JP3362634B2 - Surface light source device - Google Patents

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 that emits light from a light source portion arranged laterally from its surface.

[0002]

2. Description of the Related Art As a surface light source device used for a backlight of a liquid crystal display device, there is a surface light source device in which a light source section is arranged laterally and light from the light source section is emitted from a surface. Is generally called a side lamp type.

As the side lamp type surface light source device, a flat light guide plate is conventionally used, and a straight tubular fluorescent lamp and a plurality of LEDs (light emitting diodes) are aligned so as to face the end surface of the light guide plate. It is known that a light source unit including an LED array or the like is arranged.

This surface light source device is used with its front surface, that is, the surface of the light guide plate, opposed to the incident surface of an illuminated object such as a liquid crystal display panel, and the light from the light source section is used. The light is taken in from the end face thereof, guided in the light guide plate, and emitted to the surface.

[0005]

However, in the above-described conventional surface light source device, since the light guided in the light guide plate is emitted from the surface of the light guide plate in various directions, the angle with respect to the surface of the light guide plate is reduced. There is a lot of useless emitted light that is emitted in a very small direction and diffused to the surroundings, and therefore the amount of light emitted in the front direction and in the vicinity thereof is insufficient, resulting in high front brightness (brightness when observed from the front direction). In addition, there is a problem in that the brightness distribution of the emitted light is not uniform.

It is an object of the present invention to provide a surface light source device which emits light from a light source portion arranged laterally from its surface and which can obtain a sufficiently high front luminance.

[0007]

A surface light source device according to the present invention comprises an end face integrally formed with a light source part and made of transparent resin, and an end face facing the light source part for taking in light from the light source, and the end face. Has a front surface forming a stepped surface by a plurality of surfaces substantially vertical to and a plurality of rising surfaces that are substantially parallel to and directly face the end surface, and a back surface facing the front surface, and is taken in from the end surface. together when directly emitted light from the light source unit that is from the rising surface of the stepped surface
The light reflected by the back surface from the rising surface
A light guide plate for emitting, disposed on a surface of the light guide plate, which has a light guide member which emits towards the surface guides the light emitted from the rising surface of the stepped surface, in addition, In the surface light source device according to the first invention, the light guide member has, on its back surface, a surface for taking in light emitted from each rising surface of the stepped surface of the light guide plate and a surface for reflecting the light toward the surface direction. Is formed, and a condenser lens unit formed of a plurality of Fresnel lenses for refracting the light from each prism unit in the converging direction and emitting the refracted light is formed on the surface.

Further, in the surface light source device according to the second aspect of the invention, the light guide member takes in light emitted from each rising surface of the stepped surface of the light guide plate on its back surface and directs the light toward the front surface. A plurality of prism parts for refracting and a plurality of condensing lens parts for refracting the light from each of the prism parts in the condensing direction and for emitting the light are formed on the surface, and the prism parts have an arrangement pitch of the condensing lens parts. It is provided at a pitch smaller than that, and at least three or more odd-numbered prism parts are
It is characterized in that it faces two condenser lens portions.

Further, the surface light source device according to the third invention is
The light guide member is surface write free surface takes the light emitted from the rising surface of the stepped surface of the light guide plate on the back surface and the light
A plurality of prism parts each having a surface reflecting in a direction, and refracting the light from each of the prism parts on the surface in a condensing direction and emitting the light, and a plurality of lenses in a vertical direction and a horizontal direction of the light guide member. And a lens array in which are arranged.

The above-mentioned surface light source device guides the light from the light source portion arranged facing the light-intake end surface of the light guide plate by the light guide plate and the light guide member arranged on the surface thereof and emits the light in the surface direction. The light from the light source unit is taken into the light guide plate from its end face, guided into the light guide plate, and emitted from each rising surface of the surface of the light guide plate which is a stepped surface, and the light guide member is provided. Is taken into each prism part on the back surface of the. Then, the light taken into each of the prism parts is refracted by these prism parts and guided in the surface direction inside the light guide member, and is refracted in the condensing direction by each condensing lens part on the surface to be emitted. .

Therefore, according to this surface light source device, most of the light emitted from the surface can be emitted in the front direction without being diffused to the surroundings, and therefore a sufficiently high front brightness can be obtained. .

Moreover, in the first aspect of the present invention, since each condensing lens portion on the surface of the light guide member is a Fresnel lens, the light guide member has a plurality of prism portions arranged in an array on its back surface, Even if a plurality of condenser lens portions are formed in an array, moire fringes due to the relative pitch shift between the prism portion and the condenser lens portion will not occur.

In the second aspect of the invention, the arrangement pitch of the prism portions on the back surface of the light guide member is made smaller than the pitch of the condenser lens portion on the front surface, so that at least three or more odd-numbered prism portions are formed. Since the light is made to face one condenser lens portion, most of the light from the central prism portion out of the light that has entered the condenser lens portion from each prism portion that faces one condenser lens portion is The light is emitted in the front direction along the lens optical axis of the condenser lens, and most of the light from the prism portions on both sides is emitted in a direction inclined to some extent with respect to the lens optical axis of the condenser lens.

Therefore, according to the surface light source device of the second invention, not only the front brightness but also the brightness when observed from a direction inclined to the front direction to some extent is increased, and the brightness distribution is substantially uniform. can do.

