JP2002124114A - Flat light source device, and 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 21 is formed as a mechanism of making at least 65% of the light going out from the light guide body 11 go out to the light reflection sheet 18 side, and the light reflection sheet 18 is formed by arranging many base units 19 with a pitch of 5000 μm or less, which have an slanted surface 19a, and shaped almost equally or similarly with each other, and corrugated indentation 34 are formed at least on one surface of the light guide body 11 with a pitch of 500 μm or less, and the direction of ridge line of the indentation is almost perpendicular to the side end part 12 of the light guide body 11 to which, the light source 13 is arranged.

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.

A conventional side light type surface light source device is as follows.
As shown in FIG. 33, a linear light source 2 is disposed along a side end surface 1a on one side end of a substrate made of a light-transmitting flat plate, that is, a light guide 1, and the linear light source 2 is covered. A reflector 3 is attached to the light guide 1 so that the direct light from the linear light source 2 and the light reflected by the reflector 3 enter the light guide 1 from one side end surface 1a, which is a light incident end surface, into the inside. .

[0005] One surface 1b of the light guide 1 is a light emitting surface,
A dimming sheet 5 having an array 4 of a substantially triangular prism is disposed on the light emitting surface 1b with the apex angle directed toward the observer. A large number of dots 6 are formed on the opposite surface 1c by light scattering ink.
A light extraction mechanism 6 formed by printing a, 6b, 6c,... in a predetermined pattern is provided.

The surface 1c of the light guide 1 on which the light extraction mechanism 6 is formed is opposite to the light exit surface 1b.
On the side, a reflection sheet 7 is disposed close to the surface 1c. Further, as another example of this type of conventional surface light source device, as shown in FIG. 34, a dimming sheet 5 formed with an array 4 having a substantially triangular prism shape has an apex angle of the light exit surface of the light guide 1. It is arranged on the light emitting surface 1b toward the 1b side.

The light extraction mechanism 8 provided on the surface 1c of the light guide 1 opposite to the light exit surface 1b has a large number of projections 8a, 8b, 8c,.
…. Such a sidelight type surface light source device can be used more effectively as a backlight of a liquid crystal display device such as a portable personal computer because it can more effectively bring out the general features of a liquid crystal display device such as light weight and thinness. I have.

[0008]

However, these conventional transmission type liquid crystal display devices have a problem that the structure is still complicated. The reason for this is that the structure of the surface light source device has to be complicated because an illumination optical system having a simple structure capable of obtaining desired optical characteristics in the surface light source device and having excellent light use efficiency has not been obtained. As a result, the cost is increased, which hinders the spread of this type of liquid crystal display device.

That is, as shown in FIGS. 33 and 34,
For example, in a surface light source device used as a backlight optical system of a transmission type liquid crystal display device, 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. 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 such a conventional problem, and based on an illumination system which is simple in structure and excellent in utilization efficiency of an illumination light beam, is a novel light control member, a light control member. It is an object of the present invention to provide an inexpensive surface light source device having a simple structure and excellent assemblability, and a liquid crystal display device using the surface light source device as a backlight optical system, by effectively utilizing light by using a reflection sheet. .

[0011]

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 reflection sheet disposed on the surface of the light guide opposite to the light exit surface, and the light extraction mechanism emits at least 65% or more of the light emitted from the light guide toward the light reflection sheet. The light reflecting sheet is a mechanism, and the light reflecting sheet is formed by arranging a large number of substantially the same and / or substantially similar basic units each having an inclined reflecting surface at a pitch of 5,000 μm or less. The corrugated plate-shaped unevenness is provided at a pitch of 500 μm or less, and the ridge line of the corrugated plate-shaped unevenness is substantially perpendicular to the light guide side end where the light source is disposed. .

<Specific Configuration in the Present Invention> The surface light source device of the present invention is composed of the above-mentioned essential components. However, the present invention is established even when the components are specifically as follows. The specific component is that the corrugated plate-like unevenness is a triangular prism array having a vertical angle of 60 degrees or more, and the pitch of the triangular prism array is 300 μm or less.

Further, in the surface light source device of the present invention, it is preferable that the corrugated plate-like irregularities have a sine wave shape, and the pitch of the sinusoidal corrugated plate-like irregularities is 300 μm or less. In this case, it is preferable that the corrugated plate-shaped irregularities have a lenticular lens shape, and that the pitch of the lenticular lens-shaped corrugated irregularities is 300 μm or less.

Further, in the surface light source device of the present invention, the inclined reflecting surfaces forming the basic unit are formed in parallel and linearly with each other, and each basic unit has a pitch of 30.
The reflection surface is arranged at an angle of not more than 00 μm, and the inclination angle of the reflection surface is an angle at which the light emitted from the light guide in the direction of the light reflection sheet is reflected in the normal direction of the light guide.

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 angle of inclination of the reflecting surface is smaller than that of the light guide. It is characterized in that the light is emitted in the direction of the reflection sheet and is reflected in the normal direction of the light guide.

Further, in the surface light source device according to the present invention, the cross-sectional shape of the inclined reflecting surface forming the basic unit is concave. 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 preferable to perform a matting process on 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.

[0018]

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 configuration explanatory view schematically showing a main part of a surface light source device 10 according to an embodiment of the present invention.

The surface light source device 10 according to this embodiment includes a substrate made of a light-transmitting flat plate, that is, a light guide 11, 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. Two-lamp type, one or two cold-cathode tubes are provided at one side end, and this is also provided at the opposite side end, so that a total of two or four lamps are provided. Representative.

