JPH0955110A - Backlight and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a moirι phenomenon between the ridgeline of a lens column and a pitch line among the pixels of a liquid crystal display element without reducing the luminance of a backlight by forming the ridgeline of the lens column of a lens sheet so as to have a specified angle against the edge of a light transmission body. SOLUTION: In the light transmission body 3 of a backlight 1, at least one side surface is used as a light incident surface, one surface roughly orthogonal to the surface is used as a light exit surface and a lens sheet 2 having many lens columns formed on at least one surface in parallel with one another is mounted on the exit surface. In this sheet 2, many lens columns are formed in parallel with one another such that the ridgeline of the lens columns has 3 to 13 degree angle against the side edge of the sheet 2. Then, by mounting the sheet 2 on the light exit surface of the body 3 such that both side edges coincide with each other, the ridgeline of the lens columns has 3 to 13 degree angle against the side edge of the body 3. Thus, the moirι phenomenon between the ridgeline of the lens columns of the sheet 2 and pitch lines among the pixels of a liquid crystal element is controlled.

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 in a portable liquid crystal television or the like and a backlight used for the liquid crystal display device. More specifically, it has high brightness and suppresses a moire phenomenon that occurs between a lens sheet and a liquid crystal display element. The present invention relates to a liquid crystal display device and a backlight.

[0002]

2. Description of the Related Art In recent years, color liquid crystal display devices have been widely used in various fields as portable notebook personal computers, portable liquid crystal televisions, video integrated liquid crystal televisions and the like. This liquid crystal display device is basically composed of a backlight section and a liquid crystal display element section. As the backlight part, there are a direct type in which a light source is provided directly below the liquid crystal display element and an edge light type in which a light source is provided on the side surface of the light guide body.The edge light type has been widely used due to the compactness of the liquid crystal display device. There is. 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.

It has been demanded to extend the battery driving time of such a liquid crystal display device, but the power consumption of the backlight used in the liquid crystal display device is large, which is an obstacle to extending the battery driving time. It has become. Keeping this power consumption as low as possible is an important issue for extending the battery drive time and increasing 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, it is desired to improve the optical efficiency of the backlight in order to suppress the power consumption without sacrificing the brightness of the backlight. As a means to achieve this,
A backlight in which one or more lens sheets each having a large number of lens rows such as prism rows and lenticular rows formed on one surface as shown in FIG. 3 are mounted on the exit surface side of the light guide is put to practical use. .

[0004]

Since such a lens sheet is usually placed so that the ridge lines of its lens rows are parallel or at right angles to the edges of the light guide, it is arranged on the lens sheet. The pixel pitch line of the liquid crystal display element and the ridge line of the lens array are substantially parallel to each other. Therefore, in a region where the ratio of the pitch of the lens row and the pitch of the inter-pixel pitch line is an integer multiple, between the ridge line of the lens row formed on the lens sheet and the inter-pixel pitch line of the liquid crystal display element. However, there is a problem that the image becomes hard to see due to the moire phenomenon. For the purpose of suppressing the moire phenomenon between the ridgeline of the lens array of the lens sheet and the pixel pitch line of the liquid crystal display element, it is described in JP-A-5-203950 and Japanese Utility Model Application Laid-Open No. 5-25426. As described above, a method has been proposed in which the ridge lines of the lens rows of the lens sheet are formed so as to be inclined at about 15 to 60 degrees with respect to the edge of the light guide or the edge of the liquid crystal display element.

However, as described in Japanese Patent Laid-Open No. 5-203950 and Japanese Utility Model Laid-Open No. 5-25426, the ridge lines of the lens rows of the lens sheet are arranged at the edges of the light guide or the liquid crystal display element. On the other hand, if the lens sheet is tilted by 15 degrees or more, the moire phenomenon between the lens sheet and the liquid crystal display element can be suppressed, but the luminance of the backlight is reduced, and the lens sheet is used to improve the luminance. The effect that was done was impaired. Therefore, the present invention provides a backlight and a liquid crystal display device that can suppress the moire phenomenon between the ridge lines of the lens rows of the lens sheet and the pixel pitch lines of the liquid crystal display element without reducing the brightness of the backlight. The purpose is to do.

