JP2010168437A - Pressure-sensitive adhesive tape and lcd module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive tape capable of controlling strain of an optical film even if left under an elevated temperature when the optical film is fixed in a shape of a frame to an adherend. <P>SOLUTION: The pressure-sensitive adhesive tape by which the optical film is fixed in the shape of the frame to the adherend is disclosed, wherein a pressure-sensitive adhesive layer on the side of the adhesive tape in contact with an optical film has a loss tangent of a dynamic viscoelasticity spectrum of 0.4-0.8 at 85°C in a condition of a frequency of 0.005 Hz and a linear shearing strain. As a balance of elasticity and viscosity of an adhesive in a region of a deformation rate of the adhesive is optimized, when the optical film is fixed in the shape of the frame to the adherend, the strain of the optical film is controlled under an elevated temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adhesive tape that fixes an optical film to an adherend in a frame shape. More particularly, the present invention relates to an adhesive tape used by being stuck between an LCD (Liquid Crystal Display) panel and a backlight housing.

  LCD modules (liquid crystal display devices) are used in a wide range of fields such as word processors and personal computers. Especially, electronic notebooks, mobile phones, PHS, etc. are used as display devices for increasingly smaller electronic devices. It has become. Among such LCD modules, for example, a sidelight type backlight type LCD module (schematically shown in FIGS. 5 and 6) generally includes a reflector, a light guide plate, a diffusion sheet, A prism sheet (to increase brightness) and an LCD panel that are used as necessary are stacked in order, and a light source such as an LED (Light Emitting Diode) with a lamp reflector provided on the side of the light guide plate, a cold cathode tube, etc. Has been placed.

  Furthermore, an adhesive tape (usually punched into a frame shape, and the width is usually about 0.5 mm to about 10 mm) is sandwiched between the LCD panel and the backlight housing. Adhesive tape not only touches the backlight housing but also contacts the prism sheet, fixing the diffusion sheet installed under the prism sheet, and preventing impact of dust and cushioning. It also has a role to prevent cracking of the above parts.

  Further, the adhesive tape is strongly required to have both light shielding properties and light reflection properties in order to block light leaked from the light source and effectively use light. Such an adhesive tape has been studied for improving the characteristics, and an adhesive tape for an LCD module that is thin and has both light-shielding properties and light-reflecting properties is disclosed (see Patent Document 1).

  However, in recent years, the adhesive tape used for the part has been exposed to problems that have not been regarded as a problem in the past due to the high performance of electronic devices used, in particular, the thinning and multifunctionality of mobile phones. Yes. With the thinning of multi-function mobile phones, the thickness of internal members has been reduced, but due to the thinning of the optical film, the optical film whose periphery was fixed with double-sided adhesive tape was left at high temperature in the reliability test. Occasionally, there is a problem that the optical film is distorted. When illuminated with light passing through such a distorted portion, the image in the LCD panel lacks sharpness.

  In order to solve the above-mentioned problem, Patent Document 2 discloses an LCD module using a double-sided pressure-sensitive adhesive tape that does not have an adhesive at a location facing an optical film. However, it is extremely difficult to manufacture a double-sided pressure-sensitive adhesive tape that does not partially have an adhesive, and the cost is high. Further, since the optical film is not fixed, there arises a problem that the prism sheet is displaced during use or assembling work.

  Moreover, in patent document 3, 85 degreeC loss tangent of the dynamic viscoelastic spectrum in the frequency of 1 Hz of the adhesive layer which touches an optical film is 0.35-0.7, and the storage elastic modulus of 85 degreeC is 15000-20000Pa. An adhesive tape is disclosed. However, the above-mentioned tape cannot always suppress the distortion of the optical film. In particular, when an optical film having a large thermal deformation or an optical film of 3 inches or more is used, distortion may occur even with the above-mentioned adhesive tape.

JP 2004-156015 A JP 2006-184656 A JP 2008-248226 A

  The subject of this invention is providing the adhesive tape which can suppress distortion of an optical film, when it leaves at high temperature, when fixing an optical film to a to-be-adhered body at frame shape. Another object of the present invention is to provide an LCD module that has no optical film distortion and has a good appearance.

  The balance between elasticity and viscosity of the adhesive varies depending on the temperature and speed range. Patent Document 3 specifies the balance between the elasticity and viscosity of the pressure-sensitive adhesive under the conditions of 85 ° C. and 1 Hz, but the pressure-sensitive adhesive tape disclosed in Patent Document 3 cannot always suppress the distortion of the optical film. Therefore, the present inventors specify the deformation rate region of the pressure-sensitive adhesive by measuring the thermal deformation rate of the optical film, and optimize the balance between the elasticity and viscosity of the pressure-sensitive adhesive within the speed region. I found that I can achieve.

  That is, the present invention is an adhesive tape for fixing an optical film to an adherend in a frame shape, and the adhesive layer on the side in contact with the optical film of the adhesive tape has a frequency of 0.005 Hz and linear shear strain. The loss tangent at 85 ° C. in the dynamic viscoelastic spectrum is 0.4 to 0.8. An adhesive tape for fixing an optical film is provided.

  The pressure-sensitive adhesive tape of the present invention can suppress distortion of the optical film because the pressure-sensitive adhesive has specific viscoelasticity in the temperature and speed range where the optical film is deformed.

