JP6554827B2 - Indicator - Google Patents

Description

  The present invention relates to a display device having a multilayer film structure that is colored by reflection characteristics derived from multilayer film interference, and a display for preventing counterfeiting using a change in optical characteristics of a multilayer structure imparted with a function to respond to humidity. About the body.

  In order to prevent counterfeiting, various anti-counterfeiting technologies such as anti-counterfeiting indicators, luminescent ink, and latent image patterns are applied to vouchers, securities, certificate stamps, credit cards, membership cards, expensive items, etc. .

  Of particular note is the phenomenon of structural coloring, which reflects light by a fine periodic structure, and the structural coloring is less susceptible to fading over time, as seen in dyes, etc., has high saturation, and is vivid. There is a feature that shows the color.

  As a display member using such a structural color, a display member that expresses a structural color by arranging spherical bodies having a refractive index different from that of the matrix regularly in the matrix, particularly a display layer that expresses a structural color. There has been proposed a display member that causes a color change in response to a stimulus by changing the enclosed cell frame by a stimulus from the outside (Patent Document 1).

  In addition, a display member has been proposed that has a multilayer structure in which polymers having different refractive indexes are alternately laminated, and the polymer layer swells and causes a color change by immersing the multilayer structure in an aqueous solution. (Non-Patent Document 1).

  However, a display body having a cell structure in which a display layer is encapsulated assumes pressure and tensile stress as a stimulus, and does not respond to humidity stimulus such as moisture or exhalation. Further, an ionic liquid is used for the matrix of the display layer, and the cell needs to be sealed. If the cell is damaged by a stimulus such as pressure, the coloring function may be lost.

  In addition, in a display body using a multilayer film structure, it is necessary to immerse the multilayer film structure in an aqueous solution or an alcohol solution in order to change the reflection wavelength to the visible light region. Color change cannot be induced in the visible light region.

JP 2009-216964 A

Leibler, L .; "Theory of Microphase Separation in Block Copolymers", Macromolecules, 1980, Vol. 13, pp. 1602-1617

  The present invention has been made in view of these problems, and in a display body having a multilayer structure that is colored by reflection characteristics derived from multilayer film interference, the cell is not damaged by a stimulus such as pressure. An object of the present invention is to provide a display body capable of inducing a color change without being immersed in an alcohol solution.

As a means for solving the above problems, the invention according to claim 1 is a polymer in which two types of polymer films of a first phase and a second phase having different physical properties are alternately laminated on a substrate. A display body having a film laminate structure,
At least one phase of the polymer film has a property of swelling by absorption of moisture and shrinking by drying , the polymer film includes a block copolymer, and one or more of the block copolymers The block constitutes the first phase, the other block of the block copolymer constitutes the second phase, and at least one of the first phase and the second phase of the polymer film has a water-soluble polymer or a high A display comprising a molecular gel or hydrophilic colloidal particles .

  In the invention according to claim 4, the block copolymer is a diblock copolymer, and one block of the diblock copolymer constitutes the first phase, and the diblock copolymer 4. The display body according to claim 3, wherein the other block of the second phase constitutes the second phase.

  The invention according to claim 5 is the display body according to claim 3, wherein the polymer film has a lamellar microphase separation structure.

  The invention according to claim 6 is that the block copolymer has a weight average molecular weight of 60000 or more, and the volume fraction of the first phase is in the range of 0.35 to 0.65. It is a display body of Claim 3 characterized by the above-mentioned.

  The invention according to claim 7 is the display body according to claim 1, wherein the polymer film has a film thickness of 400 nm or more.

  The invention according to claim 8 is the display body according to claim 1, wherein at least one of the first phase and the second phase has photocrosslinkability or thermal crosslinkability.

  The invention according to claim 9 is the display body according to claim 1, wherein a part of the first phase and the second phase are crosslinked.

  The display body of the embodiment of the present invention has no fear of damage due to external stimuli such as pressure, does not need to be immersed in an aqueous solution or an alcohol solution, and has a wide range of colors from ultraviolet to visible and infrared light regions only by changing humidity. A display body that can be changed can be provided.

