WO2015025607A1 - 偏光子保護フィルムの製造方法及び偏光子保護フィルム - Google Patents
偏光子保護フィルムの製造方法及び偏光子保護フィルム Download PDFInfo
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- WO2015025607A1 WO2015025607A1 PCT/JP2014/066598 JP2014066598W WO2015025607A1 WO 2015025607 A1 WO2015025607 A1 WO 2015025607A1 JP 2014066598 W JP2014066598 W JP 2014066598W WO 2015025607 A1 WO2015025607 A1 WO 2015025607A1
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- protective film
- polarizer protective
- roll
- thermoplastic resin
- pattern
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
- G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
- G02B5/0221—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures the surface having an irregular structure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/001—Combinations of extrusion moulding with other shaping operations
- B29C48/002—Combinations of extrusion moulding with other shaping operations combined with surface shaping
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
- G02B6/0013—Means for improving the coupling-in of light from the light source into the light guide
- G02B6/0023—Means for improving the coupling-in of light from the light source into the light guide provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
- G02B6/0025—Diffusing sheet or layer; Prismatic sheet or layer
Definitions
- the present invention relates to a method for producing a polarizer protective film having a light diffusion function, and a polarizer protective film obtained using the production method.
- Liquid crystal display devices are often used as display devices for various electronic devices. In recent years, such electronic devices have been increasingly reduced in size, and liquid crystal display devices are also required to be reduced in size and weight.
- the polarizer protective film for protecting the polarizer is provided with a light diffusing layer, whereby an attempt has been made to combine the conventionally used polarizer protective film and the diffusing film into one film,
- Patent Document 1 discloses a technique for imparting a light diffusing function to a polarizer protective film by dispersing light diffusing particles made of an acrylic polymer in an acrylic thermoplastic resin.
- the polarizer protective film having a light diffusing function obtained in Patent Document 1 is obtained by dispersing light diffusing particles in an acrylic thermoplastic resin. Therefore, when the film is incorporated in a liquid crystal display device. In addition, there is a problem that the light diffusing particles fall off and are mixed as foreign matter, and a defect is generated on the display device due to the influence of the mixed foreign matter. In addition, the film obtained in Patent Document 1 has low durability and poor strength due to the effect of containing light diffusing particles.
- An object of the present invention is to provide a polarizer protective film having excellent optical characteristics, high durability and strength, and high reliability and having a light diffusion function.
- the inventors of the present invention melt-extruded a thermoplastic resin from a molding die to form a sheet, and the obtained sheet-shaped thermoplastic resin is narrowly pressed by a first roll having a concavo-convex pattern on the surface and a second roll.
- a first roll having a concavo-convex pattern on the surface and a second roll the inventors have found that the above object can be achieved by a film obtained by forming an uneven pattern on one surface, and have completed the present invention.
- the step of melt-extruding a thermoplastic resin from a molding die into a sheet shape, the melt-extruded sheet-shaped thermoplastic resin, a first roll having an uneven pattern on the surface A method of producing a polarizer protective film having a light diffusion function, comprising: a step of forming a concavo-convex pattern on one surface by narrowing with two rolls.
- the temperature of the first roll is preferably in the range of (Tg ⁇ 40) to (Tg + 20) ° C. with respect to the glass transition temperature Tg of the thermoplastic resin.
- the temperature of the second roll is preferably in the range of (Tg-50) to Tg ° C. with respect to the glass transition temperature Tg of the thermoplastic resin.
- corrugated pattern formed in the surface of the said 1st roll is a random pattern.
- the manufacturing method of the present invention further includes a step of stretching the sheet-like thermoplastic resin on which the uneven pattern is formed.
- the polarizer protective film obtained by one of the said methods is provided.
- the polarizer protective film of the present invention preferably has a haze value of 50% or more.
- the polarizer protective film of the present invention preferably has a maximum surface roughness Rmax of 20 ⁇ m or less on the surface on which the concavo-convex pattern is formed.
- the present invention it is possible to provide a polarizer protective film having excellent optical characteristics, high durability and strength, high reliability, and a light diffusion function.
- the light diffusing particles are not used as in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 2011-27777). Therefore, the light diffusing particles are incorporated into an electronic component such as a liquid crystal display device. May fall off and may be mixed in as a foreign substance, so that the quality of electronic components such as a liquid crystal display device can be improved.