[0006]

That is, the backlight of the present invention comprises 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. It is composed of at least one lens sheet that is placed on the emission surface side of the optical body and has a lens surface on which at least one surface is formed with a large number of lens rows in parallel. It is characterized in that it is formed with an angle of 3 to 13 degrees with respect to the edge of the light body. Further, the liquid crystal display device of 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 to the light entrance surface, and a light guide mounted on the exit surface side of the light guide. And a liquid crystal display element disposed on the lens sheet and at least one lens sheet having a lens surface in which a large number of lens rows are formed in parallel on at least one surface of the lens sheet. The ridgeline of the column is 3 to 1 with respect to the pitch line between pixels of the liquid crystal display element.
It is characterized in that it is formed with an angle of 3 degrees.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The backlight 1 of the present invention is shown in FIG.
As shown in, the light guide 4 and the light guide 3 are formed, and the light guide 3 has at least one side surface as a light incident surface.
A lens sheet 2 having a lens surface having one surface substantially orthogonal thereto as a light emitting surface and having a lens surface in which a large number of lens rows are formed in parallel on at least one surface is placed on the light emitting surface.
Further, the liquid crystal display device 8 of the present invention is configured by disposing the liquid crystal display element 7 on the lens sheet 2, as shown in FIG.

The lens sheet 2 is, as shown in FIG.
The ridge line of the lens row is 3 to 1 with respect to the edge of the lens sheet 2.
A large number of lens rows are formed in parallel so as to have an angle of 3 degrees, and by placing such a lens sheet 2 on the emission surface of the light guide body 3 so that the edges of both are aligned. , The ridgeline of the lens array has an angle α of 3 to 13 degrees with respect to the edge of the light guide. In this case, when the lens sheet 2 is placed so that the lens rows are substantially parallel to the light source, the ridge lines of the lens rows are 3 to 13 with respect to the side edges of the light guide parallel to the light source.
It may be configured to have an angle α of degrees. Further, when the lens sheet 2 is mounted so that the lens rows are substantially orthogonal to the light source, the ridge lines of the lens rows have an angle α of 3 to 13 degrees with respect to the side edge of the light guide which is perpendicular to the light source. Can be configured as. Further, the liquid crystal display element 7 is composed of the lens sheet 2
By mounting the liquid crystal display element 7 so that the grid-like inter-pixel pitch lines of the liquid crystal display element 7 are parallel (or right-angled) to the edges of the light guide body 3, as shown in FIG. The ridgeline of the lens array has an angle α of 3 to 13 degrees with respect to the interpixel pitch line.

As described above, the ridge lines of the lens rows of the lens sheet 2 are 3 to 13 degrees, preferably 3 to 10 degrees, with respect to the edges of the light guide 3 and the pixel pitch lines of the liquid crystal display element 7.
More preferably, it is configured to have an angle of 3 to 7 degrees, which is generated between the lens row of the lens sheet 2 and the pixel pitch line of the liquid crystal display element 7 without lowering the brightness of the backlight 1. The moire phenomenon can be suppressed. If the ridgeline of the lens row of the lens sheet 2 is less than 3 degrees with respect to the edge of the light guide 3 and the inter-pixel pitch line of the liquid crystal display element 7, the lens row of the lens sheet 2 and the pixel of the liquid crystal display element 7 are The effect of suppressing the moire phenomenon generated between the pitch line and the pitch line is not sufficient, and the image becomes difficult to see. On the contrary, the ridge line of the lens row of the lens sheet 2 is 13 with respect to the edge of the light guide 3 and the pitch line between pixels of the liquid crystal display element 7.
When it exceeds the limit, the front luminance of the backlight 1 is lowered, and the luminance improving effect of the lens sheet 2 is impaired.

