JP2000267096A - Back light device for liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-price back light device having proper distribution of luminance for a liquid crystal display, and especially to obtain a compact back light device suitable for a liquid crystal display with a large screen in which the light just under a light guide plate type back light device with a fluorescent lamp inserted is controlled to proper quantity of light by a light-transmitting reflection film or light-transmitting reflection sheet so as to decrease the difference in the luminance between the region with direct light and the region where the light propagates in the light guide plate to a level practically negligible. SOLUTION: This back light device for liquid crystal display is equipped with a diffusion sheet 16 to be attached to the light emitting face of a light guide plate 11 and with a reflection sheet 15 to be attached to the reflection face of the light guide plate 11. A groove 12 to insert a fluorescent lamp having a bottom face and side faces perpendicular to the light emitting face is formed on the reflection face of the light guide plate 11. A light transmitting reflection film 14 is formed on or a light transmitting reflection film sheet 14 is stuck to the bottom of the groove 12 to insert a fluorescent lamp. The transmittance of the light transmitting reflection film is simulated by an accurate and easy method. The luminance of the region with direct light and in the region where the light propagates in the light guide plate is controlled by the light transmitting reflection film 14 when the back light device has a fluorescent lamp 13 inserted and arranged in the groove 12 for a fluorescent lamp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight device of a liquid crystal display device which is very useful as a display of an information device such as a video device or a computer. And a low-cost backlight device.

[0002]

2. Description of the Related Art The spread of liquid crystal display devices has been remarkable and has become an indispensable device for display devices of notebook personal computers. A backlight device is used as a light source for the display device. Many types of backlight devices have been developed. Generally, a backlight device has a structure in which a fluorescent tube is arranged at the end of the light guide plate (referred to as an edge type). (Hereinafter referred to as a direct type) and a structure in which an edge type and a direct type are combined (referred to as a fluorescent tube inserted light guide plate type). Among them, the edge type is used for a portable type such as a notebook personal computer, taking advantage of its thin feature. The direct type is used for a large-screen display device such as a monitor that requires high luminance.

The fluorescent tube insertion light guide plate type incorporates the advantages of an edge type and a direct type, and is promising as a large-screen backlight device. FIG. 17 is a configuration diagram showing an example of a fluorescent tube-inserted light guide plate type backlight device. (A) is a top view thereof, and (B) is a cross-sectional view taken along a center line aa ′ shown in (A).

In FIG. 17, reference numeral 101 denotes a light guide plate;
Is a reflection sheet 1, 103 is a frame, 104 is a fluorescent tube,
110 is a lead wire of the fluorescent tube 104, 105 is a fluorescent tube insertion groove, 106 is a light curtain, and 107 is a diffusion sheet. Reference numeral 109 denotes a triangular reflecting surface formed on the frame, and the reflecting sheet 2 indicated by 108 is mounted on the reflecting surface. The reflection sheet 1 of 102 is mounted on one surface of the light guide plate 101 (hereinafter, referred to as a reflection surface) and stored in the frame 109. The other surface of the light guide plate 101 (hereinafter, referred to as
The reflective sheets 2 of the light curtains 106 and 107 are mounted on the light-emitting surface). The fluorescent tube 104 is inserted into the fluorescent tube insertion groove 105. The liquid crystal panel is arranged on the diffusion sheet 107.

The fluorescent tube insertion groove 105 is formed along the long side direction (X direction) of the central portion of the reflection surface of the light guide plate 101, and the fluorescent tube 104 is inserted therein. The fluorescent tube insertion groove 105 has a side surface perpendicular to the light emitting surface and a bottom surface parallel to the light emitting surface. The incident light from the side faces the direct light from the fluorescent tube 104 and the reflecting surface 1
09 from the reflected light. On the other hand, incident light from the bottom surface of the fluorescent tube insertion groove is light directly incident from the fluorescent tube 104 without passing through the light guide plate. Therefore, the light emitted from the vicinity of the center of the backlight device in which the fluorescent tube insertion groove is formed is light directly emitted from the fluorescent tube (hereinafter, this light is abbreviated as direct light). Light radiated from a portion outside the vicinity of the central portion is light that propagates through the light guide plate 101 and is reflected by the reflection sheet 2 (hereinafter, this light is abbreviated as light guide plate propagation light). Since the luminance due to the light directly below is significantly higher than the luminance of the light propagating through the light guide plate, the luminance of the part where the fluorescent tube is inserted and placed must be reduced and adjusted so that the luminance level becomes the same as the luminance level of the light propagation part of the light guide plate. For example, the luminance distribution of the backlight device is not suitable for liquid crystal display (in general, a uniform luminance distribution is desired for liquid crystal display). The light curtain 106 is mounted to perform the light control.

The light curtain 106 is formed by forming a light-transmitting thin film by vapor-depositing and printing aluminum on a transparent film. The brightness distribution of the backlight device is suitable for liquid crystal display by changing the shape and thickness of the aluminum film deposited and printed on the light curtain 106 in the vicinity of the light portion immediately below the fluorescent tube and in the light guide plate propagation light portion. To do.

In the configuration described above, the fluorescent tube 10
The light radiated from 4 passes directly through the light guide plate from the bottom surface of the fluorescent tube insertion groove 105 and directly reaches the light curtain 106, and the reflected light from the side surface of the fluorescent tube insertion groove 105 directly or from the reflection surface 109 of the frame. Is incident, propagates through the light guide plate, and is composed of light guide plate propagation light emitted from the light emitting surface via the light curtain 106 and the diffusion sheet 107 by reflection by the reflection sheet 2. The light immediately below and the light transmitted through the light guide plate are adjusted by the light curtain 106 to have the same luminance level, and are diffused by the diffusion sheet 107.
The backlight device emits light with an appropriate luminance distribution.

[0008]

The above-described light guide plate type backlight device with a fluorescent tube inserted therein has a high use efficiency of light radiated from the fluorescent tube, and if the performance and the number of fluorescent tubes used are the same,
It has the advantage of higher brightness than the edge type, and is thinner and more compact than the direct type.

However, it is theoretically shown that the above-mentioned light directly under the light and light propagated through the light guide plate are modulated by a light curtain to make the luminance distribution of the backlight device suitable for a liquid crystal display. Although the luminance of the light transmitted through the light guide plate is extremely small relative to the luminance of the light (10% or less of the luminance due to the light directly below), the area ratio of the light transmitted through the light guide plate to the light directly below is extremely large (10 or more). In order for the luminance distribution of the device to be the optimal luminance distribution for the liquid crystal display, advanced technology is required to optimize the combination of the shape of the reflective surface 109 and the thickness and shape of the light-transmitting film of the light curtain 106, which requires cost. There is a problem that is up.

FIG. 18 is a diagram showing a backlight device of FIG.
It is a figure which shows an example of the luminance distribution in the -a 'cross section. As shown in FIG. 18, the luminance at the center where the fluorescent tube is inserted becomes high, and a uniform luminance distribution cannot be obtained. When a backlight device having a luminance distribution as shown in FIG. 8 is used for a liquid crystal display device, the luminance becomes uneven and the image quality deteriorates.

The present invention solves such a conventional problem, and adjusts the light immediately below a fluorescent tube-inserted light guide plate type backlight device to an appropriate light amount by a light transmitting / reflecting film or a light transmitting / reflecting sheet. Lighting, the brightness difference between the direct light part and the light guide plate propagating light part is made practically negligible, and it is suitable for low-cost backlight devices with a luminance distribution suitable for liquid crystal display, especially for large-screen liquid crystal display And a compact backlight device.

