JP2012220662A - Film for improving viewing angle and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for improving a viewing angle achieving both of a viewing angle improving effect and suppression of decrease in front brightness in high levels while suppressing changes in tones and being installed in an observer's side with respect to a liquid crystal layer of a liquid crystal display device.SOLUTION: A light diffusion film is obtained by fusing and extrusion-molding a mixture composed of at least two kinds of resins incompatible with each other. In the film for improving the viewing angle, a ratio (I60/I0×100) measured by a method described in the specifications, of the transmittance (I0) at an emission angle of 0 degree of light having a wavelength of 550 nm in a main diffusion direction to the transmittance (I60) at an emission angle of 60 degrees is 0.06 to 1.0%.

Description

  The present invention relates to a viewing angle enhancement film installed on the viewer side from a liquid crystal layer of a liquid crystal display device, which achieves both a reduction in natural image quality depending on the viewing angle and suppression of a reduction in front luminance at a high level, and the viewing angle. The present invention relates to a liquid crystal display device in which a viewing angle improvement effect such as a suppression of a decrease in natural image quality using an improvement film and a suppression of a decrease in front luminance are achieved at a high level.

Liquid crystal display devices are widely used as flat panel displays by taking advantage of their features such as thinness, light weight, and low power consumption, and their applications are yearly as display devices for information such as mobile phones, personal digital assistants (PDAs), personal computers, and televisions. It is expanding.

However, the liquid crystal display device has a problem that the viewing angle is narrower than that of the CRT.
The viewing angle means that when the angle at which the screen of the liquid crystal display device is observed is changed, the angle with respect to the vertical line of the screen is increased, that is, the screen image is larger than when viewed from the front as it becomes more oblique. This refers to the phenomenon of image quality degradation. As the image quality, phenomena such as color image color tone, image contrast, brightness of white display image, white blur due to light leakage of black display image, unnaturalness of image quality in high angle observation due to distortion of gamma curve, etc. Is raised. In the deterioration of the image quality, the change in naturalness depending on the viewing direction is particularly important.

  The change in naturalness is, for example, the degree of change in tone of a phenomenon in which when a monochrome display image is observed from different angles, the tone of a bright part is lost when an image with a gradation is observed obliquely in front view. Determined. Hereinafter, the degree of gradation change is referred to as a gamma shift degree, and the effect of suppressing the gamma shift is referred to as a gamma shift improvement effect. Moreover, it may be called a viewing angle improvement effect.

As a method for expressing the above viewing angle improvement effect, a method of installing a light diffusion film on the viewing side of a liquid crystal cell of a liquid crystal display device is known. Since this method can provide an improvement effect without changing the liquid crystal alignment in the liquid crystal layer, the electrode structure, and the like, the manufacturing process of the liquid crystal display device is simple and useful without increasing the number of steps. However, since the light emitted from the screen passes through the diffusion film and the transmitted light is scattered, the brightness of the screen when viewed from the front, that is, the brightness is lowered, and the image becomes dark. Hereinafter, this is referred to as a decrease in front luminance. That is,
The effect of improving the viewing angle and the suppression of the decrease in front brightness are contradictory events and are difficult to achieve at the same time. Therefore, a viewing angle enhancement film that can exhibit a large viewing angle improvement effect with a reduction in front luminance as low as possible is desired.

For example, Patent Document 1 proposes that a light diffusing film having a function of scattering and transmitting incident light is provided on a liquid crystal display screen. This film is obtained by melt-extruding a composition having a transparent island resin having a different refractive index as a sea-island structure to form a sheet, and further stretching, but it is suggested that the front brightness is greatly reduced.

Further, Patent Document 2 proposes a spectrally anisotropic scattering film having a scattering angle distribution that varies depending on the wavelength and that has a different diffused light distribution in two directions that differ by 90 degrees in azimuth with respect to the film surface. This film is suggested to have a large reduction in front luminance.

Furthermore, Patent Document 3 proposes a transmitted light scattering control film made of a single thermoplastic resin and having a portion containing a large number of fine pores inside. This film is obtained by drawing a melt-formed polycarbonate and utilizing light scattering caused by groove-like cracks, but it is suggested that the effect of improving the gamma shift is very small.

  Further, Patent Document 4 proposes a method using a lens film. This suggests that the front brightness is greatly reduced.

Furthermore, Patent Document 5 proposes a transmitted light scattering control film in which a light diffusing layer made of translucent particles and a translucent resin is formed on the surface of a base film, but the effect of improving gamma shift is sufficient. It is suggested that it is not.

As described above, some conventional methods for improving the viewing angle with a light diffusing film satisfy either the gamma shift improvement effect or the suppression of the decrease in front luminance, but both characteristics are advanced. At present, there is no one that can achieve both levels.

Japanese Patent Laid-Open No. 7-114013 JP 2004-341309 A Japanese Patent Laid-Open No. 10-206836 JP 09-179113 A JP 2003-270409 A

  The present invention was created in view of the current state of the prior art, and its purpose is to provide a liquid crystal display device that achieves both a viewing angle improvement effect by suppressing a gamma shift and a suppression of a decrease in front luminance at a high level. Disclosed is a viewing angle improvement film installed on the viewer side from a liquid crystal layer, and a liquid crystal display device that achieves both a viewing angle improvement effect using the viewing angle improvement film and suppression of a decrease in front luminance at a high level. .

As a result of diligent studies to achieve the above object, the present inventor has controlled the optical characteristics of a light diffusion film obtained by melt-molding a resin mixture having a specific composition within a specific range, thereby achieving a trade-off event. The present inventors have found that the effect of improving the gamma shift, which is believed to be, and the suppression of a decrease in front luminance can be achieved at a high level, and the present invention has been completed.

  That is, the present invention relates to a light diffusing film obtained by melt extrusion molding a mixture of at least two incompatible resins, and the light having a wavelength of 550 nm in the main diffusion direction measured by the method described in the specification. The ratio (I60 / I0 × 100) of the transmittance (I0) at the exit angle of 0 ° and the transmittance (I60) at the exit angle of 60 ° is 0.06 to 1.0%. A viewing angle improving film.

In this case, it is preferable that at least one of the incompatible resins is a polyolefin resin.

Furthermore, in this case, it is preferable that two types of incompatible resins are polyolefin resins.

Furthermore, in this case, it is preferable that the polyolefin resin is selected from a polyethylene resin, a polypropylene resin, and a cyclic polyolefin resin.

Furthermore, in this case, it is preferable that at least one functional layer selected from a hard coat layer, a reflection reducing layer, and an antiglare layer is combined on the viewer side surface of the viewing angle improving film. .