The lens sheet 2 of the present invention has a lens surface having a large number of lens units formed in parallel on one surface. As the lens shape to be formed, various shapes are used depending on the purpose, and examples thereof include a prism shape, a lenticular lens shape, and a corrugated shape. In the present invention, the thickness of the lens sheet 2 is 0.1 mm to 3 mm.
mm, pitch of lens unit is 30 μm to 0.5 mm
It is preferable to set the degree. When a prism sheet is used as the lens sheet 2, the prism apex angle is preferably in the range of 60 to 120 °.

The lens sheet 2 of the present invention is preferably manufactured by using a material having a high visible light transmittance and a relatively high refractive index. For example, acrylic resin, polycarbonate resin, vinyl chloride resin, active Examples include energy ray-curable resins. Among them, the active energy ray curable resin is preferable from the viewpoint of scratch resistance, handleability, productivity, etc. of the lens sheet 2. In the present invention, an additive such as an antioxidant, an ultraviolet absorber, an anti-yellowing agent, a bluing agent, a pigment or a diffusing agent may be added to the lens sheet 2 if necessary.

As a method for producing the lens sheet 2 of the present invention, a usual molding method such as extrusion molding or injection molding can be used. When the lens sheet 2 is manufactured using the active energy ray-curable resin, the lens portion is formed of the active energy ray-curable resin on a transparent substrate such as a transparent film or sheet. First, an active energy ray-curable resin liquid is injected into a lens mold having a predetermined lens pattern, and transparent base materials are superposed on each other. Then, active energy rays such as ultraviolet rays and electron rays are irradiated through the transparent base material to polymerize and cure the active energy ray-curable resin liquid, and peeled from the lens mold to obtain the lens sheet 2.

Examples of the active energy ray-curable resin that composes the lens portion of the lens sheet 2 include bis (methacryloylthiophenyl) sulfoid, 2,4-dibromophenyl (meth) acrylate, and 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) acryloyloxyethoxy Phenyl) 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 (( Examples thereof include polyfunctional (meth) acrylic compounds such as (meth) acryloyloxyethoxy) phosphate and tri ((meth) acryloyloxyethoxy) phosphate. 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-1-phenylpropan-1-one, hydroxycyclohexylphenylketone or methylphenyl. Glyoxylate, 2,4,6-trimethylbenzoylphosphine oxide, benzyl dimethyl ketal and the like can be mentioned. A lens sheet 2 having a lens portion formed of an active energy ray curable resin
In the above, 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 rays, and a flexible glass plate or the like can also be used.
Transparent resins such as polyester resins, acrylic resins, polycarbonate resins, vinyl chloride resins, and polymethacrylimide resins are preferred.

In the backlight 1 of the present invention, as shown in FIG. 1, a light source 4 such as a fluorescent lamp is arranged at one end of a light guide 3 made of a transparent resin or the like, and the light guide 3 is placed above the light guide 3. The lens sheet 2 is placed on the. A diffusion sheet 6 is placed on the light exit surface of the light guide 3 as necessary, and a reflective layer 5 is formed on the surface opposite to the light exit surface by a reflective film or the like. The light guide 3 may have various shapes such as a plate shape, a wedge shape, and a boat shape, and is made of a synthetic resin having a high light transmittance. In order to effectively introduce light from the light source 4 to the light guide body 3, it is preferable that the light incident surfaces of the light source 4 and the light guide body 3 are covered with a case or film coated with a reflecting agent on the inside.

As the synthetic resin forming the light guide 3, various highly transparent synthetic resins such as methacrylic resin, acrylic resin, polycarbonate resin and vinyl chloride resin are used, and extrusion molding and injection molding are performed. It can be manufactured by a usual molding method such as. 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 methyl methacrylate is preferably 80% by weight or more.