In the present invention, the light source is not limited to a linear light source. For example, a point light source such as an LED may be used in a small surface light source device as shown in FIG. Can also. That is, FIG.
Shows an example in which an LED 37 as a point light source is disposed on a corner cut surface formed by cutting a corner portion of the light guide 11 into a triangular shape when viewed in a plane. FIG. 29
(B), an optical rod 38 is disposed close to one end of the light guide 11, and a point light source L is provided on an end face of the optical rod 38.
The example which arrange | positioned ED37 is shown.

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 rectangular thin translucent plate having a thickness of about 4 mm, and one of the upper surfaces as viewed in FIG. The other surface on the opposite side (the lower surface in FIG. 1) is a surface 16 facing the light emitting surface. In FIG. 1, reference numeral 17 denotes a line perpendicular to the light exit surface 15 of the light guide 11, that is, a normal line of the light guide 11.

A light reflection sheet 18 is provided near the surface 16 of the light guide 11 opposite to the light exit surface 15.
The light reflecting sheet 18 is configured such that a large number of basic units 19 each having an inclined reflecting surface 18a are formed on the surface of the base material 20 at a fine pitch. Here, basic unit 1
9 is an inclined surface 1 having substantially the same and / or substantially similar shape as shown in FIGS. 1 to 3 and FIGS. 20 to 25.
9a means a basic shape unit of the light reflecting sheet 18 obtained as an aggregate.

In other words, the basic unit 19 is a minimum shape unit, that is, a so-called unit cell, which loses the sameness or similarity when divided further. The pitch P is defined as the minimum length of the basic periods formed by the arrangement of the basic units 19 as shown in FIGS. 2, 3, and 20 to 25.

Further, the light guide 11 has a light extraction mechanism 21.
Is provided. The light extraction mechanism 21 is configured to selectively emit a light beam incident on the light guide 11 to the light reflection sheet 18 side.
It is necessary to configure so that 65% or more, more preferably 70% or more, and still more preferably 75% or more of the light beam emitted from the light guide 11 is emitted to the side 8. This satisfies this requirement. The light extraction mechanism used is not particularly limited.

Here, the light extraction mechanism 2 provided on the light guide 11 to emit at least 65% or more of all the outgoing light rays emitted from the light guide 11 to the light reflection sheet 18 side.
Various embodiments can be considered as 1 and are not particularly limited. However, as a most preferable embodiment, as shown in FIG. 4, a large number of convex protrusions 22 are provided on a surface (surface on the light reflection sheet side) 16 of the light guide 11 opposite to the light exit surface 15. A light extraction mechanism 21 formed by a pattern can be used.

In addition, as shown in FIGS. 5 to 9, various surface shapes are designed so that most outgoing light rays emitted from the light guide 11 are directed to the light reflecting sheet 18. It is possible to do. That is, the mode shown in FIG. 5 is different from the mode in which a large number of protrusions 23 having a triangular cross section
Are formed in a predetermined pattern to form a light extraction mechanism 21.

The embodiment shown in FIG.
The concave 16 is formed on the surface 16 on the side of the light reflecting sheet 18 in FIG.
By forming the projections 4a, the projections 24b are relatively formed to form a light extraction mechanism. Further, in the mode shown in FIG. 7, a large number of grooves 25 having a V-shaped cross section are formed at predetermined intervals on the light emitting surface 15 of the light guide 11, thereby forming the light extraction mechanism 21.

Further, in the embodiment shown in FIG. 8, a large number of grooves 26 having a V-shaped cross section are formed at predetermined intervals on the surface 16 of the light guide 11 on the side of the light reflecting sheet 18 so that the light extraction mechanism 21 is formed. It was done. In the embodiment shown in FIG. 9, the light extraction mechanism 21 is formed by forming a large number of protrusions 27 having a mountain-shaped cross section at predetermined intervals on the light emitting surface 15 of the light guide 11.

In addition to these various aspects, a mode in which a scatterer having forward scattering properties in a specific direction is provided in the light guide 11, and a diffractive optical element such as a hologram element and a surface relief element is provided in the light guide 11. There is no particular limitation on the light extraction mechanism, such as the mode provided on the surface, as long as it can emit at least 65% or more of the light emitted from the light guide 11 toward the light reflecting sheet 18 as described above. .

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 11 is at least 65% or more. However, as described above, it is necessary for the effect of the optical design according to the present invention to function effectively. The measuring means for measuring the selectivity of the direction in which the light beam is emitted is as follows. .

That is, first, the black sheet 39 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. 35, the light guide 11 is set in a normal direction and turned on in the integrating sphere, and the light exit surface side of the light guide 11 obtained at this time is set. Σa is the total luminous flux emitted from.

Next, the direction of the light guide 11 is set upside down as usual (originally, the surface facing the side of the light reflecting sheet is set to the light emitting surface side). 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, and this value is 65% or more, more preferably 7%.
It is set to 0% or more, more preferably 75% or more.

In the surface light source device of the present invention, the shape restriction required for the light extraction mechanism 21 is limited to the light guide 1 on the light reflection sheet 18 side as described above.
It should be determined in view of emitting more than 65% of the outgoing rays from one.

For example, this is shown in FIGS. 10 (a) and 10 (b).
When the projection 23 having a triangular cross section shown in FIG. 5 is formed on the surface 16 of the light guide 11, the apex angle θ of the pointed end is preferably 90 degrees or less, and Preferably it is 70 degrees or less, more preferably 50 degrees or less.

