JP5838540B2 - Light diffusing film and laminated sheet for backlight device and backlight device using the same - Google Patents

Description

  The present invention relates to a light diffusion film for a backlight device, a light diffusion film laminated sheet for a backlight device, and a backlight device. Specifically, using only one light diffusing film for backlight device or light diffusing film laminated sheet for backlight device, the capacity is not bulky, panel assembly is easy, and it is high even without using high output light source The present invention relates to a light diffusing film for a backlight device and a light diffusing film laminated sheet for a backlight device capable of imparting necessary optical properties such as luminance, luminance homogeneity, and pattern concealing properties. The present invention also relates to a high-performance and economical backlight device using the light diffusion film for backlight device or the light diffusion film laminated sheet for backlight device.

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

  The liquid crystal display device is equipped with a backlight unit on the lower surface side of the liquid crystal layer in order to suppress loss in the light transmission path from the light source to the panel and improve the luminance on the panel. Among them, those that emit light by illuminating a liquid crystal layer from the back are widespread, but are roughly classified into a side type and a direct type depending on the arrangement of light sources.

  In recent years, backlight units have been used not only in liquid crystal display devices but also in a wide range of fields such as lamps and electric signboards.

  In the backlight unit, various optical films such as a backlight, lens film, light diffusion film and brightness enhancement film, and optical members such as a diffusion plate are combined to increase the brightness on the panel or improve the uniformity of brightness. Is planned. Usually, 2 to 4 members are used (see, for example, Non-Patent Document 1).

For example, a lens film for improving luminance is disclosed (see, for example, Patent Document 1).
Since this method uses the light condensing effect of the lens to improve the luminance, it can improve the luminance when viewed from the front, but the luminance when viewed from the diagonal is viewed from the front. The brightness is greatly reduced or expensive.

  As a method for solving the problem that the brightness when viewed from the above is significantly lower than the brightness when viewed from the front, a technique using two anisotropic light diffusion films in combination with a lens film is disclosed. (For example, see Patent Document 2)

  Further, the single lens film has insufficient luminance uniformity, and a technique of combining the lens film and an anisotropic light diffusion film is disclosed (see Patent Document 3).

  Moreover, although the method of using a brightness enhancement film in combination with the lens film is disclosed (for example, see Patent Document 4), it is not effective in reducing the angle dependency of the brightness.

  In recent years, high luminance has been developed by improving the performance of the backlight device, and for large TVs and car navigation applications, improvement in the angle dependency of luminance is strongly demanded rather than the height of front luminance.

  In addition, there are strong demands for loss and cost reduction due to a reduction in the number of members and the like, as well as thinner devices.

Therefore, an attempt to impart light diffusibility to a single base film itself has also been studied. (For example, refer to Patent Document 5.)
However, it is suggested that the film described in Patent Document 5 has a low diffusivity and insufficient in-plane luminance uniformity, pattern concealment, and the like.

JP 2004-4970 A JP 2008-256797 A JP 2006-251395 A Japanese Translation of National Publication No. 09-506985 Japanese Patent Laid-Open No. 2007-10798

Supervised by Tatsuo Uchida “All about Illustrated Electronic Display” (published by Industrial Research Association) P47-48

  In the present invention, a film, a sheet, or a plate that exhibits functions such as improvement of luminance, improvement of angle dependency of luminance, uniformity of in-plane luminance, and pattern concealment on the backlight unit and the emission surface of the backlight unit. A system including a member that controls optical characteristics such as the above is referred to as a backlight device.

  The object of the present invention is to solve the above-mentioned problems in the prior art, and the use of only one member does not require a large capacity, the panel is easy to assemble, and high brightness without using a high-output light source. Light diffusion film for backlight device and light for backlight device capable of imparting necessary optical characteristics such as reduction of angle dependency of luminance, uniformity of in-plane luminance and pattern hiding property It is to provide a diffusion film laminated sheet. Another object of the present invention is to provide a high-performance and economical backlight device using the light diffusion film for backlight device or the light diffusion film laminated sheet for backlight device.

This invention was made | formed in view of the above situations, Comprising: The light-diffusion film for backlight apparatuses and backlight apparatus which were able to solve said subject consist of the following structures.
1. A light diffusing film for a backlight device, characterized in that the following characteristics are simultaneously satisfied with the configuration of only one film.
(1) By the method described in the specification, the change in the light in the main diffusion direction obtained by measuring the winding direction of the light diffusion film in a direction parallel to the vertical direction of the sample fixing base and in the horizontal direction is measured. The curvature is 4 to 100%.
(2) The diffusivity (DH0) in the main diffusion direction of the transmitted light measured at an incident angle of 0 degrees in the above method is 30 degrees or more.
2. Ratio of diffusivity in the main diffusion direction (DH0) and diffusivity in the direction orthogonal to the main diffusion direction (DL0) measured by the method described in the specification (diffusivity (DH0) / diffusivity (DL0)) The light diffusing film for a backlight device according to the above 1, wherein is 1.2 to 6.0.
3. 3. The light diffusion film for a backlight device according to 1 or 2 above, wherein the haze is 95 to 100%.
4). 4. The light diffusing film for a backlight device according to any one of the above items 1 to 3, wherein the light diffusing film for a backlight device includes a layer made of at least two incompatible thermoplastic resins.
5. 5. The light diffusing film for a backlight device according to 4 above, wherein at least one of the two incompatible thermoplastic resins is made of a polyolefin resin.
6). 6. The light diffusing film for backlight device as described in 5 above, wherein both of the two incompatible thermoplastic resins are polyolefin resins.
7). A backlight comprising a light diffusion film for a backlight device according to any one of 1 to 6 above and a plastic sheet having a thickness of 0.1 to 5 mm and a total light transmittance of 70 to 100%. Light diffusion film laminated sheet for light equipment.
8). 7. A backlight device comprising the light diffusing film for a backlight device according to any one of the above 1 to 6 on an outgoing light surface of a backlight unit.
9. 8. A backlight device comprising the light diffusion film laminated sheet for a backlight device according to 7 above installed on an outgoing light surface of a backlight unit.