In the backlight 1 of the present invention, in the lens sheet 2 placed on the emission surface of the light guide 3,
The direction of the lens surface and the prism apex angle can be appropriately selected according to the outgoing light characteristics of the light guide 3 to be used. For example, various diffusion sheets can be placed on the exit surface of the light guide 3 to change the directivity of the exit light, and the exit surface or the back surface of the light guide 3 can be a lens surface, a matte surface, or the like. The directivity of the emitted light can also be changed by forming the. In the latter case, as described in Japanese Patent Publication No. 7-27136 and Japanese Patent Publication No. 7-27137, a prism sheet having prism rows with a prism apex angle of about 60 degrees has a prism surface facing downward. It is suitable to mount it on the emission surface of the light guide.

In the present invention, the lens sheet 2 placed on the exit surface of the light guide 3 may be formed by stacking two or three or more lens sheets in an overlapping manner.
In this case, due to the relationship between the pixel size of the liquid crystal display element and the pitch of the lens array, the ridgeline of the lens array of the lens sheet is the light guide when the ridge line of the lens sheet occurs at least with the inter-pixel pitch line. It may be configured so as to have an angle of 3 to 13 degrees with respect to the edge and the pitch line between pixels of the liquid crystal display element. For example, when two lens sheets are mounted such that their lens rows are substantially orthogonal to each other, generally, the pitch lines between pixels of the liquid crystal display element have different pitch intervals in the vertical direction and the horizontal direction. Due to the relationship between the vertical or horizontal size of the pixel of the liquid crystal display element and the pitch of the lens row, only one lens sheet that causes a moire phenomenon between the pixel pitch line and the ridge line of the lens row is the light guide. By configuring so as to form an angle of 3 to 13 degrees with respect to the edge and the pitch line between pixels of the liquid crystal display element, the moire phenomenon that occurs between the liquid crystal display element and the lens sheet can be suppressed. In this case, the other lens sheet may be configured so that the ridge line of the lens row is 0 degree with respect to the side edge of the light guide and the pixel pitch line of the liquid crystal display element. It may be configured to have an angle of 13 degrees.

When both of the lens sheets cause a moire phenomenon between the pixel pitch lines due to the relationship between the vertical or horizontal size of the pixels of the liquid crystal display element and the pitch of the lens rows, whichever one of the lens sheets causes the moire phenomenon. Also in the lens sheet, it is preferable that the ridge line of the lens array is formed to have an angle of 3 to 13 degrees with respect to the light source of the light guide and the edge and the pitch line between pixels of the liquid crystal display element. Normally, the lens rows of the respective lens sheets are overlapped so as to be substantially orthogonal to each other, so that the first lens sheet is provided with a liquid crystal display in which the ridge line of the lens row of the lens sheet is parallel to the light source of the light guide 3 and the liquid crystal display. 3 to 13 for the pitch line between pixels parallel to the light source of the element 7
By mounting so as to have an angle α of degrees, the ridge line of the lens row of the second lens sheet mounted thereon also has a side edge perpendicular to the light source of the light guide 3 and the light source of the liquid crystal display element 7. And an angle of 3 to 13 degrees with respect to an inter-pixel pitch line perpendicular to.

In the backlight 1 of the present invention, FIG.
The configuration is not limited to that shown in FIG. 1, and various configurations can be adopted according to the purpose of use and the like. For example, light source 4
May be disposed at at least one end of the light guide body 3, but a plurality of light sources 4 may be disposed if necessary. Further, the light emitting surface of the light guide 3 may be formed as a diffusion surface or a lens surface, or a light amount adjusting mechanism may be provided so that light can be uniformly emitted from the entire light guide 3 by printing or the like. Further, as the shape of the light guide 3, various shapes such as a sheet shape, a cross-sectional wedge shape, and a hull shape can be used.

As shown in FIG. 3, the liquid crystal display device 8 of the present invention comprises the backlight 1 and the liquid crystal display element 7 which are constituted by the light guide 3 having the above-mentioned constitution. The liquid crystal display element 7 is not particularly limited, and either an active matrix driving TFT type liquid crystal display element or a simple matrix driving STN type liquid crystal display element can be used. Further, in the TFT type liquid crystal display element, the element and various active elements such as polysilicon, amorphous silicon and metal insulator metal can be used.

