KR101264323B1 - Plane light emitting back light unit and lamp using point light source - Google Patents

Abstract

A surface emitting backlight unit and a surface emitting lamp using a point light source are provided. The present invention provides a point light source for irradiating light to the LCD panel, a light guide plate of a translucent material formed between the LCD panel and the point light source, the light emitting means and the light shielding pattern formed on at least part of the upper and lower portions of the light guide plate The light guide plate includes a light source input unit, an upper internal reflection surface, an optical guide plate upper surface, and a stopper, wherein the light source input unit is formed under the light guide plate, and the light directed toward the top of the light source input unit is Refractive to the upper internal reflection surface, the light directed toward the side of the light source input unit is refracted to the internal reflection surface to generate total internal reflection in the light guide plate, the stopper is formed on the upper internal reflection surface of the transmissive material It is characterized in that it coincides with the shape of the upper internal reflection surface.

Description

Surface emitting backlight unit and surface emitting lamp using point light source {PLANE LIGHT EMITTING BACK LIGHT UNIT AND LAMP USING POINT LIGHT SOURCE}

The present invention relates to a surface emitting backlight unit and a surface emitting lamp using a point light source, and more particularly, refracting and reflecting the light of a point light source such as a light emitting diode to be totally reflected inside the light guide plate and dispersing it evenly forward. It relates to a surface emitting backlight unit and a surface emitting lamp.

Recently, semiconductor light emitting devices such as LED (Light Emitting Diode) and LD (Laser Diode) have been widely used for backlight of indoor / outdoor lighting devices or display devices. The LED or LD has a high luminous efficiency compared to electric power, which can reduce power consumption and provide illumination of various colors, whereas the light emission angle is narrow due to the structural characteristics of the point light source. Therefore, in order to provide light of uniform brightness over a wide area, a separate means such as a light diffusion plate is required.

For example, a liquid crystal display (LCD) includes a backlight unit that provides light to the rear side because the liquid crystal panel itself does not emit light. As a light source of the backlight unit, a conventional cold cathode flourescent lamp (CCFL) is mainly used. In recent years, LEDs have been in the spotlight as devices capable of improving image quality and energy efficiency.

Currently used LED backlight units are largely divided into two types: edge emitting and direct illumination.

In the edge type, the LED is installed at the edge of the light guide plate to inject light into the light guide plate. When the incident light rays are diffused through the total internal reflection to the entire light guide plate, and meet the projection-shaped extraction point or the uneven scattering pattern, the light guide plate is vertically forward. It has a structure that is emitted to provide diffused light. Such an edge type structure not only makes it easy to uniformize the light intensity emitted from the light guide plate, but also has an advantage of making the thickness of the backlight unit thin.

However, as the size of the screen increases, the area of the screen increases in proportion to the square for each side length of the light guide plate on which the LED is installed. Therefore, the edge type backlight unit requires a high brightness LED because the required amount of light of each light source is increased. As the distance to reach is increased, not only the brightness of the LED but also the performance improvement of the light guide plate are required, which is disadvantageous in terms of manufacturing cost and process difficulty.

In contrast, the direct type provides uniform light by arranging the LEDs in two dimensions behind the liquid crystal and dispersing the light of each LED using a diffuser plate. It is possible to implement a large screen of the display device in the trend of larger size, such as TV has a significant advantage over the edge type.

However, since point light sources such as LEDs have a non-uniform light distribution that is far from the center of light irradiation, i.e., a larger emission angle, the intensity of the light rapidly decreases, the direct backlight unit is close to the LED even when using a diffuser plate. Hot spots occur around the point, which requires diffusion plate improvement or the provision of other optical elements to remove it. In addition, in order to illuminate the required area due to the limited light irradiation angle, sufficient space must be secured between the liquid crystal and the LED, so that the thickness of the backlight unit and the liquid crystal display device must be increased.

In addition, the light distribution problem of the point light source generated when applied to the backlight unit as described above occurs even when the point light source is used in the lighting lamp.

