JPH0961818A - Transparent sheet and back light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent sheet and a back light which can improve the optical efficiency when they are used for a liquid crystal panel and to improve the brightness as a liquid crystal display device. SOLUTION: This back light is composed of a light source 1 and a planer light transmission body 2 having at least one incident plane facing to the light source 1 and an outgoing plane. A transparent sheet 8 having a fine pattern which two-dimensionally or three-dimensionally diffuses or condenses rays is formed on at least one surface of a transparent substrate having a light- controlling function corresponding to a λ/8-7λ/8 phase plate is disposed on the outgoing plane of the light transmission body 2.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a notebook computer,
The present invention relates to a backlight of a liquid crystal display device used for a portable liquid crystal TV or the like and a transparent sheet such as a diffusion sheet or a lens sheet used therefor.
The present invention relates to a transparent sheet and a backlight capable of increasing the brightness of a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, color liquid crystal display devices have been widely used in various fields as a portable notebook personal computer, a portable liquid crystal TV using a color liquid crystal panel, a video integrated liquid crystal TV, and the like. The liquid crystal display device is basically composed of a backlight and a liquid crystal display element section.
As a backlight, there are a direct type in which a light source is provided directly below a liquid crystal display element and an edge light type in which a light source is provided on a side surface of a light guide body, and the edge light type has been widely used due to downsizing of a liquid crystal display device. . The edge light system is a backlight system in which a light source is arranged on the side surface of a plate-shaped light guide so that the entire surface of the light guide is illuminated.

Since such a color liquid crystal display device is driven by a battery, the power consumption of the liquid crystal display device is an obstacle to extending the battery drive time. Above all, the power consumption of the backlight used in liquid crystal display devices is large, and it is important to keep this power consumption as low as possible in order to extend the battery drive time and increase the practical value of the above products. ing. However, by reducing the power consumption of the backlight,
If the luminous intensity of the backlight is lowered, the liquid crystal display becomes difficult to see, which is not preferable. Therefore, in order to suppress the power consumption without sacrificing the brightness of the backlight, it is desired to improve the optical efficiency of the backlight.

A typical structure of such a backlight is shown in FIG. In the figure, 1 is a light source such as a fluorescent lamp, which is installed so as to face one side surface (incident surface) of the light guide 2.
In order to effectively introduce light from the light source 1 to the light guide body 2, the incident surfaces of the light source 1 and the light guide body 2 are covered with a case or a film 4 coated with a reflective agent on the inside. Also,
Diffusing means 3 is formed on the back surface of the light guide body 2 to emit an incident light beam from the exit surface. The light from the light source 1 is guided by the light guide 2.
To the front surface of the light guide 2 by being diffused by the diffusing means 3. This emitted light 5 is 40 degrees in the normal direction as shown in FIG.
It has a directivity inclined by about 70 degrees, and is diffused on the emission surface of the light guide 2 in order to arrange this directional light and direct it in a substantially normal direction, or in order to make the emitted light uniform. One or a plurality of transparent sheets such as sheets and lens sheets are stacked and placed.

[0005]

However, it has been found that in such a backlight, the polarization of emitted light is almost random, but strictly speaking, a specific polarization component is a partial polarization. That is, as shown in FIG. 7, when the polarization intensity of the emitted light 7 when the diffusion sheet 6 is placed on the emission surface of the light guide 2 is measured, the end surface of the light guide 2 where the light source 1 is arranged is measured. The polarized light component parallel to (horizontal polarized light) was about 5% stronger than the polarized light component perpendicular to this (vertical polarized light). Therefore, in the liquid crystal panel arranged on the backlight, only one polarized component of the incident light is used. Therefore, in the backlight as described above, it is better to use the horizontal polarized light for the optical efficiency. .

On the other hand, in a lens sheet in which a lens unit such as a lenticular lens is formed, it has a property that a polarization component perpendicular to the lens array of the lens sheet is easily transmitted and a parallel polarization component is difficult to be transmitted. Therefore, the difference in the transmittance is about several percent to ten and several percent. For this reason, the polarization intensity of the backlight changes depending on the direction of the lens rows of the mounted lens sheet. Usually, such a lens sheet is placed on the diffusion sheet 6 such that the end face of the light guide 2 on which the light source 1 is arranged and the lens array are parallel to each other as shown in FIG. The directional light 7 shown is changed to an isotropic directional light 9. In this case, since the directional light 7 has a strong horizontal polarization and the lens sheet 8 transmits the vertical polarization well, the effects of both are canceled out and the isotropic directional light 9 becomes close to a random polarization, and the liquid crystal panel It was not possible to sufficiently improve the optical efficiency in.

