KR20150109703A - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, more specifically, to a liquid crystal display device which comprises: a backlight unit with a liquid crystal panel and a light source wherein the liquid crystal panel includes a color filter layer and the backlight unit includes a blue light source; and a light converting layer arranged between a red pattern and a green pattern of the backlight unit and the color filter layer wherein the light converting layer is excited by light irradiated from the light source to emit light having a longer wavelength than the wavelength of the irradiated light, thereby drastically increasing light converting efficiency, realizing high brightness, and reducing power consumption.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

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

2. Description of the Related Art In general, a liquid crystal display device is a display device which can display a desired image by individually supplying data signals according to image information to pixels arranged in a matrix form and adjusting light transmittance of the pixels.

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

The liquid crystal panel is composed of 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 so as to face each other to maintain a uniform cell gap. do.

At this time, a common electrode and a pixel electrode are formed on the liquid crystal panel in which the array substrate and the color filter substrate are bonded together 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 is rotated by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode And a character or an image is displayed by transmitting or blocking light for each pixel.

At this time, since the liquid crystal display device is a light-receiving device that can not emit light itself but displays an image by controlling the transmittance of light coming from the outside, a separate device for irradiating light to the liquid crystal panel, that is, a backlight unit is required.

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

At this time, when the cold cathode fluorescent lamp is applied as a light source of a backlight unit, a mercury (Hg) gas added with argon (Ar), neon (Ne) or the like is sealed at low pressure in order to use a penning effect A fluorescent discharge tube is used. At this time, electrodes are formed at both ends of the fluorescent discharge tube, and the cathode is formed in a wide plate shape. When a voltage is applied, the charged particles in the discharge tube collide with the plate-shaped cathode as in the sputtering phenomenon, Elements are excited to form a plasma. These elements emit strong ultraviolet rays and the emitted ultraviolet light excites the phosphor again, causing the phosphor to emit visible light.

However, the backlight unit using the above-described cold cathode fluorescent lamp has a disadvantage in that color reproduction is poor because the light emission characteristic of the light source itself is poor, and it is difficult to realize high brightness due to the limitation of the size and the capacity of the fluorescent lamp.

In addition, since mercury which is applied to the cold cathode fluorescent lamp as a phosphor is harmful to human bodies, there is a problem that it can not cope with increasing environmental regulations.

In recent years, light emitting diodes (LEDs) have been widely used as light sources for backlight units. LEDs have a longer lifetime than cold cathode fluorescent lamps and operate at 5V DC.

That is, a high-brightness light emitting diode has a longer lifetime than conventional cold cathode fluorescent lamps, and the power consumption is only 20% of that of conventional products. Further additional equipment such as an inverter is unnecessary, which is advantageous for thinning the product and improving the internal area efficiency.

Since a general light emitting device emits monochromatic light of red (R), green (G), and blue (B) colors, it has advantages of good color reproduction and reduced driving power when applied to a backlight unit .

However, when the light emitting device is used as the light source of the backlight, the following problems arise.

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

As a method for converting the monochromatic light of the light emitting element into the white light in the backlight unit, a method using a monochromatic light emitting element and a fluorescent material, a method using a light emitting element and a fluorescent material in an infrared wavelength band, And a method of mixing the monochromatic light of the above.

However, since white light is a light having a spectrum in the full range of visible light, there is a problem that luminance is lowered at the wavelength of each color when monochromatic light is converted into white light.

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

Korean Patent Publication No. 2008-88855

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

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device which realizes a high luminance and thus can reduce power consumption.

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

Wherein the backlight unit includes a blue light source,

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

2. The liquid crystal display of claim 1, wherein a wavelength of the light emitted from the light source is 350 to 450 nm.

3. The liquid crystal display of claim 1, wherein the light emitted from the light conversion layer has a wavelength of 450 to 700 nm.

4. The liquid crystal display of claim 1, wherein when light emitted from the light source and light emitted by the light conversion layer are mixed, white light is formed.

5. The liquid crystal display of claim 1, wherein the backlight unit does not include a light conversion layer.

6. The liquid crystal display of claim 1, wherein the light conversion layer is provided on the color filter side with respect to the liquid crystal layer of the liquid crystal panel.

7. The liquid crystal display of claim 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.

8. The liquid crystal display of claim 1, wherein the light conversion layer is provided below the backlight unit side polarizing plate of the liquid crystal panel.

9. The liquid crystal display of claim 1, wherein the color filter layer further comprises a transparent pattern.

10. 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.

11. The liquid crystal display as claimed in claim 1, wherein the light conversion layer comprises YAG: Ge, YAG: Ce or a silicate-based phosphor.

