JP4645074B2 - Double-sided adhesive tape and liquid crystal display module unit using the same - Google Patents

Description

  The present invention secures an LCD panel and a backlight housing sandwiched by a flexible printed circuit board (hereinafter referred to as “FPC”) of a liquid crystal display (hereinafter referred to as “LCD”) module unit. The present invention relates to a double-sided pressure-sensitive adhesive tape having a light reflection property and a light shielding property, and an LCD module unit using the tape.

  LCD modules (liquid crystal display devices) are used in a wide range of fields such as word processors and personal computers. Especially in electronic notebooks, mobile phones, PHS, and the like, they are used as display devices for increasingly smaller electronic devices. It has become like this.

As such an LCD module, for example, a sidelight type backlight LCD module unit 100 ′ shown in FIG. FIG. 7 is a schematic diagram showing a schematic configuration of a conventional LCD module unit 100 ′ using a double-sided adhesive tape for fixing an LCD panel and a backlight housing, (a) is a cross-sectional view, and (b) is a cross-sectional view. It is an exploded view. In general, the LCD module unit 100 ′ includes a reflector 18, a light guide plate 17, a diffusion sheet 15, one or more prism sheets 14 that are used as needed to increase luminance, A double-sided adhesive tape 13 and an LCD panel 20 are laminated in this order, and a light source 16 composed of an LED (Light Emitting Diode) equipped with a lamp reflector or a cold cathode tube is disposed on the side of the light guide plate 17.
As shown in FIG. 7, the double-sided adhesive tape 13 is sandwiched between the LCD panel 20 and the backlight housing 19, and the backlight housing 19 and the LCD panel 20 are fixed. This double-sided pressure-sensitive adhesive tape 13 is usually punched into a frame shape, and its width is about 0.5 to 10 mm. In addition, the double-sided adhesive tape 13 is in contact with not only the backlight housing 19 but also the prism sheet 14 to fix the diffusion sheet 15 and the like installed on the lower side of the prism sheet 14 and to prevent dust from entering. It also has a role to prevent cracking of the above parts due to impact by providing cushioning properties.

At present, LCD modules are becoming larger and smaller as the screen size is reduced and the amount of information increases. As a result, the positions of the light source 16 and the LCD panel 20 approach each other, and light from the light source 16 leaks upward through the double-sided adhesive tape 13, resulting in inconvenience that the display surface of the LCD panel 20 becomes difficult to see. .
For this reason, the double-sided pressure-sensitive adhesive tape 13 sandwiched between the LCD panel 20 and the backlight housing 19 is required to have high light shielding properties, and the LCD panel 20 is driven at the same time that the display surface of the LCD panel 20 is easily visible. Therefore, it is also required to have a role of blocking the entrance of light to the driver 12 and preventing the driver 12 from malfunctioning.

  In recent years, the double-sided adhesive tape 13 not only blocks light but also reflects light entering the periphery of the backlight housing 19 to efficiently transmit light from the light source 16 to the back surface of the LCD panel 20. It is required to have high light reflection performance for guiding. Since the double-sided pressure-sensitive adhesive tape 13 has high light reflection performance, the LCD module unit 100 ′ can cope with a thin portable device, and power saving can be achieved. Thus, the double-sided pressure-sensitive adhesive tape 13 is strongly required to be a thin film and have light reflectivity and light shielding properties.

  In order to solve such a problem, a double-sided pressure-sensitive adhesive tape in which a pressure-sensitive adhesive layer is laminated on a base material having at least two metal vapor-deposited layers has been proposed (for example, see Patent Document 1).

  In addition, a double-sided pressure-sensitive adhesive tape has been proposed in which one side of the base film is black and the opposite side is white, and a pressure-sensitive adhesive layer containing a black colorant is provided on one or both sides of the base film (for example, , See Patent Document 2).

  Furthermore, a double-sided pressure-sensitive adhesive tape has been proposed in which one surface forms a low reflectance surface and the other surface forms a high reflectance surface or a highly scattering surface (see, for example, Patent Document 3).

  The double-sided pressure-sensitive adhesive tape disclosed by these technologies reflects and effectively uses incident light from the backlight housing, and shields unnecessary light such as leakage light and external light, thereby enabling high-contrast display. It is described.

In addition, as a double-sided adhesive tape excellent in impact resistance that does not drop off parts due to impact when dropped, the maximum value of the loss tangent (tan δ) of the adhesive is −40 to −10 ° C., and the loss at that time A double-sided pressure-sensitive adhesive tape having a maximum value of tangent (tan δ) of 1.4 to 2.5 has been proposed (see, for example, Patent Document 4).
JP 2002-23663 A JP 2002-235053 A Japanese Patent Laid-Open No. 2002-249741 JP 2001-72951 A

  However, in the double-sided pressure-sensitive adhesive tapes according to Patent Documents 1 to 3, no technical consideration has been made regarding the adhesive force when the repulsive force or drop impact of the parts is applied to the double-sided pressure-sensitive adhesive tape, Further studies were necessary for such issues.

  Further, the double-sided pressure-sensitive adhesive tape excellent in impact resistance according to Patent Document 4 does not drop off the component due to the impact at the time of dropping, but peels off due to the repulsive force of the component.

Specifically, the peeling due to the repulsive force 22 of the component is as follows.
Unlike the conventional LCD module unit 100 ′ shown in FIG. 7, the recent LCD module unit 100 shown in FIG. 1 has an LCD panel 20 integrated with the FPC 21. FIG. 1 is a schematic view showing an embodiment of an LCD module unit 100 of the present invention in which the double-sided adhesive tape of the present invention is used for fixing an LCD panel integrated with an FPC and a backlight housing. a) is a sectional view, (b) is an exploded view, and (c) is an overall view. The FPC 21 is bent at approximately 180 ° in the direction shown by the arrow in FIG. 8C, sandwiches the LCD panel 20 and the backlight housing 19, and hooks or other double-sided adhesives are attached to the back surface of the backlight housing 19. It is fixed with tape. Therefore, the double-sided adhesive tape 13 that fixes the LCD panel 20 and the backlight housing 19 is always loaded with a repulsive force 22 for the FPC 21 to return horizontally.
Although the repulsive force 22 is a small force of 0.8 to 1.3 N, it is a double-sided pressure-sensitive adhesive tape that is always loaded in the direction of the arrow shown in FIG. However, there was a problem that peeling occurred for a long time.

  Therefore, in view of the above-mentioned problems of the prior art, the object of the present invention is to fix the LCD panel and the backlight housing, which are sandwiched between FPCs and are constantly loaded with a repulsive force, with a thin film. It is an object of the present invention to provide a double-sided pressure-sensitive adhesive tape that is excellent in drop impact resistance and resilience resistance, and also has excellent light reflectivity and light shielding properties.

  Another object of the present invention is to provide an LCD module unit in which components are fixed using the double-sided adhesive tape.

