid crystal layer is in contact with a gas containing oxygen. After step 1) and step (2), the step can be performed by step (3) of irradiating with ultraviolet rays in the absence of oxygen. Preferably, the step (1) and the step (2) are repeated a plurality of times, and then the step (3) of ultraviolet irradiation is performed (Japanese Patent Application No. 2004-168666).

  According to each of the above methods, a cholesteric liquid crystal polymer layer having a selective reflection wavelength bandwidth of 200 nm or more is obtained. However, when the selective reflection wavelength bandwidth is 200 nm or more, the total of the individual selective reflection wavelength bands is It means 200 nm or more. According to the above method, it is possible to obtain one in which at least one of the independent selective reflection wavelength bands has a selective reflection wavelength bandwidth of 200 nm or more.

  The polymerizable mesogenic compound (a) and polymerizable chiral agent (b) that form the cholesteric liquid crystal layer will be described below.

  As the polymerizable mesogenic compound (a), those having at least one polymerizable functional group and having a mesogenic group composed of a cyclic unit or the like are preferably used. Examples of the polymerizable functional group include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl ether group. Among these, an acryloyl group and a methacryloyl group are preferable. Further, by using a compound having two or more polymerizable functional groups, a crosslinked structure can be introduced to improve durability. Examples of the cyclic unit serving as a mesogen group include biphenyl, phenylbenzoate, phenylcyclohexane, azoxybenzene, azomethine, azobenzene, phenylpyrimidine, diphenylacetylene, diphenylbenzoate, and bicyclohexane. Cyclohexylbenzene, terphenyl and the like. In addition, the terminal of these cyclic units may have substituents, such as a cyano group, an alkyl group, an alkoxy group, a halogen group, for example. The mesogenic group may be bonded via a spacer portion that imparts flexibility. Examples of the spacer portion include a polymethylene chain and a polyoxymethylene chain. The number of repeating structural units forming the spacer portion is appropriately determined depending on the chemical structure of the mesogenic portion, but the repeating unit of the polymethylene chain is 0 to 20, preferably 2 to 12, and the repeating unit of the polyoxymethylene chain is 0 to 0. 10, preferably 1-3.

The molar extinction coefficient of the polymerizable mesogenic compound (a) is 0.1 to 500 dm ³ mol ⁻¹ cm ⁻¹ @ 365 nm, 10 to 30000 dm ³ mol ⁻¹ cm ⁻¹ @ 334 nm, and 1000 to 100,000 dm ^3. it is preferably a mol ^-1 m ^-1 @ 314nm. Those having the molar extinction coefficient have ultraviolet absorbing ability. Molar extinction coefficient is ^{0.1~50dm 3 mol -1 cm -1 @ 365nm} , a ^{50~10000dm 3 mol -1 cm -1 @ 334nm} , is 10000~50000dm ³ mol ^-1 cm ^-1 @ 314nm More preferred. Molar extinction coefficient is ^{0.1~10dm 3 mol -1 cm -1 @ 365nm} , a ^{1000~4000dm 3 mol -1 cm -1 @ 334nm} , at 30000~40000dm ³ mol ^-1 cm ^-1 @ 314nm More preferably. Molar extinction coefficient of ^{0.1dm 3 mol -1 cm -1 @ 365nm} , 10dm 3 mol -1 cm -1 @ 334nm, 1000dm 3 mol -1 cm -1 @ without stick 314nm smaller than sufficient polymerization rate difference It is difficult to increase the bandwidth. On the other ^{hand, 500dm 3 mol -1 cm -1 @} 365nm, 30000dm 3 mol -1 cm -1 @ 334nm, 100000dm 3 mol -1 cm -1 @ If 314nm greater than the polymerization curing to not proceed completely does not end There is. The molar extinction coefficient is a value measured from the absorbance at 365 nm, 334 nm, and 314 nm obtained by measuring the spectrophotometric spectrum of each material.

