KR20180095014A - Double-sided pressure-sensitive adhesive tape - Google Patents

Abstract

A double-sided pressure-sensitive adhesive tape comprising a laminated substrate having at least one bright print layer (2) between a resin film (1) and a black print layer (3) and a pressure sensitive adhesive layer (4) provided on both surfaces of the laminated substrate, The pressure-sensitive adhesive layer (4) on the side of the light reflection layer is hardly yellowed, and the pressure-sensitive adhesive layer (4) on the side of the light reflection layer is hardly yellowed, An adhesive tape is disclosed which is easy to adjust the brightness (reflectance) of a reflective layer and is useful for fixing a liquid crystal display panel and a backlight unit.

Description

{DOUBLE-SIDED PRESSURE-SENSITIVE ADHESIVE TAPE}

INDUSTRIAL APPLICABILITY The present invention is applicable to both of the functions of light reflectivity and light shielding, which are useful for improving brightness of a backlight surface for a liquid crystal display device used in, for example, a cellular phone or a touch panel and preventing deterioration in visibility due to light leakage Side adhesive tape.

BACKGROUND ART In a liquid crystal display device used in a cellular phone, a touch panel, or the like, a double-faced adhesive tape is provided between a liquid crystal display part and a backlight part, thereby fixing both members. This double-sided adhesive tape has, for example, a white light reflection layer and a black light shielding layer, contributing to improvement of the brightness of the backlight surface and prevention of deterioration of visibility due to light leakage from the backlight. The double-sided pressure-sensitive adhesive tape which contributes to both of such brightness enhancement and light-shielding properties is disclosed in, for example, Patent Documents 1 to 4.

The light reflecting layer of the double-sided adhesive tape of Patent Document 1 is composed of a biaxially oriented resin film of a polyester resin containing a white colorant. However, the light reflecting layer made of the resin film containing such a coloring agent is inferior in productivity, and it is relatively difficult to adjust the brightness (reflectance).

The light reflecting layer of the double-sided adhesive tape of Patent Document 2 is a white printing layer, and the light shielding layer is a black printing layer. The printing layer is excellent in productivity as compared with a resin film containing a colorant, and it is easy to adjust the brightness (reflectance). However, since the laminated base material used for the double-faced pressure-sensitive adhesive tape has a laminated structure of a black printing layer / a resin film / a white printing layer, when the laminated base material is wound in a roll form, So that blocking is generated. Therefore, it is necessary to provide an anti-blocking film (thin coat layer) on the outer side of one printed layer. Further, according to the knowledge of the present inventors, yellowing of the pressure-sensitive adhesive layer on the side of the white printing layer (on the light reflection layer side) tends to be problematic in the double-sided pressure-sensitive adhesive tape using such a laminated substrate. This is believed to be attributable to the fact that the ink component in the white printing layer is transferred (transferred) to the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer is discolored since the white printing layer and the pressure-sensitive adhesive layer are in direct contact with each other. Such yellowing of the pressure-sensitive adhesive layer on the side of the light reflection layer lowers the brightness of the backlight surface, which causes a decrease in visibility. In addition, since the laminated base material of Patent Document 2 has print layers on both sides, when the laminated base material is taken out in the step of coating the pressure-sensitive adhesive, the printed layer is liable to be damaged by contact with the guide roll. Further, when a fine punching process such as a narrow frame shape is performed, the printed layer may be peeled off.

In the double-sided pressure-sensitive adhesive tape of Patent Document 3, a laminated substrate provided with both a white printed layer and a black printed layer on one side of a transparent plastic substrate is used. However, according to the knowledge of the inventors of the present invention, when the laminated base material is wound up in a roll shape immediately after its production, the surface of the print layer is clumped to cause blocking or wrinkles due to frictional force during winding. These phenomena can be considered to be due to the insufficient curing rate of the black print layer at the time of producing the laminated substrate.

