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
2002-12-03
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, C428S423100, C428S474400, C252S582000, C252S586000, C252S583000
Reexamination Certificate
active
06489018
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a reversibly thermochromic light-transmitting laminate member. More particularly, the invention relates to a reversibly thermochromic light-transmitting laminate member comprising a substrate and a reversibly thermochromic layer formed thereon, which undergoes alternate color changes between a colorless transparent state and a colored transparent state with temperature.
BACKGROUND OF THE INVENTION
A laminate member which undergoes alternate color changes between a colorless transparent state and a colored transparent state with temperature is disclosed in U.S. Pat. No. 5,721,059. 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.
Furthermore, a composition which contains a microencapsulated pigment containing a reversibly thermochromic composition and has excellent transparency in a decolored state is disclosed in JP-A-3-290467 (the term “JP-A” as used herein means an unexamined published Japanese patent application). This composition is a thermochromic resin composition containing a microencapsulated pigment which has a particle diameter of 1 &mgr;m or smaller and which itself has light transmission.
This resin composition is intended to have transparency imparted thereto by the light transmission of the pigment itself. However, the small capsule particle diameter may cause troubles concerning thermochromic function, e.g., difficulties in determining a color change temperature.
SUMMARY OF THE INVENTION
An aim of the invention is to eliminate the disadvantages of the reversibly thermochromic laminate member which undergoes alternate color changes between a colorless transparent state and a colored transparent state. Namely, the aim is to provide a reversibly thermochromic 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-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 1.0 to 5.0 &mgr;m, the transparent resin having a tensile elongation at break of 400% or higher. 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 1 to 100 &mgr;m. Furthermore, the transparent resin is preferably a resin selected from the group consisting of ethylene/vinyl acetate copolymer resins, polyurethane resins, and polyamide 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 transparent state with temperature, is obtained based on a combination of a reversibly thermochromic microencapsulated pigment having an average particle diameter of from 1.0 to 5.0 &mgr;m with a transparent resin having a tensile elongation at break of 400% or higher, as stated above.
More particularly, the reversibly thermochromic layer comprising a combination of a microencapsulated pigment having an average particle diameter of from 1.0 to 5.0 &mgr;m with a transparent resin having a tensile elongation at break of 400% or higher 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 high as 400% or above and is capable of conforming to capsule shape changes with temperature. Namely, at any time when the capsules change in shape with temperature, the resin surrounding the capsules is capable of deforming so as to conform to the capsule shapes. As a result, formation of spaces between the capsule surface and the resin is inhibited and a bleaching phenomenon can be prevented. Consequently, the reversibly thermochromic layer can undergo alternate color changes between a colorless transparent state and a colored transparent state with temperature over long without impairing the light transmission of the microencapsulated pigment.
Requirements for enabling the color changes to occur include the particle diameter of the capsules which is regulated to 1.0 to 5.0 &mgr;m. The reasons for this are as follows. In case where the particle diameter of the capsules is smaller than 1.0 &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 reduced light transmission and, hence, the reversibly thermochromic layer in a colored state has reduced light transmission. The particle diameter of the capsules is preferably from 1.0 to 3.0 &mgr;m, more preferably from 1.0 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.
The proportion of the microencapsulated pigment to the transparent resin in terms of weight ratio on a solid basis is preferably from 1/0.5 to 1/20, more preferably from 1/1 to 1/10. The thickness of the reversibly thermochromic layer is preferably from 1 to 100 &mgr;m, more preferably from 10
Koide Shigehiro
Senga Kuniyuki
Sugai Jun
Chen Vivian
The Pilot Ink Co., Ltd.
Uhlir Nikolas J.
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