[0023]

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

Example 1 A transparent acrylic resin plate (Acrylite 001 manufactured by Mitsubishi Rayon Co., Ltd.) having a size of 100 mm × 90 mm × 4 mm was prepared, and one surface of the transparent acrylic resin plate was printed with a matte shape to prepare a light guide. A PET film having silver vapor-deposited on the two end faces of 90 mm of the obtained light guide was adhered by adhesion processing, and PE vapor-deposited with silver was formed on the surface opposite to the matte surface.
The T film was taped to form a reflective surface. Cold cathode tubes (KC130T4E7 manufactured by Matsushita Electric Industrial Co., Ltd.) were made of silver-deposited PET film on two 100 mm end faces of an acrylic plate.
(2, 4 mmφ × 130 mm) was wound and installed as a light source lamp to provide a backlight.

An acrylic UV-curable resin solution was poured into a mold having a prism pattern with a prism apex angle of 95 ° and a pitch of 50 μm, and a PET film having a thickness of 150 μm was overlaid with a roll. Then, 570 mJ of ultraviolet ray was irradiated through the PET film to polymerize and cure the acrylic ultraviolet ray curable resin, and peeled from the mold to obtain a prism sheet having a refractive index of 1.59 and an apex angle of 95 °. Then, it was cut into a rectangle of 100 mm × 90 mm so that the ridgeline of the prism array formed an angle of 5 ° with respect to the edge.

A diffusion film (D113 manufactured by Kimoto Co., Ltd.) is placed on the light emitting surface of the light guide body, and a prism sheet having an apex angle of 95 ° is directed upward, and the ridge line of the prism row is the light guide body. The backlight was assembled by mounting it so that it had an angle (tilt angle) of 5 ° with respect to the edge parallel to the light source. The front luminance of emitted light was measured using the obtained backlight. The results are shown in Table 1 and FIG. 5 together with the luminance ratio when the luminance is 1 when the tilt angle is 0 degree (Comparative Example 1). Furthermore, a TFT type liquid crystal display element having pixels of 168 μm (parallel to the light source) × 259 μm is formed on the prism sheet, and the ridge line of the prism row is at an angle of 5 ° (tilt angle) with respect to the pixel pitch line of the liquid crystal display element.
A liquid crystal display device was assembled by mounting the liquid crystal display device. An image was observed using the obtained liquid crystal display device, but a bright image without a moire phenomenon was obtained.

Example 2 A prism sheet having a refractive index of 1.59 and an apex angle of 95 ° was obtained in the same manner as in Example 1. Then, 100 mm × 90 so that the ridgeline of the prism array forms an angle of 10 ° with the edge.
It was cut into a rectangular shape of mm. The same light guide as in Example 1 was used, and a diffusion film (Kimoto D
113), and the prism sheet having an apex angle of 95 ° faces upward, and the ridge line of the prism column has an angle (inclination angle) of 10 ° with respect to the edge parallel to the light source of the light guide. Then, the backlight was assembled.

The front brightness of the emitted light was measured using the obtained backlight. The results are shown in Table 1 and FIG. 5 together with the luminance ratio when the luminance is 1 when the tilt angle is 0 degree (Comparative Example 1). Further, a 168 μm (parallel to the light source) × 259 μm TFT is formed on the prism sheet.
The liquid crystal display device was assembled by mounting the liquid crystal display element so that the ridge lines of the prism array had an angle (tilt angle) of 10 ° with respect to the pitch line between pixels of the liquid crystal display element. When an image was observed using the obtained liquid crystal display device, a bright image free from the moire phenomenon was obtained.

Example 3 A prism sheet having a refractive index of 1.59 and an apex angle of 95 ° was obtained in the same manner as in Example 1. Then, 100 mm × 90 mm so that the ridgeline of the prism array forms an angle of 13 ° with the edge.
It was cut into a rectangular shape of mm. The same light guide as in Example 1 was used, and a diffusion film (Kimoto D
113) and the prism sheet having an apex angle of 95 ° faces upward, and the ridgeline of the prism array has an angle (inclination angle) of 13 ° with respect to the edge parallel to the light source of the light guide. Then, the backlight was assembled.