To solve this problem,
The present invention relates to a double-sided pressure-sensitive adhesive tape having light reflectivity and light-shielding properties used for fixing an LCD panel and a backlight housing, which are sandwiched between FPCs bent at approximately 180 °, in an LCD module unit . The double-sided pressure-sensitive adhesive tape comprises a base material provided with a light reflecting surface and a light-shielding surface on a support, and a pressure-sensitive adhesive layer provided on both surfaces of the base material. It has a maximum value (M ₁ ) of loss tangent (tan δ) at a frequency of 1 Hz in the temperature range of −22 ° C. , and (A) loss tangent at a frequency of 1 Hz in the temperature range of −50 to −20 ° C. A (meth) acrylic copolymer (I) having a maximum value (M ₂ ) of (tan δ) , (b) a polymerized rosin ester as a tackifier, and the double-sided pressure-sensitive adhesive tape A triacetyl cellulose film and Speed peeling at constant load peeling test for polycarbonate plates 100 mm / time Ri der hereinafter the peeling speed, the double-sided adhesive tape of 10mm width which is backed with a polyester film 25 [mu] m, ambient temperature 23 ° C., 50% relative humidity Under the conditions, the substrate was applied to the triacetyl cellulose film and the polycarbonate plate by one reciprocating pressure with a 2 kg roller and left standing for 1 hour, and then a constant load of 0.98 N was applied to the double-sided adhesive tape at 90 °. and loading in the direction of, and provides a double-sided adhesive tape, characterized in value der Rukoto obtained by dividing the double-sided adhesive tape peeling length after 1 hour time.

Further, the present invention provides an LCD module unit characterized in that an LCD panel sandwiched between FPCs bent at approximately 180 ° and a backlight housing are fixed using the double-sided adhesive tape. It is.

Since the double-sided pressure-sensitive adhesive tape of the present invention has a low peeling speed in the constant load peel test, the LCD panel and the backlight housing that are sandwiched between FPCs and are constantly loaded with a repulsive force can be fixed. It has excellent resilience resistance that does not cause peeling.
Further, this double-sided pressure-sensitive adhesive tape has excellent drop impact resistance because the pressure-sensitive adhesive layer has a maximum value (M ₁ ) of loss tangent (tan δ) in a temperature range of −40 to −15 ° C.
Furthermore, since this double-sided pressure-sensitive adhesive tape has a light reflecting surface and a light shielding surface on the support, it has excellent light reflectivity and light shielding properties.

In addition, the LCD module unit of the present invention uses the double-sided adhesive tape to fix the LCD panel sandwiched between the FPC and the backlight housing, and thus peels off between the LCD panel and the backlight housing. In addition, it has excellent drop impact resistance and resilience resistance.
For this reason, even when a mobile phone incorporating the LCD module unit falls, the LCD panel does not break or peel off.

[Double-sided adhesive tape]
Embodiments of the double-sided pressure-sensitive adhesive tape of the present invention will be described below with reference to the drawings.

  FIG. 2 is a conceptual cross-sectional view showing an embodiment of the double-sided pressure-sensitive adhesive tape 13 of the present invention. The double-sided pressure-sensitive adhesive tape 13 of the present embodiment is generally composed of a base material 5 and pressure-sensitive adhesive layers 4 and 4 provided on both surfaces of the base material 5. And this base material 5 is comprised from the support body 1 which laminated | stacked the light reflection layer 2 and the light shielding layer 3 on both surfaces.

The pressure-sensitive adhesive layer 4 according to the present invention has a temperature at which the maximum value (M ₁ ) of loss tangent (tan δ) at a frequency of 1 Hz is −40 to −15 ° C., preferably −35 to −20 ° C. Preferably, it is −30 to −22 ° C. When the temperature showing the maximum value (M ₁ ) of the loss tangent (tan δ) is in the above range, the impact resistance and the cohesive force of the pressure-sensitive adhesive can be improved. This is because the cohesive force of the pressure-sensitive adhesive is extremely lowered when the temperature is lower than −40 ° C., whereas the impact resistance is lowered when the temperature exceeds −15 ° C.
The pressure-sensitive adhesive layers 4 and 4 may be a single layer or a multilayer composed of a plurality of layers or sheets.

Here, the physical meaning of the temperature indicating the maximum value (M ₁ ) of the loss tangent (tan δ) will be described.
Generally, when a structure in which a component is fixed with a double-sided adhesive tape falls, the structure vibrates in a frequency range peculiar to the shape due to the impact. This is called “natural frequency region”. The energy in the frequency range (vibration energy) is transmitted to the parts joined to the structure via the double-sided adhesive tape.
Therefore, the higher the vibration energy absorbability of the double-sided pressure-sensitive adhesive tape, the smaller the vibration energy transmitted to the part and the less likely the part will drop off. The term “energy absorption” as used herein refers to the ratio of converting mechanical energy to heat energy. For adhesive layers that are viscoelastic bodies having both viscous and elastic properties, The higher the ratio, the better the energy absorption.
Therefore, when the elasticity (storage elastic modulus) and viscosity (loss elastic modulus) of the pressure-sensitive adhesive layer (viscoelastic body) are measured for each frequency, it is known that both values become higher as the frequency becomes higher. . This means that when the frequency is increased, the elastic layer strongly appears in the pressure-sensitive adhesive layer.

On the other hand, the loss tangent (tan δ), which is a value obtained by dividing the viscosity by elasticity, rises toward the higher frequency side, drops again after showing a maximum value (M ₁ ) at a certain point. Maxima viscosity in (M ₁₎ from the low-frequency side, the viscoelastic elastic coexist behaved as (adhesive), behave as glassy solid in a high frequency band than the maximum value (M ₁₎ Show. Therefore, the vibration energy in the high frequency region cannot be absorbed from the frequency showing the maximum value (M ₁ ).
On the other hand, when the maximum value (M ₁ ) exceeds 1, the viscosity exceeds the elasticity and the energy absorption becomes large. Generally, in a viscoelastic body, a viscoelastic function obtained at an arbitrary temperature T can be converted into a value of a reference temperature T ₀ by converting it into a unit of time (or frequency). This property is called the temperature-time (or temperature-frequency) conversion rule. When this conversion method is applied, the high frequency range correlates with the low temperature range, for example, 10 ³ Hz at 25 ° C. is −10 ° C. This corresponds to 1 Hz.

From the above, when the frequency or temperature at which the loss tangent (tan δ) of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive tape shows the maximum value (M ₁ ) is in the natural frequency region or temperature region generated when the electronic device falls, The vibration energy in the frequency range exceeding the frequency showing the maximum value (M ₁ ) (or the temperature region below the temperature showing the maximum value (M ₁ )) reaches the part without being absorbed by the adhesive layer. Occurrence of falling off tends to occur.
The maximum value (M ₁ ) of the loss tangent (tan δ) at a frequency of 1 Hz of the pressure-sensitive adhesive layer in the double-sided pressure-sensitive adhesive tape of the present invention is in the temperature range of −40 to −15 ° C. The cohesive strength of the pressure-sensitive adhesive is improved.

The pressure-sensitive adhesive layer used for the double-sided pressure-sensitive adhesive tape of the present invention is a known natural rubber-based pressure-sensitive adhesive as long as it has a maximum value (M ₁ ) of loss tangent (tan δ) in the temperature range of −40 to −15 ° C. An adhesive, a synthetic rubber adhesive, or an acrylic adhesive can be used.
Among them, (A) a (meth) acrylic copolymer (I) having a maximum value (M ₂ ) of loss tangent (tan δ) in a temperature range of −50 to −20 ° C., and (A) a tackifier. The thing containing is preferable.
In this specification, (meth) acrylic acid means acrylic acid or methacrylic acid, and the same applies to derivatives of acrylic acid or methacrylic acid.

