JPH0691799A - Laminate with film reversibly turning opaque by tension - Google Patents

Abstract

PURPOSE: To provide a laminate excellent in heat stability and long-time storage stability, clear and marked in a reversible change of transparentization- opacification, generating a change by relatively small tensile force, simple and rapid to produce and capable of being formed into arbitrary thickness and a shape. CONSTITUTION: A laminate has an inner film opacified by pulling and again transparentized by the restoration of the original form and an outer film restoring the original form itself when pulling is released to restore the original form of the inner film and is characterized by that the inner film is constituted of a copolymer consisting of 30-70 pts.wt. of an oligomer compd. having 1.5 or more (meth)acrylic groups and 30-70 pts.wt. of methacrylic acids as polymerizable components and the outer film has Young's modulus of about 10-1,000 kg/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate having a film which becomes opaque by pulling and re-transparent by shape recovery. This process is reversible and can be repeated. Light control can be performed by utilizing this property.
An example of its application is an automatic blind. That is, the intensity of light is measured by an optical sensor, and the tension applied to the film of the present invention is controlled so that the film has an opacity according to the intensity of the light, so that the amount of light is always kept constant. It's a blind.

As light control, not only natural light but also illumination light and laser light can be controlled. Since the present invention visualizes the magnitude of tension by whitening, it is also effective in clarifying how tension works. Specific application examples thereof include tubes, joints, packings, etc. made of the material of the present invention, and these products display how much tension acts from what direction and are used as sensors. You can also

[0003]

2. Description of the Related Art As a conventionally known material which becomes opaque by pulling, Reversibly developed by Minnesota Mining and Manufacturing Company, USA
There is a transparent-translucent film (hereinafter abbreviated as RTT film) (US Patent No. 4,206,980). The RTT film is a crystalline polymer and an organic low-molecular compound that dissolves the polymer at a crystallization temperature Tc or higher, but does not dissolve below, is mixed and molded at a temperature of Tc or higher, and then rapidly cooled to a temperature of Tc or lower. Made

Since the RTT film contains a low molecular weight compound, its decomposition and evaporation cause difficulties in heat resistance and long-term storage stability. Also, the manufacturing process is complicated,
Since rapid cooling is required, only a sheet having a thickness of 500 microns or less can be obtained by the single-sided cooling system and 1000 microns or less by the double-sided cooling system.

As a material whose optical properties change by pulling, cis-1,4, -polyisoprene and trans-
Polymer blends that have been mixed with polyisoprene and cross-linked have been investigated but do not produce significant clear-opaque changes (AK Bhowmick, CCKuo, A. Mnzur, A. Mac Art.
hur and D. Mc Intyre J. Macromol. Sci. Phys., B25
(3), 283 (1986); and A. Manzur, J. Macromol. Sci.
Phys., B28 (3 & 4), 329 (1989)].

In general polymers, especially polymer blends, it is known that stress-induced stress is whitened due to bending cutting and the like. In this case, spontaneous recovery to a transparent state does not occur. Absent.
Opacification due to pulling similar to the present invention was also observed in a sheet in which fine particles of silica or the like having a refractive index close to that of silicon rubber were added to transparent silicon rubber, but this sheet was originally translucent and was in an opaque state due to pulling. Is only noticeable. In order to make this sheet opaque, it is necessary to stretch it so that its length is approximately doubled.

[0007]

Therefore, the present invention is excellent in thermal stability and storage stability for a long time, the reversible change of transparency-opacity is clear and remarkable, and the change is caused by a relatively small tension. In addition, the present invention is intended to provide a laminate which is simple and quick to manufacture and can be formed into an arbitrary thickness and shape.

[0008]

[Means for Solving the Problems] The above-mentioned problems are solved by an inner film which becomes opaque by tension and becomes transparent again by recovering its original shape, and an outer film which recovers its original shape by itself when the tension is released and thereby recovers its original shape. And the inner film is composed of a copolymer comprising 30 to 70 parts by weight of an oligomer compound having 1.5 or more (meth) acrylic groups as polymerization components and 30 to 70 parts by weight of methacrylic acid. And the outer membrane is about 10 to 1000 kg / cm
It is solved by a laminate characterized by having a Young's modulus of ² .

