JP3042842B2 - Surface light source element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface light source element used for a surface light source device. The present invention is particularly suitable for use as a back lighting means for a liquid crystal display device or the like.

[0002]

2. Description of the Related Art Conventionally, as a back illuminating means of a liquid crystal display device or the like, a shape in which a linear lamp is used as a light source, the lamp is placed at the focal point of a rotary parabolic reflector, and a milky diffusing plate is placed above the lamp. In order to optimize the shape of the reflector and to adjust the diffusivity of the diffusion plate, various measures have been taken.

In addition, as a special shape, a linear lamp and a light guide are combined, and the shape of the light guide is simulated by approximating a point light source, and the light guide is processed into an approximate curve so as to converge emitted light in a certain direction. There are a light source, a light guide whose thickness is changed along the traveling direction of light, a light source using a lenticular whose prism angle is changed depending on a distance from a light source, and a combination of some of these. If you approximate the point light source,
In most cases, it is possible to simulate the optical path, and to change the shape of the light guide layer according to the distance in the light traveling direction, and many such proposals have been made in patents and utility models. I have.

[0004] However, most surface light sources aim to emit light uniformly in all directions as far as possible from the plane of emission, but depending on the purpose of use, there are cases where it is desired to concentrate light in a certain direction. .

[0005] For example, a liquid crystal color TV for personal use having a small viewing angle is required to emit uniform light only in a certain direction and to have a uniform emission light amount over the entire emission surface.

FIG. 3 is a schematic configuration diagram of such a liquid crystal color TV device. In the figure, 1 is a liquid crystal screen, 2 is a main body of a liquid crystal color TV device, 3 is a normal line of the liquid crystal screen 1 and 4 is an eye of an observer. In this type of device, the liquid crystal screen 1 is connected to the main units 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 3. Therefore, in the drawing, if there is a back-lighting device such that the luminance of the surface light source becomes larger in the angle range indicated by X than in other angle ranges, the entire light amount can be concentrated there.
This is advantageous. In other words, the brightness of such a surface light source shows the highest brightness value in a desired direction, which is many times higher than the brightness value of the omnidirectional uniform emission type. Therefore, a display device with low power consumption and high luminance can be obtained by using it as a backlight for a display device in which only a specific direction has a viewing angle.

[0007]

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

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

In addition to the above-described light emitting directionality, to make the light source device itself as small as possible,
It is necessary to achieve the object at least as thick as the diameter of the light source lamp. In the light source device of the type in which the rotating parabolic reflector is disposed below the lamp as described above, the thickness becomes 2 to 4 times the diameter of the lamp, and the demand for miniaturization cannot be satisfied.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned 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 field of view. Thin as back lighting (same as lamp diameter)
Accordingly, it is an object of the present invention to provide a surface light source element in which concentrated light can be easily obtained in a direction seen by a user without increasing the wattage of the light source.

The above objects are achieved by the following surface light source device of the present invention.

That is, in the surface light source element of the present invention, a plate-shaped first element having at least one side end as an incident end face and a plane orthogonal to this as an exit plane, and an exit plane of the first element A reflection surface disposed on the opposite surface of the first element, a second element disposed on the emission plane side of the first element, and a light source disposed opposite the incident end surface of the first element. Wherein the first element has directivity in a specific direction having an inclination with respect to a normal direction of the emission plane of the first element on a plane orthogonal to both the incident end face and the emission plane. The emitted light is emitted from the emission plane, the second element is made to emit the emitted light from the first element, and a number of linear prism units having a prism angle of 30 ° to 66 ° are arranged in parallel. hand And a light exit surface for emitting light in a predetermined direction. The first element is configured to reflect light incident from at least one prism surface of each of the prism units on the other prism surface. And is deflected in the direction of the normal to the exit plane, and exits from the exit surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a surface light source device according to the present invention will be described 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 light of the light guide with respect to air is approximately n = about 1.5 to 1.6, and as shown in FIG. In a shape (edge lighting) in which the planes 12 are orthogonal to each other, the critical reflection angle is around 45 °, and light is not emitted to the emission plane 12 in principle. In FIG. 4A, reference numeral 14 denotes a light source such as a fluorescent lamp, 15 denotes a reflector thereof, and 13 denotes a reflection surface formed on a side of the light guide 10 opposite to the emission plane 12.

