JPH08262441A - Surface light source element - Google Patents

Abstract

PURPOSE: To provide a thin surface light source element capable of simply obtaining convergent light in the direction to which a user views as the rear lighting of a display device with a small view angle. CONSTITUTION: This element is constituted of a first element 50 making a side end 11 an incident plane, and making the plane orthogonally intersecting with the incident plane a light emission plane, a reflection plane 13, a second element 51 provided with the incident plane of the outgoing light from the first element 50 and the light emission plane 32 emitting the light having many prism units 40 formed in parallel to the incident plane of the first element 50 on the surface and a light source 14. The outgoing light having directivity in the specified direction having inclination for the normal direction of the light emission plane 16 in the plane direction orthogonally intersecting with both of the light emission plane 16 and the incident plane of the first element 50 is emitted from the light emission surface 16 of the first element 50, and the outgoing light from the first element 50 is deflected in the normal direction by the second element 51.

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 element used in a surface light source device. The present invention is particularly preferably used as a back lighting means for liquid crystal display devices and the like.

[0002]

2. Description of the Related Art Conventionally, as a back lighting means for a liquid crystal display device or the like, a linear lamp is used as a light source, the lamp is placed at the focus of a rotating parabolic reflector, and a milky diffuser plate is placed on the upper portion of the lamp. The idea is to optimize the shape of the reflector and to adjust the diffusivity of the diffuser plate.

In addition, as a special shape, a linear lamp and a light guide are combined, the shape of the light guide is simulated by approximation of a point light source, and processed into an approximate curve shape so as to collect emitted light in a certain direction. There are a thing, a thing which changed the thickness of a light guide along the advancing direction of light, a thing which uses a lenticular whose prism angle is changed according to the distance from a light source, and a combination of some of these. If you do point light approximation,
In most cases, the optical path can be simulated, and the shape of the light guide layer can be changed according to the distance in the light traveling direction. Many such proposals have been made in patents and utility models. There is.

However, most of the surface light sources are intended to emit light uniformly in all directions from the emission plane, but there are cases where it is desired to concentrate the light in a certain direction depending on the purpose of use. .

For example, a liquid crystal color TV or the like for personal use having a small viewing angle is required to emit uniform light only in a certain direction and to have the uniform quantity of emitted light on the entire emitting surface.

FIG. 9 is a schematic configuration diagram of such a liquid crystal color TV apparatus. In the figure, 1 is a liquid crystal screen, 2 is a main body of a liquid crystal color TV apparatus, 3 is a normal line of the screen of the liquid crystal screen 1, and 4 is an observer's eye. In this type of device, the liquid crystal screen 1 is connected to the main body 2 to 4 of the liquid crystal color TV device.
It is configured to stand at an angle of about 5 ° and to view the screen from a direction forming an angle of 15 ° with respect to the normal line 3. Therefore, in the figure, if there is a back lighting unit in which the brightness of the surface light source becomes larger in the angle range indicated by X than in other angle ranges, the total amount of light can be concentrated there.
Be advantageous. That is, the brightness of such a surface light source shows the highest brightness value in the desired direction, which is many times higher than the brightness value of the uniform emission type in all directions. Therefore, when it is used as the back lighting of a display device in which only a specific direction has a viewing angle, a display device with low power consumption and high brightness can be obtained.

[0007]

However, the light source used for the plane of the liquid crystal color TV device as shown in FIG.
In most cases, with the exception of special small areas, point lights are not used. The light source used is a volume light source (a light source that cannot be regarded as a point light source like a fluorescent lamp), and the point light source approximations are extremely poor in agreement. Therefore, the shape proposed in the prior art is difficult to obtain the desired characteristics as described above, although the shape is precise and complicated and the manufacturing cost is high.

Moreover, in a volume light source such as a fluorescent lamp, the light source itself is diffused light and is non-directional. That is, it is very difficult in the strict sense to secure a desired directivity by using the diffused light emitting light source.

