JP2011107694A - Viewing-angle increasing film for liquid crystal display device, protective film with viewing-angle increasing function, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viewing-angle increasing film for a liquid crystal display device, capable of striking a balance in a high degree between the increase of the viewing angle and the reduction of darkening of images occurring when the display is viewed from the front. <P>SOLUTION: The viewing-angle increasing film for the liquid crystal display device obtained by melt extrusion molding of a mixture of at least two kinds of incompatible polyolefin resins satisfies the following conditions (1) and (2) at the same time: (1) The transmittance of parallel rays ranges from 5 to 90%; and (2) The diffusivity (A) in the main diffusion direction ranges from 1° to 20°. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a viewing angle enhancement film, a protective film with a viewing angle enhancement function, and a liquid crystal display device installed on the viewer side from a liquid crystal layer of a liquid crystal display device, and in particular, an improvement in viewing angle and blackening of an image by front observation. It relates to those satisfying the antinomy phenomenon of reduction at a high level.

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

  However, the liquid crystal display device has a problem that the viewing angle is narrower than that of the CRT. In order to solve this problem, Patent Document 1 proposes to provide a light diffusing film having a function of scattering and transmitting incident light 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 shape and further stretching, but the scattered transmitted light of the film shown in FIGS. The intensity distribution suggests that in either case, improvement in viewing angle and reduction in darkening are not compatible.

  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 scattered light distribution in two directions that differ by 90 degrees in azimuth with respect to the film surface. Although this film demonstrates the effect excellent in the viewing angle improvement similarly to patent document 1, from the scattered light distribution of the film shown in FIG.3 (b) of patent document 2, the reduction of darkening is still insufficient. Has been suggested.

  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 due to groove-shaped cracks. However, the diffusion degree is dependent on the light scattering intensity angle dependency of the film of FIG. It is insufficient, and it is suggested that the reduction of darkening is good, but the effect of improving the viewing angle is not sufficient.

  Furthermore, Patent Document 4 proposes a light scattering sheet obtained by mixing, dissolving, casting and drying polymethyl methacrylate PMMA and styrene-acrylonitrile copolymer SAN. This film has a phase separation structure composed of a plurality of resins having different refractive indexes and a co-continuous phase structure formed by spinodal decomposition, but the light scattering intensity of the film of FIG. From the angle dependence, it is suggested that the degree of diffusion is large and the effect of reducing darkening is insufficient, and as described in Patent Document 4, it is effective in making the brightness uniform by changing the viewing angle. Stay.

  Many techniques using lens films have been disclosed. For example, the technique disclosed in Patent Document 5 is suggested to be the same as Patent Document 1 from the diffusivity distribution of the transmitted light of the films of FIGS. That is, although the direction of FIG. 8 has a high diffusivity, the viewing angle improvement effect is excellent, but the reduction of darkening is inferior. On the other hand, the direction of FIG. The viewing angle improvement effect is inferior.

  As described above, some of the light diffusing films of conventional liquid crystal display devices satisfy one of the characteristics of improving the viewing angle and reducing darkening, but those that have achieved both characteristics at a high level have not yet been achieved. It does not exist at present.

  Further, the display screen of the liquid crystal display device has a problem that it is easily soiled or easily damaged. For this reason, a protective film for a liquid crystal display device that prevents the display screen of the liquid crystal display device from being broken, dirty, and damaged is disclosed (for example, see Patent Document 5).

  In addition, a so-called peep prevention function is installed on the surface of the liquid crystal display device to control the visible range of the display screen so that the image can be seen from the front of the screen but not from the side. The protective film which it has is disclosed (for example, refer patent document 6).

  As described above, the liquid crystal display device has a problem that the viewing angle is narrower than that of the CRT. For example, in the case of a car navigation system, it is often installed in an oblique direction of the driver, and an improvement in viewing angle is required. In addition, for example, with the enhancement of the display information of mobile phones, the usage of viewing the display screen by a large number of people is increasing, and there is an increasing demand for improving the viewing angle, contrary to the peeping prevention function described above. Yes. With such a background, a protective film for a liquid crystal display device having a viewing angle improving function is strongly desired.

Japanese Patent Laid-Open No. 7-114013 JP 2004-341309 A Japanese Patent Laid-Open No. 10-206836 JP 2002-221608 A JP 2000-56694 A JP 2010-145976 A

  The present invention has been made in view of the current state of the prior art, and the object thereof is to provide a liquid crystal layer for a liquid crystal display device that achieves both a high viewing angle and a reduction in darkening of an image by front observation at a high level. The viewing angle improving film installed on the viewer side and the display screen surface of the liquid crystal display device can be detachably installed to improve the narrowness of the viewing angle, which is a drawback of the liquid crystal display device, and the liquid crystal display device An object of the present invention is to provide a protective film with a viewing angle improving function having a function of protecting a display screen.

  As a result of diligent studies to achieve the above object, the present inventor has made a contradictory event by controlling the parallel light transmittance and diffusivity (A) to a specific range using a specific molding method. It has been found that a certain viewing angle improvement and darkening reduction can be achieved at a high level, and the present invention has been completed.