The present invention is to solve the problems described above, by providing a point light source such as a light emitting diode in a direct type to implement a good image quality for a large display device and at the same time a good light dispersion effect even in the point light source and a short distance It is an object of the present invention to provide a surface emitting backlight unit using a point light source capable of further improving image quality while reducing the thickness of a display device by providing a guide plate. In addition, another object of the present invention is to provide a surface light emitting lamp using a point light source to uniformly diffuse and emit light of a point light source through a light guide plate to realize an even lighting effect over a wide area.

According to an aspect of the present invention, there is provided a surface light emitting unit including a point light source for irradiating light to an LCD panel, an optical guide plate formed between the LCD panel and the point light source, and the light guide. And a light emitting means and a light shielding pattern formed on at least part of an upper portion and a lower portion of the plate, wherein the light guide plate includes a light source input unit, an upper internal reflection surface, an internal reflection surface, and a stopper, and the light source input unit is the light guide plate. Light formed at the lower portion of the light source input portion to the upper portion is refracted to the upper internal reflection surface, light directed toward the side of the light source input portion is refracted to the internal reflection surface to generate total internal reflection in the light guide plate, The stopper may be formed of a light transmissive material on the upper internal reflection surface to match the shape of the upper internal reflection surface. The light source input unit may be formed to be recessed in the lower portion of the light guide plate. In addition, the upper internal reflection surface is formed to concave in the shape of a cone on the upper portion of the light guide plate, it is possible to reflect the light refracted by the light source input to the internal reflection surface. And the cone of the upper internal reflection surface may be characterized in that the vertex angle is between 80 degrees and 100 degrees. In addition, the stopper may be characterized by having a conical shape. The upper surface of the light source input unit may be a spherical surface or a curved surface to reduce the divergence angle of the light emitted from the point light source. The light emitting means may include at least one of white scattering paint, colored scattering paint, phosphor, quantum dot phosphor, and surface irregularities.

On the other hand, in the optical guide plate according to another embodiment, a cone-shaped first groove formed on the first surface of the optical guide plate, the second surface opposite to the first surface, in a position corresponding to the first groove And a second groove formed, wherein the second groove has a bottom surface of an area smaller than the opening in the second surface. The opening of the second groove is smaller than the opening of the first groove. It may be characterized by having an area. The bottom surface of the second recess may be a curved surface convex in the second surface direction. And it may be characterized in that it further comprises a stopper disposed in the first groove.

Meanwhile, in a surface light emitting unit according to another embodiment, a point light source, a light guide plate disposed on one side of the point light source, a light shielding pattern formed on a first surface of the light guide plate, and a second of the light guide plate At least one light emitting means formed on a surface, wherein the light guide plate is formed at a position corresponding to the first groove on the second surface, the first groove having a cone shape formed on the first surface, And a stopper disposed in the first groove and the second groove having a bottom surface of an area smaller than the opening in the second surface. The opening of the second recess may have a smaller area than the opening of the first recess. The bottom surface of the second recess may be a curved surface convex in the second surface direction.

1 is a cross-sectional view of a surface emitting backlight unit using a point light source according to an embodiment of the present invention.
2 is a cross-sectional view for explaining guiding of light by total internal reflection according to an exemplary embodiment of the present invention.
3 is a cross-sectional view illustrating a path of a light beam entering a LED peripheral optical system from a neighboring LED according to an exemplary embodiment of the present invention.
4 is a cross-sectional view of a surface emitting backlight unit using a point light source according to another embodiment of the present invention.
FIG. 5 is a diagram illustrating a result of simulating the intensity of light leaking around the upper internal reflection surface when there is no conical stopper of the surface emitting backlight unit using the point light source.
FIG. 6 illustrates a result of simulating the intensity of light leaking around a cone stopper when there is a cone stopper of a surface emitting backlight unit using a point light source according to an embodiment of the present invention.
7 is a cross-sectional view of a surface emitting backlight unit using a point light source according to another embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

1 is a cross-sectional view of a surface emitting backlight unit using a point light source according to an embodiment of the present invention.