Further, in the third aspect of the invention, each condensing lens portion facing each prism portion of the light guide member is a lens array in which a plurality of lenses are arranged in the vertical direction and the horizontal direction of the light guide member. , Not only refracting the light that has entered the condenser lens portion from the prism portion in the direction along the width direction of the condenser lens portion, but also along the length direction of the condenser lens portion. In the direction as well, the light can be refracted in the converging direction and emitted, and therefore the front brightness can be further increased.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, the surface is a stepped surface, light is taken in from the end surface, and the light is emitted from each rising surface of the stepped surface to the surface of the light guide plate, and the light is guided to the back surface. A plurality of prism parts are formed that take in the light emitted from each rising surface of the stepped surface of the light plate and refract the light toward the surface direction, and the light from each prism part is refracted in the condensing direction on the surface. By arranging a light guide member in which a plurality of condenser lens units that emit light are arranged, the light from the light source unit that is arranged so as to face the light receiving end surface of the light guide plate is generated by the light guide plate and the light guide member. The front luminance is sufficiently increased by guiding the light and emitting it toward the surface.

In addition to the above, according to the first aspect of the present invention, each condenser lens portion on the front surface of the light guide member is a Fresnel lens, so that the prism portion on the back surface of the light guide member and the condenser lens portion on the front surface of the light guide member. This is to eliminate the generation of moire fringes due to the relative pitch shift with respect to.

Further, in the second invention, the arrangement pitch of the prism portions on the back surface of the light guide member is made smaller than the pitch of the condenser lens portion on the front surface, and at least three or more odd-numbered prism portions are formed into one. By facing the condenser lens unit, not only the front luminance but also the luminance when observed from a direction tilted to some extent with respect to the front direction is increased, and the luminance distribution is made substantially uniform.

In the second aspect of the invention, it is desirable that the condenser lens portion is a convex lens having a curved surface that is continuous over the entire width thereof. It is possible to eliminate the occurrence of moire fringes due to the relative pitch deviation with the condenser lens portion on the surface.

Further, according to the third aspect of the invention, each condensing lens portion facing each prism portion of the light guide member is a lens array in which a plurality of lenses are arranged in a vertical direction and a horizontal direction of the light guide member. Therefore, the front luminance is further increased.

In the third invention, it is desirable that each lens of the lens array is a Fresnel lens,
With this configuration, it is possible to eliminate the occurrence of moire fringes due to the relative pitch shift between the prism portion on the back surface of the light guide member and the condenser lens portion on the front surface.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a surface light source device used for a backlight of a liquid crystal display device will be described below with reference to the drawings. 1 to 7 show a first embodiment of the present invention. FIG. 1 is a sectional view of a surface light source device without hatching, and FIG. 2 is an enlarged view of a part of FIG.

As shown in FIGS. 1 and 2, this surface light source device includes a light guide plate 1, a light source section 3 disposed on the side of the light guide end face of the light guide plate 1 so as to be opposed thereto, and The light guide member 6 is disposed on the surface of the light plate 2.

The light guide plate 1 is made of a transparent resin, the back surface of which is a flat surface, and the front surface is a stepped surface which gradually decreases from one end side to the other end side at a predetermined pitch. ing. The step pitch of the stepped surface is set to be the same as the pixel pitch of the liquid crystal display panel (not shown) or set to an integral fraction of the pixel pitch.

The light guide plate 1 can be manufactured by molding using a mold or by cutting a transparent plate. However, since the surface of the light guide plate 1 is a stepped surface with a fine pitch, the mold is In molding with, due to poor resin flow into the stepped mold surface, defects such as rounded corners and chipped corners may occur on the stepped surface of the molded light guide plate. Since cracks may occur, it is difficult to obtain a light guide plate with good shape accuracy with good yield.

Therefore, in this embodiment, the light guide plate manufactured by the manufacturing method shown in FIG. 3 is used. This light guide plate 1 is manufactured by manufacturing a light guide plate main body 1a made of a wedge-shaped plate and a surface sheet 1b having a stepped surface as shown in FIG. (B)
It is a method of manufacturing the light guide plate 1 as shown in FIG.

In this manufacturing method, the light guide plate body 1 is used.
a is molded by using a mold, but this light guide plate body 1a
Is a wedge-shaped plate with a simple shape whose front and back surfaces are both flat, so the mold may have a simple mold shape.Therefore, make sure to pour the resin into the entire mold. Thus, the light guide plate body 1a having a good shape accuracy can be molded.

As shown in FIG. 4, the surface sheet 1b has a concave portion on the surface, and the shape of each step portion 2 of the stepped surface formed on the surface of the light guide plate 1 is formed on the bottom surface of the concave portion. Using a template 10 in which a plurality of recesses having a horizontally-long triangular cross section corresponding to the above are arrayed at a pitch corresponding to the step pitch of the stepped surface, a liquid resin 11 is poured into the recess of the template 10 The surface is flattened with a squeegee (not shown) or the like, and the resin layer is cured to manufacture.

Surface sheet 1b manufactured in this way
Is a base sheet layer formed of the resin 11 filled in the area above the recesses on the bottom surface of the recess of the template 10, and a stepwise layer formed of the resin 11 that has entered the recesses on the base sheet layer. It is formed integrally.

