KR20160046844A - Method for producing polarizer protective film, and polarizer protective film - Google Patents

Abstract

Extruding the thermoplastic resin 11c into a sheet form from the molding die 30 and melt extruding the melt extruded sheet thermoplastic resin 11c into a first roll 40 having an uneven pattern on its surface, And a step of forming a convexo-concave pattern on one side by pressing the second roll (50) between the first roll (50) and the second roll (50). In the production method of the present invention, the temperature of the first roll 40 is set to be in the range of (Tg-40) to (Tg + 20) ° C with respect to the glass transition temperature Tg of the thermoplastic resin 11c .

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizer protective film and a polarizer protective film,

The present invention relates to a method for producing a polarizer protective film having a light diffusion function and a polarizer protective film obtained by using the method.

2. Description of the Related Art Liquid crystal display devices are widely used as display devices for various electronic apparatuses. In recent years, such electronic devices have been further downsized, and liquid crystal display devices are also required to be smaller and lighter.

In order to obtain desired optical characteristics, various functional films such as a polarizer protective film, a diffusion film, and a light condensing film for protecting the polarizer are used in such a liquid crystal display device. In order to meet the recent demand for miniaturization, It is attempted to use a thin film having a plurality of functions as a functional film.

For example, attempts have been made to use a conventionally used polarizer protective film and a diffusion film as a single film by providing a light diffusion layer on a polarizer protective film for protecting a polarizer. For example, Patent Document 1 discloses an acrylic thermoplastic Discloses a technique for causing a polarizer protective film to have a light diffusion function by dispersing light diffusing particles composed of an acrylic polymer in a resin.

However, since the polarizer protective film having the light diffusion function obtained in Patent Document 1 is formed by dispersing light diffusion particles in an acrylic thermoplastic resin, when the film is applied to a liquid crystal display device, the light diffusion particles fall off, There has been a problem in that defects are generated on the display device due to the influence of foreign substances mixed therein. Further, the film obtained in Patent Document 1 contains light-diffusing particles, and the durability of the film itself is low due to the influence thereof, and the strength is also low.

Patent Document 1: JP-A-2011-27777

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 present inventors have found that when a thermoplastic resin is melt-extruded from a molding die to form a sheet, and the resulting sheet-shaped thermoplastic resin is pressed between a first roll having a concavo-convex pattern on its surface and a second roll, The above object can be achieved by a film obtained by forming a concavo-convex pattern, and the present invention has been accomplished.

That is, according to the present invention, there is provided a process for producing a thermoplastic resin sheet, comprising: a step of melt-extruding a thermoplastic resin from a molding die into a sheet form; a step of melt-extruding the thermoplastic resin in sheet form onto a first roll having a concavo- And forming a concavo-convex pattern on one surface of the polarizer protective film, wherein the polarizer protective film has a light diffusion function.

In the production process of the present invention, it is preferable that the temperature of the first roll is in the range of (Tg-40) to (Tg + 20) ° C, relative to the glass transition temperature (Tg) of the thermoplastic resin.

In the production method of the present invention, it is preferable that the temperature of the second roll is in the range of (Tg-50) to Tg ° C relative to the glass transition temperature (Tg) of the thermoplastic resin.

In the manufacturing method of the present invention, it is preferable that the concavo-convex pattern formed on the surface of the first roll is a random pattern.

Further, it is preferable that the manufacturing method of the present invention further comprises a step of stretching the sheet-like thermoplastic resin on which the concavo-convex pattern is formed.

Further, according to the present invention, there is provided a polarizer protective film obtained by any one of the above-described methods.

The polarizer protective film of the present invention preferably has a haze value of 50% or more.

In the polarizer protective film of the present invention, it is preferable that the maximum surface roughness (Rmax) of the surface on which the concavo-convex pattern is formed is 20 m or less.

According to 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. Particularly, according to the present invention, since light diffusion particles are not used as in the above-described Patent Document 1 (Japanese Patent Laid-Open Publication No. 2011-27777), when applied to electronic parts such as liquid crystal displays, There is no risk of falling out and being mixed as a foreign substance, thereby improving the quality of an electronic component such as a liquid crystal display device. Further, since the polarizer protective film obtained by the present invention has a light diffusion function and also functions as a diffusion film, the use of the polarizer protective film obtained by the present invention makes it possible to miniaturize electronic parts such as liquid crystal display devices.

