JP2007165029A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the dark contrast of a display device having backlight. <P>SOLUTION: The display device has a display panel and a backlight arranged at the back of the display panel. The backlight has a fluorescent tube, a filter that absorbs light of a predetermined wavelength region from among the lights emitted from the fluorescent tube, and a light-emitting diode that emits a light of wavelength region that is absorbed by the filter. The filter is installed at the outer circumferential surface of the fluorescent tube. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a technique effective when applied to a display device in which a backlight is disposed behind a display panel.

  Conventionally, a liquid crystal display (LCD) is used for a display of a personal computer (PC), a television, a mobile phone or a personal digital assistant (PDA).

  The liquid crystal display device includes a liquid crystal display panel in which a liquid crystal material is sealed between a pair of substrates. In this liquid crystal display panel, for example, TFT (Thin Film Transistor) elements and pixel electrodes are arranged in an array on one substrate, and a common electrode (also called a counter electrode) is provided on the other substrate. The common electrode may be provided on the same substrate as the TFT element and the pixel electrode.

  The liquid crystal display device is a non-light-emitting display device that displays an image (video) using light from the outside, and is roughly classified into a transmission type, a reflection type, and a semi-transmission type depending on the light source used. The In the transmissive type, for example, a backlight is disposed behind the liquid crystal display panel, and light emitted from the backlight is irradiated to the liquid crystal display panel and transmitted to display an image (video). The reflection type displays an image (video) by reflecting light from the outside of the apparatus with a liquid crystal display panel. The transflective type is a combination of the transmissive type and the reflective type.

  In the transmissive or transflective liquid crystal display device, a fluorescent tube such as a cold cathode fluorescent tube (CCFL) is used as a light source of the backlight.

  The liquid crystal display device has a problem that the dark contrast is lower than that of a self-luminous display device using, for example, a PDP (Plasma Display Panel) or an organic EL (Electro Luminescence) panel. One of the causes of this problem will be briefly described by taking a liquid crystal display device having the backlight as an example.

  In the case of a liquid crystal display device having a backlight, polarizing plates are attached to the display side of the liquid crystal display panel, that is, the surface on the observer's viewpoint side and the surface on the back side (backlight side). At this time, the polarizing plates attached to the respective surfaces of the liquid crystal display panel are attached so that, for example, the transmission axes are orthogonal to each other. In the case of such a liquid crystal display device, for example, when the liquid crystal display panel is viewed from an oblique viewing angle direction, the transmission axes of the polarizing plates attached to the respective surfaces of the liquid crystal display panel deviate from an orthogonal relationship. Therefore, light leakage occurs and dark contrast is lowered.

In the liquid crystal display device having the backlight, as a method for preventing light leakage due to the deviation of the transmission axis of the polarizing plate, for example, between the liquid crystal display panel and the polarizing plate attached to each surface of the liquid crystal display panel, There is a method of interposing one or more retardation plates (for example, see Patent Document 1).
JP 2003-262869 A

  However, it is known that light leakage in the liquid crystal display device having the backlight is caused not only by the shift of the transmission axis of the polarizing plate but also by scattering.

  Light leakage due to scattering is caused by light that has been polarized through a polarizing plate on the backlight side of a liquid crystal display panel, for example, pigment particles contained in a color filter of a liquid crystal display panel, or an adhesive used for attaching a polarizing plate. It is caused by scattering by the material or the like and disturbing polarization. When the polarization is disturbed due to light scattering, for example, during black display, light leaks from the polarizing plate on the display side of the liquid crystal display panel. Therefore, in order to improve the dark contrast, it is necessary to consider light leakage due to this scattering.

  In the display device provided with the phase difference plate described in Patent Document 1 and the like, light leakage due to deviation of the transmission axis of the polarizing plate attached to each surface of the liquid crystal display panel from an orthogonal relationship can be suppressed. It is difficult to prevent light leakage due to scattering as described above. Therefore, there is a problem that it is difficult to further improve the dark contrast.

  The objective of this invention is providing the technique which can improve the dark contrast of the display apparatus which has a backlight.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The outline of typical inventions among the inventions disclosed in the present application will be described as follows.

  (1) A display device having a display panel and a backlight disposed behind the display panel, wherein the backlight has a predetermined wavelength among a fluorescent tube and light emitted from the fluorescent tube. The display device includes a filter that absorbs light in a region and a light emitting diode that emits light in a wavelength region absorbed by the filter, and the filter is provided on an outer peripheral surface of the fluorescent tube.

  (2) In the above (1), the filter is made of a material that absorbs light having a wavelength of 500 nm or less, and the light emitting diode is a blue light emitting diode.

