JP3092336U - Surface emitting device - Google Patents

Abstract

(57) [Problem] To provide a direct type surface emitting device excellent in high luminance and uniformity. A surface light emitting device in which a diffusion sheet (2) and a light diffusion plate (3) are arranged above a plurality of linear or curved light sources (1) and a reflection plate (4) is arranged below a light source (1) in a lamp house (5). The thickness of the light diffusing plate 3 is gradually increased from a portion where the luminance or light intensity of the light applied to the light diffusing plate 3 is low to a portion where the light intensity is high, or the luminance of the light applied to the light diffusing plate 3 is increased. Alternatively, a surface light emitting device for a liquid crystal panel 6, wherein a light diffusion plate 3 whose thickness distribution is adjusted so as to become thinner gradually from a portion having a high light intensity to a portion having a low light intensity is used.

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

  The present invention is applicable to LCD monitors, LCD TVs, laptop computers, word processors, and mobile phones. Related to surface emitting devices that can be used for liquid crystal backlights of electronic devices, illuminated lighting, etc. is there.

[0002]

[Prior art]

  Recently, colorization of liquid crystal displays such as LCD TVs and personal computers has advanced, and Higher brightness is required for the surface emitting device used for the backlight of the color liquid crystal Came to be. Therefore, in order to increase the brightness of the surface emitting device, A direct type is often used in which a light diffusing plate is placed on one side and surface emission is performed from the front of the diffusing plate. It FIG. 2 shows a general structure of a direct type surface light emitting device. Direct type surface emitting The device has a function of a backlight of the liquid crystal panel 6, and includes a cold cathode tube and a hot cathode. It is composed of a linear light source 1 such as a tube, a diffusion sheet 2, a light diffusion plate 3 and a reflection plate 4. , These are attached to the lamp house 5. Generally, the planar light emission of the above structure In the device, the portion of the light diffusing plate 3 directly above the light source 1 emits abnormal light, resulting in uneven brightness. There is a problem that ends up. Therefore, as shown in FIG. 3, it faces the light source 1 of the light diffusion plate 3. Ink dots 7 formed with printing ink are formed in stripes on the part, and the liquid crystal panel Suppresses the brightness of the high-luminance part of the light radiated to the rule 6 and eliminates the uneven brightness. There is.

[0003]

[Problems to be solved by the device]

  However, according to the conventional method, among the light amount distributions radiated from the linear light source 1 to the light diffusion plate 3, , A high-brightness area, that is, a section directly above the linear light source, 7 or a surface emitting device in which a print ink pattern in a stripe shape is formed at high density To reduce overall brightness unevenness, the overall brightness will be low and the light utilization efficiency There is a problem that is low.   Furthermore, the printing ink dots 7 are the spectra of the light emitted from the linear light source 1. Among them, since it has the property of absorbing light of a specific wavelength, the surface emitting device may have There is a problem that unevenness occurs.

[0004]   The present invention solves the above problems and achieves high brightness without uneven brightness and chromaticity. It is an object of the present invention to provide a direct type surface emitting device with high efficiency.

[0005]

[Means for Solving the Problems]

  In order to achieve the above-mentioned object, in the present invention, a surface on which a reflection plate is arranged below a light source. In the light emitting device, the thickness distribution is adjusted so that the surface light emitting device has a uniform luminance distribution. The light diffusing plate was provided on the surface facing the light source.