It is a section conceptual diagram showing composition of a display concerning an embodiment of the present invention. 1 is a conceptual cross-sectional view illustrating a configuration of a display body in which a part of a polymer film is partially crosslinked according to an embodiment of the present invention. It is a graph which showed the change of the maximum wavelength of the structural color development at the time of swelling with respect to the ultraviolet irradiation amount according to the embodiment of the present invention. It is a graph which showed the change of the maximum wavelength of the structural color development with respect to relative humidity according to the embodiment of the present invention. It is a SEM cross-sectional photograph of the display body obtained in Example 1 of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross section showing a configuration of a display body according to an embodiment of the present invention. The display body 1 is formed of a polymer film, and different types of first phase 2 and second phase 3 are films. It has a structure in which the layers are alternately stacked in the thickness direction, and at least one of the first phase 2 and the second phase 3 contains a substance that swells by absorbing moisture and contracts by drying. Features.

  The display body 1 includes a base material 4 that may be optionally provided, and a polymer film 5 on the base material 4. The polymer film 5 has a structure in which different types of first phase 2 and second phase 3 are alternately laminated in the film thickness direction. An example is shown in FIG. 1, but the second phase 3 of the polymer film 5 contains a substance having a property of swelling due to moisture absorption and shrinking due to drying.

  The polymer film 5 composed of the first phase 2 and the second phase 3 can be preferably formed using a block copolymer. A block copolymer is a polymer in which two or more different polymer blocks having low compatibility with each other are bonded at their ends.

  In the present invention, “low compatibility with each other” means that the formula of χ × N> 10.5 is satisfied (Non-patent Document 1), where χ is a Flory defined between different polymer blocks. Represents the interaction parameter of Huggins, and N represents the degree of polymerization of the block copolymer.

  Such a block copolymer forms a periodic microphase-separated structure in a self-organized manner by an annealing treatment in which the copolymer is heated to a phase transition temperature or higher. In this microphase-separated structure, polymer blocks having low compatibility form microregions so as not to cross each other.

  The dimensions of the microregion depend on the polymer chain length of each polymer block. In addition, what microphase separation structure is formed is determined by the volume fraction of each polymer block forming the block copolymer.

  In the present embodiment, the polymer film 5 in which two different organic phases (first phase 2 and second phase 3) are alternately stacked can be formed by using the above-described self-organization phenomenon. In addition to the method using the self-organization phenomenon, the polymer film 5 can also be formed using a multilayer coextrusion method in which different types of resins are simultaneously extruded onto a film to form a laminated film.

  However, in the multilayer coextrusion method, the number of layers that can be formed at one time is limited. Therefore, a method using a self-organization phenomenon that can form the polymer film 5 in which 20 or more phases are alternately laminated by only one application and annealing treatment is preferable.

  The block copolymer includes a linear block copolymer in which each polymer block is bonded in series at the end thereof, a star block copolymer in which each polymer block is bonded at one point, and the like.

  In this embodiment, any block copolymer can be used. In the present invention, it is preferable to use a diblock copolymer in which two different polymer blocks are bonded at their ends.

Examples of diblock copolymers that can be used in this embodiment include poly (styrene-b-lactic acid), poly (styrene-b-2-vinylpyridine), poly (styrene-b-4-vinylpyridine), Poly (styrene-b-dimethylsiloxane), poly (styrene-bN, N-dimethylacrylamide), poly (butadiene-b-4-vinylpyridine), poly (styrene-b-ferrocenyldimethylsilane), poly (Butadiene-b-methyl methacrylate), poly (butadiene-b-t-butyl methacrylate), poly (butadiene-b-t-butyl acrylate), poly (butadiene-b-dimethylsiloxane), poly (t-butyl methacrylate) b-4-vinylpyridine), poly (ethylene-b-methyl methacrylate), poly (t-butylmethacrylate) Chlorate-b-2-vinylpyridine), poly (ethylene-b-2-vinylpyridine), poly (ethylene-b-4-vinylpyridine), poly (isoprene-b-2-vinylpyridine), poly (methyl methacrylate) -B-styrene), poly (t-butyl methacrylate-b-styrene), poly (methyl acrylate-b-styrene), poly (butadiene-b-styrene), poly (isoprene-b-styrene), poly (butadiene- b-sodium acrylate), poly (butadiene-b-ethylene oxide), poly (t-butyl methacrylate-b-ethylene oxide), poly (styrene-b-polyacrylic acid), and poly (styrene-b-methacrylic acid). Including, but not limited to.

