TWI438499B - Light diffusing film, its laminating sheet, method for producing the same, lighting device using led source and backlight device - Google Patents

Description

Light diffusing film, laminated sheet thereof, manufacturing method thereof, lighting device using LED light source, and backlight device

The present invention relates to a light diffusing film, a laminated sheet thereof, and a method of manufacturing the same. Specifically, it relates to a light-diffusing film excellent in both light transmittance and diffusivity, for example, when used in an illumination device using an LED light source, in addition to diffusing light of a direct-intensity LED light source into a large area, Moreover, in addition to the point of the light source of the glare, further, a small amount of LED light source that has suppressed the decrease in the transmittance of the light has a uniform light amount distribution and a high illuminance and brightness. Light diffusing film, laminated sheet thereof and preparation method thereof.

In recent years, LEDs (Light Emitting Diodes) have attracted attention from the viewpoint of energy saving because of their low energy consumption and long service life. They are widely used in indoor lighting, interior lighting, exterior lighting, advertising lamps, and display devices. Use a light source. However, the light emitted by the LED light source is highly illuminating in a narrow range of dots due to its high straightness (directivity), and it is necessary to use a large number of light sources when using the above-mentioned large-area illumination. The use of energy-saving features is effective, and it is difficult to have uniform brightness.

In order to have a uniform light amount distribution over a wide area, various strategies must be made.

For example, it is provided with at least one primary light source and a plate-shaped light guide that guides light emitted from the primary light source, and has a light incident surface from which the light from the primary light source is incident and the guided light is emitted. a light emitting surface, wherein the light guiding system has a light emitting mechanism on either or both of the light emitting surface and the opposite side thereof, and at least one of the light emitting surface and the inner surface has at least one of a partial lens column forming portion, each partial lens row forming portion, comprising at least one partial lens row formed in the light incident from the primary light source and incident on the light incident end face, The direction of the peak light of the luminance distribution at the incident position of the maximum intensity light is different, and a method for solving the luminance unevenness is disclosed (refer to Patent Document 1).

Further disclosed is a lamp cover having an opening portion at one end, a light receiving portion of the light source receiving portion including the light reflecting surface on the inner side wall, and a light emitting diode mounted on the receiving portion of the light source, and a display panel mounted in front of the opening portion, which will be derived from the light emitting diode A technique in which light is diffused and reflected and made uniform (refer to Patent Document 2).

Further, a surface illumination light source including a light source that emits light, an optical transparent light guide body that emits light of the light source and has a radiation surface at a predetermined position in the radial direction, and a radiation surface other than the radiation surface that closes the light guide body are provided a coverless box for the surface, and an inner side reflection method for mounting between the box and the light guide body, and a radiation side reflection method for mounting the light from the light source at a fixed ratio on the radiation surface (refer to Patent Document 3).

The methods disclosed in the above Patent Documents 1 to 3 have problems such as a complicated structure of the light source and poor economy. Although it can be used for surface illumination, it is not easy to respond to tubular illuminators such as fluorescent lamps.

On the other hand, a method of achieving a uniform light amount distribution by using a fluorescent lamp as a light source illumination device discloses a method of using a light diffusion film obtained by various methods.

For example, a method of laminating a mixture of a diffusing substance formed of fine particles or the like and a binder resin (refer to Patent Document 4), and a method of melt-extruding a non-compatible thermoplastic resin to form a film (refer to Patent Document 5, Patent Literature) (7, etc.) and a method of controlling the surface shape by performing a shaping treatment such as embossing on the surface of the film (refer to Patent Document 6).

However, the previously known light-diffusing film, when used in an illumination device using an LED light source, has poor diffusibility and cannot meet the level of market demand. In particular, since the LED light source has strong directivity of light, the light source point does not disappear and the amount of light around the light source increases (hereinafter referred to as dot vanishing property). In order to suppress this phenomenon, the total light transmittance is lowered, and the amount of light (hereinafter referred to as total light amount) of the entire illumination device is lowered.

The inventors of the present invention have made efforts to solve the above-mentioned two-laws and find that reducing the parallel light transmittance can effectively improve the dot disappearance and increase the total light transmittance, thereby effectively increasing the overall light amount.

For example, in the comparative example of Patent Document 5, an example in which the flat light transmittance is low is disclosed, since the total light transmittance is low and the total light amount is also low. On the other hand, in the example of Patent Document 6, although an example in which the total light transmittance has been improved is revealed, the parallel light transmittance is increased, and the dot disappearance is not good.

Further, in Patent Document 7, the total light transmittance and the diffuse transmittance are described. When the parallel light transmittance is obtained by the numerical value, Examples 1 and 2 are 4.6 and 2.1%, respectively, and the parallel light is transmitted in the same manner as in the example of Patent Document 4. The rate is high and the point disappears poorly.

On the other hand, liquid crystal display devices (LCDs) are widely used in flat panel displays due to their characteristics such as thinness, light weight, and low power consumption. Applications such as mobile phones, personal digital secretary (PDA), personal computers, televisions, etc. Components, and gradually increasing year by year.

In the liquid crystal display device, in order to suppress the loss of light transmission from the light source to the panel and to increase the brightness on the panel, a backlight assembly is mounted on the lower side of the liquid crystal layer. Among them, the liquid crystal layer is irradiated from the back side to make the illuminator quite popular, but the arrangement of the light source can be classified into a side type and a lower type.

In recent years, backlight assemblies have been used not only in liquid crystal display devices, but also in a wide range of fields such as lamps or electronic signage.

The backlight assembly is an optical component such as a combination of a backlight, a lens film, a light diffusion film, and a brightness enhancement film, and the like, to improve the brightness and brightness of the panel. Usually, two to four pieces are used (refer to Non-Patent Document 1).

For example, a lens film for improving brightness is disclosed (refer to Patent Document 8).

In this method, the brightness of the lens is used to increase the brightness, so that the brightness when viewed from the front can be improved, and the brightness when viewed from the oblique angle is greatly reduced as compared with the brightness when viewed from the front. And it is a high-priced item.

In order to solve the above-mentioned method of reducing the brightness when viewed from the oblique angle as compared with the case of the front view, a technique of using two anisotropic light-diffusing films in addition to the lens film is described (refer to Patent Document 9).

The above-mentioned lens film of one piece has poor uniformity of brightness, and discloses a technique of combining the lens film and the anisotropic light-diffusing film (refer to Patent Document 10).

Further, a method of using a film having a higher brightness in the above lens film is proposed (refer to Patent Document 11), but the angle dependence on the brightness reduction is proposed. Sex does not help.

In recent years, high brightness has been improved by improving the performance of backlight devices, and in large television or car navigation applications, the improvement in the angular dependence of brightness is more strongly demanded than the improvement in frontal brightness.

Further, there is a strong demand for reducing the cost and cost of the parts, and the thinning of the device.

Here, a test for imparting light diffusibility to a single base film is also considered (refer to Patent Document 12).

However, the film of Patent Document 12 has a small degree of diffusion, and the inner surface brightness uniformity and the pattern concealing property are not good.

[Previous Technical Literature]

[Patent Document 1] JP-A-2003-186427

[Patent Document 2] JP-A-2003-186427

[Patent Document 3] JP-A-2008-027886

[Patent Document 4] JP-A-2001-166114

[Patent Document 5] Japanese Patent Publication No. Hei 10-111402

[Patent Document 6] JP-A-2007-140447

[Patent Document 7] JP-A 09-80208

[Patent Document 8] JP-A-2004-4970

[Patent Document 9] JP-A-2008-256797

[Patent Document 10] JP-A-2006-251395

[Patent Document 11] Japanese Patent Publication No. 09-506985

[Patent Document 12] JP-A-2007-10798

[Non-patent literature]

[Non-Patent Document 1] Uchida Ryuu, Supervisor, "All of the Graphical Electronic Displays" (Industrial Survey) p47~48

The object of the present invention is to solve the above problems in the prior art, and to provide a light diffusing film excellent in both light transmittance and diffusivity, for example, when used in an illumination device using an LED light source, in addition to being straightforward The light of the LED light source is diffused into a large area, and the light source point of the strong light is not seen, and further, a small amount of the light source distribution is exhibited by a small number of LED light sources which have suppressed the decrease in the transmittance of the light, And a light diffusing film and a laminated sheet thereof which can achieve high illuminance and brightness.

The present invention has been made in view of the above circumstances, and a light-diffusing film and a laminated sheet thereof which can solve the above problems are constituted as follows.

A light-diffusing film characterized by being a mixture of at least two kinds of incompatible thermoplastic resins and simultaneously satisfying the characteristics of the following (1) to (4);

(1) The total light transmittance is 66% or more,

(2) The haze is 96% or more,

(3) The parallel light transmittance is 2.0% or less,

(4) In the variable angle photometer according to the invention specification, the diffusivity ratio (DH/DL) of the transmitted light measured at an incident angle of 0 degrees is 2.0 or less.

(However, DH and DL are the widths (half-value width) of one-half height of the peak height of the variable-angle illuminance curve of the transmitted light measured by the automatic variable angle photometer, and the curling direction of the light-diffusing film is fixed in the vertical direction and As measured in the horizontal direction, a large half-value width is taken as DH, and a small half-value width is taken as DL).

2. The light-diffusing film according to item 1 above, wherein the DH is 30 degrees or more.

3. The light-diffusing film according to item 1 or 2 above, wherein the curling direction of the light-diffusing film is fixed to the vertical direction, the parallel direction and the horizontal direction of the test article fixing table according to the method of the invention, and the measured The curvature of the main diffusion direction is 4 to 100%.

4. The light-diffusing film of any one of the above-mentioned items 1 to 3, wherein at least one of the mixture of at least two kinds of incompatible thermoplastic resins is formed of a polyolefin resin.

5. The light-diffusing film according to item 4 above, wherein the mixture of at least two kinds of incompatible thermoplastic resins is formed by using two or more kinds of polyolefin-based resins.

6. The light-diffusing film of the above-mentioned item 5, wherein the mixture of the at least two kinds of polyolefin-based resins is formed of a cyclic polyolefin-based resin and a polyethylene-based resin.

7. The light-diffusing film according to item 6, wherein the cyclic polyolefin resin has a melt flow rate measured at 230 ° C of 0.1 to less than 1.5, and the polyethylene resin has a melt flow rate of 5 to 100. .

The light-diffusing film of any one of the above-mentioned items 5 to 7, wherein at least one side of the light-diffusing film formed by the mixture of the at least two kinds of incompatible thermoplastic resins is mainly composed of polyolefin a surface layer formed of a resin.

9. The light-diffusing film of item 8, wherein the polyolefin-based resin forming the surface layer is formed of a polyolefin resin containing a polar group.

10. The light-diffusing film according to item 9 above, wherein the polyolefin resin containing a polar group contains at least a carboxyl group.

11. The light-diffusing film according to any one of items 1 to 4 above, wherein the other thermoplastic resin is formed of a fluorine-based resin.

