JP2002124116A - Flat light source device, and a liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat light source device efficiently utilizing light by using a light reflection sheet which is a new light control member, with simple structure, excellent assembling property at low cost, and to provide a liquid crystal display device using the flat light source device as an optical system of backlight. SOLUTION: For the flat light source device, a light take-out system 20 is formed to a light guide body 11 having one surface as a light outgoing surface 15, and a light source 13 is arranged at the side end part 12 of the light guide body 11, and a light reflection sheet 17 is arranged at a surface 16 side facing the light outgoing surface 15 of the light guide body 11. A light take-out system 20 is formed by a pattern composed of convex protrusions 20a located at the surface 16 side facing the light outgoing surface 15 of the light guide body 11, and the light reflection sheet 17 is formed by arranging many base units 18 with a pitch of 5000 μm or less on its surface, and each base unit 18 is formed of a slanted surface 18a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device and a liquid crystal display device using the same, and more particularly, to a surface light source device using a novel light reflection sheet particularly suitably used for an illumination optical system, and a surface light source device using the same. The present invention relates to a liquid crystal display device using a light source device as a backlight optical system.

[0002]

2. Description of the Related Art In recent years, transmissive liquid crystal displays (displays) have been frequently used as monitors for personal computers and display devices such as thin TVs. A planar illumination device, that is, a backlight (surface light source device) is provided.
This surface light source device is a mechanism for converting a linear light source such as a cold cathode discharge tube into planar light.

[0003] Specifically, a method of arranging a light source immediately below the back surface of a liquid crystal element or a method of installing a light source on a side surface and converting the light into a planar shape using a translucent light guide such as an acrylic plate. A typical method is to obtain a surface light source (side light method), and a mechanism for obtaining desired optical characteristics by disposing an optical element such as a prism array on the light emitting surface.

[0004]

However, these conventional transmission type liquid crystal display devices have a problem that the structure is still complicated. The reason is that the structure of the surface light source device has to be complicated particularly because there is no appropriate light control member capable of obtaining desired optical characteristics in the surface light source device. This hinders the spread of this type of liquid crystal display device.

For example, in a surface light source device used as a backlight optical system of a transmission type liquid crystal display device, for example, optical sheets such as a prism sheet are frequently used in order to use illumination light from the surface light source device as effectively as possible. I was Therefore, the structure of the illumination optical system is complicated, and as a result, the assemblability is poor and the yield is low, resulting in an increase in cost.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems. By providing a novel illumination optical system, the illumination light can be effectively used, and the structure is simple and the assembly is easy. An object of the present invention is to provide an inexpensive surface light source device having excellent performance and a liquid crystal display device using the surface light source device as a backlight optical system.

[0007]

SUMMARY OF THE INVENTION The present invention is a surface light source device, and is configured as follows to solve the above-mentioned technical problem. That is, the surface light source device of the present invention includes a light guide having one surface as a light exit surface, a light extraction mechanism provided in the light guide, and a light source provided at a side end of the light guide. A light-reflecting sheet disposed on the surface of the light guide opposite to the light exit surface, and the light extraction mechanism includes a plurality of convex protrusions provided on the surface of the light guide opposite to the light exit surface. The light reflecting sheet is formed by arranging a large number of basic units on the surface thereof at a pitch of 5000 μm or less, and furthermore, each basic unit is formed by an inclined reflecting surface. Features.

<Specific Configuration in the Present Invention> The surface light source device of the present invention is composed of the above-mentioned essential components, but is established even when the components are specifically as follows. The specific component is that each reflecting surface forming a number of basic units is formed in parallel with each other and linearly,
The basic units are arranged at a pitch of 3000 μm or less, and the inclination angle of the inclined surface is set to an angle at which the light emitted from the light guide in the direction of the light reflecting sheet is reflected in the normal direction of the light guide. It is characterized by.

The surface light source device of the present invention is characterized in that the cross-sectional shape of the inclined reflecting surface forming the basic unit is concave, and in this case, the cross-sectional shape of the concave reflecting surface is constituted by a combination of straight lines. Is preferred. Further, in the surface light source device of the present invention, a concave mirror-shaped reflecting surface having a maximum diameter of 3000 μm or less is used as a reflecting surface forming the basic unit, and the inclination angle of the reflecting surface is emitted from the light guide toward the light reflecting sheet. An angle at which the reflected light is reflected in a direction normal to the light guide.

Further, in the surface light source device according to the present invention, the value h defined by the depth h of the convex protrusion and the minimum opening width Wmin.
/ Wmin is preferably 0.5 or more.
Further, it is preferable that a value h / Wmax defined by the depth h of the projection and the maximum opening width Wmax is 0.5 or more.

In the surface light source device of the present invention, it is preferable that 65% or more of the light flux emitted from the light guide is emitted to the light reflection sheet side by the light extraction mechanism including the convex protrusions. Further, a light-collecting element having a pitch of 2 with a ridge line substantially parallel to a normal direction to a light incident end face on a light exit surface of the light guide is provided.
It can be provided with a thickness of not more than 00 μm.

Further, the pattern composed of the convex protrusions is formed such that the opening width of each convex protrusion increases in a uniaxial direction as the distance from the light source increases, or the pattern of the convex shape has substantially the same shape as the distance from the light source increases. The protrusions can be formed so as to increase the distribution density.

Further, in the surface light source device of the present invention, it is preferable that the reflection surface of the light reflection sheet is formed of a silver or aluminum coating layer, and a coating layer of a transparent material is provided on the reflection surface. Further, the reflection surface of the light reflection sheet may be formed of a diffusely reflective white material. In that case, the coating layer made of a transparent material can be an optical thin film or a transparent bead coating layer. Then, it is also preferable to apply a mat treatment to the reflection surface. Furthermore, it is particularly preferable to use a surface light source device having the above-described features for a backlight optical system of a liquid crystal display device.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface light source device of the present invention and a liquid crystal display device using the same according to the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a partial perspective view showing a main part of a surface light source device 10 according to one embodiment of the present invention.

The surface light source device 10 according to this embodiment includes a substrate, that is, a light guide 11 made of a translucent flat plate, and one end of the light guide 11 has a line extending along the side end surface 12. The shape light source 13 is arranged. The linear light source 13 can use a fluorescent tube, an LED array, or the like, but is not particularly limited thereto. As the linear light source 13, it is most preferable to use a cold-cathode tube which has excellent luminous efficiency and can be easily miniaturized.

The arrangement of the linear light source 13 is as follows.
The present invention is not limited to this embodiment. In addition, a single-lamp type in which a cold cathode tube is provided only at one end, and two cold cathode tubes are provided at one end. A typical example is a two-lamp type, in which two cold-cathode tubes are provided at one side end and provided at the opposite side end, for a total of four lamps.

