KR20090060067A

KR20090060067A - Diffuser plate and backlight unit for lcd including the same

Info

Publication number: KR20090060067A
Application number: KR1020070127219A
Authority: KR
Inventors: 정용훈
Original assignee: 엘지디스플레이 주식회사
Priority date: 2007-12-07
Filing date: 2007-12-07
Publication date: 2009-06-11

Abstract

The present invention relates to a backlight unit for a liquid crystal display device, and more particularly to a diffuser plate of a backlight unit.

A feature of the present invention is to provide a diffuser plate having a domed lenticular lens formed on an upper surface thereof, and a diffraction grating formed on a valley portion of the lenticular lens.

Accordingly, the thickness of the liquid crystal display device can be reduced by reducing the distance between the lamp and the diffuser and the distance between the lamp and the reflector, while preventing defects such as a conventional lamp mura phenomenon.

In addition, a liquid crystal display device having more uniform luminance can be provided.

Description

Diffuser plate and backlight unit for LCD including the same}

In line with the recent information age, the display field has also been rapidly developed, and a liquid crystal display device (FPD) is a flat panel display device (FPD) having advantages of thinning, light weight, and low power consumption. LCD, plasma display panel device (PDP), electroluminescence display device (ELD), field emission display device (FED), etc. : It is rapidly replacing CRT.

Among them, liquid crystal display devices are used most actively in the fields of notebooks, monitors, TVs, etc. due to their excellent contrast ratio and high contrast ratio. These liquid crystal display devices are devices that do not have their own light emitting elements. Will require a light source.

As a result, a backlight unit having a lamp is provided on the rear side to irradiate light toward the front of the liquid crystal panel, thereby realizing an image of identifiable luminance.

On the other hand, the general backlight unit is divided into an edge type (edge type) and a direct type (direct type) according to the arrangement of the lamp, the edge type has a structure in which one or a pair of lamps are disposed on one side of the light guide plate, Two or two pairs of lamps have a structure in which both sides of the light guide plate are arranged, and the direct type has a structure in which several lamps are arranged under the optical sheet.

In recent years, in the state of active research on large-area liquid crystal display devices according to consumer demand, the direct method is more suitable for the large-area liquid crystal display device than the edge method.

1 is a cross-sectional view of a liquid crystal display using a general direct type backlight unit.

As shown in the drawing, a general liquid crystal display device includes a liquid crystal panel 10 including first and second substrates 12 and 14 and a backlight unit 20 behind the liquid crystal panel 10.

Here, the backlight unit 20 includes a reflecting plate 22, and a plurality of lamps 24 are arranged side by side on an upper surface thereof, and a diffusion plate 26 and a plurality of optical sheets (top) of the lamps 24 are arranged above. 29) is located.

The liquid crystal panel 10 and the backlight unit 20 are modularized through the top cover 40, the guide panel 30, and the cover bottom 50. That is, the edges of the liquid crystal panel 10 and the backlight unit 20 are formed. The top cover 40 covering the front edge of the liquid crystal panel 10 and the cover bottom 50 covering the back surface of the backlight unit 20 in the state where the rectangular panel-shaped guide panel 30 is wrapped are respectively coupled to the front and rear guide panels ( 30) is integrated through the medium.

On the other hand, the liquid crystal display device has recently been used in a wide range of applications, such as portable computers, desktop computer monitors and wall-mounted televisions. Recently, research on thin liquid crystal display devices with a large display area has been actively conducted. .

Accordingly, the liquid crystal thinner by reducing the distance A between the lamp 24 and the diffuser plate 26 of the backlight unit 20 or the distance B between the lamp 24 and the reflector plate 22. Attempts have been made to provide a display device.

However, in order to supply the high quality surface light source, which is the most important role of the backlight unit 20, to the liquid crystal panel 10, various optical designs for this purpose are considered, and one of them is the lamp 24 and the diffusion plate 26. Maintaining the proper spacing A between and maintaining the spacing B between the lamp 24 and the reflector plate 22 is an important factor.

That is, when the distance A between the lamp 24 and the diffuser plate 26 is too small, or when the distance B between the lamp 24 and the reflector plate 22 is small, the light from the lamp 24 has a strong straightness. Since the shape of the lamp 24 is reflected in the image as shown in FIG. 2, the lamp mura phenomenon in the form of a stripe is generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a thin liquid crystal display and to solve a defect such as a lamp mura.