Therefore, according to the present invention, a transparent sheet such as a diffusion sheet or a lens sheet is provided with a function of controlling the polarization plane of light passing through the transparent sheet, so that the light emitted from the light guide is made uniform and directed. The purpose of the present invention is to provide a transparent sheet and a backlight capable of improving the optical efficiency when used in a liquid crystal panel and improving the brightness as a liquid crystal display device without impairing the original function of the transparent sheet of controlling the brightness. And

[0008]

That is, the transparent sheet of the present invention is a two-dimensionally or two-dimensional light beam on at least one surface of a transparent substrate having a light control function equivalent to a λ / 8 to 7λ / 8 phase plate. It is characterized in that a fine shape that is three-dimensionally diffused or focused is formed. Further, the backlight of the present invention is composed of a light source and a plate-shaped light guide body having at least one entrance surface and exit surface facing the light source, and light control equivalent to a λ / 8 to 7λ / 8 phase plate. At least one surface of the transparent base material having a function, a transparent sheet having a fine shape for two-dimensionally or three-dimensionally diffusing or converging a light beam is provided on the exit surface side of the light guide. It is characterized by being present.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The backlight of the present invention, as shown in FIG. 1, is composed of a light source 1 and a light guide 2, and has at least one surface (incident) in the thickness direction of the light guide 2. Light source 1 on surface)
Are arranged. The light guide 2 has at least one side surface as an incident surface and one surface substantially orthogonal thereto as an emission surface, and is made of a synthetic resin having a high light transmittance. As the synthetic resin forming the light guide body 2, various highly transparent synthetic resins such as methacrylic resin, acrylic resin, polycarbonate resin, and vinyl chloride resin can be used. In particular, methacrylic resin has a high light transmittance,
It also has excellent heat resistance, mechanical properties, and moldability, making it ideal as a light guide material.

Such a methacrylic resin is a resin whose main component is methyl methacrylate, and it is preferable that the amount of methyl methacrylate is 80% by weight or more. Copolymer components other than methyl methacrylate include methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and (meth) acrylic acid. Phenyl, benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and other (meth) acrylic acid esters, (meth) acrylic acid, ethylene Glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, neopentyl glycol di (meth)
Polyfunctional (meth) acrylates such as acrylate, aromatic vinyl monomers such as styrene and α-methylstyrene,
Examples thereof include maleimides such as phenylmaleimide and cyclohexylmaleimide, and maleic anhydride. In addition, for the purpose of improving the impact resistance of methacrylic resin, a rubber-like copolymer containing acrylate as a main component and a copolymer containing a copolymer containing methacrylate as a main component grafted are also used. it can.

The light source 1 is installed on the incident surface side of the light guide 2 so as to face the incident surface, and an edge light type backlight is constructed. In order to effectively introduce light from the light source 1 to the light guide body 2, it is preferable that the incident surfaces of the light source 1 and the light guide body 2 are covered with a case or a film 5 coated with a reflective agent inside. A diffusion layer 3 is formed on the back surface of the light guide body 2 by metal deposition or the like to form a diffusion surface,
As a result, the incident light beam is emitted from the emission surface.

On the exit surface of the light guide 2, a transparent sheet such as a diffusion sheet 6 or a lens sheet 8 having a fine shape for two-dimensionally or three-dimensionally diffusing or converging light rays is placed. Therefore, the light emitted from the light guide 2 is made uniform and the directivity is controlled. In the present invention, it is important to use a phase film or a phase sheet having a light control function equivalent to a λ / 8 to 7λ / 8 phase plate as a transparent substrate comprising the transparent film or the sheet constituting the transparent sheet. is there. In the present invention, λ / 8
The light control function equivalent to ˜7λ / 8 phase plate is a function of controlling the plane of polarization of light when light passes through the transparent sheet.