1 is a view showing an example of a liquid crystal display device to which the optical diffusion polarizer protective film of the present invention is applied.
2 is a view showing an example of a liquid crystal display device according to a conventional example.
Fig. 3 is a view for explaining the method of producing the polarizer protective film of the present invention.
4 is a view for explaining a method of measuring the front luminance and the viewing angle in the embodiment.
5 is a diagram showing measurement results of the front luminance and the viewing angle in the embodiment.
6 is a diagram showing measurement results of the front luminance and the viewing angle in the embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a view showing an example of a liquid crystal display device to which the optical diffusion polarizer protective film of the present invention is applied. 1, a liquid crystal display device 1 according to the present invention is composed of a liquid crystal panel 100 and a backlight unit 200.

Specifically, as shown in Fig. 1, the liquid crystal panel 100 includes a first polarizing plate (first polarizing plate) 11 made of a polarizing plate 12 sandwiched between the optical diffusion polarizing protective film 11 of the present invention and the polarizing protective film 13 And a polarizer 16 sandwiched between the pair of polarizer protective films 15 and 17. The first polarizer plate 18 and the second polarizer plate 18 are bonded to each other, The liquid crystal cell 14, and the second polarizing plate 19 in this order.

The backlight unit 200 includes a light guide plate 21, a diffusion film 22, and light collecting films 23 and 24, which are stacked in order.

The liquid crystal display device 1 according to the present invention is formed by laminating the liquid crystal panel 100 and the backlight unit 200 having the above-described structure.

Here, the optical diffusion polarizer protective film 11 of the present invention is a film produced by the manufacturing method of the present invention to be described later and has an uneven surface 11a and a smooth surface 11b and protects the polarizer 12 And also serves as a diffusion film for diffusing light. As shown in Fig. 1, the optical diffusion polarizer protective film 11 of the present invention is laminated with the light-converging film 24 by opening the uneven surface 11a, and on the other side, the smooth surface 11b is opened, (12).

2 is a diagram showing an example of a liquid crystal display device according to a conventional example. 2, the liquid crystal display device 1a according to the related art includes a liquid crystal panel 100a and a backlight unit 200a. The liquid crystal panel 100a includes a polarizer protective film 110, A liquid crystal cell 14 and a pair of polarizer protective films 15 and 17 in which a polarizer 16 is sandwiched between a pair of polarizer protective films 15 and 17, 2 polarizing plate 19, and these first polarizing plates 180, the liquid crystal cell 14 and the second polarizing plate 19 are laminated 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, which are stacked in order.

Here, the liquid crystal display device 1 according to the present invention shown in Fig. 1 is different from the liquid crystal display device 1a according to the conventional example shown in Fig. 2 in that the diffusion film 25 is not provided on the light converging film 24 , And the optical diffusion polarizer protective film 11 of the present invention having the function of two films of a diffusion film and a polarizer protective film is used instead of the polarizer protective film 110 as described above. As described above, according to the optical diffusion polarizer protective film 11 of the present invention, since it has a light diffusion function in addition to the polarizer protecting function, the diffusion film (a) can be obtained as compared with the liquid crystal display device 1a according to the conventional example shown in Fig. 25) can be omitted, thereby making it possible to miniaturize the liquid crystal display device.

Hereinafter, a method of manufacturing the optical diffusion polarizer protective film 11 of the present invention will be described in detail. Here, FIG. 3 is a view for explaining the method of manufacturing the optical diffusion polarizer protective film 11 of the present invention.

As shown in Fig. 3, the optical diffusion polarizer protective film 11 of the present invention is a film obtained by removing the thermoplastic resin constituting the optical diffusion polarizer protective film 11 from the T die for extrusion 30, Extruded and extruded and a thermoplastic resin 11c in the form of a sheet is pressed between a shaping roll 40 and a nip roll 50. [

The thermoplastic resin as the material of the optical diffusion polarizer protective film 11 is not particularly limited, but a transparent amorphous resin having a glass transition temperature (Tg) of 100 캜 or more is preferable. Specific examples of the thermoplastic resin include, for example, acrylic resin, polycarbonate resin, acrylic modified polycarbonate resin, and cyclic olefin resin. In addition, a crystalline resin such as polyethylene terephthalate or polybutylene terephthalate may be used.