In order to achieve the object as described above, the present invention is a reflection plate; A lamp arranged above the reflector; A diffusion plate positioned above the lamp and including a lens in which mountains and valleys are repeatedly arranged to protrude in rows; It provides a backlight unit for a liquid crystal display device comprising a plurality of optical sheets positioned on the diffusion plate, the diffraction grating is formed in the valley portion of the diffuser lens.

The lens of the diffusion plate is characterized in that formed on one surface adjacent to the plurality of optical sheets of the base film containing a light diffusing component, the diffraction grating is characterized by consisting of slits formed at minute intervals.

In this case, the light diffusion component is characterized in that the bead (bead) or fine pattern, the lens is characterized in that the dome-shaped lenticular lens or prism acid-shaped prism lens.

In addition, the plurality of optical sheets is characterized in that it comprises a diffusion sheet and a light collecting sheet, the diffusion sheet is a base film and an acrylic resin layer containing a light diffusion component on the upper surface and the lower surface of the base film It characterized by consisting of a diffraction grating.

In addition, the present invention comprises a base film comprising a light diffusion component; A lens which is arranged to protrude in a row by repeating mountains and valleys on one surface of the base film; Provided is a diffusion plate including a diffraction grating formed in a valley of the lens.

As described above, according to the present invention by forming a domed lenticular lens on the upper surface of the diffuser plate, and forming a diffraction grating in the valley portion of the lenticular lens, the distance between the lamp and the diffuser plate and the distance between the lamp and the reflector plate It is possible to reduce the size of the liquid crystal display and reduce the defects such as the existing lamp mura phenomenon.

In addition, there is an effect that can provide a liquid crystal display device having a more uniform brightness.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

3 is an exploded perspective view illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

As illustrated, the liquid crystal display device includes a liquid crystal panel 110, a backlight unit 120, a support main 130, a cover bottom 150, and a top cover 140.

First, the liquid crystal panel 110 plays a key role in image expression, and includes the first and second substrates 112 and 114 bonded to each other with the liquid crystal layer interposed therebetween.

In this case, under the premise of an active matrix method, although a plurality of gate lines and data lines are intersected on the inner surface of the first substrate 112, which is commonly referred to as a lower substrate or an array substrate, pixels are defined. Thin film transistors (TFTs) are provided at each intersection to be connected one-to-one with the transparent pixel electrodes formed in each pixel.

In addition, an inner surface of the second substrate 114 called an upper substrate or a color filter substrate includes, for example, a color filter of R, G, and B colors, each of which includes a gate line, a data line, A black matrix covering a non-display element such as a thin film transistor is provided. In addition, a transparent common electrode covering them is provided.

The printed circuit boards 117a and 117b are connected to each other along at least one edge of the liquid crystal panel 110 through a connecting member 116 such as a flexible circuit board, thereby supporting the side or cover bottom of the support main 130 in the modularization process. 140) It is flipped to the back and adhered.

Although not clearly shown in the drawings, upper and lower alignment layers (not shown) for determining the initial molecular alignment direction of the liquid crystal are interposed between the two substrates 112 and 114 of the liquid crystal panel 110 and the liquid crystal layer. In order to prevent leakage of the liquid crystal layer filled therebetween, a seal pattern is formed along edges of both substrates 112 and 114.

In this case, upper and lower polarizers (not shown) are attached to outer surfaces of the first and second substrates 112 and 114, respectively.

A backlight unit 120 for supplying light is provided on a rear surface of the liquid crystal panel 110 such that a difference in transmittance of the liquid crystal panel 110 is expressed to the outside.

The backlight unit 120 includes a reflector plate 122, a plurality of lamps 124, a diffuser plate 300, and a plurality of optical sheets 129, and a plurality of lamps 124 are arranged side by side on the reflector plate 122. The diffusion plate 300 and the plurality of optical sheets 129 are positioned above the lamps 124.

In this case, as the light source, the lamp 124 may be a fluorescent lamp such as a cold cathode fluorescent lamp or an external electrode fluorescent lamp. Alternatively, a light-emitting diode lamp other than the fluorescent lamp may be used as the lamp 124.

