JP4852695B2 - Liquid crystal display and backlight unit - Google Patents

Description

  The present invention relates to a liquid crystal display using light from a light source as a backlight and a backlight unit used in the liquid crystal display. In particular, the present invention relates to a large liquid crystal display having a screen diagonal size of 30 inches or more and a backlight unit thereof.

  The structure of a conventional liquid crystal display is shown in FIGS. Each liquid crystal display has a structure in which a backlight unit as a light emitting unit is installed on the back surface of the liquid crystal panel 10. More specifically, FIG. 1 shows a structure that is often used for small and medium displays of mobile devices such as mobile phones and notebook PCs. A fluorescent lamp as a light source is arranged on the side of the backlight unit, and a light guide plate is used to guide light toward the liquid crystal panel. With this structure, the display can be thinned. Moreover, since the light introduced into the liquid crystal panel can be made uniform by arranging the light source on the side, a liquid crystal display with uniform luminance can be easily realized.

  FIG. 2 shows a structure used for a liquid crystal display as a large-sized flat TV. With the increase in size, it is necessary to increase the amount of emitted light, so a large number of fluorescent lamps are used. In addition, since the use of a light guide plate becomes impossible as the light emitting surface increases, a direct type structure in which a lamp is arranged on the back surface of the liquid crystal panel is adopted. The reason why the light guide plate cannot be used is that since the screen is enlarged, it is necessary to enlarge the light guide plate, it becomes thick and heavy, and it is difficult to manufacture a large light guide plate manufactured by resin injection molding. Since the fluorescent lamp is disposed on the back surface (directly below) of the liquid crystal panel, brightness unevenness occurs such that the light above the lamp is bright and the space between the lamps is dark. For this reason, a diffuser plate and a diffuser sheet are usually placed between the light source and the liquid crystal panel, and polarized light reflection is performed to suppress the absorption of polarized waves by the prism sheet and polarizer for the purpose of collecting the light that has passed through the diffuser plate. A sheet is placed. These optical components are arranged away from the light source, that is, near the liquid crystal panel.

  Japanese Patent No. 3373427 (Patent Document 1) proposes a backlight unit structure using a plurality of light guide plates. It is an effective method for efficiently and uniformly irradiating a liquid crystal panel surface with a large amount of light using multiple light sources. It is a mobile liquid crystal display for use outdoors where strong external light is used, and an in-vehicle small and medium display. It seems to be the best. However, even if this method is used, since a plurality of light guide plates are used for large-sized liquid crystal television applications, the weight is not increased.

  As described above, even in a liquid crystal display, the structure of a backlight unit that is a light source is greatly different between a small-sized display used in a mobile device and a large display for television.

  Liquid crystal displays that are in the spotlight for large flat-screen TV applications are becoming lighter and thinner than conventional CRT-type TVs, and are thus dominating the large TV market. In addition, since the liquid crystal display is so low in power consumption that it is used in mobile devices, it is highly expected as a device that can avoid the energy crisis facing humanity. However, the large liquid crystal display is lighter and thinner. However, the increase in the amount of light accompanying the increase in size requires a lot of fluorescent lamps, so there is no difference in power consumption compared to a CRT of the same size. ing. Therefore, development of a liquid crystal display that consumes much less power than CRT is inevitable.

  By the way, in general, a fluorescent lamp is mainly used as a backlight unit light source of a liquid crystal display, and the liquid crystal panel is irradiated with white light emitted from the fluorescent lamp. In addition, the fluorescent lamp is obtained by applying fluorescence to the surface of a mercury lamp (more precisely, a low-pressure mercury vapor discharge lamp). Mercury lamps are classified into a hot cathode type that emits light by thermionic emission and a cold cathode type that emits light by secondary electron emission.

  Conventionally, liquid crystal displays that have been commercialized as small and medium displays such as mobile phones and notebook PCs are mostly used in mobile applications, and the challenge is to reduce the thickness of the panel as much as possible. A cold cathode mercury lamp (referred to as a cold cathode lamp) using secondary electrons is used as a backlight of a liquid crystal display whose lamp tube diameter must be increased.

  On the other hand, as described above, liquid crystal displays that have been commercialized for use in large-sized flat TVs have become widespread to replace CRT TVs. However, it has become necessary to increase the amount of light emission with the increase in size. Therefore, as a countermeasure, cold cathode lamps have been lengthened and the number of lamps has been increased. For example, 10 to 20 cold cathode lamps having a length of 70 cm or more are used for the backlight of a liquid crystal display of 32 inches or more. As a result, power consumption has increased and it cannot be said that it is a low power consumption device that is a strength. Further, not only the number of cold cathode lamps is increased, but an inverter is required for each cold cathode lamp, so that an increase in cost has been a problem. Note that if the cold cathode lamp is made thicker and the light emission amount per lamp is increased, the luminous efficiency is inversely proportional to the tube diameter, and the power consumption of the liquid crystal display is increased. It was not effective to use 10 or more and it was necessary to use 10 or more thin cold cathode lamps having a diameter of 2 to 3 mm.