  The polymerizable mesogenic compound (a) having one polymerizable functional group is, for example, a general formula of the following chemical formula 1:

（式中、Ｒ₁〜Ｒ₁₂は同一でも異なっていてもよく、−Ｆ、−Ｈ、−ＣＨ₃、−Ｃ₂Ｈ₅または−ＯＣＨ₃を示し、Ｒ₁₃は−Ｈまたは−ＣＨ₃を示し、Ｘ₁は一般式（２）：
−（ＣＨ₂ＣＨ₂Ｏ）_a−（ＣＨ₂）_b−（Ｏ）_c−、を示し、Ｘ₂は−ＣＮまたは−Ｆを示す。但し、一般式（２）中のａは０〜３の整数、ｂは０〜１２の整数、ｃは０または１であり、かつａ＝１〜３のときはｂ＝０、ｃ＝０であり、ａ＝０のときはｂ＝１〜１２、ｃ＝０〜１である。）で表される化合物があげられる。

(In the formula, R _{1 to} R ₁₂ may be the same or different and represent —F, —H, —CH ₃ , —C ₂ H ₅ or —OCH ₃ , and R ₁₃ represents —H or —CH ₃ . X ₁ is represented by the general formula (2):
— (CH ₂ CH ₂ O) _a — (CH ₂ ) _b — (O) _c —, and X ₂ represents —CN or —F. In the general formula (2), a is an integer of 0 to 3, b is an integer of 0 to 12, c is 0 or 1, and when a = 1 to 3, b = 0 and c = 0. Yes, when a = 0, b = 1 to 12, and c = 0 to 1. ).

  Specific examples of the polymerizable mesogenic compound (a) include Merck E7, Wacker Chemical LC-Silicon-CC3767, BASF LC242, Takasago International Corporation L42, and the like.

  Examples of the polymerizable chiral agent (b) include Merck KGaA manufactured by S101, R811, CB15, and BASF manufactured by LC756.

  The amount of the polymerizable chiral agent (b) is preferably about 1 to 20 parts by weight, preferably 3 to 7 parts by weight based on 100 parts by weight of the total of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). The part is more suitable. The helical twisting force (HTP) is controlled by the ratio of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). By setting the ratio within the above range, the reflection band can be selected so that the reflection spectrum of the obtained cholesteric liquid crystal film can cover the long wavelength region.

  The liquid crystal mixture usually contains a photopolymerization initiator (c). Various kinds of photopolymerization initiators (c) can be used without particular limitation. For example, Irgacure 184, Irgacure 907, Irgacure 369, Irgacure 651, Irgacure 784, Irgacure 814, Darocur 173, Darocure 4205, BASF: TPO (trade name: Lucirin TPO (Lucirin TPO), etc. The blending amount of the agent is preferably about 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight with respect to 100 parts by weight of the total of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). Is preferred.

  As the polymerizable ultraviolet absorber (d), a compound having at least one polymerizable functional group and having an ultraviolet absorbing function can be used without any particular limitation. Specific examples of the polymerizable ultraviolet absorber (d) include RUVA-93 manufactured by Otsuka Chemical Co., and UVA935LH manufactured by BASF. The blending amount of the polymerizable ultraviolet absorber (d) is preferably about 0.01 to 10 parts by weight with respect to a total of 100 parts by weight of the polymerizable mesogenic compound (a) and the polymerizable chiral agent (b). 5 parts by weight is more preferred.

  In order to widen the bandwidth of the resulting cholesteric liquid crystal film, the mixture can be mixed with an ultraviolet absorber to increase the UV exposure intensity difference in the thickness direction. Further, the same effect can be obtained by using a photoreaction initiator having a large molar extinction coefficient.

  The mixture can be used as a solution. Solvents used in preparing the solution are usually halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, phenols such as phenol and parachlorophenol, benzene, toluene, Aromatic hydrocarbons such as xylene, methoxybenzene, 1,2-dimethoxybenzene, others, acetone, methyl ethyl ketone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene bricol monomethyl ether, diethylene glycol Dimethyl ether, ethyl cellosolve, butyl cellosolve, 2-pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, te Rahidorofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, can be used acetonitrile, butyronitrile, carbon disulfide, cyclopentanone, cyclohexanone and the like. The solvent to be used is not particularly limited, but methyl ethyl ketone, cyclohexanone, cyclopentanone and the like are preferable. Although the concentration of the solution depends on the solubility of the thermotropic liquid crystalline compound and the final film thickness of the cholesteric liquid crystal film, it cannot be generally stated, but it is usually preferably about 3 to 50% by weight.