In the double-sided pressure-sensitive adhesive tape of Patent Document 4, a laminated substrate provided with a light-shielding layer (black printing layer) on one side of a resin film is used. It is described that a polyurethane resin having a Tg (peak temperature of tan delta) of -30 DEG C to 30 DEG C is used as the binder resin of the light-shielding layer (black print layer) and an aliphatic or alicyclic isocyanate is used as a curing agent . However, according to the knowledge of the present inventors, when such a binder resin and a curing agent are used, the curing speed of the printing layer is insufficient, and blocking or wrinkling may occur as described above.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-156015 Patent Document 2: JP-A-2011-95764 Patent Document 3: JP-A-2009-197124 Patent Document 4: JP-A-2010-53240

It is an object of the present invention to provide a double-sided pressure-sensitive adhesive tape having both light-reflective and light-shielding properties, in which blocking or wrinkling of a laminate substrate is hardly generated, the pressure- Sensitive adhesive tape, and a method of manufacturing the same. Another object of the present invention is to provide a simple manufacturing method of the double-faced pressure-sensitive adhesive tape.

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted intensive studies to attain the above object and found that it is very effective to use a laminated base material having a specific layer structure and to constitute a black print layer with specific components, .

A first aspect of the present invention is a double-sided pressure-sensitive adhesive tape having a laminated base material having at least one light color printing layer between a resin film and a black printing layer and a pressure-sensitive adhesive layer provided on both surfaces of the laminated base material, Wherein the printing layer comprises a structure derived from an aromatic isocyanate-based curing agent.

A second aspect of the present invention is a double-sided pressure-sensitive adhesive tape comprising a laminate substrate having at least one bright print layer between a resin film and a black print layer and a pressure-sensitive adhesive layer provided on both surfaces of the laminate substrate, Sensitive adhesive tape according to JIS K 7125 of the black printing layer to a pressure-sensitive adhesive tape having a static friction force of 2.0 N or less.

Further, the present invention is a method for producing a double-sided pressure-sensitive adhesive tape according to the first or second aspect of the present invention, wherein the black printing layer is formed in one step.

According to the present invention, it is possible to provide a double-sided pressure-sensitive adhesive tape in which blocking and wrinkling are less likely to occur in the laminated substrate, the pressure-sensitive adhesive layer on the side of the light reflection layer is hardly yellowed, and the lightness (reflectivity) of the light- Further, according to the present invention, it is possible to provide a method of easily manufacturing such double-faced pressure-sensitive adhesive tape.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing one embodiment of a double-faced pressure-sensitive adhesive tape of the present invention.

1 is a schematic cross-sectional view showing one embodiment of a double-faced pressure-sensitive adhesive tape of the present invention. In this embodiment, the laminated substrate has the bright color printing layer 2 as a light reflecting layer between the resin film 1 and the black printing layer 3 as a light shielding layer. On both sides of the laminated substrate, a pressure-sensitive adhesive layer 4 is provided. In such a laminated structure, the pressure sensitive adhesive layer 4 on the bright color printing layer 2 (light reflection layer) side does not directly contact the bright color printing layer 2 (light reflection layer) and the pressure sensitive adhesive layer 4, The ink component is not transferred and yellowing becomes difficult to occur. As a result, the transmittance on the light reflection side is not lowered, and for example, the brightness and visibility of the backlight surface can be prevented from lowering. On the other hand, although the black print layer 3 (light-shielding layer) and the pressure-sensitive adhesive layer 4 are directly in contact with each other, the decrease in the transmittance of the pressure-sensitive adhesive layer 4 on the light-shielding layer side does not hinder the light- , This point does not matter.

Since the laminated substrate of the present invention has the above-described specific layer structure, when the laminated substrate is rolled up immediately after the laminated substrate is formed (before the pressure-sensitive adhesive layer 4 is formed), the resin film 1 And the black print layer 3 are in contact with each other, and blocking and wrinkling are less likely to occur as compared with the case where the bright print layer and the black print layer are in contact with each other in the prior art. Further, as will be described later, in the first invention, since the hardening speed of the black print layer is fast and the static frictional force is low in the second invention, they exhibit a synergistic action with a specific layer structure of the laminated substrate, And the effect of preventing the occurrence of wrinkles becomes remarkable.