In the production of the surface sheet 1b, the bottom surface of the concave portion of the template 10 is an uneven surface in which the concave portions are arranged at a fine pitch, but since the entire concave portion is open upward, this A sufficient amount of the resin 11 can be poured into the concave portion, and the resin 11 spreads over the uneven surface and spreads over the entire concave portion. Therefore, by curing the resin layer, corners are rounded or chipped off. A surface sheet 1b having a stepped surface with no defect and good shape accuracy
Can be obtained.

However, depending on the viscosity of the resin 11,
The resin 11 may not enter the corners between the peripheral surface and the bottom surface of the concave portion of the template 10 well, but as shown in FIG. If a slightly larger surface sheet is manufactured and the periphery thereof is cut off, the surface sheet 1b having a stepped surface with good shape accuracy can be obtained over the entire surface.

The surface sheet 1b can be easily manufactured by pouring the resin 11 into the concave portion of the template 10 to flatten the surface and curing the resin layer. The resin 11 is preferably a photo-curable resin, and when the photo-curable resin is used, the resin layer can be cured by irradiation with ultraviolet rays, so that the surface sheet 1b can be manufactured more easily.

The surface sheet 1 manufactured by the above method
b is a base sheet layer and a step-like layer which are integrally formed. The surface sheet 1b is a template in which concave portions having a cross section of a horizontally long triangle are formed on the surface as shown in FIG. 10 'is used, the resin 11 is poured into each of the recessed portions, the surface thereof is leveled with a flat surface at the same level as the open surface of each of the recessed portions (the surface of the template 10'), and the surface of the resin layer is transparent. It may be manufactured by a method of curing the resin layer by stacking base films 12 made of different resin films. According to this method, the resin 11 that has entered the recesses is formed on the base film 12. Thus, the surface sheet 1b having a structure in which the stepwise layers in which the resin layers having the laterally long triangular cross section are arranged integrally is obtained.

The light guide plate 1 is composed of the light guide plate body 1a.
The surface sheet 1b and the surface sheet 1b may be stacked as shown in FIG. 3 (b), and the entire opposing surface may be bonded by a transparent adhesive (not shown) to manufacture. A good light guide plate 1 can be obtained with good yield and at low cost.

The light guide plate body 1a and the surface sheet 1b
It is desirable to use, as the above-mentioned pressure-sensitive adhesive, one having a refractive index of each light as close as possible, and if these refractive indexes are the same,
Alternatively, if the refractive index is very close, the light guide plate body 1a
It is possible to obtain the light guide plate 1 having good light guide characteristics, in which light is hardly refracted at the interface between the surface sheet 1b and the surface sheet 1b.

The light guide plate 1 is not limited to the above-described manufacturing method, and for example, the resin 11 is formed on the template 10 'shown in FIG.
Manufactured by a method in which the surface of the light guide plate 1a is adhered to the stepwise layer after the stepwise layer is formed by pouring the resin to level the surface and cure the resin to form a stepwise layer in which resin layers having a laterally long triangular cross section are arranged. However, in that case, the base sheet 12 of the topsheet 1b is unnecessary.

The light guide plate 1 takes in light from the end face on the one end side (the end face having a larger height) and emits the light from the rising face 2a of each step 2 of the stepped face. The substantially parallel light emitted from the light source unit 3 is taken into the light guide plate 1 from the light receiving end face thereof, and the light traveling in parallel to each step face of the light guide plate 1 as shown by the arrow in FIG. The light directly emitted from the rising surface 2a and traveling in a direction intersecting with each staircase surface is the front and back surfaces of the light guide plate 1, that is, the interface between the surface of each step portion 2 of the staircase surface and the outside air (air) and The light guide plate 1 while refracting alternately at the interface between the back surface of the light guide plate and the outside air
The light is guided inside and is emitted from each rising surface 2a of the stepped surface.

The light source 3 used in this embodiment is composed of a straight tubular fluorescent lamp 4, and the light emitted from the fluorescent lamp 4 is directed to the light-trapping end surface of the light guide plate 1 behind it. A reflector 5 for reflecting and obtaining substantially parallel light is arranged.

On the other hand, the light guide member 6 disposed on the surface of the light guide plate 1 guides the light emitted from each rising surface 2a of the stepped surface on the surface of the light guide plate and emits the light in the surface direction. The optical member 6 is made of transparent resin.

As shown in FIGS. 1 and 2, this light guide member 6 takes in the light emitted from each rising surface 2a of the stepped surface of the light guide plate 1 on its back surface and directs the light toward the front surface. A plurality of prism parts 7 to be refracted by an array are formed,
A plurality of condenser lens portions 8 for refracting the light from the respective prism portions 7 in the condensing direction and emitting the light are arrayed on the surface.

Each of the prism portions 7 is a horizontally long prism portion having an inverted triangular cross section along the width direction of the stepped surface of the light guide plate 1. These prism portions 7 are formed on the stepped surface of the light guide plate 1. They are arranged in parallel with each other at a pitch corresponding to the step pitch.

Further, each of the condenser lens portions 8 is a horizontally long lens portion along the length direction of the prism portion 7, and these condenser lens portions 8 have a pitch corresponding to the arrangement pitch of the prism portions 7. Are arranged in parallel with each other.
In this embodiment, the width of the prism portion 7 is set to the light guide plate 1.
And the width of the condenser lens portion 8 is made the same as the width of the prism portion 7. Therefore, each prism portion 7 and each condenser lens portion 8 is formed.
Is approximately the same as the pixel width of the liquid crystal display panel, or is a width that is a fraction of the pixel width.