[0006]   Specifically, the brightness or light intensity of the light emitted to the light diffusing plate is increased from the low part to the high part. The thickness of the light diffusing plate is gradually increased toward the dark part. Or light diffusion The brightness or intensity of the light radiated to the plate gradually increases from the high intensity part to the low intensity part. It was decided to use a light diffusion plate whose thickness was adjusted to be thin.   Especially, a light diffusing plate adjusted so that the thickness of the light diffusing plate becomes thicker right above the light source. I decided to use it.   Further, the characteristics of the light diffusing plate used are the total light transmittance (JIS   K7105) is 40 to 70% and the thickness is 1 to 4 mm. And That is, in the surface emitting device of the present invention, the light diffusing plate is disposed above the plurality of light sources. A surface emitting device used as a backlight of a liquid crystal display device in which a reflector is arranged below the light source. In this case, the thickness distribution was adjusted so that the brightness distribution of the surface emitting device was uniform. It is characterized by using a light diffusion plate.   In addition, the surface emitting device of the present invention is designed to emit light above a plurality of linear or curved light sources. A backlight for a liquid crystal display device, in which a diffusion plate is arranged and a reflection plate is arranged below the light source. Brightness of the light emitted from the light source to the light diffuser in the surface emitting device Or, as the light intensity gradually increases from the lower part to the higher part, Or from the part where the brightness or light intensity of the light shining on the light diffuser is high to the part where it is low. It is recommended to use the light diffusing plate whose thickness distribution has been adjusted so that it becomes thinner gradually. Characterize.   Further, the surface emitting device of the present invention is arranged above a plurality of linear or curved light sources. A back of a liquid crystal display device in which a light diffusion plate is arranged and a reflection plate is arranged below the light source. In the surface emitting device used for the light, the thickness of the light diffusion plate is thicker right above the light source. It is characterized by using a light diffusing plate adjusted so that   Furthermore, in the above, the total light transmittance (JIS K7105) of the light diffusion plate is It is characterized by being 40 to 70% and having a thickness of 1 to 4 mm.

[0007]

[Embodiment of device]

  Since the surface emitting device of the present invention is configured as described above, the following effects can be obtained.

[0008]   The light incident on the light diffuser is repeatedly reflected, diffused and scattered inside the light diffuser. To proceed. Part of the light is reflected to the light source side, and part of it changes direction inside the light diffusion plate. The liquid crystal panel is illuminated by being emitted from the light diffusion plate while being diffused to the left, right, front and back. Light here If the diffuser plate is thick, there are many opportunities for reflection, diffusion, and scattering that occur inside the light diffuser plate. Therefore, the amount of light that goes straight to the liquid crystal panel side decreases. Ie the thickness just above the light source If a thick diffuser plate is arranged, the amount of light emitted from directly above the light source is reduced. What is this On the contrary, when the light diffusion plate is thin, there is less chance of reflection, diffusion and scattering occurring inside the light diffusion plate. The amount of light that goes straight through the light diffuser plate increases, and the light emitted from directly above the light source The amount of will increase.   A direct type surface light emitting device having excellent brightness uniformity by applying the above-described principle of operation. (LCD backlight) can be manufactured. In other words, the thickness is Measure the brightness or light intensity distribution when a single light diffusion plate is placed, and use the results as the basis. In addition, the thickness of the light diffusion plate in the portion where the brightness or the light intensity is high is partially increased. There Is a skylight by partially thinning the thickness of the light diffusion plate in the area with low brightness and light intensity. It is possible to obtain a direct type surface light emitting device having a uniform luminance distribution.   Generally, in a direct type surface emitting device, the brightness or the light intensity is higher as it is right above the light source. Tends to become. Therefore, increase the thickness of the light diffuser located directly above the light source. As a result, a direct type surface light emitting device having a uniform luminance distribution or light intensity distribution can be obtained.   The edge portion of the surface emitting device tends to have lower brightness than the center portion. Inventor By applying the method, it is possible to improve the nonuniformity of the brightness.   Since the method of the present invention does not use printing ink, it does not absorb light, resulting in uneven color and chromaticity. Another feature is that there is no unevenness.

