JP2012068626A - Film for improving viewing angle, liquid crystal display device and method for improving viewing angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for improving a viewing angle, the film achieving both of a viewing angle improving effect and suppression of decrease in front brightness in high levels while suppressing changes in tones.SOLUTION: The film for improving a viewing angle is obtained by fusing and extrusion-molding a mixture composed of at least two kinds of resins incompatible with each other. In the film, a ratio (I/I×100) of the transmittance (I) at an exiting angle of 30 degrees to the transmittance (I) at an exiting angle of 0 degree of light having a wavelength of 440 nm in a main diffusion direction is 0.25 to 5.5%.

Description

  The present invention provides a visual field installed on the outgoing light side or incoming side of the liquid crystal cell of the liquid crystal display device, which achieves both a high viewing angle improvement effect by suppressing a change in color tone depending on the viewing angle and a reduction in front luminance. The present invention relates to an angle enhancement film and a liquid crystal display device that achieves both a viewing angle improvement effect using the viewing angle enhancement film and suppression of a decrease in front luminance at a high level. Further, the present invention has a liquid crystal display device having a narrow viewing angle by a simple method of installing a viewing angle improving film having specific optical characteristics on the outgoing light side or the incoming light side of the liquid crystal cell of the liquid crystal display device. The present invention relates to a method for solving the problem and improving the viewing angle of a liquid crystal display device.

  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, for example, the angle with respect to the vertical line of the screen is increased, that is, the screen angle is larger than that when observed from the front as it becomes more oblique. This refers to a phenomenon in which the image quality deteriorates. Examples of the image quality include phenomena such as hue of a color image, image contrast, luminance of a white display image, and white blur due to light leakage of a black display image. In the deterioration of the image quality, the change in the hue of the color image is particularly important.

  The color change is, for example, the degree of change in the color tone of a phenomenon in which when a white image is observed at a different angle, an image that appears white in frontal observation is observed obliquely, the color changes to a yellowish color. Determined. Hereinafter, the degree of color change is referred to as a color shift degree, and the effect of suppressing the color shift is referred to as 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 processes. 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 luminance are anti-paradoxical events and are difficult to achieve both. 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 into a sheet, and further stretching, but the diffusion of the film shown in FIGS. The following points are suggested from the intensity distribution of transmitted light (hereinafter also referred to as a variable angle light distribution pattern).
Since the film direction in FIG. 3 has a high degree of diffusivity, the effect of improving the viewing angle is excellent, but the front brightness is greatly reduced. On the other hand, since the film direction of FIG. 4 has a low diffusivity, a decrease in front luminance is suppressed, but the effect of improving the viewing angle is inferior. In the case of the so-called anisotropic diffusion film in which the light diffusibility is different in the film direction, the front luminance reduction is governed by the larger diffusivity as will be described later. Suggested to be large.
That is, it is suggested that the anisotropic direction of the light diffusing film is set in either direction, and the effect of improving the viewing angle and the suppression of the decrease in front luminance cannot be achieved.

  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 has a high diffusivity on both the left and right and top and bottom sides as in Patent Document 1, based on the variable angle light distribution pattern of the film shown in FIGS. 3A and 3B of Patent Document 2. Therefore, although the viewing angle improvement effect is excellent, it is suggested that the reduction in frontal luminance is large and the viewing angle improvement effect and the suppression of reduction in frontal luminance are not compatible.

  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-shaped cracks. From the variable light distribution pattern of the film of FIG. It is suggested that both the 90 ° azimuth and α = 0, 180 ° azimuth are deficient in diffusivity and are good with little reduction in front luminance, but the viewing angle improvement effect is not sufficient.

  Further, Patent Document 4 proposes a method using a lens film. From the variable angle light distribution pattern of the film shown in FIGS. 8 (left and right direction) and 9 (up and down direction) of Patent Document 4, since the diffusivity is high in the left and right direction of the film of FIG. Is good, but the front brightness is greatly reduced. On the other hand, the diffusivity is low in the vertical direction of the film in FIG. 7, suggesting that the effect of improving the viewing angle is not sufficient. As described above, when an anisotropic diffusion film is used as described above, the reduction in front luminance is governed by the greater diffusivity, so in the disclosed technique, the front luminance reduction is performed regardless of the direction of use of the film. Is suggested to be large.

  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. The variable angle light distribution pattern of the film shown in FIG. 2 of Patent Document 5 suggests that the diffusivity is insufficient and the front luminance is low and good, but the viewing angle improvement effect is not sufficient. ing.

  As described above, some conventional methods for improving the viewing angle with a light diffusing film satisfy either the viewing angle 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 has been made in view of the current state of the prior art, and its object is to suppress a change in color tone of an image by installing the liquid crystal cell on the outgoing light side or the incoming light side. An object of the present invention is to provide a viewing angle improving film capable of achieving both a viewing angle improvement effect and a suppression of a decrease in front luminance at a high level, and a liquid crystal display device using the viewing angle improving film.
Another object of the present invention is to provide a method for improving the viewing angle improvement characteristic of a liquid crystal display device that solves the problem of the liquid crystal display device that the viewing angle is narrow.

  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 at least two kinds of resin mixtures to a specific range, thereby achieving a contradictory event. It was found that the viewing angle improvement effect and the suppression of the decrease in front luminance can be achieved at a high level. Further, the present inventor has a liquid crystal display device having a narrow viewing angle by a simple method of installing a viewing angle improving film having specific optical characteristics on the outgoing light side or the incoming light side of the liquid crystal cell of the liquid crystal display device. I found that the problem could be solved. The present invention has been completed based on these findings.

That is, the present invention has the following configurations (1) to (24).
(1) A viewing angle improving film obtained by melt-extruding a mixture of at least two mutually incompatible resins, and the transmittance (I ₀₎ of light having a wavelength of 440 nm in the main diffusion direction at an emission angle of 0 °. A viewing angle improving film, wherein a ratio (I ₃₀ / I ₀ × 100) of transmittance (I ₃₀ ) at an emission angle of 30 degrees to 0.25) is 0.25 to 5.5%.
(2) The viewing angle improving film as described in (1), wherein the total light transmittance of light having a wavelength of 550 nm is 79 to 95%.
(3) The viewing angle improving film according to (1) or (2), wherein the half-value width of the variable-angle light distribution pattern in the main diffusion direction of light having a wavelength of 440 nm is 18 degrees or less.
(4) The viewing angle improving film according to any one of (1) to (3), wherein at least one of the incompatible resins is a polyolefin resin.
(5) The viewing angle improving film as described in (4), wherein two types of incompatible resins are polyolefin resins.
(6) The viewing angle improving film according to (5), wherein the polyolefin resin is selected from the group consisting of a polyethylene resin, a polypropylene resin, and a cyclic polyolefin resin.
(7) The viewing angle improving film according to (5) or (6), wherein an adhesion improving layer made of a polyolefin resin containing a polar group is laminated on at least one surface of the viewing angle improving film. .
(8) At least one functional layer selected from a hard coat layer, a reflection reducing layer and an antiglare layer is laminated on the surface on the viewer side of the viewing angle improving film (1) to ( 7) The viewing angle improving film according to any one of the above.
(9) A liquid crystal display device, wherein the viewing angle improving film according to any one of (1) to (8) is installed closer to an observer than a liquid crystal cell of a liquid crystal display device.
(10) A liquid crystal display device comprising the viewing angle improving film according to any one of (1) to (7) disposed between a liquid crystal cell of a liquid crystal display device and a light source.
(11) The liquid crystal display device according to (9) or (10), wherein the main diffusion direction of the viewing angle improving film is set in a horizontal direction of the liquid crystal display device.
(12) The liquid crystal display device according to (9) or (10), wherein a main diffusion direction of the viewing angle improving film is set in a vertical direction of the liquid crystal display device.
(13) In a liquid crystal display device having a backlight light source, a liquid crystal cell, and a polarizer placed on both sides of the liquid crystal cell, (1 A viewing angle characteristic improving method for a liquid crystal display device, wherein the viewing angle improving film according to any one of (1) to (7) is disposed and used.
(14) The viewing angle characteristic improving method for a liquid crystal display device according to (13), wherein the main diffusion direction of the viewing angle improving film is a horizontal direction of the display screen.
(15) The method for improving viewing angle characteristics of a liquid crystal display device according to (13), wherein the main diffusion direction of the viewing angle improving film is a vertical direction of the display screen.
(16) It is characterized in that at least one functional layer selected from a hard coat layer, a reflection reducing layer and an antiglare layer is laminated on the viewing side of the viewing angle improving film used by being arranged on the viewing side. (13) A method for improving viewing angle characteristics of a liquid crystal display device according to any one of (15).
(17) A liquid crystal display device using the viewing angle characteristic improving method according to any one of (13) to (16).
(18) A polarizing plate, wherein the viewing angle improving film according to any one of (1) to (7) is laminated on a polarizer.
(19) Polarized light characterized in that at least one functional layer selected from a hard coat layer, a reflection reducing layer and an antiglare layer is laminated on the surface of the polarizing film for improving the viewing angle of the polarizing plate according to (18). Board.
(20) A protective film with a viewing angle improving function, wherein a self-adhesive layer is laminated on one side of the viewing angle improving film according to any one of (1) to (7).
(21) The protective film with a viewing angle improving function according to (20), wherein the self-adhesive layer is made of a flexible polymer.
(22) The viewing angle improving film according to any one of (1) to (7), on the pressure-sensitive adhesive layer surface of the double-sided adhesive film, wherein one surface is a self-adhesive layer and the other surface is a pressure-sensitive adhesive layer. The protective film with a viewing angle improving function according to (20) or (21), wherein:
(23) At least one functional layer selected from a hard coat layer, a reflection reducing layer and an antiglare layer is laminated on the opposite surface of the self-adhesive layer of the protective film with a viewing angle improving function ( The protective film with a viewing angle improvement function in any one of 20)-(22).
(24) Use of a protective film with a viewing angle improving function, wherein the protective film with a viewing angle improving function according to any one of (20) to (23) is detachably attached to the outermost surface of a liquid crystal display device Method.

