JPH11315146A - Polymer particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain polymer particles having high reflection efficiency of heat rays, or the like, and a coating material, a molding product of resin, or the like, from the polymer particles. SOLUTION: A bifunctional polymerizable group-containing low-molecular liquid crystal is polymerized and crosslinked in a finely granular state and particles having different spiral directions and pitches are mixed to further improve reflection efficiency and a reflection wavelength range to give polymer particles for reflecting a near infrared part. The polymer particles are used to give products, or the like, applicable as a window material of coating materials, transparent films, sheets, or the like, contributing to energy saving of buildings, vehicles, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to polymer particles which reflect heat rays or visible rays and to reflective articles such as cosmetics, inks, paints and resin molded articles using the same.

[0002]

2. Description of the Related Art Conventionally, as reflective particles, besides metal powder, glass beads or metal vapor-deposited particles have been known. However, these have disadvantages such as loss of light transmittance in the visible part when reflecting heat rays, and their applications are limited due to their relatively large specific gravity. On the other hand, a cholesteric liquid crystal, a chiral nematic liquid crystal, or a smectic liquid crystal is known to have a property of reflecting light in a specific wavelength region by interference to form a color. In the case of ordinary thermotropic liquid crystals, this property strongly depends on the temperature, and thus has been used as a temperature sensor by utilizing a change in color development by microencapsulation or the like. Further, a liquid crystal polymer obtained by polymerizing a low-molecular liquid crystal having a monofunctional polymerizable group known as a pendant type polymer liquid crystal is known.
Like the low-molecular liquid crystal, it exhibits thermotropic properties, and its optical properties are lost as the liquid crystal properties are lost at high or low temperatures, and thus it is not suitable for widely utilizing its reflection properties. In addition, the liquid crystal is polymerized and crosslinked to reduce the thermotropic property and applied to tabular or tabular particles to utilize the narrow wavelength range or strong directivity unique to coherent reflection not found in ordinary colorants. A coloring agent (Japanese Patent Application Laid-Open No. 10-67949) is known, but is not suitable for use as a reflector because of its narrow wavelength range or strong angle dependence. JP-A-6-281814 in which chiral pitch is continuously changed as a means for expanding the reflection wavelength range
Has a drawback that its application range is narrow, such as being limited to flat products such as sheets and films. On the other hand, the growing international recognition of the global environment, such as the recent regulations on carbon dioxide emissions, indicates the need for comprehensive energy conservation, including the efficient use of thermal energy. An object of the present invention is to provide polymer particles that reflect heat rays or the like and various reflective products such as inks, paints, and resin molded products containing the polymer particles.

[0003]

Means for Solving the Problems and Their Functions The present invention relates to
Polymer particles formed by polymerizing and crosslinking low molecular liquid crystals containing a functional polymerizable group into fine particles. Further, the polymer particles are polymerized and crosslinked at a temperature at which a low-molecular liquid crystal exhibits a liquid crystal phase. Further, the polymer particles are any of the above polymer particles obtained by dispersing a low-molecular liquid crystal in a solvent and polymerizing and crosslinking. That is, in the case of the coherent reflection, when the incident light has an angle with respect to the optical axis perpendicular to the layered structure, the wavelength region of the reflected light shifts to the longer wavelength side according to the angle. The polymer particles obtained by polymerizing and crosslinking the fine particles of the present invention are obtained in a non-flat shape such as a spherical shape. Therefore, when applied to inks, paints, etc., the direction of the optical axis of the particles is random, and the incident light from various angles is averaged, so that the reflection wavelength is wider than that of known flat plates or flat particles. An application product with improved directivity having a range is obtained.

