TW201730305A - Double sided adhesive tape - Google Patents

Abstract

Disclosed is a double sided adhesive tape having a laminated substrate comprising at least one light colored print layer 2 between a resin film 1 and a black print layer 3, and an adhesive layer 4 on both sides of the laminated substrate, wherein the black print layer 3 contains a structure derived from an aromatic isocyanate based curing agent, and the double sided adhesive tape. The blocking and wrinkle of the laminated substrate hardly occur, the adhesive layer 4 on the side of a light reflecting layer hardly causes yellowing, and the lightness (reflectance) of the light reflecting layer can be easily adjusted. The double sided adhesive tape is useful for fixing a backlight unit to a liquid crystal display.

Description

Double-sided adhesive tape

The present invention is useful for improving the brightness of a backlight surface of a liquid crystal display device used in, for example, a mobile phone or a touch panel, and preventing deterioration of visibility due to light leakage, and has both functions of light reflectivity and light blocking. Adhesive tape.

For example, in a liquid crystal display device used in a mobile phone or a touch panel, a double-sided adhesive tape is provided between the liquid crystal display unit and the backlight unit, whereby the two members are fixed. Further, the double-sided adhesive tape has, for example, a white light-reflecting layer and a black light-shielding layer, and contributes to improvement in luminance of the backlight surface and prevention of deterioration in visibility due to light leakage from the backlight. Such a double-sided adhesive tape which contributes to both the brightness enhancement and the light-shielding property is disclosed, for example, in Patent Documents 1 to 4.

The light-reflecting layer of the double-sided adhesive tape disclosed in Patent Document 1 is composed of a biaxially stretched resin film of a polyester resin containing a white colorant. However, such a light-reflecting layer composed of a resin film containing a colorant has poor productivity and is difficult to adjust brightness (reflectance).

The light-reflecting layer of the double-sided adhesive tape disclosed in Patent Document 2 is a white printed layer, and the light-shielding layer is a black printed layer. The printed layer is superior in productivity to the resin film containing the colorant, and the brightness (reflectance) is also easily adjusted. However, the laminated substrate used for the double-sided adhesive tape is formed by a laminated structure of a black printed layer/resin film/white printed layer, and if the laminated substrate is wound up in a roll shape, the printed layer is printed. Contact will cause a sticky condition. Therefore, it is necessary to provide an anti-adhesive film (thin coating layer) on the outer side of one of the printed layers. Moreover, according to the findings of the inventors of the present invention, the double-sided adhesive tape using such a laminated base material tends to cause yellowing of the adhesive layer on the side of the white printed layer (on the light-reflecting layer side). This phenomenon is considered to be because the white printed layer is in direct contact with the adhesive layer, so that the ink component in the white printed layer migrates to the adhesive layer, resulting in discoloration of the adhesive layer. The yellowing of the adhesive layer on the side of the light-reflecting layer causes the luminance of the backlight surface to decrease and the visibility to deteriorate. Moreover, since the laminated base material disclosed in Patent Document 2 is provided with a printing layer on both sides, when the laminated substrate is pulled out in the application step of the adhesive, the printed layer is in contact with the guide roller and is easily damaged. Further, when fine punching processing such as a narrow bezel shape is performed, there is a possibility that the printed layer is peeled off.

The double-sided adhesive tape disclosed in Patent Document 3 is used on one side of a transparent plastic substrate, and is provided with a laminated substrate of both a white printed layer and a black printed layer. However, according to the findings of the inventors of the present invention, if the laminated substrate is wound up in a roll form immediately after its manufacture, the surface of the printed layer may become sticky due to sticking or may be caused by friction during winding. Wrinkling occurs. These phenomena are considered to be caused by insufficient curing speed of the black printed layer at the time of production of the laminated substrate.

The double-sided adhesive tape disclosed in Patent Document 4 uses a laminated substrate provided with a light shielding layer (black printed layer) on one side of the resin film. Further, the binder resin in which the light shielding layer (black printing layer) is described is a polyurethane resin having a Tg (tan δ peak temperature) of -30 ° C to 30 ° C, and an aliphatic or alicyclic isocyanate is used as the curing agent. However, according to the findings of the inventors of the present invention, when such a binder resin and a curing agent are used, the curing rate of the printed layer is insufficient, and thus, adhesion or wrinkling may occur as described above.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-156015

Patent Document 2: Japanese Patent Laid-Open Publication No. 2011-95764

Patent Document 3: Japanese Patent Laid-Open Publication No. 2009-197124

Patent Document 4: Japanese Patent Laid-Open Publication No. 2010-53240

An object of the present invention is to provide a double-sided adhesive tape having both light reflectivity and light-shielding properties, which is less likely to cause adhesion and wrinkling of the laminated substrate, and the adhesive layer on the light-reflecting layer side is not easily yellowed, and the light-reflecting layer is A double-sided adhesive tape whose brightness (reflectance) is easily adjusted and a method of manufacturing the same. Another object of the present invention is to provide a simple manufacturing method of the double-sided adhesive tape.