That is, this invention is invention of the following (i)-(xiii).
(I) A viewing angle improving film for a liquid crystal display device obtained by melt-extrusion molding a mixture comprising at least two incompatible polyolefin resins, which simultaneously satisfies the following conditions (1) and (2) Viewing angle enhancement film characterized by:
(1) Parallel light transmittance is 5 to 90%;
(2) The diffusivity (A) in the main diffusion direction is 1 to 20 degrees.
(Ii) The viewing angle improving film according to (i), wherein the diffusivity ratio in the main diffusion direction is 0.25 to 15%.
(Iii) The viewing angle improving film according to (i) or (ii), wherein the diffusivity (B) in the main diffusion direction is 140 to 175 degrees.
(Iv) The ratio of the diffusivity (B) in the main diffusion direction and the diffusivity (B ′) in the direction orthogonal to the main diffusion direction (diffusivity (B) / diffusivity (B ′)) is 1.2 to 6 The viewing angle improving film according to any one of (i) to (iii), which is 0.0.
(V) The at least two incompatible polyolefin-based resins are composed of a polypropylene-based resin and a polyolefin resin containing ethylene and / or butene, according to any one of (i) to (iv) Viewing angle enhancement film.
(Vi) The viewing angle improving film according to any one of (i) to (iv), wherein the at least two incompatible polyolefin resins are a cyclic polyolefin resin and a polyethylene resin.
(Vii) The viewing angle improving film according to any one of (i) to (vi), which is unstretched or stretched at a stretch ratio of 10 times or less.
(Viii) (i) to (vii) 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 viewer side of the viewing angle improving film. The viewing angle improving film according to any one of 1).
(Ix) A protective film with a viewing angle improving function, wherein the viewing angle improving film according to any one of (i) to (viii) and a self-adhesive layer are laminated.
(X) The pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive film comprising the self-adhesive layer on one side and the pressure-sensitive adhesive layer on the other side of the viewing angle improving film according to any one of (i) to (vii). A protective film with a viewing angle improving function, wherein the protective film is laminated.
(Xi) The protective film with a viewing angle improving function according to (ix) or (x), wherein the self-adhesive layer is made of a flexible polymer.
(Xii) A liquid crystal display device comprising the viewing angle improving film according to any one of (i) to (ix) on the viewer side of the liquid crystal layer.
(Xii) A protective film with a viewing angle improving function according to any one of (ix) to (xi) is detachably attached to a display screen surface of a liquid crystal display device through a self-adhesive layer. A liquid crystal display device.

The viewing angle improving film of the present invention has a light distribution pattern that combines both the straight transmission property and the diffuse transmission property. Therefore, a trade-off between improving the viewing angle and reducing the darkness of the image by frontal observation. Can be provided at a high level.
Moreover, since the protective film with a viewing angle improving function of the present invention has a self-adhesive layer laminated thereon, the protective film with a viewing angle improving function can be simply and on the display screen surface of the liquid crystal display device through this self-adhesive layer, and It can be easily fixed without entraining air at the interface between the self-adhesive layer and the display screen. Further, since the viewing angle improving function is given, the viewing angle of the fixed liquid crystal display device can be improved. Further, for example, when the surface of the protective film with a viewing angle improving function is dirty or scratched, it can be easily removed. Furthermore, in the case of this removal, since the fixing is performed by the self-adhesive layer, for example, without contamination of the display screen due to the transition to the display screen of the adhesive layer that occurs when the pressure-sensitive adhesive layer is fixed. Can be done. Furthermore, since the self-adhesive layer is made of a flexible polymer, even if an external force is applied to the display screen, it is possible to suppress the destruction of the display screen by a relaxation action due to the deformation of the self-adhesive layer.

It is a figure which shows an example of the preferable light distribution pattern of the viewing angle improvement film of this invention.

(Characteristics of viewing angle enhancement film)
The viewing angle improving film of the present invention is characterized by simultaneously satisfying the following conditions (1) to (2):
(1) The average value of parallel light transmittance is 5 to 90%;
(2) The diffusivity (A) in the main diffusion direction is 1 to 20 degrees.

  The parallel light transmittance is preferably 8 to 90%, more preferably 10 to 90%, still more preferably 20 to 70%, and particularly preferably 40 to 70%. The parallel light transmittance is an index of straight light transmittance, and in the present invention, it is obtained by measuring by the method described in the examples described later. Specifically, the parallel light transmittance is displayed as an average value of measured values obtained by measuring the film winding direction in a vertical direction and a horizontal direction on a sample stage of a haze measuring device. The reason why the film winding direction is measured in the vertical direction and the horizontal direction is that the optical characteristics may change greatly in the directions. If the parallel light transmittance is less than the above lower limit, the reduction in darkening is reduced. On the other hand, if the upper limit is exceeded, the effect of improving the viewing angle is lowered, which is not preferable.

  The diffusion degree (A) in the main diffusion direction is preferably 1 to 15 degrees, more preferably 1 to 10 degrees, and particularly preferably 1 to 6 degrees. The diffusivity (A) is an index of diffusivity that is generally widely used. In the present invention, the diffusivity (A) is obtained by measurement by the method described in the examples described later. It is technically difficult to make the diffusivity (A) less than the lower limit. On the other hand, if the diffusivity (A) exceeds the above upper limit, the reduction in darkening is worsened, which is not preferable.

  The viewing angle improving film of the present invention preferably has a diffusivity ratio in the main diffusion direction of 0.25 to 15%, more preferably 0.30 to 12%, in view of improving the viewing angle. 40 to 10% is more preferable, and 1.0 to 10% is particularly preferable. The diffusivity ratio is an index for balancing the trade-off between the improvement of the viewing angle and the reduction of darkening. In the present invention, the diffusivity ratio is obtained by measurement by the method described in the examples described later. If the diffusivity ratio is less than the above lower limit, the viewing angle improvement is lowered, whereas if the upper limit is exceeded, the reduction in darkening is lowered, which is not preferable.

