JPH085809A - Capsule type retroreflective sheet - Google Patents

Abstract

PURPOSE:To provide a capsule type reflection sheet having excellent characteristics by using such a supporting film that has excellent property of hot-melt and deformation, adhesion strength with a protective film, property to form capsule walls having excellent resistance against strain, tensile strength and resistance against repeated elongation and contraction, and excellent outdoor weather resistance for a long period. CONSTITUTION:This capsule type reflection sheet consists of at least a light- transmitting protective film, supporting film and connecting walls produced by thermally fusing and deforming the supporting film. The protective film and the supporting film are partially connected with the connecting wall while spaces remain between the films. Reflection elements are densely distributed on the whole surface of the protective film and/or the supporting film. The supporting film contains a matrix resin and a fibrous material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is useful for signs such as road signs and construction signs, license plates for vehicles such as automobiles and motorcycles, safety materials such as clothing and life preservers, and marking of signs. The present invention relates to a capsule type retroreflective sheet.

[0002]

2. Description of the Related Art Conventionally, a retroreflective sheet that retroreflects light toward a light source is well known, and the sheet is widely used in the above-mentioned fields of application by utilizing its retroreflectivity. There is. Among them, so-called capsule type retroreflective sheet-consisting of at least a light-transmitting protective film, a support film, and a connecting wall formed by heating and melting and deforming the supporting film, the protective film and the supporting member by the connecting wall. The film and the film are partially connected to each other to form a capsule in which a gas is enclosed between the films, and a lens-type retroreflective property is provided on the protective film and / or the support film in the capsule. The retroreflective sheet in which the retroreflective elements such as the element and the cube-corner type retroreflective element are densely arranged has been expanding its applications year by year due to its excellent light reflecting performance.

For such a capsule type retroreflective sheet, high retroreflective performance is required as the most important function. In addition, even when it is used under severe conditions such as outdoor use, Good weather resistance capable of maintaining the excellent retroreflective performance for a long time is also required as one of the important functions.

The deterioration of the retroreflective performance when the capsule type retroreflective sheet is used outdoors for a long time is almost always caused by the capsule being broken and rainwater or the like penetrating into the capsule. For example, protection film cracks caused by repeated expansion and contraction of gas in the capsule caused by changes in outside air temperature and repeated expansion and contraction of adherends such as metal plates to which a retroreflective sheet is attached; Adhesive failure at the interface between the film and the connecting wall; destruction of the connecting wall itself or the support film itself, etc. causes loss of airtightness of the capsule, rainwater etc. penetrates into the capsule, and it is important for retroreflective performance. The retroreflecting performance is deteriorated due to a change in the refractive index condition in the capsule, which is a factor, or deterioration of the included retroreflective element to lose the light reflecting performance.

Among them, the connecting wall for connecting the protective film and the support film is most likely to be affected by distortion or the like due to its structure, and tends to be broken. In fact, the retroreflective sheet caused by the breaking of the connecting wall is Many deteriorations and deteriorations in retroreflective performance have occurred. Therefore, in order to improve the weather resistance of the capsule-type retroreflective sheet, it is most important to form the connecting wall having excellent strength.

Some attempts have been made to improve the strength of the connecting wall for the purpose of improving the weather resistance of the capsule type retroreflective sheet.
In the '121043 publication, by using a high molecular weight thermoplastic resin film as the support film forming the connecting wall, the support film is provided with toughness and flexibility, and the retroreflective sheet has better structural integrity. Is proposed.

However, in this proposal, since the toughness and flexibility of the support film are improved by increasing the molecular weight of the resin for forming the support film, the molecular weight of the resin for forming the support film is increased. If the toughness desired for the connecting wall or the support film itself is to be obtained, the heat-melt deformability of the supporting film is generally impaired, and the adhesive strength between the connecting wall and the protective film tends to decrease. On the other hand, if the molecular weight of the resin for forming the support film is kept low in order to obtain sufficient hot melt deformability and flexibility, the toughness is impaired and the initial purpose cannot be achieved. Further, the resins such as the aliphatic urethane polymer and the copolymer of ethylene or propylene used in the above proposal are difficult to obtain sufficient weather resistance, and are not suitable for applications requiring long-term weather resistance.

