JP2009216964A - Display member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display member capable of obtaining a display color obtained by a change in the structure color by a stimulus from outside with a high response speed and of restraining the degree of fluctuation (degradation) of the display color by environmental conditions, such as an aging effect, temperature, and humidity. <P>SOLUTION: This display member is made of a sphere and a matrix. A display layer to express the structure color is enclosed in a cell frame and exhibits a change in the structure color by a stimulus from outside. The cell frame has a deformable portion which is deformed by the stimulus from outside and exhibits a change in the structure color accordingly. A portion above the display layer in the cell frame is translucent. The display layer is a formed periodic structure on which a plurality of spherical layers with solid spheres regularly arranged in the plane direction are arranged regularly in the depth direction. The matrix is made of ionic liquid whose fusing point is 50°C or lower. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display member that can be used as a sensor, a display, a panel, a sheet, a label, or the like, and whose structural color changes upon receiving an external stimulus.

  In recent years, a method of using a structural color has attracted attention as a method for displaying colors that does not depend on absorption of light such as a pigment. The structural color has characteristics such as high reflectivity and high saturation due to the use of light reflection, and it is difficult to fade, and is especially used as a display member for sensors and displays. Has been.

  As a display member using such a structural color characteristic, an elastic gel is filled between particles of a periodic structure formed of solid particles, and the structural color when subjected to an external stimulus. Have been proposed (see Patent Document 1 and Patent Document 2).

  However, in the display members disclosed in Patent Document 1 and Patent Document 2, since the elastic gel contains a large amount of liquid such as water, the liquid is subject to change over time and environmental conditions such as temperature and humidity. There is a problem that the liquid crystal is volatilized and a volume change occurs due to the volatilization, and the display color obtained by changing the structural color due to external stimulation is deteriorated. Moreover, in these display members, it cannot be said that a sufficiently high response speed is yet obtained with respect to changes in structural color in response to external stimuli.

  In addition, as a display member using the characteristic of structural color, for example, a gas or a liquid containing an ionic liquid or a solid substance is filled between particles of a periodic structure formed of solid particles, When filling, what was enclosed in the cell frame so that there may be no leakage is proposed (refer patent document 3).

  However, such a display member exhibits a structural color but does not change its structural color.

JP 2004-27195 A JP 2006-28202 A JP 2006-208453 A

  The present invention has been made in view of the above circumstances, and its purpose is to obtain a display color obtained by changing a structural color by receiving an external stimulus at a high response speed. Another object of the present invention is to provide a display member that is capable of suppressing the degree of change (deterioration) in display color due to changes over time and environmental conditions such as temperature and humidity.

The display member of the present invention includes a sphere and a matrix, and has a configuration in which a display layer that expresses a structural color is enclosed in a cell frame, and generates a structural color change by receiving an external stimulus. Because
The cell frame has a deformable portion that undergoes deformation by receiving the external stimulus, and causes a structural color change along with this,
The part located above the display layer in the cell frame has translucency,
The matrix is formed of an ionic liquid having a melting point of 50 ° C. or lower.

  In the display member of the present invention, it is preferable that all materials constituting the cell frame have a transmittance of volatile components by the ionic liquid of 1% by mass or less.

  In the display member of the present invention, the absolute value of the difference between the refractive index of the sphere and the refractive index of the matrix is preferably 0.02 to 2.0.

  Moreover, in the display member of this invention, it is preferable that the average particle diameter of a sphere is 50-500 nm.

The structural color is not a color due to light absorption such as a dye, but a color due to selective light reflection due to a periodic structure, etc., and is a thin film interference, light scattering (Rayleigh scattering, Mie scattering), multilayer film interference, diffraction, Examples thereof include a diffraction grating and a photonic crystal.
As a structural color in the display member of the present invention, for example, a color represented by the following formula (1) can be displayed as a representative color.
In addition, the following formula (1) and the following formula (2) are approximate formulas, and in practice, these calculated values may not completely match.
Formula (1): λ = 2 nD (cos θ)
[In the above formula (1), λ is the peak wavelength of the structural color, n is the refractive index of the display layer represented by the following formula (2), D is the spacing between the spherical layers, and θ is the perpendicular of the display member. Is the observation angle. ]
Formula (2): n = {na · c} + {nb · (1-c)}
[In the above formula (2), na is the refractive index of the sphere, nb is the refractive index of the matrix, and c is the volume ratio of the sphere in the display layer. ]