  The viewing angle improving film of the present invention preferably has a diffusivity (B) in the main diffusion direction of 140 to 175 degrees, more preferably 150 to 175 degrees, and still more preferably 155 to 175 degrees. The diffusivity (B) is a display index of diffusivity that is not generally used. The diffusivity (B) is a new index that the present inventors have found out to be an index of the viewing angle improvement effect. In the present invention, the diffusivity (B) is obtained by measuring by the method described in Examples described later. If the diffusivity (B) is less than the above lower limit, the effect of improving the viewing angle is insufficient. On the other hand, if the diffusivity (B) exceeds the above upper limit, the reduction in darkening is undesirably reduced.

  Further, the viewing angle improving film of the present invention has a ratio (diffusivity (B) / diffusivity (B ′) between the diffusivity (B) in the main diffusion direction and the diffusivity (B ′) in the direction orthogonal to the main diffusion direction. )) (Also referred to as anisotropy) is preferably from 1.2 to 6.0, more preferably from 1.3 to 6.0. If it is less than the said lower limit, since the effect of anisotropy falls, it is not preferable. On the other hand, it is technically difficult to exceed the above upper limit.

The object of the viewing angle improving film of the present invention is to achieve a balance between a trade-off between improving the viewing angle and reducing darkening at a high level. In order to improve the viewing angle, high diffusibility is required. On the other hand, high straight transmission is required for reducing darkening. These characteristics generally exhibit a trade-off behavior. In order to balance the antinomy event, it is preferable to satisfy the above characteristics.
It has been conventionally known that a high diffusivity is necessary for improving the viewing angle. However, in the present invention, unlike the conventional knowledge, the diffusion degree (A), which is a widely used index of diffusion degree, is set to a rather low region and a specific range as described above. What is preferred is surprising. That is, in order to achieve both high diffusibility and high straight transmission required for imparting the above characteristics, it is necessary to deal with the opposite of conventional knowledge.

On the other hand, setting the parallel light transmittance and diffusivity (A) within the above ranges is effective for reducing darkening, but the diffuse transmittance is low, the viewing angle is insufficiently improved, and the above characteristics cannot be satisfied. . In order to achieve both a trade-off between improving the viewing angle and reducing darkening, in addition to the above two characteristics, it is necessary to simultaneously satisfy that the diffusivity ratio in the main diffusion direction is within the above range. The diffusivity ratio in the main diffusion direction is a measure of the base spread of the light distribution pattern in the main diffusion direction. Therefore, the diffusivity ratio can also be regarded as a scale indicating a kind of diffusivity. Only when the diffusivity ratio is set within the above range, it is possible to achieve both the antinomy of improving the viewing angle and reducing darkening. Regarding the technique disclosed in the above-described patent document, the light distribution distribution pattern described therein indicates that the above characteristics are not satisfied in any direction. Furthermore, by making the diffusivity (B) in the main diffusion direction within the above range, it is possible to stabilize the compatibility of the anti-twisting event.
An example of a preferable light distribution pattern for satisfying the above optical characteristics is shown in FIG.

  Further, by providing anisotropy, the degree of diffusion of light in a specific direction can be increased. On the other hand, even if anisotropy is imparted, for example, characteristics such as parallel light transmittance, which is an index of straight transmission, are less different depending on the film direction than the diffusivity. Therefore, light can be collected in a specific direction. Therefore, it is possible to achieve a higher level of balance between the improvement of the viewing angle and the antinomy of darkening.

  Although it is disclosed in many patent documents that anisotropy is effective for improving the viewing angle, the diffusivity for evaluating anisotropy is a widely used diffusivity index. It is effective only when the determination is made using not the diffusion degree (A) but the diffusion degree (B) which is an index of the diffusion degree newly found by the present inventors. In the case of the preferable light distribution pattern described above, in the diffusivity (A), even if anisotropy is imparted, there may be no difference in the diffusivity depending on the direction.

  The method for achieving this light distribution pattern is not particularly limited. For example, when two incompatible polyolefin resins have a sea / island structure, the island component units are oriented as narrow and long as possible in a specific direction. It is preferable to do so.

(Production method of viewing angle improving film)
Next, the manufacturing method of the viewing angle improvement film of this invention is demonstrated. The viewing angle improving film of the present invention can be obtained by melt extrusion molding a mixture of at least two incompatible polyolefin resins. The existence form of the mixture of at least two incompatible polyolefin-based resins is not particularly limited as long as the above optical characteristics are satisfied, and a so-called sea / island structure in which each resin exists independently as a continuous phase and a dispersed phase. It 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.

  In the present invention, the melt extrusion method is adopted, which is economically advantageous. Unlike the coating method, the melt-extrusion molding method does not use a solvent and is therefore environmentally friendly. Furthermore, since the melt extrusion molding method does not need to contain non-melting fine particles in order to impart light diffusibility, clogging of the filtration filter of the molten resin in the film forming process can be reduced, and the productivity is excellent. The clarity of the resulting film is also high.

  The film forming method by the melt extrusion molding method is not particularly limited, and for example, any of a T-die method and an inflation method may be used. Moreover, the film may be an unstretched film or may be subjected to a stretching process. 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 viewing angle improving film having the above structure, the other layer may be a simple transparent layer having no such characteristics. Moreover, all the layers may be the structure of a viewing angle improvement layer. 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.

