JPS6112959B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an emulsion that serves as a coating composition for forming a film containing liquid crystals. Cholesteric liquid crystals exhibit bright iridescent colors in response to environmental changes such as temperature, pressure, electric fields, or pollution. This type of response of liquid crystals changes in various ways depending on the addition of substances. Most cholesteric liquid crystals are soft, oily substances that are difficult to handle and apply. Therefore, unless measures are taken to make handling easier, the applications will be extremely limited. Several methods have been developed to encapsulate or emulsify liquid crystals to make them convenient for handling. In the encapsulation method, minute droplets of a liquid crystal composition are covered with a protective film made of a water-soluble polymer material. While the coating in this case protects the liquid crystal and simplifies its handling, it significantly weakens the intensity of the colors. The compositional and thickness requirements of the encapsulating material present manufacturing difficulties and easily prevent liquid crystal droplet-encapsulating capsule particles from being silk screened or silk printed. By vigorously stirring the liquid crystal in the latex, the liquid crystal can be dispersed like minute droplets. The percentage of liquid crystal that can be dispersed in this way is small and the resulting film has poor color. Furthermore, over time, emulsions tend to undergo phase separation and liquid crystals to rise to the surface. The various colors exhibited by cholesteric liquid crystal materials over the temperature response range are vivid in nature. However, when cholesteric substances are combined with other substances or applied, this color becomes dull. Therefore, when a liquid crystal material is combined with other materials to fix the liquid crystal to a surface and thereby protect itself, it is important that the medium be relatively inert and yet transparent to adhere to other films or coatings. This is important in addition to being something that can be done. The present invention overcomes the above-mentioned difficulties in handling conventional cholesteric liquid crystals and satisfies various requirements when using them as coating materials. To this end, the present invention provides a coating composition for forming a film containing liquid crystals. It is an emulsion used for manufacturing products, and the composition of the emulsion is as follows. (a) 25 to 80 percent by weight of a cholesteric liquid crystal composition and a polymer for forming a transparent terrace;
(b) 14 to 75 weight percent water, and a moderately water-soluble organic solvent having a boiling point of about 175° C. or less and being a solvent for the liquid crystal composition; 25 to 65 percent by weight, liquid content consisting of 20 to 65 percent by weight
70 percent by weight; (c) a trace but sufficient amount of viscosity increasing agent to provide the viscosity required for film formation. Furthermore, the method for producing the emulsion of the present invention is based on the following steps. (a) mixing a mixture of a latex polymer forming a transparent film and 30 to 95 percent by weight of water with a solution of a liquid crystal composition dissolved in an organic solvent having appropriate water solubility; (b) ) adding a viscosity increasing agent in an amount of about 0.1 to 2 percent by weight based on the total amount; (c) heating the resulting solution to a temperature of about 40°C;
a step of keeping the temperature within a range of 100℃ to 100℃; and (d)
Stirring the mixture thus produced for a sufficiently long period of time to form a substantially homogeneous emulsion. The present invention is based on US Pat.
This is a continuation in part of No. 425006. The technology behind the present invention includes U.S. Pat.