  The reason why many long cold cathode lamps are used is to suppress the occurrence of uneven brightness in the liquid crystal panel and to prevent heat generation as described above. In the case of the direct type structure shown in FIG. 2, when the number is small, a dark portion is generated between the lamps, and the fluorescence appears remarkably when viewed from an oblique direction. For this reason, attempts have been made to reduce the number of reflectors by devising the shape of the reflector or by devising the diffuser, but it has not been put into practical use. Furthermore, in order to obtain the required light quantity while reducing the number of lamps, it is necessary to increase the current supplied to the lamp. However, if the current is increased, the heat generation of the lamp increases and the ambient temperature in the backlight unit becomes too high. There is a problem that the luminous efficiency exceeds the optimum luminous efficiency temperature of the cold cathode lamp and the luminous efficiency is remarkably lowered. In order to suppress heat generation, there is an attempt to introduce and cool outside air into the unit's internal space, but dust is also introduced into the unit at the same time as the outside air, resulting in a problem that the inside of the unit becomes dirty, and an outside air introduction component is required. As a result, the cost increases. As described above, there has not yet been found a method for realizing low power consumption of a large-sized liquid crystal display with the current structure.

  By the way, conventionally, as a fluorescent lamp for a backlight, it has been proposed to use a fluorescent lamp (hot cathode type lamp) using a cathode tube that emits light by thermionic emission instead of a cold cathode type lamp. A hot cathode lamp can obtain luminous efficiency about twice as high as that of a cold cathode lamp, and even if it is made thick, the luminous efficiency does not decrease. It is known that the amount of light emitted from one lamp (total luminous flux) is 2000 lumens or more, which is about 10 times larger than that of a cold cathode lamp having a diameter of about 2 mm.

  Note that the use of a hot cathode lamp as a backlight for a liquid crystal display is disclosed in, for example, Japanese Patent Laid-Open No. 2000-187211 (Patent Document 2).

  However, the biggest problem with hot cathode lamps is that their lifetime is a fraction of that of cold cathode lamps. That is, the display is required to have a life of around 50,000 hours, and the cold cathode lamp is considered to satisfy this requirement. However, the life of a hot cathode lamp is only about 10,000 hours. Therefore, it is necessary to replace the lamp, but the current backlight unit is a direct type, and the only way to replace the lamp is to open the back side. There must be. Further, when the entire backlight unit is normally opened in a room, floating dust is mixed and the inside of the backlight unit is contaminated. Therefore, a large liquid crystal display using a backlight using a hot cathode lamp has not been realized.

Japanese Patent No. 3373427 JP 2000-187211 A

  An object of the present invention is to provide a liquid crystal display, particularly a large liquid crystal display, which can reduce power consumption, weight, and cost.

  Another object of the present invention is to provide a backlight unit for a liquid crystal display capable of making light incident on a liquid crystal panel efficiently and with low power.

  Still another object of the present invention is to provide a large liquid crystal display in which the light source can be easily replaced, and thus a lamp having a short life can be used.

  Another subject of this invention is providing the large sized liquid crystal display which can display in advance the replacement time of a light source.

  In order to solve the above problems, a backlight unit for a liquid crystal display of the present invention and a liquid crystal display using the same, the light source is disposed along at least one side of the liquid crystal panel of the liquid crystal display, and the light generated from the light source is The light is radiated to a space disposed on the back surface of the liquid crystal panel, reflected by a reflecting plate disposed at a position facing the liquid crystal panel in the space, and then light is incident from the back surface of the liquid crystal panel.

In addition, the space existing on the back surface of the liquid crystal panel and the space where the light source arranged along at least one side of the liquid crystal panel exists are partitioned by a transparent member, preferably a transparent plate having a prism function capable of controlling light. , Characterized by being independent.

  Furthermore, a temperature control function that can adjust the temperature of the space where the light source exists, that is, a heating mechanism that enables heating to an optimum temperature so that the discharge start voltage does not increase immediately before the start of lighting, and fluorescence during lighting It is characterized by having a cooling function that makes it possible to maintain the optimum light emission temperature of the lamp.

  As another aspect of the present invention, when the outer shape of the liquid crystal display is regarded as a rectangular parallelepiped, the light source is structured to be detachable in the plane including the liquid crystal panel of the display or in the direction of viewing the image. To do.

  As yet another aspect of the present invention, in order to realize low power consumption of a large-sized liquid crystal television, the backlight unit light source for the large-sized liquid crystal display is a fluorescent lamp, and more preferably, a cathode tube that emits light by thermionic emission is provided. The fluorescent lamp used is used.

