KR20080020840A - Light apparatus and liquid display apparatus - Google Patents

Abstract

A light source device and an LCD(Liquid Crystal Display) are provided to project white light using blue light so as to improve color reproducibility and display distinct images and increase price competitiveness. A light source device includes at least one LED(Light Emitting Diode)(111), a light guide pipe(112) and an excitation diffusion sheet(113). The light guide pipe converts light generated from the LED into linear light. The excitation diffusion sheet transmits a part of light emitted from the LED, excites the remaining part of the light as light having wavelength different from the wavelength of the light emitted from the LED and projects the excited light as white light. An LCD includes at least one front or back light unit(110) and at least one LCD panel(130) for displaying images by using light emitted from the front or back light unit. The front or back light unit includes the light source device.

Description

Light source device and liquid crystal display device

1 illustrates a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a view showing a front light unit according to an embodiment of the present invention.

3 is a view showing another example of a front light unit according to the embodiment of the present invention;

4 is a view showing the color gamut distribution of each light source of the present invention and the white LED.

5 is a graph showing the wavelength spectrum of the present invention and the white LED.

<Explanation of symbols for the main parts of the drawings>

110: front light unit 111: blue light emitting diode

112: light guide pipe 113113a, 113b: light excitation diffusion sheet

116: light guide plate 121,143: polarizing plate

130: liquid crystal panel 141: diffuser plate

142: reflective polarizer

The present invention relates to a light source device and a liquid crystal display device using the same.

In general, the liquid crystal display is a flat panel display having advantages of small size, thinness, and low power consumption, and is used as a portable computer such as a notebook PC, office automation equipment, and audio / video equipment.

Such a liquid crystal display device displays an image or an image by controlling an electric field applied to a liquid crystal material having dielectric anisotropy to transmit or block light. Liquid crystal displays differ from the display elements that emit light by themselves, such as electro-luminescence (EL), cathode ray tube (CRT), and light emitting diode (LED). It does not occur and uses external light.

In general, liquid crystal displays are roughly classified into a transmissive type and a reflective type according to a method of using light. The transmissive liquid crystal display device includes a liquid crystal panel in which a liquid crystal material is injected between two glass substrates, and a back light for supplying light to the liquid crystal panel.

However, the transmissive liquid crystal display device has difficulty in thinning and weighting due to the volume and weight of the backlight, and has been pointed out as an excessive power consumption of the backlight. In response to this trend, research and development of a reflective liquid crystal display device that does not use a backlight have been recently conducted.

Since the reflective liquid crystal display device does not have its own light source, it displays an image depending on natural light (or ambient light). Therefore, since a separate backlight is not required, the power consumption is low, so it is widely used as a portable display device such as an electronic notebook or personal information terminal.

However, the reflection type liquid crystal display device has a problem in that when the natural light does not have a sufficient amount of light (for example, when the surroundings are dark), the luminance level of the display image is lowered and the displayed information cannot be read. In order to solve this problem, a front light unit (FLU), which is separately installed in the reflective LCD and supplies light beams to the reflective liquid crystal display when the ambient light is dark, is used.

The front light unit includes a white light emitting diode for generating a white light source, a light guide plate for uniformly emitting a light beam toward the display surface of the liquid crystal panel, and an optical sheet such as a prism sheet and a diffusion sheet. to be.

The front light unit mainly uses a white light emitting diode as a light emitting unit. However, white light emitting diodes are relatively expensive compared to other diodes, and have a blue biased curve in the light spectrum, resulting in poor color reproducibility.

In order to solve such a problem of inferior color reproducibility, an LED color filter or an RGB LED is used to improve color reproducibility by emitting not only blue wavelengths in the wavelength spectrum but also green and red wavelength regions.

However, when a color filter with high color reproducibility is used for a white light emitting diode, luminance decreases due to a decrease in transmittance, and when using three kinds of RGB LEDs, the cost of a product increases due to an expensive LED price.

The present invention provides a light source device capable of emitting white light using a light emitting diode.

The present invention provides a light source device and a liquid crystal display device using the same to excite a part of the light generated by the light emitting diode to be emitted as white light.

The present invention provides a liquid crystal display using a front or backlight unit.

