JP2003066238A - Light transmission body, surface light source device and front light device and liquid crystal display device employing the light transmission body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device and a front light device each of which has high illumination efficiency while keeping proportionality in a picture, a small number of members, excellent assemblability and is low-cost and also to provide a light transmission body to be used for them and a liquid crystal display device employing it. SOLUTION: A material with 0%-35% haze in 1 mm thickness based on ASTM D1003 is used for the light transmission body 11 where at least one side end part 11a is adopted as a light incident surface and one front surface is as a light emitting surface 11b. A light extracting mechanism 170 which is constituted of many recessions 17 consisting of a flat and smooth surface on the opposing surface 11c of the light emitting surface 11b of the light transmission body 11 in order to uniformize an outgoing light amount on the light emitting surface 11b. A dome shape is adopted in the cross section of each recession 17 in a direction 21 for mainly propagating a light beam and also the selection ratio of the outgoing light amount in the direction of the normal 14 of the light emitting surface 11b in the light transmission body 11 is within the range of 65%-100%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide, a surface light source device using the light guide, a front light device, and a liquid crystal display device. More specifically, the present invention relates to a surface light source device having a light guide and an optical device for the front light device. The present invention relates to a technology for making a system thin and simple, and a liquid crystal display device using the surface light source device as a backlight optical system and a front light optical system.

[0002]

2. Description of the Related Art Recently, a transmissive liquid crystal display device has been widely used as a display device for a monitor for a personal computer or a flat-screen TV. In such a liquid crystal display device, a liquid crystal display device is usually provided on the back surface of a liquid crystal element. A planar illumination device, that is, a backlight (surface light source device) is provided.
This surface light source device has a mechanism for converting a linear light source such as a cold cathode discharge tube into a surface light.

Specifically, a method of disposing a light source directly below the back surface of a liquid crystal element or a method of disposing a light source on a side surface and converting light into a planar shape using a translucent light guide such as an acrylic plate is used. A typical method is to obtain a surface light source (sidelight system), and since a sidelight type is suitable as a surface light source which is particularly thin and has excellent uniformity of luminance distribution, it has been put to practical use in many cases.

The conventional side light type surface light source device is
Typically, as shown in FIG. 32, a linear light source 2 is arranged on one side end 1a of a substrate made of a light-transmissive flat plate, that is, one side end 1a of the light guide 1. The reflector 3 is attached so as to cover the light source 2, and the direct light from the linear light source 2 and the reflected light reflected by the reflector 3 are guided to the light guide 1.
The mechanism is such that light is incident from the one side end portion (light incident surface) 1a which is the light incident end surface.

One surface 1b of the light guide 1 is used as a light emitting surface, and a light control sheet 5 having a substantially triangular prism-shaped condensing element array 4 is formed on the light emitting surface 1b with the apex angle facing the observer. On the other hand, a large number of dots 6 made of light-scattering ink are provided on the surface 1c of the light guide 1 opposite to the light emitting surface 1b.
A light extraction mechanism 6 formed by printing and forming a in a predetermined pattern is provided.

On the side of the surface 1c opposite to the light emitting surface 1b of the light guide body 1 in which such a light extraction mechanism 6 is formed, a light reflection sheet 7 is arranged close to the surface 1c. There is. Further, as another typical example of this type of surface light source device, as shown in FIG. 33, a light control sheet 5 on which a converging element array 4 having a substantially triangular prism shape is formed has the apex angle of the light guide body 1.
Is disposed on the light emitting surface 1b toward the light emitting surface 1b side.

The light extraction mechanism 6 provided on the surface 1c of the light guide 1 opposite to the light emitting surface 1b is composed of a pattern of a large number of rough surface portions 6b each having a rough surface. There is. Since such a side light type surface light source device can more effectively bring out the general features of the liquid crystal display device such as light weight and thin shape, it has been widely used as a backlight of a liquid crystal display device such as a portable personal computer. It was

[0008]

However, the side light type surface light source device used in the conventional transmissive liquid crystal display device has a problem that the structure is still complicated, and it is difficult to obtain desired optical characteristics. Since no illumination optical system having a simpler structure and excellent light utilization efficiency has been obtained, the structure of the surface light source device has to be complicated, resulting in high cost, and this type of liquid crystal display device. Was hindering the spread of

More specifically, in the surface light source device shown in FIGS. 32 and 33, in order to make effective use of illumination light as much as possible, a large number of light-collecting optical sheets such as prism sheets, which are difficult to produce, are frequently used. Was. Therefore, the structure of the illumination optical system becomes complicated, the number of parts increases, and as a result, the assemblability is poor and the yield is also adversely affected, resulting in high cost.

As another problem, when the prism sheet is used to condense the illumination light beam, as shown in the angular distribution of the intensity of the emitted light in FIG.
Since the amount of light attenuates and then becomes bright again, the brightness of the image changes rapidly, giving a very unnatural impression as a display device (darkening phenomenon).

As another problem, if many optical sheets such as a prism sheet are used, many air-plastic interfaces will be present in the illumination optical system of the surface light source device. The amount of light loss due to interfacial reflection becomes so non-negligible that the efficiency is essentially limited, and if an antireflection coating is applied to prevent this, the system itself becomes expensive this time.

To solve these problems, Japanese Patent Laid-Open No. 5-224
As disclosed in Japanese Patent No. 019, it has been attempted to form a V-groove shape in the light guide body so that the light beam propagating in the light guide body is emitted in the front direction to keep the front brightness high. However,
In the conventional method of simply forming the V groove in the light guide body to increase the front luminance, a large amount of light is lost and the optical efficiency cannot be sufficiently increased. There was no problem.

In addition, there is a problem that it is difficult to maintain a high degree of image uniformity (ratio without unevenness in light amount), which is one of the most important qualities of a display device. The image quality when used as a light device was insufficient. In addition, since the V groove has to be formed by simple machining, it takes time to manufacture the light guide body, and in the case of a large liquid crystal display device, the light guide body is completed within a practically practical time. However, it is difficult to form the fine pattern and it is difficult to form a fine pattern.

Further, in the conventional surface light source device, the light extraction mechanism 6 utilizing the light scattering phenomenon represented by the light scattering ink or the rough surface 6c is provided in the light guide body 1.
The light ray 8 propagating inside interacts with the light-scattering fine particles and the rough surface 6c and is redirected as shown in FIG. 34 so that it can no longer remain inside the light guide body. It was radiating outside 1.

However, in the extraction of light by such a method, firstly, as shown in FIG. 34, since the emitted light rays are emitted through a randomly generated scattering process, the emission angle distribution of the luminous flux that is spontaneously emitted. However, there is a problem in that it is difficult to produce a luminous flux having a strong outgoing light intensity in a specific direction, and it is difficult to maintain high brightness in a certain direction.

In addition, in the outgoing light flux generated by light scattering, as shown in FIG. 29, the peak position of the outgoing light intensity usually comes in the diagonally forward direction, so that the prism array is arranged. Since it is necessary to direct the illumination light to the front using a lens sheet (condensing sheet), etc.,
There is a problem that it is difficult to omit these sheets and the structure of the surface light source device becomes complicated.

Further, in the extraction of light by the light scattering process, as shown in FIG. 35, a large number of scattering phenomena locally occur when seen microscopically, so that the scattered light rays cancel each other out. There is also a problem that the strength is reduced and the loss is large (multiple scattering loss occurs).
As described above, the light extraction due to the scattering phenomenon is naturally limited, and efficient light extraction cannot be achieved unless these limits are overcome.

The object of the present invention is to solve the above-mentioned conventional problems, and it is possible to obtain a high illumination efficiency while maintaining a high degree of image uniformity, a small number of members, and an excellent assembling property. A low-cost surface light source device and a front light device, and a liquid crystal using the surface light source device as a backlight optical system and a front light device as a front light device, and a light guide for these devices. It is to provide a display device.

[0019]

The present invention is a light guide,
In order to solve the above-mentioned technical problem, it is configured as follows. That is, the present invention is a light guide body having at least one side end portion as a light incident surface and one surface as a light emitting surface, and the light guide body has a haze of 0 at 1 mm based on ASTM D1003. % To 35% of the material is used, and a light extraction mechanism is formed by arranging a large number of recesses made of smooth surfaces on the surface of the light guide opposite to the light emitting surface in order to equalize the amount of light emitted from the light emitting surface. Is provided, the cross section of the recessed portion in the direction in which the light rays mainly propagate is dome-shaped, and the selection ratio of the emitted light amount with respect to the normal direction of the light emitting surface of the light guide is in the range of 65% to 100%. Is characterized by.

<Concrete Structure of the Present Invention> The light guide of the present invention is composed of the above-mentioned essential components, but is also established even when the components are specifically as follows.
The specific element is that the ratio H / W is 0 when the width of the dome-shaped recess is W and the height of the recess is H in the cross section in the direction in which the light rays mainly propagate in the recess. It is characterized in that the range is from 10 to 0.87.

Further, in the light guide of the present invention, it is also preferable that the arrangement pitch of the recesses is irregularly changed. Furthermore, the lengths of the multiple recesses that make up the light extraction mechanism are increased in a uniaxial direction as the distance from the light source increases, and in that case, the uniaxial direction in which the length increases is substantially perpendicular to the direction in which the light rays mainly propagate. Preferred direction.

In the light guide of the present invention, it is preferable that a large number of recesses forming the light extraction mechanism are arranged in a dot shape, a mesh shape, or a combination thereof, and further, on the light emitting surface of the light guide. , The ridge line is in a direction substantially perpendicular to the side end portion on which the light source is arranged, and the pitch is 1 μm to 50
It is also preferable to provide a condensing element having a thickness of 0 μm. In this case, the light collecting element provided in the light guide has a pitch of 10 μm.
It is preferable that the triangular prism array has an m-150 μm angle and an apex angle of 70 ° -160 °.