  The viewing angle improving film of the present invention has a characteristic variable angle light distribution pattern having both characteristics of straight transmission and diffuse transmission. In addition, since the variable-angle light distribution pattern of the light emitted through the viewing angle enhancement film is controlled to change depending on the wavelength of the light, the outgoing light side or the incoming light side of the liquid crystal cell of the liquid crystal display device To provide a liquid crystal display device that can achieve both the anti-contradictory effect of improving the viewing angle and suppressing the decrease in front luminance at a high level, and achieving both the effect of improving the viewing angle and suppressing the decrease in front luminance. Can do. That is, the light emitted from the film surface that greatly contributes to the front luminance has a high transmittance of light having a wavelength of 550 nm, and the light emitted in the direction where the angle from the perpendicular to the film surface that contributes to the viewing angle improvement effect is high is blue. It is designed to increase the transmittance of light having a wavelength of 440 nm close to, so that both the viewing angle improvement effect and the front luminance reduction can be achieved.

It is a figure which shows an example of the brightness | luminance change by an observation angle at the time of improving a viewing angle with a highly diffusible light-diffusion film. It is a figure which shows an example of the preferable variable angle light distribution pattern which the viewing angle improvement film used for this invention should have.

(Basic characteristics of viewing angle enhancement film)
The viewing angle improving film of the present invention is obtained by melt-extruding a mixture of at least two mutually incompatible resins, and measuring light having a wavelength of 440 nm in the main diffusion direction measured by the method described in the specification. The ratio (I ₃₀ / I ₀ × 100) of the transmittance (I ₃₀ ) at an exit angle of 30 degrees to the transmittance (I ₀ ) at an exit angle of ₀ degrees is 0.25 to 5.5%. .

(Half width diffusivity)
In the viewing angle improving film of the present invention, the half-value width of the variable angle light distribution pattern in the main diffusion direction of light having a wavelength of 440 nm measured by the method described in the examples is preferably 18 degrees or less.
When the half width exceeds 18 degrees, when used in the viewing angle characteristic improving method of the present invention, a decrease in front luminance of the liquid crystal display device increases, and the desired effect of the present invention cannot be obtained.
A preferable upper limit of the half width is 16 degrees, and a more preferable upper limit is 14 degrees. The lower limit of the half width is not particularly limited, but is preferably 3 degrees, and more preferably 4 degrees.
In general, diffusivity is evaluated by the half width (angle at half the height of the peak top of the variable light distribution pattern). The larger the half width, the stronger the diffusivity, and the smaller the half width, the poor diffusivity. ing. The above half-width is measured by the method described in the examples, and is a measure of diffusivity that has been widely used in the past. Hereinafter, the measured value may be referred to as a half-value width diffusivity. However, the diffusivity in the variable angle light distribution pattern suitable for achieving both the viewing angle improvement effect and the front luminance reduction suppression described later cannot be accurately shown only by using the half-value width diffusion degree as an index.
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 was installed horizontally on a sample stage, and a white image (Nokia monitor test for windows V 1.0 (manufactured by Nokia)) having a size of 131 × 131 mm in the center of this panel. Mode), drop 3 drops of water on the white image with a dropper, place a light diffusing film on it, spread the water evenly between the panel and the film, and make contact with the CCD camera and display. The distance between them is assumed to be 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. A dependency profile was obtained.
The blank measurement was performed in the same manner without attaching a 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.

  Therefore, in order to overcome the contradictory phenomenon of the effect of improving the viewing angle and suppressing the decrease in front luminance and to make both characteristics compatible at a high level, the half-value width diffusivity needs to be set to a rather low range as described above. In addition, it is necessary to impart diffusibility that can exhibit a viewing angle improvement effect.

(Preferred variable angle light distribution pattern)
As a result of intensive studies on a method for solving the seemingly contradictory problems, the present inventors have a high straight transmission property in order to achieve both the contradictory characteristics of viewing angle improvement effect and front luminance suppression, and Appropriate diffusibility needs to be imparted, that is, it can be expressed by increasing the diffusivity evaluated by the spread of the hem of the variable-angle light distribution pattern, even if the full width at half maximum is in the above range, and It has been found that the diffusibility can be evaluated with a transmittance of an emission angle of 30 degrees.

An example of a variable angle light distribution pattern that satisfies the above optical characteristics is shown in FIG. As shown in FIG. 2, it is preferable that the variable angle light distribution pattern has a characteristic characteristic having both the straight transmission and the diffuse transmission.
This variable angle light distribution pattern is obtained by the following method.
[Measurement method of variable 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 right and left, right and left), light receiving angle: -90 ° to 90 ° (angle on the equator plane), filter: ND10 used, luminous flux Under the conditions of aperture: 10.5 mm (VS-1 3.0), light receiving aperture: 9.1 mm (VS-3 4.0), it is fixed to the sample stage so that the main diffusion direction is horizontal, and transmitted light The settings of SENSITIVITY and HIGH VOLTON were adjusted so that the peak top value of the variable angle luminous intensity curve was about 80% of the full scale, and the variable angle luminous intensity curve of the transmitted light was obtained.

(Spread spreading spread)
The viewing angle enhancing film used in the present invention preferably has a light transmittance of 0.7 to 10 at a wavelength of 440 nm at an exit angle of 30 degrees in the main diffusion direction as measured by the method described in the examples. 0.8-9 is more preferable and 1.0-8 is still more preferable. The upper limit is further preferably 7 or less, particularly preferably 6 or less, and most preferably 5.5 or less.
The relative transmittance at a wavelength of 440 nm at an emission angle of 30 degrees is a measure of diffusivity that focuses on the spread of the tail of the variable-angle light distribution pattern of emitted light when light is incident in a direction perpendicular to the film surface. As the value increases, the skirt spreads, that is, the angle until the emitted light becomes zero increases. Hereinafter, this characteristic is referred to as a skirt spread diffusion degree.
If the skirt spreading diffusivity is less than 0.7, the viewing angle improvement effect is insufficient due to insufficient diffusivity, which is not preferable.
On the other hand, when the skirt spread diffusion degree exceeds 10, the effect of improving the viewing angle becomes excessive, and the color tone becomes bluish when observed obliquely, which is not preferable. In addition, the effect of suppressing the decrease in front luminance may be reduced.
The skirt spreading diffusion degree is a novel diffusibility evaluation scale newly created by the present inventors in the present invention.

(Spread spread ratio)
The above-mentioned spreading spread is important for the viewing angle improvement effect, but it is a sufficient characteristic to overcome the contradictory phenomenon of the viewing angle improvement effect and the suppression of the decrease in front luminance and to make both characteristics compatible at a high level. It can not be said.
In the above-mentioned preferable variable light distribution pattern, it is preferable that the straight transmission is high in terms of suppressing a decrease in front luminance. That is, it is preferable that the transmittance is high at an emission angle of 0 degree. Therefore, in order to make both of the above characteristics compatible at a high level, the ratio between the transmittance at the exit angle of 0 ° and the skirt spread is important. It was found that this ratio can be displayed by the ratio (I ₃₀ / I ₀ × 100) of the transmittance (I ₃₀ ) at the exit angle of 30 degrees to the transmittance (I ₀ ) at the exit angle of 0 degrees, thereby completing the present invention.
That is, the ratio (I ₃₀ ) of the transmittance (I ₃₀ ) at an exit angle of 30 degrees to the transmittance (I ₀ ) at an exit angle of 0 degrees of light having a wavelength of 440 nm in the main diffusion direction measured by the method described in the examples. / I ₀ × 100) is important to be 0.25 to 5.5%.
The skirt spreading diffusivity ratio is more preferably 0.30 to 4.5%, further preferably 0.35 to 4.0%, and particularly preferably 0.35 to 3.5%.
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. In other words, if the skirt spreading diffusivity is less than 0.25%, the suppression of lowering the front brightness is good, but the effect of improving the viewing angle is insufficient, such being undesirable. Conversely, if the skirt spread ratio exceeds 5.5%, it is not preferable because the front luminance decreases greatly. In some cases, the color shift correction effect is excessive and the color tone is bluish.
For example, when the main spreading spread ratio is obtained from the figures described in the above-mentioned patent documents, the high diffusivity side of Patent Document 1, the (b) of FIG. The side diffusivity ratios are 88%, 60% and 78%, respectively. Therefore, it can be said that the preferable skirt spread ratio described above is in a significantly lower range than the films disclosed in these patent documents.

(Wavelength dispersion)
It is also important to pay attention to the wavelength “440 nm” in the definition of the skirt spread diffusivity and the skirt spread diffusivity ratio. As described above, the phenomenon that the viewing angle characteristic is low is caused by the fact that the color tone that appears white when viewed from the front becomes a yellowish tone when observed from a high angle. The present inventors consider that it is important for blue light to be more easily transmitted at a high angle in order to cancel such color change as one means for exhibiting the effect of improving the viewing angle. We focused on the wavelength.
Accordingly, it can be said that the above-described skirt spread diffusivity and skirt spread diffusivity ratio are novel characteristic values that combine two factors of diffusibility and wavelength dispersion.
That is, the viewing angle improving film of the present invention is completely different in optical design concept from a conventionally known diffusion film.
In the present invention, attention is paid to the wavelength 440 nm for the half-value width diffusivity. As will be described later, the wavelength of 550 nm is important for the reduction in front luminance. Since the influence of the wavelength of light is small with respect to the half-value width diffusivity, there is no big difference even if it is evaluated at a wavelength of 550 nm.
(Anisotropy)
The viewing angle improving film used in the present invention preferably has an anisotropy of 2.0 or more as measured by the method described in the examples. 5.0 or more is more preferable, and 10 or more is more preferable.
If it is less than the said lower limit, since the effect of anisotropy falls, it is not preferable.
On the other hand, the upper limit is not limited, but 200 or more is technically difficult, and the effect of imparting anisotropy is saturated.
By satisfy | filling the said range, the viewing angle improvement effect and the suppression effect of a front luminance fall can be balanced in a more preferable direction.

