JPH0284618A - Panel light source element - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface light source element used in a surface light source device.The present invention is particularly suitable for use as a backlighting means for a liquid crystal display device or the like.

[Prior Art] Conventionally, back illumination means for liquid crystal display devices, etc., has a shape in which a linear lamp is used as a light source, the lamp is placed at the focal point of a rotating parabolic reflector, and a half-milk diffuser plate is placed above the lamp. This is a common practice, and efforts have been made to optimize the shape of the reflector and adjust the diffusion rate of the diffuser plate.

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 point light source approximation.
There are those processed into an approximate curve shape to condense the emitted light in a certain direction, those whose light guide thickness changes along the direction of light travel, and those whose prism angle changes depending on the distance from the light source. In most cases, it is possible to simulate the optical path by using a zero-point light source approximation, which can be used in some cases, or a combination of some of these, and the shape of the light guide layer can be adjusted accordingly by changing the distance in the direction of light propagation. It is possible to change it according to the situation, and many such proposals have been made for patents and utility models.

However, most single-sided light sources aim to emit light uniformly in all directions as possible from the output plane.
Depending on the purpose of use, you may want to concentrate the light in a specific direction.

For example, LCD color T for personal use with a small viewing angle.
V, etc., are required to emit uniform light only in the direction in which it is formed, and to have as uniform an amount of emitted light as possible over the entire exit surface. FIG. 9 is a schematic configuration diagram of such a liquid crystal color TV device. In the figure, l is a liquid crystal screen, 2 is a main body of the liquid crystal color TV device, 3 is a normal line of the liquid crystal screen l, and 4 is the viewer's eyes. In this type of device, the LCD screen 1 is set up at an angle of about 45 degrees from the main body 2 of the LCD color TV device, and the screen is viewed from a direction forming an angle of 15 degrees with respect to the normal 3. ing. therefore,
In the figure, if there is a backlighting means in which the brightness of the surface light source is greater within the angle range indicated by X than in other angle ranges,
It is advantageous in that the entire amount of light can be concentrated there. In other words, the brightness of such a surface light source exhibits the highest brightness value in a desired direction, which is many times greater than the brightness I1 of the omnidirectional uniform emission type. Therefore, if it is used as a backlight for a display device whose viewing angle is only in a certain specific direction, it is possible to obtain a high-brightness display device with low power consumption.

[Problems to be Solved by the Invention] However, in most cases, light sources used for flat surfaces such as LCD color TV devices as shown in Fig. 9 are point light sources, with the exception of special small-sided lighting. I never use . The light source used is a volumetric light source (a light source that cannot be considered as a point light source, such as a fluorescent lamp), and the consistency of the point light source approximation is extremely poor. Therefore, the shape proposed in the conventional technology is However, it is difficult to obtain the desired characteristics as described above, although the shape is precise and complicated, and manufacturing costs are high.

Moreover, volumetric light sources such as fluorescent lamps emit diffused light from the light source itself and are non-directional. That is, in a strict sense, it is very difficult to ensure desired directivity using a diffused light emitting light source.

Also, apart from the above-mentioned point of directionality of light emission, in order to make the light source device itself as small as possible, it is necessary to achieve the objective by making the thickness at least as large as the diameter of the light source lamp. . In the light source device of the above-mentioned type in which a rotating parabolic reflector is disposed at the bottom of the lamp, the thickness is 2 to 4 times the lamp diameter, and cannot meet the demand for miniaturization.

[Means for Solving the Problems] In view of the 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 that is small, has a small viewing angle, and has a limited field of view. To provide a surface light source element that is thin (comparable to the diameter of the lamp) and that can easily provide concentrated light in the direction in which the user views it without increasing the wattage of the light source. be.

The above object is to provide a first element having at least two side edges as an incident surface, a surface perpendicular to the incident surface as a light exit surface, and a reflective layer on the opposite surface of the exit surface; It is composed of a second element having an entrance surface through which light emitted from the element enters and an exit surface through which light is emitted in a predetermined direction. This is achieved by a surface light source element having a matte surface substantially parallel to the surface of the reflective layer, and a plurality of prism units formed on the incident surface of the second element. Ru.

