TWI591388B - Polypropylene resin film, and polarizing sheet, liquid crystal panel and liquid crystal display device using same - Google Patents

Description

Polypropylene resin film, polarizing plate using the same, liquid crystal panel and liquid crystal display device

The present invention relates to a polypropylene resin film, a polarizing plate using the resin film, a liquid crystal panel, and a liquid crystal display device, and more particularly to a polypropylene resin film bonded to another film via an adhesive and using the same A polarizing plate of a resin film, a liquid crystal panel, and a liquid crystal display device.

The liquid crystal display device consumes a small amount of power, operates at a low voltage, and exhibits characteristics such as light weight and thinness, and is used for various display elements. In particular, the market for LCD TVs has expanded significantly, and the requirements for cost reduction have also been significant.

In general, the polarizing plate has a structure in which a transparent protective film is laminated on both sides or a single surface of a polarizing film made of a polyvinyl alcohol-based resin which adsorbs a dichroic dye. A cellulose acetate-based resin film represented by cellulose triacetate is often used as the protective film. Further, as the laminate of the protective film, an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is often used.

A protective film made of cellulose triacetate is laminated on a double-sided or single-sided polarizing plate of a polarizing film via an adhesive, and when polarized under long-term use, the polarizing performance is lowered, and the protective film and the polarizing film are removed. Easy to peel off problems.

Therefore, attempts have been made to form at least one protective film of a resin other than cellulose acetate. For example, a technique in which at least one surface of a protective film is made of a polypropylene-based resin in a polarizing plate in which a protective film is laminated on both surfaces of a polarizing film is known (for example, see JP-A-2007-334295). Since the protective film made of a polypropylene resin has a small dimensional change and a small moisture permeability and is highly resistant to an organic solvent, it is excellent in moist heat resistance and dimensional stability. Therefore, by using a protective film made of a polypropylene-based resin, it is advantageous in that the adhesion between the polarizing film and the protective film is not easily lowered.

At this time, as one of the indexes showing the characteristics of the resin film, there is a degree of surface orientation (also referred to as "surface orientation parameter"). For example, a technique of using a biaxially stretched polyester film having a surface orientation parameter of 1 to 3 in an image-receiving paper or the like used in a printing device such as a thermal transfer method is known (refer to Japanese Patent Laid-Open No. 2005-350615) Bulletin). According to this technique, by setting the surface orientation parameter to the range, defects such as textures or pinholes of the dye absorbing layer are less likely to occur when the image receiving layer is formed, and the yield can be prevented from being lowered.

As described above, it is known that a polypropylene resin is used as a protective film, and the adhesion between the protective film and the polarizing film is good. However, until now, no one has studied to improve the adhesion between the protective film made of a polypropylene resin and the polarizing film. In particular, the relationship between the surface orientation parameter and the adhesion property of the polypropylene resin film has not been known so far.

An object of the present invention is to provide a polypropylene resin film having good adhesion.

Further, another object of the present invention is to provide a polarizing plate which is excellent in adhesion between a polypropylene resin film and a polarizing film and which is not easily peeled off, and a liquid crystal panel and a liquid crystal display device using the polarizing plate.

In order to solve the above problems, the inventors of the present invention have repeatedly studied and found that the surface orientation parameter of the polypropylene resin film can be adjusted to a certain range, thereby improving the adhesion of the polypropylene resin film, thereby completing the present invention. invention.

In detail, according to the present invention, the above problems are solved by the following polypropylene-based resin film having a surface orientation parameter measured by Raman spectroscopy using an attenuated total reflection method in the range of 0.66 to 1.50. A polypropylene resin film on the surface.

The surface orientation parameter is preferably in the range of 0.95 to 1.05.

Moreover, according to the present invention, the above problem is solved by a polarizing plate comprising a polarizing film comprising a uniaxially stretched polyvinyl alcohol resin film which adsorbs oriented iodine or a dichroic dye, A polarizing plate of the polypropylene-based resin film described above is laminated on the polarizing film via an adhesive layer, and the surface of the polypropylene-based resin film is bonded to the adhesive layer and laminated.

Further, the polarizing plate is preferably provided with a protective film or an optical compensation film laminated on the surface opposite to the surface on which the polypropylene resin film of the polarizing film is laminated.

Furthermore, according to the present invention, the above problems are solved by a liquid crystal panel including a liquid crystal cell and the above-described polarizing plate laminated on the liquid crystal cell.

Moreover, according to the present invention, the above problems are solved by a liquid crystal display device including a surface light source element and the liquid crystal panel described above.

According to the polypropylene resin film of the present invention, since the surface orientation parameter is in the range of 0.66 to 1.50, when it is laminated on another resin film via an adhesive, the adhesion to the other resin film is good. Further, since the polarizing plate of the present invention has the polypropylene-based resin film having excellent adhesion as described above, it is possible to provide a polarizing plate which is less likely to be peeled off from the polarizing film. Further, according to the liquid crystal panel or the liquid crystal display device of the present invention, since the polarizing plate which is less likely to be peeled off is provided, a liquid crystal panel or a liquid crystal display device having high durability can be provided.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Furthermore, the present invention is not limited to the members, arrangements, and the like described below, and such members and the like may be appropriately changed in accordance with the gist of the present invention. Hereinafter, a polarizing plate, a liquid crystal panel including the polarizing plate, and a liquid crystal display device will be described.

<Polarizing plate>

Fig. 2 (a) is a schematic view showing a polarizing plate according to an embodiment of the present invention, and shows a schematic cross-sectional view of the polarizing plate. As shown in the figure, the polarizing plate 20 includes at least a polarizing film 21 and a polypropylene resin film 25 laminated on one surface of the polarizing film 21. The polarizing film 21 and the polypropylene resin film 25 are bonded and laminated via the adhesive layer 29.

In the present embodiment, the transparent resin film 23 is laminated on the surface of the one side of the polarizing film 21 opposite to the side on which the polypropylene resin film 25 is laminated. However, in the present invention, the transparent resin film 23 is not an essential component.

<LCD panel and liquid crystal display device>

3 is a schematic cross-sectional view showing an example of a basic layer configuration of a liquid crystal panel 2 of the present invention and a liquid crystal display device 1 to which the liquid crystal panel is applied. As shown in the figure, the polarizing plate 20 is bonded to the liquid crystal cell 40 and used as a component of the liquid crystal panel 2. The liquid crystal panel 2 is a constituent member of the liquid crystal display device 1. The liquid crystal panel 2 is composed of a liquid crystal cell 40, a polarizing plate 20 bonded to the back side of the liquid crystal cell 40, and a polarizing plate 30 bonded to the visible side of the liquid crystal cell 40. The liquid crystal display device 1 is composed of a liquid crystal panel 2, a backlight 10, and a light diffusing plate 50. In the liquid crystal display device 1, the liquid crystal panel 2 is disposed such that the polarizing plate 20 is on the side of the backlight 10, that is, the polypropylene resin film 25 is opposed to the light diffusing plate 50. The polarizing plate 20 and the polarizing plate 30 are bonded to the liquid crystal cell 40 via the adhesive layer 27, respectively. The back side here refers to the side of the backlight 10 when the liquid crystal panel 2 is mounted on the liquid crystal display device 1. In addition, the visible side means the side opposite to the backlight 10 when the liquid crystal panel 2 is mounted on the liquid crystal display device 1.

The light diffusing plate 50 is a member having a function of diffusing light from the backlight 10. As the light-diffusing sheet 50, for example, a thermoplastic resin may be dispersed in the surface of the thermoplastic resin film to impart light diffusibility to the surface of the thermoplastic resin film, and the light-diffusing property may be imparted to the light-diffusing resin. The coating layer of the resin composition in which the particles are dispersed is provided on the surface of the film to impart light diffusibility or the like. The thickness of the light diffusing plate 50 can be set to about 0.1 to 5 mm.

Between the light-diffusing sheet 50 and the liquid crystal panel 2, a sheet or film exhibiting other optical functions can be disposed: a brightness-enhancing sheet (a reflective polarizing film "DBEF series" sold by 3M Company, etc.), a light-diffusing sheet, and the like. A sheet or film exhibiting other optical functions may be arranged in two or more and plural types as needed. Each film constituting the polarizing plate 20 on the back side will be described below.

[a] polarizing film

The polarizing film 21 is a member having a function of converting natural light into linear polarized light. As the polarizing film 21, it is possible to use a polyvinyl alcohol-based resin film which is uniaxially stretched to adsorb the dichroic dye. As the polyvinyl alcohol-based resin, those obtained by saponifying a polyvinyl acetate-based resin can be used; and a polyvinyl acetate-based resin, except for polyvinyl acetate which is a homopolymer of vinyl acetate, is a list of vinyl acetate and A polymer or the like of another monomer copolymerizable therewith. Other monomers which can be copolymerized with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, and more preferably 98 mol% or more. The polyvinyl alcohol-based resin can be denatured. For example, polyvinyl formal or polyvinyl acetal which is denatured with an aldehyde can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, and preferably about 1,500 to 5,000.

The film formed of the polyvinyl alcohol-based resin as described above is used as a raw material film of the polarizing film 21. The method of forming a film of a polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a known method. The thickness of the polyvinyl alcohol-based raw material film is not particularly limited, and is, for example, about 10 to 150 μm.

The polarizing film 21 is usually produced by a step of uniaxially stretching the polyvinyl alcohol-based resin film as described above, and by dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye. The step of treating the polyvinyl alcohol-based resin film that adsorbs the dichroic dye with a boric acid aqueous solution, and the step of washing with a boric acid aqueous solution, followed by washing with water.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be carried out before dyeing with a dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxially extending after dyeing, the uniaxial stretching can be carried out before the boric acid treatment or in the boric acid treatment. Of course, uniaxial stretching can also be performed at the complex stage referred to herein. For the uniaxial stretching, a method of uniaxially extending between rolls having different peripheral speeds, a method of using a hot roll for uniaxial stretching, or the like can be employed. In addition, the uniaxial stretching may be a dry stretching in which the film is stretched in the air, or may be a wet stretching in which the polyvinyl alcohol resin film is swollen with a solvent such as water. The stretching ratio is usually about 3 to 8 times.

The extending direction of the polyvinyl alcohol-based resin film is set to be parallel to the direction of the longitudinal direction of the elongated polarizing film 21. Therefore, the absorption axis of the polarizing film 21 is a direction in which the polyvinyl alcohol-based resin film extends, that is, a direction parallel to the longitudinal direction of the elongated polarizing film 21.

The dyeing of the polyvinyl alcohol-based resin film by the dichroic dye can be carried out, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. The dichroic dye, specifically, iodine or a dichroic dye is used. Further, the polyvinyl alcohol-based resin film is preferably subjected to a treatment of immersing in water and swelling it before the dyeing treatment.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine or potassium iodide and dyed is usually used. The content of iodine in the aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water; and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 °C. Further, the immersion time (dyeing time) of the aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic dye is used as a dichroic dye, the method of dyeing by impregnating a polyvinyl alcohol-type resin film in the aqueous solution containing the water-soluble dichroic dye is used. The content of the dichroic dye in the aqueous solution is usually about 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water, and preferably about 1 × 10 ^-3 to 1 part by weight. The aqueous solution may also contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the aqueous solution of the dichroic dye used for dyeing is usually about 20 to 80 °C. Further, the immersion time (dyeing time) of the aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with the dichroic dye can be carried out by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The content of boric acid in the boric acid-containing aqueous solution is usually from 2 to 15 parts by weight, preferably from 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually from 0.1 to 15 parts by weight, preferably from about 5 to 12 parts by weight, per 100 parts by weight of water. The immersion time of the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, and preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ° C or higher, preferably 50 to 85 ° C, and more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water to be washed is usually about 5 to 40 ° C; and the immersion time is usually about 1 to 120 seconds.