The (meth) acrylic copolymer (I) has a maximum value (M ₂ ) of loss tangent (tan δ) in a temperature range of −50 to −20 ° C. If this temperature is less than −50 ° C., the cohesive force of the (meth) acrylic copolymer (I) is extremely reduced, and on the other hand, if it exceeds −20 ° C., the pressure-sensitive adhesive layer Because it is too close to the upper limit (−15 ° C.) of the maximum temperature range (−15 ° C.) of the maximum value (M ₁ ) of the loss tangent (tan δ) of the resin, the blending amount of the tackifier is limited. This is because it becomes difficult and undesirable.

Usually, when a tackifier is added, the temperature indicating the maximum value (M ₁ ) of the loss tangent (tan δ) at a frequency of 1 Hz of the pressure-sensitive adhesive layer increases. The temperature showing the maximum value (M ₁ ) of loss tangent (tan δ) at a frequency of 1 Hz of the pressure-sensitive adhesive layer in the present invention is −40 to −15 ° C., but in order to improve the resilience resistance, a certain amount It is necessary to add a tackifier to the pressure-sensitive adhesive layer. At that time, in order to prevent the temperature showing the maximum value (M ₁ ) from rising, the temperature range of the maximum value (M ₂ ) of the loss tangent (tan δ) of the (meth) acrylic copolymer (I) is in the above range. Preferably there is.

  The type of the (meth) acrylic copolymer (I) is not particularly limited, and among them, (a) an alkyl side chain having 1 to 14 carbon atoms (meth) 90 to 99.9 parts by mass of alkyl acrylate ester, (b) 0.01 to 1.0 part by mass of a monomer containing a hydroxyl group, and (c) a monomer having a polar group other than (b) 0.1 to 6. The (meth) acrylic copolymer (I) obtained with 0 part by mass as the main component is preferred.

Specific examples of the (a) (meth) acrylic acid alkyl ester having an alkyl side chain having 1 to 14 carbon atoms include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n -Propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, n- Hexyl methacrylate, cyclohexyl methacrylate, n- octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, isodecyl methacrylate, lauryl methacrylate and the like.
Among them, a methacrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms or an acrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms is preferable, and the alkyl side having 4 to 9 carbon atoms is preferred. More preferred are alkyl acrylates having a chain.

(B) As the monomer containing a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, hydroxypropyl (meth) acrylate, caprolactone-modified (Meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol (meth) acrylate and the like.
Among these, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, or caprolactone-modified (meth) acrylate is preferable.

  (C) Monomers having polar groups other than (b) include monomers having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, acrylic acid dimer, ethylene oxide-modified succinic acid acrylate Monomers having an amide group such as N-vinyl-2-pyrrolidone, n-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide, 2- (perhydrophthalimido-N-yl) ethyl acrylate, anhydrous Examples thereof include maleic acid and itaconic anhydride.

Further, if the temperature showing the maximum value (M ₂ ) of the loss tangent (tan δ) of the (meth) acrylic copolymer (I) is within the temperature range of −50 to −20 ° C., vinyl acetate, Other copolymerizable monomers such as styrene may be added.

  The mass average molecular weight of this (meth) acrylic copolymer (I) is 400,000 to 2,000,000, preferably 600,000 to 130 in terms of polystyrene measured by gel permeation chromatography (GPC). Ten thousand. This is because if the mass average molecular weight is less than 400,000, the cohesive force and the surface adhesion strength decrease, which is not preferable. On the other hand, if it exceeds 2 million, the coating suitability is inferior, which is not preferable.

The (meth) acrylic copolymer (I) can be polymerized by known radical polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, and supercritical polymerization.
Polymerization can be initiated by peroxides such as benzoyl peroxide and lauroyl peroxide, thermal initiation methods using azo initiators such as azobisisobutyronitrile, acetophenone, benzoin, benzyl ketal. The starting method by ultraviolet rays, such as a system, an acyl phosphine oxide system, a benzophenone system, and a maleimide system, and the starting method by an electron beam can be arbitrarily selected.
Among these, a heat initiation method using an azo initiator and a light initiation method using an acylphosphine oxide initiator are preferable.

Next, (i) as a tackifier, (1) (meth) acrylic having a glass transition temperature higher by 30 ° C. or more than the temperature indicated by the maximum value (M ₂ ) and having a mass average molecular weight of 500 to 20000 Copolymer (II) or (2) polymerized rosin ester is preferred.
This tackifier (1) (meth) acrylic copolymer (II) or (2) polymerized rosin ester has a maximum loss tangent (tan δ) value of (meth) acrylic copolymer (I) ( Since the temperature of M ₂ ) does not increase so much, it can be used in a relatively large amount. These tackifiers are preferably used either alone or in combination.

This (1) (meth) acrylic copolymer (II) having a glass transition temperature higher by 30 ° C. or more than the temperature indicated by the maximum value (M ₂ ) and having a mass average molecular weight of 500 to 20000 is an acrylic resin. A (meth) acrylic copolymer (II) obtained by reacting an acid alkyl ester or methacrylic acid alkyl ester as a main component can be used. The mass average molecular weight of this resin is preferably 500 to 20000, more preferably 2000 to 20000, and particularly preferably 2000 to 10,000. This is because when the mass average molecular weight is less than 500, the cohesive force is poor, which is not preferable. On the other hand, when it exceeds 20000, the compatibility with the (meth) acrylic copolymer (I) decreases, which is not preferable. .

The glass transition temperature of the (meth) acrylic copolymer (II) is 30 ° C. or more higher than the temperature showing the maximum value (M ₂ ) of the loss tangent (tan δ) of the (meth) acrylic copolymer (I). Is preferable, and it is more preferable that it is 60 degreeC or more. The upper limit of the glass transition temperature of the (meth) acrylic copolymer (II) is not particularly limited as long as it does not impair the gist of the present invention, but the upper limit temperature is 110 ° C. Preferably, it is 80 degreeC. The glass transition temperature of the (meth) acrylic copolymer (II) is a value measured by differential scanning calorimetry (DSC).

  The main raw material component of such a (meth) acrylic copolymer (II) is not particularly limited, and among them, (a) the alkyl side chain having 1 to 14 carbon atoms is included. (Meth) acrylic acid alkyl esters are preferred, such as cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, etc. (Meth) acrylic acid alkyl esters having the following alicyclic skeleton are more preferred, and cyclohexyl (meth) acrylate is particularly preferred.

Furthermore, the monomer etc. which have polar groups other than said (b) hydroxyl group-containing monomer and said (c) (b) can be used.
Here, (a) the compounding amount of other vinyl monomers other than (meth) acrylic acid alkyl ester having an alkyl side chain having 1 to 14 carbon atoms is arbitrarily set, among them, (A) It is preferable that these are 0-10 mass parts with respect to 90-100 mass parts of (meth) acrylic-acid alkylester which has a C1-C14 alkyl side chain.

  The (meth) acrylic copolymer (II) used in the present invention can be produced by the same method as the (meth) acrylic copolymer (I).

  The (2) polymerized rosin ester as a tackifier is an ester of a dimer of rosin acid and a polyhydric alcohol, and is a resin having a softening point of 120 to 170 ° C. Among these, those which are esters of polymerized rosin and glycerin and esters of polymerized rosin and pentaerythritol are preferred, and those having a softening point of resin of 140 ° C. or less are more preferred.