12. The light-diffusing film according to any one of items 1 to 4 above, wherein the other thermoplastic resin is formed of a polyester resin.

13. The light diffusing film according to item 12 above, wherein the light diffusing film is extended by more than 2 times in one direction.

The light-diffusing film according to any one of items 1 to 13, wherein at least one side is subjected to a shaping treatment to be roughened.

The light-diffusing film according to any one of items 1 to 14, wherein the variable angle photometer described in the specification of the invention has a diffused light ratio (DH/DL) measured by an incident angle of 0 degrees. At least two of the light-diffusing thin films exceeding 2.0 are formed by overlapping in a direction perpendicular to the main diffusion direction.

A light-diffusing film laminate, characterized in that the light-diffusing film according to any one of items 1 to 15 above is laminated with a plastic sheet having a thickness of 0.1 to 5 mm and a total light transmittance of 70 to 100%. Made.

The light-diffusing film according to any one of items 1 to 15, which is an illumination device using an LED light source.

18. The light-diffusing film laminated sheet according to item 16 above, which is an illumination device using an LED light source.

An illumination device using an LED light source, characterized in that the light-diffusing film according to any one of items 1 to 15 above is mounted on an outer surface or an inner surface of a light-emitting portion of an illumination device using an LED light source.

An illuminating device using an LED light source, characterized in that the light-diffusing film laminated sheet according to item 16 above is mounted on an outer surface or an inner surface of a light-emitting portion of an illumination device using an LED light source.

A backlight device characterized in that the light-diffusing film according to any one of items 1 to 15 above is mounted on an exit surface of the backlight assembly.

A backlight device characterized in that the light-diffusing film laminate of the above item 16 is mounted on an exit surface of the backlight unit.

A process for producing a light-diffusing film according to any one of items 1 to 15, which is characterized in that a mixture of at least two kinds of incompatible thermoplastic resins is melt-extruded.

24. The method for producing a light-diffusing film according to item 22 above, wherein the resin melted in the extruder is extruded from a die into a sheet shape, and the sheet is pressed by a pressure roller on a cooling roll to be densely combined and cooled. Curing to form a film.

The light-diffusing film of the present invention and the laminated sheet thereof are light-diffusing films excellent in both light transmittance and diffusivity, in particular, because the transmittance of straight-through light is small, for example, when used in an illumination device using an LED light source, In addition to diffusing the light of the direct-intensity LED light source into a large area, and not seeing the light source point of the strong light, further, since the degree of decrease in the transmittance of the light has been suppressed, even the number of LED light sources per unit area Reduced, still have a uniform and high amount of light. Therefore, it is possible to suppress the light of the LED light source from being high in linearity and causing only a narrow range of dots, which is called illumination using an LED light source. The shortcomings of the device and the advantages of the features of the energy-saving LED light source can be maintained.

Compared with the previously known light diffusing film, the distance between the fluorescent lamp and the light diffusing film or the light diffusing film laminated sheet is shortened even when the diffusing property is greatly improved, for example, when used in a lighting device using a fluorescent lamp as a light source. It still has a high degree of light diffusivity and, therefore, has the effect of reducing the thickness of the illumination device or reducing the number of fluorescent lamps. Further, for example, when a light-diffusing film which is a display device such as a liquid crystal display is used, the thickness of the display panel can be reduced, and the number of optical function adjusting films such as a brightness enhancement film or a light-diffusing film used for improving the brightness can be reduced.

The light-diffusing film of the present invention and the laminated sheet using the same can maintain non-optical properties such as heat resistance, in addition to maintaining the above-described optical characteristics.

Therefore, it can be effectively used for various illuminations such as indoor illumination, illumination of an internal illumination type electronic panel, light irradiation of a photocopier, or illumination of a display device such as a liquid crystal display.

Further, when the light-diffusing film of the present invention and the laminated sheet to be used are used as an optical component of a backlight device, high brightness can be imparted, angle dependence of brightness can be lowered, and brightness uniformity of the inner surface can be imparted by using only one sheet. The optical characteristics required for the optical material for a backlight device such as a pattern masking property can improve the economic efficiency of the backlight device. In particular, there is a great advantage that it is possible to solve the problem of using a lens film, such as a reduction in brightness which occurs when viewing at an oblique angle, without using a high-priced lens film.

The backlight device of the present invention has a front luminance of a height close to that of a backlight device using a lens film, and has a problem of reducing the angular dependence of luminance, that is, a backlight device using a lens film. When the television is used, the brightness of the picture is reduced due to the oblique angle viewing.

With this feature, it is possible to effectively use a backlight device such as a car navigation, which is mostly viewed from an oblique angle.

When it is used for a backlight of an indoor or interior lighting fixture, it has an advantage of uniform illumination over a wide range compared to a backlight using a lens film.

Moreover, since the backlight device of the present invention can provide all of the above characteristics by using only one single component, it has an advantage of high economic efficiency.

Therefore, the backlight device of the present invention can be effectively used for a liquid crystal display device, an indoor illumination, an internal illumination type electronic panel, or the like.

According to the method for producing a light-diffusing film of the present invention, the light-diffusing film of the present invention having the above characteristics can be produced economically and stably.

Form of implementing the invention (optical properties)

The light-diffusing film of the present invention must simultaneously satisfy the following characteristics.

(1) The total light transmittance is 66% or more, (2) the haze is 96% or more, and (3) the parallel light transmittance is 2.0% or less, and (4) the variable angle photometer in the invention specification, at the incident angle The diffused light transmittance ratio (DH/DL) measured at 0 degree is 2.0 or less.

(However, DH and DL are the widths (half-value width) of one-half height of the peak height of the variable-angle illuminance curve of the transmitted light measured by the automatic variable angle photometer, and the curling direction of the light-diffusing film is fixed in the vertical direction and As measured in the horizontal direction, a large half-value width is taken as DH, and a small half-value width is taken as DL).

Hereinafter, the direction of DH is also referred to as the main diffusion direction.

The total light transmittance is preferably 68% or more, and more preferably 70% or more. It is particularly good for 80% or more, and more preferably 90% or more. 100% best. Since the principle does not exceed 100%, 100% is the upper limit. If the total light transmittance is less than 66%, the transmittance of light emitted from the LED light source is lowered, and the amount of light used for illumination is lowered and the illuminance and brightness of the illumination device are also lowered, which is not appropriate.

The haze is preferably 97% or more, more preferably 98% or more. 100% best. Since the principle does not exceed 100%, 100% is the upper limit. If the haze is less than 96%, the light diffusibility is lowered and it is not possible to uniformly illuminate, which is not appropriate. In order to evenly illuminate, it is necessary to increase the number of LED light sources, which is less economical.

The parallel light transmittance is 1.7% or less, more preferably 1.5% or less, and still more preferably 1.2% or less. Very good is 0~1.0%. 0% is the best. Since the principle is not less than 0%, 0% is the lower limit. If the parallel light transmittance exceeds 2.0%, the dot disappearance deteriorates, and the dots of the strong light from the light source are clearly seen, and cannot be uniformly illuminated, which is not appropriate.

The diffused light transmittance ratio (DH/DL) (hereinafter simply referred to as the diffusivity ratio) is preferably 1.8 or less. More preferably 1.6 or less, especially 0.7 to 1.3.

When the diffusivity ratio (DH/DL) exceeds 2.0, the anisotropy of light diffusion increases, and the light amount is diffused to a specific direction, and the amount of light on the surface, that is, the uniformity of illuminance and luminance is lowered, which is not appropriate.

The above diffusion ratio is determined by measuring according to the following method.

<Measurement method of diffuse transmittance ratio of transmitted light>

The measurement was performed using an automatic variable angle photometer (GP-200: manufactured by Murakami Color Research Co., Ltd.).

Through the measurement mode, the incident angle of light is 0° (for the test surface, the angle is at right angles up and down, left and right), the light receiving angle: -90°~90° (angle on the equator line), filter: use ND10, beam aperture: 10.5mm (VS-1 3.0), light-receiving aperture: 9.1mm (VS-3 4.0) and variable angular separation of 0.1 degrees to determine the transmission of light when changing the setting of SENSITIVITY or HIGH VOLTON The peak of the curve is 40 to 90% of the curve, and the width (half-value width) of the height of the height of the peak of the variable angle illuminance curve of the transmitted light is measured.

The measurement is performed by fixing the curling direction of the light-diffusing film in the vertical direction and the horizontal direction, and the obtained large half-value width is DH, and the smaller one is DL, and the diffusion ratio (DH/DL) is obtained ( Refer to Figure 1).

When the surface roughness of the light-diffusing film differs, the surface having a rough surface is fixed to the light-receiving side to perform the above measurement.

Further, the plane of the moving photoreceiver is defined as an equatorial plane.

The light-diffusing film of the present invention satisfies the above characteristics at the same time, and the effect of the present invention can be sufficiently exerted, and the DH is preferably 30 degrees or more. More preferably, it is 35 degrees or more, and particularly preferably 40 degrees or more. When DH is less than 30 degrees, the diffusibility of light is lowered, and it is difficult to uniformly emit light, which is not appropriate. In order to evenly illuminate, it is necessary to increase the number of LED light sources, which is less economical.

(change of light)

The degree of curvature of light of the present invention is determined by the following method.

<Method for measuring the degree of curvature of light>

The measurement was performed using an automatic variable angle photometer (GP-200: manufactured by Murakami Color Research Co., Ltd.).

Through the measurement mode, the incident angle of light is 0° (for the test surface, the angle is at right angles up and down, left and right), the light receiving angle: -90°~90° (angle on the equator line), filter: use ND10, beam aperture: 10.5mm (VS-13.0), light-receiving aperture: 9.1mm (VS-3 4.0) and variable angle interval of 0.1 degrees to determine the change of SENSITIVITY or HIGH VOLTON setting to transmit light The peak is 40 to 90% of the graph, the measured height of the peak of the transmitted light (H0), and the incident angle of the light is changed to 60° (the angle on the equatorial plane), and the same conditions as those described above are performed. The height (H60) at the angle of the peak of the transmitted light at the time of measurement at the time of measurement. Using the H60 and H0 obtained by this method, the degree of curvature was calculated by the following formula.

The degree of curvature of light = H60 / H0 × 100 (%) (1)

Refer to Figure 2.

The plane of the moving receiver is defined as the equatorial plane.

The degree of curvature of the light is determined by measuring in the main diffusion direction.

When the surface roughness of the light-diffusing film for a backlight device differs, the above measurement is performed by fixing the direction in which light passes in the same direction as that actually used in the backlight device.

The degree of curvature of the above light is preferably from 6 to 100%, more preferably from 8 to 100%.

If the degree of curvature of light is less than 4%, the effects of the present invention described above cannot be sufficiently exerted, which is not appropriate.

This characteristic is, for example, the degree of the effect of the distortion of light in the film when it is illuminated into the light diffusing film for the backlight device, that is, the light that is incident at a high angle. The measure of the extent to which it is directed toward the front. It can also be a scale indicating the effect of collecting light. The light-diffusing film of the present invention has a greater distortion effect than the previously known light-diffusing film or lens film. Therefore, the effects of the present invention can be effectively exerted.