That is, as shown in FIG. 10B, as the apex angle θ of the projection 23 formed on the surface 16 of the light guide 11 is increased and the cross-sectional shape is made to be a mountain shape, the projection 23 Light exit surface 15 of light guide 11 by total reflection
This is because an unnecessary light component 30 emitted in the direction increases, and by using a triangular cross-sectional shape having a small apex angle, as shown in FIG. It is possible to increase the light beam components 28 and 29 that draw the trajectory (the light beam component 29 emitted in the direction of the normal 17 of the light guide 11 through the reflection process on the light reflecting sheet 18).

Another example will be described. In the embodiment using the convex protrusions 22 shown in FIG.
As shown in FIG. 3, the height h / Wmin defined by the height of the projection 22, in other words, the depth h of the projection 22 and the minimum opening width Wmin when viewed from inside the light guide 11.
However, it is preferably 0.5 or more, more preferably 0.6 or more, and still more preferably 0.7 or more.

The protruding projection 22 shown in FIG. 4 has an elliptical opening as apparent from FIG. 11, but has a rectangular opening as shown in FIG. Has a minimum opening width Wm
in. In the case where the shape of the opening is substantially square as shown in FIG. 13, the dimension of one side is the minimum opening width Wmin. If the convex protrusion 22 is designed so as to satisfy such conditions, it is necessary to determine a suitable shape so that at least 65% or more of the light emitted from the light guide 11 is emitted toward the light reflection sheet 18. Can be.

As described above, the light extraction mechanism suitably used in the present invention, as exemplified in FIGS. 4 to 9, has only the shape of the light emitted from the light guide to the light reflection sheet 18 side. It is determined from the viewpoint of emitting 65% or more, but a more detailed design concept will be described.

First, in a fluorescent tube or the like often used as a light source, ultraviolet light obtained by plasma discharge excites fluorescent fine particles adhering to the tube wall to emit light.
The emission angle distribution of the emitted light beam obtained therefrom exhibits a uniform intensity at almost every angle, which is close to a so-called diffusion light source property.

FIG. 3 shows the vicinity of the light incident surface of the light guide.
At 0, the geometrical optical state distribution of the light beam propagating in the light guide is considered under the condition that the incident angle distribution of the light beam incident on the light guide is constant for 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. 31 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 that are incident at an incident angle of about 50 degrees as the incident angle on the light guide surface side where the light extraction mechanism is formed. . That is, as shown in FIG. 10A, for example, the projection 23 having a triangular cross section is
In the case of forming on the first surface 16, it is preferable that the apex angle is small. For example, in the case of using the convex protrusion 22, it is necessary that the shape be sufficiently deep with respect to the opening width. . Similarly, the other light extraction mechanisms shown in FIGS. 6 to 9 are similarly designed based on the above, taking into account the characteristics of light rays propagating in the light guide.

In the surface light source device of the present invention, as described above, most of the light emitted from the light guide 11 is emitted to the light reflecting sheet side.
Usually, as shown in FIG. 1, there are many cases where the light beam 28 has a directivity that is obliquely incident on the light reflection sheet 18.

Therefore, in the surface light source device of the present invention,
As shown in FIG. 1, by the effect of the substantially identical and / or substantially similar basic unit 19 comprising the inclined reflecting surface 19a provided on the light reflecting sheet 18, the light reflecting body 18 is moved from the light guide 11 to the light reflecting sheet 18 side. Light rays 28 selectively emitted
The direction is changed in the front direction of the light guide 11, and as a result, when the surface light source device 10 is viewed from the front, an extremely high illumination intensity can be obtained.

This can greatly simplify the configuration of the illumination optical system as compared with the conventional surface light source device shown in FIGS. 33 and 34. In the present invention, the inclined reflecting surface 1 provided on the light reflecting sheet 18 is provided, while the optical system 5 of the mold performs the function of condensing light rays and the function of changing the angle of light.
The light reflecting sheet 18 has desired optical functions such as a light condensing function and a bending function by designing a substantially identical and / or substantially similar basic unit 19 made of 9a into, for example, a shape like a concave mirror. It is possible to provide a surface light source device whose structure is extremely simplified while maintaining the same optical performance.

By the way, in the surface light source device of the present invention, as described above, the light beam selectively emitted toward the light reflecting sheet 18 is substantially the same as the light reflected from the inclined reflecting surface 19a provided on the light reflecting sheet 18. And / or converted by a substantially similar basic unit 19 into an illuminating light beam having the desired optical properties, however, in terms of light collection,
Often, this is not enough. In particular, in the case of a liquid crystal display panel used in a notebook personal computer, it is only necessary to obtain a strong outgoing light beam as an output only in the direction of the user who is directly facing the panel. It comes out.

Therefore, according to the present invention, a corrugated plate typified by a triangular prism array or a lenticular lens array is provided on at least one surface of the light guide 11 like the surface light source device 10 of the embodiment shown in FIG. The irregularities (irregularities having a wavy surface shape) 34 are formed to enhance optical characteristics such as light condensing properties.
In combination with the effect of the substantially identical and / or substantially similar basic unit 19 composed of the inclined reflecting surface 19a provided in, an extremely high light-collecting property can be realized.

This situation will be described in further detail. In the present invention, as shown in FIG. 1, the light guide 11 is temporarily stopped by the effect of the light extraction mechanism 21 as exemplified in FIGS. Most of the outgoing light rays 28 are emitted toward the light reflecting sheet 18. The direction of the emitted light beam is deflected to the direction of the normal line 17 of the light guide 11 by the effect of the substantially identical / or substantially similar basic unit 19 composed of the inclined reflecting surface 19 a provided on the light reflecting sheet 18. Then, the light enters the light guide 11 again and is condensed by corrugated plate-like irregularities 34 such as a triangular prism array provided on the light guide.