The melt extruder used when melt-extruding the thermoplastic resin is not particularly limited and both a single screw extruder and a twin screw extruder can be used. In the present embodiment, a thermoplastic resin is fed to a melt extruder such as a single-screw extruder or a twin-screw extruder, melted at a temperature higher than the glass transition temperature (Tg), and then melted from the extruding T die 30 connected to the melt extruder Is melt-extruded into a sheet form. Then, the melt-extruded sheet-like thermoplastic resin 11c is pressed between the roll 40 and the nip roll 50 as shown in Fig.

The forming roll 40 is a rigid roll having a concavo-convex pattern on the surface thereof. As shown in Fig. 3, the forming roll 40 is rotated in the direction of the arrow shown in Fig. 3 together with the nip roll 50 to form a melt- The resin 11c is pressed. When the sheet-like thermoplastic resin 11c is pressed, the concavo-convex pattern formed on the surface of the roll 40 is transferred to the thermoplastic resin 11c, so that a concave-convex pattern is formed on the surface of the thermoplastic resin 11c . As the forming roll 40, for example, a roll surface of metal may be formed by forming an uneven pattern by sandblasting, electric discharge machining, etching, or the like.

On the other hand, in the present invention, it is preferable that the concavo-convex pattern formed on the surface of the shaping roll 40 is a random pattern from the viewpoint that the light diffusion function of the resulting light diffusion polarizer protective film 11 can be improved . For example, in the production of the parting roll 40, by using sand blasting, electric discharge machining, etching, or the like as the surface processing method of forming the concave-convex pattern, the concavo-convex pattern to be formed can be a random pattern.

The concavo-convex pattern formed on the surface of the roll 40 has a maximum surface roughness Rmax of preferably 20 占 퐉 or less, more preferably 15 占 퐉 or less, still more preferably 2 to 10 占 퐉, Is 5 to 8 占 퐉, and the center line average roughness (Ra) is preferably 0.1 to 2.0 占 퐉, more preferably 0.2 to 1.5 占 퐉, and still more preferably 0.5 to 1.0 占 퐉. By setting the maximum surface roughness (Rmax) and the center line average roughness (Ra) within the above range, the light diffusion function of the resulting light diffusion polarizer protective film (11) can be improved. For example, at the time of manufacturing the shaping roll 40, these processing conditions are suitably set by using sand blasting, electric discharge machining, etching, or the like in the surface processing method of forming the concavo-convex pattern to obtain the maximum surface roughness Rmax, (Ra) can be set in the above range.

The nip roll 50 is not particularly limited, and any of rolls made of rubber or rolls made of metal may be used, but the surface thereof is preferably a mirror surface or a matte surface. On the other hand, in the case where the surface of the nip roll 50 is a matte surface, there is no irregularity and it may be determined to be a substantially flat surface. For example, the center line average roughness Ra is preferably 0.4 m or less.

The conditions under which the sheet-shaped thermoplastic resin 11c is pressed between the roll 40 and the nip roll 50 are not particularly limited, but the temperature of the roll 40 may be controlled by changing the temperature of the sheet- (Tg-10) to (Tg + 10) deg. C with respect to the glass transition temperature (Tg) of the glass transition temperature (Tg) More preferable. By setting the temperature of the shaping roll 40 to the above-mentioned range, it is possible to transfer the concave-convex pattern formed on the surface of the shaping roll 40 to the sheet-like thermoplastic resin 11c well, The concavo-convex pattern formed on the film 11 can be appropriately controlled.

The temperature of the nip roll 50 is not particularly limited, but is preferably in the range of (Tg-50) to Tg 占 폚 with respect to the glass transition temperature (Tg) of the sheet-like thermoplastic resin 11c, -30) to (Tg-10) 占 폚. Further, it is preferable that the temperature of the nip roll 50 is set to a temperature lower than the temperature of the roll 40 in the above temperature range. By setting the temperature of the nip roll 50 within the above range, it is possible to further increase the transfer accuracy of the sheet-shaped thermoplastic resin 11c of the concavo-convex pattern formed on the surface of the roll 40.