The double-sided pressure-sensitive adhesive tape shown in Fig. 1 is a preferred embodiment of the present invention, but the present invention is not limited thereto. For example, in the double-sided pressure-sensitive adhesive tape shown in Fig. 1, the first bright print layer 2 constitutes a light reflection layer, but a laminate of two or more glossy print layers 2 may constitute a light reflection layer if desired. In the double-faced pressure-sensitive adhesive tape shown in Fig. 1, one black print layer 3 constitutes a light-shielding layer, but two or more black print layers 3 may constitute a light-shielding layer if desired.

In the double-sided pressure-sensitive adhesive tape shown in Fig. 1, the bright color printing layer 2 and the black printing layer 3 are directly laminated on the resin film 1 in this order, but between the resin film 1 and the bright color printing layer 2 Or an arbitrary layer may be present between the bright color printing layer 2 and the black printing layer 3. 1, the pressure-sensitive adhesive layer 4 is directly laminated on the outer surface of the resin film 1 and the outer surface of the black printed layer 3, but the outer surface and the pressure- Or any other arbitrary layer may be present between them.

[Resin film (1)]

The resin film (1) in the present invention is not particularly limited, and various resin films known to be usable for this type of adhesive tape can be used. For example, a transparent plastic film made of a polyester, a polyolefin, a polyurethane, a polyamide, a polyimide, a polystyrene or the like is preferable, and a PET (polyethylene terephthalate) film or the like Is more preferable.

The thickness of the resin film (1) is appropriately determined according to the thickness of the double-faced pressure-sensitive adhesive tape required. The thickness is preferably 2 to 50 mu m, more preferably 6 to 38 mu m in view of reworkability and the like.

[Bright print layer (2)]

The bright print layer 2 in the present invention is not particularly limited, and various bright print layers known to be capable of imparting the light reflection function necessary for this type of adhesive tape can be used. The bright print layer 2 is easier to adjust the lightness (reflectivity) of the light reflection layer as compared with the light reflection layer made of a resin film containing a colorant as described in Patent Document 1. Here, " bright color " means a color such as white or pale color capable of imparting a light reflection function. White is particularly preferred. Specifically, the L * (lightness) defined by the L * a * b * color system of the bright color print layer 2 is preferably 65 or more, and more preferably 75 or more. The reflectance of the bright print layer 2 to a wavelength of 550 nm is preferably 45% or more, and more preferably 65% or more. The average reflectance for the wavelength of 380 to 780 nm is preferably 40% or more, and more preferably 60% or more.

The bright print layer 2 is usually formed by a known printing method using an ink composition. The ink composition includes, 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 silicone resin, an acrylic resin, a polyester resin and a polyolefin resin. Among them, a polyurethane resin is preferable. Specific examples of the curing agent include an aromatic isocyanate-based curing agent, an aliphatic isocyanate-based curing agent, and an alicyclic isocyanate-based curing agent. Among them, an aromatic isocyanate-based curing agent is preferable. As the composition ratio of each component, a known composition ratio can be adopted and it may be appropriately determined as necessary.

The ink composition used in the bright color print 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 reflection layer made of the bright color printing layer 2 is appropriately determined in accordance with the thickness of the double-sided pressure-sensitive adhesive tape and light reflectivity required. The thickness of the light reflecting layer is preferably 1 to 20 占 퐉, more preferably 3 to 12 占 퐉. The bright print layer 2 may be a single-layer light reflection layer, but it is preferable to form the light reflection layer by lamination molding two to six bright print layers 2 in view of providing sufficient light reflectivity.

[Black printing layer (3)]

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

Specific examples of the binder resin used for the black print layer 3 include a polyurethane resin, a phenol resin, an epoxy resin, a silicone resin, an acrylic resin, a polyester resin and a polyolefin resin. A urethane-based resin is preferable, and a polyester polyurethane resin is more preferable. The polyester polyurethane resin is a polyurethane resin containing an ester bond in the molecular chain. Either an aliphatic or aromatic polyester polyurethane resin can be used. The polyester polyurethane resin can be obtained, for example, by reacting a polyester polyol with a polyisocyanate and, if necessary, other components. The Tg (glass transition temperature) of the binder resin is preferably relatively high. Specifically, the Tg of the binder resin is preferably 12 占 폚 or higher. As a result, the tack is lowered even in the initial stage of the curing of the black print layer 3, and blocking and wrinkling of the laminated substrate are less likely to occur.

