JP2002203413A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device reducing the number of dot-like primary light sources for reduced power consumption, and providing a uniform distribution of brightnesses over light emitting surfaces to enable a quantity of primary light source light to be emitted as it is effectively concentrated in an observation direction. SOLUTION: LEDs 2A and 2B are positioned adjacent to the diagonal corners of a rectangular light guide 4. The light guide 4 has on its light emitting surface 43 a directed light emitting mechanism comprising a mat surface for emitting light in an inclined direction, and has a plurality of parallel first prism lines 44a on its surface 44 opposite to the light emitting surface 43, which extend in a first direction connecting the LEDs 2A and 2B together. A light polarization element 6 positioned on the light emitting surface 43 of the light guide 4 has an incident surface 61 opposite to the light emitting surface 43, and has an opposite light emitting surface 62. A plurality of parallel second prism lines 61a extending in a second direction approximately perpendicular to the first direction are provided on the incident surface 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge light type surface light source device, and more particularly to a surface light source device designed to reduce the size and power consumption.
INDUSTRIAL APPLICABILITY The surface light source device of the present invention is suitably applied to a backlight of a relatively small liquid crystal display device used as a display panel of a portable electronic device such as a mobile phone or an indicator of various devices.

[0002]

2. Description of the Related Art In recent years,
2. Description of the Related Art Liquid crystal display devices have been widely used as monitors for portable notebook personal computers and the like, or as display units for liquid crystal televisions and video integrated liquid crystal televisions, and in various other fields. The liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, an edge light type backlight is frequently used from the viewpoint of downsizing the liquid crystal display device. Conventionally, as a backlight, at least one of a rectangular plate-shaped light guide is used.
Using one end face as a light incident end face, a linear or rod-shaped primary light source such as a straight tube fluorescent lamp is arranged along the light incident end face, and light emitted from the primary light source is incident on a light guide. A light guide that is introduced into an inside of a light guide from an end face and emitted from a light emission surface which is one of two main surfaces of the light guide is widely used.

In recent years, portable electronic devices such as mobile phones and portable game machines, and various electric devices and liquid crystal display devices having relatively small screen dimensions such as indicators of electronic devices have been reduced in size and power consumption. Requested. Therefore, in order to reduce power consumption, an LED which is a point light source is used as a primary light source of the backlight. As a backlight using an LED as a primary light source, for example, as described in JP-A-7-270624, a plurality of LEDs are used in order to exhibit the same function as that using a linear primary light source. They are arranged one-dimensionally along the light incident end face of the light guide. By using a primary light source based on a one-dimensional array of a plurality of LEDs as described above, it is possible to obtain a required light amount and uniformity of luminance distribution over the entire screen.

However, in the case of a small liquid crystal display device, further reduction in power consumption is required, and in order to meet this demand, it is necessary to reduce the number of LEDs used. However, when the number of LEDs is reduced, the distance between the light emitting points becomes longer, so that the area of the light guide close to the area between the adjacent light emitting points is enlarged, and light is emitted from the light guide area in a required direction. The light intensity decreases. This causes unevenness of the luminance distribution in the viewing direction on the light emitting surface of the surface light source device. As described above, it is difficult for a conventional backlight using a point light source as the primary light source to achieve both reduction in power consumption and maintenance of uniformity of luminance distribution.

Accordingly, an object of the present invention is to provide a surface light source device capable of reducing power consumption by reducing the number of point-like primary light sources such as LEDs and maintaining uniformity of luminance distribution on a light emitting surface. To provide.

Further, according to the present invention, by increasing the directivity of emitted light, the amount of light emitted from a point-like primary light source can be effectively concentrated and emitted in the observation direction, and the observation direction can be brightly illuminated even under low power consumption. It is an object of the present invention to provide a surface light source device capable of performing the following.

[0007]

According to the present invention, as a means for achieving the above object, a point-like primary light source and light emitted from the primary light source are guided and emitted from a light emitting surface. A planar light source device comprising a plate-shaped light guide and a light deflecting element disposed adjacent to a light exit surface of the light guide,
The primary light source is disposed adjacent to a vicinity of a first corner of the light guide, and the light guide has a first main surface that is one of the light exit surface and the opposite surface. And a directional light emitting mechanism for emitting light in a direction inclined with respect to the light emitting surface, wherein the light deflecting element includes a light incident surface located opposite to a light emitting surface of the light guide. And a light exit surface on the opposite side, and a second direction substantially orthogonal to a first direction oblique to both of two edges adjacent to the first corner on the light entrance surface. Extending in parallel with each other
A surface light source device comprising a prism array,
Is provided.