[0009]

[Detailed Description] An oligomer containing 1.5 or more (meth) acrylic acid groups, which is a polymerization component of the copolymer constituting the inner film of the present invention, becomes a basic skeleton after curing and has a toughness. Are required to form the. Containing 1.5 or more (meth) acrylic groups in the molecule is 3
It is necessary to form a dimensional crosslinked structure. A soft type oligomer (an oligomer compound having a glass transition temperature after polymerization of about room temperature or lower) is desirable in order to obtain a film having a large elongation at break so that it can be stretched by pulling.

Specifically, urethane acrylate, polyester acrylate, polyethylene glycol dimethacrylate, etc. can be used. Examples of such compounds include urethane acrylate UV3000B (Nippon Gosei Kagaku), urethane acrylate UX
4101 (Nippon Kayaku, KAYARAD) Polyester acrylate M6200 (Toagosei Kagaku Kogyo, ARONI)
X), polyethylene glycol dimethacrylate 9G
(Shin Nakamura Chemical Co., Ltd. NKESTER) and the like.

Acrylic acid, which is another polymerization component constituting the copolymer of the inner film, is necessary for imparting the property of making the inner film opaque by pulling. Urethane acrylate UX4101 (Nippon Kayaku; KAYARAD), which is an orycomer having 1.5 or more (meth) acrylic groups
60 parts by weight and photoradical initiator D1 as curing catalyst
173 (Merck Japan: Darocure) 2 parts by weight of 40 parts by weight of various monomers described below in combination was bulk polymerized, and the resulting copolymer was examined for opacity due to tension, isooctyl acrylate, n-
Butyl acrylate, 2-ethylhexyl acrylate, 2-methoxyethyl acrylate, ethyl acrylate, methyl acrylate, tetrahydrofuryl acrylate, 2-hydroxyethyl acrylate, benzyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, vinyl acetate, tert-butyl acrylate, isobornyl Acrylate, acrylic acid, methacrylic acid, dicyclopentanyl acrylate,
Dicyclopentanyl methacrylate, N-vinylpyrrolidone, N-isobroxyethyl acrylonitrile, 1,
Of 6-hexanediol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane triacrylate, only methacrylic acid was effective for opacification due to tension. A polymer consisting of about 60 parts by weight urethane acrylate and about 40 parts by weight methacrylic acid is especially preferred.

The copolymer constituting the inner film preferably contains, in addition to the above-mentioned two components, a low molecular weight compound containing at least one (meth) acrylic group. This low molecular weight compound is used for adjusting the elastic modulus of the copolymer film and controlling the tension required for opacity.

In practical use, a material which becomes opaque with a small force is often required. In this case, a compound having a low Tg after polymerization is desirable in order to reduce the elastic modulus. Specifically, 2-ethylhexyl acrylate, n-butyl acrylate, octyl acrylate, 2-methoxyethyl acrylate, ethyl acrylate and the like are suitable for use.

Regarding the blending ratio of the above-mentioned polymerization components of the inner film, the content of methacrylic acid must be 30 parts or more in order to give the obtained copolymer a property of making it opaque by pulling. When the content of methacrylic acid is 70 parts or more, it becomes an opaque film even when tension is not applied, and the object of the present invention is not achieved. Since the elastic modulus of the cured film increases as the content of methacrylic acid increases, it is preferable that the amount of methacrylic acid is small in practice.
A composition of 0 parts is optimal.

The oligomer containing 1.5 or more (meth) acrylic groups is present in a portion other than mecrylic acid in an amount of 70 to 30 parts by weight based on the whole polymer. However, when this oligomer is too much, the elastic modulus of the polymer film is increased. Becomes larger,
It may be difficult to make it opaque when pulled by human power. In this case, 10-40 of the oligomer
It is desirable to replace parts by weight with a monomer containing one or more (meth) acrylic groups. However, if the amount of the monomer exceeds this range, the toughness of the film may be lost.

In order to polymerize and cure the inner film, it is preferable to use a small amount of the curing catalyst, for example, 0.5 to 5 parts by weight, in addition to the above three components, and a photocuring catalyst is used as the curing catalyst. Is preferred. As such a catalyst, for example, Darocur D1173 (Merck Japan) or the like can be used. The use of a photocuring catalyst is particularly preferable because the film can be easily cured by irradiation with ultraviolet rays. Since the inner film of the present invention is made of neat polymer, it has high heat resistance.