After washing with water, drying treatment was carried out to obtain a polarizing film 21. The drying treatment can be carried out using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ° C, and preferably about 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, and the preferred state is 120 to 600 seconds.

As described above, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment to obtain a polarizing film 21. The thickness of the polarizing film 21 can be, for example, about 2 to 40 μm.

[b]Polypropylene resin film

The polypropylene resin film 25 is mainly composed of a polypropylene resin and has a function of protecting the polarizing film 21.

In the polypropylene resin film 25 of the present invention, at least one of the surface of the film (the two main faces of the film) is characterized in that the surface (bonding surface) on which the polarizing film 21 is laminated via the adhesive layer 29 is The surface orientation parameter measured by the Raman spectrometry using the Attenuated Total Reflection method (hereinafter referred to as "ATR method") is in the range of 0.66 to 1.50. The polypropylene resin film 25 having the bonding surface as described above has a good bonding property when the bonding surface faces the adhesive layer 29 and is laminated on the polarizing film 21 via the adhesive layer 29. . Therefore, by using the polypropylene resin film 25 as a protective film of the polarizing plate 20, a polarizing plate having high adhesion strength to the polarizing film 21 and high durability can be obtained. The surface orientation parameter of the surface of the polypropylene resin film 25 is more preferably in the range of 0.95 to 1.05, and most preferably 1.00. The closer the surface orientation parameter is to 1.00, the molecular orientation of the surface of the polypropylene-based resin film 25 becomes random (non-oriented), and the adhesion to the polarizing film 21 is good. Hereinafter, the Raman spectrometry using the ATR method is referred to as "ATR-Raman spectrometry".

Surface orientation parameters can be determined using a Raman spectrophotometer. In the measurement of the surface orientation parameter, first, the Raman spectrum of the surface of the polypropylene resin film 25 was measured by the ATR method. Here, the ATR method is a method in which the bonding surface of the polypropylene resin film 25 is set as a measurement surface, and the film is directly adhered to a crucible having a large refractive index such as a high refractive index glass. Specifically, between the bonding surface of the polypropylene resin film 25 and the crucible, the measurement light is totally reflected, and the incident angle of the measurement light is set to be larger than the critical angle. Then, the measurement light was irradiated on the bonding surface, and the total reflection light reflected from the surface of the bonding surface was measured. At this time, the total reflected light is light that is slightly reflected into the interior of the surface of the polypropylene resin film 25 and reflected. Therefore, according to the ATR-Raman spectroscopy, an absorption spectrum of a layer from the surface of the polypropylene-based resin film 25 to a depth of about 100 nm can be obtained.

The surface orientation parameter herein refers to an orientation parameter of a shallow region of the depth near the surface of the polypropylene-based resin film 25. The measurement of the orientation parameter is performed by measuring the absorption spectrum of the ATR-Raman spectroscopy as described above by irradiating "parallel polarization" parallel to the plane containing the incident light and the reflected light and measuring the incident light. The plane of light and reflected light is carried out by a vertical "vertical polarization" method. Fig. 1 is a view showing the parallel polarized light and the vertical polarized light, and P indicates parallel polarized light, and S indicates vertical polarized light. The orientation parameter of the polypropylene resin film 25, with respect to the parallel polarized light and the vertical polarized light, each of which can be used as the peak intensity of the bands unique to the crystals of polypropylene of 1153 cm ^-1 and 1169 cm ^-1 by the following formula Calculate:

(In this case, I ₁₁₅₃ means the peak intensity of ₁₁₅₃ cm ^-1 ; I ₁₁₆₉ means the peak intensity of ₁₁₆₉ cm ^-1 . Further, "parallel" means the measured value using parallel polarized light; "vertical" means the measurement using vertical polarized light. value.)

Further, 1153 cm ^-1 is a basic vibration of polypropylene, and represents vertical vibration with respect to a molecular chain; 1169 cm ^-1 is vibration derived from crystals of polypropylene, and represents parallel vibration with respect to a molecular chain.

When the surface of the polypropylene resin film 25 was non-oriented, the surface orientation parameter was 1.00. Further, when the polypropylene resin film 25 is oriented in the longitudinal direction (mechanical direction: MD), the surface orientation parameter exhibits a value larger than 1.00.

Conversely, when the polypropylene-based resin film 25 is oriented in the short-side direction (vertical direction: TD), the surface orientation parameter exhibits a value smaller than 1.00.

The surface orientation parameter is in the foregoing range, especially near 1.00, and the closer the molecular orientation of the surface is to the non-oriented direction, the reason why the adhesion is better is not clear, but the mechanical surface of the membrane surface of the interface between the polypropylene resin film 25 and the adhesive layer is not clear. Strength has the potential to affect adhesion. In detail, the surface of the polypropylene-based resin film 25 is extended in a certain direction, and when the molecules are oriented, the extension strength to the direction is increased, and on the other hand, the extension strength in the direction different from the direction is lowered. Therefore, according to the direction in which the polypropylene-based resin film 25 is extended, cohesive failure occurs on the surface of the film to cause the film surface to be easily peeled off. On the other hand, the surface of the polypropylene resin film 25 is not stretched, and when the molecules are not oriented, the elongation in which direction is high is high, and cohesive failure is unlikely to occur on the surface of the polypropylene resin film 25, and the adhesion is poor. good

Further, the evaluation parameters obtained by the results of the ATR-Raman spectroscopy and the items evaluable according to the same can be exemplified by the following plural items:

(1) Evaluation item: directionality....... Evaluation parameter: peak intensity

(2) Evaluation item: orderability....... Evaluation parameter: half width of the peak

(3) Evaluation item: configuration....... Evaluation parameter: wave number position

(4) Evaluation item: degree of crystallization....... Evaluation parameter: peak intensity ratio

Among these, the orientation of (1) is the aforementioned item relating to adhesion, and the order of (2) and the configuration of (3) can also be determined. On the other hand, the degree of crystallization of (4) cannot be measured in the range of 808 to 840 cm ^-1 due to limitations in the apparatus, and thus it is impossible to evaluate. The present invention focuses on the directivity of (1) in the above (1) to (4), and has the feature that the adhesion is good as long as the surface orientation parameter is within a predetermined range.

In the present invention, since the protective film laminated on the polarizing film 21 is a polypropylene-based resin film, the following advantages are obtained. In the polypropylene resin, since the photoelastic coefficient is as low as about 2 × 10 ^-13 cm ² /dyne and the moisture permeability is low, the polarizing plate 20 having the polypropylene resin film 25 is applied to the liquid crystal cell 40. It can be used as a liquid crystal display device 1 which is excellent in durability under moist heat conditions. Further, the adhesion of the polypropylene resin film 25 to the polarizing film 21 is good even if it does not reach the cellulose triacetate film, and when various known adhesives are used, the polypropylene system can be used. The resin film 25 is adhered to the polarizing film 21 with sufficient strength.

The polypropylene-based resin may be a homopolymer of propylene, or may be a copolymer of propylene as a main component and a small amount of a copolymerizable copolymerizable monomer. The polypropylene-based resin composed of a copolymer may be, for example, a resin containing a comonomer unit in a range of 20% by weight or less, and more preferably 10% by weight or less, and more preferably 7% by weight or less. . Further, the content of the comonomer unit of the copolymer is preferably 1% by weight or more, and more preferably 3% by weight or more. By setting the content of the comonomer unit to 1% by weight or more, workability or transparency can be remarkably improved. On the other hand, when the content of the comonomer unit exceeds 20% by weight, the melting point of the polypropylene-based resin is lowered, and the heat resistance tends to be lowered. Further, in the case of a copolymer of two or more kinds of comonomers and propylene, the total content of the units derived from all the comonomers contained in the copolymer is preferably in the above range.

The co-monomer copolymerized with propylene may be, for example, ethylene or an α-olefin having 4 to 20 carbon atoms. Specific examples of the α-olefin include 1-butene and 2-methyl-1-propene (above C ₄ ); 1-pentene and 2-methyl-1-butene; 3-methyl-1-butene (above C ₅ ); 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1- Pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene (above C ₆ ); 1-heptene, 2-methyl 1-hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene (above C ₇ ); -octene, 5-methyl-1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentyl Alkene, 2,3,4-trimethyl-1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene (above C ₈ ); 1-decene ( C ₉ ); 1-decene (C ₁₀ ); 1-undecene (C ₁₁ ); 1-dodecene (C ₁₂ ); 1-tridecene (C ₁₃ ); 1-tetradecene (C) ₁₄ ); 1-pentadecene (C ₁₅ ); 1-hexadecene (C ₁₆ ); 1-heptadecen (C ₁₇ ); 1-octadecene (C ₁₈ ); 1-nonenylene (C) ₁₉ ) Wait.

Among the α-olefins, an α-olefin having 4 to 12 carbon atoms is preferable, and specific examples thereof include 1-butene and 2-methyl-1-propene; 1-pentene and 2-methyl group; 1-butene, 3-methyl-1-butene; 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl- 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene; 1-heptene, 2-methyl-1- Hexene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene; 1-octene, 5-methyl 1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3,4- Trimethyl-1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene; 1-decene; 1-decene; 1-undecene; Decadiene and the like. From the viewpoint of copolymerizability, 1-butene, 1-pentene, 1-hexene and 1-octene are preferred, and 1-butene and 1-hexene are more preferred.

The copolymer may be a random copolymer or a block copolymer. Preferred examples of the copolymer include a propylene/ethylene copolymer and a propylene/1-butene copolymer. In the propylene/ethylene copolymer and the propylene/1-butene copolymer, the content of the ethylene unit or the content of the 1-butene unit is, for example, described in the "Handbook of Polymer Analysis" (published by Kiyokiya Bookstore in 1995). The method on page 616 is obtained by infrared (IR) spectrometry.

From the viewpoint of improving the transparency or processability of the polypropylene-based resin film 25 bonded to the polarizing film 21, the copolymer is preferably a propylene-based propylene and ethylene or a random copolymer of the α-olefin, and propylene. A random copolymer with ethylene is more desirable. The content of the ethylene unit in the propylene/ethylene random copolymer is preferably from 1 to 20% by weight, more preferably from 1 to 10% by weight, and most preferably from 3 to 7% by weight, as described above.

The stereoregularity of the polypropylene resin may be any of isotactic, syndiotactic, and atactic. In the present invention, it is preferred to use a polypropylene resin which is in the same row or in the same row from the viewpoint of heat resistance.

The polypropylene resin, in accordance with JIS K 7210, has a melt flow rate (MFR) measured at a temperature of 230 ° C and a load of 21.18 N, preferably in the range of 0.1 to 200 g/10 minutes, and more preferably. The state is in the range of 0.5 to 50 g/10 minutes. By using a polypropylene-based resin having an MFR within this range, the load of the extruder is not greatly increased, and a uniform polypropylene-based resin film 25 can be obtained.

The polypropylene resin can be produced by a method of separately polymerizing propylene or a method of copolymerizing propylene with another copolymerizable comonomer by using a known catalyst for polymerization. The well-known catalyst for polymerization is as follows.

(1) a Ti-Mg-based catalyst composed of a solid catalyst component containing magnesium, titanium, and a halogen as essential components,

(2) a combination of an organoaluminum compound and a catalyst component of a third component such as an electron-donating compound, in a solid catalyst component containing magnesium, titanium, and a halogen as essential components,

(3) A metallocene catalyst or the like.

In the production of a polypropylene-based resin, in the above catalyst systems, the catalyst system of the above (2) is generally applicable. Preferred examples of the organoaluminum compound of the catalyst system of (2) include triethylaluminum, triisobutylaluminum, a mixture of triethylaluminum and diethylaluminum chloride, and tetraethylaluminum. Preferred examples of the electron-donating compound such as tetraethyl alumoxane and the like include cyclohexylethyldimethoxydecane, tert-butylpropyldimethoxydecane, and tert-butylethyldimethoxy. Decane, dicyclopentyldimethoxydecane, and the like.

