JP2000231103A - Lens sheet and back light and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a moire phenomenon without decreasing the brightness of a back light by forming prism lines in which each prism line consists of slopes constituting upper prism faces, slopes constituting lower prism faces and slopes between the upper and lower slopes and each prism has an almost triangular cross section and a specified slope angle. SOLUTION: The prism line 3 consists of first slopes 4 which constitute upper prism faces, second slopes 5 which constitute lower prism faces and third slopes 6 formed between the first slopes 4 and second slopes 5. The angles θ1, θ2, θ3 of the first slopes 4 (with slope angle θ1), second slopes 5 (with slope angle θ2) and third slopes 6 (with slope angle θ3) which constitute the prism line 3 are controlled to satisfy the relation of θ1>=θ2>=θ3 or θ2>=θ1>θ3. Namely, by forming slopes 6 which are less steep than the upper and lower prism faces, the slopes 6 act stripes produced by the pitches of the lens sheet and the pitches of the prism sheet can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a notebook computer,
The present invention relates to a liquid crystal display device used for a portable liquid crystal television and the like, and a backlight and a lens sheet used for the liquid crystal display device. More specifically, it has a high luminance and a moire phenomenon generated between the lens sheet and the liquid crystal display element. The present invention relates to a lens sheet capable of suppressing the occurrence of light, a backlight using the same, and a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, color liquid crystal display devices have been used in portable notebook personal computers, desktop personal computer liquid crystal monitors,
It has been widely used in various fields as a portable liquid crystal television or a video integrated liquid crystal television. This liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, 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. I have. The edge light system is a backlight of a system in which a light source is arranged on a side surface of a plate-shaped light guide to emit light on the entire surface of the light guide.

In such a liquid crystal display device, it is required to extend the battery driving time. However, the power consumption of the backlight used in the liquid crystal display device is large, and the battery driving time is extended. Is an obstacle for It is important to keep this power consumption as low as possible in order to extend the battery driving time and increase the practical value of the above products. However, if the brightness of the backlight is reduced by suppressing the power consumption of the backlight, the liquid crystal display becomes difficult to see, which is not preferable. Therefore, in order to reduce the power consumption without sacrificing the brightness of the backlight, as a method of improving the optical efficiency of the backlight, a lens sheet having a large number of lens rows such as a prism row or a lenticular row on one side is used. A backlight in which one or a plurality of backlights are mounted on the light exit surface side of a light guide has been put to practical use.

[0004]

Such a lens sheet is usually placed on the lens sheet so that the ridge of the lens row is parallel or perpendicular to the edge of the light guide. The pitch line between pixels of the liquid crystal display element to be formed is substantially parallel to the ridge line of the lens row. For this reason, in a region where the ratio of the pitch of the lens row to the pitch of the pixel pitch line is an integral multiple, the distance between the ridge line of the lens row formed on the lens sheet and the pixel pitch line of the liquid crystal display element is determined. Has a problem that the moire phenomenon occurs and the image becomes difficult to see. For the purpose of suppressing the moire phenomenon between the lens sheet and the liquid crystal display element, Japanese Patent Application Laid-Open No.
As described in JP-A No. 03950 and JP-A-5-25426, the ridge line of the lens row of the lens sheet is set at 15 to 15 mm with respect to the edge of the light guide or the edge of the liquid crystal display element.
There has been proposed a method of forming the film so as to be inclined at about 60 °. However, as described in JP-A-5-203950 and JP-A-5-25426,
When the ridge line of the lens row of the lens sheet is inclined with respect to the edge of the light guide or the edge of the liquid crystal display element, the moiré phenomenon between the lens sheet and the liquid crystal display element can be suppressed, but the backing can be suppressed. The brightness of the light is reduced, and the effect of using the lens sheet for improving the brightness is impaired.

Further, as described in JP-A-10-506500, the pitch of the lens rows of the lens sheet is reduced to 30 μm or less, and the ratio to the pitch of the pitch line between pixels of the liquid crystal display element is increased. A way to do that has been proposed. However, such a method of reducing the pitch of the lens rows requires high processing accuracy in a lens mold used for manufacturing a lens sheet and has a problem of productivity such as a long processing time. At the same time, the brightness of the backlight is reduced.

Therefore, the present invention uses a lens sheet which can suppress the moire phenomenon between the prism array of the lens sheet and the pitch line between pixels of the liquid crystal display element without lowering the luminance of the backlight. Backlight,
It is an object to provide a liquid crystal display device.