The inventors of the present invention have intensively studied in order to achieve the above object, and have found that it is very effective to use a laminated substrate having a specific layer structure, and the black printed layer is composed of specific components, and the present invention has been completed.

A double-sided adhesive tape according to a first aspect of the present invention, comprising: a laminated substrate having at least one layer of a bright printed layer between a resin film and a black printed layer; and an adhesive layer provided on both sides of the laminated substrate; The black printed layer contains a structure derived from an aromatic isocyanate curing agent.

A double-sided adhesive tape according to a second aspect of the present invention, comprising: a laminated substrate having at least one layer of a bright printed layer between a resin film and a black printed layer; and an adhesive layer provided on both sides of the laminated substrate; The static printing force of the black printed layer to the resin film according to JIS K 7125 in the laminated substrate is 2.0 N or less.

Further, the method for producing a double-sided adhesive tape of the present invention is a method for producing the double-sided adhesive tape of the first or second aspect of the invention, characterized in that the black printed layer is formed by a single step.

According to the present invention, it is possible to provide a double-sided adhesive tape in which the laminated substrate is less likely to be sticky and wrinkled, the adhesive layer on the side of the light-reflecting layer is less likely to yellow, and the brightness (reflectance) of the light-reflecting layer is easily adjusted. Further, according to the present invention, a method of easily manufacturing such a double-sided adhesive tape can be provided.

1‧‧‧Resin film

2‧‧‧ Bright print layer

3‧‧‧Black printed layer

4‧‧‧Adhesive layer

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing an embodiment of a double-sided adhesive tape of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing an embodiment of a double-sided adhesive tape of the present invention. In the present embodiment, the laminated substrate is provided between the resin film 1 and the black printed layer 3 serving as a light shielding layer, and is provided with a bright printed layer 2 as a light reflecting layer. Then, an adhesive layer 4 is provided on both sides of the laminated substrate. Since the bright printed layer 2 (light reflecting layer) and the adhesive layer 4 are not in direct contact with each other, the ink composition of the printed layer does not migrate to the adhesive layer on the side of the bright printed layer 2 (light reflecting layer). 4, it is not easy to yellow. As a result, the transmittance on the light reflection side is not lowered, and for example, the luminance or the visibility of the backlight surface can be prevented from being lowered. On the other hand, the black printed layer 3 (light-shielding layer) is in direct contact with the adhesive layer 4, but the transmittance of the adhesive layer 4 on the side of the light-shielding layer is lowered, and the structure does not cause any hindrance to the light-reflecting function. Therefore, it does not pose a problem in this regard.

Furthermore, the laminated substrate of the present invention has the above specific layer structure, Therefore, when the laminated substrate is just after the production (before the formation of the adhesive layer 4), when the laminated substrate is wound up in a roll shape, the resin film 1 and the black printed layer 3 are in contact with each other, compared with the conventional technique. When the printed layer is in contact with the black printed layer, it is less likely to cause sticking and wrinkling. Further, as will be described later, the black printing layer of the first aspect of the present invention has a high curing speed, and the second embodiment of the present invention has a low static friction force, and thus these layers are multiplied by a specific layer structure of the laminated base material, and The effect of preventing sticking and wrinkling is more pronounced.

The double-sided adhesive tape shown in Fig. 1 is a preferred embodiment of the present invention, but the present invention is not limited thereto. For example, the double-sided adhesive tape shown in Fig. 1 is composed of a single-layer bright printed layer 2, but a light-reflecting layer may be formed of a laminate of two or more bright-colored printed layers 2 as needed. Further, the double-sided adhesive tape shown in Fig. 1 is composed of a single layer of black printed layer 3, but a light-shielding layer may be formed of two or more black printed layers 3 as needed.

