KR20150129451A - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, and more specifically, to a liquid crystal display device which can perform ideal wavelength dispersibility, and has significantly improved photoconversion efficiency by comprising: a backlight unit comprising a blue light source, and a liquid crystal panel. The liquid crystal panel comprises photoconversion layer in a visible-side upper side of a visible-side polarizing plate. The photoconversion layer comprises a red photoconversion pattern and a green photoconversion pattern respectively arranged in corresponding areas to red and green sub-pixels of the liquid crystal panel.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

The present invention relates to a liquid crystal display device.

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 having a wide viewing angle and suppressed light leakage phenomenon.

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

1. A backlight unit including a liquid crystal panel and a backlight unit having a blue light source,

Wherein the liquid crystal panel includes a light conversion layer on an upper side of a visible side of a visual side polarizing plate,

Wherein the light conversion layer has a red light conversion pattern and a green light conversion pattern which are respectively arranged in corresponding regions of red and green sub-pixels of the liquid crystal panel.

2. The liquid crystal display of claim 1, wherein the blue light source emits light having a wavelength of 350 to 450 nm.

3. The method of claim 1, wherein the red light conversion pattern converts the light emitted from the light source into light having a wavelength of 550 to 750 nm, and the green light conversion pattern converts the light emitted from the light source into light having a wavelength of 400 to 600 nm The liquid crystal display device.

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

5. The liquid crystal display of claim 1, wherein the liquid crystal panel includes a color filter layer having red, green, and blue patterns on the visible side of the light conversion layer, and the red pattern is formed on the visible side of the red light conversion layer, And the pattern is disposed on the visible side of the green light switching layer.

6. The liquid crystal display of claim 1, wherein the polarizing plate comprises a polarizer and an optical compensation film disposed on a viewer side thereof, and the light conversion layer is disposed on a visual side of the optical compensation film.

7. The liquid crystal display of claim 6, wherein a design center wavelength of the optical compensation film is included in a wavelength range of blue light of the backlight unit.

The liquid crystal display device of the present invention can realize an ideal wavelength dispersibility. Thereby minimizing light leakage and having a wide viewing angle.

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

1 and 2 are schematic cross-sectional views of a liquid crystal display device according to an embodiment of the present invention.

The liquid crystal panel includes a light switching layer on the viewer side of the viewer side polarizing plate, and the light switching layer is disposed on the red and green sub-pixels of the liquid crystal panel. The backlight unit includes a backlight unit having a blue light source and a liquid crystal panel. The present invention relates to a liquid crystal display device capable of realizing ideal wavelength dispersibility and significantly improving light conversion efficiency by providing a red light conversion pattern and a green light conversion pattern respectively disposed in corresponding regions of the liquid crystal display device.

1 and 2 are schematic cross-sectional views of a liquid crystal display device according to an embodiment of the present invention, and the present invention will be described in detail with reference to the accompanying drawings.

A liquid crystal display device of the present invention includes a backlight unit (200) having a blue light source and a liquid crystal panel (100).

The liquid crystal panel 100 includes a first substrate 120 and a second substrate 130 which are bonded to each other with a liquid crystal layer 110 interposed therebetween. The first substrate 120 is positioned on the opposite side of the viewer side, and the second substrate 130 is positioned on the viewer 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 layer 140a is located on the opposite side of the viewer side, and the second alignment layer 140b is located on the viewer 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.

Each unit pixel is divided into red, green, and blue sub-pixels, since the liquid crystal display device must be capable of realizing colors of red, green, and blue for each unit pixel.

Red in the red sub-pixel, green in the green sub-pixel, and blue in the blue sub-pixel.

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.

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 first polarizing plate is disposed on the side opposite to the viewing side, and the second polarizing plate is disposed on the viewing side.

Specifically, the first polarizing plate 150a and the second polarizing plate 150b include a polarizer and a protective film bonded to at least one surface of the polarizer. An optical compensation film is attached to the other surface of the polarizer or one surface of the protective film. Preferably, an optical compensation film may be attached on one side of the viewing side of the second polarizing plate 150b.

The optical compensation film serves to improve the viewing angle, contrast and the like. Preferably, the optical compensation film adhered on one side of the viewing side of the second polarizing plate 150b may have a design center wavelength included in the blue light wavelength range of the backlight unit have.

The liquid crystal panel 100 of the present invention includes the light conversion layer 160 on the viewer side of the second polarizer 150b.

As described above, a second polarizing plate 150b having an optical compensation film is disposed on the liquid crystal layer 110. The optical compensation film is designed to exhibit the necessary optical function for light (monochromatic light) of a specific wavelength , And is designed based on light of a wavelength of 550 nm. This is called the design center wavelength.

Incidentally, in the case of a conventional liquid crystal display device, the backlight unit includes a white light conversion layer and white light is irradiated from the backlight unit, so that the white light reaches the optical compensation film through the liquid crystal layer. Since the white light is light having a wavelength in a range of about 380 nm to 780 nm, it is impossible to realize an ideal retardation for wavelengths other than 550 nm, so that the wavelength dispersion property deviates from an ideal value. As a result, there arises a problem that the wavelength of the light is changed and light leaks or the viewing angle becomes narrow.