The catalysts of the above-mentioned (1) and (2) are exemplified by the catalyst system described in JP-A-61-218606, JP-A-61-287904, and JP-A-7-216017. In addition, the catalyst system of the above-mentioned (3) organic metallocene-based catalyst is exemplified by Japanese Patent No. 2,587, 251, Japanese Patent No. 2,627,669, and Japanese Patent No. 2,667,732.

The polypropylene resin can be produced by, for example, a hydrocarbon compound such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene or xylene. A solution polymerization method representing an inert solvent, a bulk polymerization method using a liquid monomer as a solvent, and a gas phase polymerization method in which a monomer of a gas is directly polymerized. The polymerization by these methods can be carried out batchwise or continuously.

A well-known additive may be blended in the polypropylene resin. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, an anti-caking agent, and the like. Examples of the antioxidant include a phenolic antioxidant, a phosphorus-based antioxidant, a sulfur-based antioxidant, and a hindered amine-based light stabilizer. Further, for example, an antioxidant mechanism having both a phenolic system and a molecule can be used. A composite antioxidant of a unit of a phosphorus-based antioxidant mechanism. Examples of the ultraviolet absorber include a UV absorber such as a 2-hydroxybenzophenone type or a hydroxyphenylbenzotriazole type, and a benzoate type ultraviolet blocking agent. The antistatic agent may be any of a polymer type, an oligomer type, and a monomer type. Examples of the lubricant include higher fatty acid amines such as erucic acid amines and oleic acid amines, higher fatty acids such as stearic acid, and salts thereof. Examples of the nucleating agent include a sorbitol-based nucleating agent, an organic phosphate-based nucleating agent, and a polymer-based nucleating agent such as polyethylene cycloalkane. An anti-caking agent, a spherical or nearly fine particle, can be used regardless of inorganic or organic. The additive may be used in combination of plural kinds.

The polypropylene resin can be formed into a polypropylene resin film 25 by any method. The polypropylene resin film 25 is preferably transparent and has substantially no in-plane retardation. For example, a polypropylene which is substantially free of in-plane retardation can be obtained by a method of extrusion molding of a molten resin, casting a resin dissolved in an organic solvent on a flat plate, and removing a solvent to form a film by a solvent casting method or the like. The resin film 25 is used.

The thickness of the polypropylene resin film 25 is usually 20 to 200 μm, and preferably 20 to 120 μm. When the thickness of the polypropylene resin film 25 is less than 20 μm, the handleability tends to be poor, and in the case where the thickness exceeds 200 μm, the handleability is also lowered due to the increase in the rigidity of the film.

The polypropylene resin film 25 is required to have excellent transparency. Specifically, the haze value measured in accordance with JIS K 7361 is 10% or less, and preferably about 7% or less. When the haze value exceeds 10%, when the obtained polarizing plate 20 is applied to the liquid crystal display device 1, the white luminosity is lowered and the screen tends to be dark. Further, the haze value measured in accordance with JIS K 7361 is defined by the following formula:

(diffusion transmittance / total light transmittance) × 100 (%)

The polypropylene resin film 25 may be formed into a tantalum or lens shape by forming a surface on the surface opposite to the polarizing film 21, and serves as a light collecting film. FIG. 2(b) shows a polarizing plate 60 including a light collecting film 65. The light-collecting film 65 has a function of concentrating the light emitted from the backlight 10 to the liquid crystal cell 40, and also functions to protect the protective function of the polarizing film 21. The light-collecting film 65 changes the angle of the light obliquely emitted from the backlight 10 to the liquid crystal cell 40 at an angle of a bevel shape or a slope of the lens shape. The light obliquely emitted from the backlight 10 is concentrated to the liquid crystal cell 40 by the foregoing.

A method of forming a crucible shape or a lens shape on the surface of the polypropylene resin film 25 may be a method of thermally transferring a crucible shape or a lens shape of a polypropylene resin, or an ultraviolet ray on a polypropylene resin film. A method of forming an active energy ray-curable resin into a shape of a crucible or a shape of a lens, or the like.

In addition, the surface of the surface of the polypropylene resin film 25 on the opposite side to the polarizing film 21 is based on the viewpoint of preventing scratches in the manufacturing steps of the liquid crystal display device 1 using the liquid crystal panel 2 or the polypropylene resin film 25, Hard coating treatment can also be applied. Further, it is also possible to apply an anti-glare treatment from the viewpoint of reducing the ripple of the interference between the cymbal and the color filter.

Further, a surface of the surface of the polypropylene-based resin film 25 opposite to the polarizing film 21 may be laminated with a protective film or an adhesive layer. Further, an optical film such as a reflective polarizing film as shown by the "DBEF series" sold by 3M, may be provided through the adhesive layer.

[c]Transparent resin film

The transparent resin film 23 is a film that is bonded to the surface of the polarizing film 21, and depending on the characteristics required for the liquid crystal panel 2 or the liquid crystal display device 1, a film having various properties can be used. As the transparent resin film 23, for example, a protective film for protecting the surface of the polarizing film 21 or an optical compensation film such as a retardation film for solving the problem of the viewing angle characteristics of the liquid crystal display device 1 can be used. As the protective film, for example, a non-oriented film having a haze value of 0.5% or less and an in-plane retardation value R _{0 of} less than 30 nm can be used. Further, the retardation film may be a biaxial retardation film having an in-plane retardation value R ₀ in the range of 30 to 200 nm and a thickness direction retardation R _th in the range of 30 to 350 nm. The in-plane phase difference value R ₀ and the thickness direction phase difference value R _th referred to herein are values in the wavelength 590 nm, which are the same below.

The transparent resin film 23 has a Gurley method according to JIS L 1096, and has a bending resistance of preferably 350 mgf or less, more preferably 200 mgf or less, and most preferably 150 mgf or less. As described above, the rigidity of the obtained polarizing plate 20 is reduced by using the transparent resin film 23 having low bending resistance, so that the handleability at the time of bonding to the liquid crystal cell 40 can be improved.

The resin material constituting the transparent resin film 23 is not particularly limited. Examples of the resin material include a (meth)acrylic resin such as a methyl methacrylate resin [(meth)acrylic resin refers to a methacrylic resin or an acrylic resin], an olefin resin, and a poly Vinyl chloride resin, cellulose resin, styrene resin, acrylonitrile ‧ butadiene ‧ styrene copolymer resin, acrylonitrile ‧ styrene copolymer resin, polyvinyl acetate resin, polydichloroethylene Ethylene resin, polyamine resin, polyacetal resin, polycarbonate resin, denatured polyphenylene ether resin, polyester resin (for example, polybutylene terephthalate resin, polyparaphenylene) Ethylene dicarboxylate resin, etc., polyfluorene-based resin, polyether oxime resin, polyarylate resin, polyamidoximine resin, polyimide resin, epoxy resin, epoxy Propane resin. These resins may contain additives in a range that does not inhibit transparency or adhesion to the polarizing film 21.

[c-1] Optical compensation film

The transparent resin film 23, as described above, may employ an optical compensation film. In the optical compensation film, the unstretched film which consists of the above-mentioned resin material is extended, and the retardation film which shows the phase difference as the transparent resin film 23, etc. are mentioned. Further, there is a method in which a material having an orientation energy such as a liquid crystal is applied to a substrate, and a phase difference is exhibited by orientation, and a retardation film is formed by immobilization (for example, Japanese Patent Laid-Open) A method of forming an optically anisotropic layer containing a rod-like liquid crystalline compound on a transparent support described in Example 3 of the Japanese Patent Publication No. 2004-233872. In particular, it is preferable to exhibit birefringence in the biaxial direction by successive biaxial stretching. In the stretching ratio at this time, in the longitudinal direction and the lateral direction, the direction in which the optical axis appears (the direction in which the stretching magnification is large, which is the direction of the slow axis) is about 1.1 to 10 times, and the direction orthogonal thereto is extended. The range in which the direction of the small magnification is the direction of the fast axis is about 1.1 to 7 times, and the phase difference value required may be appropriately selected. The optical axis can be visualized in the transverse direction of the film, or the optical axis can be visualized in the longitudinal direction of the film. "KC4FR-1" (Konica Minolta Opto Co., Ltd.), "KC4HR-1" (Konica Minolta Opto Co., Ltd.), etc. are mentioned as a commercial item of the cellulose acetate-type resin film which has this phase-difference characteristic. .

Next, the retardation value of the transparent resin film 23 will be described. The refractive index in the slow axis direction of the film is set to n _x , the in-plane fast axis direction (the direction orthogonal to the slow axis and the in-plane direction) is set to n _y , and the refractive index in the thickness direction is set to n _z When the thickness is set to d, the in-plane phase difference value R ₀ and the thickness direction phase difference value R _{th are} defined by the following formulas (I) and (II).

R ₀ =(n _x -n _y )×d (I)

R _th =[(n _x +n _y )/2-n _z ]×d (II)

In addition, the transparent resin film 23 may be a condition satisfying the following formula (III) with respect to its refractive index.

n _x >n _y >n _z (III)

As described above, the transparent resin film 23 as the retardation film may have an in-plane retardation value R ₀ in the range of 30 to 200 nm, and the thickness direction retardation value R _th may be in the range of 30 to 350 nm, and this range is taken as an example. It is appropriately selected in accordance with the characteristics required for application to the liquid crystal display device 1. The in-plane phase difference value R ₀ is preferably 100 nm or less, and the thickness direction phase difference R _th is preferably 80 nm or more and 200 nm or less.

The accuracy of the in-plane phase difference R ₀ is within ±7 nm of the center value, and the ideal phase is within ±5 nm of the center value. The accuracy of the thickness direction phase difference R _th is within ±15 nm of the center value. The center value is within ±10 nm. When the accuracy of the equivalent value exceeds the range, the visual characteristics applied to the liquid crystal display device 1 tend to decrease.

The slow axis angle in the film surface of the transparent resin film 23 is substantially 0 or 90. When the slow axis deviates from the angle, light leakage occurs when the polarizing plate 20 and the polarizing plate 30 are in a state of cross nicol, and when applied to the liquid crystal display device 1, visual characteristics such as frontal contrast are largely large. The tendency to decrease. Moreover, the accuracy of the slow axis is preferably within ±0.7° of the center value, and the more desirable state is within ±0.5° of the center value. Here, when the light leakage refers to the axial precision of the polarizing film 21 with respect to the transparent resin film 23 or the difference in the accuracy of the polarizing plate 20 with respect to the axis of the liquid crystal cell 40, the liquid crystal display device 1 self-displays the area when displaying black. The phenomenon of light leakage from the surface. As described above, the deviation of the slow axis of the transparent resin film 23 is reduced, and therefore, by reducing the angle of formation of either the slow axis and the absorption axis of the polarizing film 21, or by improving the adhesion to the front and back sides of the liquid crystal cell 40, The axial precision of the polarizing plate (the polarizing plate 20 and the polarizing plate 30) reduces the deviation of the absorption axis of the two polarizing plates from the constituent angle by 90°, thereby reducing light leakage.

When the transparent resin film 23 is adhered to the polarizing film 21, the axial relationship between the two may be selected in consideration of the viewing angle characteristics or color change characteristics of the intended liquid crystal display device 1. In the large-sized liquid crystal television application in which the front contrast is highly emphasized, the slow axis of the transparent resin film 23 and the absorption axis of the polarizing film 21 are often arranged in a slightly parallel or slightly orthogonal relationship. Here, "slightly parallel or slightly orthogonal", except for the case of being completely parallel or orthogonal, includes a case where it deviates according to a parallel or orthogonal relationship within a range of about ±10°. The deviation of the angle is preferably within ±5° of the ideal state, and the ideal state is within ±2°. The slow axis of the transparent resin film 23 and the absorption axis of the polarizing film 21 are preferably in a completely parallel or orthogonal relationship.

