JPH03138138A - Laminate and secret label - Google Patents

Abstract

PURPOSE:To release without damaging documents stuck on or the like and making bonding again after releasing impossible by coextruding a layer (protection layer) constituting an opacifying layer and adjacent to a transparent resin layer and laminating them by means of bonding force to be able to release. CONSTITUTION:A layer (protection layer) composed of an opacifying layer, a transparent resin layer A and an adhesive layer laminated in said order and constituting the opacifying layer and adjacent to the transparent resin layer A is coextruded with at least the transparent resin layer A and laminated by bonding force to be able to release. It is preferable that the transparent resin layer A and the protection layer are laminated respectively in the state of being divided clearly when the two layers are coextruded and laminated by using the resin suitable for the purpose. The structure is simplified by said arrangement to make the manufacturing cost lower, and also when the laminate is used as a secret label, it is impossible to bond again once the same is released. Thus, a secret label for superior privacy protection, prevention of alteration and the like is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laminate. More specifically, it is a laminate consisting of a concealing layer/transparent resin layer A/adhesive layer, in which the concealing layer is laminated with peelable adhesion, and its use for privacy protection of communication contents, confidential documents, tampering prevention, etc. It concerns valid secret labels.

[Prior Art] Conventionally, the only way to retain the contents of mail was by mail. For this reason, confidential envelopes are used for communications such as inquiries about bank balances, resulting in high costs.

Therefore, postcards are used instead of envelopes, and the necessary information is printed on the side opposite to the address side, and a secret label is attached to this side through a transparent adhesive layer to hide the information. A secret label has been proposed in which the concealing layer of the secret label is peeled off and used when reading information. Such labels include, for example, ■ one in which a thermoplastic film (ethylene/vinyl acetate copolymer, EVA) is releasably pressed and laminated as in JP-A-63-115191;
．． As in No. 63-21069, a heat seal layer is formed on the peripheral edge of the back side of the postcard, and a tear line is provided on the inside of the heat seal layer. ■It has the following structure: cover/adhesive layer/aluminum foil/adhesive layer/transparent PET layer/adhesive layer/release paper. - There are known adhesives that do not re-adhere once removed.

[Problems to be Solved by the Invention] Each of the conventional secret labels has the following problems.

■Poor slipperiness, heat resistance, and self-supporting properties, easily stretches, and tends to cause false adhesion unevenness. ■In addition to uneven heat sealing, in order to peel off the concealing part, you can use scissors or the like to place a perforation and cut it out along with the postcard, or you can cut it out with a cutter, which can cause the postcard to be cut or damaged. This makes it unsuitable for important postcards, and at the same time, it is troublesome. ■The structure is extremely complicated, and the process is accordingly complicated, which naturally results in high costs.

Moreover, even if you remove the concealing part, be careful (if you put it back on, you won't be able to tell that it was removed, which is a serious drawback for a secret label.) Although it will not re-adhe after peeling off, it will not print because it lacks transparency. The printed text is difficult to read.

The present invention solves the above-mentioned conventional drawbacks, is suitable for industrial production, has a simple structure, and is therefore low cost, yet can be peeled off without damaging attached documents, etc., and furthermore, re-adhesion is impossible after peeling. Furthermore, another object of the present invention is to obtain a laminate which is particularly desirable for use as a secret label with a transparent layer having excellent transparency.

[Means for Solving the Problem] In order to achieve the above object, the present invention has the following configuration:
A laminate in which a hiding layer, a transparent resin layer A1 and an adhesive layer are laminated in this order, and the layer (protective layer) constituting the hiding layer and adjacent to the transparent resin layer A is removable by coextrusion with at least the transparent resin layer A. This is a laminate characterized by being laminated with a strong adhesion.

When the transparent resin layer A of the present invention is laminated with the protective layer by coextrusion, it is preferable that each layer is laminated in a clearly separated state. By doing so, both layers can be peeled off. For this purpose, it is preferable that the resins constituting both layers are different types.

The transparent resin layer A is laminated with the protective layer with peelable adhesion, but the adhesion here refers to the laminate of the present invention after co-extrusion, more preferably co-stretching. When used as a label, it is essential that it does not peel off during processing or delivery, and that it can be easily peeled off when the recipient opens the label.There are no particular restrictions on the adhesion strength, but 2. ~200g/cm, preferably 10~
It is 100g/an.