In addition to the above-described directivity of light emission, in order to make the light source device itself as small as possible,
It is necessary to achieve the object with a thickness at least as large as the diameter of the light source lamp. In the light source device of the type in which the rotating parabolic reflector is arranged in the lower part of the lamp as described above, the thickness becomes 2 to 4 times the lamp diameter, and the demand for downsizing cannot be satisfied.

[0010]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, an object of the present invention is to provide a display device such as a color liquid crystal TV device which is small in size, has a small viewing angle, and has a limited viewing field. Thin back lighting (similar to lamp diameter)
Therefore, it is an object of the present invention to provide a surface light source element that allows concentrated light to be easily obtained in a direction viewed by a user without increasing the wattage of the light source.

For the above-mentioned purpose, the first element having at least one side edge as the incident surface and the surface orthogonal to this as the light emitting surface is opposed to the opposite surface of the emitting surface of the first element. A reflecting surface, an incident surface on which the light emitted from the first element is incident, and an emitting surface on which the light is emitted in a predetermined direction, and are parallel to the incident surface of the first element. A second element having a large number of prism units formed on the surface and a light source arranged to face the incident surface of the first element, and the light is emitted from the light emitting surface of the first element. The exit surface and the first
In the plane direction orthogonal to both the incident surface of the element and the normal direction of the light emission surface of the first element, the emitted light having directivity is emitted in the specific direction and the first direction is emitted. The surface light source element is characterized in that the light emitted from the element is deflected in the direction of the normal line by the second element.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A surface light source element according to the present invention will be described below in detail with reference to the drawings.

First, the basic concept of the surface light source element according to the present invention will be described.

The refractive index n of the light with respect to the air of the light guide body is approximately n = 1.4 to 1.6, and as shown in FIG. In a shape where the planes 16 are orthogonal to each other (edge lighting), the critical reflection angle is around 45 °, and in principle no light is emitted to the emission plane 16. In FIG. 10A, 14 is a light source such as a fluorescent lamp, 15 is a reflector thereof, and 13 is a reflecting surface formed on the side of the light guide 10 opposite to the emission plane 16.

Therefore, as shown in FIG. 10 (b), the emission plane 16 is generally a diffusion-processed plane 16a or the emission-opposing reflection surface 13 is a scattering reflection surface 13a. For the purpose of this time that wants the directionality of, since such emitted light becomes scattered light, such means cannot be used.

Therefore, the inventors of the present invention have roughened the surface of the light guide body, which is the first element, or the opposite surface thereof as uniformly as possible (hereinafter, referred to as a satin-finished surface in the present invention), and formed the satin-finished surface. As a result of a detailed examination of the emission directionality of the emitted light, it is, for example, 70 to 80 with respect to the normal line of the emission surface on the plane orthogonal to both the incidence surface and the emission surface of the light guide.
It was found that light having directivity in a specific direction having an inclination of about 10 degrees is emitted, and the amount of emitted light in the normal direction i of the emission plane is extremely small, and in order to convert this direction to the normal direction, The present invention has been completed in consideration of combining a second element having a large number of linear prism units so that the prism units are parallel to the incident surface of the first element.

FIG. 4 is a perspective view showing the structure of the first element.
As shown in (a), a uniform satin surface is formed on the exit plane,
A reflecting surface 13 was formed on the opposite surface, and a linear light source 14 such as a fluorescent lamp was arranged at one end thereof. FIG. 4B shows the A-
It is an A'cross section figure.

7 (a), (b), FIG. 14 (c),
15D and FIGS. 15E and 15F are diagrams showing the angular distribution of the emission light luminance shown in FIG. 4B. That is,
Of the emitted light of each angle, the emitted light of the largest angle is 100
It is a figure which showed the ratio of the emitted light of each angle when it was set to% (a measuring sample and a measuring method are mentioned later).

5 (a) and 5 (b) are views showing the measuring method, respectively, FIG. 5 (a) is a front view showing the measuring position, and FIG. 5 (b) is a sectional view taken along line AA '. Is. Figure 5
In (b), 48 is a luminance meter.

