CN102588845B - Back lighting device and liquid crystal display device - Google Patents

Abstract

The invention discloses a backlight illuminating device, which comprises: a point light source, a rectangular light guide strip and a flat light guide film. The light guide strip includes a first light incident surface and a first light exit surface, the linearly polarized light enters from the first light incident surface and emits linearly polarized parallel light through the first light exit surface; the light guide film includes a second light incident surface and The second light exit surface, the linearly polarized parallel light enters from the second light incident surface and emits the linearly polarized parallel light through the second light exit surface. The invention also discloses a liquid crystal display device. The light energy utilization rate of the backlight illuminating device of the invention is high, the uniformity of light guiding is improved, and the obtained liquid crystal display device is light and thin.

Description

Backlight lighting device and liquid crystal display device

technical field

The invention relates to a backlight illuminating device using a linearly polarized point light source and a liquid crystal display device using the backlight illuminating device.

Background technique

With the rapid development of liquid crystal display (LCD), it occupies an increasingly important position in the field of flat panel display.

Since the liquid crystal itself does not emit light, the LCD needs a backlight module to provide lighting, that is, the light emitted by the light source (LED, CCFL, etc.) Form a uniform surface light source, and then enter the liquid crystal layer through a polarizing film and a color filter. However, in such a backlight module, the utilization efficiency of light energy is often very low, only about 5%. Wherein the light loses more than 50% of its energy when passing through the polarizing film.

In order to reduce the loss of light energy when natural light is converted into polarized light, a polarizing conversion film (P-Sconverter) can be used to replace the polarizing film. The function of the polarizing conversion film is to allow the light of a certain polarization direction (the polarization direction of the polarizing film) to pass through, while reflecting the light whose polarization direction is perpendicular to the direction. The reflected light enters the polarization conversion film again after being depolarized, and so on, which can effectively improve the utilization rate of light energy. However, this method usually requires the use of an achromatic 1/4 wave plate to convert the polarization state, and too many optical films are not conducive to the thinning of the LCD.

Therefore, it is of great research significance to try to integrate the light guiding and polarization functions on the same optical film, which can improve the light energy utilization efficiency of the backlight module without increasing the number of films.

Contents of the invention

In view of this, the present invention provides a backlight lighting device and a liquid crystal display device using the backlight lighting device. The light energy utilization rate of the backlight illuminating device is high, and the obtained liquid crystal display device is light and thin.

In order to achieve the above objectives, the technical solutions provided in the embodiments of the present application are as follows:

A backlighting device, in particular, comprising:

A point light source that emits collimated linearly polarized light;

The rectangular light guide strip includes a first light incident surface and a first light exit surface, the linearly polarized light enters from the first light incident surface and emits linearly polarized parallel light through the first light exit surface,

The light guide strip also includes a first optical element, the first optical element accepts the linearly polarized light propagating in the light guide strip, and makes at least a part of it emit toward a direction approximately perpendicular to the first light exit surface;

The flat light guide film includes a second light incident surface and a second light exit surface, the linearly polarized parallel light enters from the second light incident surface and emits the linearly polarized parallel light through the second light exit surface,

The light guide film further includes a second optical element, which receives the linearly polarized parallel light propagating in the light guide film and emits at least a part thereof in a direction approximately perpendicular to the second light exit surface.

Preferably, in the above-mentioned backlight lighting device, the point light source is a laser light source.

Preferably, in the above-mentioned backlight lighting device, the laser light source can at least emit red laser light, green laser light and blue laser light.

Preferably, in the above-mentioned backlighting device, the first optical element is a grating group A; the grating group A is separated at a set interval along the propagation direction of the linearly polarized light in the light guide strip. The configuration is continued; each grating in the grating group A diffracts at least a part of the linearly polarized light and emits it in a direction approximately perpendicular to the first light exit surface.

Preferably, in the above-mentioned backlighting device, each grating in the grating group A extends along a direction approximately perpendicular to the first light-emitting surface, and the light-emitting efficiency of the grating extends from the first light-incident surface along the The propagation direction of the linearly polarized light gradually increases, so that the brightness of the light emitted from the first light-emitting surface is uniform.

Preferably, in the above-mentioned backlighting device, the second optical element is a grating group B; the grating group B is arranged at a set interval along the propagation direction of the linearly polarized parallel light in the light guide film Discontinuous configuration; each grating in the grating group B diffracts at least a part of the linearly polarized parallel light and emits it in a direction approximately perpendicular to the second light-emitting surface.