[0012]

In order to solve such a problem, the invention according to claim 1 of the present application is directed to the light guide plate, wherein one surface of the light guide plate is used as a light emitting surface and the other surface is used as a reflection surface. A backlight device for a liquid crystal display, comprising: a diffusion sheet attached to the light emitting surface; a reflection sheet attached to the reflection surface; and a fluorescent tube, wherein a bottom surface and a side surface perpendicular to the emission surface. Forming a fluorescent tube insertion groove having a light transmission / reflection film on the bottom surface of the fluorescent tube insertion groove, and forming a light transmission / reflection film on the bottom surface of the fluorescent tube insertion groove. Affixing the sheet, and, as one to choose from, characterized in that a fluorescent tube is inserted and arranged in the fluorescent tube insertion groove, the direct light portion and the light guide plate propagation light portion Brightness level for liquid crystal display An effect that can realize a backlight device of a low cost a compact suitable for screen liquid crystal display.

The invention according to claim 2 of the present application is the invention according to claim 1, wherein the length of the short side of the light guide plate is L and the length of the long side is W, and the fluorescent tube insertion groove is The distance between the center lines of the adjacent fluorescent tube insertion grooves is 2 × S1 at a position parallel to the long side and symmetric with respect to the center line of the short side.
2n + 1 is formed on the center line, where n is a positive integer, and a total of 2n + 1 is formed on the center line, and the distance between the long side and the center line of the fluorescent tube insertion groove close to the long side is defined as S2, L = (2n−1) × 2 × S1 + 2 × S2, and the center of the adjacent fluorescent tube insertion groove at a position parallel to the short side and symmetric with respect to the center line of the long side. The distance between lines is 2 × S1, and n is a positive integer and 2
n are formed, and one is formed on the center line, for a total of 2n +
S2 is the distance between the short side and the center line of the fluorescent tube insertion groove adjacent to the short side, and W = (2n-1) ×
It is characterized in that either one of 2 × S1 + 2 × S2 is selected, and since a plurality of fluorescent tube insertion grooves are formed at appropriate positions, it is thin and compact and has high brightness. Backlight device suitable for a large-screen liquid crystal display can be realized at low cost.

The third aspect of the present invention is the invention according to the first aspect, wherein the length of the short side of the light guide plate is L and the length of the long side is W, and the fluorescent tube insertion groove is At a position parallel to the long side and symmetric with respect to the center line of the short side, the distance between the center lines of the adjacent fluorescent tube insertion grooves is 2 × S1
The distance between the long side and the center line of the fluorescent tube insertion groove adjacent to the long side is defined as S2, and L = (2n−1) × 2 × S1 + S2. And that the distance between the center lines of the adjacent fluorescent tube insertion grooves is 2 × S1, which is parallel to the short side and centered on the center line of the long side, and that n is a positive integer and 2n The distance between the short side and the center line of the fluorescent tube insertion groove adjacent to the short side is S2, and W = (2n-1) × 2 × S
1 + S2, and one of them is selected. In order to form a plurality of fluorescent tube insertion grooves at appropriate positions, a thin, compact, high-brightness large-screen liquid crystal is provided. This has the effect that a backlight device suitable for display can be realized at low cost.

The invention described in claim 4 of the present application provides claims 2 and 3
Wherein S1 and S2 are such that S1 = S
2 and has the effect of realizing a luminance distribution of the backlight device which can be regarded as practically uniform.

The invention according to claim 5 of the present application is the invention according to claim 2, wherein n = 0 and W = 2 ×
S2 or L = 2 × S2, wherein one fluorescent tube insertion groove is formed at the center of the light guide plate, and one fluorescent tube insertion groove is formed at the center of the screen. The backlight device of the present invention can be realized.

The invention described in claim 6 of the present application is the first or second invention.
3. The invention according to claim 3, wherein n = 1 in claim 3, and two fluorescent tube insertion grooves are respectively formed at positions symmetrical with respect to the center line of the long side or the short side as a reference. In addition, there is an effect that a highly efficient backlight device can be realized by forming the two fluorescent tube insertion grooves at appropriate positions.

The invention described in claim 7 of the present application is the first or second invention.
In the invention described in (3) and (3), one fluorescent tube is inserted and arranged on a line connecting the center of the fluorescent tube and the center of the fluorescent tube insertion groove, and one fluorescent tube is provided. It has the effect that the light utilization can be increased by inserting and arranging the tube at an appropriate position in the fluorescent tube insertion groove.

The invention described in claim 8 of the present application is the first or second invention.
4. The invention according to (3), wherein two fluorescent tubes are inserted one by one at positions symmetrical to each other with respect to the center of the fluorescent tube insertion groove. There is an effect that the luminance can be increased by inserting and arranging the fluorescent tubes at appropriate positions in the fluorescent tube insertion groove.

The invention according to claim 9 of the present application is the invention according to claim 8, wherein the fluorescent tube reflector is located substantially at the center of a straight line connecting the centers of the two fluorescent tubes, and The fluorescent tube reflector is disposed so as to be substantially perpendicular to the bottom surface of the insertion groove, and the height of the fluorescent tube reflector is a distance from the reflecting surface of the light guide plate. The height of the fluorescent tube reflector is the tip of the fluorescent tube reflector. And a straight line connecting the corner where the bottom surface and the side surface of the fluorescent tube insertion groove are in contact with the fluorescent tube insertion groove. It has the effect that the utilization rate can be increased.

[0021] The invention described in claim 10 of the present application is directed to claim 1,
4. The invention according to 2 or 3, wherein the light transmitting / reflecting film is formed by printing or applying a scattering material, and has a light transmittance with a proper transmittance and a high scattering property. This has the function of easily forming a reflective film.

An eleventh aspect of the present invention is the invention according to the first aspect, wherein Q1 is the sum of the emission angles of the fluorescent tubes incident on the side surface of the fluorescent tube insertion groove, and Q2 is the total of the fluorescent tubes inserted. The sum of the emission angles of the fluorescent tube incident on the bottom of the groove, Q
1 <180 ° and Q2 <360 °,
H is the length of the fluorescent tube insertion groove, d2 is the width of the fluorescent tube insertion groove, d1 is the distance from one side of the fluorescent tube insertion groove to the end of the light guide plate, and The transmittance Tr of the light transmitting / reflecting film is [(Q1 / Q2), as one of which is selected from the distance to the side surface of the second fluorescent tube insertion groove adjacent to one side surface of the groove. ) +0.5] (d2 / d1)>Tr> (Q1 / Q
2) [d2 / (2 · d1)] is satisfied, and has an effect that the maximum value and the minimum value of the transmittance of the light transmitting / reflecting film can be easily and accurately determined.

The invention according to claim 12 of the present application is the invention according to claim 1, wherein the transmittance Tr of the light transmitting / reflecting film is
Is characterized by satisfying 0.25>Tr> 0.008, and has an effect that the range of the transmittance of the light transmitting / reflecting film can be clarified.

The thirteenth aspect of the present invention is the invention according to the first aspect, wherein Q1 is the sum of the emission angles of the fluorescent tubes incident on the side surfaces of the fluorescent tube insertion groove, and Q2 is the fluorescent tube inserted. The sum of the emission angles of the fluorescent tube incident on the bottom of the groove, Q
1 <180 ° and Q2 <360 °,
H is the length of the fluorescent tube insertion groove, d2 is the width of the fluorescent tube insertion groove, d1 is the distance from one side of the fluorescent tube insertion groove to the end of the light guide plate, and Either ε is the utilization factor of the reflected light incident on the side surface, and η is the bottom surface, as one of which is selected from the distance to the side surface of the second fluorescent tube insertion groove adjacent to one side surface of the groove. Ε <1, η <1, ε
+ Η <1, and the transmittance Tr of the light transmitting / reflecting film is expressed by the following formula: T = 2 · β [(Q1 / Q2) + η / 2] (d2 / d1)
× [1 / {2 (1 + ε) + η (d2 / d1)}, satisfying 1.6T>Tr> 0.4T, and the transmittance of the light transmitting / reflecting film is calculated by a simple equation. This has the effect of enabling accurate simulation.