The outer film is necessary to regain the original size of the opaque inner film that has been stretched by pulling and re-cleared after releasing the film.
It is necessary to have a Young's modulus of 0 to 1000 kg / cm ² . When the Young's modulus of the outer film is lower than 10 kg / cm ^2, cohesive failure is likely to occur due to large elongation. On the other hand, if the Young's modulus is higher than 1000 kg / cm ² , the film is no longer elastic.

The outer film can be composed of a polymer from an oligomer containing 1.5 or more (meth) acrylic groups. This oligomer is selected from among those similar to the oligomer for the inner membrane. However, in order to reduce the viscosity of the polymerization component before curing, it is preferable to add 10 to 50 parts by weight of a monomer containing one or more (meth) acrylic groups. The monomer is selected from compounds similar to those for the inner membrane.

Also in the case of polymerization and curing of the outer film, it is preferable to use the curing catalyst as in the case of the inner film. In this case, the curing catalyst and the addition amount thereof are the same as in the case of the inner film. To prevent curling of the laminate, the two outer films preferably have the same or similar physical properties, but may also have different optical properties.
However, it is also acceptable if the two outer membranes have slightly different physical properties.

In producing the laminate according to the present invention, a laminate is prepared by sequentially coating and polymerizing a liquid polymer component on an appropriate substrate in the order of an outer film, an inner film and an outer film. Alternatively, there is a method in which the polymerization component for obtaining the inner film is sandwiched between two preformed outer films to perform polymerization. At this time, if each of the layers is not completely polymerized and is maintained in a semi-cured state, and a method of irradiating ultraviolet rays again after stacking to complete the polymerization is adopted, the inner film and the outer film can be firmly bonded. It is practically desirable because it can be done. However, it is also possible to stack completely cured films.

In the laminate of the present invention, the thickness of the inner film and the outer film can be variously changed depending on the use of the laminate, but the thickness of the inner film is preferably 50 to 5,000.
μm, and the thickness of the outer film is 50 to 5000 μm. Next, an application example of the laminate of the present invention will be described. By applying the present invention, a film whose color changes by pulling or a film which displays characters or patterns by pulling can be formed. These films can be used as display materials. Specifically, a poster or card with a different background color, a sticker that displays characters only when pulled, and the like are conceivable. The manufacturing method is as follows.

A. When two outer films are given different colors For example, when one outer film is red and the other outer film is blue, the color of the laminated film looks purple when no tension is applied. When the laminated film is pulled, the inner film becomes opaque, so that the laminated film exhibits red when viewed from one side and blue when viewed from the other side. As a method for coloring the outer film, a dye is added to the liquid polymerization component before polymerization,
Although a method of coloring after polymerization is conceivable, it is possible to manufacture a film having similar properties even if the outer film is not colored or each surface of the inner film is colored.

B. When the same color is applied to the two outer films In the laminated film in this case, the inner film becomes opaque when pulled, so that there is a slight change in color tone, but no noticeable change in color. However, if one outer film is colored uniformly and letters or patterns are written on the other outer film in the same color, the laminated film will be uniformly colored without any tension. However, when it is pulled, characters or patterns appear to float on the white opaque inner film. The letters or patterns may be written on the outer membrane or the inner membrane.

[0024]

EXAMPLES The present invention will be described below with reference to examples. The composition was prepared by mixing the components at 50 ° C. In order to indicate the polymerization component, parts by weight are used. The polymerization was carried out by irradiating with UV light of 37 mw / cm ² from a high pressure mercury lamp for 80 seconds.

Example 1. Urethane acrylate UV30
The liquid resin composition obtained by mixing 00B (Nippon Gosei Kagaku Co., Gocerac), tripropylene glycol diacrylate and the photocuring catalyst Darocur D1173 (Merck Japan) in a weight ratio of 60: 40: 2 is polyethylene terephthalate (PET). A film having a thickness of 150 μm was produced by applying it on a base material and curing with ultraviolet light, and this was used as an outer film.

Urethane acrylate UV3000B (Nippon Gosei Kagaku), methacrylic acid, 2-ethylhexyl acrylate and photo-curing agent Darocur D1
173 (Merck Japan) was mixed at a weight ratio of 40: 30: 30: 2, sandwiched between the two outer films, and a knife coater was used to adjust the thickness of the resin layer to 100 μm.
It was irradiated with ultraviolet rays and polymerized to obtain a laminate having a total thickness of 400 μm.