The light diffusing film for a backlight device or the light diffusing film laminated sheet for a backlight device according to the present invention can be used for a backlight having high brightness, reduced angle dependency of brightness, in-plane brightness homogeneity, pattern concealment, etc. Since the optical characteristics that the light device needs to have can be provided, the economic efficiency of the backlight device can be improved. In particular, it is not necessary to use an expensive lens film, and it is possible to give a great advantage that the problem of using the lens film that the luminance when viewed obliquely is reduced is solved.
Further, the backlight device of the present invention has a high front luminance close to that of a backlight device using a lens film, and the angle dependency of luminance, which is a problem of the backlight device using a lens film, is reduced. Therefore, for example, when used in a large TV, there is an advantage that a decrease in the brightness of the screen when viewed obliquely is suppressed.
In addition, because of this feature, for example, it is useful as a backlight device of a display that is often viewed from an oblique direction such as car navigation.
Further, when used with a backlight device for a lamp for indoor or in-house lighting, there is an advantage that uniform illuminance can be obtained over a wide range as compared with a backlight device using a lens film.
Furthermore, the backlight device of the present invention has the advantage that it is highly economical because all of the above characteristics can be imparted by using a single member.
Therefore, the backlight device of the present invention can be effectively used in a liquid crystal display device, indoor lighting, an interior illumination panel, and the like.

A transmitted light curve with respect to a light receiving angle measured at an incident angle of 0 degree of an automatic goniophotometer. The auxiliary figure of the inflection degree calculation method.

(Light diffusion film for backlight device)
The light diffusing film for a backlight device of the present invention needs to satisfy the following characteristics at the same time with a configuration of only one film.
(1) The inflection degree of light in the main diffusion direction measured by the following method is 4 to 100%.
(2) The diffusivity (DH0) in the main diffusion direction of transmitted light measured at an incident angle of 0 degrees in the following method is 30 degrees or more.
By satisfying the above characteristics at the same time, the effects of the present invention described later can be exhibited for the first time.
Hereinafter, in the present invention, the light diffusion film for a backlight device may be simply referred to as a light diffusion film.

(Diffusion degree of transmitted light)
The diffusivity of transmitted light in the present invention is obtained by measurement by the following method.
<Measurement method of diffusivity of transmitted light>
Measurement is 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 Measured under the conditions of aperture: 10.5 mm (VS-1 3.0), light receiving aperture: 9.1 mm (VS-3 4.0) and variable angle interval 0.1 degree, and the peak top of the transmitted light is shown in the chart The width of the angle at half the height of the peak of the variable light intensity curve of the transmitted light obtained by changing the setting of SENSITIVITY and HIGH VOLTON so that it is 40 to 90% of the peak (half width) Ask for. See FIG.
The surface on which the light receiver is moved is defined as the equator plane.
DH0 is the larger half width obtained by performing the above measurement while fixing the light diffusion film on the sample fixing base so that the winding direction of the light diffusion film is parallel to the vertical direction of the sample fixing base and the horizontal direction. The direction of DH0 is the main diffusion direction. On the other hand, the diffusion degree in the direction orthogonal to the main diffusion direction is DL0.
When there is a difference in the surface roughness of the light diffusing film, the above measurement is performed by fixing the light in the direction in which light passes in the same direction as when actually used in the backlight device.

The diffusivity (DH0) in the main diffusion direction of transmitted light is more preferably 40 degrees or more, and further preferably 50 degrees or more. The upper limit is 180 degrees, but 90 degrees is sufficient.
If DH0 is less than 30 degrees, for example, the pattern concealing property is lowered, which is not preferable.

(Light inflection)
The inflection degree of light in the present invention is obtained by measurement by the following method.
<Measurement method of light inflection>
Measurement is performed using an automatic variable angle photometer (GP-200: manufactured by Murakami Color Research Co., Ltd.).
Transmission measurement mode, light incident angle: 0 ° (angles 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, beam stop 10.5 mm (VS-1 3.0), light-receiving aperture: 9.1 mm (VS-3 4.0), measured at conditions of 0.1 degree change angle, and the peak top of transmitted light is The height (H0) of the peak of transmitted light obtained by changing the settings of SENSITIVITY and HIGH VOLTON so as to be 40 to 90% (H0), and the light incident angle is 60 ° (angle on the equator plane) The height (H60) at an angle of 0 degree of the peak of transmitted light when measured under the same conditions as the above except for changing to. The inflection degree is obtained by the following formula using H60 and H0 obtained by the method.
Inflection of light = H60 / H0 × 100 (%) (1)
See FIG.
The surface on which the light receiver is moved is defined as the equator plane.
The inflection degree of the light is obtained by measuring in the main diffusion direction.
When there is a difference in the surface roughness of the light diffusing film for the backlight device, the above measurement is carried out by fixing the light in the same direction as when it is actually used for the backlight device.

The inflection degree of the light is more preferably 6 to 100%, further preferably 8 to 100%.
If the inflection degree of light is less than 4%, the above-described effects of the present invention cannot be sufficiently exhibited, which is not preferable.
This characteristic indicates the degree of the light inflection effect in the film when the light is incident on the light diffusion film for the backlight device, that is, the degree to which the light incident at a high angle is emitted toward the front. It is a scale. In a sense, it can be regarded as a measure of the light collection effect. The light diffusion film for a backlight device of the method of the present invention has a larger inflection effect than conventionally known light diffusion films and lens films. Therefore, it is assumed that the effect of the present invention can be efficiently expressed.

Any one of the above-mentioned characteristics can be satisfied by using a single member for each of the conventionally known lens film film, light diffusing film (sheet) and light diffusing plate, but it is ideal that all the characteristics can be satisfied at the same time. This is the first time that the present invention has been achieved.
The reason why the ideal characteristics can be imparted is not clear.
Both of the above characteristics are presumed to contribute to the effects of the present invention. However, a high degree of inflection of light has a high degree of diffused transmitted light with respect to the front luminance and the angle dependency of luminance. It is assumed that this contributes greatly to in-plane luminance uniformity and pattern hiding.