The invention described in claim 14 of the present application is the invention described in claim 13
Wherein the standard value T of the transmittance is ε = 0.25 and η = 0.65, and the standard value of the transmittance of the light transmitting / reflecting film can be easily obtained. Has the effect of being able to.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A backlight device according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a configuration diagram of a backlight device for a liquid crystal display according to Embodiment 1 of the present invention.

In FIG. 1, 11 is a light guide plate, 12 is a fluorescent tube insertion groove, 13 is a fluorescent tube, 19 is a lead wire of the fluorescent tube 13, 14 is a light transmitting and reflecting film, 15 is a reflection sheet, 16 is a diffusion sheet, 17 is a lens sheet and 18 is a frame. (A) is a top view of the backlight device, and a cross-sectional view of a center line aa ′ of a long side (y direction) of the light guide plate 11.

The light guide plate 11 efficiently propagates light in the light guide plate by utilizing total reflection of light. As shown in FIG. 1, the length of the short side is L and the length of the long side is W. is there. A fluorescent tube insertion groove 12 in which a fluorescent tube 13 is inserted and arranged on the reflection surface of the light guide plate 11.
Is formed. In FIG. 1, the fluorescent tube insertion groove 12 is formed on the center line bb ′ of the light guide plate 11 (the center line of the short side), and the center of the fluorescent tube 13 coincides with the center of the fluorescent tube insertion groove 12. Inserted and placed. A diffusion sheet 16 and a lens sheet 17 are mounted on the light emitting surface of the light guide plate 11 in an overlapping manner. The diffusion sheet 16 diffuses light emitted from the light guide plate 11, and the lens sheet 17 focuses the diffused light within a certain angle. The reflection sheet 15 is mounted on the reflection surface of the light guide plate 11 and is stored in the frame 18. The reflection sheet 15 reflects light emitted from the light guide plate 11 toward the light emitting surface, and the frame 18 holds and fixes the light guide plate 11, the reflection sheet 15, the fluorescent tube 13, and the like. The light transmission / reflection film 14 is a film that transmits and reflects a part of the incident light, and adjusts the luminance by the light immediately below the fluorescent tube 13 to make the luminance distribution of the backlight device suitable for a liquid crystal display. .

The light transmission / reflection film 14 is formed by applying a substance having high light scattering property and having no coloring to the bottom surface of the fluorescent tube insertion groove 13. An example of a substance having a high light-scattering property and no coloring is titanium oxide. As a coating method, there are a method of depositing a substance having a high light scattering property such as titanium oxide and a method of printing (silk printing or the like). In the case of mass production, vapor deposition is suitable, and the formation accuracy and optical characteristics of the light transmitting / reflecting film 14 are excellent. The printing method is suitable when the number of productions is small and there are many types of backlight devices. Furthermore, for small-quantity production and test sample production, a light-transmitting / reflecting film is formed on a transparent film using a highly light-scattering substance such as titanium oxide to form a light-transmitting / reflective sheet. 13 is suitable.

FIG. 2 shows an example of the luminance distribution in the section taken along the line aa 'of FIG. The center is the position where the fluorescent tube 13 is inserted and arranged, and the end is the long side of the light guide plate 11. As shown in FIG. 2, the luminance distribution in the section taken along the line aa ′ is uniform, and is much better than the luminance / luminance distribution of the conventional backlight device (FIG. 18). This shows that the light control by the light transmitting / reflecting film of the present invention is superior to the light control by the light curtain.

FIG. 3 illustrates the backlight device of the present invention.
And FIG. FIG. 3 is a diagram illustrating light propagation of the backlight device. FIG. 3A is a diagram illustrating a state of light emitted from the backlight device, and FIG. 3B is a diagram illustrating an angle of light emitted from the fluorescent tube. (A) and (B) show the cross section taken along the line aa ′.

As shown in FIG. 3A, the light radiated from the fluorescent tube 13 is incident on the bottom surface of the fluorescent tube insertion groove 12 and is immediately below the light emission surface and is incident on the side surface of the fluorescent tube insertion groove 12. The light guide plate 11 and the reflection sheet 15 can be classified into light guide plate propagating light emerging on the light emitting surface. In FIG. 3A, the regions where the light transmitted from the light guide plate are radiated are light guide plate propagated light portions 1 and 2 (excluding the fluorescent tube insertion groove, a region of length d1), and the region where the light immediately below is radiated (fluorescent light). The width of the tube insertion groove) is defined as the light portion immediately below. In addition, the light quantity of the light-guide plate propagation light parts 1 and 2 is the same. Note that the length from the side surface of the fluorescent tube insertion groove 12 to the end of the light guide plate is d1, and the width of the fluorescent tube insertion groove 12 is d2. Therefore, L =
2 (d1 + d2 / 2). (Accurately, d1 is the distance that light travels straight through the light guide plate. For example, there are cases where a plurality of fluorescent tube insertion grooves are formed and the light does not reach the end of the light guide plate. There is no problem because there is only one groove.)

FIG. 3B shows the light emission angle assuming that light is emitted from the center of the fluorescent tube 13. Here, the center of the fluorescent tube 13 is on the center line of the fluorescent tube insertion groove 12, and the cross section shown in FIG. 3B is symmetric about the center line of the fluorescent tube insertion groove. The fluorescent tube insertion groove 12 has a light transmitting / reflecting film 1 formed on the bottom surface and side surfaces 1 and 2 and on the bottom surface.
4 and the bottom surface is parallel to the light emitting surface and the side surfaces 1 and 2
Is perpendicular to the light emitting surface, and the distance from the side surfaces 1 and 2 and the fluorescent tube 13 is the same.

The angle φ2 is an angle between straight lines connecting the corners formed by the side surfaces 1 and 2 and the bottom surface from the fluorescent tube 12 (FIG. 3).
In (B), the light transmission / reflection film 14 is exaggerated.
The film thickness is negligible). The angle φ1 is an angle between a straight line connecting the corner between the side surface 1 or 2 and the reflection surface and a straight line connecting the corner between the side surface 1 or 2 and the bottom surface.
The angle φ3 is an angle between light rays reflected by the reflection sheet 15 and incident on the bottom surface. The angle φ4 is an angle between light rays reflected on the reflection sheet 15 and incident on the side surface 1 or 2. The distance from the center of the fluorescent tube 13 to the bottom surface is k1, the distance to the diffusion sheet is k2, and the distance to the side surface 1 or 2 is k3.
And Therefore, k = k1 + k2 and d2 = 2 · k3.

The angles φ1 to φ4 can be easily obtained by using the coordinates shown in FIG. FIG. 4 shows the fluorescent tube insertion groove 12 in coordinates with the origin at a point where the center of the fluorescent tube 13 is orthogonal to the diffusion sheet. φ1 = A1 + A2, φ2 = 2
A3. The arc tangent shall be denoted as ATAN. The angles φ1 to φ4 are obtained from FIG. 4 by A1 = ATAN (k−
k2 / k3), A2 = ATAN (k2 / k3), φ4 =
ATAN (k2 / x2)-d2, φ3 = ATAN (k2
/ X1) -A2-φ4. As the transmittance T of the light transmitting / reflecting film, it is assumed that the brightness T of the backlight device is suitable for liquid crystal display. The light emitted from the fluorescent tube 13 is assumed to be emitted from the center of the fluorescent tube, and the light amount per unit angle emitted from the cross section of the fluorescent tube shown in FIG. Assuming that the reflectance of the light transmitting / reflecting film is (1-T), the utilization rates of the reflected light on the side and bottom surfaces are η and ε, respectively, and the light absorption of the fluorescent tube is γ, the light portion directly below in FIG. The luminance of the light transmitting portion of the light guide plate is determined by Equation 1.