Preferably, in the above-mentioned backlight lighting device, each grating in the grating group B extends along a direction approximately perpendicular to the second light-emitting surface, and the light-emitting efficiency of the grating extends from the second light-incident surface along the The propagation direction of the linearly polarized parallel light gradually increases, so that the brightness of the light emitted from the second light-emitting surface is uniform.

Preferably, in the above-mentioned backlighting device, the light guide strip further includes a first light guide substrate, and the first light guide substrate is a non-optical transparent light guide substrate.

Preferably, in the above-mentioned backlighting device, the light-guiding film further includes a second light-guiding substrate, and the second light-guiding substrate is a non-optical transparent light-guiding substrate.

The present invention also discloses a liquid crystal display device, especially comprising a liquid crystal display panel and the above-mentioned backlight lighting device, and the backlight lighting device is arranged on the back of the liquid crystal display panel to illuminate it.

Compared with prior art, the beneficial effect of the present invention is:

1. The light energy utilization efficiency of the liquid crystal display backlight module is improved. The quasi-linearly polarized point light source still has polarization characteristics after being expanded into a uniform surface light source by the light guide strip and the light guide film, thereby canceling the use of the polarizing film in the liquid crystal display backlight module.

2. The uniformity of light guide is improved. In the invention, the collimated point light source is first expanded into a uniform line light source through the light guide strip, and the uniform line source is expanded into a uniform surface light source through the light guide film, that is, the collimated point light source becomes a uniform surface light source through two steps, and each step of expansion only The uniformity of one dimension needs to be considered, which effectively simplifies the design of the output efficiency of the light guide strip and the light guide film, and improves the uniformity of light guide.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 is a schematic perspective view of a backlighting device in a specific embodiment of the present invention;

Figure 2 is a schematic side view of the backlighting device in Figure 1;

Figure 3 is a top view of the backlighting device in Figure 1;

Figure 4a shows a schematic diagram of the p-wave propagating in the light guide strip or light guide film in a specific embodiment of the present invention;

Fig. 4b shows a schematic diagram of s-wave propagating in a light guide strip or a light guide film in a specific embodiment of the present invention;

Figure 4c is a schematic diagram of the grating vector of the grating on the light guide strip or the light guide film in a specific embodiment of the present invention;

Fig. 5a is a schematic diagram showing that a light guide strip or a light guide film is divided into pixel units in a specific embodiment of the present invention;

Fig. 5b is a schematic structural diagram of a grating in a specific embodiment of the present invention.

Detailed ways

The purpose of the present invention is based on: how to make the final outgoing light still maintain a linearly polarized state during the process of converting the point light source into a surface light source; how to make the surface light source have good uniformity, that is, the design of the light guide strip and light guide film. .

In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described The embodiments are only some of the embodiments of the present application, but not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

The embodiment of the present invention discloses a backlight lighting device, comprising: a point light source emitting collimated linearly polarized light; The first light incident surface enters and emits linearly polarized parallel light through the first light exit surface, and the light guide strip also includes a first optical element, which receives the linearly polarized light propagating in the light guide strip, so that At least a part of it is emitted towards a direction approximately perpendicular to the first light-emitting surface; the flat light guide film includes a second light-incident surface and a second light-exit surface, and the linearly polarized parallel light enters from the second light-incidence surface and emit linearly polarized parallel light through the second light exit surface, the light guide film also includes a second optical element, the second optical element receives the linearly polarized parallel light propagating in the light guide film, and at least a part of it faces to the The second light-emitting surface emits light in a direction substantially perpendicular to it.

The purpose of the light guide strip is to expand the collimated linearly polarized point light source into a polarized line light source, and the light guide film further expands the polarized line light source into a polarized plane light source. In order to avoid or reduce the energy lost when the light passes through the polarizing film, it is necessary to keep the linear polarization state of the light unchanged during the whole process, so the embodiment of the present invention provides a first optical element and a second optical element.

Preferably, the point light source is a laser light source. The laser light source can at least emit red laser, green laser and blue laser. The laser light source is a light source with good directionality and polarization, which can emit collimated linearly polarized light.

The point light source can also be a light source that does not have very good directivity and polarization, such as LED, but becomes a collimated and polarized point light source after being collimated and polarized.

The point light source is placed in a suitable position, so that the collimated linearly polarized light is coupled into the light guide strip at a certain angle and polarization state, so as to ensure the outgoing light in the process of expanding from a point light source to a line light source and from a line light source to a surface light source. the linear polarization state.