Each condensing lens portion 8 is a linear Fresnel lens composed of three or more odd-numbered narrow lens surfaces (five lens surfaces in this embodiment), and its lens optical axis O guides light. It is in a direction parallel to the perpendicular of the member 6.

The light guide member 6 may be a molded product using a mold or a transparent plate cut product. In this embodiment, the manufacturing method as shown in FIG. 6 is used. The light guide member manufactured in 1. is used.

In the method of manufacturing the light guide member 6, a prism sheet 6a and a lens sheet 6b as shown in FIG. 6A are manufactured, and these are bonded to each other as shown in FIG. 6B. This is a method of manufacturing the light guide member 6.

In this manufacturing method, as shown in FIG. 7, the prism sheet 6a has a plurality of inverted triangular cross sections corresponding to the shapes of the prism portions 7 arranged on the front surface of the prism member 6 on the back surface thereof. A mold plate 13 having concave portions arranged at a pitch corresponding to the arrangement pitch of the prism portions 7 is used, and a liquid resin 14 is poured into each concave portion of the mold plate 13 and the surface thereof is squeegeeed (not shown). And the like to flatten the flat surface at the same level as the open surface (the surface of the template 13) of each recessed portion, and to lay the base film 15 made of a transparent resin film on the surface of the resin layer to cure the resin layer. Produce by the method.

In this case, each concave portion of the template 13 has a pole corresponding to the width of the prism portion 7 (which is almost the same as the pixel width of the liquid crystal display panel, or a width which is an integer fraction of the pixel width). Although the recesses have an inverted triangular cross section with a very small width, the entire recesses are open upward, so that a sufficient amount of resin 14 having a volume larger than that of the recesses can be poured into each recess. Since the resin 14 spreads in the recessed portion and spreads over the entire recessed portion, the resin layer is cured to form the prism portion 7 with good shape accuracy without defects such as corner rounding and chipping. Thus, the prism sheet 6a can be obtained.

However, depending on the viscosity of the resin 14,
The resin 14 may not properly enter the end of the recessed portion of the template 13, but if the length of the recessed portion is increased to some extent and a prism sheet slightly larger than a predetermined size is manufactured and the periphery thereof is cut off. , A prism sheet 6b in which prism portions 7 having good shape accuracy are arrayed over the entire length
Can be obtained.

This prism sheet 6b corresponds to the template 13
The resin 14 can be easily manufactured by pouring the resin 14 into each of the recessed portions of the surface, leveling the surface evenly, superposing the base film 15 thereon, and curing the resin layer in each of the recessed portions. The resin 14 is preferably a photo-curable resin, and if a photo-curable resin is used, the resin layer can be cured by irradiation with ultraviolet rays.
Can be made easier.

The prism sheet 6a manufactured by the above method is one in which a plurality of prism portions 7 made of the resin 14 that have entered the respective recessed portions of the template 13 are lined up and integrally laminated on the base film 15. However, the prism sheet 6a is manufactured by using a template in which a concave portion is provided on the surface and each of the concave portions is formed on the bottom surface of the concave portion, and the surface sheet 1b of the light guide plate 1 shown in FIG. The same method may be used. According to this method, the base sheet layer is formed of the resin filled in the regions above the recessed portions of the bottom surface of the recess of the template, and the base sheet layer is formed on the base sheet layer. A prism sheet in which the prism portions 7 made of resin that have entered are integrally arranged is obtained.

The lens sheet 6b is not shown in the manufacturing method, but the light guide plate 1 shown in FIG. 4 or 5 is used.
A method similar to any of the methods for producing the topsheet 1b of
That is, using a template having a concave portion on the surface and arranging concave portions having a cross-sectional shape corresponding to the shape of each Fresnel lens (linear Fresnel lens) 8 formed on the surface of the light guide member 6 on the bottom surface of the concave portion, A lens sheet in which a base sheet layer is formed of a resin filled in a region above each recessed portion on the bottom surface of the recessed portion, and Fresnel lenses 8 made of the resin that has entered into each recessed portion are integrally arranged thereon. Or get
Alternatively, a method of obtaining a lens sheet in which Fresnel lenses 8 made of a resin that has entered into each recess of the template are arranged side by side on a base film using a template having an array of the recesses formed on the surface thereof To produce.

According to such a manufacturing method, as in the case of manufacturing the surface sheet 1b of the light guide plate or the prism sheet 6a described above, the linear Fresnel having a good shape accuracy with no defects such as rounded corners and chipped corners. It is possible to obtain the lens sheet 6b in which the lenses are arranged and formed. The resin used for manufacturing the lens sheet 6b is also preferably a photocurable resin.

In the light guide member 6, the prism sheet 6a and the lens sheet 6b are superposed as shown in FIG. 6 (b), and the entire opposing surfaces thereof are bonded with a transparent adhesive (not shown). According to this manufacturing method, the light guide member 6 having a good shape accuracy can be obtained with good yield and at low cost.

Also in the light guide member 6, the prism sheet 6a, the lens sheet 6b, and the adhesive are
It is desirable to use those having the refractive indices of the respective lights as close as possible, and if these refractive indices are the same or very close to each other, the refraction of the light at the interface between the prism sheet 6a and the lens sheet 6b will be performed. It is possible to obtain the light guide member 6 having good light guide characteristics with almost no light.

