KR100397574B1 - Backlight Ink and Preparation Thereof and Backlight Production of High Intensity by Use Thereof - Google Patents

Abstract

The present invention relates to a backlight ink of a liquid crystal display (LCD), a method for manufacturing the same, and a method for generating the backlight using the same, wherein the ink manufacturing method of the present invention is 20 to 50% by weight in a mixed solvent of toluene, xylene, and cyclohexanone. Dissolved in an acrylic copolymer and a vinyl copolymer in a weight ratio of 1: 3 to 1: 1, and then mixed with 1 to 5% by weight of polydimethylsiloxane having a molecular weight of 30,000 or less containing ethylene oxide and propylene oxide groups, and the temperature of 100 ~ 150 ℃ After stirring for 2-3 hours at, the temperature was lowered to 60 ° C. or lower, and a methanol solution containing 5 to 10% by weight of tetraethoxysilane and methyl tetramethoxysilane was added dropwise for 8 to 12% by weight for 1 to 5 hours, and under the same conditions, 1 After holding for at least 8 to 12% by weight of a solution of aminomethylpropanol and methanol in a ratio of 1: 1 to 2: 1 was added dropwise, and 8 to 12% by weight of a filler (filler) was added, and then within 0.01 It characterized in that it comprises the step of adding 1% by weight of the phosphor, the ink for high brightness according to the present invention by adding a phosphor to the ink to be applied to the light guide plate surface to emit ultraviolet rays of a specific region emitted through the cold cathode tube (CCFL) It absorbs and converts it into the visible light region, thereby blocking the ultraviolet light and improving the brightness of the backlight while using the existing cold cathode tube.

Description

Backlight ink and preparation method thereof, and method for generating backlight with high brightness using same {Backlight Ink and Preparation Thereof and Backlight Production of High Intensity by Use Thereof}

The present invention relates to a backlight ink of a liquid crystal display (LCD), a method of manufacturing the same, and a method of generating a high brightness backlight using the same, and more particularly, different from a fluorescent layer coated on an inner wall of a glass tube of a light emitting lamp. Backlighting ink containing visible phosphors is dot printed on the bottom surface of the light guide plate of the backlight assembly of the LCD module to convert excess light from the cold cathode tube (CCFL), which is a light source, into visible light to increase luminance. The present invention relates to a backlight ink, a method of manufacturing the same, and a backlight generating method using the same.

With the trend toward miniaturization and lightening of electronic products, the CRT (Cathode Ray Tube), which is mainly used for monitors such as televisions, measuring devices, and information terminal devices, is able to respond to the demands for small size and light weight due to its large weight and size. Could not. Therefore, the development of liquid crystal display (LCD), which has the advantages of small size and light weight, has been actively progressed in order to replace it, and in recent years, it is enough to play a role as a flat panel display device, and the demand is continuously increasing. have.

However, since the liquid crystal display (LCD) does not emit light by itself and only modulates the amount of transmitted light, a backlight assembly for uniformly irradiating a monitor screen using liquid crystal should be installed at the rear of the LCD panel. . The performance required for the backlight in the form of a surface light source should be uniform in the luminance of the entire display surface, and sufficient luminance should be maintained in consideration that the transmittance of the liquid crystal panel is less than 10%.

As shown in FIG. 1, the conventional lamp assembly includes a backlight assembly installed at the rear of the LCD panel to transmit light to the front of the LCD panel. The backlight assembly is provided with a lamp assembly composed of a light emitting lamp 7 and a lamp reflector 6 at the rear edge of the LCD panel, and the light beam from the light emitting lamp 7 and the light from the lamp reflector 6 are disposed on the LCD panel 1. A light guide plate 4 is installed to uniformly guide the front of the light guide plate, and a reflecting plate 5 is attached to the rear surface of the light guide plate 4, and diffuser plate 3 for diffusing and condensing the light guided from the light guide plate 4; Sheets such as the prism 2 are configured to be installed between the light guide plate 4 and the LCD panel 1. The lower portion of the light guide plate 4 is printed in a pattern in which the ink is dot-shaped, and the portion near the lamp is made small and the far portion is formed of dots of larger size to control the amount of reflection and to have a uniform luminance distribution over the entire backlight surface.

The conventional backlight assembly configured as described above has been concentrated on the development of high brightness sheets, high brightness light emitting lamps, high brightness mechanism structures, etc., for high brightness and thinness, which are a measure for determining the technological competitiveness of a product.

Among them, the light emitting lamp is a cold cathode fluorescent lamp (CCFL), which converts electrical energy into light energy by using an encapsulating gas and emits ultraviolet light. Ultraviolet light cannot be seen by the naked eye, so it must be converted into visible light. An inorganic fluorescence layer is coated on the inner wall of the glass tube of the light emitting lamp. However, the ultraviolet light is not converted into 100% visible light and enters the light guide plate, but also a part of ultraviolet light is also incident. FIG. 2 shows an example of an emission spectrum emitted from the light emitting lamp 7. The spectrum shows that not only visible light but also excess ultraviolet light are emitted.