In one embodiment of the present invention, the light guide extends in the first direction on the second principal surface, which is the other of the light exit surface and the opposite surface, and is parallel to each other. And a plurality of first prism rows.

In one embodiment of the present invention, a first corner light incident end face is formed near the first corner so as to cut out a corner of the light guide. In one aspect of the present invention, the first corner light incident end face is formed such that a corner of the light guide is notched in a concave shape.

In one embodiment of the present invention, the first direction is a diagonal direction connecting the first corner and a second corner at a diagonal position of the first corner. In one embodiment of the present invention,
The first direction is a direction making substantially the same angle with respect to both of the two edges adjacent to the first corner.

In one embodiment of the present invention, the primary light source has directionality in an emitted light intensity distribution, and the primary light source has a direction in which a peak in the emitted light intensity distribution substantially matches the first direction. A light source is arranged.

In one embodiment of the present invention, a plurality of the primary light sources are arranged adjacent to the vicinity of the first corner. In one embodiment of the present invention, the plurality of primary light sources have a center-to-center distance between light-emitting portions of adjacent primary light sources of 3 mm.
It is arranged so that it becomes above.

[0013] In one embodiment of the present invention, the primary light source is further arranged adjacent to a second corner located diagonally to the first corner. In one embodiment of the present invention, a second corner light incident end face is formed near the second corner so as to cut out a corner of the light guide. In one embodiment of the present invention, the second corner light incident end face is formed such that a corner of the light guide is cut out in a concave shape. In one embodiment of the present invention, a plurality of the primary light sources are arranged adjacent to the vicinity of the second corner.

In one embodiment of the present invention, the primary light source is an LED. In one embodiment of the present invention, the LE
D is arranged so that the distance from the end face of the light guide is 0.2 mm or less.

In one embodiment of the present invention, the directional light emitting mechanism comprises a mat surface or a plurality of lens rows extending in the second direction and parallel to each other. In one aspect of the invention, the lens array is a prism array or a lenticular lens. In one embodiment of the present invention, a light reflecting element is arranged to face the back surface.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing one embodiment of a surface light source device according to the present invention. As shown in FIG. 1, the surface light source device of the present embodiment includes LEDs (light emitting diodes) 2A and 2B as point-like primary light sources, and a light emitting surface by guiding light emitted from these LEDs. A light guide 4 having a substantially rectangular shape in the XY plane and a light deflecting element 6 and a light reflecting element 8 disposed adjacent to the light guide. The light guide 4 has upper and lower two main surfaces and four side end surfaces connecting the edges of the main surfaces.

The LED 2A is disposed adjacent to the first corner of the rectangular shape of the light guide 4, and the LED 2B is
Is disposed adjacent to the second corner of the rectangular plate. The second corner is at a diagonal position of the first corner.

The light guide 4 has a first corner light incident end face 41 formed at the first corner so as to cut out the corner of the light guide. The LED 2 </ b> A is arranged close to the first corner light incident end face 41. Further, the light guide 4 has a planar second corner light incident end face 42 formed so as to cut out the corner of the light guide at the second corner. The LED 2 </ b> B is arranged close to the second corner light incident end face 42.

The first corner light incident end face or the second corner light incident end face formed on the light guide 4 is formed by notching the corner in a plane, but the present invention is not limited thereto. It is not limited, and may be formed by notching concavely so as to have a concave cylindrical surface shape or the like. In either case,
In order to improve the efficiency of incidence of light from the LED on the light guide 4, the distance between the first corner light incident end face or the second corner light incident end face and the LED light emitting surface is 0.2 mm or less. It is preferable that the LED light emitting surface and the first corner light incident end face or the second corner light incident end face have a shape in which projections and depressions are inversely fitted to each other.

The light guide 4 has one main surface (upper surface in the figure) as a light exit surface 43. The light emitting surface 43 has a directivity for emitting light guided in the light guide 4 in a direction inclined with respect to the light emitting surface 43 (that is, a direction inclined with respect to the XY plane). A light emitting mechanism is provided. The directional light emitting mechanism has, for example, a rough surface (mat surface). The directional light emitting mechanism is arranged in a direction normal to the light emitting surface 43 (Z direction).
And directivity light is emitted in an in-plane distribution including both directions (first directions) of diagonals connecting the first corner and the second corner. The angle between the direction of the peak of the emitted light distribution and the light emitting surface 43 is, for example, 10 to 40 °, and the half-value width of the emitted light distribution is, for example, 10 to 40 °.