Furthermore, a liquid crystal display device in which the viewing angle improving film according to any one of claims 1 to 5 is installed closer to the observer side than the liquid crystal cell of the liquid crystal display device is suitable.

Furthermore, a liquid crystal display device in which the main diffusion direction of the viewing angle improving film is installed in the horizontal direction of the liquid crystal display device is preferable.

Furthermore, a liquid crystal display device in which the main diffusion direction of the viewing angle improving film is set in the vertical direction of the liquid crystal display device is suitable.

The viewing angle improving film of the present invention has a light distribution pattern having both characteristics of straight transmission and diffuse transmission, and the wavelength dependence of the emitted light depends on the angle of the emitted light. It is controlled to work effectively for improvement effect and front luminance reduction, so installing it on the viewing side of the liquid crystal cell of the liquid crystal display device has advanced anti-paradox phenomenon of viewing angle improvement effect and suppression of front luminance reduction. Therefore, it is possible to provide a liquid crystal display device that can be compatible at both levels, and has both the effect of improving the viewing angle and suppressing the decrease in front luminance.

FIG. 6 is a diagram showing an example of luminance change depending on the observation angle when the viewing angle is improved with a highly diffusive light diffusion film. It is a figure which shows an example of the preferable light distribution pattern of the viewing angle improvement film of this invention. The figure which shows an example of the gamma shift improvement effect in a TN panel The figure which shows an example of the gamma shift improvement effect in a VA panel

(Basic characteristics of viewing angle enhancement film)
The viewing angle improving film of the present invention is a light diffusion film formed by melt extrusion molding a mixture of at least two incompatible resins, and has a wavelength of 550 nm in the main diffusion direction measured by the method described in the specification. The field of view characterized in that the ratio (I60 / I0 × 100) of the transmittance (I0) at an emission angle of 0 ° and the transmittance (I60) at an emission angle of 30 ° is 0.06 to 1.0%. It is a corner enhancement film. Here, when viewing the display, there is a report that it is observed within ± 60 degrees with respect to the normal direction of the display, and it is considered that a viewing angle of 60 degrees or more is not a necessary characteristic on a daily basis. We paid attention to the transmittance ratio. Furthermore, as described above, the phenomenon of reduced naturalness is caused by the fact that the gradation of bright portions is sometimes lost when observed from an oblique direction. For this reason, attention has been paid to the fact that the wavelength of 550 nm, which has the highest spectral luminous efficiency for human eyes, is important for such image quality degradation.
The present inventors diligently studied a method for solving the above-mentioned problem that was thought to be a trade-off, and the effect of improving the gamma shift increases the diffusivity evaluated by the spread of the bottom of the light distribution pattern. It has been found that the diffusibility can be evaluated by the ratio of the transmittance at an exit angle of 0 degrees and the transmittance at an exit angle of 60 degrees.

As described above, it is known that the light diffusion film can exhibit the effect of improving the viewing angle. As shown in FIG. 1, when a highly diffusive film having a half width of 57 degrees is used in the method of the present invention, the luminance when observed from an oblique direction (high angle) can be improved. The corner improvement effect can be exhibited, but at the same time, the front brightness is greatly reduced. Therefore, the viewing angle improvement effect and the front luminance reduction are anti-contradictory events.
The angle dependency of luminance in FIG. 1 was measured by the following method.

[Measurement method of luminance angle dependence]
Measurement was performed using RISA-COLOR / ONE-II (manufactured by Highland). A commercially available VA type liquid crystal display device test was installed horizontally on the pedestal, and a white image (Nokia monitor test for windows V 1.0 (manufactured by Nokia)) of 131 × 131 mm in the center of this panel. Farbe mode) is displayed, 3 drops of water are dropped on the white image with a dropper, and a light diffusing film is placed on the white image. The distance between the displays is 1 m in the vertical state, the CCD camera is moved on the equator between −70 ° and + 70 ° with respect to the panel surface of the liquid crystal display device, and the luminance is measured under the following conditions. An angle-dependent profile was obtained.
In the blank measurement, the same measurement was performed without attaching the viewing angle improving film.
The brightness was obtained by dividing the white image into 25 parts of 5 × 5, measuring the brightness of all the pixels of 9 parts of 3 × 3 at the center, and displaying the average value.

An example of a preferable light distribution pattern for satisfying the above optical characteristics is shown in FIG. That is, it is a light distribution pattern having a characteristic characteristic that has both the straight transmission and the diffuse transmission.
This light distribution pattern is obtained by measurement by the following method.
[Measurement method of light distribution pattern]
The measurement was performed using an automatic variable angle photometer (GP-200: manufactured by Murakami Color Research Co., Ltd.).
Transmission measurement mode, light incident angle: 0 ° (angle that is perpendicular to the sample surface both vertically and horizontally),
Light receiving angle: -90 ° to 90 ° (angle on the equator line), filter: using ND10, light beam stop: 10.5 mm (VS-1 3.0), light receiving stop: 9.1 mm (VS-3) 0) is fixed to the sample stage so that the main diffusion direction is the horizontal direction, and SENSITIVI is set so that the peak top value of the variable light intensity curve of the transmitted light is in the range of about 80% with respect to the full scale.
The setting of TY and HIGH VOLTON was adjusted and the variable-angle luminous intensity curve of the transmitted light was calculated | required.

(Spread spread ratio)
Ratio of transmittance (I0) at an exit angle of 0 ° and transmittance (I60) at an exit angle of 60 ° (I60 / I0 × 100) of light having a wavelength of 550 nm in the main diffusion direction measured by the method described in the examples Is 0.06 to 1.0%.
The skirt spreading diffusivity ratio is more preferably 0.07 to 0.9%, and further preferably 0.08 to 0.8%.
Hereinafter, the above characteristic is referred to as a skirt spread diffusion ratio.
Only when the skirt spread diffusivity ratio is satisfied within the above range can the above-mentioned characteristics of the antinomy event be made compatible at a high level. That is, when the skirt spread ratio is less than 0.06%, the front luminance reduction is good, but the viewing angle improvement effect is insufficient, which is not preferable. On the other hand, when the skirt spreading diffusivity ratio exceeds 1.0%, the decrease in front luminance becomes large, which is not preferable.
The skirt spreading diffusivity ratio is more preferably 0.07 to 0.9%, and further preferably 0.08 to 0.8%.
For example, when the main spread spreading ratio in the main diffusion direction is obtained from the figures described in the above-mentioned patent documents, FIG. 3 of Patent Document 1, FIG. 3B of Patent Document 2, and Patent Document 4 As can be seen from FIG. 8, the skirt spread ratios are 20%, 13%, and 5%, respectively, and the preferred skirt spread ratio is in a significantly lower range than the films disclosed in these patent documents.
Conversely, from FIG. 13 of Patent Document 3 and Table 2 of Patent Document 5, the skirt spread ratio is 0% or more and 0.02% or less, and the preferable skirt spread ratio is disclosed in these Patent Documents. It is in a higher range than the film that is being used.

