JP2004199882A - Surface illumination device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the luminance of an illumination light by effectively utilizing light leakage from a light guide plate in a surface illumination device of a back light type. <P>SOLUTION: The device is structured to have a light guide plate 1 for expanding light incident from a light source device 3 into surface illumination light to emit it from the surface thereof, and a prism mirror 2. The plate 1 is adjacent to a back surface side of an object to be illuminated, and has a 1st prism array 11 on a rear surface. The prism mirror 2 is adjacent to the plate 1, and has a sawtooth-shaped 2nd prism array 21 faced to the 1st prism array 11. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light source device, a surface lighting device that illuminates a passive display panel such as a liquid crystal display panel using the light source device, and a liquid crystal display device that is illuminated using the surface lighting device.
[0002]
[Prior art]
2. Description of the Related Art In recent years, among various display devices connected to electronic devices, a liquid crystal display device (LCD), a plasma display device (PDP), an electroluminescence display device (EL), and the like have been developed as display devices replacing CRTs. Above all, liquid crystal display devices have become lighter, thinner and smaller, have low power consumption, and have been increasingly colorized, and have been further developed from mobile phones and personal digital assistants (PDAs) to home TVs.
[0003]
By the way, PDPs and ELs are called active display devices because they emit light upon application of a drive voltage. On the other hand, the liquid crystal display device controls the transmission / shielding of external light by applying / non-applying a driving voltage, and does not emit light by itself, and is therefore called a passive display device. Therefore, in the liquid crystal display device, some kind of illumination is required for display.
[0004]
The manner of illumination of the liquid crystal display device differs depending on whether the structure of the liquid crystal display panel constituting the liquid crystal display device is a reflection type, a transmission type, or a transflective type. However, in any case, it is important to uniformly illuminate the display screen regardless of the size of the display screen.
In the configuration of the reflection type liquid crystal display device, a transparent electrode such as an ITO film is used on one of the substrates through which the illumination light enters and exits so that the illumination light is transmitted. An opaque metal electrode or the like having a high density is used.
[0005]
The reflection type liquid crystal display device has a configuration in which illumination light is incident from the front of the liquid crystal display panel, and is used by irradiating outside light such as daylight or electric light from the front side of the liquid crystal display panel, and is used in a dark place. Was not visible.
However, recently, a configuration has been developed in which a surface illumination device is provided on the front side (front side) of a liquid crystal display panel and an image can be visually recognized through the surface illumination device. There is a so-called front light type illumination type.
[0006]
FIG. 11 is a schematic diagram of an example of a front light type surface illumination device. The front light type surface illumination device 10 is arranged close to the front surface (front side) of the reflection type liquid crystal display panel 8 to constitute the liquid crystal display device 20. The light source device 3 is provided with a light source such as a light emitting diode, for example, and light emitted from the light source is incident on the light guide plate 1 from the incident end face 13 via the light guide pipe.
[0007]
The light guide plate 1 has a configuration in which a prism array 14 is provided on the front side, and incident light indicated by a broken line introduced into the inside of the light guide plate 1 from the incident end face 13 is provided on the front side of the light guide plate 1. The light is internally reflected by the prism array 14, emitted as illumination light 9 from the rear surface side, and illuminated from the front surface of the liquid crystal display panel 8. Illumination light 9 illuminating the liquid crystal display panel 8 is modulated into an image in the liquid crystal display panel 8, passes through the light guide plate 1 again from the back side, and is visually recognized as a display image (for example, see Patent Document 1).
[0008]
In a bright place, the external light 91 passes through the light guide plate 1 to illuminate the liquid crystal display panel 8, so that the liquid crystal display image can be visually recognized. However, in the case where the external light 91 is used for the illumination, there is no denying that the quality of the display image is affected by the degree of brightness or the color of the external light 91.