In addition, a pair of side supports 128 for fixing / supporting a plurality of lamps 124 are provided and fastened to the cover bottom 150.

In this case, in addition to fixing the lamp 124, the side support 128 serves to make the interval between the lamp 124 and the diffusion plate 300 constant.

Here, the reflecting plate 122 is located on the back of the plurality of lamps 124, and reflects the light emitted from the back of the lamp 124 toward the liquid crystal panel 110 to improve the brightness of the light.

In addition, the plurality of optical sheets 129 disposed to be spaced apart from the lamp 124 may include a diffusion sheet and at least one light collecting sheet.

Accordingly, the light emitted from the plurality of lamps 124 is processed to a uniform high quality while passing through the diffusion plate 300 and the plurality of optical sheets 129 and then incident on the liquid crystal panel 110, thereby using the liquid crystal. The panel 110 may display a high brightness image.

The liquid crystal panel 110 and the backlight unit 120 are modularized through the top cover 140, the support main 130, and the cover bottom 150. The top cover 140 is the top and side surfaces of the liquid crystal panel 110. A rectangular frame having a cross section bent in a "b" shape to cover an edge thereof is configured to open an entire surface of the top cover 140 to display an image implemented in the liquid crystal panel 110.

In addition, the cover bottom 150 on which the liquid crystal panel 110 and the backlight unit 120 are mounted, and which is the basis for assembling the entire structure of the liquid crystal display device module, has a rectangular plate shape, and the edges at both sides of the longitudinal direction thereof are inclined at a predetermined height. It is bent and composed.

A support main 130 having a rectangular frame shape seated on the cover bottom 150 and surrounding the edges of the liquid crystal panel 110 and the backlight unit 120 is combined with the top cover 140 and the cover bottom 150.

Meanwhile, the top cover 140 may be referred to as a case top or a top case, the guide panel 130 may also be referred to as a support main or main support, and a mold frame, and the cover bottom 150 may be referred to as a bottom cover.

The liquid crystal display of the present invention as described above is modular in a thin form compared to the conventional liquid crystal display, which will be described in more detail with reference to FIG. 4 below.

FIG. 4 is a schematic cross-sectional view of a modular display of the liquid crystal display of FIG. 3.

As shown, the liquid crystal display of the present invention can be seen that the overall height is reduced compared to the conventional liquid crystal display device, which is, the interval (between the lamp 124 and the diffuser plate 300 of the backlight unit 120 ( A ') and the distance B' between the lamp 124 and the reflector 122 are reduced compared to the existing gap (A and B in FIG. 1).

In addition, although the distance A 'between the lamp 124 and the diffuser plate 300 and the distance B' between the lamp 124 and the reflector 122 are reduced, the present invention provides the same lamp mura ( The mura phenomenon does not occur because of the diffusion plate 300 positioned on the upper part of the lamp 124, because the diffusion plate 300 according to the embodiment of the present invention has a diffraction effect of light.

5 is a view schematically showing a diffusion plate and a plurality of optical sheets according to an embodiment of the present invention, and FIG. 6 is an enlarged view of a part of the diffusion plate of FIG. 5.

As shown in FIG. 5, the diffusion plate 300 and the plurality of optical sheets 129, that is, the diffusion sheet 200 and the light collecting sheet 210 are sequentially disposed on the diffusion plate 300.

Looking at each of them in more detail, first, the diffusion plate 300 is uneven inside the base film 302 made of a transparent acrylic (acryl) -based resin, PMMA (polymethylmethacrylate), a polyethylene terephthalate (PET) plate of a thermoplastic resin, etc. Particles are configured to have a variety of haze (haze) properties according to the light uniformity.

In this case, the haze characteristic is a phenomenon in which light is diffused according to the intrinsic properties of the material in addition to reflection or absorption depending on the type of material when light passes through the transparent material, and an opaque cloudy appearance appears. Is measured according to Equation 1 below.

Equation 1

By adjusting the haze value, the desired brightness and viewing angle can be realized. When the haze value is 30% or less, the light diffusion rate is low and the viewing angle is narrowed. When the haze value is 90% or more, the light transmittance is low and the luminance is low. You lose.

The haze value of the diffusion plate 300 may include light diffusing components such as beads 308, or may be configured by forming a fine pattern (not shown) on the lower surface of the diffusion plate 300 without including the beads 308. have.