  (3) In the above (1) or (2), the fluorescent tube has a phosphor layer in which a green phosphor and a red phosphor are mixed on the inner peripheral surface of the glass tube, and the light emitting diode emits blue light The display device is a diode.

  (4) In any one of (1) to (3), the fluorescent tube and the light emitting diode are display devices arranged in a region overlapping with a display region of the display panel.

  (5) In any one of (1) to (3), the backlight includes a light guide plate that guides light emitted from the fluorescent tube and the light emitting diode, and the light guide plate is a display of the display panel. The display device is arranged to overlap with a region, and the fluorescent tube and the light emitting diode are arranged at an end portion of the light guide plate.

  (6) In the above (4) or (5), the display panel is a liquid crystal display panel in which a liquid crystal material is sealed between a pair of substrates.

  The display device of the present invention uses two types of light sources, a fluorescent tube and a light emitting diode, for the backlight. At this time, a filter that absorbs light in a predetermined wavelength region out of the light emitted from the fluorescent tube is provided on the outer peripheral surface of the fluorescent tube. If it does in this way, among the light emitted from a fluorescent tube, for example, the light of the wavelength region where scattering is remarkable can be absorbed (removed), and can be irradiated to a display panel. At this time, the filter is preferably a filter that absorbs all light on a shorter wavelength side than a certain wavelength, for example. However, when such a filter is used, light having a wavelength necessary for light applied to the display panel may be included in light in a wavelength region absorbed by the filter. Therefore, light of a wavelength necessary for light irradiating the display panel among the light in the wavelength region absorbed by the filter is supplemented by the light emitting diode. The light emitted from the light emitting diode has a sharp emission spectrum, and the intensity of light in a wavelength region unnecessary for the light irradiated on the display panel is very small. Therefore, the scattering of light in the unnecessary wavelength region due to pigment particles included in the color filter of the display panel can be reduced. As a result, light leakage due to light scattering can be reduced and dark contrast can be improved.

  Further, it is known that the light scattering intensity is generally inversely proportional to the fourth power of the wavelength, and that light having a shorter wavelength is more likely to cause scattering. It is also known that the light emitted from the fluorescent tube has a broad spectrum distribution in the blue light emitting region, and the intensity of the emitted light having an unnecessary wavelength is high. Therefore, it is desirable that the filter absorbs light emitted on the short wavelength side. For example, a filter made of a material that absorbs light having a wavelength of 500 nm or less is used. In this case, a blue light emitting diode is used as the light emitting diode. In this way, unnecessary light on the short wavelength side with high scattering intensity can be reduced as much as possible, and light leakage due to scattering can be reduced.

  Further, at this time, in the fluorescent tube, for example, it is preferable that the fluorescent material layer provided on the inner peripheral surface of the glass tube is obtained by mixing only the green fluorescent material and the red fluorescent material in advance. With such a fluorescent tube, the light emitted from the fluorescent tube can be reduced to light with very short wavelengths. Therefore, the removal rate of light on the short wavelength side emitted from the fluorescent tube can be increased, and light leakage due to scattering can be further reduced.

  In the display device of the present invention, the backlight may be either a direct type or an edge light type (also referred to as a side light type). In the case of a direct type backlight, the fluorescent tube and the light emitting diode are arranged at a position overlapping the display area of the display panel. In the case of an edge light type backlight, a light guide plate is disposed so as to overlap with a display area of the display panel, and the fluorescent tube and the light emitting diode are disposed at an end portion of the light guide plate.

  In addition, the display device of the present invention may have any configuration as long as the display device includes the backlight. In particular, a liquid crystal display in which a liquid crystal material is sealed between a pair of substrates. A display device having a panel is preferable.

Hereinafter, the present invention will be described in detail together with embodiments (examples) with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same function are given the same reference numerals and their repeated explanation is omitted.

1 to 8 are schematic views for explaining the outline of the present invention.
FIG. 1 is an exploded perspective view showing a schematic configuration of a display device to which the present invention is applied. 2 is a cross-sectional view taken along line AA ′ of FIG. FIG. 3 is a cross-sectional view showing a schematic configuration of a fluorescent tube used in a conventional backlight. FIG. 4 is a graph showing an example of an emission spectrum of a fluorescent tube used in a conventional backlight. FIG. 5 is a graph showing the relationship between the wavelength of light and the scattering intensity. FIG. 6 is a cross-sectional view illustrating an example of a light source of a backlight in the display device of the present invention. FIG. 7 is a graph showing an example of an emission spectrum in the light source shown in FIG. FIG. 8 is a cross-sectional view showing another example of the fluorescent tube in the display device of the present invention.