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.

(Total light transmittance)
The viewing angle improving film of the present invention has a total light transmittance of light having a wavelength of 550 nm measured by the method described in the specification, preferably 79 to 95%, more preferably 82 to 93%.
The upper limit is more preferably 92% or less, still more preferably 91% or less, and particularly preferably 90% or less.

The total light transmittance is an index of a reduction in front luminance, and is measured by the method described in the examples in the present invention. That is, the measurement was performed by fixing the sample diffusion spectrophotometer to the sample stage so that the main diffusion direction was horizontal. In the case of an isotropically diffusing film, the total light transmittance does not change even if the fixing direction of the film changes, but in the case of a so-called anisotropic diffusion film in which light is diffused in a specific direction, the film at the time of measurement This is because the total light transmittance varies depending on the fixed direction of the light. Since the total light transmittance is received and measured with an integrating sphere, it seems that it does not change depending on the fixing direction of the film, but in the case of an anisotropic diffusion film, the total light transmittance may vary greatly depending on the fixing direction. It is a countermeasure for some reason.
The main diffusion direction can be determined by, for example, diffusion of transmitted light when the laser marker light is allowed to pass through the film. That is, the direction in which the emitted light spreads when the light is transmitted through the film with a laser marker is defined as the main diffusion direction. It should be noted that the total light transmittance is lower when the measurement is performed with the main diffusion direction fixed in the horizontal direction.
The reason why the above phenomenon occurs is presumed to be due to the influence of the position of the light receiving portion in the integrating sphere. If the diffused light in the main diffusing direction is directly incident on the light receiving portion of the integrating sphere, it can be considered that the diffused light that is directly incident is strongly influenced by the incident light.
Note that the integrating sphere used in the measuring apparatus used in the measurement method of the present invention described in the examples described later has a light receiving portion at the top of the integrating sphere, so that it directly enters the light receiving portion. The measured value in the direction that is least susceptible to the influence of the light to be used is used, and it is assumed that the value reflects the true total light transmittance.
Therefore, it can be measured using a self-recording spectrophotometer (UV-3150; manufactured by Shimadzu Corporation) and an integrating sphere attachment device (ISR-3100; manufactured by Shimadzu Corporation) used in the measuring methods described in the examples. is important.
If the total light transmittance is less than 79%, the front luminance is greatly reduced, and the luminance may be reduced when observed from the front of the liquid crystal display device.
On the other hand, if it exceeds 95%, the effect of suppressing the decrease in front luminance may be saturated.

The present inventors have found that the decrease in front luminance is roughly governed by the transmittance of straight light, that is, by the parallel light transmittance. However, in a narrow region that satisfies both high front luminance and viewing angle improvement effect, it has been found that the conventional non-spectral parallel light transmittance using a haze meter or the like is not satisfactory.
Therefore, intensive studies were conducted to clarify the factors governing the decrease in front luminance, and the total light transmittance defined in the present invention was reached.
When viewed from the front in an actual display device, not only light that has passed straight through the diffusion film from the light source in the normal direction of the film, but also light from light sources other than in the normal direction is bent by the diffusion film, and the normal line of the film Some are emitted in the direction. The front luminance should be a total of these lights, and it is considered that the total light transmittance defined in the present invention is close to the actual observation state without being largely biased to light in a specific direction.
In addition, the fact that the wavelength of 550 nm is important is that light near the wavelength of 550 nm is considered to have the highest spectral luminous efficiency for human eyes, and it is assumed that this has a great influence. ing.

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) The standard expression for lowering the front luminance is preferably 20% or less. 18% or less is more preferable, and 15% or less is more preferable.
Although the absolute value of the front luminance varies depending on the method and type of the panel, it has been confirmed that when the evaluation is performed based on the above reduction in front luminance, the value is almost constant even if the method and type of the panel are changed.
By satisfying the total light transmittance, the above-described reduction in front luminance can be made a preferable range.

(Action mechanism)
It is publicly known that a viewing angle improvement effect can be exhibited by sacrificing front luminance with a light diffusion film. Certainly, as described above, the brightness when observed from an oblique direction (high angle) can be improved by using a highly diffusive film evaluated by a conventionally known half width method diffusion degree, but at the same time, the brightness of the front surface Is significantly reduced. Therefore, the effect of improving the viewing angle and the decrease in front luminance are contradictory events, and it is difficult to achieve both.
In order to overcome the contradictory phenomenon of this viewing angle improvement effect and front luminance reduction suppression, it is important to use the variable angle light distribution pattern shown in FIG. That is, it is important to set the skirt spreading diffusivity ratio within a specific range. By setting the skirt spreading diffusivity ratio within a specific range, it is possible to balance the straight transmission that greatly contributes to the front luminance and the diffuse transmission that greatly contributes to the improvement of the viewing angle. In this way, it is presumed that the contradictory phenomenon of front luminance and viewing angle improvement can be overcome, and both high front luminance and high viewing angle can be achieved.
Furthermore, the wavelength dispersion of the emitted light that has passed through the viewing angle improving film is also important. That is, it is important that the light emitted in the direction with a higher angle from the normal to the film surface contributing to the viewing angle improvement effect is designed so that the relative transmittance of light having a wavelength of 440 nm close to blue is high. It is presumed that the viewing angle improvement effect and front luminance can be achieved at a high level due to the synergistic effect of these factors.
Although the importance of some of the above individual factors has been disclosed in the prior art, the anti-contradictory phenomenon of the effect of improving the viewing angle and lowering the front luminance has been overcome by the action mechanism by satisfying all the above factors simultaneously. The light diffusing film can be achieved for the first time in the present invention.

  Although it is not clear why the effect of improving the viewing angle and the effect of suppressing the decrease in front luminance can be improved by increasing the degree of anisotropy, the emitted light can be condensed in a specific direction by increasing the degree of anisotropy. It is presumed that this is caused by the difference in the degree of contribution of the light condensing effect between the viewing angle improvement effect and the front luminance reduction.

(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) The standard expression for lowering the front luminance is preferably 20% or less. 18% or less is more preferable, and 15% or less is more preferable.
Although the absolute value of the front luminance varies depending on the method and type of the panel, it has been confirmed that when the evaluation is performed based on the above reduction in front luminance, the value is almost constant even if the method and type of the panel are changed.
By satisfying the total light transmittance, the above-described reduction in front luminance can be made a preferable range.

(Preferable range of viewing angle improvement effect)
In the present invention, the viewing angle improvement effect was evaluated by the method described in the examples. That is, a white image is displayed on the panel of a commercially available liquid crystal display device, the CCD camera is moved on the equator of the image, the angle dependency of the x value of the YIE system of the CIE color system is measured, and The x value at 0 degree (x0) and the x value at 70 degree (x70 _S ) were obtained. On the other hand, the x value (x70 _B ) of the panel itself on which the viewing angle improvement film sample was not installed was obtained, and Δx (70 degrees) = x70 _S −x70 _B was calculated and evaluated. Hereinafter, the Δx (70 degrees) is referred to as a color shift degree. In general, a panel of a liquid crystal display device has a positive color shift degree. The y value also behaves almost the same as the x value and is displaced in the green and red directions, resulting in a yellowish color. Since both the x value and the y value exhibit almost similar behavior, the x value is used as a representative value in the present invention.
The effect of improving the viewing angle is manifested by canceling the shift of the color shift degree to the positive side. Therefore, it is preferable that the color coordinates of the viewing angle improving film move in the negative direction. The color shift degree varies depending on the panel type and type. For example, in the case of the VA system, −0.006 to −0.02 is preferable. -0.008 to -0.018 is more preferable.
If it exceeds -0.006, the degree of color shift is insufficient and the effect of improving the viewing angle is reduced, which is not preferable. On the other hand, if it is less than -0.02, the degree of color shift is too high, so that the effect of improving the viewing angle becomes excessive, and the white image when viewed obliquely becomes a bluish tone, 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 mutually incompatible thermoplastic resins. The existence form of the mixture of at least two kinds of mutually incompatible thermoplastic resins is not particularly limited as long as the above optical characteristics are satisfied. The structure may be a structure in which both resins form a co-continuous phase. 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.

From these thermoplastic resins, at least two kinds of resins that are incompatible with each other (not compatible with each other) may be selected. The blending ratio of the at least two types of mutually incompatible thermoplastic resins is preferably 5/95 to 95/5, more preferably 10/90 to 90/10, and more preferably 20/80, respectively. Although it can be said that the ratio of ˜80 / 20 is more preferable, it is preferable to set in consideration of the type of the resin component and the layer configuration described later, the thickness of the light diffusion layer, the manufacturing method, and the like as described later.
In addition, there exists a tendency for the direction with many compounding ratios of two types of mutually 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, polypentene, polyhexene, polymethylpentene, 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, for example, the total light transmittance becomes low and 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 (Tg of 100% cyclic monomer), but is preferably 230 ° C. or lower, more preferably 200 ° C. or lower, and 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 values measured at a rate of temperature increase of 10 ° C./min according to ISO11357-1, -2, -3.