The results are shown in FIGS. 7 (a), 7 (b) and 14
As shown in (c), (d), and FIGS. 15 (e), (f), almost no light is emitted in the front direction (normal direction of the plane) required as a light source, and the light is identified at 75 to 80 degrees. It was found that the emitted light was concentrated in the direction.

Therefore, the present invention reversely utilizes the light guide body (first element) having the satin surface 60 in which the emitted light is concentrated in a specific direction and the emitted light distribution is as small as possible and the emitted light amount is large. , Emitted light 20 emitted on both sides of the normal,
21 (see FIG. 4B) is refracted by the second element having the linear prism group formed in parallel with the incident surface of the first element, so that the emitted light 20, 2
The principle is that 1 is deflected and the emitted light is concentrated and emitted in a desired direction near the normal direction.

FIGS. 6 (a) and 6 (b) show another operation of the above.
Enlarging the prism of the second element, which is one component
FIG. In the figure, 20 and 21 are respectively the first
Rightward and leftward from the matte surface 60 of element 1
Light emitted to, θ₁ , Θ₂ Are the normal and prism face, respectively
An angle formed by 30, 31 and 32 is an emission surface. Also, ψ ₁ 
~ Ψ₆ And φ₁ ~ Φ₆ Is each surface of prism unit
Or, it shows the angle with respect to the reference line.
Is taken as shown in FIGS. 6 (a) and 6 (b).

When the emitted light 21 enters from the right side of the prism, it enters from the prism surface 30, is totally reflected by the prism surface 31, and then exits from the exit surface 32 at a predetermined angle φ ₆ . When the emitted light 20 is incident from the left side of the prism, it is incident from the prism surface 31, totally reflected by the prism surface 30, and then emitted from the emission surface 32 at a predetermined angle φ ₆ .

First appearance of the matte surface 60 of the first element
Since the emission angle of the emitted light is symmetric with respect to the normal,
Prism prism of the constituent unit of the prism group of the element
Angle (θ in Fig. 6₁ , Θ₂ ) And by changing the refractive index
Desired output angle (ψ₆ And φ ₆ ) Is possible
It

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface light source element according to the present invention will be described in detail below with reference to the drawings showing the specific construction thereof.

FIG. 1 is a partial sectional view showing an embodiment of a surface light source element according to the present invention.

In the figure, 14 is a light source such as a fluorescent lamp, and 1
5 is its reflector, 13 is the exit surface 16 of the light guide 50.
Reference numeral 16 is a reflection surface formed on the opposite side, and 16 is an emission surface of the light guide body 50 (60 is a satin surface). The emission surface 16 of the light guide body 50 is a surface substantially parallel to the surface of the reflective layer 13. 40
Is a prism unit of the second element, and 32 is its exit surface. The prism unit 40 has a convex linear shape extending in a direction parallel to the light source (lamp).

In the structure of the present invention, at least one side end 11 of the light guide is an incident surface, a surface orthogonal to this is a light emitting surface 16, and a reflection layer 13 is provided on the opposite surface of the light emitting surface 16. A first element 50 having the satin-finished surface 60 on at least one surface of the light guide, and the first element 5
A second element 51 having an incident surface on which a prism unit 40 for irradiating the emitted light from 0 and emitting the light in a predetermined direction is arranged, and an emitting surface 32 for emitting the light from the prism unit 40. It consists of

The light emitted from the first element is
It is emitted as rays 54 and 55, ₆ And φ₆ Is almost the same as
By setting the prism unit to be the same,
Can be achieved.

As a material for forming the element of the present invention, an acrylic resin having the largest visible light transmittance as a light guide is suitable for the purpose of small size and light weight, but the material is not limited to this.

Although a small fluorescent lamp is used as the light source 14, a linear light source having a continuous shape (for example, a filament lamp) may be used.