The light guide member 6 is not limited to the above-described manufacturing method. For example, the resin material 14 is poured into the template 13 shown in FIG. 7 to make the surface even, and the prism portion 7 is cured. It may be manufactured by a method of forming a layer in which the lens is aligned and then laminating the lens sheet 6b to the layer with an adhesive. In that case, the base sheet 15 of the prism sheet 6a is not necessary.

The light guide member 6 is, as shown in FIG.
The top of each prism portion 7 on the back surface is brought into contact with the surface of each step portion 2 of the stepped surface of the light guide plate 1, and one side surface of these prism portions 7 is set to each of the stepped surfaces of the light guide plate 1. The light guide plate 1 is arranged on the surface of the light guide plate 1 so as to closely face the rising surface 2a.

In this surface light source device, the light from the light source section 3 arranged so as to face the light-intake end surface of the light guide plate 1 is guided by the light guide plate 1 and the light guide member 6 arranged on the surface thereof in the surface direction. Light emitted from the light source unit 3 is taken into the light guide plate 1 from its end face and guided through the light guide plate 1 as shown by the arrow in FIG. The light is emitted from each rising surface 2a on the front surface of the light guide plate and is taken into each prism portion 7 on the back surface of the light guide member 6.

Then, the light taken into each of the prism portions 7 is supplied to these prism portions 7 as shown by an arrow in FIG.
Is guided by the light-guiding member 6 in the surface direction, and is refracted in the light-collecting direction by each condensing lens portion 8 on the surface of the light-guiding member 6 to be emitted.

Therefore, according to the above-mentioned surface light source device, most of the light emitted from the surface can be emitted in the front direction without being diffused to the surroundings, and therefore a sufficiently high front brightness can be obtained. .

Moreover, in this embodiment, the light guide member 6 is used.
Since each condensing lens portion 8 on the front surface of is a Fresnel lens, the light guide member 6 has a plurality of prism portions 7 on its back surface.
Even if a plurality of condenser lens portions 8 are formed in an array on the surface, moire fringes due to the relative pitch shift between the prism portion 7 and the condenser lens portion 8 will not occur. .

That is, in FIG. 1, in order to make the configurations of the light guide plate 1 and the light guide member 6 easy to understand, the stepped surface of the light guide plate 1 and the prism portion 7 and the condenser lens portion 8 of the light guide member 6 are enlarged. As shown, the surface light source device of this embodiment is used for a backlight of a liquid crystal display device, and the step pitch of the stepped surface of the light guide plate 1 and the prism portion 7 and the condenser lens portion of the light guide member 6 are shown. Since the array pitch of 8 is the same as the pixel pitch of the liquid crystal display panel or is an integer fraction of the pixel pitch, the width of each step 2 of the stepped surface of the light guide plate 1 and each prism of the light guide member 6 are set. Part 7 and each condensing lens part 8
Width is very small.

The light guide member 6 is designed so that the arrangement pitch of the prism portions 7 on the back surface and the arrangement pitch of the condenser lens portions 8 on the front surface are equal to each other. Since the width of the condenser lens unit 8 is extremely small, it is difficult to form them with the same pitch.

Therefore, moire fringes appear due to the displacement of the arrangement pitch of the prism portion 7 and the condenser lens portion 8. However, in the surface light source device of this embodiment, since the condenser lens portion 8 is a Fresnel lens, the lens array pitch on the surface of the light guide member 6 is smaller than that when the condenser lens portion 8 is the convex lens. Apparently, it is 1 / the number of lens surfaces of the Fresnel lens (1/5 in the case of a Fresnel lens having five lens surfaces as shown in FIGS. 1 and 2).

Therefore, according to this surface light source device, since the pitch difference between the prism portion 7 on the rear surface of the light guide member 6 and the condenser lens portion 8 on the front surface is large, moire fringes can be visually observed. There is no.

FIG. 8 is a sectional view of a surface light source device showing a second embodiment of the present invention with hatching omitted.
In this surface light source device, the surface is a stepped surface, and the light guide plate 21 that takes in light from the end face and emits the light from the rising surface 22a of each step 22 of the stepped surface, and the light guide plate 21. A light source portion (not shown) arranged to face one end surface (light-intake end surface) and a light guide plate 21 are arranged on the surface and guide light emitted from each rising surface 22a of the stepped surface to guide the surface. In this embodiment, the light guide plate 21 and the light guide member 23 are configured as follows.

That is, the light guide member 2 used in this embodiment.
3 is basically an array of a plurality of prism parts 24 that take in the light emitted from each rising surface 22a of the stepped surface of the light guide plate 21 and refract the light toward the surface direction. A plurality of condenser lens portions 25 for refracting the light from the respective prism portions 24 in the condensing direction and emitting the light are arrayed on the surface. The prism portions 24 are formed on the surface of the light guide member. It is provided with a pitch smaller than the arrangement pitch of 25, and at least three or more odd-numbered prism portions (five prism portions in FIG. 8) face one condenser lens portion 25, and the condenser lens portions 25 are ,
It is a convex lens (cylindrical lens) having a continuous curved surface over the entire width.