The content of the cyclic component of the cyclic polyolefin resin is preferably 70 to 90% by mass, more preferably 73 to 85% by 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 mutually 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 a sea component, and desired optical characteristics.
The guideline has a higher composition ratio and a lower melt flow rate becomes a sea component. In the case of the same amount, a higher melt flow rate tends to be a sea component. When the melt flow rate with a higher composition ratio is high, a simple sea / island structure may be formed instead of a co-continuous phase, for example.

  In the present invention, as described above, it is preferable to impart anisotropy to the diffusivity. In order to impart this characteristic, it is preferable to give anisotropy to the island structure. In order to form an island structure having such a shape, it is preferable to make a difference in melt viscosity between the sea component resin and the island component resin. In particular, it is preferable to lower the melt viscosity of the island component than the sea component. For this purpose, for example, it is preferable to provide a difference in melt flow rate, and it is preferable to increase the melt flow rate of the island component rather than the sea component. It is also preferable to make a difference between the rigidity of the sea component resin and the island component resin. In particular, it is preferable to lower the rigidity of the island component than the sea component.

  In addition, when the melt flow rate of the island component is low, it is difficult to apply a force for thinning the island component due to the share or draft in the die, and the anisotropy may decrease. This tendency becomes stronger as the mass ratio goes away from 50/50. Each characteristic is adjusted in consideration of these tendencies.

  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.
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. The reason for this is not clear, but even if there is a change in share etc. due to differences in extrusion conditions and die shapes that occur when the film forming apparatus is changed, the sea phase resin is made softer than the island phase resin, and It is presumed that the effect is mitigated by increasing the liquidity.

  The size of the island phase when both of the two 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, if it exceeds 2 μm, the degree of backscattering increases and the total light transmittance decreases, which is not preferable.

(Lamination of adhesion improving layer)
The viewing angle improving film of the present invention is such that the adhesion improving layer mainly composed of a polyolefin resin mainly containing a polar group is the outermost surface on at least one surface of a light diffusion layer composed mainly of two mutually incompatible polyolefin-based resins. A multilayer light diffusing film laminated on the substrate is preferred.
By this correspondence, the adhesiveness of the viewing angle improving film to other members can be improved. For example, a viewing angle improving film can be attached to a polarizing plate incorporated in a liquid crystal cell with a water-based adhesive, and the viewing angle improving film can be easily incorporated into a liquid crystal display device.

(Adhesion improvement layer)
The polyolefin resin containing a polar group in the present invention preferably contains at least one monomer of ethylene, propylene, butene, hexene, octene, methylpentene and a cyclic olefin as its skeleton.
It may be a homopolymer using one kind of the above monomers or a copolymer using two or more kinds of monomers.

The polyolefin resin containing the polar group in the present invention preferably contains at least one kind of polar group. Examples of polar groups include carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, glycidyl groups, isocyanate groups, amino groups, imide groups, oxazoline groups, ester groups, ether groups, carboxylic acid metal bases, sulfonic acid metal bases, Examples thereof include phosphonic acid metal bases, tertiary amine bases, and quaternary amine bases. The polar group may be one kind or two or more kinds.
The type of the polar group may be appropriately selected depending on the composition of the polyolefin-based resin constituting the light diffusion layer, the type of the member to be adhered, the necessary adhesion, and the like, but preferably includes at least a carboxylic acid group It is an aspect.

  In the polyolefin resin containing a polar group in the present invention, even if the polar group is directly introduced into the polymer chain of the polyolefin resin, it is in a state of being introduced, added and mixed in another resin. It doesn't matter. Further, in some cases, the polyolefin resin of the present invention can be used after being modified by reacting, for example, a carboxylic acid group or a hydroxyl group with a compound capable of reacting with them introduced into the terminal or inside of the molecular chain. .

  In the present invention, the polyolefin resin containing the polar group may be used alone or in combination of two or more. Moreover, the compounding composition which mix | blended polyolefin resin and other types of resin which do not contain a polar group may be sufficient. In the case of the blended composition, the polyolefin resin containing the polar group is preferably contained in an amount of 10% by mass or more. More preferably, it is 30 mass% or more.

  The adhesion improving layer may be either a single area layer or a double-sided laminate. Although total thickness is not limited, 10-500 micrometers is preferable. Although the thickness composition ratio is not limited, it is preferable that the thickness of the adhesion layer is 2 to 100 μm on one side.

  The thickness constitution ratio of the light diffusion layer / adhesion improving layer is preferably 100/1 to 3/1, and more preferably 10/1 to 4/1. By doing so, the effect of improving the viewing angle and the effect of improving the adhesiveness can be balanced.

(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 using a gas pressure, for example, a method such as a so-called air knife method in which pressing is performed with a gas pressure such as air, a vacuum chamber method in which a vacuum nozzle sucks and closely contacts, an electrostatic contact method in which electrostatic force closes, etc. Is mentioned. 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 extending direction to form an elongated structure, the light diffusibility in the direction perpendicular 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.

The thickness of the viewing angle improving film of the present invention is preferably 10 to 500 μm, more preferably 20 to 500 μm, and even more preferably 20 to 200 μm. The optical properties vary greatly depending on the film thickness as well as the type, blending ratio, layer configuration, manufacturing method, and the like of the resin component of the light diffusion layer.
In addition, when adjusting thickness, it can adjust by changing draft ratio, extrusion flow rate, lip width, and the like.

(Viewing angle characteristics improvement method)
The viewing angle characteristic improving method in the present invention is a liquid crystal display device having at least a backlight source, a liquid crystal cell, and a polarizer disposed on the light exit side or the light entrance side of the liquid crystal cell. The viewing angle improving film is installed on the light output side or the light input side of the polarizer, respectively. Therefore, the method of the present invention can be improved without increasing the number of steps of manufacturing the liquid crystal display device, and can be applied to any liquid crystal display device, so that it is very economical and has a wide range of application. It is. Therefore, the viewing angle enhancement film described above may be installed on the outermost surface of the liquid crystal cell of the liquid crystal display device produced by a normal method, or the viewing angle enhancement film described above on the polarizer installed on the viewing side of the liquid crystal cell. May be incorporated into the panel of the liquid crystal display device so that the viewing angle improving film is on the viewing side. In addition, the viewing angle improving film described above may be installed on the outermost surface on the light incident side of the liquid crystal cell used in a liquid crystal display device, or the above viewing angle improvement may be performed on the polarizer installed on the light incident side of the liquid crystal cell. A film may be laminated and incorporated in the liquid crystal cell of the liquid crystal display device so that the viewing angle improving film is on the light incident side.

(Polarizer)
The polarizer in the present invention is not limited as long as it is made of a film or sheet having a polarizing function. For example, what dye | stained iodine or a dichroic pigment | dye to PVA etc. is mentioned. Moreover, a polarizer single-piece | unit may be sufficient, for example, the composite_body | complex with various protective films may be sufficient.

(Viewing angle improving film and polarizer laminate and adhesive used therefor)
In the present invention, as described above, it is one of the preferred embodiments that the viewing angle improving film is laminated with the polarizer incorporated in the liquid crystal cell and incorporated in the liquid crystal cell. Although the structure of this laminated body is not limited, it is one of the preferable embodiments that the viewing angle improving film and the polarizer are bonded together with an adhesive.
The adhesive is not limited as long as it is transparent and has adhesiveness with both the viewing angle improving film and the polarizing plate. For example, what has crosslinking | crosslinking property by active rays, such as a heat | fever and UV, is mentioned. For example, both the viewing angle improving film and the polarizing plate are familiar, and a blend of transparent monomers, oligomers and polymers and a crosslinking agent can be mentioned. Moreover, what has the functional group which causes a crosslinking reaction in the said method in the molecule | numerator of the said transparent monomer, oligomer, and polymer, or the compounded body of this component and a crosslinking agent may be sufficient.
Since many polarizing plates have a PVA polymer as a main component, the adhesive is preferably made of a PVA polymer. For example, polyvinyl alcohol obtained by saponifying polyvinyl acetate; derivatives thereof; saponified products of copolymers with vinyl acetate and monomers having copolymerizability; acetalization, urethanization, etherification of polyvinyl alcohol Modified polyvinyl alcohol obtained by grafting or phosphoric esterification. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins may be used alone or in combination of two or more.
The saponification degree of the PVA polymer is not limited, but is preferably 60 to 85%.
Although it does not specifically limit as a crosslinking agent at the time of using this PVA-type polymer, A water-soluble or water-dispersible thing is preferable. For example, it is not particularly limited as long as it has crosslinkability with a hydroxyl group, and examples thereof include melamine-based, isocyanate-based, carbodiimide-based, oxazoline-based, and epoxy-based compounds. From the viewpoint of the stability of the coating solution over time, melamine-based, isocyanate-based, carbodiimide-based, and oxazoline-based compounds are exemplified. Furthermore, the crosslinking agent is preferably a polyvinyl alcohol melamine compound or an isocyanate compound. Moreover, in order to promote a crosslinking reaction, you may use a catalyst etc. suitably as needed.

  When stacking with the above polarizer and incorporating it into a liquid crystal display device, it is preferable to take into account the difference in the direction of the absorption axis of the polarizer due to the difference in mode of the liquid crystal display device.