  In the above-described diblock copolymer, one of the polymer blocks forms the first phase 2 and the other forms the second phase 3. The microstructure (microphase separation structure) formed by the microphase separation of the diblock copolymer also depends on the volume fraction of the two polymer blocks.

  The obtained microphase separation structure includes a sphere (spherical) composition, a cylinder (columnar) structure, a gyroidal structure, a lamella (plate-like) structure, and the like. The microphase-separated structure of the diblock copolymer is determined by the phase diagram represented by the Flory-Huggins interaction parameter χ, the degree of polymerization N of the polymer, and the volume fraction of the polymer block. .

  In this embodiment, a diblock copolymer having a lamellar structure is used. Because, as shown in FIG. 1, each of the first phase 2 and the second phase 3 has a plate-like structure oriented in the in-plane direction of the base material 4 (direction parallel to the surface of the base material 4). This is because a structure in which the first phase 2 and the second phase 3 are alternately laminated in the vertical direction of the base material 4 (that is, the film thickness direction of the polymer film 5) can be realized.

  Since the diblock copolymer has a lamellar structure, the volume fraction of the two polymer blocks is preferably in the range of 0.35 to 0.65. When the volume fraction of the polymer block is less than 0.35 or 0.65 or more, a sphere structure or a cylinder structure is obtained, and it becomes difficult to obtain a lamella structure.

  In the example shown in FIGS. 1 and 2, the polymer film 5 has a lamellar structure. When a diblock copolymer is used, the repeated pattern size (periodic pattern size) of the lamellar structure depends on the molecular weight of the diblock copolymer.

  Therefore, by appropriately selecting the molecular weight of the diblock copolymer, the size of the periodic pattern, that is, the size of the periodic phase separation structure can be adjusted to the target size.

The polymer film 5 in which the first phase 2 and the second phase 3 made of different types of materials are alternately laminated has a specific wavelength λ ₁ determined by the equation (1) derived from Snell's law and Black's law. It has the characteristic of reflecting the light.
λ ₁ = 2d (n1 ² −cos 2θ) ^1/2 (1) [where n1 represents the ratio of the refractive indices of the first phase 2 and the second phase 3 (relative refractive index), and d represents the first phase. 2 or the thickness of the second phase 3, and θ represents the outgoing angle of the reflected light.

In the present embodiment, when the polymer film 5 is swollen by gas adsorption, the gas is adsorbed to at least one of the first phase 2 and the second phase 3 to swell them, and the film of the phase in which the gas is adsorbed the thickness d, and the wavelength lambda ₁ of the reflected light changes by the relative refractive index n1 is changed, a polymer film 5 as reflected light in a visible light region (structural color) is emitted.

  The relative refractive index n1 is the absolute refractive index of the molecules to be swollen, the absolute refractive indexes of the first phase 2 and the second phase 3 before the gas is adsorbed, and the adsorption amount of the gas with respect to the first phase 2 and the second phase 3. It is decided by.

  Therefore, it is desirable that the period of the lamellar pattern, that is, the period of the periodic phase separation structure of the organic polymer (block copolymer) forming the polymer film 5 is 20 to 400 nm from which reflected light in the visible light region can be obtained. .

  In particular, in this embodiment, since the swelling phenomenon of the polymer film 5 is used, it is more preferable to use an organic polymer (block copolymer) having a molecular weight capable of realizing a lamellar pattern period of 20 to 50 nm.