(Constitution)
The pressure-sensitive adhesive tape of the present invention has a structure having a pressure-sensitive adhesive layer on at least one surface of a base material, and specific embodiments can be exemplified by the structures illustrated in FIGS.

  FIG. 1 is an embodiment in which pressure-sensitive adhesive layers are laminated on both surfaces of a substrate. FIG. 2 shows an embodiment in which an adhesive layer is laminated on one side of a substrate. FIG. 3 shows an embodiment in which a pressure-sensitive adhesive layer is laminated on the light reflection layer side of a substrate in which a light reflection layer and a light shielding layer are laminated. FIG. 4 is an embodiment showing an example of the pressure-sensitive adhesive tape of the present invention in which a pressure-sensitive adhesive layer is provided on both surfaces of a base material on which a light reflecting layer and a light shielding layer are laminated. The pressure-sensitive adhesive tape of the present invention can take the form of a single-sided pressure-sensitive adhesive tape as shown in FIGS. 2 and 3, or a double-sided pressure-sensitive adhesive tape as shown in FIGS. The pressure-sensitive adhesive layer may be a single-layer pressure-sensitive adhesive layer, or may be a multilayer material composed of a plurality of pressure-sensitive adhesive layers and sheets such as a double-sided pressure-sensitive adhesive tape. Among these configurations, when fixing between members, in the case of a configuration having an adhesive layer on one side of the substrate, a means for fixing the other surface provided with the adhesive layer to the adherend is required. Since it can fix suitably between members without using another fixing means as it is the structure which has an adhesive layer on both surfaces, it is preferable that it is the structure which has an adhesive layer on both surfaces of a base material. Further, the configuration having the pressure-sensitive adhesive layer on both surfaces of the base material is suitable for alleviating the impact applied to the LCD panel or the like, and preventing dust from entering between the members constituting the LCD module.

  The adhesive strength of the pressure-sensitive adhesive tape of the present invention is preferably 3 to 15 N / 10 mm when only the tape is used for fixing the LCD panel and the backlight housing, and when mechanical fixing such as a metal frame is used in combination. Is preferably 0.1 to 15 N / 10 mm.

  The thickness of the pressure-sensitive adhesive tape of the present invention is preferably 100 μm or less, and more preferably 30 to 75 μm. Among them, the thickness of 40 to 65 μm is particularly preferable because the distortion of the optical film can be suitably suppressed even if it is thin.

(Adhesive loss tangent)
The pressure-sensitive adhesive layer in contact with the optical film used in the pressure-sensitive adhesive tape of the present invention has a loss tangent of 0.4 to 0.8 under dynamic viscoelasticity measurement conditions at a temperature of 85 ° C. and a frequency of 0.005 Hz. Preferably it is 0.5-0.75. More preferably, it is 0.55-0.75. If it is less than 0.4, the pressure-sensitive adhesive becomes too hard to follow the elongation of the optical film, and the pressure-sensitive adhesive is peeled off from the optical film. On the other hand, when it exceeds 0.8, the pressure-sensitive adhesive becomes too soft and easily deforms, and it becomes difficult to suppress distortion of the optical film.

The dynamic viscoelasticity of the pressure-sensitive adhesive layer in the present invention is obtained by sandwiching a test piece between parallel disks, which are measuring units of the tester, using a viscoelasticity tester (manufactured by Rheometrics, trade name: Ares 2KFRTN1). The loss tangent tan δ at a frequency of 0.005 Hz is measured under linear shear strain conditions. The loss tangent has the following relationship with the storage elastic modulus G ′ and the loss elastic modulus G ″.
tan δ = (G ″) / (G ′)
In the test piece, an adhesive having a thickness of 0.5 to 2.5 mm may be sandwiched between parallel disks alone, or a laminate of a base material and an adhesive may be stacked in layers and sandwiched between parallel disks. In the latter case, the thickness of the pressure-sensitive adhesive alone is adjusted to be in the above range. When the thickness of the pressure-sensitive adhesive is adjusted to the above range, the loss tangent similar to the case where there is no base material can be measured even if the base material is sandwiched between them.

  In evaluating the suppression of distortion of the optical film by the pressure-sensitive adhesive tape of the present invention, by evaluating the loss tangent under dynamic viscoelasticity measurement conditions of a temperature of 75 ° C. to 95 ° C. and a frequency of 0.001 to 0.02 Hz, The distortion suppression effect can be suitably evaluated.

  In the above evaluation, the frequency range for measuring the dynamic viscoelastic spectrum is a low frequency of 0.001 to 0.02 Hz, preferably 0.001 to 0.01 Hz, and particularly preferably 0.001 to 0.005 Hz. To measure. Under the high temperature range, the optical film is thermally deformed. However, the pressure-sensitive adhesive tape of the present invention has a viscoelastic property in which the pressure-sensitive adhesive layer suitably follows (deforms) the heat deformation behavior of the optical film. Distortion can be suppressed.

  When an optical film is fixed with a frame-shaped adhesive tape, the evaluation of the distortion suppression effect of the optical film at a high temperature by the adhesive tape is performed under the condition that the optical film is fixed with the adhesive tape at a high temperature. It can be evaluated from the deformation behavior of the layer.