  The present invention is applied to a display device that requires a backlight, such as a liquid crystal display device (LCD) using a liquid crystal display panel. Hereinafter, the configuration of the display device of the present invention will be described by taking the liquid crystal display device as an example.

  For example, as shown in FIGS. 1 and 2, the liquid crystal display device includes a liquid crystal display panel 1 and a backlight 2 disposed behind (in the back of) the liquid crystal display panel 1. Further, on the surface of the liquid crystal display panel 1 facing the backlight 2 (hereinafter referred to as the surface on the backlight side) and the back surface thereof (hereinafter referred to as the surface on the display side), for example, an optical element such as a polarizing plate. Films 3A and 3B are attached.

  The liquid crystal display panel 1 is a display panel in which a liquid crystal material 103 is sealed between a pair of substrates 101 and 102. For example, TFT elements and pixel electrodes are arranged in an array on one substrate 101, and the other The substrate 102 is provided with a common electrode (also referred to as a counter electrode), a color filter, and the like. The common electrode may be provided on the same substrate 101 as the TFT element and the pixel electrode.

  In the liquid crystal display panel 1, a plurality of gate signal lines and a plurality of drain signal lines are arranged in a matrix on the substrate 101 on which the TFT elements and the pixel electrodes are arranged. A region surrounded by two adjacent gate signal lines and two adjacent drain signal lines becomes one pixel region, and the TFT element and the pixel electrode are arranged in each pixel region.

  The gate signal line is a signal line that supplies a scanning signal to the gate of the TFT element, and is also called a scanning signal line. The gate signal line is connected to the wiring of the flexible circuit board 4A on which a gate driver (also referred to as a scanning driver) is mounted, for example, at the end of the substrate 101. The drain signal line is a signal line for supplying a video data signal to the drain of the TFT element, and is also called a data signal line or a video signal line. The drain signal line is connected to the wiring of the flexible circuit board 4B on which a drain driver (also referred to as a data driver) is mounted, for example, at the end of the substrate 101. These flexible circuit boards 4A and 4B are, for example, packages in a mounting form called TCP (Tape Carrier Package) or COF (Chip On Film). Further, some of the wirings of the flexible circuit boards 4A and 4B are connected to the wirings of the printed circuit boards 5A and 5B disposed on the outer periphery of the liquid crystal display panel 1. Although not shown, the printed circuit boards 5A and 5B are connected to a circuit board (TCON board) on which circuit components such as a timing controller are mounted.

  The gate driver and the drain driver may be mounted or directly formed on the substrate 101 of the liquid crystal display panel 1, for example. In this case, the wiring on the substrate 101 of the liquid crystal display panel 1 and the wiring of the printed circuit boards 5A and 5B are only formed on the surface of the insulating film instead of the flexible circuit boards 4A and 4B on which the drivers are mounted. Connect using a flexible wiring board.

  The backlight 2 emits light in a direction opposite to the liquid crystal display panel 1 among, for example, a light source 201 that emits light to irradiate the liquid crystal display panel 1 and light emitted from the light source 201 (hereinafter referred to as emitted light). A reflecting plate 202 that reflects the light to the liquid crystal display panel 1 side, and an optical sheet 203 such as a diffusion plate for increasing the in-plane uniformity of the light irradiated to the liquid crystal display panel 1. In the backlight 2 used in the conventional liquid crystal display device, the light source 201 is a fluorescent tube such as a cold cathode fluorescent tube (CCFL). The example shown in FIG. 2 is a configuration example of a direct type backlight, and the light source (fluorescent tube) 201 is disposed at a position overlapping the display area of the liquid crystal display panel 1.

  For example, as shown in FIG. 3, the fluorescent tube 201 is provided with a phosphor layer 201b on the inner peripheral surface of a glass tube 201a. The fluorescent tube 201 used in the conventional backlight 2 is usually a three-wavelength fluorescent tube, and each of the three primary colors of light, blue (B), green (G), and red (R), is provided on the phosphor layer. Are mixed. The emission spectrum of such a three-wavelength fluorescent tube is, for example, as shown in FIG. In the graph shown in FIG. 4, the horizontal axis represents the wavelength λ (nm) of the emitted light, and the vertical axis represents the light intensity IOR (arbitrary unit). Further, the light intensity IOR on the vertical axis indicates that the direction from the bottom to the top is a positive direction, and the relative value increases as it goes upward.

  In a three-wavelength fluorescent tube used in a conventional backlight, the phosphor layer 201b is a mixture of phosphors of blue, green, and red colors. Therefore, for example, as shown in FIG. 4, the emission spectrum of the three-wavelength fluorescent tube includes a blue light peak PB with a wavelength λ between 400 nm and 500 nm, and a green light peak PG with a wavelength λ near 550 nm. , Three peaks are seen, a red light peak PR with a wavelength λ between 600 nm and 650 nm.