According to the display member of the present invention, the deformable part of the cell frame is deformed by receiving an external stimulus, and the structure of the display layer that expresses the structural color changes with the deformation of the deformable part. The color can be changed.
And according to this display member, since the matrix is formed from an ionic liquid having the property of hardly generating volatile components, it can be used for a long period of time or in a severe environment such as a high temperature and low humidity environment. Even in this case, the degree of deterioration of the display color can be suppressed to a low level, and therefore, good display characteristics can be obtained over a long period of time.
Furthermore, according to this display member, since the matrix is made of an ionic liquid having a melting point of 50 ° C. or less, and the ionic liquid is a liquid or a soft solid under a normal use environment (room temperature), a response with a high display color. Speed is obtained.

  In addition, when the display member of the present invention is specified to have a material with a specific low transmittance with respect to volatile components, even if a volatile component due to ionic liquid is generated, Therefore, the degree of change in the display characteristics can be further reduced.

  Hereinafter, the present invention will be specifically described.

As shown in FIG. 1 (a), the display member of the present invention has a configuration in which a display layer 10 that expresses a structural color is enclosed in a cell frame 20, and an external stimulus (hereinafter referred to as “external”). It is a display member that causes a structural color change by receiving a stimulus.
The cell frame 20 has a translucent portion located above the display layer 10 in the cell frame 20 and is deformable by receiving an external stimulus (spacer member 23 in FIG. 1). The structural color changes with the deformation of the deformable part. The display layer 10 is a sphere in which solid spheres 12 are regularly arranged in a plane direction in a liquid or deformable solid matrix M formed of an ionic liquid having a melting point of 50 ° C. or less. A periodic structure 16 in which a plurality of layers 15 are regularly arranged in the thickness direction is formed.
In this embodiment, the deformable portion is described as a whole of the spacer member 23, but the deformable portion may be a part of the spacer member 23, for example.

[Display layer]
The display layer 10 of the display member is formed by forming the periodic structure 16 in the matrix M. Since such a periodic structure is formed in the display layer 10, a chromatic color is generated by irradiation with visible light. Is felt.

Specifically, as shown in FIG. 1, the display layer 10 includes a sphere layer 15 formed by regularly arranging spheres 12 made of solid particles, for example, in the plane direction. Twelve are regularly arranged.
The sphere layer 15 has a configuration in which spheres 12 are regularly arranged in one direction with respect to the direction in which light enters.

In the display member, the absolute value of the difference between the refractive index of the sphere 12 and the refractive index of the matrix M (hereinafter referred to as “refractive index difference”) is preferably 0.02 to 2.0, and more preferably. Is 0.1 to 1.6.
When this difference in refractive index is less than 0.02, the structural color is difficult to develop. When this difference in refractive index is greater than 2.0, the structural color becomes clouded due to large light scattering.

  Although the thickness of the display layer 10 changes with uses, it can be 0.1-100 micrometers, for example.

The thickness of the spherical layer 15 in the display layer 10 is preferably 0.1 to 100 μm, for example.
When the thickness of the sphere layer is less than 0.1 μm, the resulting structural color is light. On the other hand, when the thickness of the sphere layer is greater than 100 μm, the structural color becomes cloudy due to large light scattering. It will become.

The number of cycles of the spherical layer 15 in the display layer 10 needs to be at least 1 or more, preferably 5 to 500.
When the number of periods is less than 1, the display layer cannot exhibit a structural color.

[Structural color]
The structural color is a color having a wavelength represented by the following formula (1) based on Bragg's law and Snell's law.
Formula (1): λ = 2 nD (cos θ)
In this formula (1), λ is the peak wavelength of the structural color, n is the refractive index of the display layer 10 represented by the following formula (2), D is the spacing between the spherical layers 15, and θ is the perpendicular of the display member. It is an observation angle.
Formula (2): n = {na · c} + {nb · (1-c)}
In this formula (2), na is the refractive index of the sphere 12, nb is the refractive index of the matrix M, and c is the volume ratio of the sphere 12 in the display layer 10.

