JP2010085802A - Retardation film polarizing plate laminate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film polarizing plate laminate in which one base film constituting the polarizing plate is omitted, the retardation film polarizing plate laminate having good durability against high temperature, and to provide a liquid crystal display device using the laminate. <P>SOLUTION: The retardation film polarizing plate laminate 10 is composed of a base film 1 made of triacetyl cellulose, a first adhesive layer 2, a polarizing film 3, a second adhesive layer 4, a retardation film 5 made of a bisphenol polycarbonate resin having a fluorene skeleton, and a pressure-sensitive adhesive layer 6 made of a pressure-sensitive adhesive, laminated in this order in a direct contact state to each other. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 6 is a pressure-sensitive adhesive having a viscoelastic loss tangent tanδ of not more than 0.148 at 80°C and 1 Hz conditions, or a pressure-sensitive adhesive having a gel fraction of not less than 84.3% at room temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a retardation film / polarizing plate laminate in which a retardation film is laminated on a polarizing film, and a liquid crystal display device using the laminate.

  In a liquid crystal display (LCD), a liquid crystal layer composed of liquid crystal molecules aligned in a predetermined direction is sandwiched between opposing substrates, and a polarizing plate or a laminate of a polarizing plate and a retardation film is formed on the surface of these substrates. Etc. are pasted.

  FIG. 5 is a cross-sectional view showing an example of a laminated structure of a conventional polarizing plate and a retardation film. In this laminated structure 100, in order from the side far from the liquid crystal cell 13, a base film 101, an adhesive layer 102, a polarizing film 103, an adhesive layer 104, a base film 105, an adhesive or pressure-sensitive adhesive layer 107, a retardation film 108, And the adhesive layer 109 is laminated | stacked. The laminated structure 100 is attached to the surface of the transparent substrate 12 constituting the liquid crystal cell 13 of the liquid crystal display device by an adhesive layer 109.

101 to 105 constitute a deflecting plate 106, and both surfaces of a polarizing film 103 made of polyvinyl alcohol (PVA) or the like on which iodine I ₂ is adsorbed are formed by base films 101 and 105 made of triacetyl cellulose (TAC) or the like. It has a sandwiching structure. Since the polarizing film 103 is stretched, the dimensional stability is poor. The base films 101 and 105 serve to protect the polarizing film 103, support the polarizing film 103, and prevent deformation thereof.

  Still, the polarizing plate is likely to change in dimensions under severe conditions such as high temperature and high humidity, and when the followability of the adhesive is insufficient, peeling is likely to occur. In order to prevent this, in Patent Documents 1 and 2 to be described later, a gel fraction is 50 to 80% by mass as an adhesive 109 or 107 for attaching the polarizing plate 106 to the retardation film 108 or the glass substrate 12. A pressure-sensitive adhesive whose loss tangent (loss coefficient) tan δ (= loss elastic modulus / storage elastic modulus) of dynamic viscoelasticity measured at a temperature of 90 ° C. and a vibration frequency of 0.1 Hz is 0.3 to 0.8. Has been proposed.

  Patent Documents 1 and 2 explain the reason as follows. That is, when the gel fraction is smaller than 50% by mass, the cohesive force of the pressure-sensitive adhesive layer is too weak, which is not preferable because it causes foaming under high temperature and high humidity. When the gel fraction exceeds 80% by mass, the adhesiveness is lowered, causing peeling from the substrate. In addition, the fluidity of the pressure-sensitive adhesive (sol-gel body) is reduced, so that the ability to relieve stress concentration is reduced, and this may cause uneven color and whitening of the polarizing element. On the other hand, when the loss tangent tan δ of the dynamic viscoelasticity measured at 90 ° C. and 0.1 Hz is smaller than 0.3, the elasticity and flexibility of the adhesive layer are low, and uneven color and whitening of the polarizing element occur. It causes and is not preferable. When the loss tangent tan δ exceeds 0.8, the cohesive force of the pressure-sensitive adhesive layer is low, which causes foaming, which is not preferable.

It is described that the gel fraction is obtained as follows. First, a predetermined amount Xg of a pressure-sensitive adhesive (sol-gel body) is mixed with ethyl acetate so as to have a concentration of about 1% by mass, and left at room temperature for 3 days to dissolve. Thereafter, the insoluble residue is filtered off using a 200-mesh wire net, dried, and its mass Yg is measured. The gel fraction is given by the following formula.
Gel fraction (%) = (Y / X) × 100

  On the other hand, as a constituent material of the retardation film 108, in recent years, a retardation film made of a bisphenol-based polycarbonate resin having a fluorene skeleton, such as Pure Ace (registered trademark of Teijin Chemicals Ltd .; hereinafter abbreviated as PA) may be used. Since it has a negative retardation characteristic, it is used as a viewing angle compensation film in small liquid crystal display devices for mobile phones and the like. However, Pure Ace (PA) has problems that are difficult to apply to a large-screen liquid crystal display device, such as a large photoelastic coefficient.

JP 2002-47468 A (pages 2, 3, and 10) JP 2002-129123 A (pages 2, 5, 10, and 11)

  Now, the present inventor has aimed to improve the optical performance and to improve the productivity and reduce the cost by simplifying the polarizing plate, and from the laminated structure 100 shown in FIG. The possibility of the retardation film / polarizing plate laminate 10 shown in FIG. 1 in which the agent layer 104 was omitted was examined. At this time, a base film 1 made of triacetylcellulose (TAC) and a bisphenol-based polycarbonate resin having a fluorene skeleton, for example, a retardation film 6 made of Pure Ace (PA) were selected as a preferred combination of constituent materials.

  A retardation film / polarizing plate laminate having the above-described configuration and a liquid crystal display device using the retardation film were manufactured and tested for durability against high temperatures. Conventionally, the laminate structure 100 shown in FIG. Even when the pressure-sensitive adhesive layer 7 is formed using the pressure-sensitive adhesive, it has been found that adhesion failure of the pressure-sensitive adhesive layer 7 and light leakage of the liquid crystal display device may occur under high temperature conditions. In this case, the omission of the base film on the liquid crystal cell 13 side causes the contraction of the polarizing film 3 and the warp of the base film 1, which are considered to have an adverse effect.

  The object of the present invention is a retardation film / polarizing plate laminate in which the base film on the liquid crystal cell side is omitted among the base films sandwiching the polarizing film in view of the above situation, and is durable against high temperatures. It is providing the retardation film and polarizing plate laminated body of this, and the liquid crystal display device using the laminated body.

That is, the present invention
A polarizing film in which a polarizing film is bonded to a base film on one side of the polarizing film;
An adhesive layer disposed on a surface of the polarizing film opposite to a surface bonded to the base film;
Retardation film,
A pressure-sensitive adhesive layer made of a pressure-sensitive adhesive whose loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz is 0.148 or less is laminated in this order with each layer in direct contact with each other,
The present invention relates to a first retardation film / polarizing plate laminate that is adhered to a substrate constituting a liquid crystal cell by the pressure-sensitive adhesive layer.