In the transparent sheet of the present invention, the transparent substrate 10 used is a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin,
A film or sheet made of a transparent resin such as polymethacrylimide resin is used. In the present invention,
In order to provide the transparent substrate 10 with a light control function equivalent to a λ / 8 to 7λ / 8 phase plate, for example, in a film forming or sheeting process, a light control equivalent to that of the λ / 8 to 7λ / 8 phase plate is performed. It is necessary to appropriately adjust the birefringence index, the thickness, etc. so that the function is exhibited. This is λ on the transparent substrate 10.
By imparting a light control function equivalent to that of the / 8 to 7λ / 8 phase plate, the transparent sheet can be imparted with a function of controlling the polarization plane of light passing through the transparent sheet. It is possible to improve the optical efficiency when used in and to improve the brightness as a liquid crystal display device. If it deviates from this range, the effects of the present invention as described above cannot be obtained, and preferably λ / 4 to 5
It has a light control function equivalent to that of a λ / 8 phase plate, and more preferably has a light control function substantially equivalent to that of a λ / 2 phase plate.

As the transparent sheet of the present invention, light rays are two-dimensionally or three-dimensionally diffused or focused on at least one surface of the transparent substrate 10 as described above, as shown in FIGS. A fine shape is formed. In the present invention, when the diffusion sheet 6 is formed, the steps shown in FIGS.
As shown in (1), the irregular asperity shape 11 is provided on at least one surface. In this case, by using an active energy ray-curable resin that can be cured with active energy rays such as ultraviolet rays and electron rays, the irregular asperity 1 is formed on the surface of the transparent substrate 10.
1 may be formed, or may be formed by subjecting the transparent substrate 10 to a surface treatment by sandblasting or the like, or the transparent substrate 10 in which diffusion particles such as inorganic fine particles and resin fine particles are mixed. May be used.

When forming the lens sheet 8, FIG.
5 to 5, a large number of lens rows 13 such as lenticular lenses or corrugated lenses having a semicircular or semielliptical cross section are formed in parallel on at least one surface. In this case, the lens shape 13 may be formed on the surface of the transparent substrate 10 by using an active energy ray curable resin that can be cured by an active energy ray such as ultraviolet rays or electron beams.
The surface of 0 may be shaped by a method such as hot pressing. Further, as shown in FIG. 5, the irregular concavo-convex shape 10 may be formed on one surface of the transparent substrate 10, and the lens array 13 may be formed on the other surface. Further, in the lens sheet 8 of the present invention, it is preferable that the thickness thereof is about 0.1 to 3 mm and the pitch of the lens rows is about 30 μm to 0.5 mm.

When a transparent sheet is manufactured by using the active energy ray-curable resin, the uneven portion 11 or the lens portion 13 is formed on the transparent substrate 10 by the active energy ray-curable resin. First, the active energy ray-curable resin liquid is injected into a mold having a predetermined pattern, and the transparent substrate 10 is superposed. Then, an active energy ray such as an ultraviolet ray or an electron beam is irradiated through the transparent base material 10 to polymerize and cure the active energy ray-curable resin liquid, and peeled from the mold to obtain a transparent sheet.

As the active energy ray-curable resin forming the uneven portion 11 or the lens portion 13 of the transparent sheet,
Bis (methacryloylthiophenyl) sulfoid, 2,
4-dibromophenyl (meth) acrylate, 2,3
5-tribromophenyl (meth) acrylate, 2,2
-Bis (4- (meth) acryloyloxyphenyl) propane, 2,2-bis (4- (meth) acryloyloxyethoxyphenyl) propane, 2,2-bis (4-
(Meth) acryloyloxydiethoxyphenyl) propane, 2,2-bis (4- (meth) acryloylpentaethoxyphenyl) propane, 2,2-bis (4- (meth) acryloyloxyethoxy-3,5-dibromophenyl ) Propane, 2,2-bis (4- (meth) acryloyloxydiethoxy-3,5-dibromophenyl)
Propane, 2,2-bis (4- (meth) acryloyloxypentaethoxy-3,5-dibromophenyl) propane, 2,2-bis (4- (meth) acryloyloxyethoxy-3,5-dimethylphenyl) propane , 2,
2-bis (4- (meth) acryloyloxyethoxy-
3-phenylphenyl) propane, bis (4- (meth))
Acryloyloxyphenyl) sulfone, bis (4-
(Meth) acryloyloxyethoxyphenyl) sulfone, bis (4- (meth) acryloyloxypentaethoxyphenyl) sulfone, bis (4- (meth) acryloyloxyethoxy-3-phenylphenyl) sulfone, bis (4- (meth)) Acryloyloxyethoxy-3,5-dimethylphenyl) sulfone, bis (4
-(Meth) acryloyloxyphenyl) sulfide,
Bis (4- (meth) acryloyloxyethoxyphenyl) sulfide, bis (4- (meth) acryloyloxypentaethoxyphenyl) sulfide, bis (4-
(Meth) acryloyloxyethoxy-3-phenylphenyl) sulfide, bis (4- (meth) acryloyloxyethoxy-3,5-dimethylphenyl) sulfide, di ((meth) acryloyloxyethoxy) phosphate, tri ((meth ) Polyfunctional (meth) acrylic compounds such as acryloyloxyethoxy) phosphate and the like can be mentioned. These may be used alone or in combination of two or more.