  Moreover, you may add another tackifier in the range which does not inhibit performance as needed. It is preferable that the addition amount of other tackifiers is less than 50 mass% with respect to the said tackifier.

  The amount of the (a) tackifier used relative to 100 parts by mass of the (a) (meth) acrylic copolymer (I) is preferably 5 to 25 parts by mass, and 10 to 20 parts by mass. Is more preferable. This is because if the amount of the tackifier used is less than 5 parts by mass, the resilience resistance is lowered, which is not preferable. On the other hand, if it exceeds 25 parts by mass, the drop impact resistance is lowered, which is not preferable.

Moreover, in order to raise the cohesion force of an adhesive layer, it is preferable to bridge | crosslink an adhesive. The degree of cross-linking is preferably 15 to 45%, more preferably 15 to 40%, and most preferably 15 to 35%. This is because when the gel fraction of the pressure-sensitive adhesive layer is within the above range, the double-sided pressure-sensitive adhesive tape becomes soft, can cope with the repulsive force of the FPC that is constantly loaded, and does not peel off. If the gel fraction of the pressure-sensitive adhesive layer is less than 15%, the cohesive force of the pressure-sensitive adhesive is too low, and it is not preferred because it is inferior in processability. On the other hand, if it exceeds 45%, the double-sided pressure-sensitive adhesive tape becomes hard and peels off. Therefore, it is not preferable.
Here, the gel fraction is a value expressed as a percentage obtained by dividing the mass of the residual gel substance by the mass before immersion when the double-sided pressure-sensitive adhesive tape is immersed in toluene for 24 hours.

As a method for crosslinking the pressure-sensitive adhesive, a conventionally known method can be used, but it is preferable to perform crosslinking by adding a crosslinking agent to the pressure-sensitive adhesive.
Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, chelate-based crosslinking agents, and aziridines. Among these, an isocyanate-based crosslinking agent rich in reactivity with the component (b) of the (meth) acrylic copolymer is preferable.

  Moreover, you may add various additives, antioxidant, a ultraviolet absorber, a filler, a pigment, a thickener, etc. to the adhesive as long as it does not inhibit performance as needed.

  The pressure-sensitive adhesive layer coating solution (pressure-sensitive adhesive solution) used for the double-sided pressure-sensitive adhesive tape of the present invention can be prepared by dissolving the above pressure-sensitive adhesive and, if necessary, other additives in an organic solvent. The organic solvent is not particularly limited as long as it dissolves the above-described blending components and does not react with the functional group of the crosslinking agent, but is well-known and commonly used, such as ethyl acetate, toluene, xylene, n-hexane, acetone, methyl ethyl ketone. These organic solvents can be used alone or in combination. Of these, ethyl acetate, n-hexane, acetone, and methyl ethyl ketone are preferable.

  Next, the base material 5 constituting the double-sided pressure-sensitive adhesive tape of this embodiment will be described. This base material 5 is comprised from the support body 1 which laminated | stacked the light reflection layer 2 and the light shielding layer 3 on both surfaces.

  As the support 1, a conventionally known and commonly used support can be used as long as the light reflecting layer 2 and the light shielding layer 3 can be laminated. Among these, a highly transparent polyester film excellent in transparency and heat resistance, and polyethylene terephthalate (PET) are preferable.

The light reflecting layer 2 is a layer that is laminated on the support 1 to become a light reflecting surface. Specifically, a white ink layer, a metal thin film layer, or the like may be provided as the light reflecting surface. 1 may be kneaded with titanium oxide or barium sulfate to form a light reflecting surface. Alternatively, a white pigment such as titanium oxide or barium sulfate may be dispersed in the pressure-sensitive adhesive layer 4 to form a light reflecting surface.
The light reflecting layer 2 is a support that is placed on the backlight housing 19 side, that is, on the light source 16 side when the double-sided adhesive tape 13 is sandwiched between the LCD panel 20 and the backlight housing 19. 1 is preferably formed on one side.

In order to obtain high light reflectivity with the thin substrate 5, it is preferable to provide a vapor deposition layer mainly composed of aluminum and silver as the light reflection layer 2, and it is most preferable to provide a silver vapor deposition layer. When providing a silver vapor deposition layer, in order to improve rust prevention and the adhesiveness with respect to the support body 1, a rust prevention coating layer is provided on a silver vapor deposition layer, and a vapor deposition anchor is provided between the support body 1 and the silver vapor deposition layer. It is preferred to provide a layer.
As a commercially available silver vapor deposition film provided with a silver vapor deposition layer on the support 1, Reiko Ruil Mirror (registered trademark) 37W01, 37W02, 23S04, Sai-Ing Co., Ltd. Ag-VM PET, Tokyo Nakai Co., Ltd. Examples include Kiraraflex, manufactured by Shoji Co., Ltd.

The light shielding layer 3 is a layer that is laminated on the support 1 to be a light shielding surface. Specifically, a black ink layer, a metal vapor deposition layer, or the like may be provided as the light shielding surface. A black pigment such as black may be kneaded to form a light shielding surface. Alternatively, a black pigment such as carbon black may be dispersed in the pressure-sensitive adhesive layer 4 to form a light shielding surface.
The light shielding layer 3 is formed on one side of the support 1 so that it is placed on the LCD panel 20 side when the double-sided adhesive tape 13 is sandwiched between the LCD panel 20 and the backlight housing 19. preferable.

  Moreover, 3-50 micrometers is preferable from the viewpoint of making a double-sided adhesive tape into a thin film, and the thickness of the base material 5 which provided the light reflection surface and the light-shielding surface in the support body 1 is the most preferable. If the thickness of the substrate 5 is less than 3 μm, the processability of the double-sided pressure-sensitive adhesive tape is undesirably lowered. On the other hand, if the thickness exceeds 50 μm, the followability of the double-sided pressure-sensitive adhesive tape to the adherend is reduced. This is because the adhesive force is lost to the repulsive force of the material 5 itself, and peeling trouble is likely to occur, which is not preferable.

Moreover, it is preferable that the reflectance in the light reflection surface of the base material 5 is 65% or more, It is more preferable that it is 80% or more, It is especially preferable that it is 90% or more. This is because it is preferable that the visible light reflectance on the light reflecting surface is 65% or more because the luminance of the LCD panel is increased.
The reflectance is not a reflectance value from the light reflecting layer 2 itself, but a reflectance value at the light reflecting surface including the adhesive layer.
This reflectance is obtained by measuring the total light reflectance (Rt) of the light reflecting surface using a transmission / reflectance meter HR-100 (manufactured by Murakami Color Research Laboratory Co., Ltd.).

Moreover, it is preferable that the transmittance | permeability in the light-shielding surface of the base material 5 is less than 0.1%, and it is more preferable that it is less than 0.01%. This is because if the transmittance at the light shielding surface is less than 0.1%, light leakage hardly occurs and the visibility of the LCD panel is improved, which is preferable.
This transmittance is obtained by measuring the total light transmittance (Tt) of the light shielding surface using a transmission / reflectance meter HR-100 (manufactured by Murakami Color Research Laboratory Co., Ltd.).