[c-2] Protective film

The transparent resin film 23, as described above, may employ a protective film. As the protective film described above, a non-oriented film having no substantial phase difference in the in-plane or thickness direction can be used. The non-oriented film refers to a resin film (unstretched film) in which a resin material is formed without stretching.

Since the non-oriented film does not have a phase difference, there is no function of expanding the viewing angle of the liquid crystal display device 1 as the biaxial retardation film, but since it is not necessary to perform the stretching treatment such as the biaxial retardation film, the manufacturing cost is low. low. Therefore, the manufacturing cost of the liquid crystal display device 1 can be reduced as compared with the case where the biaxial retardation film is used as the transparent resin film 23. Further, since the non-oriented film was not subjected to the stretching treatment, the film thickness was thick and the handleability was good.

As described above, the transparent resin film 23 as the protective film may be an unstretched film obtained by forming the resin material in an arbitrary manner. The unstretched film is preferably transparent and substantially free of in-plane retardation. The film forming method may be, for example, a extrusion molding method in which a molten resin is extruded into a film to form a film, a solvent casting method in which a resin is dissolved in an organic solvent and cast on a flat plate, and a solvent is removed to form a film.

Further, from the viewpoint of the thickness direction retardation value _Rth , since the thickness of the transparent resin film 23 is thinner, the phase difference value can be reduced, which is preferable. Specifically, the thickness of the transparent resin film 23 is preferably 15 to 45 μm. In consideration of the handleability of the polarizing plate 20, it is preferable that the thickness of the transparent resin film 23 is 35 to 45 μm in consideration of the handleability of the transparent resin film 23 itself.

[d] adhesive layer

The bonding and lamination of the polypropylene resin film 25 and the transparent resin film 23 of the polarizing film 21 are usually completed by the adhesive layer 29. The adhesive for forming the adhesive layer 29 on both sides of the polarizing film 21 may be the same type or different types.

As the adhesive, an adhesive containing an epoxy resin, an urethane resin, a cyanoacrylate resin, an acrylamide resin, or the like as a binder component can be used. One of the adhesives which are more suitable for use in the present invention is a solventless type of adhesive. A solventless adhesive that does not contain a significant amount of solvent, and contains a hardening compound that is hardened by irradiation with heat or active energy rays (for example, ultraviolet light, visible light, electron rays, X-rays, etc.) (monomer or An oligomer, etc., and an adhesive layer formed by curing the curable compound, typically comprising a curable compound and a polymerization initiator which are reactively hardened by irradiation with heat or active energy rays. . In particular, as described above, since the polypropylene resin film 25 has a low moisture permeability, when the following water-based adhesive is used, there is a difference in drainage, because the moisture of the adhesive causes damage of the polarizing film 21 or deterioration of polarizing performance. Case. Therefore, when the resin film having a low moisture permeability is adhered as described above, a solvent-free adhesive is preferable.

The active energy ray which is hardened by irradiation with an active energy ray is exemplified as an example of a preferred adhesive for forming the adhesive layer 29 from the viewpoint of rapid hardenability and productivity improvement of the polarizing plate 20 accompanying the same. Hardening adhesive. Examples of the active energy ray-curable adhesive described above include, for example, a photocurable adhesive which is cured by light energy such as ultraviolet light or visible light. The photocurable adhesive is preferably cationically polymerized, and is preferably a solventless epoxy adhesive having an epoxy compound as a curable compound, because of the reactivity with the polarizing film 21, The polypropylene resin film 25 and the transparent resin film 23 are more preferable because they have good adhesion.

The epoxy compound to be contained in the curable compound of the solventless epoxy-based adhesive is not particularly limited, and is preferably cured by cationic polymerization, and particularly from the viewpoints of weather resistance, refractive index, and the like. It is more preferable to use an epoxy compound which does not contain an aromatic ring in the molecule. As the epoxy compound which does not contain an aromatic ring in the molecule, the hydride of an aromatic epoxy compound, an alicyclic epoxy compound, an aliphatic epoxy compound, etc. are shown. Further, the epoxy compound as the curable compound usually has two or more epoxy groups in the molecule.

First, a hydrogenated product of an aromatic epoxy compound will be described. The hydrogenated product of the aromatic epoxy compound can be obtained by selectively hydrogenating an aromatic ring in the presence of a catalyst under pressure and under pressure. Examples of the aromatic epoxy compound include diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and bisphenol epoxy resin such as diglycidyl ether of bisphenol S; Phenolic epoxy resin such as phenolic epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenolic novolac epoxy resin; such as glycidyl ether of tetrahydroxyphenylmethane, glycidol of tetrahydroxybenzophenone A polyfunctional epoxy resin such as an ether or an epoxidized polyvinylphenol. Among them, a glycidyl ether of hydrogenated bisphenol A which is a hydride of an aromatic epoxy compound can be suitably used.

Next, an alicyclic epoxy compound will be described. The alicyclic epoxy compound is an epoxy compound having one or more epoxy groups bonded to the alicyclic ring, and the "epoxy group bonded to the alicyclic ring" is indicated by the following formula. The crosslinked oxygen atom of the structure -O-. In the formula, m is an integer of 2 to 5.

Therefore, a group in which one or a plurality of hydrogen atoms in the formula (CH ₂ ) _m is removed is bonded to a compound having another chemical structure, and can be an alicyclic epoxy compound. The alicyclic epoxy compound usually has a total of two or more epoxy groups in the molecule. One or a plurality of hydrogen atoms in (CH ₂ ) _m may be substituted by a linear alkyl group such as a methyl group or an ethyl group. Since the adhesive having good adhesion strength is obtained, the alicyclic epoxy compound as described above has an epoxycyclopentane ring (in the above formula, m=3) or epoxycyclohexane. An epoxy compound of the ring (in the above formula, m = 4) is preferably used. The structure of the alicyclic epoxy compound is specifically shown below, but is not limited to the compounds.

3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6 -methylcyclohexanecarboxylate, ethylene bis(3,4-epoxycyclohexanecarboxylate), bis(3,4-epoxycyclohexylmethyl)adipate, bis (3) , 4-epoxy-6-methylcyclohexylmethyl) adipate, diethylene glycol bis(3,4-epoxycyclohexyl methyl ether), ethylene glycol bis(3,4-ring Oxycyclohexyl methyl ether), 2,3,14,15-diepoxy-7,11,18,21-tetraoxaspiro-[5.2.2.5.2.2] hexadecane (this compound For: it can also be named as 3,4-epoxycyclohexane spiro-2',6'-dioxo snail-3",5"-dioxo snail-3'', 4'' '-epoxycyclohexane compound), 4-(3,4-epoxycyclohexyl)-2,6-dioxa-8,9-epoxyspiro[5.5]undecane, two Oxidation of 4-vinylcyclohexene, bis-2,3-epoxycyclopentyl ether, dicyclopentadiene dioxide, and the like.

Further, examples of the aliphatic epoxy compound include an aliphatic polyhydric alcohol or a polyglycidyl ether of an alkylene oxide adduct thereof. More specifically, diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, triglycidyl ether of glycerol, and triglycidyl of trimethylolpropane are mentioned. An ether, a diglycidyl ether of polyethylene glycol, a diglycidyl ether of propylene glycol, or one or more alkylene oxides added by an aliphatic polyol such as ethylene glycol or propylene glycol or glycerin ( Polyglycidyl ether of a polyether polyol obtained by ethylene oxide or propylene oxide.

The epoxy compound may be used alone or in combination of two or more.

The epoxy equivalent of the epoxy compound contained in the solventless epoxy-based adhesive is usually 30 to 3,000 g/eq, and more preferably 50 to 1,500 g/equivalent. When the epoxy equivalent is less than 30 g/equivalent, there is a possibility that the flexibility of the polarizing plate after curing is lowered and the adhesive strength is lowered. On the other hand, when the epoxy equivalent exceeds 3,000 g/eq, the compatibility with other components contained in the epoxy-based adhesive may be lowered.

The solventless epoxy-based adhesive preferably contains a cationic polymerization initiator in order to cationically polymerize the epoxy compound. The cationic polymerization initiator is a polymerization reaction of an epoxy group by irradiation of active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, or the like, or by heating to generate a cationic species or a Lewis acid. Start. In the present invention, it is preferable from the viewpoint of workability that any type of cationic polymerization initiator can be used to impart potential. In the following, a cationic polymerization initiator which initiates polymerization of an epoxy group by generating a cationic species or a Lewis acid by irradiation of active energy rays such as visible light, ultraviolet rays, X-rays, or electron beams. Also known as "photocationic polymerization initiator".

When a photo-cationic polymerization initiator is used, since the binder component at a normal temperature is hardened, the need to consider the heat resistance or expansion strain of the polarizing film 21 can be reduced, and the polypropylene-based resin film 25 or the transparent resin can be used. The film 23 is adhered to the polarizing film 21 with good adhesion. Further, when a photocationic polymerization initiator is used, since it acts as a catalyst by light, it is mixed with an epoxy-based adhesive, and storage stability and workability are also good.

The photocationic polymerization initiator is not particularly limited, and examples thereof include an anthracene salt such as an aromatic diazonium salt, an aromatic onium salt, and an aromatic onium salt, and an iron-propadiene complex. These photocationic polymerization initiators may be used singly or in combination of two or more. Among these, the aromatic cerium salt is particularly suitable for use because it has ultraviolet absorbing properties in a wavelength region of 300 nm or more, and is excellent in hardenability and has a good mechanical strength or a bonding strength.

Such a photo-cationic polymerization initiator can be easily obtained as a commercial product, and examples thereof include "KAYARAD PCI-220" and "KAYARAD PCI-620" (above, Nippon Kayaku Co., Ltd.). ), "UVI-6990" (manufactured by Union Carbide), "ADEKA OPTOMER SP-150", "ADEKA OPTOMER SP-170" (above, ADEKA), "CI-5102", "CIT-1370" , "CIT-1682", "CIP-1866S", "CIP-2048S", "CIP-2064S" (above, Japan Soda (share) system), "DPI-101", "DPI-102", "DPI- 103", "DPI-105", "MPI-103", "MPI-105", "BBI-101", "BBI-102", "BBI-103", "BBI-105", "TPS-101" , "TPS-102", "TPS-103", "TPS-105", "MDS-103", "MDS-105", "DTS-102", "DTS-103" (above, Midori Kagaku) System), "PI-2074" (made by Rhodia Corporation).

The blending amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, more preferably 1 part by weight or more, and more preferably 15 parts by weight or less based on 100 parts by weight of the epoxy compound. .

The solvent-free epoxy-based adhesive may contain a photocationic polymerization initiator, and may contain a photosensitizer as needed. By using a photosensitizer, the reactivity can be improved and the mechanical strength or bonding strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfide compound, a redox compound, an azo and a diazo compound, a halogen compound, and a photoreductive dye. When the photosensitizer is blended, the blending amount thereof is about 0.1 to 20 parts by weight based on 100 parts by weight of the epoxy compound.

Further, a thermal cationic polymerization initiator which initiates polymerization of an epoxy group by a cationic species or a Lewis acid by heating, and examples thereof include a benzyl sulfonium salt and a thiophenium salt. ), thiolanium salt, benzylammonium salt, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonate, amidoximine, and the like. These thermal cationic polymerization initiators are easily available as commercially available products. For example, "ADEKA OPTON CP77", "ADEKA OPTON CP66" (made by ADEKA), and "CI-2639" are exemplified by the trade names. , "CI-2624" (above Japanese Soda (share) system), "San-Aid SI-60L", "San-Aid SI-80L", "San-Aid SI-100L" (above Sanxin Chemical Industry Co., Ltd.) ))). These thermal cationic polymerization initiators may be used singly or in combination of two or more. Further, it is also preferred to use a photocationic polymerization initiator and a thermal cationic polymerization initiator together.