Also,
A polarizing film in which a polarizing film is bonded to a base film on one side of the polarizing film;
An adhesive layer disposed on a surface of the polarizing film opposite to a surface bonded to the base film;
Retardation film,
A pressure-sensitive adhesive layer made of a pressure-sensitive adhesive having a gel fraction of 84.3% or more is laminated in this order in a state where the respective layers are in direct contact with each other,
The present invention relates to a second retardation film / polarizing plate laminate that is adhered to a substrate constituting a liquid crystal cell by the pressure-sensitive adhesive layer.

  Further, the present invention relates to a liquid crystal display device in which the first or second retardation film / polarizing plate laminate is bonded to one or both of the substrates constituting the liquid crystal cell by the pressure-sensitive adhesive layer.

Among the base films sandwiching the polarizing film, a retardation film / polarizing plate laminate in which the base film on the liquid crystal cell side is omitted, that is, a polarizing plate in which the polarizing film is bonded to the base film on one side,
An adhesive layer disposed on a surface of the polarizing film opposite to a surface bonded to the base film;
Retardation film,
In order to realize a laminated body in which the respective layers are laminated in such a state that the respective layers are in direct contact with each other and have a high durability against high temperatures. The inventor has conducted extensive research. As a result, as shown in the examples described later, as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer,
A pressure-sensitive adhesive having a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz of 0.148 or less;
Or
The inventors have found that the problem can be solved by using a pressure-sensitive adhesive having a gel fraction of 84.3% or more, and have completed the present invention.

  The characteristic of said adhesive is that it is a hard adhesive with strong cohesive strength. The reason can be considered as follows.

  In the first or second retardation film / polarizing plate laminate of the present invention, among the base films sandwiching the polarizing film, the base film on the liquid crystal cell side is omitted. It is almost impossible to expect the performance to suppress the deformation. For example, if the polarizing film contracts, the base film warps accordingly and the contraction of the polarizing film cannot be suppressed.

  On the other hand, as a result of omitting the base film on the liquid crystal cell side, there is only the adhesive layer and the pressure-sensitive adhesive layer other than the retardation film between the polarizing film and the substrate, The polarizing film and the substrate are arranged closer to each other. Moreover, the substrate is far superior to the base film in terms of toughness as a support. Therefore, in order to stably maintain the shape of the polarizing film and the retardation film, the retardation film and the polarizing film are adhered to the substrate so strongly that they do not leave room for deformation. It is a good idea to end up. For this purpose, the pressure-sensitive adhesive is preferably a pressure-sensitive adhesive that is strong, hard, and cohesive.

  In consideration of the fact that the maximum use temperature of the retardation film / polarizing plate laminate reaches around 80 ° C., a high temperature durability test was conducted at 80 ° C. in the examples described later. The stress applied to the retardation film / polarizing plate laminate is mainly a gentle component having a frequency of 1 Hz or less. JIS K7244-1 (Plastics-Test method for dynamic mechanical properties-Part 1: General rules, In ISO 6721-1: 1994) and JIS K7141-1 (ISO 11403-1: 2001), the glass transition temperature Tg is the temperature at which the loss factor (loss tangent) tan δ is maximized when deformed at a constant frequency of 1 Hz. Therefore, physical property values such as loss tangent tan δ of dynamic viscoelasticity were examined based on values at 80 ° C. and 1 Hz.

  In the liquid crystal display device of the present invention, the first or second retardation film / polarizing plate laminate is attached to one or both of the substrates constituting the liquid crystal cell by the adhesive layer. Therefore, the productivity of the liquid crystal display device can be improved and the cost can be reduced by simplifying the polarizing plate, and durability against high temperatures can be ensured.

  In the first or second retardation film / polarizing plate laminate of the present invention, the adhesive constituting the adhesive layer has a glass transition point of 80 ° C. or higher and a dynamic viscosity at 80 ° C. and 1 Hz. The elastic loss tangent tan δ is preferably 0.64 or less.

The retardation film may be a retardation film made of a bisphenol-based polycarbonate resin having a fluorene skeleton, such as Pure Ace (PA). These retardation films have excellent optical performance, but the absolute value of the photoelastic coefficient is as large as 1.0 × 10 ⁻¹¹ Pa ⁻¹ or more, and light leakage due to deformation tends to occur. In the first or second retardation film / polarizing plate laminate, the shape of the retardation film is stably maintained. For this reason, even when the retardation film has a large absolute value of the photoelastic coefficient, light leakage due to deformation can be prevented, and the excellent optical performance of the retardation film can be utilized.

  The base film may be made of triacetyl cellulose.

  Next, a preferred embodiment of the present invention will be specifically described with reference to the drawings.

Embodiment 1
In Embodiment 1, an example of the retardation film / polarizing plate laminate described in claims 1 to 5 will be described.

  FIG. 1 is a cross-sectional view schematically showing the structure of a retardation film / polarizing plate laminate 10 according to an embodiment of the present invention. In the laminate 10, the base film 1, the adhesive layer 2, the polarizing film 3, the adhesive layer 5, the retardation film 6, and the pressure-sensitive adhesive layer 7 are in direct contact with each other in order from the side far from the liquid crystal cell 13. They are stacked together. The laminated body 10 is bonded to the surface of the transparent substrate 12 constituting the liquid crystal cell 13 of the liquid crystal display device (LCD) with the adhesive layer 7.

1 to 3 constitute a deflecting plate 4, and a polarizing film 3 made of polyvinyl alcohol (PVA) or the like adsorbing iodine I ₂ is formed on one side of the base film 1 made of triacetyl cellulose (TAC) or the like. Bonded by the adhesive layer 2. The retardation film 6 is made of a bisphenol-based polycarbonate resin having a fluorene skeleton, such as pure ace (PA), and has an absolute value of a photoelastic coefficient of 1.0 × 10 ⁻¹¹ Pa ⁻¹ or more.

  In general, the retardation film depends on the viewing angle of the liquid crystal cell and the polarizing plate by adjusting the minute three-dimensional refractive index anisotropy of the region sandwiched between the two polarizing plates arranged so as to sandwich the liquid crystal cell. Compensate for sex. On the other hand, a triacetyl cellulose (TAC) film generally used as a base film also has a minute three-dimensional refractive index anisotropy.

  For this reason, in the conventional laminated body of the polarizing film (refer FIG. 5) which clamps both surfaces of the polarizing film 103 with the base films 101 and 105 which consist of a triacetyl cellulose (TAC), and a phase difference film, the liquid crystal cell 13 is used. It was necessary to control the three-dimensional refractive index of both the base film 105 and the retardation film 108 disposed on the side.

  On the other hand, in the retardation film / polarizing plate laminate 10 of the present embodiment, the base film 105 disposed on the liquid crystal cell 13 side is omitted, and thus the three-dimensional refractive index of the base film 105 needs to be controlled. Instead, the viewing angle dependence compensation is realized only by controlling the minute three-dimensional refractive index of the retardation film 6. In the retardation film / polarizing plate laminate 10, for example, control of the three-dimensional refractive index (Nx> Nz, Ny> Nz necessary for compensation of viewing angle dependency of a liquid crystal cell operating in a VA (vertical alignment) mode. , Nx ≧ Ny) is easily obtained.