  The cholesteric liquid crystal layer can be formed by a method according to a conventional alignment process. For example, rayon is formed by forming a film of polyimide, polyvinyl alcohol, polyester, polyarylate, polyamide imide, polyether imide, etc. on a support substrate having a birefringence retardation as small as possible such as triacetyl cellulose or amorphous polyolefin. An alignment film rubbed with a cloth or the like, an obliquely deposited layer of SiO, or a substrate using the surface properties of a stretched substrate such as polyethylene terephthalate or polyethylene naphthalate as an alignment film, or the above substrate surface is rubbed or bentara A substrate that has been processed with a fine polishing agent represented by the above and formed fine irregularities having fine alignment regulating force on the surface, or an alignment film that generates liquid crystal regulating force by light irradiation such as an azobenzene compound on the substrate film A liquid crystal polymer is applied on a suitable alignment film composed of a base material formed with Open and heat to above the glass transition temperature and below the isotropic phase transition temperature, and in a state where the liquid crystal polymer molecules are in a planar orientation, cool to below the glass transition temperature to form a solidified layer in which the orientation is fixed And how to do it. Further, the structure may be fixed by irradiation of energy such as ultraviolet rays or ion beams at the stage where the alignment state is formed.

  The liquid crystal polymer film is formed by, for example, thinning a solution of a liquid crystal polymer in a solvent by spin coating, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, or gravure printing. It can be carried out by a method of developing a layer and drying it as necessary. Examples of the solvent include chlorinated solvents such as methylene chloride, trichloroethylene, and tetrachloroethane; ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone; aromatic solvents such as toluene; cyclic alkanes such as cycloheptane; or N -Methyl pyrrolidone, tetrahydrofuran, etc. can be used suitably.

  In addition, a heating melt of a liquid crystal polymer, preferably a heating melt exhibiting an isotropic phase, is developed according to the above, and a thin layer is further developed and solidified while maintaining the melting temperature as necessary. can do. This method is a method that does not use a solvent. Therefore, the liquid crystal polymer can be developed even by a method that provides good hygiene in the working environment.

  The thickness of the liquid crystal layer (in the case of a solution, coating thickness after solvent drying) is preferably about 2 to 20 μm. When the thickness is less than 1 μm, although the reflection bandwidth can be secured, the degree of polarization itself tends to decrease, which is not preferable. The thickness is preferably 2 μm or more, more preferably 3 μm or more. On the other hand, when the thickness is larger than 20 μm, neither the reflection bandwidth nor the polarization degree is remarkably improved, and the cost is simply increased. The coating thickness is more preferably 15 μm or less, 10 μm or less, and even more preferably 7 μm or less. The coating thickness of the liquid crystal mixture is 2 to 10 μm, preferably 3 to 7 μm when importance is attached to the color covering the entire visible light.

  A pulverized product obtained by pulverizing a colored reflective material composed of the cholesteric liquid crystal layer is used as a colored reflective filler. Grinding can be done using, for example, a pestle or mechanized grinder or mill. Further, the pulverized product can be sieved to obtain a filler of a desired size. The pulverization is preferably performed while cooling the cholesteric liquid crystal layer. Cooling can be performed by, for example, a method using a carbon dioxide / acetone bath, a method of adding powdered dry ice or liquid nitrogen to a sample, and the like. In the pulverization, an anti-tacking agent can be added to avoid particle aggregation.

  The average size of the filler is usually preferably 2 mm or less, and preferably about 20 to 500 μm. The shape of the filler is preferred, and the aspect ratio expressed by the ratio of the transverse dimension to its thickness is greater than 3: 1, in particular 3: 1 to 50: 1, very preferably 5: 1 to 50: 1. .

  The colored reflective filler can be dispersed in a light transmissive resin and used as a colored coating agent. A water-based solvent and an organic solvent can be used for the coloring coating agent, and a solventless solvent may be used.