In the case of a film having a high degree of anisotropy, the effect of improving the viewing angle in the main diffusion direction, which is the direction in which the degree of diffusion is high, is increased. Therefore, it is necessary to change the installation direction of the viewing angle enhancement film depending on the direction in which the viewing angle needs to be improved. That is, when improving the viewing angle in the left-right direction of the liquid crystal display device, conversely, when improving the viewing angle in the up-down direction so that the main diffusion direction is parallel to the left-right direction of the panel, the main diffusion direction is It is preferable to install so as to be parallel to the vertical direction.
By this correspondence, there is also a merit that the effect of improving the viewing angle only in the necessary direction can be expressed.

(Preferable range of decrease in front brightness)
Although the degree of reduction in front luminance of the present invention is not limited, it is possible to achieve a viewing angle improvement effect within the allowable range of front luminance reduction without changing the system configuration of the entire liquid crystal display device such as improvement in luminance of the backlight device. , The luminance reduction rate displayed in% when the viewing angle improvement film is installed when the luminance when the viewing angle improvement film is not installed is 100% (hereinafter including the front luminance reduction rate) In the TN panel described in the examples, it is preferably 20% or less. 18% or less is more preferable, and 15% or less is more preferable. In the VA panel described in the examples, it is preferably 15% or less. 13% or less is more preferable, and 10% or less is more preferable.

(Preferable range of gamma shift improvement effect)
In the present invention, the gamma shift improvement effect was evaluated by the method described in the examples. First, the input value of the panel of a commercially available liquid crystal display device is changed by 5 gradations from 0 to 255, the CCD camera is fixed at a position of 60 ° on the equator of the image, an image is taken, and the center of the image is obtained. An average value of 50 pixel angles is obtained, the luminance of each gradation is normalized by an output value of 255, and these are plotted against the input value to obtain a gamma curve. The distortion is different between the TN panel and the VA panel with respect to the gamma curve measured from the front. The TN system has the largest distortion in the range of 200 to 255, and the VA system has the range of 125 to 230. Therefore, the respective inclinations are obtained and referred to as a gamma shift improvement effect. The liquid crystal display device used at this time is FlexScanS1901-B (manufactured by Nanao) for the TN system, and FlexScanS1921 (manufactured by Nanao) for the VA system.
It can be said that the gamma shift improvement effect is greater as the gamma curve measured in the normal direction (front) of each panel is closer to the slope of the gamma curve measured at 60 °.
The gamma shift improving effect is preferably 2.45 to 2.85, more preferably 2.50 to 2.80 in the case of a TN panel. In the VA panel, 1.05 to 1.20 is preferable, and 1.10 to 1.15 is more preferable. If the TN method is 2.45, and if the VA method is less than 1.10, the effect of improving the gamma shift is small, and the gradation of the bright part is lost. On the contrary, when the TN method is 2.85 or more and the VA method is 1.20 or more, the gamma shift improvement effect is sufficient, but the reduction rate of the front luminance becomes large, which is not preferable.

(Configuration of viewing angle enhancement film)
The light diffusion film of the present invention can be obtained by melt extrusion molding a mixture of at least two incompatible thermoplastic resins. The presence form of the mixture of at least two incompatible thermoplastic resins is not particularly limited as long as the above optical characteristics are satisfied, and a so-called sea / island structure in which each resin exists independently as a continuous phase and a dispersed phase. May be,
A structure in which both resins form a co-continuous phase may be used. The above characteristics can be controlled by light refraction and scattering at the interface between the two resins.

Examples of the thermoplastic resin used include polyethylene resins, polypropylene resins, polybutene resins, polyolefin resins such as cyclic polyolefin resins and polymethylpentene resins, polyester resins, acrylic resins, polystyrene resins, and polycarbonate resins. Examples thereof include resins and copolymers thereof.
The at least two incompatible thermoplastic resins may be blended in the film forming step, or may be used in a form blended in advance by a kneading method or the like.

In the present invention, three or more kinds of thermoplastic resins may be blended, and additives such as a compatibilizing agent and a dispersion diameter adjusting agent for improving the conformability of each resin may be used in combination. Moreover, you may mix | blend additives, such as stabilizers, such as antioxidant and a ultraviolet absorber, and antistatic agent. Further, fine particles such as inorganic particles and polymer beads may be added as long as the above optical characteristics are not impaired.

What is necessary is just to select at least two types of incompatible (incompatible with each other) resins from these thermoplastic resins. The blending ratio of the at least two incompatible thermoplastic resins is preferably 5/95 to 95/5, more preferably 10/90 to 90/10, and more preferably 20/80 to 20/80 to 20/80, respectively. Although it can be said that the ratio of 80/20 is more preferable, it varies greatly depending on the kind of the resin component, the layer configuration described later, the thickness of the light diffusion layer, the manufacturing method and the like.
In addition, there exists a tendency for the direction with many compounding ratios of two types of incompatible thermoplastic resins to become a continuous phase.
In particular, when the melt flow rate is close, it is necessary to take into account that the components of the sea-island structure are reversed depending on the ratio.

The resin may be selected from commercially available resins having high versatility. However, a custom-made product may be used for measures such as more stable production.
Polyester resins are easy to achieve the above-mentioned optical characteristics, and are excellent in mechanical and thermal characteristics other than optical characteristics, so that a single layer of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate is used. Preference is given to using copolymers and / or copolymers. It is also economically advantageous.
As the resin combined with the polyester, a polyolefin resin described later is preferable.
Also, the fluororesin is not limited as long as it satisfies the above characteristics, but from the viewpoint that the above optical characteristics are easily achieved and economically advantageous, a vinylidene fluoride resin and a fluorine-containing monomer such as perfluoroethylene It is preferable to use a copolymer with an olefin monomer such as ethylene or propylene.
The fluororesin is excellent in light resistance. For example, an anisotropic light diffusion film excellent in light resistance can be obtained by combining with a polyolefin resin.
As the resin combined with the fluorine resin, a polyolefin resin described later is preferable.

