JPWO2017109883A1 - Double-sided adhesive tape - Google Patents

Abstract

A double-sided pressure-sensitive adhesive tape comprising a laminated substrate having at least one light-colored printed layer 2 between the resin film 1 and the black printed layer 3 and an adhesive layer 4 provided on both surfaces of the laminated substrate; The black print layer 3 includes a structure derived from an aromatic isocyanate curing agent, blocking or wrinkling of the laminated base material is difficult to occur, and the pressure-sensitive adhesive layer 4 on the light reflecting layer side is hardly yellowed. In addition, an adhesive tape that is easy to adjust the lightness (reflectance) of the light reflecting layer and is useful for fixing the liquid crystal display panel and the backlight unit is disclosed.

Description

  The present invention is a double-sided surface having both light-reflecting and light-shielding functions, useful for improving the brightness of a backlight surface for a liquid crystal display device used in, for example, a mobile phone, a touch panel, and the like and preventing visibility from being deteriorated due to light leakage. It relates to an adhesive tape.

  In a liquid crystal display device used for a mobile phone, a touch panel, or the like, a double-sided adhesive tape is provided between a liquid crystal display unit and a backlight unit, thereby fixing both members. This double-sided pressure-sensitive adhesive tape has, for example, a white light reflection layer and a black light-shielding layer, and contributes to improving the luminance of the backlight surface and preventing the visibility from being lowered due to light leakage from the backlight. Such double-sided pressure-sensitive adhesive tapes that contribute to both brightness enhancement and light shielding properties are disclosed in, for example, Patent Documents 1 to 4.

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

  The light reflection layer of the double-sided pressure-sensitive adhesive tape of Patent Document 2 is a white print layer, and the light shielding layer is a black print layer. The printed layer is excellent in productivity as compared with a resin film containing a colorant, and lightness (reflectance) can be easily adjusted. However, since the laminated base material used for this double-sided pressure-sensitive adhesive tape has a laminated structure of black printing layer / resin film / white printing layer, when the laminated base material is rolled up, the printed layers come into contact with each other and block. Will occur. Therefore, it is necessary to provide an anti-blocking film (thin coat layer) on the outside of one printed layer. Furthermore, according to the knowledge of the present inventors, in the double-sided pressure-sensitive adhesive tape using such a laminated base material, yellowing of the pressure-sensitive adhesive layer on the white printing layer side (light reflection layer side) tends to be a problem. This is considered to be because the white printed layer and the pressure-sensitive adhesive layer are in direct contact with each other, and the ink component in the white printed layer is transferred to the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer is discolored. Such yellowing of the pressure-sensitive adhesive layer on the light reflecting layer side lowers the luminance of the backlight surface and causes a decrease in visibility. Furthermore, since the lamination base material of patent document 2 has a printing layer on both surfaces, when drawing out a lamination base material at the coating process of an adhesive, a printing layer contacts a guide roll and it is easy to lose | delete. In addition, when performing a fine punching process such as a narrow frame shape, the printed layer may be peeled off.

  In the double-sided pressure-sensitive adhesive tape of Patent Document 3, a laminated base material in which both a white print layer and a black print layer are provided on one side of a transparent plastic base material is used. However, according to the knowledge of the present inventors, when this laminated substrate is wound up in a roll immediately after production, the surface of the printing layer is sticky and blocking occurs, or wrinkles due to frictional force occur during winding. There is. These phenomena are thought to be due to the insufficient curing rate of the black printed layer during the production of the laminated substrate.

  In the double-sided pressure-sensitive adhesive tape of Patent Document 4, a laminated base material provided with a light shielding layer (black print layer) on one side of a resin film is used. A polyurethane resin having a Tg (tan δ peak temperature) of −30 ° C. to 30 ° C. is used as a binder resin of the light shielding layer (black printing layer), and an aliphatic or alicyclic isocyanate is used as a curing agent. Have been described. 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 printed layer is insufficient, and thus blocking and wrinkling may occur as described above.