  However, in the case of the three-wavelength fluorescent tube, in addition to the three peaks PB, PG, PR, three peaks PU1, PU2, PU3 are seen in the emission spectrum. In the case of the three-wavelength fluorescent tube, the emission spectrum also has a broad peak PU4 in the wavelength region of blue light, as shown in FIG. 4, for example. The light having the wavelengths of the four peaks PU1, PU2, PU3, and PU4 is light having a wavelength unnecessary for the light irradiating the liquid crystal display panel 1, and the liquid crystal display panel has high intensity IOR of the light having the wavelengths. 1 causes unnecessary light scattering. Therefore, the conventional liquid crystal display device has a low dark contrast. Therefore, in the liquid crystal display device of the present invention, the light intensity of the wavelength unnecessary for the light irradiated to the liquid crystal display panel 1 is lowered, thereby preventing scattering due to unnecessary light and improving the dark contrast.

  The relationship between the wavelength of light passing through the liquid crystal display panel 1 and the scattering intensity is, for example, as shown in FIG. In the graph shown in FIG. 5, as the wavelength λ is shorter, the horizontal axis represents the wavelength λ (nm) of the emitted light, and the vertical axis represents the light intensity Is (arbitrary unit). Further, the light intensity Is on the vertical axis indicates that the direction from the bottom to the top is a positive direction, and the relative value increases as it goes upward.

  For example, as shown in FIG. 5, the light passing through the liquid crystal display panel 1 tends to have higher scattering intensity as the wavelength is shorter. This is because the particles contained in the materials used for the color filters, the optical films 3A and 3B such as the polarizing plate and the retardation plate, and the adhesive material, and the structure thereof are 100 nm or less, and light (visible light) This is because it is finer than the wavelength. Scattering having such a relationship is called Rayleigh scattering and is known to be inversely proportional to the fourth power of the wavelength λ.

  Thus, the light passing through the liquid crystal display panel has higher scattering intensity as the wavelength is shorter. When the conventional three-wavelength fluorescent tube is used as a light source, for example, as shown in FIG. Very much included. Therefore, it is considered that by removing light with an unnecessary wavelength in a wavelength region where the wavelength λ is 500 nm or less, scattering due to unnecessary light can be prevented and dark contrast can be improved.

  However, in the wavelength region where the wavelength λ is 500 nm or less, for example, it is very difficult to leave only blue light having a peak PB and selectively remove only light having an unnecessary wavelength. Therefore, in the liquid crystal display device of the present invention, for example, all the light in the wavelength region having a wavelength λ of 500 nm or less is removed from the light emitted from the fluorescent tube 201. The blue light thus removed is supplemented with, for example, light from a blue light emitting diode having a sharp emission spectrum.

  That is, in the liquid crystal display device of the present invention, the light source of the backlight 2 is a combination of two types of light sources, for example, a fluorescent tube 201 and a light emitting diode 204, as shown in FIG.

  At this time, the fluorescent tube 201 is provided with wavelength filters 201c and 201d on the outer peripheral surface. The wavelength filters 201c and 201d are filters that absorb light having a wavelength equal to or less than a specific wavelength out of the light emitted from the fluorescent tube 201. For example, a filter that absorbs light having a wavelength λ of 500 nm or less is used. At this time, the wavelength filters 201c and 201d are formed, for example, by coating the outer peripheral surface of the glass tube 201a with a zinc oxide film 201c and further laminating an azo-based yellow pigment 201d on the surface. The thickness of the zinc oxide film 201c is, for example, 100 nm to 500 nm. The thickness of the azo yellow pigment 201d is, for example, 5 μm to 10 μm.

  The fluorescent tube 201 is provided with a phosphor layer 201b on the inner peripheral surface of the glass tube 201a. At this time, the phosphor layer 201b is preferably a mixture of only a green phosphor and a red phosphor, for example.

  On the other hand, as the light emitting diode 204, for example, a blue light emitting diode having an LED chip 204a having a light emission peak near 450 nm is used. For example, the light emitting diode 204 is disposed on the reflector 202 in a state of being mounted on the flexible circuit board 205. At this time, the light-emitting diode 204 is a top-view type that emits light 6 in a direction perpendicular to the mounting surface of the flexible circuit board 205.

  The emission spectrum of the emitted light in the light source having such a configuration is, for example, as shown in FIG. In the graph shown in FIG. 7, the horizontal axis represents the wavelength λ (nm) of the emitted light, and the vertical axis represents the light intensity IOR (arbitrary unit). Further, the light intensity IOR on the vertical axis indicates that the direction from the bottom to the top is a positive direction, and the relative value increases as it goes upward.