On the other hand, when the liquid crystal display device is of a transmissive type, illumination is performed from the back of the liquid crystal display panel and penetrates the liquid crystal display panel. Therefore, the entire liquid crystal display panel in the thickness direction is transparent. The two substrates sandwiching the liquid crystal are both made of a transparent material such as glass, and the electrode for applying a voltage to the liquid crystal layer is also formed of a transparent electrode such as an ITO (1ndium TinOxide) film.
[0009]
That is, in the transmissive liquid crystal display device, the surface illumination device arranged on the back (back side) of the liquid crystal display panel is indispensable and an essential component. That is why the lighting device is called a backlight. 2. Description of the Related Art Transmissive liquid crystal display devices are frequently used in small-screen mobile phones and game machines, large-screen personal computers, liquid crystal TVs, and the like.
However, in a transmissive liquid crystal display panel, an illumination light source from the back of the liquid crystal display panel is indispensable not only in a dark place but also in a bright place. Therefore, a transflective mirror is provided on the substrate on the back side of the transmissive liquid crystal display panel, and in a dark place, the liquid crystal display panel is illuminated from the back with a backlight type surface illumination device as a transmissive liquid crystal display device. In a light place, a so-called transflective liquid crystal display device that uses external light from the front surface of the liquid crystal display panel as illumination light as a reflection type liquid crystal display device is often used.
[0010]
FIG. 12 is a schematic view of an example of a backlight type surface illumination device. The backlight type surface illuminating device 10 is arranged close to the back surface (back side) of the transflective liquid crystal display panel 8 to constitute the liquid crystal display device 20. The light source device 3 is provided with a light source such as a light emitting diode, for example, and light emitted from the light source is incident on the light guide plate 1 from the incident end face 13 via the light guide pipe.
[0011]
The light guide plate 1 has a configuration in which a prism array 14 is provided on the back side. The light emitted from the light source device 3 is introduced into the light guide plate 1 from the incident end face 13 as the incident light 5 indicated by a broken line, and is internally reflected by the prism array 14 provided on the back surface side of the light guide plate 1 to be reflected on the front surface. Out of the illumination light 9. The illumination light 9 illuminates the liquid crystal display panel 8 from behind.
[0012]
In the liquid crystal display device 20 of this configuration, the liquid crystal display panel 8 functions as a transmissive liquid crystal display device by illuminating the liquid crystal display panel 8 from behind with a backlight type surface illumination device 10 in a dark place. It is configured to function as a reflection type liquid crystal display device by external light 91 from the outside. (For example, see Patent Document 2.)
[0013]
[Patent Document 1]
JP-A-11-184386 (Detailed description of the invention)
[0014]
[Patent Document 2]
JP-A-10-208530 (Detailed description of the invention)
[0015]
[Problems to be solved by the invention]
Incidentally, the front light type surface illumination device 10 using the prism array shown in FIG. 11 is a very thin surface illumination device, and this surface illumination device is a backlight of a transmissive or transflective liquid crystal display device. It would be very convenient if it could also be used as a surface illumination device of the type.
[0016]
On the other hand, it is desirable that the illumination light emitted from the rear surface of the liquid crystal display panel be incident on the liquid crystal display panel as vertically as possible.
However, when a surface illumination device using a light guide plate provided with a prism array is used as a backlight type illumination device, the illumination light emitted from the light guide plate does not effectively illuminate the liquid crystal display panel. Includes light emitted in an undesirable direction as leaked light.
[0017]
FIG. 13 shows a schematic diagram of the behavior of the leak light. In the figure, the incident light 5 indicated by a broken line guided from the light source device 3 into the light guide plate 1 is ideally totally reflected on the inner surface of the prism array 14, and is almost reflected from the light guide plate 1 to the emission surface 12. I want it to be emitted in the direction of the vertical arrow 511.
However, the light to be illuminated 4 is effectively transmitted through the prism array 14 and emitted in the direction of the arrow 512 outside the light guide plate 1 or emitted in the direction of the oblique arrow 513 that does not exist from the emission surface. Lighting occasionally happens. In the present invention, light that is emitted in the directions of the arrows 512 and 513 and does not contribute to effectively illuminating the illuminated object 4 is called leakage light.
