CN110389464B - Electrochromic/deformable film for electric heating and preparation method thereof - Google Patents

Abstract

The invention discloses an electrothermal discoloration/deformation film and a preparation method thereof. The electrothermal discoloration/deformation film comprises a base layer, an electrothermal layer, a bottom color layer and at least two discoloration layers sequentially arranged from bottom to top layer, and also includes an encapsulation layer covering and wrapping the above-mentioned layers, the upper surface of the encapsulation layer is provided with a deformation layer capable of realizing surface pattern change; wherein, the discoloration layer is composed of reversible thermochromic microcapsules, and its discoloration temperature is 35～80 ℃; The deformation layer is formed by curing a thermosetting epoxy resin with shape memory properties and imparting a pattern, and its deformation temperature is 40-120°C. The preparation method of the electrothermal color changing/deformation film is as follows: assembling the multilayer structure of the electrothermal heating layer, the background color layer, the color changing layer and the encapsulation material from bottom to top on the base layer by suction filtration, and the encapsulation material Deformation layer is constructed on the surface. By controlling the temperature of the electric heating layer through the circuit, multiple reversible color changes and synchronous changes of discoloration and deformation of the film can be realized.

Description

A kind of electrothermal heating discoloration/deformation film and preparation method thereof

technical field

The invention relates to a thin film material, in particular to an electrothermal heating discoloration/deformation thin film and a preparation method thereof, belonging to the field of intelligent thin film materials.

Background technique

Smart material is a kind of material that can obtain information about environmental conditions and its changes from its own surface or inside, and judge, process and respond to change its structure and function and make it well coordinated with the outside world. Adaptive material system. As far as intelligent color-changing materials are concerned, it can undergo reversible color changes under the action of external heat, different light wave irradiation, voltage, etc., and has broad prospects in the fields of anti-counterfeiting and decoration. Among them, thermochromic microcapsules have become widely used color-changing raw materials because of their low price and simple preparation process.

The Chinese invention patent application with publication number CN109535691A discloses a thermochromic film and a preparation method thereof. Polyvinyl alcohol is used as the base material. In order to improve its toughness, it is blended with water-based polyurethane to adjust the ratio of the two to make The thermochromic nanocapsules are added into the film-forming matrix as functional additives, and the thermochromic films are prepared by the casting film-forming method. The Chinese utility model patent with the publication number CN207274013U discloses a thermal insulation type thermochromic film, comprising: a base material; a hard scratch-resistant layer arranged on the surface of the base material; a thermochromic adhesive layer, comprising an adhesive resin, The thermochromic dye is dispersed in the adhesive resin, and is arranged on the side away from the hard scratch-resistant layer; the heat preservation layer is arranged on the side of the thermochromic adhesive layer away from the substrate.

The currently disclosed method of using thermochromic microcapsules to construct a color-changing film has the following disadvantages: the same area has a single color, and three or more color changes cannot be achieved in the same area; the simultaneous change of color and surface pattern during heating is not achieved.

SUMMARY OF THE INVENTION

Purpose of the invention: Aiming at the problems that the existing color-changing film cannot realize multiple color changes in the same area, and cannot realize the simultaneous change of color and pattern, the present application adopts an electro-heating color-changing/deforming film, which can generate multiple colors under electric control heating. Color change and surface pattern change; in addition, the present invention also provides a preparation method of the electrothermal color changing/deforming film.

Technical scheme: the electrothermally heated discoloration/deformation film of the present invention includes a base layer, an electrothermally heated layer, a bottom color layer and at least two discoloration layers arranged in sequence from bottom to top, and also includes covering and wrapping the above-mentioned various layers. The upper surface of the encapsulation layer is provided with a deformation layer that can realize the change of the surface pattern; wherein, the discoloration layer is composed of reversible thermochromic microcapsules, and its discoloration temperature is 35-80 ℃; The thermosetting epoxy resin is formed after curing and imparting a pattern, and its deformation temperature is 40-120°C.