The light guide plate 21 used in this embodiment is
The step pitch of the stepped surface is the same as the arrangement pitch of the prism portions 24 of the light guide member 23,
The light guide member 23 abuts the tops of the prism parts 24 on the back surface thereof with the surfaces of the step parts 22 of the stepwise surface of the light guide plate 21, and one side surface of the prism parts 24 is the light guide plate. The light guide plate 21 is arranged on the surface of the light guide plate 21 so as to closely face the respective rising surfaces 22 a of the staircase-shaped surface 21.

Also in the surface light source device of this embodiment, the light from the light source portion (not shown) arranged facing one end surface of the light guide plate 21 is guided by the light guide plate 21 and the light guide member 23 arranged on the surface thereof. The light is emitted in the front surface direction, and in this surface light source device, the prism portion 24 on the back surface of the light guide member 23 is used.
By making the arrangement pitch of (3) smaller than the pitch of the condenser lens portions 25 on the surface, at least three or more odd-numbered prism portions 24 are opposed to one condenser lens portion 25. Of the light incident on the condenser lens section 25 from each prism section 24 facing the section 25,
Most of the light from the central prism portion 24 is emitted in the front direction along the lens optical axis O ′ of the condenser lens,
Most of the light from the prism parts on both sides is emitted in a direction inclined to some extent with respect to the lens optical axis O ′ of the condenser lens.

That is, in FIG. 8, arrows a, b, c
Is each prism unit 2 facing one condenser lens unit 25.
4 schematically shows the light incident on the condensing lens unit 25 from No. 4, the shape of each prism unit 24 is the same, and the light to each prism unit 24 from each rising surface 22a of the light guide plate 21 is shown. If the incident conditions are almost the same,
The light a from the central prism portion 24, the light b from the prism portions 24 on both sides thereof, and the light c from the prism portion 24 outside thereof are respectively the lens optical axis O of the condenser lens portion 25. The light has a spread angle .theta. Centered on a direction substantially parallel to ".

However, the light a from the central prism portion 24 is a divergent light centered on the lens optical axis O'of the condenser lens portion 25, while the other prism portion 2
The lights b and c from 4 are spread lights centered on parallel lines that are laterally displaced from the lens optical axis O ′ of the condenser lens unit 25.

Then, the condenser lens section 25 refracts the incident light from the direction of the center of the spread on the lens optical axis O ', refracts it in the direction along the lens optical axis O', and outputs it. Since the incident light from the direction of is refracted in the direction deviated from the lens optical axis O ′ and is emitted, most of the light a incident on the condenser lens unit 25 from the central prism unit 24 is in the front direction (collected direction). Most of the lights b and c that have been emitted in the direction along the lens optical axis O ′ of the optical lens unit 25 and have entered the condenser lens unit 25 from the other prism unit 24 are emitted obliquely. The emission angle range of the light in the front direction and the oblique direction can be arbitrarily set by selecting the curvature of the lens surface of the condenser lens unit 25.

Therefore, according to the surface light source device of this embodiment, most of the light emitted from the surface is emitted in the direction of the predetermined angle range including the front direction without being diffused to the surroundings, and only the front brightness is obtained. Not only that, the brightness when observed from a direction tilted to some extent with respect to the front direction can be increased, and the brightness distribution can be made substantially uniform.

Therefore, this surface light source device is more suitable as a backlight of a liquid crystal display device, and when this surface light source device is used as a backlight, the liquid crystal display device has high front brightness and a wide viewing angle. Good display can be performed.

Further, in this embodiment, the prism portion 24 on the back surface of the light guide member 6 is replaced with the condenser lens portion 25 on the surface of the light guide member.
Since the condenser lens section 25 is a convex lens having a continuous curved surface over the entire width, the arrangement pitch of the prism section 24 and the condenser lens section 25 is significantly different. Therefore, it is possible to eliminate the occurrence of moire fringes due to the pitch shift between the prism portion 24 and the condenser lens portion 25.

FIG. 9 is a perspective view of a part of a surface light source device showing a third embodiment of the present invention. In this surface light source device, the surface is a stepped surface, and the light guide plate 31 that takes in light from the end surface and emits the light from the rising surface 32a of each step 32 of the stepped surface, and the light guide plate 31. A light source section (not shown) arranged to face one end surface (light-intake end surface) and a surface arranged on the surface of the light guide plate 31, and guides light emitted from each rising surface 32a of the stepped surface to guide the surface. And a light guide member 33 that emits light in a certain direction. In this embodiment, the light guide member 33 has the following configuration.

That is, the light guide member 3 used in this embodiment.
3 is basically formed by arraying a plurality of prism portions 34 on the back surface to take in light emitted from each rising surface 32a of the stepped surface of the light guide plate 31 and refract the light toward the surface direction. A plurality of condenser lens portions 35 for refracting the light from each prism portion 34 in the condensing direction and emitting the light are arranged in an array on the surface, and each condenser lens portion 35 facing each prism portion 34 is formed. Are arranged in the vertical direction and the horizontal direction of the light guide plate, that is, a lens array in which a plurality of lenses 35a are arranged in the longitudinal direction of the prism portion 34, and in this embodiment, Each lens 35a of the lens array (condensing lens unit) 35 is a circular Fresnel lens.

Incidentally, the prism portion 34 of the light guide member 33.
And the step pitch of the stepped surface of the light guide plate 31,
The light guide member 33 is the same as the first embodiment described above.
Covers the top of each prism portion 34 on the back surface of the light guide plate 3
While contacting the surface of each step portion 32 of the stepped surface of No. 1, one side surface of these prism portions 34 is connected to the light guide plate 31.
Are arranged on the surface of the light guide plate 21 so as to closely oppose each rising surface 32a of the stepped surface.