Furthermore, the double-sided adhesive tape shown in FIG. 1 directly laminates the bright printed layer 2 and the black printed layer 3 on the resin film 1, but may be printed between the resin film 1 and the bright printed layer 2, or in a bright color. There are any other layers between the layer 2 and the black printed layer 3. Further, the double-sided adhesive tape shown in Fig. 1 is formed by directly laminating the adhesive layer 4 on the outer surface of the resin film 1 and the outer surface of the black printed layer 3, but may be present between the outer side surfaces and the adhesive layer 4. Any other layer.

[Resin film 1]

The resin film 1 of the present invention is not particularly limited, and various known resin films which can be used for such an adhesive tape can be used. Preferably, it is made of a transparent plastic film composed of, for example, polyester, polyolefin, polyurethane, polyamide, polyimide, polystyrene, etc. From the viewpoints of easiness, strength stability, and the like, a polyester film such as a PET (polyethylene terephthalate) film is more preferable.

The thickness of the resin film 1 is appropriately determined in accordance with the thickness of the required double-sided adhesive tape. In particular, from the viewpoint of reworkability and the like, the thickness is preferably 2 to 50 μm, more preferably 6 to 38 μm.

[Bright print layer 2]

The bright color printing layer 2 of the present invention is not particularly limited, and various known bright color printing layers capable of imparting a necessary light reflecting function to the adhesive tape can be used. The bright color printed layer 2 is easier to adjust the brightness (reflectance) of the light reflecting layer than the light reflecting layer composed of the resin film containing the coloring agent described in Patent Document 1. Here, "bright color" means a color such as white or light color which can impart a light reflecting function. It is particularly preferably white. Specifically, the L* (brightness) defined by the L*a*b* chromaticity system of the bright printed layer 2 is preferably 65 or more, and more preferably 75 or more. The bright printed layer 2 preferably has a reflectance at a wavelength of 550 nm of 45% or more, more preferably 65% or more. Further, the average reflectance at a wavelength of 380 to 780 nm is preferably 40% or more, more preferably 60% or more.

The bright printed layer 2 is usually formed using an ink composition by a known printing method. The ink composition contains, for example, a coloring component (ink component), a binder resin, and a curing agent. Specific examples of the binder resin include a polyurethane resin, a phenol resin, an epoxy resin, a polyoxyn resin, an acrylic resin, a polyester resin, and a polyolefin resin. Among them, a polyurethane resin is preferred. Resin. Specific examples of the curing agent include an aromatic isocyanate curing agent, an aliphatic isocyanate curing agent, and an alicyclic isocyanate curing agent. Among them, an aromatic isocyanate curing agent is preferred. The composition ratio of each component can be a known composition ratio, and can be appropriately determined as needed.

The ink composition used in the bright printed layer 2 can be obtained, for example, by blending a curing agent in a commercially available printing ink containing a coloring component (ink component) and a binder resin.

The thickness of the light-reflecting layer composed of the bright-color printed layer 2 is appropriately determined in accordance with the thickness and light reflectivity of the required double-sided adhesive tape. The thickness of the light reflecting layer is preferably 1 to 20 μm, more preferably 3 to 12 μm. The bright printed layer 2 may be composed of a single-layer light-reflecting layer. However, from the viewpoint of imparting sufficient light reflectivity, it is preferable to form a light-reflecting layer by laminating two to six bright printed layers 2 .

[Black Print Layer 3]

The black printed layer 3 of the present invention is usually formed by a known printing method using an ink composition. The ink composition contains, for example, a coloring component (ink component), a binder resin, and a curing agent.

Specific examples of the binder resin used in the black printing layer 3 include a polyurethane resin, a phenol resin, an epoxy resin, a polyoxyn resin, an acrylic resin, a polyester resin, and a polyolefin. A resin, preferably a polyurethane resin, more preferably a polyester polyurethane resin. The "polyester polyurethane resin" refers to a polyurethane resin containing an ester bond in a molecular chain. Both aliphatic and aromatic polyester polyurethane resins can be used. The polyester polyurethane resin can be obtained, for example, by reacting a polyester polyol with a polyisocyanate and optionally other components. The Tg (glass transition temperature) of the binder resin is preferably higher. The specific binder resin Tg is preferably at least 12 ° C. Thereby, even if the black printing layer 3 is hardened at an initial stage, the viscosity can be lowered, and the laminated substrate is less likely to be sticky or wrinkled.