  When the optical film is fixed with a frame-shaped adhesive tape, the speed at which the adhesive layer follows the deformation when the optical film is thermally deformed is the thermal deformation with the optical film fixed with the adhesive tape. Calculated from quantity and deformation time. By measuring the dynamic viscoelasticity of the pressure-sensitive adhesive layer under conditions reflecting the deformation rate of the pressure-sensitive adhesive layer under this high temperature range, the pressure-sensitive adhesive layer when the optical film is fixed with a frame-shaped pressure-sensitive adhesive tape It becomes possible to obtain an evaluation result that appropriately reflects the deformation behavior under high temperature.

Specifically, by measuring the dynamic viscoelasticity of the pressure-sensitive adhesive using a frequency that can be estimated from the following equation, the effect of suppressing the distortion of the optical film at a high temperature by the pressure-sensitive adhesive tape can be suitably evaluated.
(1) Deformation speed of adhesive layer (1 / s) = [thermal deformation amount of optical film (μm) / (time (s) × thickness of adhesive layer when optical film is fixed with frame-like adhesive tape] (Μm))]
(2) Measurement frequency (Hz) of dynamic viscoelastic spectrum = [deformation speed (1 / s) / [2π × distortion during dynamic viscoelasticity measurement]
From this, in evaluation of the distortion suppression effect of the optical film by an adhesive tape, the distortion suppression effect of an optical film is suitably carried out by making the measurement frequency of a dynamic viscoelastic spectrum into the low frequency range of 0.001-0.02 Hz. Can be evaluated.

  If the measurement frequency of the dynamic viscoelastic spectrum is within the above range, the effect of suppressing the distortion of the optical film by the adhesive tape can be measured suitably. However, the measurement frequency of the image display unit is about 2.5 to 7 inches. When suitably evaluating the distortion suppressing effect of the optical film used, it is preferable to measure in a frequency range of 0.005 Hz or less, and when shortening the measurement time, measurement at 0.005 Hz is particularly preferable.

  Optical films such as prism sheets used in LCD modules stretch once when left at high temperatures and then shrink. During stretching, the optical film is distorted. If the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape is hard, the pressure-sensitive adhesive is peeled off from the optical film when the optical film is stretched, and the original state is not restored even if the optical film contracts thereafter. On the other hand, if the pressure-sensitive adhesive layer is soft, the pressure-sensitive adhesive is easily deformed, and the original state is not restored. The pressure-sensitive adhesive tape of the present invention effectively causes the pressure-sensitive adhesive layer to follow the expansion and contraction of the optical film by the pressure-sensitive adhesive layer having the loss tangent of the dynamic viscoelastic spectrum in the above range, and effectively generates distortion of the optical film. Can be suppressed.

(Preparation of adhesive)
As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention, known acrylic, rubber-based, vinyl ether-based, and silicone-based pressure-sensitive adhesives can be used. Among them, acrylic pressure-sensitive adhesives are used. preferable. In particular, an acrylic copolymer containing a (meth) acrylic acid ester having a C 1-14 alkyl group as a monomer component is preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) Examples thereof include acrylate and n-lauryl (meth) acrylate, and can be used alone or in combination of two or more. Especially, it is preferable that n-butyl acrylate is a monomer as a main component, and the amount used is preferably 70% by mass or more, more preferably 90% by mass or more in the pressure-sensitive adhesive composition. By using the above-mentioned types and amounts as the main monomer, it is easy to control the dynamic viscoelasticity range.

  Furthermore, it is preferable to add a vinyl monomer having a functional group such as a hydroxyl group, a carboxyl group or an amino group in the side chain in the range of 0.01 to 15% by mass. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid, fumaric acid , Carboxypropyl acrylate maleate, dimethylaminoethyl acrylamide, N-vinyl pyrrolidone, acrylonitrile, N-vinyl caprolactam, acrylamide, styrene, vinyl acetate, N-methylol acrylamide, glycidyl methacrylate, etc. The above can be used in combination. Among them, it is preferable to use a vinyl monomer containing a carboxyl group, more preferably acrylic acid or methacrylic acid, and the amount used is 2.5 to 5.0% by mass. Is preferred. Furthermore, it is preferable to use 2.0 to 10.0% by mass of vinyl acetate. The loss tangent value in the dynamic viscoelastic spectrum can be easily controlled within the target range by using the above-mentioned types and amounts of the carboxyl group-containing monomer.

  The acrylic copolymer can be obtained by copolymerization by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, an ultraviolet irradiation method, or an electron beam irradiation method.

  Moreover, well-known and usual additives, such as a light stabilizer, a ultraviolet absorber, a plasticizer, a softener, a filler, a pigment, a flame retardant, can be added to an adhesive, for example. Examples of the light stabilizer include a chain inhibitor, a hydroperoxide decomposing agent, a metal deactivator, and an ultraviolet absorber. By using such an additive, the above yellowing resistance can be improved.

(Adhesive type)
As the pressure-sensitive adhesive type, an emulsion type, a solvent type, a solventless type, or the like can be used.

(Molecular weight of adhesive)
The mass average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) of the acrylic copolymer is preferably 400,000 to 1,400,000, more preferably 500,000 to 1,000,000. When the average molecular weight is in the above range, it is easy to control the loss tangent value in the dynamic viscoelastic spectrum to the target range.