The front brightness of the emitted light was measured using the obtained backlight. The results are shown in Table 1 and FIG. 5 together with the luminance ratio when the luminance is 1 when the tilt angle is 0 degree (Comparative Example 1). Further, a 168 μm (parallel to the light source) × 259 μm TFT is formed on the prism sheet.
The liquid crystal display device was assembled by mounting the liquid crystal display element so that the ridge lines of the prism array had an angle (inclination angle) of 13 ° with respect to the pixel pitch line of the liquid crystal display element. When an image was observed using the obtained liquid crystal display device, a bright image free from the moire phenomenon was obtained.

Comparative Example 1 A prism sheet having a refractive index of 1.59 and an apex angle of 95 ° was obtained in the same manner as in Example 1. Next, 100 mm x 90 m so that the ridgeline of the prism array forms an angle of 0 ° with the edge.
It was cut into a rectangular shape of m. The same light guide as in Example 1 was used, and a diffusion film (D31 manufactured by Kimoto Co., Ltd.) was formed on the emission surface.
1) is mounted, and the prism sheet having an apex angle of 95 ° is directed upward, and the ridgeline of the prism row has an angle (inclination angle) of 0 ° with respect to the edge parallel to the light source of the light guide. Then, the backlight was assembled.

Using the backlight thus obtained, the front luminance of emitted light was measured and is shown in Table 1. The front luminance was set to 1 and used as a reference for comparison with others. Further, a 168 μm (parallel to the light source) × 259 μm TFT type liquid crystal display element is provided on the prism sheet, and the ridge line of the prism row is an angle of 0 ° (tilt angle) with respect to the pixel pitch line of the liquid crystal display element.
A liquid crystal display device was assembled by mounting the liquid crystal display device. When an image was observed using the obtained liquid crystal display device, moire was generated between the ridgelines of the prism rows of the prism sheet and the pixel pitch lines of the liquid crystal display element, and the image was difficult to see.

Comparative Example 2 A prism sheet having a refractive index of 1.59 and an apex angle of 95 ° was obtained in the same manner as in Example 1. Then, 100 mm x 90 m so that the ridgeline of the prism array forms an angle of 2 ° with the edge.
It was cut into a rectangular shape of m. The same light guide as in Example 1 was used, and a diffusion film (D31 manufactured by Kimoto Co., Ltd.) was formed on the emission surface.
1) is mounted, and the prism sheet having an apex angle of 95 ° faces upward, and the ridge line of the prism column has an angle (inclination angle) of 2 ° with respect to the edge parallel to the light source of the light guide. Then, the backlight was assembled.

The front luminance of emitted light was measured using the obtained backlight. The results are shown in Table 1 and FIG. 5 together with the luminance ratio when the luminance is 1 when the tilt angle is 0 degree (Comparative Example 1). Further, a 168 μm (parallel to the light source) × 259 μm TFT is formed on the prism sheet.
The liquid crystal display device was assembled by mounting the liquid crystal display element so that the ridge lines of the prism array had an angle (tilt angle) of 2 ° with respect to the pitch line between pixels of the liquid crystal display element. When an image was observed using the obtained liquid crystal display device, moire was generated between the ridgelines of the prism rows of the prism sheet and the pixel pitch lines of the liquid crystal display element, and the image was difficult to see.

Comparative Examples 3 to 6 In the same manner as in Example 1, prism sheets having a refractive index of 1.59 and an apex angle of 95 ° were obtained. Next, five types of 100 mm × 90 mm rectangles were cut so that the ridges of the prism rows were at angles of 15 °, 30 °, 45 °, 60 °, and 90 ° with respect to the edges. Using the same light guide as in Example 1, a diffusion film (D113 manufactured by Kimoto Co.) was placed on the exit surface of the prism, and five types of prism sheets with an apex angle of 95 ° were used so that the prism rows face upward. The ridges of the rows are 15 °, 30 °, and 4 with respect to the edges parallel to the light source of the light guide.
The backlight was assembled by mounting the backlight at angles of 5 °, 60 ° and 90 ° (tilt angle).