Specific examples of the hardener used in the black printed layer 3 are exemplified For example, an aromatic isocyanate curing agent, an aliphatic isocyanate curing agent, and an alicyclic isocyanate curing agent. However, in the first aspect of the invention, the curing agent used for the black printing layer 3 is an aromatic isocyanate curing agent. Thereby, the hardening speed of the black printing layer 3 is accelerated, and the laminated substrate is less likely to be sticky and wrinkled.

The "aromatic isocyanate curing agent" is a curing agent containing at least an aromatic isocyanate. The "aromatic isocyanate" means a compound having an aromatic group such as a benzene ring and an isocyanate group, and usually has two or more isocyanate groups. The aromatic isocyanate is preferably, for example, a compound having a benzene ring and two isocyanate groups, more preferably benzoyl diisocyanate. The aromatic isocyanate curing agent generally contains an adduct of an aromatic isocyanate (an adduct of a diisocyanate and trimethylolpropane) and an isocyanurate (a trimer of a diisocyanate).

The blending amount of the hardener is preferably 4 to 16 parts by mass, more preferably 6 to 12 parts by mass, per 100 parts by mass of the printing ink.

The ink composition used in the black printing layer 3 can be obtained, for example, by blending a curing agent in a commercially available printing ink containing a coloring component (ink component) and a binder resin.

The thickness of the light-shielding layer composed of the black printed layer 3 is appropriately determined in accordance with the thickness and light-shielding property of the required double-sided adhesive tape. The thickness of the light shielding layer is preferably 1 to 8 μm, more preferably 3 to 6 μm, and particularly preferably 4 to 6 μm. The black printed layer 3 may be composed of a single-layer light-shielding layer, or may be formed by laminating a plurality of black printed layers 3 to constitute a light-reflecting layer. However, since the black printing layer 3 of the present invention has a high curing speed, the light-shielding layer can be satisfactorily formed by using the single-layer black printing layer 3, and the manufacturing steps can be simplified.

[Adhesive layer 4]

The adhesive layer 4 of the present invention is not particularly limited, and various known adhesive layers which can be used for such an adhesive tape can be used. The adhesive to be used for the adhesive layer 4 may, for example, be a transparent adhesive such as an acrylic adhesive, a rubber adhesive, an amine ester adhesive, a polyester adhesive, or a polyoxygen adhesive. Among them, an acrylic adhesive, an amine ester adhesive, and a polyoxygen adhesive are preferred.

In the adhesive layer 4, an adhesive resin or a crosslinking agent may be added as needed. Examples of the tackifying resin include rosin-based, polydecene-based, petroleum-based, terpene-based, and polystyrene-based resins. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a metal chelate crosslinking agent.

The thickness of the adhesive layer 4 is appropriately determined in accordance with the thickness of the required double-sided adhesive tape. Usually, the thickness is preferably 2 to 50 μm, more preferably 5 to 30 μm.

[Laminated substrate]

The laminated substrate of the present invention is a substrate having at least the resin film 1, the bright printed layer 2, and the black printed layer 3 described above. The thickness of the laminated substrate is appropriately determined in accordance with the thickness of the double-sided adhesive tape required. Generally, the thickness is preferably 10 μm to 50 μm, more preferably 12 to 50 μm.

In the laminated substrate of the second aspect of the invention, the static printing force of the black printed layer to the resin film according to JIS K 7125 is 2.0 N or less, preferably 1.4 to 1.8 N. Since the laminated substrate has such a low static friction force, when the laminated substrate is wound up in a roll form immediately after manufacture, it is less likely to cause sticking, and it is less likely to cause wrinkles due to friction during winding.

The method of measuring the static friction force is based on JIS K 7125. On the resin film 1 of the laminated base material, another laminated base material fixed by a weight of 200 g is placed adjacent to the black printed layer 3, and the sliding piece is made to have a speed of 300 mm. /minute parallel movement, determination The maximum stress (static friction) initially obtained. Details will be described in detail in the examples to be described later.

According to the second aspect of the invention, the laminated substrate having a low static friction force can be obtained by appropriately selecting the conditions such as the type of the curing agent of the black printing layer and the type of the binder resin. The curing agent is preferably an aromatic isocyanate curing agent (first invention) as described above. However, the second invention is not limited to this. Even in the case where an aromatic isocyanate-based curing agent is not used, a laminated substrate having a low static friction can be obtained by using, for example, a binder resin having a high Tg.

[double-sided adhesive tape]

The double-sided adhesive tape of the present invention has the laminated base material described above and an adhesive tape of the adhesive layer 4 provided on both surfaces of the laminated substrate. The double-sided adhesive tape of the invention can avoid the situation that the printed layer is sticky or the adhesive layer is yellowed, so it is suitable for the liquid crystal display panel of the liquid crystal display device used in the mobile phone, the touch panel, etc., and the backlight unit. Fixed.

