JP2001184918A - Method of controlling chromaticity of plane light source apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of adjusting chromaticity of a plane light surface apparatus which controls a tone and a color shading even in case a point light source is used. SOLUTION: A plane light source apparatus receives light from a plurality of point light sources 2... placed in one of side ends of a light guide late 1 and emits light from surface of the light guide plate 1. The point light source 2 is formed of a white color light emitting diode element, and two white color diode elements having chromaticity which is the farthest from the center in the direction of color opposite in the center of chromaticity limits of target among six white color diode elements are arranged, almost at center of the white color diode element group, the emitting light from the light guide plate is measured by emitting the point light source, and it is checked if the result of measurement is within the chromaticity limits of target. If the result of the check is outside the chromaticity limits of target, the chromaticity amendment means corresponding to the emitting light is arranged in relation with light propagation path and the chromaticity can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromaticity adjusting method for a surface light source device which is composed of a point light source including a light emitting element such as a light emitting diode (LED) and is mainly used for a backlight of a liquid crystal display panel.

[0002]

2. Description of the Related Art As a surface light source for a backlight of a liquid crystal display panel, an edge light type using a light-transmitting flat plate as a light guide plate is known. In such a surface light source, light is made incident from one of the side end surfaces (edge portions) of a light guide plate made of a transparent parallel flat plate or a wedge-shaped flat plate, and the incident light is propagated uniformly throughout the entire light guide plate. A part of the light is diffused and reflected by the light reflecting member provided on the propagation path on the back surface of the light guide plate,
The diffused light is emitted from the light guide plate surface.

An edge light type light guide plate used as a light source for a liquid crystal display panel is widely used because the thickness of the light guide plate can be reduced and the structure can be simplified.

In many edge light type surface light sources, a cold-cathode tube lamp is used as a light source, and the cold-cathode tube lamp is attached to an edge portion of the light guide plate.

On the other hand, portable devices have become widespread in recent years, and there is a demand for power saving. Therefore, as a backlight light source of a portable device, a light source using an LED element that consumes less power than a conventional cold-cathode tube lamp has attracted attention and has been put to practical use.

FIG. 1 is a schematic sectional view showing a surface light source using an LED element. As shown in the figure, this surface light source is composed of a light guide plate 1, a point light source 2 composed of LED elements, and the like.

At the edge of the light guide plate 1, a plurality of point light sources 2 composed of white LED elements are arranged. A light reflecting surface 11 is provided on a side (back surface) of the light guide plate 1 which is positioned in a direction perpendicular to the point light source 2, and a white reflecting sheet 5 is further provided facing the light reflecting surface 11. The light transmitted through the light reflecting surface 11 is reflected back to the light guide plate 1.

On the other hand, a light emitting surface 12 is provided on the side (front surface) facing (facing) the light reflecting surface 11. And
Light from the point light source 2 is reflected by the light reflection surface 11, the three side surfaces 13 of the light guide plate 1,... And the reflection sheet 5, and most of the incident light is finally emitted from the light emission surface 12.

A diffusion sheet 3 and a lens sheet 4 are disposed on the upper surface of the light exit surface of the light guide plate 1, whereby surface light emission having uniform directivity can be obtained.

The structure around the point light source 2 has a structure in which the reflector 22 wraps the LED board 21 on which each LED is mounted, and is configured to guide the light from the point light source 2 to the light guide plate 1. ing.

[0011]

Incidentally, one of the performance indexes of the surface light source device is a color tone, which is usually evaluated by xy values in an xy chromaticity diagram. The color tone evaluation includes a color tone at the central portion of the light emitting surface of the surface light source device, and a color tone unevenness comparing the central portion with its peripheral portion.

In the case of a surface light source device using a cold-cathode tube lamp, one lamp is usually used for one device.
The color tone unevenness on the light emission surface is small, and the color tone difference between individual lamps is relatively small.

On the other hand, in the case of a surface light source device using an LED element as a light source, a plurality of L
Since an ED element is used and there is also a color tone difference between LED elements, there is a disadvantage in terms of color tone and color tone unevenness as compared with a surface light source device using a cold cathode tube lamp.

Normally, white LED elements are provided with a plurality of ranks according to luminous intensity and color tone, and are shipped so that each LED element belongs to the luminous intensity and color tone of which rank. However, it is difficult for a purchaser to specify a rank for purchase, and only the characteristics of the purchased LED can be confirmed. It may also be possible to specify a rank for purchase, but this is disadvantageous in terms of cost and delivery time.

FIG. 3 shows an example of the color tone rank of the white LED element. In this example, it is classified into three ranks (a rank, b rank, and c rank) on the xy chromaticity diagram.
The rank a is bluish white compared to the center b rank, c
The rank is yellowish white. Here, the color tone ranks are distinguished by the manufacturer in the distribution of each white LED element on the xy color diagram for the sake of convenience, and are classified more finely than the three distinctions of a rank, b rank, and c rank, or other names. In some cases, such as is used.

