CN201083928Y - Backlight and its reflecting sheet - Google Patents

Abstract

The utility model discloses a backlighting source, comprising a light source, a light guide plate and an optical reflector; the light source is positioned at lateral side of the light guide plate, the light guide plate comprises an attachment surface of the optical reflector which is used for contacting the optical reflector and a light-out surface used for emitting light; the thickness between the attachment surface of the optical reflector and the light-out surface decreases gradually from a near light source end to a far light source end, the attachment surface of the reflection sheet is arch-shaped bulging externally; the reflection sheet comprises a reflection surface and the reflection surface is tightly attached on the optical reflector. The utility model has the advantages that the backlight sources can effectively improve the degree of evenness of the backlight source, eliminate the dark spot or dark fringe of the light source, repair the brightness difference between the near end and far end of the distant light source and improve the utilization ratio of light rays which can improve the effectiveness of liquid crystal display screen which uses sidelight type backlight source.

Description

Backlight and its reflector

【Technical field】

The utility model relates to a backlight source of a display device.

【Background technique】

The backlight source is an important device in the display device and is located behind the display screen. Its structure is shown in Figure 1. It usually includes a light source 1, a light guide plate 2 and some optical films covering the light guide plate 2 (not shown in the figure). out), the light 3 emitted by the light source 1 enters from the light-incident side 23 of the light guide plate 2, and the bottom of the light guide plate 2 is the attachment surface 21 of the reflective sheet. The light emitting surface 22 emits and enters into the display screen. Due to the advantages of energy saving, small size, no pollution, and high color saturation, LEDs have been increasingly used as light sources in liquid crystal display backlights. And with the improvement of chip development technology and packaging technology, LED products conform to the development trend of ultra-thin and large-scale liquid crystal displays, and are gradually replacing CCFL to become the mainstream of the market. Depending on the position of the light source, there are mainly two types of backlight: direct type (that is, the light source is on the lower side of the light guide plate) and side-light type (that is, the light source is on the left and right sides of the light guide plate). Compared with the direct-lit type, the edge-lit type is more suitable for the trend of thinner, lighter and lower power consumption of liquid crystal displays, so the edge-lit type is mostly used in small and medium-sized panels. However, in the design of large-sized panels, the side-lit backlight still has the following defects: 1) On the light guide plate, the near light source end close to the light source and the far light source end far away from the light source have different incident angles of light, and the near light source The light incident angle at the end is larger than the light incident angle at the far light source end. Due to the different light emitting angles, there will be areas on the display screen where the light cannot be covered after being reflected between the LED point light sources, so that there will be dark spots or dark stripes on the light emitting surface. 2) If R, G, and B LEDs are selected as the light source, at the near light source end, when the three primary colors are not well mixed into white light, the liquid crystal has to be shifted away from the light source, thereby reducing the number of illuminable liquid crystal panels. The size of the screen also affects the coordination and beauty of the appearance of the display screen. In addition, when the brightness of the light source is constant, the farther the distance from the light source is, the lower the brightness will inevitably be, and the display effect of the liquid crystal will also obviously deteriorate.

【Content of invention】

The main purpose of the utility model is to solve the problems in the prior art, and provide a backlight source, which can improve the uniformity of light distribution of the backlight source on the light-emitting surface through optical design.

The second purpose of this utility model is to provide a backlight source, which can further improve the uniformity of the light distribution of the backlight source on the light-emitting surface, and for the three primary color LEDs, the three primary colors can be fully mixed at the end near the light source.

The secondary purpose of the utility model is to provide a backlight source, which can further improve the light utilization rate and improve the difference between the brightness of the far light source end and the near light source end.

In order to achieve the above object, the utility model provides a backlight source, including a light source, a light guide plate and a reflective sheet, the light source is located on the light incident side of the light guide plate, and the light guide plate includes a reflective sheet attachment surface for contacting the reflective sheet and a light-emitting surface for emitting light, the thickness between the attachment surface of the reflective sheet of the light guide plate and the light-emitting surface gradually decreases from the end near the light source to the end of the far light source, and the attachment surface of the reflective sheet of the light guide plate is convex The reflective sheet is arc-shaped, and the reflective sheet includes a reflective surface, and the reflective surface is in close contact with the attachment surface of the reflective sheet.

The reflective sheet is in an arc shape matched with the attachment surface of the reflective sheet.

A further improvement of the utility model is that the reflective surface of the reflective sheet has dot-shaped spherical protrusions, and the arc curvature, height and distribution density of the protrusions on the reflective surface change with their positions.

The arc curvature of the protrusions gradually increases from the near light source end to the far light source end, the height of the protrusions gradually increases from the near light source end to the far light source end, and the density of the protrusions at the near light source end is smaller than the density of the protrusions at the far light source end And greater than the density of the protrusions in the middle part.