(Protective film with viewing angle enhancement function)
In the present invention, by laminating a self-adhesive layer on one side of the viewing angle improving film, the obtained laminate can be detachably attached to the surface of a liquid crystal cell of a liquid crystal display device, for example. Therefore, not only the viewing angle of the liquid crystal display device can be improved, but also a protective function for preventing contamination and scratches on the surface of the liquid crystal display device can be added. In addition, since it is detachable, it can be replaced with a new one when, for example, the surface of the viewing angle improving film becomes dirty or scratched and the visibility deteriorates. That is, since it can be used as a protective film with a viewing angle improvement function, it is one of the preferred embodiments.

The self-adhesive layer may be formed directly on the surface of the viewing angle improving film, or may be formed on the surface of another base film, and the self-adhesive layer laminated film and the viewing angle improving film may be laminated. In particular, the latter method is preferable because it has high versatility and a wide selection range. In the latter method, the self-adhesive layer may be formed by sticking a viewing angle improving film to a so-called double-sided adhesive film made of a double-sided adhesive layer. The double-sided adhesive film may be a self-adhesive layer on both sides, and the viewing angle improving film may be fixed with a single-sided self-adhesive layer. The method of sticking the viewing angle improving film on the pressure-sensitive adhesive layer side is preferable from the viewpoint of being able to firmly fix the viewing angle improving film and the economical point.
The type and production method of the double-sided pressure-sensitive adhesive film in the case of producing a protective film with a viewing angle improving function using the double-sided pressure-sensitive adhesive film are not limited. The use of a double-sided pressure-sensitive adhesive film is preferable because it is excellent in the self-adhesive property of the self-adhesive layer and is excellent in cost performance.

  Further, for example, a method of directly combining an amorphous polyolefin-based resin layer disclosed in JP-A-2009-299021 and the above-described viewing angle improving film is preferable from the viewpoint of economy. The composite method is not limited. For example, a co-extrusion method or an extrusion lamination method can be mentioned.

(Self-adhesive layer)
The self-adhesiveness in the present invention means a property capable of adhering without applying pressure from the outside when affixing to the adherend surface.
More specifically, it is not limited as long as it can be repeatedly applied and peeled a plurality of times, but it is made of a flexible polymer, and even if the sticking and peeling are repeated, the change in the sticking performance and peeling performance is small, and the peeling is performed. In this case, it is preferable because a phenomenon that the components of the self-adhesive layer are transferred to the surface of the display screen to contaminate the display screen hardly occurs.
The flexible polymer may be a non-crosslinked polymer or a crosslinked polymer. Moreover, a gel body may be sufficient. The type of polymer is not limited. Examples thereof include polyolefin polymers, acrylic polymers, polyester polymers, polyurethane polymers, and silicone polymers. A polyolefin-based polymer, a composition of a polyolefin-based polymer and another polymer, and a silicone-based polymer are preferable because the above properties are more excellent.
The type of the silicone-based polymer and the crosslinking method are not limited, but for example, the method disclosed in JP2009-113420A is preferable. Addition type silicone polymers are preferred.

Self-adhesive layer having the above-described flexible polymer is preferably surface dynamic hardness is evaluated by the following measurement method is 0.01~100mN / μm ^2, and more preferably 0.03~80mN / μm ² .
The above surface layer dynamic hardness is lowered said repairability becomes difficult to peel is less than 0.01 mN / [mu] m ^2, the fixing force exceeds 100 mN / [mu] m ² on the opposite is insufficient.

[Surface dynamic hardness]
Using Shimadzu Dynamic Ultra Micro Hardness Tester Model DUH202, manufactured by Shimadzu Corporation, test mode: mode 3 (soft material test), indenter type: 115, test load: 1.97 mN, load speed: 0.0142 mN / sec, holding Time: Measured under conditions of 5 seconds. The sample was fixed on a slide glass with an epoxy adhesive and set on a measuring table. As the dynamic hardness evaluated by this measurement method, different measurement values are obtained depending on the depth from the surface of the sample. The measured value at a depth of 3 μm from the surface was taken as the surface hardness.

  Further, the self-adhesive layer made of the flexible polymer has an average surface roughness (Ra) of 0.12 μm or less, preferably 0.08 μm or less, particularly preferably 0.05 μm or less. . As a result, a practical fixing force due to the self-adhesiveness of the self-adhesive layer, that is, a surface tack force is developed. However, when the average surface roughness (Ra) exceeds 0.12 μm, self-adhesiveness does not appear and fixing by self-adhesion becomes impossible. The average surface roughness (Ra) is a value measured by the following method.

[Average surface roughness (Ra)]
Using a SE-200 type surface roughness meter manufactured by Kosaka Seisakusho, measurement was performed under the conditions of longitudinal magnification: 1000, lateral magnification: 20, cutoff: 0.08 mm, measurement length: 8 mm, and measurement speed: 0.1 mm / min.

(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, liquid crystal display devices in TN, VA, OCB, IPS, and ECB modes can be given.

(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 laminated on the surface on the viewer side of the viewing angle improving film. Each of the functional layers may have a single structure, or a plurality of functions may be stacked.
The scratch resistance of the viewing angle improving film surface is improved by laminating the hard coat layer. Further, 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 in which 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 composite may be laminated directly on the surface of the viewing angle improving film, or may be laminated 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.

In the present invention, as a method for installing the viewing angle improving film or the above functional layer composite on a liquid crystal display device, for example, it is attached to a polarizer or polarizing plate of a liquid crystal cell with an adhesive or an adhesive having a small reflection loss. It is preferable to wear.
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.

(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.

1. Half-value width diffusivity (half-value width of the variable-angle light distribution pattern in the main diffusion direction of light having a wavelength of 440 nm)
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: −80 ° to 80 ° (polar angle from film normal, azimuth angle is horizontal), light source: D65, field of view: 2 ° Under the conditions, the sample was fixed on the sample stage so that the main diffusion direction of the sample was horizontal, and the variable angle spectrophotometric curve of the transmitted light was obtained. The tilt angle was 0 °.
In actual use, the deviation between the axis of the sample stage and the axis in the main diffusion direction is allowed up to about 20 degrees.
Measurements were taken at 5 ° pitch.
The angle at half the height of the peak top of the variable angle light distribution pattern obtained by the above measurement was determined and used as the half-value width diffusivity.
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, each sample was measured three times and displayed as an average value.
When the surface roughness is different between the two surfaces of the sample, it is preferable to measure the sample while fixing the sample so that the light transmission directions coincide when used as a viewing angle improving film. 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.

2. Spreading skirt spread (relative transmittance of light having a wavelength of 440 nm at an emission angle of 30 degrees 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, each sample was measured three times and displayed as an average value. The transmittance was displayed at a wavelength of 440 nm at a light receiving angle (hereinafter referred to as an emission angle) of 30 degrees.
When the surface roughness is different between the two surfaces of the sample, it is preferable to measure the sample while fixing the sample so that the light transmission directions coincide when used as a viewing angle improving film. 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.

3. Flared diffusivity ratio (transmittance at the emission angle of 0 ° in the main diffusion direction of the wavelength 440nm light (transmittance at the emission angle of 30 degrees with respect to _{I 0) (ratio} of _{I 30) (I 30 / I} 0 × 100))
The transmittance at the exit angle of 30 degrees is measured with respect to the transmittance at the exit angle of 0 degree (I ₀ ) by measuring the transmittance at the exit angle of 0 ° and 30 ° at the wavelength of 440 nm by the same method as the above-mentioned skirt spread diffusivity. ₃₀ ) (I ₃₀ / I ₀ × 100) was calculated and expressed 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.

4). Anisotropy The skirt spread diffusivity obtained by the above skirt spread diffusivity measurement method was defined as (I ₃₀ ) _H.
Further, in the above hem spreading diffusivity measurement method, the sample is fixed to the sample stage so that the main diffusion direction of the sample is vertical, and the skirt in the direction orthogonal to the above (I ₃₀ ) _H is obtained by the same method as described above. (I ₃₀ ) _V , which is the spread diffusivity, was determined.
The degree of anisotropy was calculated by the following (1).
(I ₃₀ ) _H / (I ₃₀ ) _V (1)

5. Total light transmittance Self-recording spectrophotometer (UV-3150; manufactured by Shimadzu Corporation) is equipped with an integrating sphere attachment device (ISR-3100; manufactured by Shimadzu Corporation), and has a slit width of 12 nm and a wavelength range of 300 to 800 nm at high speed. The spectrum was measured by scanning at 550 nm and displayed as the transmittance at 550 nm.
In the measurement, the value when the measurement was performed with the sample fixed to the sample fixing device so that the main diffusion direction of the sample was horizontal was used. The main diffusion direction was determined by applying light to the sample with a laser marker and detecting the diffusion direction of the emitted light.
When the surface roughness differs between the two surfaces of the sample, it is better to measure by fixing the sample in the direction in which the light transmission direction in actual use matches. 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.

6). Front luminance reduction Measurement was performed using RISA-COLOR / ONE-II (manufactured by Highland). A commercially available VA type liquid crystal display device was installed horizontally on a pedestal, and a white image (Nokia monitor test for windows V 1.0 (manufactured by Nokia)) with a size of 131 × 131 mm in the center of this panel. Mode), drop 3 drops of water on the white image with a dropper, place a sample film on it, and evenly spread the water between the panel and the film. Was fixed at a position 1 m in the vertical direction, 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). Viewing angle improvement effect RISA-COLOR / ONE-II (manufactured by Highland) was used for measurement. A commercially available VA type liquid crystal display device is installed horizontally, and a white image (Farbe mode of Nokia monitor test for windows V 1.0 (manufactured by Nokia)) is displayed at the center of this panel with a size of 131 × 131 mm. Then drop 3 drops of water on the white image with a dropper, place a diffusion film on it, spread the water evenly between the panel and film, and make the distance between the CCD camera and the display vertical. Assuming 1 m in the 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 angle dependence of the x value of the Yxy system of the CIE color system under the following conditions The x value (x70 _S ) at 70 degrees was determined from the x value (x0) at 0 degrees with respect to the perpendicular. On the other hand, the x value (x70 _B ) of the panel itself on which the viewing angle improving film sample was not installed was obtained, and Δx (70 degrees) = x70 _S −x70 _B was calculated and displayed.
For the x value, the white image was divided into 25 parts of 5 × 5, and the luminance of all the pixels of 9 parts of 3 × 3 at the center was measured and displayed as an 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.
In addition, when evaluating the viewing angle improvement effect of the liquid crystal display device in the horizontal direction of the screen, the measurement was performed with the liquid crystal screen installed so that the horizontal direction of the liquid crystal screen is in the equator direction. On the other hand, when evaluating the effect of improving the viewing angle in the vertical direction of the liquid crystal display device, the liquid crystal display was installed so that the vertical direction of the liquid crystal screen was the equator direction.