(Equation 1) Brightness of the light part immediately below = (φ2 + 2φ3) (1 + ε) q · T /
(W · d2) Luminance of light propagation portion between light guides = ｛φ1 + φ4 + η (φ2 + 2 ·
φ3) / 2- (φ2 + 2φ3) T · η / 2｝ q / (W
D1) Here, η + ε + γ = 1.

The transmittance T of the light transmitting / reflecting film that makes the brightness of the light portion directly under the light and the light propagation portion of the light guide plate equal from the condition that the brightness of the light under the light portion = the brightness of the light propagation portion between the light guides is given by Equation 2. .

(Equation 2) T = {φ1 + φ4 + η (φ2 + 2 · φ3) / 2} × 2 ·
d2 / ｛(φ2 + 2φ3) (2 (1 + ε) d1 + η · d
2)｝ Calculation 1 shows the result of calculation based on Equation 2 when the diameter of the fluorescent tube is 3.6 mm. The ratio of the total amount of light emitted from the fluorescent tube to the amount of light that can be used by the backlight device is defined as a light utilization factor El.
And Calculation 1 and Calculations 2 and 3, which will be described later, are simulation results for a backlight device for a liquid crystal display having a screen size of 15 inches diagonally.

In the calculation 1, Tr, Tmax, Tmin, Tmax2, T
min2 will be described later. (Unit of length is mm) (Calculation 1) Conditions: k = 5.6, k2 = 2.8, k3 = 2.8, d1 = 116.2, d2 = 7.6 El = 90.3%, ε = 0.25, η = 0.65, γ = 0.1, d1 = 117.2, d2 = 5.6 [Φ1 = 81 °, Φ2 = 91 °, Φ3 = 6 °, Φ4 = 30 °] T = 0.072 Tmax = 0.103, Tmin = 0.035 Tmax2 = 0.116, Tmin2 = 0.029 As described above, the amount of light of the fluorescent tube is distributed in a well-balanced manner to the direct light portion and the light guide plate propagation portion based on the transmittance of the light transmission / reflection film, thereby realizing a luminance distribution suitable for liquid crystal display. Since the light utilization of the edge type is about 65%, it is shown that the light utilization of the light guide plate insertion type is extremely high.

(Embodiment 2) Embodiment 2 of the present invention derives a basic equation for determining the light transmittance and light utilization of the light transmitting / reflecting film, and determines the optimum transmittance of the fluorescent tube inserted light guide plate type backlight device. Ask for.

Q1 is the sum of the radiation angles of light incident on one side from the fluorescent tube, and Q2 is the sum of the radiation angles of light incident on the bottom surface of the fluorescent tube. Let H be the length (either the short side or the long side) of the side of the light guide plate parallel to the fluorescent tube insertion groove. In the case where there are a plurality of fluorescent tube insertion grooves, d1 is the distance between the side surfaces of adjacent fluorescent tube insertion grooves, and is the length of the light guide plate propagation light portion.

Total incident light amount from any one side surface =
{Q1 + Q2２ (1-T) η / 2｝ q, and the total amount of incident light from the bottom surface = Q2 (1 + ε) T ・ q. Therefore,
The luminance of the light transmitting portion of the light guide plate is {Q1 + Q2 · (1-T) η /
2｝ q / (H · d1), and the luminance of the light portion immediately below is Q2
(1 + ε) T · q / (H · d2). The light utilization rate is [Q1 + {η + (1 + ε−η) Q2}] / 360 °
The calculation results are shown only when η = 1 and ε = 0. Assuming that (brightness of the light portion directly below / brightness of the light transmitting portion of the light guide plate) is β, Expression 3 is obtained.

(Equation 3) T = 2 · β [(Q1 / Q2) + η / 2] (d2 / d1)
× [1 / {2 (1 + ε) + η (d2 / d1)}] where the luminance of the light part immediately below = Q2 (1 + ε) T · q / (H · d2) The luminance of the light transmitting part of the light guide plate = {Q1 + Q2 · ( 1-T) η /
2｝ q / (H · d1) H = 2 (d1 + d2 / 2) Naturally, in Equation 3, when a plurality of light guide plate propagation light portions exist, the light guide plate propagation corresponding to d1 in Equation 3 This is the luminance of the light part. Accordingly, the luminance of the light guide plate propagating light portions corresponding to the two side surfaces of the fluorescent tube insertion groove is determined by the number of fluorescent tube insertion grooves and d.
Depends on 1.

From equation (3), when η = 1 and ε = 0, T
Is maximum, and T is minimum when η = 0 and ε = 1, and d1≫d2. If the maximum value of T is Tmax and the minimum value of T is Tmin, Tmax = β (Q1 / Q2 + 1 /
2) (d2 / d1), Tmin = β (Q1 / Q2) [d2
/ (2 · d1)]. If the units of Q1 and Q2 are degrees, then Q1 <180 ° and Q2 <360 °. Since the minimum value of Q1 and Q2 is expected to be about 90 °, (Q1 / Q
The maximum value of 2) is 2 and the minimum value is 1/4. [D2 / d
1] varies depending on the screen size of the backlight device and the number of the fluorescent tube insertion grooves, but is expected to be in the range of about 0.1 to 0.06. Therefore, 2.5β × 0.1 and (0.05
/ 8) × β is rounded off, and the transmittance is 0.25β to 0.
008β.

Since the condition of constant luminance distribution is β = 1,
The practical transmittance Tr satisfies Expression 4a.

(Equation 4a) The practical transmittance Tr is Q1 <
At 180 ° and Q2 <360 °, Tmax = (Q1 / Q2
+1/2) (d2 / d1), Tmin = (Q1 / Q2)
Tmin <Tr <Tmax as [{d2 / (2 · d1)}]
Or 0.008 <Tr <0.25.

On the other hand, the practical limit of the luminance distribution of the backlight device is within ± 60% based on the luminance at the center of the light emitting surface. Therefore, using T in Equation 3 as a standard value, Tmax2 =
1.6T, Tmin2 = 0.4T. Further, γ = 0.
The case where 1, η = 0.65 and ε = 0.25 is close to the standard actual use condition. The practical transmittance Tr may be expressed by Equation 4b.

(Equation 4b) The practical transmittance Tr is Q1 <1
At 80 ° and Q2 <360 °, the standard value of the transmittance is T, ε <1, η <1, ε + η <1, and T = 2 · [(Q1 / Q2) + η / 2] (d2 / d1) ×
[1 / {2 (1 + ε) + η (d2 / d1)}], where Tmax2 = 1.6T and Tmin2 = 0.4T,
1.6T>Tr> 0.4T.

Η = 0.65 and ε = 0.25 are standard conditions.

As described above, Q1, Q2, d1, and d2 are uniquely determined if the shape of the fluorescent tube insertion groove and the arrangement of the fluorescent tubes are determined. Therefore, Q1, Q2, d1, d2, ε, η,
By using β as a parameter and simulating the practical transmittance of the light transmitting / reflecting film using Equations 4a and 4b in a simple and accurate manner, it is very easy and quick to develop and design a fluorescent tube-inserted light guide plate type backlight device. Can be.