For this reason, as shown in FIG. 4B, generally, the outgoing plane 12 is made into a plane 12a obtained by diffusion processing, and the reflecting surface 13 of the outgoing facing surface is made into a scattering reflecting surface 13a. For this purpose, which desires the above-mentioned directionality, such means cannot be used because the emitted light becomes scattered light.

Here, a linear convex lens 1 of the same shape which is perpendicular to the light traveling direction is formed on the exit plane or on the opposite surface.
6 is formed, a reflection surface 13 is formed on the opposite surface, and a linear light source 14 such as a fluorescent lamp is arranged at one end thereof in parallel with the line of the linear convex lens assembly. .
FIG. 5A is a perspective view of the configuration, and FIG.
It is A 'sectional drawing.

In such a geometrical positional relationship, the light emission direction is 40 to 40 degrees from the normal in the direction perpendicular to the line of the lens.
It becomes a 60 ° direction, and hardly emits light in the normal direction (see FIG. 5B).

FIGS. 6A and 6B are diagrams showing the angular distribution of the emitted light luminance shown in FIG. 5B. That is, outgoing light at the largest angle out of the outgoing light at each angle is 100%
It is a figure showing the ratio of the emitted light of each angle when it is set to.

FIGS. 7 (a) and 7 (b) are diagrams showing the measurement method, respectively. FIG. 7 (a) is a front view of a surface light source element showing a measurement position, and FIG. It is -A 'sectional drawing. In FIG. 7B, reference numeral 40 denotes a luminance meter.

FIG. 6A shows the angular distribution of the emitted light luminance at the center point in FIG. 7, and FIG. 6B shows the angular distribution of the emitted light luminance at a position 10 mm from the lamp. It can be seen from these graphs that there is almost no outgoing light in the normal direction.

In the present invention, the emitted light is concentrated in a specific direction as described above, and the emitted light emitted to both sides of the normal line is reversed by using the lens assembly 16 having the smallest possible emitted light distribution and a large amount of emitted light. The principle is that the outgoing lights 20, 21 are deflected by refracting the 20, 20, 21 (see FIG. 5 (b)) by a prism group, which is the second element, and the outgoing light is concentratedly emitted in a desired direction. Things.

FIGS. 8A and 8B are enlarged views of the prism of the second element which is another component of the above operation. In the figure, reference numerals 20 and 21 denote light beams emitted from the lens group 16 of the first element in the right and left directions, respectively, θ ₁ and θ ₂ denote angles formed by the normal line and the prism surfaces 30 and 31, respectively, and 32. Is an emission surface. Also, ψ
_{1 to} ψ ₆ and φ _{1 to} φ ₆ indicate angles with respect to each surface of the prism unit or the reference line, respectively, and how to determine the angles is as shown in FIGS. 8 (a) and 8 (b). is there.

[0024] In the case of entering from the right side of the prism as the emitted light 21 is incident from the prism surface 30, after totally reflected by the prism surface 31 is emitted from the emission surface 32 at an angle [psi _6. Further, in the case of incident from the left side of the prism as the emitted light 20 is incident from the prism surface 31, after totally reflected by the prism surface 30 and exits from the exit surface 32 at a predetermined angle phi _6. This predetermined angle ψ ₆ and φ ₆
Can be adjusted by the shape of the lens group of the first element, the exit angles from the lenses, the angles θ ₁ and θ _2, and the refractive index n of each lens.

The shape of the lens 16 of the first element is not particularly limited as long as 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. Further, depending on the shape of the lens group 16 of the first element, the emission angle of the primary emission light is
Although not necessarily symmetrical with respect to the normal, in this case, the desired prism angle (θ ₁ , θ _{2 in} FIG. 8) can be changed by changing the prism angle (θ ₁ , θ _{2 in} FIG. 8) which is a constituent unit of the prism group of the second element. It is possible to obtain an emission angle.