(Incompatible resin)
The viewing angle improving film of the present invention is preferably obtained by using a mixture comprising at least two incompatible (not mutually compatible) polyolefin resins. Usually, a polyolefin-based resin does not have an aromatic ring and thus has a feature that it is not easily deteriorated by ultraviolet irradiation. Therefore, since yellowing by ultraviolet irradiation is suppressed, it is suitable as a constituent material for the light diffusion film.

The said polyolefin resin will not be specifically limited if the 70 mol% or more is comprised from an olefin type monomer. Preferably, the proportion of the olefinic monomer is 90% or more, more preferably 95% or more, and even more preferably 98% or more.
Examples of polyolefin resins include polyethylene resins, polypropylene resins, polybutene resins, polyolefin resins such as cyclic polyolefin resins and polymethylpentene resins, and copolymers thereof. In addition, modified polyolefin resins in which functional groups such as a carboxyl group, an ester group, and a hydroxyl group are introduced into these resins can also be suitably used. The polyolefin resin may be a copolymer of monomers having no aromatic ring, such as acrylic acid, methacrylic acid, and ester derivatives thereof.

  In the present invention, a combination of a cyclic polyolefin-based resin and a polyethylene-based resin, or a combination of a polypropylene-based resin and a polyolefin resin containing ethylene and / or butene is a preferred embodiment because the above-mentioned characteristics are easily obtained. . Furthermore, it can be said that this combination is preferable in terms of light resistance and economy. In addition to the above combination, a nanocrystalline structure control polyolefin elastomer resin may be further combined.

  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. When the above 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. In addition, the value of the glass transition temperature is a value measured at a heating rate of 10 ° C./min in accordance with ISO11357-1, -2, -3.

  The content of the cyclic component of the cyclic polyolefin resin is preferably 70 to 90 mass%, more preferably 73 to 85 mass%. This range is preferable particularly in the case of norbornene. In particular, a cyclic polyolefin-based resin copolymerized with ethylene has a high affinity with a polyethylene-based resin, and is preferable for achieving desired characteristics. The ethylene content is preferably 30 to 10% by mass, more preferably 27 to 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.

  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 elastomer resin has a crystal size of micron order, whereas the nanocrystal structure control type polyolefin elastomer resin has a feature that the crystal size is controlled in nano order. 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.

  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 the sea phase, and the melt flow rate of the polyethylene resin or polypropylene resin of the sea phase is the island phase. It is preferable to make it 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 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.

  The blending ratio of the at least two incompatible polyolefin resins is preferably 10/90 to 90/10, more preferably 20/80 to 80/20, and more preferably 30/70 to 30/70, respectively. A ratio of 70/30 is more preferred. The at least two incompatible polyolefin-based resins may be blended in the film forming process, 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 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.

  The melt flow rate of the at least two incompatible polyolefin 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.

  In the method of melt extrusion molding a mixture of at least two incompatible polyolefin resins as described above, for example, when the sea / island method is used, as described above, anisotropy is imparted to the shape of the island component. It is preferable in terms of imparting the above optical characteristics. A thread-like shape in which the shape of the island component is elongated is preferable. The ratio of the length of the island component / the width of the island component is preferably 5 times or more, and more preferably 8 times or more. By forming a long and slender thread shape, it is possible to suppress a decrease in straight transmission and to increase the diffuse transmission in a direction orthogonal to the orientation direction of the island components.

  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.

(Film forming method)
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 preferable because the thickness accuracy of the obtained film can be increased.

  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. Thereby, 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.

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

  10-500 micrometers is preferable, as for the thickness of the viewing angle improvement film of this invention, 20-500 micrometers is more preferable, and 20-200 micrometers is more preferable.

(Use of functional layers such as hard coat layers)
In the viewing angle improving film and the protective film with a viewing angle improving function of the present invention, at least one functional layer selected from a hard coat layer, a reflection reducing layer, and an antiglare layer is formed on the surface of the viewer side of the viewing angle improving film. It is preferable to be laminated. Each of the functional layers may have a single structure, or one functional layer may have a plurality of functions.
The scratch resistance of the viewing angle improving film surface is improved by laminating the hard coat layer. Further, by stacking 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 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. The latter method of laminating a film having a functional layer is preferably fixed with a pressure-sensitive adhesive or an adhesive, but may be simply overlapped and fixed with a jig.
The adhesive and the pressure-sensitive adhesive are not limited as long as the viewing angle improving film and the film having the functional layer can be fixed, but it is preferable to use an optical one.

(Protective film with viewing angle enhancement function)
According to this invention, the protective film with a viewing angle improvement function formed by laminating | stacking the said viewing angle improvement film and a self-adhesion layer is also provided.
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 that the viewing angle improving film can be firmly fixed and economical.
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, but can be obtained by, for example, the method disclosed in JP-A-2009-73937. 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 laminating an amorphous polyolefin resin layer disclosed in JP 2009-299021 A and the like with the aforementioned viewing angle improving film is preferable from the viewpoint of economy. The lamination 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.
The self-adhesive layer is not limited as long as it can be repeatedly applied and peeled off 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. Moreover, it is preferable to use an addition type silicone polymer.

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 .
If the surface layer dynamic hardness is less than 0.01 mN / μm ² , peeling becomes difficult and the repair property is lowered. On the other hand, if it exceeds 100 mN / μm ² , the fixing force is insufficient.

