KR102075066B1 - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal panel including a color filter layer and a backlight unit including a light source, wherein the backlight unit includes a blue light source, and includes a backlight unit and the color filter layer. By including a light conversion layer disposed between red and green patterns and excited by the light irradiated from the light source to emit light having a wavelength longer than that of the irradiated light, the light conversion efficiency can be significantly improved, and accordingly The present invention relates to a liquid crystal display device capable of realizing high brightness and reducing power consumption.

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a liquid crystal display device having a markedly improved luminance.

BACKGROUND ART In general, a liquid crystal display device is a display device in which data signals corresponding to image information are individually supplied to pixels arranged in a matrix form so as to display a desired image by adjusting light transmittance of the pixels.

Accordingly, the liquid crystal display includes a liquid crystal panel in which pixels are arranged in a matrix and a driver for driving the pixels.

The liquid crystal panel includes a thin film transistor array substrate, a color filter substrate, and a liquid crystal layer formed in a cell gap between the array substrate and the color filter substrate, which are bonded to face each other to maintain a uniform cell gap. do.

In this case, a common electrode and a pixel electrode are formed in the liquid crystal panel where the array substrate and the color filter substrate are bonded to apply an electric field to the liquid crystal layer.

Therefore, when the voltage of the data signal applied to the pixel electrode is controlled while the voltage is applied to the common electrode, the liquid crystal of the liquid crystal layer rotates by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode. Characters or images are displayed by transmitting or blocking light for each pixel.

In this case, since the liquid crystal display device does not emit light by itself and is a light-receiving element that displays an image by adjusting the transmittance of light coming from the outside, a separate device for illuminating the liquid crystal panel, that is, a backlight unit is required.

As a light source of the backlight unit, a cold cathode fluorescent lamp (CCFL) in the form of a tube having a length corresponding to the long side distance or the short side distance of the liquid crystal panel is generally applied. The fluorescent lamp generates white light by the power supplied through the wires at both ends.

In this case, when the cold cathode fluorescent lamp is applied as a light source of the backlight unit, mercury (Hg) gas containing argon (Ar), neon (Ne), etc., is added at low pressure to use a penning effect. Fluorescent discharge tubes are used. In this case, electrodes are formed at both ends of the fluorescent discharge tube, and the cathode is formed in a wide plate shape, and when voltage is applied, charged particles in the discharge tube collide with the plate-shaped negative electrode to generate secondary electrons, as in the sputtering phenomenon. The elements are excited to form a plasma. These elements emit strong ultraviolet light, which in turn excites the phosphor, causing the phosphor to emit visible light.

However, the backlight unit using the cold cathode fluorescent lamp has a disadvantage in that color reproduction is not good because the light emission characteristics of the light source itself are not good, and it is difficult to realize high brightness due to the limitation of the size and capacity of the fluorescent lamp.

In addition, mercury applied as a phosphor to the cold cathode fluorescent lamp is harmful to the human body, and thus there is a problem in that it cannot cope with the stricter environmental regulations.

Recently, a light emitting diode has been spotlighted as a light source of a backlight unit, which has a longer lifespan than a cold cathode fluorescent lamp and has an advantage of not requiring a separate inverter because it operates at a DC of 5V.

In other words, high-brightness LEDs have a longer lifespan than conventional cold-cathode fluorescent lamps and consume only 20% of the power of existing products, and do not require additional equipment such as inverters.

The general light emitting device emits monochromatic light of red (R), green (G), and blue (B) colors, and thus has excellent color reproduction and reduced driving power when applied to a backlight unit. There is this.

However, when the light emitting device is used as a light source of the backlight as described above, the following problem occurs.

Generally, when light emitted from a light emitting device is supplied to a liquid crystal panel, monochromatic light is not directly supplied but white light is supplied. Therefore, the monochromatic light emitted from the light emitting device must be made into white light and supplied to the liquid crystal panel.