One end of the light guide 11 is connected to the linear light source 1.
A mechanism in which the reflector 14 is attached so as to cover the light guide 3 and the direct light from the linear light source 13 and the reflected light reflected by the reflector 14 enter the light guide 11 from the one side end surface 12 which is the light incident end surface. It has been. The light guide 11 is, for example, a light-transmitting thin plate having a square shape with a plate thickness of about 4 mm, and one surface, which is the upper surface as viewed in FIG. The other surface on the opposite side (the lower surface in FIG. 1) is the surface 16 facing the light emitting surface.

A light reflection sheet 17 is provided near the surface 16 of the light guide 11 opposite to the light exit surface 15.
The light reflection sheet 17 is configured such that a large number of basic units 18 each having an inclined reflection surface 18a are formed on the surface of a base material 19 at a fine pitch. Here, basic unit 1
8 is an inclined reflecting surface 1 having substantially the same and / or substantially similar shape as shown in FIGS. 1 to 3 and 15 to 20.
8a means a basic shape unit of the light reflecting sheet 17 obtained as an aggregate.

In other words, the basic unit 18 is a minimum shape unit, that is, a so-called unit cell, in which the identity or similarity is lost when the basic unit 18 is further divided. In addition, the pitch P is defined as the minimum length of the basic periods formed by the arrangement of the basic units 18 as shown in FIGS. 2, 3, and 15 to 20.

Further, the light guide 11 is provided with a light extraction mechanism 20 for emitting an incident light beam from a surface 16 opposite to the light emission surface 15. A representative example of this light extraction mechanism is a large number of projections 20 provided on the surface 16.
a. The light extraction mechanism 20 composed of a number of convex protrusions 20a selectively emits light rays incident on the light guide 11 to the surface 16.
From the light reflection sheet 17.

In this case, normally, the projection 20a
The directivity of the light beam selectively emitted to the side of the light reflection sheet 17 does not mean that the light beam enters the light reflection sheet 17 at right angles. Therefore, the light is reflected by the light reflection sheet 17 and is directed in the front direction of the surface light source device 10. The emitted light beam has a high light intensity in a direction deviated from the front.

However, the surface light source device 1 according to this embodiment
0, the light reflecting sheet 1 close to the surface 16 of the light guide 11
7, the light component 21 selectively emitted from the light guide 11 to the light reflection sheet 17 side by the effect of the basic unit 18 as shown in FIG. The direction is deflected in the front direction (the deflected ray component is indicated by reference numeral 22), and as a result, when the surface light source device 10 is viewed from the front, an extremely high illumination intensity can be obtained. In FIG. 4, reference numeral 23 denotes a light ray component that does not travel toward the light reflection sheet 17.

This is because the structure of the optical system of the surface light source device 10 can be extremely simplified. In the conventional surface light source device, the light condensing function and the angle changing function are performed by a prism array or the like. On the other hand, in the surface light source device 10 of the present embodiment, the substantially identical and / or substantially similar basic unit 18 formed of the inclined reflecting surface 18a provided on the light reflecting sheet 17 is formed into a shape like a concave mirror, for example. By designing and the like, it is possible to provide the light reflecting sheet 17 with desired optical functions such as a condensing function and a bending function, and a surface whose structure is extremely simplified while maintaining the same optical performance. A light source device can be provided.

Here, as the above-mentioned convex protrusions 20a which function to emit most of the light beam components 21 to the light reflecting sheet 17 side, various shapes shown in FIGS. The convex projection 20a shown in FIG. 5 has an elliptical cross section, and the convex projection 20a shown in FIG.
Has a rectangular cross section. The convex protrusion 20a shown in FIG. 7 has a rectangular cross section and a triangular shape with a sharp lower end. Further, the convex protrusion 20 shown in FIG.
a is a rectangle whose cross section is close to a square.

As described above, various shapes can be used as the shape of the convex protrusions 20a, but the condition that most of the light rays incident on the convex protrusions 20a are emitted to the light reflection sheet 17 side is satisfied. It must be something to do. More specifically, as shown in FIGS. 5 to 8, the height of the projection 20 a, in other words, the depth h and the minimum opening width Wmin of the projection 20 a when viewed from inside the light guide 11.
The value h / Wmin defined by is preferably 0.5 or more,
It is more preferably 0.6 or more, and further preferably 0.7 or more. By doing so, most of the light rays that have entered the convex protrusions 20 a are emitted toward the light reflection sheet 17.

Further, in order to sufficiently emit the light beam incident on the convex protrusion 20a to the light reflection sheet 17, the shape of the opening of the convex protrusion 20a should be the maximum opening width as shown in FIGS. The value h / Wmax defined by Wmax and the depth h of the convex protrusion 20a is preferably 0.5 or more, more preferably 0.7 or more, and still more preferably 0.9.
That is all.

This situation will be described in more detail. As shown in FIG. 9, when the minimum opening width Wmin is favorable, the light ray 24 propagating in the light guide 11 easily hits the wall surface of the convex protrusion 20a. The light beam striking the wall surface is no longer staying in the light guide 11 and is emitted toward the light reflection sheet 17 (emitted light is indicated by reference numeral 21).
It will be.

However, in the case where the minimum opening width Wmin shown in FIG. 10 is in an inappropriate range, the light ray 24 propagating in the light guide 11 easily hits the bottom of the convex protrusion 20a. As shown in the trajectory, the light component 2 which does not exit to the light reflection sheet 17 because it hits the wall surface after the total reflection at the bottom of the convex protrusion 20a and hits the wall surface
3 is generated in large numbers. That is, from the viewpoint of emitting light toward the light reflection sheet 17, the most preferable is the minimum opening width Wmi as shown in FIG.
This is a case where both n and the maximum opening width Wmax are in the suitable ranges.

Considering this situation in geometric optics theory,
First, in fluorescent tubes and the like often used as light sources,
Ultraviolet light obtained by the plasma discharge excites the phosphor fine particles attached to the tube wall to emit light, and the emission angle distribution of the emitted light beam obtained therefrom exhibits a uniform intensity at almost any angle. This is close to what is called a diffusion light source.