In the present invention, the light emitted from the first element having a small emission light distribution and having a large amount of light emitted at a specific angle is transmitted by the second element in the direction normal to the light emission surface of the light guide. The prism angle (θ ₁ + θ ₂ ) of the second element is set to 52 to 66 ° in order to deflect the light into a concentrated light. That is, by setting the prism angle of the second element within this range, the light emitted from the first element can be efficiently converted into the normal direction of the light emission surface of the light guide (the emission surface of the second element). (In the direction of the normal), and can be emitted as concentrated light having a narrow distribution angle range of the emitted light and a large amount of emitted light in the angle range.
The prism angle of the second element is preferably between 60 and 6
It is in the range of 6 °, more preferably in the range of 63 to 66 °.

As a special example of the present invention, in order for the light emitted from the first element to be focused in the normal direction by the second element, the light emitted from the first element is symmetrical with respect to the normal. It is essential that the light is emitted at 60 °, and the prism angle (θ ₁ , θ _{2 in} FIG. 8) of the second element is θ ₁ =
It is sufficient to set θ ₂ = 30 °.

[0028]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a surface light source device according to the present invention.

FIG. 1 is a partial sectional view showing an embodiment of the surface light source element according to the present invention, and is a view corresponding to FIG. 5 (b).

In FIG. 1, reference numeral 14 denotes a light source such as a fluorescent lamp,
5 is the reflector, 13 is the emission surface 12 of the light guide 10
The reference numeral 16 denotes a lens unit as described above, 16 denotes a prism unit, and 32 denotes an emission surface.
In addition, both the lens unit 16 and the prism unit 40 have a convex linear shape extending in a direction parallel to the light source (lamp).

According to the structure of the present invention, at least one side end 11 of the light guide is used as an incident surface, a surface on which the lens unit 16 is arranged on a surface orthogonal to this is used as a light output surface, and First element 5 with reflective layer 13 on opposite side
0, a prism unit 40 for receiving light emitted from the first element 50 and emitting light in a predetermined direction.
, And a second element 51 having an exit surface 32 for emitting light from the prism unit 40. The light emitted from each lens unit 16 is emitted as light beams 54 and 55, respectively, and ψ ₆ and φ ₆
The objective can be achieved by setting the lens unit and the prism unit so that the values are substantially the same.

FIG. 2 shows that, as described above, the emitted light of the first element is emitted at 60 ° symmetrically with respect to the normal line, and the angle of each prism of the second element 51 (θ ₁ , θ _{2 in} FIG. 8). FIG. 6 is a diagram showing an example in which θ ₁ = θ ₂ = 30 °. According to this embodiment, the light emitted from the light exit surface 32 of the second element can be focused in the normal direction, like the light beams 56 and 57.

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

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

Next, an example of determining the prism angle when the first-order emission angle is symmetrical with respect to the normal line by the first element will be described. Even in the case of being asymmetric with respect to the normal, it can be easily calculated by changing the incident angle of light to the left or right. Here, n is the refractive index of the material constituting the element. When incident from the left side of the prism (all symbols are based on FIG. 8A) (i) 90 ° −ψ <θ ₁ , φ ₁ = (θ ₁ + ψ) −90,
sin φ ₂ = sin (θ ₁ + ψ−90) / n, φ ₅ = 9
0− (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 + ψ),
sin φ ₂ = sin (90−θ ₁ −ψ) / n, φ ₅ = 9
0− (2θ ₂ + θ ₁ + φ ₂ ), sin φ ₆ = n × sin
φ ₅ , (iii) 90 ° −ψ = θ ₁ , φ ₁ = 0, φ ₅ = 90− (2
θ ₂ + θ ₁ ), sin φ ₆ = n × sin φ ₅ Incident from the right side of the prism (all symbols are based on FIG. 8B). (iv) 90 ° −ψ <θ ₂ , ψ ₁ = (θ ₂ + ψ) − 90,
sinψ ₂ = sin (θ ₂ + ψ−90) / n, ψ ₅ =
(2θ ₁ + θ ₂ −ψ ₂ ) −90, sinψ ₆ = n × si
nψ ₅ (v) 90 ° −ψ> θ ₂ , ψ ₁ = 90− (θ ₂ + ψ),
sinψ ₂ = sin (90−θ ₂ −ψ) / n, ψ ₅ =
(2θ ₁ + θ ₂ + ψ ₂ ) −90, sinψ ₆ = n × si
_{nψ 5 (vi) 90 ° -ψ} = θ 2, ψ 1 = 0, ψ 5 = (2θ 2 +
theta ₁₎ -90, also sinψ ₆ = n × sinψ _5, refractive index and make the material of the prism in the acrylic resin is n = 1.49, the incident angle to the prism 40 with respect to the normal, symmetrical Assuming that ψ = 55 °, the exit angle from the prism can be obtained as an angle converging to one side of the normal line by the above formula (an example of calculation in which the difference between the left and right sides is within 2 ° is shown).