As a method of converting monochromatic light of such a light emitting device into white light in a backlight unit, a method using a monochromatic light emitting device and a phosphor, a method of using a light emitting device and a phosphor of an infrared wavelength band, and emitting light from red, green, and blue light emitting devices The method of mixing the monochromatic light, etc. are mentioned.

However, since white light is a light having a spectrum of the entire visible light, when monochromatic light is converted into white light, the intensity at the wavelength of each color is lowered.

Korean Patent Publication No. 2008-88855 discloses a backlight unit and a liquid crystal display device having the same.

Korean Laid-Open Patent No. 2008-88855

An object of the present invention is to provide a liquid crystal display device with remarkably improved light conversion efficiency.

An object of the present invention is to provide a liquid crystal display device that can implement high brightness and, accordingly, reduce power consumption.

1. A liquid crystal panel including a color filter layer and a backlight unit including a light source,

The backlight unit has a blue light source,

And a light conversion layer disposed between the red and green patterns of the backlight unit and the color filter layer and excited by light irradiated from the light source to emit light having a wavelength longer than that of the irradiated light.

2. In the above 1, the wavelength of the light emitted from the light source is 350 to 450nm, the liquid crystal display device.

3. In the above 1, wherein the wavelength of the light emitted from the light conversion layer is 450 to 700nm, the liquid crystal display device.

4. In the above 1, wherein the light emitted from the light source and the light emitted from the light conversion layer is mixed with the white light is formed, the liquid crystal display device.

5. In the above 1, wherein the backlight unit does not include a light conversion layer, the liquid crystal display device.

6. In the above 1, wherein the light conversion layer is provided on the color filter side based on the liquid crystal layer of the liquid crystal panel, the liquid crystal display device.

7. In the above 1, wherein the light conversion layer is provided on the backlight unit side with respect to the liquid crystal layer of the liquid crystal panel, the liquid crystal display device.

8. In the above 1, wherein the light conversion layer is provided under the backlight unit side polarizer of the liquid crystal panel, the liquid crystal display device.

9. In the above 1, wherein the color filter layer further comprises a transparent pattern, the liquid crystal display device.

10. In the above 9, the light conversion layer is disposed between the red, green and transparent patterns of the backlight unit and the color filter layer, the liquid crystal display device.

11. The liquid crystal display device of 1, wherein the light conversion layer comprises YAG: Ge, YAG: Ce or silicate-based phosphors.

The liquid crystal display device of the present invention can significantly improve the light conversion efficiency. Accordingly, high brightness can be realized and power consumption can be reduced.

1 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.
2 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.
3 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.
4 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

The present invention includes a liquid crystal panel having a color filter layer and a backlight unit having a light source, the backlight unit having a blue light source, disposed between the backlight unit and the red and green patterns of the color filter layer, By including a light conversion layer that is excited by the irradiated light and emits light having a wavelength longer than the irradiated light, it is possible to significantly improve the light conversion efficiency, thereby realizing high brightness and reducing power consumption It relates to a liquid crystal display device.

Hereinafter, the present invention will be described in detail.

In a typical liquid crystal display device, a color is realized by using a white light source that emits white light and passing the white light through a color filter layer having a red, green, and blue pattern corresponding to each sub-pixel area.

However, since white light is a light having a spectrum of the full range of visible light, in order to implement white light, wavelengths of only a single color wavelength should be converted so that the spectrum of the full range appears. Accordingly, there is a problem in that the light conversion efficiency is low and the liquid crystal display cannot implement high brightness.

However, the liquid crystal display of the present invention includes a backlight unit that emits blue light, and thus does not require light conversion at the time of the expression of blue, so that the blue color of the markedly improved luminance can be expressed.

Further, by including a light conversion layer disposed between the backlight unit and the red and green patterns of the color filter layer and excited by the light emitted by the light source to form white light, the luminance of the red and green can also be remarkably improved. This is considered to be because the converted light can be mixed with the light irradiated from the light source to form white light even when the wavelength of blue is excluded and converted to the wavelength except this.