FIG. 2 shows the vicinity of the light incident surface of the light guide.
7, the geometrical optical state distribution of the light beam propagating through the light guide is considered under the condition that the incident angle distribution of the light beam incident on the light guide is constant at all angles.
From Snell's law, let n be the refractive index of the light guide,

(Equation 1)

Therefore, the angle between the incident angle ψ of the light beam emitted from the light source and the light beam incident on the light guide (or the angle of incidence of the light beam incident on the light guide having the refractive index n at the incident angle ψ). FIG. 28 illustrates the relationship of the outgoing angle (θ) into the light guide. State number density n (θ) of the ray at each θ
First, the amount of light reaching the region of width ± △ θ / 2 at a certain θ is, under an approximation ignoring Fresnel loss at the light guide interface, the state number density n at the corresponding ψ
Using (ψ)

(Equation 2) here,

(Equation 3) In addition, when the angle distribution of the incident light is constant, n (ψ) = Const. Because

(Equation 4) Therefore,

(Equation 5) Therefore, the ray distribution density n (θ) at θ is

(Equation 6) That is, the number of states greatly increases in the vicinity of the critical angle, which means that even if the effect due to the Fresnel loss is considered in the equation (1),

Equation 7 And the tendency is the same (fs and fp represent s-polarized light and p-polarized light, respectively).

Therefore, in the case of the transparent resin used for the light guide, there are many beams incident at an incident angle of about 50 degrees as an incident angle on the light guide surface side where the light extraction mechanism is formed. . In other words, as shown in FIG. 11, if the shape is sufficiently deep with respect to the opening width of the projection, light rays incident on the opening of the projection are necessarily emitted from the wall surface of the projection. Therefore, it is possible to selectively output the outgoing light beam in only one direction, and the suitable ranges of h / Wmin and h / Wmax described above are determined by these circumstances.

In the present invention, it is extremely important that most of the light emitted from the light guide 11 is emitted toward the light reflection sheet 17. For example, the value h / Even if a light guide having a value of Wmin in a preferable region is obtained, the side surface of the convex protrusion 20a and the surface around the opening of the convex protrusion 20a are roughened due to mold accuracy and the like. In such a case, light rays are irregularly reflected at the rough surface portion, and a situation occurs in which most of the light rays cannot be emitted to the light reflection sheet 17 side.

That is, it is extremely important that the convex protrusions 20a are formed as smooth as possible in order to properly maintain the direction selectivity of the light flux emitted from the light guide 11, and the conventional surface In an embodiment in which the light extraction mechanism is a light scattering phenomenon caused by a simple rough surface or light scattering fine particles seen in a light source device, the effect of the illumination optical system of the present invention cannot be sufficiently brought out. More specifically, the surface of the convex protrusion 20a has a ten-point average roughness Rz value defined in JIS B0601 of preferably 0.01 to 10 μm, more preferably 0.02 to 4 μm, and still more preferably 0.02 to 4 μm.
It is preferable that the thickness be in the range of 0.05 to 2 μm, particularly preferably 0.05 to 1 μm, so that unnecessary light scattering (light diffusion) phenomenon due to the rough surface portion does not occur.

Therefore, in the present invention, the light guide 11 is provided with the side end 1.
When the light ray incident from the light guide 2 is emitted, the light guide 11 is arranged such that preferably 65% or more, more preferably 70% or more, even more preferably 75% or more of the emitted light flux is emitted to the light reflection sheet 17 side. It is preferable that a pattern composed of convex protrusions 20 a is provided as the light extraction mechanism 20.

Here, in the light guide 11 used in the present invention, the ratio of the light flux selectively emitted to the light reflecting sheet side to the total light flux emitted from the light guide is preferably 6.
As described above, it is necessary for the effect of the optical design according to the present invention to be 5% or more in order for the effect of the optical design to function effectively. The outline is as follows.

That is, first, the black sheet 31 that absorbs light almost completely is provided at the position where the normal light reflection sheet is provided.
(Flocked paper or the like) is disposed, and as shown in FIG. 29, the light guide 11 is set in a normal direction and turned on in the integrating sphere 32, and the light exit surface of the light guide 11 obtained at this time is provided. The total luminous flux emitted from the side is defined as Σa.

Next, the direction of the light guide 11 is set upside down as usual (original so that the surface facing the light reflecting sheet side is on the light emitting surface side), and the integrating sphere 32 is similarly set. And the total amount of luminous flux emitted from the surface opposite to the light exit surface of the light guide 11 obtained at this time is represented by Δb. At this time, the obtained numerical value, Σb / (Σa + Σb) × 100, is the ratio (%) of the luminous flux selectively emitted to the light reflecting sheet side.
This value is preferably at least 65%, more preferably at least 70%, and even more preferably at least 75%.

As the surface light source device, in order to keep the illumination intensity constant in the plane, the outer shape of the pattern composed of the convex protrusions 20a as the light extraction mechanism 20 becomes lighter as the distance from the light source 13 is increased. It is adjusted so that the take-out efficiency can be increased. As this adjustment mode,
A mode in which the area of the opening of the convex protrusion 20a increases, a mode in which the convex protrusions 20a having substantially the same shape are used, and an arrangement density of the convex protrusions 20a increases as the distance from the light source 13 increases, and the like are exemplified.

Among these adjustment modes, the one that is particularly easy to adjust is the mode in which the area of the opening of the convex projection 20a is increased. However, in the present invention, as described above, the convex protrusion 2
The light extraction mechanism 20 realized by the light guide 11
It is necessary to perform a function of selectively emitting light propagating through the inside only to the light reflection sheet 17 side, and the value h / Wmin defined by the depth h and the minimum opening width Wmin is kept at a high value. Is preferred.

Therefore, if the area of the opening of the projection 20a is simply increased, the value of h / Wmin may deviate from a desirable value at a position away from the light source 13. You. Therefore, a pattern shape that increases the area of the opening of the convex protrusion 20a while keeping the value of h / Wmin constant is most preferable. Specifically, the light source 13 is provided as shown in FIG. Most preferably, the pattern shape is such that the opening of the protruding projection 20a is increased in the uniaxial direction as the distance from the position increases.

Further, as another adjustment mode, as shown in FIG. 13, the light source is formed by using convex protrusions of substantially the same shape in which the values of h / Wmin, h / Wmax, etc. are within the above-mentioned preferable ranges. An embodiment using a pattern shape in which the arrangement density is increased as the distance from the position where 13 is arranged is increased is also preferably used. In particular, in this embodiment, since the convex protrusions 20a having substantially the same shape are used, the convex protrusions 20a are used.
a) The single shape can be a shape having an extremely high ability to selectively emit light toward the light reflection sheet 17, which is the most preferable mode for improving the efficiency of the surface light source device 10.

Light reflecting sheet 1 used in the present invention
Reference numeral 7 denotes a flexible substrate 1 having a thickness of about 1000 μm or less.
9 is preferable, but the form such as the thickness is appropriately selected depending on the application object, and is not necessarily limited to this. Further, it is desirable that the reflectivity be made of a material having a high reflectivity from the viewpoint of high efficiency.

Here, the material having a high reflectivity in the present invention is a material having a high reflectivity in a typical wavelength region of the visible light spectrum, since it is mainly used for image display for human viewing. Means that That is, as defined in JIS-Z8120, the ratio of the reflected luminous energy to the incident luminous energy in the visible light spectrum region has the above value, and is usually 70% or more, preferably 75% or more, more preferably 85% or more. Particularly preferably at least 88%,
It is very preferably at least 91%.

