KR100512320B1 - Backlight apparatus for dual type liquid crystal displays - Google Patents

Abstract

The double-sided illumination type backlight device of the present invention comprises a light source, one light guide plate, and a reflecting plate. The light guide plate has a light incidence surface into which light from the light source is incident, a front exit surface for emitting light therein toward the upper liquid crystal display panel, and a portion of the light inside to emit toward the lower liquid crystal display panel, and a part of the light exit surface A back emission surface having a scattering pattern is formed to reflect toward the rear surface, and the back emission surface is formed of a first scattering region and a second scattering region which is a part other than the first scattering region. The reflector is disposed adjacent to the rear exit surface, and a window is formed in some areas to transmit the light directed to the window and to reflect the remaining light, so that the illumination is uniformly applied to the liquid crystal display panels disposed at the front and the rear of the backlight device. Can be provided.

Description

Backlight apparatus for dual type liquid crystal displays

The present invention relates to a backlight device used for a liquid crystal display (LCD), and more particularly, when two liquid crystal display elements are formed on both sides, such as a dual clamshell cell phone, both sides can simultaneously provide illumination to both sides of the LCD. The present invention relates to an illuminated backlight device.

Recently, in the LCD display device used in devices such as mobile phones, a dual fold type product in which two LCD panels are installed on both sides is widely used. In order to supply illumination to two LCD panels installed on both sides, a double sided backlight device was used. In the conventional double-sided backlight type device, as shown in FIG. 9, two light guide plates are used by dividing one light source, or each light guide plate is divided into two areas as in Korean Utility Model Publication No. 271744, and each area is opposite to each other. Two reflectors are arranged to illuminate to provide illumination in a direction.

9, a light source 1 made of a light emitting element (LED) and the like, and two LCDs 4 and 5 arranged on both sides to provide back lighting. It consists of the light guide plates 2 and 2 'and the reflecting plate 3 arrange | positioned between two light guide plates 2 and 2'. However, since the two light guide plates share one light source, the cost increases, the manufacturing process becomes complicated, and the light utilization efficiency is about 60% due to the use of two light guide plates. There are many disadvantages. In addition, since the light guide plate having a thickness of about 0.3 mm to 0.7 mm is laminated in two layers, the thickness of the product becomes thick.

On the other hand, a backlight device such as Korean Utility Model Publication No. 271744 may have a thin product thickness, but the light guide plate is the size of two LCD panels because the LCD panel should not be formed to overlap each other with the light guide plate therebetween. The area of the front of the product is widened because it must be large enough to add. Therefore, such a method also has a disadvantage that it is difficult to miniaturize. In addition, in the case of a dual LCD mobile phone, when the main LCD panel is formed in the center of the product, the external sub-LCD panel cannot be formed in the center of the product, but can only be formed around the edge, which limits the development of various designs of the product. have.

Accordingly, an object of the present invention is to provide an improved double-sided illumination backlight device which solves the above-mentioned problems, wherein a double-sided illumination backlight capable of supplying illumination to both sides using one light guide plate and a reflection plate having a window formed in a portion of the area is provided. To provide a device.

Another object of the present invention is to provide a double-sided illumination type backlight device capable of miniaturization and relatively freely positioning the double-sided LCD panel.

Still another object of the present invention is to provide a double-sided illumination backlight device having a uniform light quantity distribution and high light utilization efficiency.

In order to achieve the above object, the double-sided backlight device according to the present invention is

A light source;

A light incidence plane in which light from the light source is incident adjacent to the light source, a front exit surface for emitting the light from the inside toward the upper liquid crystal display panel, and a portion of the light inside to be emitted toward the lower liquid crystal display panel, A light guide plate including a rear exit surface having a scattering pattern formed to reflect toward the exit surface;

It is disposed adjacent to the rear exit surface, the window is formed in a portion is composed of a reflector that transmits the light to the window and reflects the remaining light.

The scattering pattern formed on the rear exit surface of the LGP is divided into a first scattering region formed substantially corresponding to a window of the reflecting plate and a second scattering region which is a part other than the first scattering region. The area density of the scattering patterns of the first and second scattering areas is preferably increased according to the distance from the light source, but the area density of the first scattering area is greater than the area density of the second scattering area. .

In addition, the scattering pattern of the first scattering region preferably has a cross section in the shape of a triangle or a diffraction grating (sine wave), so that the amount of light directed toward the front emission surface by the scattering pattern of the first scattering region is second scattering. It may also be configured to increase the amount of light scattered by the scattering pattern of the region.