(Gel fraction of adhesive)
Furthermore, it is preferable to add a crosslinking agent in order to increase the cohesive strength of the pressure-sensitive adhesive. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, and a chelate crosslinking agent. Of these, isocyanate-based crosslinking agents are preferred. The addition amount of the crosslinking agent is preferably adjusted so that the gel fraction of the pressure-sensitive adhesive layer is 10 to 50%. A more preferable gel fraction is 20 to 40%. Among these, 25 to 35% is most preferable. When the gel fraction is in the above range, the loss tangent value in the dynamic viscoelastic spectrum can be easily controlled within the target range.

  The gel fraction is expressed as a percentage of the original mass by immersing the composition of the pressure-sensitive adhesive layer after curing in toluene, measuring the mass after drying of the insoluble matter remaining after standing for 24 hours, and measuring the mass.

(Tackifying resin)
Furthermore, in order to improve the adhesive strength of the pressure-sensitive adhesive layer, it is preferable to add a tackifying resin. The tackifier resin to be added to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention is rosin resin such as rosin or rosin ester compound; terpene resin such as diterpene polymer or α-pinene-phenol copolymer; aliphatic Petroleum resins such as (C5) and aromatic (C9); styrene resins, phenol resins, xylene resins, and the like. Among these, in order to make the optical film highly anti-distortion and repulsion resistant, it is preferable to use a mixture of polymerized rosin pentaerythritol ester, glycerin ester of disproportionated rosin and petroleum resin.

  As addition amount of tackifying resin, it is preferable to add 20-40 mass parts with respect to 100 mass parts of acrylic copolymers. In particular, the addition amount of the polymerized rosin pentaerythritol ester and the disproportionated rosin glycerin ester is most preferably 10 to 15 parts by mass.

  An adhesive layer can be formed on a base film by the method generally used for application | coating of an adhesive tape. The composition of the pressure-sensitive adhesive layer is applied directly to the base film and dried, or once applied onto the separator, dried and then bonded to the base film.

  As for the thickness of an adhesive layer, 5-50 micrometers is preferable, More preferably, it is 10-30 micrometers. If the thickness is less than 5 μm, the amount of deformation of the pressure-sensitive adhesive is small, and sufficient optical film distortion prevention properties cannot be obtained. On the other hand, if the thickness exceeds 50 μm, the thickness of the pressure-sensitive adhesive tape is increased, so that it is not suitable for use in electronic devices that are further reduced in size and thickness.

(Type of base material)
The substrate used for the pressure-sensitive adhesive tape of the present invention may be a substrate made of a resin film alone, or a substrate made of a resin film provided with a light-shielding property or reflectivity on the resin film itself, Or a substrate provided with a reflective layer. Examples of the resin film used for the substrate include polyethylene terephthalate (PET), triacetyl cellulose, polyarylate, polyimide, polyether, polycarbonate, polysulfone, polyethersulfone, cellophane, aromatic polyamide, polyethylene, and polypropylene. It is done. In particular, polyethylene terephthalate having excellent heat resistance and low cost is preferable.

(Base material shrinkage)
The shrinkage rate at 85 ° C. of the base material used in the pressure-sensitive adhesive tape of the present invention is preferably 1.5% or less in both the flow direction and the width direction. Preferably it is 0.8% or less, More preferably, it is 0.1% or less. If it exceeds 1.5%, the distortion of the optical film increases. Here, the shrinkage ratio X of the base material is X = 100 × (L ₂₃ −L ₈₅ ) / L, where L ₂₃ is a state at 23 ° C. and L ₈₅ is a length after being left at 85 ° C. for 24 hours. Required by ₂₃ .

  In the case of providing the light shielding layer, the light shielding layer can be formed, for example, by applying black ink. In order to make the ink layer black, a known and commonly used pigment or dye may be contained. Among these, carbon black is particularly preferable. The ink vehicle is preferably a halogen-free type.

  The light reflecting layer can be formed by laminating a light reflecting layer on a base film or by using the base film itself as a light reflecting film. For example, a white pigment or a silver pigment may be dispersed in the base film to form a white resin film or a silver resin film, a white ink or a silver ink may be coated on the film to form a printed film, or a metal vapor deposition layer It is good also as a vapor deposition film by providing. Among them, it is preferable to coat the film with color ink or silver ink and use a printing film because the shrinkage ratio of the substrate is low.

  In this invention, the adhesive tape which used the base material which provided the adhesive layer on both surfaces of the base material which laminated | stacked the light reflection layer and the light shielding layer illustrated in FIG. 4, and has both light reflectivity and light-shielding property It is preferable that

  When the adhesive tape of this invention has a light reflection layer, it is preferable that the light reflectivity by the side of a light reflection layer is 60% or more. Among them, the visible light reflectance is more preferably 65% or more, and further preferably 70% or more. When the visible light reflectance is 60% or more, the brightness of the LCD panel is preferably increased. In addition, the light reflectance of an adhesive tape may measure the light reflectance in the case where the light reflectance of the light reflection layer itself is measured, and the case where the adhesive layer is laminated | stacked on the light reflection layer. In the case where the pressure-sensitive adhesive layer is laminated on the light reflecting layer, the light reflectance is not the light reflectance value of the light reflecting layer itself, but the light reflectance value including the pressure-sensitive adhesive layer.