In the present invention, the first direction is the first direction.
It is a direction oblique to both the first edge (side) and the second edge (side) adjacent to the corner, and from the second edge as the distance from the first edge increases. It is a direction that goes away.

The other main surface (the lower surface in the figure) of the light guide 4 is a prism forming surface 44. The prism forming surface 4
As shown in FIG. 2, each of the first prism rows 44a extends in the first direction oblique to both of the two edges adjacent to the first corner and is parallel to each other (see FIG. 2). FIG.
In FIG. 5, only the ridge lines are shown for each prism row 44a). The angle θ1 between the first direction and the X direction is preferably in the range of 30 to 60 °, more preferably 35 to 55 °,
More preferably, it is in the range of 40 to 50 °. The arrangement pitch P1 of the first prism rows 44a is preferably in the range of 10 to 100 μm, more preferably 10 to 80 μm.
μm, more preferably in the range of 20 to 70 μm.

The vertex angle of the first prism row 44a is, for example, 70 to 150 °. This is because, by setting the apex angle in this range, the light emitted from the light guide 4 can be sufficiently collected in a plane substantially orthogonal to the first direction, and the luminance in the required direction is sufficiently improved. This is because you can do it. That is, by setting the prism apex angle within this range, the half-value width of the emission light distribution is 35 to 35 on the plane including the main emission light orthogonal to the first direction and parallel to the direction (second direction) in the XY plane. The collected outgoing light of 65 ° can be emitted, and the brightness as the surface light source device can be improved. When the first prism row is formed on the light exit surface 43, the apex angle of the first prism row 44a is 80 to
When the prism row is formed on the main surface (lower surface in the figure) 44 opposite to the light exit surface 43, the prism apex angle is 70 to 80 ° or 100 °.
It is preferable that the angle be in the range of 150 °.

The light deflecting element 6 is provided on the light exit surface 43 of the light guide 4.
Is placed on top. The two main surfaces of the light deflecting element 6 are respectively positioned as a whole in parallel with the XY plane. One of the two main surfaces (the main surface located on the light exit surface 43 side of the light guide) is a light incident surface 61, and the other is a light exit surface 62. The light exit surface 62 is a flat surface parallel to the light exit surface 43 of the light guide 4. The light incident surface 61 is a prism forming surface on which a number of second prism rows 61a are arranged in parallel with each other.

FIG. 3 is an explanatory view of the shape of the prism array on the light incident surface 61 of the light deflecting element 6. The second prism rows 61a of the light incident surface 61 extend in the second direction and are formed parallel to each other. The angle θ2 between the second direction and the X direction is:
The angle is preferably in the range of 30 to 60 °, more preferably 35 to 55 °, even more preferably 40 to 50 °. The arrangement pitch P2 of the second prism row 61a is:
It is preferably in the range of 10 to 100 μm, more preferably 10 to 80 μm, and still more preferably 20 to 70 μm.
It is in the range of μm. The vertex angle of the second prism row 61a is preferably in the range of 50 to 80 °, and more preferably in the range of 50 to 70 °.

In this embodiment, when the shape of the light guide 4 is a square, θ1 = θ2 = 45 °. Further, when the shape of the light guide 4 is rectangular, the first direction and the second direction are set to θ1 = θ2 = 45 ° or its vicinity (for example, θ1 = θ2 = 45 °).
1 = θ2 = 45 ° ± 15 °).

In the present invention, as the light emitting mechanism of the light guide 4, in addition to the above-described rough surface, a number of lens arrays such as a prism array, a lenticular lens array, or a V-shaped groove are used.
In 3, it is possible to use those formed in parallel with each other in a second direction substantially orthogonal to the first direction. FIG. 4 shows a light emitting surface 43 of the light guide 4 having such a light emitting mechanism. Here, a third prism row 43a is used as a lens row. The third prism rows 43a extend in the second direction and are formed in parallel with each other. The arrangement pitch P3 of the third prism row 43a is, for example, 10 to 100.
It is preferably in the range of mm μm, more preferably in the range of 10 to 80 μm, and still more preferably in the range of 20 to 70 μm. The vertex angle of the third prism row 43a is 13
It is preferably in the range of 0 to 179 °, more preferably in the range of 140 to 179 °.

