KR102130553B1 - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, and more specifically, includes a backlight unit and a liquid crystal panel having a blue light source, and the liquid crystal panel includes a light conversion layer on the viewing side of the viewing side polarizing plate, and the light conversion The layer is provided with a red light conversion pattern and a green light conversion pattern respectively disposed in corresponding regions of the red and green sub-pixels of the liquid crystal panel, thereby realizing an ideal wavelength dispersion and a liquid crystal display device in which light conversion efficiency is remarkably improved. It is about.

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a liquid crystal display device.

In general, a liquid crystal display device is a display device capable of displaying a desired image by individually supplying data signals according to image information to pixels arranged in a matrix form and adjusting the light transmittance of the pixels.

Therefore, the liquid crystal display device is provided with 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 and 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 maintain a uniform cell gap facing each other. 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 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. Each pixel transmits or blocks light to display text or images.

At this time, since the liquid crystal display device is a light-receiving element that does not emit light itself and displays an image by adjusting 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 or short side distance of a liquid crystal panel is usually applied, and the cold cathode The fluorescent lamp generates white light by power supplied through the wiring at both ends.

At this time, when the above cold cathode fluorescent lamp is applied as a light source of a backlight unit, mercury (Hg) gas to which argon (Ar), neon (Ne), etc. is added is sealed at a low pressure in order to use a penning effect. Fluorescent discharge tube is used. At this time, electrodes are formed on both ends of the fluorescent discharge tube, and the cathode is formed in a wide plate shape. When voltage is applied, charged particles in the discharge tube collide with the plate-shaped cathode to generate secondary electrons, as in sputtering. The elements are excited to form a plasma. These elements emit strong ultraviolet light and the emitted ultraviolet light excites the phosphor again, 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 of the poor light-emitting characteristics of the light source itself, and it is difficult to realize high luminance due to the size and capacity limitation of the fluorescent lamp.

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

Recently, a light emitting diode is receiving attention as a light source of a backlight unit. Since the light emitting diode has a longer life than a cold cathode fluorescent lamp and operates at DC of 5V, it has an advantage of not requiring a separate inverter.

That is, the high-brightness light-emitting diode has a longer lifespan than the existing cold-cathode fluorescent lamp, and the power consumption is only 20% of that of the existing product, and it is also advantageous for thinning the product and improving the internal area efficiency because there is no need for additional equipment such as an inverter.

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

However, when using the light emitting device as a light source of the backlight as described above, the following problems occur.

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 element must be made into white light and supplied to the liquid crystal panel.

As a method for converting the monochromatic light of such a light emitting element into white light in a backlight unit, a method using a monochromatic light emitting element and a phosphor, a method using a light emitting element and a phosphor in the infrared wavelength band, and emitting light from red, green and blue light emitting elements And a method of mixing monochromatic light.

However, since white light is light having a spectrum in the entire range of visible light, when monochromatic light is converted to white light, the intensity at the wavelength of each color is lowered, and thus there is a problem that luminance is lowered.

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

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 suppressing light leakage.

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

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

The liquid crystal panel includes a light conversion layer on the viewing side of the viewing side polarizing plate,

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

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

3. In the above 1, the red light conversion pattern converts light irradiated from the light source to light of a wavelength of 550 to 750 nm, and the green light conversion pattern converts light irradiated from the light source to light of a wavelength of 400 to 600 nm. A liquid crystal display device.

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

5. In the above 1, the liquid crystal panel includes a color filter layer having red, green, and blue patterns on the visual side of the light conversion layer, and the red pattern is green on the visual side of the red light conversion layer. The pattern is disposed on the viewing side of the green light conversion layer, a liquid crystal display device.

6. In the above 1, wherein the polarizing plate includes a polarizer and an optical compensation film disposed on the viewing side, the light conversion layer is disposed on one side of the viewing side of the optical compensation film, a liquid crystal display device.

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

The liquid crystal display device of the present invention can realize ideal wavelength dispersion. This minimizes light leakage and has a wide viewing angle.

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

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

The present invention includes a backlight unit and a liquid crystal panel having a blue light source, wherein the liquid crystal panel includes a light conversion layer on the viewing side of the viewing side polarizing plate, and the light conversion layer includes red and green sub-pixels of the liquid crystal panel. By providing a red light conversion pattern and a green light conversion pattern, which are respectively disposed in corresponding regions of the present invention, it is possible to implement an ideal wavelength dispersion property and relates to a liquid crystal display device in which light conversion efficiency is significantly improved.

1 and 2 are schematic cross-sectional views of a liquid crystal display according to an exemplary 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 backlight unit 200 and a liquid crystal panel 100 having a blue light source.

The liquid crystal panel 100 includes a first substrate 120 and a second substrate 130 that are adhered to each other with the liquid crystal layer 110 interposed therebetween. The first substrate 120 is located on the opposite side of the viewing side, and the second substrate 130 is located on the viewing side.