  The large-sized liquid crystal display of the present invention uses a hot cathode lamp as the fluorescent lamp in a liquid crystal display using a fluorescent lamp, and has at least three of the cumulative lighting time, the cumulative number of lighting times, and the relative light emission intensity of the fluorescent lamp. It is a large liquid crystal display that has a function to display an indication of the replacement time of the fluorescent lamp based on the information, and the guide of the replacement time of the fluorescent lamp is displayed on the display screen when the display is attached. And

  The present invention makes it possible to realize a backlight unit for a large-sized liquid crystal display with low cost and low power consumption and a large-sized liquid crystal display using the backlight unit by devising the configuration of the backlight unit such as the position and type of the light source.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that these are merely examples, and only need to be in line with the gist of the present invention.

  FIG. 3 is an overview showing the large-sized liquid crystal display 100 according to the first embodiment of the present invention. The large liquid crystal display in the present invention refers to a liquid crystal display as a commercially available large flat television, and generally refers to a screen having a diagonal size of 30 inches or more. However, the present invention is not limited to this, and the present invention can be applied to a liquid crystal display having a size of 30 inches or less. FIG. 3 shows a large liquid crystal display 100 standing upright. The large liquid crystal display includes a liquid crystal panel 10 that forms a screen and a backlight unit 11 that emits light from the back surface of the liquid crystal panel 10. The backlight unit 11 includes two light source units 20 a and 20 b disposed above and below the liquid crystal panel 10.

  FIG. 4 is a cross-sectional view showing the large-sized liquid crystal display structure of the present invention more specifically and clearly. The large-sized liquid crystal display 100 includes a liquid crystal panel 10, a diffusion plate 31, and a polarizing reflection sheet 34 disposed between the liquid crystal panel 10 and the diffusion plate 31 on the front side, and from the diffusion plate 31 on the back side. It has the reflector 30 arrange | positioned at intervals spatially. In this structure, a reflection space is defined between the reflection plate 30 and the diffusion plate 31 (or the liquid crystal panel 10). Two light source parts 20a and 20b are arranged on both sides of the liquid crystal panel 10 forming the screen (up and down in FIG. 3, left and right in FIG. 4). In the illustrated example, the light source parts 20a and 20b are respectively A fluorescent lamp is arranged as a light source. In addition, transparent prisms 35a and 35b are disposed between the light source units 20a and 20b and the reflection space, respectively. These transparent prisms 35a and 35b serve as partition walls that partition the reflection space, and from the light source units 20a and 20b. It serves as a guide that guides the light to the space for reflection.

  In this configuration, the light emitted from the light source units 20a and 20b is transmitted through the transparent prisms 35a and 35b constituting the partition walls and introduced into the space on the back surface of the liquid crystal panel. The light introduced into the reflection space is controlled not to be directly irradiated onto the liquid crystal panel 10 by the transparent prisms 35a and 35b, and most of the light faces the liquid crystal panel 10 through the reflection space. The light is reflected by the reflecting plate 30 installed at the position. The reflected light is applied to the opposed liquid crystal panel 10.

  The position of the light source unit is preferably arranged along at least one side of the liquid crystal panel. When the light source is reduced in the emission of mercury excited by discharge, such as a cold cathode lamp or a hot cathode lamp, if the lamp is placed vertically, the mercury is heavy and uneven emission occurs at the bottom and top of the lamp. Therefore, it is more preferable to arrange the lamps on at least one of the upper and lower sides of the panel so that the lamps are generally horizontal. If the lamps are arranged side by side on the back of the liquid crystal panel as in the current situation, the light directly emitted from the fluorescent light causes uneven brightness on the panel, and many optical members are required to correct it, causing light loss. This is not preferable because the cost increases.

  With reference to FIG. 5, the structure of the light source unit 20 (subscript omitted) will be described more specifically. The illustrated light source unit 20 includes a light source 21 and a lamp reflector 22. As is apparent from the drawing, the light source 21 is disposed in a space defined by the lamp reflector 22 of the light source unit 20, and the space of the light source unit 20 is partitioned by a transparent prism 35. The illustrated lamp reflector 22 has a cross-sectional shape that is a combination of two parabolic shapes.

  In the illustrated configuration, the light emitted from the light source 21 travels in all directions. Therefore, in order to increase the light utilization efficiency, it is necessary to send as much light as possible to the space on the back surface of the liquid crystal panel 10.

  For this reason, as shown in FIG. 5, it is preferable that the light incident surface and the light exit surface of the transparent prism 35 each have a prism shape, that is, a zigzag chevron surface. It is also preferable to provide a microlens array shape instead of the prism shape. The surface structure is preferably as fine as possible, but usually the height between peaks is preferably 1 mm to 1 μm, more preferably 0.5 mm to 10 μm. The material of the transparent prism 35 may be anything as long as it is a transparent material, and is preferably a transparent plastic material in consideration of processability and cost. Moreover, in order to suppress surface reflection at the time of incidence, a surface antireflection coating may be performed. Note that the transparent prism 35 used depends on the optical design and is not limited to the shape shown in FIG. Further, when the transparent prism 35 is incorporated, or when a polarizing element such as a polarizing reflection sheet is incorporated separately from the transparent prism 35, the polarized light in the backlight space is concentrated, and thus reaches the liquid crystal panel. This is preferable because absorption at the polarizing plate passing immediately before decreases.