There is number 3600060. No. 3,620,889 integrates a liquid crystal into a transparent plastic resin from a resin solution in an aromatic hydrocarbon solvent. Same No. 3655971
No. 3,663,390, and No. 3,666,948 disclose various techniques for forming images on a film surface of a liquid crystal composition using electromagnetic radiation. Upon preparation, the emulsion or liquid crystal ink according to the invention can be applied as a wide range of films to a wide range of non-greasy surfaces with bright colors and excellent adhesion. This liquid crystal film has little miscibility among the liquid crystals, and can be made into a layered product having a substrate and a backing film, which is stable for a long period of time and does not cause separation or peeling of the films. Liquid crystal inks according to the invention employ addition polymerization polymers which are usually good film formers as oil-in-water latexes. The liquid crystal is combined with an oil-in-water latex in combination with a small amount of organic solvent. The above-mentioned organic solvent is usually a polar oxidizing solvent that has an appropriate vapor pressure at room temperature and is capable of dissolving the liquid crystal. Viscosity increasing agents are usually added to the composition along with other small amounts of additives. The novel film produced with the emulsion according to the present invention comprises as an intermediate film a liquid crystal film composition made using a liquid crystal ink. This laminate consists of at least three layers, and depending on the application, there may be four or five or more layers. The liquid crystal film contains as main ingredients a liquid crystal, a film-forming polymer which is usually an addition polymer and capable of forming a stable oil-in-water latex, and a small amount of a viscosity increasing agent, as well as other small amounts of additives. This liquid crystal film is considered to be a matrix in which liquid crystal particles are distributed in a highly discontinuous manner in a film-forming polymer. It has been found that the liquid crystal film of the present invention substantially reduces the oiliness of the liquid crystal composition itself, provides clear colors, and has a small amount of liquid crystal mixed therein. Furthermore, the liquid crystal film according to the present invention exhibits excellent adhesion to various other organic or inorganic films. The liquid crystal ink used to produce the film has various advantages in addition to producing an excellent liquid crystal film. This liquid crystal ink readily produces uniform coatings with virtually no defects such as bubbles, ie, the generation of bubbles, such as during silk screening, is minimized. The above liquid crystal composition is easy to standardize in color, easy to handle, and can be easily applied using various commercially available equipment. Additionally, emulsion or liquid crystal inks according to the present invention produce sharp delineation patterns. Emulsions according to the invention can be easily prepared using commercially available latex compositions. The latex composition can be diluted or concentrated with water to have the desired solids composition. Latex solutions are usually handled at room temperature or higher, but can be handled at temperatures below 40°C. A second solution containing a liquid crystal composition is prepared. The solution includes a liquid crystal composition, an organic solvent for the liquid crystal composition, usually a polar solvent having moderate water solubility, an organic viscosity increaser, and a suitable wetting agent. Viscosity increasing agents can also be added to the latex and liquid crystal solution composition. Wetting agents can be added to the latex or the second solution before mixing. When the second solution is added to the latex solution, it is usually 20 to 80% by weight, more preferably 30 to 70% by weight.
It contains a solid content of . The liquid crystal-containing mixture is heated at a temperature of at least 40°C or above and about
Heated at temperatures below 100℃. This temperature is preferably 85° C. or lower in order to obtain a uniform liquid crystal solution. It is not necessary that all contained substances be dissolved. This temperature range is about 50 to 80°C depending on the composition used, the boiling point of the organic solvent, etc. It has been found that the properties of the final composition vary depending on the temperature of use. Therefore, some experimentation within the above range is necessary in order to optimize the properties of the final product. The liquid crystal-containing solution is added to the latex at about room temperature with moderate stirring and without further heating. The liquid crystal composition is added with gentle stirring and continued stirring for 5 to 30 minutes, or for a longer period of time if necessary. Stirring speed is 200-3000r.pm. The resulting composition can be used to make films for printing and the like. Various techniques such as roller coating, spraying, doctor blade, silk screen, rotogravure etc. can be used. The coating films made using these coating techniques dry quickly, do not have discontinuities such as bubbles, and produce vivid colors within the temperature response range of liquid crystals, and are soft to the touch and do not have oily or oily properties. Creates an oil-free coating. The emulsion or coating composition according to the invention typically contains a solids content of at least 30% by weight, up to 80%;
More preferably it contains 35-60% by weight solids, especially 35-50% by weight. The total amount of liquid is therefore 20-70% by weight, usually 40-65% by weight, more preferably 50-60% by weight. The main components of the solids are organic polymers and liquid crystal compositions in the latex. Typically, liquid crystal compositions are at least about 25% by weight, with a solids content of about
The content is preferably 80% by weight or less, more preferably 75% by weight or less, preferably 40-75% by weight, and preferably 50-75% by weight. Therefore, the organic polymer is at least about 20% by weight.