  The light reflectance is measured using a spectroscopic color difference meter SE-2000 type (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS Z-8722, measuring the spectral reflectance in the range of 400 to 700 nm at 10 nm intervals. Calculated as an average value (average reflectance). Moreover, it is preferable that the light transmittance of the adhesive tape of this invention is 1% or less. If it is 1% or less, light leakage hardly occurs and the appearance of the LCD panel is improved.

  The light transmittance was measured using a spectrophotometer V-520-SR type (manufactured by JASCO Corporation), the spectral transmittance in the range of 400 to 700 nm was measured at 10 nm intervals according to JIS Z-8722, and the average was obtained. Calculated as a value (average transmittance). In order to shield the entry of light to the driver that drives the LCD panel and to prevent the malfunction, it is preferable that the light transmittance is 0.1% or less over 200 to 1100 nm. Especially, it is most preferable that it is 0.01% or less.

(Thickness of base material)
The thickness of the substrate is preferably 3 μm to 50 μm, and more preferably 10 μm to 30 μm. If it is less than 3 μm, the processability is poor, and if it exceeds 50 μm, it becomes too thick and is not suitable for an adhesive tape for an LCD module that requires thinning.

(LCD module)
The adhesive tape of the present invention is an LCD module having a backlight housing provided with at least one optical film and an LCD panel, and between the optical film and the LCD panel or between the optical film and the backlight housing. Between the body, at least a part of the surface of the pressure-sensitive adhesive layer is used so as to contact the surface of the optical film.

  In the present invention, the LCD module refers to a backlight case provided with at least one optical film and an LCD panel, and the LCD panel and the backlight case are integrated. This refers to a configuration used as an LCD module having a configuration used in a backlight type liquid crystal display device. The backlight housing in the present invention has a configuration in which a light source for backlight is provided and at least one optical film is provided. The pressure-sensitive adhesive tape of the present invention is used in such a manner that at least a part of the pressure-sensitive adhesive layer is in contact with the surface of the optical film.

(Optical film)
Examples of the optical film provided on the surface layer of the backlight housing include a prism sheet, a diffusion film, a light shielding film, and a reflective film. Among them, an optical film in which distortion is particularly likely to occur is an optical film in which a prism layer is provided on a film having a polarization reflection function. Examples of such an optical film include BEF-RP2RC and BEF-RP3 manufactured by 3M.

  The pressure-sensitive adhesive tape of the present invention can suitably suppress the distortion of the optical film, and in particular, the distortion is particularly remarkable for an optical film having a size of about 2.5 to 7 inches (diagonal). There is an inhibitory effect. An optical film exceeding 7 inches can suppress distortion due to thermal deformation by the pressure-sensitive adhesive tape of the present invention, but it may be difficult to completely eliminate the distortion with only the pressure-sensitive adhesive tape. An optical film of less than 2.5 inches may have a small amount of thermal deformation, and in this case, distortion may be suppressed by other adhesive tapes.

The greater the rate of change in the outer shape of the optical film, the more easily the distortion occurs, and the distortion becomes severe when the behavior changes in the flow direction and the width direction. In particular, distortion is likely to occur when it is + 0.06% or more in the flow direction and -0.06% or less in the width direction. The pressure-sensitive adhesive tape of the present invention can suppress distortion even with the optical film. In addition, the external shape change rate of an optical film is represented by the following formula before and behind standing at 85 degreeC for 5 minutes.
External form change rate = [(length after standing−length before standing) / (length before standing)] × 100 (%)

  When the optical film has a prism layer and the ridge line of the prism layer obliquely intersects the flow direction of the adhesive tape, distortion of the optical film is likely to occur. Can be suitably suppressed.

  The configuration of the LCD module of the present invention includes (1) a configuration in which an optical film is provided on the outermost layer of the backlight housing, and the optical film and the LCD panel are integrated via an adhesive tape. ) An optical film is integrated with a backlight housing via an adhesive tape, and another configuration is laminated on the optical film and an LCD panel is integrated. The adhesive tape used here is for the purpose of securing the image display portion in the configuration of (1), and in the configuration of (2) the purpose is to match the shape of the frame that has been framed to reduce the thickness and weight. A frame-shaped adhesive tape is used.

  The frame-shaped adhesive tape may be fixed by a single adhesive tape punched out and cut out, or may be fixed in a frame shape by combining a plurality of elongated adhesive tapes.

  As an example of a specific configuration of the LCD module, the side light type backlight type LCD module unit 100 shown in FIG. 5 and FIG. 5 and 6 are schematic views showing a schematic configuration of the LCD module unit 100 in which an adhesive tape is provided between the LCD panel and the backlight housing, FIG. 5 is a sectional view, and FIG. 6 is an exploded view. It is. In general, the LCD module unit 100 includes one or more prisms used as necessary in the backlight housing 16 as a reflection plate 15, a light guide plate 14, a diffusion sheet 12, and an optical film to increase luminance. A sheet 11, an adhesive tape 10, and an LCD panel 17 are laminated in this order, and a light source 13 composed of an LED (Light Emitting Diode) having a lamp reflector or a cold cathode tube is disposed on the side of the light guide plate 14. Yes.