An optical sheet may be disposed below the rear emitting surface of the light guide plate, or a polarizing reflection sheet may be disposed to selectively reflect and transmit according to a partial reflecting plate or a polarization state, thereby increasing light efficiency and obtaining a uniform light distribution.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention. In general, in the case of a double-sided LCD used in a dual type mobile phone, the LCD which is seen from the outside when the lid of the mobile phone is closed is called a sub LCD, and the internal LCD that is visible when the lid is opened is called a main LCD. Hereinafter, a case in which the main LCD is larger than the sub LCD, for example, the main LCD is about 2 inches long and the sub LCD is about 1 inch will be described. However, the present invention is not limited thereto. The size of the sub LCD can be varied in accordance with the design specifications, and the size of both LCDs can be the same.

First, the double-sided backlight device according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3.

The double-sided backlight device according to the first embodiment is disposed adjacent to a light guide plate 20, a light source 10 made of a light emitting element (LED), and the like, and a rear exit surface 22 of the light guide plate 20. It consists of a reflector plate 30.

For convenience of explanation, if the main LCD 40 is disposed on the front exit surface 21 side of the light guide plate 20 and the sub LCD 50 is disposed on the rear exit surface 22 side, the rear exit surface of the light guide plate 20 is As shown in FIG. 2, the first scattering area 23 may be divided into a region substantially corresponding to the position and form of the sub LCD 50 and a remaining region, and a region formed corresponding to the position and form of the sub LCD 50. ) And the remaining area is referred to as the second scattering area 24.

If the sub LCD 50 is smaller than the main LCD 40 and located at the center of the main LCD, as shown in FIG. 2, the first scattering area 23 is formed as a quadrangular area substantially corresponding to the sub LCD, and the second scattering is performed. The area 24 is an area of the remaining 'ㅁ' characters.

As shown in FIG. 3, the reflective plate 30 has an opening formed to correspond to the position and shape of the sub LCD 50 in the general opaque reflective sheet, that is, the window 31 is formed so that the light directed to the window is transmitted as it is. The light is configured to reflect.

In addition, although not shown, an optical sheet such as a diffusion sheet and / or a prism plate may be disposed between the light guide plate 20 and the main LCD 40 to be used as an auxiliary means to provide uniform illumination to the main LCD 40. Moreover, an optical sheet such as a diffusion sheet and / or a prism plate is disposed between the light guide plate 20 and the reflector plate 30 or the reflector plate 30 and the sub LCD 50 to provide more uniform illumination to the sub LCD 50. can do.

The scattering pattern formed on the rear exit surface 22 of the light guide plate will be described with reference to FIGS. 4 and 5A-5B. The scattering pattern of the rear exit surface 22 of the light guide plate directs a part of the light emitted from the light source 10 toward the sub LCD 50 and also enables uniform illumination toward the main LCD 40. If the light guide plate having the fine projections or grooves generally used in the prior art is used together with the reflective plate 30 of the present invention in which the window 31 is formed, the illumination to the main LCD 40 is a portion corresponding to the window 31. It becomes dark and the illumination toward the main LCD 40 is not uniform. Therefore, in order to uniformly illuminate the sub LCD 50 and at the same time the main LCD 40, the present inventors have developed a method of adjusting the area density of the scattering pattern and a method of changing the cross-sectional shape of the scattering pattern. It was.

First, the method of adjusting the area density of the scattering pattern is to increase the scattering pattern area density of the first scattering area 23 of the rear emission surface than the scattering pattern area density of the second scattering area 24. For example, the rear emission surface 22 may be formed as a scattering pattern having fine hemispherical protrusions or hemispherical grooves, wherein the area density of the scattering pattern increases with distance from the light source 10, but the first scattering area If the scattering pattern area density of (23) is set to a value larger than the scattering pattern area density of the second scattering area 24, a uniform light amount distribution toward the main LCD 40 can be obtained. In this case, an area density of the first scattering area 23 is preferably about 20% to about 50% larger than that of the second scattering area 24. 4 is a scattering pattern density distribution graph illustrating a case where the area density of the first scattering area 23 is about 20% larger than the area density of the second scattering area 24.