[Manufacturing method of double-sided adhesive tape]

The laminated substrate of the present invention can be produced, for example, by forming a bright printed layer 2 on the resin film 1 and forming a black printed layer 3 thereon.

The method for producing the double-sided pressure-sensitive adhesive tape according to the first aspect of the invention includes, for example, a step of forming a black printed layer 3 using an ink composition containing a coloring component (ink component), a binder resin, and an aromatic isocyanate-based curing agent. Preferably, the method includes the steps of: forming a bright printed layer 2 on the resin film 1, forming a black printed layer 3 on the bright printed layer 2 using the ink composition, and obtaining a laminated substrate, and the laminated substrate. The step of forming the adhesive layer 4 on both sides.

The method for producing the double-sided adhesive tape according to the second aspect of the invention includes, for example, a step of forming a black printed layer 3 with a laminated base material having a static frictional force of 2.0 N or less according to JIS K 7125. Preferably, the method includes the steps of: forming a bright printed layer 2 on the resin film 1; forming a black printed layer 3 on the bright printed layer 2, and obtaining a black printed layer 3 against the resin film 1 according to JIS K 7125 a step of laminating a substrate having a force of 2.0 N or less; and a step of forming an adhesive layer 4 on both sides of the laminated substrate.

According to each of the above production methods, when the laminated base material is wound up in a roll shape immediately after the production, the adhesion is less likely to occur, and wrinkles are unlikely to occur due to the frictional force during winding.

Another method of the present invention forms the black printed layer 3 in a single step. Preferably, the method comprises the steps of: forming a bright printed layer on the resin film, forming a black printed layer on the bright printed layer in a single step to obtain a laminated substrate; and forming an adhesive on both sides of the laminated substrate. The step of the agent layer.

A conventional black printed layer for light-shielding is formed by stacking 2 to 3 layers in order to obtain sufficient light-shielding properties. However, the black printed layer 3 of the present invention can form a sufficient light shielding layer in a single step. Thereby, it is possible to avoid the problem that the unevenness of the unevenness of the surface of the coating surface is large, and the adhesion is likely to occur, and the manufacturing step of the laminated substrate can be greatly reduced.

A printing method of the bright printed layer 2 and the black printed layer 3 can be a known printing method. Specific examples of the printing method include, for example, a gravure printing method, an elastic printing method, a lithography method, a letterpress printing method, and a screen printing method. Among them, a gravure printing method is preferred.

[Examples]

Hereinafter, the present invention will be further described by way of examples, but the present invention is not limited to the examples. In the following description, "parts" means "parts by mass".

<Binder resin composition 1 to 3 and comparative binder resin composition C1 to C7>

The binder resin composition 1 to 3 and the comparative binder resin composition C1 to C7 were obtained by blending 13.0 parts of the curing agent with respect to 100 parts of the binder resin shown in Tables 1 and 2. In the glass transition temperature (Tg) described in the table, the Tg-based DSC measurement value of the binder resin b1 and the glass transition temperature (Tg) of the binder resins b2 to b5 are based on the values provided by the manufacturer's information.

(phase adhesion test)

A binder resin composition was laminated on one side of a transparent PET (polyethylene terephthalate) film having a thickness of 12 μm so as to have a thickness of 5 μm to obtain a binder coating film having a total thickness of 17 μm. The adhesive coating film was cut into a size of 30 mm × 40 mm to obtain a test piece. The test piece was superposed on 5 sheets, sandwiched by a glass plate having a thickness of 1.5 mm, and placed in a 2 kg hammer, and allowed to stand at 40 ° C for 2 days. Then, each test piece was peeled off and evaluated visually according to the following criteria. The results are shown in Tables 1 and 2.

"○": There is a stickiness.

"X": No stickiness occurred.

(probe viscosity)

The viscosity of the probe was measured by a test method according to JIS Z 0237. Specifically, the adhesive resin coating layer side of the same adhesive film as the phase adhesion test was placed on a SUS cylinder having a diameter of 3 mm for 1.0 second under a load of 20 g, and then torn at a speed of 1.0 cm/sec. The adhesion force at this time was measured, and the average value of the five test values was set as the probe viscosity (N). The results are shown in Tables 1 and 2.