Equations 3 and 4 were obtained by assuming that d1 was the same for the two side surfaces of the fluorescent tube insertion groove, but when different, correction was made based on the luminance of the light guide plate propagating light from the side surface compared to the immediately lower light portion. There is a need to. For example, when d1 is set to one side and 2d1 is set to the other side, the luminance of the light guide plate propagation light by the other side is １ ／.
(Because the light amount is constant and the area is doubled).

(Embodiment 3) FIG. 5 is a configuration diagram of a backlight device for a liquid crystal display according to Embodiment 3 of the present invention. FIG. 5 shows the fluorescent tube insertion groove 12 of FIG. 1 formed on the center line aa 'of the long side of the light guide plate 11, wherein (A) is a top view and (B) is a bb' cross-sectional view. is there. The description is omitted because it is the same as FIG. 1 except that the formation position of the fluorescent tube insertion groove is changed. By replacing W in Expression 1 with L, W = 2 (d1 +
If d2 / 2), the same applies and the effect is the same as in the first embodiment. Of course, equations 3, 4a and 4b are equally applicable.

(Embodiment 4) FIG. 6 shows a configuration diagram of a backlight device for a liquid crystal display according to Embodiment 4 of the present invention. FIG. 6 shows two fluorescent tubes 13 inserted and arranged in parallel in the fluorescent tube insertion groove 12 (hereinafter, abbreviated as a two tube arrangement). The fluorescent tubes 13 are arranged symmetrically with respect to the center of the fluorescent tube insertion groove 12 (center line aa 'in FIG. 6). As described above, except that two fluorescent tubes are inserted and arranged, detailed description is omitted.

FIG. 7 is a diagram showing light propagation of the backlight device shown in FIG. (A) is a diagram showing a state of light emitted from the backlight device. (B) is a diagram showing the angle of light emitted from the fluorescent tube 13. This corresponds to FIG. 3 in the case where the number of fluorescent tubes is one (hereinafter, abbreviated as a single tube arrangement). As shown in FIG. 6, the light emitting surface is divided into a light guide plate propagating light portion and a direct light portion also in the two-tube arrangement as in the single-tube arrangement.

FIG. 7 (B) shows the light passing through the fluorescent tube 13 as in FIG.
And the radiation angle when the light is radiated from the center of the graph, and shows the fluorescent tube insertion groove 12 and the fluorescent tube 13 on the coordinates. P1 and P2 indicate the coordinates of the center of the fluorescent tube 13, and P3 indicates the origin of the coordinate axes. Since the fluorescent tubes are arranged symmetrically with respect to each other, the radiation angles are also symmetrical. Therefore, only the radiation angle of one fluorescent tube is shown.

Θ1 is the angle at which the light from the fluorescent tube 13 is directly incident on the bottom surface, θ2 is the angle at which the light from the fluorescent tube 13 is directly incident on the side surface, and θ4 and θ5 are the light reflected by the reflection sheet 15 incident on the bottom surface. The angle, θ3, θ7 and θ8 are the reflection sheet 1
This is the angle at which the light reflected by 5 enters the side surface.

From FIG. 7B, Q1 and Q2 of the light portion immediately below and the light portion propagating in the light guide plate can be obtained by equation (5). Let T2 be the transmittance of the light transmission / reflection film of the two tube arrangement, and ε, η, γ, d1, d2, r
Is the same as the expressions 1 to 4.

[0059]

## EQU5 ## Q2 = 2 (.theta.1 + .theta.4 + .theta.5) Q1 = (. Theta.2 + .theta.3 + .theta.7 + .theta.8) Q2 in equation 5 is different from the case of a single tube in that it is the sum of the radiation angles of light by two fluorescent tubes. From Expressions 3 and 5, if the transmittance T2 of the light transmitting / reflecting film in the case of the two-tube arrangement is given by Expression 6,
Given by

[0060]

[Equation 6] T2 = β ｛(θ2 + θ3 + θ7 + θ8) + (θ1 + θ
4 + θ5) η｝ d2 × 1 / [2 (θ1 + θ4 + θ5)
{(1 + ε) · d1 + η · β · d2 / 2} However, η + ε + γ = 1 Further, even in the case of the two-tube arrangement, the practical transmittance of the light transmitting / reflecting film is determined by Equations 4a and 4b.

Calculation 2 shows the result of a simulation using the expressions 4a, 4b and 6 for the case where the diameter of the fluorescent tube is 3.6 mm. (The unit of length is mm)

(Calculation 2) Conditions: k = 6.6, k2 = 2.8, k3 = 6.6, k4 = 2.8, d1 = 113.4, d2 = 13.2, El = 74.8%, ε = 0.25, η = 0.65, γ = 0.1 [ θ1 = 113 °, θ2 = 82 °, θ3 = 31 °, θ4 = 6 °, θ5 = 20 °, θ6 = 22 °, θ7 = 13.5 °, θ8 = 3.7 °, d1 = 113.4, d2 = 13.2] T = 0.072 Tmax = 0.113, Tmin = 0.027 Tmax2 = 0.115, Tmin2 = 0.029 Thus, when two fluorescent tubes are arranged in the fluorescent tube insertion groove 12, the same effect as in FIG. 1 can be obtained. Although the drawings are omitted,
The fluorescent tube insertion groove 12 is formed at the center line bb 'to
It goes without saying that the same applies to the case where the tube is inserted and arranged. In either case, equations 3, 4a and 4b can be applied.

(Embodiment 5) FIG. 8 shows a configuration diagram of a backlight device for a liquid crystal display according to Embodiment 5 of the present invention. FIG. 8 shows a fluorescent tube reflector 20 formed on the center line (center line aa ′) of the fluorescent tube insertion groove 12 in FIG. 6 (hereinafter, referred to as a two-tube reflector). The purpose is to increase the light utilization rate of the backlight device. Otherwise, it is exactly the same as FIG.

FIG. 8 is a diagram showing the light propagation state of the backlight device, the fluorescent tube and the fluorescent tube insertion groove on the coordinate axis, and the light emission angle. FIG. 9A shows the state of light propagation in the light guide plate propagating light part and the light part immediately below, as in FIG. 7A, and FIG. 9B shows a fluorescent tube and a fluorescent tube as in FIG. 7B. The insertion groove is represented on the coordinate axis and indicates the light emission angle, and the symbol is the same. The distance between the fluorescent tube reflector 20 and the reflection sheet 15 is defined as a height,
It is represented by coordinates (0, j).

FIG. 9 (C) shows the brightness of the direct light portion according to the height of the fluorescent tube reflector 20, as shown in FIG. 9C. There is a difference. This may be the shadow of the fluorescent tube reflector 20, but it impairs the uniformity of the brightness of the backlight device. Therefore, in the present invention, the height of the fluorescent tube reflector 20 is lower than a straight line connecting the tip of the fluorescent tube reflector (coordinate (0, j) in FIG. 9B) and the corner between the side surface and the bottom surface. Shall be. Fluorescent tube 13
Is the radius of r, the height of the fluorescent tube reflecting plate 20, that is, j satisfies j <r + k2.

9B, θ1 is the angle at which the light from the fluorescent tube 13 is directly incident on the bottom surface, θ2 is the angle at which the light from the fluorescent tube 13 is directly incident on the side surface, and θ4 is the light reflected by the reflection sheet 15. The angle of incidence on the bottom surface, θ3 is the angle at which the light reflected by the reflection sheet 15 is incident on the side surface, θ7 and θ8 are the angles of incidence on the bottom surface reflected by the reflection sheet 15 and the fluorescent tube reflector 20, and θ5 and θ6. θ10 is an angle reflected by the reflection sheet 15 and the fluorescent tube reflection plate 20 and incident on the side surface. From the above angles, Q1 and Q2 with the two-tube arrangement reflecting plate can be obtained by Expression 7.