Specific examples of the curing agent used for the black print layer 3 include an aromatic isocyanate curing agent, an aliphatic isocyanate curing agent and an alicyclic isocyanate curing agent. However, in the first invention, an aromatic isocyanate-based curing agent is used as a curing agent used for the black print layer (3). As a result, the curing speed of the black print layer 3 is increased, and blocking and wrinkling of the laminated substrate are less likely to occur.

The aromatic isocyanate-based curing agent is a curing agent containing at least an aromatic isocyanate. The aromatic isocyanate is a compound having an aromatic group and an isocyanate group such as a benzene ring and usually has two or more isocyanate groups. As the aromatic isocyanate, for example, a compound having a benzene ring and two isocyanate groups is preferable, and xylene diisocyanate is particularly preferable. The aromatic isocyanate-based curing agent generally includes an adduct of an aromatic isocyanate (an adduct of a diisocyanate and trimethylol propane) and an isocyanurate (a trimer of a diisocyanate).

The blending amount of the curing agent is preferably 4 to 16 parts by mass, and more preferably 6 to 12 parts by mass with respect to 100 parts by mass of the printing ink.

The ink composition used for the black print 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 made of the black print layer 3 is appropriately determined according to the thickness or light shielding property of the double-sided adhesive tape required. The thickness of the light-shielding layer is preferably 1 to 8 占 퐉, more preferably 3 to 6 占 퐉, and particularly preferably 4 to 6 占 퐉. The black print layer 3 may be a single-layer light-shielding layer, or a plurality of black print layers 3 may be laminated to form a light reflection layer. However, since the black printing layer 3 in the present invention has a relatively high curing speed, the light-shielding layer can be structured well with one black printing layer 3, and the manufacturing process can be simplified.

[Pressure-sensitive adhesive layer (4)]

The pressure-sensitive adhesive layer (4) in the present invention is not particularly limited, and various pressure-sensitive adhesive layers known to be applicable to this kind of pressure-sensitive adhesive tapes can be used. As the pressure- A transparent adhesive such as an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a polyester pressure-sensitive adhesive, and a silicone pressure-sensitive adhesive. Above all, acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, and silicone pressure-sensitive adhesives are preferable.

A pressure-sensitive adhesive resin or a crosslinking agent may be added to the pressure-sensitive adhesive layer (4), if necessary. Examples of the tackifier resin include rosin-based, polyterpene-based, petroleum-based, terpene-phenol-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 chelating crosslinking agent.

The thickness of the pressure-sensitive adhesive layer (4) is appropriately determined according to the thickness of the double-sided pressure-sensitive adhesive tape required. Usually, the thickness is preferably 2 to 50 占 퐉, more preferably 5 to 30 占 퐉.

[Laminated substrate]

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

In the second aspect of the present invention, the static friction force of the black print layer with respect to the resin film of the laminated base material is 2.0 N or less, preferably 1.4 to 1.8 N, in accordance with JIS K 7125. By having such a low static friction force, the laminated base material is less liable to block when the laminated base material is wound into a roll shape immediately after production, and it is also less likely to cause wrinkles due to frictional force at the time of winding.

The static friction force was measured in accordance with JIS K 7125 by placing the other laminated base material fixed on the sliding piece weighing 200 g on the resin film 1 of the laminated base material in contact with the black printing layer 3 at a speed of 300 mm / , The maximum stress (static friction force) initially obtained is measured. Details thereof will be described in the column of the embodiment to be described later.

The laminated substrate having low static friction in the second aspect of the present invention can be obtained by appropriately selecting conditions such as, for example, the kind of the curing agent of the black print layer and the kind of the binder resin. As the curing agent, the above-described aromatic isocyanate curing agent (the first invention) is particularly preferable. However, the second invention is not limited to this. Even when an aromatic isocyanate-based curing agent is not used, it is also possible to obtain a laminated base material having a low static friction force, for example, by using a binder resin having a relatively high Tg.

[Double-sided adhesive tape]

The double-faced pressure-sensitive adhesive tape of the present invention is the pressure-sensitive adhesive tape having the above-described laminated base material and the pressure-sensitive adhesive layer (4) provided on both surfaces of the laminated base material. The double-faced pressure-sensitive adhesive tape of the present invention can be used suitably for fixation between a backlight unit and a liquid crystal display panel of a liquid crystal display device used in a cellular phone, a touch panel, etc., because blocking of the printing layer and yellowing of the pressure- have.