Preferably, the first optical element is a grating group A; the grating group A is intermittently arranged at a set interval along the propagation direction of the linearly polarized light in the light guide strip; Each of the gratings respectively diffracts at least a part of the linearly polarized light and emits it in a direction approximately perpendicular to the first light emitting surface. Each grating in the grating group A extends in a direction approximately perpendicular to the first light exit surface, and the light exit efficiency of the grating gradually increases from the first light incident surface along the propagation direction of the linearly polarized light, so that The brightness of the light emitted from the first light-emitting surface is uniform.

Preferably, the second optical element is a grating group B; the grating group B is intermittently arranged at a set interval along the propagation direction of the linearly polarized parallel light in the light guide film; the grating group B Each of the gratings respectively diffracts at least a part of the linearly polarized parallel light and emits it in a direction approximately perpendicular to the second light-emitting surface. Each grating in the grating group B extends in a direction approximately perpendicular to the second light exit surface, and the light exit efficiency of the grating gradually increases from the second light incident surface along the propagation direction of the linearly polarized parallel light, so that The brightness of the light emitted from the second light-emitting surface is made uniform.

Light extraction efficiency=area ratio*diffraction efficiency, which can be achieved by controlling the diffraction efficiency, or the desired light extraction efficiency can be obtained by controlling the area ratio.

The first optical element and the second optical element are grating structures, and the grating orientation should ensure that the outgoing light maintains a linearly polarized state during the process of expanding from a point light source to a linear light source; Near the vertical direction of the surface; the output efficiency determined by the size of the area occupied by the grating structure, the depth of the grating, and the duty cycle meets the requirements of light guide uniformity.

The first optical element and the second optical element may also be semi-transmissive mirrors.

In the aforementioned backlight lighting device, the light guide strip further includes a first light guide substrate, and the first light guide substrate is a non-optical transparent light guide substrate. The light-guiding film further includes a second light-guiding substrate, and the second light-guiding substrate is a non-optical transparent light-guiding substrate.

Both the first light-guiding substrate and the second light-guiding substrate are non-optical transparent light-guiding substrates, so as to ensure that the linear polarization state of the light does not change during the propagation of light.

The embodiment of the present invention also discloses a liquid crystal display device, which includes a liquid crystal display panel and the above-mentioned backlight lighting device, and the backlight lighting device is arranged on the back of the liquid crystal display panel to illuminate it.

Since the polarizer is omitted, the liquid crystal display device is thinner and lighter.

In order to further illustrate the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

Referring to FIG. 1 , the backlighting device includes a point light source 1 , a rectangular light guide strip 2 and a flat light guide film 3 .

The point light source 1 is a laser light source, which is red (632.8nm), green (532nm), blue (441.6nm) three-color polarized collimated laser, and can emit red laser, green laser and blue laser.

As shown in FIG. 3 , the light guide bar 2 includes a first light guide substrate 21 and a first optical element 22 , and the first optical element 22 is formed on the upper surface of the first light guide substrate 21 .

The first light-guiding substrate 21 is a non-optical transparent light-guiding substrate, preferably a resin material that is transparent and has excellent optical properties, especially acrylic resin and polyolefin resin with low birefringence.

The first light guide substrate 21 includes a first light incident surface 211 and a first light exit surface 212 , the first light incident surface 211 is located at the end of the light guide bar 2 and is perpendicular to the first light exit surface 212 . The linearly polarized light emitted by the point light source 1 may enter from the first light incident surface 211 at a certain angle and exit from the first light exit surface 212 .

The first optical element 22 is a grating, and a plurality of the gratings are intermittently arranged at a set interval along the propagation direction of the linearly polarized light in the first light guide substrate 21 (from right to left in FIG. 3 ); Each of the gratings respectively diffracts at least a part of the linearly polarized light and emits it in a direction substantially perpendicular to the first light emitting surface 212 . Each of the gratings extends in a direction approximately perpendicular to the first light-emitting surface 212, and the light-emitting efficiency of the grating gradually increases from the first light-incoming surface 211 along the propagation direction of the linearly polarized light, so that from the first light-emitting surface 211 to The brightness of the light emitted from a light emitting surface 212 is uniform.

As shown in FIG. 2 , the light guide film 3 includes a second light guide substrate 31 and a second optical element 32 , and the second optical element 32 is formed on the upper surface of the second light guide substrate 31 .