  4, 6, and 7, an example of a reflection plate 30 that is installed facing the liquid crystal panel 10 is shown. The reflection plate 30 defines a reflection space on the back surface of the liquid crystal panel. It functions as a wall surface. The reflecting plate 30 shown in FIG. 4 has a flat reflecting surface, and reflects the light radiated from the light source parts 20a, 20b on the left and right sides of FIG. 4 to the reflecting space toward the liquid crystal panel 10. Although the illustrated reflecting plate 30 is constituted by a flat plate, it may be constituted by a curved surface having a curvature.

  The liquid crystal display 300 shown in FIG. 6 includes light source units 20 a and 20 b on the upper and lower sides of the liquid crystal panel 10, and the reflector 10 disposed on the back surface of the liquid crystal panel 10. The illustrated reflector 10 has a peripheral portion shaped so as to be tapered from the liquid crystal panel 10 and a flat portion located at the center of the back surface of the liquid crystal panel 10. Furthermore, the light source units 20 a and 20 b arranged above and below are detachably attached from light source outlets 23 a and 23 b provided on the front side of the liquid crystal panel 10.

  Further, the reflection plate 30 of the liquid crystal display 200 shown in FIG. 7 has an inner surface that is inclined from the light source portion provided above and below to the center portion, and is not provided with a flat portion at the center portion. It is different from the plate 30. In FIG. 7, the light source units arranged above and below include spare light sources 25 a and 25 b that can be replaced with the working light sources 21 a and 21 b in addition to the working light sources 21 a and 21 b in use. The structure of these light source parts will be described later.

  As the reflecting plate 10 shown in FIGS. 4, 6, and 7, it is preferable to use a metal reflecting surface from the viewpoint of ease of optical design. Is preferably a white diffuse reflector. In this case, aluminum or silver is usually used as the metal reflector, but silver having high reflectivity is preferable. These metals may be used as the material of the reflector itself, but from the viewpoint of cost reduction and weight reduction, they were formed on the surface of a lightweight and easy-to-process plastic plate by vapor deposition or sputtering. Those are preferred.

  On the other hand, in the case of a white reflecting plate, a light reflectance reflecting plate coated with an inorganic compound such as titanium oxide or barium oxide is preferable. It is also preferable to use a film-laminated reflector utilizing a difference in refractive index or a reflector obtained by blending and dispersing materials having different refractive indices. Furthermore, in order to efficiently guide light from the side to the central portion, it is also preferable to install transparent sheets at narrow intervals via an air layer in front of the reflector.

  As described above, various shapes can be adopted as the shape of the reflector 30 depending on the optical design. For example, various shapes such as a flat plate and a curved plate as shown in FIG. 4 or a shape shown in FIG. 6 and FIG. 7 can be taken. Although the fine shape of the surface of the reflector 30 also depends on the optical design, it is preferable to perform fine processing in order to uniformly irradiate the liquid crystal panel with the reflected light.

  When the light reflected by the reflecting plate 30 is introduced into the liquid crystal panel 10, it is incident on the liquid crystal panel 10 at a low incident angle, so that it is optically reflected on the surface of the liquid crystal panel 10, and a lot of light is reflected again. Return to space. Therefore, usually, means for efficiently transmitting light with a low incident angle is taken. As a means for efficiently transmitting light having a low incident angle, one or more prism sheets are inserted so as to protrude toward the space on the back of the liquid crystal panel 10 immediately before the light enters the liquid crystal panel 10. Is preferred. By inserting the prism sheet, it is possible to efficiently send light with a low incident angle to the liquid crystal panel 10 side. Further, in order to make the luminance uniform, a diffusion plate or a diffusion sheet may be used simultaneously with the prism sheet. Since a polarizing sheet is installed in the liquid crystal panel 10 because of the structure, about half of the light is absorbed by the polarizing sheet. Therefore, a polarizing reflection sheet may be installed immediately before the liquid crystal panel 10.

  FIGS. 8A and 8B show a liquid crystal display according to another embodiment of the present invention and its characteristics, respectively. The liquid crystal display shown in FIG. 8A is configured by the liquid crystal panel 10 and the backlight unit, as described above, and the backlight unit includes the reflector 30 that defines the reflection space, Two light sources 21a and 21b arranged on the left and right sides are provided. Further, the illustrated reflector 30 has a shape in which the central part of the two light sources 21a, b, that is, the central part of the liquid crystal panel 10 is projected in a triangular shape. Such a reflection plate 30 may be configured by attaching a triangular reflection plate to a reflection plate arranged at a fixed interval with respect to the liquid crystal panel 10, or a reflection plate having a triangular shape at the center. You may comprise by integrally forming.