- the polarizer protective film obtained by the present invention has a light diffusing function, and also acts as a diffusing film. Therefore, by using the polarizer protective film obtained by the present invention, a liquid crystal display device, etc. Electronic components can be miniaturized.
- FIG. 1 is a diagram showing an example of a liquid crystal display device to which the light diffusing polarizer protective film of the present invention is applied.
- FIG. 2 is a diagram illustrating an example of a liquid crystal display device according to a conventional example.
- FIG. 3 is a view for explaining the method for producing the polarizer protective film of the present invention.
- FIG. 4 is a diagram for explaining a method of measuring the front luminance and the viewing angle in the embodiment.
- FIG. 5 is a diagram illustrating measurement results of front luminance and viewing angle in the example.
- FIG. 6 is a diagram showing measurement results of front luminance and viewing angle in the example.
- FIG. 1 is a diagram showing an example of a liquid crystal display device to which the light diffusing polarizer protective film of the present invention is applied.
- the liquid crystal display device 1 according to the present invention includes a liquid crystal panel 100 and a backlight unit 200.
- the liquid crystal panel 100 includes a first polarizing plate 18 in which a polarizer 12 is sandwiched between a light diffusing polarizer protective film 11 and a polarizer protective film 13 of the present invention. And a liquid crystal cell 14 and a second polarizing plate 19 in which a polarizer 16 is sandwiched between a pair of polarizer protective films 15 and 17, and the first polarizing plate 18, the liquid crystal cell 14, and the second polarizing plate.
- the plate 19 is configured by laminating in this order.
- the backlight unit 200 includes a light guide plate 21, a diffusion film 22, and light collecting films 23 and 24, and is configured by laminating them in this order.
- the liquid crystal display device 1 is formed by laminating the liquid crystal panel 100 having such a configuration and the backlight unit 200 with each other.
- the light diffusing polarizer protective film 11 of the present invention is a film manufactured by the manufacturing method of the present invention described later, and includes a concavo-convex surface 11a and a smooth surface 11b, for protecting the polarizer 12.
- the film functions as a diffusion film for diffusing light.
- the light diffusing polarizer protective film 11 of the present invention is laminated with the condensing film 24 via the uneven surface 11a, and on the other hand, with the polarizer 12 via the smooth surface 11b. Laminated.
- FIG. 2 is a diagram showing an example of a liquid crystal display device according to a conventional example.
- the liquid crystal display device 1a according to the conventional example includes a liquid crystal panel 100a and a backlight unit 200a.
- the liquid crystal panel 100a includes a polarizer protective film 110, a polarizer protective film 13, and the like.
- the first polarizing plate 180, the liquid crystal cell 14, and the second polarizing plate 19 are stacked in this order.
- the backlight unit 200a includes a light guide plate 21, a diffusion film 22, light collecting films 23 and 24, and a diffusion film 25, and is configured by laminating these in this order.
- the liquid crystal display device 1 according to the present invention shown in FIG. 1 does not have the diffusion film 25 on the condensing film 24 as compared with the liquid crystal display device 1a according to the conventional example shown in FIG.
- the light diffusion polarizer protective film 11 of the present invention having the functions of two films of the diffusion film and the polarizer protective film is used.
- the light diffusing polarizer protective film 11 of the present invention since it has a light diffusing function in addition to the polarizer protecting function, it is compared with the liquid crystal display device 1a according to the conventional example shown in FIG.
- the diffusion film 25 can be omitted, and thus the liquid crystal display device can be miniaturized.
- FIG. 3 is a figure for demonstrating the manufacturing method of the light-diffusion polarizer protective film 11 of this invention.
- the light diffusing polarizer protective film 11 of the present invention is a sheet from the extrusion T-die 30 in a state where the thermoplastic resin that constitutes the light diffusing polarizer protective film 11 is heated and melted.
- the sheet-like thermoplastic resin 11c is melt-extruded into a shape, and the sheet-like thermoplastic resin 11c is narrowed by the shaping roll 40 and the nip roll 50, thereby being manufactured.
- thermoplastic resin as the material of the light diffusing polarizer protective film 11 is not particularly limited, but a transparent amorphous resin having a glass transition temperature Tg of 100 ° C. or higher is preferable.
- thermoplastic resin include acrylic resin, polycarbonate resin, acrylic modified polycarbonate resin, and cyclic olefin resin.