Here, in the case where a surface light source device which is to fall within the color tone range shown in the backlight specification surrounded by the broken line in FIG. 1 is to be constructed using only the b-rank LED elements, the central color tone, It is preferable in terms of color tone unevenness and the like. However, in the case of the configuration using only the b-rank product, there is a problem that the a-rank product and the c-rank product are not required, and the total cost is high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides a chromaticity adjusting method for obtaining a surface light source device in which color tone and color tone unevenness are suppressed even when a point light source is used. The purpose is to provide. For example, white LED
In addition to configuring the element only with the b-rank product, adding the a-rank product and the c-rank product to the b-rank product, or the configuration of only the a-rank product and the c-rank product, and without strictly managing such ranks It is another object of the present invention to provide a chromaticity adjusting method capable of obtaining a surface light source device which is comparable to that constituted by only a b-rank product in terms of center chromaticity and color tone unevenness.

[0018]

According to a first aspect of the present invention, there is provided a surface light source device which receives light from a plurality of point light sources disposed on one of side end surfaces of a light guide plate and emits light from the surface of the light guide plate. A method of adjusting the chromaticity, comprising: arranging a plurality of point light sources having chromaticity deviating in the hue directions opposite to each other from the center of the target chromaticity range, and emitting light from the light guide plate by causing the point light sources to emit light. Measuring the emitted light and examining whether the light is included in a target chromaticity range; and, if the light is not included in the target chromaticity range as a result of the inspection, guiding chromaticity correction means according to the emitted light. Arranging the light plate in relation to the light propagation path of the light plate.

According to a second aspect of the present invention, light is incident from a light source disposed on one of the side end surfaces of the light guide plate, and is reflected by a reflection member disposed close to the rear surface facing the front surface of the light guide plate. A chromaticity adjustment method for a surface light source device that emits planar light from the surface of a light guide plate, wherein the light source emits light, the emitted light from the light guide plate is measured, and a chromaticity difference from a target chromaticity range is measured. Measuring, based on the chromaticity difference of the measurement result, a step of selecting a colored reflective member to correct the emitted light to a target chromaticity range as a reflective member disposed close to the back surface of the light guide plate, It is characterized by having.

Further, in the invention according to claim 3, the point light source or the light source is a group of point light sources composed of four or more white light emitting diode elements, wherein the point light source is located in a hue direction opposite to the center of the target chromaticity range. 5. The invention according to claim 4, wherein the two white light emitting diode elements having the most deviated chromaticity are arranged substantially at the center of the point light source group. Characterized in that it is a colored reflecting member provided on the back surface opposite to the surface from which light is emitted.

According to the first aspect of the present invention, since point light sources having opposing hues are arranged adjacent to each other, these colors are mixed, and the color becomes a color located in the middle of the light sources. It becomes a surface light source device, and many surface light source devices can satisfy the target chromaticity range, and chromaticity correction means for those not included in the target chromaticity range are arranged in relation to the light propagation path of the light guide plate. Thus, a surface light source device having a target chromaticity range can be obtained.

According to a second aspect of the present invention, a chromaticity difference from a target chromaticity range is measured, and based on the chromaticity difference of the measurement result,
A surface light source device having a target chromaticity range can be obtained by arranging a colored reflecting member for correcting the emitted light to a target chromaticity range close to the back surface of the light guide plate.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a perspective view showing a schematic configuration of a surface light source device utilizing the present invention. In this figure, a diffuser sheet and a lens sheet 4 arranged on the light emitting surface side and a reflector covering around a point light source are omitted. The present invention is applied to the surface light source device shown in FIG. 1, and as shown in FIG. 2, a surface light source device having a configuration in which a plurality of point light sources 2 are arranged in parallel on the light incident surface side of the light guide plate 1. It is.

As shown in FIG. 2, the surface light source device according to the present invention includes a light guide plate 1, a point light source 2 composed of white LED elements, and various control circuits (not shown). The control circuit includes, for example, the light exit surface 12 of the light guide plate 1.
And a circuit for detecting the total amount of light emitted from the light source and adjusting and supplying power to the point light source 2 so that the amount of emitted light is optimized.

Point light sources 2 composed of white LED elements are arranged opposite to a light incident surface 1a provided at the edge of the light guide plate 1. In this embodiment, six white LED elements are mounted on a substrate 21 as point light sources 2. The white LED element includes, for example, a structure in which three LEDs of R, G, and B are housed in one package and emits white light, or a single-color LED is converted from an LED using a fluorescent substance. What is necessary is just to use what was comprised so that emitted light may be converted into white light. For example, when a GaN-based blue LED is used as this fluorescent material, YAG
(Yttrium Aluminum Garnet) based fluorescent material may be used.