The light diffusion film for a backlight device of the present invention has a diffusivity (DH0) / diffusivity (DL0 of 1.2 to 6.0, which is a diffusivity ratio of transmitted light at an incident angle of 0 degree measured by the above method. It is preferably 1.3 to 6.0, more preferably.
This property is a measure of the degree of anisotropy of the light diffusibility of the light diffusing film. The larger the value, the higher the anisotropy. Therefore, it can be said that a higher degree of anisotropy is preferable.
By satisfying these characteristics, the balance of individual characteristics such as high front luminance, luminance angle dependency, in-plane luminance uniformity, and pattern hiding characteristics, which are the characteristics of the film of the present invention, should be changed. it can. For example, the front luminance can be increased without reducing the angle dependency of luminance, the in-plane luminance uniformity, and the pattern concealing property.
The reason is not clear, but it is presumed that it is caused by the condensing effect in a specific direction due to the addition of anisotropy.

  The light diffusing film for a backlight device of the present invention preferably satisfies the above characteristics and has a haze of 95% to 100%. 97-100% is more preferable. By the correspondence, the above-described effects of the present invention can be expressed more stably.

  The light diffusion film for a backlight device of the present invention preferably has an average surface roughness (Ra) on the emitted light side of 2 μm or less. More preferably, it is 1.5 μm or less. If it exceeds 2 μm, the angle dependency of luminance may be lowered, which is not preferable.

(Configuration of light diffusion film for backlight device)
In order to satisfy the above characteristics, it is preferable that the film has the following structure.
The configuration is not limited as long as the configuration has a light diffusion function. For example, a method for scattering light by blending light scattering components in the film, a method for scattering light by providing a void such as void or craze in the film, and a difference in refractive index at the interface with the void Examples thereof include a method of providing irregularities on the surface and scattering light by the irregularities and a method combining these. Hereinafter, the scattering of the light may be simply referred to as scattering.
The method that satisfies the above characteristics is not limited. In the above method, it is executed by controlling the size of scattering, the direction of scattering, and the like. For example, depending on the number of scattering units, the size of the scattering units, the shape of the scattering units, the refractive index difference at the interface between the scattering unit component and the film component, and the height, number, and shape of the protrusions on the film surface, Is controlled.
The influence of these factors on the above properties is complex and not simple because they have a synergistic effect on each other.
For example, the diffusivity is greatly affected by the number of scattering units, the difference in refractive index at the interface, the height of protrusions on the film surface, the number of protrusions, and the like.
The anisotropy is greatly influenced by the shape and has a correlation with the anisotropy of the shape. In general, the larger the anisotropy of the shape, the higher the anisotropy of the light diffusion degree. Since light is scattered in a direction orthogonal to the longitudinal direction of the shape, the diffusivity in the direction is increased. Accordingly, the anisotropy of light can be increased by increasing the anisotropy of the shape and orienting the direction of the shape anisotropy in a specific direction.
Regarding the inflection, the contribution of each factor is complicated, and the preferred direction is not clear, but it is one way to reduce the difference in refractive index between the scattering component and the film and increase the number of scattering units. I guess there is.
As described above, the contribution of each factor is complicated, and a configuration that satisfies all of the above characteristics cannot be specified in a simplified form. This can be achieved by optimizing the above factors. The methods shown in the examples are examples of preferred embodiments.
In the examples, a method of melt-extrusion molding a mixture of two kinds of incompatible thermoplastic resins and a method of forming a resin layer containing beads by a coating method are preferred embodiments.

(Manufacturing method of light diffusion film for backlight device)
The method for producing such a film is not limited. For example, (1) a film formed from a resin composition containing a non-melting fine particle diffusible component such as crosslinked organic polymer beads or inorganic particles, (2 ) A film formed from a mixture of at least two incompatible resins, (3) A resin layer containing organic polymer beads and inorganic particles laminated by a coating method, etc. (4) Film surface by molding treatment And (5) a method of forming wrinkles on the film surface by a heat shrink method and a method of combining these.

Among the above production methods, the light diffusing film for a backlight device of the present invention comprises (2) a method of forming a mixture of at least two incompatible thermoplastic resins, and (3) organic polymer beads or inorganic. A method based on a method of laminating a resin layer containing particles by a coating method or the like is preferable. In addition to the advantage of the method, the above characteristics can be obtained stably and economically excellent, which is a recommended embodiment. In particular, the method (2) of forming a film of a mixture of at least two incompatible thermoplastic resins is particularly preferable.
The form of the mixture of the two incompatible thermoplastic resins in the method of forming the mixture of the at least two incompatible thermoplastic resins in (2) is not particularly limited as long as the above characteristics are satisfied. . A so-called sea / island structure in which each resin exists independently as a continuous phase and a dispersed phase may be used, or a structure in which both resins form a co-continuous phase may be used. The above characteristics are imparted by light refraction and scattering at the interface between the two resins.

The production method of the method of forming a mixture of at least two incompatible thermoplastic resins in (2) above is not particularly limited as long as the above optical characteristics are satisfied. However, in terms of economy, it is produced by melt extrusion molding. A filming method is preferred.
In this method, for example, unlike the method (1) in which a resin composition containing a non-melting fine particle diffusible component such as crosslinked organic polymer beads or inorganic particles is formed, non-melting fine particles are contained. Even if it is carried out by the melt extrusion molding method, it is possible to reduce clogging of the filtration filter in the filtration of the molten resin in the film forming process, and it has excellent productivity and high film clarity. Have

  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.

Moreover, the light diffusing film for a backlight device 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 made of a light diffusion film for a backlight device 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.

Regarding the method of laminating resin layers containing organic polymer beads and inorganic particles by coating method, etc., organic polymer beads are used, because the particle size distribution is sharp, so the optical characteristics can be controlled easily and the above characteristics are stabilized. It is useful in that it can be obtained.
Although the kind of organic polymer bead is not limited, an acrylic type, a styrene type, and these copolymerization systems are mentioned.
The type of resin for forming the resin layer is not limited. Examples thereof include polyester resins, polyurethane resins, acrylic resins, and copolymers and blends thereof.
Either a non-crosslinked body or a crosslinked body may be used. Further, the crosslinking method, the coating method and the like are not limited.