- crystalline resins such as polyethylene terephthalate and polybutylene terephthalate can be used.
- the melt extruder used for melt extrusion of the thermoplastic resin is not particularly limited, and any of a single screw extruder and a twin screw extruder can be used.
- a thermoplastic resin is supplied to a melt extruder such as a single screw extruder or a twin screw extruder and melted at a temperature equal to or higher than the glass transition temperature Tg, and then connected to the melt extruder.
- the extruded thermoplastic resin is melt-extruded into a sheet form from the extrusion T-die 30. Then, the melt-extruded sheet-like thermoplastic resin 11c is narrowed by the shaping roll 40 and the nip roll 50 as shown in FIG.
- the shaping roll 40 is a rigid roll having a concavo-convex pattern on its surface. As shown in FIG. 3, the shaping roll 40 rotates in the direction of the arrow shown in FIG. The thermoplastic resin 11c is narrowed. When the sheet-like thermoplastic resin 11c is narrowed, the concave / convex pattern formed on the surface of the shaping roll 40 is transferred to the thermoplastic resin 11c, whereby the concave / convex pattern is formed on the surface of the thermoplastic resin 11c. Will be formed.
- the shaping roll 40 for example, a surface of a metal roll having a concavo-convex pattern formed by sandblasting, electric discharge machining, etching, or the like can be used.
- the uneven pattern formed on the surface of the shaping roll 40 is a random pattern from the viewpoint that the light diffusing function of the obtained light diffusing polarizer protective film 11 can be improved. It is preferable that For example, by using sandblasting, electric discharge machining, etching, or the like as a surface processing method for forming a concave / convex pattern when forming the shaping roll 40, the formed concave / convex pattern can be a random pattern.
- the uneven pattern formed on the surface of the shaping roll 40 has a maximum surface roughness Rmax of preferably 20 ⁇ m or less, more preferably 15 ⁇ m or less, still more preferably 2 to 10 ⁇ m, particularly preferably 5 to 8 ⁇ m.
- the center line average roughness Ra is preferably 0.1 to 2.0 ⁇ m, more preferably 0.2 to 1.5 ⁇ m, and still more preferably 0.5 to 1.0 ⁇ m.
- the maximum surface roughness Rmax, The center line average roughness Ra can be within the above range.
- the nip roll 50 is not particularly limited and may be either a rubber roll or a metal roll, but the surface thereof is preferably a mirror surface or a grain. In addition, when the surface of the nip roll 50 is grainy, it is sufficient that the surface of the nip roll 50 can be determined to be substantially flat without being uneven. For example, the center line average roughness Ra is 0.4 ⁇ m or less. It is preferable that
- the temperature of the shaping roll 40 is the glass transition temperature of the sheet-like thermoplastic resin 11c.
- the Tg is preferably in the range of (Tg ⁇ 40) to (Tg + 20) ° C., and more preferably in the range of (Tg ⁇ 10) to (Tg + 10) ° C.
- the temperature of the nip roll 50 is not particularly limited, but is preferably in the range of (Tg-50) to Tg ° C. with respect to the glass transition temperature Tg of the sheet-like thermoplastic resin 11c, (Tg-30) It is more preferable that the temperature be in the range of (Tg-10) ° C.
- the temperature of the nip roll 50 is preferably in the above temperature range and lower than the temperature of the shaping roll 40. By setting the temperature of the nip roll 50 within the above range, it is possible to further improve the transfer accuracy of the uneven pattern formed on the surface of the shaping roll 40 with respect to the sheet-like thermoplastic resin 11c.
- the narrow pressure load when the sheet-shaped thermoplastic resin 11c is narrowed by the shaping roll 40 and the nip roll 50 is not particularly limited, but the transfer accuracy of the concavo-convex pattern formed on the surface of the shaping roll 40 is not limited.
- a rubber roll it is preferably 0.5 kg / mm or more, more preferably 4 to 20 kg / mm, still more preferably 8 to 10 kg / mm.
- a metal roll is used, it is preferably 0.5 kg / mm or more, more preferably 10 to 100 kg / mm, still more preferably 40 to 50 kg / mm.
- the temperature condition of the sheet-shaped thermoplastic resin 11c when the sheet-shaped thermoplastic resin 11c is extruded and melted from the extrusion T die 30 is not particularly limited, but is just before contacting the shaping roll 40.