In the display member of the present invention, as shown in FIG. 1B, the deformable portion (spacer member 23) of the cell frame 20 is deformed by receiving an external stimulus (pressing force P in FIG. 1). Along with this, the matrix M is transformed, whereby the position of the spherical layer 15 in the matrix M is displaced in the thickness direction and the layer interval D is changed, resulting in a structural color change. When receiving an external stimulus, the volume of the space in the cell frame 20 does not change. Here, the change in the layer interval D due to the transformation of the matrix M includes a change resulting from the deformation of the sphere 12 with the transformation of the matrix M. It is considered that the influence of the deformation of the sphere 12 is fine.
As the layer distance D changes, the peak wavelength λ of the structural color changes, that is, the structural color after receiving an external stimulus.
The display member of the present invention changes from a structure that develops an initial structural color to an ordered structure that develops a new structural color by an external stimulus, and changes randomly from the initial structure. Therefore, it does not lose order and prevent structural colors from appearing.

The layer interval D in the display layer 10 is preferably 50 to 500 nm regardless of whether the layer is subjected to external stimulation.
If the layer spacing D is less than 50 nm, there is a risk that the structural color change is clearly not visible. On the other hand, if the layer spacing D is larger than 500 nm, the resulting display layer exhibits a structural color. There is a risk that it will not be.

Here, the peak wavelength λ of the structural color can be measured using, for example, a spectrocolorimeter “CM-3600d” (manufactured by Konica Minolta Sensing) under the condition that the observation angle θ is 8 °.
The layer distance D can be calculated from the peak wavelength λ of the structural color using the above formula (1).

In the present invention, the external stimulus refers to a force that deforms the deformable portion (spacer member 23) of the cell frame 20 and transforms the matrix M along with this to change the layer interval D in the above formula (1). Specific examples include pressure and tensile stress.
In the display member of the present invention, the structural color after the change is determined based on the magnitude of the external stimulus.
The external stimulus is not specifically defined in its size, but preferably refers to a substance that can change the peak wavelength λ of the structural color in the above formula (1) indicated by the display layer 10 by 30 nm or more.

In the display member of the present invention, the structural color and / or the structural color after receiving an external stimulus is not limited to a color having a peak wavelength in the visible region, but a color having a peak wavelength in the ultraviolet region or the infrared region. Also good.
Such a color display member having a peak wavelength in the ultraviolet region or the infrared region can be used as a sensor in a state where the display member is incorporated in a detection device capable of recognizing ultraviolet rays or infrared rays, for example.

〔sphere〕
In the present invention, a sphere is a substance having a sphere shape in three dimensions, and is not limited to a true sphere, but may be approximately a sphere shape. This substance is solid and has a refractive index different from that of the matrix M.

The material which comprises the spherical body 12 which comprises the display layer 10 can be suitably selected by a combination with the ionic liquid which should form the matrix M further according to a use.
Specifically, the refractive index is required to be different from the refractive index of the matrix M and to be incompatible with the ionic liquid to form the matrix M.
Further, the spheres 12 constituting the display layer 10 are preferably made of a material having a high affinity with the ionic liquid for forming the matrix M.

Various things can be mentioned as the spherical body 12 constituting the display layer 10.
Specifically, for example, styrene monomers such as styrene, methylstyrene, methoxystyrene, butylstyrene, phenylstyrene, chlorostyrene; methyl acrylate, ethyl acrylate, (iso) propyl acrylate, butyl acrylate, acrylic Acrylic acid ester or methacrylic acid ester monomer such as hexyl acid, octyl acrylate, ethyl hexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl hexyl methacrylate; acrylic acid, methacrylic acid, itaconic acid, fumarate The particle | grains which superposed | polymerized 1 type in polymerizable monomers, such as carboxylic acid monomers, such as an acid, or the organic particle which copolymerized 2 or more types can be mentioned.
Alternatively, organic particles obtained by adding a crosslinkable monomer to a polymerizable monomer and polymerizing may be used. Examples of the crosslinkable monomer include divinylbenzene, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and trimethylol. Examples thereof include propane trimethacrylate.
Moreover, for example, inorganic oxides and composite oxides such as silica, titanium oxide, aluminum oxide, and copper oxide, inorganic particles formed of glass, ceramics, and the like can be given.
Further, for example, core-shell type particles in which the above organic particles or inorganic particles are used as core particles, and a shell layer made of a material different from the material constituting the core particles is formed on the surface thereof. The shell layer can be formed using metal fine particles, metal oxide fine particles made of titania, metal oxide nanosheets made of titania, or the like.
Further examples include hollow particles obtained by removing the core particles from the core-shell particles by a method such as firing or extraction.
Of these particles, organic particles are preferably used.