[0018]
FIG. 14 shows a view angle characteristic diagram of the leaked light, and FIG. 14A shows the definition of the view angle. At the central portion 15 of the light guide plate 1, the light emitted from the light source device 3 is emitted. The output angle parallel to the traveling direction of the light of the thick arrow incident on the light guide plate, that is, the angle measured by looking down at the center of the light guide plate 1 in the direction of the light source device 3 when viewing it is + X °, and looking down from the opposite direction. The measured angle is set to ─X °. In addition, the output angle to the right in the direction orthogonal to the traveling direction of the light of the thick arrow incident on the light guide plate 1, that is, the angle measured when the central portion of the light guide plate 1 is viewed from the right when viewed from the right is + Y. °, and the angle measured while looking down from the left is -Y °.
[0019]
FIG. 14B illustrates the measurement results. In FIG. 6B, the horizontal axis indicates the angle (°) of the emitted light that is emitted in the center of the light guide plate while being inclined in the X or Y direction. The vertical axis represents the luminance (cd / m) of the emitted light at each angle (°). ^Two ).
The curve indicated by a circle indicates that when 0 ° is set as the vertical direction of the center of the light guide plate, the light emitted from the light source device when it is swung from −90 ° to + 90 ° in the X direction, that is, in the X direction. Luminance of emitted light (cd / cm ^Two ), The curve marked with a triangle indicates that when the head of the luminance meter is swung from −90 ° to + 90 ° in the Y direction orthogonal to the light traveling direction, with 0 ° being the vertical direction of the center of the light guide plate. Luminance of emitted light (cd / cm ^Two ).
[0020]
As can be seen from FIG. 14 (B), first, in the luminance curve indicated by the triangle marked in the Y direction, the luminance of the emitted light rapidly decreases symmetrically at 0 °, that is, as it inclines from the vertical direction to the left and right directions. I do. That is, so-called leaked light emitted in a direction that does not exist is not measured.
However, in the luminance curve of the mark 振 shaked in the X direction in which light travels, when measured at an angle near 30 ° to 60 °, that is, at an angle obliquely looking down from the traveling direction of light in the light guide plate, leakage It can be seen that light largely appears. This leaked light does not deviate from, for example, the leaked light indicated by the arrow 513 shown in FIG.
[0021]
Further, the light leaking through the prism array indicated by the arrow 512 shown in FIG. 13 leaks at an extremely obtuse angle when viewed from the light guide plate 1. Therefore, if the light is simply reflected by a flat reflecting mirror or the like, it is not possible to effectively return the light to the light guide plate and relatively increase the amount of illumination from the emission surface of the light guide plate.
Therefore, in the present invention, a surface illuminating device having an increased illumination light amount as a surface illuminating device by effectively utilizing leak light of a surface illuminating device having a backlight type prism array, and a liquid crystal display using the surface illuminating device It is intended to provide a device.
[0022]
[Means for Solving the Problems]
The above-mentioned subject has a light guide plate, which expands light incident from a light source device into surface illumination light and emits the light from a surface, and a prism mirror, wherein the light guide plate is a light guide for an object to be illuminated. A first prism array is provided on the back side and has a first prism array on the back surface, and the prism mirror is provided near the light guide plate and has a sawtooth shape facing the first prism array. The problem is solved by a surface illuminator configured to have two prism arrays.
[0023]
In other words, the surface illumination device of the present invention employs a so-called backlight type illumination method for illuminating an object to be illuminated from behind. Therefore, the light guide plate is provided near the back side of the illumination target.
The light guide plate is provided with a first prism array on a back surface that is not opposed to the object to be illuminated. Then, the light that has entered the light guide plate from the light source device is reflected by the first prism array and emitted from the facing surface side, so that the nearby object to be illuminated can be illuminated from the back.
[0024]
Further, a prism mirror is provided near the light guide plate. This prism mirror is provided with a second prism array so as to face the first prism array of the light guide plate. Then, light leaked from the first prism array of the light guide plate is reflected and returned into the light guide plate.