- the temperature is preferably in the range of 150 to 250 ° C., and more preferably in the range of 180 to 220 ° C.
- the temperature immediately before contacting the shaping roll 40 of the sheet-like thermoplastic resin 11c is within the above range, so that the thermoplastic resin 11c is immediately after contacting the shaping roll 40 and the nip roll 50.
- the concavo-convex pattern can be easily transferred by the shaping roll 40 in a molten state.
- the temperature of the shaping roll 40 and the nip roll 50 is set within the above range, so that after the concavo-convex pattern is transferred by the shaping roll 40, the thermoplastic resin 11c becomes the shaping roll 40. Then, it is cooled and solidified by the nip roll 50, whereby the transferred uneven pattern can be maintained well.
- the molten thermoplastic resin is melt-extruded into a sheet form from the extrusion T-die 30, and the melt-extruded sheet-like thermoplastic resin is extruded.
- the light diffusion polarizer protective film 11 of the present invention is manufactured.
- the light diffusing polarizer protective film 11 of the present invention thus obtained includes an uneven surface 11 a and a smooth surface 11 b, and the uneven surface 11 a is formed by the shaping roll 40. It is formed by transferring a concavo-convex pattern formed on the surface.
- the smooth surface 11b on the opposite side of the concavo-convex surface 11a is brought into contact with the nip roll 50 when being narrowed by the shaping roll 40 and the nip roll 50, thereby forming a smooth surface without unevenness.
- the uneven surface 11a of the light diffusing polarizer protective film 11 of the present invention thus obtained has an uneven shape with a random pattern, and the maximum surface roughness Rmax of the uneven surface 11a is preferably 20 ⁇ m or less. More preferably, it is 2 to 10 ⁇ m, more preferably 5 to 8 ⁇ m, and the center line average roughness Ra is preferably 0.1 to 2.0 ⁇ m, more preferably 0.2 to 1.5 ⁇ m, still more preferably 0. It is preferably 5 to 1.0 ⁇ m.
- the shaping roll 40 having a random pattern unevenness on the surface and having the maximum surface roughness Rmax and the centerline average roughness Ra in the above-described range is used.
- the uneven surface 11a of the light diffusing polarizer protective film 11 of the present invention thus obtained has a concavo-convex shape of a random pattern, and has a maximum surface roughness Rmax and a center line average roughness.
- Ra can be in the above range, whereby the light diffusing polarizer protective film 11 of the present invention can be excellent in light diffusing function.
- the uneven surface 11a of the diffused polarizer protective film 11 has an uneven shape of a random pattern, thereby effectively preventing an interference pattern when it is incorporated in a liquid crystal display device.
- the center line average roughness Ra of the concavo-convex surface 11a to 2.0 ⁇ m or less, a good image quality with high front luminance and no unevenness can be obtained.
- the light diffusing polarizer protective film 11 of the present invention has a haze value of preferably 50% or more, more preferably 60% or more, from the viewpoint of dot pattern concealment of the light guide plate.
- the haze value of the light diffusing polarizer protective film 11 of the present invention can be controlled, for example, by appropriately adjusting the maximum surface roughness Rmax and the center line average roughness Ra of the uneven surface 11a.
- the light diffusing polarizer protective film 11 has a smooth surface 11b as a surface opposite to the concavo-convex surface 11a, thereby providing a smooth surface 11b as shown in FIG. Due to the smoothness of the polarizer 12, it is possible to appropriately protect the polarizer 12. Furthermore, the light diffusing polarizer protective film 11 of the present invention is a film made of a single material that does not contain other materials such as light diffusing particles as in the technique of Patent Document 1 (Japanese Patent Laid-Open No. 2011-27777). Therefore, material cost and manufacturing cost can be kept low.
- the forming roll obtained in the existing film-forming equipment may be replaced with the predetermined shaping roll of the present invention, and therefore the investment cost for production can be kept low. It becomes possible.
- the light diffusion polarizer protective film 11 of the present invention has the functions of the diffusion film 25 and the photon protective film 110 constituting the liquid crystal display device 1a according to the conventional example shown in FIG. Therefore, compared with the liquid crystal display device 1a according to the conventional example, the diffusion film 25 can be omitted, whereby the manufacturing process when manufacturing the liquid crystal display device can be reduced by one step, and the foreign matter at the time of manufacturing is reduced. The rate of occurrence of defects such as contamination of the liquid crystal can be kept low, thereby improving the quality of the liquid crystal display device as the final product in addition to improving the production efficiency. Further, by omitting the diffusion film 25, it is possible to reduce the size of the liquid crystal display device.