For this reason, it has been proposed that a triangular prism array or the like be formed integrally with the light guide 11 to improve the light condensing property even in a conventional surface light source device. The surface light source device described above is completely different from an optical point of view, and an essentially advantageous optical system can be obtained in terms of light collecting properties. This situation is shown in FIGS. 14 (a) and (b).

In other words, in the conventional surface light source device, since there were many light components 30 going directly from the inside of the light guide 11 toward the light emitting surface 15 of the light guide 11, FIG.
As shown in FIG. 14B, even if the light component does not go in the direction of the normal line 17 of the light guide 11 and originally wanted to condense, as shown in the trajectory of the light beam shown in FIG. ,
Since the light passes only once through the interface between the light guide 11 and the air layer, sufficient light collection could not be achieved.

However, in the surface light source device of the present invention,
As shown in FIG. 14A, most of the light rays 28 emitted from the light guide 11 are once emitted to the side of the light reflecting sheet 18, so that they can be seen in the trajectories of the light rays shown in FIG. As described above, the light guide 11 can pass through the interface between the light guide 11 and the air layer twice, so that the light guide 11 itself functions as a thick lens array sheet, and the light-collecting property is improved. Thus, it is possible to obtain extremely excellent performance.

In order to consider this effect more specifically, the state number distribution of the light beam emitted from the light emitting surface by geometrical optics is calculated. Referring to FIG. 14 which is a cross-sectional view of the light guide viewed from the light incident surface 11 side, the emission angle of a light beam emitted by the light extraction mechanism provided on the light guide is γ, and the triangular prism provided on the light guide Let δ be the top angle of the array.

In a conventional light guide provided with a triangular prism array, an optical design for selectively guiding outgoing light rays to the light reflection sheet 18 side by a light extraction mechanism is not made, and therefore, as shown in FIG. There are a large number of light components 30 which are directly incident on the triangular prism portion from the light guide and undergo refraction by the prism portion. The emission angle ζb of such a light component 30 is a function of γ and δ,

(Equation 8) It is expressed as

On the other hand, in the optical system shown in FIG. 14A in which the emitted light beam is once emitted toward the light reflecting sheet 18 of the present invention and the light guide can act as a prism sheet, The light emission angle distribution ζa is

[Equation 9] It is expressed as

Therefore, as a simple example, when the light emitted from the light extraction mechanism is completely diffused light and the top angle of the triangular prism is 90 degrees, the same state number density is obtained as shown in FIG. When the light ray 341 has passed through the optical system shown in FIG. 14A, the state number density of the exit angle of the exit ray 29 has a large number of ray components in the front direction having a peak near 45 degrees as indicated by reference numeral 342. It can be seen that the light is converted into a gathered state and exhibits a high light-collecting property.

On the other hand, a conventional optical system, FIG.
In (b), although a slight light-condensing action is recognized by the triangular prism portion, as indicated by reference numeral 343, many light components that remain in the vicinity of 0 to 30 degrees greatly deviated from the front are large, and sufficient light-condensing is performed. No action can be obtained.

That is, the optical design according to the present invention, in which light is once emitted toward the light reflecting sheet 18 and the light guide 11 itself acts as a prism sheet, plays a very essential role in ensuring light-collecting properties. You can see that it is playing.

The corrugated plate-like irregularities (irregularities having a corrugated surface shape) 34 are appropriately designed in shape from the viewpoint of realizing optical functions such as increasing the light condensing property. The surface structure is not particularly limited. However, if the function of propagating light rays incident from the side end, which is originally required for the light guide 11, without loss based on the condition of total reflection is impaired, the function as the surface light source device will not be achieved.

Therefore, at least the corrugated plate-like unevenness 34
Is provided so as to be substantially parallel to the direction in which the incident light mainly propagates. By doing so, the condition of total reflection is disturbed by the corrugated plate-like unevenness 34, and the light does not stop propagating in the light guide 11. That is, as shown in FIG. 1, the corrugated plate-shaped unevenness 34 is set in a direction substantially perpendicular to the side end 12 where the light source 13 is provided.

The corrugated plate-like unevenness 34 typified by a triangular prism array or a lenticular lens array provided on the light guide 11 is desirably miniaturized to the extent that it cannot be visually recognized.
Or less, preferably 300 μm or less, more preferably 20 μm or less.
The pitch is set to 0 μm or less. As the specific shape of such corrugated plate-like unevenness 34, a triangular prism array 31 as shown in FIG. 15, a lenticular lens array 33 as shown in FIG. 17, or a cross section as shown in FIG. An array-like element 34 having sinusoidal irregularities can be used.

In particular, from the viewpoints of light condensing properties and easiness of processing, a mode using a triangular prism array 31 as shown in FIG. 15 is preferable. As shown in FIGS. No. 11 has an ascending angle of 60 to 150 degrees, preferably 70 to 120 degrees, more preferably 80 to
A triangular prism array of 110 degrees is provided, and a light source 13
Is used so that the ridge line of the prism array 31 is substantially perpendicular to the side end portion 12 where is disposed.

As described above, since the triangular prism array 31 is integrally formed on the light exit surface 15 of the light guide 11,
As described above, since the light guide itself functions as a thick prism sheet, it is possible to easily obtain a high light-collecting property.

In the embodiment in which the light guide 11 in which the triangular prism array 31 is integrally formed on the light exit surface 15 as described above, as shown in FIGS. 4 to 6 and FIG. A light extraction mechanism 21 for selectively emitting light is provided on a surface 16 of the light guide 11 that faces the light emission surface 15.