Further, the present invention is a surface light source device, which is configured as follows in order to solve the above-mentioned technical problems. That is, the present invention provides a light guide having any of the features described above, a light source arranged near a side end of the light guide, and a light guide arranged on the side facing the light emitting surface of the light guide. A surface light source device comprising the above described light reflection sheet, wherein the light reflection sheet is made of a diffuse reflective material.

<Specific Configuration of the Present Invention> The surface light source device of the present invention is composed of the above-mentioned essential components, but is also established even when the components are specifically as follows. The specific elements are that the width W of the recesses constituting the light extraction mechanism is 2000 μm or less, and the pitch of the recesses is 4000 μm or less, and the components are arranged below the transmissive or semi-transmissive liquid crystal panel for use. Is characterized by.

Further, in the surface light source device of the present invention, the light reflection sheet has a basic unit of a substantially similar shape having a light reflection surface inclined at an inclination angle of 7 to 50 degrees with a pitch of 5000 μm.
It is characterized in that a plurality of them are arranged below and the main reflection direction of the basic unit is substantially constant.

Further, in the surface light source device of the present invention, it is preferable that the light reflecting surface provided in the basic unit is made of a metal material, and a protective layer made of a transparent insulating material is provided on the light reflecting surface. In this case, silver or aluminum is preferable as the metal substance, while the resistivity of the protective layer made of the transparent insulating substance is preferably 1.0 × 10 6 Ω · cm or more.

Furthermore, in the surface light source device of the present invention, the surface of the light reflecting sheet is covered with a light transmissive material, and the irregularities due to the many inclined light reflecting surfaces are embedded with the light transmissive material. preferable. Then, it is preferable to provide a printing pattern on the surface of the light reflecting sheet which is made substantially flat by embedding the light transmitting substance in the irregularities of the basic unit.

Further, the present invention is a front light device, which is configured as follows in order to solve the above-mentioned technical problems. That is, the present invention is a front light device including a light guide body having any one of the above-mentioned features and a light source arranged near a side end portion of the light guide body, which constitutes a light extraction mechanism. The width W of the recess is 50 μm
It is characterized in that the arrangement pitch of the recesses is 800 μm or less, and the recesses are arranged above the reflective liquid crystal panel.

<Specific Configuration of the Present Invention> The front light device of the present invention is composed of the above-mentioned essential components, but is also established even when the components are specifically as follows. The specific elements are the light emitting surface of the light guide,
It is characterized by being subjected to antireflection processing so that the light reflectance at a wavelength of 550 nm is 2% or less.

The present invention also uses a surface light source device having any of the above-mentioned features as a backlight optical system or a front light device as a front light optical system to solve a conventional technical problem. But also.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The light guide according to the present invention and the surface light source device, front light device and liquid crystal display device using the same will be described in more detail based on the embodiments shown in the drawings. 1 is a partial perspective view schematically showing a main part of a surface light source device 10 according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line 2-2 of FIG. It is sectional drawing which shows the cross section of 10 roughly.

The surface light source device 10 according to this embodiment is provided with a substrate, that is, a light guide body 11 made of a light-transmissive flat plate, and one end portion 11a of the light guide body 11 is arranged along the side end surface thereof. A linear light source 12 is arranged. This linear light source 12
A fluorescent tube, an LED array, or the like can be used, but it is not particularly limited thereto. As the linear light source 12, it is most preferable to use a cold cathode tube which is excellent in luminous efficiency and which can be easily miniaturized.

The arrangement of the linear light source 12 is as follows.
However, the present invention is not limited to this mode. In addition to this, a one-lamp type mode in which a cold cathode tube is provided only at one side end, and two cold cathode tubes are provided at one side end Two-lamp type, one or two cold-cathode tubes are arranged at one side end, and this is also provided at the opposite side ends, for a total of two or four lights. Other typical examples are those in which light sources are arranged at three or four side end portions.

Further, the aspect of the light source is not limited to the linear light source in the present invention. For example, in a small surface light source device, a point light source such as an LED is used as shown in FIG. You can also That is, FIG.
An example is shown in which the LED 12a as a point light source is arranged on a corner cut surface 11d formed by cutting the corner portion of the light guide 11 in a triangular shape when seen in a plan view. Also, FIG.
(B) shows an example in which the optical rod 12b is arranged in close proximity to one end of the light guide 11, and the LED 12a which is a point light source is arranged on the end face of the optical rod 12b.

A reflector 13 is attached to one end 11a of the light guide 11 so as to cover the linear light source 12, and direct light from the linear light source 12 and reflected light reflected by the reflector 13 are guided. The mechanism is such that light is incident on the inside of the light body 11 from one side end portion 11a which is a light incident end surface.

The light guide 11 has, for example, a plate thickness of about 2 to 4 m.
1 is a light-transmitting thin plate having a rectangular shape of about m, and one surface which is an upper surface in FIGS. 1 and 2 is a light emitting surface 11b which emits light, and the other surface on the opposite side ( The lower surface (as viewed in FIGS. 1 and 2) is a surface 11c that faces the light emitting surface 11b. In FIG. 2, reference numeral 14 is a light emitting surface 1 of the light guide 11.
A line perpendicular to 1b, that is, a normal line of the light guide 11 is shown.

When the surface light source device of the present invention is used as a backlight of a liquid crystal display device, the light guide 11 is used.
The light reflection sheet 15 is disposed close to the surface 11c side opposite to the light emitting surface 11b. Here, the light reflection sheet 15
Is not particularly limited as long as it has a high light reflectance, for example, a foamable thermoplastic resin film, a thermoplastic resin film in which a white pigment or a fluorescent whitening agent is kneaded, a thermoplastic resin in which silver or aluminum is deposited. A film or the like is typical.

In the present invention, the light reflecting sheet 15 is also used.
Particularly preferably, as shown in FIG. 1, a large number of basic units 16 having inclined light reflecting surfaces 16a are formed on the surface of the base material 30 (see FIGS. 26 and 31) at a fine pitch. It Here, the basic unit 16 means a basic shape unit of the light reflection sheet 15 obtained as an assembly of inclined light reflection surfaces 16a having substantially the same and / or substantially similar shapes as shown in FIGS. 7 to 14. To do.

That is, the basic unit 16 is a so-called unit cell, which is the smallest shape unit whose identity or similarity disappears when it is further divided. The pitch P1 is defined as the minimum length of the basic period created by the arrangement of the basic units 16 as shown in FIGS. Basic unit 16 like this
The advantage of using the light reflection sheet 15 having the arrangements will be described later.

The illumination light beam incident from the one end portion 11a of the light guide 11 is provided with the light extraction mechanism 17 provided in the light guide 11.
However, the light extraction mechanism 170 used in the present invention is similar to a mode in which a light-scattering ink is printed or a pattern in which a rough surface is patterned, which is often found in conventional surface light source devices. Unlike the structure that utilizes the general light scattering phenomenon, the structure is extremely efficient using the total reflection phenomenon.

That is, in the present invention, as the light extraction mechanism 170, a recessed portion having a dome-shaped cross section as shown in FIG. 1 (hereinafter referred to as a dome-shaped recessed portion) 17
5 are formed in a dot shape or in a mesh shape as shown in FIG. 5 on the surface 11c of the light guide 11, and the surface of the dome-shaped recessed portion 17 is a smooth surface to prevent the total reflection phenomenon. It is supposed not to happen.

As a result, as shown in FIG. 16 (a), many illumination light rays pass through the locus as shown by reference numeral 18, and many light rays are emitted toward the front direction of the light guide 11. Therefore, compared to the conventional light extraction mechanism 6 utilizing light scattering as shown in FIG. 34, the brightness in the front direction can be kept much higher. Further, the loss of light amount due to multiple scattering can be brought close to zero as long as the smoothness of the dome-shaped recessed portion 17 is kept high. From this point as well, it can be said that it is convenient for improving the optical efficiency.

Here, surface roughness or the like may be used as an index for evaluating the smoothness of the dome-shaped recessed portion 17, but most preferably, as shown by a ray trace 19 in FIG. 15 (b). It is preferable to quantify using the ratio of the light ray 19a emitted in the total reflection mode. That is, the dome-shaped recess 1
If the smoothness of No. 7 is sufficiently maintained, as shown in FIG. 15 (a), a large amount of light rays 18a are emitted in the normal direction to the light emitting surface 11b side of the light guide, but the light emitting surface 11b Almost no illuminating light beam is emitted in the direction of the normal to the facing surface 11c.

On the other hand, when the smoothness of the dome-shaped recess 17 is insufficient, light scattering occurs in the dome-shaped recess 17 as shown in FIG. This is because the illumination light ray 19a is also emitted in the normal direction on the surface 11c side facing 11b, and the dome required as the light guide 11 depends on the ratio of the luminance of the light guide 11 to the normal direction. This is because the smoothness of the concave portion 17 can be properly evaluated.

Specifically, the black sheet 20 having a light reflectance of 5% or less is arranged at the position where the normal light reflecting sheet 15 is arranged, and as shown in FIG. 17A, the light emitting surface 11b of the light guide body is formed. The brightness in the normal direction near the center is measured and set as LN (photometric distance 500 mm, photometric angle 2 °). Next, the light guide 11 is turned upside down, and the luminance is similarly measured so that the light emitting surface 11b is on the black sheet 20 side, as shown in FIG.
And Using LN and LA measured in this way

[Equation 1] Is calculated as a selection ratio λ of the amount of emitted light with respect to the normal direction of the light emitting surface 11b of the light guide 11, and the λ is at least 65%.
-100%, preferably 75% -100%, more preferably 85% -100%, very preferably 90% -1.
00%, most preferably 95% to 100%,
By maintaining the smoothness of the light extraction mechanism 170, it is possible to obtain an ideal light extraction mechanism 170 that fully utilizes the emitted light in the total reflection mode.

The cross-sectional shape of the dome-shaped recessed portion 17 suitable for efficiently directing the emitted light in the front direction is as follows.
With respect to a cross section in the main traveling direction (direction perpendicular to the side end 11a where the light source 12 is arranged) 21 of the light beam shown in FIG.
When the width of the dome-shaped recessed portion 17 is W and the height of the dome-shaped recessed portion 17 is H as shown in FIG.
The ratio H / W is preferably 0.10 to 0.87, more preferably 0.15 to 0.68, and even more preferably 0.1.
It is set to 20 to 0.50. By taking such a range, it becomes possible to efficiently emit the illumination light beam in the front direction.