The liquid crystal layer 110 is filled with liquid crystal, and the upper and lower portions include an alignment layer 140a. 140b for aligning the liquid crystal in a predetermined direction. The first alignment layer 140a is located on the opposite side of the viewing side, and the second alignment layer 140b is located on the viewing 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, and Various image information is displayed by changing the amount of transmitted light.

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, a unit pixel area is defined by the intersection, and the defined pixel area is formed in a matrix form.

In addition, a pixel electrode is formed in each of the pixel regions, and a thin film transistor is formed at a point where each gate line and a data line intersect.

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

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 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 an electric field is generated by a switching operation of the thin film transistor to control the orientation 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.

First polarizers 150a and second polarizers 150b that selectively transmit only specific light may be attached to the outer surfaces of the first substrate 120 and the second substrate 130, respectively. The first polarizing plate is disposed on the opposite side of 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 adhered to at least one surface thereof. In addition, 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 to 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 attached 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 a light conversion layer 160 on the viewing side of the second polarizing plate 150b.

As described above, on the upper side of the liquid crystal layer 110, a second polarizing plate 150b to which an optical compensation film is attached is disposed. The optical compensation film is designed to exhibit optical functions required for light of a specific wavelength (single color light). , It is usually designed based on the light of 550nm wavelength band. This is called the design center wavelength.

However, in the case of a normal liquid crystal display device, since the backlight unit includes a white light conversion layer, white light is irradiated from the backlight unit, and white light passes through the liquid crystal layer to reach the optical compensation film. Since white light is light having a wavelength in the entire range of visible light of about 380 nm to 780 nm, an ideal phase difference cannot be realized for wavelengths other than 550 nm, and wavelength dispersibility deviates from an ideal value. Accordingly, there is a problem that the wavelength of light is distorted and light leaks or the viewing angle is narrowed.

The wavelength dispersibility is an ideal value as the ratio of each wavelength is closer, for example, it is closer to 0.82 (450 nm/550 nm) for short wavelength dispersion (delay value for incident light at 450 nm/delay value for incident light at 550 nm). Is the ideal value, and in the case of long wavelength dispersion (retardation value for incident light of 650 nm/retardation value for incident light of 550 nm), the closer to 1.18 (650 nm/550 nm), the ideal value.

However, since the liquid crystal display device of the present invention transmits the blue light 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 necessary optical functions for blue light. have. That is, it is possible to implement an ideal wavelength dispersion, thereby suppressing the light leakage problem, it is possible to implement a wide viewing angle.

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

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

As described above, since the light irradiated from the light source is converted to light having a wavelength of a single color, not white light having a wavelength in a full range, light conversion efficiency is significantly improved.

The red light conversion pattern 161 may convert irradiated light into light having a wavelength of 550 to 750 nm, and the green light conversion pattern 162 may convert irradiated light into light having a wavelength of 400 to 600 nm, but is not limited thereto. It does not work.

If the light conversion layer 160 is above the viewing side polarizing plate 150b of the liquid crystal panel 100, its position is not particularly limited. For example, the light conversion layer 160 may be disposed on one side of the viewing side of the second polarizing plate 150b. 2 A single layer or a plurality of layers may be further positioned between the polarizing plate 150b and the light conversion layer 160.

When located 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 on the opposite side of the viewing side.

The red light conversion pattern 161 is not particularly limited as long as it can convert light irradiated from a light source into red light. For example, Eu-doped sulfo selenide, and Eu- and/or Ce-doped It is preferably selected from nitrides, oxynitrides, alumosiliconitrides and/or Mn(IV)-doped oxides and/or fluorides. The red-emitting phosphors here are nitridic phosphors, preferably (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 0.005 to 1, and y represents a value from the range 0.01 to 3) , Or variants in which individual lattice positions in the compounds are substituted by other chemical elements such as alkali metals, aluminum, gallium or gadolinium, or additional elements of this type occupy flaws as a dopant. It may be particularly preferred to be selected from.

Suitable material systems known to those skilled in the art are silicon nitrides and aluminosilicon nitrides (see Xie, Sci. Technol. Adv. Mater. 2007, 8, 588-600), 2-5-8 nitrides, such as (Ca,Sr,Ba) ₂ Si ₅ N ₈ :Eu ^{2 +} (Li et al., Chem. Mater. 2005, 15, 4492), and aluminosilicon nitrides, such as (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 light emitted from a 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 region of 580 nm or more and less than 660 nm, it is known that it is suitable for use as a light emitting device such as a white LED light source, for example.

(1) M ₂ Si ₅ N ₈ : Eu ^{2 +} (See Japanese Patent Publication 2003-515665)

(2) MSi ₇ N ₁₀ : Eu ^{2 +} (See Japanese Patent Publication 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 Japanese Patent Laid-Open No. 2003-203504)

(5) Ca1.5A1 ₃ Si ₉ N ₁₆ : Eu ^{2 +} (See Japanese Patent Laid-Open No. 2003-124527)

(6) CaA1 ₂ Si ₁₀ N ₁₆ : Eu ^{2 +} (See Japanese Patent Laid-Open No. 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 Laid-Open No. 2003-206481)

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

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

(11) Sr ₂ Si ₄ A _lO N ₇ : Eu ^{2 +} (See Japanese Patent Laid-Open No. 2003-206481)

(12) CaSiN ₂ : Eu ^{2 +} (SS Lee, S. Lim, SS Sun and JF Wager, Proceedings of SPIE-the International Society for Optical Engineering, Vol. 3241, (1997), p. 75-83).