  When the light intensity distribution in the liquid crystal display shown in FIG. 8A was simulated by the Monte Carlo method, a very uniform light intensity distribution was obtained as shown in FIG. 8B. That is, it has been found that the light intensity at the central portion of the liquid crystal panel 10 is improved by projecting the central portion of the reflector 30 toward the liquid crystal panel 10. In addition, the shape of the center part of the reflecting plate 10 may not be a triangle shape but a curved surface shape.

  Referring to FIG. 9, a liquid crystal display according to another embodiment of the present invention includes temperature adjustment mechanisms 40b and 40b on the back side of the liquid crystal panel. In the illustrated example, a heat dissipation mechanism is provided as a temperature adjustment mechanism 40b on the upper and lower sides of the light source unit rear surface 12 of the liquid crystal display, adjacent to the light source units 20a and 20b.

  The installation position, shape, and mechanism of the temperature adjusting mechanism 40b can be arbitrarily designed depending on the types of the light sources 20a and 20b, the heat generation status, and the necessity of heating. For example, when the light source units 20a and 20b are LEDs, if the light emission is continued, the temperature increases and the light emission efficiency decreases. In particular, in the case of a light source using red, blue, and green three-color LEDs, there is a problem that the color changes during use because the temperature dependency of each efficiency is different.

  On the other hand, when the light source is a fluorescent lamp, the temperature is low at the start of lighting, so the mercury concentration in the lamp tube is not sufficient, and not only a lot of energy is needed to light up, There is a problem that the color changes due to the emission of argon or neon, which is an enclosed gas, rather than the emission. Also, fluorescent lamps have a luminous efficiency optimum temperature that depends on mercury concentration, and it is important to maintain the optimum temperature in order to optimize luminous efficiency. In particular, in response to the recent reduction in the number of parts due to lower prices, the number of lamps has been reduced to increase the discharge current and maintain the amount of light emitted. However, when the discharge current is increased, the lamp generates heat. Therefore, it becomes difficult to maintain the optimum temperature.

  As shown in FIG. 9, the liquid crystal display according to the present invention enables the mounting of a temperature management system that has been difficult with the ordinary direct backlight unit shown in FIG. Specifically, when an LED is used as a light source, in order to prevent temperature rise thoroughly, measures such as installing a heat dissipation mechanism such as a heat dissipation fin or venting the light source space can be used. Allows control.

  On the other hand, when a fluorescent lamp is used as the light source, at the start of discharge, the discharge start voltage is lowered, so that the temperature is increased and the mercury concentration is increased to reduce the power consumption. During lighting, depending on the discharge current, it is usually efficient to maintain the lamp ambient temperature at 20 to 30 ° C. As a method for maintaining the optimum temperature, a heater can be installed, or simple means such as the radiating fins and ventilation described above can be used. When ventilating, it is also preferable to use air whose temperature has been adjusted by a heater or cooler before venting.

  In the conventional direct type, the lamp is placed on the entire back surface of the liquid crystal panel, so it was necessary to dissipate heat from the entire surface. However, an inverter and circuit are installed on the back surface of the backlight. It was impossible to install. In addition, the method of ventilating the backlight unit makes it difficult to design the airflow, and dust mixed in from the environment adheres to the backlight unit, causing black spots and bright spots, and dust is attached to the hot part of the lamp. It was impossible because it caused a fire.

  When the method of the present invention is used, since the lamp is localized and arranged in a part of the liquid crystal panel 10, it is possible to reduce the heating and cooling area, and the airflow design can be achieved even if ventilated. Easy and environmental dust is no problem by installing a filter. Further, since the light source section and the reflective space on the back surface of the liquid crystal panel 10 are separated, dust does not enter the back surface of the liquid crystal panel 10 and does not cause black spots or bright spots. Furthermore, since the back surface of the liquid crystal panel 10 does not reach a high temperature, the liquid crystal panel 10 can be prevented from being heated at a high temperature, and the life of the liquid crystal panel 10 can be extended. The temperature of the light sources 20a and 20b may be controlled using a temperature sensor, a heater, and a cooling fan.

  An example of the structure of the light source unit 20 when various light sources are used will be described with reference to FIGS. In addition, FIG.10, FIG.11, FIG.12 is an illustration to the last, and is not restrict | limited to this arrangement | sequence and this structure. As a light source installed in the light source unit 20, a fluorescent lamp or an LED array is preferable.

  FIG. 10 shows an example of the light source unit including the LED array 201 and the lamp reflector 22. The LED array 201 includes a red / green / three-color array lighting method, a white lighting method, and the like, but any method may be used.

However, since LED currently has low luminous efficiency (10 to 30 lm / W), it is more preferable to use a fluorescent lamp in order to reduce power consumption. As the fluorescent lamp, a cold cathode type lamp usually used for a liquid crystal display is used.

