KR20180072656A - Light guide panel, backlight unit having the same and eletronic device having the same - Google Patents

Abstract

The present invention provides a light guide plate capable of preventing the yellowish or reddish of exited light by dispersing nanoparticles in the light guide plate and effectively scattering light in a short wavelength band, a backlight unit having the same and an electronic device including the same. The light guide plate guiding light generated in a light source according to an embodiment includes a light-entering surface which the generated light enters; a light-facing surface facing the light-entering surface; a reflection surface perpendicular to the light-entering surface and the light-facing surface and reflecting the entered light; a light exiting surface facing the reflection surface and emitting the entered light; and scattering particles dispersed in the inside surrounded by the light-entering surface, the light-facing surface, the reflection surface, and the light exiting surface, and scattering the entered light.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate, a backlight unit including the light guide plate,

The present invention relates to a light guide plate for guiding light generated from a light source to a display panel, a backlight unit including the light guide plate, and an electronic apparatus including the same.

Electronic devices having displays such as TVs, monitors, smart phones, tablet PCs, smart watches, and the like can be used in various fields such as LCD (Liquid Crystal Display) panel, LED (Light Emission Display) panel, OLED (Organic Light Emission Display) Panel, a CRT (Cathode Ray Tube) panel, and the like.

Among these, a display panel that can not emit light by itself, such as an LCD panel or an LED panel, needs a light source for supplying light.

The light guide plate is a component of a backlight unit that supplies light to the display panel, and guides the light supplied from the light source to the transparent plate to uniformly spread the light on the front plate.

In recent years, efforts have been made to reduce the thickness of components in order to realize slimming of electronic devices. When the light guide plate, which is a component of the backlight unit, is thinned, the incident light is guided by a large amount of reflection, and due to the difference in total reflection angle depending on the wavelength, the light of a long wavelength is first emitted and the light of a short wavelength is emitted toward the light- . ≪ / RTI > Thus, the emitted light may be yellowish or reddish.

Korean Patent Publication No. 10-2010-0005293 US2011-0103095A1

The present invention provides a light guide plate, a backlight unit including the light guide plate, and an electronic apparatus including the light guide plate, which can prevent yellowing or redening of light emitted by scattering light in a short wavelength band by dispersing nanoparticles in a light guide plate.

An incidence surface to be incident; A facing surface facing the light incidence surface; A reflection surface that is perpendicular to the light incidence surface and the light reflection surface and reflects the incident light; A light exiting surface facing the reflective surface and from which the incident light is emitted; And scattering particles dispersed inside the light-entering surface, the light-receiving surface, the reflection surface, and the light-outgoing surface, and scattering the incident light.

The scattering particles may include nanoparticles causing Rayleigh scattering.

The light guide plate may include an ultraviolet ray hardening resin.

The scattering particles may have a diameter of 5 nm or more and 100 nm or less.

The scattering particles can scatter light in the blue wavelength band.

The scattering particles may be dispersed at a concentration of 5% or more and 30% or less.

The ultraviolet curable resin may be at least one selected from the group consisting of an epoxy acrylate resin, a polyester acrylate resin, a urethane acrylate resin, a polybutadiene acrylate resin, Based resin, a silicon acrylate-based resin, and an alkyl acrylate-based resin.

A backlight unit according to an exemplary embodiment includes a light source; And a light guide plate guiding the light generated from the light source, wherein the light guide plate includes scattering particles scattered in the light source and scattering light incident from the light source.

The scattering particles may include nanoparticles causing Rayleigh scattering.

The light guide plate may include an ultraviolet ray hardening resin.

The scattering particles may have a diameter of 5 nm or more and 100 nm or less.

The scattering particles can scatter light in the blue wavelength band.

The scattering particles may be dispersed at a concentration of 5% or more and 30% or less.

The ultraviolet curable resin may be at least one selected from the group consisting of an epoxy acrylate resin, a polyester acrylate resin, a urethane acrylate resin, a polybutadiene acrylate resin, Based resin, a silicon acrylate-based resin, and an alkyl acrylate-based resin.