The solvent-free epoxy-based adhesive may further contain a compound which promotes cationic polymerization, such as a propylene oxide or a polyhydric alcohol.

When a solventless epoxy adhesive is used, the adhesion to the polarizing film 21, the polypropylene resin film 25 or the transparent resin film 23 can be adhered to the polarizing film 21 or the polypropylene resin film 25. The bonding surface is applied to the coated surface of the polarizing film 21 or the transparent resin film 23 by applying an adhesive, and bonding the respective films. The method of applying the solventless epoxy-based adhesive to the polarizing film 21, the polypropylene resin film 25, and the transparent resin film 23 is not particularly limited, and various coating methods such as a doctor blade can be used. A wire bar, a die coater, a comma coater, a gravure coater, or the like. Furthermore, since each coating method has a viscosity range that is most suitable for each application, a small amount of solvent can also be used for viscosity adjustment. Therefore, the solvent to be used may be such that the optical properties of the polarizing film 21 are not lowered and the epoxy-based adhesive is well dissolved. For example, a hydrocarbon represented by toluene or an ester represented by ethyl acetate may be used. Organic solvents such as the class.

The adhesive layer composed of the uncured epoxy-based adhesive is irradiated with active energy rays or heated after the polarizing film 21 is bonded to the polypropylene resin film 25 or the transparent resin film 23. The adhesive layer is cured, and the polypropylene resin film 25 or the transparent resin film 23 is fixed to the polarizing film 21. When it is hardened by irradiation with an active energy ray, it is preferably used for an active energy ray having a light-emitting distribution at a wavelength of 400 nm or less, and among them, ultraviolet rays are particularly preferably used. Specific ultraviolet light sources include low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra high pressure mercury lamps, chemical lamps, black lamps, microwave excited mercury lamps, and metal halide lamps. The active energy ray, for example, the irradiation intensity or the irradiation amount of the ultraviolet ray, sufficiently activates the cationic polymerization initiator, and does not impart a bad film influence on the adhesive layer or the polarizing film 21 after curing (for example, the polarizing film 21) The degree of polarization, the transmittance, and the hue are appropriately selected from the transparency of the transparent resin film 23 and the polypropylene resin film 25, and the various functions of the polarizing plate 20 are not lowered.

Specifically, the light-irradiating strength of the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and is not particularly limited. However, in the wavelength region effective for activation of the polymerization initiator The irradiation intensity is preferably 0.1 to 6000 mW/cm ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time does not become long, and when it is 6000 mW/cm ² or less, light hardening by heat radiated from the light source and heat generation during curing of the photocurable adhesive is generated. The yellowing of the epoxy resin or the possibility of deterioration of the polarizing film 21 is small. The light irradiation time of the photocurable adhesive is controlled according to the resin to be cured, and is not particularly limited. However, the integrated light amount which is the product of the irradiation intensity and the irradiation time is set to be 10 to 10000 mJ/cm ^{2 .} More ideal. When the integrated light amount of the photocurable adhesive is 10 mJ/cm ² or more, a sufficient amount of the active species derived from the polymerization initiator can be generated, and the curing reaction can be more reliably performed, and when it is 10000 mJ/cm ² or less, The irradiation time does not become too long, and good productivity can be maintained.

Further, when it is hardened by heating, it can be heated by a generally known method, and the temperature or time at this time also sufficiently activates the cationic polymerization initiator, and does not give the cured adhesive layer or The film of the polarizing film 21 or the like is appropriately selected and appropriately selected.

The thickness of the adhesive layer composed of the cured epoxy-based adhesive is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less, and usually 1 μm or more.

Further, as the adhesive, a water-based adhesive can be used from the viewpoint of making the adhesive layer 29 thin, that is, the adhesive component can be dissolved in water or the adhesive component can be dispersed in water. Adhesive. For example, a water-based adhesive which uses a polyvinyl alcohol-based resin or a urethane resin as a main component is preferably a water-based adhesive.

The polyvinyl alcohol-based resin as a main component of the adhesive may be a carboxylated polyvinyl alcohol, an ethylene-modified vinyl alcohol, or a hydroxyl group, in addition to a partially saponified polyvinyl alcohol or a fully saponified polyvinyl alcohol. A denatured polyvinyl alcohol-based resin such as a modified polyvinyl alcohol or an amine-modified polyvinyl alcohol. The water-based adhesive which is a polyvinyl alcohol-based resin as a main component of the adhesive is usually prepared as an aqueous solution of a polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol-based resin in the water-based adhesive is usually about 1 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of water.

In order to improve the adhesion, the water-based adhesive containing a polyvinyl alcohol-based resin as a main component is preferably a curable component or a crosslinking agent such as glyoxal or a water-soluble epoxy resin. The water-soluble epoxy resin may, for example, be a polymer obtained by a reaction of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid. A polyamide polyamine epoxy resin obtained by reacting an epichlorohydrin. Commercially available products of the polyamine polyamine epoxy resin include "Sumirez Resin 650" and "Sumirez Resin 675" sold by Sumika Chemtex Co., Ltd., and "WS-525" sold by Japanese P MC Co., Ltd. And so on, and these can be used as appropriate. The amount of the curable component or the crosslinking agent to be added is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, per 100 parts by weight of the polyvinyl alcohol-based resin. When the amount of addition is small, the effect of improving the adhesion is small, and on the other hand, when the amount of addition is large, the adhesive layer 29 tends to become brittle.

When a urethane resin is used as a main component of the adhesive, examples of a suitable water-based adhesive include a polyester-based ionic polymer-type urethane resin and a compound having a glycidoxy group. mixture. Here, the polyester-based ionic polymer type urethane resin is a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced therein. Since the ionic polymer type urethane resin is emulsified directly into water as an emulsion without using an emulsifier, it is suitable as a water-based adhesive. The polyester-based ionic polymer type urethane resin is known per se. A polyester-based ionic polymer type urethane resin as an example of a polymer dispersant for dispersing a phenol resin in an aqueous medium is described in Japanese Laid-Open Patent Publication No. Hei 7-97504, and JP-A-2005-070140 and JP-A-2005-181817 show that a mixture of a polyester-based ionic polymer type urethane resin and a compound having a glycidoxy group is used as a binder. A form in which a cycloolefin film is bonded to a polarizing film made of a polyvinyl alcohol-based resin.

A method known in the art for bonding the polypropylene resin film 25 and the transparent resin film 23 to the surface of the polarizing film 21 using a water-based adhesive can be used. For example, a casting method, a mayer bar coating method, a gravure coating method, a notch wheel coating method, a doctor blade method, a slit coating method, a dip coating method, a spray method, etc. Further, a method of applying an adhesive to the polarizing film 21 and/or the bonding surface of the film attached thereto is a method of laminating the two. The casting method is a method in which a film as a material to be coated is moved in an approximately vertical direction, an approximately horizontal direction, or an oblique direction therebetween, and a binder is allowed to flow down on the surface thereof.

After the water-based adhesive is applied by the above method, the polarizing film 21 and the film bonded thereto are sandwiched by a nip roll or the like, and the two are joined by bonding. Further, after the adhesive is added dropwise between the polarizing film 21 and the film bonded thereto, it is also suitable to use a method in which the laminate is pressurized by a roller or the like and spread uniformly. In this case, the material of the roller may be metal or rubber. Further, after the adhesive is dropped between the polarizing film 21 and the film bonded thereto, it is also suitable to use a method in which the laminate is passed between a roll and a roll and pressurized. In this case, the rolls may be of the same material or different materials.

Further, before the drying or hardening, the thickness of the adhesive layer 29 composed of a water-based adhesive which is bonded by using a nip roll or the like is preferably 5 μm or less, and the desired state is 0.01 μm or more.

The polarizing film 21 and/or the bonding surface of the film attached thereto may be subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, etc. in order to improve adhesion. . The saponification treatment may be a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

The laminate bonded by the water-based adhesive is usually subjected to a drying treatment to dry and harden the adhesive layer 29. The drying treatment can be carried out, for example, by blowing hot air. The drying temperature is usually selected from the range of about 40 to 100 ° C, and preferably 60 to 100 ° C. The drying time is, for example, about 20 to 1,200 seconds. The thickness of the adhesive layer 29 after drying is usually about 0.001 to 5 μm, more preferably 0.01 μm or more, and more preferably 2 μm or less, and more preferably 1 μm or less. When the thickness of the adhesive layer 29 is excessively large, the appearance of the polarizing plate 20 is liable to be deteriorated.

After the drying treatment, it can be cured at room temperature or higher for at least half a day, usually for more than one day, to obtain sufficient adhesive strength. This curing is typically carried out in a state where the coil is wound into a roll. The preferred curing temperature is in the range of 30 to 50 ° C, and more preferably in the range of 35 ° C or more and 45 ° C or less. When the curing temperature exceeds 50 ° C, in the state of the roll, so-called "winding" is likely to occur. Further, the humidity at the time of curing is not particularly limited, but it is preferably selected such that the relative humidity is in the range of about 0% RH to 70% RH. The maintenance time is about 1 to 10 days, and the ideal form is about 2 to 7.

<Method for Producing Polypropylene Resin Film>

4 to 6 are schematic views showing an example of a film production apparatus which can be applied to the production of the polypropylene resin film 25 of the present invention. In the following, a configuration of a film production apparatus which can be applied to the production of the polypropylene resin film 25 of the present invention and a method of producing the polypropylene resin film 25 using the film production apparatus will be described with reference to FIG. 4 to FIG.

(extrusion machine)

In the production of the polypropylene resin film 25 using the film production apparatus 100 shown in Fig. 4 (the same as the film production apparatuses 200 and 300 shown in Fig. 5 and Fig. 6), first, the hopper (not shown) will be used. This polypropylene resin is put into the extruder 11. In this case, in order to suppress deterioration, decomposition, and the like of the polypropylene resin in the kneading, the resin is supplied at a temperature of 40° C. or higher and (Tm − 20° C.) or less in the nitrogen gas before the resin is supplied to the extruder 11 . The pellet of the polypropylene resin is preferably dried in advance for about 1 hour to 10 hours (Tm [° C.] is the melting peak temperature of the polypropylene resin measured by the differential scanning calorimetry specified in JIS K 7121). Further, in the extruder 11, it is preferable to carry out gas substitution with a nitrogen gas of 20 ° C to 120 ° C or an inert gas such as argon gas. In addition, the extruder 11 is a device which melts and melts the polypropylene resin to be charged, and transfers the molten polypropylene resin to the T-die 12.

When the polypropylene resin is melt-kneaded in the extruder 11, a screw is used, and in the case where the extruder 11 is a uniaxial extruder, L/D = 24 to 36 can be used. And the compression ratio of 1.5 to 4 has a full-thread type, a barrier type or a cross-type type. It is preferable to use a barrier type screw having an L/D of 28 to 36 and a compression ratio of 2.5 to 3.5 from the viewpoint of suppressing deterioration and decomposition of the polypropylene resin and uniformly melting and kneading.

In addition, in order to remove the volatile gas generated during the deterioration and decomposition of the polypropylene resin, an opening of 1 mm or more and 5 mm Φ or less is provided at the tip end of the extruder 11, and the resin pressure at the tip end portion of the extruder 11 is also increased. More ideal. Increasing the resin pressure at the tip end portion of the extruder 11 means increasing the back pressure at the tip end, and by which the stability of the extrusion can be improved. The preferred aperture is 2mm Φ or more and 4mm Φ or less. Further, since the extrusion change of the polypropylene resin is suppressed, it is preferable to mount the gear pump between the extruder 11 and the T die 12 via the adapter. Further, in order to remove foreign matter in the polypropylene resin, it is preferable to install a leaf disc filter (not shown).