[Method of producing double-faced adhesive tape]

The laminated base material in the present invention can be produced by, for example, forming a bright color printing layer 2 on a resin film 1 and forming a black printing layer 3 thereon.

The method for producing the double-sided pressure-sensitive adhesive tape according to the first aspect of the present invention includes the steps of forming the black print layer 3 by using an ink composition containing, for example, a coloring component (ink component), a binder resin and an aromatic isocyanate- Process. Preferably, the step of forming the bright color printing layer 2 on the resin film 1, the black printing layer 3 is formed on the bright color printing layer 2 using the ink composition to obtain a laminated substrate And a step of forming a pressure-sensitive adhesive layer (4) on both surfaces of the laminated substrate.

The method for producing the double-sided pressure-sensitive adhesive tape according to the second aspect of the present invention includes a step of producing a laminated base material having a static friction force of 2.0 N or less according to JIS K 7125 of the black printed layer 3 with respect to the resin film 1 . Preferably, a step of forming a bright color printing layer 2 on the resin film 1, a black printing layer 3 on the bright color printing layer 2 to form a black printing layer 3 for the resin film 1, (3) having a static friction force according to JIS K 7125 of 2.0 N or less, and a step of forming a pressure-sensitive adhesive layer (4) on both surfaces of the laminated substrate.

According to each of the above-described manufacturing methods, blocking is not easily generated when the laminated base material is wound into a roll shape immediately after production, and wrinkles due to frictional force at the time of winding are also less likely to occur.

Further, the method of the present invention is characterized in that the black printing layer 3 is formed in one step. Preferably, a step of forming a bright color printing layer on a resin film, a step of forming a black printing layer on the bright color printing layer in one step to obtain a laminated substrate, and a step of forming an adhesive layer on both surfaces of the laminated substrate .

A conventional black printing layer for light shielding is generally formed by stacking two or three layers in order to obtain sufficient light shielding properties. However, the black printing layer 3 of the present invention can form a sufficient light-shielding layer in one step. As a result, it is possible to avoid the problem that the height difference between the concavities and convexities of the coating surface becomes large and blocking tends to occur, and furthermore, the manufacturing process of the laminated substrate can be greatly reduced.

As a method for printing the bright color print layer 2 and the black print layer 3, a known printing method can be used. Specific examples of the printing method include a gravure printing method, a flexo printing method, an offset printing method, an iron plate printing method, and a screen printing method. Among them, a gravure printing method is preferable.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. And " part " means " part by mass ".

<Binder Resin Compositions 1 to 3 and Comparative Binder Resin Compositions C1 to C7>

13.0 parts of a curing agent was added to 100 parts of the binder resin shown in Tables 1 and 2 to obtain binder resin compositions 1 to 3 and comparative binder resin compositions C1 to C7. Among the glass transition temperatures (Tg) listed in the table, the Tg of the binder resin (b1) is a DSC measurement value, and the glass transition temperature (Tg) of the binder resin (b2 to b5) is a value based on maker information.

(Blocking test)

A binder resin composition was laminated on one side of a 12 占 퐉 -thick transparent PET (polyethylene terephthalate) film so as to have a thickness of 5 占 퐉 to obtain a binder coat film having a total thickness of 17 占 퐉. The binder coat film was cut into a size of 30 mm x 40 mm to obtain a test piece. Five test pieces were superimposed, sandwiched by a glass plate with a thickness of 1.5 mm, and weighed 2 kg and allowed to stand at 40 占 폚 for 2 days. Thereafter, each test piece was peeled off and visually evaluated according to the following criteria. The results are shown in Tables 1 and 2.

&Quot; o &quot;: blocking occurred.

"X": No blocking occurred.

(Probe tack)

The probe tack was measured by the test method according to JIS Z 0237. Specifically, when the side of the binder resin composition layer of the same binder coat film as in the blocking test was pressed with a load of 20 g for 1.0 second onto a column made of SUS having a diameter of 3 mm and then peeled at a speed of 1.0 cm / sec And the average value of the measured values of the five tests was taken as the probe tip (N). The results are shown in Tables 1 and 2.