  The double-sided pressure-sensitive adhesive tape of the present invention has a peeling rate of 100 mm / hour or less in a constant load peel test on a triacetyl cellulose film and a polycarbonate (hereinafter referred to as “PC”) plate. The peeling speed is preferably 70 mm / hour or less, and more preferably 40 mm / hour or less.

  The peeling speed in this constant load peeling test is a triacetyl cellulose which is an adherend of a 10 mm wide double-sided adhesive tape of the present invention lined with a polyester film 25 μm under the conditions of an environmental temperature of 23 ° C. and a relative humidity of 50%. The film and PC board are pressed and reciprocated once with a 2 kg roller and left for 1 hour. Thereafter, a constant load of 0.98 N was loaded in the direction of 90 ° with respect to the double-sided pressure-sensitive adhesive tape, the peel length of the double-sided pressure-sensitive adhesive tape after 1 hour was measured, and the peel length was divided by time.

  When the peeling speed in the constant load peeling test is 100 mm / hour or less, a force corresponding to the repulsive force that the FPC tries to return to the horizontal is applied to the part where the parts of the LCD module unit are joined by the double-sided adhesive tape of the present invention. Even when the load is always applied, the double-sided adhesive tape does not peel off, and troubles such as part falling off are less likely to occur.

  Moreover, although the thickness of the double-sided adhesive tape of this invention is suitably set according to a required performance, 30-300 micrometers is preferable and 30-120 micrometers is more preferable.

  The double-sided pressure-sensitive adhesive tape of the present invention can be produced by forming a pressure-sensitive adhesive layer on a substrate. The pressure-sensitive adhesive layer can be formed by forming a pressure-sensitive adhesive solution on a release sheet with a roll coater or a die coater, and then transferring the pressure-sensitive adhesive layer to the substrate. A conventionally known method such as a coating method can be appropriately used.

  Examples of the release sheet include synthetic resin films such as polyethylene, polypropylene, and polyethylene terephthalate (PET), paper, nonwoven fabric, cloth, foamed sheets and metal foils, and laminates thereof. The surface of the release sheet is preferably subjected to a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment in order to improve the peelability from the pressure-sensitive adhesive. Among these, silicone treatment is more preferable.

  The coating amount of the pressure-sensitive adhesive layer is appropriately set according to the required performance, but the coating amount on each surface of the base material is preferably 10 to 100 μm, more preferably 20 to 80 μm, It is especially preferable that it is 30-70 micrometers. This is because if the coating amount of the pressure-sensitive adhesive layer is less than 10 μm, the impact resistance and repulsion resistance are lowered, which is not preferable. On the other hand, if it exceeds 100 μm, the workability of the tape is lowered, which is not preferable. .

The double-sided pressure-sensitive adhesive tape of the present invention is excellent in drop impact resistance because the pressure-sensitive adhesive layer has a maximum value (M ₁ ) of loss tangent (tan δ) in a temperature range of −40 to −15 ° C.

  Further, the double-sided pressure-sensitive adhesive tape of the present invention has a peeling rate in a constant load peel test as small as 100 mm / hour or less, so that it is sandwiched between FPCs and is constantly loaded with a repulsive force. It is excellent in repulsion resistance that does not cause peeling.

  Furthermore, since the double-sided pressure-sensitive adhesive tape of the present invention has a light reflecting surface and a light shielding surface on the support, it has excellent light reflectivity and light shielding properties.

[LCD module unit]
Embodiments of an LCD module unit according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic view showing an embodiment of an LCD module unit of the present invention in which the double-sided pressure-sensitive adhesive tape of the present invention is used for fixing an LCD panel integrated with an FPC and a backlight housing. ) Is a sectional view, (b) is an exploded view, and (c) is an overall view. The LCD module unit 100 according to the present embodiment is schematically configured from a backlight housing 19, an LCD panel 20, and an FPC 21 connected integrally to the LCD panel 20. As shown in FIG. 1C, this FPC 21 is bent at about 180 ° in the direction of the arrow, sandwiches the LCD panel 20 and the backlight housing 19, hooks and others on the back surface of the backlight housing 19. It is fixed with double-sided adhesive tape.

As shown in FIG. 1 (b), in the backlight housing 19, there are a reflecting plate 18, a light guide plate 17, a diffusion sheet 15, and one or more prism sheets 14 used as necessary to increase the luminance. The double-sided adhesive tape 13 and the LCD panel 20 are stacked and accommodated in this order. On the side of the light guide plate 17, a light source 16 including an LED or a cold cathode tube provided with a lamp reflector is disposed. A double-sided adhesive tape 13 is sandwiched between the LCD panel 20 and the backlight housing 19, and the backlight housing 19 and the LCD panel 20 are fixed.
The double-sided pressure-sensitive adhesive tape 13 has the configuration shown in FIG. 2 and is attached so that the light reflecting layer 2 is on the backlight housing 19 and the prism sheet 14 side, and the light shielding layer 3 is on the LCD panel 20 side.

  The FPC 21 is generally a circuit board that can be freely bent using a polyimide film as a base material. Therefore, as shown in FIG. It is possible to sandwich the housing 19. However, since the force that always tries to return to the horizontal acts on the FPC 21, the double-sided adhesive tape 13 that fixes the LCD panel 20 and the backlight housing 19 has an upward repulsion that the FPC 21 tries to return to the horizontal. The force 22 (indicated by an arrow in FIG. 1A) is always loaded. The repulsive force 22 is greatest in the vicinity where the LCD panel 20 and the FPC 21 are connected, and decreases as the distance L increases from the vicinity of the connecting portion.

The repulsive force 22 was measured by the present inventors using only a spring. The repulsive force 22 was 0.8 to 1.3 N when the distance L was 1 cm from the connecting portion, and 0.1 to 0.2 N when the distance L was 4 cm. And a small force. And as the distance L increases, the repulsive force 22 also becomes weaker. Therefore, what is required of the double-sided pressure-sensitive adhesive tape 13 according to the present invention is not an initial high adhesive force or a high adhesive force that can withstand peeling at a high speed, but a small repulsive force 22 that is always permanently applied. Long-term adhesive strength.
JIS or the like does not describe such a method for measuring the adhesive force over a long period of time, but it can be approximated by the peeling rate in the above-described constant load peel test. When the peeling speed is 100 mm / hour or less, the LCD panel 20 and the backlight housing 19 that are sandwiched between the FPCs 21 and are constantly loaded with the repulsive force 22 are fixed by the double-sided adhesive tape 13. Can be peeled off. Further, even if a force corresponding to the repulsive force that the FPC tries to return horizontally is always applied to the portion where the parts of the LCD module unit 100 are joined by the double-sided adhesive tape 13, the double-sided adhesive tape peels off. Therefore, it is possible to make it difficult to cause troubles such as part dropping.

Since the LCD module unit 100 of the present invention uses the double-sided adhesive tape 13 to fix the LCD panel 20 sandwiched between the FPCs 21 and the backlight housing 19, the LCD module unit 100 is between the LCD panel 20 and the backlight housing 19. It does not cause peeling and has excellent drop impact resistance and resilience resistance.
Therefore, even when a mobile phone incorporating the LCD module unit 100 is dropped, the LCD panel 20 is not broken or peeled off.

  In addition, since the double-sided adhesive tape 13 is excellent in light reflectivity and light shielding properties, the LCD module unit 100 of the present invention can effectively reflect the light from the light source 16 toward the LCD panel 20. Thus, it is possible to prevent the light from entering the driving driver 12.

    Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Preparation of adhesive solution>
(Preparation of adhesive solution A)
In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 44.9 parts by mass of butyl acrylate, 50 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate 4-hydroxybutyl acrylate (0.1 part by mass) and 2,2′-azobisisobutylnitrile (0.1 part by mass) as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate. This was polymerized at 70 ° C. for 10 hours to obtain a (a) (meth) acrylic copolymer (I) solution having a mass average molecular weight of 800,000.
Next, “Pencel D135” (registered trademark) manufactured by Arakawa Chemical Industries (tackifier, (I) (2) pentamer of polymerized rosin with respect to 100 parts by mass of (U) (meth) acrylic copolymer (I) Erythritol ester) 10 parts by mass was added, and ethyl acetate was added and mixed uniformly to obtain a pressure-sensitive adhesive solution A having a nonvolatile content of 45%.

(Preparation of adhesive solution B)
In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 97.9 parts by weight of butyl acrylate, 2 parts by weight of acrylic acid, 0.1 part by weight of 4-hydroxybutyl acrylate, polymerization started As an agent, 0.1 part by mass of 2,2′-azobisisobutylnitrile was dissolved in 100 parts by mass of ethyl acetate. This was polymerized at 70 ° C. for 10 hours to obtain a (a) (meth) acrylic copolymer (I) solution having a mass average molecular weight of 800,000.
Next, “Pencel D135” (registered trademark) manufactured by Arakawa Chemical Industries (tackifier, (I) (2) pentamer of polymerized rosin with respect to 100 parts by mass of (U) (meth) acrylic copolymer (I) Erythritol ester) 10 parts by mass was added, and ethyl acetate was added and mixed uniformly to obtain an adhesive solution B having a nonvolatile content of 45%.

(Preparation of adhesive solution C)
In a reaction vessel equipped with a stirrer, a cold flow condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, 89.8 parts by mass of butyl acrylate, 10.0 parts by mass of acrylic acid, 0.2 parts by mass of 2-hydroxyethyl acrylate, As a polymerization initiator, 0.1 part by mass of 2,2′-azobisisobutylnitrile was dissolved in a mixed solvent consisting of 90 parts by mass of ethyl acetate and 10 parts by mass of n-hexane. This was polymerized at 70 ° C. for 10 hours to obtain a (a) (meth) acrylic copolymer (I) solution having a mass average molecular weight of 900,000.
Next, n-hexane was added and mixed uniformly to obtain an adhesive solution C having a nonvolatile content of 45%.

(Preparation of adhesive solution D)
In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 60.9 parts by mass of butyl acrylate, 33 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate Then, 0.1 part by mass of 2-hydroxyethyl acrylate and 0.2 part by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate. This was polymerized at 80 ° C. for 8 hours to obtain a (a) (meth) acrylic copolymer (I) solution having a mass average molecular weight of 700,000.
Next, ethyl acetate was added and mixed uniformly to obtain an adhesive solution D having a nonvolatile content of 45%.

(Preparation of adhesive solution E)
In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 97.9 parts by mass of butyl acrylate, 2 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate, polymerization started As an agent, 0.2 part by mass of 2,2′-azobisisobutylnitrile was dissolved in 100 parts by mass of ethyl acetate. This was polymerized at 80 ° C. for 8 hours to obtain a (a) (meth) acrylic copolymer (I) solution having a mass average molecular weight of 700,000.
Next, with respect to 100 parts by mass of (A) (meth) acrylic copolymer (I), “Pencel D135” (registered trademark) (tackifier, (A) (2) polymerized rosin penta 5 parts by weight of erythritol ester) and 30 parts by weight of petroleum-based resin “FTR6100” (registered trademark) manufactured by Mitsui Petrochemical Co., Ltd. are added and mixed uniformly with an adhesive solution having a nonvolatile content of 45%. E was obtained.

<Preparation of ink to be a light reflecting layer and a light shielding layer>
(Adjustment of white ink used as light reflection layer)
Dainippon Ink & Chemicals, Inc. White ink “Panacia CVL-SP709 White” (vinyl chloride / vinyl acetate) 100 parts, Dainippon Ink & Chemicals “CVL Hardener No. 10”, Dainippon Ink Chemical 35 parts of “Di Reducer V No. 20” manufactured by Kogyo Co., Ltd. was added to prepare white ink.

(Adjustment of black ink used as light shielding layer)
Dainippon Ink & Chemicals, Inc. Sumiink "Panacia CVL-SP805 Sumi" (vinyl chloride / vinyl acetate) 100 parts, Dainippon Ink & Chemicals "CVL Hardener No. 10", 4 parts, Dainippon Ink & Chemicals A black ink was prepared by adding 35 parts of “Die Reducer V No. 20”.

(Preparation of base material)
A silver (Ag) vapor-deposited PET “Ruil Mirror 37W01W” (registered trademark) manufactured by Reiko Co., Ltd. is corona-treated so that the wetting tension is 5 × 10 ⁻⁴ N / cm, and the white ink is dried on this corona-treated surface. Gravure coating was performed twice so as to be 2 μm.
Subsequently, the black ink was gravure-coated twice on the white ink layer so that the dry thickness was 2 μm.
Further, this was cured at 40 ° C. for 2 days to obtain an ink coat film (a).

  Ink coated film except that white PET film “Teflex FW2 # 13” (registered trademark) manufactured by Teijin DuPont Films was used in place of Reiko's silver (Ag) vapor-deposited PET “Ruil mirror 37W01W” (registered trademark) Ink coat film (b) was obtained in the same manner as (a).

(Preparation of double-sided adhesive tape)
[Example 1]
1.1 parts by mass of “Coronate L-45” (registered trademark) (isocyanate-based crosslinking agent, 45% solid content) manufactured by Nippon Polyurethane Co., Ltd. was added to 100 parts by mass of the above-mentioned pressure-sensitive adhesive solution A.
Next, after stirring for 15 minutes, it was coated on a 75 μm-thick PET film having been subjected to a release treatment so that the thickness after drying was 20 μm, and dried at 70 ° C. for 3 minutes to obtain an adhesive tape.
Next, the two adhesive tapes were bonded to both sides of the ink coat film (a) and laminated with a hot roll having a surface temperature of 80 ° C. and a linear pressure of 2 N / cm. Then, it aged at 40 degreeC for 2 days, and obtained the double-sided adhesive tape of thickness 85micrometer. The gel fraction was 40%.

[Example 2]
Double-sided adhesion in the same manner as in Example 1 except that the addition amount of “Coronate L-45” (registered trademark) (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was changed to 0.9 parts by mass. I got a tape. The gel fraction was 35%.

[Example 3]
Double-sided adhesion in the same manner as in Example 1 except that the addition amount of “Coronate L-45” (registered trademark) (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane Co., Ltd. was changed to 0.7 parts by mass. I got a tape. The gel fraction was 25%.