Hereinafter, the surface light source element according to the present invention will be explained in detail based on the drawings.

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

The refractive index n of light with respect to air of the light guide is approximately n; 1.4 ~
1. δ, and as shown in FIG. 10(a), the critical reflection angle is 45° when the incident end surface 11 and the exit plane 16 of the light guide 10 are perpendicular to each other (edge lighting).
In principle, no light is emitted to the emitting plane 16 at the front or rear. In addition, in FIG. 1O(a), 14 is a light source such as a fluorescent lamp;
5 is the reflector 113 is the output plane 1 of the light guide 10
6 is a reflective surface formed on the opposite side.

Therefore, as shown in FIG. 10(b), in general, the emission plane 16 is made into a diffused plane 16a, the reflection surface 13 opposite to the emission surface is made into a scattering reflection surface 13a, or the direction of the light emission is For the present purpose of wanting sex, such means cannot be used because the light will be emitted or scattered.

Moreover, as shown in the embodiment of the present invention, the amount of emitted light in the normal direction i of the emitting plane is extremely small (see FIG. 4(b)), so the inventors of the present invention The surface of the light guide was roughened as uniformly as possible (hereinafter referred to as a satin surface in the present invention), and as a result of a detailed study of the formed matte surface and the directionality of the output light, it was found that the normal to the exit surface On the other hand, it was discovered that most of the light is emitted in a direction of 70 to 80 degrees, and in order to convert this direction to the normal direction, the present invention was completed by considering the combination of a second element.

A perspective view of the configuration of the first element is shown in FIG. 4(a), in which a uniform matte surface is formed on the output plane, a reflective surface 13 is formed on the opposite surface, and a fluorescent lamp-like surface is formed at one end. A linear light source 14 was provided. FIG. 4(b) is a sectional view taken along the line AA'.

FIGS. 7(a) to 7(f) are diagrams showing the angular distribution of the output light brightness shown in FIG. 4(b). That is, it is a diagram showing the ratio of the emitted light at each angle when the emitted light at the largest angle among the emitted light at each angle is taken as 100% (the measurement sample and the measurement method will be described later).

FIGS. 5(a) and 5(b) are diagrams showing each measurement method, FIG. 5(a) is a front view showing the measurement position, and FIG. 5(b) is a sectional view taken along line A-A'. It is. In Fig. 5(b), 48 is a luminance meter.As shown in Fig. 7(a) to (''), almost no light is emitted in the front direction (normal direction of the plane), which is necessary as a light source. First, it was found that the emitted light was concentrated in a specific direction of 75 to 80 degrees (also shown in FIG. 4(b)).

Therefore, the present invention concentrates the emitted light in a specific direction in this way,
By conversely using the light guide (first element) having a pear-shaped surface 60 with a small output light distribution and a large amount of output light, the output light 20.21 is output on both sides of the normal line (Fig. 4(b)). The principle is to focus the emitted light intensively in a desired direction by refracting all the emitted light by a prism group, which is a second element.

FIGS. 6(a) and 6(b) are enlarged views of the prism of the second element, which is another component of the above action. In the figure, 20, 21 are the lights emitted from the pear-shaped surface 60 of the first element in the right direction and the left direction, respectively, θ1, 0. are the normal and prism surface 30.31 respectively.
The angle 32 formed is the exit surface. In addition, ψ□~ψ6 and φbreath~φ6 each indicate an angle with respect to the reference line for each surface area of the prism unit, and how to take the angle is shown in tiSa diagrams (a) and (b). Tooritual.

When the emitted light 21 enters from the right side of the prism, it enters from the prism surface 30.

After total reflection on the prism surface 31, the light is emitted from the emission surface 32 at a predetermined angle ψ6. In addition, when the outgoing light 20 enters from the left side of the prism, it enters from the prism surface 31 and is totally reflected at the prism surface 30, then the exit surface 32
The light is emitted at a predetermined angle φ6.