(T-mode)

The T-die 12 is connected to the extruder 11 and has a manifold 12b for expanding the molten polypropylene-based resin transferred from the extruder 11 in the lateral direction. Further, in the lower portion of the T-die 12, the manifold 12b is communicated with the manifold 12b, and the outlet port 12a of the molten polypropylene resin which flows out through the manifold 12b is provided. Therefore, the molten polypropylene resin which flows out from the outflow port 12a of the T-die 12 is formed into a sheet shape (hereinafter, the molten polypropylene resin which is formed into a sheet shape is referred to as a "melted sheet").

The temperature of the molten flakes flowing out is preferably 180 ° C or more and 300 ° C or less. The temperature of the molten resin was measured at the outlet 12a of the T-die 12 and measured using a resin thermometer. When the temperature of the molten flakes is less than 180 ° C, the ductility is poor, and there is a tendency that thickness unevenness occurs due to unevenness in the elongation in the air gap. On the other hand, when the temperature of the molten sheet exceeds 300 °C, the resin is deteriorated, and the decomposition gas or the like is generated to contaminate the outlet 12a, and the mold line is generated, and the appearance of the polypropylene resin film 25 tends to be deteriorated. .

The T-die 12 is preferably one which does not have a slight step or damage on the wall surface of the flow path of the molten polypropylene resin. The portion (portion portion) of the outflow port 12a of the T-die 12 is a material having a small coefficient of friction with the molten polypropylene resin, and is plated, coated, or the like by a hard material (for example, a tungsten carbide system, In the case of the fluorine-based special plating, the radius of curvature of the tip end portion of the outflow port 12a can be reduced (the tip end portion of the outflow port 12a is formed into a shape called a sharp edge), which is preferable.

The tip end portion of the outflow port 12a of the T-die 12 is preferably a sharp edge shape having an opening radius of 0.1 mm or less in the opening formed on the wall surface of the flow path of the molten polypropylene resin. The radius of curvature of the tip end portion of the outflow port 12a is more preferably 0.05 mm or less, and more preferably 0.03 mm or less. By using the T-die 12 as described above, the generation of "glue" of the outflow port 12a can be suppressed, and the mold line can be suppressed. Therefore, the uniformity of the appearance of the produced polypropylene-based resin film 25 can be further improved. However, when the radius of curvature is 0.01 mm or less, the effects of the above-described effects are improved, but the strength of the tip end portion of the outflow port 12a is lowered, and the breakage of the outflow port 12a is seen because it causes a larger mold line or the like.

The length (the length of the air gap) H between the outflow port 12a of the molten resin of the T-die 12 and the front side of the molten sheet by the elastic roller 13 and the metal roll 14 disposed at the lower portion thereof is preferable. The state is about 50 mm to 250 mm, and more preferably about 50 mm to 180 mm. When the length H of the air gap exceeds 250 mm, the cooling efficiency tends to decrease due to prolonged exposure to the air, and orientation is generated in the air gap, and the polypropylene resin film 25 produced has a large phase difference. tendency. The lower limit of the length H of the air gap depends on the size of the T-die 12 or the diameter of the elastic roller 13 and the metal roller 14, and is always about 50 mm.

(elastic roller)

Elastic roller means an elastically deformable metal roller or rubber roller. The elastically deformable metal roll is particularly suitable for the elastic roll 13 shown in Fig. 4. The elastic roller 13 provided in the film manufacturing apparatus 100 shown in FIG. 4 is equivalent to the forming roll described in Japanese Patent No. 3422798, and specifically, is a metal strip having a cylindrical shape (also The rubber belt 13b (one in the example of FIG. 4) disposed inside the belt-shaped body 13a, and the liquid L filling the space between the belt-shaped body 13a and the rubber roller 13b An elastically deformable metal roll for a temperature adjustment mechanism (not shown) for adjusting the temperature of the liquid L.

The strip 13a is formed into a cylindrical shape by an elastically deformable metal film such as spring steel, stainless steel, or nickel steel, and has no seam on its surface. Both sides of the strip 13a are closed by a closing member (not shown). The strip 13a may have a thickness of about 100 μm to 1500 μm, a diameter of about 200 mm to 600 mm, and a surface roughness of 0.5 S or less. Preferably, the surface roughness is 0.2 S or less. In addition, the diameter of the strip-shaped body 13a is set to an appropriate size in accordance with the processing speed of the polypropylene-based resin film 25, and when the diameter of the strip-shaped body 13a is in the above range, the processing speed of the polypropylene-based resin film 25 can be adjusted. Corresponds to a range of several m/min to 100 tens of m/min.

The rubber roller 13b has a cylindrical shape and is elastically deformed and rotatable inside the strip 13a. The rubber roll 13b can be formed by EPDM (ethylene-propylene-diene rubber), chloroprene rubber or fluorenone having a hardness of about 30 to 90. Further, the diameter of the rubber roller 13b can be set to about 100 mm to 250 mm.

As the liquid L, for example, water, ethylene glycol, oil, or the like can be used. The temperature of the liquid L is adjusted by a temperature adjustment mechanism (not shown), whereby the surface temperature of the strip 13a is indirectly adjusted.

The thickness of the strip 13a is preferably from 350 μm to 500 μm, and the hardness of the rubber roll 13b is preferably from about 60 to 75. When the thickness of the strip 13a is less than 350 μm and the hardness of the rubber roll 13b is less than 60, the elasticity of the elastic roll 13 is too low, and it tends to be difficult to be uniform in the width direction of the elastic roll 13. In addition, when the thickness of the strip-shaped body 13a exceeds 500 μm and the hardness of the rubber roll 13b exceeds 75, the rigidity of the elastic roller 13 is too high, and the effect of soft pressing tends to be weak.

Further, as the elastic roller, the elastic roller 16 having the configuration shown in Fig. 5 is also preferably used. The elastic roller 16 provided in the film production apparatus 200 shown in the figure is equivalent to the molding tape method described in Japanese Laid-Open Patent Publication No. Hei 7-40370. Specifically, the elastic roller 16 is an elastically deformable metal roller having a metal strip-shaped body (also referred to as an endless belt) 16a and a strip-shaped body 16a in the interior of the strip-shaped body 16a. The outer peripheral surfaces of 14 are arranged at the same time, and are arranged in parallel with the two rolls 16b, 16c in the longitudinal direction, and a temperature adjusting mechanism (not shown) for adjusting the surface temperature of the strip 16a. The roller 16b is a rubber roller, and the roller 16c is a metal roller. The surface temperature of the strip 16a is adjusted by adjusting the surface temperature of the roller 16c by a temperature adjustment mechanism.

The strip 16a is formed into a cylindrical shape by an elastically deformable metal film such as spring steel, stainless steel, or nickel steel, and has no seam on its surface. The strip 16a is stretched over the rubber roller 16b and the metal roller 16c, and the tension (extension) of the strip 16a can be adjusted by bringing the distance between the rollers 16b, 16c close to or apart. The strip-shaped body 16a may have a thickness of about 300 μm to 800 μm, and a diameter of 200 mm to 600 mm when it is a cylindrical shape, and preferably has a surface roughness of 0.2 S or less.

The rollers 16b, 16c have a cylindrical shape and are rotatable inside the strip 16a. The rubber roll 16b can be formed by EPDM (ethylene-propylene-diene rubber), chloroprene rubber or fluorenone having a hardness of about 30 to 90. Further, the rollers 16b and 16c can be used having a diameter of about 80 mm to 200 mm.

When the elastic roller 16 is used, the molten sheet which flows out from the outflow port 12a of the T-die 12, according to the strip-shaped body 16a and the metal roll 14, is initially held at the starting point of extrusion, and the extruded resin leaves the belt. The position of the body 16a and the metal roll 14 is the end point of the extrusion.

The thickness of the strip 16a is about 350 μm to 600 μm, and the hardness of the rubber roll 16b is preferably about 60 to 80. When the thickness of the strip-shaped body 16a is less than 350 μm and the hardness of the rubber-made roll 16b is less than 60, the elasticity of the elastic roller 16 is too low, and it tends to be less uniform in the width direction of the elastic roller 16. When the thickness of the strip-shaped body 16a exceeds 600 μm and the hardness of the rubber-made roll 16b exceeds 80, the rigidity of the elastic roll 16 is too high, and it is easy to form a stagnation (bank; resin accumulation) as appropriate. The obtained polypropylene resin film 25 tends to have a phase difference.

Further, the elastic roller 17 can be suitably applied to the elastic roller 17 shown in Fig. 6. The elastic roller 17 of the film manufacturing apparatus 300 shown in Fig. 6 is equivalent to the pressing roller described in Japanese Laid-Open Patent Publication No. Hei 11-235747. Specifically, the elastic roller 17 is made of metal having high rigidity. The cylinder 17a, the thin metal outer cylinder 17b disposed on the outer side of the metal inner cylinder 17a, the fluid shaft cylinder 17c disposed inside the metal inner cylinder 17a, and the space between the metal inner cylinder 17a and the thin metal outer cylinder 17b And an elastically deformable metal roll of the liquid L in the fluid barrel 17c and a temperature adjusting mechanism (not shown) for adjusting the temperature of the liquid L.

The metal inner cylinder 17a, the thin metal outer cylinder 17b, and the fluid shaft cylinder 17c are disposed coaxially. The metal inner cylinder 17a is provided with a plurality of through holes 17d along the circumferential direction thereof. Therefore, the liquid L sequentially circulates inside the elastic roller 17 in the space between the fluid axial tube 17c, the through hole 17d, the metal inner cylinder 17a, and the thin metal outer cylinder 17b.

The thin-walled metal outer cylinder 17b is formed of stainless steel or the like, and has no seam on its surface and has flexibility. In order to have flexibility, flexibility, and restorability similar to rubber elasticity, the thin-walled metal outer cylinder 17b is attempted to be thinned in the range of a thin-walled cylinder theory to which elastic mechanics can be applied. The thin-walled metal outer cylinder 17b can be used having a thickness of about 2000 μm to 5000 μm, a diameter of about 200 mm to 500 mm, and a surface roughness of 0.5 S or less. Preferably, the surface roughness is 0.2 S or less. When the thickness of the thin-walled metal outer cylinder 17b is less than 2000 μm, the elastic roller 17 and the metal roller 14 tend to have a non-uniform pressure when the molten sheet is pressed, and when it exceeds 5000 μm, the elasticity of the thin-walled metal outer cylinder 17b When the thickness of the molten sheet which has flowed out from the outflow port 12a of the T-die 12 is increased, there is a tendency for the material to be stagnant when the molten sheet is pressed.

As the liquid L, for example, water, ethylene glycol, oil, or the like can be used. The temperature of the liquid L is adjusted by a temperature adjustment mechanism (not shown), whereby the surface temperature of the thin-walled metal outer cylinder 17b is indirectly adjusted.

Further, as described above, a rubber roller can be used as the elastic roller. When a rubber roller is used as the elastic roller, the surface hardness is preferably 65 to 80, and more preferably 70 to 80. By using a rubber roller having a surface hardness as described above, it is easy to maintain the pressure (linear pressure) uniform when the molten sheet is pressed, and no stagnant material is generated between the metal roller 14 and the rubber roller, and It is easy to form a molten sheet. When the hysteresis is generated, the phase difference of the obtained polypropylene resin film 25 tends to be large, and the visibility may be deteriorated when disposed in the liquid crystal display device 1, which is not preferable.

When a rubber roller is used as the elastic roller, it is preferable to insert the support into the gap between the molten sheet and the rubber roller when the molten sheet is pressed by the rubber roller and the metal roller. As the support, for example, a biaxially stretched film made of a thermoplastic resin can be used.