This light emitting mechanism is composed of a light emitting surface 4 of the light guide 4.
3 can be provided such that the emission rate has a non-uniform distribution. For example, when a rough surface is used as the light emission mechanism, the surface roughness is subjected to a roughening process so that the distribution within the light emission surface 43 becomes non-uniform. Can be formed.

In the above description, the light exit surface 43 of the light guide 4
The main surface on the opposite side is the prism forming surface 44 of the first prism row 44a, but in the present invention, the light emitting surface is the prism forming surface of the first prism row and the opposite. A light emitting mechanism may be formed on the main surface on the side.

The rough surface and the lens array as the light emitting mechanism are
It is preferable that the average inclination angle θa according to SO4287 / 1-1984 is in the range of 0.5 to 25 °.
3 is preferable from the viewpoint of achieving the uniformity of the luminance in 3. The average inclination angle θa is more preferably in the range of 0.5 to 20 °. It is preferable that the optimum range of the average inclination angle θa is set by the ratio (L / t) of the thickness (t) of the light guide 4 and the length (L) in the direction in which the incident light propagates. That is,
When using a light guide 4 having an L / t of about 100 to 200, the average inclination angle θa is preferably set to 0.5 to 8 °, and more preferably in the range of 0.5 to 6 °. And more preferably in the range of 0.5 to 4 °. When the light guide 4 has an L / t of about 50 to 100, the average inclination angle θa is preferably 0.8 to 15 °, more preferably 0.5 to 10 °. And more preferably in the range of 1 to 6 °. Further, when the light guide 4 having L / t of about 50 or less is used, the average inclination angle θa is preferably set to 1.5 to 25 °, more preferably 2 to 20 °. .

The average inclination angle θ of the rough surface formed on the light guide 4
a is obtained by measuring the rough surface shape using a stylus type surface roughness meter in accordance with ISO 4287 / 1-1984, and setting the coordinate in the measurement direction to x, from the obtained inclination function f (x), the following (1)
It can be obtained by using the equation and the equation (2). Here, L is the measurement length, and Δa is the tangent of the average inclination angle θa.

[0033] Δa = (1 / L) ∫ 0 L | (d / dx) f (x) | dx ··· (1) θa = tan -1 (Δa) ··· (2) In addition, the light guide 4, the light emission rate is 0.5 to 5;
%, More preferably 1 to 3
% Range. This is because when the light emission rate is smaller than 0.5%, the amount of light emitted from the light guide 4 tends to be small and sufficient luminance cannot be obtained, and when the light emission rate is larger than 5%, the vicinity of the light sources 2A and 2B tends to be small. This causes a large amount of light to be emitted, and the light in the first direction in the light emitting surface 43 is significantly attenuated, and the uniformity of luminance on the light emitting surface 43 tends to decrease. By setting the light emission rate of the light guide 4 to 0.5 to 5%, the angle of the peak light emitted from the light emission surface is in the range of 50 to 80 degrees with respect to the normal to the light emission surface. The light guide 4 can emit light having high directivity such that the half value width of the emitted light distribution on a plane perpendicular to the light emitting surface 43 including the first direction is 10 to 40 °, The emission direction can be efficiently deflected by the light deflecting element 6, and a surface light source device having high luminance can be provided.

In the present invention, the light emission rate from the light guide 4 is defined as follows. The light intensity (I ₀ ) of the outgoing light at the corner of the light emitting surface 43 on the first corner light incident end face 41 side or the second corner light incident end face 42 side, and the light emitted at a distance L from the corner. The relationship with the light emission intensity (I) satisfies the following formula (3), where t is the thickness (dimension in the Z direction) of the light guide 4.

I = I ₀ · α (1−α) ^{L / t} (3) Here, the constant α is the light emission rate, and the unit length of the light emission surface 43 in the first direction (conductivity) The ratio (%) of light emitted from the light guide 4 per the length corresponding to the thickness t of the light body). The light emission rate α can be obtained from the gradient by plotting the logarithm of the light intensity of the light emitted from the light emission surface 43 on the vertical axis and (L / t) on the horizontal axis.