  The adhesive layer 5 is the adhesive layer, and is disposed on the surface of the polarizing film 3 opposite to the surface bonded to the base film 1, and serves to affix the deflection plate 4 to the retardation film 6. . As shown in the examples described later, the adhesive constituting the adhesive layer 5 has a glass transition point of 80 ° C. or higher and a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz is 0. An adhesive that is .64 or less is preferable.

  The pressure-sensitive adhesive layer 7 is the pressure-sensitive adhesive layer and serves to affix the retardation film 6 to the surface of the transparent substrate 12. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 7 is a pressure-sensitive adhesive whose loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz is 0.148 or less, as shown in the examples described later, or a gel component. It is preferable that the pressure-sensitive adhesive has a rate of 84.3% or more. These physical property values all indicate that the pressure-sensitive adhesive is hard and has high cohesive strength.

  In the retardation film / polarizing plate laminate 10, among the base films sandwiching the polarizing film 3, the base film on the liquid crystal cell 13 side is omitted. Therefore, the polarizing film 3 is deformed to the base film 1 made of TAC. You can hardly expect the performance to suppress. For example, if the polarizing film 3 contracts, the base film 1 made of TAC warps accordingly, and the contraction of the polarizing film 3 cannot be suppressed.

  On the other hand, as a result of omitting the base film on the liquid crystal cell 13 side, only the adhesive layer 5 and the pressure-sensitive adhesive layer 7 are provided between the polarizing film 3 and the transparent substrate 12 in addition to the retardation film 6. The polarizing film 3 and the transparent substrate 12 are arranged closer to each other. Moreover, in terms of toughness as a support, the transparent substrate 12 is far superior to the base film 1 made of TAC. Therefore, in order to stably maintain the shapes of the polarizing film 3 and the retardation film 6, the retardation film 6 and the polarizing film 3 are affixed to the transparent substrate 12 so strongly that they do not leave room for deformation. It is a good idea to end up. For this purpose, the pressure-sensitive adhesive is preferably a pressure-sensitive adhesive that is strong, hard, and cohesive.

  As described above, in the retardation film / polarizing plate laminate 10, the polarizing film 3 and the retardation film 6 are strongly attached to the transparent substrate 12 by the adhesive layer 5 and the adhesive layer 7, and the shape is stably maintained. Is done. As a result, the retardation film / polarizing plate laminate 10 has high temperature durability that does not cause peeling even in a high temperature environment. Moreover, even if the retardation film 6 is a pure ace (PA) having a large absolute value of the photoelastic coefficient, light leakage due to deformation can be prevented, and its excellent optical performance can be utilized.

Embodiment 2
In the second embodiment, an example of a transmissive liquid crystal display device will be described as an example of the liquid crystal display device described in claim 6.

  FIG. 2 is a schematic cross-sectional view showing a configuration of a transmissive liquid crystal display device 40 based on the second embodiment. The transmissive liquid crystal display device 40 includes a liquid crystal display panel 20 and a backlight device 30 that irradiates illumination light on the back surface (lower surface in FIG. 2).

  In the liquid crystal display panel 20, a liquid crystal cell 13 is formed by a liquid crystal layer 11 made of a liquid crystal material and transparent substrates 12 a and 12 b facing each other with the liquid crystal layer 11 interposed therebetween. Retardation film / polarizing plate laminates 10a and 10b are respectively arranged on the outer surfaces of the transparent substrates 12a and 12b, and are attached to the transparent substrates 12a and 12b by respective adhesive layers.

  The configuration of the liquid crystal layer 11 is not particularly limited, and is a liquid crystal material in which the dielectric anisotropy is positive and the molecular long axis is aligned substantially parallel to the electric field direction when an electric field is applied, or the molecular long axis is negative and has a negative dielectric anisotropy. A vertical alignment type liquid crystal material or the like that is aligned substantially perpendicular to the electric field direction is used.

  The transparent substrates 12a and 12b are made of a glass substrate, and although not shown, a striped transparent electrode, an insulating film, and an alignment film are formed on the inner surface of the transparent substrate 12a. A color filter of three primary colors of red (R), green (G), and blue (B), an overcoat layer, a striped transparent electrode, and an alignment film are formed. The alignment film is made of polyimide, for example, and is provided in contact with the liquid crystal material.

  The backlight device 30 is generally configured by appropriately combining a backlight light source 31 and a diffusion plate 32, a diffusion sheet 33, a prism sheet 34, a polarization separation element 35, and the like disposed on the light emission side.

  The backlight light source 31 is a direct-type backlight light source that irradiates illumination light from the back side of the liquid crystal display panel 20. The backlight light source 31 includes, for example, a linear light source 31a composed of a plurality of cold cathode tubes, and a reflection plate 31b that covers the back side and the side of the light source 31a. Light emitted from the backlight light source 31 enters the liquid crystal display panel 20 through various optical films 32 to 35.

  The diffuser plate 32 scatters the light emitted from the backlight light source 31 (backlight light), averages the variation of the light path, and uniforms the luminance, and from the liquid crystal display panel 20 side, the diffusion light source 31 Make the bright lines invisible. The diffusion sheet 33 diffuses the backlight light in a predetermined angle range. The prism sheet 34 has a function of condensing the backlight light diffused by the diffusion sheet 33 and causing it to enter the polarization separation element 35. The polarization separation element 35 transmits the linearly polarized light component in a certain direction included in the incident light and reflects the other linearly polarized light component. As a result, only polarized light in a certain direction enters the liquid crystal display panel 20.

  The polarized light that has passed through the polarization separation element 35 passes through the polarizing plate 4a having a transmission axis parallel to the polarization direction, and enters the liquid crystal layer 11 through the retardation film 6a and the transparent substrate 12a. The liquid crystal molecules constituting the liquid crystal layer 11 are driven by the voltage applied between the electrodes for each pixel region sandwiched between the transparent electrodes, the orientation direction is controlled, and the polarization direction of the incident light is determined by the liquid crystal layer. 11 is changed by the above-mentioned aligned liquid crystal molecules. As a result, the amount of light transmitted through the polarizing plate 4b on the front surface side of the liquid crystal display panel 20 is controlled for each pixel, and an image is formed on the front surface of the liquid crystal display panel 20.

  The phase difference films 6a and 6b cancel the phase difference between light waves caused by light having different wavelengths passing through the liquid crystal layer 11, and prevent the liquid crystal layer from being colored. That is, it functions to cancel the wavelength dispersion characteristic of the liquid crystal layer 11 and realize an achromatic background display. In addition, the liquid crystal display device functions as a viewing angle compensation film that suppresses the decrease in luminance, chromaticity, and contrast due to the difference in viewing angle and improves the viewing angle characteristics of the liquid crystal display device 40.

  In the liquid crystal display device 40, the retardation film / polarizing plate laminates 10a and 10b are bonded to the substrates 11a and 11b constituting the liquid crystal cell 13 by the adhesive layers 7a and 7b, respectively. As a result, the productivity of the liquid crystal display device can be improved and the cost can be reduced by simplifying the polarizing plate, and durability against high temperatures can be ensured.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

1. Examination of physical properties to be satisfied by adhesives In Examples 1 to 4 and Examples 1 to 3, various adhesives are used as adhesives constituting the adhesive layer 5 as the adhesive layer, and the description is made in Embodiment 1. Of the retardation film / polarizing plate laminate 10, a test piece having a layer configuration of base film 1 / adhesive layer 2 / polarizing film 3 / adhesive layer 5 / retardation film 6 was produced. Then, the high temperature durability test which heats a test piece to 80 degreeC for 24 hours was done, and the adhesiveness before and behind that was evaluated. Based on this evaluation result, the physical properties to be satisfied by the adhesive were examined.