More than 75% by weight, usually about 25% by weight and even 25−
60% by weight, especially in the range 25-50% by weight. To obtain a satisfactory product, water will normally be present at least 40% by weight, generally in the range of about 45-75%, more preferably in the range of about 50-70%. Therefore, the organic solvent should be less than about 60% by weight, generally about 25% by weight or less.
−55%, more preferably about 30− of the total liquid component.
Make it 50% by weight. Other substances included are viscosity increasing agents in amounts to give a consistency similar to that of mayonnaise. 20
The viscosity of the final composition at °C is often greater than about 1000 centipoise, usually greater than 1500 centipoise. The maximum amount of the viscosity increaser added is determined by the consistency required depending on the intended use of the emulsion. Various anionic and nonionic latexes are used. Latex is usually
It consists of an organic addition polymer with a viscosity average molecular weight of about 10 ⁴ to 10 ⁶ . This addition polymer consists of acrylics, including acrylic acid, methacrylic acid, and their esters, and usually contains an alkyl group having 1 to 18 carbon atoms in the alkane moiety, hydroxylation of 1 to 6 carbon atoms. Alkyl can be, for example, hydroxyethyl, vinyl chloride polymers, vinylidene chloride, vinyl acetate, acrylonitrile, styrene, vinylpyrrolidone, and the like. Particularly preferred are acrylic esters and methacrylic esters, vinyl chloride,
This is an acrylic latex that does not contain vinylidene chloride or a copolymer of one of these monomers with 30% or less of other monomers. These polymers make transparent films. Suitable latexes are obtained from alkyl acrylates in which the alkyl group has 1-18 carbon atoms, usually 1-6 and even 1-4 carbon atoms, and in which the alkyl group of the alkyl acrylate has 1-4 carbon atoms. If it has atoms, it is an acrylic emulsion latex with at least 60 mole percent monomer, usually at least 80 mole percent. The above-mentioned polymers may be those without cross-linking, those that are cross-linked when a cross-linking agent is added with or without a catalyst, or those that are cured by heating. If a curable resin is used, this may include a small amount, usually less than 5 mol %, but at least 0.1 mol %, especially about 0.5-2 mol %.
This is especially true when the active group is glycidyl acrylate, aziridinyl methyl acrylate, etc. The above latex used contains about 15-70% by weight,
Usually about 35-65% by weight polymer and about 30-85% by weight
In particular, about 35-70% by weight water. The viscosity of the latex is usually about 10-10,000 cps (measured with a Bruckfield viscometer at 25 DEG C.), more preferably about 50-3,000 cps. Various commercially available emulsifiers may be included in the latex. Carboxyl fatty acids, alkylbenzenesulfonic acids, alkyl phosphates, etc. as anionic emulsifiers can be used alone or together with alkyl phenyl polyoxyethylene, polyoxyethylated fatty acid alcohols, etc. as nonionic emulsifiers. . The amount of emulsifier is about 0.1-5% by weight of the latex composition. Commercially available cholesteric liquid crystals that are not microencapsulated can be used alone or in combination. Common cholesteric liquid crystal compounds include cholesteryl chloride, cholesteryl bromide,
These include cholesteryl acetate, cholesteryl oleic acid, cholesteryl caprylic acid, and cholesteryl oleyl carbonate. These cholesteric liquid crystals are referenced in the aforementioned US Pat. No. 3,600,060. The solvent used has a boiling point of 175°C, preferably about 120°C.
Especially those below 100℃ and higher than about 50℃.
Although either polar or non-polar solvents may be used, polar solvents are more preferred, and oxidized solvents are particularly preferred.