JP 2004-156015 A JP 2011-95764 A JP 2009-197124 A JP 2010-53240 A

  An object of the present invention is a double-sided pressure-sensitive adhesive tape having both functions of light reflectivity and light-shielding property, and it is difficult for blocking and wrinkle of a laminated base material to occur, and the pressure-sensitive adhesive layer on the light reflection layer side is hardly yellowed. And it is providing the double-sided adhesive tape with which the adjustment of the brightness (reflectance) of a light reflection layer is easy, and its manufacturing method. A further object of the present invention is to provide a simple method for producing the double-sided pressure-sensitive adhesive tape.

  As a result of intensive studies to achieve the above object, the present inventors have 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 a specific component, The present invention has been completed.

  1st this invention is a double-sided adhesive tape which has the lamination base material which has at least one layer of bright printing layer between the resin film and the black printing layer, and the adhesive layer provided in both surfaces of this lamination base material. The double-sided pressure-sensitive adhesive tape is characterized in that the black print layer includes a structure resulting from an aromatic isocyanate curing agent.

  2nd this invention is a double-sided adhesive tape which has a lamination base material which has at least 1 layer of bright printing layer between a resin film and a black printing layer, and the adhesive layer provided in both surfaces of this lamination base material. The double-sided pressure-sensitive adhesive tape is characterized in that a static frictional force according to JIS K 7125 of the black printed layer with respect to the resin film of the laminated substrate is 2.0 N or less.

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

  According to the present invention, the double-sided pressure-sensitive adhesive tape is less prone to blocking and wrinkling of the laminated base material, the light-sensitive adhesive layer side is hardly yellowed, and the lightness (reflectance) of the light-reflective layer can be easily adjusted. Can provide. Furthermore, according to this invention, the method of manufacturing such a double-sided adhesive tape easily can be provided.

It is typical sectional drawing which shows one Embodiment of the double-sided adhesive tape of this invention.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of the double-sided pressure-sensitive adhesive tape of the present invention. In this embodiment, the laminated substrate has a light color printing layer 2 as a light reflection layer between a resin film 1 and a black printing layer 3 as a light shielding layer. And the adhesive layer 4 is provided in both surfaces of the laminated base material. In such a laminated structure, since the light color print layer 2 (light reflection layer) and the pressure-sensitive adhesive layer 4 are not in direct contact, the light-color print layer 2 (light reflection layer) side has the pressure-sensitive adhesive layer 4 on the pressure-sensitive adhesive layer 4. Ink components do not migrate and yellowing is less likely to occur. As a result, the transmittance on the light reflection side does not decrease, and for example, it is possible to prevent a decrease in luminance and visibility of the backlight surface. On the other hand, the black print layer 3 (light-shielding layer) and the pressure-sensitive adhesive layer 4 are in direct contact with each other. This is not a problem.

  Furthermore, since the laminated base material in the present invention has the specific layer structure described above, the resin film 1 is used when the laminated base material is rolled up immediately after production of the laminated base material (before formation of the pressure-sensitive adhesive layer 4). And the black print layer 3 are in contact with each other, and blocking and wrinkles are less likely to occur as compared with the case in which the light color print layer and the black print layer in the prior art are in contact with each other. Moreover, as described later, in the first aspect of the present invention, the black printed layer has a fast curing speed, and in the second aspect of the present invention, the static frictional force is low, so that these have a synergistic effect with a specific layer structure of the laminated base material. The effect of preventing the occurrence of blocking and 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 to this. For example, in the double-sided pressure-sensitive adhesive tape shown in FIG. 1, one light-colored printing layer 2 constitutes a light reflecting layer, but a laminate of two or more light-colored printing layers 2 constitutes a light reflecting layer as desired. Also good. Further, in the double-sided pressure-sensitive adhesive tape shown in FIG. 1, one black printing layer 3 constitutes a light shielding layer, but two or more black printing layers 3 may constitute a light shielding layer as desired.

  In addition, in the double-sided pressure-sensitive adhesive tape shown in FIG. 1, a light color printing layer 2 and a black color printing layer 3 are directly laminated on the resin film 1 in this order, but between the resin film 1 and the light color printing layer 2 or light color printing. Another arbitrary layer may exist between the layer 2 and the black print layer 3. In the double-sided pressure-sensitive adhesive tape shown in FIG. 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. Any layer may be present.

[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 polyester, polyolefin, polyurethane, polyamide, polyimide, polystyrene or the like is preferable, and a polyester film such as a PET (polyethylene terephthalate) film is more preferable from the viewpoints of easy availability and strength stability. .