The 400-micron laminated film thus obtained was transparent, but it became opaque in white by pulling 25% or more under tension, and returned to its original length within a few seconds when the tension was removed. And returned to transparent. Further repeated stretchings (100 times or more) did not change the properties of the film at all. To examine the heat resistance of this film, it was placed in an oven at 120 ° C. for 5 hours, but no change was observed in the properties of the film.

Example 2. In this example, urethane acrylate UV3000B (component 1) was used as an oligomer containing 1.5 or more (meth) acrylic groups.
By using the one shown in the table as a monomer compound containing one or more (meth) acrylic groups (component 3) and Dalocure D1173 (component 4) as a photocuring catalyst, it is necessary to change the amount of methacrylic acid. I checked the quantity.

The results are shown in Table 1. The case where the laminated film was pulled to make it transparent was evaluated as O, and the case where it was not made transparent was evaluated as X. Since an opaque film cannot serve the purpose of the present invention even when no tension is applied, X
It was evaluated by X. The results obtained are shown in Table 1. As a result, it was found that the required weight part of methacrylic acid was 30 parts or more and less than 70 parts.

Table 1 ───────────────────────────────── Component 1 Methacrylic acid component 3 Component 3 type Component 4 Evaluation 20 80-2 XX 30 70 0-2 XX 40 60 0-2 O 50 50 0-2 O 60 40 0-2 O 70 30 0-2 O 80 20 0-2 X 40 30 30 2 EHA 2 O 30 40 30 2EHA 2 O 40 20 40 2EHA 2 X 60 20 20 2EHA 2 X ──────────────────────────────────

Example 3. In this example, the Young's modulus of the outer membrane is considered. Various formulations shown in Table 2 were applied to each side of an inner film having the same composition as described in Example 1 and UV-cured to form an outer film. After pulling the finished laminated film until it became opaque, the tension was removed and the mixture was allowed to stand at room temperature, and those that returned to a transparent state within 10 minutes were evaluated as O, and those that were not evaluated were evaluated as X. When the outer film was broken before being pulled to make it opaque, it was evaluated by XX.

Table 2 ─────────────────────────────────── Resin fat Young's modulus evaluation UX4101 15 O UX4101 / cyclohexyl acrylate (60:40) 70 O UX4101 / tripropylene glycol diacrylate (70:30) 270 O UX4101 / 1,6-hexanediol diacrylate (65:35) 900 O UX4101 / 1,6-hexanediol Diacrylate (70:30) 1500 XX UX4101 / n-vinylpyrrolidone (60:40) 12000 X ───────────────────────────── ───────

[0033]

Since the laminate according to the present invention has the above-mentioned constitution, it is excellent in thermal stability and storage stability for a long time, and the reversible change of transparency-opacity is clear and remarkable,
This produces a great effect that a change is caused by a comparatively small tension, and that the manufacturing is simple and quick, and the thickness and shape can be arbitrarily set.

Claims (5)

[Claims] 1. An inner film that becomes opaque by pulling and becomes transparent again by recovering its original shape, and an outer film that recovers its original shape by itself when pulling is released, and thereby recovers the original shape of the inner film. Oligomer compound 30 having 1.5 or more (meth) acrylic groups as a polymerization component
A laminate comprising a copolymer comprising 70 parts by weight and 30 to 70 parts by weight of methacrylic acid, wherein the outer membrane has a Young's modulus of about 10 to 1000 kg / cm ² . 2. The laminate according to claim 1, wherein the inner film has a thickness of 0.5 to 5 mm, and each of the outer films has a thickness of 0.05 to 5 mm. 3. The (meth) acrylic group in the molecule is 1.
The laminate according to claim 1 or 2, wherein the oligomer compound having 5 or more is urethane acrylate or polyester acrylate. 4. The laminate according to claim 1, wherein the copolymer constituting the inner film further contains 10 to 40 parts by weight of a low molecular weight compound having at least one (meth) acrylic group as a polymerization component. . 5. The low molecular compound having at least one (meth) acrylic group in the molecule is ethyl acrylate, propyl acrylate, n-butyl acrylate, octyl acrylate, 2-methoxyethyl acrylate or 2-methacrylate.
The laminate according to claim 1, which is ethylhexyl acrylate.