These solvents include hydrocarbons, halogenated hydrocarbons, especially aromatic chlorinated carboxylic acids such as chlorobenzene and trichlorobenzene, nitrile acids,
There are oxidizing solvents. Non-oxidized solvents are not normally used on their own, but are used in conjunction with other solvents. Suitable solvents are polar organic solvents in which 3-8 carbon atoms are oxidized with 1-2 oxygen atoms. These solvents are preferably alcohols, ketones, esters, and ethers containing 4 to 8 carbon atoms, with methyl ethyl ketone being particularly preferred. The oxidized solvent is
Although soluble in water to at least 0.5% by weight at 20°C, these solvents are highly miscible with water and the solubility of preferred solvents is about 50% by weight of the total solution at 20°C, more preferably greater than 40% by weight. It's also small. Oxidized solvents include isobutanol, methyl ethyl ketone,
Examples include ethyl acetate, butyl acetate, amyl acetate, methyl isobutyl ketone, etc. If a sufficient amount of solvent is used, the liquid crystal composition can be completely dissolved. It is advantageous to use a mixed solvent consisting mainly of a highly volatile solvent mixed with a low proportion of a low volatile solvent. The ratio of highly volatile solvents is 55−90
% by volume, and therefore 10-45% by volume of high boiling point solvent. For example, a mixture of methyl ethyl ketone and methyl isobutyl ketone can be used. Furthermore, a mixture of methyl ethyl ketone and amyl acetate is also suitable. The choice of solvent is determined to some extent by the ink used. For example, when using a silk screen method, it is preferable to combine a small amount of a high-boiling point solvent that boils at about 100-175°C with a low-boiling point solvent that boils at about 50-100°C. Solvents play a critical role in the present invention.
This is because the solvent mixture must be capable of dissolving the liquid crystal. The solvent must not cause phase separation of the latex emulsion when added to the emulsion. That is, in the cholesteric liquid crystal emulsion according to the present invention, the dispersion medium is a combination of a moderately water-soluble organic solvent and water. In this emulsion dispersion medium, latex is first dispersed as a dispersoid, and liquid crystal dissolved in a portion of an organic solvent is dispersed as another dispersoid. In this emulsion, two dispersoids, the latex and the liquid crystal dissolved in the organic solvent, separate from each other to form independent phases while forming part of the emulsion. The emulsion dispersion medium described above consists of two compositions,
If one of the components (water) disperses a portion of one of the two dispersoids, and the other component (organic solvent) disperses a portion of the other dispersoid, these two Each component has the above two dispersoids and is suspended from each other,
Under these conditions, the entire emulsion can establish the stable dispersion required for the formation of a liquid crystal film. Furthermore, the solvent should have a sufficiently high vapor pressure so that when a film is formed with the liquid crystal ink, the solvent does not contaminate the ink and reduce the temperature response range of the liquid crystal composition, or deteriorate the color of the mesophase liquid crystal composition. It needs to be something that lasts. There are a variety of viscosity increasing agents, usually used in amounts sufficient to bring the composition to the desired consistency during application or film formation. The viscosity increasing agent is 0.1% by weight based on the total amount of the emulsion composition, and 0.2 to about 2% by weight,
In particular, it may be present in an amount of about 0.5-1.5% by weight. Viscosity increasing agents used include carboxyvinyl polymers and their salts, e.g. with sodium (Carbopol resins such as Carbopol 934, 940, 941, 960, 961, commercially available from Gutdrich Chemical Co.), carboxymethyl cellulose, e.g. salts of polyacrylic acid, e.g. ) Cellulose (for example, methylcellulose and hydroxyethylcellulose), 2-aminomethylpropanol, and the like. Small amounts of especially nonionic or anionic emulsifiers may also be used as wetting agents in the emulsions of the invention. The nonionic emulsifier may have an esterified or etherified terminal group. These are primarily ethylene oxide and propylene oxide polymers. Various nonionic wetting agents are commercially available under the names of Emalphor, Triton, and the like. Other wetting agents such as 2.