At this time, polyvinyl alcohol (PVA) adsorbed with iodine I ₂ was used as a material for the polarizing film 3. Further, as the retardation film 6, Pure Ace (PA), which is a retardation film made of a bisphenol-based polycarbonate resin having a fluorene skeleton, was used. The photoelastic coefficient of Pure Ace (PA) is 3.5 to 4.0 × 10 ⁻¹¹ Pa ⁻¹ . The planar shape of the prepared test piece is a square of 2 cm × 2 cm in length and width, and the thickness of each layer is as follows.

Base film (TAC) 1
Adhesive layer 2
Polarizing film (PVA) 3
Polarizing plate 4 (1 + 2 + 3): 105 μm
Adhesive layer 5: 2 μm
Retardation film (PA) 6: 40 μm

Example 1
<Preparation of test piece>
First, a polyvinyl alcohol (PVA) film was stretched in an aqueous iodine solution to prepare a polarizing film (PVA) 3. Next, one surface of the polarizing film (PVA) 3 was bonded to the base film 1 made of triacetyl cellulose (TAC) through the polyvinyl alcohol adhesive layer 2.

  Next, each bonding surface of the polarizing film (PVA) 3 having the base film (TAC) 1 bonded to one surface and the retardation film (PA) 6 was subjected to corona discharge treatment. The corona discharge treatment was performed using a corona treatment apparatus AGI-021S (trade name; manufactured by Kasuga Denki Co., Ltd.), and the treatment was performed twice under the treatment conditions of 400 W and table speed 30. Subsequently, the polyester urethane adhesive a was applied to the bonding surface of the retardation film (PA) 6 by a bar coater blade method using a # 7 wire bar, and then heated to 60 ° C. for 120 seconds to adhere. An adhesive layer 5 made of the agent a was formed.

  Next, the bonding surface of the retardation film (PA) 6 on which the adhesive layer 5 was formed and the bonding surface of the polarizing film (PVA) 3 were bonded using a portable roller. Thereafter, aging is performed at 40 ° C. for 3 days for curing, and base film (TAC) 1 / adhesive layer 2 / polarizing film (PVA) 3 / adhesive layer (adhesive a) 5 / retardation film ( A test piece on which PA) 6 was laminated was prepared.

<Measurement of dynamic viscoelasticity of adhesive>
For measuring the dynamic viscoelasticity of the adhesive a, a rheometer ARES (trade name; manufactured by TA Instruments) was used as a dynamic viscoelasticity measuring apparatus. A film of adhesive a was prepared and used as a sample, and a parallel plate having a diameter of 8 mm was used as a measurement jig. The measurement temperature was 0 to 100 ° C., and the temperature was changed from the low temperature side to the high temperature side at a temperature increase rate of 10 ° C./min. The adhesive a had a glass transition point of 80 ° C. or higher, and a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz was 0.64.

<High temperature durability test and evaluation>
The above test piece was subjected to a high temperature durability test for 24 hours under dry conditions at 80 ° C. The adhesion after the test was examined by visual observation.

Example 2
The adhesive b was used as an adhesive that forms the adhesive layer 5. Adhesive b was a polyester urethane adhesive and had a glass transition point of 80 ° C. or higher and a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz was 0.50. Except this, a test piece was prepared in the same manner as in Example 1, and a high temperature durability test was conducted.

Example 3
An adhesive c was used as an adhesive for forming the adhesive layer 5. Adhesive c was a polyester urethane adhesive, had a glass transition point of 80 ° C. or higher, and had a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz of 0.30. Except this, a test piece was prepared in the same manner as in Example 1, and a high temperature durability test was conducted.

Example 4
The adhesive d was used as an adhesive for forming the adhesive layer 5. Adhesive d was an ultraviolet curable acrylic adhesive having a glass transition point of 95 ° C. and a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz of 0.10 or less.

In the preparation of the test piece, as in Example 1, first, each of the polarizing film (PVA) 3 having the base film (TAC) 1 bonded to one surface and the retardation film (PA) 6 was used. The bonded surface was subjected to corona discharge treatment. Next, the adhesive d was applied to the bonding surface of the retardation film (PA) 6 by a spin coat method using a spin coater for 10 seconds at 100 rpm and for 10 seconds at 2000 rpm. Next, the bonding surface of the retardation film (PA) 6 to which the adhesive d was applied and the bonding surface of the polarizing film (PVA) 3 were bonded using a portable roller. Thereafter, ultraviolet rays having a wavelength of 365 nm are irradiated from the phase difference film (PA) 6 side at an intensity of 22.9 mJ / cm ² for 200 seconds to cure the adhesive d, and form an adhesive layer 5 made of the cured adhesive d. did. Except this, a test piece was prepared in the same manner as in Example 1, and a high temperature durability test was conducted.

Example 1
The adhesive e was used as an adhesive for forming the adhesive layer 5. Adhesive e was an ultraviolet curable acrylic adhesive having a glass transition point of 39 ° C. and a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz of 0.10 or less. Except this, a test piece was prepared in the same manner as in Example 4, and a high temperature durability test was conducted.

Example 2
An adhesive f was used as an adhesive for forming the adhesive layer 5. The adhesive f was an ultraviolet curable acrylic adhesive, had a glass transition point of −30 ° C. and −16 ° C., and had a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz of 0.10 or less. Except this, a test piece was prepared in the same manner as in Example 4, and a high temperature durability test was conducted.

Example 3
Adhesive g was used as an adhesive for forming the adhesive layer 5. Adhesive g was a polyurethane-based adhesive having a glass transition point of 80 ° C. or higher and a loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz was 0.70. Except this, a test piece was prepared in the same manner as in Example 1, and a high temperature durability test was conducted.

  Table 1 summarizes the adhesives used, their physical properties and evaluation results. In the table, the ○ mark in the column of the evaluation result is a case where no change was observed in the appearance after the high temperature durability test, and the Δ mark indicates that the peeling occurred after the high temperature durability test and the adhesion was maintained. This is the case when there was something that could not be done. In any bonding with any adhesive, adhesion deterioration and abnormality were not observed immediately after the bonding.

  As shown in Table 1, the glass transition point of the adhesive constituting the adhesive layer 5 is 80 ° C. or higher, and the loss tangent of dynamic viscoelasticity at 80 ° C. and 1 Hz is 0.64 or lower. In Examples 1 to 4, the test pieces had good high temperature durability. On the other hand, even when the loss tangent of the adhesive constituting the adhesive layer 5 is also 0.64 or less, in Examples 1 and 2 where the glass transition point is 80 ° C. or less, the high temperature durability of the test piece is not sufficient. There was a thing. This indicates that it is necessary for the durability that deformation of the adhesive constituting the adhesive layer 5 hardly occurs in the use temperature range. Further, even when the glass transition point of the adhesive constituting the adhesive layer 5 is 80 ° C. or higher, in Example 3 where the loss tangent of dynamic viscoelasticity at 80 ° C. and 1 Hz is 0.70, the high temperature of the test piece Durability may not be sufficient. This indicates that the adhesive constituting the adhesive layer 5 requires a certain degree of hardness for durability.