1 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The liquid crystal display of the present invention includes a liquid crystal panel 100 having a color filter layer 160 and a backlight unit 200 having a light source.

The liquid crystal panel 100 includes a first substrate 120 (array substrate) and a second substrate 130 (color filter substrate) bonded to each other with the liquid crystal layer 110 interposed therebetween. The first substrate 120 is located at the backlight unit 200 side, and the second substrate 130 is located at the color filter side.

The liquid crystal layer 110 is filled with a liquid crystal, and upper and lower portions include alignment layers 140a and 140b for aligning the liquid crystal in a predetermined direction. The first alignment layer 140a is positioned at the backlight unit 200 side, and the second alignment layer 140b is positioned at the color filter side.

The liquid crystal layer 110 varies the alignment of liquid crystal molecules according to a vertical electric field between the first substrate 120 and the second substrate 130, or a horizontal electric field inside the first substrate 120. Various image information is displayed by changing the amount of light transmitted.

The liquid crystal layer 110 may operate by a twisted nemastic (TN) method, a vertical alignment (VA) method, an in-plane switching (IPS or Fringe Field Switching (FFS) method, etc.). have.

In the first substrate 120, a plurality of gate lines and a plurality of data lines are arranged to cross each other, and a unit pixel area is defined by the crossing, and the defined pixel areas are formed in a matrix form.

A pixel electrode is formed in each pixel area, and a thin film transistor is formed at a point where each gate line and data line cross each other.

The thin film transistor is a switching element and transmits a data signal applied to the data line to the pixel electrode in response to the gate signal of the gate line.

The pixel electrode may be made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), and generates an electric field by switching a thin film transistor to control the alignment of the liquid crystal layer 110.

The second substrate 130 is formed to maintain a predetermined gap while facing the first substrate 120 with the liquid crystal layer 110 therebetween.

A lattice-like black matrix 170 is formed on one surface of the first substrate 120 to cover only the pixel electrode while covering the non-display elements such as the gate line, the data line, and the thin film transistor.

In addition, the color filter layer 160 including the red, green, and blue patterns sequentially arranged to correspond to the unit pixel region in the grid is formed.

The color filter layer 160 may include an organic pigment or an organic dye that partially absorbs and partially transmits wavelengths of light incident from the light source, and may include a binder resin as necessary.

The overcoat layer 180 may be further formed on the color filter layer 160. The overcoat layer covers the color filter layer 160 and serves to planarize these steps. This overcoat layer is comprised from transparent resin materials and the like. And a transparent common electrode (not shown) covering all of them.

According to another embodiment of the invention, as illustrated in FIGS. 3 and 4, the color filter layer 160 may further comprise a transparent pattern, in which case the pixels may be red, green, blue and transparent, respectively. It is defined as a subpixel area.

When further including a transparent pattern, the light conversion layer 300 is also disposed between the backlight unit 200 and the transparent pattern as will be described later. In such a case the light passing through it represents white, which serves to complement the luminance of red, green and blue.

First and second polarizers 150a and 150b may be attached to the outer surfaces of the first and second substrates 120 and 130, respectively.

The backlight unit 200 supplies light to the liquid crystal panel 100.

The backlight unit 200 may be a direct type, an edge type, or a dual type.

In the edge type, light sources are arranged in a line (or string) form on one side of the liquid crystal panel 100. In the dual type, light sources are arranged in the form of a string (or a string) on both sides of the liquid crystal panel 100. In the direct type, the light source is disposed in the form of a block or a matrix under the liquid crystal panel 100. Among these, in view of weight reduction and large area of the thin film, it may be preferably an edge type.

Hereinafter, an edge type backlight will be described as an example, but is not limited thereto.

The backlight unit 200 may include a light source, a light guide plate, a reflecting plate, an optical sheet, and the like.

The light source may be a light emitting diode (LED) emitting blue light, and the wavelength of the emitted light may be, for example, 350 to 450 nm.