In the present invention, it is necessary to avoid a change in color tone in the light reflection sheet portion, and it is preferable that the light reflection sheet portion has reflection characteristics as flat as possible in the visible light spectrum range. Therefore, the value of the spectral reflectance at 550 nm, which is located substantially at the center of the visible spectrum, is used as the reflectance, and a preferable value range can be defined.

In addition, the above-mentioned reflectance means the reflectance of the material located on the surface of the inclined surface which substantially causes reflection, and specifically, the surface of the inclined surface is typified by silver or aluminum. As described above, it is preferable to provide a material having a high reflectance and a small change in color tone. In addition, a transparent coat layer or the like may be provided on the reflective surface, but the reflectivity referred to here is the reflectivity of the surface of the material itself which does not have a coat layer or the like and which substantially contributes to reflection such as a metal material. It means.

Regarding the directivity of reflection, specular reflection and diffuse reflection are determined according to the required optical characteristics of illumination light.
It is appropriately selected, but in general, a mirror reflection layer made of silver, aluminum, or the like is preferably used for obtaining high directivity, and a white pigment is used for obtaining a wide emission angle distribution. A diffuse reflection layer made of a kneaded resin or a foamable resin is preferably used.

In order to make the arrangement of the basic units 18 unrecognizable on the screen, it is important that the arrangement pitch P of the substantially identical and / or substantially similar basic units 18 is as fine as possible. Yes, specifically 5
The thickness is set to 000 μm or less, preferably 1000 μm or less, more preferably 500 μm or less.

As a substantially identical and / or substantially similar basic unit 18 composed of an inclined reflecting surface 18a provided on the surface of the light reflecting sheet 17, typically, FIG.
3A and 3B, the basic unit 18 has a sawtooth cross section, or as shown in FIGS. 3A and 3B, the basic unit 18 has a mountain shape. 18 is a structure having periodicity only in one axial direction,
Pitch 3000 μm or less, preferably 800 μm or less,
More preferably, an array of basic units 18 having a parallel linear and flat inclined reflecting surface 18a, which is 300 μm or less and in which the ridge lines 18b are arranged in parallel when the light reflecting sheet 17 is viewed from above, is used. An embodiment is mentioned.

This is shown in FIGS. 2A and 2B and FIG.
As shown in (a) and (b), in a mode in which the ridge lines 18b of the inclined flat reflecting surface 18a are arranged substantially in parallel, cutting using a diamond bite or an end mill is easy to apply, and thus the This is because the metal mold is easy to manufacture, miniaturization is easy, and mass productivity is extremely high.

By using such a light reflecting sheet 17 in which a large number of parallel linear and flat inclined reflecting surfaces 18a are arranged, the pattern composed of the above-mentioned convex projections 20a is used as the light extraction mechanism 20 and the light flux of the emitted light flux is formed. Most of the light emitted from the light guide 11 designed to be directed to the side on which the light reflecting sheet 17 is provided is parallel straight and flat inclined reflecting surface 1.
Since the light is reflected in the normal direction of the light guide 11 by the effect of 8a, it is possible to obtain an illuminating light beam having extremely suitable characteristics as the surface light source device 10.

More specifically, when the angle between the flat reflecting surface 18a and the horizontal line is α as shown in FIG. 14, the inclination angle α of the inclined reflecting surface 18a is preferably in the range of 50 to 7 degrees. More preferably, a range of 40 to 10 degrees is used, and still more preferably, a range of 34 to 15 degrees is used.

The cross section of the inclined reflecting surface 18a constituting each basic unit 18 is concave as shown in FIGS. 15 (a) and 15 (b) and FIGS. 16 (a) and 16 (b). This is preferable from the viewpoint of light collecting properties. Making the cross-sectional shape of the reflecting surface 18a concave in this manner is not only a mode in which a large number of parallel linear inclined reflecting surfaces 18a suitably used in the present invention are arranged, but also a concave mirror as shown in FIGS. It is also suitably used in an embodiment in which the basic units 18 are arranged in a shape. Also in this case, the range preferably used as the inclination angle α of the inclined reflecting surface 18a conforms to the above, and the inclination angle of the tangent at the center of the concave cross section is preferably 50 to 7 as shown in FIG. Degree, more preferably 40 to 10 degrees, still more preferably 3 degrees.
The range is 4 degrees to 15 degrees.

The effect of making the cross-sectional shape of the inclined reflecting surface 18a concave will be described. For example, in the case where a large number of parallel linear and concave concave reflecting surfaces 18a are arranged, as shown in FIG. The light beam 21 emitted with a broad spread of the emission angle distribution in the direction of the parallel linear inclined reflection surface 18a from the projection 20a is converted into a light beam 22 (a light beam closer to a parallel light beam) having a sharper angular characteristic. The light can be emitted in the normal direction of the light guide 11 during the conversion, in other words, the effect of the concave mirror can be imparted to the parallel linear inclined reflection surface 18a.

That is, in the conventional surface light source device, the light-collecting effect which is difficult to manufacture and is realized by using an expensive member such as a prism array even if it can be manufactured can be achieved without using such a member. Therefore, the surface light source device can have an extremely simplified configuration while maintaining substantially the same optical characteristics, and as a result, the number of assembly steps can be reduced.
Improvement of yield, reduction of dust mixing probability, cost reduction, etc.
It has a great many advantages as a practical surface light source device.

Further, in the conventional surface light source device, as shown in FIG. 22, at the side end 12 of the light guide 11 where the light source 13 is disposed, a phenomenon called a bright line 28 which deteriorates the appearance occurs. Was. However, this is mainly caused by light rays incident on the upper and lower surfaces of the light guide 11 through the reflection sheet near the side end 12 of the light guide 11, and the reflector arrangement was changed to remove the bright line 28. Or taking measures such as applying light-absorbing printing to the reflective sheet,
This has further complicated the structure and increased the cost.

However, in the surface light source device of the present invention, as described above, the light reflection sheet 17 uses the substantially identical and / or substantially similar basic unit 18 composed of the inclined reflection surface 18a. As shown in (1), in the conventional surface light source device, light rays incident as much as possible to become bright line components are rebounded by the basic unit 18 composed of the inclined reflecting surface 18a, and are no longer emitted onto the light guide 11 as bright lines. In addition, the appearance quality as a surface light source is also extremely excellent.

Here, from the viewpoint of the light condensing property of the surface light source device of the present invention, it is preferable that an inclined reflecting surface 18 a having a concave cross section is used for the basic unit 18.
As described above, it is more preferable that the inclined reflecting surface 18a having a concave cross section has a polygonal cross section.
This is because, when a mold is manufactured, cutting using a diamond tool or the like is generally used. The reason why the tool is easy to create is that it has a polygonal cross section.