As mentioned above, the methods shown in the examples are examples of preferred embodiments. In this example, a method of melt extrusion molding a mixture of two kinds of incompatible thermoplastic resins and a method of forming a resin layer containing organic polymer beads by a coating method are disclosed. The method is not limited as long as the above characteristics are satisfied.
In the case of carrying out by the above method, in the method of melt extrusion molding a mixture of two kinds of incompatible thermoplastic resins, a resin having a small refractive index difference between the two kinds of incompatible thermoplastic resins is used. It is preferable to select and not to generate a void at the interface between the two resins. It is preferable that the refractive index difference between the two resins is 0.01 to 0.1.
In the method of forming a resin layer containing organic polymer beads by a coating method, it is preferable to dry at a temperature of 130 ° C. or less.
By the above measures, the above characteristics can be stably imparted.

  Although the film thickness of the light-diffusion film for backlight apparatuses of this invention is not limited, Usually, 10-1000 micrometers is preferable. 30-500 micrometers is more preferable.

(At least two incompatible thermoplastic resins)
Examples of the thermoplastic resin used as the at least two incompatible thermoplastic resins in the present invention include polyolefin resins such as polyethylene resins, polypropylene resins, polybutene resins, cyclic polyolefin resins, and polymethylpentene resins. Examples thereof include resins, polyester resins, acrylic resins, polystyrene resins, polycarbonate resins, and copolymers thereof.
What is necessary is just to select at least 2 sorts of incompatible (it does not melt | dissolve in each other) thermoplastic resin from these thermoplastic resins.
The blending ratio of the at least two incompatible thermoplastic resins is not particularly limited as long as the above optical characteristics are satisfied, but is preferably 10/90 to 90/10 in terms of mass ratio, respectively. ~ 80/20 is more preferable, and a ratio of 30/70 to 70/30 is still more preferable.
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.

  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 compatibility of the resins 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 thermoplastic resin used as the at least two incompatible thermoplastic resins is not particularly limited as long as the above properties are satisfied. What is necessary is just to select suitably according to the characteristic of the film obtained.

  If you select at least two types of incompatible (incompatible with each other) resins from these thermoplastic resins, the types of these thermoplastic resins are not limited, but both types are in light and economical. It is preferable to use a polyolefin resin. In the case where both types of polyolefin resins are used, the combination is not particularly limited, but a combination of a cyclic polyolefin resin and a polyethylene resin is preferable because the above optical characteristics can be easily obtained.

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-polymerized 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.

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 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 the present invention, the configuration is not limited as long as the layer made of the at least two incompatible thermoplastic resins is included. That is, it may be composed of at least two layers of incompatible thermoplastic resins, or one layer in a multilayer structure may be a layer of at least two incompatible thermoplastic resins. In addition, in the multilayer structure, two or more layers may be layers made of at least two incompatible thermoplastic resins. In the case of a configuration including two or more layers made of at least two types of incompatible thermoplastic resins, the layers may have the same composition or different compositions.

(Roughening by forming process)
In the light diffusing film for a backlight device of the present invention, at least one surface of the film obtained by the above method may be roughened by a molding treatment as long as the average surface roughness (Ra) is 2 μm or less. If it exceeds 2 μm, the angle dependency of luminance may be lowered, which is not preferable.
The roughening treatment is not particularly limited as long as it can be roughened by forming irregularities on the surface of the light diffusion film for a backlight device obtained by the above method, and may be mat processing or embossing. . For example, the roughening treatment may be performed by passing a light diffusion film for a backlight device between rolls on which irregularities (such as grid-like irregularities and random irregularities) are formed, or using a roll on which irregularities are formed. This can be done by pressing.

  The shape and depth of the surface irregularities formed by the roughening treatment are not limited. The shaped surface irregularities may be oriented in a specific direction or may be random. A method of roughening the surface by shaping the irregular surface with a special shape is not excluded.

The roughening treatment may be an inline processing method performed in a film forming process or an off-line processing method performed in a separate process.
Moreover, you may shape | mold and roughen the below-mentioned light-diffusion film lamination sheet for backlight apparatuses.

(Light diffusion film laminated sheet for backlight device)
Another invention in the present invention is formed by laminating a light diffusion film for a backlight device obtained by the above method and a plastic sheet having a thickness of 0.1 to 5 mm and a total light transmittance of 70 to 100%. It is a light diffusible film lamination sheet for backlight devices.
The light diffusing film for a backlight device obtained by the above-described method has excellent optical characteristics as described above, and can be produced economically. In some applications, the characteristics other than the optical characteristics, for example, In some cases, mechanical properties such as heat resistance, heat-resistant dimensional stability and rigidity, or properties such as flame retardancy cannot be satisfied. By laminating the transparent plastic sheet and the light diffusing film for a backlight device of the present invention, it is possible to complement characteristics other than the optical characteristics and satisfy the comprehensive characteristics required by the market.

As long as the transparent plastic sheet used in the present invention satisfies the above characteristics of thickness and total light transmittance, the type of resin and the layer structure are not limited.
As for the thickness of the transparent plastic sheet used for this invention, 0.5-3 mm is more preferable. If it is less than 0.1 mm, the reinforcing effect or the complementary effect is insufficient. Moreover, when 5 mm or more, it may become economically disadvantageous or flexibility may be impaired.
The total light transmittance of the transparent plastic sheet used in the present invention is more preferably 80 to 100%. 85-100% is still more preferable. If it is less than 70%, the above-mentioned characteristics of the light diffusion film for a backlight device cannot be utilized effectively. A non-diffusible material having a high total light transmittance as much as possible is preferable. Also preferred is a method of producing a lamination effect by using a diffusible plastic sheet.

  As the resin used for the plastic sheet, it is preferable to use resins used for optical applications such as polyester resins, acrylic resins, styrene resins, cyclic polyolefin resins, and polycarbonate resins, but are particularly limited. is not.