It is preferable that at least one kind is made of a polyolefin resin from the viewpoint that the above-mentioned characteristics can be stably expressed.
Examples of the polyolefin resin include polyethylene, polypropylene, polybutene, potipentene, polyhexene, polymethylpentene and the like, copolymers thereof, cyclic polyolefin and the like.

In view of light resistance and economy, it is preferable to use two types of polyolefin resins. When both types use polyolefin resin, the combination is not particularly limited, but the difference in refractive index between the two types of polyolefin resin is preferably in the range of 0.003 to 0.07. The range of 0.005 to 0.06 is more preferable, and 0.01 to 0.05 is more preferable. By making this refractive index difference into a range, the above-mentioned viewing angle improvement of optical characteristics can be obtained more stably. For example, when the difference in refractive index exceeds 0.07, the skirt spread diffusivity ratio increases and the front luminance reduction rate increases, so that the above characteristics cannot be satisfied.
That is, the greater the difference in refractive index, the greater the angular change at the interface between the two incompatible thermoplastic resins, which favors diffusion, while the reflection at the interface increases exponentially. it is conceivable that.
Therefore, it becomes easy to satisfy the above-described various optical characteristics at the same time in the above range.

Examples of the cyclic polyolefin-based resin include those having a cyclic polyolefin structure such as norbornene and tetracyclododecene. For example, (1) a ring-opening (co) polymer of a norbornene monomer is subjected to polymer modification such as maleic acid addition or cyclopentadiene addition as necessary, and then a hydrogenated resin, (2) a norbornene monomer Examples include addition-polymerized resins, and (3) addition-copolymerized resins with norbornene monomers and olefin monomers such as ethylene and α-olefin. The polymerization method and the hydrogenation method can be performed by conventional methods.

These can increase the glass transition temperature, and it is considered that the island components thinned by the shear and draft in the die are solidified quickly during cooling, and stable characteristics are easily obtained.
The glass transition temperature is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and particularly preferably 120 ° C. or higher. The upper limit is naturally determined by the monomer type (cyclic monomer 10
0% Tg), preferably 230 ° C. or lower, more preferably 200 ° C. or lower, particularly preferably 190 ° C. or lower. If the upper limit is exceeded, a high temperature is required at the time of melt extrusion, and coloring may occur or undissolved matter may be generated. The values are ISO11357-1, -2,-.
3 is a value measured at a rate of temperature increase of 10 ° C./min.

The content of the cyclic component of the cyclic polyolefin resin is preferably 70 to 90% by mass.
More preferably, it is 73-85 mass%. This range is preferable particularly in the case of norbornene. In particular, a cyclic polyolefin resin copolymerized with ethylene is preferable in order to achieve high properties with high affinity with a polyethylene resin.
The ethylene content is preferably 30-10% by mass, more preferably 27-15.
% By mass.

The polyethylene resin may be a single polymer or a copolymer. In the case of a copolymer, it is preferable that 50 mol% or more is an ethylene component. The density and polymerization method of the polyethylene resin are not limited, but it is preferable to use a copolymer having a density of 0.909 or less. For example, a copolymer with octene is mentioned. The polymerization method may be either a metallocene catalyst method or a nonmetallocene catalyst method.
In particular, the use of a block copolymer of ethylene and octene is preferred in that high diffusibility can be stably imparted. For example, the resin may include INFUSE (TM) manufactured by Dow Chemical Company. Since the resin has a crystalline part because of the block structure, it has a feature that it has a low melting point and a high melting point, and is preferable because it can improve the heat resistance and the like of the obtained viewing angle improving film. .

The polypropylene resin may be a single polymer or a copolymer. In the case of a copolymer, it is preferable that 50 mol% or more is a propylene component. The production method, molecular weight and the like of the resin are not particularly limited, but those having high crystallinity are preferable from the viewpoint of heat resistance. Specifically, the crystallinity is determined by the heat of fusion measured by a differential scanning calorimeter (DSC), and preferably has a heat of fusion of 65 J / g or more.

Examples of polyolefin resins containing ethylene and / or butene include homopolyethylene resins, homopolybutene resins, copolymers of these resins with other olefinic monomers, acrylic acid, methacrylic acid, and ester derivatives thereof. And the like. In the case of a copolymer with other olefinic monomers, any of random, block and graft copolymers may be used. Further, a dispersion such as EP rubber may be used. There are no particular limitations on the production method and molecular weight of the resin. For example, use of the above-described polyethylene resin or a copolymer of ethylene and butene is preferable.

The nano-crystal structure control type polyolefin elastomer resin is a thermoplastic polyolefin-based elastomer in which the crystal / amorphous structure of the polymer is controlled in the nano order and the crystal has a network structure in the nano order. For example, manufactured by Mitsui Chemicals, Inc. Notio (registered trademark). The conventional polyolefin-based elastomer resin has a crystal size on the order of microns, whereas the nanocrystal structure control-type polyolefin-based elastomer resin has a feature that the crystal size is controlled on the order of nanometers. For this reason, it is often superior in transparency, heat resistance, flexibility, rubber elasticity and the like as compared with conventional polyolefin-based elastomer resins. Therefore, there are cases where the appearance of the resulting film can be improved by blending the nanocrystalline structure control polyolefin elastomer resin.

The melt flow rate of the at least two incompatible thermoplastic resins is not particularly limited as long as the above optical characteristics are satisfied. Each thermoplastic resin is appropriately selected in the range of a melt flow rate measured at 230 ° C. of 0.1 to 100, preferably 0.2 to 50.

The melt flow rate of the resin is appropriately selected in consideration of the resin composition, composition ratio, which resin is used as the sea, desired optical characteristics, and the like.
The guideline is that the higher the composition ratio and the lower the melt flow rate becomes the sea. In the case of the same amount, the higher the melt flow rate, the more likely to become the sea. When the melt flow rate with the higher composition ratio is high, a structure such as a co-continuous phase may be formed instead of a simple sea / island structure.

When the two types of resins are both polyolefin-based resins, a combination of a cyclic polyolefin-based resin and a polyethylene-based resin or a polypropylene-based resin, or the combination of the three types is easy to obtain a film having the above-mentioned characteristics and is economical. Is preferable.

In the case of a combination of a cyclic polyolefin resin and a polyethylene resin or polypropylene resin, the polyethylene resin or polypropylene resin is used as the sea phase, and the melt flow rate of the polyethylene resin or polypropylene resin in the sea phase is changed to the island phase. It is preferably higher than the melt flow rate of the cyclic polyolefin resin.