The wavelength dispersibility is closer to the ratio of the respective wavelengths and is an ideal value. For example, the wavelength dispersion is close to 0.82 (450 nm / 550 nm) in the case of short wavelength dispersion of wavelength (retardation value for incident light at 450 nm / retardation value for incident light at 550 nm) And is an ideal value closer to 1.18 (650 nm / 550 nm) in the case of long wavelength dispersion (retardation value for incident light at 650 nm / retardation value for incident light at 550 nm).

However, since the blue light is transmitted through the liquid crystal layer 110 and enters the optical compensation film of the second polarizing plate 150b, the optical compensation film can be designed to exhibit the necessary optical function for the blue light have. That is, it is possible to realize an ideal wavelength dispersibility, thereby suppressing the light leakage problem and realizing a wide viewing angle.

The light conversion layer 160 includes a red light conversion pattern 161 and a green light conversion pattern 162 which are respectively disposed in corresponding regions of red and green sub-pixels of the liquid crystal panel.

The red light conversion pattern 161 is disposed in a corresponding region of the red sub-pixel of the liquid crystal panel 100 to convert the light emitted from the light source into red light so that the liquid crystal display device can implement red. The green light switching pattern 162 is disposed in a corresponding region of the green sub-pixel of the liquid crystal panel 100 so that light emitted from the light source is converted into green light so that the liquid crystal display can implement green. Of course, since the blue light is emitted from the light source, the blue light is realized without conversion, and a separate blue light conversion pattern is not required.

As described above, since light emitted from the light source is converted into light having a single color wavelength instead of white light having a full range of wavelengths, the light conversion efficiency is remarkably improved.

The red light conversion pattern 161 can convert the light to be irradiated into light having a wavelength of 550 to 750 nm and the green light conversion pattern 162 can convert the light to be irradiated into light having a wavelength of 400 to 600 nm, It is not.

The position of the light switching layer 160 is not particularly limited as long as it is above the visibility side polarizing plate 150b of the liquid crystal panel 100 and may be disposed on one side of the viewer side of the second polarizing plate 150b, A single or a plurality of layers may be further disposed between the two polarizing plate 150b and the light switching layer 160. [

When it is positioned on one side of the viewing side of the second polarizing plate 150b, specifically, it may be disposed on one side of the viewing side of the optical compensation film of the second polarizing plate 150b. In addition, when the liquid crystal panel 100 includes the color filter layer 180, it may be formed on one side of the color filter layer 180 opposite to the viewer side.

The material of the red light conversion pattern 161 is not particularly limited as long as it can convert the light emitted from the light source into red light. Examples thereof include Eu-doped sulfoselenide, Eu- and / or Ce- It is preferably selected from oxides, nitrides, oxynitrides, alumosiliconitrides and / or Mn (IV) -doped oxides and / or fluorides. (Ca, Sr, Ba) ₂ Si ₅ N ₈ : Eu, (Ca, Sr) AlSiN ₃ : Eu, A _{2-0.5y- x} Eu _{x Si 5 N 8 - y O} y ( where a represents one or more elements selected from Ca, Sr and Ba, x represents a value from the range from 0.005 to 1, y represents a value from the range of 0.01 to 3) , Or in which the individual lattice positions in the compounds are replaced by other chemical elements such as alkali metals, aluminum, gallium or gadolinium, or where additional elements of this type occupy flaws as dopants May be particularly preferred.

Suitable material systems known to those skilled in the art include, but are not limited to, silico-nitrides and alumoxyliconitrides (see Xie, Sci. Technol.Ad. Mater. 2007,8,88-600), 2-5-8 nitrides, _{(Ca, Sr, Ba) 2} Si 5 N 8: Eu 2 + (... Li et al, Chem Mater 2005, 15, 4492), and aluminate serve Rico nitride acids, temyeon them (Ca, Sr) AlSiN ₃ : Eu ^{2 +} (K. Uheda et al., Electrochem. Solid State Lett. 2006, 9, H22).

The green light conversion pattern 162 is not particularly limited as long as it can convert the light emitted from the light source into green light. For example, the following nitride-based phosphors are known. Since such a nitride phosphor emits visible light having an emission peak in a wavelength range of 580 nm or more and less than 660 nm, it is also known that it is suitable for a light emitting device such as a white LED light source.

_{(1) M 2 Si 5 N} 8: Eu 2 + ( see Japanese Patent Application Publication No. 2003-515665)

(2) MSi ₇ N ₁₀ : Eu ^{2 +} (see Japanese Patent Application Laid-Open No. 2003-515665)

(3) M ₂ Si ₅ N ₈ : Ce ^{3 +} (see Japanese Patent Laid-Open No. 2002-322474)

_{(4) Ca1.5A1 3 Si 9 N} 16: Ce 3 + ( see JP 2003-203504 No.)

_{(5) Ca1.5A1 3 Si 9 N} 16: Eu 2 + ( see JP 2003-124527 No.)