At this time, the bead 308 has a feature that can prevent the light is partially concentrated by dispersing the light incident to the diffuser plate (300).

In addition, the diffusion plate 300 that does not include the bead 308 has a feature that can adjust the light scattering angle according to the shape of the fine pattern (not shown), the fine pattern (not shown) is an elliptical pattern (elliptical pattern) ), A polygon pattern, etc., and a hologram pattern is used to refract the light incident by the interference pattern in an asymmetrical direction so that the collected light is angled at a more inclined angle. It can be spread.

As a result, the light is dispersed to prevent the light from being partially concentrated.

In addition, a plurality of domed lenticular lenses 304 for condensing light are formed on the upper surface of the diffusion plate 300 so as to protrude in a row. The plurality of lenticular lenses 304 are arranged adjacent to each other in a band shape so that the peaks and valleys are repeated.

At this time, although not shown, in addition to the lenticular lens 304, a prism having a vertex angle of 90 ° may be configured to have a constant arrangement.

Due to the lenticular lens 304, the diffusion plate 300 condenses light with a plurality of optical sheets 129 positioned on the diffusion plate 300 to thereby increase the luminance.

In particular, the diffusing plate 300 according to the embodiment of the present invention forms a diffraction grating 306 on the valley portion of the lenticular lens 304 and enters the diffusing plate 300 through the grating 306. The light has a diffraction effect.

That is, referring to FIG. 6, it can be seen that the diffraction grating 306 is formed on the valley portions of the lenticular lenses 304 adjacent to each other.

The diffraction grating 306 is arranged in the form of slits in a lattice form, and some of the light passing through the diffraction grating 306 of the light incident through the diffraction grating 306 through the diffraction grating 306 is diffracted and interferes with each other. Done.

At this time, constructive interference and offset interference will occur. That is, some of the light passing through the diffraction grating 306 is combined with each other to appear brighter or darker repeatedly.

As a result, the light incident on the diffuser plate 300 becomes weaker than the conventional one, and thus may have a more uniform light diffusion effect.

At this time, although the diffraction grating 306 including one slit is formed in the valleys of the lenticular lens 304 adjacent to each other on the drawing, the diffraction grating 306 is a lenticular within a limit smaller than the wavelength of light A plurality of valleys of the lens 304 may be formed.

The diffraction grating 306 may have a larger diffraction effect by decreasing the straightness of light as the distance between the slits is narrower.

Accordingly, the diffusion plate 300 according to the present invention allows the light emitted from the lamp 124 of FIG. 3 to be directed toward the liquid crystal panel 110 of FIG. 3, and the liquid crystal panel 110 of FIG. 3 from a wide range of angles. It spreads the light so that it can be incident to.

In addition, some light is diffracted to weaken the straightness of the light to have a more uniform light diffusion effect, it is possible to prevent the existing lamp mura phenomenon.

As such, the diffusion plate 300 may realize more uniform brightness and condensing effect even through adjustment of a haze value or a distance between the diffraction gratings 306 according to the intended purpose.

The diffusion sheet 200 positioned on the diffusion plate 300 includes a base film made of PET and an acrylic resin layer including light diffusion components such as beads on both sides of the base film.

The diffusion sheet 200 serves to control the direction of the light so that light is propagated toward the light collecting sheet 210 by dispersing the light incident through the diffusion plate 300 so as not to cause stains due to partial concentration of light. Do it.

In addition, the light collecting sheet 210 is formed so that the base film made of PET resin and the lenticular lens or prism acid are arranged on the upper surface of the base film.

The light collecting sheet 210 collects light diffused from the diffusion sheet 200 in a direction perpendicular to the plane of the upper liquid crystal panel 110 of FIG. 3. As a result, the light passing through the light collecting sheet 210 almost passes perpendicular to the liquid crystal panel 110 (see FIG. 3) to provide a uniform luminance distribution.

In this case, the light collecting sheet 210 may be configured to use one, but in order to implement high brightness, several light collecting sheets 210 may be overlapped.

That is, only the prism type sheet may be used by overlapping, only the lenticular lens light collecting sheet may be used by overlapping, or the prism type light collecting sheet and the lenticular lens light collecting sheet may be overlapped and used.