When the amount of light emitted from the light source is 100%, the amount of light finally perceived by our eyes through the light guide plate, diffuser plate, and prism LCD panel is about 10% or less. Therefore, in order to use higher light efficiency, much research has been conducted to reduce the light lost by each component and to increase the efficiency of the light using each component.

According to Korean Patent Application No. 98-28271, the fluorescent material is coated on the entire surface of the light guide plate instead of the inner wall of the light emitting lamp glass tube to increase the luminance by increasing the coating area of the fluorescent material. However, for this purpose, there is a disadvantage in that an ultraviolet light guide plate must be used so that ultraviolet light can reach the fluorescent layer without energy loss.

The present invention is to solve the above-mentioned problems, and unlike the enlarged coating area of the fluorescent layer focusing on the light emitting lamp, by absorbing ultraviolet light partially emitted from the cold cathode tube (CCFL) of the LCD backlight assembly It aims to increase brightness by switching to visible light.

In addition, another object of the present invention is to provide an ink for backlight for increasing the brightness of the liquid crystal display device.

1 is a schematic view showing a backlight assembly according to the prior art.

2 is an example of a cold cathode tube (CCFL) emission spectrum.

3 and 4 is a schematic view showing a backlight assembly for high brightness according to the present invention.

5 is a reflection spectrum showing the effect of adding a primary ultraviolet absorbing phosphor.

6 is an absorption and emission spectrum of a primary ultraviolet absorbing phosphor.

7 is a reflection spectrum showing visible light conversion of some ultraviolet regions.

8 is a schematic diagram of a luminance measurement point;

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

1 LCD Panel 2 Prism 3 Diffusion Plate

4: Light guide plate 5: Reflector 6: Lamp reflector

7 light emitting lamp 8 fluorescent ink layer 9 fluorescent layer

In the method of preparing the ink of the present invention, 20 to 50% by weight of an acrylic copolymer and a vinyl copolymer are dissolved in a mixed solvent of toluene, xylene and cyclohexanone at a weight ratio of 1: 3 to 1: 1, and then ethylene oxide group 1 to 5 weight percent of polydimethylsiloxane having a molecular weight of 30,000 or less containing propylene oxide group was mixed, stirred at 100 to 150 ° C. for 2 to 3 hours, and then the temperature was lowered to 60 ° C. or less, and tetraethoxysilane and methyl tetramethoxysilane were 5 to 10 8 to 12% by weight of the methanol solution containing 1% by weight was added dropwise for 1 to 5 hours, and maintained for 1 hour or more under the same conditions, and then 8 to 12% by weight of a solution containing aminomethylpropanol and methanol in a ratio of 1: 1 to 2: 1. Adding dropwise, adding 8-12 wt.% Dispersant, and then adding 0.01-1 wt.% Phosphor.

In the backlight generation method of the present invention, the backlight ink manufactured as described above is dot-printed on the bottom surface of the light guide plate of the backlight assembly of the LCD module to convert ultraviolet light into visible light, thereby inducing high brightness.

Hereinafter, the present invention will be described in detail.

Referring to FIG. 3, the backlight ink is dot printed on the bottom surface of the light guide plate 4. Therefore, ultraviolet rays of a specific region emitted from the cold cathode tube (CCFL) are absorbed in this portion, causing fluorescence emission and scattering, and moving toward the front surface. However, the ultraviolet rays causing the fluorescent emission of the phosphor go through various stages from the cold cathode tube (CCFL) to the reflecting plate 5 through the light guide plate 4, so that there is a risk of loss.

In FIG. 4, a backlight ink, which does not include a filler, is applied to the long side of the light guide plate 4 to reduce a loss of ultraviolet light that causes fluorescence emission of the phosphor. That is, the ultraviolet rays emitted from the cold cathode tube (CCFL) are converted into white light by the fluorescent layer 9 applied to the long side of the light guide plate, thereby inducing degradation of the light guide plate and increasing brightness.

FIG. 5 is a reflection spectrum showing the effect of adding a primary ultraviolet absorbing phosphor (2,2 '-(2,5-Thiophenediyl) bis [5- (1,1-dimethylethyl) benzoxazole]) to a maximum absorption wavelength. Is 375 nm and the maximum fluorescence wavelength is 437 nm. It can be seen that the luminance of visible light is increased by effectively absorbing a specific ultraviolet region and emitting blue fluorescence.

6 is an absorption and emission spectrum of a primary ultraviolet absorbing phosphor. Phosphors that can be used equivalently to the primary ultraviolet absorbing phosphor include 2,2- (4,4-Diphenolvinyl) dibenzoxazol or 1,4-Bis (benzoxazolyl-2-yl) naphthalene.