Next, an example of determining the prism angle when the first-order emission angle is symmetric with respect to the normal line by the first element will be shown. Even if it is asymmetrical to the normal, it can be easily calculated by changing the incident angle of light to the left or right. Note that n is the refractive index of the material forming the element. When incident from the left side of the prism (all symbols are according to FIG. 6A) (i) 90 ° −ψ <θ ₁ , φ ₁ = (θ ₁ + φ) −90, sin φ ₂ = sin (θ ₁ + φ− 90) / n, φ ₅ = 90− (2θ ₂ + θ ₁ −φ ₂ ), sin φ ₆ = n × sin φ ₅ , φ ₆ = sin ⁻¹ (n × sin φ ₅ ) (ii) 90 ° −ψ> θ ₁ , Φ ₁ = 90− (θ ₁ + φ), sin φ ₂ = sin (90−θ ₁ −φ) / n, φ ₅ = 90− (2θ ₂ + θ ₁ + φ ₂ ), sin φ ₆ = n × sin φ ₅ , ( iii) 90 ° −ψ = θ ₁ , φ ₁ = 0, φ ₅ = 90− (2θ ₂ + θ ₁ ), sin φ ₆ = n × sin φ ₅ Incident from the right side of the prism (all symbols are as shown in FIG. 6 (b). ) (Iv) 90 ° -ψ <θ ₂ , ψ ₁ = (θ ₂ + ψ) -90, sin ψ ₂ = sin (θ ₂ + ψ-90) / n, ψ ₅ = (2θ ₁ + θ ₂ −ψ ₂ ) − 90, sin ψ ₆ = n × sin ψ ₅ (V) 90 ° −ψ> θ ₂ , ψ ₁ = 90− (θ ₂ + ψ), sin ψ ₂ = sin (90−θ ₂ −ψ) / n, ψ ₅ = (2θ ₁ + θ ₂ + ψ ₂ ) −90 , Sin ψ ₆ = n × sin ψ ₅ (vi) 90 ° −ψ = θ ₂ , ψ ₁ = 0, ψ ₅ = (2θ ₂ + θ ₁ ) −90, sin ψ ₆ = n × sin ψ ₅ The prism material is acrylic. When made of resin, the refractive index is n = 1.49, and assuming that the incident angle on the prism 40 is ψ = 65 ° with respect to the normal line, the exit angle from the prism is the normal line according to the above calculation formula. The angle of focusing on one side of is obtained (showing a calculation example in which the difference between left and right is within 2 °).

Incident angle ψ = 65 ° Left prism angle θ ₁ Right prism angle θ ₂ θ ₁ θ ₂ Light from the left Light from the right (φ ₆ ) (ψ ₆ ) 35 ° 28 ° 8.5 ° 8.9 ° 36 ° 27 ° 11.0 ° 11.5 ° 37 ° 26 ° 13.5 ° 14.0 ° 38 ° 25 ° 16.0 ° 16.5 ° 39 ° 24 ° 18.6 ° 19.1 ° 40 ° 23 ° 21.1 ° 21.7 ° 41 ° 22 ° 23.7 ° 24.3 ° 42 ° 21 ° 26.3 ° 26.9 ° 43 ° 20 ° 29.0 ° 29.6 ° Fig. 2 and FIG. 3 is a partial cross-sectional view of a surface light source element showing another configuration example of the present invention.

In FIG. 2, the first element (light guide) 50-1 has a matte surface 60 formed on the side opposite to the light emitting surface 16 and is formed as a reflection layer 13 formed independently or integrally.
Are arranged to face each other, and the emission surface 16 of the first element 50-1 is a smooth surface. FIG. 3 shows an example of a configuration using a light guide body 50-2 in which a satin surface is arranged on the upper and lower surfaces of the light guide body 50. In the present invention, the fact that the imaginary plane of the satin surface, which is the emission surface 16 of the transparent light guide, is substantially parallel to the surface 13 of the reflective layer means that the plate-shaped body has a uniform thickness. One of the features is the use of a transparent light guide that can be easily manufactured and assembled.

In FIG. 12, the light emitted from the first element 50 is emitted symmetrically with respect to the normal line, and the angles (θ ₁ , θ _{2 in} FIG. 6) of the prism element of the second element 51 are θ ₁ = θ _2. = 3
It is a figure which shows an Example when it is set to 1.5 °. According to this embodiment, the light emitted from the light emitting surface 32 of the second element, such as the light rays 56 and 57, can be focused in the normal direction.