Further, for example, in Japanese Patent Publication No. 61-13561, a binder material is heated and melted and deformed to form a connecting wall (connecting part structure), and then the connecting wall is irradiated with radiation to form the connecting wall. It has been proposed to crosslink to improve the strength of the connecting wall. However, in this proposal,
Since the connecting wall is crosslinked to be hard and brittle, it is difficult to obtain flexibility that can withstand repeated expansion and contraction,
There is also a problem that the retroreflective sheet itself becomes hard. Further, the crosslinking of the connecting wall by radiation has a drawback that the connecting wall is contracted in volume and a large strain is generated.

Further, a crosslinking component having an unsaturated bond, which is used in a radiation crosslinking reaction, is rarely completely reacted during the crosslinking reaction, and in many cases, the unreacted component is directly returned to the product. Since it remains on the support film and the connecting wall of the reflective sheet, undesired crosslinking proceeds due to external factors such as heat and sunlight during the use of the retroreflective sheet, and the adhesive force between the protective film and the connecting wall. It has also been found that there is a problem that the capsule is easily broken due to deterioration of the film thickness and brittleness of the support film and the connecting wall.

In addition, in JP-A-60-194405 and JP-A-2-196653, a support film is used as a surface layer (binder layer, upper layer side) and a reinforcing layer (support layer, lower layer side).
A surface formed by a cross-linking resin or a non-cross-linking resin using a cross-linking agent, which has the same two-layer structure as the cross-linking resin layer using a cross-linking agent such as isocyanate as the reinforcement layer and imparts tensile strength to the support film. Attempts have been proposed in combination with layers to solve the above-mentioned problems.

However, in these proposals, the reinforcing layer can improve the tensile strength of the support film and the weather resistance to some extent, but if the surface layer is formed of the above-mentioned cross-linking resin, it is cross-linked. It is difficult to select the timing for forming the connecting wall by heat-melting and deforming the agent-containing surface layer, and the same problem as described above in Japanese Patent Publication No. 61-13561 may occur. On the other hand, if the surface layer is formed of a non-crosslinking resin, the same problems as those described in JP-A-62-121043 may occur, which is not always sufficient.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a protective film and a connecting wall which have excellent heat melt deformability that can be easily heat deformed and formed, and which, when heat melt deformed as a connecting wall. It is possible to achieve excellent adhesive strength between the two, and further, there is little distortion of the support film and the connecting wall as the wall surface that forms the capsule, excellent tensile strength and excellent flexibility that can withstand repeated expansion and contraction. In addition, by developing a support film having excellent outdoor long-term weather resistance, it is possible to solve the drawbacks of the prior art as described above and to provide a capsule-type retroreflective sheet having excellent properties. is there.

The inventors of the present invention have conducted various studies on the support film of the capsule-type retroreflective sheet, and as a result, the support film is formed in a matrix resin such as whiskers (fibrous metal compound single crystal). It was found that an excellent retroreflective sheet in which the above-mentioned drawbacks of the prior art were eliminated can be obtained by forming the sheet containing a fibrous substance, and completed the present invention.

[0014]

Thus, according to the present invention, at least a light-transmitting protective film, a support film, and a connecting wall formed by heating and melting and deforming the supporting film are formed. Capsule type in which the protective film and the support film are partially connected to each other with a gap left therebetween, and the retroreflective elements are densely arranged on the entire surface of the protective film and / or the support film. In the retroreflective sheet, there is provided a capsule-type retroreflective sheet characterized in that the support film contains a matrix resin and a fibrous substance.

The capsule-type retroreflective sheet of the present invention will be described in more detail below.

The capsule-type retroreflective sheet of the present invention comprises:
A major feature is that the support film is composed of a matrix resin and a fibrous substance.

The above-mentioned fibrous substance functions as a modifier of the support film, does not impair the heat-melt deformation characteristics of the support film, and has excellent stretch resistance and heat resistance, which are excellent for the support film. Impact strength, high elasticity, high fracture toughness,
It is thought to add functions such as dimensional stability, and as a result,
It is presumed that the capsule type retroreflective sheet of the present invention is provided with excellent properties such as weather resistance.