Furthermore, the transparent resin layer A needs to have transparency. For example, when the laminate of the present invention is used as a secret label, the transparent resin layer A and the adhesive layer can be passed through to display the information written below. It is preferable that information such as characters can be read accurately. For this reason, although not particularly limited, it is preferable that the Haze is 30% or less, preferably 10% or less. From this point of view, it is desirable that the transparent resin layer A has excellent transparency and dimensional stability, and is also inexpensive.

Furthermore, the transparent resin layer A is a non-oriented, -axially oriented, or biaxially oriented film, and the thickness is not particularly limited, but is 0.0000.
A thickness of 2 to 30 μm, preferably 2 to 20 μm, is suitable for the present invention.

Examples of the resin A constituting the transparent resin layer A include polyethylene, polypropylene, polyester, polycarbonate, vinyl chloride, vinyl acetate, copolymers and mixtures thereof, and among them, polyester, more preferably polyethylene terephthalate, has transparency. Preferable in terms of physical properties, price, etc.

The polyesters used in the present invention include polyethylene terephthalate (hereinafter sometimes abbreviated as PET) and its copolymers, polybutylene terephthalate and its copolymers, polyethylene terephthalate and its copolymers, polyethylene bis(2-chloro phenoxy)
Examples include ethane-44'-dicarboxylate and its copolymer, 1,4-polycyclohexylene dimethylene terephthalate (hereinafter sometimes abbreviated as PCT) and its copolymer, polyethylene-2,6-naphthalate, etc. can do. Among them, PET is preferred, but is not limited thereto.

In addition, other polymers may be blended into the resin A, and various known additives such as coloring pigments, lubricants, antistatic agents, antiblocking agents, ultraviolet absorbers, inorganic or organic fillers, etc. may be added. There is no problem even if it contains things.

The concealing layer of the present invention means that, when the laminate of the present invention is used as a secret label, for example, the concealing layer has a concealing property that prevents secret information from being completely read, and is laminated with the transparent resin layer A so that it can be peeled off. There is no particular limitation as long as it is possible.

Examples of the structure of such a concealing layer include ■ a case where it consists only of an opaque protective layer ■ a case where it consists of a light shielding layer/transparent protective layer ■ a case where it consists of a light shielding layer/transparent resin layer B/transparent protective layer. There is no particular limitation as long as the purpose of the invention can be achieved.

The hiding property of the hiding layer requires that it be opaque, and specifically, the OD value measured by the Macbeth densitometer is 0.
．． A value of 7 or more, preferably 1.0 or more is desirable.

The protective layer used in the present invention is a layer that constitutes the hiding layer, is adjacent to the transparent resin layer A, is laminated with the transparent resin layers A and B by coextrusion, and is preferably further co-stretchable.
It is a non-oriented, -axially oriented or biaxially oriented film, and the size is not particularly limited, but it is preferably 5 to 50 μm.
A thickness of 30 μm is suitable for the present invention.

Polymers for the protective layer include polyethylene, polypropylene, polyester, polycarbonate, vinyl chloride,
Examples include vinyl acetate, copolymers and mixtures thereof, but any polymer that can be coextruded with the transparent resin layer A (and transparent resin layer B) and can be peeled off from the transparent resin layer A may be used. Although not limited, polyolefin copolymers are preferred.

Furthermore, the protective layer may contain various known additives such as coloring pigments, lubricants, antistatic agents, antiblocking agents, ultraviolet absorbers, and organic or inorganic fillers. do not have.

The opaque protective layer is generally obtained by adding various known hiding pigments to the protective layer, but is not limited thereto.

Typical hiding pigments include, but are not limited to, titanium oxide, zinc oxide, barium sulfate, calcium carbonate, clay, and kaolin. Also, by adding different types of polymers to create voids,
A method of making it opaque is also possible.

In the present invention, the shielding layer refers to the method and type of shielding as long as the characters are reliably hidden when the laminate of the present invention is applied to the printed area of a postcard, etc., and the shielding layer can be protected as described above. In addition to providing concealment properties to the layer itself to create an opaque protective layer,
Another layer having a hiding property (light-shielding layer) can also be laminated on the protective layer.

At this time, as long as it has the function as a light shielding layer, it is not particularly limited, but it is generally preferable to laminate the light shielding layer by metal vapor deposition or by a method of laminating aluminum foil. Other methods include printing, ink paste application, and opaque paper lamination.