In order to adjust the refractive index of the active energy ray-curable resin together with these polyfunctional (meth) acrylic compounds, styrene, vinyltoluene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, divinylbenzene. , 1-vinylnaphthalene, 2
Vinyl compounds such as vinylnaphthalene and N-vinylpyrrolidone, phenyl (meth) acrylate, benzyl (meth) acrylate, biphenyl (meth) acrylate,
(Meth) acrylic acid esters such as, allyl compounds such as diallyl phthalate, dimethallyl phthalate and diallyl biphenylate, barium, lead, antimony, titanium,
It is also possible to use a metal salt of a metal such as tin or zinc and (meth) acrylic acid. These may be used alone or in combination of two or more. In the present invention, the photoradical generating catalyst used in the active energy ray-curable resin is, for example, 2-hydroxy-2-methyl-
Examples thereof include 1-phenylpropan-1-one, hydroxycyclohexylphenyl ketone, methylphenylglyoxylate, 2,4,6-trimethylbenzoylphosphine oxide, and benzyldimethylketal.

In the backlight of the present invention, the diffusion sheet 6 and / or the lens sheet 8 is placed on the emission surface of the light guide 2, but when the diffusion sheet 6 and the lens sheet 8 are used together. For at least one sheet, a sheet exhibiting a light control function equivalent to that of the above λ / 8 to 7λ / 8 phase plate is used. When a transparent sheet exhibiting a light control function equivalent to that of the λ / 8 to 7λ / 8 phase plate is used as the diffusion sheet 6, the transparent base material 10 is used.
The optical axis 12 is arranged at an angle of 35 to 55 ° with the lens array 13 of the lens sheet 8 placed thereon.
In particular, the greatest effect can be obtained when the angle at this time is 45 °. Further, when the irregular sheet 11 is formed on only one surface of the diffusion sheet 6, it is preferable to mount the sheet so that the surface faces the emission surface of the light guide 2.

In this case, the outgoing light 5 emitted from the light guide 2 as shown in FIG. 6 becomes the outgoing light 7 whose directivity is converted by the diffusion sheet 6 as shown in FIG.
At this time, the light is transmitted through the transparent base material 10 that constitutes the diffusion sheet 6, so that the polarization plane is rotated, and the emitted light 7 becomes a light beam having a strong vertical polarization. This emitted light 7 is transmitted through the lens sheet 8 to become the emitted light 9 whose directivity is converted as shown in FIG. 1, and the vertically polarized light of the lens sheet 8 is easily transmitted. The emitted light 9 has a stronger vertical polarization. Therefore, the emitted light 9 has vertical polarization of about 10 to 20% stronger than that of horizontal polarization, and by using this vertical polarization in the liquid crystal panel, the brightness of the liquid crystal display device is increased by several% to 10%. It is possible to raise it by several percent. When the transparent base material 10 is used in the lens sheet 8, it is preferable that the transparent base material 10 is arranged so that the optical axis of the transparent base material 10 and the lens array form an angle of 35 to 55 °. The maximum effect can be obtained when the angle is 45 °.

[0021]

The present invention will be described below in detail with reference to examples. Diffusion sheet Using a mold that has been subjected to a signed blast treatment on one side of a polycarbonate stretched phase film having the same light control function as a λ / 2 phase plate, using an acrylic UV curable resin (refractive index 1.52) Diffusion sheet A was obtained by forming fine irregular irregular shapes. Using a mold that has been subjected to a signed blast treatment on both sides of a polycarbonate stretched phase film that has a light control function equivalent to that of a λ / 2 phase plate, using an acrylic UV curable resin (refractive index 1.52) An irregular asperity shape was formed to obtain a diffusion sheet B.