The manufacturing method of the said light-diffusion film laminated sheet for backlight apparatuses is not specifically limited. The method of bonding together the light-diffusion film for backlight apparatuses, and a plastic sheet is mentioned.
In the case of a method of bonding using a pressure-sensitive adhesive or an adhesive, specific examples of the pressure-sensitive adhesive include a rubber-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a vinyl-based pressure-sensitive adhesive. Since the light diffusion film laminated sheet for a backlight device of the present invention may be used at a high temperature, an adhesive that is stable even at room temperature to 120 ° C. is preferable. Among them, acrylic pressure-sensitive adhesives are widely used because they are inexpensive. Whichever adhesive is used, the thickness is preferably 0.5 to 50 μm.
Adhesives include adhesives that are bonded with the aid of heat or a catalyst. Specifically, a silicon-based adhesive, a polyurethane-based adhesive, a polyester-based adhesive, an epoxy-based adhesive, a cyanoacrylate-based adhesive, an acrylic-based adhesive, or the like can be used. Since the light diffusion film laminated sheet for a backlight device of the present invention may be used at a high temperature, an adhesive that is stable even at room temperature to 120 ° C. is preferable. Among these, epoxy adhesives are excellent in strength and heat resistance, and can be suitably used. Since the cyanoacrylate adhesive is excellent in immediate effect and strength, it can be used for efficient production of laminated sheets. Polyester adhesives are particularly suitable for the production of laminated sheets because they are excellent in strength and processability. These adhesives are roughly classified into a thermosetting type, a hot melt type, and a two-component mixed type depending on the bonding method, and a thermosetting type or a hot melt type capable of continuous production is preferably used. Whichever adhesive is used, the thickness is preferably 0.5 to 50 μm.

  The above plastic sheet and the light diffusion film for the backlight device are bonded together with an adhesive or a pressure-sensitive adhesive, such as a roll-to-roll or roll-to-sheet process using a laminator. Is obtained. For example, when an adhesive is used, the adhesive is coated on either a plastic sheet or a light diffusing film for a backlight device, and after drying, laminated with a mating material and a roller.

  There are many methods for coating the adhesive depending on the type of the substrate and the adhesive, but the gravure coater method, the comma coater method, and the reverse coater method are widely used. In the gravure coater method, coating is performed by rotating a gravure roll that is partially immersed in an adhesive and bringing the film fed by a backup roll into contact with the gravure roll to which the adhesive is attached. The coating amount can be adjusted by controlling the number of rotations of the roll and the viscosity of the adhesive. The reverse coater method is also a method similar to the gravure coater method, but the amount of adhesive adhering to the coating roll is adjusted by a metering roll installed in contact therewith.

  When the above bonding is performed, heating may be performed as necessary. Moreover, in order to obtain a required adhesive strength, it can also heat-process after lamination.

  When pasting together with an adhesive, a double-sided adhesive sheet may be used. In the case of this method, it is a preferred embodiment to use an optically highly transparent pressure-sensitive adhesive, but it is not particularly limited. For example, an adhesive sheet having light diffusibility may be used. In the case of the pressure-sensitive adhesive sheet, light diffusibility may be imparted to the pressure-sensitive adhesive layer.

In this invention, you may implement by the method which integrated manufacture of said light diffusing film for backlight apparatuses, and manufacture of said light diffusing film lamination sheet for backlight apparatuses.
That is, for example, it may be produced by a so-called extrusion laminating method in which the thermoplastic resin composition constituting the light diffusion film for a backlight device is melted and extruded and directly laminated on the transparent plastic sheet surface. Moreover, you may perform the above-mentioned roughening process simultaneously in the process of this melt extrusion laminating method.
In the case of carrying out by the extrusion laminating method, in order to improve the adhesion and adhesion durability between the light diffusion film for the backlight device and the transparent plastic sheet, an anchor coat treatment or an easy adhesion treatment transparent Incorporating means such as using a plastic sheet is one preferred embodiment.

(Usage method of light diffusion film for backlight device or light diffusion film laminated sheet for backlight device)
It is necessary to install the light diffusion film for backlight device or the light diffusion film laminated sheet for backlight device of the present invention on the light exit surface of the backlight unit. In this case, the installation method of the light diffusion film for backlight devices or the light diffusion film laminated sheet for backlight devices is not limited. It can be simply placed and fixed with an adhesive or a pressure-sensitive adhesive. Moreover, you may fix with a double-sided adhesive tape.
Moreover, you may install in the lowest surface of the liquid crystal panel installed in the upper surface of a backlight apparatus.
When the light diffusion film for backlight device or the light diffusion film laminated sheet for backlight device has anisotropy, the installation direction of the light diffusion film for backlight device or the light diffusion film laminated sheet for backlight device is not limited. . What is necessary is just to install in the direction where the effect of this invention can be efficiently expressed with the kind, shape, installation place, etc. of a light source. For example, when the light source is a cold cathode tube, the main diffusion direction of the light diffusion film for the backlight device or the light diffusion film laminated sheet for the backlight device is set in a direction orthogonal to the longitudinal direction of the cold cathode tube. preferable.
By the correspondence, the above-described effects of the present invention can be expressed.

(Backlight unit)
The backlight unit in which the light diffusing film for a backlight device or the light diffusing film laminated sheet for a backlight device of the present invention is used is not limited in its structure as long as it is a unit having an outgoing light surface on at least one side. . The edge light method or the direct method may be used. The structure of the light guide plate in the case of the edge light system is not limited.
There are no restrictions on the type of reflective film or reflector used in the backlight unit. Any of white reflection type, metal reflection type and other types may be used.
The light source used for the backlight unit is not limited. For example, any of a light bulb, a light emitting diode (LED), an electroluminescence panel (EL), a cold cathode tube (CCFL) and a hot cathode tube (HCFL) may be used, or a combination of these or other light sources may be used.

  The light diffusing film for a backlight device and the light diffusing film laminated sheet for a backlight device of the present invention have high luminance, reduced angle dependency of luminance, in-plane luminance uniformity and pattern even when only one of these members is used. Since it is possible to provide the optical characteristics necessary for the backlight device such as concealment, it is important to use one piece, but two or more pieces may be used together, or a conventionally known lens film Or a light diffusion film or the like. Further, other light diffusion sheets and light diffusion plates may be used in combination. In this case, a plurality of types of optical members may be used in combination. It is preferable to select and use it appropriately according to market demand characteristics and economic efficiency.