  The adhesive tape provided between the LCD panel 17 and the backlight housing 16 is provided so that the adhesive layer is in contact with the prism sheet 11, and a part of the adhesive layer is also in contact with the backlight housing 16. It is provided as follows. Accordingly, the prism sheet 11 and the diffusion sheet 12 installed below the prism sheet 11 are fixed to the backlight housing. This pressure-sensitive adhesive tape 10 is usually punched into a frame shape, and its width is about 0.5 to 10 mm.

  In this configuration, even when the prism sheet 11 expands and contracts due to a change in temperature environment, the adhesive layer of the adhesive tape can follow the expansion and contraction, and the occurrence of distortion in the prism sheet 11 can be suppressed. If the adhesive tape 10 is a double-sided adhesive tape, the upper LCD panel 17 can also be fixed together. If the adhesive tape 10 is light-shielding or light-reflective, the light from the light source 16 can be effectively used. The function of reflecting to the 17 side and the function of preventing light from entering the driving driver 9 greatly contribute to beautiful image display.

  Further, as a configuration example of the above (2), there is a side light type backlight type LCD module unit 100 ′ shown in FIGS. 7 and 8. 7 and 8 are schematic views showing a schematic configuration of an LCD module unit 100 ′ in which an adhesive tape is provided between the backlight housing and the optical film. The LCD module unit 100 ′ has a configuration in which the adhesive tape is provided between the LCD panel 17 and the backlight housing 16, in addition to the configuration shown in FIGS. It is the structure by which the adhesive tape was provided between the reflecting plates which are two.

  9 and 10 show an LCD module of the present invention in which the adhesive tape of the present invention is used for fixing an LCD panel 17 integrated with a flexible printed circuit board (hereinafter abbreviated as FPC) 18 and a backlight housing. It is the schematic which shows one Embodiment of a unit, FIG. 9 is sectional drawing, Fig.10 (a) is an exploded view, FIG.10 (b) is a general view. The LCD module unit 100 ″ of this embodiment, the backlight housing 16, an LCD panel 17, and an FPC 18 connected integrally to the LCD panel 17. As shown in FIG. Is bent substantially 180 ° in the direction of the arrow, sandwiches the LCD panel 17 and the backlight housing 16 and is fixed to the back surface of the backlight housing 16 with a hook or other adhesive tape.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In addition, the part displayed below is a mass part.

(Adjustment of black ink)
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 The black ink A was prepared by adding 35 parts of “Die Reducer V No. 20” manufactured by the company.

(White ink adjustment)
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 The white ink W was prepared by adding 35 parts of “Die Reducer V No. 20” manufactured by Kogyo Co., Ltd.

(Preparation of base material)
Teflex FW2 # 13 manufactured by Teijin DuPont Films Co., Ltd. was subjected to corona treatment so that the wetting tension was 50 dynes / cm, and white ink W was gravure coated twice on the corona-treated surface so that the dry thickness was 2 μm. Further, black ink A was gravure-coated twice on the white ink layer so that the dry thickness was 5 μm.
The drying was left at room temperature for 2 minutes.
Further, the film was cured at 40 ° C. for 2 days to obtain an ink coat film (a) having the black ink surface as the light shielding layer side and the other surface as the reflection layer side.

(Adjustment of acrylic pressure-sensitive adhesive composition A):
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 91.1 parts of n-butyl acrylate, 4.9 parts of vinyl acetate, 3.9 parts of acrylic acid, 0.1 part of β-hydroxyethyl acrylate, Then, 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer having a mass average molecular weight of 500,000. Combined (1) was obtained. To 100 parts of the solid content of the acrylic copolymer (1), 12 parts of “Superester A100” manufactured by Arakawa Chemical Co., Ltd., 12 parts of “Pencel D135” manufactured by Arakawa Chemical Industries, and “FTR6100 manufactured by Mitsui Petrochemical Industries, Ltd.” 6 parts diluted with toluene to obtain an acrylic pressure-sensitive adhesive composition A having a solid content of 50%.

(Adjustment of acrylic pressure-sensitive adhesive composition B):
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 93.4 parts of n-butyl acrylate, 3 parts of vinyl acetate, 3.5 parts of acrylic acid, 0.1 part of β-hydroxy-ethyl acrylate, polymerization As an initiator, 0.2 part of 2,2′-azobisisobutylnitrile is dissolved in 100 parts of ethyl acetate, substituted with nitrogen, polymerized at 80 ° C. for 8 hours, and an acrylic copolymer having a mass average molecular weight of 700,000 ( 2) was obtained. To 100 parts of the solid content of the acrylic copolymer (2), 12 parts of “Superester A100” manufactured by Arakawa Chemical Co., Ltd., 12 parts of “Pencel D135” manufactured by Arakawa Chemical Industries, and “FTR6100 manufactured by Mitsui Petrochemical Industries, Ltd.” 6 parts diluted with toluene to obtain an acrylic pressure-sensitive adhesive composition B having a solid content of 38%.