[0009]

【Example】

  Hereinafter, the present invention will be described in more detail with reference to the drawings.   FIG. 1 is a sectional view showing an embodiment of a direct type surface emitting device according to the present invention, and FIG. It is a top view which shows the thickness distribution of a board.   The light diffusion plate 3 has a thickness distribution as shown in FIGS. 8 in FIG. Indicates a thin portion of the light diffusing plate 3, and 9 indicates a thick portion of the light diffusing plate. Between 8 and 9, the thickness changes smoothly.   These thickness distributions are based on the arrangement of the number of light sources, the distance between the light sources and the reflector, and the distance between the light sources and the light diffuser. It is optimized according to the distance. In FIG. 1, 2 is a diffusion sheet, 3 is a light diffusion plate, and 4 is A reflection sheet, 5 is a lamp house, and 6 is a liquid crystal panel. As the light source 1, as shown in FIG. 2, a plurality of linear cathode ray tube light sources are arranged. . Also, one or more cathode ray tubes bent in a U shape or a W shape may be used. Yes.   The light diffusing plate of the present invention may be arranged in one or several layers depending on the nature of the light source. You can

[0010]   The light diffusing plate 3 diffuses the light emitted from the light source 1 and emits it to the upper surface as described above. It has a function to make it. Its material is a milky white acrylic plate or polyethylene tere Phthalate resin, polycarbonate resin, polystyrene resin, methyl methacrylate Resin plates such as resin can be used. Generally, air and inorganic materials are included in the synthetic resin. By blending materials or resin beads with different refractive indices, light scattering, reflection, and bending A foldable composite material is used.   As a method of obtaining the light diffusion plate having the thickness distribution of the present invention using the above materials, Machining methods such as grinding, grinding, and polishing, injection molding methods using dies, compression molding methods, vacuum forming methods There are various plastic molding methods such as the molding method.

[0011]   If necessary, a diffusion sheet 2 may be provided on the surface of the light diffusion plate 3 facing the light source 1. You can The diffusion sheet 2 is a UV-curable accompaniment containing resin beads in a polyester film. It is a 100-300 micron thick film that is uniformly coated with ril resin. It has a function of compensating for light diffusivity and is arranged as necessary.   The reflector 5 may be arranged below the light source 1 (see FIGS. 1, 2, and 3). a reflector Reference numeral 5 reflects the downward irradiation light from the light source 1 to the light diffusion plate 3 side. So Polystyrene resin, polycarbonate resin, acrylonitrile A resin plate made of butadiene styrene resin, etc., or white ink was applied to the surface Aluminum plates and aluminum foil are available. Made of polyethylene terephthalate resin Sheet-like resin with an air-foaming layer in the resin has high light diffusion and reflectivity, resulting in less loss. It is a preferable material because it is scarce.

[0012]   As a concrete configuration of the present invention, there is one shown in FIG. 5 in addition to FIG. That is, FIG. (a) is an example in which the thick part of the light diffusion plate is arranged in the direction facing the light source. . In addition, in FIG. 5B, the transparent plate 10 is further arranged in the thickness distribution with respect to the configuration of FIG. 5A. This is an example in which the upper surface of the light diffusion plate is flattened. Further, FIG. 5C shows a light diffusion plate. This is a structure in which two sheets of 3 and 3'are stacked. FIG. 5D shows a diffusion sheet on the upper surface of the light diffusion plate. 2 is a configuration in which the sheet 2, the prism sheet 11, and the polarization separation sheet 12 are arranged. prism The surface of the sheet 11 facing the light diffusion plate 3 is smooth, and a large number of triangles or It has a prismatic part such as a waveform, and increases the light traveling in the direction perpendicular to the smooth surface. A configuration in which the amount of light emitted from the front surface of the light diffusion plate 2 is increased to improve the front brightness. Is. That is, the light is incident on the smooth surface of the prism sheet 11 at an angle other than vertical. The light is refracted on the smooth surface and then refracted again on the slope of the prism part. The light is emitted at an angle close to perpendicular to the diffuser plate 3. As the material of the prism sheet 11, , Acrylic resin, polycarbonate, and polyester carbonate resin. Priz Two musheets can be arranged as needed. The polarization separation sheet 12 , Which is composed of a transparent multilayer film, transmits light having a predetermined polarization, It reflects the polarized light component in the direction perpendicular to, and consequently improves the transmittance of the liquid crystal panel and This is a sheet that has the function of improving the brightness of the display. When using this sheet, polarized light The light reflected by the separation sheet 12 travels to the light source side again, and there is a lamp house. Or, it is reflected by the reflection plate and is incident on the light diffusion plate again. That is, the light emitted from the light source is Since the light passes through the light diffusion plate twice, it is possible to obtain planar illumination light with a wide viewing angle and high brightness uniformity. It has a characteristic that it is easy to be damaged.