Incident angle ψ = 55 ° Left prism angle θ ₁ Right prism angle θ ₂ θ ₁ θ ₂ Light from left light from right (φ ₆ ) (ψ ₆ ) 32 ° 25 ° 8.9 ° 8.5 33 ° 24 ° 11.5 ° 11.0 ° 34 ° 23 ° 14.0 ° 13.5 ° 35 ° 22 ° 16.5 ° 16.0 ° 36 ° 21 ° 19.1 ° 18.6 ° 37 20 ° 21.7 ° 21.1 ° 38 ° 19 ° 24.3 ° 23.7 ° 39 ° 18 ° 26.9 ° 26.3 ° 40 ° 17 ° 29.6 ° 29.0 ° 41 ° 16 ° 32.3 ° 31.7 ° 42 ° 15 ° 35.1 ° 34.4 ° Furthermore, when the prism material is made of polycarbonate resin, the refractive index is n = 1.59, and under the same conditions as acrylic resin. The calculation is as follows.

However, ψ = 55 ° (showing a calculation example in which the difference between the left and right emission angles is within 2 °).

Θ ₁ θ ₂ Light from left side Light from right side (φ ₆ ) (ψ ₆ ) 32 ° 25 ° 9.7 ° 8.4 ° 33 ° 24 ° 12.4 ° 11.0 ° 34 ° 23 ° 15.0 ° 13.6 ° 35 ° 22 ° 17.7 ° 16.2 ° 36 ° 21 ° 20.3 ° 18.9 ° 37 ° 20 ° 23.1 ° 21.6 ° 38 ° 19 ° 25 2.8 ° 24.3 ° 39 ° 18 ° 28.6 ° 27.0 ° 40 ° 17 ° 31.4 ° 29.8 ° 41 ° 16 ° 34.3 ° 32.6 ° Assuming a rear light source for a liquid crystal color TV, the panel size was set to 61 mm wide × 56 mm long.

The first element was made of a transparent acrylic resin having a thickness of 5 mm, and the second element was made of an acrylic resin and a polycarbonate resin having a thickness of 1 mm. It is clear that the material is not limited to this.

[Detailed Example] {1} Example-1 As a first element, a smooth curved multi-line lens gold having a pitch of 0.38 mm and a lens curved surface height of 0.051 mm (see FIG. 9) was used. Using a mold, the pattern was transferred to an acrylic resin plate having a thickness of 5 mm by hot pressing. on the other hand,
The effective viewing angle of the screen of the portable liquid crystal TV and the inclination angle from the normal (see FIG. 3) are measured, and the emission angle is determined to be 15 ° (ψ ₆ = φ ₆ ) with respect to the screen normal. The prism angle was set to 35 ° (= θ ₁ ) on the left side and 22 ° (= θ ₂ ) on the right side (see FIGS. 8A and 8B). Then, a mold having a multi-prism pattern of 57 ° with a prism tip angle (= θ ₁ + θ ₂ ) of 57 ° and a pitch of 0.38 mm is created.
It was thermally transferred to an acrylic resin plate having a thickness of 1 mm by a hot press to form a second element. Each element was cut to a predetermined size.

Next, 2 mm of 61 mm in width of the first element
The sides were polished by a conventional method, and a polyester film with an aluminum vapor-deposited film with an adhesive was stuck on two sides of 56 mm in length, and a polyester film with a silver vapor-deposited film was provided on the opposite side of the transferred lens surface. 61m beside the first element
Along the two sides of m, a lamp having a diameter of 8 mm and a length of 90 mm (FLE-8.90AD1P3 manufactured by Elevum Co., Ltd.) is wound around an aluminum foil as a reflector, and DC5V
Lit through the inverter. A luminance meter (luminance meter nt-1 manufactured by Minolta Co., Ltd.) for each of the center of the first element on the lamp side and the center point (see FIG. 7A).
The measurement was performed while changing the angle with respect to the normal line to obtain the emission light distribution (see FIG. 7B). The data obtained in this manner are shown in FIGS. 6A and 6B described above. Table 1 shows the peak luminance values of those points.