[Example 4]
1.1 parts by mass of “Coronate L-45” (registered trademark) (isocyanate-based crosslinking agent, 45% solid content) manufactured by Nippon Polyurethane Co., Ltd. was added to 100 parts by mass of the above-mentioned pressure-sensitive adhesive solution B.
Next, after stirring for 15 minutes, it was coated on a 75 μm-thick PET film having been subjected to a release treatment so that the thickness after drying was 20 μm, and dried at 70 ° C. for 3 minutes to obtain an adhesive tape.
Next, the two adhesive tapes were bonded to both sides of the ink coat film (a) and laminated with a hot roll having a surface temperature of 80 ° C. and a linear pressure of 2 N / cm. Then, it aged at 40 degreeC for 2 days, and obtained the double-sided adhesive tape of thickness 85micrometer. The gel fraction was 45%.

[Example 5]
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the ink coat film (a) was changed to the ink coat film (b) and the thickness after drying was changed from 20 μm to 34 μm.

[Comparative Example 1]
Example except that adhesive solution C was used, and the addition amount of “Coronate L-45” (registered trademark) (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane was changed to 1.0 part by mass. In the same manner as in Example 1, a double-sided pressure-sensitive adhesive tape was obtained.

[Comparative Example 2]
Example except that adhesive solution D was used and the addition amount of “Coronate L-45” (registered trademark) (isocyanate-based crosslinking agent, solid content 45%) manufactured by Nippon Polyurethane was changed to 0.8 parts by mass. In the same manner as in Example 1, a double-sided pressure-sensitive adhesive tape was obtained.

[Comparative Example 3]
Example except that adhesive solution E was used and the addition amount of “Coronate L-45” (registered trademark) (isocyanate-based cross-linking agent, solid content 45%) manufactured by Nippon Polyurethane was changed to 1.3 parts by mass. In the same manner as in Example 1, a double-sided pressure-sensitive adhesive tape was obtained.

(Evaluation of double-sided adhesive tape)
About the double-sided adhesive tape created in Examples 1-5 and Comparative Examples 1-3, it tested and evaluated by the method shown below.

(1) Measurement of dynamic viscoelasticity of pressure-sensitive adhesive layer Aged pressure-sensitive adhesive layer was laminated to a thickness of about 2 mm to obtain a test piece. A parallel plate having a diameter of 7.9 mm was attached to a viscoelasticity testing machine (ARES 2kSTD) manufactured by T.A. Instruments Japan, and the test piece was sandwiched with a compression load of 40 to 60 g. A temperature range of −60 to 100 ° C. was measured at a frequency of 1 Hz, and a temperature showing a maximum value (M ₁ ) of loss tangent (tan δ) was measured.

(2) Constant load peeling test The double-sided adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 3 having a 10 mm width lined on an adherend with a polyester film of 25 μm were subjected to conditions of an environmental temperature of 23 ° C. and a relative humidity of 50%. Below, the pressure was applied by one reciprocating press with a 2 kg roller and left for 1 hour. Thereafter, a constant load of 0.98 N (100 gf) was loaded in a direction of 90 ° with respect to the double-sided tape, and the peel length of the double-sided tape after 1 hour was measured. The peeling speed was obtained by dividing the peeling length by time.
LCD with laminated PC board (plate made of polycarbonate resin with smooth surface) or LCD panel (iodine polarizing film with surface of triacetyl cellulose film (high luminance SR grade made by Sumitomo Chemical Co., Ltd.)) on the adherend Panel).

(3) Measurement of gel fraction The composition of the pressure-sensitive adhesive layer after aging is immersed in toluene, and the mass after drying of the insoluble matter remaining after being allowed to stand at 23 ° C. for 24 hours is measured and expressed as a percentage of the original mass. expressed.

(4) Adhesive strength measurement Adhesive strength S was calculated | required by the following procedure based on the test method of 180 degree peeling adhesive strength of JIS-Z0237 (2000).
(I) 20 kg wide double-sided adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 3 lined with a polyester film 25 μm on the adherend were subjected to 2 kg under conditions of an environmental temperature of 23 ° C. and a relative humidity of 50%. 1 reciprocating with a roller and left for 1 hour. Thereafter, Tensilon universal tensile tester (Orientec Ltd., RTA100) used, under the same temperature and humidity conditions, pulled at 300 mm / min, to measure the 180 ° peel adhesion _{S 20.}
(Ii) Next, the adhesive force S was determined by the following equation. The adhesive force S is determined as a value converted to N / 10 mm according to JIS Z 8401. S was calculated by rounding off the third decimal place to the second decimal place.
S = (10 × S ₂₀ ) ÷ W = (10 × S ₂₀ ) ÷ 20
Where S: Adhesive strength (N / 10 mm)
S ₂₀ : 180 ° peeling adhesive strength (N) when a ₂₀ mm width tape is peeled off
W: Specimen width (mm)
The adherend is laminated with a PC plate (polycarbonate resin plate with a smooth surface) or an LCD panel (iodine polarizing film with a surface of triacetyl cellulose film (high luminance SR grade manufactured by Sumitomo Chemical Co., Ltd.)). LCD panel) was used.

(5) Drop impact resistance test 1 (DuPont impact resistance tester)
(I) Two-sided pressure-sensitive adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 3 having a length of 5 mm and a width of 40 mm on a PC plate 7 having a thickness of 2 mm, a length of 50 mm, and a width of 50 mm under the condition of 23 ° C. As shown in FIG. 3, 13 was attached in parallel with an interval of 40 mm. FIG. 3 is a plan view of a PC board with a double-sided pressure-sensitive adhesive tape according to the present invention, which is a test piece used in the drop impact resistance test 1.
(Ii) A plate 8 in which a high-luminance SR grade manufactured by Sumitomo Chemical Co., Ltd. is attached to a PC / ABS plate having a thickness of 2 mm, a length of 150 mm, and a width of 100 mm is prepared. As shown in FIG. The PC board 7 with the double-sided pressure-sensitive adhesive tape 13 was affixed, and a 2 kg roller was reciprocated once, and then allowed to stand at 23 ° C. for 1 hour. FIG. 4 is a schematic plan view in which the PC plate shown in FIG. 3 is attached to the PC / ABS plate with the high luminance SR grade attached.
(Iii) A U-shaped measuring table 9 (made of aluminum having a thickness of 5 mm) having a length of 150 mm, a width of 100 mm, and a height of 45 mm on the base of a DuPont impact tester (manufactured by Tester Sangyo Co., Ltd., not shown). As shown in FIG. 5, the board 8 produced in (ii) was placed thereon so that the PC board 7 was on the lower side. FIG. 5 is a schematic bottom view of the measurement table in which the plate 8 shown in FIG. 4 is placed on the U-shaped measurement table so that the PC plate 7 is on the lower side.
Next, as shown in FIG. 6, a stainless steel strike core 11 (tip diameter 12.7 mm) having a diameter of 25 mm and a mass of 300 g was dropped from the upper side of the plate 8 from a position having a height of 100 mm. An impact was applied to the central portion 10 of the plate 8, and it was evaluated whether or not the PC plate 7 attached to the side opposite to the surface to which the impact was applied dropped. When it did not fall off, the height of the hitting core 11 was raised by 100 mm, an impact test was performed again, and finally the height of the hitting core 11 until dropping was measured. FIG. 6 is a conceptual cross-sectional view showing the measurement method of the drop impact test 1. When the hitting core 11 was dropped from a height of 500 mm and did not fall off, “500 <” was displayed.