The amount of the fibrous substance contained in the support film in the present invention is preferably 0.1 to 30 with respect to 100 parts by weight of the matrix resin constituting the support film.
The amount is preferably 0.5 to 20 parts by weight, more preferably 1 to 15 parts by weight. When the content of the fibrous substance is at least the lower limit value, sufficient impact strength and heat resistance can be obtained, which is preferable. Further, when the content is less than or equal to the upper limit, problems such as deterioration of heat melting deformation characteristics and failure to obtain sufficient adhesive strength between the protective film and the connecting wall are less likely to occur, which is preferable.

The shape of the fibrous substance to be used is not particularly limited, and a fibrous substance having a needle-like shape or a tetrapot-like shape is used, but a fiber having a significantly long fiber length or a fiber diameter is used. If you use a significantly large one,
The heat melt deformability tends to be impaired, and since the modification effect on the supporting film tends to be difficult to obtain when a fiber length is extremely small or a fiber diameter is extremely small, the average fiber length is 1 to 100 μm. , And more preferably 1
-70 μm, more preferably 2-50 μm,
Average fiber diameter 0.01 to 10 μm, more preferably 0.05 to 5 μm,
It is more preferably 0.1 to 3 μm. The average aspect ratio of the fibrous substance is preferably 2 to 5000, more preferably 3 to 1000, further preferably 5 to 800, and particularly preferably 10 to 500.

The type of fibrous substance used is not particularly limited, and examples thereof include natural cellulosic fibers such as pulp, cotton and hemp; natural protein fibers such as silk and wool; eg viscose rayon and acetate rayon. , Synthetic fibers such as Bembell rayon, polyester fibers, polyamide fibers, acrylic fibers, polypropylene fibers; and inorganic fibers such as glass fibers, carbon fibers, asbestos fibers, whiskers, and the like. These fibrous substances may be cut, crushed or crushed as needed, preferably within the ranges of the above-mentioned average fiber length, average fiber diameter and aspect ratio. Further, these fibrous substances are used alone or in combination of two or more kinds. Among these fibrous substances, use of whiskers is preferable from the viewpoint of remarkable improvement effect.

The whiskers are fibrous single crystals of metal compounds, and examples thereof include sapphire-based, beryllia-based, boron carbide-based, silicon carbide-based, silicon nitride-based, zinc oxide-based, alkali metal titanate-based, and the like. Of these, it is particularly preferable to use a silicon carbide type, a zinc oxide type, or an alkali metal titanate type, which is relatively inexpensive and has excellent shape uniformity.

In the capsule type retroreflective sheeting of the present invention, the matrix resin constituting the support film is
Any non-crosslinked resin or low-crosslinked resin can be used as long as it exhibits hot melt fluidity at the time of forming a connecting wall by heating and melting deformation of the support film, and specifically, for example, acrylic resin. Resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate resins, polyolefin resins, fluorine resins, polyamide resins, etc. can be mentioned, and these can be used alone or in combination with other resins. In a form copolymerized with the ingredients,
Or it is used in a blended form, but among them, an acrylic resin which has excellent weather resistance and whose heat-melting property is easy to adjust is particularly preferably used. Among them, an acrylic resin having a glass transition temperature in the range of −50 to 30 ° C. Resin is most preferably used.

In the resin composition forming the support film, in addition to the matrix resin and the fibrous substance, if necessary, a colorant, a filler, an ultraviolet absorber, a light stabilizer, an optical brightener, You may mix | blend various additives, such as a modifier.

If desired, a cross-linking agent is added, and the support film is heated and melted and deformed to form a connecting wall, and the light-transmitting protective film and the support film are partially connected and then a matrix resin is added. Although it can be crosslinked to improve the tensile strength, impact strength, etc. of the support film, addition of an excessive crosslinking agent causes distortion due to shrinkage of the support film due to a crosslinking reaction, and also the support film. It is better to avoid as much as possible because it will reduce the stretch resistance of
Even if the addition amount of the cross-linking agent is the maximum, it is preferable that the addition amount is within a range that does not impair the thermoplasticity of the obtained support film.

The thickness of the support film used for the capsule-type retroreflective sheet of the present invention is not particularly limited, but it is usually appropriate to set it in the range of about 20 to 150 μm.