Also in the surface light source device of this embodiment, the light from the light source portion (not shown) arranged facing one end surface of the light guide plate 31 is guided by the light guide plate 31 and the light guide member 33 arranged on the surface thereof. In this surface light source device, each condensing lens portion 35 facing each prism portion 34 of the light guide member 33 is provided in the surface light source device.
4 is a lens array in which a plurality of lenses 35a are arranged in the length direction, the light incident on the condenser lens portion 35 from the prism portion 34 is collected in a direction along the width direction of the condenser lens portion 35. Not only can the light be refracted in the light direction, but also in the direction along the length direction of the condensing lens portion 35, the light can be refracted in the condensing direction and emitted, and therefore the front brightness can be further increased.

In this embodiment, the condenser lens section 35 is a lens array in which a plurality of lenses 35a are arranged in the length direction of the prism section 34, and each lens 35a is a circular Fresnel lens. Therefore, similarly to the first embodiment, it is possible to eliminate the occurrence of moire fringes due to the pitch shift between the prism portion 34 on the back surface of the light guide member 33 and the condenser lens portion 35 on the front surface.

In each of the above embodiments, the light guide plates 1 and 2 are used.
Step pitch of the stair-like surface of 1,31 and the light guide member 6,23,3
Although the arrangement pitch of the prism portions 7, 24, 34 on the back surface of 3 is made the same, the step pitch of the stepped surface of the light guide plate is reduced to an integer fraction of the arrangement pitch of the prism portions of the light guide member, Light emitted from a plurality of rising surfaces of the stepped surface may be taken into one prism portion of the light guide member.

In each of the above embodiments, the light guide plates 1, 21,
As 32, a surface having a stepped surface which becomes lower from one end side to the other end side and an end face on the one end side being a light receiving end face was used. The other end side is a stepped surface that decreases from its end toward the intermediate part, and both end faces are light-trapping end surfaces, that is, for example, the light guide plate 1 having the shape shown in FIG. The light guide plate may have a symmetrical shape, and the light guide plates may be arranged in a state where the ends thereof are brought into contact with each other. By arranging them, a surface light source with higher brightness can be obtained.

In this case, the light taken in from the one end surface of the light guide plate is emitted from each rising surface of the stepped surface on that side,
Since the light taken in from the other end surface is emitted from each rising surface of the stepped surface on that side, the light taking-in direction of each prism part in the one half area of the light guide member and each prism part in the other half area Although the direction of taking in the light is reversed, all the prism parts are symmetrically formed, or the shape of each prism part in the one half area and the shape of each prism part in the other half area are changed. By designing according to the respective light taking-in directions, it is possible to refract the light taken into the prism portion in any region toward the surface direction of the light guide member.

Further, the light source section used in the surface light source device of the present invention is not limited to the one using the straight tubular fluorescent lamp 4 as shown in FIG. 1, but for example, an LED in which a plurality of LEDs (light emitting diodes) are aligned. An array or the like may be used. Further, the present invention is not limited to the surface light source device used for the backlight of the liquid crystal display device, but can be widely applied to surface light source devices for various purposes.

[0084]

According to the surface light source device of the present invention, the light from the light source portion arranged facing the light-intake end surface of the light guide plate is guided in the surface direction by the light guide plate and the light guide member arranged on the surface thereof. According to the surface light source device, the light is emitted from the end face of the light guide plate, emitted from each rising face of the stepped face, and introduced into each prism portion of the back face of the light guide member. Most of the light emitted from the surface is refracted by these prisms and guided in the surface direction inside the light guide member, and then refracted in the converging direction by each condenser lens on the surface to be emitted. Can be emitted in the front direction without being diffused to the surroundings, and thus a sufficiently high front brightness can be obtained.

Moreover, in the first invention, since each condensing lens portion on the surface of the light guide member is a Fresnel lens, the light guide member has a plurality of prism portions arrayed on its back surface, and a plurality of prism portions are formed on the front surface. Even if the condensing lens units are formed in an array, moire fringes due to the pitch shift between the prism unit and the condensing lens units will not occur.

Further, in the second invention, the arrangement pitch of the prism portions on the back surface of the light guide member is made smaller than the pitch of the condenser lens portions on the front surface, so that at least three or more odd-numbered prism portions are set to one. Since the two condenser lenses are opposed to each other, most of the light from the central prism portion out of the light incident on the condenser lenses from the respective prism portions opposed to one condenser lens portion. Light is emitted in the front direction along the lens optical axis of the optical lens, and most of the light from the prism parts on both sides is emitted in a direction inclined to the lens optical axis of the condenser lens to some extent. However, it is possible to increase the brightness when observed from a direction inclined to the front direction to some extent and to make the brightness distribution substantially uniform.

In the second aspect of the present invention, it is desirable that the condenser lens section is a convex lens having a continuous curved surface over the entire width thereof. It is possible to eliminate the occurrence of moire fringes due to the deviation of the pitch between the surface and the condenser lens portion.