For example, when used in a backlight device for a liquid crystal display, each of the previously known lens films, light-diffusing films (sheets), and light diffusing plate members can be used to meet the above-described characteristics of any one of them. It is the founding of the present invention that meets the desirable characteristics of all of the features at the same time.

Although the reason for attaching this ideal characteristic is not known, the inference is achieved by simultaneously meeting the majority of the above-mentioned optics. For example, the high degree of curvature of light is dependent on the angle of brightness, and the high degree of diffusivity contributes to the uniformity of the inner surface brightness or the masking property.

(surface roughness of the surface of the light diffusing film)

In the light-diffusing film of the present invention, it is preferred that the surface roughness of at least one surface is the same. That is, the average surface roughness of the curling direction of the light-diffusing film and the direction perpendicular to the direction is measured, and the ratio of the average surface roughness RaV to RaH, that is, the surface roughness ratio (RaV/RaH) is preferably measured. It is 0.83~1.20. If it is out of this range, for example, the anisotropy of light diffusion, that is, the above-described diffusivity ratio (DH/DL), the light amount, that is, the uniformity of illuminance or brightness, is not appropriate. The above surface roughness is preferably 0.91 to 1.1.

(Composition of light diffusing film)

The light-diffusing film of the present invention is formed from a mixture of at least two kinds of incompatible thermoplastic resins.

The form in which the mixture of at least two kinds of incompatible thermoplastic resins is present is a structure in which the respective resins of the continuous phase and the dispersed phase are independently present, that is, a sea/island structure, or a structure in which the two resins form a co-continuous phase. The above characteristics are exhibited by the refraction or scattering of light at the resin interface.

The film thickness of the light-diffusing film of the present invention is not particularly limited, but is preferably 10 to 1000 μm. Especially suitable for 30~500μm.

(a mixture of at least two non-compatible thermoplastic resins)

In the present invention, a thermoplastic resin used in a mixture of at least two kinds of incompatible thermoplastic resins, for example, a polyethylene resin, a polypropylene resin, a polybutene resin, a cyclic polyolefin resin, and a polymethyl pentane A polyolefin resin such as an olefin resin, a polyester resin, an acrylic resin, a polystyrene resin, a polycarbonate resin, a fluorine resin, a copolymer thereof, or the like.

From such a thermoplastic resin, at least two kinds of incompatible (incompatible with each other) thermoplastic resin may be selected, but the above characteristics and economical properties can be stably achieved, and at least one polyolefin-based resin is preferably formed. .

Among the two types of resins, the other resin is preferably a polyolefin resin, a polyester resin, a fluorine resin or the like. The demand characteristics, economics, and the like other than the optical characteristics are considered, and are appropriately selected.

In particular, from the viewpoints of light resistance and economy, it is preferred that both types are polyolefin-based resins. When both types are polyolefin-based resins, the combination is not particularly limited, and the difference in refractive index between the two types of polyolefin-based resins is preferably in the range of 0.003 to 0.07. More preferably, it is in the range of 0.005 to 0.05, and more preferably 0.01 to 0.02. When the refractive index difference is within this range, the light-diffusing film having the above optical characteristics can be more stably obtained. For example, if the refractive index difference exceeds 0.07, it contributes to the haze and the parallel light transmittance in the above range, but the total light transmittance is not easily balanced. On the other hand, if it is less than 0.003, it is easy to achieve total light transmittance, but it is difficult to achieve a balance between haze and parallel light transmittance.

Therefore, within the above range, various optical characteristics described above can be simultaneously satisfied. If it is out of the above range, even if the above mixing ratio and melt flow rate are satisfied, it is impossible to satisfy all the characteristics.

The type of the polyolefin resin that satisfies the above-mentioned refractive index difference is not particularly limited, but a combination of a cyclic polyolefin resin and a polyethylene resin can satisfy the above characteristics and is excellent in economic efficiency, and therefore is suitable.

The cyclic polyolefin-based resin has a cyclic polyolefin structure such as norptene or tetracyclododecene.

For example, (1) a ring-opening (co)polymer of a decene-based monomer is added to maleic acid or cyclopentadiene to carry out polymer-modified hydrogenation, and (2) a deuterated system is used. A resin in which a monomer is subjected to addition polymerization, a resin in which (3) a decylene-based monomer, and an olefin-based monomer such as ethylene or an α-olefin are subjected to addition polymerization. The polymerization method and the method of adding hydrogen can be carried out in accordance with a general method.

The polyethylene resin may be a single polymer or a copolymer. In the case of a copolymer, it is 50 mol% or more, preferably an ethylene component.

The density of the resin, the polymerization method, and the like are also not limited, but a copolymer having a density of 0.909 or less is preferably used. For example, copolymers such as propylene, butene, hexene and octene. The polymerization method may be any one of an aromatic cycloolefin metal derivative catalytic method and a non-aromatic cycloolefin metal derivative catalytic method.

In particular, a block copolymer of ethylene and octene is preferably used from the viewpoint of stably attaching high diffusibility. For this resin, for example, INFUSE (TM) manufactured by Daiwa Chemical Co., Ltd. can be used.

The melt flow rate of the thermoplastic resin which is at least two kinds of incompatible thermoplastic resins is preferably added to the difference in melt flow rate of each of the thermoplastic resins. Thereby, the above optical characteristics can be attached more stably.

For example, when a polyolefin resin is used for both of the above types, the thermoplastic resin having a low melt flow rate preferably has a melt flow rate of 0.1 to 1.5 or less as measured at 230 °C. More preferably 0.1~1.2, especially 0.1~1.0. When it is less than 0.1, the stability of the film formation is lowered, which is not appropriate. On the other hand, when it is more than 1.5 or more, the surface roughness ratio or the light diffusivity ratio is increased, and the optical characteristics such as an increase in the anisotropy of light diffusion are deteriorated, which is not preferable.

On the other hand, the thermoplastic resin having a high melt flow rate preferably has a melt flow rate of 5 to 100 as measured at 230 °C. More preferably 10~100, especially good 15~100. If it is less than 5, optical characteristics such as an increase in anisotropy of light diffusion are deteriorated, which is not preferable. On the other hand, when it exceeds 100, since the stability of film formation falls, it is inadequate.

When a mixture of at least two kinds of incompatible thermoplastic resins is a mixture of the above cyclic polyolefin resin and a polyethylene resin, a cyclic polyolefin resin is preferably used as the resin having a low melt flow rate, and another A polyethylene resin is preferably used as the resin having a high melt flow rate.

The mixing ratio of the at least two kinds of incompatible thermoplastic resins is preferably 10/90 to 90/10, more preferably 20/80 to 80/20, and particularly preferably 30/70 to 70/30.

Within the above range, the various optical characteristics described above can be simultaneously met. If it is not within the above range, it will not be able to meet all or a part of the characteristics even if it meets the following contents.

The above-mentioned resin may be selected from a resin which is generally commercially available and which is highly versatile, and a special product may be used in order to produce it more stably.

(Layer of polyolefin resin forming layer)

In the present invention, when a mixture of at least two kinds of incompatible thermoplastic resins is used, in the case where a polyolefin-based resin is used in both types, it is preferable that at least two layers of the polyolefin-based resin are formed of a mixture of at least two kinds of polyolefin-based resins. One side is formed by laminating a surface layer mainly composed of a polyolefin resin. Hereinafter, a layer formed of a mixture of at least two kinds of polyolefin resins is simply referred to as a light diffusion layer.

When melt-extruded to form a film, it occurs at the exit of the extrusion die, for example, a phenomenon called "eye stain" which occurs as a result of the deterioration of the resin at the exit of the extrusion die, because the surface layer can be used Since it is suppressed by formation, it is suitable for continuous film formation for a long time and stability. In addition, it is preferable to suppress the shielding property of the light-diffusing film which occurs when a flexible polyolefin-based resin such as a block copolymer of ethylene or octene is used.

The polyolefin-based resin to be used for the formation of the surface layer is preferably a crystalline resin because it exhibits an effect of suppressing the shielding property.

It is preferable to use a polyolefin resin containing a polar group for the polyolefin resin to be used for the formation of the above surface layer. Therefore, the method can improve the adhesion of the light-diffusing film to other materials, so it is more appropriate. For example, in the production of a light-diffusing film laminated sheet to be described later, it is suitable because the adhesion to the plastic sheet can be improved. Moreover, it is widely used as an optical material, and it is suitable for the thermal adhesiveness with an acrylic resin or a polycarbonate resin.

The polar group-containing polyolefin resin preferably has a skeleton of a monomer containing at least one of ethylene, propylene, butene, hexene, octene, methylpentene, and a cyclic olefin.

A homopolymer of the above-mentioned monomers of one type may be used, or a copolymer of two or more kinds of monomers may be used.

The above polar group-containing polyolefin resin of the present invention preferably contains at least one kind of polar group. Polar groups such as carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, glycidyl groups, isocyanate groups, amine groups, oxime imido groups, oxazolines, ester groups, ether groups, metal carboxylate groups, sulfonic acids A metal salt group, a phosphonic acid metal salt group, a tertiary amine salt group, a 4-grade amine salt group, and the like. It may contain one or more of these polar groups.

The composition of the polyolefin-based resin constituting the light-diffusing layer, the type of the component to be adhered to, the desired adhesion force, and the like may be appropriately selected, and at least the carboxyl group-based embodiment is preferably used.

In the polyolefin resin containing a polar group in the present invention, the polar group may be directly introduced into the polymer chain of the polyolefin resin, or may be introduced into another polymer, and may be added or mixed. Depending on the situation, the polyolefin resin of the present invention may be modified by, for example, a carboxylic acid group or a hydroxyl group introduced into the terminal or inside of a molecular chain, and a compound reactive with such a group may be used.

In the present invention, the polyolefin resin containing the above-mentioned polar group may be used singly or in combination of two or more kinds thereof. Further, it may be a polyolefin resin containing no polar group or a compounding composition of another type of resin. When the composition is blended, the polyolefin resin containing the above polar group is preferably contained in an amount of 10% by mass or more. More preferably, it is 30% by mass or more.

The polyolefin resin containing the above polar group is preferably formed of a crystalline resin. It is preferred to use a melting point of 100 to 180 ° C.

The polyolefin resin containing the above-mentioned polar group is not particularly limited as long as it has the above characteristics. For example, a commercially available resin can be suitably used as the binder polyolefin resin. For example, Aduman Resin (TM, manufactured by Mitsui Chemicals Co., Ltd.), Maudeke Resin (TM, manufactured by Mitsubishi Chemical Corporation) or Adudex Resin (TM, manufactured by Nippon Polyethylene Co., Ltd.) and Montesto Resin (TM) , Sumitomo Chemical Co., Ltd.), but is not limited to this.