Another preferred embodiment of the present invention in the substantially identical and / or substantially similar basic unit 1 composed of the inclined reflecting surface 18a has a maximum diameter as shown in FIGS. An embodiment in which a structure in which concave mirror-like reflecting surfaces 18a each having a size of 3000 μm or less, preferably 800 μm or less, and more preferably 300 μm or less are arranged is used. The advantage of using such an embodiment is that light can be condensed not only in one direction but also in two orthogonal directions. It is possible to improve the light collecting property.

Here, even in the embodiment using the structure in which the concave mirror-shaped inclined surfaces are arranged, the light component emitted from the pattern portion composed of the convex protrusions toward the light reflecting sheet side is reflected by the light guide. Needless to say, the shape is designed so as to reflect in the linear direction, thereby simultaneously condensing light in two directions and changing the direction of the light beam in the front direction of the light guide. Excellent illumination light can be obtained.

In order to further improve the light-collecting property of the surface light source device in the present invention, the upper surface 15 of the light guide (the surface on which the pattern composed of the convex protrusions is not disposed) is provided with
At a pitch of 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less, a mountain-shaped unevenness 25 as shown in FIG. 24 or a corrugated plate-shaped unevenness 26 as shown in FIG. It is preferable to provide a lenticular lens element 27 as shown in FIG.

At this time, peak-shaped or corrugated unevenness 2
The directions of 5 and 26 are provided such that the ridge line is substantially perpendicular to the side end 12 where the light source 13 is provided. Thereby, in addition to the light condensing effect obtained from the inclined reflecting surface 18 a having a concave cross section provided on the light reflecting sheet 17,
An extremely high light-collecting effect can be obtained.

The reflective material used for the light reflecting sheet 17 in the present invention is not particularly limited, but it is most preferable to coat the surface with silver or aluminum to form the reflective surface 18a from the viewpoint of ease of manufacture. It is. In particular, a method of forming a thin silver reflective layer using a dry process such as vacuum evaporation, sputtering, or ion plating and coating the surface is most preferable.

For example, before the vacuum deposition with silver, the surface of the base sheet on which the basic unit 18 having the substantially identical and / or substantially similar shape formed of the inclined reflecting surface 18a is formed by sandblasting or the like. Alternatively, a mat treatment can be performed. By performing such processing, it becomes possible to impart a proper light diffusing property to the specular reflection surface, to increase the angular distribution characteristics of the emitted light, suppress the glare of the illumination light, or reduce the liquid crystal cell. It is possible to obtain effects such as prevention of generation of a moiré pattern due to interference with the gate array.

Also, since the glossy metal surface such as the silver reflection layer is very easily damaged and easily oxidized and deteriorated, an ultraviolet-curable acrylic resin paint is applied to the surface as a protective layer. It is preferable to prevent the deterioration of the optical characteristics due to scratches or the like. Furthermore, by providing a coating layer of a light-transmitting bead represented by an acrylic bead or the like as a protective layer, a matting treatment is applied to the above-described basic unit having substantially the same and / or substantially similar shape composed of the inclined reflecting surface. The same effect can be obtained.

In addition, the function of the transparent coat layer as an optical thin film can be imparted to further enhance the controllability of incident light. For example, an optical thin film such as a λ / 4 plate or a λ / 2 plate can be provided, and a function of controlling the polarization state of an incident light beam such as a beam splitter function or a polarization conversion function by further laminating these optical thin films. It is also possible to obtain a light reflecting sheet having the following.

The reflection layer is not limited to a reflection layer made of a regular reflection metal material. For example, a diffusion reflection layer made of a polyester resin kneaded with a white pigment such as titania is used. Can also. In this case, since the incident light is scattered in various directions by the diffuse reflection surface, the directivity of the reflected light can be expanded, and the viewing angle characteristics of the illumination light can be changed to the regular reflection property of an Ag thin film or the like. Thus, it is possible to further enlarge the case where the reflecting surface is used.

As a method of forming the diffuse reflection layer, besides the above,
Foamable polyester resin, foamable polyolefin resin,
Examples include a mode in which a reflective layer having a diffuse reflection property is obtained from a foamable ABS resin and the like, and a mode in which a base material surface is coated with a paint made of a white pigment.

In a preferred embodiment of the present invention, the light reflection sheet 17 is formed of a resin material. In particular, a polyester resin, an acrylic resin, a polycarbonate resin, or a cyclic polyolefin resin is preferably used,
For forming the concave reflecting surface array, shaping by hot press molding,
Alternatively, shaping with a photocurable resin is suitably used.

In the present invention, the liquid crystal display device uses an electro-optical effect of liquid crystal molecules, that is, optical anisotropy (refractive index anisotropy), orientation, and the like, and applies an electric field or applies an electric current to an arbitrary display unit. It refers to a device that performs display by using a liquid crystal cell, which is an array of optical shutters, driven by changing the alignment state of liquid crystal and changing light transmittance and reflectance.

More specifically, transmission type simple matrix driving super twisted nematic mode, transmission type active matrix driving twisted nematic mode, transmission type active matrix driving in-plane switching mode, transmission type active matrix driving multi-domain vertical aligned mode, etc. Liquid crystal display device.

By configuring the surface light source device of the present invention as a backlight light source for these liquid crystal display elements in a liquid crystal display device, the surface light source device using the light reflecting sheet described above can be reduced in thickness (less sheets). It is possible to obtain a liquid crystal display device with improved image quality, particularly with less bright lines, with a simple structure, improved assemblability, high yield, and reduced cost.

[0073]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. (Example 1) 350.0 × 285.0 as the light guide 11
Assuming that a linear light source 13 composed of a cold-cathode tube is disposed on two long sides using an acrylic resin having a thickness of 5 mm and a thickness of 5 mm, the length becomes relatively larger in the uniaxial direction as the distance from the linear light source 13 increases. A convex protrusion 20a having a rectangular opening shape and patterned as described above was formed on the light guide 11.
FIG. 6 shows an enlarged view of the projection 20a. Convex protrusion 20a
Has a depth h of 30.0 μm, and the minimum opening width Wmin of the projection 20 a when viewed in a cross section in a direction perpendicular to the linear light source 13 is 25.0 μm.

Here, the mold used to form the projections 20a was formed by laminating a dry film resist having a thickness of 30 μm on a glass plate, forming a pattern by photolithography, and performing patterning with the dry film resist. Electrodes are deposited on a glass plate and used as a master by nickel electroforming.