FIG. 1 illustrates an example in which an LED is provided as a point light source, and includes a plurality of LED point light sources 101, a light guide plate 103, a light emitting means 107, and a light shielding pattern 108 provided at predetermined intervals on a circuit board. Is done.

The point light source 101 is not provided at the outer end portion of the light guide plate like the edge type, but is arranged one-dimensionally or two-dimensionally at equal intervals behind the light guide plate 103 like the direct type.

The light guide plate 103 is preferably made of a synthetic resin material having high light transmittance, and is preferable in terms of moldability and cost. Particularly, the optical guide plate 103 preferably has a refractive index of 1.3 or more in order to provide light diffraction and internal total reflection effects required by the present invention. In the following embodiment, PMMA, which is widely used as the light guide plate 103, is assumed, and the refractive index is 1.5.

The optical guide plate 103 is composed of an upper internal reflection surface 105, a light guide plate upper surface 109, and a conical stopper 106 in the shape of a concave groove. The light source input unit 104 is disposed at a lower portion of the light guide plate 103 at a position corresponding to the upper internal total reflection surface 105 of the upper portion, and includes a light guide plate lower surface 110. The opening of the light source input unit 104 (area having a diameter DD 'in FIG. 1) has a smaller area than the opening (area having EE' in FIG. 1 in diameter) of the upper internal reflection surface 105. The opening of the light source input unit 104 is larger than the area of the bottom surface (area having CC ′ in FIG. 1 as the diameter). The light source input unit 104 has an appropriate size according to the light irradiation range of the point light source 101. The light source input unit 104 is divided into two parts, and is divided into an upper surface corresponding to CC ′ and a side surface corresponding to CD or C′D ′ in FIG. 1. These two parts mainly serve to refract the light emitted from the point light source 101 such as an LED and enter the light guide plate 103. OC is located about 45 degrees with OB perpendicular to the plane, and CD is also 45 degrees with DD '. The light emitted from the point light source is divided into light passing through the upper surface of the light source input unit 104 and two parts passing through the side according to the angle. Light passing through the upper surface of the input unit 104 is refracted to meet the upper internal reflection surface 105 and the angle with the vertical line OB is reduced to within 28 degrees.

2 shows such a light diagram in detail. The upper internal reflection surface 105 has a conical shape (conical groove shape), and the edge AE of the cone forms 45 degrees with OB in FIG. 1. Since the ray refracted by the upper surface of the light source input unit 104 has an angle of 0 degrees to 28 degrees with respect to the vertical line OB, it is reflected at an angle of 0 degrees to 28 degrees with respect to the horizontal plane DD 'of the light guide plate 103. As can be seen in Figure 2, these rays meet the upper internal reflection surface 105 and the light guide plate upper surface 109, both enter the total reflection mode and move horizontally along the light guide plate. The light entering the side CD of the light source input unit 104 has an angle of 0 to 28 degrees when the incident angle is refracted between 0 degrees and 45 degrees, so the angle between the horizontal plane DD 'of the optical guide plate 104 and 17 degrees to 45 degrees after the refraction. Will be achieved. Since this also satisfies the internal total reflection condition, all enter the total reflection mode and move horizontally along the light guide plate. Here, the CD is at an angle of 45 degrees to the BO, which is tilted to produce the smallest reflectance at 45 degrees because the light from the point light source at O is usually a small area Lambertion light source. If the CD has a 0 degree angle between BO and there is a significant amount of reflection on the surface. Since the Lambertion light source emits the highest energy at 45 degrees, reducing the reflectance at this angle contributes to the light entering efficiency. The angle between CD and BO should therefore be about 30-60 degrees. Alternatively, if the CD line is part of a circle centered at O, the structure can reduce surface reflection. In this manner, the light emitted from the point light source passes through the light source input unit 104, the upper internal reflection surface 105, and the light guide plate upper surface 109, and is all guided horizontally to the light guide plate 103. Here, the point light source includes a surface light source smaller than the size of the light source input unit 104 such as an LED.