By laminating the layer formed of the polar resin-containing polyolefin resin to the light-diffusing layer, the light-diffusing film having a single layer of the light-diffusing layer can improve the adhesion to other materials. The film is improved in blocking resistance or slidability, and the operability of the light-diffusing film is improved. Thermal adhesion to a variety of materials is also available.

(by roughing the shape processing)

In the light-diffusing film of the present invention, at least one side of the film obtained by the above method is preferably roughened by a shaping treatment.

This roughening treatment is carried out on the surface of the light-diffusing film obtained by the above method, and it is not particularly limited, and it may be subjected to matte processing or embossing. In the roughening treatment, the light-diffusing film is passed through, for example, a roll in which irregularities (lattice-like irregularities, irregular irregularities, and the like) have been formed, and the sheet-form material is extruded on a roll having irregularities.

The formation or depth of the surface unevenness formed by the roughening treatment is not particularly limited, but the surface unevenness to be shaped is preferably a shape having no irregular orientation which is not aligned in a specific direction. That is, a processing method of matting processing or satin finished surface processing is usually employed. It is also possible to use a roughening method for forming a special surface unevenness.

The roughening treatment may be an in-line treatment method performed in a film forming step of a film, or an off-line processing method performed in other steps.

The light-diffusing film laminated sheet to be described later may be shaped and roughened.

By the roughening of the above-described shaping treatment, the blocking resistance and the slidability of the film can be improved, and the operability of the light-diffusing film can also be improved. And can increase the spread of light. It can reduce the diffusion ratio and also reduce the anisotropy of light diffusibility.

The film thickness of the light-diffusing film of the present invention is not particularly limited, but is preferably 10 to 1000 μm. More preferably 30~500μm.

The light-diffusing film of the present invention may be used in one piece or in a mixture of two or more sheets. When two or more sheets are used in combination, they may be used only for overlapping, and may be used by adhering a binder or an adhesive.

The present invention also includes a mode in which, when used in two or more sheets, each of the films is a light-diffusing film which does not conform to the characteristics of the present invention, and is superposed to conform to the characteristics of the present invention described above. For example, a plurality of films having a high anisotropy are superimposed in a direction in which the main diffusion direction is perpendicular to reduce the diffusion ratio, and a method conforming to other optical characteristics is an ideal embodiment.

By this method, the degree of anisotropy can be widely suppressed, which is an ideal implementation.

The light-diffusing film of the present invention may be used by being superposed on another work film such as a light-diffusing film or a lens film having other characteristics. When using this method of use, it can be used only by overlapping, and it can also be used by sticking adhesive or adhesive.

(Method of producing light diffusing film)

The method for producing the light-diffusing film of the present invention is not particularly limited as long as it satisfies the above optical characteristics, and from the viewpoint of economy, it is preferably a method of forming a film by melt extrusion molding.

In the present invention, in order to impart light diffusibility, it is possible to reduce the clogging of the filter film of the molten resin in the film forming step by performing the melt extrusion molding method without containing the non-melting fine particles, and it is excellent in productivity. The resulting film has a high degree of clarity.

The film forming method by the above melt extrusion molding method is not particularly limited, and is, for example, any of the T die method and the blow molding method. It can be an unextended film and can be extended.

The ideal aspect of the present invention is based on an extruder in which a molten resin is extruded from a die into a sheet shape, and the sheet is pressed against a cooling roll by a press roll to form a film by compacting, cooling, and solidification.

The content is not particularly limited as long as it conforms to the pressure roller to press the sheet with a pressure roller to make it adhere. For example, it may be pressed by a press roll having a smaller diameter than a commonly used chill roll, or the sheet may be extruded between two chill rolls having the same diameter, and the two chill rolls may be pressed.

In this method, it is also possible to use a roll having a roughening treatment on the surface of the squeezing roller and/or the chill roll, and at the same time, roughening the above-described shaping treatment.

By the above treatment, the isotropic property of the light diffusion characteristics of the light-diffusing film can be improved.

One of the characteristics of the light-diffusing film of the present invention must be diffused in the same direction in the same direction. That is, since the isotropic light diffusing film is not limited to being manufactured without extension. For example, when a polyester resin is used for the light diffusion layer, one-axis stretching is preferably performed. By the above-described treatment, the island phase is stretched in the extending direction to form an elongated structure, and the light diffusibility in the direction perpendicular to the alignment direction of the island phase is remarkably enhanced, and the high diffusibility of the object of the present invention can be secured. However, in the light-diffusing film obtained by this method, most of the anisotropy is improved, and the diffusivity ratio exceeds the range of the present invention. Therefore, in an ideal embodiment, as described above, two or more films are stacked so that the main diffusion direction is vertical.

The light-diffusing 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, if at least one layer is a layer formed of the above-described light-diffusing film, the other layer may be a simple transparent layer having no light diffusibility. Moreover, it may be a structure of a full-layer light-diffusion layer.

In the case of the above multilayer structure, it may be produced by a multilayer co-extrusion method, or may be carried out by extrusion lamination or dry lamination.

The mixture of at least two kinds of incompatible thermoplastic resins may be blended with each of the thermoplastic resins in an extruder such as a film forming step, or may be used in advance as a mixture by kneading or the like.

(Mechanism)

The present invention must simultaneously conform to the above-mentioned various optical characteristics such as total light transmittance, parallel light transmittance, haze, diffusivity, and diffusivity ratio. With regard to conforming to most of the characteristics at the same time, it is first of all to achieve a height characteristic which cannot be achieved by a previously known light-diffusing film. Thereby, a high-performance light-diffusing film suitable for use in an illumination device for an LED light source or a backlight device can be obtained.

The above characteristics include the characteristics of the behavior indicating the opposite of the law. For example, total light transmittance and other characteristics are indicative of a bipolar behavior. On the other hand, the parallel light transmittance, haze, and diffusivity, in terms of macroscopic view, indicate the characteristic value of the proportional behavior, which is not yet proportional to the microscopic aspect. Therefore, it is not easy to clearly express the contribution to the individual elements of the respective characteristics, but the resin characteristics such as the refractive index difference or the melt flow rate of the above-mentioned incompatible resin, or the kind or mixing ratio of each resin, etc. Within the scope, it can be achieved with stability.

The diffusion ratio of one of the above characteristics is greatly changed due to the difference in the manufacturing apparatus used, and as a result of research, in the above-described melt film forming method, the molten resin is extruded from the die into a sheet shape in an extruder. The sheet is pressure-bonded to the chill roll by a press roll to form a film by heat-sealing and solidification, whereby the film can be produced more stably.

The above diffusion ratio is governed by the influence of the phase structure formed by the two kinds of incompatible resins of the light diffusion layer. For example, if it is a sea/island structure, it is governed by the anisotropy of the shape of the island. It is proportional to the anisotropy of the island shape and increases the diffusion ratio. That is, it is important to reduce the anisotropy of the island shape, that is, to improve the isotropic nature of the island shape.

With the above manufacturing method, although the mechanism for improving the isotropic property of the island shape is not clear, the inference is as follows.

The shape of the island component in the sheet extruded by the melt extrusion method is distributed in the die, and the shape in the direction of extrusion is tapered. After being extruded from the die, the sheet is inclined in a molten state, and the shape of the island is tapered in the extrusion direction, and is cooled and solidified in this state, and generally, the shape is elongated in the shape of the extrusion direction. Since it is immobilized, the diffusivity ratio of the light-diffusing film is increased.

However, according to the above manufacturing method, when the cooling roller is pressed by the pressure roller, the sheet at the entrance of the crimping portion is in an uncured state, so that a liquid storage region is formed at the inlet of the crimping portion (also It is called a hopper), and the resin in the uncured state is retained in this zone, and the island component which is thinned in the extrusion direction is caused by the surface tension, and the force of the same direction droplets is restored to the original shape, and the difference is moderated. The degree of orientation is changed to a more isotropic shape, and since the shape of the deformation is cooled and solidified, the isotropic property of the island shape is improved, and as a result, the light diffusivity is also increased in the same direction, and the diffusion ratio is stabilized in the above range.

(Light diffusing film laminate)

Another invention of the present invention is an optically diffusive film laminated sheet obtained by laminating a light diffusing film 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%. .

The light-diffusing film obtained by the above method has the above-mentioned excellent optical characteristics and can be economically produced, but in some applications, it cannot conform to characteristics other than optical characteristics, such as heat resistance, heat-resistant dimensional stability, rigidity, and the like. Mechanical properties or flame retardancy. By laminating a transparent plastic sheet with the light-diffusing film of the present invention, it is possible to complement the characteristics other than the optical characteristics, and it is possible to meet the general characteristics of the market.

The transparent plastic sheet used in the present invention can satisfy the above characteristics of thickness and total light transmittance, and does not limit the type of resin or the layer constitution.

The thickness of the transparent plastic sheet used in the present invention is particularly preferably 0.5 to 3 mm. If it is thinner than 0.1mm, the reinforcing effect or complementing effect is not good. If it exceeds 5 mm, it is unfavorable for economy and detracts from softness.

The total light transmittance of the transparent plastic sheet used in the present invention is preferably 80 to 100%. Better 85~100%. If it is less than 70%, the characteristics of the above light-diffusing film cannot be effectively exhibited. It is advisable to use a high total light transmittance and non-diffusion. Further, it is also possible to use a diffuser as the plastic sheet to exert a laminated effect.

The resin used for the plastic sheet is not particularly limited, and a resin for optical use such as a polyester resin, an acrylic resin, a styrene resin, a cyclic polyolefin resin, or a polycarbonate resin is preferably used.

The method for producing the above light diffusing film laminate is not particularly limited. For example, a method of adhering a light diffusing film to a plastic sheet.

When pasting with an adhesive or a binder, specifically, an adhesive such as a rubber adhesive, an acrylic adhesive, a silicone adhesive, a vinyl adhesive, or the like. Since the light-diffusing film laminate of the present invention may be used at a high temperature, it is preferably an adhesive which is stable at a normal temperature of ~120 ° C. Among them, acrylic adhesives are widely used because of their low price. Regardless of the type of adhesive used, the thickness is preferably from 0.5 to 50 μm.

The binder is bonded to the adhesive, for example, by the aid of heat or a catalyst. Specifically, for example, a fluorene-based adhesive, a polyurethane-based adhesive, a polyester-based adhesive, an epoxy-based adhesive, a cyanoacrylate-based adhesive, an acrylate-based adhesive, or the like can be used. Since the light-diffusing film laminate of the present invention may be used at a high temperature, it is preferably a binder which is stable at a normal temperature of ~120 ° C. Among them, the epoxy-based adhesive is excellent in strength and heat resistance and can be suitably used. Since the cyanoacrylate-based adhesive is excellent in immediate effect and strength, it can be used for the production of an efficient laminated sheet. The polyester-based adhesive is particularly suitable for the production of laminated sheets because of its excellent strength and processability. Such adhesives are classified into a heat-curing type, a hot-melt type, a two-liquid mixing type according to a bonding method, and a heat-hardening type or a hot-melt type which can be continuously produced is preferably used. Regardless of the binder used, the thickness should be 0.5 to 50 μm.