(Static friction force)

The static friction force (the binder resin composition layer of the transparent PET film of the binder coat film versus the binder coat film same as the blocking test) was measured by the test method according to IS K 7125. Specifically, the binder coat film was fixed on the test table so that the side of the transparent PET film was positioned above. On the other hand, another binder coat film (size: 25 mm x 25 mm) was fixed to a sliding piece having a weight of 200 g. Then, a sliding piece was stuck on the test table so that the transparent PET film surface of the binder coat film fixed on the test table and the binder resin composition layer surface of the binder coat film fixed on the sliding piece came into contact with each other. The maximum stress (static friction) initially obtained was measured by moving the sliding piece in parallel at a speed of 300 mm / min. The results are shown in Tables 1 and 2.

In Tables 1 and 2, each abbreviation represents the following products.

"B1": polyester polyurethane resin (trade name: E039 Methium Z, manufactured by Toyo Ink Co., Ltd.)

"B2": polyester polyurethane resin (trade name UR1400, manufactured by Toyobo Co., Ltd.)

"B3": polyester polyurethane resin (trade name: Nipporan 2304, manufactured by Nippon Polyurethane Industry Co., Ltd.)

"B4": polyester polyurethane resin (trade name: Nipporan 3124, manufactured by Nippon Polyurethane Industry Co., Ltd.)

"B5": polyester polyurethane resin (trade name: Sanprene IB-129, manufactured by Sanyo Chemical Industries, Ltd.)

&Quot; ar-i &quot;: xylenediisocyanate (aromatic isocyanate-based curing agent) (trade name: TK Hardener,

&Quot; al-i &quot;: hexamethylene diisocyanate (aliphatic isocyanate-based curing agent) (trade name: LP Hardener,

<Evaluation>

As apparent from the results shown in Table 1, the binder resin compositions 1 and 2 using the aromatic isocyanate curing agent (ar-i) were excellent in all the properties. On the other hand, in the binder resin compositions C1 to C4 using the aliphatic isocyanate curing agent (al-i), blocking occurred in the blocking test, and the probe tack was high.

As is clear from the results shown in Table 2, the aromatic isocyanate curing agent (ar-i) was not used, but instead the binder resin composition 3 having high static friction was excellent in all properties. On the other hand, in the binder resin compositions (C5 to C7) having low static friction, blocking occurred in the blocking test, and the probe tack was also high.

&Lt; Example 1 &gt;

(Preparation of black ink composition 1)

Black ink (manufactured by TOYOBOK INC., Trade name E039PETAK Mukin) was prepared. This black ink is a product in which the same resin as the binder resin (b1) in the above-mentioned binder resin composition 1 is colored in black. To 100 parts of the black ink, 8.0 parts by mass of the same aromatic isocyanate curing agent (trade name: TK HARDNER, manufactured by Toyoko Co., Ltd.) as the curing agent (ar-i) in the binder resin composition 1 were blended to obtain a black ink composition 1.

(Preparation of white ink composition)

White ink (manufactured by TOYOBOK INC., Trade name: E039PET63 white) was prepared. This white ink is a product colored white with the same resin as the binder resin (b1) in the binder resin composition 1 described above. To 100 parts of this white ink, 6.0 parts by mass of the same aromatic isocyanate curing agent (trade name: TK Hardener, manufactured by TOYO INK CO., LTD.) Was added to the curing agent (ar-i) in the binder resin composition 1 to obtain a white ink composition.

(Production of laminated substrate A)

Gravure printing was carried out twice on one side of a 12 占 퐉 -thick transparent PET film using a white ink composition to obtain a white printed layer having a thickness of 6 占 퐉 (L * (lightness) = 83.47, reflectance of 74.4% , And the average reflectance for a wavelength of 380 to 780 nm = 69.5%). On the surface of the white printing layer, gravure printing was performed once using the black ink composition 1 to form a black printing layer having a thickness of 5 占 퐉 to obtain a laminated base material A having a total thickness of 23 占 퐉.