- the light diffusing polarizer protective film 11 obtained by the above method may be subjected to post-processing such as stretching.
- post-processing such as stretching.
- the light diffusing polarizer protective film 11 is stretched, it is preferably (Tg + 10) to (Tg + 20) ° C. with respect to the glass transition temperature Tg of the thermoplastic resin using a conventionally known film stretching apparatus or the like.
- the film is preferably stretched 1.2 to 1.5 times.
- a single screw extruder UST-50, manufactured by Plastic Engineering Laboratory Co., Ltd.
- melt extruder for melt extruding polycarbonate as a thermoplastic resin through a molding die 30.
- the surface of the shaping roll 40 is processed by electric discharge machining, and has a random pattern irregularity shape (textured shape), the maximum surface roughness Rmax is 16 ⁇ m, and the center line average roughness Ra.
- the nip roll 50 a roll with a diameter of 230 mm whose surface was mirror finished was used.
- the temperature of the shaping roll 40 was 135 ° C.
- the temperature of the nip roll 50 was 120 ° C.
- the narrow pressure load when narrowing by these was 4 kg / mm.
- the maximum surface roughness Rmax, centerline average roughness Ra, haze, total light transmittance, front luminance and viewing angle were measured by the following methods.
- the haze of the haze light diffusing polarizer protective film was measured according to JIS K7136 using a turbidimeter (haze meter NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 1.
- Total light transmittance The total light transmittance of the light diffusion polarizer protective film was measured according to JIS K7105 using a turbidimeter (Hazemeter NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 1.
- the front luminance and viewing angle of the light diffusing polarizer protective film were measured by the following method. That is, first, using a light diffusion polarizer protective film, as shown in FIG. 4, the light collecting films 23 and 24, the light diffusion polarizer protective film 11, the polarizer 12, the polarizer protective film 13, the liquid crystal cell 14, A measurement sample 100 was prepared by laminating the polarizer protective film 15, the polarizer 16, and the polarizer protective film 17 in this order. In the measurement sample 100, the contact surface (uneven surface 11a) of the light diffusing polarizer protective film 11 with the shaping roll 40 of the light diffusing polarizer protective film is on the condensing film 24 side and the nip roll 50.
- the contact surface (flat surface 11b) is arranged in a direction facing the polarizer 12 side.
- two condensing films (prism films) 23 and 24 are used in the same manner as in a general liquid crystal display device, and the prisms provided in these are stacked in a state where they are orthogonal to each other. .
- a front surface luminance (90) is obtained using a CCD camera in a state where a diffusion light source is arranged on the light collecting film 23 side and the diffusion light source is irradiated with the diffusion light.
- Example 2 Except having changed the temperature of the shaping roll 40 from 135 degreeC to 145 degreeC, it carried out similarly to Example 1, and obtained the light-diffusion polarizer protective film, About the obtained light-diffusion polarizer protective film similarly Maximum surface roughness Rmax, centerline average roughness Ra, haze, total light transmittance, front luminance and viewing angle were measured. The results are shown in Table 1 and FIG.
- Example 3 A light diffusing polarizer protective film was obtained in the same manner as in Example 2 except that the shaping roll 40 was changed from that having a maximum surface roughness Rmax of 16 ⁇ m to 8 ⁇ m, and the obtained light diffusing polarizer was obtained.
- the maximum surface roughness Rmax, centerline average roughness Ra, haze, total light transmittance, front luminance and viewing angle were measured in the same manner. The results are shown in Table 1 and FIG.
- Example 4 The stretched light diffusing polarizer protective film obtained in Example 2 was stretched 1.5 times in an atmosphere of 155 ° C. to obtain a stretched light diffusing polarizer protective film, and the obtained stretched light diffusing polarizer was obtained.
- front luminance and viewing angle were measured in the same manner. The results are shown in FIG.
- Example 5 The light diffusion polarizer protective film obtained in Example 2 was stretched 1.5 times in an atmosphere of 160 ° C. to obtain a stretched light diffusion polarizer protective film, and the obtained stretched light diffusion polarizer For the protective film, front luminance and viewing angle were measured in the same manner. The results are shown in FIG.