In one embodiment, a light source device includes at least one light emitting diode; A light guide pipe for converting light generated from the light emitting diode into a line light source; And a light excitation diffusion sheet that transmits a part of the incident light of the light emitting diode and excites the rest with light of a different wavelength, and emits the light by a white light source.

In addition, a light source device according to an embodiment of the present invention, at least one light emitting diode; A fluorescent sheet positioned in a path of the light emitting diode light and emitting light of the light emitting diode to white light by a phosphor included therein; The light guide plate which irradiates the said white light to a liquid crystal panel is included.

According to an exemplary embodiment of the present invention, a liquid crystal display includes: at least one front or backlight unit including the light source device of claim 1; At least one liquid crystal panel for displaying a screen by using light emitted from the front or backlight unit.

A liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a side cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is a front view of the front light unit of FIG. 1.

1 and 2, the liquid crystal display includes a front light unit (FLU) 110, a liquid crystal panel 130, a diffusion plate 141, a reflective polarizer 142, and an upper / lower polarizer ( 121,143).

The front light unit 110 generates light and converts the generated light into a surface light source to emit light toward the liquid crystal panel 130. To this end, the front light unit 110 includes a light emitting diode 111, a light guide pipe 112, a light excitation diffusion sheet 113, and a light guide plate 116. The light emitting diode 111 may be a blue light emitting diode, an ultraviolet light emitting diode, or the like. Hereinafter, a blue light emitting diode will be described.

The blue light emitting diode 111 generates light having a blue wavelength at both ends of the light guide pipe 112, and the generated light is incident on the light guide pipe 112.

The light guide pipe 112 converts the point light source incident from the blue light emitting diode 111 into a line light source and emits the light. The light guide pipe 112 is formed to have the same width as that of the light guide plate 116, and a metal coating film for reflection such as Ni and Al for reflecting light with a line light source is formed at a portion except for the light exit surface 112a. Will be.

The line light source emitted by the light guide pipe 112 is incident on the light excitation diffusion sheet 113, and the light excitation diffusion sheet 113 emits a blue light source as a white light source. To this end, the optical excitation diffusion sheet 113 functions as a fluorescent sheet including a diffusing material and a phosphor therein, the diffusion material allows a uniform light can be emitted, the phosphor is an inorganic phosphor, an organic phosphor, an organic It may be made of pigments, nanomaterials, etc., and emits blue light at wavelengths of green and red light.

The light excitation diffusion sheet 113 is positioned between the light guide pipe 112 and the light guide plate 116, and transmits some light from the incident blue light and absorbs other light to emit light of different wavelengths. For example, part of the light having a blue wavelength is transmitted, and the remaining light that is not transmitted is excited by the phosphor to be emitted as light such as green and red. In the light excitation diffusion sheet 113, partially transmitted blue light and the excited green and red light are mixed to emit white light.

The white light emitted from the light excitation diffusion sheet 113 is incident on the light guide plate 116, and the light guide plate 116 is uniformly reflected on one surface 114 having an uneven shape and transmitted to the other surface 115. Light emitted from the light guide plate 116 is irradiated to the liquid crystal panel with a surface light source. In addition, light incident from the liquid crystal panel 130 to the light guide plate 116 is transmitted. The light excitation diffusion sheet 113 may be installed at any position in the light traveling path of the front light unit 110.

The liquid crystal panel 130 has a liquid crystal layer 132 in which liquid crystal is injected between the first substrate 131 and the second substrate 133 and the first and second substrates 131 and 133 facing each other at predetermined intervals. It includes, and functions as a transmissive liquid crystal panel. The first and second substrates 131 and 133 are transparent glass substrates. Each of the pixels of the transparent electrode, the color filter, and the liquid crystal element is defined on the first substrate 131 and / or the second substrate 133. A thin film transistor (TFT) element may be installed to serve as a switching element of each pixel.

The liquid crystal layer 132 changes the alignment angle of the liquid crystal (eg, circularly polarized light) by the electric field and changes the light transmittance according to the changed alignment angle to obtain a desired image. In this case, a driving signal and a timing signal are applied to the gate line and the data line of the TFT in order to control the alignment angle of the liquid crystal and the timing of the liquid crystal. Here, the liquid crystal is described as a twist nematic (TN) mode, but may form a liquid crystal panel to which ECB, OCB, IPS (In-Plane Switching) or VA (Vertically Aligned) mode is applied.