The average particle diameter of the sphere 12 needs to be set in relation to the refractive index of the sphere 12 and the refractive index of the matrix M, and at least preferably has a size that makes the dispersion into a stable colloidal solution. For example, it is preferable that it is 50-500 nm.
When the average particle diameter of the spheres 12 is in the above range, the dispersion liquid can be made into a stable colloid solution, and the structural color expressed in the obtained display member is in the near ultraviolet to visible to near infrared region. The color has a peak wavelength.

The CV value representing the particle size distribution is preferably 10 or less, more preferably 8 or less, and particularly preferably 5 or less.
When the CV value is larger than 10, the spherical layer of spheres cannot be regularly arranged in the matrix, and as a result, there is a possibility that a display member that expresses a structural color cannot be obtained.
The average particle size was obtained by taking a photo of 50,000 times using a scanning electron microscope “JSM-7410” (manufactured by JEOL Ltd.), measuring the maximum length of each of the 200 spheres in this photographic image, It is obtained by calculating the number average value. Here, the “maximum length” refers to the maximum distance between two points by any two points on the circumference of the sphere.
When the sphere is photographed as an aggregate, the maximum length of primary particles (sphere) that form the aggregate is measured.
The CV value is calculated from the following formula (CV) using the standard deviation in the number-based particle size distribution and the above average particle size value.
Formula (CV): CV value (%) = ((standard deviation) / (average particle size)) × 100

The refractive index of the sphere 12 can be measured by various known methods, and the refractive index of the sphere 12 in the present invention is a value measured by an immersion method.
Specific examples of the refractive index of the sphere 12 include, for example, 1.59 for polystyrene, 1.49 for polymethyl methacrylate, 1.60 for polyester, 1.40 for fluorine-modified polymethyl methacrylate, and polystyrene / butadiene. Polymerization 1.56, polymethyl acrylate 1.48, polybutyl acrylate 1.47, silica 1.45, titanium oxide (anatase type) 2.52, titanium oxide (rutile type) 2. 76, copper oxide is 2.71, aluminum oxide is 1.76, barium sulfate is 1.64, and ferric oxide is 3.08.

  The sphere 12 constituting the sphere layer 15 may be a single composition or a single composition, but may be one in which a substance for adhering the spheres is attached to the surface of the sphere, or In addition, a substance for adhering the spheres may be introduced into the sphere. By using such an adhesive substance, the spheres can be bonded to each other even if the spheres are made of a substance that hardly causes self-alignment when the sphere layer 15 is formed. Further, when the sphere is formed of a material having a high refractive index, a low refractive index substance may be internally added.

The spheres 12 constituting the sphere layer 15 are preferably highly monodispersed because they are easily arranged regularly when the sphere layer 15 is formed.
To obtain highly monodispersed spheres, if the spheres are particles of organic matter, the spheres should be obtained by polymerization methods such as commonly used soap-free emulsion polymerization methods, suspension polymerization methods, and emulsion polymerizations. Is preferred.

  The particles 12 may be subjected to various surface treatments in order to increase the affinity with the matrix M.

〔matrix〕
The matrix M in the display layer 10 is formed of an ionic liquid having a melting point of 50 ° C. or lower, preferably 20 ° C. or lower. An ionic liquid having such a melting point is a liquid or a solid having a deformable property at room temperature (25 ° C.).

Examples of the ionic liquid to form the matrix M in the present invention include organic compound salts composed of cations such as imidazolium ions and pyridinium ions and anions such as BF ⁴⁻ and PF ⁶⁻ .