[Surface dynamic hardness]
Using Shimadzu Dynamic Ultra Hardness Tester DUH202 type 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. 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, cut-off: 0.08 mm, measurement length: 8 mm, measurement speed: 0.1 mm / min.

(Use of liquid crystal display device and viewing angle improving film or protective film with viewing angle improving function)
According to this invention, the liquid crystal display device comprised by installing the said viewing angle improvement film and the protective film with a viewing angle improvement function in the observer side from a liquid crystal layer is also provided.
As the liquid crystal display device, any of active matrix drive, simple matrix drive, etc., twisted nematic, super twisted nematic, ferroelectric liquid crystal, antiferroelectric liquid crystal, etc. can be used. In the case of a liquid crystal display device using a polarizing plate, the viewing angle improving film of the present invention may be on the viewer side from the liquid crystal layer, and may be inside or outside the polarizing plate, but the outside of the polarizing plate is closer to the visual field. This is preferable because the occurrence of polarized spots due to the corner enhancement film is suppressed. As a method for installing the viewing angle improving film of the present invention in a liquid crystal display device, for example, it is preferable to adhere as closely as possible to a liquid crystal layer substrate, a polarizing plate, a retardation plate, etc. by an adhesive with low reflection loss, They may be simply overlapped and fixed with a jig.
Moreover, sticking to the display screen surface of the liquid crystal display device of a protective film with a viewing angle improvement function is implemented through the self-adhesion layer of a protective film with a viewing angle improvement function. Therefore, the protective film with a viewing angle improving function can be detachably fixed to the display screen surface. In addition, the protection function of the display screen is manifested.

  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. It is also possible. The measurement / evaluation methods employed in the examples are as follows. In the examples, “parts” and “%” mean “parts by mass” and “% by mass”, respectively, 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. Parallel light transmittance It measured based on JISK7136 using the Nippon Denshoku Industries Co., Ltd. haze measuring device "NDH-2000".
Measured by fixing the winding direction of the film in the vertical and horizontal directions on the sample stage of the measuring device, using the average value of the measured values obtained in three measurements, and the average value of the measured values in both directions. Displayed asking for. The reason for measuring in both the vertical direction and the horizontal direction is that the parallel light transmittance may vary greatly depending on whether the film winding direction is the vertical direction or the horizontal direction.
In addition, when there was a difference in the surface roughness of both surfaces of the film, it was measured by fixing in the direction in which light passes in the same direction as when the viewing angle improvement performance was actually evaluated.

2. Diffusivity B
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 Aperture: 10.5 mm (VS-1 3.0), light receiving aperture: 9.1 mm (VS-3 4.0), SENSITIVITY: 950, HIGH VOLTON: 600, and variable angle interval 0.1 degree, The frequency of the angle between the peak rising angle and the peak ending angle of the variable angle luminous intensity curve of the transmitted light obtained by moving the light receiver from 90 degrees to +90 was obtained (see FIG. 1). . With respect to the rising and ending angles of the peak, the portion was observed with a magnifying glass 10 times, and the most advanced angle where the line of the peak disappeared was defined as each angle. A clear determination can be made if this is done.
The surface on which the light receiver is moved is defined as the equator plane.
The above measurement was performed by fixing the film so that the film winding direction was parallel to the vertical direction of the sample fixing base and the horizontal direction, and the value with the larger angle was defined as the diffusivity B.
In addition, when there was a difference in the surface roughness of both surfaces of the film, it was measured by fixing in the direction in which light passes in the same direction as when the viewing angle improvement performance was actually evaluated.
The larger diffusion degree (B) was defined as the main diffusion direction.
In the measurement, before the measurement of the sample, the light-up film (product registration) 100DX2 film, which is a light diffusion film manufactured by Kimoto Co., Ltd., the film winding direction is parallel to the vertical direction of the sample fixing table, and The sample was fixed to the sample fixing base so that the diffusion layer side was the light output side, and the variable angle photometric measurement was performed under the same conditions as described above. In the measurement, when the height of the peak top of the variable angle light curve exceeds 80% or less than 70% with respect to the full scale, the value becomes 70 to 80% with respect to the full scale. The numerical value of the SENSITIVITY or HIGH VOLTON dial was finely adjusted.

3. Diffusivity A
Similarly to the diffusivity B, the measurement was performed using an automatic variable angle photometer (GP-200: manufactured by Murakami Color Research Co., Ltd.).
The sample was fixed in the main diffusion direction obtained by the measurement of the diffusivity B, and the measurement was performed under the same conditions as the diffusivity B except for SENSITIVITY and HIGH VOLTON.
The SENSITIVITY and HIGH VOLTON settings are adjusted so that the peak top value of the transmitted light angle curve is 20 to 80% of the full scale. A light curve was determined.
The angle of the angle width (half-value width) at the half height of the peak height of the obtained variable-angle luminous intensity curve of the transmitted light was defined as diffusivity A (see FIG. 1).
In the case of a sample having a high parallel light transmittance, even if the measurement sensitivity is lowered, the peak top of the variable angle luminous intensity curve may be traded off, and the peak at the top of the head may not appear. In this case, the diffusivity A was defined as a peak width of 50% of the full scale as measured at SENSITIVITY: 150 and HIGH VOLTON: 500.
In addition, when the value of the diffusivity A was small, the half value width was calculated | required using the 10 times magnifier.