When the light starting from the point light source 101 is guided horizontally from the light guide plate, the light cannot be emitted. However, the light emitting means 107 is required to extract the light. The light emitting means 107 is a means for extracting the light trapped by the total internal reflection in the light guide plate 103 to the outside may be made of white paint or uneven pattern. When light enters the white paint, it is scattered in all directions by scattering, and some of the light exits the light guide plate 103 without total internal reflection. The use of colored paint other than white paint has the advantage that the color can be adjusted according to the position of the light guide plate 103. For example, if you print blue, green or red paint as a pattern, you can extract the light and adjust the color of the patterned area. In addition to paints containing pigments, printing a pattern by mixing phosphors with a binder absorbs shorter wavelengths and converts the wavelengths into longer wavelengths, thereby reducing the energy loss and changing the color. For example, when the point light source is a blue LED or an LED having a high color temperature, the light emitting means 107 including the YAG phosphor can be used to extract the light while enhancing the yellow color, thereby realizing more natural white color. In the case of using the quantum dot phosphor, the color purity is increased, thereby improving the color reproducibility of the backlight unit. The optical waveguide can be locally adjusted according to various materials of the light emitting means 107, thus providing more freedom in designing the surface light emitting lamp. Finally, the uneven pattern also serves to emit light out of the light guide plate by disturbing the internal total reflection condition.

The conical stopper 106 is shaped like the upper internal reflection surface 105 and includes an air layer between the two portions so that the upper internal reflection surface 105 causes total internal reflection. The main function of the conical stopper is that when the light guiding from the neighboring point light source arrives at the upper internal reflection surface 105, it is raised to the upper surface of the conical stopper 106 to cause total internal reflection, as if the upper internal reflection surface 105 It produces the same effect as a flat light guide plate without this. Without the conical stopper 106, light is emitted through the upper internal reflection surface 105 to obtain a very bright hot spot compared to the surroundings. 3 shows the light rays coming from the neighboring point light sources reflected through the conical stopper. Among the light rays coming from the neighbors, the light rays which are directed downward are mainly reflected by the upper internal reflection surface 105 or reflected by the substrate 102 and guided again, and some of them exit around the light source input unit 104. The emitted light may control the uniformity of the emitted light by using the light shielding pattern 108. The shading pattern usually controls the intensity of transmitted light using scattering paint or a reflection pattern. The substrate 102 may also be a reflector or a plate coated with absorbing paint to prevent glare.

In FIG. 1, for example, the sizes of the light source input unit 104 and the upper internal reflection surface 105 are calculated as follows. If the diameter of the point light source is 0.5 mm and the length of the OB is 1 mm, the length of BC is 1 mm. Therefore, the radius OD of the light source input unit 104 is 2 mm. When the thickness of the light guide plate 103 is 5 mm, EE 'is 6.2 mm because CE forms 28 degrees with OB. The cone bottom radius of the upper internal reflection surface 105 is 3.12 mm and the height is 3.12 mm.

In order to reduce the thickness of the light guide plate 103, the radius of the upper cone should be reduced, and for this purpose, the angle of refraction of the light beam passing through the upper surface of the light input unit 104 should be reduced. To this end, if the upper surface of the light input unit 104 is formed in the shape of a lens instead of a plane, the angle can be reduced.

4 is a cross-sectional view of a surface emitting backlight unit using a point light source according to another embodiment of the present invention. In FIG. 4, the point light source 201, the substrate 202, the light guide plate 203, the conical stopper 206, the light emitting means 207, the light shielding pattern 208, and the light guide plate upper surface 209 are shown in FIG. Since it is the same as the description of 1, detailed description is abbreviate | omitted.

In FIG. 4, when the lens curved surface having the radius of curvature of the upper portion of the light source input unit 204 is 1.25 mm, the angle of refraction decreases from 28 degrees to 14 degrees. In FIG. 4, for example, the thickness of the light guide plate 203 is calculated. If the distance from the point light source 201 to the highest point of the light source input unit 204 is 1.0 mm, the lens radius is 1.0 mm and the radius of the light source input unit 204 is 2.0 mm. Since the refraction light passing through the lens forms an angle of 14 degrees from the vertical, the thickness of the light guide plate 103 can be reduced to 3.0 mm. At this time, the bottom radius of the cone of the upper internal reflection surface 205 is 1.5 mm and the height is also 1.5 mm so that the cone tip does not meet the lens, there is room to further reduce the thickness of the light guide plate 203.