An acrylic UV-curable resin (refractive index 1.52) was prepared by using a mold subjected to a signed blast treatment on one side of a polyester stretched phase film having a light control function equivalent to that of a λ / 5 phase plate. Thus, a fine and irregular uneven shape was formed to obtain a diffusion sheet C. Using a mold that has been subjected to a signed blast treatment on both sides of a polyester stretched phase film having a light control function equivalent to that of a λ / 5 phase plate,
A fine irregular irregular shape was formed from an acrylic ultraviolet curable resin (refractive index 1.52) to obtain a diffusion sheet D.

A polymethylmethacrylate stretched film having no light control function as a phase film is provided with an acrylic UV-curable resin (refractive index 1.52) on one side of a mold subjected to a signed blast treatment. Diffusion sheet E was obtained by forming fine irregular irregular shapes. Using a mold that has been subjected to a signed blast treatment on both sides of a polymethylmethacrylate stretched film that does not have a light control function as a phase film, using an acrylic UV-curable resin (refractive index 1.52), it is fine and non-existent. Diffusion sheet F was obtained by forming regular irregular shapes.

Lens sheet : Acrylic UV curing using a mold in which a cylindrical lens pattern having a pitch of 100 μm and a radius of curvature of 70 μm is formed on one surface of a polycarbonate stretched phase film having a light control function equivalent to that of a λ / 2 phase plate. A lenticular lens was formed from a mold resin (refractive index 1.52) to obtain a lens sheet α. Using a mold in which a cylindrical lens pattern having a pitch of 100 μm and a radius of curvature of 70 μm is formed on one surface of a polyester stretched phase film having a light control function equivalent to that of a λ / 5 phase plate, an acrylic ultraviolet curable resin (refractive index A lenticular lens was formed according to 1.52) to obtain a lens sheet β. Using a mold in which a cylindrical lens pattern having a pitch of 100 μm and a radius of curvature of 70 μm is formed on one surface of a polymethylmethacrylate stretched film having no light control function as a phase film, an acrylic ultraviolet curable resin (refractive index 1 .52) to form a lenticular lens to obtain a lens sheet γ.

An acrylic UV-curable resin (refractive index: 1.00) was prepared by using a mold subjected to a signed blast treatment on one surface of a polycarbonate stretched phase film having a light control function equivalent to that of a λ / 2 phase plate. 52), a fine irregular irregular shape is formed, and a mold having a cylindrical lens pattern with a pitch of 100 μm and a radius of curvature of 70 μm formed on the other surface is used to mold an acrylic ultraviolet curable resin (refractive index 1.52). ) To form a lenticular lens to obtain a lens sheet 1. Using an acrylic UV-curable resin (refractive index 1.52) on one side of a polyester stretched phase film having a light control function equivalent to that of a λ / 5 phase plate, using a mold subjected to a signed blast treatment. Fine irregular irregular shape is formed on the other surface with a pitch of 100 μm,
A lenticular lens was formed from an acrylic ultraviolet curable resin (refractive index 1.52) using a mold having a cylindrical lens pattern with a radius of curvature of 70 μm to obtain a lens sheet 2. On one side of the polymethylmethacrylate stretched film that does not have a light control function as a phase film, using a mold that has been subjected to a signed blast treatment,
Acrylic UV curable resin (refractive index 1.52) is used to form fine irregular irregular shapes, and pitch 1 is applied to the other surface.
A lenticular lens was formed with an acrylic UV-curable resin (refractive index 1.52) using a mold having a cylindrical lens pattern with a diameter of 00 μm and a radius of curvature of 70 μm to obtain a lens sheet 3. The lens sheet α,
In β, 1 and 2, the lenticular lens was formed so that the optical axis of the phase film and the lens array of the lenticular lens were at 45 °.

Examples 1 to 4 and Comparative Examples 1 to 2 Using the diffusion sheet and lens sheet shown in Table 1,
A backlight as shown in FIG. 1 was assembled. In Examples 1 to 4, the optical axis of the phase film of the diffusion sheet and the lens array of the lens sheet were placed at an angle of 45 °. Further, in Examples 1 and 3 and Comparative Example 1,
It was placed so that the uneven surface formed on the diffusion sheet was located on the exit surface side of the light guide. The front luminances of the horizontally polarized light and the vertically polarized light at this time were measured, and the results were compared with the front luminance of Comparative Example 1 of 10.
The relative values when 0 is shown in Table 1.