The convex protrusion 20a, which is the light extraction mechanism 20 of the light guide 11, is provided on the side where the light reflection sheet 17 is provided, and the convex projection 20a having the above-described shape is used as the light extraction mechanism 20. Thus, a light guide suitable for use in the present invention, in which 87% of the light flux emitted from the light guide 11 is emitted toward the light reflecting sheet, was obtained.

As the light reflection sheet, a light reflection sheet 17 having a basic unit 18 having a parallel linear inclined reflection surface 18a having the shape shown in FIG. 3 and ridge lines arranged in parallel was used. The pitch is 120 μm, and the reflective layer (surface)
, A silver sputtering layer is used, and the surface of the silver sputtering layer is coated with an acrylic resin.
The inclination angle of the inclined reflecting surface 18a is 24.5 degrees,
The light emitted from the light guide 11 obtained by the light extraction mechanism 20 including the convex protrusions 20a to the light reflection sheet 17 side is changed in direction by the light reflection sheet 17, and the light guide 1
An optical system that emits light in the normal direction of 1 was obtained.

As the light source 13, a cold cathode tube having a diameter of 2.6 mm is used.
The light diffusion sheet 30 obtained by coating acrylic beads having a haze of 65% was disposed immediately above the light emission surface 15 of the first light-emitting surface 15 to obtain a surface light source device. With a tube current of 6 mA, the average luminance at 25 points in the plane was measured using a luminance measuring device (manufactured by Tobcom, BM-7). As a result, an average luminance of 2250 nit was obtained. It was confirmed that the optical characteristics were sufficient for practical use as a light source.

Further, since a prism sheet normally provided was not used, there was little dust mixed between the sheets and the assembling property was good. In addition, due to the effect of the light reflecting sheet 17, a bright line appearing in the vicinity of the light source, which was generated in the conventional surface light source device, was removed, and the image quality was excellent.

(Example 2) As the light guide 11, 210.0
× 190.0 mm, a thickness of 2 mm near the light source, 0.6 mm at the position farthest from the light source, a wedge-shaped acrylic plate whose thickness changes in the short side direction is used, and a cold cathode tube is used for the thick part Assuming that a linear light source is provided, a convex protrusion 20a having an elliptical opening is formed on the light guide 11 so as to be patterned such that the length becomes relatively large in the uniaxial direction as the distance from the linear light source increases. . FIG.
The enlarged view of a is shown.

The depth h of the projection 20a is 50.0 μm, and the minimum opening width Wmin of the projection 20a when viewed in a section perpendicular to the linear light source is 55.0 μm. Here, the mold used for forming the projections 20a is formed by laminating a dry film resist having a thickness of 50 μm on a glass plate, forming a pattern by photolithography, and forming a pattern by the dry film resist on the glass plate. An electrode is formed by vapor deposition, and this is used as a master by nickel electroforming.

On the side of the light guide 11 where the light extraction mechanism 20 composed of the convex projections 20a is not provided, in order to further enhance the light condensing property of the light guide 11, as shown in FIG. A prism array having a pitch of 50 μm is formed, and the ridge line of the prism array is arranged to be perpendicular to the side end 12 where the linear light source 13 is provided.

The convex projection 20a, which is the light extraction mechanism 20 of the light guide 11, is provided on the side on which the light reflecting sheet 17 is provided, and the convex projection 20a having the above-described shape is used as the light extraction mechanism 20. Thus, a light guide suitable for use in the present invention in which 74% of the light flux emitted from the light guide 11 is emitted toward the light reflection sheet 17 was obtained.

The light reflecting sheet has a parallel linear inclined reflecting surface 1 having a shape shown in FIG. 15 and ridge lines arranged in parallel.
A light reflection sheet 17 having a base unit 8a was used. The pitch is 100 μm, and a silver sputtering layer is used for the reflection layer (surface), and the surface of the silver sputtering layer is coated with an acrylic resin. The inclination angle α of the inclined reflecting surface 18a is set to 27 degrees, and the light emitted from the light guide 11 obtained by the light extraction mechanism 20 including the convex protrusions 20a to the light reflection sheet 17 side is reflected by the light reflection sheet 17. Change direction, light guide 11
An optical system that emits light in the normal direction was obtained.

A cold cathode tube having a tube diameter of 2.0 mm was used as the light source 13, and was turned on at a high frequency via an inverter.
A light diffusion sheet 30 obtained by coating acrylic beads having a haze of 42% was disposed immediately above the light exit surface 15 of the first light-emitting surface 15 to obtain a surface light source device. With a tube current of 6 mA, an average luminance of 1820 nits was obtained as a result of measuring the average luminance at 25 points in the plane using a luminance measuring device (BM-7, manufactured by Topcom). It was confirmed that the optical characteristics were sufficient for practical use as a light source.

Also, since no prism sheet is usually provided, two dust sheets are not mixed between the sheets, the assembling property is very good, and there is no extra sheet. Thus, a thin and lightweight surface light source device was obtained. In addition, due to the effect of the light reflection sheet 17, a bright line which occurs in the conventional surface light source device and appears near the light source, which requires special measures, is removed, and the image quality is excellent.

(Embodiment 3) As the light guide 11, 45.0 ×
Using an acrylic plate with a thickness of 37.0 mm and a thickness of 1 mm,
A linear light source 13 composed of a white LED is provided at a corner, and the opening is shaped like a rhombus that is patterned so that the length becomes relatively larger in a uniaxial direction as the distance from the corner where the light source 13 is provided. Are formed on the light guide 11. FIG. 8 shows an enlarged view of the projection 20a.

The depth h of the projection 20a is 27.0 μm, and the minimum opening width Wmin of the projection 20a when viewed in a section perpendicular to the linear light source 13 is 31.0 μm. Here, as in the case of the first and second embodiments, the mold used for forming the convex protrusions 20a is obtained by depositing an electrode on a glass plate patterned with a dry film resist and using this as a master by nickel electroforming. Was.

On the side of the light guide 11 on which the light extraction mechanism 20 composed of the convex protrusions 20a is not provided, the apex angle is 90 degrees and the pitch is 50 μm in order to further enhance the light condensing property of the light guide 11.
The prism array is formed such that the ridge line of the prism array is perpendicular to the side end where the white LED light source is arranged.

The convex projection 20a, which is the light extraction mechanism 20 of the light guide 11, is provided on the side where the light reflection sheet 17 is provided, and the convex projection 20a having the above-described shape is used as the light extraction mechanism 20. Thus, a light guide suitable for use in the present invention was obtained, in which 72% of the light flux emitted from the light guide 11 was emitted toward the light reflection sheet 17.