The phosphor used as the secondary phosphor that will partially absorb the light of the emitted fluorescence is (3- (5-Chloro-1,3-benzoxazol-2-yl) -7- (diethylamino) coumarin), and the maximum fluorescence wavelength Is 510 nm, and the tertiary phosphor which will absorb some of the fluorescence light is 2-Cyano-13-N, N-diethylamino-3-iminobenzimidazolo [1,2-a] pyridino [3,4-b] -2H- Chromium is used and the maximum fluorescence wavelength is 600 nm.

Hereinafter, the manufacturing method of the ink for backlight is disclosed.

First, 20-50 weight% of an acryl-type copolymer and a vinyl-type copolymer are melt | dissolved in the mixed organic solvent of toluene, xylene, and cyclohexanone in the weight ratio of 1: 3-1: 1. When the addition ratio of the copolymer exceeds the above range, there is a problem in that printability is inferior due to fluidity change, and in the case below the above range, there is a problem in that mechanical properties are poor when printing on the light guide plate. Moreover, when the ratio of an acrylic copolymer exceeds the said range, there exists a possibility that adhesive fall may occur, and when it is below the said range, there exists a problem that the water resistance of a printed matter falls.

1-5 weight% of polydimethylsiloxane having a molecular weight of 30,000 or less containing an ethylene oxide group and a propylene oxide group were mixed in the obtained solution, stirred at 100-150 ° C. for 2-3 hours, and then the temperature was lowered to 60 ° C. or lower. When the molecular weight of the polydimethylsiloxane is more than the above range, there is a problem in that compatibility is lowered and the orientation of the filler is lowered, and when the addition amount exceeds the above range, the print tension is inferior due to excessive drop in surface tension.

Subsequently, a methanol solution containing 5 to 10% by weight of tetraethoxysilane and methyl tetramethoxysilane is added dropwise to 8 to 12% by weight for 1 to 5 hours, and maintained for 1 hour or more under the same conditions. When the content of tetraethoxysilane and methyl tetramethoxysilane is less than the above range, it does not function as a diffusion aid and thus does not improve the brightness of the ink, and when it exceeds the above range, the diffuse reflection effect is deteriorated due to the increase in cloudiness. When the dropwise addition of the methanol solution is less than the above range, it does not function as an adjuvant and thus does not improve the diffusivity, and when it exceeds the above range, the workability is poor due to the increase of the drying rate.

Subsequently, 8 to 12% by weight of a solution containing aminomethylpropanol and methanol in a weight ratio of 1: 1 to 2: 1 is added dropwise to the solution. When the ratio of methanol is less than the above range, it does not improve the dispersion by inhibiting even dispersion, and when it exceeds the above range, it does not function as an adjuvant and does not improve the dispersibility of the solution. In addition, when the dropwise addition amount of the mixed solution of aminomethylpropanol and methanol is less than the above range, problems may occur in optical properties and dispersibility. If the addition amount exceeds the above range, the drying speed of the ink may be increased during printing to reduce printability. Let's do it.

To the obtained solution is added 8 to 12% by weight of a filler. The filler added preferably contains less than 10 μm SiO ₂ , TiO ₂ , and BaSO ₄ . By adding a filler, scattering of light guided into the light guide plate may be achieved.

Finally, the addition of 0.01 to 1% by weight of the phosphor yields the ink of the present invention. Usable phosphors are as described above.

An embodiment of the present invention is as follows.

<Production Example 1>

Toluene, xylene, and cyclohexanone were dissolved in a mixed solvent mixed in the same ratio composition to dissolve 30% by weight of an acrylic copolymer having a molecular weight of 100,000 and a vinyl copolymer having a molecular weight of 30,000. The solution was mixed with polydimethylsiloxane having a molecular weight of 25,000 containing ethylene oxide and propylene oxide, and then stirred for 2 hours at a speed of 300 rpm at a temperature of 130 ° C., and then the temperature was lowered to 60 ° C. or less, and tetraethoxysilane and methyl tetramethoxysilane were 8 weights. Methanol solution containing% was added dropwise for 2 hours. After maintaining for 1 hour under the same conditions, a solution of aminomethylpropanol and methanol in a 1: 1 weight ratio was added dropwise for 30 minutes, and maintained for 4 hours under the same conditions. Then, SiO ₂ , TiO ₂ , and BaSO having an average particle diameter of 7 μm were added. ₄ was added in the same ratio (filler) was mixed with Dispermat (VMA-Getzmann, Germany) for 30 minutes and finally, 2,2 '-(2,5-Thiophenediyl) as a primary phosphor bis [5- (1,1-dimethylethyl) benzoxazole], as a secondary phosphor (3- (5-Chloro-1,3-benzoxazol-2-yl) -7- (diethylamino) coumarin), 2 as a tertiary phosphor -Cyano-13-N, N-diethylamino-3-iminobenzimidazolo [1,2-a] pyridino [3,4-b] -2H-chromene were added in 0.2% by weight of each composition and dispersed for 30 minutes To prepare a back ink including the.