An electronic apparatus according to an embodiment includes a display panel; And a backlight unit for supplying light to the display panel, wherein the backlight unit includes: a light source for generating light; And a light guide plate guiding the generated light and scattering particles scattering light incident from the light source.

The scattering particles may include nanoparticles causing Rayleigh scattering.

The light guide plate may include an ultraviolet ray hardening resin.

The scattering particles may have a diameter of 5 nm or more and 100 nm or less.

The scattering particles can scatter light in the blue wavelength band.

The scattering particles may be dispersed at a concentration of 5% or more and 30% or less.

According to the light guide plate, the backlight unit including the light guide plate, and the electronic apparatus including the light guide plate according to the embodiment of the present invention, nanoparticles are dispersed in the light guide plate to effectively scatter light in a short wavelength band, thereby preventing yellowing or reddening .

FIG. 1 is a view showing the appearance of a smartphone in an example of an electronic device according to an embodiment.
2 is a side view illustrating an internal structure of a display panel included in an electronic device according to an exemplary embodiment.
3 is an exploded perspective view of a backlight unit according to an embodiment of the present invention.
4 is a view for explaining an outgoing light mechanism inside a backlight unit according to an embodiment.
5 is a side view of the light guide plate.
FIGS. 6 and 7 are views showing a path through which light travels inside the light guide plate.
8 is a view for explaining Rayleigh scattering.
9 is a sectional view of a light guide plate in which scattering particles are dispersed.
10 is a graph showing scattering irradiance according to the radius of the scattering particles.
11 is a graph showing the relationship between the size of the scattering particles and the Rayleigh scattering ratio.
12 is a graph showing the relationship between the concentration of the scattering particles and the transmittance.

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

The electronic device according to one embodiment may be one of electronic devices such as a TV, a monitor, etc., or a portable terminal having a display function such as a smart phone, a tablet PC, a smart watch, and the like. There is no limitation on the kind of the electronic device, and an electronic device according to an embodiment may be an apparatus capable of displaying an image including a display.

FIG. 1 is a view showing an external appearance of a smartphone electronic device in an example of an electronic device according to an embodiment, and FIG. 2 is a side view showing an internal structure of a display panel included in an electronic device according to an embodiment.

Referring to Fig. 1, the electronic apparatus 1 may include a main body 20 which forms an appearance and accommodates or supports various constituent elements constituting the electronic apparatus 1. As shown in Fig.

A display panel 30 for displaying an image is disposed on the front surface of the main body 20 and a backlight unit 10 for supplying light is disposed on the rear surface of the display panel 30 as shown in FIG. In the embodiment of the present invention, the direction in which the image is displayed is defined as forward and the reverse direction is defined as the backward direction.

In one area of the main body 20, an input unit 21 for receiving a control command from a user and a speaker 23 for outputting sound may be provided. The input unit 21 may be implemented in the form of a button, a touch pad, a dial or a jog shuttle, and an input unit 21 in the form of a touch pad may be disposed on the front surface of the display panel 30 to form a touch screen It is also possible.

The display panel 30 may be implemented as a display panel that does not emit light itself, such as a liquid crystal display (LCD) panel.

2, the light L supplied from the backlight unit 10 is incident on the rear polarizer 31a of the display panel 30, and the rear polarizer 31a polarizes the incident light L, Only the light oscillating in the same direction as the axis can be transmitted to the rear substrate 32a.

A plurality of gate lines (not shown), a data line (not shown), a switching element (not shown) and a rear electrode 33a may be provided on the rear substrate 32a. The rear electrode 33a may be a pixel electrode And the front electrode 33b may be a common electrode. The rear substrate 32a may be made of a transparent material such as PMMA or glass.

A front polarizer 31b may be disposed on the front side of the rear substrate 32a and a front electrode 33b may be disposed on the rear side of the front polarizer 31b. The front electrode 33b may be a common electrode.