[0007]

That is, a lens sheet according to the present invention is a lens sheet in which a large number of prism rows are formed in parallel on at least one surface of a light-transmitting sheet, and the prism rows are formed on an upper prism surface. The first that constitutes
An inclined surface, a second inclined surface constituting a lower prism surface, and a third inclined surface located between the first inclined surface and the second inclined surface, the sectional shape being substantially triangular; First
(3) The inclination angle of the inclined surface satisfies the following expression (1) or expression (2).

[0008]

(2) (1) θ2 ≧ θ1> θ3 (2) (θ1: the inclination angle of the first inclined surface, θ2: the inclination angle of the second inclined surface, and θ3: the inclined angle of the second inclined surface (3. Inclination Angle of Inclined Surface) The backlight according to the present invention includes a light source, a light guide having at least one light incident surface facing the light source, and a light exit surface substantially orthogonal thereto, and the light guide. And the above-described lens sheet placed on the light exit surface side of the lens. Further, the liquid crystal display device of the present invention, a light source, a light guide having at least one light incident surface facing the light source and a light exit surface substantially orthogonal thereto,
It is characterized by comprising the above-mentioned lens sheet mounted on the light emitting surface side of the light guide, and a liquid crystal display element arranged on the lens sheet.

In the present invention, the pitch of the prism sheet caused by the moire phenomenon is not one pitch but one prism by forming a third inclined surface having a gentle inclination angle on the prism surface of the prism row of the lens sheet. Since the distance between the third inclined planes existing in the row, the distance between the groove between the prism rows and the third inclined plane, and the distance between the ridge line of the prism row and the third inclined plane, the actual pitch of the prism row is set. The pitch of the prism sheet caused by the moiré phenomenon can be made fine without making it fine, and the ratio to the pitch of the pitch line between pixels of the liquid crystal display element can be increased, so that the productivity of the lens sheet is reduced and the brightness of the backlight is reduced. The moiré phenomenon that occurs between the lens sheet and the liquid crystal display element can be suppressed without lowering the image quality.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lens sheet 1 according to the present invention is shown in FIG.
As shown in (1), a plurality of prism rows 3 having a substantially triangular cross section are formed in parallel on at least one surface of the light transmitting sheet 2. In the present invention, as shown in FIG. 2, the prism array 3 has a first inclined surface 4 constituting an upper prism surface, a second inclined surface 5 constituting a lower prism surface, and the first inclined surface 4 and the second inclined surface 4. Slope 5
And the third inclined surface 6 located between Further, the first inclined surface 4 (inclination angle = θ1) and the second inclined surface 5 (inclination angle =
θ2), the inclination angle θ of the third inclined surface 6 (inclination angle = θ3)
It is necessary that 1, θ2 and θ3 satisfy the following expression (1) or expression (2).

[0011]

Θ1 ≧ θ2> θ3 (1) θ2 ≧ θ1> θ3 (2) This is an intermediate position (prism array 3) in the prism plane of the lens array 3 of the lens sheet 1. Is formed at an intermediate position between the substantially triangular oblique sides in the cross-sectional shape of the lens sheet), the inclined surface 6 is inclined more gradually than the upper prism surface and the lower prism surface. This is because the pitch of the prism sheet can be reduced. That is, in the conventional lens sheet, the pitch of the prism rows formed on the lens sheet is the pitch of the lens sheet. However, in the present invention, the distance between the third inclined surfaces existing in one prism row and the prism The distance between the groove between the rows and the third inclined plane and the distance between the ridge line of the prism rows and the third inclined plane are the pitches of the lens sheet 1, and the pitch of the lens sheet 1 can be reduced without reducing the pitch of the prism rows 3. It can be made finer. As a result, the ratio between the pitch of the lens sheet 1 and the pitch of the pitch line between pixels of the liquid crystal display element can be increased, so that the productivity of the lens sheet 1 and the brightness of the backlight are not reduced. And the moiré phenomenon occurring between the liquid crystal display elements can be suppressed.