Thus, it is possible to further increase the illumination light amount of the surface illumination device using the light guide plate using the prism array.
[0025]
Next, in claim 2, the second prism array is arranged side by side so as to intersect with the direction of the incident light from the light source device, and the inclination angle of the slope facing the incident direction of the incident light is 40 ± 5. The problem is solved by the surface illumination device according to claim 1, wherein the surface illumination device is configured to be in degrees.
In other words, the second prism array provided on the prism mirror is provided with sawtooth-shaped prisms in a direction intersecting the optical path of light incident on the light guide plate from the light source device, and leaks from the first prism array of the light guide plate. The reflected light is reflected by the slope of the prism.
[0026]
In addition, it is preferable that the light reflected by the second prism array efficiently enters the light guide plate in the vertical direction as much as possible. From the result of examining the relationship between the inclined surface of the prism and the amount of light emitted from the light guide plate, the optimal inclination angle of the inclined surface of the prism is set to 40 ± 5 °.
Then, in the third aspect, the second prism array is solved by the surface illumination device according to the third aspect, wherein the first reflection film is applied to at least a slope of a sawtooth shape.
[0027]
In other words, the prism mirror has an effect of picking up light leaked from the first prism array of the light guide plate if the slope of the saw-toothed prism is a mirror surface. However, in order to make it more effective, the slope of the prism is covered with the first reflection film.
Then, since the leaked light incident on the second prism array of the prism mirror is almost completely reflected, the leaked light can be used more effectively.
[0028]
Next, according to claim 4, a light guide plate that expands light incident from the light source device to surface illumination light and emits the light from the surface, a lens sheet, and a reflection sheet, wherein the light guide plate is provided on the back surface of the illuminated object Side, and has a first prism array on the back surface, and the lens sheet is near the back surface side of the light guide plate, and the lens surfaces facing the first prism array are arranged side by side. A surface illumination device configured as a prism-type lens provided, wherein the reflection sheet is provided near the back side of the lens sheet, and a second reflection film is applied to the surface. Solved by
[0029]
That is, as another method of effectively utilizing the light leaked from the light guide plate, a lens sheet is provided near the rear surface of the light guide plate. This lens sheet is like a so-called lenticular lens in which prism type lenses are arranged in a stripe pattern in parallel on a lens surface of the light guide plate facing the first prism array.
The leaked light transmitted through the first prism array of the light guide plate is condensed on the lens surface of the lens sheet and enters the sheet. The leaked light passing through the sheet is reflected by the reflection sheet, returns to the lens sheet, passes through the lens surface again, enters the first prism array of the light guide plate, and is effectively used.
[0030]
Then, in claim 5, the lens surface intersects the incident light from the light source device and is solved by a surface illuminating device configured to be a prism type lens having an apex angle θt = 60 to 90 °.
That is, the lens surfaces arranged in a stripe pattern are provided in a direction intersecting with the optical path of the light incident on the light guide plate from the light source device, and the light leaking out from the first prism array of the light guide plate is emitted by the lens surface. I am going to receive it.
[0031]
By the way, in general, a lenticular lens has a semi-cylindrical cross section, but a prism type lens arranged side by side on a lens sheet of the present invention has a very fine pitch of at most several tens to several hundreds μm.
Here, the "vertical angle" is described for the prism type lens because the vertex angle is a finished angle in the design of the mold. When manufacturing a lens sheet by resin molding or embossing, the resin does not sufficiently enter the valley of the V-shaped engraved at a fine pitch as the shape of the mold, and The top of the mountain has a rounded shape. In other words, the vertices are rounded, and the cross section has a kamaboko shape.
[0032]
In this manner, the prism lens having the apex angle θt = 60 to 90 ° in the mold design is rounded at the vertex, and is completed like a lenticular lens. It has been confirmed that this shape sufficiently functions as a lens. Moreover, it has been confirmed that the range of the apex angle: θt = 60 to 90 ° is the apex angle for returning the leaked light to the light guide plate most efficiently as the lens sheet.