The present invention also relates to any one of the above polymer particles having a cholesteric, chiral nematic phase or smectic phase molecular arrangement. Further, it is a polymer particle obtained by mixing any one of the above-mentioned polymer particles having a cholesteric or chiral nematic phase molecular arrangement and different in the helix direction and / or helix pitch of the helix.
Further, any one of the above polymer particles having a reflection region in the infrared region. That is, reflection by liquid crystal often has a property that a specific liquid crystal phase reflects only specific polarized light in a specific wavelength range. For example, in the case of a cholesteric or chiral nematic phase-like molecular arrangement that shows remarkable reflection, only circularly polarized light in a specific rotation direction is reflected, and this property may be used as an optical component. By mixing particles in different directions, the reflection efficiency can be increased. Also, particles having different spiral pitches can be mixed to further broaden the reflection wavelength range. This makes it easy to efficiently reflect heat rays in the near-infrared region of 700 nm to 3000 nm contained in sunlight. Also,
Mixed particles having reflection peaks in both the visible and near-infrared regions can be obtained.

[0005] The present invention also relates to a fluid product such as an oily or paste-like product or a solid product such as a resin molded product which contains any of the above polymer particles and which may be solidified when used in cosmetics, inks, paints and the like. It is. In addition, the flowable product or the solid product described above, wherein the difference in refractive index between the base material such as an oily or pasty base material or the base resin and the polymer particles is 0.1 or less, preferably 0.02 or less. That is, the polymer particles of the present invention have a specific gravity closer to various base materials such as oils, pastes, and resins than conventional reflective particles, and are granular, so that oily, paste-like fluid products, etc. It can be applied in various forms, and can produce functional products such as cosmetics, inks, paints, adhesives, fillers, adhesives, etc. that have coherent reflection, as well as resin molded products such as films. Also, in application, generally, when a material having a different refractive index from the base material is mixed, the characteristic of coherent reflection is lost due to multiple reflections at the interface, and when fine particles are mixed, the appearance often becomes cloudy. Cheap. Although the reflection at this interface depends on the refractive index difference, the refractive index difference of the particles of the present invention can be adjusted by selecting the material and can be adjusted to the refractive index of the base material. The following is 2
The reflection loss at the interface can be suppressed to 10% or less even when passing through the interface of about 0. In particular, in the case of a transparent product such as a window material or an optical component, the transparency is enhanced by setting the content to 0.02 or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The low-molecular liquid crystal having a bifunctional polymerizable group used in the present invention is a mixture of a low-molecular liquid crystal material having a bifunctional polymerizable group or a mixture of a monofunctional low-molecular liquid crystal material with the mixture. Although a mixture is preferable, a non-liquid crystal substance may be contained as long as liquid crystallinity is not lost. Further, it may contain a non-polymerizable substance. A liquid crystal substance having a polymerizable group such as bifunctional has a polymerizable group with or without a spacer group at a terminal portion of a liquid crystalline skeleton, and a substance having a nematic phase or a cholesteric phase. Particularly preferred. Examples of the polymerizable group include a double bond such as an acrylate group, a methacrylate group, an alkenyl group, and a vinyl group, and a functional group having an epoxy bond such as a glycidyl group. Examples of the spacer group include a C1 to C12 alkylene group which may have a branched or optically active center such as a methylene group, an ethylene group and a propylene group, and a flexible bifunctional linking group such as an ether and a polyether group. Is mentioned.

As the liquid crystal skeleton, a bicyclic skeleton in which rings such as biphenyl and phenylcyclohexane are directly connected; rings such as phenyl and cyclohexyl groups are formed from esters, thioesters, azomethines, ethylene, amides, azos and triple bonds. Other than the two-ring skeleton linked through
A skeleton of three or more rings in which a ring such as a phenyl group or a cyclohexyl group is further bonded directly or via an ester, thioester, azomethine, ethylene, amide, azo or triple bond to the ring skeleton; steroids such as cholesterol And an aliphatic cyclic skeleton such as a system. 2
Preferred examples of the liquid crystalline substance having a polymerizable group such as a functional group include a biphenyl skeleton such as 4,4′-bis (ω-acryloyloxyalkoxy) biphenyl or a phenylbenzoate such as bisbenzoylhydroquinone. Bifunctional or monofunctional in which a C2 to C10 optically active or inactive alkyl group having a polymerizable group substituent such as an acrylate group at the terminal is bonded to both ends or one end of these skeletons by an ether bond. A group of optically active or inactive compounds having a polymerizable group is exemplified. Further, by mixing these liquid crystal substances, the liquid crystal temperature range of the low molecular liquid crystal can be extended to a lower temperature side.