- the light diffusing polarizer protective films of Examples 1 to 3 produced by the production method of the present invention all have a haze of 50% or more, a total light transmittance of 90% or more, and optical properties. It can be confirmed that they are excellent. Furthermore, from the results shown in FIG. 5, all of the light diffusing polarizer protective films of Examples 1 to 5 produced by the production method of the present invention have a high front luminance (90 ° direction luminance) and a viewing angle. It can be confirmed that (luminance in 60 ° direction, 75 ° direction, 105 ° direction, 120 ° direction) is also good. In FIG.
- a bead-coated diffusion plate (haze 93%, about 200 ⁇ m) has an uneven surface facing the light-collecting film 24 and a flat surface facing the polarizer 12 as shown in FIG.
- the measurement results in the case of the above arrangement are also shown as reference data.
- the front luminance and the viewing angles in the 75 ° direction and the 105 ° direction were significantly inferior.
- the light diffusing polarizer protective film obtained by the production method of the present invention is excellent in optical characteristics and can be favorably applied to a liquid crystal display device.
- Example 7 A light diffusing polarizer protective film was obtained in the same manner as in Example 6 except that the shaping roll 40 was changed from that having a maximum surface roughness Rmax of 16 ⁇ m to 8 ⁇ m, and the obtained light diffusing polarizer was obtained.
- the maximum surface roughness Rmax, centerline average roughness Ra, haze, total light transmittance, front luminance and viewing angle were measured in the same manner. The results are shown in Table 2 and FIG.
- the obtained light diffusing polarizer protective film was similarly measured for maximum surface roughness Rmax, centerline average roughness Ra, haze, total light transmittance, front luminance and viewing angle. The results are shown in Table 2 and FIG.
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Abstract
Description
本発明の製造方法において、前記熱可塑性樹脂のガラス転移温度Tgに対して、前記第2ロールの温度を、(Tg-50)~Tg℃の範囲とすることが好ましい。
また、本発明の製造方法において、前記第1ロールの表面に形成された凹凸パターンがランダムパターンであることが好ましい。
さらに、本発明の製造方法は、凹凸パターンを形成した前記シート状の熱可塑性樹脂を延伸する工程をさらに備えることが好ましい。