In the present invention, the inclination angle θ3 of the third inclined surface 6 constituting the prism surface is set to a range that satisfies the expression (1) or (2), that is, the first inclined surface 4 and the second inclined surface 6 By making the inclination of the third inclined surface 6 gentler than the inclined surface 5, an effect of suppressing a moire phenomenon occurring between the lens sheet 1 and the liquid crystal display element can be obtained.
The third inclined surface 6 can improve the effect of suppressing the moire phenomenon as the inclination angle θ3 approaches 0 °, and the inclination angle θ3 is preferably set in a range of 0 ° to 20 °,
More preferably, it is in the range of 0 ° to 10 °. Further, the formation position of the third inclined surface 6 is an intermediate position in the prism plane,
That is, there is no particular limitation as long as it is between the first inclined surface 4 and the second inclined surface 5, but from the viewpoint of the appearance of the lens sheet 1 and the uniformity of the emitted light as a backlight, etc. Preferably, it is formed near the center.

Further, the length of the third inclined surface 6 (in the sectional shape of the prism array 3) can be made relatively long when the inclination angle θ3 is large, but the inclination angle θ3
If the distance is too long, if the distance is too long, the area where the optical characteristics are greatly different increases, and the appearance of the lens sheet 1 is impaired or the optical characteristics such as uniformity as a backlight are reduced. Is preferred. For example, when the inclination angle θ3 is 0 ° to 20 °, the length of the third inclined surface 6 is preferably 2 μm or less,
More preferably, it is 1.7 μm or less. Further, from the viewpoint of the productivity of the lens mold and the like, the length of the third inclined surface 6 is 0.3
μm or more, more preferably 0.1 μm or more.
5 μm or more.

The inclination angles θ1 and θ2 of the first inclined surface 4 and the second inclined surface 5 formed above and below the third inclined surface 6 are determined from the viewpoint of the refraction of light of the lens sheet 1, the light condensing function, and the like. The apex angle (imaginary apex angle in the case of the second inclined surface) is 60 ° or more.
It is preferable to set the range of 25 ° to 60 ° so as to be in the range of 130 °, more preferably 30 ° to 50 °.
Range. Further, the inclination angles θ1 and θ2 of the first inclined surface 4 and the second inclined surface 5 may be the same or different.
By adjusting the inclination angles θ1 and θ2, backlights having various luminance distributions can be obtained.

In the present invention, the third inclined surface 6 provided in the prism array 3 may be formed by forming a plurality of third inclined surfaces 6 between the first inclined surface 4 and the second inclined surface 5 in the prism surface. Good. In this case, a plurality of third inclined surfaces having different inclination angles θ3 may be continuously formed, or the third inclined surface may have a third inclination angle between the third inclined surfaces.
A fourth inclined surface larger than the inclined angle θ3 of the inclined surface may be formed. Also, the first inclined surface and the second inclined surface may be constituted by a plurality of inclined surfaces having different inclination angles θ1 and θ2.

The lens sheet 1 of the present invention is preferably manufactured using a light-transmitting sheet 2 having a high visible light transmittance and a relatively high refractive index. For example, acrylic resin, polycarbonate resin, vinyl chloride, etc. Resin, active energy ray-curable resin and the like. Among them, a lens sheet using an active energy ray-curable resin is preferable from the viewpoints of scratch resistance, handleability, productivity and the like of the lens sheet 1. In the present invention, additives such as an antioxidant, an ultraviolet absorber, a yellowing inhibitor, a bluing agent, a pigment, and a diffusing agent can be added to the lens sheet 1 as needed.

As a method for producing the lens sheet 1 of the present invention, a usual molding method such as extrusion molding and injection molding can be used. When manufacturing the lens sheet 1 using an active energy ray-curable resin, a lens portion is formed on a transparent substrate such as a transparent film or a sheet using the active energy ray-curable resin. First, an active energy ray-curable monomer mixture is injected into a lens mold on which a predetermined lens pattern is formed, and a transparent base material is overlaid. Next, an active energy ray such as an ultraviolet ray or an electron beam is irradiated through the transparent base material, and the active energy ray-curable monomer mixture is polymerized and cured, and is separated from the lens mold to obtain the lens sheet 1.

The active energy ray-curable monomer mixture liquid constituting the lens portion of the lens sheet 1 includes bis (methacryloylthiophenyl) sulfide, 2,4-dibromophenyl (meth) acrylate, 2,3,5-tri Bromophenyl (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-biz (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 ((meta) And polyfunctional (meth) acrylic compounds such as) acryloyloxyethoxy) phosphate. These can be used alone or in combination of two or more.

In addition, together with these polyfunctional (meth) acrylic compounds, styrene, vinyl toluene, 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 diallyl phthalate, dimethallyl phthalate, allyl compounds such as diallyl biphenylate, barium, lead, antimony, titanium,
Metal salts of metals such as tin and zinc with (meth) acrylic acid and the like can also be used. These can be used alone or in combination of two or more.