(Preparation of acrylic pressure-sensitive adhesive composition C):
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 92.9 parts of n-butyl acrylate, 3 parts of vinyl acetate, 4 parts of acrylic acid, 0.1 part of β-hydroxy-ethyl acrylate, and a polymerization initiator As an acrylic copolymer (3) having a mass average molecular weight of 800,000 by dissolving 0.2 part of 2,2′-azobisisobutylnitrile in 100 parts of ethyl acetate, substituting with nitrogen and polymerizing at 80 ° C. for 8 hours. Got. To 100 parts of the solid content of the acrylic copolymer (3), 10 parts of “Superester A100” manufactured by Arakawa Chemical Co., Ltd. and 15 parts of “Pencel D135” manufactured by Arakawa Chemical Industries were diluted with toluene, and the solid content was 40%. An acrylic pressure-sensitive adhesive composition C was obtained.

(Preparation of acrylic pressure-sensitive adhesive composition D):
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 93.4 parts of n-butyl acrylate, 3.4 parts of vinyl acetate, 3.5 parts of acrylic acid, 0.1 part of β-hydroxy-ethyl acrylate, Then, 0.2 part of 2,2′-azobisisobutylnitrile as a polymerization initiator is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer having a mass average molecular weight of 800,000. Combined (4) was obtained. 10 parts of “Superester A100” manufactured by Arakawa Chemical Co., Ltd. and 10 parts of “Pencel D135” manufactured by Arakawa Chemical Industries are diluted with toluene to 100 parts of the solid content of the acrylic copolymer (4) to give a solid content of 40%. Acrylic pressure-sensitive adhesive composition D was obtained.

Example 1
(Production of adhesive tape)
On an acrylic pressure-sensitive adhesive composition A, 1.6 parts of “Coronate L-45” (isocyanate-based cross-linking agent) manufactured by Nippon Polyurethane Industry Co., Ltd., and after sufficient stirring, on a 75 μm-thick polyester film The film was coated so that the thickness after drying was 20 μm, and dried at 85 ° C. for 2 minutes to obtain a pressure-sensitive adhesive layer. This was transferred to both sides of the ink coat film (b), laminated with a 80 ° C. hot roll at a pressure of 4 kgf / cm, and further cured at 40 ° C. for 2 days to obtain a double-sided adhesive tape.

(Example 2)
The same procedure as in Example 1 was conducted, except that the acrylic adhesive composition B was used in place of the acrylic adhesive composition A, and the amount of “Coronate L-45” was changed from 1.6 parts to 1.0 part. Thus, a double-sided adhesive tape was obtained.

(Example 3)
A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the amount of “Coronate L-45” was changed from 1.6 parts to 2.4 parts.

(Comparative Example 1)
The same procedure as in Example 1, except that the acrylic pressure-sensitive adhesive composition C was used instead of the acrylic pressure-sensitive adhesive composition A, and the amount of “Coronate L-45” was changed from 1.6 parts to 2.0 parts. Thus, a double-sided adhesive tape was obtained.

(Comparative Example 2)
The same procedure as in Example 1 was conducted except that the acrylic pressure-sensitive adhesive composition D was used instead of the acrylic pressure-sensitive adhesive composition A, and the amount of “Coronate L-45” was changed from 1.6 parts to 0.5 parts. Thus, a double-sided adhesive tape was obtained.

(Measurement of dynamic viscoelasticity)
Using a viscoelasticity tester (trade name: Ares 2KFRTN1), a test piece obtained by laminating an adhesive cured at 40 ° C. for 2 days to a thickness of 1 mm is used as a parallel disk-shaped measuring unit having a diameter of 7.9 mm. The test piece was sandwiched, and dynamic viscoelasticity measurement was performed under the conditions of a temperature of 85 ° C. and a shear strain of 10% while changing the frequency from 16 Hz to 0.0016 Hz, and loss tangent tan δ was measured.

  The double-sided pressure-sensitive adhesive tapes prepared in Examples and Comparative Examples were evaluated for optical film distortion prevention, adhesive strength, tape thickness, light reflectivity, and light-shielding property (light transmittance) by the following methods. The evaluation results are shown in Tables 1 to 3.

(Distortion prevention of optical film)
A light-shielding reflective tape (outer shape: 74 mm × 54 mm, width: 2 mm) punched into a frame shape as shown in FIG. 11 at 23 ° C. is pasted on glass, and the reflective layer side is a brightness enhancement film manufactured by 3M. It is affixed to “BER-RP2RC” (external shape: 72 mm × 54 mm) (FIG. 11). Note that the width of contact between the tape and the optical film is 1 mm on each side. The part is left at 85 ° C. for 72 hours and then left at 23 ° C. for 1 hour. Observe whether the appearance changes before and after standing at 85 ° C.
A: No distortion occurs in the optical film.
○: Slight distortion occurs in the optical film.
X: Large distortion occurs in the optical film.