Next, assuming a rear light source for a 3-inch liquid crystal color TV, a configuration example of the present invention in which the panel size is 61 mm in width × 56 mm in length will be described.

The following specific examples were prepared with the first element as a transparent acrylic resin having a thickness of 5 mm and the second element as an acrylic resin having a thickness of 1 mm. Obviously, it is not limited to this.

[Detailed Example-1] Preparation and evaluation of the configuration example shown in FIG. 1 (preparation of light guide) First, a polished brass plate (about 3 mm × 25)
The surface of the metal plate is subjected to honing by a conventional honing method in which glass beads of 60 mesh are blown onto one surface (0 mm × 250 mm) to produce a replica mold.
Five types of molds were produced depending on the degree of honing.

Next, a replica of the honing surface was taken by hot pressing using the mold on one surface of an acrylic resin plate having a thickness of 5 mm, and this was used as a light guide.

(Production of Second Element) The effective viewing angle of the screen of the portable liquid crystal TV and the inclination angle from the normal line (see FIG. 9) are measured, and the emission angle is set at 15 ° (ψ) with respect to the screen normal line.
₆ = φ ₆ ) and set the prism angle to the left 38 °
(= Θ ₁ ) 25 ° on the right side (= θ ₂ ) (FIG. 6A,
(B)). Then, a multi-prism in which a large number of prism sides with the tip angle (= θ ₁ + θ ₂ ) 63 ° of the prism of that setting are arranged in parallel and a die having a pitch of 0.38 mm is prepared, and a thickness of 1 mm is obtained by hot pressing. Was thermally transferred to the acrylic resin plate of No. 2 to obtain a second element.

(Measurement of haze value of light guide) (1) 50 mm each from replica acrylic resin plate 5 mm using 5 kinds of molds in the above (manufacture of light guide)
A × 50 mm test piece was cut out and used as a sample for measuring a haze value. As a control sample, a transparent acrylic resin plate before taking a replica was similarly cut into 50 mm × 50 mm and used.

The haze value is measured according to ASTM-D1003-6.
According to 1, the replica surface was placed on the light incident side of the measuring instrument and the measurement was performed, and the haze value was determined by the following formula: Haze value = {(diffused light transmittance) / (total light transmittance)} × 10
0% (2) The measurement results are shown in Table 1.

[0043]

[Table 1] (Fabrication of First Element and Evaluation of Angular Distribution of Emitted Light) Next, a plate having a size of width 61 mm × length 56 mm was cut from the above light guide, and two sides of width 61 mm were polished by a conventional method.
A polyester film with an aluminum vapor deposition film with an adhesive was attached to two sides of a length of 56 mm, and a polyester film with a silver vapor deposition film was arranged on the opposite side of the transferred mat surface. Width 61
A lamp having a diameter of 7 mm and a length of 245 mm along two sides of mm (CB7-245W cold cathode tube manufactured by Stanley Electric Co., Ltd.)
Wrap the aluminum foil as a reflector, DC
It was lit at 12V via an inverter. The center of the first element (portion in FIG. 5A) was measured with a luminance meter (luminance meter nt-1 manufactured by Minolta Co., Ltd.) at different angles with respect to the normal line, and the emitted light distribution was obtained ( See FIG. 5B).

The data thus obtained are shown in Table 2 and FIGS. 7 (a) and 7 (b) and FIGS. 14 (c) and 14 (d). In FIG. 7 and others, the luminance is taken in the radial direction and the light emission angle is taken in the circumferential direction. The sample-5 and the control sample were omitted because the amount of emitted light was small in any direction and the measurement became inaccurate.

[0045]

[Table 2] The brightness of the tube surface at the center of the lamp used was 5 each.
It was 000 cd / m ² and 5200 cd / m ² .