FIG. 5 shows how light is deflected by the light deflector 6. This figure shows the traveling direction of the peak emission light from the light guide 4 in a plane including both the first direction and the Z direction. The light emitted obliquely from the light exit surface 43 of the light guide 4 enters the first surface of the second prism row 61a, is totally reflected by the second surface, and exits almost in the direction of the normal to the light exit surface 62. .

Further, in a plane including both the second direction and the Z direction, the luminance in the direction of the normal to the light exit surface 62 can be sufficiently improved by the action of the first prism row 44a as described above. .

Further, the LEDs 2A and 2B have a directionality as shown in FIG. 6 in the emission light intensity distribution in the XY plane. In the present embodiment, the direction of the peak light in the emission light intensity distribution is substantially the same as the first direction. Since the LEDs 2A and 2B are arranged so as to coincide with each other, the two edges adjacent to the first corner and the second
In the light guide region adjacent to the two edges adjacent to the corners of the light guide (that is, the four sides of the light guide 4 in a rectangular shape) is small.

As the light reflection element 8, for example, a plastic sheet having a metal vapor deposition reflection layer on the surface can be used. In the present invention, instead of the reflecting sheet as the light reflecting element 8, the main surface 44 on the opposite side of the light emitting surface of the light guide 4 is used.
It is also possible to use a light reflection layer or the like formed by metal evaporation or the like. In addition, it is preferable to attach reflecting members also to the four side end surfaces of the light guide 4.

The light guide 4 and the light deflecting element 6 of the present invention can be made of a synthetic resin having a high light transmittance. Examples of such a synthetic resin include a methacrylic resin, an acrylic resin, a polycarbonate resin, a polyester resin, a vinyl chloride resin, and a cyclic polyolefin resin. In particular, methacrylic resin is optimal because of its high light transmittance, heat resistance, mechanical properties, and moldability. Such a methacrylic resin is a resin containing methyl methacrylate as a main component, and is preferably a resin having 80% by weight or more of methyl methacrylate. When forming the surface structure of the rough surface of the light guide 4 and the light polarizing element 6 and the surface structure such as the prism rows, the transparent synthetic resin plate is formed by hot pressing using a mold member having a desired surface structure. The shape may be provided simultaneously with the molding by screen printing, extrusion molding, injection molding, or the like. Further, the structural surface can also be formed by using heat or photo-curable resin. Further, on a transparent substrate such as a transparent film or sheet made of a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin, or the like, a rough surface structure made of an active energy ray-curable resin. Further, a lens array arrangement structure may be formed on the surface, or such a sheet may be joined and integrated on a separate transparent substrate by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylates, allyl compounds, metal salts of (meth) acrylic acid and the like can be used.

A liquid crystal display element is provided on the light emitting surface (light emitting surface 62 of the light polarizing element 6) of the surface light source device including the LEDs 2A and 2B, the light guide 4, the light deflecting element 6, and the light reflecting element 8 as described above. By arranging them, a liquid crystal display device is configured. The liquid crystal display device is observed by an observer through the liquid crystal display element from above in FIG. Further, in the present invention, since a sufficiently collimated light having a narrow distribution can be incident on the liquid crystal display element from the surface light source device,
An image display with good brightness and uniformity of hue can be obtained without gradation inversion in a liquid crystal display element, and light irradiation concentrated in a desired direction can be obtained. Use efficiency can be improved.

In the above-described embodiment, the LEDs 2A, 2A, 2B, and 2D are adjacent to both the first corner and the second corner of the light guide 4, respectively.
Although 2B is arranged, in the present invention, a point-like primary light source such as an LED may be arranged adjacent only to the first corner. In particular, when the size of the light guide is relatively small, sufficient light emission luminance can be obtained.

FIG. 7 shows a surface light source device according to the present invention.
It is a schematic diagram which shows the primary light source and light guide of one embodiment. In this embodiment, two point-like primary light sources LEDs 2A1 and 2A2 are arranged adjacent to the first corner of the light guide 4. The LEDs 2A1 and 2A are arranged such that the peak light emitted from each of these two LEDs travels in the first direction.
2 is set. By arranging the primary light source only in the first corner as described above, the electric wiring for the primary light source is simplified. By simultaneously lighting the same ones as the LEDs 2A1 and 2A2, the light guide 4 having a larger size
Can be used to increase the amount of light. Also, L
A plurality of luminescent colors can be obtained by lighting the EDs 2A1 and 2A2 having different luminescent colors simultaneously or by switching. Others are the same as in the above embodiment.