A method of adhering the above-mentioned plastic sheet to a light-diffusing film with an adhesive or a binder is carried out by using a roll-to-roller or a roll-to-sheet treatment of a laminator to obtain a roll-shaped or sheet-shaped article. For example, when a binder is used, a binder is applied to either the plastic sheet or the light-diffusing film, and after drying, it is laminated with a target material and laminated by a roller.

The coating method of the adhesive is various depending on the type of the substrate or the adhesive, and the gravure coater method, the standard coater method, and the reverse coater method are often used. The gravure coater method rolls a gravure roll partially impregnated with a binder so that the film conveyed by the backing roll comes into contact with the gravure roll to which the adhesive has adhered, thereby performing coating. The amount of coating can be adjusted by controlling the number of rolls of the roll, the viscosity of the adhesive, and the like. Although the reverse coater method is similar to the gravure coater method, the meter attached thereto is used to adjust the amount of the adhesive adhered to the coating roll.

When the above paste is applied, it can be heated according to the demand. Further, in order to have the necessary adhesive strength, heat treatment may be performed after lamination.

When pasting with an adhesive, a double-sided adhesive sheet can also be used. When using this method, an optically high transparent type of adhesive should be used without particular limitation. For example, a light-diffusing adhesive sheet can also be used. When the adhesive sheet is used, the adhesive layer can also have light diffusibility.

The present invention can also be carried out by a method of integrating the production of the light-diffusing film and the production of the light-diffusing film laminate.

In other words, the thermoplastic resin composition constituting the light-diffusing film may be melted and extruded on the surface of the transparent plastic sheet to be directly laminated, that is, so-called extrusion. The above roughening treatment may be simultaneously performed in the step of the melt extrusion lamination method.

When the extrusion lamination method is carried out, in order to improve the adhesion or adhesion durability of the light-diffusing film and the transparent plastic sheet, it is preferable to adopt a method of using a transparent plastic sheet which has been subjected to an adhesion-promoting coating treatment and is easy to be bonded.

The light-diffusing film or the light-diffusing film laminated sheet of the present invention is preferably a light-diffusing film using an illumination device using an LED light source because of the above-described excellent optical characteristics. However, there is no particular limitation, and for example, it can be effectively used for an illumination device using a light source other than an LED light source such as a fluorescent lamp. For example, when used in an illumination device of a fluorescent light source, even if the distance between the fluorescent lamp and the light diffusing film or the light diffusing film laminated sheet is pulled, the light diffusing property is high, and therefore, the thickness and the thickness of the lighting device are reduced. The number of fluorescent lights and other effects.

The light-diffusing film or the light-diffusing film laminated sheet of the present invention can greatly reduce the diffusibility when compared with the previously known light-diffusing film, and can reduce the light when used for brightness enhancement of an LCD using a fluorescent lamp as a light source. The number of films for optical function adjustment such as a diffusion film.

(lighting device using LED light source)

According to another aspect of the invention, the light diffusing film and the light diffusing film layered sheet described above are applied to an outer surface or an inner surface of a light-emitting portion of an illumination device using an LED light source, thereby forming an illumination device using an LED light source.

The previously known light-diffusing film is usually used on the outer surface or the inner surface of the light-emitting portion of the light guide plate. When the light-diffusing film of the present invention and the laminated sheet thereof are used as far as possible from the LED light source, the light diffusing property and the dot-disappearing property are improved. Therefore, it is preferable to use the illumination device using the LED light source in the above method.

The method of dispersing the light-diffusing film and the laminated sheet thereof is not particularly limited. For example, an adhesive or a binder is adhered to the outer surface or the inner surface of the outer panel of the light-emitting portion, and only the device is covered. If it is pasted, it can be fixed by using an adhesive or a binder as a whole, or it can be partially used and fixed. In the case of a fluorescent lamp-like tubular lighting device, the light-diffusing film or its laminated sheet may be inserted into the inner surface of the outer tube along the inner side of the outer tube.

It is also possible to install only the light-diffusing film of the present invention or a laminated sheet thereof without an outer sheet.

(used as a backlight device)

The light-diffusing film or the light-diffusing film laminated sheet of the present invention can be applied as a component for improving the brightness or illuminance of the backlight device because of the above-described excellent optical characteristics.

It is important to attach the above-described light-diffusing film or light-diffusing film laminate of the present invention to the light-emitting surface of the backlight unit. In this case, the method of mounting the light-diffusing film or the light-diffusing film laminate is not particularly limited. They can be installed only by overlapping, or they can be fixed by adhesive or adhesive. It can also be fixed with double-sided tape.

Further, it may be mounted on the lowermost surface of the liquid crystal panel provided on the upper surface of the backlight device.

By this measure, the effects of the present invention described above can be exerted.

(backlight assembly)

The backlight assembly using the light-diffusing film or the light-diffusing film laminated sheet of the present invention may be a member having an emitting surface on at least one side, and the structure and the like are not limited in any way. It can be side light or down. In the case of the side light mode, the structure of the light guide plate is also not limited.

The type of reflective film or reflector used in the backlight assembly is also not limited. It can be any of a white reflection type, a metal reflection type, and the like.

The light source used in the backlight assembly is also not limited. It can be, for example, any of an electric bulb, a light emitting diode (LED), an electroluminescent panel (EL), a cold cathode tube (CCFL), and a hot cathode tube (HCFL), or a combination thereof or other light source.

The light-diffusing film or the light-diffusing film laminated sheet of the present invention is required to provide a high brightness, a reduction in brightness angle dependency, an inner surface brightness uniformity, and a pattern masking property, even if only one such component is used. Since the optical characteristics are used, it is important to use one sheet, but two or more sheets may be used in combination, and may be used in combination with a previously known lens film or light diffusing film. Other light diffusers or light diffusers can be used in combination. In this case, most types of optical parts can also be used in combination. It should be appropriately selected and used according to the characteristics of the market demand or economy.

Instance

In the following, the present invention will be more specifically described by the following examples, but the present invention is not limited to the following examples, and may be appropriately modified within the scope of the invention, and the like are included in the technical scope of the present invention. . ^‧ measurement and evaluation methods employed in Examples, the following lines. In the example, "parts" means "parts by mass" and "%" means "mass%".

<Full light transmittance, parallel light transmittance and haze>

The haze meter "NDH-2000" manufactured by Nippon Denshoku Industries Co., Ltd. was used in accordance with JIS K 7136.

This measurement was fixed to the fixed portion of the test piece so that the curling direction of the light-diffusing film was perpendicular, and the measured value obtained by the measurement was used. When the surface roughness of the light-diffusing film differs, the surface having a rough surface is fixed to the light-receiving side and measured. For example, a light-diffusing film which has only one surface roughening treatment is actually measured and used in the direction in which light passes.

<Transmission ratio of transmitted light>

The measurement was performed using an automatic variable angle photometer (GP-200: manufactured by Murakami Color Research Co., Ltd.).

Through the measurement mode, the incident angle of light is 0° (for the test surface, the angle is at right angles up and down, left and right), the light receiving angle: -90°~90° (angle on the equator line), filter: use ND10, beam aperture: 10.5mm (VS-1 3.0), light-receiving aperture: 9.1mm (VS-3 4.0) and variable angular separation of 0.1 degrees to determine the transmission of light when changing the setting of SENSITIVITY or HIGH VOLTON The peak of the curve is 40 to 90% of the curve, and the width (half-value width) of the height of the height of the peak of the variable angle illuminance curve of the transmitted light is measured.

The measurement is performed by fixing the curling direction of the light-diffusing film in the vertical direction and the horizontal direction, and the obtained large half-value width is DH, and the smaller one is DL, and the diffusion ratio (DH/DL) is obtained ( Refer to Figure 1).

When the surface roughness of the light-diffusing film differs, the surface having a rough surface is fixed to the light-receiving side to perform the above measurement.

<The curvature of light>

The measurement was performed using an automatic variable angle photometer (GP-200: manufactured by Murakami Color Research Co., Ltd.).

Through the measurement mode, the incident angle of light is 0° (for the test surface, the angle is at right angles up and down, left and right), the light receiving angle: -90°~90° (angle on the equator line), filter: use ND10, beam aperture: 10.5mm (VS-1 3.0), light-receiving aperture: 9.1mm (VS-3 4.0) and variable angular separation of 0.1 degrees to determine the transmission of light when changing the setting of SENSITIVITY or HIGH VOLTON The peak is 40 to 90% of the graph, the measured height of the peak of the transmitted light (H0), and the incident angle of the light is changed to 60° (the angle on the equatorial plane), and the same conditions as described above. The height (H60) at which the angle of the peak of the transmitted light at the time of measurement is 0 degrees. Using the H60 and H0 obtained by this method, the degree of curvature was calculated by the following formula.

The degree of curvature of light = H60 / H0 × 100 (%) (1)

Refer to Figure 2.

The plane of the moving receiver is defined as the equatorial plane.

The degree of curvature of the light is determined by measuring in the main diffusion direction.

When the surface roughness of the light-diffusing film differs, the above measurement is performed by fixing the direction in which light passes in the same direction as in actual use.

<Light resistance>

Using a twilight aging tester (S300, manufactured by Sijia Test Instruments Co., Ltd.), the test surface illuminance: 78 W/m2, wavelength range: 300 to 400 nm, continuous irradiation, and rainfall (12 minutes of rain in 60 minutes) The conditions were exposed to an environment of 63 ° C × 50% RH for 400 hours, and the change in color difference (Δ * ab) was evaluated.

<Average surface roughness ratio>

The universal surface shape measuring instrument MODEL SE-3C manufactured by Otaru Institute Co., Ltd. was used to measure the longitudinal magnification: 2000 to 10000, the cutoff: 0.25 mm, the measurement length: 8 mm, and the measurement speed: 0.5 mm/min.

The measurement is performed by measuring the average surface roughness of the direction in which the light-diffusing film is curled and the direction perpendicular to the direction, and the obtained average surface roughness, that is, the surface roughness ratio (RaV/RaH) of the ratio of RaV to RaH. This measurement was performed 5 times separately, and the average value was used.

<Melt flow rate of thermoplastic resin>

The measurement was carried out under the conditions of 230 ° C and 2.16 kgf according to JIS K 7210 A method. A part of the resin is determined by the conditions of the examples.

<Evaluation of light diffusibility when using an illumination device using an LED light source>

The light diffusing film or the light diffusing film laminated sheet was adhered to the surface of the transparent lamp cover using a 40W fluorescent transparent lamp type fluorescent lamp type LED lamp (MLT-40KC) manufactured by Maurice Co., Ltd., 5 cm directly above. At the same time, a digital camera (Kanocam MINOLTA, Tima A700, shooting conditions: manual mode, shutter speed 1/1000 second, aperture value 6.3) was taken to take a photo of the lighting portion, and each performance evaluation was performed on the basis of the following criteria.