As the light reflecting sheet, a reflecting surface 18a having the shape shown in FIG.
The light reflection sheet 17 was used. The maximum diameter of the concave mirror portion is 70 μm, and a silver sputtering layer is used for the reflection layer (surface), and the surface of the silver sputtering layer is coated with an acrylic resin containing beads. The inclination angle α of the inclined reflection surface 18a is set to 24 degrees, and the light emitted from the light guide 11 obtained by the light extraction mechanism 20 including the convex protrusions 20a to the light reflection sheet 17 side is
The direction of the light was changed by the light reflection sheet 17, and an optical system in which light was emitted in the normal direction of the light guide 11 was obtained.

The light source has an outer shape of 2.0 × 3.0 × 1.6 mm.
DC voltage of 3.3 using a chip type white LED
A surface light source device which was turned on at V and used a white LED as a light source was obtained. As a result of measuring the average luminance at five points in the plane using a luminance measuring device (BM-7, manufactured by Topcom), the average luminance was 430 ni.
t was obtained, and it was confirmed that both the luminance performance and the luminance unevenness were optical characteristics sufficient for practical use as a backlight light source of a portable liquid crystal display panel.

Further, since a prism sheet which is generally used is not used, the assembling property is extremely good, and since there is no extra sheet, a thin and lightweight surface light source device can be obtained. In addition, since the glare of the illumination light is also improved by the effect of the acrylic beads coated on the surface of the light reflection sheet 17, the liquid crystal panel can be put to practical use even if the liquid crystal panel is arranged right above the light guide 11. A surface light source device was obtained.

(Example 4) A light reflection sheet 17 in which a parallel linear inclined reflection surface 18a in which ridge lines are arranged in parallel is used as a basic unit 18, and the cross-sectional shape of the basic unit 18a is concave as shown in FIG. A surface light source device was obtained in the same manner as in Example 1 except for using. Due to the effect of the reflecting surface having a concave cross section, the light flux emitted to the light reflecting sheet side is changed in the direction of the normal line of the light guide and collected at the same time, so that the average luminance is 2880 nits compared to the first embodiment. Heightened. The practicality as a surface light source device is extremely high as in the first embodiment.

(Embodiment 5) In the surface light source device described in Embodiment 2, the patterning is changed, and the distribution density increases as the protrusions 20a of the same shape move away from the linear light source 13 as shown in FIG. It was a patterned shape. The depth h of the projection 20a is 50 μm, and the minimum opening width W
A convex protrusion having a square opening shape and having a minimum opening width of 55 μm and a maximum opening width Wmax of 55 μm is used.

By using the above-described pattern shape, as shown in FIG. 11, the ability to selectively emit light toward the light reflecting sheet 17 is enhanced, and 88% of the light flux emitted from the light guide 11 is reduced. An extremely suitable light guide for use in the present invention, which is emitted to the light reflection sheet 17 side, was obtained. The average luminance at 25 points in the plane was 2150 nits, and the practicability as the surface light source device was extremely high as in Example 2.

[0096]

As described above, according to the surface light source device of the present invention, it is possible to obtain an inexpensive surface light source device having the above-mentioned excellent optical characteristics, a simple structure, and an excellent assembling property. Further, by using this surface light source device as a backlight light source means, an inexpensive liquid crystal display device having a simple structure and excellent assemblability can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a light reflection sheet used in the surface light source device of the present invention, in which a plurality of basic units each having a parallel ridge line and arranged in parallel and having a flat inclined reflection surface are formed on the surface. Partial plan view of reflection sheet and 2b-2b
It is sectional drawing cut | disconnected and shown by a line.

FIG. 3 is a light reflection sheet used in the surface light source device of the present invention, in which a plurality of basic units each having a parallel linear ridge and a flat inclined reflection surface are formed on the surface, and ridge lines are arranged in parallel. 3A and 3B are a partial plan view and a cross-sectional view taken along line 3b-3b of the light reflecting sheet according to the embodiment.

FIG. 4 is a configuration explanatory view schematically showing a state in which a light beam incident on a light guide becomes a surface light source in the surface light source device of the embodiment shown in FIG. 1;

FIG. 5 is a schematic structural explanatory view showing definitions of a depth h, a minimum opening width Wmin, and a maximum opening width Wmax for an example of a convex protrusion constituting a light extraction mechanism provided in a light guide.

FIG. 6 shows a depth h and a minimum opening width Wmin of another example of the convex protrusion constituting the light extraction mechanism provided in the light guide.
FIG. 4 is a schematic configuration explanatory view showing definitions of a maximum opening width Wmax.

FIG. 7 shows a depth h and a minimum opening width Wm of still another example of the convex protrusion constituting the light extraction mechanism provided in the light guide.
It is a schematic structure explanatory view showing the definition of in and the maximum opening width Wmax.

FIG. 8 shows a depth h and a minimum opening width Wm of still another example of the convex protrusion constituting the light extraction mechanism provided in the light guide.
It is a schematic structure explanatory view showing the definition of in and the maximum opening width Wmax.

FIG. 9 is a configuration explanatory view showing a state in which the ability to selectively emit a light beam toward the reflection sheet changes depending on the shape of a convex protrusion constituting a light extraction mechanism provided in the light guide.

FIG. 10 is a configuration explanatory view showing a state in which the ability to selectively emit a light beam to the reflection sheet side changes depending on the shape of a convex protrusion constituting a light extraction mechanism provided in the light guide.

FIG. 11 is a configuration explanatory view showing a state in which the ability to selectively emit a light beam to the reflection sheet side changes depending on the shape of a convex protrusion constituting a light extraction mechanism provided in the light guide.

FIG. 12 is a plan view schematically showing an example of an arrangement pattern of convex protrusions constituting a light extraction mechanism provided in a light guide.

FIG. 13 is a plan view schematically showing another example of an arrangement pattern of convex protrusions constituting a light extraction mechanism provided in a light guide.

FIG. 14 is a cross-sectional view showing a parallel linear and flat inclined reflecting surface of the basic unit formed on the light reflecting sheet shown in FIG. 2 in a partially enlarged manner, and showing an inclination angle of the inclined reflecting surface;

FIG. 15 is a light reflection sheet used in the surface light source device of the present invention, wherein a plurality of basic units each having a parallel linear ridge and a concave inclined reflection surface are formed on the surface, and the ridge lines are arranged in parallel. It is the partial top view of the light reflection sheet of another aspect, and sectional drawing cut | disconnected and shown by 15b-15b line.

FIG. 16 is a light reflection sheet used in the surface light source device of the present invention, in which a plurality of basic units each having parallel ridge lines arranged in parallel and formed of parallel linear and concave inclined reflection surfaces are formed on the surface. FIG. 2 is a partial plan view of a light reflecting sheet according to an embodiment, and a cross-sectional view cut along line 16b-16b.

FIG. 17 is a light reflection sheet used in the surface light source device of the present invention, further comprising a plurality of basic units formed of parallel linear and concave inclined reflection surfaces in which ridge lines are arranged in parallel. It is the partial top view of the light reflection sheet of another aspect, and sectional drawing cut | disconnected and shown by 17b-17b line.