[0033]
Finally, in claim 6, the object to be illuminated according to claim 1 or 4 is solved by a liquid crystal display device constituted by a liquid crystal display panel.
That is, the surface illuminating device of the present invention is obtained by expanding a small light source such as a point light source into a surface light source and is thin. Therefore, when the surface illumination device of the present invention is used as a backlight that illuminates from the back of a transmissive or transflective liquid crystal display panel, one of which is a thin type, many effects can be exerted.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic perspective view of a first embodiment of the present invention, FIG. 2 is an exploded perspective view of FIG. 1, and FIG. 3 is a schematic partially cutaway perspective view of second and third embodiments of the present invention. 4 is a view showing a first effect of the present invention, FIG. 5 is a schematic perspective view of a fourth embodiment of the present invention, FIG. 6 is an exploded perspective view of FIG. 5, and FIG. FIG. 8 is a view showing a second effect of the present invention, FIG. 9 is a schematic perspective view of a sixth embodiment of the present invention, and FIG. FIG. 16 is a schematic perspective view of a sixth other embodiment.
[0035]
In the figure, 1 is a light guide plate, 11 is a first prism array, 2 is a prism mirror, 21 is a second prism array, 22 is a slope, 23 is a first reflection film, 3 is a light source device, 4 is illumination. Object, 5: incident light, 51: leak light, 6: lens sheet, 61: lens surface, 62: apex angle, 7: reflective sheet, 71: second reflective film, 8: liquid crystal display panel, 9: illumination light Reference numeral 10 denotes a surface illumination device, and reference numeral 20 denotes a liquid crystal display device.
[0036]
[Example 1]
In FIGS. 1 and 2, a surface illumination device 10 is a so-called backlight type that illuminates an object 4 to be illuminated from behind, and includes a light guide plate 1 and a prism mirror 2 provided near the back surface of the light guide plate 1. The light source device 3 is provided near a side end surface of the light guide plate 1 to guide light into the light guide plate 1.
[0037]
The light guide plate 1 has a light source device 3 densely provided on one end face. Although not shown, the light source device 3 expands a point-like light source such as an LED provided on an end surface in the length direction of the light source device 3 and emits the light from one side surface. The light emitted from the light source device 3 is uniformly enlarged in the width direction of the nearby end face when viewed from the light guide plate 1 side, and is guided into the light guide plate 1 as incident light 5.
[0038]
The light guide plate 1 is provided on its back side with, for example, a sawtooth-shaped first prism array 11 having a pitch of 100 μm unit. The light guide plate 1 is formed, for example, by molding transparent plastics such as PMMA. The incident light 5 is internally reflected by the steeply inclined surface of the first prism array 11 and is emitted from the other emission surface 12 as uniform illumination light 9.
[0039]
On the other hand, the prism mirror 2 is provided on the front side with, for example, a sawtooth-shaped second prism array 21 having a pitch of 10 μm unit, which faces the first prism array 11 on the back surface of the light guide plate 1. It is nearby. The second prism array 21 is formed by, for example, molding of plastics such as PC, and has a mirror-finished surface.
[0040]
The second prism array 21 reflects the leaked light 51 transmitted through the first prism array 11 and emitted to the outside of the light guide plate 1 on the inclined surface 22, returns the leaked light 51 into the light guide plate 1 again, and returns from the emission surface 12 to the vertical direction. It is used as illumination light 9 in the direction.
[Example 2]
In FIG. 3, the saw-toothed prisms of the second prism array 21 are arranged side by side at a predetermined pitch so as to intersect with the direction of the incident light 5 incident on the light guide plate 1 from the light source device 3. At least one slope 22 arranged side by side is opposed to the incident direction of the incident light 5, and the slope angle of the slope 22 is θ = 40 ± 5 °.
[0041]
[Example 3]
In FIG. 3, the second prism array 21 in the surface lighting device 10 has a mirror surface on the inclined surface 22, and can reflect the leaked light 51 transmitted through the first prism array 11 of the light guide plate 1. I have. However, depending on the angle of incidence of the leak light 51 on the slope 22, the light may be transmitted through the slope 22. Therefore, in order to perform the reflection on the slope 22 more effectively, the first reflection film 23 is attached to at least the slope 22.