By the way, conventionally, a light extraction mechanism having a V-shaped cross section is formed on the surface of the light guide facing the light emitting surface.
An attempt was made to draw a ray as shown in FIG. 6 (a) and emit a light beam in the front direction. However, with a cross-sectional shape having a sharp apex such as a V-groove shape, it is difficult to maintain the processing accuracy at the apex, so light scattering or stray light occurs at the sharp portion, and the normal direction of the light-emitting surface is generated. There is a problem that the selection ratio of the emitted light amount is adversely affected and a sufficient selection ratio cannot be obtained.

Moreover, when the light guide provided with the light extraction mechanism having the V-groove shape in cross section is used as the front light device of the reflection type liquid crystal panel, the illuminating light beam directly reaches the observer. Therefore, when the front light device is turned on, the V groove portion looks bright and shining, which adversely affects the appearance and lowers the contrast. This problem is more serious.

Further, the machining of the die for forming the V-groove shape is generally performed by mechanical shaving using a diamond bite, but it is extremely difficult to machine a large area in a short time by such a method. It is difficult, and there is also a problem that it becomes difficult to uniformize the unevenness of brightness, which is one of the most important characteristics as a surface light source device. It was difficult to say that a sharp cross-sectional shape such as a V groove is suitable for practical use in terms of optical characteristics and productivity.

On the other hand, in the mode in which a large number of dented portions 17 having a dome-shaped cross section are arranged in a dot shape and / or a mesh shape like the light guide body 11 of the present invention, since there are no sharp vertices, It does not adversely affect the selection ratio λ of the emitted light amount, and particularly when used as a light guide for the front light device, the dome-shaped recessed portion 17 does not shine brightly and is not conspicuous. An image with high contrast can be obtained.

Further, since a die for transferring and molding the dome structure can be prepared by a method of forming a fine pattern using photolithography with high accuracy and efficiency, manufacturing is also performed from this point. It is much more practical than the difficult V-shaped cross-section structure.

Specifically, first, as shown in FIG. 18, a substrate (for example, copper, brass, nickel or the like) is preferably made of a metal material having excellent adhesiveness to a substance such as nickel which can be electroplated. However, a substrate obtained by coating (plating) copper or the like on stainless steel or the like) 40 is used, and the photoresist layer 41 is directly formed on the surface of the metal substrate 40.
To form.

At this time, the resist layer 41 is preferably as thin as possible, preferably 10 μm or less, and more preferably 5 μm or less. Next, the photomask 42 in which the light-shielding pattern is drawn at the position where the recess is to be formed is shown in FIG.
As shown in FIG. 18A, the photoresist 41 is placed on the photoresist 41, and a desired pattern is exposed and developed on the photoresist 41. As shown in FIG. 18B, the resist 41 is provided at a position other than the recess forming position. To remain.

Then, the metal substrate 40 on which the resist 41 remains is electrodeposited (electroplated) to deposit the metal 43 only on the exposed portion of the metal, and further the electrodeposition proceeds beyond the layer thickness of the photoresist 41. 18
As shown in (c), a dome-shaped protrusion can be formed. The electrodeposition is stopped after the desired H / W ratio is reached.

That is, since the resist 41 has no electrical conductivity, the resist layer 4 is selectively plated only on the exposed portion of the metal substrate 40 and is masked.
When the electrodeposition exceeds 1 thickness, the growth in the horizontal direction also proceeds at the same time, so that the dome-shaped structure can be easily formed.

Moreover, since a fine pattern can be formed by photolithography, it is much faster than mechanical processing, and there is a merit that even a high-definition pattern that does not appear as a dot exceeding 1 million dots can be easily created. is there. This is an extremely great advantage when used as a light guide for a large-sized liquid crystal display exceeding 10 inches.

Further, the cross section V seen in the conventional light guide is
With the groove shape, when molding by the injection molding method usually used for molding light guides, heat shrinkage tends to cause bite to the mold, and warp such as warp remains unfavorable as an optical component when removed from the mold. Therefore, there is a problem in that it is not practical to mold a light guide for a large-sized liquid crystal display. However, when the shape of the light extraction mechanism having a dome-shaped cross section and a smooth surface according to the present invention is transferred, such a problem is caused. From this point, it can be said that it is extremely practical because no problems occur.

In this way, electrodeposition (electroplating) is performed so that the metal 43 is deposited on the exposed metal portion of the metal substrate 40 where the resist 41 remains, and further, the photoresist 41.
After forming a dome-shaped projection by advancing electrodeposition over the layer thickness of, the residual resist 41 is peeled off to obtain a mold. In order to secure strength, after removing the resist,
The plating 44 may be applied as shown in FIG.

Since the light guide of the present invention is used as a backlight light source means of an image display device such as a liquid crystal display device, the dot-shaped and / or mesh-shaped dome-shaped recessed portion 17 which is the light extraction mechanism 170 can be visually recognized. It must be miniaturized to a difficult degree. Specifically, for example, as a light guide of a backlight disposed below a transmissive or semi-transmissive liquid crystal panel, the width W of the dome-shaped recess 17 with respect to the main traveling direction of light rays is preferably 200.
The thickness is 0 μm or less, more preferably 1000 μm or less, and further preferably 500 μm or less. The arrangement pitch P2 of the dome-shaped recessed portions 17 is preferably 4000 μm or less, more preferably 2000 μm or less, still more preferably 1000 μm or less.

Further, as shown in FIG. 19, when the light guide 11 is arranged above the reflection type liquid crystal panel 50 and is used as a front light device, the width W of the dome-shaped recess 17 is increased.
Is preferably 50 μm or less, more preferably 30 μm
Hereafter, the thickness is more preferably 20 μm or less. Also,
The arrangement pitch P2 of the dome-shaped recessed portions 17 is preferably 8
The thickness is 00 μm or less, more preferably 500 μm or less, and further preferably 300 μm or less.

In addition, the light guide 11 according to the present invention is shown in FIG.
When used as a component of the front light device as shown in FIG.
It is preferable that an antireflection coating, that is, an antireflection coating layer 22 is provided so that the light reflectance at 0 nm is 2% or less. The mode of the antireflection treatment is not particularly limited, but typically, there are a mode in which the light guide 11 is directly subjected to vacuum deposition and sputtering, and a mode in which the film subjected to the antireflection process is attached to the light guide 11. Is typical.

In the light guide of the present invention, the arrangement pitch P2 of the dome-shaped recessed portions 17 arranged as the light extraction mechanism 170 causes an optical interference phenomenon with the liquid crystal panel 50 as shown in FIG. It is preferable that they are arranged irregularly so as not to exist. This is the case where it is used as a front light device, and even when it is a backlight device.
This is particularly effective when the number of sheets is not so large on the first light emitting surface 11b.

Further, especially in the case of the front light device arranged on the upper part (front surface) of the reflection type liquid crystal panel 50, it is extremely important to consider the problem of interference with the liquid crystal panel 50, and the arrangement pitch P2 is also RGB. It is determined in consideration of the arrangement pitch P3 of the stripes 51a, 51b, 51c.

That is, as shown in FIG. 19, the recessed portion 1 is formed in a direction substantially parallel to the RGB stripes 51a, 51b, 51c of the color filter arranged on the liquid crystal panel 50.
When forming the dome part of 7, RGB stripe 5
1a, 51b, 51c pitch P3, the pitch P2 of the dome-shaped recessed portion 17 is preferably 0.588-0.
909 times or 1.1 to 1.7 times, more preferably 0.769 to 0.909 times or 1.1 to 1.3 times.
The range is preferably double, more preferably 0.833 to 0.893 or 1.12 to 1.2.

In the light guide of the present invention, a light-extracting mechanism has a dome-shaped cross section in the direction 21 in which light rays mainly propagate, and a recessed portion formed of a smooth surface formed in a dot shape and / or a mesh shape. As described above, in No. 17, it is possible to efficiently extract the illumination light beam 18 in the front direction by total reflection on a smooth slope portion, as shown in FIG. 16A, not by light scattering with large loss. On the street.

Among these, the light extraction mechanism 17 which is particularly excellent in the uniformity (controllability) of the luminance distribution in the light emitting surface 11b.
0 is a dome-shaped recess 17 as shown in FIGS.
Is arranged in a dot shape, and the dot shape can be finely controlled, so that the luminance distribution of the display can be accurately and uniformly maintained.

At this time, it is particularly preferable to change the shape of each dome-shaped recess 17 arranged in a dot pattern as shown in FIG.
As shown in 0 (a), along the direction substantially perpendicular to the direction 21 in which the illumination light rays mainly propagate with distance from the light source 12, that is, the direction substantially parallel to the side end portion 11a where the light source 12 is arranged. In this embodiment, the length of the dome-shaped recessed portion 17 changes in the uniaxial direction, and such a shape change keeps the ratio H / W substantially constant irrespective of the distance from the light source 12. The brightness distribution can be finely controlled while maintaining high light beam utilization efficiency, and a high quality surface light source can be obtained.

As described above, the light guide body of the present invention has a high emission efficiency of the illumination light beam and a liquid crystal panel 50 which is required to have high brightness.
As described above, it is extremely suitable as the light guide for the backlight device, but in order to further increase the illumination efficiency of the light guide according to the present invention, as shown in FIG. It is desirable that the light condensing element 23 is provided on the light emitting surface 11b side of the optical body 11.

At this time, the light condensing element 23 is arranged in the light guide 1.
1 should be arranged so as not to interfere with the propagation of the light flux in 1 as much as possible, and as shown in FIGS. 3 (a), 22 and 23, triangular prism array 24a,
Lenticular lens array 25a, corrugated plate array 26
The light condensing element 23 such as a is arranged in each of the arrays 24a to 26a.
The ridge lines 24b to 26b are arranged so as to be in a direction substantially perpendicular to the side end 11a where the light source 12 is arranged.