2-1. Examination of physical properties to be satisfied by pressure-sensitive adhesives ... Dynamic viscoelasticity of pressure-sensitive adhesives In Examples 11 to 13 and Comparative Examples 11 to 13, various pressure-sensitive adhesives constituting the pressure-sensitive adhesive layer 7 as the pressure-sensitive adhesive layer The same as the retardation film / polarizing plate laminate 10 described with reference to FIG. 1 in the first embodiment, using the base material 1 / adhesive layer 2 / polarizing film 3 / adhesive layer 5 / retardation film A test piece having a layer structure of 6 / adhesive layer 7 / transparent substrate (glass substrate) 12 was produced. Then, the high temperature durability test which heats a test piece to 80 degreeC for 24 hours was done, and the adhesiveness before and behind that was evaluated. Moreover, the dynamic viscoelasticity of the adhesive was measured, and the relationship between this and the result of the high temperature durability test was investigated.

At this time, polyvinyl alcohol (PVA) adsorbed with iodine I ₂ is used as the material of the polarizing film 3, and the retardation film 6 is a retardation film made of a bisphenol-based polycarbonate resin having a fluorene skeleton. Was used. The photoelastic coefficient of Pure Ace (PA) is 3.5 to 4.0 × 10 ⁻¹¹ Pa ⁻¹ . Also, the adhesive layer 5 was formed using the adhesive a obtained with good results in Example 1. The planar shape of the prepared test piece is a square of 2 cm × 2 cm in length and width, and the thickness of each layer is as follows.

Base film (TAC) 1
Adhesive layer 2
Polarizing film (PVA) 3
Polarizing plate 4 (1 + 2 + 3): 105 μm
Adhesive layer (adhesive a) 5: 2 μm
Retardation film (PA) 6: 40 μm
Adhesive layer 7: 25 μm

Example 11
<Preparation of test piece>
First, a polyvinyl alcohol (PVA) film was stretched in an aqueous iodine solution to prepare a polarizing film (PVA) 3. Next, one surface of the polarizing film (PVA) 3 was bonded to the base film 1 made of triacetyl cellulose (TAC) through the polyvinyl alcohol adhesive layer 2.

  Next, each bonding surface of the polarizing film (PVA) 3 having the base film (TAC) 1 bonded to one surface and the retardation film (PA) 6 was subjected to corona discharge treatment. The corona discharge treatment was performed using a corona treatment apparatus AGI-021S (trade name; manufactured by Kasuga Denki Co., Ltd.), and the treatment was performed twice under the treatment conditions of 400 W and table speed 30. Subsequently, the adhesive a was applied to the bonding surface of the retardation film (PA) 6 by a bar coater blade method using a # 7 wire bar, and then heated to 60 ° C. for 120 seconds. An adhesive layer 5 was formed.

  Next, the bonding surface of the retardation film (PA) 6 on which the adhesive layer 5 was formed and the bonding surface of the polarizing film (PVA) 3 were bonded using a portable roller. Thereafter, aging is performed at 40 ° C. for 3 days for curing, and base film (TAC) 1 / adhesive layer 2 / polarizing film (PVA) 3 / adhesive layer (adhesive a) 5 / retardation film ( A laminate in which PA) 6 was laminated was produced.

  Next, the respective bonding surfaces of the retardation film (PA) 6 to which the polarizing plate 4 was bonded and the glass substrate 12 were subjected to corona discharge treatment in the same manner as described above. Next, an adhesive sheet in which an adhesive layer made of adhesive A is sandwiched between two protective films is prepared, one protective film of the adhesive sheet is peeled off, and the exposed adhesive layer surface and retardation film ( The bonded surface of PA) 6 was bonded using a portable roller. The pressure-sensitive adhesive A is an acrylic pressure-sensitive adhesive manufactured by Toyo Ink Co., and is obtained by blending 1.45 parts by weight of a curing agent with respect to 100 parts by weight of the main agent. Subsequently, the other protective film was peeled off from the pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive layer surface and the bonding surface of the glass substrate 12 were bonded together using a portable roller to prepare a test piece.

<Measurement of dynamic viscoelasticity of adhesive>
For measurement of the dynamic viscoelasticity of the adhesive, DVA-220 (trade name; manufactured by IT Measurement Control Co., Ltd.) was used as a dynamic viscoelasticity measuring device. The sample is a sheet-like pressure-sensitive adhesive (length 5 mm × width 25 mm × thickness 25 μm), and the measurement temperature is −80 to 100 ° C. The measurement temperature was changed from the low temperature side to the high temperature side at a heating rate of 5 ° C./min.

<High temperature durability test and evaluation>
The prepared test piece was subjected to a high temperature durability test in an oven kept at a high temperature of 80 ° C. for 24 hours immediately after being bonded. The adhesion after the test was examined by visual observation and observation by a microscope with a magnification of 75 times.

Example 12
An adhesive B was used as an adhesive constituting the adhesive layer 7. The adhesive B is a non-support acrylic adhesive sheet SK2057 manufactured by Soken Chemical Co., Ltd. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

Example 13
Adhesive C was used as the adhesive constituting the adhesive layer 7. The pressure-sensitive adhesive C is an acrylic pressure-sensitive adhesive made by Toyo Ink Co., which is different from the pressure-sensitive adhesive A, and contains 0.37 parts by weight of a curing agent with respect to 100 parts by weight of the main agent. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

Comparative Example 11
Adhesive F was used as the adhesive constituting the adhesive layer 7. The pressure-sensitive adhesive F is a non-support acrylic pressure-sensitive adhesive sheet SK1478 manufactured by Soken Chemical. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

Comparative Example 12
The pressure-sensitive adhesive G was used as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 7. The pressure-sensitive adhesive G is an acrylic pressure-sensitive adhesive made by Toyo Ink Co., different from pressure-sensitive adhesives A and C, and is obtained by blending 2.0 parts by weight of a curing agent with respect to 100 parts by weight of the main agent. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

Comparative Example 13
An adhesive H was used as an adhesive constituting the adhesive layer 7. The pressure-sensitive adhesive H is an acrylic pressure-sensitive adhesive EG300 manufactured by Toyo Ink Co., Ltd. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

2-2. Examination of physical properties to be satisfied by pressure-sensitive adhesive: gel fraction of pressure-sensitive adhesive Examples 14 and 15 and Comparative Examples 12 and 14 are the same as the retardation film / polarizing plate laminate 10 in the same manner as in Example 11. A test piece having a layer configuration of base film 1 / adhesive layer 2 / polarizing film 3 / adhesive layer 5 / retardation film 6 / adhesive layer 7 / transparent substrate (glass substrate) 12 was prepared, and 80 test pieces were prepared. A high temperature durability test was performed by heating to ° C for 24 hours, and the adhesion before and after the evaluation was evaluated. Under the present circumstances, the various adhesives from which a gel fraction differs as an adhesive which comprises the adhesive layer 7 were used, and the relationship between the gel fraction and the result of a high temperature durability test was investigated.