The pressing load when the sheet-shaped thermoplastic resin 11c is pressed between the forming roll 40 and the nip roll 50 is not particularly limited. However, the pressing load when the sheet-like thermoplastic resin 11c is pressed between the forming roll 40 and the nip roll 50 is not particularly limited, In the case of using a rubber roll, it is preferably 0.5 kg / mm or more, more preferably 4 to 20 kg / mm, even more preferably 8 to 10 kg / mm, from the viewpoint that the transfer precision can be further increased , And when the metal roll is used, it is preferably 0.5 kg / mm or more, more preferably 10 to 100 kg / mm, and further preferably 40 to 50 kg / mm.

On the other hand, the temperature condition of the sheet-shaped thermoplastic resin 11c at the time of extrusion-melting the sheet-like thermoplastic resin 11c from the extrusion T die 30 is not particularly limited, The immediately preceding temperature is preferably in the range of 150 to 250 캜, and more preferably in the range of 180 to 220 캜.

Particularly, in the present invention, by setting the temperature immediately before the sheet-shaped thermoplastic resin 11c comes into contact with the forming roll 40 to fall within the above range, immediately after the forming roll 40 and the nip roll 50 come into contact with the thermoplastic resin 11c, The convexo-concave pattern can be easily transferred by the shaping roll 40 by making the convex portion 11c molten. In addition, in the present invention, by setting the temperatures of the roll 40 and the nip roll 50 within the above range, the thermoplastic resin 11c is transferred to the roll 40 after the transfer of the roughened pattern by the roll 40, And the nip roll 50 to be solidified, thereby making it possible to keep the transferred uneven pattern well.

3, the thermoplastic resin in a molten state is melt-extruded from the extrusion-use T-die 30 into a sheet form, and the melt-extruded sheet-like thermoplastic resin ( 11c are pressed between the roll roll 40 and the nip roll 50 to produce the optical diffusion polarizer protective film 11 of the present invention.

As shown in Fig. 3, the optical diffusion polarizer protective film 11 of the present invention thus obtained is provided with an uneven surface 11a and a smooth surface 11b, and the uneven surface 11a is covered with a roll 40 ) Formed on the surface of the substrate (not shown). On the other hand, when the nip roll 50 is pressed between the roll 40 and the nip roll 50, the smooth surface 11b on the opposite side to the uneven surface 11a is brought into contact with the nip roll 50 to provide a smooth surface without irregularities.

The uneven surface 11a of the optical diffusion polarizer protective film 11 of the present invention thus obtained has a random pattern irregularity and the maximum surface roughness Rmax of the irregular surface 11a is preferably More preferably 2 to 10 占 퐉, more preferably 5 to 8 占 퐉, the center line average roughness Ra is preferably 0.1 to 2.0 占 퐉, more preferably 0.2 to 1.5 占 퐉, Is preferably 0.5 to 1.0 mu m.

Particularly, according to the present invention, by using the embossing roll 40 having a concavo-convex shape of a random pattern on its surface and having a maximum surface roughness Rmax and a center line average roughness Ra in the above-mentioned range, The uneven surface 11a of the optical diffusion polarizer protective film 11 of the present invention thus obtained has a concavo-convex pattern of a random pattern and the maximum surface roughness Rmax and the center line average roughness Ra satisfy the above- And the optical diffusion polarizer protective film 11 of the present invention can be made excellent in light diffusion function. Specifically, by making the uneven surface 11a of the optical diffusion polarizer protective film 11 have a random pattern irregular shape, it is possible to effectively prevent occurrence of an interference pattern when applied to a liquid crystal display device, By setting the centerline average roughness Ra of the uneven surface 11a to be 2.0 占 퐉 or less, it is possible to obtain a good image quality with high frontal brightness and no unevenness.

The haze value of the optical diffusion polarizer protective film 11 of the present invention is preferably 50% or more, more preferably 60% or more, from the viewpoint of dot pattern concealability of the light guide plate. On the other hand, the haze value of the optical diffusion 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.