[0042]
As the first reflection film 23, a metal film having a high reflectance can be used. For example, a reflection film of aluminum formed by vapor deposition, a reflection film of nickel formed by electroless plating, or the like can be used.
FIG. 4 shows the first effect of the surface illumination device according to the present invention in which the leakage light is effectively used by using the prism mirror. The configuration of the surface illumination device 10 in FIG. 4 is such that a prism mirror 2 in which a first reflective film 23 is coated with a vapor-deposited aluminum film is arranged close to the back surface of the light guide plate 1.
[0043]
The intensity of the illuminating light 9 vertically emitted from nine grid-like measurement points on the surface of the light guide plate 1 is determined by the luminance (cd / cm). ^Two ). The X direction indicates a direction away from the light source device 3, and the Y direction indicates a width direction of the light guide plate 1.
Open marks indicate the luminance of the illumination light 9 when the prism mirror 2 is not used, and black filled marks indicate the luminance of the illumination light 9 when the prism mirror 2 is used. In the Y direction, if the distance from the light source device 3 is equal, almost the same luminance is shown. However, in the X direction, the luminance of the illumination light 9 increases as the distance from the light source device 3 increases. This tendency is a feature of the prism array type surface illumination device, but it has been found that, for example, in the case of illumination of a liquid crystal display panel or the like, diffusion occurs in the panel, so that uniform illumination is obtained.
[0044]
At any of the measurement points, the luminance of the illumination light 9 is higher in the black solid mark to which the prism mirror 2 is applied, and the average luminance when the prism mirror 2 is not applied is 1020 cd / cm. ^Two In contrast, when the prism mirror 2 is applied, the average luminance is 1144 cd / cm. ^Two It was confirmed that the efficiency was improved by 12%.
[0045]
[Example 4]
5 and 6, the surface illumination device 10 is of a so-called backlight type that illuminates the object 4 from behind. The light source device 3 includes a light guide plate 1, a lens sheet 6 provided near the back surface of the light guide plate 1, and a reflection sheet 7 provided near the back surface of the lens sheet 6, and the light source device 3 guides light into the light guide plate 1. The light guide plate 1 is provided near a side end surface for light emission.
[0046]
The specifications of the light guide plate 1 are the same as in the first embodiment. That is, the incident light 5 emitted from the light source device 3 and having the light incident on the light guide plate 1 is internally reflected by the steeply inclined surface of the first prism array 11, and becomes uniform illumination light 9 from the other emission surface 12. It is designed to be emitted.
On the other hand, the lens sheet 6 is provided close to the rear side of the light guide plate 1, and the lens surface 61 of the light guide plate 1 facing the first prism array 11 is a stripe-shaped prism type lens having a triangular prism tilted sideways. It has become juxtaposed.
[0047]
The reflection sheet 7 reflects the leaked light 51 transmitted through the lens sheet 6 and returns to the light guide plate 1 again via the lens sheet 6 for effective use. The reflection sheet 7 has a configuration in which, for example, a second reflection film 71 is attached to a polyester film or the like. As the second reflection film 71, a metal film having a high reflectance can be used. For example, a metallized film such as an aluminum reflection film formed by vapor deposition or a nickel reflection film formed by electroless plating can be used.
[0048]
[Example 5]
In FIG. 7, a lens surface 61 of a lens sheet 6 which is located near the first prism array 11 of the light guide plate 1 in the surface illumination device 10 intersects with the incident direction of the incident light 5 from the light source device 3, The prism type lens has an apex angle 62 of θt = 60 to 90 °.
[0049]
The lens sheet 6 in which the prism type lenses are juxtaposed is made of, for example, a transparent plastic such as PMMA, and is manufactured by molding. The mold for molding the lens surface 61 of the mold has a V-shaped groove formed at a very fine pitch of, for example, 100 μm.