Also, as shown in FIGS. 7 and 9, with respect to a mode in which the light extraction mechanism 21 is provided on the light exit surface 15 side of the light guide 11, as shown in FIG. Corrugated plate-like irregularities 34 such as a triangular prism array are provided on the surface 16 facing the light emitting surface 15. Also in this embodiment, it goes without saying that the ridge line 34a of the corrugated plate-like unevenness 34 is substantially perpendicular to the side end 12 which is the light incident surface of the light guide 11 as described above.

Light reflecting sheet 1 used in the present invention
8 is a flexible substrate 2 having a thickness of about 1000 μm or less.
Although 0 is preferable, the form such as the thickness is appropriately selected depending on the application object, and is not necessarily limited to this. For example, the effect of the light reflection sheet can be obtained by integrally molding the frame portion of the surface light source device that houses the light guide 11. 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 reflectance in the present invention is a material having a high reflectance 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 flux energy to the incident luminous flux energy in the visible light spectrum region has the above value, and is usually 70% or more, preferably 75% or more, and more preferably 85%. As described above, it is particularly preferably at least 88%, 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 a material located on the surface of the inclined surface which substantially causes reflection. Specifically, the surface of the inclined surface is represented 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 prevent the arrangement of the basic units 19 from being recognized on the screen, it is important that the arrangement pitch P of the substantially identical and / or substantially similar basic units 19 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 19 comprising an inclined reflecting surface 19 a provided on the surface of the light reflecting sheet 18, as shown in FIG.
3B, the basic unit 19 has a sawtooth cross section, or the basic unit 19 has a mountain shape as shown in FIGS. 3A and 3B, and a pitch of 3000 μm.
m, preferably 800 μm or less, more preferably 3 μm or less.
A mode in which a basic unit 19 having a parallel linear and flat inclined reflecting surface 19a with a ridge line 19b arranged parallel to each other when the light reflecting sheet 18 is viewed from above is used. Can be

This is shown in FIGS. 2A and 2B and FIG.
As shown in (a) and (b), in a mode in which the ridge lines 19b of the inclined flat reflecting surface 19a are arranged substantially in parallel, cutting using a diamond bite or an end mill is easy to apply, so that shaping is performed. 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 18 in which a large number of parallel linear and flat inclined reflecting surfaces 19a are arranged, the pattern composed of the above-mentioned convex protrusions 22 is used as the light extraction mechanism 21 and the light guide mechanism is used. The light emitted from the light guide 11 designed so that most of the emitted light flux goes to the side where the light reflection sheet 18 is provided is parallel to the light guide 11 by the effect of the flat inclined reflection surface 19a. A very simple configuration is provided because corrugated plate-like irregularities 34 are reflected in the direction of the normal 17 and are provided on at least one surface of the light guide 11 to improve optical properties such as light condensing properties. Nevertheless, an extremely high quality illumination light beam can be obtained as the surface light source device 10.

As shown in FIG. 19, almost the same and / or
Alternatively, a suitable range for the inclination angle α of the inclined surface used in the substantially similar basic unit 19 varies depending on the form of the light extraction mechanism 21 used, and the direction of the light beam emitted from the light guide 11 is changed to the light emission surface 15. Should be appropriately determined from the viewpoint of conversion in the direction of the normal 17.

For example, as shown in FIG. 4, a mode in which a convex projection 22 is used as the light extraction mechanism 21, or FIG.
In the embodiment using the projections 23 having a triangular cross section as shown in the above, the inclination angle α of the inclined reflecting surface 19a is preferably in the range of 50 to 7 degrees, more preferably in the range of 40 to 10 degrees, and still more preferably. A range of 34 degrees to 15 degrees is preferably used.

It is preferable that the cross section of the inclined reflecting surface 19a constituting each basic unit 19 be concave as shown in FIGS. 20 and 21 from the viewpoint of light condensing. This is not limited to the embodiment in which a large number of parallel linear and inclined reflecting surfaces preferably used in the present invention are arranged, as well as the embodiment in which concave mirror-shaped basic units 19 are arranged as shown in FIGS. Is also preferably used.

Also in this case, the range preferably used as the inclination angle α of the inclined reflecting surface 19 a is from the viewpoint of converting the direction of the light beam emitted from the light guide 11 into the direction of the normal line 17 of the light emitting surface 15. For example, in each of the embodiments using the convex protrusion 22 or the triangular protrusion 23 as the light extraction mechanism 21 as shown in FIGS. 4 and 5, the concave cross section as shown in FIG. Is preferably in the range of 50 ° to 7 °, more preferably in the range of 40 ° to 10 °, and still more preferably 3 °.
The range is 4 degrees to 15 degrees.

The light reflecting sheet 18 is formed by using the basic unit 19 having such a concave reflecting surface 19a as a reflecting element.
To convert the light beam 28 having a broad spread emitted from the light extraction mechanism 21 provided in the light guide 11 into a light beam 29 having a sharper angle characteristic (a light beam closer to a parallel light beam). In other words, the light can be emitted in the direction of the normal line 17 of the light guide 11, in other words, the light emitted from the light guide 11 is more collimated by the converging effect of the concave mirror. This makes it possible to convert the emitted light into an emitted light with extremely high brightness in the direction of the normal 17.