Particularly preferably, a fine triangular prism array 24a is arranged as shown in FIG. 3A, and the arrangement pitch P4 of the triangular prism array 24a is also preferable.
Is preferably 10 μm to 150 μm, more preferably 2
0 μm to 100 μm, more preferably 30 μm to 70
.mu.m, and as shown in FIG. 3B, the climbing angle .beta. of the triangular prism array 24a is preferably 70 degrees to 16 degrees.
The range is 0 degrees, more preferably 80 degrees to 150 degrees, and further preferably 85 degrees to 145 degrees. As a result, the dome-shaped recessed portion 17 having a smooth surface according to the present invention sufficiently collects the outgoing luminous flux directed in the front direction, and it is possible to further enhance the illumination efficiency in the front direction.

In the surface light source device using the light guide according to the present invention, when it is used as a backlight of the liquid crystal panel 50, the light reflection sheet 15 is provided as described above, but in particular, foaming is performed. It is preferable to use a light reflection sheet having light diffusive reflectivity such as a transparent polyester film, a polyester film in which a white pigment is kneaded, a matte-treated silver reflection film, and a silver reflection film coated with acrylic beads.

As shown in FIG. 16B, which shows the dome-shaped recessed portion 17 in an enlarged manner, this directly impinges on the dome slope of the dome-shaped recessed portion 17, and the total reflection condition is no longer satisfied. This is because there is an illumination light component 27 that cannot be emitted and is emitted.
If a light reflecting sheet 60 having a specular light reflecting surface 60a like a mirror is used, as shown in FIG. 21 (a), the light is emitted obliquely forward and the front brightness is improved. This is because it will not function effectively in order to allow it.

On the other hand, in the case where another light reflecting sheet 61 whose light reflecting surface 61a has diffuse reflectivity is used, FIG.
As shown in (b), the light ray component 27 emitted from the dome slope of the recess 17 toward the light reflection sheet 115.
Also, with respect to the above, since the proportion toward the front direction increases, the lighting efficiency can be improved.

In the present invention, as described above, in order to make the most effective use of the illumination light component that is directly incident on the dome slope of the recess 17 and is emitted to the side of the light reflecting sheet. As shown in FIGS. 1 to 3 and 5, a light reflection sheet 15 is used in which a large number of basic units 16 having inclined light reflection surfaces 16a are formed on the surface of a base material at a fine pitch P1. To be

As a result, the light beam emitted in the direction of the light reflecting sheet 15 can be selectively directed to the front direction. Therefore, by using the above-mentioned diffuse reflecting light reflecting sheet 61, the light is diffused to the front side. It is possible to direct the illumination light to the front side much more efficiently than securing the amount of light emitted to the front side.

Here, in order to make the array of the basic units 16 composed of the inclined light reflecting surfaces 16a unrecognizable on the screen, the array pitch P1 of the basic units 16 of substantially similar shape is made as fine as possible. It is important that it is 5000 μm or less, preferably 1000 μm or less.
It is not more than μm, more preferably not more than 500 μm.

As a basic unit 16 having a substantially identical and / or similar shape formed of an inclined light reflecting surface 16a provided on the surface of the light reflecting sheet 15, typically, FIG. 7B is used.
The basic unit 16 has a saw-toothed cross section as shown in FIG. 8 or the basic unit 16 has a mountain shape as shown in FIG. 8B, and the pitch is 3000 μm or less, preferably 800 μm or less, more preferably 300 μm. Below, when the light reflection sheet 15 is viewed from above, as shown in FIGS. 7A and 8A, the ridge lines (ridge lines) 16b are arranged substantially in parallel, and are parallel straight lines and flat. A mode in which an array of the basic units 16 composed of the inclined light reflection surface 16a is used can be mentioned.

This is shown in FIGS. 7 (a), 7 (b) and FIG.
As shown in (a) and (b), in a mode in which the ridge lines 16b of the inclined flat light reflecting surface 16a are arranged substantially in parallel,
This is because cutting work using a diamond bite or an end mill is easy to apply, a die for shaping is easy to manufacture, finer fabrication is easier, and mass productivity is extremely high.

By using the light reflecting sheet 15 in which a large number of parallel linear and flat inclined light reflecting surfaces 16a are arranged, the light reflecting sheet 15 is formed from the dome slope of the recessed portion 17.
The light flux emitted to the side of is also reflected in the direction of the normal line 14 of the light guide 11 by the effect of the inclined light reflection surface 16a, and
The dome-shaped recesses 17 arranged in the light guide 11 in a dot shape, a mesh shape, or a combination thereof are preferably arranged randomly (randomly), which causes an optical interference phenomenon. It is possible to obtain an illuminating light beam with extremely high frontal brightness without using the surface light source device.

Also in this case, the light emitting surface 11b of the light guide body 11 is formed with a triangular prism array 24a, a lenticular lens array 25a, or a corrugated plate as shown in FIGS. 3 (a), 22 and 23. It goes without saying that the light condensing property can be further improved by using the surface on which the light condensing element 23 such as the array 26a is formed.

As shown in FIG. 24, substantially the same and / or
Alternatively, the suitable range of the inclination angle α of the inclined light reflection surface used in the substantially similar basic unit 16 is the light guide 1.
It should be appropriately determined from the viewpoint of converting the direction of the emitted light beam emitted from 1 to the light reflection sheet 15 side to the direction of the normal line 14 of the light emitting surface 11b. More specifically, the inclination angle α of the inclined light reflecting surface 16a is preferably in the range of 7 degrees to 50 degrees, more preferably in the range of 10 degrees to 40 degrees, and further preferably in the range of 15 degrees to 34 degrees. To be

Further, it is preferable from the viewpoint of light converging property that the inclined light reflection surface 16a constituting each basic unit 16 has a concave cross section as shown in FIGS. 9 and 10. This is not only a mode in which a large number of parallel linear and inclined light reflecting surfaces 16a are preferably used in the present invention, but also a mode in which concave mirror-shaped basic units 16 are arrayed as shown in FIGS. 11 to 14. It is also preferably used in such cases.

Also in this case, the range preferably used as the inclination angle α of the inclined light reflection surface 16a is that the direction of the light ray emitted from the light guide 11 is converted to the direction of the normal line 14 of the light emitting surface 11b. Should be determined, for example, FIG.
5, the inclination angle α of the tangent line at the center of the concave cross section is preferably in the range of 7 degrees to 50 degrees, more preferably in the range of 10 degrees to 40 degrees, and further preferably in the range of 15 degrees to 34 degrees.
It is a range of degrees.

The light reflecting sheet 1 uses the basic unit 16 including the light reflecting surface 16a having a concave cross section as a reflecting element.
21. As shown in FIG. 21C, the light beam 27 having a broad spread, which is emitted from the light extraction mechanism 170 provided in the light guide 11 as shown in FIG. The light can be emitted in the direction of the normal line 14 of the light guide 11 while being converted into a light beam closer to a parallel light beam. In other words, the light is emitted from the light guide 11 by the condensing effect of the concave mirror. The normal line 14 of the light guide 11 in which the light rays are collimated more
It is possible to convert the emitted light to have extremely high brightness with respect to the direction.

On the contrary, depending on the application, a wider emission angle distribution is required, but in this case, FIG.
As shown in FIG. 5, by using the basic unit 16 including the light reflecting surface 16a having a convex cross section, it is possible to obtain effects such as expansion of the emission angle distribution and prevention of glare.

As described above, the light guide sheet 11 according to the present invention is combined with the light guide sheet 11 according to the present invention by combining the light reflection sheet 15 in which a large number of basic units 16 each having a substantially similar inclined light reflection surface 16a are arranged. The light condensing effect that was achieved by using a prism array or other member that is difficult and expensive to manufacture in a light source device can be realized without using such a member. The device can be made into a very simplified configuration,
As a practical surface light source device, it is possible to provide an extremely large number of advantages such as a reduction in the number of assembling steps, an improvement in yield, a reduction in dust mixing probability, and a cost reduction.

FIG. 27 shows the light guide of the present invention.
As shown in FIG. 3, a prism sheet 37 having a condensing element 29 such as a triangular prism array 29a is disposed on the light emitting surface 11b of the light guide 11 to secure the converging property and maintain the illumination intensity. Can also be implemented.

However, in the light guide according to the present invention, the recesses 17 having a smooth surface and having a dome-shaped cross section in the main traveling direction of the light beam propagating in the light guide are provided in a dot shape to extract light. Since the mechanism 170 is used, in the total reflection mode, as shown in FIG. 16A, there is a large amount of illumination light 18a that rises in the direction normal to the light emitting surface 11b.

If a triangular prism array 29a or the like having a high light-converging property is used to condense the emitted light component 18a as described above, contrary to the intention, as indicated by reference numeral 18b in FIG. Illumination light is guided by total reflection 1
Since it will be pulled back to the first side, there is a problem that the illumination light beam emitted from the light guide body in the front direction cannot be effectively utilized sufficiently.

On the other hand, in the mode in which the light reflection sheet 15 in which a large number of substantially similar basic units 16 each having the inclined light reflection surface 16a are arranged is used, the light guide 1
The light emitting surface 1 of the light guide body 1 in the total reflection mode is formed by the recessed portion 17 having a dome-shaped cross section and formed of a smooth surface in 1
Illumination light directed in the normal direction of 1b, that is, FIG. 16 (a)
While the illumination light emitted through the path as shown in FIG. 16 is sufficiently effectively used, only the light beam emitted in the direction of the light reflection sheet 15, that is, only the light beam emitted from the light guide through the path as shown in FIG. 21 (c), it is possible to efficiently direct the light in the direction normal to the light emitting surface of the light guide body. Therefore, even if the prism sheet 37 is not used, it is extremely equal to or more than the case where the prism sheet is used. It is possible to obtain a high lighting effect.