The second light-guiding substrate 31 is a non-optical transparent light-guiding substrate, preferably a resin material that is transparent and has excellent optical properties, especially acrylic resin and polyolefin resin with low birefringence.

The second light guide substrate 31 includes a second light incident surface 311 and a second light exit surface 312 , the second light incident surface 311 is located at the end of the light guide film 3 and is perpendicular to the second light exit surface 312 . The linearly polarized parallel light from the light guide strip 2 can enter from the second light incident surface 311 at a certain angle and exit from the second light exit surface 312 .

The second optical element 32 is a grating, and a plurality of the gratings are intermittently arranged at set intervals along the propagation direction of the linearly polarized parallel light in the second light guide substrate 31 (from left to right in FIG. 2 ). Each of the gratings respectively diffracts at least a part of the linearly polarized parallel light and emits it in a direction approximately perpendicular to the second light-emitting surface 312 . Each of the gratings extends in a direction approximately perpendicular to the second light exit surface 312, and the light exit efficiency of the grating gradually increases from the second light entrance surface 311 along the propagation direction of the linearly polarized parallel light, so that from The brightness of the light emitted from the second light emitting surface 312 is uniform.

The principle of the backlight lighting device in the above specific embodiments will be described below.

Polarization maintenance: During the process of expanding the point light source into a line light source and expanding from a line light source into a surface light source, the linearly polarized light undergoes the following physical process: the linearly polarized light is on the upper and lower surfaces of the first light guide substrate 21 of the light guide strip 2 Total reflection occurs and is diffracted by the first optical element 22, and the linearly polarized light enters the light guide film 3 after coming out of the light guide strip 2, and then total reflection occurs on the upper and lower surfaces of the second light guide substrate 31 of the light guide film 3, and is diffracted by the second optical element 32.

The angles (α ₁ , α ₂ ) of the light incident on the light guide strip 2 and the light guide film 3 and the angles (θ ₁ , θ ₂ ) at which the light is coupled into the transparent substrate (21, 31) satisfy the law of refraction. Total reflection occurs in the substrate, that is, the total reflection condition should be satisfied. In addition, the light exiting from the light guide strip 2 and the light guide film 3 should be near the vertical direction of the exit surface. Therefore, the period of the grating on the surface of the light guide strip 2 and the light guide film 3 can be determined by the grating equation according to the above analysis. Considering that when the point light source is expanded into a line light source and the line light source is expanded into a surface light source, the linear polarization state of the outgoing light should be maintained, so the light should enter the light guide strip 2 and the light guide film 3 with a certain polarization state to ensure that the light is in the When total reflection occurs on the upper and lower surfaces of the transparent substrate (21, 31), it is p-wave or s-wave, and the grating vector of the grating structure (22, 32) on the surface of the substrate should be within the incident plane of the light.

For total reflection, due to the difference in phase retardation between p-wave and s-wave, linearly polarized light usually becomes elliptically polarized or circularly polarized after total reflection. Only when the incident light is p-wave or s-wave, the reflected light can maintain The original polarization state remains unchanged. Therefore, the linearly polarized light emitted by the point light source 1 should be coupled into the light guide strip at a specific incident angle and polarization direction.

Referring to Fig. 4a, the light is totally reflected in the first light guiding substrate 21 or the second light guiding substrate 31. When the incident light is p-wave, the total reflection does not change the polarization state of the light, and the reflected light is still p-wave.

Referring to FIG. 4b, the light is totally reflected in the first light guiding substrate 21 or the second light guiding substrate 31. When the incident light is s-wave, the total reflection does not change the polarization state of the light, and the reflected light is still s-wave.

When the diffraction grating destroys the total reflection condition and the light exits from the surface of the light guide strip and the light guide film, the grating vector should be within the incident plane (that is, the grating stripe is perpendicular to the incident plane), so as to ensure that the linear polarization state of the light remains unchanged.

4c, in order to ensure the linear polarization state of the outgoing light, the grating vectors of the first optical element 22 and the second optical element 32 are in the light incident plane, wherein the grating vector is in the x-axis direction, and the incident light is in the xz plane.