In the electrothermal discoloration/deformation film, the material of the base layer can be filter paper, cotton cloth, fabric, etc., such as chemical fiber fabric. The color-changing layer, etc.; the electric heating layer is composed of conductive materials, which can be selected from carbon nanotubes, graphene, graphite, nano-metal powder, etc.; the bottom color layer can be composed of organic and/or inorganic pigments and fillers; the encapsulation layer can be composed of thermosetting ring Oxygen resin cures to form.

Preferably, patterns are constructed on the base color layer and/or the color-changing layer through reversible thermochromic microcapsules, so that multiple changes of different color patterns can be realized.

Preferably, the thickness of the electric heating layer, the background color layer and the color changing layer is 10-100 μm. The thickness of the deformed layer is preferably 100 to 150 μm.

The preparation method of the electrothermal discoloration/deformation film of the present invention comprises the following steps:

(1) ultrasonically disperse the electro-heating material, the background color filler and the thermochromic microcapsules with water respectively;

(2) Using the suction filtration method, the electro-heating material dispersion, the background color pigment and filler dispersion and the thermochromic microcapsule dispersion are filtered layer by layer on the base material, and the electro-heating layer, the bottom layer and the thermochromic microcapsule dispersion are sequentially obtained on the base layer. Chromatic layers and color-changing layers;

(3) by suction filtration, the mixed solution of the epoxy resin prepolymer and the curing agent is completely covered and wrapped around each layer, and cured to obtain an encapsulation layer;

(4) A mixture of an epoxy resin prepolymer with shape memory properties and a curing agent is constructed on the encapsulation layer by a doctor blade method, and a temporary pattern is applied after curing to obtain a deformed layer.

Preferably, in step (2), when each layer is suction filtered, a mask can be used to construct patterns on this layer; for example, reversible thermochromic microcapsules with different discoloration temperatures can be used to construct different patterns on the base color layer and the discoloration layer , by controlling the temperature, multiple changes of different color letter patterns can be realized, which can be used in anti-counterfeiting and other fields.

In the above-mentioned step (2), during suction filtration, it is better to control the surface area of the electric heating layer to be 1.2 to 1.5 times that of the layer with the largest surface area among the bottom color layer and the discoloration layer. Through the above arrangement, the electric heating layer can be conveniently connected to the electrodes to perform electric control heating.

In step (3), when constructing the encapsulation layer, the epoxy resin prepolymer used is preferably DGEBA (bisphenol A epoxy resin), and the curing agent is preferably MXDA (m-xylylenediamine), wherein the epoxy group and The molar ratio of the amino groups is preferably 1:0.4 to 1:0.5.

Preferably, in step (4), a hot pressing method is used to construct a temporary pattern: first, the temperature is raised to a temperature above the glass transition temperature of the epoxy resin used in the deformation layer, and the template with a pattern on the surface is used to heat it. Press, lower the temperature and remove the template while maintaining the hot pressing state.

Beneficial effects: Compared with the existing color-changing film, the advantages of the present invention are: (1) the temperature of the electro-heating layer is controlled by the circuit, and the electro-heating color-changing/deforming film of the present invention can undergo multiple reversible color changes; and, A pattern is given on the deformation layer, and the surface color and surface pattern can be changed at the same time by controlling the heating temperature; (2) By adjusting the shape recovery temperature of the epoxy resin, a variety of color pattern changes can be realized as required, and the color can be changed first and then deformed. , it can also be deformed first, then discolored, or changed to one color, then deformed, and then changed to another color; (3) By constructing patterns on the background color layer and/or color changing layer, it is possible to construct different color patterns. (4) The present invention prepares the film by suction filtration, and the discoloration layers of different colors are assembled layer by layer through suction filtration, so that uniform and dense layers of different colors can be obtained. The discoloration layer will not have problems such as collapse of the discoloration layer.