  In the case of the light source configured as shown in FIG. 6, light having a wavelength λ of 500 nm or less among the emitted light from the fluorescent tube 201 is absorbed by the wavelength filters 201 c and 201 d. That is, in FIG. 7, the spectrum in the wavelength region where the wavelength λ is 500 nm or more is the emission spectrum of the emitted light from the fluorescent tube 201. In FIG. 7, the spectrum in the wavelength region where the wavelength λ is 500 nm or less is the spectrum of the emitted light from the blue light emitting diode 204.

  As can be seen by comparing the emission spectrum shown in FIG. 5 with the emission spectrum shown in FIG. 7, when the fluorescent tube 201 from which light having a wavelength of 500 nm or less is removed and the blue light-emitting diode 204 are combined, the wavelength is 500 nm or less. There is very little unnecessary light in the short wavelength region. Therefore, scattering due to unnecessary light in the short wavelength region can be prevented, and light leakage due to scattering can be reduced. As a result, the dark contrast of the liquid crystal display device can be improved.

  The wavelength filter provided on the outer peripheral surface of the fluorescent tube 201 is not limited to the configuration in which the azo yellow pigment 201d is laminated on the zinc oxide film 201c as described above, and various configurations are conceivable. Another configuration example of the wavelength filter is shown in FIG.

  In the liquid crystal display device of the present invention, the wavelength filter provided on the outer peripheral surface of the fluorescent tube 201 may be a filter that removes light having a specific wavelength region, particularly a wavelength of 500 nm or less. Therefore, for example, as shown in FIG. 8, a triacetyl cellulose (TAC) film 201f having an adhesive layer 201e added with an ultraviolet absorber is attached to the outer peripheral surface of the glass tube 201a, and the surface of the TAC film 201f is azo-based. The yellow pigment 201d may be laminated to form a wavelength filter. At this time, the adhesive layer 201e is, for example, one obtained by adding 1% to 10% of a benzotriazole-based ultraviolet absorber to an acrylic adhesive. The thickness of the adhesive layer 201e is, for example, 5 μm to 50 μm. Further, the thickness of the TAC film 201f is, for example, 10 μm to 200 μm. The thickness of the azo yellow pigment 201d is, for example, 5 μm to 10 μm.

  The fluorescent tube 201 is provided with a phosphor layer 201b on the inner peripheral surface of the glass tube 201a. At this time, the phosphor layer 201b is preferably a mixture of only a green phosphor and a red phosphor, for example.

  Even when the fluorescent tube 201 having the configuration as shown in FIG. 8 and the blue light emitting diode 204 are combined, the emission spectrum of the emitted light is as shown in FIG. 7, for example. Therefore, scattering due to unnecessary light in the short wavelength region can be prevented, and light leakage due to scattering can be reduced. As a result, the dark contrast of the liquid crystal display device can be improved.

  As described above, in the liquid crystal display device of the present invention, the light source of the backlight 2 is combined with the fluorescent tube 201 provided with the wavelength filter that absorbs light having a wavelength of 500 nm or less on the outer peripheral surface, and the blue light emitting diode 204. By using it, light leakage due to scattering of light passing through the liquid crystal display panel 1 can be reduced. Therefore, the dark contrast of the liquid crystal display device can be improved.

  Further, as in the display device of the present invention, for example, when light having a wavelength of 500 nm or less emitted from the fluorescent tube 201 is absorbed by the wavelength filter, the ultraviolet light emitted from the fluorescent tube 201 can also be absorbed by the filter. . Therefore, it is possible to prevent display panel deterioration (yellowing change) due to ultraviolet rays emitted from the fluorescent tube 201.

  Further, as in the present invention, for example, when light having a wavelength of 500 nm or less emitted from the fluorescent tube 201 is absorbed by the wavelength filter and the absorbed blue component is supplemented by the blue light emitting diode 204, the blue purity is increased. . Further, when the phosphor layer 201b of the fluorescent tube 201 is made only of the green phosphor and the red phosphor, for example, the red purity can be improved by adding a deep red phosphor to the red phosphor. . That is, in the display device of the present invention, the color purity of blue and red can be improved, and the color reproduction range can be widened. In order to improve the color purity of red, specifically, for example, a red phosphor having an emission peak near 630 nm and a deep red phosphor having an emission peak between 640 nm and 700 nm are formed on the phosphor layer 201b. Mixed.

  In addition, the wavelength filter provided in the outer peripheral surface of the fluorescent tube 201 is not limited to the above-described configuration, and for example, one type of inorganic yellow pigments such as lead chromate or organic yellow pigments such as azo, or two You may comprise combining a kind or more. Moreover, you may coat what added ultraviolet absorption materials, such as a benzotriazole type and a zinc oxide, as needed.