The liquid crystal display device of the present invention can remarkably 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 embodiment of the present invention.
2 is a schematic cross-sectional view of a liquid crystal display according to an embodiment of the present invention.
3 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention.
4 is a schematic cross-sectional view of a liquid crystal display device according to an embodiment of the present invention.

The present invention relates to a liquid crystal display device comprising 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 and disposed between the backlight unit and the red and green patterns of the color filter layer, The light conversion layer is excited by the irradiated light and emits light having a wavelength longer than the wavelength of the irradiated light. Thus, the light conversion efficiency can be remarkably improved, thereby realizing high brightness and reducing power consumption And a liquid crystal display device.

Hereinafter, the present invention will be described in detail.

In a typical liquid crystal display device, a white light source that emits white light is used, and a color is realized by passing white light through a color filter layer having red, green, and blue patterns corresponding to respective sub pixel regions.

However, since white light is a spectrum having a full spectrum of visible light, in order to realize white light, wavelengths must be converted so that a spectrum having a full color range appears only in a single color wavelength. As a result, the light conversion efficiency deteriorates and the liquid crystal display device can not realize high brightness.

However, the liquid crystal display device of the present invention includes a backlight unit that emits blue light, so that it does not require light conversion at the time of blue color expression, and thus can exhibit blue color with remarkably improved brightness.

And the light conversion layer disposed between the backlight unit and the red and green patterns of the color filter layer and excited by the light irradiated by the light source to form white light, the brightness of red and green can be remarkably improved. This is because the converted light can be mixed with the light irradiated from the light source to form white light even if the wavelength of blue is excluded at the maximum when the color conversion is performed and the wavelength is switched to the excluded wavelength.

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

The liquid crystal display device 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 and a second substrate 130 (color filter substrate) which are bonded to each other with a liquid crystal layer 110 interposed therebetween. The first substrate 120 is located on the backlight unit 200 side and the second substrate 130 is located on the color filter side.

The liquid crystal layer 110 is filled with liquid crystal, and upper and lower portions thereof include alignment films 140a and 140b for orienting the liquid crystal in a predetermined direction. The first alignment film 140a is located on the backlight unit 200 side and the second alignment film 140b is located on the color filter side.

The liquid crystal layer 110 has different orientations of liquid crystal molecules depending on the vertical electric field between the first substrate 120 and the second substrate 130 or the horizontal electric field inside the first substrate 120, Thereby varying the amount of light transmitted by the light source.

The liquid crystal layer 110 can be operated by a twisted nematic (TN) method, a vertical alignment (VA) method, an in-plane switching (IPS) method or a Fringe Field Switching have.

In the first substrate 120, a plurality of gate lines and a plurality of data lines are arranged so as to intersect with each other, a unit pixel region is defined by intersection, and a defined pixel region is formed in a matrix form.

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

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

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

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

On one side of the first substrate 120, a lattice-shaped black matrix 170 is formed to cover the pixel region so as to expose only the pixel electrodes while covering the gate lines, the data lines, and the non-display elements such as the thin film transistors of the first substrate 120.

Further, a color filter layer 160 including red, green, and blue patterns sequentially and repeatedly arranged so as to correspond to the unit pixel regions is formed in these lattices.

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

A further 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 the stepped portions. The overcoat layer is made of a transparent resin material or the like. And a transparent common electrode (not shown) covering all of them.

According to another embodiment of the present invention, as illustrated in FIGS. 3 and 4, the color filter layer 160 may further include a transparent pattern, in which case the pixel may be red, green, blue, Sub-pixel region.

When a transparent pattern is further included, 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 therethrough represents white, which serves to complement the luminance of red, green and blue.

A first polarizer 150a and a second polarizer 150b may be attached to the outer surfaces of the first substrate 120 and the second substrate 130 to selectively transmit only specific light.

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, a light source is arranged in a line (or string) shape on one side of a liquid crystal panel 100. In the dual type, light sources are arranged on both sides of the liquid crystal panel 100 in a line (or string) form. In the direct type, a light source is arranged in a block or matrix form in a lower part of the liquid crystal panel 100. [ Of these, it may preferably be of an edge type in terms of thin film weight and large surface area.

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

The backlight unit 200 includes a light source, a light guide plate, a reflection plate, an optical sheet, and the like.

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

The light guide plate on which the light emitted from the light source is incident is incident on the light guide plate through the light guide plate by total reflection several times to spread over the wide area of the light guide plate to provide the surface light source to the liquid crystal panel 100.

The light guide plate may include a pattern of a specific shape on the back surface to supply a uniform surface light source. Here, the pattern may be formed in various shapes such as an elliptical pattern, a polygon pattern, a hologram pattern, and the like in order to guide the light incident into the light guide plate. In a printing method or an injection method.

The reflection plate is positioned on the back surface of the light guide plate and reflects light passing through the back surface of the light guide plate toward the liquid crystal panel 100, thereby improving the brightness of light.