Therefore, in the conventional surface light source device, the light condensing effect which has been realized by using expensive members which are difficult to manufacture such as a prism array can be realized without using such members. While maintaining almost the same optical characteristics, the surface light source device can be made to have a very simplified configuration, reducing the number of assembly steps, improving the yield, reducing the probability of dust contamination, reducing cost, 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. 27, there occurs a phenomenon called the bright line 35 at the side end 12 of the light guide 11 where the light source 13 is disposed, which deteriorates the appearance. 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 7 in the vicinity of the side end portion 12 of the light guide 11, and a reflector arrangement is necessary to remove the bright line 35. The countermeasures have been taken such as by changing or applying light-absorbing printing to the reflection sheet 7, but this has resulted in further complicated structure and higher cost.

However, in the surface light source device of the present invention, as described above, the light reflecting sheet 18 uses the substantially identical and / or substantially similar basic unit 19 composed of the inclined reflecting surface 19a. In the surface light source device described above, a light ray incident to become a bright line component is also bounced back by the basic unit 19 composed of the inclined reflecting surface 19a as shown in FIG. Therefore, the appearance quality as a surface light source is also extremely excellent.

By the way, from the viewpoint of the light collecting property of the surface light source device according to the present invention, the inclined reflecting surface 19a having a concave cross section is used.
Is preferably used for the basic unit 19 as described above, but the substantially identical and / or substantially similar basic unit 19 composed of the inclined reflecting surface 19a is preferred.
In another embodiment, as shown in FIGS. 22 to 25, a concave mirror-like reflecting surface 1 having a maximum diameter of 3000 μm or less, preferably 800 μm or less, and more preferably 300 μm or less.
An embodiment in which a structure in which 9a are arranged is used. In such an embodiment, light can be converged not only in one direction but also in two orthogonal directions. Therefore, as compared with the above-described embodiment in which a large number of parallel linear and inclined reflecting surfaces 19a are arranged, the light is collected further. This makes it possible to improve optical characteristics such as optical properties.

The reflective material used for the light reflecting sheet 18 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 19a 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.

Before the vacuum deposition with silver, for example, the surface of the base material sheet on which the basic unit 19 having the substantially identical and / or substantially similar shape composed of the inclined reflecting surface 19a is formed is subjected to 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, the surface is coated with an ultraviolet-curable acrylic resin paint as a protective layer. It is preferable to prevent the deterioration of the optical characteristics due to scratches or the like. Further, by providing a coating layer of light transmissive beads typified by glass beads or the like as a protective layer, a mat 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 (protective 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 for forming the diffuse reflection layer, other than 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 reflecting sheet 18 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 utilizes the 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 made thinner (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.

[0095]

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) 214.0 × 163.0 as the light guide 11
mm, thickness is 2.0 mm, thickness is 0.6 mm, thickness is 0.6 mm, thickness is changed in the short side direction, wedge-shaped acrylic resin is used, and the long side of the thick side is made of a cold cathode tube The light source 13 is arranged, and patterned so that the arrangement density becomes relatively large as the distance from the linear light source 13 increases,
As shown in FIG. 13, a convex protrusion 22 having a square opening was formed on the light guide 11. Depth h of convex protrusion 22
Is 30.0 μm, and the opening width Wmin of the projection 22 is 35.0 μm.

The mold used for forming the projections 22 is formed by laminating a 30 μm thick dry film resist on a glass plate, forming a pattern by photolithography, and forming a pattern on the glass plate by the dry film resist. An electrode is formed by vapor deposition, and this is used as a master by nickel electroforming.

Further, as shown in FIG. 15, the convex protrusion 22 as the light extraction mechanism 21 is provided on the surface on which the light reflecting sheet 18 is provided, and further, the light emitting surface 1 of the light guide 11 is provided.
On the 5th side, corrugated plate-shaped irregularities 34 of a triangular prism-shaped array 31 having a vertex angle of 90 degrees are provided so that the ridge line 34a is perpendicular to the side end portion 12 of the light guide 11 which is a light incident surface. ing.

The projection 22 is a light extraction mechanism 21,
The triangular prism array 31 is placed on the light exit surface 15 of the light guide 11.
Is provided, a light guide suitable for use in the present invention, in which 69% of the luminous flux emitted from the light guide 11 is emitted to the light reflection sheet 18 side, is obtained.

As the light reflecting sheet, FIG.
A linear and concave reflecting surface 19a having the shape shown in FIG.
9 was used. Pitch is 10
The thickness is 0 μm, and a silver sputtering layer is used for the reflection layer, and the surface of the silver sputtering layer is coated with an acrylic resin.

The inclination angle α of the reflecting surface 19a is 23 degrees, and the light beam selectively emitted from the light guide 11 toward the light reflecting sheet 18 is changed in direction by the action of the light reflecting sheet 18, and An optical system that emits illumination light in the direction of the normal line 17 of the light guide 11 while condensing light by the effect of the triangular prism array 31 provided on the light exit surface 15 side of the light guide 11 was obtained.

As the light source 13, a cold cathode tube having a tube diameter of 1.8 mm was used, and was lit at a high frequency via an inverter.
As shown in FIG. 15, a light diffusing sheet 36 obtained by coating acrylic beads having a haze of 47.2% was disposed immediately above the light emitting surface 15 of 1 to obtain a surface light source device.
With a tube current of 5 mA, a luminance measuring device (BM-
As a result of measuring the average luminance of five points in the plane using 7), an average luminance of 1630 nit 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 source of a liquid crystal display panel. Was done.

The characteristics of the illuminating light beam are sufficiently focused both in the horizontal direction and the vertical direction, so that it is particularly suitable as a pack light for a liquid crystal display device used in a notebook personal computer or a handheld computer. Had properties. In addition, since a prism sheet normally provided is not used, defects due to dust entering between the sheets are hardly generated, and the assembling property is also good. In addition, the generation of bright lines near the light source, which was generated by the conventional surface light source device, was small, and the image quality was extremely excellent.