Since the output angle of the primary output light from the pear-shaped surface 60 of the first element is symmetrical with respect to the normal, the prism angle of the constituent unit of the prism group of the second element (0+ in FIG. 6,
02) and the refractive index, the desired exit angle (ψ
6 and φ6).

[Example] Hereinafter, a specific configuration of a surface light source element according to the present invention will be described in detail based on one drawing.

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, 15 is a reflector thereof, 13 is a reflective surface formed on the side opposite to the exit surface 16 of the light guide 50, and 16 is an exit surface of the light guide 50 ( 6
Note that the output surface 16 of the light guide 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).

The configuration of the present invention is such that at least one side end 11 of the light guide is an incident surface, a surface perpendicular to this is a light exit surface 16, a reflective layer 13 is provided on the opposite surface of the exit surface 16, and the light guide A first element 50 having the matte surface 60 disposed on at least one surface of the body, and a prism unit 40 for receiving the light emitted from the first element 50 and emitting the light in a predetermined direction. It is composed of a second element 51 having an entrance surface and an exit surface 32 from which light from the prism unit 40 is output.

Each light emitted from the first element has a light source of 54.5
The purpose can be achieved by setting the prism units so that the beams are emitted as shown in FIG. 5 and ψ6 and φ6 are approximately the same.

As a material constituting the element of the present invention, acrylic 4, which has the highest visible light transmittance as a light guide for the purpose of small and light counterfeiting, is selected. III is preferred, but need not be limited thereto.

In addition, a small fluorescent lamp is used as the light l114,
It may be a continuous linear light source (for example, a filament lamp).

Next, an example of determining the prism angle when the first element makes the first-order exit angle symmetrical with respect to one normal line will be shown.
Even if it is asymmetrical to the normal, it can be easily calculated by changing the incident angle of the light to the left or right. Note that n is the refractive index of the material constituting the element.

■In case of incidence from the left side of the prism (all symbols are based on Figure 6 (a)) (i) 90°-ψ×θ1 φ1-(θ1+ψ)-90
゜sinφ,=sin(θ1+ψ-90)/nφ5=
90- (2θ2+θ, -φ2).

sinφ6=nXsinφ5゜φa = sin-'(n x sinφ,) (ii) 90
”−ψ〉θ, φ, =90−(0,+ψ).

sinφ2 = sjn(90−θ, −ψ)/nφ! 1
=90- (2θ2+01+φ2).

sinφ, =nxsin *5 (iii) 90@ −ψ=θ1 φ1=0φ, =!
! Q-(2θ2+θ,).

sin φ6 = nxsjn φ5■Incidence from the right side of the prism (all symbols are based on Fig. 6(b)) (i) 90' −ψ θ 2ψ1 = (θ2
+ψ)-90°sinψ* = sin(θ2+ψ-90)/nψ5=(
2θ, +02-4ψ2)-90°sinψa=nXsi
nψ5 (v) 90°ψ〉θ.

ψ, = 90−(θ friend + ψ).

sin * t = 5in(90-02-ψ)/nψ
5=(2e, 10, +ψt)-90°sinψa”
n X Sinψ5 (vi) 90°−ψ=0□ ψ, wQψ, = (2θ
, a + 0+ ) −”sinψ6==fiXSin
ψ5 Also, if the prism is made of acrylic resin, the refractive index is n = 1.49, and if the angle of incidence on the prism 40 is symmetrical with respect to the normal and ψ = 65°, then according to the above calculation formula, The exit angle from the prism is an angle that converges on one side of the normal line (an example of calculation is shown in which the difference between the left and right sides is within 2'').