[0067]

## EQU7 ## Q1 = (. Theta.2 + .theta.3 + .theta.5 + .theta.6 + .theta.10) Q2 = 2 (.theta.1 + .theta.4 + .theta.7 + .theta.8) Accordingly, the transmittance T3 of the light transmitting / reflecting film in the case of the two-tube reflector is given by Formula 3 and Formula 8 from Formulas 3 and 7.

[0068]

[Equation 8] T3 = β ｛(θ2 + θ3 + θ5 + θ6 + θ10) + η
(Θ1 + θ4 + θ7 + θ8)｝ × d2 / [(θ1 + θ4 + θ7
+ Θ8) {2 (1 + ε) d1 + η · β · d2}] Needless to say, the expressions 4a and 4b can be applied to the case where the two-tube reflector is provided.

Calculation 3 shows the result of a simulation using the equations 4a, 4b and 8 for the case where the diameter of the fluorescent tube is 3.6 mm. (The unit of length is mm)

(Calculation 3) Conditions: k = 6.6, k2 = 2.8, k3 = 6.6, k4 = 2.8, d1 = 113.4, d2 = 13.2, El = 80.6%, ε = 0.25, η = 0.65, γ = 0.1 [θ1 = 113 °, θ2 = 81 °, θ3 = 31 °, θ4 = 6 °, θ5 = 11.5 °, θ6 = 1 °, θ7 = 4 °, θ8 = 27.5 °, θ9 = 0 °, θ10 = 15 °] T = 0.071 Tmax = 0.112, Tmin = 0.027 Tmax2 = 0.114, Tmin2 = 0.029 As described above, in the case where the two-tube reflector is provided, the light utilization efficiency is improved. The fluorescent tube reflecting plate 20 may be configured to be mounted on the reflecting sheet 15. In addition, the fluorescent tube reflector 20 and the reflection sheet 15
A reflective film may be formed on resin or metal to form an integrated reflector. Further, FIG.
As an example, a reflector having a configuration in which a horizontal portion, a vertical portion, and a connection between the vertical portion and the horizontal portion as shown in FIG. 10 have a curved surface may be fitted into the fluorescent tube insertion groove.

(Embodiment 6) FIG. 11 shows a configuration diagram of a backlight device according to Embodiment 6 of the present invention. FIG.
Numeral 1 shows the fluorescent tube insertion groove 12 of FIG. 8 formed on the center line bb ′ of the short side of the light guide plate 11. Except that the formation position of the fluorescent tube insertion groove is changed, it is the same as FIG. Equations 3, 4a, 4b, 7, and 8 can be similarly applied to the case of FIG. 11, and the effect is exactly the same as that of the fourth embodiment.

(Embodiment 7) FIG. 12 shows a configuration diagram of a backlight device according to Embodiment 7 of the present invention. FIG.
(A) is a top view, (B) is an aa ′ cross-sectional view. This embodiment has a configuration in which the fluorescent tube insertion grooves 12 are formed at a position of a distance S1 that is symmetric with respect to the center line Co on the short side, and one fluorescent tube is inserted and arranged in each of the fluorescent tube insertion grooves 12. It is assumed that.

The center lines of the two fluorescent tube insertion grooves 12 are respectively denoted by C
1, C2. In FIG. 12, the distance between the end of the light guide plate and the center lines C1 and C2 of the fluorescent tube insertion groove 12 is S2,
The distance between C2 and C2 is set to 2 × S1, and the luminance distribution (luminance distribution in the Y direction) of the light guide plate is adjusted by S1 and S2.

This is suitable for improving the brightness of a single-tube backlight device. It is characterized by high light utilization.

FIG. 13 shows an example of the luminance distribution in the sectional view taken along the line aa ′ of FIG. FIG. 13A shows a luminance distribution when S1> S2, and FIG. 13B shows a luminance distribution when S1 = S2. Thus, the luminance distribution can be adjusted by changing S1 and S2.

For example, assuming that S2 = 1.2 × S1, based on Equation 3, the luminance of the S1 area is 1.2 times the luminance of the S2 area. Therefore, it is useful for a liquid crystal display of a large-screen television receiver for increasing the luminance at the center of the screen. In the case of S1 = S2, it is useful for a liquid crystal display of a large screen monitor such as a CAD which requires high quality image quality. Although not shown, the fluorescent tube insertion groove 1 shown in FIG.
The same effect can be obtained by forming 2 at a position of a distance S1 that is symmetric with respect to the center line aa ′. However,
The luminance distribution changes in the X direction.

The same effect can be obtained by forming a plurality of (n> 2) fluorescent tube insertion grooves in the X direction or the Y direction. That is, the fluorescent tube insertion is symmetrical with respect to the center line (center line aa 'or bb') of the short side or long side of the light guide plate, and the interval between adjacent fluorescent tube insertion grooves is 2 × S1. 2n grooves are formed. Here, n is a positive integer. The distance between the end (short side or long side) of the light guide plate parallel to the fluorescent tube insertion groove and the center of the fluorescent tube insertion groove adjacent thereto is S2. Therefore, if the fluorescent tube insertion groove is parallel to the short side, W = (2n−1) × 2 × S1 + 2 × S2, and if the fluorescent tube insertion groove is parallel to the long side, L = (2n−1) × 2 × S1 + 2 × S2.
It is. Therefore, FIG. 12 corresponds to the case where n = 1 and the fluorescent tube insertion groove is parallel to the long side.

Further, the distance between adjacent fluorescent tube insertion grooves is symmetric with respect to the center line (center line aa 'or bb') of the short side or long side of the light guide plate, and the distance between adjacent fluorescent tube insertion grooves is 2 × S1. 2n fluorescent tube insertion grooves, center line aa 'or b-
A total of 2n + 1 fluorescent tubes are formed on b '. The distance between the end (short side or long side) of the light guide plate parallel to the fluorescent tube insertion groove and the center of the fluorescent tube insertion groove adjacent thereto is S2. Therefore, if the fluorescent tube insertion groove is parallel to the short side, W =
(2n-1) × 2 × S1 + 2 × S2, and L = (2n−1) × 2 × S1 + 2 × S2 if parallel to the long side. FIGS. 1, 5, 6, 8, and 11 correspond to the case where n = 0 and W or L is 2 × S2.

A backlight device in which a plurality of fluorescent tube insertion grooves are formed is suitable for an ultra-large screen liquid crystal display requiring high luminance. Of course, equations 3 and 4 can be applied without problems.

(Eighth Embodiment) FIG. 14 shows a configuration diagram of a backlight device according to an eighth embodiment of the present invention. FIG.
Is a top view, and (B) is a bb 'sectional view. In this embodiment, fluorescent tube insertion grooves 12 are formed at a distance S1 symmetrical with respect to the center line Co on the short side, and two fluorescent tubes are inserted in each of the fluorescent tube insertion grooves 12 in parallel. It is configured to be arranged. The arrangement of the two tubes is the same as in FIG. 6, and the fluorescent tubes 13 are arranged symmetrically with respect to the center line (C1 and C2 in FIG. 14) of the fluorescent tube insertion groove 12.