In addition, in the present invention, the optical diffusion polarizer protective film 11 of the present invention has the uneven surface 11a and the smooth surface 11b as the opposite surface, as shown in Fig. 1, The polarizer 12 can be appropriately protected by the smoothness of the polarizers 11a and 11b. In addition, the optical diffusion polarizer protective film 11 of the present invention is a film made of a single material which does not contain other materials such as light diffusion particles such as the technique of the above-described Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-27777) , It is possible to suppress the material cost and the manufacturing cost to be low. Further, since the film is made of a single material, it has high durability and strength. Further, when applied to the liquid crystal display device 1, there is no possibility that foreign substances are mixed due to dropout of the light diffusion particles, The reliability of the device 1 can be improved. Further, in the production method of the present invention, the molding rolls provided in the existing film-forming equipment can be replaced with the predetermined rolls of the present invention, thereby making it possible to suppress the investment cost associated with the production to a low level.

As described above, the optical diffusion polarizer protective film 11 of the present invention is the same as the optical film of the diffusion film 25 constituting the liquid crystal display device 1a according to the conventional example shown in Fig. 2 and the polarizer protective film 110 It is possible to omit the diffusion film 25 as compared with the liquid crystal display device 1a according to the conventional example. Accordingly, the manufacturing process for manufacturing the liquid crystal display device can be reduced by one step, It is possible to suppress the occurrence rate of troubles such as the incorporation of foreign matters at the time, thereby improving the production efficiency and improving the quality of the liquid crystal display device as the final product. In addition, by omitting the diffusion film 25, the liquid crystal display device can be downsized.

On the other hand, in the present invention, post-processing such as drawing may be performed on the optical diffusion polarizer protective film 11 obtained by the above method. For example, when the optical diffusion polarizer protective film 11 is stretched, it is preferably (Tg + 10) to (Tg + 10) to the glass transition temperature (Tg) of the thermoplastic resin by using a conventionally known film stretching device, 20 < [deg.] ≫ C, preferably 1.2 to 1.5 times. In addition to the effect of improving the production efficiency by increasing the area of the optical diffusion polarizer protective film 11 by stretching, the optical characteristics can be improved (particularly, the front luminance is high and the viewing angle can be widened).

&Quot; Example &

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

≪ Example 1 >

Polycarbonate (Caliber (registered trademark), 301-10, product of Sumika Styron Polycarbonate Limited, glass transition temperature (Tg) = 149 占 폚) was prepared as a thermoplastic resin. Using the prepared polycarbonate, 30, a shaping roll 40 and a nip roll 50, a protective film of a light diffusion polarizer having a width of 300 mm and a thickness of 135 m was produced. In this embodiment, a single screw extruder (UST-50, manufactured by PLABOR Research Laboratory of Plastics Technology Co., Ltd.) was used as a melt extruder for melt extruding polycarbonate as a thermoplastic resin through a molding die 30 . In this embodiment, the surface of the embossing roll 40 is processed by electric discharge machining to have a random pattern irregular shape (folded shell shape), a maximum surface roughness Rmax of 16 占 퐉, a center line average roughness Ra ) Having a diameter of 1 mm and a diameter of 250 mm, and the surface of the nip roll 50 was subjected to a mirror finishing process. On the other hand, in the present embodiment, the temperature of the forming roll 40 was set at 135 占 폚, the temperature of the nip roll 50 was set at 120 占 폚, and the pressing load was set at 4 kg / mm.

The maximum surface roughness (Rmax), centerline average roughness (Ra), haze, total light transmittance, front luminance and viewing angle of the obtained optical diffusion polarizer protective film were measured by the following methods.

Maximum surface roughness ( Rmax ), Center line average roughness (Ra)

The maximum surface roughness Rmax and the maximum surface roughness Rmax of the contact surface (irregular surface 11a) of the light diffusion polarizer protective film with the adhering roll 40 were measured by a contact type surface roughness meter (Surfcom 1500A, product of TOKYO SEIMITSU CO., LTD. And the centerline average roughness (Ra) was measured. The results are shown in Table 1.