In order to obtain a lamellar pattern period of 20 nm or more, the block copolymer needs to have a weight average molecular weight of 60000 or more. When a block copolymer using a weight average molecular weight of less than 60000 is used, the lamellar pattern period is 20 nm or less, and the wavelength λ _{1 of} reflected light is in the ultraviolet region, which cannot be visually confirmed.

  In addition, since the reflected light from the polymer film 5 has an intensity that can be visually observed, the polymer film 5 has a high phase so that the polymer layer 5 has the first phase 2 having 10 layers or more and the second phase 3 having 10 layers or more. It is desirable to set the film thickness of the molecular film 5.

  In particular, the total number of layers of the first phase 2 and the second phase 3 is in the range of 20 to 50 from the viewpoint that the reflected light is clearly observed and the self-organization easily proceeds. Is preferred. In order to realize this number of layers, the film thickness of the polymer film 5 is preferably in the range of 400 nm to 2000 nm.

  When the total number of layers of the first phase 2 and the second phase 3 is less than 20 (that is, the film thickness of the polymer film 5 is less than 400 nm), the intensity of reflected light becomes small and difficult to observe visually. It becomes.

  As described above, the self-assembly of the block copolymer is induced by annealing (heating) above the phase transition temperature. However, as the molecular weight of the block copolymer increases, the fluidity of the block copolymer decreases.

  Therefore, the phase separation behavior becomes dull and it is difficult to form a microphase separation structure. Therefore, a very long annealing process is required for self-assembly of a block copolymer having a large molecular weight.

  In order to promote the self-assembly phenomenon, an annealing treatment can be performed under a solvent vapor having affinity for the block copolymer. It is known that the presence of the solvent vapor improves the fluidity of the block copolymer and promotes self-organization, so that the annealing time can be shortened and the heating temperature can be reduced.

The solvent used in the annealing treatment under a solvent vapor is not particularly limited as long as it is a solvent having an affinity for the block copolymer. Examples of solvents that can be used include chloroform, toluene, tetrahydrofuran, propylene glycol-1-monomethyl ether-2-acetate (PGMEA), and the like.

  Moreover, the annealing treatment under the solvent vapor is preferably performed at a temperature lower than the boiling point of the solvent used. When the treatment is performed at a temperature equal to or higher than the boiling point, the solvent is volatilized around the polymer film 5, the solvent vapor does not sufficiently penetrate into the polymer film 5, and the fluidity of the organic polymer cannot be improved.

  Next, a method for introducing a substance having the property of swelling into moisture at least one of the first phase 2 and the second phase 3 of the polymer film 5 and shrinking by drying will be described.

  The moisture described in the present specification refers to a molecule that includes water vapor, alcohol vapor, or the like and can be absorbed by at least one of the polymer blocks forming the first phase 2 and the second phase 3 of the polymer film 5.

  Examples of the substance that swells by absorbing moisture and shrinks by drying include water-soluble polymers, polymer gels, and hydrophilic colloid particles.

  Examples of water-soluble polymers that can be used in the present embodiment include, but are not limited to, polyurethane, polyvinyl alcohol, polyacrylic acid, gelatin, methylcellulose, hydroxyethylcellulose, and polyvinylpyrrolidone. Examples of the polymer gel include polyvinyl alcohol hydrogel, polyacrylamide gel, or various acrylamide derivatives (N-isopropylacrylamide, N-ethylacrylamide, N-methylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, N- Gels formed from (methylol acrylamide, N-methylol methacrylamide), but are not limited thereto.

  The water-soluble polymer or polymer gel may be introduced into the polymer film 5 as a polymerized polymer structure, but may be introduced into the polymer film 5 as a monomer and then polymerized in the film. .

  As a method for introducing the polymer structure 5 into the polymer film 5, the polymer film 5 is not dissolved, and the water-soluble high-soluble solvent is used in a solvent in which at least one of the first phase 2 or the second phase 3 of the polymer film 5 swells. It can be introduced by dissolving molecules and polymer gel, immersing the polymer film 5 in the solution to infiltrate the film, and then removing the polymer film 5 and drying it.