Metal vapor deposition refers to forming a metal thin film on a film surface by a method such as vacuum vapor deposition. The most common method is vacuum evaporation, but other methods include sputtering, ion blasting, and the like. Examples of the metal to be formed into a thin film include aluminum, zinc, and nickel, and among these, aluminum is preferable in terms of vapor deposition properties and characteristics. The thickness of the deposited film is not particularly limited, but is preferably in the range of 3° to 5,000°, preferably 1,000 to 2,000°. If the thickness of the deposited film is too thin, the hiding property will be impaired, and if the thickness of the deposited film is too thick, cracks in the deposited film may occur, which is not preferable.

In the case where the opaque protective layer has sufficient hiding properties, the laminate of the present invention consisting of the hiding layer/transparent resin layer A/adhesive layer may have the structure of the opaque protective layer/transparent resin layer A/adhesive layer. Another light shielding layer may be provided on the opaque protective layer,
When a transparent resin layer B is further provided on the protective layer, a light shielding layer may be provided on the transparent resin layer B.

In this case, the thicknesses of the transparent resin layer A and the transparent resin layer B on both sides of the protective layer may be the same or different within the scope of the present invention. Here, as the resin B constituting the transparent resin layer B, the description for the resin layer A can be applied as is.

The resin B may be the same as or different from the resin A, but if they are the same, it is preferable because they can be laminated by coextrusion using the same extruder.

Further, the transparent resin layer B does not necessarily need to have sufficient transparency since it will be peeled off and removed when a secret label is formed by providing a light shielding layer separately. Furthermore, the above-mentioned various additives may be added to the layer within the scope of the purpose of the present invention.

The adhesive layer can be appropriately selected from known transparent adhesives such as acrylic, silicone, and urethane adhesives, but is not limited thereto.

Further, it is a necessary condition for the purpose of the present invention that the adhesive force be greater than the adhesion force of the concealing layer.

Further, from the spirit of the present invention, it is particularly desirable that the adhesion of each layer constituting the concealing layer is at least greater than the adhesion of the transparent resin layer A and the protective layer.

The laminate having a concealing layer of the present invention can be attached to printed postcards, confidential documents, etc., thereby forming a secret label etc. with extremely excellent confidentiality. It is also applicable to secret documents, etc., in which the secret label of the present invention is attached to pressure-sensitive coloring type paper and then stamped and printed.

Further, the concealing layer can be used by directly printing a company name, a mark, a message, etc., or a layer having another function can be laminated thereon.

The laminate of the present invention has an extremely simple structure of concealing layer/transparent resin layer A/adhesive layer, and is an extremely excellent laminate for secret labels from the viewpoints of process simplification, manufacturing cost reduction, and privacy protection. It can be said.

Next, when actually peeling off the hiding layer and reading the content printed on a postcard, etc., for example, in the case of hiding layer/transparent resin layer A/adhesive layer/printed postcard, which is an example of the laminate of the present invention, , the contents printed on the postcard can be read simply by peeling off the concealing layer.

Next, a specific example of the method for manufacturing a laminate of the present invention will be described.

However, it is not limited to this example.

First, the polymer and resin A used for the protective layer are each supplied to separate extruders, melted, merged in the nozzle and formed into a sheet, and the sheet is wound around a metal roll at about 60°C. It is cooled to form an unstretched two-layer laminated sheet.

Furthermore, the resin B may be supplied to the extruder in the same manner as above and merged with the protective layer in the die to form a three-layer laminate sheet of transparent resin layer A/protective layer/transparent resin layer B. In this case, the thicknesses of the transparent resin layers A and B on both sides may be the same or different.

In addition, when the protective layer has concealing properties and is used as a concealing layer,
The masking agent may be added to the polymer in advance.

Next, the laminated sheet is stretched 3.0 to 4.5 times in the longitudinal direction at a temperature of 80 to 120 °C and 3.0 to 5.5 times in the transverse direction at a temperature of 90 to 120 °C, then 120-25
Heat treatment at a temperature of 0°C.

If the thus obtained laminated film has a protective layer with concealing properties, it will remain as it is; if it does not, it will be added to the protective layer in the case of two layers, and the transparent resin layer B in the case of three layers.
is provided with at least one light-shielding layer. Thereafter, by providing an adhesive layer on the transparent resin layer A on the opposite side to the light shielding layer, a laminate having a concealing layer of the present invention can be obtained.