  In addition, yellow pigments and ultraviolet absorbing materials such as those described above are used for films (sheets) such as polyethylene terephthalate (PET), polycarbonate (PC), acrylic resin, polyvinyl chloride (PVC), and triacetyl cellulose (TAC). What coated on the surface or mixed in the film may be used as a wavelength filter, and may be attached to the outer peripheral surface of the fluorescent tube. Further, instead of coating the film or mixing it in the film, the film may be attached to the outer peripheral surface of the fluorescent tube with an adhesive material mixed with the yellow pigment or ultraviolet absorbing material as described above.

  The wavelength filter provided on the outer peripheral surface of the fluorescent tube 201 is not limited to a filter that absorbs light having a wavelength of 500 nm or less, but may be any filter that absorbs light in an arbitrary wavelength region.

  The fluorescent material layer 201b of the fluorescent tube 201 is not limited to the fluorescent material layer in which only the green fluorescent material and the red fluorescent material are mixed as described above, and a blue fluorescent material such as a three-wavelength fluorescent tube may also be mixed. Of course it is good.

  In addition, the present invention is not limited to the liquid crystal display device as long as it is a display device having the backlight 2, and can be applied to various display devices.

9 and 10 are schematic views showing a schematic configuration of the backlight according to the first embodiment of the present invention.
FIG. 9 is a plan view showing a configuration example of a direct type backlight to which the present invention is applied. 10 is a cross-sectional view taken along line BB ′ of FIG.

  In the first embodiment, as described above, for example, a light source combining a fluorescent tube 201 provided with a wavelength filter that absorbs light having a wavelength of 500 nm or less on the outer peripheral surface and a blue light emitting diode 204 is used as a direct-type backlight 2. A configuration example when applied to the above will be described.

  For example, as shown in FIGS. 9 and 10, the direct-type backlight 2 is arranged at a position where a plurality of fluorescent tubes 201 overlap with a display area of the liquid crystal display panel 1. As the fluorescent tube 201, for example, a glass tube 201a coated with a zinc oxide film 201c on the outer peripheral surface and further laminated with an azo organic yellow pigment 201d is used. The phosphor layer 201b on the inner peripheral surface of the glass tube 201a is a phosphor layer in which only green phosphor and red phosphor are mixed. At this time, the light emitting diodes 204 are arranged between the fluorescent tubes 201.

  Further, at this time, the plurality of fluorescent tubes 201 are supported by, for example, a support member 206 provided on the reflecting surface of the reflecting plate 202, and a gap of a predetermined distance is formed between the fluorescent tubes 201 and the reflecting plate 202. Has occurred. Therefore, for example, the light emitting diodes 204 may be disposed between the fluorescent tubes 201 so that the flexible circuit board 205 on which the blue light emitting diodes 204 are mounted is passed between the fluorescent tubes 201 and the reflecting plate. At this time, the wiring of the flexible circuit board 205 on which the light emitting diode 204 is mounted is connected to, for example, an inverter circuit board 207 used for light emission of the fluorescent tube 201. In FIG. 9, only some of the fluorescent tubes 201 and the flexible circuit board 205 are connected to the inverter circuit board 207 and the wiring 208, but in reality, all the fluorescent tubes 201 and the flexible circuit board 205 are connected to the inverter circuit. The substrate 207 and the wiring 208 are connected.

  In addition to the blue light emitting diode 204 and the fluorescent tube support member 206, for example, light disposed between the fluorescent tube 201 and the blue light emitting diode 204 and the liquid crystal display panel 1 is provided on the reflective surface of the reflective plate 202. A support member (pin mold) 209 that supports the optical sheet 203 such as a diffusion plate is disposed.

  If the direct type backlight 2 has such a configuration, the emission spectrum of the light 7 irradiated from the backlight 2 to the liquid crystal display panel 1 is as shown in FIG. Therefore, light leakage due to unnecessary light scattering on the short wavelength side can be reduced, and dark contrast can be improved.

  In addition, since the ultraviolet light emitted from the fluorescent tube 201 is absorbed by the wavelength filters 201c and 201d, it is possible to prevent deterioration (yellowing change) of the liquid crystal display panel due to the ultraviolet light.

  In addition, by using the blue light-emitting diode 204, the emission spectrum of blue light becomes sharp and the blue purity can be improved. Furthermore, if the phosphor layer 201b of the fluorescent tube 201 is mixed with a deep red phosphor in addition to the green phosphor and the red phosphor, the purity of red can be improved. As a result, the color reproduction range can be improved.