FIG. 29 shows a surface light source device in which the light guide according to the present invention and the light reflection sheet 15 having a large number of basic units 16 each having the substantially similar inclined light reflection surface 16a are arranged. The output angle distribution characteristics shown are
Since there is little phenomenon in which light and dark are swiftly switched (darkening phenomenon) when viewed from an angle, the appearance when viewed from an angle is superior to that of a surface light source device equipped with a conventional prism sheet. There is also an advantage that a natural impression can be given as the back lighting means.

In the present invention, the inclined light reflecting surface 16a
The reflective material used in the basic unit 16 consisting of is not particularly limited, but the reflective layer 31 is formed by coating the surface of the base material 32 with silver or aluminum.
It is most preferable to form the light reflection surface 16a as the above because of the ease of manufacturing. It is preferable to use silver in terms of light reflectance, and it is preferable to use aluminum in terms of ease of production and low cost. A typical method for forming a thin film on the coating of these light-reflecting metal substances (the reflective layer 31 in the embodiment shown in FIG. 26) is to use a dry process such as vacuum deposition, sputtering, and ion plating. is there.

Before vacuum-depositing silver, for example, the surface of the base sheet 30 on which the basic unit 16 having the inclined light-reflecting surface 16a and having substantially the same and / or similar shape is formed is sandblasted. For example, matte treatment can be performed. By performing the processing as described above, it becomes possible to give the light reflecting surface 16a having regular reflectivity an appropriate light diffusing property, and expand the angular distribution characteristic of the emitted light, suppress the glare of the illumination light, or liquid crystal. It is possible to obtain the effect of preventing the generation of a moire pattern due to the interference of the cell with the gate array.

The same effect is obtained by using a white resin material having a high light reflectance, which is represented by a foaming resin or a resin in which a white pigment is kneaded, for the inclined light reflecting surface 16a of the basic unit 16. Can also be obtained by

Here, the glossy metal surface used as the light reflecting surface 16a is very likely to be scratched and is susceptible to oxidative deterioration, and leak current occurs when the metal surface is exposed. Since the electrical characteristics are also adversely affected, it is preferable to coat the surface with silica, which is an insulating material, or an ultraviolet curable acrylic resin paint as the protective layer 32, as in the light reflecting sheet 15 of the embodiment shown in FIG. . At this time, the coat layer (protective layer) 32
Of 1.0 × 10 ⁶ Ω · cm or more, preferably 1.0 × 10 ⁷ Ω · cm or more, and more preferably 1.0 × 10 ⁸ Ω · cm or more.

Further, as shown in FIG. 30, it is preferable that the surface of the light reflecting sheet 15 can be partially subjected to light-shielding printing or color adjustment printing to adjust the brightness and chromaticity in the surface light source. preferable. Therefore, as shown in FIG. 31 (a), the unevenness formed by the inclined light reflecting surface 16a in the basic unit 16 is covered with the covering layer 33 made of a light transmitting material such as an ultraviolet curable acrylic resin, and the surface is flat. Therefore, it is devised to facilitate printing.

In the light reflecting sheet 15, the base material 30 is used.
Is preferably formed of a thermoplastic resin or a thermosetting resin, but since this substrate alone lacks rigidity and often adversely affects optical properties, a biaxially stretched film of polyester or polypropylene is used. It may be used as the back support 34. In addition, as shown in FIG. 31 (b), the base material 30 is the surface side facing the light guide 11, and the base material 3 is
A mode in which a transparent biaxially stretched polyester film is provided as the surface support 38 on the surface of No. 0 is also preferable. At this time, it is preferable that the surface of the surface support 38 be treated as a matte surface or an acrylic bead coating surface 39 to prevent adhesion with the light guide 11.

As described above, according to the surface light source device of the present invention,
The light reflecting sheet 15 is formed by covering the substantially similar basic unit 16 with a light transmissive material so as to be completely embedded, and forming a smooth light reflecting sheet 15 on the surface of the coating layer 33 so as not to reflect the shape of the basic unit 16. This is the surface light source device 10
As a result, since it becomes possible to print a very fine pattern 35 on the surface of the light reflection sheet 15, it is practically very important to improve the optical characteristics, for example, to prevent the occurrence of a bright portion near the light source. It is possible to correct color unevenness when the size is increased.

In the present invention, the liquid crystal display device utilizes the electro-optical effect of liquid crystal molecules, that is, optical anisotropy (refractive index anisotropy), orientation, etc., and an electric field is applied or energized to any display unit. A display is performed using a liquid crystal cell that is an array of optical shutters and is driven by changing the alignment state of liquid crystal and changing the light transmittance or reflectance.

Specifically, transparent simple matrix driving super twisted nematic mode, transparent active matrix driving twisted nematic mode, transparent active matrix driving in-plane switching mode, transparent active matrix driving multi-domain vertical aligned mode, etc. The liquid crystal display element of is mentioned.

According to the present invention, with respect to the sidelight type surface light source device which is often used as the back lighting means of a liquid crystal display or the like, even if it is large, it maintains high image uniformity and imparts a higher light converging characteristic than before. It is possible to provide a light guide body capable of performing the above. Further, it is possible to provide a low-cost surface light source device that suppresses a darkening phenomenon that gives an unnatural impression to image quality, has a small number of members, and is excellent in assembling. The surface light source device having these characteristics is extremely useful as a back lighting means for a liquid crystal display panel, which is required to achieve both low cost and high performance in recent years.

[0102]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. (Example 1) 309.6 × 234.6 as the light guide 11
A flat light guide having a thickness of 4.0 mm and a thickness of 4.0 mm was prepared. A cyclic polyolefin resin (Zeonor 1060R manufactured by Nippon Zeon) is used as the material, and a linear light source 12 made of a cold cathode tube (made by Harrison Toshiba Lighting) having a tube diameter of 2.2 mm is arranged on two long sides. Further, the periphery of the cold cathode tube is covered with a reflector plate (Mitsui Chemicals silver reflector plate) having an Ag vapor deposition layer as a light reflecting surface, and a linear shape is efficiently formed on the side end portion (light incident surface) 11a of the light guide 11. The light beam emitted from the light source 12 is made incident.

Surface 1 facing the light emitting surface 11b of the light guide 11.
1 c is a dot-shaped concave portion 17 having a dome-shaped cross section and having a smooth surface, which gradually increases in length in a direction parallel to the side end portion 11 a on which the light source is arranged, as the distance from the linear light source 12 increases. Formed in large numbers. The width W of the recess 17 is 160 μ
The length is 180 to 230 μm.
The range is changing. Further, the height H is 40 μm and is substantially constant, and the ratio H / W is 0.25.

The dot-shaped dome-shaped recess 17 is arranged as follows.
As shown in FIG. 20 (a), the concave portions 17 are randomly distributed to the extent that they do not contact each other, and the appearance-unfavorable optical interference phenomenon is caused by the regular arrangement of the concave portions 17. Has been devised to prevent the occurrence of.

Here, as shown in FIG. 18, the mold used to mold the recess 17 having a smooth surface has a photoresist 41 having a thickness of 5.8 μm on a mirror-polished copper substrate 40.
Was applied, and the photoresist 41 was left at positions other than the positions where the recesses 17 were to be formed by photolithography using a parallel light source, and the copper substrate 40 patterned by the photoresist 41 was used.

Nickel is electrodeposited 43 on the copper substrate 40 which is opened only at the position corresponding to the formation of the recess 17 and the electrodeposition is advanced far beyond the film thickness of 5.8 μm of the resist 41. As a result, FIG. As shown in the drawing, nickel electrodeposition 43 progresses on the resist to form a projection having a dome-shaped cross section having a smooth slope, and a surface shape suitable for forming the recess 17 in a dot shape in the light guide. A mold having

When the height of the protrusion reaches 40 μm, the electrodeposition is stopped, the photoresist 41 is peeled off, and then nickel is further plated 44 by about 5 μm to improve the surface smoothness and secure the strength. It was a mold. A conventional injection molding method is used for molding the light guide 11, and a large number of recesses 17 having a dome-shaped cross section and having a smooth surface are transferred to the surface by using the mold obtained as described above as a stamper. Light guide 11
Was molded.

In order to measure the emission direction selectivity with respect to the normal direction of the light emitting surface 11b of the light guide body 11, as shown in FIG. 17, the light reflectance of 1% is provided at the position where the light reflecting sheet 15 is originally arranged. The following black flocked paper is provided, and the light emitting surface 11
Luminance meter (Topcom B
M-7) 52 was set and LN was measured.

Next, the light guide 11 is turned upside down and set, and the light extraction mechanism 170 is set so as to come to the upper side.
Was measured. The selection ratio of the emitted light amount with respect to the normal direction of the light emitting surface calculated from these values is 87%, and a high-intensity illumination light beam is emitted in the total reflection mode with respect to the normal direction of the light emitting surface. It was confirmed that the dot-shaped dome-shaped recess 17 having smoothness suitable for use as a body was formed.

A white foamable polyester film having diffuse reflectance as a light reflecting sheet (Lumirror E manufactured by Toray Industries, Inc.)
60 L), and a light diffusion sheet (made by Tsujiden, D117T) in which acrylic beads are coated on a transparent polyester film on the light emitting surface 11b of the light guide 11.
6 was arranged to provide a surface light source device.

A cold cathode tube light source is lit at a high frequency through an inverter (Harrison Toshiba Lighting Co., Ltd.), and the tube current is set to 5
As the mA, an average luminance and chromaticity at 25 points in the plane were measured by using a luminance measuring device (BM-7, manufactured by Topcom). The results are shown in Table 1. No unsightly bright or dark parts were observed on the light emitting surface, and a high quality surface light source with excellent uniformity of brightness distribution was obtained.

(Embodiment 2) Using the light guide described in Embodiment 1, a parallel linear inclined surface in which ridge lines 16b are arranged in parallel is formed as a basic unit 16 as a light reflection sheet having a sectional shape shown in FIG. The light reflection sheet 15 in which a large number of finely inclined light reflection surfaces 16a are arranged is used. The arrangement pitch P1 of the basic units 16 is set to 50 μm, and the reflection layer 31
A vapor-deposited layer of aluminum is used as the protective layer 3 of silica, which is a transparent insulating material, on the surface of the vapor-deposited aluminum layer.
It is deposited as 2.