(Example 2) 250.0
× 195.0 mm, thickness 2.1 mm near the light source, 0.7 mm at the position farthest from the light source, using a wedge-shaped acrylic resin whose thickness changes in the short side direction, the long side of the thick side A linear light source 13 composed of a cold cathode tube,
A convex protrusion 22 having a rectangular opening shape as shown in FIG. 12 was formed on the light guide 11 by patterning so that the length of one side became relatively larger as the distance from the linear light source 13 increased. The depth h of the projection 22 is 25.0 μm.
m, and the opening width Wmin of the projection 22 is 35.0 μm.
It has been.

Further, the convex protrusion 22 serving as a light extraction mechanism is provided.
As shown in FIG. 17, a lenticular lens array 32 having a pitch of 100 μm is provided on the light emitting surface 15 side of the light guide 11.
The ridgeline 34a of the lenticular lens array 32 is the light incident surface of the light guide 11
Is provided so as to be perpendicular to the side end 12.

The projection 22 is used as a light extraction mechanism 21,
By providing the lenticular lens array 32 on the light exit surface 15 side of the light guide 11, 71% of the light flux emitted from the light guide 11 exits to the light reflection sheet 18 side, which is suitable for use in the present invention. Light guide was obtained.

FIGS. 2A and 2B show examples of the light reflecting sheet.
And a light reflection sheet 18 having a parallel linear flat flat inclined reflection surface 19a in which a ridge line 19b is arranged in parallel as a basic unit 19 is used. The pitch of the basic unit 19 is 80 μm, a silver sputtering layer is used for the reflection layer, and the surface of the silver sputtering layer is coated with a photocurable resin in which glass beads having an average particle diameter of 7.2 μm are dispersed. .

The inclination angle α of the inclined reflecting surface 19a is 25
The light selectively emitted from the light guide 11 toward the light reflecting sheet 18 is changed in direction by the action of the light reflecting sheet 18, and is further provided on the light emitting surface 15 side of the light guide 11. An optical system that emits an illumination light beam in the direction of the normal line 17 of the light guide 11 while condensing light by the effect of the lenticular lens array 33 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 36 obtained by coating acrylic beads having a haze of 35.6% directly above the light exit surface 15
To obtain a surface light source device. With a tube current of 6 mA, the average luminance at five points in the plane was measured using a luminance measurement device (BM-7, manufactured by Topcom). As a result, an average luminance of 1980 nit was obtained. It was confirmed that the optical characteristics were sufficient for practical use as a light source.

The characteristics of the illuminating light beam are sufficiently focused both in the horizontal direction and the vertical direction, so that it is extremely suitable as a backlight for a liquid crystal display device used in a notebook personal computer or a handheld computer. Had properties. In addition, since a prism sheet that is normally arranged is not used, defects due to dust entering between the sheets are unlikely to occur, and assemblability is good. In addition, the generation of bright lines near the light source, which was generated by the conventional surface light source device, was small, and the image quality was extremely excellent.

[0110]

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 partial configuration explanatory 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 shows an embodiment of a light extraction mechanism including a large number of convex protrusions formed on a surface of the surface light source device of the present invention opposite to the light exit surface of the light guide. It is sectional drawing which expands and shows schematically.

FIG. 5 shows another embodiment of the light extraction mechanism including a large number of triangular cross-section projections formed on the surface of the light guide opposite to the light exit surface in the surface light source device of the present invention. It is sectional drawing which expands a part and shows roughly.

FIG. 6 is a view showing a light extraction mechanism according to still another embodiment of a light extraction mechanism including a large number of concave dents formed on a surface of the surface light source device opposite to the light exit surface of the light guide. It is sectional drawing which expands and is shown roughly.

FIG. 7 is an enlarged view of a part of the light guide of the surface light source device according to another embodiment of the light extraction mechanism including a large number of V-shaped cross-sectional grooves formed on the light exit surface of the light guide in the surface light source device of the present invention. FIG.

FIG. 8 shows another aspect of the light extraction mechanism including a large number of V-shaped cross-section grooves formed on the surface of the surface light source device of the present invention opposite to the light exit surface of the light guide. It is sectional drawing which expands a part and shows roughly.

FIG. 9 is a view showing still another aspect of the light extraction mechanism including a large number of mountain-shaped projections formed on the light exit surface of the light guide in the surface light source device of the present invention, by enlarging a part of the light guide. It is sectional drawing which shows schematically.

10 is a configuration explanatory view schematically showing a state in which a light beam incident on a light guide becomes a surface light source and a state in which a light beam does not become a surface light source depending on a light extraction mechanism in the surface light source device of the embodiment shown in FIG. 1; It is.

FIG. 11 shows a depth h and a minimum opening width Wmin of an example of a convex protrusion constituting a light extraction mechanism provided in a light guide.
FIG. 3 is a schematic configuration explanatory diagram showing the definition.

FIG. 12 shows a depth h and a minimum opening width Wmi of another example of the convex protrusion constituting the light extraction mechanism provided in the light guide.
It is a schematic structure explanatory view which shows the definition of n.

FIG. 13 shows a depth h and a minimum opening width W 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 min.

FIG. 14 shows a trajectory of a light beam in the surface light source device of the present invention and a light beam in a conventional surface light source device when a light guide having corrugated plate-like irregularities on the light exit surface is used as a component of the surface light source device. FIG. 4 is a configuration explanatory diagram showing a trajectory.

15 is a partial perspective view showing the surface light source device of the present invention shown in FIG. 1 more specifically and in detail.