The support film may be provided with a reinforcing layer formed of a cross-linking resin or the like on the back surface of the support film in order to impart better tensile strength, better stretch resistance and the like. An intermediate layer may be provided between the support film and the reinforcing layer for the purpose of improving the bonding strength between the two.

In order to impart more preferable weather resistance to the capsule type retroreflective sheet of the present invention, the tensile strength of the support film at 23 ° C. is 50 kg / cm ² or more and the elongation at break is 5 or more.
It is suitable to be about 0% or more.

The capsule-type retroreflective sheeting of the present invention comprises
The support film can be manufactured using conventionally known materials and methods, except that the support film is composed of a matrix resin and a fibrous substance. The example is as follows.

In the production of the capsule lens type retroreflective sheet, first, polyethylene terephthalate (PE
T) A liquid resin composition in which a fibrous substance is uniformly dispersed in a matrix resin solution is applied onto a process substrate such as a film and dried to form a support film. On the other hand, a microsphere lens such as glass beads is scattered on a temporary support such as polyethylene (PE) laminated paper, and about 1/5 to 1/3 of the diameter of the microsphere lens is embedded by heating. The layer is densely embedded in the PE layer, and then a metal such as aluminum is vapor-deposited on the exposed surface of the microsphere lens to form a light reflecting layer so as to cover almost the hemisphere part of the microsphere lens. Thereby forming a lens-type retroreflective element consisting of a large number of microsphere lenses. Next, it is placed so that the surface of the support film is in contact with the lens-type retroreflective element formed on this temporary support, and about 1/5 to 1/2 of the diameter of the microsphere lens is heated by heating. After bonding so as to be embedded in the support film, the temporary support is peeled off, and the lens type retroreflective element is transferred onto the support film. Then, on the protruding lens-type retroreflective element, a light-transmitting protective film such as an acrylic film having a thickness of about 20 to 200 μm is laid on top of the other, and the support film is heated while using an embossing roll or the like. Then, it is thermally melt-deformed to form a connecting wall for connecting the support film and the protective film. Thus, a capsule lens type retroreflective sheeting having a large number of capsules containing a large number of lens type retroreflective elements is manufactured.

In the production of the capsule cube-corner type retroreflective sheet, a support film is formed in the same manner as described above, and a large number of cube-corner type retroreflective elements are formed on one surface of the support film. A light-transmitting protective film having a is placed so that the cube-corner retroreflective element faces the support film,
The support film is partially heated and melt-deformed while being heated using an embossing roll or the like to form a connecting wall that connects the support film and the protective film. Thus, an encapsulated cube-corner retroreflective sheeting having multiple capsules containing multiple cube-corner retroreflective elements is manufactured.

If desired, the capsule-type retroreflective sheet of the present invention has an adhesive layer for adhering the retroreflective sheet to a predetermined adherend and dust or the like attached to the adhesive layer. A release substrate or the like for preventing the above may be sequentially formed and used on the back surface of the support film.

[0032]

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 A process paper in which PE having a softening temperature of about 105 ° C. is laminated on paper is about 1
Heat to 05 ℃, average particle size of about 65μm, refractive index on this
The glass beads of 1.91 were uniformly and densely dispersed in a single layer, and then pressured by a nip roll to embed the glass beads in PE up to about 1/5 of their diameter. Then, aluminum was vacuum-deposited on the surface where the glass beads were exposed to form a vapor deposition film having a thickness of about 0.1 μm on the substantially hemispherical surface of the glass beads.