The inclination angle α of the inclined light reflecting surface 16a provided on the light reflecting sheet 15 is 32 degrees, and the light reflecting sheet 15 is provided with a dome-shaped recess 17 having a smooth surface provided on the light guide. The structure is such that the luminous flux emitted in the direction is efficiently emitted in the direction of the normal line 14 of the light emitting surface 11b. With this effect, the luminous flux emitted in the direction of the light reflection sheet 15 can be utilized more effectively as compared with the first embodiment.
Furthermore, an optical system with high illumination efficiency was obtained. The results are shown in Table 1.

(Comparative Example 1) In the light guide member described in Example 1, the light extraction mechanism was not provided with a recess having a dome-shaped cross section having a smooth surface, but a pattern having a rough surface was used. A surface light source device was prepared in the same manner as in 1.

Here, photoetching of a mirror-polished stainless steel plate with ferric chloride is used to create a pattern having a rough surface, and the side end where the light source is arranged as the rectangular pattern moves away from the light source. It is configured such that the length in the direction perpendicular to is gradually increased. The width is 160 μm, which is almost constant, and the length is 180 μm.
It varies from m to 230 μm.

As a result of lighting evaluation of the light source in the same manner as in Example 1, unlike Example 1, since the illumination light is emitted to the outside of the light guide mainly due to the light scattering by the rough surface, the light is emitted in various directions. Therefore, it was possible to obtain only a surface light source device having low brightness in the front direction. The results are shown in Table 1.

Comparative Example 2 A surface light source device was constructed by using the light guide body having the rough surface pattern described in Comparative Example 1 as a light extraction mechanism and disposing the light reflection sheet described in Example 2. When the light is taken out by light scattering, the emitted light beam is diffused, and even if the light reflecting sheet 15 having the basic unit composed of the inclined reflecting surface on the surface is used, the sufficient luminance improving effect cannot be obtained. The results are shown in Table 1.

(Example 3) 246.6 as the light guide 11
A wedge-shaped light guide body 11 having a thickness of × 186.1 mm, a thickness of 2.0 mm and a thickness of 0.6 mm, and having a thin thickness in the short side direction was prepared. A cyclic polyolefin resin (Zeonor 1060R made by Nippon Zeon) is used as the material, and a linear light source 12 made of a cold cathode tube (made by Harrison Toshiba Lighting Co., Ltd.) having a tube diameter of 1.6 mm is arranged on the long side. The cold cathode tube is covered with a reflector plate (silver reflector plate manufactured by Mitsui Chemicals, Inc.) having an Ag vapor deposition layer as a light reflection surface, and the linear light source 12 is efficiently provided on the side end portion (light incidence surface) 11a of the light guide 11. The light rays emitted from are incident.

Surface 1 facing the light emitting surface 11b of the light guide 11.
1 c is a dot-shaped concave portion 17 having a dome-shaped cross section and having a smooth surface, which gradually increases in length in a direction parallel to the side end portion 11 a on which the light source is arranged, as the distance from the linear light source 12 increases. Formed in large numbers. The width W of the recess 17 is 120μ
m is almost constant, and the length is 120 μm to 320 μm
The range is changing. Further, the height H is 40 μm and is substantially constant, and the ratio H / W is 0.33.

Dome-shaped recess 17 formed in a dot shape
As shown in FIG. 20A, the arrangement of the
They are randomly distributed to the extent that they do not contact each other, and are devised so as not to cause an unfavorable optical interference phenomenon caused by the regular arrangement of the recesses.

Here, the mold used for molding the dome-shaped recessed portion 17 having a smooth surface arranged in a dot pattern is as shown in FIG.
As shown in, the photoresist 4 having a thickness of 5.8 μm
1 is coated on a mirror-polished copper substrate 40, and a photoresist 41 is left at a position other than the position where the recess 17 is formed in a dot shape by photolithography using a parallel light source, and the copper substrate is patterned by the photoresist 41. 40 was used.

18 (d). As a result of electrodeposition of nickel 43 on the copper substrate 40 having openings only at the positions corresponding to the formation of the recesses 17 and allowing the electrodeposition to proceed far beyond the resist film thickness of 5.8 μm, FIG. As shown in FIG. 3, nickel electrodeposition progresses on the resist to form a projection having a dome-shaped cross section having a smooth slope, and the light guide 11 has a dot-shaped dome-shaped recess 1.
A mold having a surface shape suitable for forming 7 was obtained. When the height of the protrusion reaches 40 μm, the electrodeposition is stopped and the photoresist 41 is peeled off. Then, in order to improve the surface smoothness and secure the strength, nickel is further plated about 5 μm 44 to form a mold. did.

Further, as shown in FIG. 3, on the light emitting surface 11b of the light guide body 11, the ridge line (ridge line) 24b is set in the direction perpendicular to the side end 11a where the light source is arranged, and the pitch (P3) 5
The condensing element 23, which is a triangular prism array 24a having an angle of 0 μm and an apex angle (β) of 120 degrees, is provided, and has a structure for enhancing the condensing property.

The light guide 11 is molded by using a conventional injection molding method, and the metal mold obtained as described above is used as a stamper to form a concave portion 17 having a dome-shaped cross section on the surface in a dot shape. A large number of transferred light guides were molded. In order to measure the emission direction selectivity with respect to the normal line 14 direction of the light emitting surface 11b of the light guide body 11, as shown in FIG.
Black flocking paper with a light reflectance of 1% or less is arranged at the position where 5 is originally arranged, and a luminance meter (Topcom BM-7) 52 is set at the center of the light emitting surface 11b in a direction perpendicular to the light emitting surface. Then, the luminance LN was measured.

Next, the light guide 11 is turned upside down and set, and the light extraction mechanism 170 is set so that it is on the upper side.
Was measured. Light emitting surface 11b calculated from these values
The selection ratio of the amount of emitted light with respect to the direction of the normal line 14 is 91%, and a high-intensity illumination light beam is emitted in the total reflection mode with respect to the direction of the normal line 14 of the light emitting surface 11b. It was confirmed that the dome-shaped recess 17 having a suitable smoothness was formed in a dot shape.

A white foamable polyester film having diffuse reflectivity as a light reflecting sheet (Lumirror E manufactured by Toray Industries, Inc.)
The light reflecting sheet 61 composed of 60 L) is provided, and the light guide 1
On the light emitting surface 11b of No. 1, a light diffusion sheet (D120) manufactured by Tsujiden Co., which is a transparent polyester film coated with acrylic beads, is disposed to form a surface light source device.

The cold cathode tube light source 12 was lit at a high frequency through an inverter (Harrison Toshiba Lighting Co., Ltd.) and the tube current was set to 6 mA, and a brightness measuring device (Topcom, BM-
Using 7), the average luminance and chromaticity of 25 points in the plane were measured.
The results are shown in Table 1. No unsightly bright part or dark part was observed on the light emitting surface 11b, and a high quality surface light source excellent in uniformity of luminance distribution was obtained.

(Example 4) Using the light guide 11 described in Example 3, a cross-sectional shape is shown as a light reflection sheet in FIG.
A light reflection sheet 15 in which a large number of finely inclined light reflection surfaces 16a are arranged is used, in which a basic linear unit 16 is a parallel linear inclined surface in which ridge lines 16b are arranged in parallel (the cross-sectional shape is asymmetric). The arrangement pitch P1 of the basic unit 16 is 50
.mu.m, a silver vapor deposition layer is used for the reflecting layer 31, and the surface of the silver vapor deposition layer is coated with a photocurable acrylic resin 33 which is a transparent insulating material.

The inclination angle α of the inclined light reflection surface 16a provided on the light reflection sheet 15 is 31 degrees (the inclination angle of the steep inclination surface which does not substantially contribute to light reflection is 74 degrees).
The light guide 11 has a structure in which the light flux emitted from the concave portion 17 having a smooth surface and having a dome-shaped cross section toward the light reflection sheet 15 is efficiently emitted in the direction normal to the light emitting surface.
Due to this effect, the light reflection sheet 15 is different from that of the third embodiment.
In this way, the light flux emitted in the direction of can be utilized more effectively, and in addition, the converging effect of the triangular prism array 24a provided on the light emitting surface 11b of the light guide 11 is combined, and an optical system with extremely high illumination efficiency can be obtained. Was obtained. The results are shown in Table 1.

(Embodiment 5) In the surface light source device described in Embodiment 3, an optical element 29 consisting of a triangular prism array 29a having an apex angle of 90 degrees and a pitch of 50 μm is arranged on the light emitting surface 11b of the light guide 11. The optical characteristics were measured in the same manner as in Example 3 except that the prism sheet 37 was disposed with its apex facing up as shown in FIG. The results are shown in Table 1.
Shown in.

(Comparative Example 3) In the light guide according to the third embodiment, the light extraction mechanism is not provided with a recess having a dome-shaped cross section having a smooth surface, but a pattern having a rough surface is used. A surface light source device was produced in the same manner as in 3.

Here, in order to create a pattern having a rough surface, a dry film resist (manufactured by DuPont, thickness 25 μm) is laminated on a mirror-polished stainless steel plate, and the dry film resist portion is subjected to opening processing by photolithography, Further, the spherical glass beads of # 600 were sandblasted at a discharge pressure of 0.4 MPa to roughen the surface. As the rectangular pattern is separated from the light source, the length in the direction perpendicular to the side end portion on which the light source is arranged gradually increases and changes. The width is 120 μm, which is almost constant, and the length is 120 μm.
It varies in the range from μm to 320 μm.

As a result of lighting evaluation of the light source in the same manner as in Example 3, unlike Example 3, since the illumination light is emitted to the outside of the light guide mainly due to light scattering by the rough surface, the light is emitted in various directions. Therefore, it was possible to obtain only a surface light source device having low brightness in the front direction. The results are shown in Table 1.