Example 1
10 parts by mass of cyclic polyolefin resin (TOPAS (TM) 6013F-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.)) 90 parts by mass is melt-mixed at a resin temperature of 250 ° C. using a PCM45 extruder manufactured by Ikekai Tekko Co., Ltd., extruded with a T-die, and cooled with a mirror-like cooling roll to obtain a 90 μm thick field of view. A corner enhancement film was obtained. 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. The film was wound up at a speed of 3 m / min.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example was high in quality because the reduction in front luminance was suppressed within 20%, and a significant viewing angle improving effect was exhibited.
In addition, (DELTA) x (70 degree | times) of panel itself when not bonding a viewing angle improvement film was +0.016.

(Example 2)
Using two melt extruders and a first extruder as a base layer, cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) 35 mass 65 parts by mass of a block copolymer resin composed of ethylene, octene, INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.) manufactured by Dow Chemical Co., Ltd. In the extruder of No. 2, a polypropylene-based adhesive resin (Admer (TM) QF551, manufactured by Mitsui Chemicals, Ltd., melt flow rate: 5.7 (190 ° C.)) was supplied, and after melt coextrusion by the T-die method, A viewing angle improving film having a thickness of 56 μm was obtained by cooling with a satin cooling roll. 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. The layer thickness configuration was 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, except that the film thickness and the layer thickness configuration are 40 μm and 6/28/6 (μm), both the outlet temperature of the extruder is changed to 270 ° C., and the winding speed is changed to 18 m / min. A viewing angle improving film was obtained in the same manner as in Example 2.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example was excellent in both the viewing angle improving effect and the front luminance reduction, and was high quality.

Example 4
Using two melt extruders and a first extruder as a base layer, cyclic polyolefin resin (TOPAS (TM) 5013S-04 Topas Advanced Polymers melt flow rate: 8.6 (230 ° C.)) 50 mass Part block copolymer resin consisting of ethylene and octene (INFUSE (TM) D9100.15 melt flow rate: 2.4 (230 ° C.), manufactured by Dow Chemical Co., Ltd.) A polypropylene resin 2011D (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene melt flow rate: 2.5 (230 ° C.)) is supplied by a machine, melt-coextruded by a T-die method, and then cooled by a mirror surface cooling roll. A viewing angle improving film having a thickness of 115 μm and a layer thickness of 30/55/30 (μm) was obtained. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. The first extruder was a biaxial system, and the second extruder was a uniaxial system. The outlet temperature was 250 ° C. for both extruders. The surface temperature of the cooling roll was set to 20 ° C. The film was wound up at a speed of 3.0 m / min.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improvement film obtained in this example was slightly inferior to the viewing angle improvement film obtained in Example 1, but the front luminance reduction was small and high quality.

(Example 5)
In the method of Example 2, the outlet temperatures of the first extruder and the second extruder were 250 and 230 ° C., respectively, except that the surface of the cooling roll was changed to a satin surface and the winding speed was changed to 15 m / min. A viewing angle improving film was obtained in the same manner as described above.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improvement film obtained in this example was slightly worse in front luminance than the viewing angle improvement film obtained in Example 2, but the viewing angle improvement effect was improved.

(Example 6)
In the method of Example 1, cyclic polyolefin resin (TOPAS (TM) 6013F-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 mixing ratio of rate: 2.5 (230 ° C.) was changed to 35 parts by mass and 65 parts by mass, respectively, and the film thickness was changed to 30 μm.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example is less effective in improving the viewing angle than the viewing angle improving film obtained in Example 1, but the front luminance reduction is improved.

(Example 7)
A viewing angle improving film was obtained in the same manner as in Example 1 except that the film thickness was changed to 60 μm by the method of Example 1.
Table 1 shows the characteristics of the obtained viewing angle improving film.
Although the viewing angle improvement film obtained in the present example has a lower front luminance than the viewing angle improvement film obtained in Example 1, the effect of improving the viewing angle is reduced.

(Example 8)
In Example 2, the resin composition supplied to the first extruder was 20 parts by mass of cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers, melt flow rate: 2.0 (230 ° C.)) and ethylene. Block copolymer resin consisting of octene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.)) manufactured by Dow Chemical Co., Ltd. 80 parts by mass, and the film thickness and layer thickness constitution are 108 μm and 24/60/24 (Μm) A viewing angle improving film was obtained in the same manner as in Example 2 except that the change was made.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example was excellent in both the viewing angle improving effect and the front luminance reduction, and was high quality.

Example 9
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 (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.)) manufactured by Dow Chemical Co., Ltd., having a thickness of 108 μm and a layer thickness of 24/60 / A viewing angle improving film was obtained in the same manner as in Example 2 except that the thickness was changed to 24 (μm).
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle enhancement film obtained in this example had the same characteristics as the viewing angle enhancement film obtained in Example 2 and was of high quality.

(Example 10)
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 84 μm and the layer thickness configuration was changed to 12/60/12 (μm).
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example had a higher front angle reduction than the viewing angle improving film obtained in Example 2, but the viewing angle improving effect was improved and the quality was high.

(Example 11)
In the method of Example 5, the viewing angle improving film is the same as Example 5 except that the surface of the cooling roll is changed to a mirror surface, the surface temperature of the cooling roll is changed to 20 ° C., and the winding speed is changed to 23 m / min. Got. Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle enhancement film obtained in this example had the same characteristics as the viewing angle enhancement film obtained in Example 5 and was of high quality.

(Example 12)
Using two melt extruders, 50 parts by mass of a cyclic polyolefin-based resin (TOPAS (TM) 5013S-04 Topas Advanced Polymers melt flow rate: 8.6 (230 ° C.)) in the first extruder as a base layer Block copolymer resin (INFUSE (TM) D9100.15 melt flow rate: 2.4 (23 ° C.) manufactured by Dow Chemical Co., Ltd.) and 50 parts by mass of a second extruder as a surface layer The polypropylene resin 2011D (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene melt flow rate: 2.5 (230 ° C.)) is supplied, melt coextruded by the T-die method, and then cooled by a mirror surface cooling roll. A viewing angle improving film having a thickness of 90 μm and a layer thickness of 30/30/30 (μm) was obtained. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. The first extruder was a biaxial system, and the second extruder was a uniaxial system. The outlet temperature was 250 ° C. for both extruders. The surface temperature of the cooling roll was set to 20 ° C. The film was wound up at a speed of 3.0 m / min. Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example was slightly inferior to the viewing angle improving film obtained in Example 5, but was high in quality with a small decrease in front luminance.

(Example 13)
In the method of Example 8, 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 composed of ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.) manufactured by Dow Chemical Co., Ltd.) 80 parts by mass, thickness is 56 μm, and layer thickness constitution is 12/32/12 A viewing angle improving film was obtained in the same manner as in Example 8 except that the thickness was changed to (μm). Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improvement film obtained in this example was superior to the viewing angle improvement film obtained in Example 8 in that the viewing angle improvement effect was inferior, but the front luminance reduction was small.

(Example 14)
In the method of Example 1, cyclic polyolefin resin (TOPAS (TM) 6013F-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) and polypropylene resin 2011D (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene Melt) A viewing angle improving film was obtained in the same manner as in Example 1 except that the blending ratio of flow rate: 2.5 (230 ° C.) was changed to 35 parts by mass and 65 parts by mass, respectively. Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example was slightly worse in front luminance than the viewing angle improving film obtained in Example 1, but the viewing angle improving effect was improved.

(Example 15)
In the method of Example 5, 35 parts by mass of cyclic polyolefin-based resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) supplied to the first extruder, ethylene, A block copolymer resin composed of octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.) manufactured by Dow Chemical Co., Ltd.) 65 parts by mass is supplied without kneading in advance, the thickness is 40 μm, the layer thickness The configuration was 6/28/6 (μm), and the outlet temperatures of the first extruder and the second extruder were 270 and 290 ° C., respectively. Moreover, the viewing angle improvement film was obtained by the same method as Example 5 except changing the surface temperature of a cooling roll into 20 degreeC, and film winding speed | velocity | rate to 9.5 m / min. Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle enhancement film obtained in this example had the same characteristics as the viewing angle enhancement film obtained in Example 5 and was of high quality.

(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 PN3560) A kneaded polyolefin resin composition obtained by melt-extruding 20 parts by mass of a biaxial extruder in advance with a resin temperature of 240 ° C. in a 60 mmφ single screw extruder (L / D; 22). After being melt-mixed and extruded with a T-die, it was cooled with a casting roll at 20 ° C. to obtain an unstretched sheet. 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. Subsequently, one side was subjected to corona treatment to obtain a light diffusion film having a thickness of 25 μm.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example had a low front luminance, but the effect of improving the viewing angle was poor and the quality was low.