Next, a general method for processing a secret label, which is a typical application example of the laminate of the present invention, will be described.

This is just an example and is not limiting.

First, a secret label, which is an application example of the present invention, can be made by attaching a release paper to the adhesive layer side of the laminate having the concealing layer obtained as described above.

Next, a pressure-sensitive coloring type secret document will be described. The paper used for secret documents is coated almost entirely on one side with a well-known self-coloring layer that is colored by the coloring reaction of a coloring agent released when the capsules break when pressurized. be. When the secret label of the present invention is attached to this paper and predetermined information is stamped (blank stamp) using a wire dot printer or the like without using a printing ribbon, the printing pressure of the printer head is applied via the secret label to the color development in the self-coloring layer. When the drug capsule is destroyed, a coloring reaction occurs, and a predetermined color is developed, resulting in colored printing on the paper mount. This coloring state is
It is hidden from the outside by a secret label with a concealing layer and does not appear on the surface at all. The color-printed description can only be read through the transparent resin layer A after the recipient of the document peels off the concealing layer.

Such a secret document can be used as a confidential document, a confidential document, a postcard, or the like.

The actual method of using a secret label is to attach the secret label of the present invention with the release paper removed to a pre-printed postcard or confidential document, and when the recipient opens the package, the protective layer and transparent resin layer A are attached. If the gap is peeled off, the transparent resin layer A with the transparent adhesive layer remains on the printed surface of the postcard, etc., and the printed content can be clearly read.

This hiding layer is ideal as a secret label because it will not stick again once it is peeled off.

[Effects of the Invention] The laminate of the present invention has an extremely simplified structure and low manufacturing cost, and when used as a secret label, unlike conventional secret labels,
- Once peeled off, no adhesive is used, so re-adhesion is impossible, making it a secret label with excellent privacy protection and tampering prevention.

In addition, it is possible to directly print company names, marks, messages, etc. on the surface of the concealing layer, and the secret label of the present invention can also be applied to secret documents of the pressure-sensitive coloring type without any changes in the structure. be.

[Measurement method] The measurement method and evaluation criteria for physical properties, etc. used in the present invention are as follows.

(1) Film adhesion When the width of the laminate is W (cm), the transparent resin layer when the hiding layer and the transparent resin layer A are continuously peeled off at a peeling angle of 180 degrees at a speed of 200 mm/min. The tension applied to A was measured using a tension meter. If this tension is T (g), the adhesion force can be determined as T/W (g /cm).

■ Film thickness of metal vapor deposition Measured by atomic absorption spectrophotometry.

(3) Hiding property OD optical density was measured using a transmission densitometer model TD-504 manufactured by Macbeth. 106-Visual was used as a filter. The measured OD value is a value derived from the following formula,
OD = −l o g (T/10
0)(4) Transparency (Haze) Measured using a Haze meter according to JIS K 6714.

[Example] Hereinafter, the present invention will be described in detail based on examples.

Example 1 (1) Manufacture of laminated film The following two types of raw materials were prepared.

Protective layer: Propylene/ethylene random copolymer (hereinafter sometimes abbreviated as EPC) with a melting point of 130°C and an ethylene content of 6% by weight.Transparent resin layers A, B, and B: Polyethylene terephthalate (hereinafter abbreviated as PET) IVQ.

65, melting point 260℃, average as external Wet silica with a particle size of 0.5 μm. Contains 5%.

These two types of raw materials are supplied to separate extruders and melt-extruded at 280°C, and the respective melts are combined in a T-type nozzle to form a three-layer structure of PET/EPC/PET.
It was wrapped around a hot water drum at ℃ and cooled and solidified to form a three-layer laminated sheet.

After heating this sheet to 90°C, 3.
It was stretched 5 times and immediately cooled. Then again at 100'C
Stretched by 4.5 times in the width direction, heat treated at 180°C for 6 seconds while maintaining tension, then stretched by 5%
The sample was relaxed, slowly cooled to room temperature, and rolled up. In this way, a three-layer laminate film was obtained, each having a thickness of 2 μm for PET and 5 μm for EPCJi.

This film roll was applied to a vacuum evaporator with a width of 500 nm, and 1000 nm of aluminum was applied to one side of the PET film.
It was deposited to a thickness of .

■ Manufacture of secret label Using this vapor-deposited laminated film, a 5 μm adhesive layer was provided on the transparent PET layer on the opposite side to the vapor-deposited surface using an acrylic adhesive, and a secret label with the following structure was made.