  FIG. 11 shows an example of the light source unit 20 including the cold cathode lamp 202 and the lamp reflector 22. The luminous efficiency of the cold cathode lamp 202 is 30 to 50 lm / W, which is about twice that of the LED. However, the cold cathode lamp 202 has a small diameter of 3 to 5 mm, and the total luminous flux per one is 200 lm to 400 lm. For this reason, it is necessary to use a plurality of liquid crystal displays 10. In the example of FIG. 11, an example of a one-side light source unit in which four cold cathode lamps 202 are arranged is shown, but the number may be increased or decreased as necessary. Further, in the current direct type backlight, the inverter is used one by one for each lamp because of the variation in the light quantity due to the difference in lamp, but in the method of the present invention, the light quantity due to the difference in lamp is different. Since the standard for variation can be relaxed, a plurality of lights can be turned on by a single inverter, and the cost can be greatly reduced.

  Furthermore, in order to reduce power consumption, it is possible to use a hot cathode lamp with a luminous efficiency as high as 70 to 100 lm / W. FIG. 12 shows an example of the light source unit 20 including the hot cathode lamp 203 and the lamp reflector 22. Since the hot-cathode lamp 203 is 2000 to 5000 lm, if one or two are used, the amount of light is sufficient. As described above, by using the method of the present invention, it is possible to use the hot cathode lamp 203 which has been unusable due to its large tube diameter.

  Here, referring to FIGS. 6, 7, and 13, light source units 20 a and 20 b that can exchange light sources are shown. The hot cathode lamp has a shorter life than the cold cathode lamp, and thus the lamp needs to be replaced. By adopting the method of the present invention, for example, when the liquid crystal display 10 is installed on a wall or when the back surface of the display is narrow, it is possible to save the trouble of moving and replacing the lamp.

  6 and 13 show an example in which light source units 20a and 20b are provided above and below the liquid crystal panel 10 and light source replacement outlets 23a and 23b for exchanging lamps from the front surface of the liquid crystal panel 10 are provided. . In this example, the lamp, which is the light source of the light source unit, can be replaced by opening the light source replacement outlets 23 a and 23 b provided on the front surface of the liquid crystal panel 10.

  In order to replace the lamp, in addition to the examples shown in FIGS. 6 and 13, as shown in FIG. 7, in addition to the working light sources (working lamps) 21a and 21b, a spare light source (spare lamp) 25a. , 25b can be installed in the light source sections 20a and 20b in advance, and a mechanism for rotating and replacing them at the end of the service life can be provided. As shown in FIG. 7, the rotating and exchanging mechanism includes a rotary lamp reflector 24b having a rotating shaft, two working light sources 21a and a spare light source surrounded by the curved reflector of the reflector 24b. What has the structure which installed 25a, 25b can be used. According to this mechanism, the working light sources 21a and 21b and the auxiliary light source 25a can be easily exchanged by opening the light source outlets 23a and 23b and rotating the rotary lamp reflector 24b.

  Furthermore, if the light source units 20a and 20b are cartridge type, the replacement of the light source (lamp) becomes very simple. In this case, it is preferable that the partition wall for defining the lamp space of the light sources 20a and 20b is a transparent plate. At the same time as the lamp, it is also possible to replace the partition with the space on the back of the liquid crystal panel 10. Since the partition can be replaced, for example, when the light source is a fluorescent lamp, the UV prevention prescription treated for the fluorescent lamp in order to prevent deterioration of the resin member due to the ultraviolet light can be omitted. It becomes possible to use a light extraction efficiency from the lamp that has been lowered, that is, a lamp with high luminous efficiency. Since it is expensive to replace the transparent prism, an ultraviolet prevention sheet may be installed in front of the transparent prism.

  Next, with reference to FIG. 14, one embodiment of a large-sized liquid crystal display according to the present invention will be described. FIG. 14 is an example of a configuration diagram of a lamp replacement warning display system for informing the replacement timing of the light source in the large liquid crystal display. In the present invention, particularly when a hot cathode lamp is used, the lamp life is shorter than that of a conventional liquid crystal display. Therefore, it is necessary to replace the lamp, but it is necessary to warn the lamp replacement to some extent in advance. In order to calculate the replacement time for this purpose, calculation is performed by the lamp life prediction algorithm 51 to predict the lamp life. As a result, when the lamp replacement time is near, a lamp replacement warning display 52 is displayed.

  In this embodiment, the cumulative lighting time 501 of the hot cathode lamp, the number of times the hot cathode lamp is turned on (that is, the cumulative lighting number) 502, and the hot cathode monitored by the photosensor provided in the large liquid crystal display. The lifetime of a lamp in use, for example, a hot cathode lamp, is predicted based on three pieces of information on the relative emission intensity 503 from the lamp. Based on the life expectancy, when it reaches the end of the life and about one week before the light emission intensity drops significantly, a warning to instruct lamp replacement will be displayed on the display screen when the display is turned on. ing.

  In order to perform such a lamp replacement warning display 52, this embodiment uses a microprocessor (computer) that operates according to the lamp life prediction algorithm 51, and uses a cumulative lighting time 501, a cumulative ON count 502, and a relative light emission intensity. The lamp replacement warning display 52 is displayed by processing the three pieces of information 503. That is, the liquid crystal display according to this embodiment includes a computer that performs the above-described processing and a program therefor.