The front brightness of the emitted light was measured using the obtained backlight. The results are shown in Table 1 and FIG. 5 together with the luminance ratio when the luminance is 1 when the tilt angle is 0 degree (Comparative Example 1). Further, a 168 μm (parallel to the light source) × 259 μm TFT is formed on the prism sheet.
Type liquid crystal display device, in which the ridge lines of the prism array are 15 °, 30 °, 45 °, 60 with respect to the pitch line between pixels of the liquid crystal display device
A liquid crystal display device was assembled by mounting the liquid crystal display device at an angle of 90 ° (tilt angle). When an image was observed using the obtained liquid crystal display device, no moire phenomenon was observed.

[0037]

[Table 1]

As is clear from Table 1 and FIG. 5, in Examples 1 to 3, the ridge lines of the lens rows of the lens sheet and the inter-pixel pitch lines of the liquid crystal display element were hardly reduced while reducing the front brightness of the backlight. It is possible to suppress the moire phenomenon between the two. On the other hand, in Comparative Examples 1 and 2 in which the ridge lines of the lens rows were mounted so as to have an angle of less than 3 degrees with respect to the edge of the light guide and the pitch line between pixels of the liquid crystal display element, Although the front brightness did not decrease, moire occurred between the ridge lines of the prism rows of the prism sheet and the pixel pitch lines of the liquid crystal display element, and the image was difficult to see. Further, in Comparative Examples 3 to 6 mounted such that the ridge lines of the lens rows have an angle of more than 10 degrees with respect to the edges of the light guide and the pixel pitch lines of the liquid crystal display element, the front brightness of the backlight is lowered. Will be invited.

[0039]

According to the present invention, the lens sheet is mounted such that the ridge lines of the lens rows form an angle of 3 to 13 degrees with respect to the edges of the light guide and the pixel pitch lines of the liquid crystal display element. As a result, it is possible to provide a backlight and a liquid crystal display device that can suppress the moire phenomenon between the ridge lines of the lens rows of the lens sheet and the pixel pitch lines of the liquid crystal display element without lowering the brightness of the backlight. is there.

[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 schematic view showing the relationship between the lens sheet of the present invention and a light guide.

FIG. 3 is a perspective view showing a configuration example of a liquid crystal display device of the present invention.

FIG. 4 is a schematic view showing the relationship between the lens sheet of the present invention and a liquid crystal display device.

FIG. 5 is a graph showing front luminance ratios of backlights of Examples and Comparative Examples.

[Explanation of symbols]

 1 ... Backlight 3 ... Prism sheet 3 ... Light guide 4 ... Light source 5 ... Diffusion sheet 6 ... Reflective layer 7 ... Liquid crystal display element 8 ... Liquid crystal display device

Claims (2)

[Claims] 1. A light source, a light guide having at least one light entrance surface facing the light source and a light exit surface substantially orthogonal to the light entrance surface, and at least one mounted on the exit surface side of the light guide. Is formed of at least one lens sheet having a lens surface in which a large number of lens rows are formed in parallel with each other,
A backlight, wherein the ridge lines of the lens rows of the lens sheet are formed at an angle of 3 to 13 degrees with respect to the edge of the light guide. 2. A light source, a light guide having at least one light entrance surface facing the light source and a light exit surface substantially orthogonal to the light entrance surface, and at least one mounted on the exit surface side of the light guide. Is formed of at least one lens sheet having a lens surface in which a large number of lens rows are formed in parallel with each other, and a liquid crystal display element arranged on the lens sheet. A liquid crystal display device, which is formed at an angle of 3 to 13 degrees with respect to a pitch line between pixels of a display element.