Next, a method of changing the cross-sectional shape of the scattering pattern will be described with reference to FIGS. 5A and 5B. The second scattering region 24 is formed of a simple scattering pattern, for example, a scattering pattern in which fine hemispherical protrusions or hemispherical grooves are formed, and the first scattering region 23 has a triangular or diffraction grating (sine wave) in cross section. The light scattered toward the main LCD 40 by the scattering pattern of the first scattering region 23 is scattered toward the main LCD 40 by the scattering pattern of the second scattering region 24. Increase than the amount of light

First, FIG. 5A illustrates a light guide plate having a prism plate shape in which the uneven shape of the first scattering region 23 has a triangular cross section. The incident light R ₀ incident on the first scattering region of the triangular cross section comes out of the upper light R ₁ partly by the boundary reflection, and part of the incident light R ₀ comes out of the lower light R ₂ by refraction. At this time, the light quantity ratio of the upper light R ₁ and the lower light R ₂ varies depending on the base angle θ of the cross section. A number of experiments have shown that the ratio of R ₁ and R ₂ is approximately 80%: 20% when θ is 10 °, and the ratio of R ₁ and R ₂ is approximately 50%: 50% when θ is 45 °. Could know.

Next, in FIG. 5B, a light guide plate in which the uneven shape of the first scattering region 23 has a diffraction grating (sine wave) cross section is shown. The incident light R ₀ incident on the first scattering region of the diffraction grating (sine wave) cross section comes out of the boundary light and partly comes out as the top light R ₁ , and partly comes out as the bottom light R ₂ by diffraction. At this time, the light quantity ratio of the upper light R ₁ and the lower light R ₂ varies according to the height d and the interval p of the uneven pattern. Height d: interval p = 2: 1 ratio of the R ₁ and R ₂ when approximately 50%: 50% and, as the d / p is lower the greater the amount of light of the upper light R _1.

The operating principle of the backlight device according to the first embodiment is that the light incident from the light source 10 to the light guide plate 20 proceeds along the inside of the light guide plate and is scattered by the scattering pattern formed on the rear exit surface 22 of the light guide plate 20. As it is scattered, a part is directed toward the main LCD 40 through the front exit surface 21, and a part of the light exits from the rear exit surface 22 to the outside of the light guide plate.

At this time, the light scattered toward the front exit surface 21 in the second scattering region immediately exits toward the main LCD 40 through the front exit surface 21 of the light guide plate, and goes outside the LGP through the rear exit surface 22. The emitted light is reflected by the reflector 30 and comes out through the front exit surface 21 toward the main LCD 40. Therefore, the light scattered in the second scattering area is mostly directed toward the main LCD 40.

On the other hand, the light incident on the first scattering area is partly directed toward the front exit surface 21 by scattering, and part of the light exits the rear exit surface 22 and proceeds downward to become the illumination toward the sub LCD 40. .

In the main LCD 40, when the amount of light in the first scattering region and the second scattering region is a method of adjusting the area density of the scattering pattern as described above, the area density of the first scattering region is the area of the second scattering region. Since the amount of light emitted from the first scattering region toward the main LCD 40 in the first scattering region is relatively large, the amount of light emitted from the first scattering region becomes relatively large.

In addition, as a method of changing the cross-sectional shape of the scattering pattern of the rear emission surface 22 of the light guide plate 20, the scattering pattern of the first scattering region 23 is shaped like a triangle or a diffraction grating, so that the first scattering region The amount of light directed toward the front emission surface 21 by the scattering pattern of 23 is increased to be greater than the amount of light scattered by the scattering pattern of the second scattering region 24. Therefore, the illumination can be uniform at the main LCD 40 side.

Next, referring to FIG. 6, a double-sided backlight device according to a second embodiment of the present invention will be described. The backlight device according to the second embodiment includes a light guide plate 20, a light source 10 including a light emitting element (LED), and the like, and a partial reflection disposed adjacent to the rear emission surface 22 of the light guide plate 20. It consists of the sheet | seat 60 and the reflecting plate 30.

In the second embodiment, like the first embodiment, the main LCD 40 is disposed on the front exit surface 21 of the light guide plate 20, and the sub LCD 50 is disposed on the rear exit surface 22.

The partial reflection sheet 60 is formed by forming a metal thin film or a non-conductive layer on a transparent film, and serves to allow incident light to partially reflect and partially transmit. At this time, the ratio of transmittance: reflection can be adjusted from 1: 0 to 0: 1 according to the thickness of the metal thin film or the non-conductive layer. For example, when using a reflector having a reflection characteristic of 50%, 50% of light emitted downward is directed toward the sub LCD 50 and the remaining 50% is directed toward the main LCD 40. Therefore, it can select suitably according to the light quantity ratio of the designed main LCD 40 and the sub LCD 50. FIG.