As a specific example of the ionic liquid,
1,3-dimethylimidazolium dimethyl phosphate (<−65 ° C.)
1-butyl-2,3-dimethylimidazolium hexafluorophosphate (38 ° C.)
1-butyl-2,3-dimethylimidazolium tetrafluoroborate (32 ° C.)
1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (-2 ° C.)
1-butyl-3-methylimidazolium hexafluorophosphate (7 ° C.)
1-butyl-3-methylimidazolium trifluoromethanesulfonate (16 ° C.)
1-ethyl-3-methylimidazolium 2- (2-methoxyethoxy) ethyl sulfate (<−65 ° C.)
1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (-15 ° C.)
1-ethyl-3-methylimidazolium ethyl sulfate (−65 ° C.)
1-ethyl-3-methylimidazolium-p-toluenesulfonate (37 ° C.)
1-ethyl-3-methylimidazolium tetrafluoroborate (15 ° C.)
1-hexyl-3-methylimidazolium tetrafluoroborate (−81 ° C.)
1-butyl-4-methylpyridinium hexafluorophosphate (48 ° C.)
1-ethyl-3- (hydroxymethyl) pyridinium ethyl sulfate (<−65 ° C.)
1-ethyl-3-methylpyridinium ethyl sulfate (<−65 ° C.)
Methyltri-n-octylammonium bis (trifluoromethanesulfonyl) imide (−75 ° C.)
1-butyl-4-methylpyridinium hexafluorophosphate (43 ° C.)
1-ethyl-3- (hydroxymethyl) pyridinium ethyl sulfate (<−65 ° C.)
1-ethyl-3-methylpyridinium ethyl sulfate (<−65 ° C.) and the like. These ionic liquids may be used alone or in combination of two or more.
The melting points of the ionic liquids exemplified above are shown in parentheses.

The ionic liquid that should form the matrix M can be appropriately selected depending on the application and further by the combination with the material of the sphere 12 constituting the sphere layer 15.
Specifically, the refractive index is required to be different from the refractive index of the sphere 12 and to be incompatible with the material constituting the sphere 12.
The ionic liquid to form the matrix M is preferably made of a material having a high affinity with the sphere 12.

  Although the refractive index of the matrix M can be measured by various known methods, the refractive index of the matrix M in the present invention is such that only the matrix M is separately enclosed in the cell frame 20, and this is the Abbe refractometer. The value measured at.

[Cell frame]
At least a part of the cell frame 20 of the display member is translucent. Specifically, for example, an upper substrate 21 and a lower substrate 22 are arranged via a frame-shaped spacer member 23. The space inside the cell frame 20 is partitioned from the outside.

The spacer member 23 of the cell frame 20 is deformed by receiving an external stimulus and is a deformable portion that causes a structural color change in the display layer 10 along with the deformation.
In the display member of the present invention, the deformation caused by receiving an external stimulus may be reversible or irreversible.

  Examples of the material constituting the spacer member 23 that is a deformable portion include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polyamides such as nylon 6 and nylon 12, Polyvinyl chloride, ethylene vinyl acetate copolymer or saponified product thereof, polystyrene, polycarbonate, polysulfone, polyphenylene oxide, polyphenylene sulfide, aromatic polyamide, polyimide, polyamideimide, cellulose, cellulose acetate, polyvinylidene chloride, polyacrylonitrile, polyvinyl alcohol , Polysilicon and copolymers thereof. Of these, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, and polysilicon are preferable.

  When the spacer member 23 is irreversibly deformed by receiving an external stimulus, a material constituting the spacer member 23 is a material that plastically deforms between the yield point and the break point. ) Polyethylene, polystyrene, gelatin and the like.

  As the spacer member 23, for example, a material obtained by molding the above material so as to have a thickness (vertical direction in FIG. 1) of 0.5 to 200 μm and a width (horizontal direction in FIG. 1) of 10 to 500 μm is used. it can.