In addition, although not shown, a protective sheet (not shown) for protecting the prism acid of the light collecting sheet 210 may be further provided on the light collecting sheet 210, which may include a light diffusion component. Can be.

On the other hand, the diffusion sheet 200 to further have a diffraction effect of the light to be located on the diffusion plate 300 of the present invention, it is possible to further improve the light diffusion performance.

7A to 7B schematically illustrate the structure of a diffusion sheet according to an embodiment of the present invention.

As shown in FIG. 7A, the diffusion sheet 200 includes a base film 201 made of PET and an acrylic resin layer including light diffusion components such as beads on the top surface of the base film 201. : 203).

At this time, the diffraction grating 205 is arranged on the lower surface opposite to the acrylic resin layer 203, the slits having fine spacing arranged in a lattice form.

Part of the light passing through the diffraction grating 205 of the diffusing sheet 200 of the light incident through the diffraction grating 205 through the diffraction grating 205 is diffracted and interferes with each other, thereby entering the diffusing sheet 200. Disperse the light so that no partial condensation of light occurs.

Figure 7b is a non-bead type diffusion sheet 200 does not contain beads, it is possible to adjust the light scattering angle in the vertical and horizontal direction, there is a feature that can adjust the light in the desired direction.

In this case, an elliptical pattern (elliptical pattern: 207) is formed on the base film 201, and slits having fine intervals on the lower surface thereof constitute a diffraction grating 205 arranged in a lattice form. It is done.

Due to this, it also disperses the light, preventing the light from being partially concentrated.

Such a diffusing sheet 200 having a diffraction grating 205 may be used to form one sheet, but in order to realize a more uniform surface light source, the diffusing sheet 200 having a plurality of diffraction gratings 205 may be overlapped with each other. Can be.

At this time, when using a plurality of diffusion sheet 200 overlap, it is possible to delete the light collecting sheet (210 in FIG. 5).

In the above description, for convenience, the direct-type method is used as a liquid crystal display device in which the diffusion plate 300 and the plurality of optical sheets 129 according to the present invention may be used. However, this may be applied to the photometric method. In a state in which the light guide plate (not shown) is further configured, the lamp 124 of FIG. 3 is configured along one side or both sides of the light guide plate (not shown) in the longitudinal direction, and the diffusion plate according to the embodiment of the present invention is formed thereon. 300 and a plurality of optical sheets 129 may be interposed.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

1 is a cross-sectional view of a liquid crystal display device using a general direct type backlight unit.

2 is a photograph showing a lamp mura phenomenon.

3 is an exploded perspective view showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically illustrating the modularity of the liquid crystal display of FIG. 3.

5 is a view schematically showing a diffusion plate and a plurality of optical sheets according to an embodiment of the present invention.

FIG. 6 is an enlarged view of a part of the diffusion plate of FIG. 5; FIG.

7a to 7b schematically show the structure of a diffusion sheet according to an embodiment of the present invention.

Claims

A reflector;

A lamp arranged above the reflector;

A diffusion plate positioned above the lamp and including a lens in which mountains and valleys are repeatedly arranged to protrude in rows;

A plurality of optical sheets positioned on the diffusion plate

And a diffraction grating is formed in a valley of the diffuser lens.

The method of claim 1,

And the lens of the diffusion plate is formed on one surface adjacent to the plurality of optical sheets of the base film including a light diffusion component.

The method of claim 2,

And the diffraction grating is composed of slits formed at minute intervals.

The method of claim 2,

And the light diffusion component is a bead or a fine pattern.

The method of claim 2,

The lens is a backlight unit for a liquid crystal display device, characterized in that the dome-shaped lenticular lens or prism acid-shaped prism lens.

The method of claim 1,

The plurality of optical sheets are a backlight unit for a liquid crystal display device comprising a diffusion sheet and a light collecting sheet.

The method of claim 6,

The diffusion sheet is a backlight unit for a liquid crystal display device, characterized in that the base film and an acrylic resin layer including a light diffusion component on the upper surface thereof, and a diffraction grating on the lower surface of the base film.

A base film comprising a light diffusion component;

A lens which is arranged to protrude in a row by repeating mountains and valleys on one surface of the base film;

Diffraction grating formed in the valley of the lens

Diffusion plate comprising a.