  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.

1. Diffusion degree of transmitted light 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 Measured under the conditions of aperture: 10.5 mm (VS-1 3.0), light receiving aperture: 9.1 mm (VS-3 4.0) and variable angle interval 0.1 degree, and the peak top of the transmitted light is shown in the chart The width of the angle at half the height of the peak of the variable light intensity curve of the transmitted light obtained by changing the settings of SENSITIVITY and HIGH VOLTON so that it is 40 to 90% of the peak (half width) Ask for. See FIG.
The surface on which the light receiver is moved is defined as the equator plane.
DH0 is the larger half width obtained by performing the above measurement while fixing the light diffusion film on the sample fixing base so that the winding direction of the light diffusion film is parallel to the vertical direction of the sample fixing base and the horizontal direction. The direction of DH0 is the main diffusion direction. On the other hand, the diffusivity in the direction orthogonal to the main diffusion direction is DL0.
When there is a difference in the surface roughness of the light diffusing film, the above measurement was performed by fixing the light in the direction in which light passes in the same direction as when actually used in the backlight device.

2. Inflection degree of light 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 ° (angles 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, beam stop 10.5 mm (VS-1 3.0), light-receiving aperture: 9.1 mm (VS-3 4.0), measured at conditions of 0.1 degree change angle, and the peak top of transmitted light is The height (H0) of the peak of transmitted light obtained by changing the settings of SENSITIVITY and HIGH VOLTON so as to be 40 to 90% (H0), and the light incident angle is 60 ° (angle on the equator plane) The height (H60) at an angle of 0 degree of the peak of transmitted light when measured under the same conditions as the above except for changing to. Inflection degree was calculated | required by the following formula using H60 and H0 which were calculated | required by this method.
Inflection of light = H60 / H0 × 100 (%) (1)
See FIG.
The surface on which the light receiver is moved is defined as the equator plane.
The inflection degree of the light is obtained by measuring in the main diffusion direction.
When there is a difference in the surface roughness of the light diffusing film for the backlight device, the above measurement was carried out by fixing the light in the same direction as when actually used in the backlight device.

3. Haze It measured based on JISK7136 using the Nippon Denshoku Industries Co., Ltd. haze measuring device "NDH-2000".
This measurement used the measured value obtained by measuring and fixing to a sample fixing part so that the winding direction of a light-diffusion film might become a perpendicular direction. Moreover, when there was a difference in the surface roughness of the light diffusion film, the measurement was performed by fixing in the direction in which light passes in the same direction as when actually used in the backlight device.

4. Average surface roughness (Ra)
Using a universal surface shape measuring device MODEL SE-3C manufactured by Kosaka Laboratory Ltd., longitudinal magnification: 2000 to 10000, cutoff: 0.25 mm, measurement length: 8 mm, measurement speed: 0.5 mm / min. .
The said measurement measured the average surface roughness (Ra) of the winding direction of a light-diffusion film, and the direction orthogonal to this direction, and let the one with a larger value be the average surface roughness (Ra). Each measurement was performed 5 times, and the average value was used.

5. Melt flow rate of thermoplastic resin Measured under the condition of 2.16 kgf in accordance with JIS K 7210 A method.

6. Front brightness Acrylic plate on the outgoing light side of a 19-inch light guide plate type (mesh type using a white reflective film) with three cold cathode tubes on each side of the major axis side (lateral direction). A 40 mm × 60 mm square (60 mm side is the horizontal direction) evaluation sample was set in the substantially central portion above (if the sample was curled and the sample was curled, etc., the four corners were fixed with tape. Then, a black shading paper provided with a 30 mm × 50 mm square (50 mm side is the horizontal direction) cut-out portion was placed so that the center of the cut portion was the center of the evaluation sample, and the luminance was measured in a dark room. The black light-shielding paper was fixed so that the entire backlight unit was covered, and measurement was performed so that light did not leak.
Moreover, the backlight unit was installed horizontally and measured.
The brightness is measured using a Topcon Spectroradiometer SR-3A manufactured by Topcon Technohouse Co., Ltd., at a measurement angle of 2 degrees, at a distance of 40 cm from the backlight unit surface, and at the position where the center of the sample for evaluation is directly below. It was measured.
In this measurement, the sample for evaluation was installed such that the main diffusion direction was perpendicular to the longitudinal direction of the cold cathode tube.

7. Luminance angle dependence Topcon spectroradiometer SR-3A is installed so that the angle between Topcon spectroradiometer SR-3A and the center of the sample for evaluation is tilted 35 degrees from the perpendicular to the surface of the backlight unit. Except for this, the luminance was measured by the same method as the above-described front luminance. A value obtained by dividing the luminance by the above-mentioned front luminance was defined as luminance angle dependency. It can be said that the larger the value, the better the angle dependency of the luminance. 1.0 is the best.

8. Pattern concealing property The following determination was made by visual observation of the opening in the front luminance measurement with the backlight turned on.
If the light guide plate mesh is completely invisible: ○
If the light guide mesh looks faint: △
When the light guide plate mesh is clearly visible: ×

9. In-plane brightness uniformity The light diffusion acrylic plate of the direct-type backlight unit in which 12 cold cathode fluorescent lamps are installed with 20 inches is replaced with a transparent acrylic plate. Place a sample of 4 sizes, fix the four corners with tape, and use the high-functional brightness measurement system (ZERO ONE) manufactured by Highland to turn the backlight knit on in the dark room and place the center of the sample at 100 The luminance of an area of × 220 pixels was measured. As for luminance, the maximum luminance, the minimum luminance, and the luminance were measured. The in-plane brightness homogeneity was displayed as the ratio of minimum brightness / maximum brightness obtained by the above method. The smaller the value, the smaller the luminance unevenness.
The cold cathode tube used was set so that the longitudinal direction of the cold cathode tube was the longitudinal direction (lateral direction) of the backlight unit. The luminance measuring device was measured just above the center of the sample, and the distance between the transparent acrylic plate surface and the luminance meter incident light surface was set at a position of 120 cm.
The backlight unit was installed horizontally and measured.
In this measurement, the sample for evaluation was installed so that the main diffusion direction was perpendicular to the longitudinal direction of the cold cathode tube.