Incident angle ψ=65° Left prism Right prism angle 0
．． Angle θ2 θ1 0° Light from the left Light from the right (φ6
) (ψ6) 35° 28° 8.5° 8.9°3
6"27"11.0' 11
．． 5637' 26° 13.5'
14.0': 18"25"' 16
．． 0″16.5’39’ 24” 18.6
” 19.1'40' 23° 2
1.1'21.7°41'22"
23.7″24.3″42″ 21'
26.3 ” 26.
9 9436 20° 29.0° 29
．． 6. FIGS. 2 and 3 are partial cross-sectional views of a surface light source element showing another configuration example of the present invention.

In FIG. 2, the first element (light guide) 50-1
The satin surface 60 is formed on the opposite side to the light emitting surface 16, and is arranged to face the reflective layer 13 formed independently or integrally, and the emitting surface of the first element 50-1. 16 is a smooth surface. FIG. 3 shows a light guide 50
This figure shows an example of a configuration using a light guide 50-2 having a matte surface 60 on the upper and lower surfaces of the light guide 50-2. Note that in the present invention, the virtual plane of the satin surface, which is the output surface 16 of the transparent light guide, is substantially parallel to the surface 13 of the reflective layer.

One of the features of the present invention is that it uses a transparent light guide that can be easily manufactured and assembled, which is a plate-shaped body having a uniform thickness.

FIG. 12 shows that the light emitted from the first element 50 is emitted symmetrically with respect to the normal line, and the angle of the prism unit of the second element 51 (01,0□ in FIG. 6) is 01=02=31.5. @
It is a figure which shows the Example in the case of. According to this embodiment, the output light from the output surface 32 of the second element can be focused in the normal direction, like the light rays 58 and 57.

Next, a configuration example of the present invention will be described assuming a back light source for a 3-inch liquid crystal color TV, and in which the panel size is 61 mm wide x 56 mm high.

The first element is a transparent acrylic resin with a thickness of 5-1,
Although the second element is made of acrylic resin having a thickness of 1 liter in the following specific example, it is clear that the present invention is not limited to this in terms of size, thickness, and material.

[Detailed Example-1] Fabrication and evaluation of the configuration example shown in Figure 1 (fabrication of light guide) First, a polished brass plate (approximately 3 m IIX 2505 m
The surface of the metal plate is honed using a conventional honing method in which 60 mesh glass beads are sprayed onto one side of a 250 mm (250 mm) piece, and a mold for a replica is produced. Five types of molds were produced depending on the degree of honing.

Next, a replica of the honed surface was made on one side of a 5 mm thick acrylic resin plate by hot pressing using the mold, and this was used as a light guide.

(Production of the second element) Measure the effective viewing angle and tilt angle from the normal line of the portable LCD TV screen (see Figure 9), and set the output angle to 15'' (ψ6・φ6) with respect to the screen normal line. The prism angle is set to 38” (-0t) on the left side and 25° on the right side.
), see Figures 6 (a) and (b)), and 5. A multi-prism with many parallel prism sides with a tip angle (=θ, +02) of 63° and a pitch of 0. A mold of .38 mm was created and thermally transferred onto a 1 m thick acrylic resin plate using a heat press to form a second element.

(Measurement of haze value of light guide) (1) Each 50 x 5
A 0sm specimen was cut out and used as a sample for haze value measurement. As a control sample, a transparent acrylic resin plate before making a replica was similarly cut into 50×50-1 pieces and used.

The haze value was measured according to ^5TI-D 1003-61 by placing a replica surface on the light incident side of a measuring instrument, and the haze value was determined using the following formula.

Haze value = ((diffuse light transmittance)/(total light transmittance)) x 1
00% (2) The measurement results are as shown in Table 1. (Manufacturing of the first element and evaluation of the angular distribution of the emitted light) Next, from the above light guide, a A board of the same size was cut, two sides of 61+ ui (width) were polished using the usual method, and polyester with an adhesive-coated aluminum vapor-deposited film was pasted on the two sides (56 m-), and the opposite side of the transferred matte surface was A polyester film with a silver tint coating was provided. Along two sides of width 61am, diameter 7■■, length 245am
Lamp (CB 7-245 manufactured by Stansea Electric Co., Ltd.)
A W cold cathode tube) was wrapped with aluminum foil as a reflector and turned on at 12 V DC via an inverter.