(6) CaAl ₂ Si ₁₀ N ₁₆ : Eu ^{2 +} (see JP-A 2003-124527)

_{(7) Sr 1 .5 Al 3} Si 9 N 16: Eu 2 + ( see JP 2003-124527 No.)

(8) MSi ₃ N ₅ : Eu ^{2 +} (see Japanese Patent Application Laid-Open No. 2003-206481)

(9) M ₂ Si ₄ N ₇ : Eu ^{2 +} (see Japanese Patent Application Laid-Open No. 2003-206481)

(10) CaSi ₆ A ₁₀ N ₉ : Eu ^{2 +} (see Japanese Patent Application Laid-Open No. 2003-206481)

_{(11) Sr 2 Si 4 A} lO N 7: Eu 2 + ( see JP 2003-206481 No.)

^{_{(12) CaSiN 2: Eu 2}} + ( see SS Lee, S. Lim, SS Sun and JF Wager, Proceedings of SPIE-the InternationalSociety for Optical Engineering, No. 3241 (1997), p 75-83..

Herein, M represents Mg, Ca, Sr, Ba, or Zn independently of each other. Such a nitride phosphor has been conventionally used mainly in combination with a compound containing an element which forms a luminescent center ion by using a nitride or a metal of the element M, a nitride of silicon and / or a nitride of aluminum as a raw material of the phosphor matrix, In a nitrifying gas atmosphere.

The liquid crystal panel 100 according to the present invention includes red 181, green 182, and blue (red) regions 182, 183, and 184 sequentially arranged in a repeating pattern corresponding to red, green, and blue sub- 183 < / RTI >

2, the red pattern 181 of the color filter layer 180 is formed on the viewer side upper side of the red light conversion pattern 161 and the green pattern 182 is arranged on the viewer side upper side of the green light conversion pattern 162 . The blue pattern 183 is arranged in the corresponding region of the blue sub-pixel.

When the color filter layer 180 is provided, the color filter layer 180, which already has colors of red, green, and blue, respectively, passes through the color filter layer 180, and thus, more colors can be expressed with higher purity.

The color filter layer 180 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 needed

The overcoat layer 190 may further be formed on the opposite side of the visible side of the color filter layer 180. The overcoat layer 190 covers the color filter layer 180 and serves to planarize the stepped portions. The overcoat layer 190 is made of a transparent resin material or the like.

The liquid crystal display device of the present invention further includes a black matrix 170.

The black matrix 170 serves to improve the contrast, and is disposed in the boundary-corresponding region of the red, green, and blue sub-pixels of the liquid crystal panel 100 to prevent the transmittance from deteriorating.

For example, the black matrix 170 may be formed on one surface of the second substrate 130, one surface of the second polarizer 150b, or may be formed on one surface of the second substrate 130, Or a layer structure of the liquid crystal panel 100 in addition to the above.

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.

As described above, since the liquid crystal panel 100 of the present invention includes the light conversion layer 300, the backlight unit 200 does not include a white light conversion layer and emits blue light.

The liquid crystal display device of the present invention including the above-described structure can realize an ideal wavelength dispersibility, suppress light leakage, and realize a wide viewing angle. In addition, the light conversion efficiency is remarkably improved and an advantage of high brightness can be achieved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be apparent to those skilled in the art that various changes and modifications can be made to the embodiments, and it is obvious that such variations and modifications fall within the scope of the appended claims.

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: light conversion layer 161: red light conversion pattern
162: green light conversion pattern 170: black matrix
180: Color filter layer 181: Red pattern
182: green pattern 183: blue pattern
190: overcoat layer 200: backlight unit

Claims (7)

A backlight unit having a blue light source, and a liquid crystal panel,
Wherein the liquid crystal panel includes a light conversion layer on an upper side of a visible side of a visual side polarizing plate,
Wherein the light conversion layer has a red light conversion pattern and a green light conversion pattern which are respectively arranged in corresponding regions of red and green sub-pixels of the liquid crystal panel.
The liquid crystal display of claim 1, wherein the blue light source emits light having a wavelength of 350 to 450 nm.
The red light conversion pattern according to claim 1, wherein the red light conversion pattern converts light emitted from the light source into light having a wavelength of 550 to 750 nm, and the green light conversion pattern converts light emitted from the light source into light having a wavelength of 400 to 600 nm. Liquid crystal display device.
The liquid crystal display of claim 1, wherein the backlight unit does not include a white light conversion layer.
The liquid crystal display device according to claim 1, wherein the liquid crystal panel includes a color filter layer having red, green, and blue patterns on the visible side of the light conversion layer, the red pattern is on the viewer side of the red light conversion layer, And is disposed on the viewer side of the green light switching layer.
The liquid crystal display according to claim 1, wherein the polarizing plate comprises a polarizer and an optical compensation film disposed on a viewer side thereof, and the light conversion layer is disposed on a visual side of the optical compensation film.
7. The liquid crystal display according to claim 6, wherein a design center wavelength of the optical compensation film is included in a wavelength range of blue light of the backlight unit.

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