(1) Brightness

Based on the brightness of the light-diffusing film of Example 1, the brightness was brighter than the brightness, and the brightness of the same degree was ○, and the brightness was worse than ×. Brightness is determined by the whiteness of the photo.

(2) point disappearance

In the above photo, the following determination is made.

Can not see the point of the light source: ◎

A little bit of the light source: ○

Clearly see the point of the light source: ×

(3) Extension of brightness

In the above photo, the following determination is made.

More than 90% of the outer tube of the fluorescent lamp type LED illuminator is bright and visible: ◎

70~90% of the outer tube of the fluorescent lamp type LED lighting is brightly visible: ○

50~69% of the outer tube of the fluorescent lamp type LED illuminator is bright and visible: △

50% or less of the outer tube of the fluorescent lamp type LED illuminator is not visible: X

(Example 1)

Using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd., 50 parts by mass of a cyclic polyolefin resin (TOPAS(TM) 6015 Topas Advanced Polymers, Inc., melt flow rate: 0.41 (230 ° C, 2.16 kgf) at a resin temperature of 250 ° C )) and 50 parts by mass of a block copolymer resin formed of ethylene and octene (GFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C, 2.16 kgf) manufactured by Daewoo Chemical Co., Ltd.) The head was extruded, and cooled by a cooling roll (Ra = 0.55) processed by a pear skin pattern to obtain a light-diffusing film having a thickness of 400 μm. The opposite surface of the above cooling roll uses a mirror press roll.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in the present example is excellent in all optical characteristics, and is a high-quality light-diffusing film for an illumination device using various light sources such as an LED light source.

The color difference measured by the light resistance test was 1.0, and the light resistance was also excellent.

(Example 2)

Using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd., 35 parts by mass of a cyclic polyolefin resin (TOPAS(TM) 6015 Topas Advanced Polymers Co., Ltd. melt flow rate: 0.41 (230 ° C, 2.16 kgf) at a resin temperature of 250 ° C )) and 65 parts by mass of a block copolymer resin formed of ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 29 (230 ° C, 2.16 kgf) manufactured by Daewoo Chemical Co., Ltd.), and T-die The head was extruded and cooled by a mirror-finished cooling roll to obtain a light-diffusing film having a thickness of 300 μm. At the time of the above cooling, the vacuum box is used to adhere the film to the cooling roll.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this example is slightly inferior to the light-diffusing film of Example 1, but has a better brightness and is a high-quality light-diffusing film.

The color difference measured by the light resistance test was 1.0, and the light resistance was also excellent.

(Example 3)

In the method of Example 2, a light-diffusing film was obtained in the same manner as in Example 2 except that the thickness of the film was 150 μm.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this example is slightly inferior in brightness extension than the light-diffusing film of Example 1, but is more excellent in brightness and is a high-quality light-diffusing film.

(Example 4)

In the method of Example 2, a light-diffusing film was obtained in the same manner as in Example 2 except that the thickness of the film was 200 μm.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in this example has the same characteristics as the light-diffusing film of Example 3, and is a high-quality light-diffusing film.

(Example 5)

In the method of Example 1, a light-diffusing film was obtained in the same manner as in Example 2 except that the thickness of the light-diffusing film was 200 μm.

The characteristics of the obtained light-diffusing film are shown in Table 1.

The light-diffusing film obtained in this example has a slightly worse spread of dot disappearance and brightness than the light-diffusing film of Example 1, but has a better brightness and is a high-quality light-diffusing film.

(Example 6)

Using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd., 35 parts by mass of a cyclic polyolefin resin (TOPAS(TM) 6015 Topas Advanced Polymers Co., Ltd., melt flow rate: 0.41 (230 ° C, 2.16) at a resin temperature of 250 ° C. Kgf)) and 65 parts by mass of a random copolymer resin formed of ethylene and octene (ENGAGE (TM) 8137 melt flow rate: 30 (190 ° C, 2.16 kgf) manufactured by Daewoo Chemical Co., Ltd.) The film was extruded and cooled by a mirror-finished cooling roll to obtain a light-diffusing film having a thickness of 300 μm. At the time of the above cooling, the vacuum box is used to adhere the film to the cooling roll.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in this example has the same characteristics as the light-diffusing film of Example 3, and is a high-quality light-diffusing film.

(Example 7)

Drying at 180 ° C for 3 hours in a vacuum dryer, 85 parts by mass of the actual lubricant-free polyethylene terephthalate resin sufficiently dehydrated, and 15 parts by mass of Prime Polymers Co., Ltd. The mixture of low-density polyethylene resin (SP1540) is fed into a single-axis extruder, melted at 280 ° C, passed through a filter and a gear pump to remove foreign matter, and the amount of extrusion is homogenized, and the temperature is controlled at 25 ° C. On the cooling drum, it is extruded into a sheet by a T die. At this time, a metal wire electrode having a diameter of 0.1 mm was used, and static electricity was applied to adhere to the cooling drum to obtain an unstretched film. Next, in the longitudinal direction, the film was stretched 5.0 times in the longitudinal direction at a temperature of 103 ° C to obtain a master of a light-diffusing film having a thickness of 100 μm. The diffused ratio of the original of the obtained light-diffusing film was 2.5.

The light diffusion film is obtained by bonding the original sheets of the two light-diffusing films with an optical adhesive in a direction in which the main diffusion direction is orthogonal. The thickness of the adhesive layer was 10 μm.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light diffusing film obtained in this example is a high quality light diffusing film. However, the change in color difference measured by the light resistance test was 3.7, which was slightly inferior in light resistance to the light-diffusing film of Example 1 or 2.

(Example 8)

Using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd., 50 parts by mass of a fluorine-based resin (Kynar 720 (PVDF) Alcoma melt flow rate: 10 (230 ° C, 5 kgf)) and 50 at a resin temperature of 250 ° C A mass fraction of polymethylpentene resin (TPX(TM) DX820, manufactured by Mitsui Chemicals Co., Ltd., melt flow rate: 110 (260 ° C, 5 kgf)) was melt-mixed, extruded by a T die, and cooled by a mirror cooling roll. A master of a light diffusing film having a thickness of 100 μm was obtained. At the time of the above cooling, the vacuum box is used to adhere the film to the cooling roll. Corona treatment is performed on one side. The original version of the obtained light-diffusing film had a diffusivity ratio of 12.7.

The light diffusion film is obtained by bonding the original sheets of the two light-diffusing films with an optical adhesive in a direction in which the main diffusion direction is orthogonal. The thickness of the adhesive layer was 10 μm.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light diffusing film obtained in this example is a high quality light diffusing film.

(Example 9)

Using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd., 50 parts by mass of a fluorine-based resin (Kynar 720 (PVDF) Alcoma melt flow rate: 10 (230 ° C, 5 kgf)) and 50 at a resin temperature of 250 ° C A part by mass of a cyclic polyolefin resin (melt flow rate: 2.1 (230 ° C, 2.16 kgf) manufactured by TOPAS (TM) 6013 Topas Advanced Polymers Co., Ltd.) was melt-mixed, extruded by a T die, and cooled by a mirror cooling roll. A precursor of a light diffusing film having a thickness of 70 μm was obtained. At the time of the above cooling, the vacuum box is used to adhere the film to the cooling roll. Corona treatment is performed on one side. The original version of the obtained light-diffusing film had a diffusivity ratio of 11.2.

The light diffusion film is obtained by bonding the original sheets of the two light-diffusing films with an optical adhesive in a direction in which the main diffusion direction is orthogonal. The thickness of the adhesive layer was 10 μm.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light diffusing film obtained in this example is a high quality light diffusing film.

(Comparative Example 1)

Using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd., 35 parts by mass of a cyclic polyolefin resin (TOPAS(TM) 6013 Topas Advanced Polymers Co., Ltd., melt flow rate: 2.0 (230 ° C, 2.16) at a resin temperature of 250 ° C Kgf)) and 65 parts by mass of a block copolymer resin formed of ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C, 2.16 kgf) manufactured by Daewoo Chemical Co., Ltd.), melted to T The die was extruded and cooled by a mirror-finished cooling roll to obtain a light-diffusing film having a thickness of 400 μm. At the time of the above cooling, the vacuum box is used to adhere the film to the cooling roll.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in the comparative example has better brightness than the light-diffusing film of Example 1, but the light-diffusing anisotropy is high and the brightness is poorly expanded, from the viewpoint of having a uniform light amount. A poor quality light diffusing film.

(Comparative Example 2)

Using a coater, 50 parts by mass of spherical acrylic resin particles having an average particle diameter of 3 μm (manufactured by Toyobo Co., Ltd., Tawaguchi (TM) FH-S300) and 50 parts by mass of polyurethane resin The mixture was applied to one side of a highly transparent polyester film (Cosmosha A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 250 μm and dried to have a thickness of 25 μm after drying to obtain a light-diffusing film.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in this comparative example is superior in brightness to the light-diffusing film of Example 1, but has a poor spread of dot disappearance and brightness, and is a low-quality light-diffusing film.

(Comparative Example 3)

Using a coater, a very thin flaky cerium oxide particle (AGC Yerside) Sanpulli (TM) LFS HN050, which is not mixed with a binder resin and has a thickness of nanometer, is applied to a thickness of A light-diffusing film was obtained by drying one side of a 250 μm high-transparency polyester film (manufactured by Toyobo Co., Ltd., Cosmosha A4 300) to a thickness of 30 μm after drying.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in the comparative example has the same characteristics as the light-diffusing film of Example 4 in that the dot-dissipation property and the brightness are expanded, but the total light transmittance is low and the brightness is poor, and the quality is low. Light diffusing film.

(Comparative Example 4)

Using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd., 50 parts by mass of a cyclic polyolefin resin (TOPAS(TM) 6015 Topas Advanced Polymers Co., Ltd., melt flow rate: 0.41 (230 ° C, 2.16) at a resin temperature of 250 ° C Kgf)) and 50 parts by mass of a block copolymer resin formed of ethylene and octene (INFUSE (TM) D9100.05 manufactured by Daewoo Chemical Co., Ltd., melt flow rate: 2.1 (230 ° C, 2.16 kgf)) was melt-mixed to The T die was extruded and cooled by a mirror cooling roll to obtain a light diffusing film having a thickness of 175 μm. At the time of the above cooling, the vacuum box is used to adhere the film to the cooling roll.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in the comparative example has a high parallel light transmittance and a high diffusivity ratio, and has poor dot spread and brightness expansion, and is a low-quality light-diffusing film.

(Comparative Example 5)

35 parts by mass of a cyclic polyolefin resin (melt flow rate: 2.1 (230 ° C), manufactured by TOPAS (TM) 6013 Topas Advanced Polymers Co., Ltd.) at a resin temperature of 250 ° C using a PCM45 extruder manufactured by Chiba Iron Works Co., Ltd. And 65 parts by mass of a block copolymer resin formed of ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C) manufactured by Daewoo Chemical Co., Ltd.), and extruded by a T die, The mirror cooling roll was cooled to obtain a light diffusing film having a thickness of 175 μm. At the time of the above cooling, the vacuum box is used to adhere the film to the cooling roll.