The optical sheet on the upper side of the light guide plate includes a diffusion sheet and at least one light collecting sheet and diffuses or condenses the light passing through the light guide plate so that a more uniform planar light source is incident on the liquid crystal panel 100. At this time, the optical sheet may include a reflective polarizing sheet that regenerates linear polarized light to improve light efficiency.

The backlight unit 200 includes the light switching layer 300 provided between the backlight unit 200 and the color filter layer 160 and between the red and green patterns of the color filter layer 160, And does not include the conversion layer 300 to emit blue light.

A liquid crystal display device 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 to emit light of a wavelength longer than the wavelength of the light excited by the light emitted from the light source, It mixes with the light emitted 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 red and green colors with remarkably improved brightness as described above.

The wavelength of 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 switching layer 300 is not required on the blue pattern side.

The light switching layer 300 is disposed between the backlight unit 200 and the red and green patterns of the color filter layer 160. The position of the light switching layer 300 is not particularly limited and may be a liquid crystal layer of the liquid crystal panel 100 110 on the backlight unit 200 side.

More specifically, it may be disposed below the first alignment film lower portion 140a, the first substrate 120, or below the first polarizer 150a as illustrated in FIGS.

The light conversion layer 300 may emit light for a certain period of time even after the light irradiation is interrupted (powered on or off), but the light conversion layer 300 is disposed on the backlight unit 200 side with respect to the liquid crystal layer 110 It is preferable to block such light. In this respect, it may be more preferably disposed below the first polarizer 150a.

Further, the light conversion layer 300 may be disposed on the color filter side with respect to the liquid crystal layer 110.

More specifically, it may be disposed under the color filter layer 160, under the overcoat layer 180, or on the second alignment film 140b as illustrated in FIGS.

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

The material of the light converting layer 300 is not particularly limited as long as it is excited by the light emitted from the light source and can emit light having a longer wavelength as described above. For example, YAG (yttrium aluminum garnet) A phosphor of YAG: Ge or YAG: Ce series doped with Ge (germanium) or Ce (cerium), or a silicate-based phosphor.

The liquid crystal display device of the present invention including the above configuration remarkably improves the light conversion efficiency. Accordingly, it is possible to realize a high luminance and an advantage that power consumption can be reduced.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Example  1. Manufacturing of Liquid Crystal Display

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

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

Example  2. Manufacture of Liquid Crystal Display

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

Example  3. Manufacture of Liquid Crystal Display

A liquid crystal display 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 on the lower portion of the array substrate corresponding to the transparent pattern .

Example  4. Manufacture of Liquid Crystal Display

A liquid crystal display 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 part 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 that emits light having a wavelength of 440 nm to a liquid crystal panel not including a light conversion layer.

Experimental Example . Luminance measurement

The luminance of red, green and blue light of the liquid crystal display of the above embodiment 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 devices of Examples 1 to 4, the brightness was remarkably improved in red, green, and blue light.

In the liquid crystal display devices of Examples 2 and 4, light was observed for 2 seconds even after the light irradiation was stopped (power was turned off), but in the liquid crystal display devices of Examples 1 and 3, no light was confirmed after the power was turned off I did.

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

100: liquid crystal panel 110: liquid crystal layer
120: first substrate 130: second substrate
140a: first alignment layer 140b: second alignment layer
150a: first polarizer 150b: second polarizer
160: Color filter layer 170: Black matrix
180: protection 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,
Wherein the backlight unit includes a blue light source,
And a light conversion layer disposed between the backlight unit and the red and green patterns of the color filter layer and excited by light irradiated from the light source to emit light having a wavelength longer than the wavelength of the irradiated light.
The liquid crystal display of claim 1, wherein a wavelength of light emitted from the light source is 350 to 450 nm.
The liquid crystal display of claim 1, wherein a wavelength of light emitted from the light conversion layer is 450 to 700 nm.
The liquid crystal display of claim 1, wherein when light emitted from the light source and light emitted by the light conversion layer are mixed, white light is formed.
The liquid crystal display of claim 1, wherein the backlight unit does not include a light conversion layer.
The liquid crystal display of claim 1, wherein the light conversion layer is provided on the color filter side with respect to the liquid crystal layer of the liquid crystal panel.
The liquid crystal display of claim 1, wherein the light switching layer is provided on the backlight unit side with respect to the liquid crystal layer of the liquid crystal panel.
The liquid crystal display of claim 1, wherein the light conversion layer is provided below the backlight unit side polarizing plate of the liquid crystal panel.
The liquid crystal display of claim 1, wherein the color filter layer further comprises a transparent pattern.
The liquid crystal display device according to 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 of claim 1, wherein the light conversion layer comprises YAG: Ge, YAG: Ce or a silicate-based phosphor.

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