Design of output efficiency: As the distance from the light source increases, the light energy in the light guide strip 2 and the light guide film 3 decreases. In order to obtain a uniform line light source and surface light source, the output efficiency needs to be increased. For this reason, the light guide strip 2 and the light guide film 3 can be divided into several small enough pixel units, each pixel unit has an area of S _p , and there is a grating structure on the area of the pixel unit with an area of S _g , such as Figure 5a shows. Assuming that the diffraction efficiency of the grating is e _g , the light extraction efficiency at a certain pixel unit is η=S _g e _g /S _p . The diffraction efficiency of the grating is related to factors such as the material of the grating, the duty ratio f, and the depth h, as shown in Figure 5b. Therefore, the output efficiency of each pixel can be calculated according to the requirements of uniformity, and the required output efficiency can be obtained by changing the area of the grating area, the material of the grating, the duty cycle and the depth.

In summary, the beneficial effects of the present invention are:

1. The light energy utilization efficiency of the liquid crystal display backlight module is improved. The quasi-linearly polarized point light source still has polarization characteristics after being expanded into a uniform surface light source by the light guide strip and the light guide film, thereby canceling the use of the polarizing film in the liquid crystal display backlight module. In the prior art, the polarizing film can filter out more than 50% of light energy, so the invention effectively improves the utilization rate of light energy.

2. The uniformity of light guide is improved. In the invention, the collimated point light source is first expanded into a uniform line light source (linearly polarized parallel light) through the light guide strip, and the uniform line light source is expanded into a uniform surface light source through the light guide film, that is, the collimated point light source becomes a uniform surface light source through two steps, And each step of expansion only needs to consider the uniformity of one dimension, which effectively simplifies the design of the output efficiency of the light guide strip and the light guide film, and improves the uniformity of light guide.

Finally, it should also be noted that in this text, relational terms such as first and second etc. are only used to distinguish one entity or operation from another, and do not necessarily require or imply that these entities or operations, any such actual relationship or order exists. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced. Without departing from the spirit and scope of the technical solution of the present invention.

Claims (8)

1. A backlighting device, characterized in that, comprising: A point light source that emits collimated linearly polarized light; The rectangular light guide strip includes a first light incident surface and a first light exit surface, the linearly polarized light enters from the first light incident surface and emits linearly polarized parallel light through the first light exit surface, The light guide strip also includes a first optical element, the first optical element receives the linearly polarized light propagating in the light guide strip, and makes at least a part of it emit toward a direction approximately perpendicular to the first light exit surface, The first optical element is a grating group A; the grating group A is intermittently arranged at a set interval along the propagation direction of the linearly polarized light in the light guide strip; Each grating respectively diffracts at least a part of the linearly polarized light and emits it in a direction approximately perpendicular to the first light exit surface; The flat light guide film includes a second light incident surface and a second light exit surface, the linearly polarized parallel light enters from the second light incident surface and emits the linearly polarized parallel light through the second light exit surface, The light guide film also includes a second optical element, the second optical element receives the linearly polarized parallel light propagating in the light guide film, and makes at least a part of it emit toward a direction approximately perpendicular to the second light exit surface, The second optical element is a grating group B; the grating group B is intermittently arranged at a set interval along the propagation direction of the linearly polarized parallel light in the light guide film; Each of the gratings respectively diffracts at least a part of the linearly polarized parallel light and emits it in a direction approximately perpendicular to the second light-emitting surface. 2. The backlight lighting device according to claim 1, wherein the point light source is a laser light source. 3. The backlight lighting device according to claim 2, wherein the laser light source can at least emit red laser light, green laser light and blue laser light. 4. The backlight lighting device according to claim 1, characterized in that: each grating in the grating group A extends along a direction approximately perpendicular to the first light-emitting surface, and the light-emitting efficiency increases from the first light-incoming surface to The plane increases gradually along the propagating direction of the linearly polarized light, so that the brightness of the light emitted from the first light exiting plane is uniform. 5. The backlighting device according to claim 1, wherein each grating in the grating group B extends along a direction approximately perpendicular to the second light-emitting surface, and the light-emitting efficiency of the gratings increases from the second to the second light-emitting surface. The light incident surface gradually increases along the propagation direction of the linearly polarized parallel light, so that the brightness of the light emitted from the second light exit surface is uniform. 6 . The backlight lighting device according to claim 1 , wherein the light guide strip further comprises a first light guide substrate, and the first light guide substrate is a non-optical transparent light guide substrate. 7. The backlight lighting device according to claim 1, wherein the light guiding film further comprises a second light guiding substrate, and the second light guiding substrate is a non-optical transparent light guiding substrate. 8. A liquid crystal display device, characterized by comprising a liquid crystal display panel and the backlight lighting device according to claim 1, the backlight lighting device being arranged on the back of the liquid crystal display panel to illuminate it.