The reflection plate 30 is formed in the general opaque reflection sheet is formed with a window 31 corresponding to the position and shape of the sub LCD 50 is configured to transmit the light to the window as it is and reflect the remaining light.

In the second exemplary embodiment, the rear exit surface of the light guide plate 20 may be formed by forming a general scattering pattern as a whole. The area of the scattering pattern may be divided into a first scattering region and a second scattering region 24 as in the first embodiment. A method of adjusting the density or a method of changing the cross-sectional shape of the scattering pattern may be used.

In addition, although not shown, an optical sheet such as a diffusion sheet and / or a prism plate may be disposed between the light guide plate 20 and the main LCD 40 to be used as an auxiliary means to provide uniform illumination to the main LCD 40. Moreover, an optical sheet such as a diffusion sheet and / or a prism plate may be disposed between the reflecting plate 30 and the sub LCD 50 to provide more uniform illumination to the sub LCD 50.

The operation principle of the backlight device according to the second embodiment is similar to that of the first embodiment, and part of the light emitted from the rear exit surface of the light guide plate is incident on the partial reflection sheet 60 and the partial reflection sheet 60. Some of the incident light is reflected and then enters the light guide plate 20 again and becomes light exiting toward the front exit surface of the light guide plate, and some passes through the partial reflection sheet 60 and then through the window 31 of the reflector 30. It is directed to the sub LCD 50.

Next, referring to FIG. 7, a double-sided backlight device according to a third embodiment of the present invention will be described. The backlight device according to the third embodiment includes a light guide plate 20, a light source 10 including a light emitting element (LED), and the like, and polarized light reflections disposed adjacent to the rear emission surface 22 of the light guide plate 20. It consists of the sheet | seat 70 and the reflecting plate 30.

In the third embodiment, like the first embodiment, the main LCD 40 is disposed on the front exit surface 21 of the light guide plate 20, and the sub LCD 50 is disposed on the rear exit surface 22.

The polarization reflecting sheet 70 transmits light polarized in a specific direction and reflects the rest of the incident light. For example, the light of p-polarized light is reflected upward and the light of s-polarized light is transmitted as it is. Therefore, in the present exemplary embodiment, the polarized light reflection sheet 70 is used to direct the light of s-polarized light, which is 50% of the amount of light emitted downward, toward the sub LCD 50, and the remaining 50% of p-polarized light is directed to the main LCD ( It is directed toward 40) to uniformly illuminate the main LCD 40 and the sub LCD 50.

Moreover, in general, light incident on the LCD panel has an optical loss of about 50% while passing through a polarizer (not shown) attached to the LCD panel itself, but when used in the third embodiment, the main LCD 40 When the polarizing plate of P is used as the p-transmissive polarizing plate and the polarizing plate of the sub LCD 50 is used as the s-permeable polarizing plate, the additional effect of doubling the light utilization efficiency can also be obtained.

The reflection plate 30 is formed in the general opaque reflection sheet is formed with a window 31 corresponding to the position and shape of the sub LCD 50 is configured to transmit the light to the window as it is and reflect the remaining light.

In the third exemplary embodiment, the rear exit surface of the light guide plate 20 may be formed by forming a general scattering pattern as a whole. The area of the scattering pattern may be divided into a first scattering region and a second scattering region 24 as in the first embodiment. A method of adjusting the density or a method of changing the cross-sectional shape of the scattering pattern may be used.

In addition, although not shown, an optical sheet such as a diffusion sheet and / or a prism plate may be disposed between the light guide plate 20 and the main LCD 40 to be used as an auxiliary means to provide uniform illumination to the main LCD 40. Moreover, an optical sheet such as a diffusion sheet and / or a prism plate may be disposed between the reflecting plate 30 and the sub LCD 50 to provide more uniform illumination to the sub LCD 50.

The operation principle of the backlight device according to the third embodiment is similar to that of the first embodiment, and when the polarizing reflection sheet 70 uses the p transmissive reflecting sheet, some of the light emitted to the rear exit surface of the light guide plate is partially polarized reflection sheet. It enters 70. In addition, the light of the s-wave component among the light incident on the polarization reflecting sheet 70 reflects and enters the light guide plate 20 again and exits toward the front exit surface of the light guide plate, and the light of the p-wave component is the polarization reflecting sheet ( After passing through the light 70, the light is directed toward the sub LCD 50 through the window 31 of the reflector 30.