The gate lines are arranged in the row direction to transmit gate signals, and the data lines are arranged in the column direction to transmit data signals. The back electrode 33a may be connected to the gate line and the data line.

The switching element may be implemented as a thin film transistor (TFT) and is formed at the intersection of the gate line and the data line. The source electrode of the thin film transistor is connected to the data line, the gate electrode of the thin film transistor is connected to the gate line, and the drain electrode of the thin film transistor is connected to the back electrode 33a and the capacitor.

The gate line and the data line may be made of a material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

When a scanning signal is supplied to the gate line, the thin film transistor is turned on to supply a data signal supplied from the data line to the rear electrode 33a.

A liquid crystal layer 34 may be filled between the rear substrate 32a and the front polarizing plate 31b. When a predetermined voltage is applied to the front electrode 33b, an electric field is formed between the front electrode 33b and the rear electrode 33a and the arrangement of the liquid crystal molecules constituting the liquid crystal layer 34 is controlled by the electric field formed.

Depending on the arrangement of the liquid crystal, the direction of vibration of the light incident on the liquid crystal layer 34 may be changed or maintained. For example, when the rear polarizing plate 31a is a vertical polarizing plate, the front polarizing plate 31b is a horizontal polarizing plate, and the liquid crystal molecules are arranged in a helical shape, light vertically polarized through the rear polarizing plate 31a, (34) and is polarized in the horizontal direction. The light polarized in the horizontal direction can be incident on the color filter layer 35 disposed on the front surface of the front polarizer 31b through the front polarizer 31b.

For example, the color filter layer 35 may be composed of a dye or a pigment that absorbs or transmits a wavelength of a specific region. The color filter layer 35 is composed of a blue filter transmitting blue light and absorbing colors other than blue, a green filter transmitting green light and absorbing colors other than green, and a red filter transmitting red light and absorbing colors other than red .

FIG. 3 is an exploded perspective view of a backlight unit according to an embodiment of the present invention, and FIG. 4 is a view illustrating an outgoing light mechanism inside a backlight unit according to an exemplary embodiment.

 3 and 4, the backlight unit 10 disposed behind the display panel 30 includes a light source 11 for generating light, a light guide plate 100 for guiding the path of light generated from the light source 11, And a reflective sheet 13 disposed on the rear side of the light guide plate 100. The light source 11 is disposed on one side of the light guide plate 100.

The backlight unit can be classified into an edge type BLU in which a light source is disposed on a side of a display panel and a direct type BLU in which a light source is located in a rear of the display panel. In this embodiment, an edge type backlight unit in which the light source is located on the side of the display panel is applied.

For example, the light source 11 may include at least one light emitting diode. Or a cold cathode fluorescent lamp (CCFL), or an external electrode fluorescent lamp (EEFL) having electrodes formed on the outer surfaces of both ends thereof.

The light guide plate 100 changes the traveling direction of light incident from the side surface and emits light toward the front surface. A fine scattering pattern may be formed on the front surface or the rear surface of the light guide plate 100 to change the traveling direction of light.

For example, a plurality of convex stripes may be formed on the front surface of the light guide plate 100, and a plurality of dots may be formed on the rear surface of the light guide plate 100. Also, the size and spacing of the convex stripes can be adjusted so that uniform light is emitted toward the front surface of the light guide plate 100, and the size and spacing of the dots can be adjusted.

The convex stripe on the entire surface of the light guide plate 100 may be formed in an embossed shape through a printing technique and the dots on the back surface of the light guide plate 100 may be formed in an engraved shape using a laser.

A part of the light incident into the light guide plate 100 may be scattered by the dots formed on the rear surface of the light guide plate 100 and may be emitted to the front surface of the light guide plate 100, Is reflected by the light guide plate (13) into the light guide plate (100). In addition, a part of the reflected light can be moved to the center of the light guide plate 100 and can be scattered at the center of the light guide plate 100 and emitted to the front surface of the light guide plate 100.