The light guide plate into which the light emitted from the light source is incident is spread evenly over a large area of the light guide plate while the incident light propagates through the light guide plate by several total reflections, thereby providing a surface light source to the liquid crystal panel 100.

The light guide plate may include a pattern of a specific shape on the back side to supply a uniform surface light source. Here, the pattern may be configured in various ways, such as an elliptical pattern, a polygonal pattern, a hologram pattern, and the like to guide the light incident into the light guide plate. It is formed on the lower surface of the printing method or injection method.

The reflecting plate is positioned on the rear surface of the light guide plate, and reflects light passing through the rear surface of the light guide plate toward the liquid crystal panel 100 to improve the brightness of the light.

The optical sheet on the light guide plate includes a diffusion sheet, at least one light collecting sheet, and the like, and diffuses or collects light passing through the light guide plate so that a more uniform surface light source is incident on the liquid crystal panel 100. In this case, the optical sheet may include a reflective polarizing sheet for reproducing linear polarization to improve light efficiency.

As will be described later, the liquid crystal display device of the present invention includes the light conversion layer 300 provided between the backlight unit 200 and the red and green patterns of the color filter layer 160, so that the backlight unit 200 has a separate light. It does not include the conversion layer 300 emits blue light.

The liquid crystal display of the present invention includes a light conversion layer 300.

The light conversion layer 300 is disposed between the red and green patterns of the backlight unit 200 and the color filter layer 160, and is excited by the light irradiated from the light source to emit light having a wavelength longer than that of the irradiated light, It is mixed with the light irradiated from the light source to form white light. The white light thus formed passes through the red pattern and the green pattern of the color filter layer 160, thereby realizing the red and the green with the markedly improved luminance as described above.

The wavelength of the light emitted from the light conversion layer may be, for example, 450 to 700 nm, but is not limited thereto.

Since the blue light source is used, the light conversion layer 300 is not required on the blue pattern side.

The light conversion layer 300 is disposed between the red and green patterns of the backlight unit 200 and the color filter layer 160, and the position thereof is not particularly limited. For example, the liquid crystal layer of the liquid crystal panel 100 ( It may be disposed on the backlight unit 200 side based on the 110.

More specifically, it may be disposed below the first alignment layer 140a, below the first substrate 120, or below the first polarizer 150a as illustrated in FIGS. 1 and 3.

The light conversion layer 300 may emit light even after the light irradiation is stopped (power supply off), but the light conversion layer 300 is disposed on the backlight unit 200 with respect to the liquid crystal layer 110. If such light is blocked, it is preferable. In this aspect, it may be more preferably disposed below the first polarizer 150a.

In addition, the light conversion layer 300 may be disposed on the color filter side based on the liquid crystal layer 110.

More specifically, it may be disposed below the color filter layer 160, below the overcoat layer 180, or above the second alignment layer 140b as illustrated in FIGS. 2 and 4.

When the above-described color filter layer 160 further includes a transparent pattern, the light conversion layer 300 is also disposed between the backlight unit 200 and the transparent pattern of the color filter layer 160.

If the light conversion layer 300 is excited by the light irradiated from the light source, and can emit light of a longer wavelength as described above, the material is not particularly limited, for example, YAG (yttrium aluminum garnet) The YAG: Ge or YAG: Ce-based phosphors doped with Ge (germanium) or Ce (cerium) may be used, or may include silicate-based phosphors.

In the liquid crystal display device of the present invention comprising the above configuration, the light conversion efficiency is remarkably improved. Accordingly, it is possible to implement high brightness and to reduce power consumption.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but these examples are merely illustrative of the present invention and are not intended to limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications can be made to the present invention, and such modifications and changes belong to the appended claims.

Example  1. Manufacturing of LCD

A backlight unit was prepared by removing the light conversion layer from a backlight unit using a blue LED emitting light having a wavelength of 440 nm as a light source.