In the present invention, examples of the photoradical generation catalyst used in the active energy ray-curable monomer mixture include 2-hydroxy-2-methyl-1-phenylpropan-1-one, hydroxycyclohexylphenylketone, and the like. Methylphenylglyoxylate, 2,
4,6-trimethylbenzoylphosphine oxide, benzyldimethyl ketal and the like can be mentioned.

In the lens sheet 1 having a lens portion formed of an active energy ray-curable resin, the material of the transparent substrate used is not particularly limited as long as it is a material that transmits active energy rays such as ultraviolet rays and electron beams. Although a flexible glass plate or the like can be used, a light-transmitting sheet made of a transparent resin such as a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, and a polymethacrylimide resin is preferable. An anchor coat layer for improving the adhesion to the lens portion may be formed on the surface of the transparent substrate on which the lens portion is formed, or a fine uneven shape may be provided. Further, the surface of the transparent substrate on which the lens portion is not formed can also be processed to have fine irregularities.

In the present invention, the thickness of the lens sheet 1 is preferably about 70 μm to 1 mm, more preferably about 100 to 500 μm, and the pitch of the prism rows 3 is preferably about 35 to 200 μm. And more preferably about 40 to 150 μm.

As shown in FIG. 3, the backlight 7 of the present invention has a light source 9 such as a fluorescent lamp disposed at one end of a light guide 8 made of a transparent resin or the like. The lens sheet 2 is placed on the camera. Also, if necessary, the light guide 8
A diffusion sheet 11 is placed on the light exit surface of the light emitting device, and a reflection layer 10 is formed on a surface opposite to the light exit surface by a reflection film or the like. If the light guide 8 has at least one side surface facing the light source 9 as a light incident surface and a surface substantially perpendicular to the light incident surface as a light exit surface, a plate shape, a wedge shape, or a boat shape is used. And the like, and is made of a synthetic resin having a high light transmittance. Light source 9 to light guide 8
In order to effectively introduce light into the light source, it is preferable to cover the light incident surfaces of the light source 9 and the light guide 8 with a case or a film coated with a reflective agent on the inside. Furthermore, the lens sheet 2 can be placed on the light emitting surface of the light guide 8 by stacking two or three or more lens sheets. The light source 9 may be arranged at at least one end of the light guide 8, but a plurality of light sources 9 may be arranged as necessary.

Various synthetic resins having high transparency such as methacrylic resin, acrylic resin, polycarbonate resin, vinyl chloride resin and the like are used as the synthetic resin constituting the light guide 8, and extrusion molding, injection molding, etc. Can be manufactured by the usual molding method. In particular, methacrylic resin is excellent in light transmittance, heat resistance, mechanical properties, and moldability, and is most suitable as a light guide material. Such a methacrylic resin is a resin containing methyl methacrylate as a main component, and it is preferable that methyl methacrylate is 80% by weight or more.

In the backlight 7 of the present invention, the orientation of the lens surface and the prism apex of the lens sheet 1 placed on the light exit surface of the light guide 8 depend on the emission light characteristics of the light guide 3 used. It can be appropriately selected depending on the situation. For example, various diffusion sheets can be placed on the light exit surface of the light guide 8 to change the directivity of the emitted light, and the light exit surface or back surface of the light guide 8 has a lens surface or a matte surface. The directivity of outgoing light can be changed by forming such a method. In the former case, a lens sheet is placed via a diffusion sheet on the light exit surface of the light guide 8 so that the prism surface is in the opposite direction to the light guide 8, and the prism apex angle is set to 80 ° to 13 °.
Preferably, it is 0 °. In the case of the latter, Tokuhei 7
As described in JP-A-27136 and JP-B-7-27137, a lens sheet is placed on the light exit surface of the light guide such that the prism surface is on the light guide side, and the prism apex angle is set. It is preferable that the angle be 60 ° to 80 °.

In the liquid crystal display device of the present invention, a liquid crystal display element is mounted on the prism sheet 2 of the backlight 7 having the above configuration. The liquid crystal display element is not particularly limited, and the active matrix driving T
Either an FT type liquid crystal display element or a simple matrix driven STN type liquid crystal display element can be used. In the TFT type liquid crystal display device, various active devices such as polysilicon, amorphous silicon, metal insulator and metal can be used.

