Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2001-12-03
2002-11-26
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S332000, C428S913000, C428S413000, C428S423100, C428S474400, C428S480000, C252S582000, C252S583000, C252S586000
Reexamination Certificate
active
06485824
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a reversibly thermochromic light-shielding/light-transmitting laminate member. More particularly, the invention relates to a reversibly thermochromic light-shielding/light-transmitting laminate member, which changes not only in color but in transmittance with temperature.
BACKGROUND OF THE INVENTION
A laminate member which undergoes alternate color changes between a colorless transparent state and a colored opaque state with temperature is disclosed in U.S. Pat. No. 5,490,956. This laminate member comprises a substrate and formed thereon a reversibly thermochromic layer comprising a vinyl chloride/vinyl acetate copolymer resin matrix and dispersed therein a reversibly thermochromic composition comprising (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium determining the temperatures at which the color reactions of component (a) with component (b) take place.
The thermochromic composition contained in the reversibly thermochromic layer is not encapsulated, i.e., of the so-called non-capsule type. Because of this, not only the thermochromic layer has a factor contributing to chemical instability, but also the substrate is limited in material. With respect to thermochromic properties, the laminate member has such color-memorizing properties that it is wide hysteretic and memorizes and retains a color-changed state resulting from a temperature change.
SUMMARY OF THE INVENTION
An aim of the invention is to eliminate the drawbacks of the known reversibly thermochromic laminate member which undergoes alternate color changes between a colorless transparent state and a colored opaque state. Namely, the aim is to provide a reversibly thermochromic light-shielding/light-transmitting laminate member which has a satisfactory thermochromic function and is free from the factor contributing to chemical instability inherent in the system employing a non-capsule type reversibly thermochromic composition.
The invention provides a reversibly thermochromic light-shielding/light-transmitting laminate member which comprises a substrate and formed thereon a reversibly thermochromic layer comprising a transparent resin and fixedly dispersed therein a reversibly thermochromic microencapsulated pigment containing a reversibly thermochromic composition comprising (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium determining the temperatures at which the color reactions of component (a) with component (b) take place, the reversibly thermochromic microencapsulated pigment being a deformable pigment which has an average particle diameter of from 0.1 to 5.0 &mgr;m, the transparent resin having a tensile elongation at break of 350% or lower. In the laminate member of the invention, the proportion of the reversibly thermochromic microencapsulated pigment to the transparent resin is preferably from 1/0.5 to 1/20 (in terms of weight ratio on a solid basis) and the reversibly thermochromic layer preferably has a thickness of from 5 to 100 &mgr;m. Furthermore, the transparent resin is preferably a resin selected from the group consisting of methyl methacrylate resins, acrylic resins, vinyl chloride/vinyl acetate copolymer resins, ethylene/vinyl acetate copolymer resins, saturated polyester resins, unsaturated polyester resins, butyral resins, polyurethane resins, polyamide resins, styrene resins, acrylic/styrene resins, ketone resins, and epoxy resins. In one embodiment of the invention, the laminate member has, formed over the reversibly thermochromic layer, a metallic glossy layer containing a metallic luster pigment having transparency. This metallic glossy layer preferably has a light transmittance of 5% or higher.
DETAILED DESCRIPTION OF THE INVENTION
The laminate member of the invention, which undergoes alternate color changes between a colorless transparent state and a colored opaque state with temperature, is obtained based on a combination of a reversibly thermochromic microencapsulated pigment having an average particle diameter of from 0.1 to 5.0 &mgr;m with a transparent resin having a tensile elongation at break of 350% or lower, as stated above.
More particularly, the reversibly thermochromic layer comprising a combination of a reversibly thermochromic microencapsulated pigment having an average particle diameter of from 0.1 to 5.0 &mgr;m with a transparent resin having a tensile elongation at break of 350% or lower is presumed to undergo the following phenomena.
The microencapsulated pigment has different capsule shapes depending on whether the reversibly thermochromic composition contained therein is in a solid state, i.e., a colored state, or is in a dissolved state, i.e., a decolored state. Specifically, when the encapsulated composition is in a dissolved state (decolored state), then the capsules have a degree of freedom and are deformable because the reversibly thermochromic composition is liquid. However, when the encapsulated composition is in a solid state (colored state), the capsules have recesses in the surface thereof, which were formed upon solidification of the reversibly thermochromic composition, and are hard and less apt to be deformed.
On the other hand, the transparent resin used in the invention has an elongation as low as 350% or below and does not conform to capsule shape changes with temperature. In addition, the microencapsulated pigment is kept fixed while retaining a given shape. From these, the following can be presumed. When the encapsulated reversibly thermochromic composition is in a dissolved state (decolored state), the capsules have a degree of freedom in shape change and are dispersed while in close contact with the surrounding transparent resin. However, when the reversibly thermochromic composition is in a solid state (colored state), the capsules have recesses in the surface thereof, resulting in spaces between the capsules and the transparent resin which has been in close contact therewith or resulting in spaces inside the capsules. This change in combination with color changes produces the following effects. When the reversibly thermochromic composition is in a solid state, the reversibly thermochromic layer is in a colored state and is opaque due to a bleaching phenomenon caused by light scattering by the spaces. When the reversibly thermochromic composition is in a dissolved state, the reversibly thermochromic layer is in a decolored state and is transparent because the light-scattering phenomenon attributable to the spaces does not occur since the capsules are in close contact with the transparent resin.
Requirements for enabling the color changes to occur include the particle diameter of the capsules which is regulated to 0.1 to 5.0 &mgr;m. The reasons for this are as follows. In case where the particle diameter of the capsules is smaller than 0.1 &mgr;m, not only satisfactory thermochromic properties cannot be obtained, but also such capsules should have a reduced wall thickness and hence have poor durability in secondary processing, making it difficult to satisfy suitability for practical use. In case where the particle diameter thereof exceeds 5.0 &mgr;m, the microencapsulated pigment itself has considerably reduced light transmission and, hence, the reversibly thermochromic layer in a decolored state has reduced light transmission. The particle diameter of the capsules is preferably from 0.3 to 3.0 &mgr;m, more preferably from 0.5 to 2.0 &mgr;m. Use of such capsules enables the reversibly thermochromic layer to show transparency and a sufficient color density in a colored state, be reduced in a residual color in a decolored state, and have excellent sharpness in color change. Namely, the reversibly thermochromic layer can have an excellent balance among thermochromic functions.
As described above, the invention is based on such an epoch-making technique that light transmission in a decolored state and opacity (hiding properties) in a colored state are attained re
Koide Shigehiro
Senga Kuniyuki
Sugai Jun
Chen Vivian
Sughrue & Mion, PLLC
The Pilot Ink Co., Ltd.
Uhlir Nikolas J
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