5 and 6 show the results of calculating the intensity of light leaking upward from the structure without the cone plug and the structure with the cone plug. In the structure without the conical stopper, roughness of 2 ~ 3 times more light can be seen than the structure with the conical stopper. This shows that the structure with the cone stopper can produce more uniform illumination. Very bright spots are visible at the center of the conical stopper structure, which can be eliminated by using a shading pattern.

In FIG. 7, the light source input unit of the light guide plate is the same as the embodiment shown in FIG. 4, and an example of using the reflective diffraction grating 306 instead of the conical upper internal reflection surface is shown. By adjusting the period of the diffraction grating 306, 0th-order diffraction light L2 and +/- 1st diffraction light L3 and L4 can be obtained with respect to the input light L1. At this time, if the height of the diffraction grating 306 is 1/4 of the wavelength, the zeroth order diffracted light disappears, so that only the + / 1 first diffracted light propagates to enter the total internal reflection mode. For example, if the angle between the first-order diffraction light and the zero-order diffraction light is 60 degrees, the following equation may be satisfied.

If the wavelength is 450 nm, the period of the diffraction grating 306 is 346 nm. The height of the diffraction grating 306 to dissipate the zeroth order diffraction pattern is near 76 nm. The reflective diffraction grating 306 is much easier to manufacture the diffraction grating 306 because the zero-order diffraction pattern can be eliminated even when the height of the grating is half of that of the transmission diffraction grating. In addition, unlike the transmission diffraction grating, the reflective diffraction grating 306 has excellent mechanical strength because the uneven portion of the grating faces the inside of the light guide plate 303 and the opposite side is coated with metal, so that even if the dust is on the surface of the light guide plate, It has the advantage of not being impaired in function. Diffraction gratings generally have diffraction characteristics that vary with wavelength. If the point light source is a white light source, a large enough angle of the first diffracted light can cause a significant portion of the visible light to enter the total internal reflection mode. Even if different wavelengths of light are separated, uniform color may be obtained because they are mixed with each other in the light guide plate 303. In order to fundamentally solve this problem, white may be implemented by using a monochromatic light source 301 such as a blue LED and using a phosphor in the light extraction pattern 307. Usually, the diffraction grating is composed of parallel straight lines, but the diffraction grating used herein may implement uniform illuminance in all directions in the light guide plate 303 in the case of a concentric circular or elliptic shape.

In the above-described embodiment, the present invention has been exemplarily applied to the backlight unit of the display device. However, the present invention is not limited thereto, and the light of the point light source 101 is applied to the light guide plate 103. It can be applied to a surface emitting lamp that diffuses through and provides an even intensity of illumination over a wide area.

According to the present invention as described above, by directing and refracting the light of the point light source to be totally reflected inside the light guide plate, and uniformly distributed emission forward through a plurality of light extraction, direct light source arrangement and edge type By providing the advantages of the light source arrangement method at the same time, it is possible to provide a backlight unit for a large display device without using a high-quality light guide plate and a high brightness point light source and realizing uniform brightness while using a smaller number of point light sources. In addition, even if the distance between the light guide plate and the point light source is short, the effect of guiding light with the light guide plate is generated the same, thereby reducing the thickness of the display device.

In addition, there is an effect that can provide a high-quality illumination lamp for irradiating light of uniform brightness over a wide area by uniformly diffused emission of the point light source through the light guide plate.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention.