It is preferable to use a smoother support for the support. Since the surface of the molten sheet that is in contact with the metal roll is the surface on the opposite side and is pressed between the rolls in a state of being in contact with the support, the surface of the obtained polypropylene resin film 25 is a transfer support. Surface state. Therefore, the surface roughness of the support used is small, and the smoothness of the surface obtained as the smoother is better. The surface roughness of the support to be used is preferably 0.01 μm or more and 1.5 μm or less, and more preferably 0.01 μm or more and 1.0 μm or less. Further, the thickness of the support to be used needs to be 5 μm or more and less than 50 μm, and preferably 10 μm or more and 30 μm or less. When the support used is thinner than 5 μm, it is less desirable because of handling problems such as wrinkles, which is less desirable. On the other hand, when the thickness is 50 μm or more, the cooling efficiency of the molten flakes is deteriorated, and the obtained polypropylene is obtained. The transparency of the resin film 25 is deteriorated, which is not preferable. The thermoplastic resin constituting the support may be a resin which is not thermally fused to the polypropylene resin, and is specifically a polyester, a polyamide, a polyvinyl chloride, a polyvinyl alcohol, or an ethylene vinyl alcohol. Copolymer, polyacrylonitrile, and the like. Among these, polyesters having a small dimensional change due to humidity or heat are particularly preferred.

Between the rubber roller and the metal roller, the molten sheet which is pressed simultaneously with the support body is cooled and hardened, and then, in the state of laminating the support body, the end portion is cut as necessary, and then taken up by a coiler. A laminate of the polypropylene resin film 25 and the support can be obtained. The support may be peeled off before the coiler, and only the polypropylene resin film 25 may be taken up. When the support extruded between the rolls is peeled off from the polypropylene resin film 25, the temperature of the polypropylene resin film 25 is cooled to 60 ° C or lower, and preferably 40 ° C or less, and then preferably removed. When the support is peeled off in a state where the temperature of the polypropylene resin film 25 is high, the film is deformed and oriented, and the phase difference is increased.

In the elastic roller, the smoothness of the surface contacting the elastic roller is more preferable, and it is preferable to use an elastically deformable metal roller. The surface of the elastically deformable metal roll is preferably mirror-finished.

(metal roller)

The metal roll 14 provided in the film manufacturing apparatus 100 (the same as the film manufacturing apparatuses 200 and 300 shown in FIG. 5 and FIG. 6) shown in FIG. 4 has a metal outer cylinder 14a having high rigidity and is disposed inside the metal outer cylinder 14a. The fluid barrel 14b fills a space between the metal outer cylinder 14a and the fluid barrel 14b, a liquid L in the fluid barrel 14b, and a temperature adjustment mechanism (not shown) for adjusting the temperature of the liquid L. The fluid shaft tube 14b is provided with a plurality of through holes 14c along the circumferential direction thereof. The diameter of the metal roll 14 can be set to about 200 mm to 600 mm. In the metal roll 14, like the elastic roll 13, the temperature of the liquid L is adjusted by a temperature adjustment mechanism (not shown), thereby indirectly adjusting the surface temperature of the metal outer cylinder 14a, simultaneously with the elastic roller. The molten sheet flowing out of the outflow port 12a of the T-die 12 is cooled and hardened.

In the case of producing a polypropylene-based resin film 25 in which one of the elastic rolls 13 and the metal roll 14 is provided with a transfer type, the one of the elastic rolls 13 and the metal roll 14 is provided with a transfer type. Since the shape of the transfer type is more accurately transferred, it is preferable to provide a transfer type on the surface of the metal roll 14. Hereinafter, the metal roll 14 provided with a transfer type on the surface is also referred to as a "transfer roller".

This transfer type is provided on the surface of the transfer roller against the surface of the molten sheet, and the surface shape thereof is transferred to the molten sheet as a reverse type. The shape of the concave portion, the groove depth, the pitch of the grooves, and the like are determined in accordance with the surface uneven shape of the desired polypropylene-based resin film 25. The transfer type groove may be parallel to the circumferential direction of the transfer roller, may be parallel to the width direction of the transfer roller, or may be at a certain angle to the circumferential direction.

A known method can be employed as the method for producing the transfer type. For example, after plating treatment such as chromium plating, copper plating, nickel plating, or nickel-phosphorus plating on the surface of a transfer roller made of stainless steel, steel, or the like, a diamond drill or metal is used for the plating surface. A method of removing the shape, laser processing, or chemical etching of a grindstone or the like, and processing the shape.

Further, after forming the transfer type, the surface of the transfer roller may be subjected to chrome plating, copper plating, nickel plating, nickel-phosphorus plating, or the like, for example, at a level that does not impair the accuracy of the surface shape. Plating treatment.

(cooling roll)

The cooling roll is a roll for further cooling the molten sheet extruded by the elastic roll and the metal roll. The cooling roll 15 provided in the film manufacturing apparatus 100 (the same as the film manufacturing apparatuses 200 and 300 shown in FIG. 5 and FIG. 6) shown in FIG. 4 has the same configuration as the metal roller 14, and specifically has high rigidity. The metal outer cylinder 15a, the fluid shaft cylinder 15b disposed inside the metal outer cylinder 15a, the space between the metal outer cylinder 15a and the fluid shaft cylinder 15b, and the liquid L in the fluid shaft cylinder 15b, for adjusting the liquid L Temperature temperature adjustment mechanism (not shown). The fluid shaft cylinder 15b is provided with a plurality of through holes 15c along the circumferential direction thereof. As the cooling roll 15, a mirror having a diameter of about 200 mm to 600 mm and a surface roughness of 0.2 S or less can be used. In the cooling roll 15, the temperature of the liquid L is also adjusted by a temperature adjustment mechanism (not shown), whereby the surface temperature of the metal outer cylinder 15a is indirectly adjusted.

The polypropylene resin film 25 is a molten sheet that flows out from the outlet 12a of the T-die 12, and is pressed by the elastic roller and the metal roller (including a transfer roller) to be cooled and hardened. Made in this way. The pressing pressure (linear pressure) is determined according to the pressure at which the elastic roller is pressed against the metal roller. The preferred state is 1 to 300 N/mm, and more preferably 1 to 200 N/mm. When the linear pressure is less than 1 N/mm, it is difficult to control the linear pressure of the molten sheet to be uniform, and when the metal roll is a transfer roller, it is difficult to transfer the transfer type with good precision. Further, when the linear pressure exceeds 300 N/mm, since the molten flakes are excessively strongly pressed, the molten flakes are accumulated in the pressed portion, and at the same time, the formed stagnant material is formed, and the obtained polypropylene is obtained. The resin film 25 tends to have a large phase difference.

The method of controlling the line pressure generally has (1) a wedge-shaped "filler" called a pin of a pin in the pressed portion, and a method of adjusting the interval of the roll by adjusting the pin, and (2) elasticity. Both the roller and the metal roller abut against a method of pressing the pin adjusted with a predetermined pressure using oil pressure, air, or the like. Others include a method of controlling the number of revolutions of the screw without using a pin, and a method of crimping to a predetermined position on the machine in a stepless manner, and using a servo motor in a hydraulic system.

Further, the distance by the elastic roller and the metal roller is 1 to 30 mm, and preferably 1 to 15 mm. When the distance of the pressing is within the range, when the metal roll is a transfer roll, the transfer type can be transferred with good precision. The method of controlling the distance of the extrusion generally has (1) a wedge-shaped "filler" called a triangle of a pin in a pressed portion, and a method of adjusting the interval of the roller by adjusting the pin, (2) A method of adjusting the elasticity of the elastic roller.

The surface temperature of the elastic roller and the metal roll when the molten sheet is extruded is not particularly limited, but the polypropylene-based resin film 25 having high transparency is easily obtained by rapidly cooling the molten sheet. As a specific surface temperature, it is preferable that the surface temperature of the roller of at least one of the elastic roller or the metal roller is 0 to 60 ° C, and more preferably, the surface temperature of at least one of the rollers is 0 to At 40 ° C, it is more desirable that at least one of the rolls has a surface temperature of 0 to 30 ° C.

Further, the processing speed of the polypropylene resin film 25 is as large as the metal roll diameter of the transfer roller or the like is larger. For example, when the diameter of the metal roll is 600 mm, the processing speed of the polypropylene resin film 25 can be set to a maximum of about 50 m/min, and usually about 30 m/min.

The elastic roller and the metal roller are arranged below the T-die 12, generally in a row. The elastic roller and the metal roller are disposed at predetermined intervals, and according to the interval between the elastic roller and the metal roller, the rotational speed of the elastic roller, the metal roller and the cooling roller, and the molten sheet flowing out from the outflow port 12a of the T-die 12 The thickness of the polypropylene resin film 25 is defined by the amount of outflow or the like.

The polypropylene resin film 25 which is further cooled by the cooling roll is cut (cut) as needed, wound up by a winder, or cut into a single piece. Before the ear portion of the polypropylene resin film 25 is cut or cut, a surface of the polypropylene resin film 25 may be laminated on one surface or both sides to protect the surface for the period before use. Protective film.

The polypropylene resin film 25 can be produced by the above production method. The polarizing plate 20 using the polypropylene resin film 25 is bonded to the surface of the liquid crystal cell 40 and used as the liquid crystal panel 2. The liquid crystal panel 2 is used as the liquid crystal display device 1 as in the above-described combination backlight 10 or light diffusing plate 50. The mode of the liquid crystal cell 40 to which the polarizing plate 20 is applied is not particularly limited. Various modes of the liquid crystal cell 40 can be used, for example, a VA mode, an IPS mode, a TN mode, and the like.

example

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples.

[Example 1] (a) Production of a polypropylene resin film

Using the film production apparatus 200 shown in Fig. 5, a polypropylene resin film was produced in the following procedure. First, a polypropylene resin A [propylene homopolymer, melt flow rate (MFR) = 7 g/10 min, melting point Tm = 164 ° C] in the same row, and a 50 mm φ extruder 11 (screw) heated to 270 ° C will be included. : L/D = 32, full-thread screw) melt-kneaded, starting from the extruder 11, to the gear pump, adapter and T-die 12 provided next to the extruder 11 (all set to 270 ° C) In this order, the polypropylene resin sheet (molten resin) in a molten state flows out from the outflow port 12a (lip) of the T-die 12. The temperature of the molten resin in the portion of the outflow port 12a of the T-die 12 was 270 °C. Then, the molten resin was extruded by the elastic roller 16 (without transfer type) and the metal roll 14 (without transfer type) under the manufacturing conditions shown in Table 1, and further by the cooling roll 15 The film was cooled to prepare a polypropylene resin film. Further, the MFR of the polypropylene resin A was measured under the conditions of a temperature of 230 ° C and a load of 21.18 N in accordance with JIS K7210. Further, the melting point Tm is obtained by measuring the heat of the differential scanning in accordance with JIS K 7121.

The thickness of the polypropylene-based resin film obtained by this method, the haze, the following phase difference R ₀ by means of the measured values within the plane. The above results were as follows: a polypropylene resin film having a thickness of 107.1 μm, a haze of 1.3%, and an in-plane retardation value R ₀ of 20.6 nm. The results are shown in Table 1.

(thickness of polypropylene resin film)

The thickness of 5 points was measured using a contact thickness meter ("MS-5C" manufactured by NIKON Co., Ltd.), and the average value thereof was defined as the thickness of the polypropylene resin film.

(Haze of polypropylene resin film)

The measurement was carried out using a haze meter "HM-150" manufactured by Murakami Color Technology Research Institute, JIS K 7136.

(In-plane retardation value R _{0 of} polypropylene resin film)

The in-plane retardation value R ₀ at a wavelength of 590 nm was measured using a phase difference measuring device ("KOBRA-WPR" manufactured by Oji Scientific Instruments Co., Ltd.).