[0013]   As another specific configuration, there is a configuration shown in FIG. In FIG. 6 (A), 8 is reflection The reflector is a plate, and has a shape that surrounds the light source 1, that is, a V shape. As well FIG. 6B shows a structure in which a V-shaped reflection plate 8 is provided and two light diffusion plates 3 and 3'are arranged. Is. FIG. 6C shows a nucleic acid sheet 2, a prism sheet 11, and a prism sheet 11 above the light diffusion plate 3. This is a configuration in which the polarization separation sheet 12 is arranged. To make this V-shaped reflector This allows the light that spreads from the light source to the left and right to be reflected upward efficiently, increasing the light utilization efficiency. It Furthermore, there is an advantage that the brightness directly above the light source is reduced and the brightness distribution becomes more uniform. .

[0014]   On the other hand, in order to obtain the direct type surface light emitting device of the present invention, the optical characteristics of the light diffusing plate 3 are appropriate. Need to be converted. That is, the material that can be used as the light diffusion plate has sufficient light diffusion property. is necessary. Specifically, the total light transmittance, which is a measure of light diffusivity, is measured according to JIS K7. 105-35% of the material used in the measurement method specified in 105, and the thickness is 1 m. It is necessary to make it m or more. Here, the total light transmittance is the light the smaller the value. It shows that the diffusivity is large. Material with total light transmittance greater than 70% was used In this case, although the brightness uniformity of the LCD panel is good, the viewing angle characteristics may vary depending on the location. There is a problem that they are different. Increase the thickness of the light diffuser to improve this However, it is not practical because the material cost becomes high and the weight increases. On the other hand, when a material having a total light transmittance of less than 35% is used, with regard to the uniformity of brightness, Although there is no problem, the absolute value of the brightness becomes small, and it is difficult to obtain a bright display device.   The proper thickness of the light diffusion plate is 1 to 4 mm. By choosing the right material It is possible to develop a light diffuser that is thinner than 1 mm. But the lighting of the surface emitting device At times, the temperature may rise, and the creep phenomenon may occur in the light diffusion plate material, causing deformation. Less preferred. On the other hand, it is possible to use a light diffusion plate thicker than 4 mm, This leads to an increase in weight of the liquid crystal display device and an increase in material cost, which is not a preferable design.

[0015]   Next, a specific design of the light diffusion plate 3 will be described with reference to FIG. Figure 7 shows the thickness of the light diffusion plate It is a detailed view of distribution. As a material for the light diffusion plate, the total light transmittance is JIS K7105. Direct type with 50% acrylic material containing diffusing material A surface emitting device was prototyped. Inside the cold cathode tube, a φ2 mm cold cathode tube is used as the light source 1. The distance from the core to the reflector is 4 mm, and the distance from the center of the cold cathode tube to the light diffuser is 7 m. m. Eight cold-cathode tubes were used and the distance between the cold-cathode tubes was 35 mm. A backlight for an inch LCD panel was constructed.   Regarding the thickness of the light diffusion plate, the minimum thickness was 1.5 mm and the maximum thickness was 2 mm. In Figure 7 Where x = 0 mm and 35 mm are directly above the light source, and x = 17.5 mm Is the midpoint between the light sources. Prior to designing, a light diffuser with a uniform thickness distribution (thickness 1 Brightness was measured by arranging (0.8 mm). Based on this measurement result, Determine the cloth. That is, increase the thickness of the high brightness part and the thickness of the low brightness part. make it thin. A method for continuously obtaining the thickness of the light diffusion plate based on the obtained brightness data and Then, in this embodiment, fitting using a special function as shown in FIG. 7 was performed. . That is, the relationship between the thickness T (mm) and x (mm) is         T = To + a / [1 + exp {-(X-Xo) / b}] here       At x = 0 to 17.5 mm           a = 0.5014           b = -1.3054           Xo = 8.1285           To = 1.5       At x = 17.5 to 35 mm           a = 0.5014           b = 1.3054           Xo = 26.8715           To = 1.5   Although detailed description is omitted for the region of x = 35 mm or more, the position of the light source is The thickness distribution has a repeat corresponding to the position. That is, the thickness of the light diffusion plate 3 is , Thickest directly above the light source, thinnest between light sources. Meanwhile, the thickness is smooth Changed to.