FIG. 11 and FIG. 12 are schematic views illustrating modifications of the backlight of the first embodiment.
FIG. 11 is a plan view showing another configuration example of a direct type backlight to which the present invention is applied. 12 is a cross-sectional view taken along the line CC ′ of FIG.

  The backlight 2 of Example 1 is a direct type, and a light emitting diode 204 is disposed between a plurality of fluorescent tubes 201. At this time, it is conceivable that the flexible circuit board 205 that supplies power to the light emitting diode 204 is disposed so as to pass between the fluorescent tube 201 and the reflection plate 202, as shown in FIGS. 9 and 10, for example. However, in this case, by disposing the flexible circuit board 205, the reflection efficiency of the light emitted from the fluorescent tube 201 on the reflecting plate 202 is lowered, and a shadow is formed at the position where the flexible circuit board 205 is disposed. The in-plane uniformity of the light irradiated to one display area is lowered.

  As a method for preventing the reflection efficiency from being lowered by the flexible circuit board 205, for example, as shown in FIGS. 11 and 12, a through hole 202a is provided in the reflecting plate 202, and the flexible circuit board 205 disposed on the back surface of the reflecting plate 202 is provided. A method of inserting the mounted light emitting diode 204 from the through hole 202a to the reflecting surface side is conceivable. In this case, the light emitting diode 204 is mounted on the flexible circuit board 205 using, for example, a spacer substrate 210. In this way, the dark contrast can be improved without impairing the in-plane uniformity of the light applied to the display area of the liquid crystal display panel 1.

  9, 10, 11, and 12 are examples of the arrangement of the fluorescent tubes 201 and the light emitting diodes 204 in the direct type backlight 2, and it goes without saying that other arrangements may be used. .

13 and 14 are schematic views showing a schematic configuration of the backlight according to the second embodiment of the present invention.
FIG. 13 is a plan view showing a configuration example of an edge light type backlight to which the present invention is applied. 14 is a cross-sectional view taken along line DD ′ of FIG.

  In the second embodiment, as described above, for example, a light source that combines a fluorescent tube having a wavelength filter that absorbs light having a wavelength of 500 nm or less on the outer peripheral surface and a blue light emitting diode is used as an edge light type (side light type A configuration example in the case of application to a backlight of (also called) will be described.

  In the edge light type backlight 2, for example, as shown in FIGS. 13 and 14, a light guide plate 211 is disposed at a position overlapping the display area AR of the liquid crystal display panel 1. At this time, for example, a light semi-transmissive film 212 is attached to the surface of the light guide plate 211 facing the liquid crystal display panel 1. In addition, a reflective film 213 is attached to the back surface of the light guide plate 211 on which the light translucent film 212 is attached.

  In the case of an edge light type backlight, the fluorescent tube 201 and the light emitting diode 204 are disposed at the end of the light guide plate 211. At this time, the light emitted from the fluorescent tube 201 and the light emitting diode 204 is incident on the light guide plate from the side surface of the end portion of the light guide plate 211 and is guided while being repeatedly reflected at the interface with the light transflective film 212 and the interface with the reflective film 213. Propagates through the light plate 211. At this time, a part of the light is reflected at the interface between the light guide plate 211 and the light translucent film 212, and the remaining light 7 is refracted and applied to the liquid crystal display panel 1.

  As the fluorescent tube 201, for example, a glass tube 201a coated with a zinc oxide film 201c on the outer peripheral surface and further laminated with an azo organic yellow pigment 201d is used. The phosphor layer 201b on the inner peripheral surface of the glass tube 201 is a phosphor layer in which only a green phosphor and a red phosphor are mixed. Further, the fluorescent tube 201 is supported by, for example, a socket 215 attached to a printed circuit board 214 disposed outside the reflection plate 202. Moreover, the socket 215 has a terminal for supplying electric power to the fluorescent tube 201, for example.

  At this time, for example, the light emitting diode 204 is mounted on the printed circuit board 214 disposed outside the reflecting plate 202, and is disposed so as to be inserted into the reflecting surface side from the through hole 202a provided in the reflecting plate 202. . In this case, the light emitting diode 204 is mounted on the printed circuit board 214 using the spacer board 210, for example. At this time, for example, as shown in FIG. 14, the light emitting diode 204 is disposed so as to emit light 6 in the direction of the mounting surface of the printed circuit board 214 and in the direction of the light incident surface of the light guide plate 211.

  If the edge light type backlight 2 is configured in this way, the emission spectrum of the light 7 irradiated from the backlight 2 to the liquid crystal display panel 1 is as shown in FIG. Therefore, light leakage due to unnecessary light scattering on the short wavelength side can be reduced, and dark contrast can be improved.