As the upper substrate 21 and the lower substrate 22, for example, glass, ceramics, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) film or sheet can be used.
When the display layer 10 is produced using an aqueous dispersion of the sphere 12, the upper substrate 21 and the lower substrate 22 preferably have a surface contact angle with water that is somewhat low, and have a high surface smoothness. Since it is preferable, an appropriate surface treatment can be performed. Moreover, it can be used in a state where the spheres are easily attached by performing blasting or the like.

In the cell frame 20, it is preferable that all the materials constituting the cell frame 20 have a volatile component transmittance of 1% by mass or less by the ionic liquid that should form the matrix M.
The size of the cell frame 20 is 20 μm × 20 μm × 20 μm to 10 cm × 10 cm in width (horizontal direction in FIG. 1) × depth (direction perpendicular to the paper surface in FIG. 1) × thickness (vertical direction in FIG. 1). It is preferable to be in the range of × 100 μm.

[Production method of display member]
The display member of the present invention is prepared, for example, by preparing an aqueous dispersion of the sphere 12 and filling it into the cell frame 20 by opening the two spacer members 23, 23 facing each other by capillary permeation or the like. The periodic structure 16 is obtained by drying, and then the gap between the spheres 12 constituting the periodic structure 16 is filled with the ionic liquid to form the matrix M, and then the removed two spacer members 23 and 23 are removed. It can be obtained by installing again and closing the opening to form the display layer 10 in the cell frame 20.

According to the display member as described above, the deformable portion (spacer member 23) of the cell frame 20 is deformed by receiving an external stimulus, and a structural color is developed along with the deformation of the deformable portion (spacer member 23). Since the structure of the display layer 10 changes, the structural color can be changed.
And according to this display member, since the matrix M is formed from the ionic liquid which has the characteristic that it is hard to produce a volatile component, it is used for a long period of time, or in severe environments, such as a high-temperature, low-humidity environment. Even when it is used, the degree of deterioration of the display color can be suppressed to a small extent, and therefore, good display characteristics can be obtained over a long period of time.
Furthermore, according to this display member, since the matrix M is made of an ionic liquid having a melting point of 50 ° C. or less, and the ionic liquid is a liquid or a soft solid under a normal use environment (room temperature), the display color is high. Response speed is obtained.

  Further, when the display member is specified to have a material having a specific low transmittance with respect to the volatile component, even if a volatile component due to the ionic liquid is generated, the cell frame hardly transmits the volatile component. Therefore, the degree of change in the display characteristics can be further reduced.

Although the embodiments of the present invention have been specifically described above, the embodiments of the present invention are not limited to the above examples, and various modifications can be made.
For example, the deformable portion is not limited to the spacer member as long as it is a portion constituting the cell frame, and may be, for example, the upper substrate 21 and / or the lower substrate 22 in FIG.

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto. In the following, the average particle diameter, CV value, and refractive index were measured by the same method as described above.
In the following, the color of the periodic structure and the display member was visually observed from the front direction perpendicular to them.

<Example 1>
[Production Example 1 of Display Member]
(Production of cell frame)
According to the configuration of FIG. 1, a transparent polyethylene terephthalate (PET) plate “Lumirror” (manufactured by Toray Industries, Inc.) having a thickness of 125 μm, each subjected to a hydrophilic treatment via a spacer member made of polyethylene having a thickness of 50 μm and a width of 100 μm to be a deformable part By stacking the upper substrate and the lower substrate, a cell frame [1] in which a space was partitioned was manufactured. The space size in the cell frame is 5 cm in width (length in the left-right direction in FIG. 1), 5 cm in depth (length in the direction perpendicular to the paper surface in FIG. 1), and thickness (length in the vertical direction in FIG. 1). 50 μm.

(Production Example 1 of sphere)
100 parts by mass of styrene, 0.2 parts by mass of sodium styrenesulfonate, and 360 parts by mass of ion-exchanged water were mixed in a reaction vessel equipped with a stirrer, a heating / cooling device, a nitrogen introduction device, and a raw material / auxiliary charging device. The monomer solution was charged, and the internal temperature was raised to 70 ° C. while stirring at a stirring speed of 200 rpm under a nitrogen stream. On the other hand, a polymerization initiator solution in which 0.01 parts by mass of sodium persulfate was dissolved in 20 parts by mass of water was prepared and charged into the reaction solution, followed by a polymerization reaction for 24 hours to obtain a highly monodispersed sphere dispersion ( Hereinafter, “spherical dispersion [1]”) was obtained. The sphere [1] in the sphere dispersion [1] had an average particle size of 200 nm and a CV value of 4.3.