[0042]

[Table 1] Further, the prism side of the second element is disposed on the first element so as to match the lens side of the first element, and is fixed along the side of the lamp with a double-sided adhesive tape having a width of about 5 mm. The same measurement as that of the element No. was performed in exactly the same manner, and the emission light distribution was obtained. The data is shown in FIG.
(A), (b) and (c) show. Table 2 shows peak luminance values and peak emission angles at those points.

[0043]

[Table 2] The emission angle peak was concentrated light at 12 to 20 °, and the distribution angle was about 40 °.

The luminance of the lamp surface in the lighting state of the lamp used in this embodiment was 10,000 cd / m ² .

{2} Example-2 The first element uses the same element as that of Example-1.
The same mold as in Example 1 was used for the transfer mold for the element, and only the material was made of a polycarbonate resin having a thickness of 1 mm. The angle distribution of the emitted light was set in exactly the same manner as in Example 1. It was measured by a luminance value. The data is shown in FIG.
(A), (b) and (c) show. Table 3 shows the peak luminance values and the peak emission angles at those points.

[0046]

[Table 3] {3} Example-3 The same first element as in Example-1 was used. In order to make the emission angle the same direction as the normal direction, the emission angle is 60
Is an indispensable condition, but FIGS. 6 (a) and 6 (b)
In the figure, since there is a luminance value of 90% or more at a peak value at an emission angle of 60 °, a prism angle is set to θ ₁ = θ ₂ = 30 °, and a mold having a multi-prism pattern with a pitch of 0.38 mm is formed. It was thermally transferred to an acrylic resin having a thickness of 1 mm by a press to form a second element.

The same setting as in Example 1 was performed, and the angle distribution of the emission angle was measured by a luminance value. The data is shown in FIGS. 12 (a), (b) and (c). Table 4 shows the peak luminance values and the peak emission angles at those points.

[0048]

[Table 4] {4} Comparative Example Rutile-type titanium oxide was dry-blended with acrylic resin pellets (Hypet HBS (registered trademark), manufactured by Mitsubishi Rayon Co., Ltd.) by 1.5% by weight, and a 50 μm thick film was formed with a normal extruder. did. 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.

{5} Comparative Evaluation The plate of the comparative example produced in this manner was 61 mm wide by 56 mm long.
mm, and two sides of 61mm in width are polished by a conventional method, and two sides of 56mm in length are attached with a film with an aluminum vapor-deposited film with an adhesive, and silver is vapor-deposited on the surface of the white thin layer formed on the plate surface. Polyester film with membrane (Example-
(Same as 1). Next, evaluation was performed in exactly the same manner as the method for measuring the first element in Example-1. The data is shown in FIGS. Table 5 shows the luminance values of those points.

[0050]

[Table 5] {6} Summary For example, FIGS. 10 (a), (b), (c) and FIG.
As can be seen by comparing (a) and (b), the comparative example has a characteristic that light is uniformly emitted in all directions, whereas the surface light source element of the present invention is concentrated in a specific direction. It can be seen that there is an advantage that light can be obtained and a high luminance value whose peak luminance value at the center point is about 3.5 times can be obtained.