As described above, the light guide plate 100 can emit uniform light to the front surface due to refraction, reflection, and scattering of light generated in the light guide plate 100.

The light guide plate 100 may be made of PMMA or PC having high transparency and high strength. Further, the light guide plate 100 may be made of an ultraviolet ray hardening resin.

The reflective sheet 13 is provided on the rear surface of the light guide plate 100 and reflects a part of the light directed toward the rear surface of the light guide plate 100 inside the light guide plate 100 into the light guide plate 100.

The reflective sheet 13 can be manufactured by coating a base material with a material having high reflectance. For example, the reflective sheet 13 can be manufactured by coating a polymer having a high reflectance on a base material such as PET (polyethylene terephthalate).

The optical member 50 may be disposed on the front surface of the backlight unit 10. The optical member 50 refracts or scatters light to widen the viewing angle of the electronic device 1 and increase the brightness of the electronic device 1. [

The optical member 50 may include a diffusion sheet 51, a prism sheet 53, and a protective sheet 55.

The diffusion sheet 51 spreads the light emitted from the backlight unit 10 along the surface so that the color and brightness of the entire screen of the electronic device 1 are uniform. Since the light emitted from the light guide plate 100 is emitted through a pattern formed on the entire surface of the light guide plate 100, a pattern formed on the entire surface of the light guide plate 100 can be viewed from the light emitted from the light guide plate 100.

The diffusion sheet 51 diffuses the light emitted from the light guide plate 100 in a direction perpendicular to the emission direction in order to prevent the pattern formed on the entire surface of the light guide plate 100 from being visually recognized from the light emitted from the light guide plate 100, To maintain the brightness uniformly.

The light having passed through the diffusion sheet 51 is diffused in a direction perpendicular to the surface of the diffusion sheet 51, whereby the brightness is drastically reduced. The prism sheet 53 increases the brightness by refracting or condensing the light diffused by the diffusion sheet 51.

The prism sheet 53 includes a triangular prism-shaped prism pattern, and a plurality of these prism patterns are arranged adjacently to form a plurality of strips. That is, the prism pattern is formed by protruding toward the display panel 30 in a row in which a mountain and a valley are repeated.

In addition, the prism sheet 53 may be divided into a vertical prism sheet 53a and a horizontal prism sheet 53b.

The light guide plate 100 guides the path of light incident from the light source 11. The light guide plate 100 changes the path of the light incident from the light source 11 disposed on the left or right of the light guide plate 100 toward the front of the light guide plate 100 so that the light generated from the light source 11 is reflected by the display panel 30, .

The protective sheet 55 protects various components included in the backlight unit 10 from external shocks or foreign substances. In addition, the protective sheet 55 can protect the prism sheet 53, which is prone to scratching.

5 is a side view of the light guide plate.

Referring to FIG. 5, the light generated from the light source 11 is incident into the light guide plate 100 through the light entrance surface 110. And the exit surface 130 extends vertically from the upper side of the light incidence surface 110 and is connected to the upper side of the light incidence surface 120. The light incidence surface 120, The reflection surface 140 extends from the lower side of the light incidence surface 110 and is connected to the lower side of the light reflection surface 120.

That is, the plane on which the light source 11 is disposed is the light incidence plane 110, the plane facing the light incidence plane 110 becomes the light converging plane 120, The light emitting surface 110 and the light receiving surface 120 are perpendicular to the light receiving surface 110 and the light receiving surface 120 and are located on the rear side, And the facing surface becomes the reflecting surface 140. [

The light is reflected and emitted through the interior 150 surrounded by the light-entering surface 110, the light-facing surface 120, the exit surface 130, and the reflection surface 140 to supply light to the display panel 30 do.

As described above, a plurality of scattering patterns are formed on the reflecting surface 140 of the light guide plate 100. The area of the reflective surface 140 positioned between the plurality of scattering patterns is formed to be substantially parallel to the exit surface 130 so that the light guided into the light guide plate 100 mostly satisfies the total reflection condition.