The distance between the center lines of adjacent fluorescent tube insertion grooves 12 is 2 · S1, and the short side end of the light guide plate and the center lines C1 and C2
The distance to is S2. Since the control of the luminance by adjusting S1 and S2 is the same as in the case of FIG. 12, the description is omitted. Needless to say, the same effect can be obtained with a configuration obtained by adding the two-tube arrangement to the configuration of FIG.

FIG. 15 shows a second configuration diagram of the backlight device according to the seventh embodiment of the present invention. FIG. 15 shows the center line C.
1 and C2 are provided with a two-tube arrangement reflecting plate in which a fluorescent tube reflecting plate 20 is mounted. Except for this, the configuration is the same as that of FIG.

Also in this embodiment, the same effect can be obtained even if a plurality of fluorescent tube insertion grooves (n> 2) are formed in the X direction or the Y direction, and an ultra-large screen liquid crystal display back which requires high luminance is obtained. Suitable for light equipment. Further, the same effect can be obtained even in a configuration in which a two-tube arrangement with a reflection plate is added to FIG.
It goes without saying that 4a and 4b can be applied.

(Embodiment 9) FIGS. 1, 3 to 9 and 1
Although the cross-sectional shape of the fluorescent tube insertion groove 12 is rectangular in 1, 12, 14, and 15, it is an example, and the present invention is not limited to this. FIG. 16 shows an example of a sectional view of the fluorescent tube insertion groove 12 according to Embodiment 9 of the present invention.

FIG. 16 (A) is a view similar to FIG. 1, FIGS. 3-9, FIG.
The cross-sectional shapes of the fluorescent tube insertion grooves 12 indicated by 12, 14, and 15 are such that the transmittance at the center is Ta, and the transmittance at both ends is T.
The light transmission / reflection film 14 is formed on the bottom surface. (B) shows a trapezoidal cross section of the bottom surface, in which the light transmitting / reflecting film 14 is formed on the oblique side and upper side of the trapezoid, the transmittance of the light transmitting / reflecting film 14 formed on the oblique side is Ta, and the light formed on the upper side is The transmittance of the transmission / reflection film 14 is Tb.
(C) is a curve of the corner between the bottom surface and the side surface, and the transmittance T (shown by oblique lines) is shown on the bottom surface parallel to the light guide plate.
The light transmitting / reflecting film 14 having a transmittance Tb is formed at a corner portion of the light transmitting / reflecting film 14 of FIG. (D) is to form a light transmission / reflection film 14 having a curved bottom surface (an ellipse or a circle), a transmittance at the central portion Ta, and transmittances at both ends Tb. Of course, Ta = Tb may be satisfied. In addition, the light transmission / reflection film 14 in FIG. 16 is an exaggerated figure for ease of explanation.

As shown in FIGS. 16 (A) to 16 (D), the cross-sectional shape of the bottom surface is changed so that the transmittance of the light transmitting / reflecting film is not uniform and varies depending on the location of the bottom surface portion. Transmittance) to control the luminance of the fluorescent tube inserted light guide plate type backlight device. The fluorescent tube insertion groove of FIG. 16 can be applied to the fluorescent tube insertion groove 12 in FIGS. 1, 3 to 9, 11, 12, 14 and 15. The luminance and the transmittance of the light transmitting / reflecting film can be obtained in the same manner as in the equations 1 to 8.

Although the above description has been made only with the fluorescent tube, the fluorescent tube includes a hot cathode type and a cold cathode type. The hot cathode fluorescent tube has a large tube diameter and requires a large thickness of the light guide plate, and is suitable for a liquid crystal display of an ultra-large screen size capable of increasing the thickness of the backlight device. For liquid crystal display except super large screen size,
Alternatively, it is added that a cold cathode fluorescent tube is suitable for a liquid crystal display in which the thickness of the light guide plate is reduced.

The reflection sheet 15 may be formed by forming a metal film having a high reflectance and a high scattering property on a film, or a metal plate having a high reflectance and a high scattering property. Further, a configuration in which the frame 18 and the reflection sheet 15 are integrated may be employed.

The lens sheet 17 is mounted as needed, and the effect of the present invention is not impaired even if the lens sheet 17 is not mounted. In addition, it is added that a light curtain can be mounted instead of the lens sheet 17 or a diffusion sheet can be mounted in an overlapping manner to perform dimming of the backlight device.

[0090]

As described above, by forming the light transmission / reflection film on the bottom surface of the fluorescent tube insertion groove, it is possible to eliminate the uneven brightness of the fluorescent tube insertion portion which is a drawback of the fluorescent tube insertion light guide plate type backlight device. The transmissivity of the light transmission / reflection film can be accurately simulated by a simple method, and a compact backlight device having a high light utilization factor suitable for liquid crystal display can be realized at a low price. The above effect is more remarkably exhibited in a backlight device of a large screen liquid crystal device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a backlight device according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing an example of a luminance distribution in an aa ′ section of FIG. 1;

FIG. 3 is a diagram showing light propagation of a backlight device.

FIG. 4 is a diagram showing a fluorescent tube and a fluorescent tube insertion groove on a coordinate axis.

FIG. 5 is a configuration diagram of a backlight device according to Embodiment 3 of the present invention.

FIG. 6 is a configuration diagram of a backlight device according to a fourth embodiment of the present invention.

FIG. 7 is a light emission angle diagram showing the light propagation state of the backlight device shown in FIG. 6, the fluorescent tube and the fluorescent tube insertion groove on the coordinate axis.

FIG. 8 is a configuration diagram of a backlight device according to a fifth embodiment of the present invention.

FIG. 9 is a light emission angle diagram showing the state of light propagation and the fluorescent tube and the fluorescent tube insertion groove on a coordinate axis in the backlight device shown in FIG. 8;

FIG. 10 shows an example of a fluorescent tube reflector.

FIG. 11 is a configuration diagram of a backlight device according to Embodiment 6 of the present invention.

FIG. 12 is a configuration diagram of a backlight device according to a seventh embodiment of the present invention.

FIG. 13 is a diagram showing an example of a luminance distribution in an aa ′ section of FIG. 12;

FIG. 14 is a configuration diagram of a backlight device according to an eighth embodiment of the present invention.

FIG. 15 is a second configuration diagram of a backlight device according to Embodiment 8 of the present invention.

FIG. 16 shows an example of a cross section of a fluorescent tube insertion groove in the ninth embodiment.

FIG. 17 is a diagram showing a configuration diagram of a conventional backlight device.

18 is a diagram showing an example of a luminance distribution in an aa ′ section of FIG. 17;

[Explanation of symbols]

11, 101 Light guide plate 12, 105 Fluorescent tube insertion groove 13, 104 Fluorescent tube 14 Light transmitting diffusion sheet or film 15 Reflection sheet 16 Diffusion sheet 17 Lens sheet 18, 103 Frame 19, 110 Lead wire 20 Fluorescent tube reflection plate 102 Reflection sheet 1 106 Light curtain 107 Diffusion sheet 108 Reflecting surface 109 Reflecting sheet 2 a, a 'Long side center line b, b' Short side center line Co Center line of light guide plate C1, C2 Center line of fluorescent tube insertion groove d Back Light device thickness d1 Fluorescent tube insertion groove width d2 Length of light guide plate propagating light section H Length of fluorescent tube insertion groove El Light utilization L Length of light guide plate short side W Length of light guide plate long side P1, P2 The coordinates of the center of the fluorescent tube P3 The origin of the coordinates Φ1 to Φ4, θ1 to θ11, A1 to A3 Radiation angle of light k Depth of fluorescent tube insertion groove k2 Reflection from center of fluorescent tube Distance to sheet k3 Distance from center of fluorescent tube to side surface k4 Distance between center of fluorescent tube insertion groove and center of fluorescent tube S, S1 Distance between center line of fluorescent tube insertion groove and center line of light guide plate S, S2 Distance between the center line of the fluorescent tube insertion groove and the end of the light guide plate T, T2, T3, Tr, Ta, Tb Transmittance of light transmitting / reflecting film Tr Practical transmittance Tmax, Tmax2 Maximum value of transmittance Tmin, Tmin2 Minimum value of transmittance ε Utilization of reflected light incident on the bottom surface η Utilization of reflected light incident on the side surface γ Light absorption of fluorescent tube