(6) Drop impact resistance test 2 (LCD panel cracking / peeling when dropped)
The NEC mobile phone N503is is disassembled, and the double-sided adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 3 are applied to the fixing part of the LCD panel and the backlight housing in place of the genuine products, and the mobile phone is again used. And left for 1 hour.
Thereafter, the reassembled mobile phone was dropped 60 times onto the concrete floor from a height of 1.5 m, and the cracking / peeling of the LCD panel was evaluated.
This test was performed 10 times (N = 10), and the evaluation criteria were as follows.
○: No breakage or peeling of LCD panel.
×: LCD panel cracking and peeling occurred with a probability of 10% or more.

(7) Resilience resistance NEC mobile phone N503is is disassembled, and the double-sided adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 3 are pasted on the fixing portions of the LCD panel and the backlight housing instead of genuine products. The LCD module unit was reassembled and left for 1 hour.
Thereafter, the LCD module unit was left in an environmental tester at 80 ° C. for 7 days to evaluate the LCD panel floating and peeling.
This test was performed 10 times (N = 10), and the evaluation criteria were as follows.
○: LCD panel does not float or peel off.
×: LCD panel floating or peeling occurs with a probability of 10% or more.

(8) Total light transmittance The double-sided pressure-sensitive adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 3 were JIS-transmitted using a transmission / reflectometer HR-100 type (manufactured by Murakami Color Research Laboratory Co., Ltd.). The total light transmittance (Tt) (%) was measured according to K-7105.

(9) Total light reflectance Each of the double-sided adhesive tapes of Examples 1 to 5 and Comparative Examples 1 to 3 was transmitted using a transmission / reflectometer HR-100 (manufactured by Murakami Color Research Laboratory Co., Ltd.). The total light reflectance (Rt) (%) of the reflecting surface was measured.

(10) Tape thickness The thickness of each double-sided adhesive tape of Examples 1-5 and Comparative Examples 1-3 was measured with a thickness meter. The case where the thickness was 120 μm or less was regarded as suitable.

(11) Brightness of Screen In a thin LCD module unit that is standardly mounted on a mobile phone N503is manufactured by Matsushita Communication Industrial Co., Ltd., a glass LCD panel with a polarizing film and a PC backlight housing are used in Examples 1 to 5 and Using the double-sided tapes of Comparative Examples 1 to 3, the substrate 5 was fixed so that the light reflection layer 2 side of the substrate 5 was the backlight housing 19 side.
Separately, the LCD panel of the same type of LCD module unit and the backlight case are made of a light-shielding double-sided tape “# 8616DJ black” (produced by Dainippon Ink & Chemicals, Inc.). What was fixed with the black double-sided tape was manufactured, and the brightness | luminance of both LCD panels was compared.
The evaluation criteria for luminance were as follows.
◎: Brightness improvement is 6% or more ○: Brightness improvement is 3% or more,
X: Improvement in luminance is less than 3%

  The above results are shown in Table 1, respectively.

  According to Table 1, when Examples 1-5 were compared with Comparative Examples 1-3, the double-sided pressure-sensitive adhesive tapes of Examples 1-5 were superior in drop impact resistance and resilience resistance.

  From the above results, it was confirmed that the double-sided pressure-sensitive adhesive tape of the present invention was excellent in drop impact resistance, resilience resistance, light reflectivity, and light shielding properties. Further, it was confirmed that the LCD module unit of the present invention did not cause cracking or peeling between the LCD panel and the backlight housing, had excellent drop impact resistance and repulsion resistance, and high panel brightness.

  Electronic devices suitable for fixing parts using the double-sided pressure-sensitive adhesive tape of the present invention are those that are expected to drop under the assumed usage conditions. Specific examples include mobile phones and portable personal computers. Portable information terminal equipment (PDA), digital still camera, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows one Embodiment of the LCD module unit of this invention which used the double-sided adhesive tape of this invention for fixation with the LCD panel integrated with FPC, and a backlight housing | casing, (a) is sectional drawing. , (B) is an exploded view, and (c) is an overall view. It is a conceptual sectional view showing one embodiment of the double-sided adhesive tape of the present invention. It is a top view of the PC board with the double-sided adhesive tape of this invention which is a test piece used for the drop impact test 1. FIG. It is the schematic plan view which affixed the PC board shown in FIG. 3 on the PC / ABS board with a high luminance SR grade affixed. FIG. 5 is a schematic bottom view of a measurement table on which a plate 8 shown in FIG. 4 is placed on a U-shaped measurement table so that a PC plate 7 is on the lower side. It is a conceptual sectional view showing a measuring method of drop impact resistance test 1. It is the schematic which shows schematic structure of the conventional LCD module unit which used the double-sided adhesive tape for adhering with an LCD panel and a backlight housing | casing, (a) is sectional drawing, (b) is an exploded view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 4 Adhesive layer 5 Base material 13 Double-sided adhesive tape 19 Backlight housing | casing 20 Liquid crystal display panel (LCD panel)
21 Flexible Printed Circuit Board (FPC)
100 Liquid crystal display module unit (LCD module unit)

Claims (6)

In a liquid crystal display module unit , a double-sided adhesive having light reflectivity and light shielding properties used for fixing a liquid crystal display panel sandwiched between flexible printed circuit boards bent at approximately 180 ° and a backlight housing. A tape,
The double-sided pressure-sensitive adhesive tape comprises a base material provided with a light reflecting surface and a light-shielding surface on a support, and an adhesive layer provided on both surfaces of the base material.
This pressure-sensitive adhesive layer has a maximum value (M ₁ ) of loss tangent (tan δ) at a frequency of 1 Hz in a temperature range of −40 to −22 ° C. , and (A) a temperature of −50 to −20 ° C. (Meth) acrylic copolymer (I) having a maximum value (M ₂ ) of loss tangent (tan δ) at a frequency of 1 Hz in the region and (b) a polymerized rosin ester as a tackifier And
Furthermore, the double-sided adhesive tape, the speed peeling at constant load peeling test on a triacetyl cellulose film and a polycarbonate plate 100 mm / time Ri der hereinafter the peeling speed, the double-sided adhesive tape of 10mm width which is backed with a polyester film 25μm Is attached to a triacetyl cellulose film and a polycarbonate plate, which are adherends, by one reciprocating pressure with a 2 kg roller under a condition of an environmental temperature of 23 ° C. and a relative humidity of 50%. double-sided adhesive tape of the constant load and loading in the direction of 90 ° with respect to the double-sided adhesive tape, and wherein the value der Rukoto obtained by dividing the double-sided adhesive tape peeling length after 1 hour time. The amount of the tackifier used in the pressure-sensitive adhesive layer is 5 to 25 parts by mass with respect to 100 parts by mass of ( U) the (meth) acrylic copolymer (I). Double-sided adhesive tape as described.   The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a gel fraction of 15 to 45%. The substrate has a thickness of 3 to 50 μm,
The reflectance at the light reflecting surface of the substrate is 65% or more,
The transmittance | permeability in the light-shielding surface of the said base material is less than 0.1%, The double-sided adhesive tape as described in any one of Claims 1-3 characterized by the above-mentioned.   The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the light reflecting surface of the substrate is formed of a layer containing silver as a main component. Using the double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 5, the liquid crystal display panel sandwiched between the flexible printed circuit boards bent at about 180 ° and the backlight housing are fixed. A featured liquid crystal display module unit.

Images