Measure the central part of the first element (0 part in Figure 5 (a)) using a luminance meter (Minolta Co., Ltd. luminance meter nt-1) at different angles with respect to the normal line, and calculate the output light distribution. (See Figure 5(b)).

The data obtained in this way are shown in Table 2 and the 7th table mentioned above.
Figures (a) to (d). In FIG. 7, the luminance is measured in the radial direction and the light emission angle is taken in the circumferential direction.

Sample-5 and the control sample were omitted because the amount of emitted light was small in both directions, resulting in inaccurate measurements.

Table 2 Note that the tube surface brightness at the center of the lamps used was 5 [100 and 520 cd/s'', respectively.

(Production of surface light source element according to the present invention and evaluation thereof) The second element is cut into a piece of 16IIIl x 56mm so that the line direction of the multiprism is parallel to the long side, and the light emitting surface of the first element is The convex parts of the prisms are arranged so that they face each other, and the prisms are arranged so that the protrusions face each other.
A surface light source element according to the present invention was manufactured by fixing with double-sided adhesive tape in the tray.

The angular distribution of the emitted light from the water surface light source element was determined to be constant using the same method as the method for evaluating the angular distribution of the emitted light from the first element. The measurement results are shown in Table 3 and Figures 8 (a) to (d).
Shown below.

Table 3 *Distribution angle The performance of the pear-shaped surface of the light guide, as shown in the angle at which the luminance value becomes 1/2 of the peak luminance, is approximately 3
If it is 0% or more, preferably 50% or more, sufficient brightness and distribution angle can be obtained as a surface light source element.

[Detailed Example-2] Fabrication of the configuration example shown in FIGS. 2 and 3 and its evaluation Using the mold from which Sample-2 of [Detailed Example-1] was made, both sides of acrylic resin with a thickness of 511 mm were used. A replica was taken and designated as sample-6. This light guide is 50-2 shown in Figure 3.
corresponds to

(Measurement of haze value of light guide) The haze value of sample-6 was measured in exactly the same manner as in [Detailed Example-1].

Haze value sample - 681.5% (Production of first element and evaluation of angular distribution of emitted light) Produced in exactly the same manner as [Detailed Example-1]. The sample-2 and sample-6 were used as light guides, and the procedure was exactly the same as [Detailed Example-1] except for the following points.

Differences Same as Sample-2, a silver-deposited polyester film was provided on the matte surface of the light guide (see Figure 2).

The sample arranged in this way is called sample-7. do. This is the light guide 50- in FIG. Corresponds to l.

The measurement results of the angular distribution of the emitted light are shown in Figure 7 (e) - (f).
It is.

Table 4 Table 5 The brightness of the tube surface at the center of the lamps used was 500 for each.
0.5200 cd/s".

(Production of surface light source element according to the present invention and evaluation thereof) A surface light source element was manufactured in exactly the same manner as in [Detailed Example-1], and the angular distribution of emitted light from the surface light source element was measured.

The results are shown in Table 5 and FIGS. 8(e) to (f).

As described above, when the satin surface is on both sides (Sample-6) or in close contact with the reflective layer (Sample-7), the distribution angle of the concentrated light can be widened (the peak brightness is correspondingly reduced).

(Comparative example) Rutile type titanium oxide was triblended to an acrylic resin pellet (manufactured by Mitsubishi Rayon Co., Ltd., Hibet HBS [registered trademark]) in an amount of 1.5% by weight, and a film with a final thickness of 50 mm was formed using an ordinary extruder. . The film was spread on an inorganic glass flat plate without air bubbles, temporarily fixed with methyl methacrylate, and then polymerized and solidified in a conventional manner to obtain an acrylic resin plate with a thickness of 51 cm.