4,7,9-tetramethyl-5-decyne-4,7
-There are polyhydric alcohols such as diols (Sulfinol 104, available from Air Products, And Chemical Company). The wetting agent used can be used in small amounts and is
0.1-2% by weight, more usually 0.2-1% by weight. This wetting agent, together with the emulsifier used in the latex, makes the total amount of emulsifier approximately 4% by weight of the total composition. The emulsion liquid crystal ink prepared by the present invention has vivid colors and excellent adhesion to various films, and can be easily silk-printed to display sharp pattern paintings and letter-number displays. It can also be used to stretch onto a stretchable or formable substrate surface to form a layered material with a wide range of applications. The laminate according to the invention usually has a preformed stable, inert film. Typical films include polyester condensation polymers such as polyethylene terephthalate and polycarbonate, addition polymers such as ABC polymer (acrylonitrile-butadiene-styrene), acrylate and methacrylate films, polyvinylidene chloride film, polyvinyl chloride film, Fluorocarbons such as Kel-F, polyvinyl fluoride, polyolefin films such as polyethylene and polypropylene, cellulose esters such as cellulose acetate, cellulose propionate, butyl cellulose, ethylene-vinyl acetate, vinyl chloride-vinyl acetate, nylon and polycaprolactam, etc. Examples include polyamide, polystyrene, and copolymers thereof, especially vinyl chloride-vinylidene chloride. The thickness of the film is approximately 0.00063−0.076cm (0.25−
30 mils), usually about 0.005-0.038cm (2-15 mils),
More particularly, it may range from about 3 to 10 mils. Depending on the function of the substrate film, this film can be transparent, colored, or contain black pigments. The preformed film serving as the substrate is a transparent film, and the liquid crystal film is one to which one transparent film is directly adhered, and also directly or indirectly through one or more films to create a black background. This is convenient. The thickness of one coating of one or more liquid crystal compositions applied almost uniformly to the substrate is 0.0013-0.050 cm.
(0.5-20 mil), usually about 0.0025-0.038 cm (1-15
mils) more particularly about 0.0025-0.028 cm (1-12 mils). This liquid crystal composition coating film can draw stripes, pictures, etc. with uniform thickness and in a continuous or discontinuous manner. After application to the substrate surface, the liquid crystal emulsion coating is coated with one or more layers of clear or pigmented, particularly black, preformed film or paint. 0.0013-0.013cm (0.5-5 mil) for the liquid crystal layer
It is best to apply a blackened ink or paint. This may be acrylate, active, semi-reactive or reactive. Various paints such as latex, vinyl chloride polymers and copolymers, vinyl chloride polymers and copolymers, vinyl acetate polymers and copolymers, cellulose esters, etc. can be used. These polymers are well compatible with liquid crystal films and create strong adhesive layers. If no additional film is used or paint or ink is used as a single layer protective coating, the thickness is 0.005-0.05 cm.
(2-20 mil) more preferably 0.0076-0.038 cm
(3-15 mil). In addition to the organic material film, a metal foil can be used, on which a liquid crystal coating film can be applied or a previously formed liquid crystal film can be adhered. When directly adhering metal foil to a liquid crystal film, the adhesion surface must be blackened, for example, by anodic oxidation. Usually, a coating of black paint or ink is provided between the liquid crystal layer and the metal film. Aluminum, magnesium, etc. are used as the metal film. The compositions of the present invention are particularly useful in the production of blown or vacuum formed films that are formed into layered bodies of particular shapes or configurations by stretching or shaping the film. For example, a laminate using the composition according to the present invention can be blow-molded or vacuum-formed into a mask so that the mask's surface becomes speckled with color due to the temperature response of the liquid crystal composition. It can also be used to make decorative plastic containers such as small works of art, packaging, and ribbons. Examples of films made using emulsions according to the invention will now be described. The cross-sectional view of the layered film in FIG. 1 shows a transparent film 10, a liquid crystal coating 12, and a dark colored backing material 14. In FIG. 3, the layered flexible and elastic sheet includes a layer 16 of an elastic transparent polymer such as ethylene-propylene rubber, a liquid crystal emulsion coating 18 prepared according to the present invention, and a layer 16 of a transparent elastic polymer such as ethylene-propylene rubber, It is made of a black polymeric backing 20 which may be made of commercially available elastic materials such as SBR, nitrile rubber, etc. In FIG. 2, the mask 22 is blow molded from a layered film, and when pressed against the face,
distance from the skin, response temperature range of the liquid crystal film,
Various color changes 24 are produced depending on the mesophase range. EXAMPLE To prepare the composition of the present invention, a commercially available latex was first diluted with water to the required solids concentration. A polar organic solvent, a liquid crystal composition, a viscosity increaser, and an appropriate wetting agent were placed in a separate container. Next, gradually add the latex solution to the liquid crystal composition while stirring.