(Preparation of acrylic pressure-sensitive adhesive composition)

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

(Production of double-faced adhesive tape)

A pressure-sensitive adhesive layer having a thickness of 18 占 퐉 was formed by applying a transparent acrylic pressure-sensitive adhesive composition on both sides of the laminated substrate A, and the pressure-sensitive adhesive layer 4 / black printing layer 3 / white printing layer Sided pressure-sensitive adhesive tape having a total thickness of about 60 占 퐉 consisting of a laminated structure of the pressure sensitive adhesive layer (4) and the resin film (1) / the pressure sensitive adhesive layer (4)

&Lt; Example 2 &gt;

(Production of laminated substrate B)

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

(Production of double-faced adhesive tape)

A double-sided pressure-sensitive adhesive tape having a total thickness of about 60 占 퐉 was produced in the same manner as in Example 1 except that the thickness of the pressure-sensitive adhesive layer was changed to 21 占 퐉 by using the laminated substrate B.

&Lt; Comparative Example 1 &

(Preparation of black ink composition 2)

In the same manner as in the black ink composition 1 of Example 1 except that the same aliphatic isocyanate curing agent (trade name: LP Hardner, manufactured by Toyoko Co., Ltd.) was used as the curing agent (al-i) in the comparative binder resin composition C1, Composition 2 was prepared.

(Production of laminated substrate C)

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

(Production of double-faced adhesive tape)

A double-faced pressure-sensitive adhesive tape having a thickness of about 60 占 퐉 was produced in the same manner as in Example 1 except that the laminated substrate C was used.

&Lt; Comparative Example 2 &

(Production of laminated substrate D)

Gravure printing was carried out twice on the side of one side of a 12 占 퐉 -thick transparent PET film using a white ink composition to form a white printing layer having a thickness of 6 占 퐉. On the other side of the transparent PET film, gravure printing was performed once using the black ink composition 1 to form a black printing layer having a thickness of 5 占 퐉 to obtain a laminated base material D having a total thickness of 23 占 퐉.

(Production of double-faced adhesive tape)

A pressure-sensitive adhesive layer having the same thickness of 18 占 퐉 as in Example 1 was formed on both sides of the laminated substrate D and the pressure-sensitive adhesive layer 4 / black printing layer 3 / resin film 1 / white printing layer Sensitive adhesive layer 4 having a total thickness of about 60 占 퐉 was obtained.

The double-faced pressure-sensitive adhesive tape and the laminated substrates A to D of the above Examples and Comparative Examples were evaluated according to the following methods. The results are shown in Table 3.

(Blocking test)

The laminated substrates A to D were cut into a size of 30 mm x 40 mm to obtain test pieces. Each of the test pieces was subjected to the same test as the blocking test of the binder resin composition and evaluated.

(Static friction force)

Regarding Examples 1 and 2 and Comparative Example 1, a static frictional force (a transparent PET film of a laminated substrate versus a black printed layer of a laminated substrate) was measured by a test method according to JIS K 7125. Specifically, the laminated substrate was fixed to the test table so that the side of the transparent PET film was positioned above. On the other hand, another laminated substrate (size: 25 mm x 25 mm) was fixed to a sliding piece having a weight of 200 g. Then, the sliding piece was kept quiet on the test table so that the transparent PET film surface of the laminated base fixed to the test table and the black printed layer surface of the laminated base fixed to the sliding piece came into contact with each other, and the sliding pieces were moved in parallel at a speed of 300 mm / The maximum stress (static friction force) initially obtained was measured. With respect to Comparative Example 2, the static friction force of the black printed layer of the white printed layer vs. the laminated base material of the laminated base material was measured by the same method.

(Transmittance)

The average transmittance of the double-sided pressure-sensitive adhesive tape at a wavelength of 380 to 780 nm was measured using an ultraviolet visible infrared spectrophotometer (manufactured by Nihon Bunko Co., Ltd., trade name V-670).

(Transmission density)

The transmittance density of the double-faced pressure-sensitive adhesive tape was measured using a portable black and white permeation densitometer (trade name: TM-5, manufactured by Lardenshi Kogyo Co., Ltd.). Since the measurement range of the apparatus is 0.0 to 6.0, the permeation density exceeding the range is indicated as &quot; 6.0 or more &quot;.