Further, in the third invention, each condensing lens portion facing each prism portion of the light guide member is a lens array in which a plurality of lenses are arranged in the vertical direction and the horizontal direction of the light guide member. Therefore, not only is the light incident on the condenser lens portion from the prism portion refracted in the converging direction in the width direction of the condenser lens portion, but also along the length direction of the condenser lens portion. Even in this direction, the light can be refracted and emitted in the converging direction, and therefore the front brightness can be further increased.

In the third invention, it is desirable that each lens of the lens array is a Fresnel lens,
By doing so, it is possible to eliminate the occurrence of moire fringes due to the pitch deviation between the prism portion on the back surface of the light guide member and the condenser lens portion on the front surface.

[Brief description of drawings]

FIG. 1 is a sectional view of a surface light source device showing a first embodiment of the present invention with hatching omitted.

FIG. 2 is an enlarged view of a part of FIG.

FIG. 3 is a diagram showing a method of manufacturing a light guide plate used in the surface light source device.

FIG. 4 is a diagram showing a method of manufacturing a topsheet when manufacturing a light guide plate by the manufacturing method of FIG.

FIG. 5 is a view showing another method of manufacturing the topsheet.

FIG. 6 is a diagram showing a method of manufacturing a light guide member used in the surface light source device.

FIG. 7 is a diagram showing a method of manufacturing a prism sheet when manufacturing a light guide member by the manufacturing method of FIG.

FIG. 8 is a sectional view of a surface light source device showing a second embodiment of the present invention, in which hatching is partially omitted.

FIG. 9 is a perspective view of a part of a surface light source device showing a third embodiment of the present invention.

[Explanation of symbols]

1, 21, 31 ... Light guide plate 2a, 21a, 31a ... rising surface 3 ... Light source 6, 23, 33 ... Light guide member 7, 24, 34 ... Prism part 8, 25, 35 ... Condensing lens section

Continuation of the front page (56) References JP-A-61-15104 (JP, A) JP-A-8-54517 (JP, A) JP-A-7-191319 (JP, A) JP-A-9-54556 (JP , A) JP 2-17 (JP, A) JP 8-55507 (JP, A) JP 61-34583 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) F21V 8/00 601 G02B 6/00 331 G02F 1/13357

Claims (6)

(57) [Claims] 1. An end face which is integrally formed with a light source part and made of a transparent resin and which faces the light source part and takes in light from the light source, a plurality of faces substantially perpendicular to the end face and the end face. It has a front surface that forms a stepped surface by a plurality of parallel and directly opposed rising surfaces, and a back surface that faces the front surface, and the light from the light source unit taken in from the end surface is stepped. Emitting directly from each rising surface of the surface,
A light guide plate that emits the reflected light from the rising surface, and a light guide member that is disposed on the surface of the light guide plate and that guides the light emitted from each rising surface of the stepped surface and emits the light in the surface direction. The light guide member, on the back surface thereof, a plurality of prism portions each having a surface for capturing light emitted from each rising surface of the stepped surface of the light guide plate and a surface for reflecting the light toward the surface direction, A surface light source device comprising a condenser lens portion formed on a surface thereof, the condenser lens portion including a plurality of Fresnel lenses for refracting light from each of the prism portions in a condensing direction and emitting the refracted light. 2. A light guide plate which has a stepped surface and takes in light from an end surface and emits the light from each rising surface of the stepped surface, and a light guide plate which is arranged so as to face a light receiving end surface of the light guide plate. And a light guide member that is disposed on the surface of the light guide plate and that guides the light emitted from each rising surface of the stepped surface and emits the light in the surface direction. A plurality of prism parts that take in the light emitted from each rising surface of the stepped surface of the light guide plate and refract the light toward the surface direction, and refract the light from each prism part on the surface in the focusing direction. A plurality of condensing lens units that emit the light are formed, the prism units are provided at a pitch smaller than the arrangement pitch of the condensing lens units, and at least three or more odd-numbered prism units are provided.
A surface light source device characterized in that it faces two condenser lenses. 3. The surface light source device according to claim 2, wherein the condenser lens portion is formed of a convex lens having a continuous curved surface over the entire width thereof. 4. An end face which is integrally formed with a light source part and made of transparent resin, and which faces the light source part and takes in light from the light source, a plurality of faces substantially perpendicular to the end face and the end face. It has a front surface that forms a stepped surface by a plurality of parallel and directly opposed rising surfaces, and a back surface that faces the front surface, and the light from the light source unit taken in from the end surface is stepped. Directly emitted from each rising surface of the surface, and by the back surface
A light guide plate that emits the reflected light from the rising surface, and a light guide member that is disposed on the surface of the light guide plate and that guides the light emitted from each rising surface of the stepped surface and emits the light in the surface direction. The light guide member has a plurality of prism portions on a back surface thereof, each of which has a surface for taking in light emitted from each rising surface of the stepped surface of the light guide plate and a surface for reflecting the light toward the surface direction, and a front surface. A surface light source characterized by comprising a lens array in which a plurality of lenses are arranged in the vertical direction and the horizontal direction of the light guide member to refract the light from each of the prism parts in the condensing direction and emit the refracted light. apparatus. 5. The surface light source device according to claim 4, wherein each lens of the lens array is a Fresnel lens. 6. The light guide plate has a surface on which a step-like layer is formed.
From the sheet and the wedge-shaped plate to which this surface sheet is attached
2. A light guide plate pair body consisting of
Alternatively, the surface light source device according to claim 4 .