In the case of forming a cholesteric or chiral nematic phase molecular arrangement, a chiral substance having an optically active group is required.
In addition to chiral substances having a functional polymerizable group, cholesterol nonanoates, substituted benzoates or acrylates having an optically active skeleton can be mentioned. Compounds described in "Liquid Crystal Device Handbook" having a group, edited by Japan Society for the Promotion of Science; pages 199 to 202. In addition, the chiral substance is not liquid crystalline and may be used depending on the concentration of addition even in the smectic liquid crystal,
A compound exhibiting a cholesteric phase is easy to use.

In the case of a cholesteric or chiral nematic phase molecular arrangement, the turning direction of reflected circularly polarized light differs depending on the twisting direction of the spiral. Since the torsion direction depends on the chemical structure of the chiral substance to be used, a substance that produces a desired torsion direction can be selected from various chiral substances.
For example, each chiral material separated from a racemate is a potential material candidate for an inverted helix. Further, the reflection wavelength is correlated with the helical pitch, and the helical pitch depends on the intrinsic helical forming ability and concentration of the chiral substance.
The reflected wavelengths are both shorter. For this reason, it is necessary to adjust the concentration of the chiral substance according to the target reflection wavelength range. However, when the visible wavelength short wavelength range is included in the target range, it is generally necessary to increase the chiral substance to 50% or more. In order to provide a reflection wavelength to the outside, the concentration may be about 30% or less. In addition, if a chiral substance that produces a reverse spiral is added in advance, the spiral forming ability is offset depending on the amount added,
It may be used for adjusting the reflection wavelength.

[0010] In addition to the liquid crystalline substance and the chiral substance, a reactive diluent having a polymerizable group may be added to adjust the refractive index as long as the liquid crystallinity of the low molecular liquid crystal is not lost. Examples of the reactive diluent include cyclohexyl acrylate, 2-ethylhexyl acrylate, hexanediol diacrylate, 1,4-bis (ω-acryloyloxyalkoxy) benzenes, and the like. In addition, additives such as ultraviolet absorbers and dyes and pigments may be added.

The above bifunctional liquid crystal material, chiral material,
A low-molecular liquid crystal is prepared by mixing a reactive diluent or the like, and a composition exhibiting a liquid crystal phase at a desired polymerization reaction temperature is obtained. A polymerization initiator such as a peroxide such as benzoyl peroxide, an azo such as azobisbutyronitrile, or a photopolymerization initiator such as an acetophenone when using a photopolymerization method is added thereto. These various polymerization initiators may usually be added at a concentration of 5% or less.

The polymerization reaction can be used in the present invention as long as it is a process that can be obtained in the form of particles. That is, thermal polymerization or photopolymerization is performed by dispersing in a gas phase or a liquid phase by various methods. The low-molecular liquid crystal or a solution thereof may be dispersed and polymerized in a gas phase by spraying or the like. However, a method in which a polymerization reaction is performed by dispersing the liquid crystal in an inexpensive liquid phase such as water by emulsification or suspension is preferable. . As an example of the process, a tetrahydrofuran solution of a low-molecular liquid crystal to which a polymerization initiator has been added is mixed with a surfactant several times to several tens of times containing several percent to 50 to tens times the volume.
The mixture is dropped and dispersed in water heated to 100 ° C. with vigorous stirring, and the stirring and heating are continued until the reaction sufficiently proceeds.
The particles obtained after the reaction are filtered, dried or heated to complete the reaction, and if necessary, classified to obtain polymer particles. Alternatively, a photopolymerization initiator may be added to the low-molecular liquid crystal, dispersed in a medium, and irradiated with ultraviolet rays to perform photopolymerization.