Description of drawings

Fig. 1 is the structural representation of the electrothermal discoloration/deformation film made by Example 1;

Fig. 2 is the structural representation of the electrothermal discoloration/deformation film made by Example 2;

Fig. 3 is the structural representation of the electrothermal discoloration/deformation film made by Example 4;

FIG. 4 is a schematic structural diagram of the electrothermally discolored/deformed film produced in Example 5. FIG.

Detailed ways

The technical solutions of the present invention will be further described below with reference to the accompanying drawings.

An electrothermal discoloration/deformation film of the present invention comprises a base layer, an electrothermal layer, a base color layer and at least two discoloration layers sequentially arranged from bottom to top, and also includes an encapsulation layer covering and wrapping the above-mentioned layers, A deformation layer is provided on the upper surface of the encapsulation layer.

Wherein, the base material used in the base layer is filter paper, cotton cloth, fabric (such as chemical fiber fabric) and other materials with a certain pore size. The electric heating layer is made of conductive material, and the conductive material can be carbon nanotube, graphene, graphite or nano metal powder. The base color layer can be composed of organic or inorganic pigments and fillers. The encapsulation material used in the encapsulation layer is thermosetting epoxy resin. The discoloration layer is composed of reversible thermochromic microcapsules, and the discoloration temperature of the reversible thermochromic microcapsules is 35-80°C. The discoloration layer can be provided with two or more layers as required.

The deformation layer is composed of a thermosetting epoxy resin with shape memory properties, and its deformation temperature is 40-120°C. The deformation layer is made of epoxy resin, and a temporary pattern is given on the deformation layer through the mask. When used, when the electric heating layer heats the deformation layer above the glass transition temperature of the epoxy resin, due to the thermosetting epoxy resin With the shape memory effect, the temporary pattern will return to the initial plane state, so that the deformation layer can realize the change of the pattern.

The multi-layer structure of the electrothermal heating layer, the background color layer, the discoloration layer and the encapsulation layer is assembled on the base layer from bottom to top by the suction filtration method, and the deformation layer is constructed on the surface of the encapsulation layer to obtain the electrothermal heating layer of the present invention. Discolored/deformed films. By controlling the temperature of the electric heating layer through the circuit, multiple reversible color changes and synchronous changes in the process of discoloration and deformation of the film can be realized.

Example 1

(1) Weigh 1g of carbon nanotubes into 20ml of distilled water, 0.5g of inorganic yellow pigment into 20ml of distilled water, and 0.5g of blue thermochromic microcapsules with a discoloration temperature of 80°C into 20ml of distilled water, 0.5 g of blue thermochromic microcapsules with a discoloration temperature of 35° C. were added to 20 ml of distilled water and dispersed by ultrasonic machine for 10 min respectively.

(2) Bake DGEBA in a 60°C oven for 0.5h, weigh 2g of DGEBA, and add 0.1g of MXDA and stir evenly for later use; in addition, weigh 2g of DGEBA, 0.17g of MXDA and 10ml of DMF, stir and mix for use.

(3) Take an appropriate amount of filter paper, cut out circles with radii of 2cm, 1.7cm, 1.4cm, and 1.1cm in the middle of the filter paper, respectively, to obtain No. 1, No. 2, No. 3 and No. 4 annular filter papers for use.

(4) Wet the complete filter paper on the bottom layer of the suction filtration funnel, make it closely fit with the suction filtration funnel through suction filtration, and then tightly fit the No. 1 annular filter paper to the bottom filter paper through suction filtration.

(5) The uniformly dispersed electrothermal heat generating powder in step (1) is closely distributed in the center ring of the No. 1 ring filter paper by suction filtration, and the thickness of the electrothermal heating layer is controlled to be 50 μm.