[0016]   FIG. 8 shows the measurement results of the luminance distribution of the direct type surface light emitting device thus obtained. It FIG. 8 (a) is a luminance distribution when the light diffusion plate of the above design is used, and FIG. 8 (b) is the thickness. As a result of using a light diffusion plate having a constant length of 1.8 mm, FIG. This is the result when using a hood. Direct type with higher brightness and better brightness uniformity than the conventional direct type surface emitting device (c) A surface emitting device was obtained. In the surface emitting device of the present invention, the light diffusion plate does not absorb light. , There was no chromaticity change seen in the conventional ink dot system.

[0017]

[Effect of device]

  Since this invention has the above-mentioned configuration and operation, the following effects can be obtained. That is, the thickness of the portion of the light diffusing plate where the brightness of the light is low is reduced to reduce the brightness. The thickness of the high-brightness part of the light emitted to the light diffusion plate By suppressing the brightness by increasing the thickness of the A direct type surface emitting device with high brightness of the light device and high light utilization efficiency was obtained. Be done. Also, there is no chromaticity change found in the conventional ink dot system.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a direct type surface light emitting device according to the present invention.

FIG. 2 is a perspective view showing an embodiment of a direct type surface light emitting device according to the present invention.

FIG. 3 is a cross-sectional view showing an example of a conventional direct type surface light emitting device.

FIG. 4 is a plan view showing an embodiment of a light diffusion plate according to the present invention.

FIG. 5 is a sectional view showing an embodiment of a direct type surface emitting device according to the present invention.

FIG. 6 is a sectional view showing an embodiment of a direct type surface light emitting device according to the present invention.

FIG. 7 is a diagram showing a thickness distribution of a light diffusion plate according to the present invention.

FIG. 8 is a diagram showing a luminance distribution of a direct type surface emitting device according to the present invention.

[Explanation of symbols]

1: Light source 2: Diffusion sheet 3, 3 ': Light diffusion plate 4: Reflector 5: Lamphouse 6: LCD panel 7: Ink dots 8: Area where the light diffusion plate is thin 9: Area where the light diffusion plate is thick 10: transparent plate 11: Prism sheet 12: Polarization separation sheet

Claims (4)

[Scope of utility model registration request] 1. A light diffusion plate is arranged above a plurality of light sources,
In a surface emitting device used as a backlight of a liquid crystal display device in which a reflecting plate is arranged below the light source, a light diffusing plate whose thickness distribution is adjusted so that the luminance distribution of the surface emitting device is uniform is used. A surface emitting device characterized by the above. 2. A surface emitting device used for a backlight of a liquid crystal display device, wherein a light diffusion plate is arranged above a plurality of linear or curved light sources, and a reflection plate is arranged below the light sources. The brightness or intensity of the light emitted to the light diffuser plate gradually increases from the low part to the high part, or from the part where the brightness or light intensity of the light emitted to the light diffuser plate is high to the low part. A surface emitting device using the light diffusing plate whose thickness distribution is adjusted so as to become gradually thinner. 3. A surface emitting device used for a backlight of a liquid crystal display device, wherein a light diffusion plate is arranged above a plurality of linear or curved light sources, and a reflection plate is arranged below the light sources. A surface emitting device comprising a light diffusing plate adjusted such that the thickness of the diffusing plate becomes thicker right above the light source. 4. The total light transmittance (JISK7105) of the light diffusion plate according to claim 1, which is 40 to 40.
A surface emitting device having a thickness of 70% and a thickness of 1 to 4 mm.