(Production of Surface Light Source Element According to the Present Invention and Evaluation thereof) The first element is cut into 16 mm in width × 56 mm in length so that the line direction of the multi-prism is parallel to the long side from the second element. The prism convex portions are arranged so as to face the light emitting surface of (1), and fixed along the lamp side (side of 61 mm in width) with a double-sided adhesive tape having a width of about 5 mm to manufacture a surface light source element according to the present invention.

The angle distribution of the light emitted from the surface light source element was measured by the same method as the method of evaluating the angle distribution of the light emitted from the first element. The measurement results are shown in Table 3 and FIG.
16 (b) and FIGS. 16 (c) and 16 (d).

[0048]

[Table 3] * Distribution angle: The angle at which the brightness value becomes half the peak brightness.

As described above, as the performance of the light guide for the matte surface, if the haze value is about 30% or more, preferably 50% or more, sufficient brightness and distribution angle can be obtained as a surface light source element.

[Detailed Example-2] Production and evaluation of the configuration example shown in FIG. 2 and FIG. 3. Using a mold prepared as Sample-2 of [Detailed Example-1], both sides of acrylic resin 5 mm thick A replica was taken and designated as Sample-6. This light guide corresponds to 50-2 shown in FIG.

(Measurement of Haze Value of Light Guide) [Detailed Examples-
1] and the haze value of sample-6 was measured. The haze value of sample-6 was 81.5%.

(Fabrication of First Element and Evaluation of Angular Distribution of Emitted Light) Fabrication was performed in exactly the same manner as in [Detailed Example-1]. Using Sample-2 and Sample-6 as light guides, the procedure is exactly the same as in [Detailed Example-1] except for the following points.

Difference: A polyester film with silver vapor deposition was arranged on the matte surface of the same light guide as Sample-2 (see FIG. 2). The sample thus arranged is referred to as Sample-7. This corresponds to the light guide body 50-1 in FIG.

The measurement result of the angular distribution of the emitted light is shown in FIG.
(E) and (f).

[0055]

[Table 4] The brightness of the tube surface at the center of the lamp used was 5 each.
It was 000 cd / m ² and 5200 cd / m ² .

(Production of Surface Light Source Element According to the Present Invention and Evaluation thereof) A surface light source element was produced in exactly the same manner as in [Detailed Example-1], and the angular distribution of the emitted light of the main surface light source element was measured. The results are shown in Table 5 and FIGS. 17 (e) and 17 (f).

[0057]

[Table 5] As described above, if the satin-finished surface is on both sides (Sample-6) or in close contact with the reflection layer (Sample-7), the distribution angle of the concentrated light can be widened (the peak luminance is reduced accordingly).

Comparative Example Acrylic resin pellets (HI-PET HBS [registered trademark] manufactured by Mitsubishi Rayon Co., Ltd.) were dry-blended with rutile-type titanium oxide in an amount of 1.5% by weight, and a film having a thickness of 50 μm was formed using an ordinary extruder. It was created. The film was spread on an inorganic glass flat plate so that air bubbles did not enter, temporarily fixed with methyl methacrylate, and then polymerized and solidified in a usual manner to obtain an acrylic resin plate having a thickness of 5 mm.

The plate of the comparative example made in this way is made into a horizontal 61
mm x 56 mm long, 61 mm wide is ground by a conventional method, and 56 mm long is coated with a film with an aluminum vapor deposition film with an adhesive on the two sides, facing the white thin layer formed on the plate surface. A polyester film with a silver vapor deposition film was placed on. Then, the same measurement as that of the first element was carried out by the completely same method to obtain the emitted light distribution. The results are shown in Table 6 and FIG.

[0060]

[Table 6] (Summary) For example, FIG. 8 (a), (b), FIG. 16 (c),
As can be seen by comparing (d) and FIGS. 17 (e) and (f) with FIG. 11, the comparative example has a characteristic that light is uniformly emitted in all directions. It can be seen that the surface light source element of 1 has the advantage that concentrated light can be obtained in a specific direction and that the peak luminance value of the central point is about 3.5 to 4 times higher. .