[Detailed Example 2] {1} Production of Various First Elements As described above, the shape of the lens 16 of the first element is such that the emitted light is concentrated in a specific direction and the emitted light distribution is as small as possible. Any lens shape that is small and has a large amount of emitted light is sufficient, and is not particularly limited. As an example of such a lens shape, the following first element including the first element of the convex cylindrical lenticular lens of the above detailed Example 1 was prepared. (1) The lens has substantially the same shape as the convex cylindrical lenticular lens shown in FIG. 9. The pitch P is 0.38 mm, the height H is 0.05 mm, and the thickness t of the first element is 6 mm. (2) Triangular lenticular lens A lenticular lens having a shape as shown in FIG. 14, having a pitch P = 0.5 mm, a vertex angle θ = 25 °, and a thickness t of the first element t = 6 mm. (3) Concave Lenticular Lens The concave lenticular lens has a shape as shown in FIG. 15, and has a cylindrical concave pitch P = 0.5 mm, a depth D = 0.06 mm, and a first element thickness t = 6 mm. Things. (4) Polygonal pyramidal lenticular lens It has a shape as shown in FIG. 16, where pitch P ₁ = 0.10 mm, θ ₁ = 30 °, pitch P ₂ = 0.15 mm, θ ₂ = 10 °, pitch P ₃ = 0.15 mm, θ ₃ = 5 °, overall pitch P = 0.8 mm, height H = 0.097 mm, thickness t of the first element = 6 mm. (5) Anisotropic lenticular lens Anisotropic lenticular lens A has a shape as shown in FIG. 17A, a pitch P = 0.41 mm, a height H ₁ = 0.051 mm, and a thickness of the first element. The length t = 6 mm. Anisotropic lenticular lens B has a shape as shown in FIG. 17 (b), and has a pitch P = 0.41 mm, a height H ₂ = 0.102 mm, and a thickness t of the first element t = 6 mm. Things. These first elements were prepared by using a mold having a predetermined shape and transferring a pattern to a 6 mm thick acrylic resin plate by hot pressing.

{2} Emission Characteristics of Each First Element The angular distribution of the emitted light luminance of each first element was determined by the same method as that described with reference to FIG. 7B. That is, two sides of the first element having a width of 61 mm are polished by a conventional method, and two sides of a length of 56 mm are attached with a polyester film having an aluminum vapor-deposited film with an adhesive, and a silver-deposited film is formed on the opposite surface of the transferred lens surface. A polyester film is provided, and a lamp having a diameter of 8 mm and a length of 90 mm (FL, manufactured by Elevum Co., Ltd.) is provided along two sides of the first element, 61 mm wide.
E-8.90AD1P3) was wrapped around an aluminum foil as a reflector so that it could be turned on at 5 VDC through an inverter. The configuration in this case is called a surface type. When examining the angular distribution of the emission light luminance, the lens 16 of the first element 50 faces the reflection surface 13, and after the light from the lens 16 is reflected by the reflection surface 13, the light is emitted from the emission surface 30. In order to confirm whether or not a configuration (hereinafter referred to as a back type) that can be adopted,
The lens surfaces of the elements (1) to (5) were turned to mirrors, and the angular distribution of the emitted light luminance was measured. The state of the measurement is shown in FIG. 18 taking the case of a concave lenticular lens as an example.

<Results of Measurement of Angular Distribution of Emitted Light Luminance> FIG. 19B shows the angle distribution of the emitted light luminance of the back surface type of the first element employing the same shape as the cylindrical convex lenticular lens shown in FIG. Show. FIG. 19A shows a surface-type luminance distribution as a comparative example. The peak luminance was in the direction of about 70 ° from the normal line in the case of the back type, and in the direction of 70 to 80 ° in the case of the front type. FIG. 20A shows the angular distribution of the emitted light luminance of the surface type of the first element employing the triangular prism lenticular lens.
Shown in FIG. 20B shows the luminance distribution of the back surface type.
The peak luminance was about 70 to 80 ° from the normal in the case of the front type, and was 30 to 35 ° from the normal in the case of the back type. FIG. 21A shows the angular distribution of the emitted light luminance of the surface type of the first element employing the cylindrical concave lenticular lens. FIG. 21 shows the luminance distribution of the back side.
(B). The peak luminance was in the direction of about 75 to 80 ° from the normal line for both the front type and the back type. FIG. 22 shows the angular distribution of emitted light luminance of the surface type of the first element employing the convex polygonal lenticular lens.
(A). FIG. 22B shows the luminance distribution of the back surface type. The peak brightness is about 75 from the normal line for both the front and back types.
８０80 ° direction. FIG. 23A shows the angular distribution of the emission light luminance of the first element employing the anisotropic lenticular lens A.
FIG. 23 shows the luminance distribution of the anisotropic lenticular lens B.
(B). The peak brightness is about 60 from the normal in the case of A
Direction, the case of B was about 50 ° from the normal line.