[Example 1]
Cyclic polyolefin resin (TOPAS (TM) 6013F04 Topas Advanced Polymers, melt flow rate: 2.0 (230 ° C.)) 35 parts by mass, ethylene and octene block copolymer resin (INFUSE (TM)) D9817.15 Melt flow rate: 26 (230 ° C)) 65 parts by mass using a PCM45 extruder manufactured by Ikekai Tekko Co., Ltd., melt-mixed at a resin temperature of 250 ° C, extruded with a T-die, and cooled with a mirror surface cooling roll Thus, a light diffusion film for a backlight device having a thickness of 400 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 light diffusion film for a backlight device.
The light diffusing film for a backlight device obtained in this example was excellent in all properties and high quality.

[Example 2]
In the method of Example 1, the resin was blended with a cyclic polyolefin resin (TOPAS (TM) 6015 Topas Advanced Polymers, melt flow rate: 0.41 (230 ° C.)) 50 parts by mass, a block copolymer composed of ethylene and octene. Except for changing to 50 parts by mass of resin (INFUSE (TM) D9107.15 melt flow rate: 2.1 (230 ° C.) manufactured by Dow Chemical Co.) and changing the film thickness to 200 μm, the same method as in Example 1 Thus, a light diffusion film for a backlight device was obtained.
Table 1 shows the characteristics of the obtained light diffusion film for a backlight device.
The light diffusing film for backlight device obtained in this example also had the same characteristics as the light diffusing film for backlight device obtained in Example 1, and was of high quality.

Example 3
Cyclic polyolefin resin (TOPAS (TM) 6015 manufactured by Topas Advanced Polymers, melt flow rate: 0.41 (230 ° C)), block copolymer resin composed of ethylene and octene (INFUSE (TM) manufactured by Dow Chemical Co., Ltd.) 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., extruded with a T-die, and a satin-finished cooling roll (Ra = A light diffusion film for a backlight device having a thickness of 400 μm was obtained by cooling in 0.55). The opposite surface of the cooling roll was a pressing roll whose surface was subjected to mold release treatment (Ra = 1.0).
Table 1 shows the characteristics of the obtained light diffusion film for a backlight device.
The light diffusing film for backlight device obtained in this example also had the same characteristics as the light diffusing film for backlight device obtained in Example 1, and was of high quality.

Example 4
In the method of Example 3, a light diffusing film for backlight device was obtained in the same manner as in Example 3 except that the thickness of the light diffusing film for backlight device was 200 μm.
Table 1 shows the characteristics of the obtained light diffusion film for a backlight device.
The light diffusing film for backlight device obtained in this example also had the same characteristics as the light diffusing film for backlight device obtained in Example 1, and was of high quality.

Example 5
Cyclic polyolefin resin (TOPAS (TM) 6015, manufactured by Topas Advanced Polymers, melt flow rate: 0.41 (230 ° C.)) 35 parts by mass, a block copolymer resin consisting of ethylene and octene (INFUSE (TM) manufactured by Dow Chemical Co., Ltd.) D9807.15 Melt flow rate: 29 (230 ° C)) 65 parts by mass using a PCM45 extruder manufactured by Ikekai Tekko Co., Ltd., melt-mixed at a resin temperature of 250 ° C, extruded with a T-die, and cooled with a mirror cooling roll Thus, a light diffusion film for a backlight device having a thickness of 300 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 light diffusion film for a backlight device.
The light diffusing film for a backlight device obtained in this example also had the same characteristics as the light diffusing film obtained in Example 1 and was of high quality.

Example 6
In the method of Example 1, the resin compounding was a random polyolefin resin composed of 50 parts by mass of cyclic polyolefin resin (TOPAS (TM) 6015 Topas Advanced Polymers, melt flow rate: 0.41 (230 ° C.)), ethylene and octene. (Dow Chemical Co., Ltd. ENGAGE (TM) 8137 Melt Flow Rate: 30 (190 ° C.)) A light diffusion film for a backlight device in the same manner as in Example 1 except that the film thickness is changed to 200 μm. Got.
Table 1 shows the characteristics of the obtained light diffusion film for a backlight device.
The light diffusing film for backlight device obtained in this example also had the same characteristics as the light diffusing film for backlight device obtained in Example 1, and was of high quality.

Example 7
On one side of a highly transparent polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 250 μm, true spherical acrylic resin particles having an average particle size of 0.9 μm (absorbing and releasing fine particles Tuftic (TM) HU700E manufactured by Toyobo Co., Ltd.) By coating a mixed part of 55 parts by weight and 45 parts by weight of a water-based polyurethane resin (Sparflex (TM) E200, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) to a thickness of 35 μm after drying, and drying at room temperature A light diffusion film for a backlight device was obtained.
Table 1 shows the characteristics of the obtained light diffusion film for a backlight device.
The light diffusion film for a backlight device obtained in this example was slightly inferior in front luminance, but was excellent in luminance angle dependency and pattern disappearance.

[Comparative Example 1]
A light diffusion film was obtained by the same method as in Example 1 except that the film thickness was changed to 175 μm by the method of Example 1.
Table 1 shows the characteristics of the obtained light diffusion film.
The light diffusion film obtained in this comparative example was inferior in pattern concealment.

[Comparative Example 2]
Table 1 shows the characteristics of the commercially available microlens film.
The microlens has high front luminance, but is inferior in angle dependency of luminance. Further, when the microlens is used alone, the pattern concealing property is also inferior.

[Comparative Example 3]
Table 1 shows the characteristics of the light diffusing film produced by the bead coating method used in a commercially available backlight device.
When only one light diffusing film is used, the angle dependency of brightness and the pattern concealing property are inferior.

[Comparative Example 4]
Table 1 shows the characteristics of the optical film set composed of the upper diffusion film / prism lens film / lower diffusion film incorporated in the backlight unit used for the measurement of the front luminance and the angle dependency of luminance.
The film set was excellent in front luminance and pattern concealment, but inferior in luminance angle dependency. Also, the number of sheets was large and the economy was inferior.