As described above, when a plurality of primary light sources are arranged adjacent to each other, the luminous efficiency of each primary light source tends to decrease due to heat generation of the adjacent primary light sources. It is preferable to arrange the primary light sources adjacent to each other such that the distance between the centers of the light emitting units is at least 3 mm. Further, if the distance between the primary light sources is too large, the luminance may be reduced beyond the allowable design range as the point light source, so that the distance between the centers of the light emitting units of the adjacent primary light sources is set appropriately. It is preferable that the size be 6 mm or less for a small surface light source device. Further, when a plurality of primary light sources are arranged adjacent to each other, 1
A plurality of primary light sources may be fixed and integrated in one chip.

FIG. 8 is a schematic view showing a primary light source and a light guide according to still another embodiment of the surface light source device according to the present invention.
In this embodiment, the light guide 4 is a square first portion 4A '.
And a square second portion 4B '. The light guide first portion 4A 'mainly receives light from the LED 2A disposed adjacent to the first corner, and the light guide second portion 4B' mainly receives light from the LED 2A disposed adjacent to the second corner.
Receives light from ED2B. Others are the same as in the above embodiment.

FIGS. 9 to 11 are schematic views showing a primary light source and a light guide according to still another embodiment of the surface light source device according to the present invention. In these embodiments, the light guide 4 has a substantially triangular light introducing portion 4A, 4B integrally formed outside at least one side of a rectangular (may be square) effective area 5. The short end faces of the light introducing portions 4A and 4B are defined as a first corner light incident end face 41 or a second corner light incident end face 42, and the LEDs 2A or 2B are arranged to face the end faces. By forming the light introducing portion in this manner, the LE
The light from D2A or 2B can be uniformly distributed over the entire surface of the light guide 4. Further, the shape of the light guide 4 is set in this way, so that the primary light source is opposed to the short end surfaces of the light introducing portions 4A and 4B near the first corner or the second corner of the light guide 4. Is arranged, it is possible to cope with the case where the primary light source cannot be arranged at the corner of the light guide 4 due to the arrangement of the LCD drive circuit.

When such a light introducing section is formed,
In order to prevent light from being emitted from the light guide in the light introducing section, it is preferable that neither the light emitting mechanism nor the first prism row be formed in the light introducing section. Further, the light deflecting element does not need to be located at a position corresponding to the light introducing portion, and may have a shape corresponding to the effective area 5 of the light guide 4.

In the embodiment shown in FIG. 9, the light introducing portions 4A, 5A are provided outside the two opposing sides of the effective area 5 of the light guide 4.
A short end face of the first light introducing section 4A is defined as a first corner light incident end face 41, and a short end face of the second light introducing section 4B is defined as a second corner light incident end face 42. To L
The EDs 2A and 2B are substantially diagonally arranged. FIG.
In the embodiment shown in FIG. 0, the light introducing portion 4A is formed outside one side of the effective region 5 of the light guide 4, and the short end surface of the light introducing portion 4A is defined as the first corner light incident end surface 41. , Two LEDs 2A1 and 2A2 are arranged on the end face. In the embodiment shown in FIG. 11, the light introducing portions 4A and 5A are formed outside two adjacent sides of the effective area of the light guide 4, and the short end face of the first light introducing portion 4A is formed in the first corner. A partial light incident end face 41, a short end face of the second light introducing section 4B is a second corner light incident end face 42, and LEDs 2A and 2B are substantially diagonally arranged on the respective end faces.

[0049]

As described above, according to the present invention,
Place a point primary light source adjacent to the corner of the rectangular light guide,
The light exit surface of the light guide or the surface on the opposite side is formed as a prism forming surface composed of a plurality of first prism rows extending in a first direction oblique to the edge, and the light incident surface of the light deflecting element is formed as a first light guide surface. By forming a prism forming surface composed of a plurality of second prism rows extending in a second direction substantially orthogonal to one direction, power consumption can be reduced, uniformity of luminance distribution is good, and emission light It is an object of the present invention to provide a surface light source device that has high directivity and can effectively concentrate the amount of light emitted from a primary light source in a required direction even under low power consumption, thereby illuminating the surface light source brightly.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a surface light source device according to the present invention.

FIG. 2 is an explanatory diagram of a light guide.

FIG. 3 is an explanatory diagram of a light deflecting element.

FIG. 4 is an explanatory diagram of a light guide.