{3} Production of Each Surface Light Source Element On the surface of each of the first elements obtained as described above, the second element (substantially the same as that used in the detailed example 1) The same) was placed according to the shape, and a surface light source element (surface type) having a configuration in which the lens surface 16 of the first element was provided on the emission surface 30 side was manufactured.

On the other hand, for each of the first elements, a polyester film provided with a silver vapor-deposited film is provided on the lens surface side, and the second element (used in the detailed embodiment 1) is provided on the opposite side of the lens surface. (Substantially the same as the above) was placed in correspondence with the shape, and a surface light source element (back surface type) having a configuration in which the lens surface 16 was on the opposite side to the emission surface 30 was produced. As an example of such a surface light source element, a front type and a rear type surface light source element using a concave lenticular lens are shown in FIG.
(A) and (b) show.

{4} Measurement of Luminance etc. of Each Surface Light Source Element The peak luminance, its angle and distribution angle were examined for each of the above surface light source elements. Table 6 shows the results.
Here, the distribution angle refers to an angle range until the luminance becomes 50% of the peak luminance.

[0057]

[Table 6] As can be seen from Table 6, convex wrench, triangular prism, concave wrench,
In the surface light source element provided with the first element having each lens unit of the convex polygonal pyramid, the difference in the back side type is slightly smaller than that of the front side type, but the difference is small, and the surface type is sufficiently practical. Can be done.

{5} Outgoing light distribution of each surface light source element For each of the above surface light source elements, the outgoing light distribution at the center (the position of FIG. 7 (a)) is used for measuring the above-mentioned outgoing light distribution of the first element. It measured according to. FIG. 25 shows the angular distribution of the emission light luminance of the back surface type of the surface light source element employing the first element having the same lens unit as the cylindrical convex lenticular lens shown in FIG.
(B). FIG. 25 shows a surface type luminance distribution as a comparative example.
(A). The emission angle peak is 15 to 2 for the surface type.
The light was concentrated at 0 °, and the distribution angle was about 57 °. The emission angle peak in the case of the back type is concentrated light at 15 to 20 ° in the case of the back type, and the distribution angle is about 77 °.
°. FIG. 26A shows the angular distribution of the emitted light luminance of the surface type of the first element employing the triangular prism lenticular lens.
Shown in FIG. 26B shows a surface-type luminance distribution.
The emission angle peak was concentrated light at 13 to 15 ° in the case of the surface type, and the distribution angle was about 75 °. In the case of the back type, the emission angle peak was concentrated light at 15 to 17 °, and the distribution angle was about 90 °. FIG. 27A shows the angular distribution of the emitted light luminance of the surface type of the first element employing the cylindrical concave lenticular lens. FIG. 27 shows the luminance distribution of the back surface type.
(B). The emission angle peak is 13 to 1 in the case of the surface type.
The light was concentrated at 5 °, and the distribution angle was about 60 °. In the case of the back type, the emission angle peak is 13 to 15 °.
And the distribution angle was about 60 °. FIG. 28 shows the angular distribution of the emitted light luminance of the surface type of the first element employing the convex polygonal pyramidal lenticular lens.
(A). FIG. 28B shows a luminance distribution of the back surface type. The emission angle peak was concentrated light at 15 to 17 ° in the case of the surface type, and the distribution angle was about 85 °. Also,
In the case of the back surface type, the emission angle peak was concentrated light at 13 to 15 °, and the distribution angle was about 65 °. FIG. 29A shows the angular distribution of the emission light luminance of the first element employing the anisotropic lenticular lens A.
FIG. 29 shows the luminance distribution of the anisotropic lenticular lens B.
(B). The emission angle peak is 15 to 17 ° for A
And the distribution angle was about 95 °. In the case of B, the emission angle peak was concentrated light at 13 to 17 °, and the distribution angle was about 55 °.

{6} Summary Regardless of whether the emitted light of the first element is symmetric or asymmetric with respect to the normal line as shown in FIGS. 19 to 23, if the shape of the second element is optimally set, FIGS. As shown in Table 6, it is possible to emit concentrated light at a predetermined emission angle and obtain practically sufficient luminance (2-3.5 times the omnidirectional emission).