In the case of a combination of a cyclic polyolefin resin and a polyethylene resin or polypropylene resin, it is preferable that 10 to 60 mass% of the cyclic polyolefin resin is blended in the total resin amount, and more preferably 10 to 50 mass%. is there.
For example, if it is less than 10% by mass, the skirt spread diffusivity ratio becomes small and the effect of improving the gamma shift becomes small. Conversely, if it exceeds 60% by mass, the skirt spread diffusivity ratio becomes large and the front luminance decrease is large. Therefore, the above characteristics cannot be satisfied.
The said range is preferable with respect to the implementation | achievement of the preferable embodiment which makes the below-mentioned polyethylene-type resin and polypropylene-type resin a sea phase.
When the cyclic polyolefin resin, which is the reverse of the above configuration, is used as the sea phase, the desired optical properties, especially the degree of anisotropy, are related to the share in the die and the flexibility and fluidity of the sea phase. High viewing angle improvement film is difficult to obtain.

According to the above embodiment, even when the film forming apparatus is changed, there is an effect that a light diffusion film having desired optical characteristics can be stably obtained. I don't know why,
Even if there is a change in share due to differences in extrusion conditions or die shapes that occur when the film forming equipment is changed, by making the sea phase resin softer than the island phase resin and increasing its fluidity , I guess that the effect will be mitigated.

The size of the island phase when both of the two types are made of polyolefin resin is not particularly limited, but the average size of the minor axis determined by the laser scattering method is preferably 0.1 to 2 μm. If it is less than 0.1 μm, the degree of diffusion is insufficient, which is not preferable. On the other hand, when the thickness exceeds 2 μm, the degree of spreading spread increases and the total light transmittance decreases, which is not preferable.

(Production method of viewing angle improving film)
The method for producing the viewing angle improving film of the present invention is not particularly limited as long as it satisfies the above-mentioned optical characteristics, but a method of forming a film by melt extrusion molding is preferred from the viewpoint of economy.
In the present invention, since it is not necessary to contain non-meltable fine particles in order to impart light diffusibility, clogging of the filtration filter of the molten resin in the film forming process is reduced even when the melt extrusion method is used. It has the characteristics that it is excellent in productivity and the clarity of the film obtained is high.

The film forming method by the melt extrusion method is not particularly limited, and may be, for example, either a T-die method or an inflation method. Moreover, the film may be an unstretched film or may be subjected to a stretching process.

In the melt extrusion molding method, generally, a resin melted by an extruder is extruded from a die into a sheet shape, and the sheet is brought into close contact with a cooling roll to be cooled and solidified to form a film. The close contact with the cooling roll may be performed by pressing with a generally used pressure roll. However, in the point of imparting anisotropy, the close contact portion may It is preferable that no liquid pool zone (sometimes referred to as a bank) is formed at the entrance. Since the formation of the liquid pool zone occurs when it is pressed against the cooling roll, that is, when it is pressed with a strong pressure, it is preferable to reduce the contact pressure during the contact. For example, it is better to avoid the method of being brought into close contact by pressing with a generally used pressure roll.
Although it will not be limited if it is the method of making it adhere | attach with a weak pressure, For example, the resin fuse | melted with the extruder is extruded to a sheet form from die | dye, and this sheet | seat is pressed by the gas pressure and / or the suction method and / or the electrostatic contact method. It is preferable that the film is formed by close contact and cooling and solidification. By this method, a viewing angle improving film having anisotropy can be stably obtained.

There is no limitation on the method of pressing by the gas pressure and / or the method of adhering and cooling and solidifying by the suction method and / or the electrostatic adhesion method. For example, as a pressing method by gas pressure, for example,
Examples thereof include a method such as a so-called air knife method in which the gas is pressed with a gas pressure such as air, a vacuum chamber method in which the gas is sucked and adhered by a vacuum nozzle, and an electrostatic adhesion method in which it is adhered by an electrostatic force. The method may be used alone or a plurality of methods may be used in combination. The latter is a preferred embodiment in that it can increase the thickness accuracy of the film obtained.

The viewing angle improving film of the present invention may be produced by either a non-stretching method or a stretching method. For example, when a polyester resin is used for the light diffusion layer, it is preferable to perform uniaxial stretching. The draw ratio is preferably 2 times or more. The upper limit is not limited, but is preferably less than 10 times. By this correspondence, the island phase is stretched in the stretching direction to form an elongated structure, the light diffusibility in the direction orthogonal to the orientation direction of the island phase is remarkably improved, and an anisotropic and high diffusibility can be secured.

When manufacturing by a non-stretching method, you may manufacture by the method of extending | stretching before melt-extruding the sheet | seat extruded by extrusion, ie, the method of raising a draft rate.

In addition, the viewing angle improving film of the present invention may be a single layer or a multilayer structure of two or more layers. In the case of a multilayer structure, as long as at least one layer is a layer made of a light diffusion film having the above structure, the other layer may be a simple transparent layer having no light diffusibility. Moreover, the structure of the light-diffusion layer may be sufficient as all the layers.
In the case of the multilayer structure, it may be produced by a multilayer coextrusion method, or may be carried out by an extrusion lamination method or a dry lamination method.

The mixture of the at least two incompatible thermoplastic resins may be blended with each of the thermoplastic resins by an extruder in the film forming process, or in a form that has been previously mixed by a kneading method or the like. It may be used.

10-500 micrometers is preferable and the thickness of the viewing angle improvement film of this invention has 20-500 micrometers.
More preferably, 20 to 200 μm is more preferable, but it varies greatly depending on the type of resin component of the light diffusion layer, the compounding ratio, the layer configuration, the production method, and the like.
When the thickness is adjusted, if the sea-island structure changes greatly due to changes in draft ratio, extrusion flow rate, lip width, etc., the above tendency may be reversed or extremely increased.

(Liquid crystal display device)
The liquid crystal display device to which the present invention can be applied is not limited as long as the liquid crystal display device has at least a backlight light source, a liquid crystal cell, and a polarizer disposed on the viewing side of the liquid layer cell. For example, T
Examples include N, VA, OCB, IPS, and ECB mode liquid crystal display devices.