  In order to introduce the polymer gel, the monomer film, the crosslinking agent, and the initiator are dissolved in a solvent in which the polymer film 5 is not dissolved and at least one of the first phase 2 or the second phase 3 of the polymer film 5 swells. And the polymerization reaction may be allowed to proceed.

  The amount of the substance that swells by absorbing moisture and shrinks by drying varies depending on the change in film thickness upon absorption of moisture and the refractive index of the introduced substance, but is derived from Snell's law and Black's law (1) The color change in the visible light region can be induced.

  Next, the structural color patterning that appears when the polymer film 5 is swollen will be described.

FIG. 2 is an enlarged cross-sectional view of a main part of the display body 1 in which a part of the polymer film 5 is partially cross-linked. In the example shown in FIG. 2, the polymer film 5 is partially crosslinked in the crosslinked region 6. In the crosslinked region 6, at least one of the first phase 2 and the second phase 3 of the polymer film 5, or both,
It may be partially crosslinked.

  In the present embodiment, a phenomenon is used in which structural coloring is developed by changing the phase thickness d and the relative refractive index n1 in the formula (1) by swelling the polymer film 5 by gas adsorption.

  Therefore, as shown in FIG. 2, if the swelling of the first phase 2, the second phase 3, and the first phase 2 and the second phase 3 in the bridging region 6 due to gas adsorption is suppressed, the change in the phase thickness d is suppressed. Thus, the development of structural color development can be suppressed.

  In other words, by patterning the bridging region 6, it is possible to define a region that exhibits structural color development in the visible light region and a region in which structural color development is suppressed. This effect is effective in improving the color contrast of structural coloring in visual observation.

  The block copolymer in the polymer film 5 can be crosslinked by heat or light. For example, it is known that a block copolymer containing a polymer block containing a pyridine ring or a pyrrolidine ring is crosslinked at the α-position carbon of the pyridine ring or pyrrolidine ring by light irradiation.

  Moreover, the block copolymer containing the polymer block derived from butadiene can impart thermal crosslinkability or photocrosslinkability by mixing a thermal polymerization initiator or a photopolymerization initiator. Alternatively, for block copolymers comprising polymer blocks having reactive substituents such as hydroxyl groups, amino groups, isocyanate groups, crosslinkers that are compatible with the reactive substituents, optionally a photoacid generator or Photocrosslinking property can be imparted by mixing a photobase generator or the like.

  Photocrosslinking by ultraviolet irradiation or the like is particularly preferable in that the induced polymer can be crosslinked and patterned in a short time using a simple process. More specifically, photocrosslinking by ultraviolet irradiation or the like makes it possible to carry out fine patterning of the polymer film 5 collectively by irradiation through an ultraviolet shielding photomask patterned in an image shape.

  In the present embodiment, at least one of the first phase 2 and the second phase 3 of the polymer film 5 may be crosslinked, or both may be crosslinked. At least a phase exhibiting a swelling phenomenon due to moisture absorption is crosslinked.

  In the case of crosslinking by light irradiation, the light irradiation may be performed from a direction perpendicular to the surface of the polymer film 5 or from an oblique direction. When light irradiation is performed from the vertical direction, the boundary between the irradiated area (that is, the bridging area 6) and the non-irradiated area becomes clear, and an image having high contrast (clear outline) is obtained.

  On the other hand, when light irradiation is performed from an oblique direction, a gradation of the crosslinking rate occurs in the depth direction of the polymer film 5 at the boundary between the irradiated area and the non-irradiated area. As a result, the image after moisture absorption is an image having a soft outline.

  The procedure for patterning is to photocrosslink the polymer film 5 in a dry state before introduction of a substance having a property of swelling by moisture absorption and shrinking by drying using an ultraviolet shielding photomask. Is preferred.

When patterning is carried out after introduction, the density between organic polymers decreases due to swelling due to the introduction of substances that swell due to moisture absorption and shrink by drying, and the organic polymers are not sufficiently crosslinked, resulting in UV irradiation. There is no difference in the swelling rate when absorbing moisture between the area and the unirradiated area, and color contrast cannot be obtained.