4). Diffusivity ratio The transmitted luminous intensity at −30 degrees and 0 degrees of the variable angle luminous intensity curve obtained by the above-described measurement of the diffusivity A was measured, calculated by the following formula (1), and displayed in%.
Transmitted light intensity at −30 degrees / transmitted light intensity at 0 degrees × 100 (1)
When the transmitted light intensity at −30 degrees was very low, the height was determined using a 10 × magnifier.
In addition, -30 degrees is an angle from the center on the rising side of the peak. Most samples have a target shape, and +30 degrees is almost the same value.
Further, when the peak at the top does not appear as described above, the transmitted light intensity at −30 degrees is set to −30 degrees and the full scale height is 0 degrees as measured at SENSITIVITY: 150 and HIGH VOLTON: 500. Calculated as the transmitted light intensity.

5. Anisotropy The diffusivity B in the main diffusion direction obtained in 2 above and the ratio of the diffusivity B ′ in the direction orthogonal to the main diffusion direction (diffusivity B / diffusivity B ′) were defined as anisotropy.

6). Viewing angle improvement effect Acer's TN liquid crystal monitor (V173A) is installed horizontally on a table, and a sample film is overlaid on the surface of the liquid crystal monitor or fixed with an adhesive. A color bar for viewing angle judgment is displayed with a signal generator (model: CM50), and it is observed from the front of the liquid crystal monitor at an angle of about 60 degrees to the left and right in a dark room. Ranking was done.
Ranking was determined by comparison with a standard sample divided into five stages. Judgment was made by 10 persons and displayed as an average value. The middle of each rank was determined using 0.5. For example, the intermediate value between ranks 2 and 3 is 2.5.
The blank (panel only) was set to 1. A higher rank is better.
Rank 3 or higher was judged as practical.
The evaluation was performed by placing or pasting the samples so that the main diffusion direction of the light diffusion film was parallel to the long side of the liquid crystal monitor. When the film was placed on top of each other, when the film was lifted by curl or the like, the four corners were fixed with tape and evaluated.

7). Blackening In the same manner as the viewing angle improvement effect, ranking was performed by sensory evaluation of blackening when the white background portion was observed from substantially the front. The ranking was judged by comparison with a standard sample divided into six stages. Judgment was made by two people and displayed as an average value. The middle of each rank was determined using 0.5. For example, the intermediate value between ranks 2 and 3 is 2.5.
The blank (panel only) was 6. A rank value of 2 or more was judged as practical. Rank 3 or higher is more preferable.
The characteristics can be improved by changing the color temperature of the liquid crystal panel.

8). Comprehensive evaluation A visual angle improvement effect determination rank of 3 or more and a darkening rank of 2 or more were judged to be practical. Moreover, it was judged that the thing whose sum total number of those ranks is 6 or more is practically very excellent.

Example 1
Cyclic polyolefin resin (TOPAS (TM) 6013F-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) 50 parts by mass, a block copolymer resin composed of ethylene and octene (INFUSE (manufactured by Dow Chemical) TM) D9100.05 Melt flow rate: 2.4 (230 ° C)) 65 parts by mass using a PCM45 extruder manufactured by Ikekai Tekko Co., Ltd. at a resin temperature of 250 ° C, extruded with a T-die, By cooling with a cooling roll, a viewing angle improving film having a thickness of 120 μm was obtained. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example was excellent in improving the viewing angle, and had a low degree of darkening and high quality.

(Comparative Example 1)
Using two melt extruders, 100 parts by mass of polypropylene resin WF836DG3 (Sumitomo Chemical Co., Ltd., Sumitomo Noblen) was melted in the first extruder to form a base layer A, and polypropylene resin WF836DG3 ( Sumitomo Chemical Co., Ltd., Sumitomo Nobrene) 17 parts by mass and propylene / ethylene copolymer HF3101C (manufactured by Nippon Polypro Co., Ltd.) 83 parts by mass are melt-mixed to form a light diffusion layer B, so that it becomes A / B in the die. In addition, after melt coextrusion by a T-die method, an 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, heat fixation was performed at 166 ° C. to obtain a viewing angle improving film in which the thicknesses of the A / B structure 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 little darkening and high characteristics, but the viewing angle improving effect was inferior.

(Comparative Example 2)
Using two melt extruders, in the first extruder, 60 parts by mass of cyclic polyolefin resin (TOPAS (TM) 6013F-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) Block copolymer resin consisting of ethylene and octene (INFUSE (TM) D9100.05, melt flow rate: 2.4 (230 ° C.), manufactured by Dow Chemical Co., Ltd.) 40 parts by mass as a base layer A, with a second extruder, View angle of 180μm in total thickness by melt coextrusion by T-die method and cooling with mirror cooling roll so that nano-crystal structure control type polyolefin elastomer resin (Mitsui Chemicals, Notio PN3560) becomes the surface layer An improved film was obtained. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. The layer thickness configuration was 20/140/20 (μm).
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example had little darkening and high characteristics, but the viewing angle improving effect was inferior.

(Comparative Example 3)
Cyclic polyolefin resin (TOPAS (TM) 6015S-04 Topas Advanced Polymers melt flow rate: 0.41 (230 ° C.)) 50 parts by mass, a block copolymer resin composed of ethylene and octene (INFUSE (manufactured by Dow Chemical) TM) D9817.15 Melt flow rate: 26 (230 ° C.) 50 parts by mass was melt-mixed at a resin temperature of 250 ° C. using a PCM45 extruder manufactured by Ikekai Tekko Co., Ltd. By cooling at Ra = 0.70), a viewing angle improving film having a thickness of 200 μm was obtained. The opposite surface of the cooling roll was a mirror-side presser roll that was anti-adhesive processed.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example has a very good viewing angle improving effect, but the darkening reducing effect is remarkably inferior.