(6) the No. 2 ring filter paper is closely attached to the No. 1 ring filter paper by suction filtration, and the inorganic pigments that are uniformly dispersed in the step (1) are closely distributed in the center ring of the No. 2 ring filter paper by suction filtration, Control the thickness of the bottom color layer at 50μm; use blue thermochromic microcapsules with a discoloration temperature of 80℃ to construct the letter pattern TECH on the bottom color layer;

(7) The No. 3 ring filter paper is closely attached to the No. 2 ring filter paper by suction filtration, and the uniformly dispersed blue thermochromic microcapsules with a discoloration temperature of 80°C in step (1) are closely distributed by suction filtration. In the center ring of the No. 3 ring filter paper, the thickness of the color-changing layer 1 is controlled at 50 μm; the letter pattern NJ is constructed on the color-changing layer 1 with blue thermochromic microcapsules at 35°C;

(8) The No. 4 ring filter paper is tightly attached to the No. 3 ring filter paper by suction filtration, and the uniformly dispersed blue thermochromic microcapsules with a discoloration temperature of 35°C in step (1) are closely distributed in the In the center ring of the No. 4 ring filter paper, the thickness of the control discoloration layer 2 is 50 μm;

(9) withdraw No. 4, No. 3, No. 2, No. 1 ring filter paper in order, take the epoxy resin/MXDA/DMF mixture in step (2) and carry out suction filtration to make it penetrate through each layer structure to obtain encapsulation layer;

(10) Take the DGEBA/MXDA in step (2) to coat the surface of the structure assembled by suction filtration, and cure at 60° C. for 24 hours to construct a deformation layer;

(11) Transfer the circular array pattern on polydimethylsiloxane to the deformed layer of the color-changing film by hot pressing.

The electrothermal color-changing/deforming film is obtained, which includes, from bottom to top, an electro-heating layer (carbon nanotubes), a bottom color layer (inorganic yellow, a letter pattern TECH with a discoloration temperature of 80° C.), a color-changing layer 1 (blue heat Thermochromic microcapsules, the discoloration temperature is 80℃, the discoloration temperature is 35℃, the letter pattern NJ), the discoloration layer 2 (blue thermochromic microcapsules, the discoloration temperature is 35℃), the encapsulation layer and the deformation layer (bisphenol A type glycidyl ether type epoxy resin, circular array pattern, deformation temperature 80 ℃).

Gold spray treatment is performed on both ends of the exposed electric heating layer, and the circuit control system is connected to the outside.

A 12V external power supply, heating pad, temperature controller and temperature sensor are connected to form a circuit, and the temperature to be heated is controlled and set by the temperature controller.

The changes in the color and pattern of the film during heating and cooling are as follows:

The blue film in the initial state has a transparent circular array pattern on the outermost surface—the temperature is raised to 35°C for about 30s, the color-changing layer 2 is heated and the blue disappears, and at the same time, the transparent color letter NJ appears on the blue color-changing layer 1, and the outermost surface The transparent circular array pattern remains unchanged - the temperature is raised to 80 ℃ for about 2 minutes, the circular array pattern on the outermost surface disappears, the blue color on the entire film surface disappears, and the transparent color letters TECH appear on the yellow background layer - cooling When the temperature reaches 35°C for about 30s, the transparent letters TECH disappear, the base layer yellow is covered by blue, and the transparent letters NJ appear again on the blue color-changing layer 1—the temperature drops to room temperature, and the transparent letters NJ disappear, The surface of the film is completely blue

Example 2

Referring to Example 1 to prepare electrothermal discoloration/deformation films, the difference is that the color-changing layer 1 uses blue thermochromic microcapsules with a discoloration temperature of 80°C, and the discoloration layer 2 uses red thermochromic microcapsules with a discoloration temperature of 35°C .

Example 3

The electrothermal discoloration/deformation film was prepared with reference to Example 1, the difference being that: the color-changing layer 1 adopts red thermochromic microcapsules with a discoloration temperature of 60°C, and the discoloration layer 2 adopts blue thermochromic microcapsules with a discoloration temperature of 55°C .

Example 4

The electrothermal color-changing/deforming film was prepared with reference to Example 2, the difference being that: the base color layer was made of phenolphthalein green pigment.