However, M represents Mg, Ca, Sr, Ba, or zinc (Zn) independently of each other. Conventionally, such nitride phosphors mainly use the above-mentioned element M nitride or metal and silicon nitride and/or aluminum nitride as raw materials for the phosphor matrix, together with a compound containing an element that forms a luminescent center ion, It was manufactured by the manufacturing method of reacting in a nitriding gas atmosphere.

The liquid crystal panel 100 according to the present invention includes red 181, green 182, and blue (which are sequentially arranged to correspond to red, green, and blue sub-pixel regions of the liquid crystal panel on the viewing side of the light conversion layer, respectively. A color filter layer 180 including the pattern of 183) may be provided.

As illustrated in FIG. 2, the red pattern 181 of the color filter layer 180 is above the viewing side of the red light conversion pattern 161, and the green pattern 182 is above the viewing side of the green light conversion pattern 162. Is placed on. Further, the blue pattern 183 is disposed in a corresponding region of the blue sub-pixel.

When the color filter layer 180 is provided, light that already represents red, green, and blue colors may pass through the color filter layers 180 corresponding to colors, thereby expressing more various colors with higher purity.

The color filter layer 180 may include an organic pigment or an organic dye that partially absorbs and partially transmits a wavelength of light incident from the light source, and may include a binder resin as necessary.

An overcoat layer 190 may be further formed on the opposite side of the color filter layer 180 from the viewing side. The overcoat layer 190 covers the color filter layer 180 to planarize the step difference between them. 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 a boundary corresponding region of red, green, and blue sub-pixels of the liquid crystal panel 100 to prevent a decrease in transmittance.

The location of the black matrix 170 is not particularly limited as long as it is a region corresponding to the boundary of each sub-pixel, and may be formed on one surface of the second substrate 130 and one surface of the second polarizing plate 150b, for example. Alternatively, it may be any one of the layer structures of the liquid crystal panel 100.

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 row (or string) form on one side of the liquid crystal panel 100. In the dual type, light sources are arranged in rows (or strings) on both sides of the liquid crystal panel 100. In the direct type, a light source is disposed in a block or matrix form under the liquid crystal panel 100. Among them, the thin film may be preferably edge-shaped in terms of weight reduction and large area.

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

The backlight unit 200 includes a light source, a light guide plate, a reflector 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 to which light emitted from the light source is incident spreads evenly over a wide area of the light guide plate while the incident light proceeds in the light guide plate by multiple total reflections to provide 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 surface 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, etc. in order to guide the light incident inside the light guide plate. It is formed on the lower surface of the printing method or injection method.

The reflector is located 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 luminance of the light.

The optical sheet on the light guide plate includes a diffusion sheet and at least one light collecting sheet, and diffuses or collects light passing through the light guide plate so that a more uniform surface light source enters the liquid crystal panel 100. In this case, the optical sheet may include a reflective polarizing sheet that improves light efficiency by regenerating linear polarized light.

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 the white light conversion layer and emits blue light.

The liquid crystal display device of the present invention comprising the above-described structure realizes ideal wavelength dispersion, thereby suppressing light leakage and realizing a wide viewing angle. And, the light conversion efficiency is significantly improved, there is an advantage that can realize a high brightness.

As described above, in order to help the understanding of the present invention, preferred embodiments have been presented, but these embodiments are merely illustrative of the present invention and do not limit the scope of the appended claims, and fall within the scope and technical scope of the present invention. It is apparent to those skilled in the art that various changes and modifications to the embodiments are possible, and it is natural that such modifications 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 polarizing plate 150b: second polarizing plate
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)

It includes a backlight unit and a liquid crystal panel having a blue light source in the wavelength range of 350 to 450nm,
The liquid crystal panel includes a viewing side polarizing plate, and the polarizing plate includes a polarizer and an optical compensation film having a design center wavelength disposed on the viewing side of the polarizer and included in a wavelength range of the blue light source,
Includes a light conversion layer on the viewing side of the polarizing plate,
The light conversion layer includes a red light conversion pattern and a green light conversion pattern, which are respectively disposed in corresponding regions of the red and green sub-pixels of the liquid crystal panel.
delete The method according to claim 1, wherein the red light conversion pattern converts light emitted from the light source to light having a wavelength of 550 to 750 nm, and the green light conversion pattern converts light emitted from the light source to light having a wavelength of 400 to 600 nm, Liquid crystal display device.
The liquid crystal display device of claim 1, wherein the backlight unit does not include a white light conversion layer.
The method according to claim 1, The liquid crystal panel includes a color filter layer having a red, green and blue pattern on the viewing side of the light conversion layer, the red pattern is on the viewing side of the red light conversion layer, the green pattern is A liquid crystal display device, which is disposed on the viewing side of the green light conversion layer.
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