(Comparative Example 2)
Using two melt extruders, supplying 100 parts by mass of polypropylene resin WF836DG3 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nobrene) as the A layer of the base material layer using the first extruder, as the B layer of the diffusion layer, In the second extruder, 17 parts by mass of polypropylene resin WF836DG3 (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene) and 83 parts by mass of propylene / ethylene copolymer HF3101C (Nippon Polypro Co., Ltd.) were supplied. Thus, after melt coextrusion by the T-die method, the unstretched sheet was obtained by cooling with a 20 ° C. casting roll. Next, this unstretched sheet was stretched 4.8 times at a stretching temperature of 120 ° C. using the difference in roll peripheral speed of a longitudinal stretching machine, and subsequently heated at 165 ° C. by a tenter-type stretching machine, and then stretched at 155 ° C. The film was stretched 9 times in the transverse direction at the temperature. Subsequently, the film was heat-set at 166 ° C. to obtain viewing angle improving films in which the thicknesses of the A layer and the B layer were 22.2 μm and 2.8 μm, respectively. The corona treatment was performed on the surface of the base layer A immediately before winding.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example had a low front luminance, but the effect of improving the viewing angle was poor and the quality was low.

(Comparative Example 3)
In the method of Example 9, a viewing angle improving film was obtained in the same manner as in Example 9 except that the thickness was changed to 28 μm and the layer thickness configuration was changed to 6/16/6 (μm).
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example had a low front luminance, but the effect of improving the viewing angle was poor and the quality was low.

(Comparative Example 4)
In the method of Example 1, a viewing angle improving film was obtained in the same manner as in Example 1 except that the thickness was changed to 30 μm.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example had a low front luminance, but the effect of improving the viewing angle was poor and the quality was low.

(Comparative Example 5)
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 5.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example has a good viewing angle improving effect, but has a large reduction in front luminance and low quality.

(Comparative Example 6)
In the method of Example 6, a viewing angle improving film was obtained in the same manner as in Example 6 except that the thickness was changed to 150 μm.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example has a good viewing angle improving effect, but has a large reduction in front luminance and low quality.

(Comparative Example 7)
In the method of Example 9, a viewing angle improving film was obtained in the same manner as in Example 9 except that the film thickness was changed to 216 μm and the layer thickness configuration was changed to 48/120/48 (μm).
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example has a good viewing angle improving effect, but has a large reduction in front luminance and low quality.

(Comparative Example 8)
On one side of a 100 μm thick highly transparent polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) A viewing angle improving film was obtained by coating and drying using a coating machine so that a mixed part of 50 parts by mass of the polyurethane resin had a thickness of 30 μm after drying.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example has a good viewing angle improving effect, but has a large reduction in front luminance and low quality.

(Example 16 and Example 17)
The viewing angle improving films obtained in Example 1 and Example 2 were attached to the surface of a commercially available VA liquid crystal monitor with a double-sided adhesive tape for optics so that the main diffusion direction was substantially horizontal to the monitor. The effect of improving the viewing angle in the direction and the decrease in front luminance were evaluated. The results are shown in Table 2.
The same results as in Example 1 and Example 2 were obtained, and the effect of improving the viewing angle was exhibited in a form in which the decrease in front luminance was suppressed. The visual angle improvement effect in the horizontal direction was also confirmed by naked eye observation. Moreover, the brightness | luminance fall when it observed from the front was also small.

(Comparative Example 9 and Comparative Example 10)
The viewing angle improving films obtained in Comparative Example 3 and Comparative Example 4 were attached to the surface of a commercially available VA liquid crystal monitor with a double-sided adhesive tape for optical use so that the main diffusion direction was substantially horizontal to the monitor. The effect of improving the viewing angle in the direction and the decrease in front luminance were evaluated. The results are shown in Table 2.
The same results as in Comparative Example 3 and Comparative Example 4 were obtained, and the decrease in front luminance was small, but the viewing angle improvement effect was small. The visual angle improvement effect was also small by visual observation.

(Comparative Example 11 and Example 12)
The viewing angle improving films obtained in Comparative Example 5 and Comparative Example 8 were attached to the surface of a commercially available VA liquid crystal monitor with an optical double-sided adhesive tape so that the main diffusion direction was substantially horizontal to the monitor. The effect of improving the viewing angle in the direction and the decrease in front luminance were evaluated. The results are shown in Table 2.
Although the result equivalent to the comparative example 6 and Example 7 was obtained and the viewing angle improvement effect was favorable, the front brightness fall was large. The viewing angle improvement effect in the horizontal direction was also good by naked eye observation, but the luminance was greatly reduced when observed from the front.

(Example 18 and Example 19)
A protective film for anti-reflection type display made by Kureha Elastomer Co., Ltd., which is hard-processed, is attached to the opposite side of the surface to which the double-sided adhesive tape of the viewing angle improving film of Example 16 and Example 17 is attached. Were combined to obtain a viewing angle improving film composite. Remove the separator on the double-sided adhesive tape side of the viewing angle enhancement film composite and attach it to the surface of a commercially available VA liquid crystal monitor so that the main diffusion direction is substantially horizontal to the monitor. The improvement effect and front luminance reduction were evaluated.
Results equivalent to those of Example 16 and Example 17 were obtained. Furthermore, since an antireflection effect is added, even when the liquid crystal panel is observed in a bright environment, the viewing angle improvement effect is not reduced. In addition, even when used in a place where external light is reflected, since the reflection of external light is suppressed, the visibility of the image is improved. Moreover, since it was hard-worked, it became difficult to be damaged.

(Example 20 and Example 21)
A protective film for display of hard anti-glare type manufactured by Kureha Elastomer Co., Ltd. is attached to the opposite side of the surface to which the double-sided adhesive tape of the viewing angle improving film of Example 16 and Example 17 is attached. The layers were combined to obtain a viewing angle enhancement film composite. Remove the separator on the double-sided adhesive tape side of the viewing angle enhancement film composite and attach it to the surface of a commercially available VA liquid crystal monitor so that the main diffusion direction is substantially horizontal to the monitor. The improvement effect and front luminance reduction were evaluated.
Results equivalent to those of Example 16 and Example 17 were obtained. Furthermore, since an antireflection effect is added, even when the liquid crystal panel is observed in a bright environment, the viewing angle improvement effect is not reduced. In addition, even when used in a place where external light is reflected, since the reflection of external light is suppressed, the visibility of the image is improved. Moreover, since it was hard-worked, it became difficult to be damaged.

(Example 22 and Example 23)
In Example 16 and Example 17, the affixing direction of the main diffusion direction film was changed so that the main diffusion direction of the viewing angle improving film was substantially perpendicular to the panel. The effect of improving the viewing angle in the vertical direction of the panel image was developed.

(Example 24 and Example 25)
In the methods of Example 16 and Example 17, the liquid crystal display device was changed to the TN type, and the application direction of the viewing angle enhancement film was applied in a substantially horizontal direction to improve the horizontal viewing angle and the front luminance. We evaluated the decline.
The results are shown in Table 3.

(Example 26 and Example 27)
In the methods of Example 16 and Example 17, the liquid crystal display device was changed to the TN type, and the application direction of the viewing angle enhancement film was applied in a substantially vertical direction, thereby improving the vertical viewing angle and the front luminance. We evaluated the decline.
The results are shown in Table 3.

(Comparative Example 13 and Comparative Example 14)
In the method of Example 23 and Example 24, except having used the film of the comparative example 4 and the comparative example 5 as the film stuck on a liquid crystal display device, the result evaluated like Example 23 and Example 24 is shown. 3 shows.

(Comparative Examples 15 and 16)
In the method of Example 25 and Example 26, except having used the film of the comparative example 4 and the comparative example 5 as a film stuck on a liquid crystal display device, the result evaluated like Example 25 and Example 26 is shown. 3 shows.

  When the viewing angle improving film was not attached, Δx (70 degrees) of the panel itself was +0.048, −0.05, and +0.014 in the horizontal direction, the downward direction, and the upward direction, respectively.

Table 3 shows the following.
Regarding the horizontal direction, by using the viewing angle improving film of the present invention, the viewing angle characteristics can be improved in a manner that suppresses a decrease in front luminance as in the VA type liquid crystal display device.
In the vertical direction, the improvement effect differs between the observation from the upper side and the observation from the lower side. Viewing from the lower direction is less effective than the horizontal direction, but the viewing angle characteristics can be improved. However, the effect of improving the viewing angle characteristics when observed from above is negligible. In the observation from the upper side, it is presumed that the difference in behavior is caused by the viewing angle characteristics of the liquid crystal display device itself being superior to the observation from the lower side and the observation in the horizontal direction.
In the TN type liquid crystal display device, the magnitude of color tone inversion is considered to be important. Although the above-described effect of the color shift in the upward direction is slight, the color tone reversal property is markedly improved in any direction including the upward direction in the viewing angle improving film of the present invention. Therefore, it can be said that the viewing angle characteristic improving method of the present invention is also effective for a TN type liquid crystal display device.

(Example 28)
In the method of Example 24, evaluation was performed in the same manner as in Example 25 except that the attachment position of the viewing angle improving film was changed to the light incident side of the liquid crystal cell.
Δx (70 degrees) was −0.014, and the front luminance reduction rate was 13.6%. Even if the viewing angle improving film was installed on the light incident side of the liquid crystal cell, the viewing angle improving effect was exhibited.