Next, referring to FIG. 8, a double-sided illumination type backlight device according to a fourth embodiment of the present invention will be described. In the backlight device according to the fourth embodiment, a composite reflector is disposed adjacent to a light guide plate 20, a light source 10 including a light emitting element (LED), and the like, and a rear exit surface 22 of the light guide plate 20. It consists of 80.

In the fourth embodiment, like the first embodiment, the main LCD 40 is disposed on the front exit surface 21 of the light guide plate 20, and the sub LCD 50 is disposed on the rear exit surface 22.

The composite reflector 80 divides the area formed to correspond to the position and shape of the sub LCD 50 and the remaining area to reduce the reflectance to a portion corresponding to the sub LCD 50 with a low reflectance, for example, about 20%, and the remaining portion is 100. It is a reflective sheet configured to have a reflectance of%. By varying the thickness of the metal layer or the non-conductor layer to be laminated, the composite reflector 80 may be manufactured to have different reflectivity of each region.

In the fourth exemplary embodiment, the rear exit surface of the light guide plate 20 may be formed by forming a general scattering pattern as a whole. The area of the scattering pattern may be divided into the first scattering region and the second scattering region 24 as in the first embodiment. A method of adjusting the density or a method of changing the cross-sectional shape of the scattering pattern may be used.

In addition, although not shown, an optical sheet such as a diffusion sheet and / or a prism plate may be disposed between the light guide plate 20 and the main LCD 40 to be used as an auxiliary means to provide uniform illumination to the main LCD 40. Moreover, an optical sheet such as a diffusion sheet and / or a prism plate may be disposed between the composite reflector plate 80 and the sub LCD 50 to provide more uniform illumination to the sub LCD 50.

The operation principle of the backlight device according to the fourth embodiment is similar to the first embodiment, and the light emitted from the rear exit surface of the light guide plate is incident on the composite reflector 70, and the incident light is incident on the partially reflective region 81. Some of the light is reflected and incident again to the light guide plate 20 to be light exiting toward the front exit surface of the light guide plate, and part of the light is transmitted through the partial reflection sheet 60 to the sub LCD 50. On the other hand, the light incident on all of the reflection area 82 may be light entering the light guide plate 20 again and proceeding from the inside or outward toward the main LCD 40.

In the exemplary embodiment of the present invention, the scattering pattern of the light guide plate and the window of the reflecting plate are all described as quadrangles by using a rectangular LCD. However, the LCD may be formed in a circular shape according to the type of LCD used.

The double-sided illumination backlight device according to the present invention can provide a relatively uniform illumination to the LCD disposed on both sides by using a light guide plate and a reflection plate having a window formed in a portion of the region, and can also increase the light utilization efficiency. In addition, the double-sided illumination type backlight device according to the present invention can be positioned relatively freely on both sides of the LCD panel is not only a variety of designs possible, but also the thickness and the area is compact, it is possible to miniaturize the product.

Although the technical features of the present invention have been described above with reference to specific embodiments, those skilled in the art to which the present invention pertains may make various changes and modifications within the scope of the technical idea according to the present invention. It is obvious.

1 is a side view schematically showing a first embodiment of the present invention,

FIG. 2 is a plan view illustrating a rear exit surface of the light guide plate illustrated in FIG. 1;

3 is a plan view illustrating the reflector shown in FIG. 1;

4 is a graph showing the density distribution of the scattering pattern of the rear exit surface of the light guide plate;

5A and 5B are cross-sectional views illustrating a scattering pattern of a triangular cross section and a scattering pattern of a diffraction grating, respectively;

6 is a side view schematically showing a second embodiment of the present invention,

7 is a side view schematically showing a third embodiment of the present invention,

8 is a side view schematically showing a fourth embodiment of the present invention.

9 is a view showing a conventional double-sided backlight device.