A further improvement of the utility model is that: the far light source end of the reflective surface also includes a plurality of prismatic protrusions parallel to the light-incident side of the light guide plate, with the inclined surface facing the incident light, and the clip between the inclined surface and the reflective surface Angles greater than 45 degrees.

The reflective surface and the protrusion are covered with a reflective material layer.

In order to achieve the above purpose, the utility model also provides a reflective sheet for a backlight source, the reflective sheet includes a reflective surface, and the reflective surface is in a concave arc shape.

A further improvement of the utility model is: the reflective surface of the reflective sheet has dot-shaped spherical protrusions, and the arc curvature, height and distribution density of the protrusions on the reflective surface change with their positions.

The arc curvature and height of the protrusions near the light source end on the reflective surface are smaller than the arc curvature and height of the protrusions at the far light source end, and greater than the arc curvature and height of the protrusions on the middle part of the reflective surface. The near light source on the reflective surface The density of the protrusions at the end and the far light source end is greater than the density of the protrusions at the middle part.

A further improvement of the utility model is that: the far light source end of the reflective surface also includes a plurality of prismatic protrusions parallel to the light-incident side of the light guide plate, with the inclined surface facing the incident light, and the clip between the inclined surface and the reflective surface Angles greater than 45 degrees.

The beneficial effects of the utility model are:

1) Compared with the existing reflective sheets, the main structure of this reflective sheet adopts a curved surface design, and at the same time, spherical protrusions are arranged on the curved reflective surface. Through the function of the curved surface and spherical protrusions, the light source can be projected to the reflective front Part of the parallel light at the end is reflected to the rear end of the reflective sheet. Since the arc curvature, height and distribution density of the protrusions on the reflective surface change with their positions, the main function of the protrusions near the light source is to diffuse reflection of light. It is conducive to the mixing of light, so that the three primary colors can be mixed more fully, so that the phenomenon of dark spots (dark stripes) on the light-emitting surface can be eliminated.

2) A prism-shaped protrusion is arranged on the far light source end on the reflective surface, and the light is reflected upward through the prismatic protrusion to achieve the purpose of compensating for the weaker light at the rear end. The brightness difference is reduced.

3) Coating non-light-absorbing reflective material on the surface of the reflective sheet to improve the utilization rate of light.

【Description of drawings】

FIG. 1 is a schematic cross-sectional view of an existing backlight source;

2 is a schematic cross-sectional view of a backlight source according to an embodiment of the present invention;

Fig. 3 is a sectional view of the reflective sheet of the present utility model;

Fig. 4 is a schematic diagram of the distribution of protrusions on the reflective surface of the reflective sheet of the present invention;

Fig. 5 is a schematic diagram of the effect of light on the curved reflective surface;

Fig. 6 is a schematic diagram of spherical protrusions reflecting parallel rays;

Figure 7-1 and Figure 7-2 are schematic diagrams of the distribution of reflected light after parallel rays are projected onto spherical protrusions with different curvatures;

Fig. 8 is a schematic diagram of light reflected by prismatic protrusions;

FIG. 9 is a schematic cross-sectional view of a backlight source according to another embodiment of the present invention.

【Detailed ways】

The features and advantages of the utility model will be described in detail through embodiments in conjunction with the accompanying drawings.

Embodiment one:

Please refer to FIG. 2, the backlight source includes a light source 1, a light guide plate 2 and a reflective sheet 4, the light source 1 is located at the light incident side 23 on one side of the light guide plate 2, and the light guide plate 2 includes a reflective sheet attachment surface 21 and a light output for emitting light Surface 22, the thickness between the reflective sheet attachment surface 21 of the light guide plate 2 and the light output surface 22 gradually decreases from the near light source end 100 to the far light source end 300, and the reflective sheet attachment surface 21 of the light guide plate 2 is convex The reflective sheet 4 includes a reflective surface with dot-shaped spherical protrusions, and the reflective surface is in close contact with the reflective sheet attachment surface 21, for example, the reflective sheet 4 is pasted on the reflective sheet attachment surface 21, or by external The pressure compresses the reflective sheeting 4 against the reflective sheet attachment surface 21 . Since the reflective sheet attachment surface 21 of the light guide plate is in a convex arc shape, the reflective sheet 4 is in a concave arc surface shape matched with the reflective sheet attachment surface 21 . The light 3 emitted by the light source 1 enters from the light incident side 23 of the light guide plate 2, and is reflected by the reflective sheet 4, so that the light is emitted from the light exit surface 22 on the light guide plate 2, and finally enters the display screen. The light source 1 usually adopts LEDs, and can also adopt LEDs of three primary colors arranged side by side.