(static friction)

The static friction force (the layer of the adhesive resin composition of the transparent PET film of the same adhesive film as the adhesion test film to the adhesive coating film) was measured by the test method according to JIS K 7125. Specifically, the transparent PET film was placed side up, and a binder coating film was fixed on the test platform. On the other hand, another adhesive coating film (size: 25 mm × 25 mm) was fixed on a slide having a weight of 200 g. Then, according to the surface of the transparent PET film on which the adhesive film is fixed on the test platform, and the layer of the adhesive resin composition of the adhesive film fixed on the sliding film, the slide is quietly placed on the test platform. sheet. The slide was moved in parallel at a speed of 300 mm/min, and the maximum stress (static friction) initially obtained was measured. The results are shown in Tables 1 and 2.

In Tables 1 and 2, each code indicates the following product.

"b1": polyester polyurethane resin (trade name, manufactured by Toyo Ink Co., Ltd.) E039 ink medium Z)

"b2": Polyester polyurethane resin (manufactured by Toyobo Co., Ltd., trade name UR1400)

"b3": polyester polyurethane resin (manufactured by Nippon Polyurethane Industrial Co., Ltd., trade name Nipporan 2304)

"b4": polyester polyurethane resin (manufactured by Nippon Polyurethane Industrial Co., Ltd., trade name Nipporan 3124)

"b5": Polyester polyurethane resin (manufactured by Sanyo Chemical Industry Co., Ltd., trade name SANPRENN IB-129)

"ar-i": benzoyl diisocyanate (aromatic isocyanate curing agent) (manufactured by Toyo Ink Co., Ltd., trade name TK HARDENER)

"al-i": hexamethylene diisocyanate (aliphatic isocyanate curing agent) (manufactured by Toyo Ink Co., Ltd., trade name LP HARDENER)

<evaluation>

As is apparent from the results shown in Table 1, the binder resin compositions 1 and 2 using an aromatic isocyanate curing agent (ar-i) were excellent in all characteristics. On the other hand, the binder resin compositions C1 to C4 using an aliphatic isocyanate-based curing agent (al-i) have a phase stickiness in the phase adhesion test, and the probe has high viscosity.

Further, as a result of the results shown in Table 2, it was found that the aromatic isocyanate curing agent (ar-i) was not used, and the low static friction binder resin composition 3 was used, and all of the properties were excellent. On the other hand, the high static friction binder resin composition C5~C7 has a sticky state in the phase adhesion test, and the probe viscosity is also high.

<Example 1> (Preparation of black ink composition 1)

Black ink (manufactured by Toyo Ink Co., Ltd., trade name E039PETAK ink) was prepared. This black ink is a product in which the resin is colored black in the same manner as the binder resin b1 of the binder resin composition 1 described above. 8.0 parts by mass of an aromatic isocyanate curing agent (trade name: TK HARDENER, manufactured by Toyo Ink Co., Ltd.) having the same curing agent (ar-i) as that of the binder resin composition 1 is blended with 100 parts of the black ink. Black ink composition 1 was obtained.

(Preparation of white ink composition)

White ink (manufactured by Toyo Ink Co., Ltd., trade name E039PET63 white) was prepared. This white ink is a product in which the same resin as the binder resin b1 of the binder resin composition 1 described above is colored in white. An amount of 6.0 parts by mass of an aromatic isocyanate-based curing agent (manufactured by Toyo Ink Co., Ltd., trade name TK HARDENER) having the same curing agent (ar-i) as that of the binder resin composition 1 was added to 100 parts of the white ink. A white ink composition was obtained.

(Production of laminated substrate A)

On a single side of a transparent PET film having a thickness of 12 μm, a white ink composition was used for two times of gravure printing to form a white printed layer having a thickness of 6 μm (L* (brightness) = 83.47, and a reflectance of 74.4% for a wavelength of 550 nm, The average reflectance at a wavelength of 380 to 780 nm = 69.5%). Further, on the surface of the white printed layer, the black ink composition 1 was subjected to gravure printing once to form a black printed layer having a thickness of 5 μm, thereby obtaining a laminated substrate A having a total thickness of 23 μm.