(Examples 29 and 30)
The viewing angle enhancement films of Example 2 and Example 5 were attached to one side of a polarizer made of PVA and iodine so that the absorption axis of the polarizing film and the main diffusion direction of the viewing angle enhancement film were orthogonal to each other, and vice versa. A TAC film (manufactured by FUJIFILM Corporation, thickness 80 μm) was attached to the surface to prepare a polarizing plate.
Remove the polarizing plate on the upper surface side of the panel of a commercially available VA type liquid crystal display device, change it to the above polarizing plate, and install it so that the main diffusion direction of the viewing angle improving film is horizontal, The angle improvement effect and the front brightness reduction were evaluated.
Results equivalent to those of Example 2 and Example 5 were obtained.

In addition, the viewing angle improvement film of Example 2 and Example 5 had favorable adhesiveness as a result of evaluating by adhesive evaluation by the method shown below.
On the other hand, the viewing angle improving films in which the adhesion improving layer made of the polyolefin resin containing a polar group was not laminated on the surface layer of Examples 1, 4 and 12, etc., had poor adhesion.

(Adhesion evaluation method)
A catalyst comprising a block polyisocyanate crosslinking agent and an organotin compound obtained by polymerizing a polyvinyl alcohol polymer aqueous solution having a saponification degree of 74 mol% adjusted to a solid content concentration of 5% by mass on the surface of the viewing angle improving film by the following method. Was added with a wire bar so that the thickness of the polyvinyl alcohol polymer layer after drying was 5 μm with respect to the polyvinyl alcohol polymer so that the solid content ratio was 0.04 and 0.02. And dried at 70 ° C. for 5 minutes. As the polyvinyl alcohol polymer aqueous solution, a solution in which a red dye was added so as to facilitate the determination was used. The prepared sample for evaluation was attached to a glass plate having a thickness of 5 mm to which a double-sided tape was attached, and the opposite surface of the evaluation sample on which the polyvinyl alcohol polymer layer was formed was attached to the double-sided tape. Next, 100 grid-like cuts that penetrated the polyvinyl alcohol polymer layer and reached the base film were made using a cutter guide having a gap interval of 2 mm. Then, an adhesive tape (Nichiban Co., Ltd. cello tape (registered trademark) CT-24; 24 mm width) was attached to the grid-shaped cut surface. The air remaining at the interface at the time of pasting was pushed with an eraser to bring it into close contact, and then the adhesive tape was vigorously peeled off vertically 10 times. The number of squares on which the polyvinyl alcohol polymer layer was not peeled was counted to evaluate the adhesion. The case where the average number of 10 squares from which the polyvinyl alcohol polymer layer was peeled was 50 or less was good, and the case where it exceeded 50 was regarded as bad.

(Example 31 and Example 32)
The viewing angle enhancement films of Example 2 and Example 5 were attached to one side of a polarizer made of PVA and iodine so that the absorption axis of the polarizing film and the main diffusion direction of the viewing angle enhancement film were 45 degrees, A TAC film (manufactured by FUJIFILM Corporation, thickness 80 μm) was attached to the opposite surface to prepare a polarizing plate.
Remove the polarizing plate on the upper surface side of the panel of a commercially available TN type liquid crystal display device, change it to the above polarizing plate, and install it so that the main diffusion direction of the viewing angle improving film is horizontal, The angle improvement effect and the front brightness reduction were evaluated.
Results equivalent to those in Example 25 were obtained.

(Example 33 and Example 34)
An optical double-sided adhesive film produced by the method described in paragraphs 0204 to 0205 of Example 1 of JP-A-2009-73937, comprising a self-adhesive layer on one side and an acrylic adhesive layer on the other side (base) The thickness of the material film was changed to 38 μm) and the separate film on the acrylic adhesive layer side was peeled off, and the viewing angle improving films of Example 1 and Example 2 were adhered to the surface of the acrylic adhesive layer, respectively. A protective film with a viewing angle improving function was obtained.
The surface dynamic hardness of the surface of the self-adhesive layer of the optical double-sided adhesive film was 0.09 mN / μm ² . The average surface roughness (Ra) was 0.04 μm.
The separation film on the self-adhesive layer side of each of the obtained protective films with viewing angle enhancement function is peeled off, and the main diffusion direction of the viewing angle enhancement film is formed on the surface of the TN type liquid crystal display device used in Example 24 and Example 25. Sticking in a substantially horizontal direction, the effect of improving the viewing angle in the horizontal direction and the reduction in front luminance were evaluated.
The viewing angle improvement performance equivalent to Example 24 and Example 25 was expressed, and the viewing angle improvement performance was excellent. In addition, since the self-adhesive layer is attached to the surface of the display screen, the adhesive property is excellent, and the adhesive can be attached without air entrainment. For example, even when a small amount of air is caught, the air escapes over time. Further, since the self-adhesive layer has repairability, it could be easily removed and pasted again. Once removed, there was no glue residue on the display screen and no contamination of the display screen was observed. Furthermore, since the self-adhesive layer has cushioning properties, it has a function of protecting the display screen.

  The viewing angle improving film of the present invention has a variable-angle light distribution pattern having both the straight transmission property and the diffuse transmission property, and the wavelength dependency of the emitted light according to the angle of the emitted light improves the viewing angle. Since it is controlled to work effectively and to suppress the front luminance reduction, installing it on the outgoing light side or the incoming light side of the liquid crystal cell of the liquid crystal display device is a trade-off between the viewing angle improvement effect and the front luminance reduction suppression. The phenomenon can be satisfied at a high level, and a liquid crystal display device in which the effect of improving the viewing angle and the suppression of the decrease in front luminance can be provided, which is extremely useful for improving the function of the liquid crystal display device. In addition, the liquid crystal display device has both a viewing angle 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 (24)

A viewing angle improving film formed by melt-extrusion molding a mixture of at least two mutually incompatible resins, and emitting light with a wavelength of 440 nm in the main diffusion direction with respect to transmittance (I ₀ ) at 0 ° A viewing angle improving film, wherein a transmittance (I ₃₀ ) ratio (I ₃₀ / I ₀ × 100) at an angle of 30 degrees is 0.25 to 5.5%.   The viewing angle improving film according to claim 1, wherein the total light transmittance of light having a wavelength of 550 nm is 79 to 95%.   3. The viewing angle improving film according to claim 1, wherein the half-value width of the variable-angle light distribution pattern in the main diffusion direction of light having a wavelength of 440 nm is 18 degrees or less.   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 4, wherein the two types of incompatible resins are polyolefin resins.   The viewing angle improving film according to claim 5, wherein the polyolefin resin is selected from the group consisting of a polyethylene resin, a polypropylene resin, and a cyclic polyolefin resin.   The viewing angle improving film according to claim 5 or 6, wherein an adhesion improving layer made of a polyolefin resin containing a polar group is laminated on at least one outermost surface of the viewing angle improving film.   The functional layer selected from a hard coat layer, a reflection reducing layer, and an antiglare layer is laminated on at least one layer of the viewer side surface of the viewing angle improving film. The viewing angle improving film described in 1.   9. A liquid crystal display device comprising the viewing angle improving film according to claim 1 installed on an observer side of a liquid crystal cell of the liquid crystal display device.   A liquid crystal display device comprising the viewing angle improving film according to claim 1 placed between a liquid crystal cell and a light source of the liquid crystal display device.   The liquid crystal display device according to claim 9 or 10, wherein a main diffusion direction of the viewing angle improving film is set in a horizontal direction of the liquid crystal display device.   The liquid crystal display device according to claim 9 or 10, wherein a main diffusion direction of the viewing angle improving film is set in a vertical direction of the liquid crystal display device.   In a liquid crystal display device having a backlight source, a liquid crystal cell, and a polarizer installed on both sides of the liquid crystal cell, either one of the polarizers installed on both sides of the liquid crystal cell is provided on one of the surfaces. A method for improving the viewing angle characteristics of a liquid crystal display device, comprising using the viewing angle improving film according to any one of the above.   14. The method for improving the viewing angle characteristics of a liquid crystal display device according to claim 13, wherein the main diffusion direction of the viewing angle improving film is a horizontal direction of the display screen.   14. The method for improving the viewing angle characteristics of a liquid crystal display device according to claim 13, wherein the main diffusion direction of the viewing angle improving film is a vertical direction of the display screen.   14. A functional layer selected from a hard coat layer, a reflection reducing layer and an antiglare layer is laminated on the viewing side of a viewing angle improving film used by being arranged on the viewing side. The viewing angle characteristic improving method of the liquid crystal display device according to any one of -15.   17. A liquid crystal display device using the viewing angle characteristic improving method according to claim 13.   A polarizing plate, wherein the viewing angle improving film according to claim 1 is laminated on a polarizer.   The polarizing plate according to claim 18, wherein at least one functional layer selected from a hard coat layer, a reflection reducing layer and an antiglare layer is laminated on the surface of the viewing angle improving film of the polarizing plate.   A protective film with a viewing angle improving function, wherein a self-adhesive layer is laminated on one side of the viewing angle improving film according to claim 1.   The protective film with a viewing angle improving function according to claim 20, wherein the self-adhesive layer is made of a flexible polymer.   The viewing angle improving film according to any one of claims 1 to 7 is laminated on the pressure-sensitive adhesive layer surface of a double-sided adhesive film having one surface made of a self-adhesive layer and the other surface made of a pressure-sensitive adhesive layer. The protective film with a viewing angle improvement function according to claim 20 or 21, wherein the protective film has a viewing angle improvement function.   21. A functional layer selected from a hard coat layer, a reflection reducing layer, and an antiglare layer is laminated on the opposite surface of the self-adhesive layer of the protective film with a viewing angle improving function. The protective film with a viewing angle improving function according to any one of 22.   A method for using a protective film with a viewing angle improving function, wherein the protective film with a viewing angle improving function according to any one of claims 20 to 23 is detachably attached to the outermost surface of a liquid crystal display device.