The “vertical angle” of a prism-type lens having a cross-sectional shape of a semi-cylindrical shape is a design finished angle of a mold when the lens sheet 6 is manufactured. When manufacturing the lens sheet 6 by resin molding, embossing, or the like, the resin does not sufficiently enter the valleys of the mold engraved in a V-shape at a fine pitch according to the shape of the mold. Of the mountain has a rounded shape. In other words, the ridge line becomes round, and the cross section becomes a kamaboko shape.
[0050]
Thus, it was confirmed that the prism type lens having the apex angle 62: θt = 60 to 90 degrees in the mold design exhibits a lens effect like a lenticular lens in which the peaks of the round ridges are connected in parallel, and functions sufficiently as a lens. is made of. Moreover, it has been confirmed that the range of the vertical angle 62: θt = 60 to 90 ° is the angle at which the leaked light 51 is returned to the light guide plate 1 most efficiently as a lens sheet.
[0051]
FIG. 8 shows a second effect of the surface illumination device according to the present invention in which the leak light is effectively used by using the lens sheet and the reflection sheet. The surface illumination device 10 in FIG. 8 has a lens sheet 6 disposed close to the rear surface of the light guide plate 1, and further has a second reflection film 71 on the rear surface of the lens sheet 6 covered with a vapor-deposited aluminum film. It has a close configuration.
[0052]
The intensity of the illuminating light 9 vertically emitted from nine grid-like measurement points on the surface of the light guide plate 1 is determined by the luminance (cd / cm). ^Two ). The X direction indicates a direction away from the light source device 3, and the Y direction indicates a width direction of the light guide plate 1.
Open marks indicate the luminance of the illumination light 9 when the light guide plate 1 without the lens sheet 6 and the reflection sheet 7 is used, and black filled marks indicate the use of the lens sheet 6 and the reflection sheet 7. The luminance of the illumination light 9 in the case is shown.
[0053]
The illumination light 9 in the Y direction shows almost the same brightness when the distance from the light source device 3 is equal, but in the X direction, the brightness of the illumination light 9 gradually increases as the distance from the light source device 3 increases. This tendency is a feature of the prism array type surface illumination device. For example, it has been found that, for example, in the case of illumination of a liquid crystal display panel, diffusion occurs in the panel, resulting in uniform illumination.
[0054]
At any of the measurement points, the luminance of the illumination light 9 is higher in the black solid mark to which the lens sheet 6 and the reflection sheet 7 are applied. On average, the average luminance when the lens sheet 6 and the reflection sheet 7 are not applied: 1041 cd / cm ^Two In contrast, when the lens sheet 6 and the reflection sheet 7 are applied, the average luminance is 1163 cd / cm. ^Two It was confirmed that the efficiency was improved by 10%.
[0055]
[Example 6]
In FIG. 9, if the illuminated object 4 illuminated in a backlight manner by the surface illumination device 10 including the light guide plate 1 and the prism mirror 2 of the first embodiment is a transmissive or transflective liquid crystal display panel 8, The liquid crystal display device 20 according to the present invention is obtained.
In FIG. 10, the illuminated object 4 illuminated in a backlight manner by the surface illumination device 10 including the light guide plate 1, the lens sheet 6, and the reflection sheet 7 according to the fourth embodiment is a transmissive or transflective liquid crystal display. If the panel 8 is used, the liquid crystal display device 20 according to the present invention is obtained.
[0056]
Since any of the liquid crystal display devices 20 effectively utilizes the leakage light of the illumination light, the surface illumination device 10 that does not employ the prism mirror 2 or the lens sheet 6 and the reflection sheet 7 according to the present invention. In contrast, a bright display image of 10 to 12% increase can be obtained.
The emission angle of the leaked light depends on the configuration of the first prism array of the light guide plate. Therefore, in this example, the angle of the slope of the prism mirror has been described as the optimal range of the angle of the slope being θ = 45 ± 5 °, but various deformations may occur along with the pitch of the second prism array of the illustrated prism mirror. It is possible.