(Preparation of acrylic adhesive composition)

In a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, 70.0 parts of 2-ethylhexyl acrylate, 29.9 parts of n-butyl acrylate, and 0.1 part of 4-hydroxybutyl acrylate were charged. 0.1 parts of a chain transfer agent and 0.1 part of a peroxide-based radical polymerization initiator. Nitrogen gas was sealed in the reaction apparatus, and polymerization was carried out at 68 ° C for 3 hours while stirring under a nitrogen stream, and then polymerization was carried out at 78 ° C for 3 hours. Then, it was cooled to room temperature, and ethyl acetate was added. Thereby, an acrylic copolymer having a solid concentration of 30% was obtained. In the acrylic copolymer, 0.3 part of a curing agent (manufactured by Nippon Polyurethane Co., Ltd., trade name: CORONATE L-45E) was blended to obtain a transparent acrylic pressure-sensitive adhesive composition.

(production of double-sided adhesive tape)

A transparent acrylic adhesive composition was applied to both surfaces of the laminated substrate A to form an adhesive layer having a thickness of 18 μm, and the adhesive layer 4/black printed layer 3/white printed layer shown in Fig. 1 was obtained. The laminated structure of the bright printed layer 2)/resin film 1/adhesive layer 4 formed by the secondary printing constitutes a double-sided adhesive tape having a total thickness of about 60 μm.

<Example 2> (Production of laminated substrate B)

A laminated substrate B having a total thickness of 17 μm was produced in the same manner as the laminated substrate A of Example 1 except that a transparent PET film having a thickness of 6 μm was used.

(production of double-sided adhesive tape)

A double-sided adhesive tape having a total thickness of about 60 μm was produced in the same manner as in Example 1 except that the laminated substrate B was used and the thickness of the adhesive layer was changed to 21 μm.

<Comparative Example 1> (Preparation of black ink composition 2)

The black ink of Example 1 was used except that an aliphatic isocyanate curing agent (manufactured by Toyo Ink Co., Ltd., trade name LP HARDENER) similar to the curing agent (al-i) of the binder resin composition C1 was used. Composition 1 The black ink composition 2 was prepared in the same manner.

(Production of laminated substrate C)

A laminated substrate C having a total thickness of 23 μm was obtained in the same manner as the laminated substrate A of Example 1 except that the black ink composition 2 was used.

(production of double-sided adhesive tape)

A double-sided adhesive tape having a thickness of about 60 μm was produced in the same manner as in Example 1 except that the laminated substrate C was used.

<Comparative Example 2> (Production of laminated substrate D)

On the one side of the transparent PET film having a thickness of 12 μm, the white ink composition was subjected to secondary gravure printing to form a white printed layer having a thickness of 6 μm. Then, on the other side of the transparent PET film, the black ink composition 1 was subjected to gravure printing once to form a black printed layer having a thickness of 5 μm, thereby obtaining a laminated substrate D having a total thickness of 23 μm.

(production of double-sided adhesive tape)

An adhesive layer having a thickness of 18 μm was formed on both surfaces of the laminated substrate D in the same manner as in Example 1 to obtain an adhesive layer 4/black printed layer 3/resin film 1/white printed layer (formed by secondary printing). The bright printed layer 2)/adhesive layer 4 is formed by a laminate structure, and a double-sided adhesive tape having a total thickness of about 60 μm.

The double-sided adhesive tape and the laminated base materials A to D of the above examples and comparative examples were evaluated in accordance with the following methods. The results are shown in Table 3.

(phase adhesion test)

The laminated substrates A to D were cut into a size of 30 mm × 40 mm to obtain test pieces. For each test piece, the same test as the adhesion test of the resin composition of the adhesive was carried out and evaluated.

(static friction)

In the related examples 1 and 2 and the comparative example 1, the static friction force (the transparent printed film of the laminated base material to the black printed layer of the laminated base material) was measured by the test method according to JIS K 7125. Specifically, the laminated PET substrate was fixed on the test platform with the transparent PET film side up. On the other hand, another laminated substrate (size: 25 mm × 25 mm) was fixed on a slide having a weight of 200 g. Then, the slide piece was quietly placed on the test platform in such a manner that the transparent PET film surface of the laminated substrate fixed on the test platform was in contact with the black printed surface of the laminated substrate fixed on the slide. The slide was moved in parallel at a speed of 300 mm/min, and the maximum stress (static friction) initially obtained was measured. Further, in Comparative Example 2, the white printed layer of the laminated substrate was measured for the black printed layer of the laminated substrate in the same manner. Friction.

(penetration rate)

The average transmittance of the double-sided adhesive tape at a wavelength of 380 to 780 nm was measured using an ultraviolet-visible infrared spectrophotometer (manufactured by JASCO Corporation, trade name: V-670).