The light incident into the light guide plate 100 through the light incidence surface 110 is totally reflected by the reflection surface 140 and the exit surface 130 and the reflection angle is changed by the scattering pattern formed on the reflection surface 140 And is emitted through the exit surface 130.

FIGS. 6 and 7 are views showing a path through which light travels inside the light guide plate.

6 and 7, when the light L generated from the light source 11 is incident on the intent light plate 100 at an angle of 45 degrees, the light L reaches a predetermined distance D When the thickness of the light guide plate 100 is reduced to t / 2, which is half of the thickness of the light guide plate 100, the light L collides against the exit surface 130 and the reflection surface 140, (140). However, the optical path P is equal to Mt? 2.

That is, when the thickness of the light guide plate 100 is reduced, the length of the light path that is transmitted to the predetermined distance D is not different, but the number of times of reflection on the surface of the light guide plate 100 increases. As shown in this example, when the thickness is doubled, the collision with the surface increases twice.

In other words, when the thickness of the light guide plate 100 is reduced, the light is guided and reflected a lot, and the light of a long wavelength is emitted first and the light of a short wavelength is emitted to the light receiving surface 120 due to the difference in total reflection angle along the wavelength . Accordingly, the emitted light becomes yellowish or reddish, and the light that exits to the corresponding light surface 120 becomes blue.

Scattering particles are dispersed in the inner portion 150 so that the light of a short wavelength can be emitted through the emitting surface 130 without escaping to the light-receiving surface 120 while realizing a thin thickness of the LGP 100 according to one embodiment. It is possible to efficiently scatter light of short wavelength. Hereinafter, the present invention will be described in detail with reference to the drawings.

Fig. 8 is a view for explaining Rayleigh scattering, and Fig. 9 is a sectional view of a light guide plate in which scattering particles are dispersed.

Rayleigh scattering is a phenomenon in which electromagnetic waves are scattered by particles of a size much smaller than the wavelength, and the short wavelength band is scattered more than the long wavelength band. As shown in Fig. 8, when light L meets particles P having a size smaller than its wavelength, light L is scattered in all directions.

The Rayleigh scattering coefficient (R) can be defined by the following equation (1).

Here,? Represents a proportional constant, c represents a concentration of particles, d represents a size of a particle,? Represents a wavelength of light, and n represents a refractive index.

Referring to Equation (1), the intensity of the Rayleigh scattering is inversely proportional to the fourth power of the wavelength of the light, and the intensity of the scattered light sharply decreases as the wavelength becomes longer. Accordingly, the Rayleigh scattering effectively appears for light in a short wavelength band, so that blue light in a short wavelength band can be more effectively scattered than light in a long wavelength band.

As shown in FIG. 9, scattering particles 160, which may cause Rayleigh scattering, are dispersed in the interior 150 of the light guide plate 100. As an example of the scattering particles 160, a polymer-inorganic nanohybrid material can be used. For this purpose, the polymer and inorganic scattering particles having a high refractive index can be bonded. For example, at least one scattering particle of TiO ₂ , CdS, ZnO, ZnS, ZrO ₂ , SnO 2 and PbS ^9-13 may be used. However, the materials are merely examples, and the type of the scattering particles 160 dispersed in the light guide plate 100 is not limited thereto.

The size and concentration of scattering particles can be optimized to suit the characteristics or design of each electronic device (1). By optimizing the size and concentration of the scattering particles 160 dispersed in the light guide plate 100, short wavelength light having high waveguide characteristics can be emitted, thereby solving the problem of unevenness in color due to nonuniform outgoing.

FIG. 10 is a graph showing the scattering irradiance according to the radius of the scattering particles, FIG. 11 is a graph showing the relationship between the scattering particle size and the Rayleigh scattering ratio, and FIG. 12 is a graph showing the relationship between the scattering particle concentration and the transmittance Graph. In the graph of FIG. 11, R is an index indicating a Rayleigh scattering ratio.