[Examples 8 to 10]
In-plane luminance uniformity was measured for the light diffusion films for backlight devices obtained in Examples 1, 3 and 4, respectively. The light diffusing film obtained in any of the examples also had high average brightness, high in-plane luminance uniformity, and high quality as a light diffusing film for a backlight device.

[Comparative Example 5]
In-plane brightness uniformity was measured without installing a light diffusion film for a backlight device. Although the maximum brightness was remarkably high, the in-plane brightness uniformity was remarkably large. The magnitude | size of the optical characteristic control effect of the said Example film is shown notably.

[Comparative Examples 6-8]
In-plane brightness uniformity was evaluated for the light diffusion films of Comparative Examples 1 to 3, respectively.
The light diffusion film obtained in Comparative Example 1 had a high maximum luminance but low in-plane luminance uniformity, and performance was insufficient with only one light diffusion film.
The films obtained in Comparative Examples 2 and 3 had a maximum brightness significantly higher than that of the light diffusion film of the above example, but the in-plane brightness uniformity was low, and the performance was insufficient with only one light diffusion film.

[Comparative Example 9]
In-plane brightness uniformity was measured for an optical film set consisting of an upper diffusion film / prism lens film / lower diffusion film incorporated in the backlight unit used for in-plane brightness uniformity measurement.
Although the maximum brightness was high, the in-plane brightness homogeneity was poor. Moreover, the number of films was large and the economy was inferior.

Examples 11 and 12
In each of the methods of Examples 1 and 2, the film was prevented from sticking to the cooling roll at the time of cooling and switched to a roll system, and the thickness of the surface treated with a polyurethane-based anchor coating agent on the pressing roll side was 200 μm, By passing a polycarbonate sheet having a transmittance of 88%, a light diffusion film laminated sheet for a backlight device on which the polycarbonate sheet was laminated was obtained.
The light diffusion film laminated sheet for a backlight device obtained in these examples has the same optical characteristics as the light diffusion film for a backlight device obtained in Examples 1 and 2, and Example 1 Compared with the light diffusion film for a backlight device obtained in 2 and 2, non-optical properties such as heat resistance and strength were improved. Therefore, it was high quality as a light diffusion film laminated sheet for a backlight device.

The light diffusing film for backlight device and the light diffusing film laminated sheet for backlight device of the present invention each have high luminance, reduced angle dependency of luminance, in-plane luminance homogeneity, pattern hiding property, etc. Since the optical characteristics that the backlight device needs to have can be provided, the economic efficiency of the backlight device can be improved. In particular, it is not necessary to use an expensive lens film, and it is possible to give a great advantage that the problem of using the lens film that the luminance when viewed obliquely is reduced is solved.
Further, the backlight device of the present invention has a high front luminance close to that of a backlight device using a lens film, and the angle dependency of luminance, which is a problem of the backlight device using a lens film, is reduced. Therefore, for example, when used in a large TV, there is an advantage that a decrease in the brightness of the screen when viewed obliquely is suppressed.
In addition, because of this feature, for example, it is useful as a backlight device of a display that is often viewed from an oblique direction such as car navigation.
Further, when used with a backlight device for a lamp for indoor or in-house lighting, there is an advantage that uniform illuminance can be obtained over a wide range as compared with a backlight device using a lens film.
Furthermore, the backlight device of the present invention has the advantage that the economy is remarkably high because all the above-mentioned characteristics can be imparted by a single member.
Therefore, the backlight device of the present invention can be effectively used in a liquid crystal display device, indoor lighting, an interior illumination panel, and the like.
Furthermore, the backlight device of the present invention has the advantage that it is economically remarkably high because all of the above properties can be imparted with a single film.
Therefore, the backlight device of the present invention can be effectively used in a liquid crystal display device, indoor lighting, an interior illumination panel, and the like.
Therefore, the contribution to the industry is great.

Claims (7)

A light diffusing film for a backlight device comprising a layer made of at least two incompatible thermoplastic resins, wherein the light for a backlight device satisfies the following characteristics at the same time with the configuration of only one film. Diffusion film.
(1) The inflection degree of light measured by the following method is 4 to 100%.
Fix the light diffusion film on the automatic goniophotometer so that the winding direction of the light diffusion film is parallel to the vertical direction of the sample fixing table and in the horizontal direction. A light beam was incident at an angle (0 °), the light receiver was moved, and the transmitted light was measured.
The width of the angle (half-value width) at half the height of the peak of the variable light intensity curve of the transmitted light was determined. The larger half width was DH0 and the smaller half width was DL0.
The upper and lower directions when DH0 is obtained are defined as the main diffusion direction of the film, and fixed so that the main diffusion direction of the film is the upper and lower direction. The height of the peak of transmitted light at a light receiving angle of 0 ° measured as 60 ° on the equator line plane from this angle was defined as H0 and H60, respectively.
Inflection degree was calculated | required by the following formula using H60 and H0.
Inflection of light = H60 / H0 × 100 (%) (1)

(2) DH0 measured by the method described in (1) above is 30 degrees or more.
(3) The two incompatible thermoplastic resins are both polyolefin resins.   The light diffusion film for a backlight device according to claim 1, wherein the ratio DH0 / DL0 of DH0 to DL0 is 1.2 to 6.0.   The light diffusion film for a backlight device according to claim 1 or 2, wherein the haze is 95 to 100%. The light diffusing film for a backlight device according to any one of claims 1 to 3, wherein at least one of the two incompatible thermoplastic resins is made of a polyolefin resin. A light diffusion film for a backlight device according to any one of claims 1 to 4 and a plastic sheet having a thickness of 0.1 to 5 mm and a total light transmittance of 70 to 100% are laminated. Light diffusion film laminated sheet for backlight devices. A backlight device comprising the light diffusion film for a backlight device according to any one of claims 1 to 4 disposed on an outgoing light surface of a backlight unit. 6. A backlight device comprising the light diffusion film laminated sheet for a backlight device according to claim 5 disposed on an outgoing light surface of the backlight unit.