  Various materials are used as the light transmissive resin depending on the application of the coating agent. For example, polyester resins such as polyethylene terephthalate and polyethylene naphthalate; styrene resins such as polystyrene and acrylonitrile / styrene copolymer (AS resin); polyolefins having polyethylene, polypropylene, cyclo or norbornene structures, and ethylene / propylene copolymers And olefin resins such as polyvinyl alcohol resins. Furthermore, vinyl chloride resin, cellulose resin, acrylic resin, amide resin, imide resin, sulfone polymer, polyether sulfone resin, polyether ether ketone resin polymer, polyphenylene sulfide resin, vinylidene chloride Examples thereof include resins, vinyl butyral resins, arylate resins, polyoxymethylene resins, silicone resins, urethane resins and the like. These can be used alone or in combination of two or more. Further, a cured product of a thermosetting or ultraviolet curable resin such as phenol, melamine, acrylic, urethane, acrylurethane, epoxy, silicone, alkyd resins, and the like can also be used.

  In addition to the colored reflective filler and the light-transmitting resin, the coloring coating agent includes other additives such as other pigments, dyes, curing agents, dispersants, fillers and the like commonly used in the field of inks and paints. Can be contained. Other pigments include conventional inorganic pigments such as titanium dioxide, iron (III) oxide, iron oxide yellow, chromium oxide, iron blue, carbon black, organic dyes or pigments such as azo, metal complexes and such as phthalocyanine, perylene, It can be selected from polycyclic dyes or pigments based on pyrrolopyrrole, polymethine or triphenylmethane. It can also be selected from platelet-shaped effective pigments such as copper or aluminum metal pigments, coated mica, pearlescent or interference pigments that are aluminum or carbon black, metal oxide pigments or coated glass flakes.

  Hereinafter, the present invention will be specifically described with reference to examples. In addition, the reflection spectrum of the cholesteric liquid crystal layer was measured with a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., instantaneous multi-photometry system MCPD-2000). Further, UVC321AM1 manufactured by USHIO INC. Was used as the ultraviolet exposure machine used in each example.

Example 1
A solution prepared by adjusting and blending 94.6 parts by weight of a photopolymerizable mesogen compound (manufactured by Takasago International Corporation, L42), 5.4 parts by weight of a polymerizable chiral agent (LC756 manufactured by BASF) and 233 parts by weight of a solvent (cyclopentanone). A coating solution (solid content 20% by weight) was prepared by adding 2% by weight of a photopolymerization initiator (Ciba Specialty Chemicals, Irgacure 369) to the solid content. The coating solution is applied on a stretched polyethylene terephthalate film (alignment substrate: Toray Lumirror, 38 μm thickness) using a wire bar so that the thickness after drying is 6 μm, and the solvent is 100 ° C. for 2 minutes. Dried. As a step (1), the obtained film was irradiated with ultraviolet rays at 30 mW / cm ² for 0.3 seconds in an air atmosphere at 120 ° C. from the liquid crystal layer side. Next, as step (2), heat treatment was performed in an air atmosphere at 100 ° C. for 2 seconds. Further, step (1) and step (2) were repeated. Then, as process (3), ultraviolet irradiation was performed at 60 mW / cm ² for 30 seconds from the liquid crystal layer side in a nitrogen atmosphere at 50 ° C. to obtain a cholesteric liquid crystal film. The reflection spectrum of the cholesteric liquid crystal film is shown in FIG. The cholesteric liquid crystal film had two selective reflection wavelength bands with a selective reflection center wavelength of 460 nm and a bandwidth of 110 nm, and a selective reflection center wavelength of 830 nm and a bandwidth of 300 nm.

  In FIG. 5, a valley having a low reflectance exists in the vicinity of 600 nm, and the cholesteric liquid crystal film was observed to be markedly colored. The maximum reflectance is about 50%, which is not much different from a cholesteric liquid crystal that reflects only a single wavelength at a normal single pitch. However, in the total reflectance in the entire visible light region, it was possible to obtain a brightness about twice that of a cholesteric liquid crystal that reflects only a single wavelength at a normal single pitch. As for the color tone, magenta was obtained in the front direction and green in the oblique direction.