Example 14
The pressure-sensitive adhesive D was used as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 7. The pressure-sensitive adhesive D is an acrylic pressure-sensitive adhesive manufactured by Toyo Ink Co., the main agent is the same as the main agent of the pressure-sensitive adhesive G, and the curing agent is different from the pressure-sensitive adhesive G. The gel fraction of the adhesive D is 84.9%. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

Example 15
The pressure-sensitive adhesive E was used as a pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 7. The pressure-sensitive adhesive E is an acrylic pressure-sensitive adhesive manufactured by Toyo Ink Co., the main agent is the same as the pressure-sensitive adhesives D and G, and the type of the curing agent is different from the pressure-sensitive adhesives D and G. The gel fraction of the adhesive E is 84.3%. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

Comparative Example 14
Adhesive I was used as the adhesive constituting the adhesive layer 7. Adhesive I is an acrylic adhesive manufactured by Toyo Ink Co., Ltd. The main agent and curing agent are the same as the main agent and curing agent of adhesive E, respectively, but the amount of curing agent is different from that of adhesive E. The gel fraction of adhesive I is 69.3%. Except this, a test piece was prepared in the same manner as in Example 11, and a high temperature durability test was conducted.

Comparative Example 12
The gel fraction of the pressure-sensitive adhesive G constituting the pressure-sensitive adhesive layer 7 of Comparative Example 12 is 65.6%.

  Table 2 is a table summarizing the values of storage elastic modulus and loss tangent tan δ of dynamic viscoelasticity and loss tangent tan δ at 80 ° C. and 1 Hz for each of the pressure-sensitive adhesives used in Examples 11 to 13 and Comparative Examples 11 to 13. is there.

  Table 3 summarizes the gel fractions and evaluation results of each adhesive in Examples 14 and 15 and Comparative Examples 12 and 14 using the same main agent but different types or amounts of curing agents. It is a table.

The evaluation results described in Table 2 and Table 3 were classified as follows based on visual observation and observation using a microscope.
◎… Almost no bubbles are observed even with a microscope.
○: There are bubbles (size of tens of μm or less) that cannot be seen by visual observation but are visible by observation with a microscope.
×: Bubbles (size of several tens to several hundreds of μm) that can be clearly seen by visual observation exist.

  3A and 3B are microscopic observation images showing the results of the high-temperature durability test according to Example 14 and Comparative Example 11, respectively. As shown in FIG. 3, in Example 14, the generation of bubbles was slight, whereas in Comparative Example 11, the generation of bubbles was remarkable. This bubble is not a true bubble made of gas, but a boundary where peeling has started to look like a bubble, and the generation of bubbles is a sign that peeling is about to occur. In that sense, hereinafter, bubbles are referred to as bubbles (peeling). Further, in any bonding with any pressure-sensitive adhesive, no deterioration or abnormality in adhesion was observed immediately after the bonding.

  As shown in Table 2, the loss tangent tan δ value is as small as 0.148 or less in Example 11 in which the generation of bubbles (peeling) is suppressed, and Examples 12 and 13 in which generation of bubbles is suppressed to some extent. On the other hand, in Comparative Examples 11 to 13 where the generation of bubbles (peeling) was remarkable, the tan δ value was as large as 0.226 or more. From these results, it can be considered that the smaller the loss tangent tan δ value, the more the generation of bubbles (peeling) tends to be suppressed. From this, it is considered that a pressure-sensitive adhesive having stronger rigidity, less fluidity, and less strain absorption suppresses deformation of the adjacent layer and suppresses generation of bubbles (peeling).

  Moreover, as shown in Table 3, when Example 15 and Comparative Example 14 in which the main agent and the curing agent constituting the pressure-sensitive adhesive are the same, but the amount of the curing agent is different, the curing agent is In Example 15 using the adhesive E contained in a large amount, the generation of bubbles (peeling) was less. In the pressure-sensitive adhesive E of Example 15 in which no bubbles (peeling) occurred, the gel fraction was 84.3%, whereas in the pressure-sensitive adhesive I of Comparative Example 14 in which bubbles (peeled) occurred, the gel content was reduced. The rate is 69.3%. Further, when Example 14 and Comparative Example 12 having the same main component constituting the pressure-sensitive adhesive are compared, although the type of the curing agent is different, the pressure-sensitive adhesive D of Example 14 having a gel fraction of 84.9% is obtained. When used, no bubble (peeling) was generated, and when the adhesive of Comparative Example 12 having a gel fraction of 65.3% was used, bubbles (peeling) were generated.

  From these results, it is considered that the larger the gel fraction, the more the generation of bubbles (peeling) tends to be suppressed. A high gel fraction means a high crosslink density and a strong cohesive force in the gel-sol body (see Adhesion, Vol. 50, No. 2, p. 14, 2006). From this, the crosslink density is large and the pressure-sensitive adhesive hardens with a stronger cohesive force, and the more closely it adheres to the adjacent layer (the harder it is the pressure-sensitive adhesive, the harder the adjacent layer is), the stronger the force to suppress peeling. it is conceivable that.

  From the above results, the pressure-sensitive adhesive used in the present invention preferably has high rigidity, poor fluidity, and strong cohesive force. Specifically, the loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz is higher. It turns out that a small adhesive or an adhesive with a large gel fraction is good.

  Generally, there are the following two policies for selecting / designing an adhesive that does not generate bubbles (peeling) (Adhesion, 50, 2, p. 10-15, 2006). These policies are conceptually opposite design policies.

  One is that the cohesive force of the pressure-sensitive adhesive and adhesive is strengthened, and the pressure-sensitive adhesive and adhesive existing around the polarizing film and the retardation film are not deformed, so that the polarizing film or the position where the shrinkage or warping is likely to occur. It is a method that does not cause deformation against the phase difference film. Such a pressure-sensitive adhesive is a pressure-sensitive adhesive having a small viscosity, a large elasticity, and a small loss tangent tan δ of dynamic viscoelasticity. In order to obtain such a pressure-sensitive adhesive, the high molecular weight / high glass transition temperature of the polymer constituting the pressure-sensitive adhesive, the removal of low molecular weight components, the increase of the crosslinking agent by increasing the crosslinking agent and improving the crosslinking efficiency (gel) There is a method of increasing the fraction). The present invention is consistent with this design policy.

  The other is to weaken the cohesive force of the pressure-sensitive adhesive and adhesive, follow the shrinkage and warpage of the polarizing film and retardation film, and deform the pressure-sensitive adhesive and adhesive present around them, It is a method of relieving stress. Such a pressure-sensitive adhesive is a pressure-sensitive adhesive having a large viscosity, a small elasticity, and a large loss tangent tan δ of dynamic viscoelasticity. In order to obtain such an adhesive, there are methods such as lowering the molecular weight / lowering the glass transition temperature of the polymer constituting the adhesive and reducing the crosslinking density (reducing the gel fraction) by reducing the amount of the crosslinking agent. The selection of the pressure-sensitive adhesive shown in Patent Documents 1 and 2 is in line with this design policy because it relaxes deformation of the polarizing film and the like.