本発明の偏光子保護フィルムは、ヘイズ値が50%以上であることが好ましい。
本発明の偏光子保護フィルムは、凹凸パターンが形成されている面の最大表面粗さRmaxが20μm以下であることが好ましい。
図1は、本発明の光拡散偏光子保護フィルムが適用される液晶表示装置の一例を示す図である。図1に示すように、本発明に係る液晶表示装置1は、液晶パネル100と、バックライトユニット200とからなるものである。
熱可塑性樹脂として、ポリカーボネート(カリバー(登録商標)、301-10、住化スタイロン ポリカーボネイト(株)製、ガラス転移温度Tg=149℃)を準備し、準備したポリカーボネートを用いて、図3に示す成形用ダイ30、賦形ロール40、およびニップロール50を備えてなる製造設備を用いて、幅300mm、厚さ135μmの光拡散偏光子保護フィルムの製造を行なった。本実施例においては、成形用ダイ30を介して、熱可塑性樹脂としてのポリカーボネートを溶融押出するための溶融押出機として、単軸押出機(UST-50、(株)プラスチック工学研究所製)を用いた。また、本実施例においては、賦形ロール40として、その表面が放電加工により加工され、ランダムパターンの凹凸形状(梨地形状)を有し、最大表面粗さRmaxが16μm、中心線平均粗さRaが1μmである直径250mmのロールを、ニップロール50として、表面が鏡面仕上げ加工された直径230mmのロールをそれぞれ用いた。なお、本実施例では、賦形ロール40の温度を135℃、ニップロール50の温度を120℃とし、これらにより狭圧する際の狭圧荷重を4kg/mmとした。
触針式表面粗さ計(サーフコム1500A、東京精密(株)製)により、光拡散偏光子保護フィルムの賦形ロール40との接触面(凹凸面11a)について、最大表面粗さRmax、および中心線平均粗さRaの測定を行なった。結果を表1に示す。
光拡散偏光子保護フィルムのヘイズを、濁度計(ヘイズメーター NDH2000、日本電色工業(株)製)を用いて、JIS K7136に準拠して測定した。結果を表1に示す。
光拡散偏光子保護フィルムの全光線透過率を、濁度計(ヘイズメーター NDH2000、日本電色工業(株)製)を用いて、JIS K7105に準拠して測定した。結果を表1に示す。
光拡散偏光子保護フィルムの正面輝度および視野角の測定は、次の方法により行なった。
すなわち、まず、光拡散偏光子保護フィルムを用いて、図4に示すように、集光フィルム23,24、光拡散偏光子保護フィルム11、偏光子12、偏光子保護フィルム13、液晶セル14、偏光子保護フィルム15、偏光子16、および偏光子保護フィルム17を、この順に積層してなる測定用サンプル100を作製した。なお、測定用サンプル100においては、光拡散偏光子保護フィルム11を、光拡散偏光子保護フィルムの賦形ロール40との接触面(凹凸面11a)が、集光フィルム24側に、ニップロール50との接触面(平坦面11b)が、偏光子12側に向くような方向に配置した。また、測定用サンプル100においては、一般的な液晶表示装置と同様に2枚の集光フィルム(プリズムフィルム)23,24を用い、これらに備えられたプリズムの山を直交させた状態で重ねた。
そして、このような測定用サンプル100に対して、集光フィルム23側に、拡散光源を配置し、拡散光源により拡散光の照射を行なった状態にて、CCDカメラを用いて、正面輝度(90°方向の輝度)の測定、および視野角(60°方向、75°方向、105°方向、120°方向の輝度)の測定を行なった。得られた結果を図5に示す。なお、図5においては、光拡散偏光子保護フィルム11を使用しない場合をリファレンスとし、リファレンスに対する輝度比をプロットして示した(後述する図6についても同様。)。
賦形ロール40の温度を135℃から145℃に変更した以外は、実施例1と同様にして、光拡散偏光子保護フィルムを得て、得られた光拡散偏光子保護フィルムについて、同様にして、最大表面粗さRmax、中心線平均粗さRa、ヘイズ、全光線透過率、正面輝度および視野角の測定を行なった。結果を表1および図5に示す。
賦形ロール40を、最大表面粗さRmaxが16μmのものから8μmのものに変更した以外は、実施例2と同様にして、光拡散偏光子保護フィルムを得て、得られた光拡散偏光子保護フィルムについて、同様にして、最大表面粗さRmax、中心線平均粗さRa、ヘイズ、全光線透過率、正面輝度および視野角の測定を行なった。結果を表1および図5に示す。
実施例2で得られた光拡散偏光子保護フィルムを、155℃の雰囲気で、1.5倍に延伸することにより、延伸光拡散偏光子保護フィルムを得て、得られた延伸光拡散偏光子保護フィルムについて、同様にして、正面輝度および視野角の測定を行なった。結果を図5に示す。
実施例2で得られた光拡散偏光子保護フィルムを、160℃の雰囲気で、1.5倍に延伸することにより、延伸光拡散偏光子保護フィルムを得て、得られた延伸光拡散偏光子保護フィルムについて、同様にして、正面輝度および視野角の測定を行なった。結果を図5に示す。