[Detailed Embodiment-3] As shown in FIG. 12, the prism angle is symmetrically set to 31.5 ° (= θ ₁ ), 31.5 ° ( = Θ
₂ ), a die having a pitch of 0.5 mm was prepared, and was thermally transferred to an acrylic resin having a thickness of 1 mm by hot pressing to prepare a second element.

The light guide of Sample-1 in Table 2 was used as the first element, and the above-mentioned 31.5 ° / 3 was used as the second element.
Using a multi-prism of 1.5 ° (θ ₁ = θ ₂ ), a surface light source element was prepared in exactly the same manner as in [Detailed Example-1], and the angular distribution of emitted light was measured. Table 7 shows the measurement results of the peak luminance of the first element, Table 8 shows the peak luminance of the surface light source element, and FIG. 13 shows the angular distribution of the emitted light luminance of the surface light source element.

[0063]

[Table 7]

[0064]

[Table 8] As can be seen from Table 8 and FIG. 13, by setting θ ₁ and θ ₂ as described above, a surface light source element capable of directing concentrated light in the normal direction of the screen as compared with the normal case can be created. .

[0065]

As described above, according to the surface light source element of the present invention, it is as small as a liquid crystal color TV and has a small viewing angle.
Moreover, as the back lighting of the display whose field of view is limited, it is possible to provide an optimum light source device that is thin (about the same as the diameter of the lamp) and can easily obtain concentrated light without increasing the wattage of the light source. . Concentrated light can be easily obtained by using a fluorescent lamp which is essentially a diffused light source, and the emission direction of the concentrated light can be easily and freely determined. effective.

[Brief description of drawings]

FIG. 1 is a sectional view of a surface light source element.

FIG. 2 is a cross-sectional view of a surface light source element.

FIG. 3 is a cross-sectional view of a surface light source element.

FIG. 4 is a perspective view and a cross-sectional view of a first element.

FIG. 5 is a conceptual diagram of a method for measuring an angular distribution of emitted light brightness.

FIG. 6 is an optical path analysis diagram when the peak light of the emitted light from the first element enters the prism.

FIG. 7 is a diagram showing an angular distribution of emission light brightness of a light guide.

FIG. 8 is a diagram showing an angular distribution of emission light brightness of a surface light source element.

FIG. 9 is a diagram showing a relative angle in a viewing state of a liquid crystal color TV.

FIG. 10 is a cross-sectional view of a conventional surface light source device.

FIG. 11 is a diagram showing an angular distribution of emission light brightness of a surface light source element.

FIG. 12 is a cross-sectional view of a surface light source element in which a _second element is θ ₁ = θ ₂ type.

FIG. 13 is a diagram showing an angular distribution of emission light brightness of a θ ₁ = θ ₂ type surface light source element.

FIG. 14 is a diagram showing an angular distribution of emission light brightness of a light guide.

FIG. 15 is a diagram showing an angular distribution of emission light brightness of a light guide.

FIG. 16 is a diagram showing an angular distribution of emission light brightness of a surface light source element.

FIG. 17 is a diagram showing an angular distribution of emission light brightness of a surface light source element.

[Explanation of symbols]

13 reflective surface 14 light source 15 reflector 16 exit surface 50, 50-1, 50-2 light guide (first element) 51 second element 40 prism unit 60 satin surface

Claims (1)

[Claims] 1. A first element having at least one side end as an incident surface and a surface orthogonal to the side surface as a light emitting surface, and the first element is disposed so as to face the surface opposite to the light emitting surface of the first element. A reflecting surface, an incident surface on which the light emitted from the first element is incident, and an emitting surface on which the light is emitted in a predetermined direction, and a large number of elements are formed in parallel with the incident surface of the first element. It is composed of a second element having a prism unit on the surface thereof and a light source arranged so as to face the incident surface of the first element, and the light emitting surface of the first element and the light emitting surface of the first element. In the plane direction orthogonal to both the incident surface of the first element, the emitted light having directivity is emitted in a specific direction having an inclination with respect to the normal direction of the light emitting surface of the first element, and Element of 1 A surface light source device of the light emitted from the preparative characterized by comprising as to deflect towards the normal direction by said second element.