  The reason why the present invention does not take the latter policy is a result of omitting the base film on the liquid crystal cell 13 side among the base films sandwiching the polarizing film 3. Since the base film on the liquid crystal cell 13 side is omitted, the transparent substrate 12 is the only support that holds the forms of the polarizing film 3 and the retardation film 6. For this reason, if the adhesive layer 5 and the pressure-sensitive adhesive layer 7 existing between the polarizing film 3 and the retardation film 6 and the transparent substrate 12 are easily deformed, deformation of the polarizing film 3 and the like can be suppressed. Disappear. For this reason, the latter design policy cannot be taken. On the other hand, as a result of omitting the base film on the liquid crystal cell 13 side, the polarizing film 3 and the transparent substrate 12 are arranged closer to each other. For this reason, in the present invention, it is easy to adopt the former design policy.

3. In the light leakage test examples 21 to 26, the same base film 1 / adhesive layer 2 / polarizing film 3 / adhesive as the retardation film / polarizing plate laminate 10 described in the first embodiment (see FIG. 1). A test piece having a layer structure of layer 5 / retardation film 6 / adhesive layer 7 was produced and incorporated in the liquid crystal display panel 20 (see FIG. 2) described in the second embodiment. Then, the high temperature durability test which heats the liquid crystal display panel 20 to 80 degreeC for 24 hours was done, and the light leak in the liquid crystal display panel 20 before and after that was evaluated.

At this time, polyvinyl alcohol (PVA) adsorbed with iodine I ₂ is used as the material of the polarizing film 3, and the retardation film 6 is a retardation film made of a bisphenol-based polycarbonate resin having a fluorene skeleton. Was used. The photoelastic coefficient of Pure Ace (PA) is 3.5 to 4.0 × 10 ⁻¹¹ Pa ⁻¹ . Further, as the adhesive and the pressure-sensitive adhesive constituting the adhesive layer 5 and the pressure-sensitive adhesive layer 7, respectively, the adhesive and the pressure-sensitive adhesive obtained with good results in the above-described examples were used. The prepared test piece has a planar shape of 15 cm × 15 cm square, and the thickness of each layer is as follows.

Base film (TAC) 1
Adhesive layer 2
Polarizing film (PVA) 3
Polarizing plate 4 (1 + 2 + 3): 105 μm or 70 μm
Adhesive layer (adhesive a) 5: 2 μm
Retardation film (PA) 6: 40 μm
Adhesive layer 7: 25 μm

Example 21
<Preparation of test piece and incorporation into liquid crystal display panel>
First, a polyvinyl alcohol (PVA) film was stretched in an aqueous iodine solution to prepare a polarizing film (PVA) 3. Next, one surface of the polarizing film (PVA) 3 was bonded to the base film 1 made of triacetyl cellulose (TAC) through the polyvinyl alcohol adhesive layer 2.

  Next, each bonding surface of the polarizing film (PVA) 3 having the base film (TAC) 1 bonded to one surface and the retardation film (PA) 6 was subjected to corona discharge treatment. The corona discharge treatment was performed using a corona treatment apparatus AGI-021S (trade name; manufactured by Kasuga Denki Co., Ltd.), and the treatment was performed twice under the treatment conditions of 400 W and table speed 30. Subsequently, the adhesive a was applied to the bonding surface of the retardation film (PA) 6 by a bar coater blade method using a # 7 wire bar, and then heated to 60 ° C. for 120 seconds. An adhesive layer 5 was formed.

  Next, the bonding surface of the retardation film (PA) 6 on which the adhesive layer 5 was formed and the bonding surface of the polarizing film (PVA) 3 were automatically bonded using a film laminator apparatus. At this time, the light transmission axis of the polarizing film (PVA) 3 and the optical axis having the phase difference of the retardation film (PA) 6 were arranged in parallel. This was followed by aging at 40 ° C. for 3 days for curing.

  Next, the bonded surface of the retardation film (PA) 6 to which the polarizing plate 4 was bonded was subjected to corona discharge treatment in the same manner as described above. Next, an adhesive sheet in which an adhesive layer made of adhesive B is sandwiched between two protective films is prepared, one protective film of the adhesive sheet is peeled off, and the exposed adhesive layer surface and retardation film ( The laminated surface of PA) 6 was automatically laminated using a film laminator apparatus. As a result, base film (TAC) 1 / adhesive layer 2 / polarizing film (PVA) 3 / adhesive layer (adhesive a) 5 / retardation film (PA) 6 / adhesive layer (adhesive B) 7 / A test piece on which a protective film was laminated was produced.

  Next, the liquid crystal television BRAVIA32 (trade name; manufactured by Sony Corporation) was removed in a state where the transmissive color liquid crystal panel operating in the VA (vertical alignment) mode can be driven. A polarizing film made of polyvinyl alcohol (PVA) and a polarizing film sandwiched from both sides by a base film made of triacetylcellulose (TAC) is mounted on the light emitting surface of the liquid crystal cell constituting the liquid crystal panel. However, no retardation film is attached. Next, the polarizing plate was removed from the liquid crystal panel, the protective film was peeled off from the test piece, and the test piece was bonded to the liquid crystal cell instead of the attached polarizing plate (see FIG. 2).

<High temperature durability test and evaluation>
The liquid crystal panel on which the test piece was mounted was subjected to a high temperature durability test in an oven maintained at a high temperature of 80 ° C. for 24 hours. Before and after the high temperature durability test, the backlight device 30 was operated with the liquid crystal display panel 20 displayed in black, and the amount of light leakage from the test piece was examined by visual observation and luminance measurement. 4A is a visual image showing the result of the light leakage test before and after the high temperature durability test of the test piece according to Example 21. FIG.

The luminance (light leakage amount) in the black display state is measured first by the luminance, illuminance, and chromaticity measurement system ProMetric1400 (trade name; manufactured by Radiant Imaging). The average luminance with respect to the entire surface of the test piece was determined. Since the brightness at all positions of the test piece could not be calculated due to the amount of data, the average brightness of several adjacent pixels was obtained as preprocessing, and these several pixels had the same brightness as the average brightness. Considered 1 pixel. As a result of calculating the luminance shown in FIG. 4A, in Example 21, the luminance in black display before the high temperature durability test was 0.32 (standard deviation 0.10) Cd / m ^2. The luminance in black display after the high temperature durability test was 0.32 (standard deviation 0.10) Cd / m ² , and there was no deterioration of the light leakage amount.

Example 22
The pressure-sensitive adhesive D was used as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 7. Except this, it carried out similarly to Example 21, and produced the test piece, and measured the brightness | luminance (light leakage amount) in the black display before and behind a high temperature durability test.

Example 23
The pressure-sensitive adhesive E was used as a pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 7. Except this, it carried out similarly to Example 21, and produced the test piece, and measured the brightness | luminance (light leakage amount) in the black display before and behind a high temperature durability test.

Example 24
The thickness of the polarizing plate was 70 μm. Except this, it carried out similarly to Example 21, and produced the test piece, and measured the brightness | luminance (light leakage amount) in the black display before and behind a high temperature durability test.