The particle size can be controlled by stirring conditions in the process of dispersing in the gas phase or liquid phase. Depending on the application, it can be selected in the range of submicron to several thousand microns, but a particle size of several microns to several tens of microns, especially several tens of microns, is easy to reflect in the infrared region.

The polymer particles of the present invention can be prepared by a known method using a liquid such as a high-boiling solvent, a cosmetic base such as a cream, or the like.
Adhesives, adhesive-based or cellulose-based such as nitrocellulose, vinyl-based such as vinyl chloride-vinyl acetate copolymer, acrylic-based, urethane-based, epoxy-based and various vehicles such as epoxy-based copolymers, alcohol-based with binder resin, It constitutes a fluid product that may be mixed with inks and paint bases containing various solvents such as ether-based and ketone-based solvents and solidified when used. In addition, coloring agents such as pigments and various additives may be added. The paint of the present invention can be applied as a heat-reflective coating film to roofs and outer walls of buildings, vehicles such as automobiles, and low-temperature storage facilities.

The particles of the present invention may be of various thermosetting types such as styrene, acrylic, vinyl and ester.
It can be applied to thermoplastics, films and sheets as well as molded products of various shapes. In particular, since the particles of the present invention have excellent transparency, they are suitable for a heat ray reflective film or resin glass to be attached to a glass surface. When applied to the above-mentioned various applications, it is desirable that the difference in the refractive index from the base resin is small, except for the case where an effect such as frosted glass is obtained. For example, it is desirable that the refractive index difference is 0.1 or less, preferably 0.02 or less.

The refractive index of the polymer particles is a bifunctional liquid crystal material,
It can be adjusted by selecting materials such as chiral substances and reactive diluents. That is, generally, in the case of an organic compound, an aliphatic ring such as a cyclohexane ring is converted to an aromatic ring such as a benzene ring, a single bond is converted to a conjugated system such as a double bond, or oxygen is converted to sulfur, and chlorine is converted to bromine. When the chemical structure is changed to a homologous element having a large atomic weight in the periodic table, the refractive index increases, and as a substituent, a fluorine atom has the effect of exceptionally reducing the refractive index. For example, by adjusting the aliphatic / aromatic ratio of the liquid crystalline skeleton portion of the above material, the refractive index of various substrates such as a binder, a vehicle, and a molding resin can be adjusted. Further, the refractive index of a base material such as a binder, a vehicle or a molding resin may be changed by the same method.

[0016]

According to the present invention, different spiral orientations,
By using polymer particles having improved reflection wavelength range and efficiency such as those having a pitch, the polymer particles can be applied to a paint or a resin molded product to provide a reflection function such as heat ray reflectivity.

Claims (9)

[Claims] 1. Polymer particles obtained by polymerizing and crosslinking a low molecular liquid crystal containing a bifunctional polymerizable group into fine particles. 2. The polymer particles according to claim 1, wherein the polymer particles are polymerized and crosslinked at a temperature at which the low molecular liquid crystal exhibits a liquid crystal phase. 3. The polymer particles according to claim 1, wherein low molecular liquid crystals are dispersed in a solvent and polymerized and crosslinked. 4. A cholesteric, chiral nematic phase or a smectic phase molecular arrangement.
Any polymer particles. 5. A polymer particle comprising a mixture of the polymer particles according to any one of claims 1 to 4, wherein the polymer particles have a cholesteric or chiral nematic phase-like molecular arrangement, and have different helix direction and / or helix pitch. 6. The polymer particles according to claim 1, which has a reflection region in an infrared region. 7. A fluid product, such as an oily or pastey product, which may be solidified when using cosmetics, inks, paints and the like containing the polymer particles according to claim 1. 8. A solid product such as a resin molded product containing the polymer particles according to claim 1. 9. The flowable product according to claim 7, wherein the difference in refractive index between the base material such as an oily or paste-like base material and a base resin and the polymer particles is 0.1 or less, preferably 0.02 or less. Or the solid product of claim 8.