[0057]
Further, the angle of the vertex of the lens sheet is determined by the configuration of the first prism array of the light guide plate, and the exit angle of the leaked light depends on the angle. : Various modifications are possible for θt = 60 to 90 degrees, the illustrated pitch, and the like. In particular, when molding a lens sheet due to the fine pitch, it is important that the vertices of the triangular prism lens be rounded and function like a semi-cylindrical lens.
[0058]
Furthermore, it goes without saying that the surface illumination device of the present invention is not limited to the liquid crystal display device configured to be used for illuminating the liquid crystal display panel as illustrated, but can be applied to various applications requiring surface illumination.
[0059]
【The invention's effect】
Advantageous Effects of Invention According to the present invention, by combining a prism mirror or a lens sheet and a reflection sheet with a front light type surface illumination device provided with a prism array on a light guide plate, it is possible to effectively use leakage light scattered from the light guide plate. And is useful as a backlight type surface lighting device.
[0060]
That is, the brightness of the illumination light can be increased by 12% by the prism mirror or by 10% by combining the lens sheet and the reflection sheet. As a result, the main surface illumination device greatly contributes to further improvement of image display quality as a backlight type illumination device of a liquid crystal display device to be incorporated in a mobile phone, which is expected to be increasingly used in the future.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of FIG.
FIG. 3 is a schematic partially cutaway perspective view of a second and a third embodiment of the present invention.
FIG. 4 is a diagram showing a first effect of the present invention.
FIG. 5 is a schematic perspective view of a fourth embodiment of the present invention.
6 is an exploded perspective view of FIG.
FIG. 7 is a schematic partially cutaway perspective view of a fifth embodiment of the present invention.
FIG. 8 is a diagram showing a second effect of the present invention.
FIG. 9 is a schematic perspective view of a sixth embodiment of the present invention.
FIG. 10 is a schematic perspective view of a sixth other embodiment of the present invention.
FIG. 11 is a schematic view of an example of a front light type surface illumination device.
FIG. 12 is a schematic diagram of an example of a backlight type surface illumination device.
FIG. 13 is a schematic diagram of the behavior of light leakage.
FIG. 14 is a viewing angle characteristic diagram of leaked light.
[Explanation of symbols]
1 light guide plate 11 first prism array
2 prism mirror 21 second prism array 22 slope 23 first reflection film
3 Light source device
4 Illuminated objects
5 Incident light 51 Leakage light
6 Lens sheet 61 Lens surface 62 Apex angle
7 Reflective sheet 71 Second reflective film
8 LCD panel
9 Illumination light
10-side lighting device
20 Liquid crystal display device

Claims (6)

A light guide plate that expands light incident from the light source device to surface illumination light and emits light from the surface, and a prism mirror,
The light guide plate is provided near the back side of the object to be illuminated, and has a first prism array on the back side,
The surface illuminating device, wherein the prism mirror has a second prism array which is provided near the light guide plate and has a sawtooth shape facing the first prism array. The second prism array is arranged side by side so as to intersect with the direction of the incident light from the light source device, and an inclination angle of a slope facing the incident direction of the incident light is 40 ± 5 °. The surface lighting device according to claim 1, wherein 3. The surface illumination device according to claim 2, wherein the second prism array has a first reflection film attached to at least a slope. A light guide plate that expands light incident from the light source device to surface illumination light and emits light from the surface, a lens sheet, and a reflection sheet,
The light guide plate is provided near the back side of the object to be illuminated, and has a first prism array on the back side,
The lens sheet is provided near the back side of the light guide plate, and is a prism type lens in which lens surfaces facing the first prism array are arranged side by side,
The surface illumination device, wherein the reflection sheet is provided near a back side of the lens sheet, and a second reflection film is applied to a surface of the reflection sheet. The surface illumination device according to claim 4, wherein the lens surface is a prism type lens that intersects the incident light from the light source device and has an apex angle of 60 to 90 degrees. 5. A liquid crystal display device according to claim 1, wherein the object to be illuminated comprises a liquid crystal display panel.

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