Example 25
The thickness of the polarizing plate was 70 μm, and the adhesive b was used as an adhesive for forming the adhesive layer 5. Except this, it carried out similarly to Example 21, and produced the test piece, and measured the brightness | luminance (light leakage amount) in the black display before and behind a high temperature durability test.

Example 26
The thickness of the polarizing plate was 70 μm, and the adhesive c was used as an adhesive for forming the adhesive layer 5. Except this, it carried out similarly to Example 21, and produced the test piece, and measured the brightness | luminance (light leakage amount) in the black display before and behind a high temperature durability test.

Comparative Example 21
The liquid crystal television BRAVIA32 (trade name; manufactured by Sony Corporation) was taken out in a state where the transmissive color liquid crystal display panel can be driven. This liquid crystal display panel was subjected to a high temperature durability test that was maintained in an oven at a high temperature of 80 ° C. for 24 hours. Before and after the high-temperature durability test, the backlight device 30 was operated with the liquid crystal display panel in black display, and the luminance (light leakage amount) in black display was examined by visual observation and luminance measurement. FIG. 4B is a visual image showing the result of the light leakage test before and after the high temperature durability test of the liquid crystal display panel according to Comparative Example 21. As a result of calculating the luminance shown in FIG. 4B, in Comparative Example 21, the luminance in black display before the high temperature durability test is 0.28 (standard deviation 0.04) Cd / m ^2. The luminance in black display after the high-temperature durability test was 0.28 (standard deviation 0.07) Cd / m ² , and there was no deterioration in the amount of light leakage.

  Table 4 summarizes the thicknesses of the polarizing plates in Examples 21 to 26 and Comparative Example 21, the adhesives and pressure-sensitive adhesives used, and the luminance (light leakage amount) and the difference in black display before and after the high temperature durability test. It is a table. In the table, the numerical value in parentheses in the luminance column in the black display before or after the high temperature durability test is a standard deviation. In any of the examples, no adhesion deterioration or abnormality was observed immediately after bonding.

  From the above results, in the high temperature durability test of the liquid crystal display panel 20 provided with the retardation film / polarizing plate laminate 10, good results were obtained in the above-described examples as the adhesive constituting the adhesive layer 5. When the adhesives B, D, and E obtained with good results in the above-described examples are used as the adhesive constituting the adhesive layer 7 using the adhesives a to c, the retardation film / polarizing plate laminate 10 It was shown that there was almost no deterioration of the light leakage of the liquid crystal display panel 20 provided with. Therefore, the adhesive d obtained with good results in the above-mentioned example is used as the adhesive constituting the adhesive layer 5, and the good results are obtained with the above-mentioned example as the adhesive constituting the pressure-sensitive adhesive layer 7. Even when the pressure-sensitive adhesives A and C are used, it is considered that there is almost no deterioration of light leakage of the liquid crystal display panel 20 provided with the retardation film / polarizing plate laminate 10 with almost no deterioration of light leakage. The high temperature durability of the retardation film / polarizing plate laminate 10 is such that a polarizing film made of polyvinyl alcohol (PVA) is attached to a polarizing plate sandwiched from both sides by a base film made of triacetyl cellulose (TAC). It was shown that there is no difference even when compared with the high temperature durability of the current liquid crystal display panel in which no retardation film such as Pure Ace (PA) is attached.

  Although the present invention has been described based on the embodiments and examples, it is needless to say that the present invention is not limited to these examples and can be appropriately changed without departing from the gist of the invention. .

  According to the retardation film / polarizing plate laminate of the present invention and the liquid crystal display device including the same, the durability against high temperatures, the price reduction, and the image quality improvement of the liquid crystal display device used as a large-sized liquid crystal television or the like are provided. Can contribute.

It is sectional drawing which shows the structure of the phase difference film and polarizing plate laminated body based on Embodiment 1 of this invention. It is principal part sectional drawing which shows the structure of the liquid crystal display device based on Embodiment 2 of this invention. It is a microscope observation image which shows the result of the high temperature durability test by the Example of this invention. FIG. It is an image which shows the result of the light leakage test before and behind a high temperature durability test by an Example and a prior art example. It is sectional drawing which shows the example of the laminated structure of the conventional phase difference film and a polarizing film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base film which consists of triacetylcellulose (TAC), 2 ... Adhesive layer,
3, 3a, 3b ... polarizing film, 4, 4a, 4b ... polarizing plate, 5 ... adhesive layer,
6, 6a, 6b ... retardation film comprising a bisphenol-based polycarbonate resin having a fluorene skeleton,
7 ... Adhesive layer, 10, 10a, 10b ... Retardation film / polarizing plate laminate,
11 ... Liquid crystal layer, 12, 12a, 12b ... Transparent substrate, 13 ... Liquid crystal cell,
20 ... Liquid crystal display panel, 30 ... Backlight device, 31 ... Backlight light source,
31a ... linear light source, 31b ... reflector, 32 ... diffuser plate, 33 ... diffuser sheet,
34 ... Prism sheet, 35 ... Polarization separation element, 50 ... Transmission type liquid crystal display device,
100 ... Laminated structure of conventional polarizing plate and retardation film, 101 ... Base film,
102 ... Adhesive layer, 103 ... Polarizing film, 104 ... Adhesive layer,
105 ... base film, 106 ... polarizing plate, 107 ... adhesive or pressure-sensitive adhesive layer,
108 ... retardation film, 109 ... adhesive layer

Claims (6)

A polarizing film in which a polarizing film is bonded to a base film on one side of the polarizing film;
An adhesive layer disposed on a surface of the polarizing film opposite to a surface bonded to the base film;
Retardation film,
A pressure-sensitive adhesive layer made of a pressure-sensitive adhesive whose loss tangent tan δ of dynamic viscoelasticity at 80 ° C. and 1 Hz is 0.148 or less is laminated in this order with each layer in direct contact with each other,
A retardation film / polarizing plate laminate, which is attached to a substrate constituting a liquid crystal cell by the pressure-sensitive adhesive layer. A polarizing film in which a polarizing film is bonded to a base film on one side of the polarizing film;
An adhesive layer disposed on a surface of the polarizing film opposite to a surface bonded to the base film;
Retardation film,
A pressure-sensitive adhesive layer made of a pressure-sensitive adhesive having a gel fraction of 84.3% or more is laminated in this order in a state where the respective layers are in direct contact with each other,
A retardation film / polarizing plate laminate, which is attached to a substrate constituting a liquid crystal cell by the pressure-sensitive adhesive layer.   The glass transition point of the adhesive constituting the adhesive layer is 80 ° C or higher, and the loss tangent tan δ of dynamic viscoelasticity at 80 ° C and 1 Hz is 0.64 or lower. Retardation film / polarizing plate laminate.   The retardation film / polarizing plate laminate according to claim 1, wherein the retardation film comprises a bisphenol-based polycarbonate resin having a fluorene skeleton.   The retardation film / polarizing plate laminate according to claim 1, wherein the base film is made of triacetylcellulose.   6. A liquid crystal display device, wherein the retardation film / polarizing plate laminate according to claim 1 is attached to one or both of substrates constituting a liquid crystal cell by the pressure-sensitive adhesive layer. .