[0027]

[Table 1]

Examples 5-8, Comparative Examples 3-4 Using the diffusion sheet and lens sheet shown in Table 2,
A backlight as shown in FIG. 1 was assembled. Further, in Examples 5 and 7 and Comparative Example 3, the uneven surface formed on the diffusion sheet was placed so as to be located on the emission surface side of the light guide.
The front luminances of the horizontally polarized light and the vertically polarized light at this time were measured, and the results are shown in Table 2 as relative values when the front luminance of Comparative Example 4 was 100.

[0029]

[Table 2]

[0030]

INDUSTRIAL APPLICABILITY In the present invention, a transparent sheet such as a diffusion sheet for a backlight or a lens sheet is formed by using a transparent substrate having a light control function equivalent to that of a specific phase plate. The function of controlling the plane of polarization of the light that passes through is applied to the liquid crystal panel without impairing the original light control function of the transparent sheet such as uniformization of the light emitted from the light guide and control of directivity. It is possible to improve the optical efficiency of and improve the brightness of the liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration example of a backlight of the present invention.

FIG. 2 is a partial perspective view showing a configuration example of a diffusion sheet of the present invention.

FIG. 3 is a partial perspective view showing a configuration example of a diffusion sheet of the present invention.

FIG. 4 is a partial perspective view showing a configuration example of a lens sheet of the present invention.

FIG. 5 is a partial perspective view showing a configuration example of a lens sheet of the present invention.

FIG. 6 is a partial perspective view showing a partial configuration example of a backlight.

FIG. 7 is a partial perspective view showing a partial configuration example of a backlight.

[Explanation of symbols]

 1 ... Light source 2 ... Light guide 3 ... Diffusion layer 4 ... Covering film 5 ... Light emitted from light guide 6 ... Diffusion sheet 7 ... Output from diffusion sheet Emitted light 8 ・ ・ ・ Lens sheet 9 ・ ・ ・ Light emitted from lens sheet 10 ・ ・ ・ Transparent base material 11 ・ ・ ・ Irregular uneven surface 12 ・ ・ ・ Optical axis of phase film 13 ・ ・ ・ Lenticular lens surface

Claims (6)

[Claims] 1. A fine shape for diffusing or converging light rays in a two-dimensional or three-dimensional manner is formed on at least one surface of a transparent substrate having a light control function equivalent to a λ / 8 to 7λ / 8 phase plate. A transparent sheet that is characterized by being. 2. An optical axis of a transparent base material and a lens array having a fine shape in which a large number of lens arrays are formed in parallel and having a light control function equivalent to a λ / 8 to 7λ / 8 phase plate. ~ 55
The transparent sheet according to claim 1, wherein the transparent sheet is configured to form an angle of °. 3. A transparent material having a light source and a plate-shaped light guide body having at least one entrance surface and an exit surface facing the light source, and having a light control function equivalent to a λ / 8 to 7λ / 8 phase plate. A transparent sheet having a fine shape for two-dimensionally or three-dimensionally diffusing or converging light rays on at least one surface of the base material is provided on the exit surface side of the light guide. And backlight. 4. A light diffusing sheet and a lens sheet are installed as transparent sheets on the light emitting surface side of the light guide, and at least one of the light diffusing sheet and the lens sheet has a light control function equivalent to a λ / 8 to 7λ / 8 phase plate. 4. The backlight according to claim 3, wherein a fine shape for diffusing or converging light rays in a two-dimensional or three-dimensional manner is formed on at least one surface of the transparent base material having the. 5. λ / 8 to 7λ / 8 constituting a diffusion sheet
5. The backlight according to claim 4, wherein the optical axis of the transparent base material having a light control function corresponding to the phase plate and the lens array of the lens sheet are arranged so as to form an angle of 35 to 55 [deg.]. 6. λ / 8 to 7λ / constituting a lens sheet
The backlight according to claim 4, wherein the optical axis of the transparent base material having a light control function equivalent to that of the eight-phase plate and the lens array of the lens sheet form an angle of 35 to 55 °.