(penetration concentration)

The penetration density of the double-sided adhesive tape was measured using a portable black-and-white transmission densitometer (manufactured by Ihara Electronics Co., Ltd., trade name: TM-5). Since the measurement range of the device is 0.0 to 6.0, the penetration concentration exceeding the range is marked as "6.0 or more".

(yellowing test)

The double-sided adhesive tape was heated at 85 ° C for 240 hours, and the yellow chromaticity after heating was measured by a spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: SE6000). For hue evaluation, b* (yellow direction) of the L*a*b* chromaticity system specified in JIS Z 8729 was selected. The b* difference Δb*=(85°C value)-(initial value) before and after the heating means that the degree of yellowing is larger.

In Tables 3 and 4, each code indicates the following product.

"b1": polyester polyurethane resin (manufactured by Toyo Ink Co., Ltd., trade name E039 ink medium Z)

"ar-i": benzoyl diisocyanate (aromatic isocyanate curing agent) (manufactured by Toyo Ink Co., Ltd., trade name TK HARDENER)

"al-i": hexamethylene diisocyanate (aliphatic isocyanate curing agent) (manufactured by Toyo Ink Co., Ltd., trade name LP HARDENER)

<evaluation>

From the results shown in Table 3, all the characteristics of the double-sided adhesive tapes of Examples 1 and 2 were obtained. Both are excellent. On the other hand, the double-sided adhesive tape of Comparative Example 1 using an aliphatic isocyanate-based curing agent (al-i) and having a high static friction force was sticky during the adhesion test.

Further, from the results shown in Table 4, the laminated structure of the adhesive layer 4/black printed layer 3/resin film 1/white printed layer (bright print layer 2 formed by secondary printing)/adhesive layer 4 was obtained. In the formed double-sided adhesive tape of Comparative Example 2, the degree of yellowing (Δb*) was large. This phenomenon is considered to be because the white printed layer is in direct contact with the adhesive layer, and the ink component in the white printed layer migrates into the adhesive layer, resulting in discoloration of the adhesive layer. Further, in Comparative Example 2, a phase sticking occurred in the adhesion test of the laminated substrate. The reason is due to the high affinity between the white printed layer that is in direct contact and the black printed layer.

(industrial availability)

Since the adhesive layer of the double-sided adhesive tape of the present invention has less yellowing, it is stable for a long period of time, and light-shielding property and light reflectivity can be ensured. Further, since the ink of the printing layer is rapidly hardened, it is not necessary to provide an anti-adhesive film in the form of a roll-up, and the printing layer can be formed in a small number of steps, and the manufacturing steps of the substrate can be greatly reduced. Therefore, the double-sided adhesive tape of the present invention can be used very effectively for a liquid crystal display panel of a liquid crystal display device used in, for example, a mobile phone or a touch panel, and a double-sided adhesive tape for fixing between the backlight unit.

1‧‧‧Resin film

2‧‧‧ Bright print layer

3‧‧‧Black printed layer

4‧‧‧Adhesive layer

Claims (8)

A double-sided adhesive tape comprising: a laminated substrate having at least one bright printed layer between a resin film and a black printed layer; and an adhesive layer disposed on both sides of the laminated substrate; wherein the black printed layer is Contains a structure derived from an aromatic isocyanate-based hardener. The double-sided adhesive tape of claim 1, wherein the thickness of the laminated substrate is 12 μm to 50 μm. The double-sided adhesive tape of claim 1, wherein the double-sided adhesive tape is used for fixing between the liquid crystal display panel and the backlight unit. A double-sided adhesive tape comprising: a laminated substrate having at least one layer of a bright printed layer between a resin film and a black printed layer; and an adhesive layer disposed on both sides of the laminated substrate; wherein the laminated substrate is The static printing force of the black printed layer to the resin film according to JIS K 7125 is 2.0 N or less. The double-sided adhesive tape of claim 4, wherein the thickness of the laminated substrate is 12 μm to 50 μm. The double-sided adhesive tape of claim 4, wherein the double-sided adhesive tape is used for fixing between the liquid crystal display panel and the backlight unit. A method of manufacturing a double-sided adhesive tape, which is a method for producing the double-sided adhesive tape of any one of claims 1 to 6, characterized in that the black printed layer is formed by a single step. The method for producing a double-sided adhesive tape according to claim 7, comprising the steps of: forming a bright printed layer on the resin film; forming a black printed layer on the bright printed layer in a single step to obtain a laminated substrate; And a step of forming an adhesive layer on both sides of the laminated substrate.