(Adhesive strength)
The adhesive strength was determined by the following procedure in accordance with the JIS-Z0237 (2000) 180-degree peeling adhesive strength test method.
(1) 25 mm wide adhesive tapes of Examples and Comparative Examples lined with a polyester film of 25 μm on polycarbonate were pasted and pressed for 1 hour with a 2 kg roller under conditions of 23 ° C. and 50% humidity. Thereafter, using a Tensilon universal tensile tester (Orientec, RTA100), the film was pulled at a speed of 300 mm / min under the same temperature and humidity conditions, and then peeled off by 180 degrees to measure the adhesive force S25.
(2) The adhesive force S was determined by the following formula. (Adhesive force S is determined as a value converted to N / 10 mm in accordance with JIS Z 8401. Note that S is rounded off to the second decimal place and calculated to the second decimal place.)
S = (10 × S25) ÷ W = (10 × S25) ÷ 25
Where S: Adhesive strength (N / 10 mm)
S25: Adhesive strength when stripping 25mm wide tape (N)
W: Specimen width (mm)

(Tape thickness)
The thickness of the double-sided tape was measured with a thickness meter. The case where the thickness was 75 μm or less was regarded as suitable.

(Light reflectivity)
The reflectance on the reflective layer side of the pressure-sensitive adhesive tapes of Examples and Comparative Examples at wavelengths of 400 to 700 nm was measured at intervals of 10 nm using a spectral color difference meter “SE-2000” manufactured by Nippon Denshoku Industries Co., Ltd., and the average reflectance was measured. Was calculated.

(Light shielding (light transmittance))
Using a spectrophotometer V-520-SR type (manufactured by JASCO Corporation), the spectral transmittance in the range of 400 to 700 nm was measured at 10 nm intervals according to JIS Z-8722, and the average value (average transmittance) was measured. ).

  As is apparent from the results shown in Table 1, the adhesive tapes of the examples have excellent optical film distortion prevention properties because the adhesive has appropriate elasticity and viscosity.

  On the other hand, as is clear from the results shown in Table 2, the pressure-sensitive adhesive tape of the comparative example was inferior in distortion resistance of the optical film, although it was excellent in adhesive strength.

It is a conceptual sectional view showing one embodiment of the adhesive tape of the present invention. It is a conceptual sectional view showing one embodiment of the adhesive tape of the present invention. It is a conceptual sectional view showing one embodiment of the adhesive tape of the present invention. It is a conceptual sectional view showing one embodiment of the adhesive tape of the present invention. It is sectional drawing which shows schematic structure of the LCD module unit which provided the adhesive tape between the LCD panel and the backlight housing | casing. It is an exploded view which shows schematic structure of the LCD module unit which provided the adhesive tape between the LCD panel and the backlight housing | casing. It is sectional drawing which shows one Embodiment of the LCD module unit which provided the double-sided adhesive tape between the optical film and the backlight housing | casing. It is an exploded view which shows schematic structure of the LCD module unit which provided the adhesive tape between the optical film and the backlight housing | casing. It is sectional drawing which shows one Embodiment of the LCD module unit which used the double-sided adhesive tape for adhering with the LCD panel integrated with FPC, and a backlight housing | casing. It is the schematic which shows one Embodiment of the LCD module unit which used the double-sided adhesive tape for adhering with the LCD panel integrated with FPC, and a backlight housing | casing, (a) is an exploded view, (b) is the whole FIG. It is a conceptual diagram which shows the measuring method of the distortion prevention property of the optical film in an Example.

DESCRIPTION OF SYMBOLS 1: Adhesive layer 2: Base material 3: Light-shielding layer 4: Light reflection layer 9: Driver 10: Adhesive tape 11: Prism sheet 12: Diffusion sheet 13: Light source 14: Light guide plate 15: Reflection plate 16: Backlight housing 17: LCD panel 20: Adhesive tape 21: Optical film 22: Glass

Claims (8)

An adhesive tape for fixing an optical film to an adherend in a frame shape, wherein an adhesive layer in contact with the optical film of the adhesive tape has a frequency of 0.005 Hz and a dynamic viscoelastic spectrum in a linear shear strain condition of 85. An adhesive tape for fixing an optical film, wherein a loss tangent at 0 ° C is 0.4 to 0.8. The adhesive tape for fixing an optical film according to claim 1, wherein the adherend is at least one of a backlight housing or an LCD panel in an LCD module having a backlight housing and an LCD panel. 2. The outer shape change rate of the optical film expressed by the following formula before and after standing at 85 ° C. for 5 minutes is + 0.06% or more in the flow direction and −0.06% or less in the width direction. Or the adhesive tape for optical film fixation of 2.
External form change rate = [(length after standing−length before standing) / (length before standing)] × 100 (%) The pressure-sensitive adhesive tape according to claim 1, wherein the optical film is an optical film having a polarization reflection function. The pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the optical film has a size of 2.5 to 7 inches. The pressure-sensitive adhesive tape according to any one of claims 1 to 5, wherein the optical film has a prism layer, and a ridge line of the prism layer intersects a flow direction of the pressure-sensitive adhesive tape. It is an LCD module which has the backlight housing | casing by which the optical film was provided in the surface layer, and an LCD panel, Comprising: The adhesive tape for optical film fixation in any one of Claims 1-6 is the said optical film and said LCD An LCD module provided between a panel or between the optical film and a backlight housing. A method for evaluating the suppression of distortion of an optical film that occurs in a high-temperature and high-humidity test when the optical film is fixed with an adhesive tape, the dynamic viscoelasticity of the adhesive layer on the side of the adhesive tape in contact with the optical film A method for evaluating suppression of distortion of an optical film by an adhesive tape, characterized by measuring a spectrum at a frequency of 0.001 to 0.02 Hz and evaluating a loss tangent at 75 to 95 ° C.

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