  In the above-described embodiment, the case where the lamp replacement warning display 52 is displayed by calculating the three information of the cumulative lighting time 501, the cumulative ON number 502, and the relative light emission intensity 503 has been described. The lamp replacement warning display 52 may be displayed using at least one of the information 501, the cumulative ON count 502, and the relative light emission intensity 503.

  According to this embodiment, there is no fear that the hot-cathode lamp in use is suddenly cut off and the display cannot be seen while watching the display.

  Next, an embodiment of a lamp replacement warning display system configuration different from the above-described embodiment for notifying the replacement timing of the light source in the large-sized liquid crystal display according to the present invention will be described with reference to FIG. In this embodiment, first, a signal of a desired set light amount 61 on a television screen operated by a television remote controller is input to the lamp power source 62, and the hot cathode lamp 203 is caused to emit light based on the signal. The amount of light emitted from the hot cathode lamp 203 is monitored by a light amount sensor 64 provided in the large liquid crystal display, and feedback is applied to the lamp power source 62 so that the brightness of the television screen becomes the desired set light amount 61. The lamp life is predicted based on the desired set light amount 61 and the value of the current applied to the hot cathode lamp 203 by the lamp power source 62 or the voltage value applied to the electrodes at both ends of the hot cathode lamp 203. That is, the desired set light quantity 61 and the current value or voltage value of the hot cathode lamp 203 are input parameters of the lamp life prediction algorithm 51. Based on these pieces of information, the desired set light amount 61 is maintained by the amount of light emitted from the hot cathode lamp 203. At that time, if the current value or voltage value becomes higher than a certain set level, it is determined that the life of the hot cathode lamp 203 is near. Accordingly, in this embodiment, the red LED provided in the display main body blinks as an alarm instructing lamp replacement.

  Note that the lamp current value or the lamp voltage value as an input value of the lamp life prediction algorithm 51 differs depending on whether constant current control or constant voltage control is performed in the lamp power source, and constant current control is performed. If it is, the lamp voltage value is input, and if constant voltage control is being performed, the lamp current value may be input.

  According to the present embodiment, the number of input values of the lamp life prediction algorithm 51 is as small as two, and there is a feature that it can be configured with a simple circuit.

  By the way, in the embodiment described above, the case where the current value or voltage value of the hot cathode lamp 203 becomes higher than a certain set level is used as the judgment criterion of the lamp life, or the judgment criteria as follows. May be provided. That is, if it is attempted to keep the amount of light emitted from the hot cathode lamp 203 constant, the frequency of increasing the current value or the voltage value increases when the lamp life is near. If the value obtained by dividing the increased current or increased voltage by the lamp lighting time before and after the increase exceeds a certain level, it may be determined that the lamp life is near.

The present invention is not only extremely effective when applied to a large-sized liquid crystal display of 30 inches or more, but is also applicable to a small-sized liquid crystal display. Furthermore, according to the present invention, the light source unit can be replaced with a replaceable cassette, and the light source unit of the liquid crystal display can be handled as a component. In the above-described embodiments, only the case where the light source unit is arranged above and below the liquid crystal panel has been described. However, the present invention is not limited to this, and the light source unit is provided either above or below the liquid crystal panel. Depending on the size of the liquid crystal panel, it may be arranged on at least one of the left and right sides of the liquid crystal panel.

It is the schematic which shows the example of the conventional light-guide plate type liquid crystal display. It is the schematic which shows the example of the conventional direct type | mold liquid crystal display. It is a general-view figure which shows the external appearance of the large sized liquid crystal display which concerns on this invention. FIG. 4 is a side sectional view of the large liquid crystal display of the present invention shown in FIG. 3. It is a figure which shows the example of the transparent prism used for the large sized display shown by FIG. It is side surface sectional drawing which shows the other example of the large sized liquid crystal display which concerns on this invention. It is side surface sectional drawing which shows the further another example of the large sized liquid crystal display which concerns on this invention. (A) And (b) is a schematic sectional drawing which shows the other Example of the large sized display which concerns on this invention, and its characteristic diagram. It is a figure which shows an example of the back surface of the large sized liquid crystal display which concerns on this invention. It is a figure which shows the LED array which can be used for the light source part of this invention. It is a figure which shows the example of the cold cathode type lamp which can be used as a light source part of this invention. It is a figure which shows the example of the hot cathode type | mold lamp light source part which can be used as a light source part of this invention. It is a figure explaining the light source exchange part of the liquid crystal display which concerns on this invention. It is a block diagram which shows the example of a structure of the light source replacement warning display system for large sized liquid crystal displays which concerns on this invention. It is a block diagram which shows the example of a structure of the light source replacement warning display system for large sized liquid crystal displays which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal panel 11 Backlight unit 12 Liquid crystal display and backlight unit back surface 20, 20a, 20b Light source part 21, 21a, 21b Light source 22 Lamp reflector 23a, 23b Light source outlet 24b Rotary lamp reflector 25a, 25b Spare light source 201 LED array 202 Cold Cathode Lamp 203 Hot Cathode Lamp 30 Reflector 31 Diffusion Plate 32 Light Guide Plate 33 Prism Sheet 34 Polarized Reflective Sheets 35, 35 a, 35 b Transparent Prism 40 b Temperature Control Mechanism 501 Accumulated Lighting Time 502 Accumulated ON Count 503 Relative Intensity 51 Lamp life prediction algorithm 52 Lamp replacement warning display 61 Desired set light intensity 62 Lamp power supply 64 Light intensity sensor