Further, the "squeezing distance" shown in Table 1 indicates the length at which the molten resin is pressed between the elastic roller 16 and the metal roller 14, and the pressure sensitive paper (FUJIFILM) is sandwiched between the elastic roller 16 and the metal roller 14. BUSINESS SUPPLY (PRECALE LLW), measure the distance in the MD direction of the colored portion of the pressure sensitive paper, and use it as the extrusion distance. Further, the elastic roller 16, the metal roller 14, and the cooling roller 15 used have the following configurations.

(elastic roller 16)

Band 16a: made of metal, surface roughness 0.2S, thickness 300μm

Roller 16b: made of fluorenone, diameter 160mm, hardness 60

Roller 16c: metal, diameter 160mm

(metal roller 14)

Metal outer cylinder 14a: metal, diameter 300mm

(cooling roller 15)

Metal outer cylinder 15a: metal, diameter 300mm, surface roughness 0.1S (mirror surface)

[Comparative Example 1] (b) Production of polypropylene resin film

The polymerization of Comparative Example 1 was prepared in the same manner as in Example 1 except that the film production conditions (surface temperature, extrusion distance, line pressure, and linear velocity of the metal roll 14 and the elastic roll 16) were changed as described in Table 1. A propylene resin film. As shown in the table, the obtained film had a thickness of 97.0 μm, a haze of 21.8%, and an internal phase difference R ₀ of 55.6 nm.

(c) Determination of surface orientation parameters

The surface orientation parameters of the polypropylene resin films of Example 1 and Comparative Example 1 obtained in the above (a) and (b) were measured by ATR-Raman spectroscopy. The measurement of the surface orientation parameters was carried out under the following apparatus and measurement conditions.

<Measurement device>

Ramanor T-6400 (made by Jobin Yvon / 宕 宕 )

<Measurement conditions>

Measurement mode: ATR Raman (Ge30°),

稜鏡: high refractive index glass

Incidence angle: 56.5° (ATR), 51.0° (main body)

Beam diameter: 100μm

Light source: Ar laser / 514.5nm

Laser power: 400mW (in the tube)

Diffraction grating: single 1800gr/nm

Slit: 100μm

Detector: CCD/Jobin Yvon 1024 channel

Number of measurements: n = 3 (the numerical data such as peak intensity is the average value of N = 3)

<Measurement method>

The surface of the polypropylene resin film was directly pressed against a high refractive index glass crucible, and the ATR-Raman spectrum was measured. Further, the depth of penetration of the measurement light was calculated according to the following formula. As a result, it was found that the immersion depth was about 100 nm.

(where v is the reciprocal of the wave number of incident laser light (v = (1/514.5) = 0.001943634...), n _s is the refractive index of the polypropylene resin film (n _s : about 1.5), n _p Is the refractive index of 稜鏡 (n _p =1.88: high refractive index glass), θ is the incident angle (θ=56.5°)

With respect to the polypropylene resin film of Example 1 and Comparative Example 1, the absorption spectrum was measured for parallel polarized light and vertical polarized light by the above-described measuring apparatus and measurement conditions, and the surface orientation parameter was obtained. The obtained absorption spectrum is shown in Fig. 7 (Example 1) and Fig. 8 (Comparative Example 1). Further, the values of the obtained surface orientation parameters are shown in Table 3.

(d) Production of a sample for adhesion test (polarizer)

With respect to the example 1 obtained in the above (a) and the polypropylene resin film of the comparative example 1 obtained in (b), the samples for the adhesion test (peeling test) were prepared in the following order. The first and comparative examples 1 were simultaneously used as samples, and a polarizing plate having the layer structure shown in Fig. 9 was used.

(1) Production of polarizing film

The polyvinyl alcohol film having an average polymerization degree of about 2400, a degree of saponification of 99.9 mol% or more and a thickness of 75 μm was immersed in pure water at 30° C., and the weight ratio of iodine/potassium iodide/water at 30° C. was 0.02/2/100. Immersion in an aqueous solution. Thereafter, it was immersed in an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 12/5/100 at 56.5 °C. Subsequently, the mixture was washed with pure water at 8 ° C, and then dried at 65 ° C to obtain a polarizing film in which iodine was adsorbed and directed to polyvinyl alcohol. The extension is mainly carried out in the steps of iodine dyeing and boric acid treatment, and the total stretching ratio is 5.3 times.

(2) Modulation of adhesive

The following components were mixed in the blending ratio (unit: parts by weight) shown in Table 2, and then defoamed to prepare a photocurable adhesive (adhesive A). Further, the photocationic polymerization initiator (b1) was blended as a 50% by weight propylene carbonate solution, and Table 2 is a solid component thereof.

(A) epoxy compound

(a1) 3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate

(a2) 1,4-butanediol diglycidyl ether

(B) Photocationic polymerization initiator (abbreviated as "starter" in the table)

(b1) 4,4'-bis(diphenylfluorenyl)diphenyl sulfide bis(hexafluorophosphate) photocationic polymerization initiator ["SP-150" manufactured by ADEKA)

(3) Production of polarizing plate

On the one side of the polarizing film, the polypropylene resin film obtained in the first embodiment or the first embodiment was bonded to the measurement surface of the surface orientation parameter to be the polarizing film side, and the other side was used. A cyclic olefin resin film ("ZEONOR" manufactured by ZEON Co., Ltd.) having a thickness of 75 μm was bonded together using the adhesive A. In addition, a corona treatment device (high-frequency power supply; "CT-0212" manufactured by Kasuga Electric Co., Ltd., transmitter body; Kasuga Electric Co., Ltd.) is used in advance on the bonding surface of the polypropylene resin film and the cyclic olefin resin film. "CT-0212" and high-voltage transformer; "CT-T022" manufactured by Kasuga Electric Co., Ltd.), the distance between the surface of the membrane and the electrode of the corona treatment device is 3 mm, the output is 280 W, the linear velocity is 1.0 m/min, and the ambient temperature is 23 °C. Corona treatment was carried out three times in a row under conditions of a relative humidity of 55% RH. Then, in the ultraviolet irradiation apparatus ("HAL400NL" 80W, the irradiation distance is 50 cm) of the Japanese battery (the ultraviolet light system), the adhesive was made by passing once at a linear velocity of 1.0 m/min. A hardens to obtain a polarizing plate.

(e) Determination of adhesion

Each of the samples for adhesion test (polarizing plate) of Example 1 and Comparative Example 1 obtained as described above was subjected to a 90° peel test under the following equipment and conditions.

<Evaluation device>

Automatic map meter AG-1 (made by Shimadzu Corporation)

<Measurement conditions>

Test speed: 300mm / min

Test piece: 200 mm long × 25 mm wide (with the cyclic olefin resin film side facing down, the sample was fixed to the glass plate with paste)

<Measurement method>

The end portion of the sample fixed to the glass plate was pinched, as shown in Fig. 10, and pulled in a direction perpendicular to the glass plate (about 90°: arrow direction of the drawing) to peel off between the polypropylene resin film and the polarizing film. The load at the time of peeling was measured by this evaluation apparatus, and the adhesive force was evaluated.

The results of the orientation parameter (surface orientation parameter) measurement and adhesion measurement of Example 1 and Comparative Example 1 are shown in Table 3. Furthermore, as a reference, the orientation parameters of the subject are also described. The orientation parameter (main body) is an orientation parameter calculated based on the Raman spectrum of Raman scattered light from the entire polypropylene resin film. The orientation parameter (main body) is different from the orientation parameter (ATR) indicating the orientation of the molecules in the vicinity of the surface layer, and indicates the molecular orientation of the entire polypropylene resin film in the thickness direction.

According to the results shown in the table, as in Example 1, when the orientation parameter (ATR) was 1.05, the adhesion was 11.6 N/25 mm and was good. On the other hand, as in Comparative Example 1, when the orientation parameter (ATR) was 1.82, the adhesion was considerably inferior to that in Example 1. According to these results, as shown in Example 1, in the range of the surface orientation parameter of 0.95 (=1/1.05) to 1.05, the adhesion was better than the range other than the above.

P. . . Parallel polarization

S. . . Vertical polarization

L. . . liquid

H. . . Length of air gap

MD. . . Mechanical direction

TD. . . Vertical direction

1. . . Liquid crystal display device

2. . . LCD panel

10. . . Backlight

11. . . Extrusion machine

12. . . T-mode

12a. . . Outflow

12b. . . Manifold

13. . . Elastic roller

13a. . . Band

13b. . . Rubber roller

14. . . Metal roller

14a. . . Metal outer tube

14b. . . Fluid shaft

14c. . . Through hole

15. . . Cooling roller

15a. . . Metal outer tube

15b. . . Fluid shaft

15c. . . Through hole

16. . . Elastic roller

16a. . . Band

16b. . . Roll

16c. . . Roll

17. . . Elastic roller

17a. . . Metal inner tube

17b. . . Thin-walled metal outer tube

17c. . . Fluid shaft

17d. . . Through hole

20. . . Polarizer

twenty one. . . Polarizing film

twenty three. . . Transparent resin film

25. . . Polypropylene resin film

27. . . Adhesive layer

29. . . Adhesive layer

30‧‧‧Polar plate

40‧‧‧Liquid Crystal Box

50‧‧‧Light diffuser

60‧‧‧Polar plate

65‧‧‧Photo film

100‧‧‧ film manufacturing equipment

200‧‧‧film manufacturing equipment

300‧‧‧film manufacturing equipment

Fig. 1 is a perspective view showing an ATR-Raman spectrometry.

2(a) and 2(b) are schematic cross-sectional views showing a polarizing plate according to an embodiment of the present invention.

3 is a schematic cross-sectional view showing a liquid crystal panel and a liquid crystal display device using a polarizing plate.

FIG. 4 is a schematic view showing an example of a film production apparatus which can be suitably applied to the production of the polypropylene resin film of the present invention.

FIG. 5 is a schematic view showing another example of a film production apparatus which can be suitably used in the production of the polypropylene resin film of the present invention.

FIG. 6 is a schematic view showing still another example of a film production apparatus which can be suitably applied to the production of the polypropylene resin film of the present invention.

Fig. 7 is an ATR-Raman spectrum of the polypropylene resin film of Example 1.

8 is an ATR-Raman spectrum of the polypropylene resin film of Comparative Example 1.

Fig. 9 is a schematic cross-sectional view showing a layer configuration of a sample for peeling test.

Fig. 10 is a plan view showing a test method of a peeling test.

L. . . liquid

H. . . Length of air gap

11. . . Extrusion machine

12. . . T-mode

12a. . . Outflow

12b. . . Manifold

14. . . Metal roller

14a. . . Metal outer tube

14b. . . Fluid shaft

14c. . . Through hole

15. . . Cooling roller

15a. . . Metal outer tube

15b. . . Fluid shaft

15c. . . Through hole

16. . . Elastic roller

16a. . . Band

16b. . . Roll

16c. . . Roll

25. . . Polypropylene resin film

200. . . Membrane manufacturing device

Claims (6)

A polarizing plate comprising: a polarizing film comprising a uniaxially stretched polyvinyl alcohol resin film adsorbing oriented iodine or a dichroic dye; and a polypropylene resin film laminated on the polarized light via an adhesive layer a film having a surface orientation parameter of 0.66 to 1.50 obtained by Raman spectroscopy using an attenuated total reflection method; the polypropylene resin film being laminated so as to be The surface is in contact with the layer of adhesive. The polarizing plate of claim 1, wherein the surface orientation parameter is in the range of 0.95 to 1.05. The polarizing plate of claim 1, wherein the adhesive layer is composed of a cured product of an active energy ray curable resin composition containing an epoxy resin. The polarizing plate of the first aspect of the invention, further comprising a protective film or an optical compensation film laminated on a surface of the polarizing film opposite to a surface on which the polypropylene resin film is laminated. A liquid crystal panel comprising a liquid crystal cell and a polarizing plate laminated on the liquid crystal cell as in the first aspect of the patent application. A liquid crystal display device comprising a surface light source element and a liquid crystal panel according to item 5 of the patent application.