In consideration of the fact that the light guide plate 100 should be colorless and transparent, the size of the scattering particles 160 may be 1/4 or less of the wavelength? Of light to be scattered. For example, the scattering particles 160 may have a size of 100 nm or less. Here, the size of the scattering particles 160 is based on the diameter.

Referring to FIG. 10, it can be seen that when the size of the scattering particles 160 is about 5 nm or more, the scattered irradiance starts to increase. Accordingly, for efficient scattering, the scattering particles 160 may have a size of 5 nm or more and 100 nm or less.

In addition, referring to FIG. 11, the scattering particles 160 may have a size of 40 nm or less so that the Rayleigh scattering is a main scattering condition. That is, the scattering particles 160 may have a size of 5 nm or more and 40 nm or less. In this case, scattering of the short-wavelength light by the scattering particles 160 can be more easily controlled.

12 is a graph showing the transmittance of each TiO ₂ -polymer scattering particle having a concentration of TiO ₂ of 0%, 2.7%, 5.3%, 10%, 17.6%, and 30% by wavelength. Here, the concentration may be Vol.% Based on the volume.

Referring to the graph of FIG. 12, it can be seen that when the concentration of TiO ₂ is 30% or more, the maximum transmittance is lowered to about 80%, and the maximum transmittance is maintained at about 90 to 100% at a concentration below that. Therefore, the concentration of the scattering particles 160 can be adjusted to 30% or less. For example, the concentration of the scattering particles 160 can be adjusted to 5% or more and 30% or less.

Meanwhile, as described above, the light guide plate 100 may be made of an ultraviolet ray hardening resin. The ultraviolet ray hardening resin is a resin which is polymerized and cured by ultraviolet ray irradiation. When the ultraviolet ray is irradiated, the photoinitiator contained in the resin receives ultraviolet energy to initiate a polymerization reaction, and a monomer and an oligomer The polymerization reaction can be carried out instantaneously. The photoinitiator may be a radical capable of causing a polymerization reaction.

The monomer or oligomer having a small molecular weight is present in a liquid state, and is converted into a solid state polymer having a very high molecular weight. Since such an ultraviolet curing resin has a low viscosity, scattering particles 160 can be effectively dispersed.

The oligomer used for the ultraviolet curable resin constituting the light guide plate 100 may be an epoxy acrylate oligomer, a polyester acrylate oligomer, a urethane acrylate oligomer, a polybutadiene acrylate polybutadiene acrylate oligomers, silicon acrylate oligomers, alkyl acrylate oligomers, and the like.

When such an oligomer is polymerized by ultraviolet curing to become a polymer, an epoxy acrylate-based resin, a polyester acrylate-based resin, a urethane acrylate-based resin, a polybutadiene acrylate ) Based resin, a silicon acrylate based resin, and an alkyl acrylate based resin.

According to the light guide plate, the backlight unit including the light guide plate, and the electronic apparatus including the light guide plate, scattering particles are dispersed in the light guide plate to efficiently scatter light having a short wavelength such as a blue wavelength band to be emitted, It is possible to solve the problem of uneven outflow caused by the unevenness.

In addition, scattering particles can be effectively dispersed in the light guide plate by manufacturing the light guide plate using an ultraviolet hardening resin having a low viscosity.

1: Electronic device
10: Backlight unit
30: Display panel
50: optical member
100: light guide plate
110: mouth surface
120:
130: exit surface
140: Reflecting surface
150: inside
160: scattering particles

Claims (1)

A light guide plate for guiding light generated in a light source,
A light incidence surface on which the generated light is incident;
A facing surface facing the light incidence surface;
A reflection surface that is perpendicular to the light incidence surface and the light reflection surface and reflects the incident light;
A light exiting surface facing the reflective surface and from which the incident light is emitted; And
Scattering particles dispersed inside the light-entering surface, the light-receiving surface, the reflection surface, and the light-outgoing surface, and scattering the incident light.

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