  The thickness of the resin film 1 is appropriately determined according to the required thickness of the double-sided pressure-sensitive adhesive tape. In particular, from the viewpoint of reworkability, the thickness is preferably 2 to 50 μm, more preferably 6 to 38 μm.

[Light color printing layer 2]
The light color print layer 2 in the present invention is not particularly limited, and various light color print layers that are known to be capable of providing a light reflection function necessary for this type of pressure-sensitive adhesive tape can be used. The light color print layer 2 is easy to adjust the lightness (reflectance) 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 light color that can provide a light reflection function. White is particularly preferable. Specifically, L ^* (brightness) defined by the L ^* a ^* b ^* color system of the light color printing layer 2 is preferably 65 or more, more preferably 75 or more. The reflectance of the light color printing layer 2 with respect to the wavelength of 550 nm is preferably 45% or more, more preferably 65% or more. Moreover, the average reflectance with respect to the wavelength of 380 to 780 nm is preferably 40% or more, 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 polyurethane resins, phenol resins, epoxy resins, silicone resins, acrylic resins, polyester resins, and polyolefin resins. Of these, polyurethane resins are preferable. Specific examples of the curing agent include aromatic isocyanate curing agents, aliphatic isocyanate curing agents, and alicyclic isocyanate curing agents. Of these, aromatic isocyanate curing agents are preferred. As the composition ratio of each component, a known composition ratio can be adopted, and it may be appropriately determined if necessary.

  The ink composition used for the light-color printing layer 2 is obtained, for example, by blending a curing agent with 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 print layer 2 is appropriately determined according to the required thickness of the double-sided pressure-sensitive adhesive tape and light reflectivity. The thickness of the light reflecting layer is preferably 1 to 20 μm, more preferably 3 to 12 μm. The light-colored printing layer 2 may be a single layer and may constitute a light-reflective layer. However, in order to provide sufficient light reflectivity, the light-reflective layer is formed by laminating 2 to 6 light-colored printed layers 2. It is preferable to configure.

[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 printing layer 3 include polyurethane resins, phenol resins, epoxy resins, silicone resins, acrylic resins, polyester resins, and polyolefin resins. Among them, polyurethane resins Is preferable, and a polyester polyurethane resin is more preferable. The polyester polyurethane resin is a polyurethane resin that also contains an ester bond in the 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 polyisocyanate and, if necessary, other components. The binder resin preferably has a relatively high Tg (glass transition temperature). Specifically, the Tg of the binder resin is preferably 12 ° C. or higher. As a result, tack is lowered even at the initial stage of curing of the black print layer 3, and blocking and wrinkles of the laminated base material are less likely to occur.

  Specific examples of the curing agent used for the black print layer 3 include aromatic isocyanate curing agents, aliphatic isocyanate curing agents, and alicyclic isocyanate curing agents. However, in the first aspect of the invention, an aromatic isocyanate curing agent is used as the curing agent used for the black print layer 3. Thereby, the hardening rate of the black printing layer 3 becomes quick, and it becomes difficult to generate | occur | produce blocking and a wrinkle of a laminated base material.

  The aromatic isocyanate curing agent is a curing agent containing at least an aromatic isocyanate. An aromatic isocyanate is a compound having an aromatic group such as a benzene ring and an isocyanate group, 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 xylylene diisocyanate is particularly preferable. The aromatic isocyanate curing agent generally includes an adduct of an aromatic isocyanate (adduct of diisocyanate and trimethylolpropane) and an isocyanurate (triisomer of diisocyanate).

  The amount of the curing agent is preferably 4 to 16 parts by mass, 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 printing layer 3 is obtained, for example, by blending a curing agent with a commercially available printing ink containing a coloring component (ink component) and a binder resin.

  The thickness of the light shielding layer comprising the black print layer 3 is appropriately determined according to the required thickness and light shielding properties of the double-sided pressure-sensitive 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 print layer 3 may be a single layer constituting a 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 fast curing speed, the light-shielding layer can be satisfactorily constituted by the single black printing layer 3, and the manufacturing process can be simplified.