(Comparative Example 4)
A polycarbonate film having a thickness of 250 μm with one surface embossed with an average surface roughness Ra of 0.56 μm and a satin type was used as a viewing angle improving film.
The properties of the viewing angle enhancement film are shown in Table 1.
The viewing angle enhancement film was evaluated in the direction of entering light from the anti-embossed surface for all characteristics.
The viewing angle improvement film of this comparative example was inferior in the viewing angle improvement effect.

(Comparative Example 5)
A polyester film having a thickness of 100 μm and one surface of which was embossed (satin texture type) with an average surface roughness Ra of 0.97 μm was used as a viewing angle improving film.
The properties of the viewing angle enhancement film are shown in Table 1.
The viewing angle enhancement film was evaluated in the direction of entering light from the anti-embossed surface for all characteristics.
Similar to the viewing angle improving film obtained in Comparative Example 1, the viewing angle improving film of this comparative example was inferior in the viewing angle improving effect.

(Comparative Example 6)
On one side of a highly transparent polyester film (Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 250 μm, 50 parts by mass of true spherical acrylic resin particles (Toughtic (TM) FH-S300, 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 was evaluated in the direction of entering light from the anti-coating surface with respect to all characteristics.
Although the viewing angle improving film of this comparative example has a good viewing angle improving effect, it has strong darkening and inferior darkening reducing effect.

(Comparative Example 7)
95 parts by mass of polyethylene terephthalate resin (RE553 manufactured by Toyobo Co., Ltd.), a substantially non-lubricating agent that has been sufficiently dried to be dried at 180 ° C. for 3 hours in a vacuum dryer, syndiotactic polystyrene resin (Zarek manufactured by Idemitsu Kosan Co., Ltd. TM) 300ZC) 5 parts by mass and a polar group-modified hydrogenated polymer (JSR Dynalon (TM) 4630) 5 parts by mass are fed to a single screw extruder, melted at 280 ° C., passed through a filter, gear pump, After removing foreign substances and leveling the amount of extrusion, the sheet was discharged from a T-die onto a cooling drum whose temperature was controlled at 25 ° C. At that time, a wire-like electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain an unstretched film. Next, the film was stretched 5.0 times in the longitudinal direction at a temperature of 103 ° C. in the longitudinal direction to obtain a viewing angle improving film having a thickness of 50 μm.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this comparative example had strong darkening, and the darkening reduction effect was extremely inferior.

(Example 2)
Using two melt extruders, 35 parts by mass of a cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) in the first extruder Block copolymer resin composed of ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.), manufactured by Dow Chemical Co., Ltd.) 65 parts by mass is used as a base layer A. Adhesive resin (Admer (TM) QF551, made by Mitsui Chemicals Co., Ltd., melt flow rate: 5.7 (190 ° C.)) is melt coextruded by a T-die method and cooled with a mirror-cooled roll. Thus, a viewing angle improving film having a total thickness of 56 μm was obtained. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. 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 is slightly inferior to the viewing angle improving film obtained in Example 1, but the darkening is improved, and the viewing angle obtained in Example 1 is improved. Like the corner enhancement film, both the viewing angle enhancement effect and the darkening reduction effect were excellent.

(Example 3)
Using two melt extruders, in the first extruder, 60 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 consisting of ethylene and octene (INFUSE (TM) D9100.05, melt flow rate: 2.4 (230 ° C.), manufactured by Dow Chemical Co., Ltd.) 40 parts by mass as a base layer A, with a second extruder, Block copolymer resin made of ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.) manufactured by Dow Chemical Co., Ltd.) is melt-extruded by the T-die method so that the surface layer is mirror-finished A viewing angle enhancement film having a total thickness of 120 μm was obtained by cooling with a cooling roll of The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. The layer thickness configuration was 10/100/10 (μm).
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 darkening reducing effect as in the viewing angle improving film obtained in Example 2.

Example 4
In the method of Example 2, a viewing angle improving film was obtained in the same manner as in Example 2 except that the layer thickness configuration was changed to 30/140/30 (μm) and the layer thickness of the film was changed to 200 μm. It was.
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle enhancement film obtained in this example was slightly darker than the viewing angle enhancement film obtained in Example 1, but the viewing angle enhancement effect was superior to the film obtained in Example 1.

(Example 5)
Block copolymer resin composed of 65 parts by mass of polypropylene resin (Sumitomo Chemical Co., Ltd., Sumitomo Noblen FS2011DG3) and ethylene and octene (INFUSE (TM) D9817.15, melt flow rate: 26 (230 ° C)) 35 mass by mass The part was melt-mixed at a resin temperature of 240 ° C. in a 60 mmφ single-screw extruder (L / D; 22), extruded with a T die, and then 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 then one side of the sheet was subjected to corona treatment to obtain a viewing angle improving film having a thickness of 200 μm. .
Table 1 shows the characteristics of the obtained viewing angle improving film.
The viewing angle improving film obtained in this example had a good balance between both the viewing angle improving effect and the darkening reducing effect in the same manner as the viewing angle improving film obtained in Example 1.