(Comparative Example 4) A light source having the rough surface pattern described in Comparative Example 3 as a light extraction mechanism was used, and the light reflection sheet described in Example 4 was arranged to form a surface light source device. When the light is taken out by light scattering, the emitted light beam is diffused, and even if a light reflecting sheet having a basic unit having a light reflecting surface inclined on the surface is used, a sufficient brightness improving effect cannot be obtained. The results are shown in Table 1.

(Comparative Example 5) In the surface light source device described in Example 3, using the light guide having the rough surface pattern described in Comparative Example 3 as a light extraction mechanism, a vertical angle of 90 degrees was set on the light emitting surface of the light guide. ,
Optical characteristics were measured in the same manner as in Example 3 except that a prism sheet having a triangular prism array with a pitch of 50 μm was arranged with its apex facing upward. The results are shown in Table 1.

Example 6 35.9 × 4 as a light guide
A flat light guide 11 having a thickness of 4.6 mm and a thickness of 1.0 mm was prepared. Cyclic polyolefin resin (Zeonor 1430R manufactured by Nippon Zeon) is used as the material, and three chip mount type gallium nitride white light emitting diode elements (NSCW215T manufactured by Nichia Chemical Co., Ltd.) are arranged on the short side. The periphery of the white light emitting diode is covered with a white reflector plate (made by Toray, Lumirror E60L) so that the light emitted from the linear light source 12 is efficiently incident on the side end portion (light incident surface) 11a of the light guide 11. I chose

Surface 1 facing the light emitting surface 11b of the light guide 11.
Reference numeral 1c is a dome-shaped section having a smooth surface, which is miniaturized to the extent that it cannot be visually recognized, and its length in the direction parallel to the side end portion 11a on which the light source is disposed gradually increases as the distance from the light source 12 increases. A large number of recesses 17 were formed in a dot shape.
The width W of the recess 17 is set to be substantially constant at 15 μm, and the length thereof varies in the range of 30 μm to 45 μm. Further, the height H is set to be substantially constant at 10 μm, and the ratio H / W is 0.6.
It is 7.

The arrangement of the dot-shaped dome-shaped recesses 17 is as follows.
The recesses 17 are randomly distributed to the extent that they do not contact each other, and the regular arrangement of the recesses 17 causes a moire pattern that is not desirable in appearance due to interference with the black matrix of the liquid crystal panel 50. It is designed so that it does not exist.

Here, as shown in FIG. 18, the die for molding the concave portion 17 having a smooth surface into a dot shape has a thickness of 3 mm.
A photoresist 41 of μm is coated on a mirror-polished nickel substrate 40, and the photoresist 41 is left at a position other than the position where the recess 17 is to be formed by photolithography using a parallel light source (using a Cr-based photomask). The nickel substrate 40 patterned by the resist 41 was used.

As a result of electrodeposition of nickel on the nickel substrate 40 having openings only at the positions corresponding to the formation of the recesses 17 and the electrodeposition of the resist film having a thickness significantly exceeding 3 μm, as shown in FIG.
As shown in (d), nickel electrodeposition progresses on the resist to form a dome-shaped protrusion having a smooth inclined surface, and a dome-shaped recess 17 having a dome-shaped cross section is formed in the light guide 11. A mold having a surface shape suitable for forming the mold was obtained. When the height of the protrusion reaches 15 μm, the electrodeposition is stopped and the photoresist is peeled off. After that, in order to improve the surface smoothness and to secure the strength, nickel is further plated with about 20 μm 44 to form a mold. .

The light guide 11 is molded by a conventional injection molding method, and the mold obtained as described above is used as a stamper to form an extremely fine dome-shaped recess 17 having a smooth surface on the surface. A large number of dot-shaped light guides were molded. In order to measure the emission direction selectivity with respect to the direction of the normal line 14 of the light emitting surface 11b of the light guide body 11, as shown in FIG. 17, the light reflectance is 1% or less at the position where the light reflecting sheet 15 is originally arranged. A black flocked paper is provided, and a luminance meter (BM-7 manufactured by Topcom) 52 is provided in the center of the light emitting surface 11b in a direction perpendicular to the light emitting surface.
Was set and the luminance LN was measured.

Next, the light guide 11 is turned upside down and set, and the light extraction mechanism 170 is set so that it is on the upper side.
Was measured. The selection ratio of the emitted light amount with respect to the normal direction of the light emitting surface calculated from these values is 98.3%, and a high intensity illumination light beam is emitted in the total reflection mode in the normal direction of the light emitting surface. It was confirmed that recesses having a dome-shaped cross section, which were extremely suitable for use as a light guide, were formed in a dot shape.

Further, the light emitting surface 11b of the light guide 11 is coated with an optical thin film of magnesium fluoride and silica by electron beam vacuum evaporation, and an antireflection coating is applied so that the light reflectance at 550 nm is 1% or less. gave. As shown in FIG. 19, a reflection type liquid crystal panel 50 is disposed below the light guide body 11, and the light emitting surface 11b is covered by the liquid crystal panel 50.
The reflective liquid crystal display with the front light device was constructed. It was confirmed that due to the effect of the recess 17 having a dome-shaped cross section having a smooth surface, a display image with high contrast can be obtained without causing the image to be whitish even when the front light is turned on.

Table 1 shows the results of lighting evaluation with a forward current of 20 mA in order to evaluate the characteristics of the emitted light.
Since the brightness distribution is controlled by the dot pattern, the brightness unevenness is small and a high quality surface light source can be obtained.

(Comparative Example 6) In the light guide according to the sixth embodiment, the light extraction mechanism is not provided with a recess having a dome-shaped cross section having a smooth surface, but a pattern having a rough surface is used. A surface light source device was prepared in the same manner as in No. 6. Here, photoetching of a mirror-polished stainless steel plate with ferric chloride is used to create a pattern having a rough surface, and as the rectangular pattern is separated from the light source, it is perpendicular to the side end where the light source is arranged. It is configured such that the length in the direction gradually increases and changes. Width is 15 μm
Is almost constant, and the length varies in the range of 30 μm to 45 μm.

As a result of lighting evaluation of the light source in the same manner as in Example 6, unlike in Example 6, the illumination light is emitted to the outside of the light guide mainly due to light scattering by the rough surface, so that the front light portion is whitish. It was shining and I could only obtain images with low contrast. The results are shown in Table 1.

[0147]

[Table 1]

As described above, according to the light guide of the present invention, a large number of dents having a dome-shaped cross section are formed in a dot shape and / or a mesh shape on the surface facing the light emitting surface, so that the appearance quality is improved. And an image with high contrast can be obtained. Further, by using such a light guide, it is possible to provide a low-cost front light device having a small number of parts, excellent assembling property.

Further, according to the surface light source device of the present invention using such a light guide, it is difficult to manufacture the conventional surface light source device by combining the light reflecting sheets having a large number of basic units. The light condensing effect can be achieved without using an expensive member such as a prism array, and the structure of the surface light source device can be extremely simplified while maintaining high optical characteristics. Therefore, the number of assembling steps can be reduced and the yield can be improved. As a practical surface light source device, an extremely large number of advantages such as improvement, reduction of dust mixing probability, and cost reduction can be imparted.

Further, according to the surface light source device of the present invention, since there is little phenomenon in which the emission angle distribution characteristics are swiftly changed between light and dark when viewed obliquely (darkening phenomenon), the surface on which the conventional prism sheet is arranged is small. Compared to the light source device, it has an excellent appearance when viewed obliquely, and can give a natural impression particularly as a back lighting unit of a liquid crystal display device.

According to the liquid crystal display device of the present invention using such a surface light source device, the number of members is small, the assembling property is excellent, the cost is low, and the image uniformity is large even if it is large. It is possible to obtain the excellent advantage that the value can be kept high.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a main part of a surface light source device according to an embodiment of the present invention.

2 is a schematic cross-sectional view showing the surface light source device shown in FIG. 1 taken along line 2-2 in FIG.

FIG. 3 (a) is a perspective view schematically showing a main part of a surface light source device according to another embodiment of the present invention, and FIG. 3 (b) shows a light guide member constituting this surface light source device. It is a schematic side view shown from the light source arrangement side.

FIG. 4 is a perspective view schematically showing a main part of a surface light source device according to still another embodiment of the present invention.

FIG. 5 is a perspective view schematically showing a main part of a surface light source device according to still another embodiment of the present invention.

FIG. 6 is a plan view schematically showing another configuration example of the light source arranged at the side end of the light guide according to the present invention.

FIG. 7 is a light-reflecting sheet used in the surface light source device of the present invention, in which a large number of basic units each having a flat light-reflecting surface that is parallel and linear and has ridges arranged in parallel are formed on the surface. Plan view of a light reflecting sheet and 7b
FIG. 7 is a cross-sectional view taken along line -7b.

FIG. 8 is a light-reflecting sheet used in the surface light source device of the present invention, in which a large number of basic units each having a flat light-reflecting surface that is parallel and linear and has ridge lines arranged in parallel are formed on the surface. FIG. 8 is a partial plan view of a light reflecting sheet of another embodiment and a cross-sectional view taken along line 8b-8b.

FIG. 9 is a light-reflecting sheet used in the surface light source device of the present invention, further comprising a plurality of basic units each having a parallel linear straight and concave light-reflecting surface in which ridge lines are arranged in parallel. It is a partial top view of the light reflection sheet of another aspect, and sectional drawing cut and shown by the 9b-9b line.

FIG. 10 is a light-reflecting sheet used in the surface light source device of the present invention, in which a large number of basic units having parallel linear and concave light-reflecting surfaces in which ridge lines are arranged in parallel are formed on the surface. It is the partial top view of the light reflection sheet of another aspect, and sectional drawing cut | disconnected and shown by the 10b-10b line.

FIG. 11 is a partial plan view of a light-reflecting sheet used in the surface light source device of the present invention, in which a plurality of basic units each having a concave light-reflecting surface are formed on the surface. FIG. 11 is a cross-sectional view taken along line 11b-11b.