(Formation of periodic structure)
The sphere dispersion [1] was diluted with ion-exchanged water to adjust the concentration of the sphere [1] to 10% by mass. In this prepared dispersion, the opening from which the two spacer members facing each other of the cell frame [1] are removed is crushed and left in this state for 24 hours at room temperature, and the dispersion is permeated into the interior space by capillary passage. Then, when it was taken out from the dispersion liquid, it was confirmed that a structural color was developed. This was left to stand at room temperature for 3 days to dry, thereby forming a periodic structure [1]. Thereafter, the removed two spacer members were installed again.

(Ion liquid filling)
1 mL of 1-butyl-3-methylimidazolium trifluoromethanesulfonate “B2337” (manufactured by Tokyo Chemical Industry Co., Ltd., melting point: 16 ° C.) is dropped as an ionic liquid from the opening of the cell frame [1] from which the upper substrate is removed. Thus, the periodic structure [1] was filled in the gaps between the spheres [1] until there was no contact between the particles. Thereafter, the opening was covered again with the upper cover, and the periphery of the opening was sealed with a UV curable resin, thereby producing a display member [1]. This display member [1] was green.

<Example 2>
In the production example 1 of the display member, 1-ethyl-3-methylimidazolium ethyl sulfate “E0650” (manufactured by Tokyo Chemical Industry Co., Ltd., melting point: −65 ° C.) was used as the ionic liquid, A display member [2] was produced. This display member [2] exhibited green.

<Example 3>
In the display member production example 1, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate “B2474” (manufactured by Tokyo Chemical Industry Co., Ltd., melting point: 38 ° C.) was used as the ionic liquid. Thus, a display member [3] was produced. This display member [3] exhibited green.

<Example 4>
In the display member production example 1, a 50/50 mixture of “B2337” / “E0650” (manufactured by Tokyo Chemical Industry Co., Ltd.) (melting point: 16 ° C./−65° C., respectively) was used as the ionic liquid. Thus, a display member [4] was produced. This display member [4] was green.

<Example 5>
Display member [5] was manufactured in the same manner as in Display member manufacturing example 1 except that a spacer member made of polyvinyl chloride was used. This display member [5] was green.

<Example 6>
Display member [6] was prepared in the same manner as in Display member production example 1 except that the following sphere dispersion liquid [2] was used instead of sphere dispersion liquid [1]. This display member [6] was green.
(Production example 2 of sphere)
Spherical dispersion liquid [2] was obtained in the same manner as in Sphere Production Example 1 except that the amount of sodium persulfate was changed to 0.03 parts by mass. The sphere [2] in the sphere dispersion [2] had an average particle size of 510 nm and a CV value of 5.1.

<Example 7>
Display member [7] was prepared in the same manner as in Display member production example 1, except that the following sphere dispersion liquid [3] was used instead of sphere dispersion liquid [1]. This display member [7] was blue.
(Production example 3 of sphere)
In the sphere production example 1, as a monomer solution, a mixture of 100 parts by mass of styrene, 0.2 parts by mass of sodium styrenesulfonate, 0.1 parts by mass of sodium dodecyl sulfate, and 360 parts by mass of ion-exchanged water was used. A spherical dispersion [3] was obtained in the same manner except that a solution obtained by dissolving 0.05 part by mass of sodium persulfate in 20 parts by mass of water was used as the polymerization initiator solution. The sphere [3] in the sphere dispersion [3] had an average particle size of 45 nm and a CV value of 6.0.

<Comparative Example 1>
Display member [8] was manufactured in the same manner as in Display member manufacturing example 1, except that ethanol (manufactured by Kanto Chemical Co., Inc., melting point: −117 ° C.) was used instead of the ionic liquid. This display member [8] exhibited blue-green.