[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 usable for this type of pressure-sensitive adhesive tape can be used. Examples of the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer 4 include transparent adhesives such as acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. Among these, acrylic adhesives, urethane adhesives, and silicone adhesives are preferable.

  A tackifier resin or a crosslinking agent may be added to the pressure-sensitive adhesive layer 4 as necessary. Examples of tackifying resins include rosin-based, polyterpene-based, petroleum-based, terpene-phenol-based, and polystyrene-based resins. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and metal chelate crosslinking agents.

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

[Laminated substrate]
The laminated base material in the present invention is a base material having at least the resin film 1, the bright print layer 2 and the black print layer 3 described above. The thickness of the laminated substrate is appropriately determined according to the required thickness of the double-sided pressure-sensitive adhesive tape. Usually, the thickness is preferably 12 μm to 50 μm, more preferably 10 to 50 μm.

  In 2nd this invention, the static frictional force according to JISK7125 of the black printing layer with respect to the resin film of a lamination | stacking base material is 2.0 N or less, Preferably it is 1.4-1.8N. When the laminated base material has such a low static frictional force, it becomes difficult for blocking to occur when the laminated base material is wound into a roll immediately after production, and it is also difficult to generate wrinkles due to frictional force at the time of winding. Become.

  The measuring method of the static friction force is in accordance with JIS K 7125, and another laminated base material fixed to a sliding piece having a weight of 200 g is placed on the resin film 1 of the laminated base material so that the black printed layer 3 is in contact, and the speed is 300 mm. Move the sliding piece in parallel at / min and measure the maximum stress (static friction force) that can be obtained first. Details thereof will be described in the column of Examples described later.

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

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention is a 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. Since the double-sided pressure-sensitive adhesive tape of the present invention can avoid blocking of the printing layer and yellowing of the pressure-sensitive adhesive layer, it can be used for fixing a liquid crystal display panel and a backlight unit of a liquid crystal display device used in a mobile phone, a touch panel, etc. It can be used suitably.

[Production method of double-sided adhesive tape]
The laminated base material in the present invention can be produced, for example, by forming the bright print layer 2 on the resin film 1 and forming the black print layer 3 thereon.

  The method for producing the double-sided pressure-sensitive adhesive tape of the first invention includes, for example, a step of forming the black print layer 3 using an ink composition containing a coloring component (ink component), a binder resin, and an aromatic isocyanate curing agent. Have Preferably, a step of forming a light print layer 2 on the resin film 1, a step of forming a black print layer 3 on the light print layer 2 using the ink composition to obtain a laminated substrate, and this It has the process of forming the adhesive layer 4 on both surfaces of a laminated base material.

  The method for producing the double-sided pressure-sensitive adhesive tape of the second invention includes, for example, a step of producing a laminated base material in which the static friction force according to JIS K 7125 of the black printing layer 3 against the resin film 1 is 2.0 N or less. Have. Preferably, the step of forming the light color printing layer 2 on the resin film 1, the black color of the black color printing layer 3 on the light color printing layer 2, and the static friction according to JIS K 7125 of the black color printing layer 3 against the resin film 1 It has the process of obtaining the laminated base material whose force is 2.0 N or less, and the process of forming the adhesive layer 4 on both surfaces of this laminated base material.

  According to each manufacturing method described above, blocking when the laminated base material is wound into a roll immediately after manufacturing is less likely to occur, and wrinkles due to frictional force during winding are less likely to occur.

  A further inventive method is characterized in that the black print layer 3 is formed in one step. Preferably, a step of forming a light color printing layer on the resin film, a step of forming a black printing layer on the light color printing layer in one step to obtain a laminated base material, and an adhesive on both sides of the laminated base material Forming a layer.

  Conventional black print layers for light shielding applications are generally formed by laminating 2 to 3 layers in order to obtain sufficient light shielding properties. However, the black print layer 3 of the present invention can form a sufficient light shielding layer in one step. Thereby, it is possible to avoid the problem that the unevenness of the unevenness of the coating surface becomes large and blocking easily occurs, and the manufacturing process of the laminated base material can be greatly reduced.

  As a method for printing the bright 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 flexographic printing method, an offset printing method, a relief printing method, and a screen printing method. Of these, the gravure printing method is preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In the following description, “part” means “part by mass”.