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G09F 9/00 336 G09F 9/00 336F (72) Inventor Hideki Yamauchi 1006 Odakazuma, Kadoma, Osaka Matsushita Electric Industrial Co., Ltd. F term (reference) 2H038 AA52 AA55 2H042 DA06 DA21 DB01 DC01 DC02 DE00 2H091 FA16Z FA23Z FA32Z FA42Z FC12 FD06 FD13 LA12 LA18 5G435 AA01 BB12 EE26 FF03 FF06 GG24 LL08 LL13

Claims (14)

[Claims] 1. A light guide plate, a diffusion sheet attached to the light emission surface, and a reflection sheet attached to the reflection surface, wherein one surface of the light guide plate is a light emission surface and the other surface is a reflection surface. A backlight device for a liquid crystal display comprising a fluorescent tube, wherein a fluorescent tube insertion groove having a bottom surface and a side surface perpendicular to the light emitting surface is formed on a reflection surface of the light guide plate, and the fluorescent tube insertion groove As one of selecting from forming a light transmission / reflection film on the bottom surface and attaching a sheet having a light transmission / reflection film on the bottom surface of the fluorescent tube insertion groove, the fluorescent light is inserted into the fluorescent tube insertion groove. A backlight device for a liquid crystal display, wherein a tube is inserted and arranged. 2. The light guide plate according to claim 1, wherein the length of the short side of the light guide plate is L and the length of the long side is W. At a symmetrical position, the distance between the center lines of the adjacent fluorescent tube insertion grooves is 2 × S1, 2n n is formed as a positive integer, and one is formed on the center line, for a total of 2n + 1, The distance between the long side and the center line of the fluorescent tube insertion groove adjacent to the long side is S2, and L = (2n-1) × 2 × S1
+ 2 × S2, and n is a distance between the center lines of the adjacent fluorescent tube insertion grooves at 2 × S1 at positions parallel to the short side and symmetric with respect to the center line of the long side. 2n positive integers are formed, and one is formed on the center line, for a total of 2n + 1, where the distance between the short side and the center line of the fluorescent tube insertion groove adjacent to the short side is S2, and W = (2n-1) × 2 × S1 +
2. The backlight device for a liquid crystal display according to claim 1, wherein any one of 2 × S2 is selected. 3. 3. The fluorescent tube insertion groove is parallel to the long side and symmetric with respect to a center line of the short side, wherein the length of the short side is L and the length of the long side is W. In the position, the distance between the center lines of the adjacent fluorescent tube insertion grooves is 2 × S1, 2n n is formed as a positive integer, and the distance between the long side and the center line of the fluorescent tube insertion groove adjacent to the long side is set. Is S2, and L = (2n−
1) 2 × S1 + S2, and the distance between the center lines of adjacent fluorescent tube insertion grooves that are parallel to the short side and are symmetric with respect to the center line of the long side, and are set as 2 × S1 n is a positive integer and 2n pieces are formed. The distance between the short side and the center line of the fluorescent tube insertion groove close to the short side is S2, and W = (2n-1) × 2 × S1 +
The backlight device for a liquid crystal display according to claim 1, wherein one of S2 and S2 is selected. 4. The liquid crystal display backlight device according to claim 2, wherein S1 and S2 satisfy S1 = S2. 5. The method according to claim 2, wherein n = 0 and W = 2 × S2.
3. The backlight device for a liquid crystal display according to claim 2, wherein L = 2 × S2, and one of the fluorescent tube insertion grooves is formed at a central portion of the light guide plate. 4. 6. The fluorescent lamp according to claim 3, wherein n = 1, and two fluorescent tube insertion grooves are formed at positions symmetrical with respect to the center line of the long side or the short side. Backlight device for liquid crystal display. 7. The liquid crystal display according to claim 1, wherein one of the fluorescent tubes is disposed on a line connecting the center of the fluorescent tube and the center of the fluorescent tube insertion groove. Backlight device. 8. The apparatus according to claim 1, wherein two fluorescent tubes are inserted one by one at positions symmetric with respect to the center of the fluorescent tube insertion groove. Backlight device for liquid crystal display. 9. The fluorescent tube reflecting plate is disposed substantially at the center of a straight line connecting the centers of the two fluorescent tubes and substantially perpendicular to the bottom surface of the fluorescent tube insertion groove. The height of the reflector is defined as the distance from the reflection surface of the light guide plate, and the height of the fluorescent tube reflector connects the tip of the fluorescent tube reflector with the corner where the bottom surface and the side surface of the fluorescent tube insertion groove are in contact. 9. The liquid crystal display backlight device according to claim 8, wherein the backlight does not exceed a straight line. 10. The backlight device for a liquid crystal display according to claim 1, wherein the light transmitting / reflecting film is formed by printing or applying a scattering material. 11. Q1 is the sum of the emission angles of the fluorescent tubes incident on the side surfaces of the fluorescent tube insertion grooves, Q2 is the sum of the emission angles of the fluorescent tubes incident on the bottom surfaces of the fluorescent tube insertion grooves, and Q1 <
180 ° and Q2 <360 °, where H is the length of the fluorescent tube insertion groove, d2 is the width of the fluorescent tube insertion groove, and d1 is a distance from one side of the fluorescent tube insertion groove. The distance to the end of the light plate, and the distance to the side surface of the second fluorescent tube insertion groove adjacent to one side surface of the fluorescent tube insertion groove, as one selected from the above, The transmittance Tr of the light transmitting / reflecting film is [(Q1 / Q2) +0.5] (d2 / d1)>Tr> (Q1 / Q
2) The backlight device for liquid crystal display according to claim 1, wherein [d2 / (2 · d1)] is satisfied. 12. The transmittance Tr of the light transmitting / reflecting film is:
The backlight device for a liquid crystal display according to claim 1, wherein 0.25>Tr> 0.008 is satisfied. 13. Q1 is the sum of the emission angles of the fluorescent tubes incident on the side surfaces of the fluorescent tube insertion groove, Q2 is the sum of the emission angles of the fluorescent tubes incident on the bottom surface of the fluorescent tube insertion groove, and Q1 <
180 ° and Q2 <360 °, where H is the length of the fluorescent tube insertion groove, d2 is the width of the fluorescent tube insertion groove, and d1 is a distance from one side of the fluorescent tube insertion groove. The distance to the end of the light plate and the distance to the side surface of the second fluorescent tube insertion groove adjacent to one side surface of the fluorescent tube insertion groove may be selected from the following: ε Is the utilization of the reflected light incident on the side surface and η is the utilization of the reflected light incident on the bottom surface, ε <1, η <1, ε + η <
1, and the transmittance Tr of the light transmitting / reflecting film is expressed by the following formula: T = 2 · β [(Q1 / Q2) + η / 2] (d2 / d1)
2. The backlight device for a liquid crystal display according to claim 1, wherein 1.6T>Tr> 0.4 T is satisfied as × [1 / {2 (1 + ε) + η (d2 / d1)}. 3. 14. In the standard value T of the transmittance, ε =
14. The backlight device for a liquid crystal display according to claim 13, wherein 0.25 and η = 0.65.