Example 2
Instead of the coating liquid prepared in Example 1, a coating liquid whose composition was changed to the ratio shown in Table 1 was used. The coating solution was applied onto a stretched polyethylene terephthalate film (alignment substrate) using a wire bar so that the thickness after drying was 12 μm, and the solvent was dried at 100 ° C. for 2 minutes. Next, steps (1) to (3) were performed under the conditions shown in Table 1 to obtain a cholesteric liquid crystal film. The reflection spectrum of the cholesteric liquid crystal film is shown in FIG. The cholesteric liquid crystal film had two selective reflection wavelength bands with a selective reflection center wavelength of 400 nm and a bandwidth of 90 nm, and a selective reflection center wavelength of 670 nm and a bandwidth of 220 nm.

  In FIG. 6, a valley having a low reflectance exists in the vicinity of 500 nm, and the cholesteric liquid crystal film was observed to be markedly colored. The maximum reflectance is about 50%, which is not much different from a cholesteric liquid crystal that reflects only a single wavelength at a normal single pitch. However, in the total reflectance in the entire visible light region, it was possible to obtain a brightness about twice that of a cholesteric liquid crystal that reflects only a single wavelength at a normal single pitch. The color tone was the front direction, the front direction was blue, and the diagonal direction was magenta.

Example 3
Instead of the coating liquid prepared in Example 1, a coating liquid whose composition was changed to the ratio shown in Table 1 was used. The coating solution was applied onto a stretched polyethylene terephthalate film (alignment substrate) using a wire bar so that the thickness after drying was 12 μm, and the solvent was dried at 100 ° C. for 2 minutes. Next, steps (1) to (3) were performed under the conditions shown in Table 1 to obtain a cholesteric liquid crystal film. The reflection spectrum of the broadband cholesteric liquid crystal film is shown in FIG. The cholesteric liquid crystal film had two selective reflection wavelength bands with a selective reflection center wavelength of 470 nm and a bandwidth of 150 nm, and a selective reflection center wavelength of 830 nm and a bandwidth of 230 nm.

  In FIG. 7, a valley having a low reflectance exists in the vicinity of 650 nm, and the cholesteric liquid crystal film is observed to be markedly colored. The maximum reflectance is about 50%, which is not much different from a cholesteric liquid crystal that reflects only a single wavelength at a normal single pitch. However, the overall reflectivity in the entire visible light region could be about twice as bright as that of a cholesteric liquid crystal that reflects only a single wavelength at a normal single pitch. The color tone was yellowish green in the front direction and light blue in the diagonal direction.

本発明では、上記コレステリック液晶フィルムを着色反射材として用いる。かかる着色反射材の粉砕物を着色反射フィラーとして用いた着色コーティング剤は、反射率が高く、色調鮮やかな反射塗料となった。

In the present invention, the cholesteric liquid crystal film is used as a colored reflector. A colored coating agent using such a pulverized colored reflective material as a colored reflective filler has a high reflectance and a brightly colored reflective paint.

Comparative Example 1
A cholesteric liquid crystal polymer having a selective reflection center wavelength of 550 nm was prepared. The cholesteric liquid crystal polymer is composed of a liquid crystal monomer A which is a polymerizable mesogen compound (LC242 manufactured by BASF), a polymerizable chiral agent B (LC756 manufactured by BASF), and a monomer A / chiral agent B (mixing weight ratio) = 95.5. It was produced by polymerizing a liquid crystal mixture blended at 4.5.

  The liquid crystal mixture is made into a 20 wt% solution in which each is dissolved with cyclopentane, and then a photoinitiator (Ciba Specialty Chemicals, Irgacure 907, 1 wt% with respect to the mixture) is added. A solution was prepared.

  The solution was applied to the alignment substrate with a wire bar so that the thickness upon drying was about 2 μm. As the alignment base material, a Toray polyethylene terephthalate film: Lumirror 75 μm subjected to an alignment treatment with a rubbing cloth was used. After coating, the film is dried at 90 ° C. for 2 minutes, heated once to the isotropic transition temperature (130 °), and then gradually cooled and irradiated with ultraviolet rays in an environment of 80 ° C. while maintaining a uniform orientation state (10 mW / The cholesteric liquid crystal layer was obtained by curing at a square cm × 1 minute.

  Although the obtained cholesteric liquid crystal layer reached a reflectance near 50% at 550 nm, the reflectance decreased rapidly as the distance from the selective reflection center wavelength increased. For this reason, although reflected light with high saturation is obtained, the brightness is not sufficient.