  In addition, since the ultraviolet light emitted from the fluorescent tube 201 is absorbed by the reflection filter, the liquid crystal display panel can be prevented from being deteriorated (yellowing change) by the ultraviolet light.

  In addition, by using the blue light-emitting diode 204, the emission spectrum of blue light becomes sharp and the blue purity can be improved. Furthermore, if the phosphor layer 201b of the fluorescent tube 201 is mixed with a deep red phosphor in addition to the green phosphor and the red phosphor, the purity of red can be improved. As a result, the color reproduction range can be improved.

  In addition, by forming a through hole 202a in the reflecting plate 202 and arranging a printed circuit board 214 that supplies power to the light emitting diode 204 outside the reflecting plate 202, light emitted from the fluorescent tube 201 can be used without waste. 201 can be incident.

  13 and 14 show an example of the arrangement of the fluorescent tube 201 and the light emitting diode 204 in the edge light type backlight 2, and it goes without saying that other arrangements may be used.

  In addition, the light guide plate 211, the light semi-transmissive film 212, and the reflective film 213 are shown in FIG. 14 as an example of the configuration, and the light emission of the fluorescent tube 201 and the light emitting diode 204 arranged at the end of the light guide plate 211. Any configuration may be used as long as it can irradiate the display area AR of the liquid crystal display panel 1 with light.

  The present invention has been specifically described above based on the above-described embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. is there.

It is a disassembled perspective view which shows schematic structure of the display apparatus with which this invention is applied. It is sectional drawing in the A-A 'line of FIG. It is sectional drawing which shows schematic structure of the fluorescent tube used with the conventional backlight. It is a graph which shows an example of the emission spectrum of the fluorescent tube used with the conventional backlight. It is a graph which shows the relationship between the wavelength of light, and scattering intensity. It is sectional drawing which shows an example of the light source of the backlight in the display apparatus of this invention. It is a graph which shows an example of the emission spectrum in the light source shown in FIG. It is sectional drawing which shows another example of the fluorescent tube in the display apparatus of this invention. It is a top view which shows one structural example of the direct type | mold backlight which applied this invention. FIG. 10 is a cross-sectional view taken along line B-B ′ of FIG. 9. It is a top view which shows another structural example of the direct type backlight which applied this invention. It is sectional drawing in the C-C 'line | wire of FIG. It is a top view which shows one structural example of the edge light type backlight to which this invention is applied. It is sectional drawing in the D-D 'line | wire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel 101,102 ... Board | substrate 103 ... Liquid crystal material 2 ... Back light 201 ... Light source (fluorescent tube)
201a ... Glass tube 201b ... Phosphor layer 201c ... Wavelength filter (zinc oxide film)
201d: Wavelength filter (yellow pigment)
201e ... Wavelength filter (adhesive layer)
201f ... Wavelength filter (TAC film)
DESCRIPTION OF SYMBOLS 202 ... Reflecting plate 202a ... Through-hole 203 ... Optical sheet 204 ... (blue) Light emitting diode 205 ... Flexible circuit board 206 ... Support member 207 ... Inverter circuit board 208 ... Wiring 209 ... Support member (pin mold)
210 ... Spacer substrate 211 ... Light guide plate 212 ... Light translucent film 213 ... Reflective film 214 ... Printed circuit board 215 ... Socket 3A, 3B ... Optical film 4A, 4B ... Flexible circuit board 5A, 5B ... Printed circuit board 6, 7 ... Light AR ... Display area

Claims (6)

A display device having a display panel and a backlight disposed behind the display panel,
The backlight includes a fluorescent tube,
Among the light emitted from the fluorescent tube, a filter that absorbs light in a predetermined wavelength region,
A light emitting diode that emits light in a wavelength region absorbed by the filter;
The display device, wherein the filter is provided on an outer peripheral surface of the fluorescent tube. The filter is made of a material that absorbs light having a wavelength of 500 nm or less,
The display device according to claim 1, wherein the light emitting diode is a blue light emitting diode. The fluorescent tube has a phosphor layer obtained by mixing a green phosphor and a red phosphor on the inner peripheral surface of a glass tube,
The display device according to claim 1, wherein the light emitting diode is a blue light emitting diode.   4. The display device according to claim 1, wherein the fluorescent tube and the light emitting diode are disposed in a region overlapping with a display region of the display panel. 5. The backlight has a light guide plate that guides light emitted from the fluorescent tube and the light emitting diode,
The light guide plate is arranged so as to overlap with a display area of the display panel,
4. The display device according to claim 1, wherein the fluorescent tube and the light emitting diode are arranged at an end portion of the light guide plate. 5.   The display device according to claim 4, wherein the display panel is a liquid crystal display panel in which a liquid crystal material is sealed between a pair of substrates.

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