(Combination use of functional layers such as hard coat layers)
In the liquid crystal display device of the present invention, it is preferable that at least one functional layer selected from a hard coat layer, a reflection reducing layer, and an antiglare layer is combined on the surface on the viewer side of the viewing angle improving film. Each of the functional layers may have a single configuration, or a plurality of functions may be used in combination.
Combing the hard coat layer improves the scratch resistance of the viewing angle improving film surface. Also,
Due to the combination of the reflection reducing layer and / or the antiglare layer, even when the liquid crystal display device is used in an environment where external light is reflected, the reflection of external light is reduced and the visibility of the image is improved. In addition, even when used in a bright environment, the reduction in viewing angle improvement effect cannot be seen. The surface of the reflection reducing layer or the antiglare layer only needs to have an antireflection function. For example, an antiglare type, an antireflection type, or a type having both functions can be used. In particular, the latter two are preferred.
The functional layer may be combined directly on the surface of the viewing angle improving film, or may be combined with a plastic film such as TAC or PET having the functional layer.
The latter may be preferable because it can be carried out using products widely distributed in the market.
In the latter method, the film having the functional layer is preferably fixed with a pressure-sensitive adhesive or an adhesive, but may be simply overlapped and fixed with a jig.
The adhesive and the pressure-sensitive adhesive are not limited as long as the viewing angle improving film and the film having the functional layer can be fixed, but it is preferable to use an optical product.

(Installation method for liquid crystal display)
In the present invention, as a method for installing the viewing angle improving film or the functional layer composite on a liquid crystal display device, for example, a polarizer disposed on the viewing side of the liquid crystal cell with an adhesive or an adhesive having a small reflection loss. It is preferable to stick to the viewing side of the polarizing plate.
The adhesive and the pressure-sensitive adhesive are not limited as long as the viewing angle improving film and the object can be fixed, but it is preferable to use an optical product.

  The viewing angle improving film in the present invention may be laminated on the viewing side of the polarizer disposed on the viewing side of the liquid crystal cell and incorporated in the panel of the liquid crystal display device so that the viewing angle improving film is on the viewing side.

  When used by laminating with a polarizer, for example, it may be laminated directly on a polarizer in which PVA or the like is dyed with iodine, or may be laminated through a polarizer protective film.

  In the case of stacking and laminating the above-described polarizer or a polarizer having a configuration in which a polarizer and a polarizer protective film are bonded, it is preferable to take into account the difference in mode of the liquid crystal display device.

  Further, in the present invention, a self-adhesive layer may be laminated on one side of the viewing angle improving film and attached to a display screen of a liquid crystal display device in a detachable manner.

(Attaching direction of viewing angle improving film)
The viewing angle improving film of the present invention can change the direction in which the viewing angle improving effect of the liquid crystal display device is manifested by increasing the degree of anisotropy.
For example, TVs are required to improve the viewing angle in the horizontal direction, but monitors for personal computers and various devices and display devices for digital signage may also be required to improve the viewing angle in the vertical direction.
Answering this requirement can be achieved by changing the installation direction of the viewing angle enhancement film.
That is, since the viewing angle in the main diffusion direction of the viewing angle enhancement film is improved, for example, when it is desired to improve the viewing angle in the horizontal direction, the main diffusion direction of the viewing angle enhancement film is substantially the lateral direction of the liquid crystal display device. It is preferable to install. On the other hand, when it is desired to improve the viewing angle in the vertical direction, it is preferable that the main diffusion direction of the viewing angle improving film is set in a substantially vertical direction of the liquid crystal display device.
The installation direction is displayed in the direction when the liquid crystal display device is installed in the vertical direction. Accordingly, the horizontal direction can be expressed as the left-right direction, and the vertical direction can also be expressed as the up-down direction.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and is implemented with appropriate modifications within a range that can be adapted to the gist of the present invention. These are all included in the technical scope of the present invention. The measurement / evaluation methods employed in the examples are as follows. In the examples, “parts” means “parts by mass” unless otherwise specified, and “%” means “% by mass” unless otherwise specified.
In this example, a comparative film that does not satisfy the characteristics of the present invention is also referred to as a viewing angle improving film for convenience.

3. Bottom spread diffusivity ratio (ratio of transmittance (I0) at an emission angle of 0 ° and transmittance (I60) at an emission angle of 60 ° (I60 / I0 × 100) of light having a wavelength of 550 nm in the main diffusion direction)
Measurement was performed using a variable angle spectrophotometric system GCMS-4 type (GSP-2 type: manufactured by Murakami Color Research Co., Ltd., variable angle spectrophotometer GPS-2 type). Transmission measurement mode, light incident angle: 0 ° (film normal direction), light receiving angle: 0 ° -80 ° (polar angle from film normal, azimuth angle is horizontal), light source: D65, field of view: 2 ° Then, the sample is fixed to the sample stage so that the main diffusion direction of the sample is horizontal (the deviation between the axis of the sample stage and the axis of the main diffusion direction is allowed up to about 20 degrees), and variable angle spectroscopy of transmitted light A light curve was determined. The tilt angle was 0 °.
Measurement was performed at a 1 ° pitch from a light receiving angle of 0 ° to 10 °, and at a 5 ° pitch from 10 ° to 80 °.
Prior to the measurement, the apparatus was calibrated using a transmission diffusion standard plate (opal glass) for GCMS-4 manufactured by Murakami Color Research Co., Ltd., and the transmitted light intensity at the light receiving angle of 0 degrees was used as a reference ( Relative permeability was measured as 1.000). The transmission diffusion standard plate had a transmittance at 440 nm of 0.3069 when the air layer was 1.000 by integrating sphere spectroscopic measurement.
In this measurement, the transmittance at an emission angle of 0 ° and 60 ° at a wavelength of 550 nm is measured, and the ratio of the transmittance (I0) at the output angle of 0 ° and the transmittance at the output angle of 60 ° (I60) (I60 / I0 × 100 ) Was calculated and displayed in%.
When the surface roughness is different between the two surfaces of the sample, the sample is fixed in the direction in which the light transmission directions in actual use coincide with each other. In the present invention, the measurement was carried out with the surface being fixed in the direction in which light enters from the lower surface roughness.
The main diffusion direction is the direction in the film plane where the maximum light diffusibility can be obtained, and can be easily determined using a laser pointer or the like.

6). Front luminance reduction Measurement was performed using RISA-COLOR / ONE-II (manufactured by Highland). A TN-type panel (FlexScanS1901-B, manufactured by Nanao) or a VA-type panel (FlexScanS1921, manufactured by Nanao) was installed horizontally on the pedestal, and a white portion of 131 × 131 mm in the center of this panel. Display the image (Farbe mode of Nokia monitor test for windows V 1.0 (manufactured by Nokia)), drop 3 drops of water with a dropper on the white image, place a sample film on it, The water between the films was uniformly spread and brought into close contact, and the CCD camera was fixed at a position 1 m in the vertical direction from the display surface, and the luminance was measured under the following conditions. The obtained luminance was defined as Is.
On the other hand, the luminance of the panel itself without the sample film was measured by the same method.
The calculated luminance was set to Ib, the front luminance reduction was calculated by the following formula (1), and the front luminance reduction was displayed in%.
Decrease in luminance = (Ib−Is / Ib) × 100 (%) (1)
The brightness was obtained by dividing the white image into 25 parts of 5 × 5, measuring the brightness of all the pixels of 9 parts of 3 × 3 at the center, and displaying the average value.
Moreover, the sample film was installed and measured so that the main diffusion direction was substantially parallel to the horizontal direction of the panel.