[0027]

The present invention will be described below in detail with reference to examples. Inverter the cold cathode tube of the measuring light guide luminance (TDK Corp. CXA-
M10L) to connect to a DC power supply, and apply DC 12 V to light up. The backlight was placed on a measurement table, and the center was adjusted so as to rotate on a rotation axis parallel to the axis of the cold-cathode tube. Next, a black paper having a pinhole of 3 mmφ is fixed on the light guide such that the pinhole is located at the center of the light guide, and the measurement circle is measured using a luminance meter (Minolta nt-1 タ). Was adjusted to be 8 to 9 mm.
After 30 minutes or more of the aging time of the cold cathode tube, the front luminance of the emitted light when the rotation axis was set to 0 ° was measured.

Evaluation of Moire Phenomenon The liquid crystal display was operated to display an image, and the occurrence of the moire phenomenon was visually observed, and evaluated according to the following criteria. ：: Not observed. Δ: Although slightly observed, there is no practical problem. X: Moire is remarkable.

Example 1 JIS having a thickness of 3 mm and a size of 300 mm × 400 mm
A prism pattern was formed by cutting a prism array having the cross-sectional shape shown in FIG. 4 at a pitch of 50 μm on the surface of a copper plate of three types of brass, and then applying ganigen plating to prepare a lens mold. An appropriate amount of the following UV-curable monomer mixture is injected into one end of this lens-type prism pattern, and a 125 μm-thick polyester film (A4300 manufactured by Toyobo Co., Ltd.) is injected from one end of the lens mold into which the UV-curable monomer mixture is injected. Then, the mixture was gradually overlapped in the other end direction while applying pressure with a roll, and the injected ultraviolet curable monomer mixture was spread over the entire lens mold. Then, ultraviolet rays were irradiated from three 6.4 kW ultraviolet lamps (manufactured by Western Quartz Co., Ltd.) having an irradiation intensity of 80 W / cm disposed above the polyester film.
Irradiation was performed for 5 seconds to polymerize and cure the ultraviolet-curable monomer mixture, and then separated from the lens mold to obtain a prism sheet having a refractive index of 1.53.

UV curable monomer mixture liquid Ethylene oxide-modified bisphenol A dimethacrylate 50 parts by weight (Fancryl FA-321M manufactured by Hitachi Chemical Co., Ltd.) neopentyl glycol-modified trimethylolpropane di 20 parts by weight acrylate (Nippon Kayaku Chemical Co., Ltd.) KAYARAD R-604) Phenoxyethyl acrylate (30 parts by weight Biscoat # 192 manufactured by Osaka Organic Chemical Industry Co., Ltd.) 2-hydroxy-2-methyl-1-phenylpropane 1.5 parts by weight 1-one (Darocur 1173 manufactured by Merck).

A light guide made of a transparent methacrylic resin plate (Acrylite # 001 manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of about 3 mm and a size of about 10.4 inches was prepared, and two light guides on the short side of the light guide were prepared. Silver deposited on one end face and one end face on the long side
An ET film was adhered by adhesive processing, and a PET film on which silver was vapor-deposited was taped to one surface to form a reflective surface. On the other end face on the long side of the light guide, PE with silver deposited
A cold cathode tube made by T film (Matsushita Electric Co., Ltd., 2mmφ × 25
0 mm) and installed as a light source lamp. Next, a translucent methacrylic resin plate (Acrylite # manufactured by Mitsubishi Rayon Co., Ltd.) is placed on the light exit surface opposite to the reflection surface of the light guide.
432) is placed thereon, and the obtained prism sheet is cut into substantially the same size as the light guide, so that the prism row is directed upward, and the ridge line of the prism row is parallel to the light source of the light guide. Then, the backlight having the structure shown in FIG. 3 was assembled.

The front luminance of the emitted light was measured using the obtained backlight. The results are shown in Table 1 as a luminance improvement rate based on the luminance of the backlight when the prism sheet was not mounted. Further, the pixel pitch on the prism sheet of the obtained backlight is 0.264.
A liquid crystal display device having a size of 10.4 inches and a size of 800 × 600 dots was mounted on the liquid crystal display device. Using the obtained liquid crystal display device, an image was observed to evaluate the occurrence of the moire phenomenon, and the results are shown in Table 1.

Example 2 A prism sheet was manufactured in the same manner as in Example 1 except that a lens pattern in which a prism pattern having a prism array having a sectional shape shown in FIG. 5 was formed was used.
The backlight was assembled in the same manner as described above. The front luminance of the emitted light was measured using the obtained backlight, and the results are shown in Table 1. Further, a liquid crystal display device was assembled in the same manner as in Example 1, the image was observed, and the occurrence of the moiré phenomenon was evaluated. The results are shown in Table 1.