(Example 6 and Example 7)
The protective film for anti-reflection type display manufactured by Kureha Elastomer Co., Ltd., which is hard-processed, is attached to the surface of the viewing angle improving film surface of Example 1 and Example 2 to obtain the viewing angle improving film in which the functional layer is laminated. It was.
The viewing angle improvement performance was evaluated in the same manner as in Example 1 and Example 2. Results equivalent to those in Example 1 and Example 2 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 8 and Example 9)
Protection with a viewing angle improving function in which a hardened anti-glare type display protective film manufactured by Kureha Elastomer Co., Ltd. is pasted on the surface of the viewing angle improving film surface of Example 1 and Example 2 and a functional layer is laminated. A film was obtained.
The viewing angle improvement performance was evaluated in the same manner as in Example 1 and Example 2. Results equivalent to those in Example 1 and Example 2 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 10 to Example 14)
An optical double-sided pressure-sensitive adhesive film (base material) produced as 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 opposite side The thickness of the film was changed to 38 μm) and the separation film on the acrylic adhesive layer side was peeled off, and the viewing angle improving films of Examples 1 to 11 were adhered to the surface of the acrylic adhesive layer, respectively. A protective film with a corner enhancement 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 side of the self-adhesive layer of each of the obtained protective films with the viewing angle improving function is peeled off, and the display screen of the TN type liquid crystal monitor (V173A) manufactured by Acer used in the evaluation method of the viewing angle improving effect described above The surface of the light diffusing film was stuck on the surface so that the main diffusion direction was parallel to the long side of the liquid crystal monitor, and the viewing angle improvement performance was evaluated according to the above-described evaluation method for improving the viewing angle. The viewing angle improvement performance equivalent to the results obtained with the viewing angle improvement films of Examples 1 to 11 was exhibited, respectively, 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.

(Example 15 and Example 16)
A protective film for anti-reflection type display manufactured by Kureha Elastomer Co., Ltd., which is hard-processed, is pasted on the surface of the protective film with the viewing angle improving function of Example 10 and Example 11 and is laminated with a functional layer. A protective film with an improved viewing angle function was obtained.
The viewing angle improvement performance was evaluated in the same manner as in Example 10 and Example 11. Results equivalent to those in Example 10 and Example 11 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 17 and Example 18)
A protective film for anti-glare type display manufactured by Kureha Elastomer Co., Ltd., which is hard-processed, is attached to the surface of the protective film with the viewing angle improving function of Example 10 and Example 11 and laminated with a functional layer. A protective film with an improved viewing angle function was obtained.
The viewing angle improvement performance was evaluated in the same manner as in Example 10 and Example 11. Results equivalent to those in Example 10 and Example 11 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.

The viewing angle improving film of the present invention has a light distribution pattern that combines both the straight transmission property and the diffuse transmission property. Therefore, a trade-off between improving the viewing angle and reducing the darkness of the image by frontal observation. Can be provided at a high level.
Moreover, since the protective film with a viewing angle improving function of the present invention has the above viewing angle improving function and a self-adhesive layer is laminated, it is detachably attached to the display surface of the liquid crystal display device. be able to. Therefore, by sticking to the surface of the display screen of a commercially available liquid crystal display device, the viewing angle of the liquid crystal display device can be improved and a display screen protection function can be further provided.

Claims (13)

A viewing angle improving film for a liquid crystal display device obtained by melt-extrusion molding a mixture comprising at least two incompatible polyolefin-based resins, satisfying the following conditions (1) and (2) simultaneously: Featured viewing angle enhancement film:
(1) Parallel light transmittance is 5 to 90%;
(2) The diffusivity (A) in the main diffusion direction is 1 to 20 degrees.   The viewing angle improving film according to claim 1, wherein the diffusion ratio in the main diffusion direction is 0.25 to 15%.   The viewing angle improving film according to claim 1 or 2, wherein a diffusivity (B) in a main diffusion direction is 140 to 175 degrees.   The ratio of the diffusivity (B) in the main diffusion direction and the diffusivity (B ′) in the direction orthogonal to the main diffusion direction (diffusivity (B) / diffuse (B ′)) is 1.2 to 6.0. The viewing angle improving film according to claim 1, wherein the viewing angle improving film is provided.   The viewing angle improving film according to any one of claims 1 to 4, wherein the at least two incompatible polyolefin resins are made of a polypropylene resin and a polyolefin resin containing ethylene and / or butene. .   The viewing angle improving film according to claim 1, wherein the at least two incompatible polyolefin resins are a cyclic polyolefin resin and a polyethylene resin.   The viewing angle improving film according to any one of claims 1 to 6, wherein the viewing angle improving film is unstretched or stretched at a stretch ratio of 10 times or less.   The 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. The viewing angle improving film as described.   A protective film with a viewing angle improving function, wherein the viewing angle improving film according to claim 1 and a self-adhesive layer are laminated.   The viewing angle improving film according to any one of claims 1 to 7 is laminated via a pressure-sensitive adhesive layer of a double-sided pressure-sensitive adhesive film having one surface made of a self-adhesive layer and the other surface made of a pressure-sensitive adhesive layer. A protective film with a viewing angle improving function.   The protective film with a viewing angle improving function according to claim 9 or 10, wherein the self-adhesive layer is made of a flexible polymer.   A liquid crystal display device comprising the viewing angle improving film according to any one of claims 1 to 9 installed on the viewer side of the liquid crystal layer.   A liquid crystal display device comprising a protective film with a viewing angle enhancement function according to any one of claims 9 to 11 detachably attached to a display screen surface of the liquid crystal display device through a self-adhesive layer. .

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