Hayes

The haze of the optical diffusion polarizer protective film was measured in accordance with JIS K7136 using a haze meter (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 optical diffusion polarizer protective film was measured in accordance with JIS K7105 using a haze meter (Haze meter NDH2000, manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.). The results are shown in Table 1.

Front luminance · Viewing angle

The front luminance and viewing angle of the optical diffusion polarizer protective film were measured by the following method.

4, the light-condensing films 23 and 24, the light diffusion polarizer protective film 11, the polarizer 12, the polarizer protective film 13, the liquid crystal cell 12, A sample for measurement 100 was prepared by sequentially laminating a protective film 14, a polarizer protective film 15, a polarizer 16 and a polarizer protective film 17 in this order. On the other hand, in the measurement sample 100, the contact surface (irregular surface 11a) of the light diffusion polarizer protective film with the negative roll 40 faces the light collecting film 24 on the contact surface with the nip roll 50 (11b) facing the polarizer (12). The optical diffusion polarizer protective film (11) Further, in the measurement sample 100, two prism films (prism films) 23 and 24 were used in the same manner as a general liquid crystal display device, and the prisms provided in these prisms were superimposed in a state of being orthogonal to each other.

A diffuse light source is disposed on the side of the condensing film 23 for the measurement sample 100 and the front luminance (luminance in the 90 占 direction) of the sample for measurement 100 is measured using a CCD camera in the state that the diffused light is irradiated by the diffused light source. Measurement, and viewing angles (luminance in 60 deg. Direction, 75 deg., 105 deg. And 120 deg.) Were measured. The obtained results are shown in Fig. On the other hand, in Fig. 5, the case where the optical diffusion polarizer protective film 11 is not used is referred to, and the luminance ratio to the reference is plotted (the same also applies to Fig. 6 to be described later).

≪ Example 2 >

A light diffusion polarizer protective film was obtained in the same manner as in Example 1 except that the temperature of the roll 40 was changed from 135 占 폚 to 145 占 폚 and the maximum surface roughness (Rmax) , Center line 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 diffusion polarizer protective film was obtained in the same manner as in Example 2 except that the shape roll 40 was changed from having a maximum surface roughness Rmax of 16 占 퐉 to 8 占 퐉, (Rmax), center line average roughness (Ra), haze, total light transmittance, front luminance and viewing angle were measured. The results are shown in Table 1 and FIG.

<Example 4>

The optical diffusion polarizer protective film obtained in Example 2 was stretched 1.5 times in an atmosphere at 155 캜 to obtain a stretched light diffusive polarizer protective film and a frontal brightness and a viewing angle were similarly measured for the obtained stretched light diffusive polarizer protective film . The results are shown in Fig.

&Lt; Example 5 &gt;

The stretched light diffusive polarizer protective film obtained in Example 2 was stretched 1.5 times in an atmosphere at 160 캜 to obtain a stretched light diffusive polarizer protective film and a frontal luminance and a viewing angle were similarly measured for the obtained stretched light diffusive polarizer protective film . The results are shown in Fig.

<Evaluation>

From the results shown in Table 1, it was confirmed that all of the optical diffusion polarizer protective films of Examples 1 to 3 produced by the production method of the present invention had a haze of 50% or more and a total light transmittance of 90% or more, have. 5, all of the optical diffusion polarizer protective films of Examples 1 to 5 produced by the manufacturing method of the present invention had a high front luminance (luminance in 90 ° direction) and a viewing angle (60 ° direction, 75 占 direction, 105 占 direction, and 120 占 direction) is also good. On the other hand, FIG. 5 shows the case where the bead coating type diffuser plate (haze 93%, about 200 m) is formed so that the uneven surface is directed toward the light collecting film 24, and the flat surface is directed toward the polarizer 12 And the results of measurement in the case where they are arranged as reference data. In the case of the bead coating type diffusion plate, the front luminance and the viewing angles in the 75 ° and 105 ° directions were remarkably poor.

From these results, it can be said that the optical diffusion polarizer protective film obtained by the production method of the present invention has excellent optical properties and can be suitably applied to a liquid crystal display device.