  Next, a method for controlling the wavelength λ of structural color development in the polymer film 5 will be described.

  The first method of controlling the wavelength λ of structural color development is to control the wavelength of color development by controlling the crosslinking rate of the organic polymer in the polymer film 5. As the polymer crosslinking rate increases, the swelling rate when the polymer film 5 swells decreases.

  And the fall of a swelling rate brings about suppression of the dimensional change (expansion and elongation) of a polymer film. Due to the decrease in the swelling rate, the change in the phase thickness d becomes smaller, and the phase thickness d during swelling due to gas adsorption becomes smaller.

As described above, the wavelength λ ₁ of the structural color development decreases in proportion to the decrease in the phase thickness d in the equation (1). In other words, as the phase thickness d during swelling decreases, the structural color development shifts by a short wavelength. From the above, it is possible to select the color of the structural color by controlling the crosslinking rate of the polymer.

When photocrosslinking by ultraviolet rays is used, the crosslinking rate of the organic polymer in the polymer film 5 can be controlled by the amount of light irradiation. In this embodiment, a structural color to be expressed in a visible light region, typically an ultraviolet irradiation amount is preferably selected in 5 mJ / cm ² or more 500 mJ / cm ² or less.

  The wavelength region of the ultraviolet rays to be irradiated is selected within the range of 200 nm to 500 nm. Moreover, although the light source to be used includes a high pressure mercury lamp, a metal halide lamp, and an LED lamp, it is not limited to these.

  FIG. 3 shows the relationship between the ultraviolet irradiation amount and the maximum wavelength λ for structural color development. Here, a poly (styrene-b-2-vinylpyridine) (PS-b-P2VP) film having a film thickness of 800 nm was irradiated with ultraviolet rays having a wavelength of 365 nm with various irradiation amounts. Thereafter, the PS-b-P2VP membrane was annealed in the presence of chloroform vapor at 50 ° C. for 12 hours.

  Finally, water was dropped onto the obtained PS-b-P2VP film, and the maximum wavelength λ of the structural color obtained at that time was measured. As is apparent from FIG. 3, it can be seen that the maximum wavelength of structural color development decreases with an increase in the amount of ultraviolet irradiation, and the structural color development shifts by a short wavelength.

  As another method for controlling the crosslinking rate when performing photocrosslinking, light irradiation using a gray scale mask can be used. The gray scale mask is a mask that forms a light shielding pattern in a halftone dot shape and controls the amount of light incident on the sample by the density of the halftone dot.

  A structural color pattern (so-called color image) having different wavelengths can be obtained in the same surface of the display 1 by a single light irradiation process using a gray scale mask. As a result, the design of the display body 1 is significantly improved.

  A second method for controlling the wavelength λ for structural color development is to absorb different gases into the polymer film. The state of swelling of the polymer film 5 changes depending on the affinity between the polymer film 5 (specifically, the first phase and / or the second phase) and gas.

  As a result, the phase thickness d at the time of swelling changes by using different types of gases. Furthermore, each gas has a specific refractive index. Further, the amount of gas contained in the first phase and / or the second phase also changes during swelling. Therefore, by using different types of gases, the relative refractive index n1 of the first phase and the second phase also changes.

Accordingly, since the both phases thickness d and relative refractive index n1 is changed, also changes the wavelength lambda ₁ of the reflected light obtained by the equation (1). Therefore, the gas used for the swelling can be selected in accordance with the target structural color development wavelength λ.

  The gas to be swollen can be arbitrarily selected as long as it has affinity for the organic polymer forming the polymer film 5. Examples of gases that can be used include water vapor, alcohols, and organic solvents.

  However, since the structural color development is lost when the microphase separation structure of the polymer film 5 is collapsed, an organic solvent that dissolves the organic polymer constituting the polymer film 5 cannot be used.

  A third method for controlling the wavelength λ of structural color development is to chemically modify the organic polymer that forms the polymer film 5. For example, when a polymer block constituting a phase that swells by gas absorption contains a pyridine ring, a positive charge can be imparted to the polymer block constituting the phase by protonating or quaternizing the pyridine ring. .