表1に示す結果より、本発明の製造方法により製造した実施例1~3の光拡散偏光子保護フィルムは、いずれもヘイズが50%以上、全光線透過率が90%以上であり、光学特性に優れるものであることが確認できる。さらに、図5に示す結果より、本発明の製造方法により製造した実施例1~5の光拡散偏光子保護フィルムは、いずれも、正面輝度(90°方向の輝度)が高く、また、視野角(60°方向、75°方向、105°方向、120°方向の輝度)も良好であることが確認できる。なお、図5中においては、ビーズ塗布型の拡散板(ヘイズ93%、約200μm)を、図4に示すように、凹凸面が集光フィルム24側に、平坦面が偏光子12側に向くように配置した場合における、測定結果も参考データとして併せて示しており、ビーズ塗布型の拡散板においては、正面輝度、および75°方向、105°方向における視野角に著しく劣る結果となった。
熱可塑性樹脂として、ポリカーボネートの代わりに、アクリル変性ポリカーボネート樹脂(MB6001UR、三菱エンジニアリングプラスチックス(株)製、ガラス転移温度Tg=105℃)を用いた以外は、実施例1と同様にして、光拡散偏光子保護フィルムを得て、得られた光拡散偏光子保護フィルムについて、同様にして、最大表面粗さRmax、中心線平均粗さRa、ヘイズ、全光線透過率、正面輝度および視野角の測定を行なった。結果を表2および図6に示す。
賦形ロール40を、最大表面粗さRmaxが16μmのものから8μmのものに変更した以外は、実施例6と同様にして、光拡散偏光子保護フィルムを得て、得られた光拡散偏光子保護フィルムについて、同様にして、最大表面粗さRmax、中心線平均粗さRa、ヘイズ、全光線透過率、正面輝度および視野角の測定を行なった。結果を表2および図6に示す。
熱可塑性樹脂として、ポリカーボネートの代わりに、ポリエチレンテレフタレート(TR3000H、帝人(株)製、ガラス転移温度Tg=75℃)を用いた以外は、実施例1と同様にして、光拡散偏光子保護フィルムを得て、得られた光拡散偏光子保護フィルムについて、同様にして、最大表面粗さRmax、中心線平均粗さRa、ヘイズ、全光線透過率、正面輝度および視野角の測定を行なった。結果を表2および図6に示す。
表2に示す結果より、熱可塑性樹脂として、ポリカーボネートの代わりに、アクリル変性ポリカーボネート樹脂、ポリエチレンテレフタレートを用いた場合でも、得られる光拡散偏光子保護フィルムは、いずれもヘイズが50%以上、全光線透過率が90%以上であり、光学特性に優れるものであることが確認できる。さらに、図6に示す結果より、得られる光拡散偏光子保護フィルムは、いずれも、正面輝度(90°方向の輝度)が高く、また、視野角(60°方向、75°方向、105°方向、120°方向の輝度)も良好であることが確認できる。なお、図6においても、図5と同様に、ビーズ塗布型の拡散板の測定結果を参考データとして併せて示した。
11a…凹凸面
11b…平坦面
11c…熱可塑性樹脂
30…押出用Tダイ
40…賦形ロール
50…ニップロール
Claims (10)
- 熱可塑性樹脂を成形用ダイからシート状に溶融押出しする押出工程と、
溶融押出しされた前記シート状の熱可塑性樹脂を、表面に凹凸パターンを有する第1ロールと、第2ロールとにより狭圧し、一方の面に凹凸パターンを形成するパターン形成工程と、を備えることを特徴とする光拡散機能を有する偏光子保護フィルムの製造方法。 - 前記熱可塑性樹脂のガラス転移温度Tgに対して、前記第1ロールの温度を、(Tg-40)~(Tg+20)℃の範囲とすることを特徴とする請求項1に記載の偏光子保護フィルムの製造方法。
- 前記熱可塑性樹脂のガラス転移温度Tgに対して、前記第2ロールの温度を、(Tg-50)~Tg℃の範囲とすることを特徴とする請求項1または2に記載の偏光子保護フィルムの製造方法。
- 前記第1ロールの表面に形成された凹凸パターンがランダムパターンであることを特徴とする請求項1~3のいずれかに記載の偏光子保護フィルムの製造方法。
- 前記パターン形成工程において、前記第1ロールとして、最大表面粗さRmaxが所定の範囲にあるロールを用いることで、前記パターン形成工程後における、前記シート状の熱可塑性樹脂の凹凸パターンが形成されている面の最大表面粗さRmaxを20μm以下とする請求項1~4のいずれかに記載の偏光子保護フィルムの製造方法。
- 前記パターン形成工程において、前記第1ロールとして、最大表面粗さRmax及び中心線平均粗さRaがそれぞれ所定の範囲にあるロールを用いることで、前記パターン形成工程後におけるヘイズ値を50%以上とする請求項1~5のいずれかに記載の偏光子保護フィルムの製造方法。
- 凹凸パターンを形成した前記シート状の熱可塑性樹脂を延伸する工程をさらに備えることを特徴とする請求項1~6のいずれかに記載の偏光子保護フィルムの製造方法。
- 請求項1~7のいずれかに記載の方法により得られることを特徴とする偏光子保護フィルム。
- ヘイズ値が50%以上であることを特徴とする請求項8に記載の偏光子保護フィルム。
- 凹凸パターンが形成されている面の最大表面粗さRmaxが20μm以下であることを特徴とする請求項8または9に記載の偏光子保護フィルム。
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