Next, an acrylic resin solution having a solid content of 30% by weight as a matrix resin [53% by weight of ethyl acrylate (EA), 46% by weight of methyl acrylate (MA)] was applied on a PET film having a thickness of 20 μm which had been subjected to a peeling treatment. %, 2-hydroxyethyl methacrylate (HEMA) 1% by weight, acrylic acid (AA) 0.1% by weight, an acrylic copolymer having a weight average molecular weight of about 300,000, methyl isobutyl ketone (MIB
K) / toluene solution; "Nisetsu KP-1684A" manufactured by Nippon Carbide Industry Co., Ltd.] 167 parts by weight, similarly acrylic resin solution having a solid content of 40% by weight as a matrix resin [EA 66% by weight, methyl methacrylate (MMA) 33] MIBK / toluene solution of acrylic polymer having a weight average molecular weight of about 250,000, which is obtained by copolymerizing 1% by weight of AA and 1% by weight of AA; Nippon Carbide Industry Co., Ltd.
"Nissetsu KP-1703A"] 125 parts by weight, potassium titanate whiskers [Otiska Chemical Co., Ltd. "Tismo D"] 10 parts by weight as fibrous substance, and rutile titanium oxide 50
A dispersion liquid in which 30 parts by weight of MIBK and 30 parts by weight of MIBK were mixed by stirring was applied, and most of the solvent was removed to prepare a support film having a thickness of about 80 μm.

This support film was superposed on the vapor-deposited glass bead embedding step paper prepared in advance so that the support film and the glass beads were in contact with each other, and a linear pressure of 900 kg / m was applied while heating at 70 ° C. About 1/3 of the diameter of the glass beads was embedded in the support film by pressurizing with, the PE laminated paper was peeled off, and the glass beads were transferred to the support film.

Next, a non-stretched acrylic film having a thickness of about 75 μm and a total light transmittance of about 93% on the support film on which the glass beads were transferred (in the methyl methacrylate resin matrix phase, an average particle diameter of about 0.1 μm). Of MMA and butyl acrylate (BA) as a main component, and a multilayer resin composition film having a dispersed phase of multilayer polymer cross-linked particles] are laminated so that the glass beads and the acrylic film are in contact with each other, and the line width is about 0.3 mm. Surface temperature with mesh-like convex engraving Approx. 1
While passing the acrylic film side between the 90 ° C metal roll and the rubber roll with a surface temperature of about 60 ° C so that the acrylic film side is in contact with the rubber roll, press the metal roll from the release-treated PET film side to partially deform it by heat melting. Molded.

From the obtained hot melt deformation molded product, peeling treatment
Remove the PET film, on the back side of the support film,
Retroreflective by laminating an acrylic pressure-sensitive adhesive with a thickness of about 40 μm (made by Nippon Carbide Industry Co., Ltd. “Nissetsu KP-997”) that was separately formed on a silicone-treated PET release film with a thickness of about 75 μm. I made a sex sheet.

The performance of the obtained retroreflective sheet is as shown in Table 1, and the capsule type retroreflective sheet of the present invention shows a small reduction rate of the reflective performance and a small shrinkage even in a severe weather resistance test. Further, the protective film was hardly peeled off and had excellent weather resistance.

Example 2 In the same manner as in Example 1 except that the fibrous substance added to the matrix resin composition was changed to 10 parts by weight of zinc oxide fibrous substance [“Panatetra” manufactured by Matsushita Amtech Co., Ltd.]. I made a retroreflective sheet. The performance of the obtained retroreflective sheet is as shown in Table 1, and the capsule-type retroreflective sheet of the present invention shows that even in a severe weather resistance test,
The rate of reduction in reflection performance was low, the shrinkage was low, the protective film was scarcely peeled off, and the weather resistance was excellent.

Comparative Example 1 A retroreflective sheeting was prepared in the same manner as in Example 1 except that the addition of fibrous substance was omitted. The performance of the obtained retroreflective sheet is as shown in Table 1, and in a severe weather resistance test, the rate of decrease in reflection performance was large and the shrinkage was large, and sufficient weather resistance could not be obtained.

[0041]

[Table 1]

The measuring methods of the tests used in this example and the comparative example are as follows.

[0043](1) Tensile test of support film  The measurement sample is cut into a width of 10 mm and a length of 50 mm under the condition of 23 ℃
After leaving it for 30 minutes at `` Tenshiro, '' manufactured by Orientec Co., Ltd.
With a gripping interval of 10 mm and a pulling speed of 200 mm / min.
Tensile strength is determined by the maximum stress at that time.
The elongation up to the breaking point was defined as the breaking elongation.