Heated to 50-70°C. This stirring is continued for at least 5 minutes even after the liquid crystal composition has been added until a consistency similar to that of mayonnaise is obtained. The resulting composition was then applied by drawing with a knife blade or by silk printing to a dry film thickness after liquid evaporation of 1 to 5 mils. After drying, the film was visually inspected to examine its appearance and feel, as well as the presence of residual oil.Furthermore, the temperature response range of the liquid crystal was examined by heating to see if the colored contours of the liquid crystal were good or not. The following table lists the test results for the compositions prepared and their respective films.

【table】

[Table] The composition according to the invention has various advantages and excellent properties. It is easy to prepare and handle, and the color tone in the mesophase of liquid crystals is excellent and clear. Furthermore, since the oiliness of the liquid crystal composition is reduced, a strong adhesive layer can be easily formed on the liquid crystal film by applying various paints and inks to the liquid crystal coating or thin film. Further, since the layered material formed using the liquid crystal ink according to the present invention can be easily shaped or formed without damaging the liquid crystal film, it is possible to maintain the continuous nature of the desired shape or to hold the film containing the liquid crystal. Furthermore, since the pattern created by the liquid crystal composition is not easily lost due to migration, the liquid crystal itself can be stably present at a fixed position. This liquid crystal composition can be silk-screened without generating bubbles. Further, the coating film can be applied to various substrate surfaces, or a substrate can be applied thereon. Furthermore, because a significant portion of the liquid crystal composition is used in combination with a polymeric binder, a high percentage of the liquid crystal composition results in a very thin film and enhanced color development. Films and laminated materials according to the invention can be used for various decorative and practical purposes. It can also be a thermometer as a temperature indicator or alarm device. Furthermore, since cholesteric substances are degraded by radiation, photographs can also be reproduced by irradiating the surface of the film of the present invention with light through a negative image. The illuminated area changes depending on the temperature responsive area. When the film is heated to this temperature response range, the photograph is regenerated and becomes visible. The laminated material can be manufactured by stretching, blow molding, vacuum forming, etc. while maintaining a continuous thin liquid crystal layer.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view of the laminated material, FIG. 2 shows a perspective view of a mask made of the laminated material according to the invention, and FIG. 3 shows a perspective view of the rubber laminated material according to the invention. 10...Transparent film, 12...Liquid crystal film, 14...Black lining, 22...Mask, 24...
...discoloration area.

Claims (1)

[Claims] 1. An emulsion used as a coating composition for forming a film containing liquid crystal, characterized by containing the following composition: (a) Cholesteric liquid crystal composition 25 to 80 % by weight and solids content consisting of 75 to 20% by weight of polymer for forming transparent latex.
30 to 80 percent by weight; (b) 14 to 75 percent by weight of water and a boiling point of approx.
175°C or below and a liquid content of 20 to 70 weight percent consisting of 25 to 65 weight percent of a moderately water-soluble organic solvent which is a solvent for the liquid crystal composition; (c) to provide the necessary viscosity for film formation; A small but sufficient amount of viscosity increasing agent. 2. A process for producing an emulsion according to claim 1, which comprises the following steps: (a) a latex polymer forming a transparent film and water comprising 30 to 95 percent by weight; (b) Adding about 0.1 to 2 percent by weight of a viscosity increasing agent based on the total amount; c) maintaining the resulting solution at a temperature in the range of about 40 to 100°C; and (d) stirring the mixture thus formed for a sufficiently long period of time to form a substantially homogeneous emulsion.