The characteristics of the obtained light-diffusing film are shown in Table 1. The light-diffusing film obtained in the comparative example has a high parallel light transmittance and a high diffusivity ratio, and has a poor spread of dot disappearance and brightness, and is a low-quality light-diffusing film.

(Comparative Example 6)

A light-diffusing film formed of a polycarbonate resin whose surface was embossed was subjected to property evaluation.

The results are shown in Table 1.

The light-diffusing film obtained in the comparative example has a high parallel light transmittance and a high diffusivity ratio, and has a poor spread of dot disappearance and brightness, and is a low-quality light-diffusing film.

Moreover, the change in chromatic aberration is as high as 9.5, and the light resistance is poor.

[Manufacture of Light-Diffusion Film Laminates] (Example 10)

The light-diffusing film obtained in Examples 1 to 6 and a highly transparent polyester film (Cosmo Xiain A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 250 μm and a total light transmittance of 92% were used as optical double-sided adhesive sheets. Adhesively formed into a light diffusing film laminate.

Any of the laminated sheets has the same optical characteristics as the respective light-diffusing films, and is a high-quality light-diffusing material. Further, the obtained light-diffusing film laminated sheets have better non-optical properties such as heat resistance and strength than the light-diffusing films of Examples 1 to 6.

(Example 11)

In the method of Example 1, a polycarbonate sheet having a thickness of 200 μm and a total light transmittance of 88% which was surface-treated with a polyurethane-based tackifying coating agent was passed through the press roll side, thereby producing A light-diffusing film laminated sheet formed by laminating polycarbonate sheets.

The light-diffusing film laminated sheet obtained in the present example has optical characteristics equivalent to those of the light-diffusing film of Example 1, and is high in quality when used as a light-diffusing material for an illumination device using various light sources such as LEDs. Moreover, the light-diffusing film of Example 1 has better non-optical properties such as heat resistance and strength.

(Example 12)

The light diffusing film of Example 1 and the light diffusing film of Example 8 were used with a 40 W white light transparent lampshade type fluorescent lamp type LED lighting lamp (MLT-40KC) manufactured by Maurice. The laminated sheet is adhered to the surface of the transparent lamp cover. It can present a uniform and stable illumination light with a light that spreads over the entire outer tube and does not see the point of the LED light source.

(Comparative Example 7)

In Example 12, when the light diffusing film of Comparative Example 2 was replaced, the light diffusibility was lowered, the light could not spread over the entire outer tube, and the point of the LED light source was clearly seen.

(Example 13)

Using a two-stage melt extruder, 35 parts by mass of a cyclic polyolefin resin (TOPAS(TM) 6013S-04 Topas Advanced Polymers Co., Ltd., melt flow rate: 2.0 (230 ° C) in the first extruder , 2.16kgf)) and 65 parts by mass of a block copolymer resin formed of ethylene and octene (INFUSE(TM) D9817.15 melt flow rate: 26 (230 ° C, 2.16 kgf) manufactured by Daewoo Chemical Co., Ltd.) as light diffusion Layer, in the second extruder, polypropylene-based adhesive resin (made by Adumama (TM) QF551 Mitsui Chemicals Co., Ltd., melt flow rate: 5.7 (190 ° C, 2.16 kgf)) is two skin layers (heat tightness) The layer was melt-co-extruded by a T-die method, and then cooled by a mirror-finished cooling roll to obtain a light-diffusing film in which two sides of a total thickness of 400 μm were laminated with a heat-adhesive layer. In the above cooling, the adhesion of the film to the cooling roll was carried out in the same manner as in Example 1. Even if the film is continuously formed for a long time, eye stains do not occur.

The obtained light-diffusing film had the same optical characteristics as those of Example 1, and was excellent in thermal adhesiveness, and the dimensional stability of the light-diffusing film was improved by heat-bonding to the substrate.

Thermal adhesion and dimensional stability were evaluated by the following methods. Either one is ○.

<Hot adhesion>

A smooth and transparent acrylic plate having a thickness of 3 mm (manufactured by Mitsubishi Rayon Co., Ltd.: Acrylic) was placed on a fixing table of a hot press, and a test piece was placed on the acrylic plate, and further, The ruthenium rubber sheet having a thickness of 3 mm (hardness HsA50°) was placed on the ruthenium rubber sheet with a surface temperature set at 180 ° C, and pressed at a pressure of 49 N/cm ² for 30 seconds. . After heating and pressure-bonding, it was allowed to stand for 30 minutes in an environment of a temperature of 23 ° C and a relative humidity of 65%, and the resistance value at the time of peeling at a speed of 300 mm/min at 180 ° using the "Tai Xi Long" (UTM-IIIL) manufactured by Toyo Seiki Co., Ltd. For the adhesion.

The determination of the adhesion is performed on the basis of the following criteria.

The adhesion is 0.1N/15mm or more: ○

The adhesion is less than 0.1N/15mm: ×

<Size stability>

According to the above-mentioned thermal adhesion evaluation method, the light-diffusing film was thermally bonded to the test piece of the acrylic plate, and it was allowed to stand in an oven adjusted to 80 ° C for 240 hours, and after heating, the longitudinal and transverse directions of the light-diffusing film were measured. The dimensional stability is compared with the individual dimensions before the warming treatment, and is determined on the basis of the following criteria.

The dimensional change from warming treatment, regardless of the direction, is less than 0.1%: ○

The dimensional change caused by the warming process is at least 0.1% or more of either side: ×

(Example 14)

In the method of Example 13, the extruded resin of the second extruder was changed to a polypropylene-based adhesive resin (melt flow rate: 5.7 (190 ° C) manufactured by Amoi (TM) QF551, Mitsui Chemicals Co., Ltd.), and used. A light-diffusing film was obtained in the same manner as in Example 13 except that polypropylene resin FS2011DG3 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Nopland (TM)).

The obtained light-diffusing film is excellent in light-diffusion characteristics, and does not cause eye stains even if it is continuously formed for a long period of time. However, compared to the light-diffusing film prepared in Example 13, the thermal adhesion was poor.

(Examples 15~18)

Using the respective light-diffusing films obtained in Examples 1, 5, 7, and 18, the front luminance, the luminance dependency, and the pattern concealing property when used in a backlight device for a liquid crystal display device were measured by the following methods. The results are shown in Table 2.

The light-diffusing film produced by any of the examples has excellent characteristics as described in the respective examples, and has a high degree of curvature of light, by using a light diffusing film of one sheet, that is, having a high front luminance, and The angle dependence of brightness is small, and the image masking property is excellent, and it is a high-quality part which improves the brightness of the backlight device for liquid crystal display devices.

<Front brightness when used in a backlight device for a liquid crystal display device>

Three cold cathode tubes are respectively mounted on the acrylic plate on the light-emitting side of the backlight unit of a 19-inch light guide plate type (mesh type using a white reflective film) on both sides of the long diameter side (lateral direction). 40mm × 60mm angle (60mm side is the horizontal direction) evaluation test equipment installation (overlapping and installation, when the test product is exposed by curling, etc., tape The four corners are fixed to the center of the part, and the black shading paper which has been cut at an angle of 30 mm × 50 mm (the horizontal direction of the 50 mm side) is placed so that the center of the cut portion evaluates the center of the test piece, and the brightness is measured in the dark room. . The black light-shielding paper is fixed to cover the size of the entire backlight assembly, and is measured without exposing light. The backlight assembly was measured horizontally.

This brightness was measured using a Depotcon Spectroradiometer SR-3A manufactured by O&P Technology Co., Ltd. to measure an angle of 2 degrees, and the distance from the surface of the backlight assembly was 40 cm, and the center of the evaluation test article was directly below. The measurement was carried out.

In this measurement, the test test product was attached to the direction in which the main diffusion direction was perpendicular to the longitudinal direction of the cold cathode tube.

<Angle dependence of brightness when used in a backlight device for a liquid crystal display device>

In addition to the placement of the Opcon spectroradiometer SR-3A at a position where the angle between the center of the sample of the sample and the evaluation test article is inclined at 35 degrees with respect to the perpendicular to the surface of the backlight assembly, The brightness was measured in the same manner as the above-described front luminance. The value of this luminance is divided by the above-mentioned front luminance to be angularly dependent. The larger the value, the better the angular dependence of brightness. 1.0 best.

<Graphic masking property when used in a backlight device for a liquid crystal display device>

In the measurement of the front luminance described above, the opening portion was visually observed in a state where the backlight was lit, and the following determination was made.

When the mesh of the light guide plate is completely invisible: ○

When the mesh of the light guide plate is slightly seen: △

When the mesh of the light guide plate is clearly seen: ×

(Comparative Example 8)

Using the light-diffusing film obtained in Comparative Example 4, the angle dependence of the front luminance and the brightness and the pattern masking property when used in a backlight device for a liquid crystal display device were measured in the same manner as in Examples 15 to 18. The results are shown in Table 2.

The light-diffusing film obtained in this comparative example had poor pattern masking property.

(Comparative Example 9)

Using the commercially available microlens film, the angle dependence of the front luminance and the brightness and the pattern concealing property when used in a backlight device for a liquid crystal display device were measured in the same manner as in Examples 15 to 18. The results are shown in Table 2.

Although this microlens has a high front luminance, the angular dependence of luminance is poor. Moreover, when only one of the microlenses is used, the pattern masking property is also poor.

(Comparative Example 10)

Using a light-diffusing film manufactured by a bead coating method using a commercially available backlight device, the front brightness and brightness when used in a backlight device for a liquid crystal display device were measured in the same manner as in Examples 15 to 18. Angle dependence and graphic masking. The results are shown in Table 2.

When only one of the light diffusing films is used, the angular dependence of the brightness and the pattern masking property are inferior.

(Comparative Example 11)

In the backlight assembly for measuring the angle dependence of front brightness and brightness, an optical film set formed by assembling an upper diffusion film/稜鏡 lens film/lower diffusion film, using this set, and Example 11 And the same method as 12, measuring the front side when used in a backlight device for a liquid crystal display device Angle dependence of brightness and brightness and pattern masking. The results are shown in Table 2.

Although the film set is excellent in front brightness and pattern masking, the angle dependence of brightness is poor. And because of the large number of films, it is not conducive to economics.

(Examples 19 and 20)

The light-diffusing film of Examples 1 and 5 was measured for the uniformity of the inner surface brightness when used in a backlight device for a liquid crystal display device by the following method. The results are shown in Table 3.

Regardless of the light diffusing film of any of the examples, the average brightness is high, and the brightness of the inner surface is uniform, which is a high-quality light diffusing film for a backlight device.