<Binder resin compositions 1-3 and comparative binder resin compositions C1-C7>
13.0 parts of a curing agent was blended with 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) described in the table, Tg of the binder resin b1 is a DSC measurement value, and the glass transition temperatures (Tg) of the binder resins b2 to b5 are values according to manufacturer information.

(Blocking test)
The binder resin composition was laminated on one side of a 12 μm thick transparent PET (polyethylene terephthalate) film to a thickness of 5 μm to obtain a binder coat film with a total thickness of 17 μm. This binder coat film was cut into a size of 30 mm × 40 mm to obtain a test piece. Five test pieces were overlapped, sandwiched between 1.5 mm thick glass plates, placed with a 2 kg weight, and allowed to stand at 40 ° C. for 2 days. Then, each test piece was peeled off and visually evaluated according to the following criteria. The results shown in Tables 1 and 2 are “◯”: Blocking occurred.
“×”: Blocking did not occur.

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

(Static friction force)
The static frictional force (transparent PET film of binder coat film same as blocking test vs. binder resin composition layer of binder coat film) was measured by a test method according to JIS K 7125. Specifically, the binder coat film was fixed to the test table with the transparent PET film side facing up. On the other hand, another binder coat film (size: 25 mm × 25 mm) was fixed to a sliding piece having a weight of 200 g. Then, the slip piece was gently placed on the test table so that the transparent PET film surface of the binder coat film fixed to the test table and the binder resin composition layer surface of the binder coat film fixed to the slide piece were in contact with each other. The sliding piece was moved in parallel at a speed of 300 mm / min, and the maximum stress (static friction force) obtained first was measured. The results are shown in Tables 1 and 2.

In Tables 1 and 2, each abbreviation indicates the following product.
“B1”: Polyester polyurethane resin (trade name E039 Medium Z, manufactured by Toyo Ink Co., Ltd.)
“B2”: Polyester polyurethane resin (trade name UR1400, manufactured by Toyobo Co., Ltd.)
“B3”: Polyester polyurethane resin (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name NIPPOLAN 2304)
“B4”: Polyester polyurethane resin (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name “Nipporan 3124”)
“B5”: Polyester polyurethane resin (manufactured by Sanyo Chemical Industries, Ltd., trade name Samprene IB-129)
“Ar-i”: xylylene diisocyanate (aromatic isocyanate curing agent) (trade name TK Hardener, manufactured by Toyo Ink Co., Ltd.)
“Al-i”: Hexamethylene diisocyanate (aliphatic isocyanate-based curing agent) (trade name LP Hardener, manufactured by Toyo Ink Co., Ltd.)

<Evaluation>
As is clear from the results shown in Table 1, binder resin compositions 1 and 2 using an aromatic isocyanate curing agent (ar-i) were excellent in all 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.

  Further, as is clear from the results shown in Table 2, the binder resin composition 3 having no static isocyanate curing agent (ar-i) but having a high static friction force was excellent in all properties. On the other hand, the binder resin compositions C5 to C7 having a low static friction force showed blocking in the blocking test and high probe tack.

<Example 1>
(Preparation of black ink composition 1)
Black ink (manufactured by Toyo Ink Co., Ltd., trade name: E039 PETAK black) was prepared. This black ink is a product in which the same resin as the binder resin b1 in the binder resin composition 1 described above is colored black. To 100 parts of this black ink, 8.0 parts by mass of the same aromatic isocyanate curing agent (trade name TK Hardener, Toyo Ink Co., Ltd.) as the curing agent (ar-i) in the binder resin composition 1 is blended. A black ink composition 1 was obtained.

(Preparation of white ink composition)
White ink (trade name E039PET63 white, manufactured by Toyo Ink Co., Ltd.) was prepared. This white ink is a product in which the same resin as the binder resin b1 in the binder resin composition 1 described above is colored white. 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.) as the curing agent (ar-i) in the binder resin composition 1, A white ink composition was obtained.

(Preparation of laminated substrate A)
Gravure printing was performed twice on one side of a transparent PET film with a thickness of 12 μm using a white ink composition, and a white printing layer with a thickness of 6 μm (L ^* (lightness) = 83.47, reflectance for a wavelength of 550 nm). 74.4%, average reflectivity for a wavelength of 380 to 780 nm = 69.5%). Further, gravure printing was performed once on the surface of the white print layer using the black ink composition 1 to form a black print layer having a thickness of 5 μm, and a laminated substrate A having a total thickness of 23 μm was obtained.