Then, a liquid crystal panel in which a YAG: Ge phosphor layer was formed on an array substrate under a portion corresponding to the red and green patterns of the color filter layer was prepared, and a backlight unit was bonded to the lower liquid crystal panel to manufacture a liquid crystal display device.

Example  2. Manufacturing of LCD

A liquid crystal display device was manufactured in the same manner as in Example 1, except that the phosphor layer was formed under the overcoat layer of a portion corresponding to the red and green patterns of the color filter layer.

Example  3. Manufacturing of LCD

A liquid crystal display device was manufactured in the same manner as in Example 1, except that a transparent pattern was further formed on the color filter layer in the liquid crystal panel, and a YAG: Ge phosphor layer was further formed below the array substrate corresponding to the transparent pattern. .

Example  4. Manufacturing of LCD

A liquid crystal display device was manufactured in the same manner as in Example 2, except that a transparent pattern was further formed on the color filter layer in the liquid crystal panel, and a YAG: Ge phosphor layer was further formed on the lower portion of the array substrate corresponding to the transparent pattern. .

Comparative example

A liquid crystal display device was manufactured by bonding a backlight unit including a blue LED light source and a light conversion layer to a light emitting layer having a wavelength of 440 nm to a liquid crystal panel that does not include a light conversion layer.

Experimental Example . Luminance measurement

The luminance of the red, green, and blue light of the liquid crystal display of the above example was measured using a spectrometer.

division Red light luminance (Y) Green Light Luminance (Y) Blue Light Luminance (Y) Example 1 24.4 72.4 13.0 Example 2 24.4 72.5 13.3 Example 3 24.1 72.6 13.8 Example 4 24.0 72.1 13.9 Comparative example 17.8 64.2 11.1

Referring to Table 1, in the liquid crystal display of Examples 1 to 4, the luminance of the red, green, and blue light was remarkably improved.

In the liquid crystal display of Examples 2 and 4, the light was observed for 2 seconds even after the light irradiation was stopped (power-off). Did.

However, in the liquid crystal display device of the comparative example, the brightness of light was remarkably decreased.

100: liquid crystal panel 110: liquid crystal layer
120: first substrate 130: second substrate
140a: first alignment layer 140b: second alignment layer
150a: first polarizing plate 150b: second polarizing plate
160: color filter layer 170: black matrix
180: protective layer 200: backlight unit
300: light conversion layer

Claims (11)

A liquid crystal panel having a color filter layer and a backlight unit having a light source,
The backlight unit has a blue light source,
A light conversion layer disposed between the backlight unit and the color filter layer and excited by light irradiated from the light source to emit light having a wavelength longer than that of the irradiated light,
The light conversion layer continuously extends under the red and green patterns of the color filter layer to overlap the red and green patterns in common, and is not formed below the blue pattern of the color filter layer.
And white light is formed when light emitted from the light source and light emitted by the light conversion layer are mixed.
The liquid crystal display device of claim 1, wherein a wavelength of light emitted from the light source is 350 to 450 nm.
The liquid crystal display device of claim 1, wherein a wavelength of light emitted from the light conversion layer is 450 to 700 nm.
delete The liquid crystal display device of claim 1, wherein the backlight unit does not include a light conversion layer.
The liquid crystal display device of claim 1, wherein the light conversion layer is provided on a color filter side based on the liquid crystal layer of the liquid crystal panel.
The liquid crystal display device of claim 1, wherein the light conversion layer is provided on a backlight unit side of the liquid crystal layer of the liquid crystal panel.
The liquid crystal display device according to claim 1, wherein the light conversion layer is provided under the backlight unit side polarizer of the liquid crystal panel.
The liquid crystal display device of claim 1, wherein the color filter layer further comprises a transparent pattern.
The liquid crystal display of claim 9, wherein the light conversion layer is disposed between the red, green, and transparent patterns of the backlight unit and the color filter layer.
The liquid crystal display device of claim 1, wherein the light conversion layer comprises YAG: Ge, YAG: Ce, or silicate-based phosphors.

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