7). Gamma shift improvement effect The measurement was performed using RISA-COLOR / ONE-II (manufactured by Highland). A TN panel (FlexScanS1901-B, manufactured by Nanao) or a VA panel (FlexScanS1921, manufactured by Nanao) is installed horizontally. The tone is changed gradually, the CCD camera is fixed at a position of 60 ° on the equator of the image, the image is taken, the average value of the center 50 pixel angle of the image is obtained, and the luminance of each gradation is set to 255 output values. Normalize and plot them against the input values to obtain a gamma curve.
The gamma curve measured from the front (same with and without film) differs in distortion between the TN panel and the VA panel. The input value is 200 to 255 in the TN system and 125 in the VA system. Since the distortion becomes the largest in the range from 230 to 230, the respective inclinations were obtained and the values were displayed. The liquid crystal display device used at this time is FlexScanS1901-B (manufactured by Nanao) for the TN system, and FlexScanS1921 (manufactured by Nanao) for the VA system.
Moreover, the sample film was installed and measured so that the main diffusion direction was substantially parallel to the horizontal direction of the panel.

Example 1
Cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Ad
20 manufactured by vanced Polymers, melt flow rate: 2.0 (230 ° C.)) 20
1 part by mass and 80 parts by mass of polypropylene resin 2011D (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene melt flow rate: 2.5 (230 ° C.)) are melt-mixed at a resin temperature of 250 ° C. using a PCM45 extruder manufactured by Ikekai Tekko Co., Ltd. Then, the film was extruded with a T-die and cooled with a mirror-like cooling roll to obtain a 90-μm-thick viewing angle improving film. The film was adhered to the cooling roll during the cooling by an electrostatic adhesion method. The surface temperature of the cooling roll was set to 20 ° C. 3 films
Winding was performed at a speed of m / min.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example has a reduction in front luminance within 20% for the TN panel and within 15% for the VA panel, and exhibits a significant gamma shift improvement effect. It was quality.

(Example 2)
Using two melt extruders and a first extruder as a base layer, a cyclic polyolefin-based resin (TOPAS ™ 6013S-04 Topas Advanced
Polymer copolymer melt flow rate: 2.0 (230 ° C.) 35 parts by mass, block copolymer resin composed of ethylene and octene (Dow Chemical INFUSE (TM)
) D9817.15 Melt flow rate: 26 (230 ° C.) 65 parts by mass kneaded in advance and supplied as a surface layer with a second extruder, polypropylene adhesive resin (Admer (TM) QF551 Mitsui) (Chemical company melt flow rate: 5.7 (190 ° C.))
After melt coextrusion by the T-die method, the film was cooled with a satin cooling roll to obtain a 56 μm-thick viewing angle improvement film. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. The first extruder and the second extruder were both uniaxial, and the outlet temperatures were 230 and 250 ° C., respectively. The surface temperature of the cooling roll was set to 50 ° C. The film was wound up at a speed of 21 m / min. Layer thickness configuration is 8/40
/ 8 (μm).
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example was higher in quality than the viewing angle improving film obtained in Example 1 with less reduction in front luminance.

(Example 3)
In the method of Example 2, a viewing angle improving film was obtained in the same manner as in Example 2 except that both the outlet temperatures of the extruder were changed to 230 ° C.

Example 4
In the method of Example 2, the resin composition supplied to the first extruder was 10 parts by mass of cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)). A block copolymer resin composed of styrene, ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.) manufactured by Dow Chemical Co., Ltd.) is 90 parts by mass, and the film thickness and layer thickness configuration are 162 μm and 36/90. A viewing angle improving film was obtained in the same manner as in Example 1 except that the thickness was changed to / 36 (μm).

(Example 5)
In the method of Example 2, the resin composition supplied to the first extruder was 20 parts by mass of a cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)). Block copolymer resin (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.)) made of styrene, ethylene and octene, and the film thickness and the layer thickness composition are 162 μm and 36/90. A viewing angle improving film was obtained in the same manner as in Example 1 except that the thickness was changed to / 36 (μm).

(Example 6)
In the method of Example 2, the resin composition supplied to the first extruder was 35 parts by mass of cyclic polyolefin-based resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)). A block copolymer resin composed of styrene, ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.) manufactured by Dow Chemical Co., Ltd.) 90 parts by mass, the film thickness and the layer thickness constitution are 56 μm and 8 / A viewing angle improving film was obtained in the same manner as in Example 1 except that the thickness was changed to 40/8 (μm).

(Example 7)
In the method of Example 2, the resin composition supplied to the first extruder was 10 parts by mass of cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)). Block copolymer resin composed of styrene, ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C)) manufactured by Dow Chemical Co., Ltd. A viewing angle improving film was obtained in the same manner as in Example 1 except that the thickness was changed to / 24 (μm).

(Example 8)
In the method of Example 2, the resin composition supplied to the first extruder was 20 parts by mass of a cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)). A block copolymer resin composed of styrene, ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.) manufactured by Dow Chemical Co., Ltd.) is 80 parts by mass, and the film thickness and layer thickness are 56 μm and 8/40. A viewing angle improving film was obtained in the same manner as in Example 1 except that the thickness was changed to / 8 (μm).

Example 9
In the method of Example 2, the resin composition supplied to the first extruder was a cyclic polyolefin-based resin (TOPAS (TM) 6013S-04 Topas Advanced).
Polymer copolymer melt flow rate: 2.0 (230 ° C.) 35 parts by mass, block copolymer resin composed of ethylene and octene (Dow Chemical INFUSE (TM)
D9817.15 Melt flow rate: 26 (230 ° C.)) Field of view in the same manner as in Example 2 except that the thickness is changed to 84 μm and the layer thickness configuration to 12/60/12 (μm). A corner enhancement film was obtained.