[0060]

As described above, according to the surface light source device of the present invention, it can be used as a backlight for a display device such as a liquid crystal color TV which is small, has a small viewing angle, and has a limited field of view. Can provide an optimal light source device that is thin (approximately 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 obtained, and the emission direction of the concentrated light can be easily and freely determined.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram showing a relative angle in a viewing state of a liquid crystal color TV.

FIG. 4 is a cross-sectional view of a conventional surface light source device.

FIG. 5 is a perspective view and a sectional view of a first element.

FIG. 6 is a diagram showing an angular distribution of emission light luminance of a first element of Example-1.

FIG. 7 is a front view of the surface light source element (after the lamp set) (
FIG. 1 is a sectional view taken along the line AA ′ of FIG. 1 and a conceptual diagram of a measuring method.

FIG. 8 is an optical path analysis diagram when peak light of emission light from a first element enters a prism.

FIG. 9 is a diagram illustrating an example of a lens unit of a first element.

FIG. 10 is a diagram showing an angular distribution of emission light luminance in Example-1.

FIG. 11 is a diagram showing an angular distribution of emission light luminance in Example-2.

FIG. 12 is a diagram showing an angular distribution of emission light luminance in Example-3.

FIG. 13 is a diagram showing an angular distribution of emission light luminance of a light source device of a comparative example.

FIG. 14 is a diagram illustrating a case where the lens unit of the first element is a triangular prism lenticular lens.

FIG. 15 is a diagram showing a case where the lens unit of the first element is a cylindrical concave lenticular lens.

FIG. 16 is a diagram showing a case where the lens unit of the first element is a convex polygonal pyramidal lenticular lens.

FIG. 17 is a diagram showing a case where the lens unit of the first element is an anisotropic lenticular lens.

FIG. 18 is a diagram illustrating a state in which a lens surface is turned to a mirror and an angular distribution of emitted light luminance is measured.

FIG. 19 is a diagram showing a front-side and a back-side light emission distribution of a cylindrical convex lenticular lens.

FIG. 20 is a diagram showing a front-side and back-side emission light distribution of a triangular prism lenticular lens.

FIG. 21 is a diagram showing a front-side and a back-side light emission distribution of a cylindrical concave lenticular lens.

FIG. 22 shows a surface type of a convex polygonal pyramidal lenticular lens;
It is a figure which shows the emitted light distribution of a back type.

FIG. 23 is a diagram showing the distribution of emitted light from the anisotropic lenticular lenses A and B.

FIG. 24 is a diagram showing a front surface type and back surface type surface light source element using a cylindrical concave lenticular lens.

FIG. 25 is a diagram showing a front-side and back-side emission light distribution of a surface light source element having a cylindrical convex lenticular lens.

FIG. 26 is a diagram showing a front-side and back-side emission light distribution of a surface light source element having a triangular prism lenticular lens.

FIG. 27 is a diagram showing a front-side and a back-side emission light distribution of a surface light source element having a cylindrical concave lenticular lens.

FIG. 28 is a diagram showing a front-side and back-side emission light distribution of a surface light source element having a convex polygonal pyramidal lenticular lens.

FIG. 29 is a diagram showing an emitted light distribution of a surface light source element having anisotropic lenticular lenses A and B.

[Explanation of symbols]

 Reference Signs List 16 lens unit 40 prism unit 13 reflecting surface 14 light source 15 reflector 50 first element 51 second element 30 emission surface

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/13357

Claims (1)

(57) [Claims] At least one side end is an incident end face,
A plate-shaped first element having a plane orthogonal to the plane as an emission plane, a reflection surface provided on a surface opposite to the emission plane of the first element, and an emission plane side of the first element. A second element provided, and a light source arranged to face the incident end face of the first element, wherein the first element is orthogonal to both the incident end face and the emission plane. Surface, the emitted light having directivity in a specific direction inclined with respect to the normal direction of the emission plane of the first element is emitted from the emission plane, and the second element is formed of the first element. From a plurality of linear prism units having a prism angle of 30 ° to 66 ° in parallel, and an emitting surface for emitting light in a predetermined direction. , Each of the above The light incident from at least one prism surface of the prism unit is reflected by the other prism surface and the first light is reflected.
A surface light source element, which is deflected in the direction of the normal to the emission plane of the element and emits light from the emission surface.