<Inside brightness uniformity when used in a backlight device for a liquid crystal display device>

A 20-inch light-diffusing acrylic plate of a backlight assembly of 12 cold cathode tubes was replaced with a transparent acrylic plate, and an A-4 size test article was placed at a nearly central portion of the transparent acrylic plate. The four corners were fixed with tape, and the high-performance brightness & colorimetric measurement system (RISA) manufactured by Highland Co., Ltd. was used to illuminate the backlight unit in the dark room. The center of the test piece was measured at 100×220 set-top boxes. The brightness of the area. Brightness measures maximum brightness, minimum brightness, and brightness. The inner surface brightness uniformity is expressed by the ratio of the minimum brightness/maximum brightness obtained in the above method. The smaller the value, the smaller the brightness spot.

The cold cathode tube is installed such that the long direction of the cold cathode tube is the longitudinal direction (lateral direction) of the backlight unit. The brightness measuring device was attached to the vicinity of the near center portion of the test piece, and the surface of the transparent acrylic plate was measured at a position where the distance from the luminance meter was 120 cm.

The backlight assembly is mounted at a level for measurement.

In this measurement, the test test product was attached to the direction in which the main diffusion direction was perpendicular to the longitudinal direction of the cold cathode tube.

(Comparative Example 12)

The inner surface brightness uniformity was measured without installing a light diffusing film. The results are shown in Table 3.

The maximum brightness is significantly improved, and the brightness uniformity of the inner surface is also significantly increased. The film showing the above example has a large optical property control effect.

(Comparative examples 13 to 15)

The light diffusing films used in Comparative Examples 8 to 10 were used to measure the uniformity of the inner surface brightness. The results are shown in Table 3.

The light-diffusing film used in Comparative Example 8 had a high maximum brightness, but the inner surface brightness uniformity was low, and only one piece of the light-diffusing film had insufficient performance.

The films used in Comparative Examples 9 and 10 exhibited a markedly higher maximum brightness than the light-diffusing film of the above examples, but the inner surface brightness uniformity was low, and only one piece of the light-diffusing film was insufficient in performance.

(Comparative Example 16)

The optical film set formed by the upper diffusing film/稜鏡 lens film/lower diffusing film incorporated in the backlight assembly for measuring the brightness uniformity of the inner surface is replaced with a light diffusing film for a backlight device, and the inner surface thereof is measured. Brightness uniformity. The results are shown in Table 3.

Although the maximum brightness is high, the brightness of the inner surface is poor. Moreover, the number of films is large, which is not economical.

Possibility of application in industry

The light-diffusing film of the present invention and the laminated sheet thereof are light-diffusing films excellent in both light transmittance and diffusivity, in particular, because the transmittance of straight-through light is small, for example, when used in an illumination device using an LED light source, In addition to diffusing the light of the direct-intensity LED light source into a large area, and not seeing the light source point of the strong light, further, since the degree of decrease in the transmittance of the light has been suppressed, even the number of LED light sources per unit area Reduced, still have a uniform and high amount of light. Therefore, it is advantageous in that the light of the LED light source can be suppressed from being high in straightness, and the narrow range which can be made only in a dot shape is bright, that is, the illuminating device using the LED light source, and the characteristics of the energy-saving LED light source can be maintained.

Compared with the previously known light diffusing film, when the diffusing property is greatly improved, for example, when used in a lighting device using a fluorescent lamp as a light source, even if the distance between the fluorescent lamp and the light diffusing film or the light diffusing film laminated sheet is shortened, It still has a high degree of light diffusivity and, therefore, has the effect of reducing the thickness of the illumination device or reducing the number of fluorescent lamps. Further, for example, when a light-diffusing film which is a display device such as a liquid crystal display is used, the thickness of the display panel can be reduced, and the number of optical function adjusting films such as a brightness enhancement film or a light-diffusing film used for improving the brightness can be reduced.

The light-diffusing film of the present invention and the laminated sheet using the same can maintain non-optical properties such as heat resistance, in addition to maintaining the above-described optical characteristics.

Therefore, it can be effectively used for various illuminations such as indoor illumination, illumination of an internal illumination type electronic panel, light irradiation of a photocopier, or illumination of a display device such as a liquid crystal display.

Further, when the light-diffusing film of the present invention and the laminated sheet to be used are used as an optical component of a backlight device, high brightness can be imparted, angle dependence of brightness can be lowered, and brightness uniformity of the inner surface can be imparted by using only one sheet. The optical characteristics required for the optical material for a backlight device such as a pattern masking property can improve the economic efficiency of the backlight device. In particular, there is a great advantage that it is possible to solve the problem of using a lens film, such as a reduction in brightness which occurs when viewing at an oblique angle, without using a high-priced lens film.

Since the backlight device of the present invention has a front luminance of a height close to that of a backlight device using a lens film, and reduces the angular dependence of luminance, that is, a backlight device using a lens film, it is suppressed when used in a large-sized television. The advantage of reducing the brightness of the picture caused by the oblique angle viewing.

Therefore, it is possible to effectively use a backlight device such as a car navigation, which is mostly viewed from an oblique angle.

When it is used for a backlight of an indoor or interior lighting fixture, it has an advantage of uniform illumination over a wide range compared to a backlight using a lens film.

Moreover, since the backlight device of the present invention can provide all of the above characteristics by using only one single component, it has an advantage of high economic efficiency.

Therefore, the backlight device of the present invention can be effectively used for a liquid crystal display device, an indoor illumination, an internal illumination type electronic panel, or the like.

According to the method for producing a light-diffusing film of the present invention, the light-diffusing film of the present invention having the above characteristics can be produced economically and stably.

Therefore, the contribution to the industry is great.

Figure 1 is an auxiliary diagram of the method for calculating the diffusivity.

Figure 2 is an auxiliary diagram of the calculation method of the degree of curvature.

Claims (22)

A light-diffusing film characterized by being a mixture of at least two kinds of incompatible thermoplastic resins, and simultaneously meeting the following characteristics (1) to (4); (1) a total light transmittance of 66% or more (2) Haze is 96% or more, (3) Parallel light transmittance is 2.0% or less, (4) Using an automatic variable angle photometer, in the transmission measurement mode, the light incident angle is 0°, and the light receiving angle is -90°. 90°, filter ND10, beam aperture 10.5 mm, light-receiving aperture 9.1 mm, and variable-angle interval 0.1°, as measured by fixing the curling direction of the light-diffusing film in the vertical direction and the horizontal direction One of the peak widths of the half-height angle of one of the peak heights of the variable angle illuminance curve of the light, the large half-value width is taken as DH, and the small half-value width is taken as the diffusion ratio of the transmitted light by DL ( DH/DL) is 2.0 or less. The light diffusing film of claim 1, wherein the DH is 30 degrees or more. The light-diffusing film according to claim 1 or 2, wherein the curling direction of the light-diffusing film is fixed to the vertical direction and the parallel direction and the horizontal direction of the test article fixing table, and the measurement is performed by using an automatic variable angle photometer. The height H0 of the transmitted light peak obtained under the conditions of mode, light incident angle of 0°, light receiving angle of -90° to 90°, filter ND10, beam aperture of 10.5 mm, light-receiving aperture of 9.1 mm, and angular separation of 0.1°. And the incident angle is 60°, and the transmitted light is obtained under the same conditions as when the H0 is measured. The height H60 of the peak is 4 to 100% in the main diffusion direction obtained by the following formula (1), and the light curvature is H60/H0 × 100 (%) (1). The light-diffusing film of claim 1 or 2, wherein at least one of the mixture of at least two kinds of incompatible thermoplastic resins is formed of a polyolefin-based resin. The light-diffusing film of claim 4, wherein the mixture of at least two kinds of incompatible thermoplastic resins is formed of two or more kinds of polyolefin-based resins. The light-diffusing film of claim 5, wherein the mixture of at least two kinds of polyolefin-based resins is formed of a cyclic polyolefin-based resin and a polyethylene-based resin. The light-diffusing film of claim 6, wherein the cyclic polyolefin resin has a melt flow rate measured at 230 ° C of 0.1 to less than 1.5, and the polyethylene resin has a melt flow rate of 5 to 100. The light-diffusing film according to any one of claims 5 to 7, wherein at least one side of the light-diffusing film formed of the mixture of at least two kinds of incompatible thermoplastic resins is mainly composed of A surface layer formed of a polyolefin resin. The light-diffusing film of claim 8, wherein the polyolefin-based resin forming the surface layer is formed of a polyolefin resin containing a polar group. The light-diffusing film of claim 9, wherein the polyolefin resin containing a polar group contains at least a carboxyl group. The light-diffusing film of claim 4, wherein the other thermoplastic resin is formed of a fluorine-based resin. The light-diffusing film of claim 4, wherein the other thermoplastic resin is formed of a polyester resin. For example, the light diffusing film of claim 12, wherein the light diffusing film is extended by more than 2 times in one direction. The light-diffusing film of claim 1 or 2, wherein at least one side of the film is subjected to a shaping treatment to be roughened. A light-diffusing film laminated sheet characterized by a light-diffusing film which is formed of a mixture of at least two kinds of incompatible thermoplastic resins and which simultaneously meets the characteristics of the following (1) to (4) to be perpendicular to the main diffusion direction The directions are superimposed and formed; (1) the total light transmittance is 66% or more, (2) the haze is 96% or more, (3) the parallel light transmittance is 2.0% or less, and (4) the automatic variable angle photometer is used. The light is transmitted by the measurement mode, the light incident angle of 0°, the light receiving angle of -90° to 90°, the filter ND10, the beam aperture of 10.5 mm, the light receiving aperture of 9.1 mm, and the variable angular interval of 0.1°. The half-value width obtained by measuring the width of the half-height of the peak height of the obtained variable angle luminosity curve of the diffused film is fixed in the vertical direction and the horizontal direction, and the large half-value width is taken as DH and small. The half value width of the transmissive light obtained as DL has a diffusivity ratio (DH/DL) of more than 2.0. A light diffusing film laminate, characterized by the scope of the patent application The light-diffusing film of any one of items 1 to 14 is formed by laminating a plastic sheet having a thickness of 0.1 to 5 mm and a total light transmittance of 70 to 100%. An illumination device using an LED light source, characterized in that the light-diffusing film according to any one of claims 1 to 14 is mounted on the outer or inner surface of a light-emitting portion of an illumination device using an LED light source. An illuminating device using an LED light source, characterized in that a light-diffusing film laminated sheet according to claim 15 or 16 is mounted on an outer surface or an inner surface of a light-emitting portion of an illuminating device using an LED light source. A backlight device characterized in that a light-diffusing film according to any one of claims 1 to 14 is mounted on an exit surface of a backlight assembly. A backlight device characterized in that a light-diffusing film laminate according to claim 15 or 16 is mounted on an exit surface of a backlight assembly. A process for producing a light-diffusing film according to any one of claims 1 to 14, which is characterized in that a mixture of at least two kinds of incompatible thermoplastic resins is melt-extruded. The method for preparing a light-diffusing film according to claim 21, wherein the molten resin is extruded from a die into a sheet in an extruder, and the sheet is crimped by a pressure roller on a cooling roll to be densely combined. It is cooled and solidified to form a film.