AI vapor-deposited PET/EPC/PET, "Adhesive Layer (3)" A secret label that has been evaluated is pasted on a printed postcard.This postcard with a secret label has concealability even when viewed through or when exposed to light from the back. Unfortunately, it was impossible to read the print on the postcard.Next, when I peeled the surface from the edge, it peeled off cleanly between the AI vapor-deposited PET/EPC and the transparent PET, and the print on the postcard could be clearly read. This peeled surface could not be re-adhered and the two layers could not be restored to their original state.The adhesive strength of this peeled surface was 20 g/cm, and an extremely excellent secret label was obtained.

Example 2 A film was formed in exactly the same manner as in Example 1, except that 20 wt % of calcium carbonate was added to the EPC of the protective layer to make an opaque protective layer, and a two-layer structure of opaque EPC/PET was formed.
A laminated film having a thickness of 0 μm and a thickness of PET of 5 μm was created.

Using this light-shielding laminated film, a 5 μm adhesive layer was applied to the transparent PET surface using a silicone adhesive.
I created a secret label with the following configuration.

Opaque EPC/PET, Adhesive Layer The secret label was extremely excellent as in Example 1, and the adhesion between the opaque EPC and PET was 30 g/cm.

Example 3 The following two types of raw materials were prepared.

Protective layer: copolymerized with 95 mol% of tephthalic acid and 5 mol% of isophthalic acid as acid components and 100% of cyclohexane dimetatool as diol component, melting point 284°C, average particle size 0. Contains 0.5% wet silica of 5 μm (
Hereinafter, it may be abbreviated as PCT. ) Transparent resin layer A: polyethylene terephthalate, IvO 165, melting point 26
0°C, containing 0.5% wet silica with an average particle size of 0.5 μm externally. These two types of raw materials were fed into separate extruders and melt-extruded at 295°C, and each melt was placed in a T-shaped nozzle. They were combined to form a two-layer structure of PCT/PET, which was wound around a hot water drum at 60° C. and cooled and solidified to form a two-layer laminated sheet.

After heating this sheet to 105℃,
．． It was stretched 5 times and immediately cooled. Next, the film was heated again to 105° C., stretched 3.5 times in the width direction, and heat-treated at 230° C. for 6 seconds while maintaining tension, followed by 5% relaxation, slow cooling, cooling to room temperature, and winding. Thus, the thickness of the PCT layer is 10 μm and the thickness of the PET layer is 5 μm.
A laminated film was obtained.

A 50 μm AI foil is laminated on the PCT side of this laminated film using a urethane adhesive to provide a concealing layer, and an adhesive layer is formed on the transparent PET side using a urethane adhesive. Created a secret label for the configuration.

AI foil/PCT/PET, - Adhesive layer evaluation results were extremely excellent as in Example 1.2, and the adhesion between the AI foil/PCT and PET layer was 50 g/cm.

Comparative Example 1 A secret label having the most common configuration as follows was created by using an acrylic adhesive for the adhesive layer without using the laminate having the concealing layer of the present invention.

Cover - Adhesive layer/Al foil, Adhesive layer transparent PET,
It has a very complicated structure, including an adhesive layer and release paper, which is time-consuming and expensive.

The obtained secret label was attached to a printed postcard by peeling off the release paper. Although the hiding property was good, it often took time to peel between the AI foil and the transparent PET.

If you peel it off, you can read the print on the postcard. When I carefully put it back, I found out that it was a secret label that had no way of knowing that it had been opened, and had a very serious drawback in terms of privacy protection.

Note that the adhesion between the AI foil and PET was 80 g/cm.

Claims (5)

[Claims] (1) A laminate in which a hiding layer, a transparent resin layer A, and an adhesive layer are laminated in this order, and the layer (protective layer) that constitutes the hiding layer and is adjacent to the transparent resin layer A is at least the same as the transparent resin layer A. A laminate characterized by being laminated by extrusion with adhesive strength that allows for peeling. (2) The laminate according to claim (1), wherein the hiding layer comprises an opaque protective layer. (3) The laminate according to claim (1), wherein the hiding layer consists of a light shielding layer/transparent resin layer B/transparent protective layer. (4) A secret label using the laminate according to any one of claims (1) to (3). (5) A secret document obtained by attaching the secret label according to claim (4) to pressure-sensitive coloring type paper.