FIG. 18 is a partial plan view of a light reflection sheet used in the surface light source device of the present invention, which is a light reflection sheet of still another embodiment in which a large number of basic units formed in a concave mirror shape are formed on the surface; It is sectional drawing cut | disconnected and shown by 18b-18b line.

FIG. 19 is a light reflection sheet used in the surface light source device of the present invention, wherein a plurality of basic units each having parallel ridges arranged in parallel and formed of parallel rectilinear and concave inclined reflection surfaces are formed on the surface. It is the partial top view of the light reflection sheet of other aspect, and sectional drawing cut | disconnected and shown by 19b-19b line.

FIG. 20 is a partial plan view of a light reflection sheet used in the surface light source device of the present invention, which is a light reflection sheet of still another embodiment in which a number of basic units formed in a concave mirror shape are formed on the surface; It is sectional drawing cut | disconnected and shown by 20b-20b line.

FIG. 21 is a cross-sectional view showing a partially inclined concave reflecting surface of the basic unit formed on the light reflecting sheet shown in FIG. 15, and showing an inclination angle of the concave inclined reflecting surface;

FIG. 22 is a configuration explanatory view showing a state in which a bright line is generated in the light guide near the light source provided in the surface light source device.

FIG. 23 is a configuration explanatory view showing that it is difficult to generate a bright line in the light guide near the light source arrangement in the case of the surface light source device of the present invention.

FIG. 24 is a perspective view partially showing a surface light source device according to another embodiment of the present invention in which one means having a light collecting function is provided on the upper surface of a light guide.

FIG. 25 is a perspective view partially showing a surface light source device according to another embodiment of the present invention in which another unit having a light collecting function is provided on the upper surface of the light guide.

FIG. 26 is a perspective view partially showing a surface light source device according to another embodiment of the present invention in which still another means having a light collecting function is formed on the upper surface of a light guide.

FIG. 27 is a partial sectional view schematically showing the vicinity of a light incident surface of a light guide.

FIG. 28 is a characteristic diagram showing a relationship between an incident angle へ to a light guide and an emission angle θ into the light guide after being subjected to a refraction action.

FIG. 29 is an explanatory view showing a method for measuring the direction selectivity of a light beam of the light guide according to the present invention.

[Explanation of symbols]

Reference Signs List 10 surface light source device 11 light guide 12 side end (light incident surface) 13 linear light source (cold cathode tube) 14 reflector 15 light emitting surface 16 surface opposite to light emitting surface 17 light reflecting sheet 18 basic unit 18a Inclined reflective surface 18b Ridge line 19 Base material 20 Light extraction mechanism (pattern) 20a Convex projection 21 Light ray component going from light guide to light reflection sheet side 22 Light ray deflected by light reflection sheet 23 Light in light guide Light ray component not going to the reflection sheet side 24 Light ray propagating in the light guide 25 Corrugated irregularities 26 Corrugated irregularities 27 Lenticular lens element 28 Bright line 30 Light diffusion sheet

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13357 G02F 1/13357 // F21Y 103: 00 F21Y 103: 00 F term (Reference) 2H038 AA55 BA06 2H042 BA02 BA03 BA04 BA15 BA20 DA02 DA04 DA11 DA17 DC02 DC12 DE04 2H091 FA14Z FA16Z FA21X FA23Z FA41Z FA42Z LA30

Claims (17)

[Claims] 1. A light guide having one surface as a light exit surface, a light extraction mechanism provided on the light guide, a light source disposed on a side end of the light guide, and the light guide. A light-reflecting sheet disposed on a surface of the body facing the light-emitting surface, wherein the light-extracting mechanism includes a plurality of convex portions provided on a surface of the light guide that faces the light-emitting surface The light reflecting sheet is formed by arranging a large number of basic units on the surface thereof at a pitch of 5000 μm or less, and the respective basic units are formed by inclined reflecting surfaces. A surface light source device. 2. The inclined reflecting surfaces forming a large number of the basic units are formed in parallel with each other and linearly, and the basic units are arranged at a pitch of 3000 μm or less. The surface light source device according to claim 1, wherein the angle is an angle at which a light beam emitted from the light guide in the direction of the light reflecting sheet is reflected in a direction normal to the light guide. 3. The surface light source device according to claim 1, wherein a cross-sectional shape of the inclined reflecting surface forming the basic unit is concave. 4. The surface light source device according to claim 3, wherein the inclined concave reflecting surface forming the basic unit is formed by a combination of straight lines viewed in cross section. 5. A concave mirror-like reflecting surface having a maximum diameter of 3000 μm or less is used as the reflecting surface forming the basic unit, and the angle of inclination of the reflecting surface is emitted from the light guide toward the light reflecting sheet. The surface light source device according to any one of claims 1 to 4, wherein an angle at which the reflected light beam is reflected in a direction normal to the light guide. 6. A depth h and a minimum opening width Wm of the projection.
The surface light source device according to claim 1, wherein a value h / Wmin defined by “in” is 0.5 or more. 7. A depth h and a maximum opening width Wm of the projection.
The surface light source device according to claim 6, wherein a value h / Wmax defined by ax is 0.5 or more. 8. The light reflection sheet according to claim 1, wherein 65% or more of the light flux emitted from the light guide is emitted toward the light reflection sheet by the light extraction mechanism including the convex protrusion. The surface light source device according to any one of the above. 9. A light condensing element having a ridge line substantially parallel to a normal direction to a light incident end face at a pitch of 200 μm or less is provided on the light exit surface of the light guide. The surface light source device according to claim 1. 10. The surface light source device according to claim 1, wherein an opening width of the pattern formed by the convex protrusions increases in a uniaxial direction as the pattern is separated from the light source. 11. The pattern comprising the convex protrusions is formed by arranging convex protrusions having substantially the same shape so that the distribution density increases as the distance from the light source increases. 10. The surface light source device according to any one of claims 9 to 9. 12. The light reflection sheet according to claim 1, wherein the reflection surface is made of a silver or aluminum coating layer, and a coating layer made of a transparent material is provided on the reflection surface. 12. The surface light source device according to any one of 11. 13. The light reflection sheet according to claim 1, wherein the reflection surface is made of a diffusely reflective white material.
12. The surface light source device according to any one of items 11 to 11. 14. The surface light source device according to claim 12, wherein the coat layer made of the transparent material is an optical thin film. 15. The method according to claim 12, wherein the coat layer made of the transparent material is a transparent bead coat layer.
A surface light source device according to claim 1. 16. The surface light source device according to claim 12, wherein a matting process is performed on the reflection surface. 17. A liquid crystal display device using the surface light source device according to claim 1 in a backlight optical system.