[0044](2) Weather resistance test  Cut the retroreflective sheet into 50 mm x 50 mm and use silicone.
Peel off the treated PET release film and attach the retroreflective sheet.
Affixed to a Luminium panel and promoted adhesion sample Weather resistance
Tester [Suga Tester Co., Ltd. "Optical control weather ome
) ”And carry out a 500-hour accelerated weathering test.
It was

Then, the pasted sample was taken out, and a cooling / heating cycle test was carried out using a cooling / heating cycle tester [“Heat Shock Chamber TSR-63” manufactured by Tabay Tech Co., Ltd.]. The cooling / heating cycle was carried out 300 times with the following conditions as one cycle.

(Cooling cycle condition) −40 ° C. × 30 minutes → room temperature × 15 minutes → 145 ° C. × 30 minutes → room temperature × 15 minutes

(Measurement method)(2-1) Reflection performance deterioration rate (%)  Advanced Retro Technology's retroreflective performance measurement
Retesting the test piece after the weather resistance test using the calibrator "MODEL 920".
Measure the retroreflective performance and compare it with the retroreflective performance of the specimen before the test.
Compare and calculate the reflection performance deterioration rate using the following formula.
It was The angle conditions were an observation angle of 0.2 ° and an incident angle of 5 °.

[0048]

[Equation 1]

[0049](2-2) Shrink length (mm)  The shrinkage length of the protective film of the test piece after the weather resistance test
Measured at the part that contracted the most from the
The length was reduced.

[0050](2-3) Protective film peeling length (mm)  The protective film of the test piece after the weather resistance test is the support film
The broken part of the connecting part of the
Measure the broken part and measure the length of the protective film
The peel length was set.

[0051]

INDUSTRIAL APPLICABILITY The present invention comprises at least a light-transmitting protective film, a support film, and a connecting wall formed by heating and melting and deforming the supporting film, the protective film and the supporting film being formed by the connecting wall. In the capsule-type retroreflective sheet, in which the two are partially connected to each other with a gap left between them, and the retroreflective elements are densely arranged over the entire surface of the protective film and / or the support film. The present invention relates to a capsule type retroreflective sheet characterized in that a support film contains a matrix resin and a fibrous substance.

As a result, the support film according to the present invention has an excellent heat melt deformability that can be easily heat deformed and formed, and when subjected to heat melt deformation and formed as a connecting wall,
It is possible to achieve an excellent adhesive strength between the protective film and the connecting wall, and further, it has little distortion as a wall surface forming a capsule, has excellent tensile strength and excellent flexibility capable of withstanding repeated expansion and contraction. In addition, it has excellent outdoor long-term weather resistance, and by doing so, it is possible to solve the drawbacks of the prior art and provide a capsule-type retroreflective sheet having excellent properties.

Claims (9)

[Claims] 1. At least a light-transmitting protective film, a support film, and a connecting wall formed by heating and melting and deforming the supporting film, and the connecting wall forms both the protective film and the supporting film. A capsule-type retroreflective sheet in which retroreflective elements are densely arranged on the entire surface of the protective film and / or the support film, the support film being partially connected while leaving a gap therebetween. A capsule-type retroreflective sheet comprising a matrix resin and a fibrous substance. 2. The capsule type retroreflective sheet according to claim 1, wherein the fibrous substance is contained in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the matrix resin. 3. The capsule-type retroreflective sheet according to claim 1, wherein the fibrous substance has an average fiber length of 1 to 100 μm. 4. The capsule type retroreflective sheet according to claim 1, wherein the fibrous substance has an average fiber diameter of 0.01 to 10 μm. 5. The average aspect ratio of the fibrous material is 2 to 5000.
The capsule type retroreflective sheet according to any one of claims 1 to 4. 6. The fibrous material is a whisker.
5. The capsule-type retroreflective sheet according to any one of 5 above. 7. The capsule-type retroreflective sheet according to claim 6, wherein the whiskers are at least one kind of whiskers selected from the group consisting of alkali metal titanate type whiskers, zinc oxide type whiskers, and silicon carbide type whiskers. 8. The capsule-type retroreflective sheet according to claim 1 or 2, wherein the matrix resin is an acrylic resin having a glass transition temperature in the range of -50 to 30 ° C. 9. The tensile strength of the support film at 23 ° C.
The capsule type retroreflective sheet according to claim 1, which has a breaking elongation of 50% or more and 50 kg / cm ² or more.