(Yellowing test)

The double-faced pressure-sensitive adhesive tape was heated at 85 占 폚 for 240 hours, and the yellowness after heating was measured by a spectral colorimeter (SE6000, trade name, manufactured by Nippon Denshoku Kogyo Co., Ltd.). As the color evaluation, b * (lateral direction) of the L * a * b * colorimetry specified in JIS Z 8729 was selected. The difference in b * before and after the heating means that the degree of yellowing is larger as the difference DELTA b * = (value at 85 DEG C) - (initial value) is larger.

In Tables 3 and 4, the respective abbreviations represent the following products.

"B1": polyester polyurethane resin (trade name: E039 Methium Z, manufactured by Toyo Ink Co., Ltd.)

&Quot; ar-i &quot;: xylenediisocyanate (aromatic isocyanate-based curing agent) (trade name: TK Hardener,

&Quot; al-i &quot;: hexamethylene diisocyanate (aliphatic isocyanate-based curing agent) (trade name: LP Hardener,

<Evaluation>

As apparent from the results shown in Table 3, the double-faced pressure-sensitive adhesive tapes of Examples 1 and 2 were excellent in all properties. On the other hand, in the double-sided pressure-sensitive adhesive tape of Comparative Example 1 in which the aliphatic isocyanate curing agent (al-i) was used and the static friction was relatively high, blocking occurred in the blocking test.

As is clear from the results shown in Table 4, the pressure-sensitive adhesive layer 4 / black print layer 3 / resin film 1 / white print layer (bright print layer 2 formed by printing twice) The double-faced pressure-sensitive adhesive tape of Comparative Example 2 having a laminated structure of the layer 4 had a large degree of yellowing (? B *). This is considered to be due to the fact that the ink component in the white printing layer is transferred to the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer is discolored since the white printing layer and the pressure-sensitive adhesive layer are in direct contact with each other. Further, in Comparative Example 2, blocking occurred in the blocking test of the laminated substrate. This is due to the high affinity between the black print layer and the white print layer in direct contact with each other.

Industrial availability

In the double-sided pressure-sensitive adhesive tape of the present invention, the yellowing of the pressure-sensitive adhesive layer is small, so that light shielding and light reflectivity can be secured stably for a long period of time. In addition, since the ink of the print layer is quickly cured, there is no need to provide a blocking prevention film when winding into a roll, and a printed layer can be formed with a small number of steps, have. Therefore, the double-faced pressure-sensitive adhesive tape of the present invention is very useful as a double-faced pressure-sensitive adhesive tape used for fixing a liquid crystal display panel of a liquid crystal display device used in a cellular phone, a touch panel or the like and a backlight unit.

1 resin film
2 print layers
3 black printed layer
4 pressure-sensitive adhesive layer

Claims (8)

A double-sided pressure-sensitive adhesive tape comprising a laminated substrate having at least one light color printing layer between a resin film and a black printing layer and a pressure-sensitive adhesive layer provided on both surfaces of the laminated substrate, wherein the black printing layer comprises an aromatic isocyanate- Wherein the adhesive tape comprises a structure derived from the double-sided adhesive tape. The method according to claim 1,
A double-sided pressure-sensitive adhesive tape having a thickness of a laminate substrate of 12 탆 to 50 탆. The method according to claim 1,
A double-sided pressure-sensitive adhesive tape used for fixing a liquid crystal display panel and a backlight unit. A double-sided pressure-sensitive adhesive tape comprising a laminated substrate having at least one glossy printing layer between a resin film and a black printing layer and a pressure-sensitive adhesive layer provided on both sides of the laminated substrate, And a static friction force according to K 7125 of 2.0 N or less. The method of claim 4,
A double-sided pressure-sensitive adhesive tape having a thickness of a laminate substrate of 12 탆 to 50 탆. The method of claim 4,
A double-sided pressure-sensitive adhesive tape used for fixing a liquid crystal display panel and a backlight unit. A method for producing a double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 6, wherein the black printing layer is formed in one step. The method of claim 7,
A step of forming a bright color printing layer on the resin film,
A step of forming a black print layer on the bright print layer in one step to obtain a laminated substrate, and
And a step of forming a pressure-sensitive adhesive layer on both surfaces of the laminated substrate.

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