The board of the comparative example made in this way is 61sax in width and 56sax in length.
Cut it into ■■, polish the two horizontal sides of 611- by the usual method, stick the adhesive-coated aluminum vapor-deposited film on the two vertical sides of 56 g, and remove the white thin layer formed on the board surface. Measurements similar to those of the first element having a silver-deposited polyester film disposed on the opposite side were carried out in exactly the same manner, and the output light distribution was determined. The results are shown in Table 6 and Figure 11.

Table 6 (Summary) For example, as you can see by comparing Figures 8 (a) to (f) and Figure 11, the comparative example has the characteristic of emitting light uniformly in all directions. In contrast, the surface light source element of the present invention has the advantage of being able to obtain concentrated light in a specific direction, and also being able to obtain a high brightness value that is about 3.5 to 4 times the peak brightness value at the center point. I know that there is.

[Detailed Example-3] As shown in Fig. 12, as an example of directing the output angle in the screen normal direction, the prism angle is 31.5@C-0r with left and right symmetry.
)-31,5@<=0*), pitch 0.5mm
A mold was prepared, and the mold was thermally transferred onto an acrylic resin having a thickness of 1 day using a heat press to form a second element.

The light guide of sample-1 in Table 2 was used as the first element, and the above 31.5/31.5'' was used as the second element.
Using a (0,=f)□) multi-prism, a surface light source element was created 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 brightness of the first element.
Further, the peak brightness of the surface light source element is shown in Table 8, and the angular distribution of the output light brightness of the surface light source element is shown in FIG.

Table 7: Peak luminance in the left and right direction (±80''') As can be seen from Table 8 and Figure 13, by setting θ1゜0□ as above, the concentration is higher than in the normal case. We were able to create a surface light source element that can direct light in the normal direction of the screen.

[Effects of the invention] That's it! 11, according to the surface light source element of the present invention, ■It is compact like an LCD color TV and has a small viewing angle;
Moreover, for the backlighting of displays with limited fields of view, we offer an optimal light source device that is thin (about the same diameter as the lamp) and can easily provide concentrated light without increasing the wattage of the light source. Ru.

■By using a fluorescent lamp, which is a diffused light source, it is easy to obtain concentrated light, and the direction of emission of the concentrated light can be easily and freely determined. It can be realized).

It's effective.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a surface light source element of this device. 2 and 3 are respective partial cross-sectional views of other embodiments of the invention. FIGS. 4(a) and 4(b) are a perspective view and a sectional view of the first element of the device. FIGS. 5(a) and 5(b) are conceptual diagrams of a method for measuring the angular distribution of the luminance of emitted light according to the present invention, respectively. 6th [, 4] is an optical path analysis diagram when the peak light of the light emitted from the first element enters the prism. FIGS. 7(a) to 7(f) are diagrams each showing the angular distribution of the luminance of the light emitted from the light guide according to this embodiment. No. EH'-1 (a) to (f) are diagrams showing the angular distribution of the emitted light brightness of the surface light source element according to the present invention. FIG. 9 is a diagram showing relative angles in the viewing state of a liquid crystal color TV. FIGS. 10(a) and 10(b) are cross-sectional views of a conventional surface light source device. FIG. 11 is a diagram showing the angular distribution of the output light brightness of the surface light source element of the comparative example. FIG. 12 is a sectional view of a surface light source element according to an embodiment of the present invention in which the second element is of the θ=02 type. FIG. 13 is a diagram showing the angular distribution of the luminance of the emitted light of the surface light source element according to the present invention of the θ1=02 type.

Claims (1)

[Claims] (1) A first element having at least one side end as an incident surface, a surface perpendicular to the incident surface as a light emitting surface, and a reflective layer on the opposite surface to the emitting surface; and light emitted from the first element. a second element having an entrance surface through which light is incident and an exit surface through which light is output in a predetermined direction, and the light exit surface of the first element has a virtual plane that is the surface of the reflective layer. A surface light source element having a substantially parallel pear-shaped surface and having a large number of prism units formed on the entrance surface of the second element.