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

(Production of double-sided adhesive tape)
A transparent acrylic pressure-sensitive adhesive composition is applied to both surfaces of the laminated base material A to form a pressure-sensitive adhesive layer having a thickness of 18 μm, and the pressure-sensitive adhesive layer 4 / black printing layer 3 / white printing layer (2 A double-sided pressure-sensitive adhesive tape having a total thickness of about 60 μm composed of a laminated structure of light-colored printing layer 2) / resin film 1 / adhesive layer 4 formed by repeated printing was obtained.

<Example 2>
(Preparation 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 pressure-sensitive adhesive tape having a total thickness of about 60 μm was prepared in the same manner as in Example 1 except that the laminated base material B was used and the thickness of the pressure-sensitive adhesive layer was changed to 21 μm.

<Comparative Example 1>
(Preparation of black ink composition 2)
The black ink composition 1 of Example 1 except that the same aliphatic isocyanate curing agent (trade name LP Hardener, manufactured by Toyo Ink Co., Ltd.) as the curing agent (al-i) in the comparative binder resin composition C1 was used. A black ink composition 2 was prepared in the same manner as described above.

(Preparation 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 prepared in the same manner as in Example 1 except that the laminated substrate C was used.

<Comparative Example 2>
(Preparation of laminated substrate D)
On one side of a 12 μm thick transparent PET film, gravure printing was performed twice using the white ink composition to form a white printed layer having a thickness of 6 μm. Then, gravure printing is performed once on the other surface of the transparent PET film using the black ink composition 1 to form a black printed layer having a thickness of 5 μm, and a laminated substrate D having a total thickness of 23 μm is obtained. It was.

(Production of double-sided adhesive tape)
A pressure-sensitive adhesive layer having the same thickness of 18 μm as that of Example 1 was formed on both surfaces of the laminated substrate D, and pressure-sensitive adhesive layer 4 / black printing layer 3 / resin film 1 / white printing layer (light formed by two printings). A double-sided pressure-sensitive adhesive tape having a total thickness of about 60 μm composed of a laminated structure of color printing layer 2) / pressure-sensitive adhesive layer 4 was obtained.

  The double-sided pressure-sensitive adhesive tapes and laminated base materials 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)
Laminated substrates A to D were cut into a size of 30 mm × 40 mm to obtain test pieces. Each test piece was evaluated by performing the same test as the blocking test of the binder resin composition.

(Static friction force)
For Examples 1 and 2 and Comparative Example 1, the static friction force (transparent PET film of laminated substrate vs. black printed layer of 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 transparent PET film side was on the top. On the other hand, another laminated substrate (size: 25 mm × 25 mm) was fixed to a sliding piece having a weight of 200 g. Then, gently place the sliding piece on the test table so that the transparent PET film surface of the laminated base material fixed to the test table and the black printed layer surface of the laminated base material fixed to the sliding piece contact each other at a speed of 300 mm / min. The sliding piece was moved in parallel, and the maximum stress (static friction force) obtained first was measured. Moreover, regarding the comparative example 2, the static frictional force of the white printed layer of a laminated base material vs. the black printed layer of a laminated base material was measured by the same method.

(Transmittance)
The average transmittance | permeability of wavelength 380-780 nm of a double-sided adhesive tape was measured using the ultraviolet visible infrared spectrophotometer (The JASCO Corporation make, brand name V-670).

(Transmission density)
Using a portable black and white transmission densitometer (trade name TM-5, manufactured by Ihara Denshi Kogyo Co., Ltd.), the transmission density of the double-sided adhesive tape was measured. Since the measurement range of the apparatus is 0.0 to 6.0, the transmission density exceeding the range is expressed as “6.0 or more”.

(Yellowing test)
The double-sided pressure-sensitive adhesive tape was heated at 85 ° C. for 240 hours, and the yellowness after the heating was measured with a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name SE6000). For the hue evaluation, b * (yellow direction) of the L * a * b * color system defined in JIS Z 8729 was selected. This means that the greater the difference in b * before and after heating Δb * = (value at 85 ° C.) − (Initial value), the greater the degree of yellowing.