<Comparative Manufacturing Example>

The same procedure as in Preparation Example was carried out, but the ink for backlight was prepared by omitting the process of inserting the phosphor.

<Examples and Comparative Examples>

The ink obtained by the Preparation Example and Comparative Preparation Example was screen printed and measured with a spectrophotometer, and the CIE L ^* a ^* b ^* values thereof are shown in Table 1.

As shown in Table 1, both of the inks generate the same white light, but in the reflection spectrum of FIG. 7, when the phosphor is added, the ultraviolet region is almost eliminated and the luminance of the visible region is increased.

Also, Table 2 and FIG. 8 show the points and the results of luminance measurement by dot-printing the backlight ink obtained by the Production Example and Comparative Production Example on the bottom surface of the light guide plate of the backlight assembly of the LCD module. . As a result, it can be seen that the ultraviolet ray area, which did not affect the luminance, is converted to the visible ray area, and the luminance increase rate is about 10% (60 to 180 cd / m ² ).

illuminant L ^* a ^* b ^* C ^* h Comparative example D65 / 10 ° 60.18 -0.42 -1.83 1.88 257.08 A / 10 ° 60.00 -0.90 -2.04 2.23 246.25 F2 / 10 ° 60.06 -0.27 -2.10 2.11 262.76 Example D65 / 10 ° 68.58 -0.08 -1.57 1.57 267.11 A / 10 ° 68.45 -0.44 -1.74 1.80 255.68 F2 / 10 ° 68.51 0.14 -1.79 1.79 274.34

point Comparative Example (Unit cd / m ² ) Example (Unit cd / m ² ) One 1966 1989 2 1909 1994 3 1929 1987 4 1933 1986 5 1950 1980 6 1784 1887 7 1767 1874 8 1808 1888 9 1875 1888 10 1939 1932 11 1816 1917 12 1793 1900 13 1831 1902 medium 5 points 1937 1987 13 points 1869 1933 Uniformity 5 points 1.03 1.01 13 points 10.65 6.21

As can be seen from the above examples and comparative examples, the backlight ink according to the present invention absorbs ultraviolet rays from a specific region coming out through the cold cathode tube (CCFL) of the LCD backlight assembly by adding a phosphor and converts it into a visible ray region. It is possible to block the excess ultraviolet light and improve the brightness of the backlight while using the existing cold cathode tube.

Claims (5)

20 to 50% by weight of an acrylic copolymer and a vinyl copolymer are dissolved in a mixed solvent of toluene, xylene, and cyclohexanone at a weight ratio of 1: 3 to 1: 1, followed by ethylene oxide and propylene oxide (propylene). 1-5 wt% of polydimethylsiloxane having a molecular weight of 30,000 or less containing an oxide group is mixed, stirred at 100-150 ° C. for 2-3 hours, and then the temperature is lowered to 60 ° C. or lower, and tetraethoxy Methanol solution containing 5 to 10% by weight of silane (tetraethoxysilane) and methyl tetramethoxysilane was added dropwise to 8 to 12% by weight for 1 to 5 hours, and maintained for 1 hour or more at the same condition below 60 ℃. After the addition of 8 to 12% by weight of a solution of aminomethylpropanol and methanol 1: 1 to 2: 1 dropwise added, and the filler (adder) 8 to 12% by weight, then 0.01 to 1% by weight ofA method of manufacturing an ink for backlight comprising the step of adding the housing. The phosphor of claim 1, wherein the phosphor to be added is 2,2 '-[2,5-thiophenediyl] bis (bis) [5- {1,1-dimethylethyl} benzojazolbenzoxazole] , 2,2- [4,4-diphenolvinyl] dibenzoxazol, 1,4-bis (Bis) [benzoxazolyl-2-yl (yl)] naphthalene ( naphthalene), 3- [5-Chloro-1,3-benzoxazol-2-yl (yl)]-7- [diethylamino] coumarin, 2-sia Cyano-13-N, N-diethylamino-3-iminobenzimidazolo [1,2-a] pyridino [3,4-b] -2H- Method for producing a backlight ink, characterized in that it comprises at least one selected from chromene (chromene). The method of claim 1, wherein the filler contains SiO ₂ , TiO ₂ , and BaSO ₄ of less than 10 μm. The bag obtained by the method of claim 1 and applied to the bottom surface or long side surface of the backlight assembly 4 of the LCD module to convert ultraviolet light emitted from the cold cathode tube (CCFL) into visible light. Ink for Like. delete