<Comparative Example 2>
Display member [9] was manufactured in the same manner as in Display member manufacturing example 1, except that sodium polyacrylate was used instead of the ionic liquid, and this was heated and melted at 80 ° C. did. This display member [9] was green.

<Comparative Example 3>
In the display member production example 1, the display member [1] -butyl-3-methylimidazolium chloride “B2194” (manufactured by Tokyo Chemical Industry Co., Ltd., melting point: 65 ° C.) was used in the same manner. 10]. This display member [10] was green.

<Comparative example 4>
Display member [11] was manufactured in the same manner as in Display member manufacturing example 1 except that glass having a thickness of 50 μm and a width of 5 cm was used as the spacer member. This display member [11] exhibited green.

<Evaluation>
(1) Structural color change due to external stimulus For the above display members [1] to [11], in a black box in a normal temperature and normal humidity environment (temperature 25 ° C., humidity 50% RH), While projecting using a D65 light source from a position separated by 30 cm, a pressure test is performed in a thickness direction using a pressure tester at a rate of 1 kgf / s for 1 second, and a pressure test is performed to maintain the pressure state. A monitor test in which the pressure test is visually observed by five monitors selected arbitrarily from the observation hole of the black box located at a distance of 50 cm in a direction 30 ° from the vertical direction of the display member [A And the number of monitors that recognized the change in the structural color was evaluated. In addition, the case where the number of the monitors which recognized the change of the structural color is 3 or more is judged as a pass. The results are shown in Table 1.

(2) Response speed of structural color change due to external stimulus The above monitor test [A] was performed, and evaluation was performed based on the number of monitors recognized that the structural color change occurred within 2 seconds. In addition, the case where the number of the monitors recognized that the change of the structural color has occurred within 2 seconds is three or more is determined to be acceptable. The results are shown in Table 1.

(3) Display color retention In the above pressurization test, the environment inside the black box is a high temperature and low humidity environment (temperature 50 ° C., humidity 30% RH), and the pressure state is maintained for 48 hours. A deterioration test was performed, and the display color and pressurization at the initial pressurization state were applied to five arbitrarily selected monitors from the observation hole of the black box located at a position 50 cm away from the vertical direction of the display member. A monitor test [B] for visually observing the display color after 48 hours was performed, and the evaluation was performed based on the number of monitors recognized that the display color did not change. A case where the number of monitors recognized that the display color has not changed is three or more is determined to be acceptable. The results are shown in Table 1.

  The display member of the present invention can be used as, for example, a sensor, a display, a panel, a sheet, or a label.

It is sectional drawing for description which shows an example of a structure of the display member of this invention typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display layer 12 Sphere 15 Sphere layer 16 Periodic structure 20 Cell frame 21 Upper substrate 22 Lower substrate 23 Spacer member D Layer interval M Matrix

Claims (5)

A display layer composed of a sphere and a matrix, which has a structure in which a display layer that expresses a structural color is enclosed in a cell frame, and generates a structural color change by receiving an external stimulus,
The cell frame has a deformable portion that undergoes deformation by receiving the external stimulus, and causes a structural color change along with this,
The part located above the display layer in the cell frame has translucency,
The display member, wherein the matrix is formed of an ionic liquid having a melting point of 50 ° C. or lower.   2. The display member according to claim 1, wherein all materials constituting the cell frame have a transmittance of a volatile component by the ionic liquid of 1% by mass or less.   The display member according to claim 1 or 2, wherein the absolute value of the difference between the refractive index of the sphere and the refractive index of the matrix is 0.02 to 2.0.   The display member according to any one of claims 1 to 3, wherein an average particle size of the sphere is 50 to 500 nm. The display member according to any one of claims 1 to 4, wherein the structural color is a color represented by the following formula (1).
Formula (1): λ = 2 nD (cos θ)
[In the above formula (1), λ is the peak wavelength of the structural color, n is the refractive index of the display layer represented by the following formula (2), D is the spacing between the spherical layers, and θ is the perpendicular of the display member. Is the observation angle. ]
Formula (2): n = {na · c} + {nb · (1-c)}
[In the above formula (2), na is the refractive index of the sphere, nb is the refractive index of the matrix, and c is the volume ratio of the sphere in the display layer. ]