In this embodiment, the reflective sheet 4 can be flexible or rigid, and when the reflective sheet 4 is flexible, its shape can be determined according to the shape of the attachment surface 21 of the reflective sheet. When the reflective sheet 4 is rigid, the reflective surface 41 of the reflective sheet 4 is in a concave arc shape, matching the shape of the reflective sheet attachment surface 21 of the light guide plate 2, as shown in FIG. 3 . The reflective surface has spherical protrusions. According to the principle of light reflection, it can be known that under the same light irradiation, the greater the curvature of the spherical surface, the greater the degree to which the light propagation direction is changed, that is, the more light is projected to the light-emitting surface. In the case of the same light irradiation and the same curvature of the spherical protrusions, the higher the protrusion height, the greater the degree to which the light propagation direction is changed. The positions of the spherical protrusions 42 on the reflective surface are different, and their optical effects are also different. Therefore, the arc curvature, height and distribution density of the spherical protrusions 42 change with their positions. The arc curvature, distribution density and height of the protrusions are set according to the optical functions they play. As shown in FIG. 4 , at the near light source end 100 , the mixing of light is very important. If the mixing is not sufficient, there will be dark spots on the light emitting surface. Therefore, the main function of the spherical protrusions in this part is to diffusely reflect light, which determines that the arc curvature of the spherical protrusions is small and the height is low. In order to ensure that the light is fully mixed, its distribution density is relatively large. At the far light source end 300, in order to improve the utilization rate of light and balance the brightness difference with the near light source end, it is necessary to reflect the light projected from the front to the light emitting surface as much as possible. Therefore, the arc curvature and height of this part of the spherical protrusion and higher distribution density. The spherical protrusion of the middle part 200 plays a transitional role, the arc curvature and height are between the proximal end and the distal end, and the density is relatively small. In summary, in order to effectively improve the brightness difference between the far end and the near end of the light source on the light emitting surface, the farther away from the light source, the larger the curvature of the spherical protrusions and the higher the height, and the density of the protrusions near the light source end is smaller than that of the far light source end. The density and greater than the density of the protrusions in the middle part. In actual production, the specific values of the arc curvature, density and height of each part of the spherical protrusions should be determined based on the brightness of the reference light source, the distance between each point light source and the size of the backlight source. The higher the density of the protrusions, the better, but the higher the density, the higher the manufacturing cost. Generally, the lower the brightness of the light source, the higher the required protrusion density; the larger the backlight source, the higher the required protrusion density. Taking the spherical projection near the light source as a reference, the density setting standard is: it can effectively eliminate the dark spots or dark stripes formed on the light emitting surface caused by the point light source due to the light emitting angle and distribution interval. The protrusions at the end of the far light source need to direct as much light as possible to the light-emitting surface to improve light utilization. Therefore, the distribution density of spherical protrusions in this area is also relatively large. The density value should refer to the comprehensive index such as process and cost to achieve the best. The effect shall prevail. The spherical protrusion in the middle area is a transition part, and the density can be small.

How this embodiment improves the uniformity of outgoing light will be described below with reference to the accompanying drawings.

As shown in Figure 5, the parallel light rays 301, 302, and 303 projected from the light source are reflected by the arc-shaped reflective surface, leading the light to the end of the reflective sheet, and changing the horizontal light into an upward projecting light, thereby compensating Insufficient light at the end of the reflector. The horizontal light 304 is also guided to the end of the reflective sheet after multiple reflections by the curved reflective surface. Since the LED light source has a certain light emitting angle, it is not difficult to imagine that the horizontal and downward light emitted by it will be reflected by the reflective sheet, and part of the light will be directed to the end of the reflective sheet, so that it can compensate the far light source end to a certain extent. Brightness difference near the light source.

As shown in Figure 6, when parallel rays are projected onto the spherical reflective surface, the reflected rays diverge in all directions. Therefore, in FIG. 4 , the spherical protrusions densely distributed at the end 100 of the reflective sheet near the light source will diffusely reflect the light projected by the light source, so that the light can be mixed more evenly.

As shown in Figure 7-1 and Figure 7-2, when parallel rays of the same nature are projected onto spherical reflective surfaces with different curvatures, the reflected effects are different. The smaller the spherical curvature, the smaller the distribution angle of the reflected light; the larger the spherical curvature, the larger the distribution angle of the reflected light. It can be seen from this that the curvature and density of the spherical protrusions arranged in the middle part 200 and the far light source end 300 in Fig. The proportion of light at the end of the chip gradually decreases, which also improves the uniformity of light distribution to a certain extent.