Claims (10)

delete In the backlight device for providing illumination to the liquid crystal display panel installed on both upper and lower sides, A light source; A light incidence surface in which light from the light source is incident adjacent to the light source, a front emission surface for emitting the light therein toward the upper liquid crystal display panel, and a portion of the light therein to be emitted toward the lower liquid crystal display panel A light guide plate including a rear exit surface having a scattering pattern formed to reflect toward the front exit surface; A partial reflector disposed below the rear exit surface of the light guide plate, the partial reflector allowing light to be partially transmitted and partially reflected; The reflector is disposed adjacent to the partial reflector, and a window is formed in a partial region to transmit light directed to the window and reflect the remaining light. Double-sided illumination type backlight device, characterized in that it further comprises. In the backlight device for providing illumination to the liquid crystal display panel installed on both upper and lower sides, A light source; A light incidence surface in which light from the light source is incident adjacent to the light source, a front emission surface for emitting the light therein toward the upper liquid crystal display panel, and a portion of the light therein to be emitted toward the lower liquid crystal display panel A light guide plate including a rear exit surface having a scattering pattern formed to reflect toward the front exit surface; A polarization reflecting sheet disposed below a rear exit surface of the light guide plate and selectively reflecting and transmitting in accordance with a polarization state; The reflector is disposed adjacent to the polarizing reflective sheet, the window is formed in a portion of the region to transmit the light toward the window and reflect the remaining light Double-sided illuminated backlight device comprising a. In the backlight device for providing illumination to the liquid crystal display panel installed on both upper and lower sides, A light source; A light incidence surface in which light from the light source is incident adjacent to the light source, a front emission surface for emitting the light therein toward the upper liquid crystal display panel, and a portion of the light therein to be emitted toward the lower liquid crystal display panel A light guide plate including a rear exit surface having a scattering pattern formed to reflect toward the front exit surface; It is disposed adjacent to the rear exit surface, the window is formed in a portion of the reflector to transmit the light toward the window and reflect the remaining light Including, The scattering pattern formed on the rear exit surface of the light guide plate is formed of a first scattering region formed substantially corresponding to the window of the reflecting plate, and a second scattering region which is a part other than the first scattering region, The area density of the scattering patterns of the first and second scattering areas increases with the distance from the light source, wherein the area density of the first scattering area is formed to be larger than the area density of the second scattering area. Illuminated backlight device. The method of claim 4, wherein The double-sided backlight type device of claim 1, wherein the area density of the first scattering area is 20% to 50% greater than the area density of the second scattering area. In the backlight device for providing illumination to the liquid crystal display panel installed on both upper and lower sides, A light source; A light incidence surface in which light from the light source is incident adjacent to the light source, a front emission surface for emitting the light therein toward the upper liquid crystal display panel, and a portion of the light therein to be emitted toward the lower liquid crystal display panel A light guide plate including a rear exit surface having a scattering pattern formed to reflect toward the front exit surface; It is disposed adjacent to the rear exit surface, the window is formed in a portion of the reflector to transmit the light toward the window and reflect the remaining light Including, The scattering pattern formed on the rear exit surface of the light guide plate is formed of a first scattering region formed substantially corresponding to the window of the reflecting plate, and a second scattering region which is a part other than the first scattering region, The scattering pattern of the first scattering region has a triangular shape or a diffraction grating (sine wave) in cross section, and the amount of light directed toward the front emission surface by the scattering pattern of the first scattering region is determined by the second scattering pattern. A double-sided illumination type backlight device, characterized in that to increase than the amount of light scattered by the scattering pattern of the scattering region. The method according to any one of claims 2 to 6, At least one optical sheet disposed on a front exit surface of the light guide plate Double-sided illumination type backlight device characterized in that it further comprises. The method according to any one of claims 2 to 6, At least one optical sheet disposed between the rear exit surface of the light guide plate and the reflecting plate or under the reflecting plate Double-sided illumination type backlight device characterized in that it further comprises. The method according to claim 2 or 3 or 6, The scattering pattern formed on the rear exit surface of the light guide plate is formed of a first scattering region formed substantially corresponding to the window of the reflecting plate, and a second scattering region which is a part other than the first scattering region, The area density of the scattering patterns of the first and second scattering areas increases with the distance from the light source, wherein the area density of the first scattering area is greater than the area density of the second scattering area. Illuminated backlight device. The method according to claim 2 or 3 or 4, The scattering pattern formed on the rear exit surface of the light guide plate is formed of a first scattering region formed substantially corresponding to the window of the reflecting plate, and a second scattering region which is a part other than the first scattering region, The scattering pattern of the first scattering region has a triangular shape or a diffraction grating (sine wave) in cross section, and the amount of light directed toward the front emission surface by the scattering pattern of the first scattering region is determined by the second scattering pattern. A double-sided illumination type backlight device, characterized in that to increase than the amount of light scattered by the scattering pattern of the scattering region.