FIG. 12 is a partial plan view of a light reflecting sheet used in the surface light source device of the present invention, wherein a plurality of basic units each having a concave mirror-shaped light reflecting surface are formed on the surface. FIG. 12 is a sectional view taken along the line 12b-12b.

FIG. 13 is a partial plan view of a light reflection sheet used in the surface light source device of the present invention, which is another embodiment of the light reflection sheet in which a plurality of basic units each having a concave mirror-shaped light reflection surface are formed on the surface. FIG. 13B is a cross-sectional view taken along line 13b-13b.

FIG. 14 is a partial plan view of a light reflection sheet used in the surface light source device of the present invention, which is another embodiment of the light reflection sheet in which a plurality of basic units each having a concave mirror-shaped light reflection surface are formed on the surface. And FIG. 14b is a cross-sectional view taken along line 14b-14b.

FIG. 15 is a structural explanatory view schematically showing an emitted light beam which is formed in a dot shape or a mesh shape and has a dome-shaped recessed portion in the light guide according to the present invention.

FIG. 16 is a structural explanatory view showing an enlarged concave portion having a dome-shaped cross section and having a smooth surface in the light guide according to the present invention, and showing a locus of a light beam emitted to the outside of the light guide by the concave portion.

FIG. 17 is a structural explanatory view showing a method of measuring the direction selectivity of the light flux of the light guide according to the present invention.

FIG. 18 is a structural explanatory view schematically showing a manufacturing process of a mold for manufacturing the light guide according to the present invention.

FIG. 19 is a perspective view schematically showing a main part of a front light device for illuminating a liquid crystal panel, which is configured by using the light guide body of the invention.

FIG. 20 is a plan view showing various arrangement modes when dome-shaped recessed portions constituting the light extraction mechanism provided in the light guide according to the present invention are arranged in a dot shape or a mesh shape.

FIG. 21 is a light reflection sheet having a specular reflection surface on the side opposite to the light emitting surface of the light guide of the present invention, a light reflection sheet having a diffuse reflection surface, and an inclined light reflection surface. FIG. 3 is a configuration explanatory view showing a trajectory of a light beam when a light reflection sheet having a basic unit consisting of is arranged.

FIG. 22 is a schematic perspective view showing a main part of a surface light source device using the light guide of the present invention in which a light-collecting element is further formed on a light emitting surface.

FIG. 23 is a schematic perspective view showing a main part in another example of the surface light source device using the light guide of the present invention in which a light-collecting element is further formed on the light emitting surface.

24 is a cross-sectional view showing a tilt angle of the light reflecting surface by partially enlarging the tilted flat light reflecting surface of the basic unit formed on the light reflecting sheet shown in FIG.

25 is a cross-sectional view showing a tilted angle of the light reflecting surface by partially enlarging the concave light reflecting surface of the basic unit formed on the light reflecting sheet shown in FIG.

FIG. 26 is a partial perspective view showing another specific example of the light reflecting sheet used in the surface light source device of the present invention.

FIG. 27 is configured by using a light-reflecting sheet made of a diffusible material and disposing a light-condensing sheet having a light-collecting element formed on the light-emitting surface side of a light guide having a light-collecting element formed on the light-emitting surface. It is a perspective view which shows the principal part of the surface light source device of this invention.

FIG. 28 is a schematic structural explanatory view showing a situation in which an illumination light beam raised to the front in a total reflection mode is repelled by a prism array in one embodiment of the surface light source device of the present invention.

FIG. 29 is a characteristic diagram of a light guide showing the emission angle distribution in the surface light source device of the present invention.

FIG. 30 is a perspective view schematically showing a main part of still another embodiment of the light guide according to the invention.

FIG. 31 is a cross-sectional view showing another specific example of the light reflecting sheet used in the surface light source device of the present invention.

FIG. 32 is a sectional view schematically showing an example of a conventional surface light source device.

FIG. 33 is a cross-sectional view schematically showing another example of the conventional surface light source device.

FIG. 34 is a structural explanatory view schematically showing an outgoing light flux generated by light scattering of a rough surface or the like in a conventional light guide.

FIG. 35 is a schematic configuration explanatory diagram illustrating a situation in which scattered light cancels each other out due to multiple scattering in light extraction by light scattering due to a rough surface or fine particles in a conventional light guide, and illumination light loss occurs. Is.

[Explanation of symbols]

10 Surface light source device 11 Light guide 11a One end (light incident surface) 11b Light emitting surface 11c Surface opposite to light emitting surface 11d corner cut surface 12 Light source (Linear light source) 12a LED 12b optical rod 13 reflector 14 Normal about the light emitting surface 15 Light reflection sheet 16 basic units 16a Inclined light reflection surface 16b Ridge line (ridge line) 17 Domed cross section 18 Trajectory of illumination rays 19 Ray trajectory 19a Ray trajectory 20 black sheet 21 Light propagation direction 22 Anti-reflection coating layer 23 Condensing element 24a triangular prism array 24b Ridge of triangular prism array 25a lenticular lens array 25b Lenticular lens array ridge 26a Corrugated array 26b Ridge of corrugated array 27 Illumination light component 28 Luminous flux with sharp angle characteristics 29 Focusing element 29a Triangular prism array 30 substrates 31 reflective layer 32 Protective layer (coat layer) 33 coating layer 34 Back support 35 Fine pattern 36 Light diffusion sheet 37 Prism sheet 60 Regular reflective light-reflecting sheet 60a specular light-reflecting surface 61 Diffuse reflective light reflection sheet 61a Diffuse reflective light reflecting surface 170 Light extraction mechanism

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 G02F 1/1335 520 520 1/13357 1/13357 G09F 9/00 336 G09F 9/00 336B 336J // F21Y 101: 02 F21Y 101: 02 103: 00 103: 00 F Term (reference) 2H038 AA55 BA06 2H091 FA16Z FA21Z FA23X FA23Z FA29Z FA37X FA42X FA42Z FA45X FA45Z FB02 FC19 FD06 LA12 LA18 5G435 AA02 BB12 BB15 BB17 DD13FF03 EE22EE23EE23EE

Claims (18)

[Claims] 1. A light guide body having at least one side end portion as a light incident surface and one surface as a light emitting surface, wherein the light guide body has a haze of 0% at a thickness of 1 mm based on ASTM D1003. A light having a material of ˜35% is provided on the surface of the light guide opposite to the light emitting surface, and is provided with a large number of recesses made of smooth surfaces so as to equalize the amount of light emitted from the light emitting surface. An extraction mechanism is provided, the cross section of the recess in the direction in which light rays mainly propagate is dome-shaped, and the selection ratio of the amount of emitted light with respect to the normal direction of the light emitting surface of the light guide is 65% to 100%. The light guide characterized by being in the range of. 2. The ratio H / W when the width of the dome-shaped recess is W and the height of the recess is H in the cross section of the recess in the direction in which the light rays mainly propagate. The light guide according to claim 1, wherein the light guide has a range of 0.10 to 0.87. 3. The light guide according to claim 1, wherein the arrangement pitch of the recesses changes irregularly. 4. The length of the plurality of recesses forming the light extraction mechanism increases in a uniaxial direction as the distance from the light source increases, and the uniaxial direction in which the length further increases is:
The light guide according to claim 1, wherein the light guide is in a direction substantially perpendicular to a direction in which the light rays mainly propagate. 5. The light guide according to claim 4, wherein a large number of the recesses forming the light extraction mechanism are arranged in a dot shape, a mesh shape, or a combination thereof. 6. The light-emitting surface of the light guide is provided with a light-collecting element having a ridge line in a direction substantially perpendicular to a side end portion on which the light source is arranged and having a pitch of 1 μm to 500 μm. The light guide according to any one of claims 1 to 5, wherein. 7. The conductor according to claim 6, wherein the light-collecting element provided in the light guide is a triangular prism array having a pitch of 10 μm to 150 μm and an apex angle of 70 ° to 160 °. Light body. 8. The light guide according to claim 1, a light source disposed near a side end of the light guide, and a surface facing the light emitting surface of the light guide. 1. A surface light source device comprising a light reflection sheet disposed on the side, wherein the light reflection sheet is made of a diffuse reflective material. 9. The width W of the recesses is 2000 μm or less, the arrangement pitch of the recesses is 4000 μm or less, and the recesses are arranged below the transmissive or semi-transmissive liquid crystal panel for use. The surface light source device according to claim 8. 10. The light reflection sheet has an inclination angle of 7 degrees to 5 degrees.
It is characterized in that a large number of substantially similar basic units each having a light reflecting surface inclined at 0 degree are arranged at a pitch of 5000 μm or less, and the main reflection direction of the basic units is substantially constant. Item 10. The surface light source device according to item 8 or 9. 11. The light reflecting surface provided in the basic unit is made of a metal material, and a protective layer made of a transparent insulating material is provided on the light reflecting surface. The surface light source device according to. 12. The surface according to claim 11, wherein the metal substance is silver or aluminum, and the resistivity of the protective layer made of a transparent insulating substance is 1.0 × 10 6 Ω · cm or more. Light source device. 13. The surface of the light-reflecting sheet is covered with a light-transmitting substance, and the unevenness due to the plurality of inclined light-reflecting surfaces is filled with the light-transmitting substance. 13. The surface light source device according to any one of 12. 14. The printed pattern is provided on the surface of the light reflecting sheet which is made substantially flat by embedding the light transmitting material in the irregularities of the basic unit. Surface light source device. 15. A front light device comprising the light guide according to any one of claims 1 to 7 and a light source arranged near a side end of the light guide, wherein: A front light device having a width W of 50 μm or less, an arrangement pitch of the recesses of 800 μm or less, and being arranged and used on an upper portion of a reflective liquid crystal panel. 16. The light emitting surface of the light guide has a wavelength of 550 n.
The frontlight device according to claim 15, wherein antireflection processing is performed so that the light reflectance at m is 2% or less. 17. A liquid crystal display device using the surface light source device according to claim 8 in a backlight optical system. 18. A liquid crystal display device using the front light device according to claim 15.