Claims (19)

In a large liquid crystal display, a light source is disposed along at least one side of the liquid crystal panel of the liquid crystal display, and light generated from the light source is emitted to a space disposed on the back surface of the liquid crystal panel and is positioned at a position facing the liquid crystal panel in the space. After being reflected by the arranged reflector, light enters from the back surface of the liquid crystal panel, and
A space existing in the liquid crystal panel back, and the space in which the light source arranged along at least one side of the liquid crystal panel is present, the incident and exit surfaces of the light is partition by a transparent member are each prism shape, independently Backlight unit for large liquid crystal displays characterized by   2. A backlight unit for a large-sized liquid crystal display, wherein the transparent member according to claim 1 also has a prism function capable of controlling light emitted from a light source.   A backlight unit for a large-sized liquid crystal display having a temperature adjustment function capable of adjusting the temperature of a space in which the light source according to claim 1 or 2 is present.   In any one of Claims 1-3, when the external shape of a liquid crystal display is regarded as a rectangular parallelepiped, it is set as the structure which can attach or detach a light source in the surface in which the liquid crystal panel of a display is included, or the direction which looks at an image. Features a backlight unit for large LCD displays.   5. A backlight unit for a large-sized liquid crystal display, wherein the light source according to claim 1 is a fluorescent lamp.   6. A backlight unit for a large-sized liquid crystal display, wherein the light source according to claim 5 uses a fluorescent lamp using a cathode tube that emits light by thermal electron emission.   2. The backlight for a large-sized liquid crystal display according to claim 1, further comprising means for calculating a replacement time of the fluorescent lamp and displaying an indication of the replacement time of the fluorescent lamp in a liquid crystal display using a fluorescent lamp. Liquid crystal display using unit liquid crystal.   The liquid crystal display according to claim 7, wherein the standard for replacing the fluorescent lamp is displayed on a display screen when the liquid crystal display is attached.   9. The liquid crystal display according to claim 8, wherein the fluorescent lamp is a hot cathode lamp.   10. The fluorescent lamp replacement time according to claim 8, wherein the fluorescent lamp replacement time is calculated based on at least one information of a cumulative lighting time, a cumulative lighting frequency, a relative light emission intensity, a current value, and a voltage value of the fluorescent lamp. LCD. In a backlight unit used for a liquid crystal display, the liquid crystal panel is configured to define a reflection space between the light source unit disposed along at least one side of the liquid crystal panel of the liquid crystal display and the liquid crystal panel. A reflective plate disposed on the back surface at an interval, and the light from the light source unit is radiated to the reflective space between the reflective plate and the liquid crystal panel, and
Defined between the reflective space and the light source unit, the incident and exit surfaces of the light has a transparent partition wall is provided respectively prism shape, by the partition wall, said a reflection space by the light source unit The backlight unit is independent of the light source space.   12. The backlight unit according to claim 11, wherein the transparent partition wall is constituted by a transparent prism.   A backlight unit having a temperature adjustment function capable of adjusting the temperature of a space in which the light source according to claim 11 is present.   14. The backlight unit according to claim 11, wherein the light source unit includes a light source and a support mechanism that supports the light source, and the support mechanism is removable from the backlight unit. In a liquid crystal display including a liquid crystal panel and a backlight unit, the backlight unit defines a reflective space between a light source disposed along at least one side of the liquid crystal panel and the liquid crystal panel. A reflective plate disposed on the back surface of the liquid crystal panel at an interval, and the light from the light source is radiated to the reflective space between the reflective plate and the liquid crystal panel, and
Defined between the reflective space and the light source unit, the incident and exit surfaces of the light has a transparent partition wall is provided respectively prism shape, by the partition wall, said a reflection space by the light source unit A liquid crystal display characterized by being independent of the light source space.   16. The liquid crystal display according to claim 15, wherein the transparent partition wall is constituted by a transparent prism.   17. A liquid crystal display having a temperature adjustment function capable of adjusting the temperature of a space in which the light source according to claim 15 is present.   18. A liquid crystal display, wherein the light source unit according to claim 15 is provided with a mechanism that can be detached from the reflection space.   19. A liquid crystal display, wherein the light source according to claim 15 uses a fluorescent lamp using a cathode tube that emits light by thermal electron emission.

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