In Tables 3 and 4, each abbreviation indicates the following product.
“B1”: Polyester polyurethane resin (trade name E039 Medium Z, manufactured by Toyo Ink Co., Ltd.)
“Ar-i”: xylylene diisocyanate (aromatic isocyanate curing agent) (trade name TK Hardener, manufactured by Toyo Ink Co., Ltd.)
“Al-i”: Hexamethylene diisocyanate (aliphatic isocyanate-based curing agent) (trade name LP Hardener, manufactured by Toyo Ink Co., Ltd.)

<Evaluation>
As is clear from the results shown in Table 3, the double-sided pressure-sensitive adhesive tapes of Examples 1 and 2 were excellent in all properties. On the other hand, the double-sided pressure-sensitive adhesive tape of Comparative Example 1 using an aliphatic isocyanate-based curing agent (al-i) and having a relatively high static friction force showed blocking in the blocking test.

  Further, as is clear from the results shown in Table 4, lamination of pressure-sensitive adhesive layer 4 / black printing layer 3 / resin film 1 / white printing layer (light color printing layer 2 formed by two printings) / pressure-sensitive adhesive layer 4 The double-sided pressure-sensitive adhesive tape of Comparative Example 2 having a structure had a large degree of yellowing (Δb *). This is considered to be because the white printed layer and the pressure-sensitive adhesive layer are in direct contact with each other, and the ink component in the white printed layer is transferred to the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer is discolored. Moreover, in the comparative example 2, blocking generate | occur | produced in the blocking test of the laminated base material. This is due to the high affinity between the white printed layer and the black printed layer that are in direct contact.

  Since the double-sided pressure-sensitive adhesive tape of the present invention has little yellowing of the pressure-sensitive adhesive layer, it can stably ensure light-shielding properties and light reflectivity for a long period of time. Moreover, since the ink of a printing layer hardens | cures rapidly, it is not necessary to provide an antiblocking film | membrane when winding up in roll shape, and a printing layer can be formed with few processes, and the manufacturing process of a base material can be reduced significantly. Therefore, the double-sided pressure-sensitive adhesive tape of the present invention is very useful as a double-sided pressure-sensitive adhesive tape used for fixing a liquid crystal display panel and a backlight unit of a liquid crystal display device used for mobile phones, touch panels and the like.

DESCRIPTION OF SYMBOLS 1 Resin film 2 Light color printing layer 3 Black printing layer 4 Adhesive layer

Claims (8)

  A double-sided pressure-sensitive adhesive tape comprising a laminated substrate having at least one light-colored printed layer between a resin film and a black printed layer, and an adhesive layer provided on both surfaces of the laminated substrate, wherein the black printed layer A double-sided pressure-sensitive adhesive tape comprising a structure resulting from an aromatic isocyanate curing agent.   The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the thickness of the laminated base material is 12 μm to 50 μm.   The double-sided pressure-sensitive adhesive tape according to claim 1, which is used for fixing the liquid crystal display panel and the backlight unit.   A double-sided pressure-sensitive adhesive tape comprising a laminated base material having at least one light-colored printed layer between a resin film and a black printed layer, and an adhesive layer provided on both sides of the laminated base material, wherein the laminated base material A double-sided pressure-sensitive adhesive tape, wherein the black printed layer has a static frictional force of 2.0 N or less according to JIS K 7125 for the resin film.   The double-sided pressure-sensitive adhesive tape according to claim 4, wherein the thickness of the laminated base material is 12 μm to 50 μm.   The double-sided pressure-sensitive adhesive tape according to claim 4, which is used for fixing the liquid crystal display panel and the backlight unit.   It is a method for manufacturing the double-sided adhesive tape as described in any one of Claims 1-6, Comprising: A black printed layer is formed in 1 process, The manufacturing method of the double-sided adhesive tape characterized by the above-mentioned. Forming a bright print layer on the resin film;
The double-sided pressure-sensitive adhesive tape according to claim 7, comprising a step of forming a black printed layer on the light-colored printed layer in one step to obtain a laminated substrate, and a step of forming an adhesive layer on both sides of the laminated substrate. Production method.

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