(Application example)
The cholesteric liquid crystal film produced in Example 1 was wet pulverized with a ball mill to obtain a scaly filler having an average particle size of 50 μm. 20 parts by weight of the filler, 80 parts by weight of an ultraviolet curable resin (Dainippon Ink & Chemicals, Unidic 17-807) and 2 parts by weight of an ultraviolet polymerization initiator (Ciba Specialty Chemicals, Irgacure 187) are added to toluene. A coating solution having a solid content of 20% by weight was prepared by dispersing in the solution. The coating solution was applied on an 80 μm thick triacetylcellulose film (manufactured by Fuji Photo Industry Co., Ltd., TD-TAC) with an applicator, dried, and then heated at 100 ° C. for 2 minutes to form a coating film. Thereafter, the film was cured by irradiating with 50 mW / square centimeter for 1 second with an ultraviolet irradiator (Ushio Electric Co., Ltd., UVC321AM1) to obtain a cured film having a thickness of 50 μm. The obtained cured coating film was an optical film whose color tone changed according to the incident angle.

  The cholesteric liquid crystal film produced in Example 2 was wet pulverized with a mill to obtain a scale-like filler having an average particle size of 500 μm. A photopolymerizable transparent paint (Adekaoptomer BY310 manufactured by Asahi Denka Co., Ltd.) was pattern-printed on the substrate by screen printing to obtain a printed material having a thickness of 100 μm. The scale-like filler was sprayed on this surface, and the surplus was removed with an air gun. The filler adhered to the resin surface was 50 mW / square centimeter × 1 second with an ultraviolet irradiator (USHIO Inc., UVC321AM1). The coating film was cured by irradiating with ultraviolet rays to obtain a cured coating film. The obtained cured coating film was an optical film whose color tone changed according to the incident angle, and the design of letters and figures was high.

  The cholesteric liquid crystal film produced in Example 3 was wet-ground with a ball mill to obtain a scale-like filler having an average particle size of 100 μm. The filler was added to a transparent polishing liquid (479 Clear Manucia manufactured by Essie) so as to be 10% by weight. The obtained manicure was highly designable with color change.

It is the schematic diagram of the twist pitch which looked at the cholesteric liquid crystal layer used for the colored reflective material of this invention from the thickness cross-sectional direction. It is a conceptual diagram of the reflection spectrum which shows the relationship between each wavelength and a reflectance corresponding to FIG. It is the schematic diagram of the twist pitch which looked at the conventional cholesteric liquid crystal layer from the thickness cross-section direction. It is a conceptual diagram of the reflection spectrum which shows the relationship between each wavelength and a reflectance corresponding to FIG. 2 is a reflection spectrum of a cholesteric liquid crystal film produced in Example 1. 3 is a reflection spectrum of a cholesteric liquid crystal film produced in Example 2. 4 is a reflection spectrum of a cholesteric liquid crystal film produced in Example 3.

Explanation of symbols

  C: Cholesteric liquid crystal layer

Claims (8)

  A colored reflector comprising a cholesteric liquid crystal layer having at least two independent selective reflection wavelength bands in a single layer.   2. The colored reflector according to claim 1, wherein the cholesteric liquid crystal layer has discontinuous cholesteric twist pitch lengths corresponding to independent selective reflection wavelength bands in the thickness direction.   The colored reflector according to claim 1 or 2, wherein the cholesteric liquid crystal layer is capable of producing color by a complementary color mode using at least two independent selective reflection wavelength bands.   A colored reflective filler comprising the pulverized product of the colored reflective material according to claim 1.   The colored reflective filler according to claim 4, comprising a pulverized product of at least two kinds of colored reflective materials.   6. A colored coating agent, wherein the colored reflective filler according to claim 4 or 5 is dispersed in a light-transmitting resin.   A reflective film or coating layer obtained from the colored coating agent of claim 6. Use of the colored reflective material according to any one of claims 1 to 3, the colored reflective filler according to claim 4 or 5, or the colored coating agent according to claim 6 for decorative use, cosmetic or pharmaceutical composition, optical element or crime prevention. Use in applications.

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