For larger display screens, the brightness of the far light source end of the backlight is relatively small. In order to improve the brightness of the far light source end of the backlight, a number of parallel prismatic protrusions are distributed on the farthest part 310 of the far light source end 300 of the reflective sheet. 43 , as shown in FIG. 4 , the prismatic protrusion 43 is parallel to the light-incident side of the light guide plate, and the inclined surface faces the incident light.

As shown in Figure 8, the slope of the reflective surface of the prismatic protrusion is designed according to the light projected from the front. Usually, the angle between the slope and the reflective surface is greater than 45 degrees, the purpose is to ensure the maximum reflection of light upward, so as to increase the intensity of the outgoing light away from the light source, make up for the brightness difference between the far end and the near end of the light source on the LCD screen, and also improve the utilization rate of light.

Embodiment two:

Please refer to Fig. 9, the difference between the backlight source in this embodiment and the first embodiment is that there are two light sources 1, which are respectively located on the left and right sides of the light guide plate 2, and the attachment surface of the reflective sheet of the light guide plate 2 is a double arc shape. There are also two curved reflectors 4, which are close to the attachment surface of the reflector. The structure of the reflective sheet 4 is the same as in the first embodiment.

In the above embodiments, in order to further enhance the light reflectivity of the reflective surface, a non-light-absorbing reflective material is coated on the reflective surface and the protrusions to form a covering layer.

In summary, the utility model can effectively improve the light distribution uniformity of the backlight source (especially the side-light type), eliminate dark spots or dark stripes near the light source, and compensate for the brightness difference between the far end and the near end of the light source. And the utilization rate of light is improved, so that the display effect of the liquid crystal display screen using the side-light backlight source is better.

The above content is a further detailed description of the utility model in combination with specific preferred embodiments, and it cannot be assumed that the specific implementation of the utility model is only limited to these descriptions. For a person of ordinary skill in the technical field to which the utility model belongs, without departing from the concept of the utility model, some simple deduction or substitutions can also be made, which should be regarded as belonging to the protection scope of the utility model.

Claims (12)

1. backlight, comprise light source, light guide plate and reflecting piece, described light source is positioned at the light incident sides of light guide plate, described light guide plate comprises and is used for the reflecting piece attachment surface that contacts with reflecting piece and is used for irradiant exiting surface, it is characterized in that: the reflecting piece attachment surface of described light guide plate and the thickness between the exiting surface reduce to source ends far away gradually from the close to sources end, the reflecting piece attachment surface of described light guide plate is the arc surfaced of evagination, and described reflective surface and reflecting piece attachment surface are close to.

2. backlight as claimed in claim 1 is characterized in that: the arc surfaced of described reflecting piece for matching with the reflecting piece attachment surface.

3. backlight as claimed in claim 1 is characterized in that: described reflecting piece is for flexible.

4. as each described backlight in the claim 1 to 3, it is characterized in that: have net-point shape sphere projection on the reflective surface of described reflecting piece, circular arc curvature, height and the distribution density of the projection on the described reflective surface followed its residing position and changed.

5. backlight as claimed in claim 4, it is characterized in that: the circular arc curvature of described projection increases to source ends far away gradually from the close to sources end, the height of described projection increases to source ends far away gradually from the close to sources end, and the density of the projection of described close to sources end is less than the density of the projection of source ends far away and greater than the density of the projection of center section.

6. backlight as claimed in claim 5 is characterized in that: the source ends far away of described reflective surface also comprises the prismatic projection of many parallel with the light incident sides of light guide plate, inclined-planes towards incident light, and the angle between described inclined-plane and the reflective surface is greater than 45 degree.

7. backlight as claimed in claim 4 is characterized in that: be coated with reflective material layer on described reflective surface and the projection.

8. backlight reflecting piece, it is characterized in that: described reflecting piece comprises reflective surface, described reflective surface is the arc surfaced of indent.

9. reflecting piece as claimed in claim 8 is characterized in that: have net-point shape sphere projection on the reflective surface of described reflecting piece, circular arc curvature, height and the distribution density of the projection on the described reflective surface followed its residing position and changed.

10. reflecting piece as claimed in claim 9, it is characterized in that: the circular arc curvature of the projection of close to sources end and height are less than the circular arc curvature and the height of the projection of source ends far away on the described reflective surface, and greater than the circular arc curvature and the height of the projection of center section on the reflective surface, the density of the projection of close to sources end and source ends far away is greater than the density of the projection of center section on the described reflective surface.

11. reflecting piece as claimed in claim 10 is characterized in that: the source ends far away of described reflective surface also comprises the prismatic projection of many parallel with the light incident sides of light guide plate, inclined-planes towards incident light, and the angle between described inclined-plane and the reflective surface is greater than 45 degree.

12., it is characterized in that: be coated with reflective material layer on described reflective surface and the projection as each described reflecting piece in the claim 8 to 11.

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