&Lt; Example 6 &gt;

Except that an acrylic modified polycarbonate resin (MB6001UR, product of Mitsubishi Engineering-Plastics Corporation, glass transition temperature (Tg) = 105 deg. C) was used as the thermoplastic resin instead of the polycarbonate, a protective film for optical diffusion polarizers The maximum surface roughness (Rmax), centerline average roughness (Ra), haze, total light transmittance, front luminance and viewing angle were similarly measured for the obtained optical diffusion polarizer protective film. The results are shown in Table 2 and Fig.

&Lt; Example 7 &gt;

A light diffusion polarizer protective film was obtained in the same manner as in Example 6 except that the rolls 40 were changed from the maximum surface roughness Rmax of 16 占 퐉 to the thickness of 8 占 퐉, (Rmax), center line average roughness (Ra), haze, total light transmittance, front luminance and viewing angle were measured. The results are shown in Table 2 and Fig.

&Lt; Example 8 &gt;

A light diffusion polarizer protective film was obtained in the same manner as in Example 1 except that polyethylene terephthalate (TR3000H, product of Teijin Limited, glass transition temperature (Tg) = 75 캜) was used as a thermoplastic resin instead of polycarbonate, The maximum surface roughness Rmax, the center line average roughness Ra, the haze, the total light transmittance, the front luminance and the viewing angle were measured for the polarizer protective film in the same manner. The results are shown in Table 2 and Fig.

<Evaluation>

From the results shown in Table 2, even when an acrylic-modified polycarbonate resin or polyethylene terephthalate was used instead of polycarbonate as the thermoplastic resin, all of the resulting light diffusion polarizer protective films had a haze of 50% or more and a total light transmittance of 90% It can be confirmed that the optical characteristics are excellent. 6, all of the obtained optical diffusion polarizer protective films had a high front luminance (luminance in the 90 占 direction) and a viewing angle (luminance in the 60 占 direction, 75 占 direction, 105 占 direction, 120 占 direction) Is also good. On the other hand, also in Fig. 6, measurement results of the bead spreading type diffusion plate are shown together as reference data as in Fig.

11 ... Optical diffusion polarizer protective film
11a ... Uneven surface
11b ... Flat face
11c ... Thermoplastic resin
30 ... T die for extrusion
40 ... Form roll
50 ... Nip roll

Claims (10)

An extruding step of melt-extruding the thermoplastic resin from the forming die into a sheet form,
And a pattern forming step of pressing the sheet-shaped thermoplastic resin melt-extruded between the first roll having the concavo-convex pattern and the second roll to form a concavo-convex pattern on one side A method for producing a polarizer protective film having a diffusing function. The method according to claim 1,
Wherein the temperature of the first roll is set in a range of (Tg-40) to (Tg + 20) 占 폚 with respect to the glass transition temperature (Tg) of the thermoplastic resin. 3. The method according to claim 1 or 2,
Wherein the temperature of the second roll is set in a range of (Tg-50) to Tg 占 폚 relative to the glass transition temperature (Tg) of the thermoplastic resin. 4. The method according to any one of claims 1 to 3,
Wherein the concavo-convex pattern formed on the surface of the first roll is a random pattern. 5. The method according to any one of claims 1 to 4,
Wherein in the pattern forming step, a roll having a maximum surface roughness (Rmax) in a predetermined range is used as the first roll, and after the pattern forming step, a maximum surface of the surface on which the concavo- And the roughness (Rmax) is 20 占 퐉 or less. 6. The method according to any one of claims 1 to 5,
In the pattern formation step, a roll having a maximum surface roughness (Rmax) and a center line average roughness (Ra) in a predetermined range is used as the first roll, and a polarizer protecting the haze value after the pattern forming step by 50% &Lt; / RTI &gt; 7. The method according to any one of claims 1 to 6,
Further comprising the step of stretching the sheet-like thermoplastic resin having the concavo-convex pattern formed thereon. A polarizer protective film obtained by the method according to any one of claims 1 to 7. 9. The method of claim 8,
And a haze value of 50% or more. 10. The method according to claim 8 or 9,
Wherein a maximum surface roughness (Rmax) of the surface on which the concavo-convex pattern is formed is 20 占 퐉 or less.

Images