Comparative Example 1 A prism sheet was manufactured in the same manner as in Example 1, except that a prism pattern of a prism array having a cross-sectional shape of an isosceles triangle with a vertex angle of 90 ° was used as a lens type. A backlight was assembled in the same manner as in Example 1. Using the obtained backlight, the front luminance of the emitted light was measured, and the results are shown in Table 1. Example 1
A liquid crystal display device was assembled in the same manner as described above, the image was observed, and the occurrence of the moiré phenomenon was evaluated. The results are shown in Table 1.

Comparative Example 2 A prism sheet was formed in the same manner as in Example 1 except that a lens type having a prism pattern of a prism array having a pitch of 25 μm and a cross section of an isosceles triangle having a vertex angle of 90 ° was used. Was manufactured, and a backlight was assembled in the same manner as in Example 1. Using the obtained backlight,
The front luminance of the emitted light was measured, and the results are shown in Table 1.
A liquid crystal display device was assembled in the same manner as in Example 1,
The image was observed and the occurrence of the moiré phenomenon was evaluated. The results are shown in Table 1.

[0036]

[Table 1]

As is clear from Table 1, in Examples 1 and 2 of the present invention, the ridge line of the lens row of the lens sheet and the pitch line between pixels of the liquid crystal display element were substantially reduced without substantially reducing the front luminance of the backlight. The moiré phenomenon can be suppressed. On the other hand, in Comparative Example 1, although the front luminance of the backlight did not decrease, a moire phenomenon occurred between the ridge line of the prism row of the prism sheet and the pitch line between pixels of the liquid crystal display element, making it difficult to view an image. Was something. Also,
In Comparative Example 2, although the moire phenomenon between the ridge line of the prism row of the prism sheet and the pitch line between pixels of the liquid crystal display element can be suppressed to some extent, the front luminance of the backlight is reduced.

[0038]

According to the present invention, by forming a third inclined surface having a gentle inclination angle on the prism surface of the prism row of the lens sheet, the brightness of the backlight is not reduced.
An object of the present invention is to provide a backlight and a liquid crystal display device capable of suppressing a moiré phenomenon between a ridge line of a lens row of a lens sheet and a pitch line between pixels of a liquid crystal display element.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a lens sheet of the present invention.

FIG. 2 is a schematic diagram showing a cross-sectional shape of a prism row of the lens sheet of the present invention.

FIG. 3 is a schematic perspective view showing a configuration example of a backlight according to the present invention.

FIG. 4 is a schematic diagram illustrating a cross-sectional shape of a prism row of the lens sheet according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating a cross-sectional shape of a prism row of a lens sheet according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lens sheet 2 ... Light transmissive sheet 3 ... Prism row 4 ... 1st inclined surface 5 ... 2nd inclined surface 6 ... 3rd inclined surface 7 ... Backlight 8 light guide 9 light source 10 reflection layer 11 diffusion sheet

Claims (3)

[Claims] 1. A lens sheet having a plurality of prism rows formed in parallel on at least one surface of a light-transmitting sheet, wherein the prism rows form a first inclined surface constituting an upper prism surface and a lower prism surface. A second inclined surface to be constituted;
It is constituted by a third inclined surface located between the first inclined surface and the second inclined surface, has a substantially triangular cross section, and has an inclination angle of the first to third inclined surfaces represented by the following equation (1). Or equation (2)
A lens sheet that satisfies the following. Θ1 ≧ θ2> θ3 (1) θ2 ≧ θ1> θ3 (2) (θ1: the inclination angle of the first inclined surface, θ2: the inclination angle of the second inclined surface, θ3: the second inclined surface (3 inclination angle of inclined surface) 2. A light guide having a light source, at least one light incident surface facing the light source, and a light exit surface substantially orthogonal to the light source, and a light guide mounted on the light exit surface of the light guide. Item 1
A backlight comprising the lens sheet according to any one of the preceding claims. 3. A light guide having a light source, at least one light incident surface facing the light source, and a light exit surface substantially orthogonal to the light source, and a light guide mounted on the light exit surface side of the light guide. Item 1
A liquid crystal display device, comprising: the lens sheet according to claim 1; and a liquid crystal display element disposed on the lens sheet.