An upper polarizer 121 is attached between the liquid crystal panel 130 and the light guide plate 110. The upper polarizer is coated with an antireflection (AR) to transmit incident or transmitted light along the transmission axis of the upper polarizer.

A diffuser plate 141, a reflective polarizer 142, and a lower polarizer 143 are formed below the liquid crystal panel 130, and the diffuser plate 141 scatters light passing through the liquid crystal panel 130. The luminance of the light is uniform, and the reflective polarizer 142 transmits the light corresponding to the transmission axis of the reflective polarizer 142 among the light passing through the upper polarizer 121 and the liquid crystal panel 130, and the remaining light. Rereflects. The reflective polarizer 142 may be formed of a high brightness film (Display Brilliance Enhancement Film).

The lower polarizer 143 polarizes the light incident from the reflective polarizer 142 according to the transmission axis. The lower polarizer 143 forms 90 degrees with the transmission axis of the upper polarizer 121, and the lower polarizer 143 is formed on the same axis as the transmission axis of the reflective polarizer 142.

As such, the light transmitted through the transmission axis of the lower polarizer 143 is displayed as a sub screen as the liquid crystal panel is turned on and off, and the light reflected from the reflective polarizer 142 is diffuser plate 141 and the liquid crystal panel 130. The light guide plate 116 passes through the upper polarizer 121 and is displayed as a main screen.

3 is a view showing another example of the front light unit of the present invention. 3 is only the position of the light excitation diffusion sheet in the structure of FIG. 2 is changed, and description of the same portions will be omitted.

Referring to FIG. 3, blue light generated by the blue light emitting diode 111 is incident on the light excitation diffusion sheets 113a and 113b. In this case, the light excitation diffusion sheets 113a and 113b are positioned between the blue light emitting diode 111 and the light guide pipe 112, and the incident blue light is emitted as white light. That is, the light excitation diffusion sheets 113a and 113b transmit some of the incident blue light, and excite the remaining light to the green and red light, which are other lights. White light in which blue light, green light and red light are mixed is emitted.

The white light is converted into a line light source in the light guide pipe 112, and converted into a surface light source in the light guide plate 116 and irradiated in the liquid crystal panel direction.

4 is a graph illustrating color gamut of an embodiment of the present invention and a conventional white LED, and FIG. 5 is a graph comparing a wavelength spectrum of a white light of the present invention and a conventional white LED. As shown in FIG. 4 and FIG. 5, using the light unit according to the present invention can improve color reproducibility.

The liquid crystal display according to the present invention is a light unit that provides a white light source, and may be applied to one or more light units, or selectively applied to a front light unit, a back light unit, and the like. Various light units may be applied depending on the number of panels.

Although the present invention has been described above with reference to the embodiments, these are only examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains may have an abnormality within the scope not departing from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not illustrated.

For example, each component shown in detail in the embodiment of the present invention may be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

According to the light source device and the liquid crystal display device according to the present invention, by outputting blue light using white light, it is possible to improve color reproducibility and display a clear screen.

In addition, the price competitiveness can be improved by using a blue light emitting diode.

Claims (9)

One or more light emitting diodes; A light guide pipe for converting light generated from the light emitting diode into a line light source; And a light excitation diffusion sheet that transmits a part of the incident light of the light emitting diodes and excites the rest with light having a different wavelength and emits the light by a white light source. The method of claim 1, The light emitting device is a light source device, characterized in that the blue light emitting diode. The method of claim 1, The light emitting device is disposed on both sides of the light guide pipe. The method of claim 1, The light excitation diffusion sheet transmits a part of incident light and emits remaining light as green and red light. The method of claim 1, The light excitation diffusion sheet is provided on the incidence side or the exit side of the light guide pipe. The method of claim 1, The light excitation diffusion sheet is provided on the incident side of the light guide plate. The method of claim 1, The light excitation diffusion sheet is provided on the emission side of the light emitting diode. One or more light emitting diodes; A fluorescent sheet positioned in a path of the light emitting diode light and emitting light of the light emitting diode to white light by a phosphor included therein; And a light guide plate for irradiating the white light to the liquid crystal panel. At least one front or back light unit comprising the light source device of claim 1; And at least one liquid crystal panel configured to display a screen by using light emitted from the front or backlight unit.

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