FIG. 16 is a perspective view partially showing a surface light source device according to another embodiment of the present invention in which a light-collecting function unit of another mode is formed on a light exit surface of a light guide.

FIG. 17 is a perspective view partially showing a surface light source device according to still another embodiment of the present invention in which a light-collecting function unit of still another mode is formed on a light emitting surface of a light guide.

FIG. 18 is a perspective view partially showing a surface light source device according to still another embodiment of the present invention, in which a light-collecting function unit of still another mode is formed on a light-emitting surface of a light guide.

19 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. 20 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 ridge lines arranged in parallel and formed of parallel linear 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 20b-20b line.

FIG. 21 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 rectilinear and concave inclined reflection surfaces are formed on the surface. It is the partial top view of the light reflection sheet | seat of an aspect, and sectional drawing cut | disconnected and shown by 21b-21b line.

FIG. 22 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 and concave inclined reflection surface 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 22b-22b line.

FIG. 23 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 plurality of basic units formed in a concave mirror shape are formed on the surface; It is sectional drawing cut | disconnected and shown by 23b-23b line.

FIG. 24 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 ridges arranged in parallel and formed of parallel linear and concave inclined reflection surfaces 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 24b-24b line.

FIG. 25 is a partial plan view of a light reflecting sheet used in a surface light source device according to another embodiment of the present invention, in which a plurality of basic units formed in the shape of a concave mirror are formed on the surface; It is sectional drawing cut | disconnected and shown by line 25b-25b.

FIG. 26 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. 27 is a configuration explanatory view showing a state in which a bright line is generated in the light guide near the light source arrangement in the surface light source device.

FIG. 28 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. 29 is a plan view schematically showing an arrangement example when a point light source is used in the surface light source device of the present invention.

FIG. 30 is a partial sectional view schematically showing the vicinity of a light incident surface of a light guide.

FIG. 31 is a characteristic diagram showing a relationship between an incident angle へ to the light guide and an emission angle θ into the light guide after being subjected to a refraction action.

FIG. 32 is a characteristic diagram showing a state number density of an emitted light beam by each optical system.

FIG. 33 is a cross-sectional view schematically showing a main part of an example of a conventional surface light source device.

FIG. 34 is a cross-sectional view schematically showing a main part of another example of the conventional surface light source device.

FIG. 35 is an explanatory view showing a method for measuring the direction selectivity of a light beam of the light guide of 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 normal to light guide 18 Light reflection sheet 19 Basic unit 19a Inclined reflection surface 19b Ridge line 20 Base material 21 Light extraction mechanism (pattern) 22 Convex projection 23 Triangular projection 24a Concave dent 24b Projection 25 Groove 26 Groove 27 Cross section 27 Projection 28 Light ray component going from light guide to light reflection sheet side 29 Light ray deflected by light reflection sheet 30 Light ray component not going to light reflection sheet side in light guide 31 Triangular prism array 32 Lenticular lens array 33 Sectional sine Wavy irregularity array element 34 Corrugated irregularities 35 Bright lines 36 Light diffusion sheet

Claims (13)

[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 provided at a side end of the light guide, and the light guide. A light reflecting sheet disposed on a surface side of the body opposite to the light emitting surface, wherein the light extraction mechanism emits at least 65% or more of light rays emitted from the light guide toward the light reflecting sheet side. The light reflecting sheet has a substantially identical and / or substantially similar basic unit having an inclined reflecting surface and a pitch of 5000 μm.
m or less, and at least one surface of the light guide is provided with corrugated irregularities at a pitch of 500 μm or less, and the ridge line of the corrugated irregularities is the light source. A surface light source device, wherein the direction is substantially perpendicular to the light guide side end provided. 2. The corrugated plate-like unevenness is a triangular prism array having an apex angle of 60 degrees or more, and a pitch of the triangular prism array is 300 μm or less. Surface light source device. 3. The corrugated plate-like unevenness has a sine wave shape,
And the pitch of the sinusoidal corrugated irregularities is 300
2. The surface light source device according to claim 1, wherein the distance is set to be equal to or less than μm. 4. The corrugated plate-shaped unevenness is a lenticular lens shape, and the pitch of the lenticular lens shaped corrugated unevenness is 300 μm or less. Surface light source device. 5. The inclined reflecting surfaces forming a large number of the basic units are formed parallel to each other and linearly, and the basic units have a pitch of 3000 μm.
The light guide is arranged below, and the inclination angle of the reflection surface is an angle at which the light emitted from the light guide in the direction of the light reflection sheet is reflected in the normal direction of the light guide. The surface light source device according to claim 1. 6. A reflecting surface having a concave mirror shape with 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 in the direction from the light guide to the light reflecting sheet. The surface light source device according to any one of claims 1 to 4, wherein the emitted light beam is reflected at an angle in a direction normal to the light guide. 7. The surface light source device according to claim 1, wherein the reflection surface constituting the basic unit has a concave cross-sectional shape. 8. The light reflection sheet according to claim 5, 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. The surface light source device according to any one of the above. 9. The light reflection sheet according to claim 5, wherein the reflection surface is made of a diffusely reflective white material.
8. The surface light source device according to any one of 7. 10. The surface light source device according to claim 8, wherein the coat layer made of the transparent material is an optical thin film. 11. The surface light source device according to claim 8, wherein the coat layer made of the transparent material is a transparent bead coat layer. 12. The surface light source device according to claim 8, wherein a matting process is performed on the reflection surface. 13. A liquid crystal display device using the surface light source device according to claim 1 in a backlight optical system.