Example 5

The electro-heating discoloration/deformation film was prepared with reference to Example 2, except that the material of the electro-heating layer was carbon black.

Example 6

Referring to Example 1, an electro-heating discoloration/deformation film was prepared, with the difference that the thicknesses of the electro-heating layer, the base color layer and the discoloration layer were 100 μm.

Example 7

The electro-heating discoloration/deformation film was prepared with reference to Example 1, the difference being that the thicknesses of the electro-heating layer, the base color layer and the discoloration layer were 75 μm.

With reference to the method of Example 1, the films prepared in Examples 6 and 7 were respectively connected to the circuit, and the temperature was increased to observe the color and pattern changes of the films; it was found that, at the same temperature, compared with Example 1, the results obtained in Examples 6 and 7 The discoloration of the film is slower; this is because the thickness will affect the heating rate of the film, which in turn affects the overall discoloration behavior of the film; the greater the thickness, the slower the film is heated and the slower the change.

Claims (9)

1. a preparation method of electrothermal discoloration/deformation film, is characterized in that, The film includes a base layer, an electric heating layer, a background color layer and at least two color-changing layers sequentially arranged from bottom to top, and also includes an encapsulation layer covering and wrapping the above-mentioned layers. The deformation layer; wherein, the discoloration layer is composed of reversible thermochromic microcapsules, and its discoloration temperature is 35-80 ° C; Its deformation temperature is 40 ~ 120 ℃; The method includes the following steps: (1) ultrasonically disperse the electro-heating material, the background color filler and the thermochromic microcapsules with water respectively; (2) Using the suction filtration method, the electro-heating material dispersion, the background color pigment and filler dispersion and the thermochromic microcapsule dispersion are filtered layer by layer on the base material, and the electro-heating layer, the bottom layer and the thermochromic microcapsule dispersion are sequentially obtained on the base layer. Chromatic layers and color-changing layers; (3) by suction filtration, the mixed solution of the epoxy resin prepolymer and the curing agent is completely covered and wrapped around each layer, and cured to obtain an encapsulation layer; (4) A mixture of an epoxy resin prepolymer with shape memory properties and a curing agent is constructed on the encapsulation layer by a doctor blade method, and a temporary pattern is applied after curing to obtain a deformed layer. 2 . The method for preparing electrothermal discoloration/deformation film according to claim 1 , wherein the base layer material is filter paper, cotton cloth or fabric. 3 . 3. The preparation method of electrothermal discoloration/deformation film according to claim 1, wherein the electrothermal layer is made of conductive material, and the conductive material is selected from carbon nanotube, graphene, graphite or nanometer metal powder. 4 . The method for preparing electrothermal discoloration/deformation film according to claim 1 , wherein the base color layer is composed of organic and/or inorganic pigments and fillers. 5 . 5 . The method for preparing an electrothermal discoloration/deformation film according to claim 1 , wherein the encapsulation layer is formed by curing a thermosetting epoxy resin. 6 . 6 . The method for preparing electrothermal discoloration/deformation film according to claim 1 , wherein the thickness of the electrothermal heating layer, the base color layer and the discoloration layer is 10-100 μm. 7 . 7 . The method for preparing electrothermal discoloration/deformation film according to claim 1 , wherein, in step (2), during suction filtration of each layer, a mask is used to construct a pattern on this layer. 8 . 8. The preparation method of electrothermal discoloration/deformation film according to claim 1, characterized in that, in step (2), during suction filtration, the surface area of the controlled electrothermal layer is a ground color layer, a discoloration The surface area of the layer is 1.2 to 1.5 times that of the largest layer. 9. The preparation method of electrothermal discoloration/deformation film according to claim 1, characterized in that, in step (4), a hot pressing method is used to construct the temporary pattern: first, the temperature is raised to the deformation layer The glass transition temperature of the epoxy resin used is higher than the glass transition temperature, and it is obtained by hot pressing the template with a pattern on the surface, lowering the temperature and removing the template while maintaining the hot pressing state.

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