(Example 10)
In the method of Example 2, the resin composition supplied to the first extruder was a cyclic polyolefin-based resin (TOPAS (TM) 6013S-04 Topas Advanced).
Polymer copolymer melt flow rate: 2.0 (230 ° C.) 20 parts by mass, block copolymer resin composed of ethylene and octene (Dow Chemical INFUSE (TM)
) D9817.15 Melt flow rate: 26 (230 ° C.)) Field of view in the same manner as in Example 2 except that the thickness was changed to 84 μm and the layer thickness configuration to 24/60/24 (μm). A corner enhancement film was obtained.

(Example 11)
In the method of Example 1, a cyclic polyolefin resin (TOPAS (TM) 6013S) was used.
-04 Topas Advanced Polymers melt flow rate:
2.0 (230 ° C.)) and polypropylene resin 2011D (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene melt flow rate: 2.5 (230 ° C.)), respectively, 35 parts by mass and 65 parts by mass.
A viewing angle improving film was obtained in the same manner as in Example 1 except that the film thickness was changed to 90 μm in mass parts.

(Example 12)
In the method of Example 1, a cyclic polyolefin resin (TOPAS (TM) 6013S) was used.
-04 Topas Advanced Polymers melt flow rate:
2.0 (230 ° C.)) and polypropylene resin 2011D (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene melt flow rate: 2.5 (230 ° C.)), respectively, 10 parts by mass and 90 parts by mass.
A viewing angle improving film was obtained in the same manner as in Example 1 except that the film thickness was changed to 150 μm in mass parts.

(Comparative Example 1)
Polypropylene resin (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene FS2011DG3) 50 parts by mass, ethylene butene copolymer (Mitsui Chemicals, Tuffmer A0585X) 30 parts by mass and nanocrystal structure control type polyolefin elastomer resin (Mitsui Chemicals, Notio P
N3560) A kneaded polyolefin resin composition obtained by melt-extruding 20 parts by mass with a biaxial extruder in advance at a resin temperature of 240 ° C. in a 60 mmφ single screw extruder (L / D; 22). After melt mixing and extruding with a T-die, the unstretched sheet was obtained by cooling with a 20 ° C. casting roll. Next, this unstretched sheet was stretched 4.5 times at a stretching temperature of 118 ° C. using the difference in roll peripheral speed of a longitudinal stretching machine, and further stretched 8.2 times at 145 ° C. in the transverse direction at 158 degrees. Heat set. Next, corona treatment was applied to one side to obtain a thickness of 25μ
m light diffusion film was obtained.

(Comparative Example 2)
In the method of Example 1, the resin composition is a block copolymer composed of 50 parts by mass of a cyclic polyolefin resin (TOPAS (TM) 5013S-04 Topas Advanced Polymers, melt flow rate: 8.6 (230 ° C.)), ethylene and octene. The field of view is the same as in Example 1 except that 50 parts by mass of resin (INFUSE (TM) D9100.15 melt flow rate: 2.4 (230 ° C.)) manufactured by Dow Chemical Company is changed to 120 μm. A corner enhancement film was obtained.

(Comparative Example 3)
In the method of Example 1, 35 parts by mass of a cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 8.6 (230 ° C.)) and a polymethylpentene polymer (Mitsui Chemicals, Inc.) were used. Manufactured TPX (TM) DX350 Melt flow rate: 110 (260 ° C.) A viewing angle improving film was obtained in the same manner as in Example 1 except that the film thickness was changed to 100 μm.

(Comparative Example 4)
A viewing angle improving film was obtained in the same manner as in Example 5 except that the thickness was changed to 175 μm and the layer thickness configuration was changed to 25/125/25 (μm) by the method of Example 2.

(Comparative Example 5)
In the method of Example 2, a viewing angle improving film was obtained in the same manner as in Example 2 except that the thickness was changed to 126 μm and the layer thickness configuration was changed to 28/70/28 (μm).

(Comparative Example 6)
In the method of Example 1, a cyclic polyolefin resin (TOPAS (TM) 6013S) was used.
-04 Topas Advanced Polymers melt flow rate:
2.0 (230 ° C.)) and polypropylene resin 2011D (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene melt flow rate: 2.5 (230 ° C.)) are respectively 20 parts by mass and 80 parts by mass.
A viewing angle improving film was obtained in the same manner as in Example 1 except that the film thickness was changed to 150 μm in mass parts.

(Comparative Example 7)
In the method of Example 1, cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) and polypropylene resin 2011D (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene melt flow) A viewing angle improving film was obtained in the same manner as in Example 1 except that the blending ratio of rate: 2.5 (230 ° C.) was changed to 10 parts by weight and 90 parts by weight, respectively, and the film thickness was changed to 30 μm.

The viewing angle improving film of the present invention has a light distribution pattern having both the straight transmission property and the diffuse transmission property, and the wavelength dependency of the light emitted according to the angle of the emitted light is effective in improving the viewing angle. Since it is controlled to work effectively to suppress the decrease in frontal brightness, it is installed at the viewing side of the liquid crystal cell of the liquid crystal display device, satisfying the antinomy phenomenon of improving the viewing angle and suppressing the decrease in frontal brightness at a high level. It is possible to provide a liquid crystal display device in which both the effect of improving the gamma shift and the suppression of the decrease in front luminance can be provided.
In addition, the liquid crystal display device has both a gamma shift improvement effect and a suppression of a decrease in front luminance, and has a high commercial value. Therefore, the contribution to the industry is great.

Claims (8)

Transmission of light having a wavelength of 550 nm in the main diffusion direction measured by the method described in the specification in a light diffusing film formed by melt extrusion molding a mixture of at least two incompatible resins. The ratio (I60 / I0 × 100) of the transmittance (I60) at a degree (I0) and an emission angle of 30 degrees is 0.06 to 1.0%. A viewing angle improving film. The viewing angle improving film according to claim 1, wherein at least one of the incompatible resins is a polyolefin resin. The viewing angle improving film according to claim 2, wherein two of the incompatible resins are polyolefin resins. The viewing angle improving film according to claim 2, wherein the polyolefin resin is selected from a polyethylene resin, a polypropylene resin, and a cyclic polyolefin resin. 5. The functional layer selected from a hard coat layer, a reflection reducing layer and an antiglare layer is combined with at least one layer on the viewer side surface of the viewing angle improving film.
The viewing angle improvement film in any one of. 6. A liquid crystal display device comprising the viewing angle improving film according to claim 1 placed on an observer side of a liquid crystal cell of the liquid crystal display device. The liquid crystal display device according to claim 6, wherein a main diffusion direction of the viewing angle improving film is set in a horizontal direction of the liquid crystal display device. 7. The liquid crystal display device according to claim 6, wherein a main diffusion direction of the viewing angle improving film is set in a vertical direction of the liquid crystal display device.