FIG. 5 is a diagram illustrating a state of light deflection by a light deflection element.

FIG. 6 is a diagram showing an emission light intensity distribution of an LED.

FIG. 7 is a view showing a primary light source and a light guide of the surface light source device according to the present invention.

FIG. 8 is a view showing a primary light source and a light guide of the surface light source device according to the present invention.

FIG. 9 is a view showing a primary light source and a light guide of the surface light source device according to the present invention.

FIG. 10 is a view showing a primary light source and a light guide of the surface light source device according to the present invention.

FIG. 11 is a view showing a primary light source and a light guide of the surface light source device according to the present invention.

[Explanation of symbols]

 2A, 2B LED 2A1, 2A2 LED 4 Light guide 4A ′ Light guide first part 4B ′ Light guide second part 41 First corner light incident end face 42 Second corner light incident end face 43 Light emitting face 43a 3 prism array 44 prism forming surface 44a first prism array 4A, 4B light introducing portion of light guide 5 light guide effective area 6 light deflecting element 61 light incident surface 61a second prism array 62 light emitting surface

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13357 G02F 1/13357 // F21Y 101: 02 F21Y 101: 02 F21Y 101: 02

Claims (18)

[Claims] 1. A point-shaped primary light source, a plate-shaped light guide that guides light emitted from the primary light source and emits the light from a light emission surface, and is disposed adjacent to a light emission surface of the light guide. A light deflecting element, wherein the primary light source is disposed adjacent to a vicinity of a first corner of the light guide, and wherein the light guide has a light exit surface. And a first main surface, which is one of the opposite surfaces, includes a directional light emission mechanism that emits light in a direction inclined with respect to the light emission surface, and the light deflection element includes: The light guide has a light incident surface facing the light exit surface and a light exit surface opposite to the light exit surface, and the light incident surface has two edges adjacent to the first corner. A plurality of second prism rows extending in a second direction substantially orthogonal to the first direction oblique to both and parallel to each other are provided. Surface light source device. 2. A plurality of first prisms extending in the first direction and parallel to each other on a second main surface, which is the other of the light exit surface and the surface on the opposite side, from the light guide. The surface light source device according to claim 1, further comprising a row. 3. The first corner light incident end face is formed near the first corner so as to cut out a corner of the light guide. A surface light source device according to claim 1. 4. The surface light source device according to claim 3, wherein the first corner light incident end face is formed such that a corner of the light guide is concavely notched. 5. The method according to claim 1, wherein the first direction is a diagonal line connecting the first corner and a second corner located at a diagonal position of the first corner. A surface light source device according to claim 1. 6. The method according to claim 1, wherein the first direction is a direction forming substantially the same angle with respect to both of two edges adjacent to the first corner. A surface light source device according to any one of the above. 7. The primary light source has directionality in an emitted light intensity distribution, and the primary light source is arranged so that a direction of a peak in the emitted light intensity distribution substantially matches the first direction. The surface light source device according to claim 1, wherein: 8. The surface light source device according to claim 1, wherein a plurality of said primary light sources are arranged adjacent to a vicinity of said first corner. 9. The surface light source device according to claim 8, wherein the plurality of primary light sources are arranged such that the distance between the centers of the light emitting portions of the adjacent primary light sources is 3 mm or more. 10. A second diagonal position of the first corner.
The surface light source device according to any one of claims 1 to 9, wherein the primary light source is further arranged adjacent to a corner of the light source. 11. The light incident end face of the second corner is formed near the second corner so as to cut out the corner of the light guide. Surface light source device. 12. The surface light source device according to claim 11, wherein a second corner light incident end face is formed so that a corner of the light guide is concavely notched. 13. The surface light source device according to claim 10, wherein a plurality of the primary light sources are arranged adjacent to the vicinity of the second corner. 14. The surface light source device according to claim 1, wherein the primary light source is an LED. 15. The surface light source device according to claim 14, wherein the LEDs are arranged so that a distance from an end face of the light guide is 0.2 mm or less. 16. The directional light emitting mechanism according to claim 1, wherein the directional light emitting mechanism includes a mat surface or a plurality of lens rows extending in the second direction and parallel to each other. Surface light source device. 17. The lens array according to claim 16, wherein the lens array is a prism array or a lenticular lens.
A surface light source device according to claim 1. 18. The surface light source device according to claim 1, wherein a light reflection element is arranged to face the back surface.