  The polymer block to which a positive charge is applied has an increased swelling rate due to electrostatic repulsion of the positive charge. When protonation is performed, an aqueous solution with a controlled pH can be allowed to act on the polymer membrane. The lower the pH of the aqueous solution, the higher the protonation rate. As a result, the structural color development upon swelling due to gas adsorption shifts by a longer wavelength. The aqueous solution that can be used preferably has a pH of 1 or more and 5 or less.

  Further, the quaternization of the pyridine ring includes treating the polymer film 5 with a solution containing an alkyl halide. By this treatment, the nitrogen atom of the pyridine ring is quaternized with an alkyl group and is positively charged.

  Therefore, the higher the quaternization rate, the higher the electrical repulsion due to positive charges, and the structural color development shifts by longer wavelengths. Examples of alkyl halides that can be used include, but are not limited to, methyl bromide, ethyl bromide, propyl bromide, methyl iodide, and ethyl iodide.

  Moreover, in this embodiment, the base material 4 may have a glossy reflective layer or a black layer on the interface with the polymer film 5 or on the opposite surface (back surface of the base material). By providing these layers, the visibility at the time of visual observation of the structural color development can be improved, and the design of the display body can be improved.

<Example 1>
Using a spin coating method, a 7% PGMEA solution of poly (styrene-b-2-vinylpyridine) (PS-b-P2VP) is applied on a glass plate as a substrate, and a polymer film having a thickness of 800 nm Formed. The PS-b-P2VP used had a weight average molecular weight of 107000 and a polydispersity of 1.05. Moreover, the volume fraction of the polystyrene (PS) block in PS-b-P2VP was 0.52, and the rotation speed at the time of spin coating was 400 rpm.

  Next, the glass substrate on which the polymer film was formed was placed in a glass bottle containing 3 mL of chloroform. The glass bottle was heated to 50 ° C. for 12 hours and annealed in the presence of solvent vapor to self-assemble the polymer film to form a first phase and a second phase.

  Next, an aqueous solution of acrylamide is dropped into the polymer film after annealing, acrylamide is soaked into the second phase of the surface layer, irradiated with ultraviolet rays from a metal halide lamp to form an acrylamide gel, and the polymer and swelling shrinkage substance The 2nd phase which is a mixed layer of was formed.

The composition of the acrylamide aqueous solution was Acrylamide; 24% by weight, N, N′-Methylenebisacrylamide; 1.9% by weight, 2,2-Diethylacetophenone; 1.9% by weight. The irradiation amount of ultraviolet rays was 300 mJ / cm ² .

  A sample of the obtained display body was embedded in an ultraviolet curable resin, and the display body was cut in the vertical direction using a microtome equipped with a diamond cutter. Next, the display body of Example 1 was obtained by exposing the cross section of the display body to the element atmosphere for 3 hours.

  The cross section of the obtained display body of Example 1 was observed with a scanning electron microscope (SEM). The obtained SEM photograph is shown in FIG. From FIG. 5, it was found that the polymer film had a structure in which white layers and black layers were alternately laminated.

  The white layer is a phase composed of a poly-2-vinylpyridine (P2VP) block dyed with iodine and a polyacrylamide gel, and the black layer is a phase composed of a PS block. This result shows that the polymer film has a structure in which two phases are alternately stacked in the vertical direction by self-assembly, and the film thickness of the P2VP phase (the film thickness before the introduction of the polyacrylamide gel is 20 nm). ) Swells to 120 nm, meaning that a polyacrylamide gel is introduced.

  The formed polymer film was placed in a constant temperature and humidity chamber, and the reflection spectrum was measured while changing the humidity at 25 degrees. FIG. 4 shows the result of plotting the maximum wavelength change of the reflection spectrum against the humidity. As the humidity increases, the maximum wavelength of the reflection spectrum changes to the longer wavelength side in the visible light region, indicating that it responds to humidity.