101: point light source 102: substrate
103: light guide plate 104: light source input unit
105: upper internal reflection surface 106: conical stopper
107: light emitting means 108: shading pattern
109: light guide plate upper surface
201: point light source 202: substrate
203: light guide plate 204: light source input unit
205: upper internal reflection surface 206: conical stopper
207: light emitting means 208: light shielding pattern
209: light guide plate upper surface
301: point light source 302: substrate
303: light guide plate 304: light source input unit
306: diffraction grating
307: light emitting means 308: light shielding pattern
309: light guide plate upper surface

Claims (19)

Point light source for irradiating light with the LCD panel;
An optical guide plate of a translucent material formed between the LCD panel and the point light source; and
And light emitting means and light blocking patterns formed on at least some of the upper and lower portions of the light guide plate.
The optical guide plate includes a light source input unit, an upper internal reflection surface, an upper surface of the optical guide plate, and a plug.
The light source input unit is formed under the light guide plate so that light directed to the upper portion of the light source input unit is refracted to the upper internal reflection surface, and light directed toward the side of the light source input unit is refracted to the upper surface of the light guide plate. In the light guide plate to generate total internal reflection,
The plug is formed of a light transmissive material on the upper internal reflection surface, the surface of the light emitting backlight unit, characterized in that the same as the shape of the upper internal reflection surface. The method of claim 1,
The light source input unit,
Surface-emitting backlight unit, characterized in that formed to be recessed in the lower portion of the light guide plate. The method of claim 1,
The upper internal total reflection surface,
Is formed to concave in the shape of a cone on the upper portion of the light guide plate,
And a light refracted by the light source input unit to reflect the light guide plate upper surface. The method of claim 3,
The cone of the upper internal reflection surface is a surface-emitting backlight unit, characterized in that the vertex angle is between 80 degrees and 100 degrees. The method of claim 1,
Wherein the stopper
Surface-emitting backlight unit, characterized in that the conical shape. The method according to any one of claims 1 to 5,
The upper surface of the light source input unit is a surface light emitting unit, characterized in that the spherical or curved surface to reduce the divergence angle of the light emitted from the point light source. The method of claim 1,
The light emitting means,
A surface emitting backlight unit comprising at least one of white scattering paint, colored scattering paint, phosphor, quantum dot phosphor, and surface irregularities. In the light guide plate,
Cone-shaped first grooves formed on the first surface of the optical guide plate; And
And a second groove formed at a position corresponding to the first groove at a second surface opposite to the first surface.
The second recess has a bottom surface of an area smaller than an opening in the second surface,
The bottom surface of the said 2nd groove is a curved guide surface which convex toward the said 2nd surface direction. 9. The method of claim 8,
And the opening of the second groove has a smaller area than the opening of the first groove. delete 10. The method according to claim 8 or 9,
And a stopper disposed in the first recess. In the surface emitting backlight unit,
Point light source;
An optical guide plate disposed on one side of the point light source;
At least one light blocking pattern formed on the first surface of the light guide plate; And
At least one light emitting means formed on the second surface of the light guide plate;
The optical guide plate,
A first groove having a cone shape formed on the first surface;
A second groove formed at a position corresponding to the first groove on the second surface and having a bottom surface of an area smaller than an opening in the second surface; And
And a stopper disposed in the first groove. The method of claim 12,
And the opening of the second recess has a smaller area than the opening of the first recess. The method of claim 13,
The bottom surface of the second recess is a surface light emitting unit, characterized in that the curved surface convex in the second surface direction. In the surface emitting backlight unit,
Point light source;
An optical guide plate disposed on one side of the point light source;
At least one light blocking pattern formed on the first surface of the light guide plate; And
At least one light emitting means formed on the second surface of the light guide plate;
The optical guide plate,
A diffraction grating formed on the first surface;
And a second groove formed at a position corresponding to the diffraction grating on the second surface, the second groove having a bottom surface of an area smaller than the opening on the second surface. 16. The method of claim 15,
The bottom surface of the second recess is a surface light emitting unit, characterized in that the curved surface convex in the second surface direction. 16. The method of claim 15,
The light emitting means,
A surface emitting backlight unit comprising at least one of white scattering paint, colored scattering paint, phosphor, quantum dot phosphor, and surface irregularities. 16. The method of claim 15,
The diffraction grating,
Surface-emitting backlight unit, characterized in that the concentric circular or oval shape. 16. The method of claim 15,
And the diffraction grating is a reflective diffraction grating.

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