  When exhaled air was blown onto the formed polymer membrane, a colorless and transparent to green structural color was observed, indicating exhalation responsiveness.

  When ethanol vapor was sprayed on the display body of Example 1, structural color development from colorless and transparent to blue was observed, and it was found that it responded to ethanol vapor.

<Example 2>
In the same procedure as in Example 1, the polymer film is self-assembled to form the first phase and the second phase, and a patterned ultraviolet shielding mask made of a Cr thin film is placed on the polymer film, A 200 mJ / cm ² ultraviolet ray was irradiated from a metal halide lamp, and a part of the polymer film was crosslinked.

  A polyacrylamide gel was introduced into the polymer film in the same procedure as in Example 1 to obtain the display of Example 2. Subsequently, when the display body of Example 2 was observed at a humidity of 20%, a colorless and transparent polymer film was visually recognized, and an image patterned by ultraviolet irradiation was not visually recognized.

  Furthermore, when the display body after irradiation with ultraviolet rays was observed by standing in an atmosphere of a temperature of 25 ° C. and a humidity of 70%, glossy structural coloration was visible due to swelling of the polymer film. In addition, color development at different wavelengths was observed in the region irradiated with ultraviolet light and the region shielded from ultraviolet light. In other words, the image pattern resulting from the ultraviolet shielding mask could be visually observed.

When ethanol vapor was sprayed on the display body of Example 2, the colorless and transparent to blue structural color was observed as an image pattern caused by the ultraviolet shielding mask, and it was found that the display body responded to ethanol vapor.

<Comparative Example 1>
A display body of Comparative Example 1 was obtained under the same conditions as in Example 1 except that the polymer film was self-assembled by annealing under the same conditions as in Example 1 and the subsequent step of acrylamide soaking was omitted. . When the display of Comparative Example 1 in which no polyacrylamide gel was introduced was placed in a thermo-hygrostat and the reflection spectrum was measured while changing the humidity at 25 degrees, the maximum wavelength was observed in the visible light region. However, it was not possible to observe the humidity responsiveness by visual observation, and breathing was applied to the polymer membrane, but it remained colorless and transparent, and no visual color change was observed.

  As described above, a swelling and shrinking substance that forms a first phase and a second phase by self-organization, swells by absorption of moisture and shrinks by drying in at least one of the first phase and the second phase. By introducing it, it was possible to provide a display body that can change color only by changing humidity.

  The display body of the present invention that uses responsiveness to changes in humidity can be used for an anti-counterfeit display body and an image display body such as a toy, or a sensor device that responds to humidity or pH.

DESCRIPTION OF SYMBOLS 1 ... Display body 2 ... 1st phase 3 ... 2nd phase (mixed layer of a polymer and a swelling shrinkage substance)
4 ... Base material 5 ... Polymer film 6 ... Cross-linked region

Claims (7)

A display body of a polymer film laminate structure in which two types of polymer films of a first phase and a second phase having different physical properties are alternately laminated on a substrate,
At least one phase of the polymer film swells by absorbing moisture and has a property of shrinking by drying ,
The polymer film comprises a block copolymer;
One or more blocks of the block copolymer constitute the first phase, and the other blocks of the block copolymer constitute the second phase;
Wherein the first and second phases of at least one of the phases, the display body and further comprising said Rukoto water-soluble polymer or a polymer gel, or the hydrophilic colloid particles. The block copolymer is a diblock copolymer, one block of the diblock copolymer constitutes the first phase, and the other block of the diblock copolymer constitutes the second phase. The display body according to claim 1 , wherein: The display body according to claim 1 , wherein the polymer film has a lamellar microphase separation structure. The display body according to claim 1 , wherein the block copolymer has a weight average molecular weight of 60000 or more, and the volume fraction of the first phase is in the range of 0.35 to 0.65. .   The display body according to claim 1, wherein the polymer film has a thickness of 400 nm or more.   The display body according to claim 1, wherein at least one of the first phase and the second phase has photocrosslinkability or heat crosslinkability.   The display body according to claim 1, wherein a part of the first phase and the second phase are cross-linked.

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