A light-reflecting sheet 5 functioning as a light-reflecting member is disposed close to a back surface, which is one main surface of the light guide plate 1 in the direction perpendicular to the point light sources 2. The light reflecting surface 11 is constituted in cooperation.

A light exit surface 12 is provided on the surface of the light guide plate 1 which is the main surface on the side facing the light reflection surface 11. Then, light from each LED of the point light source 2 is reflected by the light reflecting surface 11 including the reflecting sheet 5 and the three side surfaces 13 of the light guide plate 1, and almost all of the incident light is finally emitted from the light emitting surface 12. Is done.

The material of the above-mentioned light guide plate 1 is selected from light-transmissive materials, and acrylic or polycarbonate resin is usually used. The shape of the light guide plate 1 is a parallel flat plate or a wedge-shaped flat plate having a cross section of about 1 to 5 mm. The thickness of the light guide plate 1 is further reduced by using an LED compared to the case of using a cold cathode tube lamp. It becomes possible.

Other translucent materials include acrylate or methacrylate homo- or copolymers such as polymethyl methacrylate and polymethyl acrylate, and polyesters such as polyethylene terephthalate and polybutylene terephthalate. Thermoplastic resins such as polycarbonate, polystyrene and polymethylpentene; or acrylates such as polyfunctional urethane acrylates and polyester acrylates cross-linked by ultraviolet rays or electron beams; transparent resins such as unsaturated polyesters; transparent glass; transparent ceramics Is used.

Although not shown in FIG. 2, on the upper surface of the light exit surface 11 of the light guide plate 1, a diffusion sheet and a lens sheet are arranged so that the light exiting from the light exit surface 11 is Has a uniform directivity. The seat configuration is 1
One sheet or two sheets may be used, and the order of stacking may be reversed.

Then, an LED board 21 on which each LED element is mounted is fixed to an outer frame (not shown) located outside the light guide plate 1 with screws or an adhesive, and point light sources 2. Is arranged.

Each LED light from the point light source 2 enters the inside of the light guide plate 1 and is reflected by the light reflection pattern provided on the light reflection surface 11 and the three side end surfaces 13 to repeatedly converge.
The light exits from the light exit surface 12 to the diffusion plate 3, is uniformly and isotropically diffused within a desired angle range by the lens sheet, and exits as combined light. A liquid crystal display panel is arranged close to the lens sheet.

In the surface light source device configured as described above, the point light sources 2...
The surface light source device of the first example was formed using six D elements.
FIG. 4 shows the color tone of this surface light source device. In the figure, the mark ○ indicates the chromaticity of each of the six white LED elements, and the mark □ indicates the chromaticity on the surface light source when the surface light source device is configured by these white LED elements. . As shown in FIG. 4, all the white LED elements belong to the color tone rank b, and in this case, the chromaticity on the surface light source also satisfies the specification.

Next, a white LED element having a color b rank
A surface light source device constituted by using a single LED and white LED elements of rank a and rank c will be described.

As shown in Table 1 below, the arrangement of the LED elements on the LED substrate 21 is from rank b, rank a,
The surface light source device of the second example was formed in the order of b rank, b rank, c rank, and b rank.

[0036]

[Table 1] FIG. 5 shows the chromaticity of each white LED element of the surface light source device of the second example and the chromaticity on the surface light source. Also in this figure, a circle in the figure indicates the chromaticity of each of the six white LED elements, and a square indicates the color on the surface light source when these white LED elements are used to form a surface light source device. Indicates the degree. From FIG. 5, it can be seen that the chromaticity on the surface light source satisfies the specifications also in this configuration.

However, the surface light source device of this configuration has
As shown in FIG. 6, color tone unevenness that becomes yellowish is seen on the right side (a portion surrounded by a broken line in the figure) where the white LED elements of rank c are arranged, which is not preferable.

Then, the white LE used in the second example is used.
Prepare a white LED element with almost the same chromaticity as the D element,
The order of arrangement on the D substrate 21 was changed as shown in Table 2 below, and the surface light source device in this embodiment was formed.

Also in this embodiment, as in the second example described above, four LEDs having a color tone b rank, a rank a
One white LED element of each rank was used, and the arrangement was as shown in Table 2 below, from the left end, rank b, rank b, c
Rank, a rank, b rank, b rank, and so on.

[0040]

[Table 2] Each white light L of the surface light source device having the configuration according to this embodiment.
FIG. 7 shows the chromaticity of the ED element and the chromaticity on the surface light source. Also in this figure, a circle in the figure indicates the chromaticity of each of the six white LED elements, and a square indicates the color on the surface light source when these white LED elements are used to form a surface light source device. It can be seen that the chromaticity on the surface light source satisfies the specification also in the present configuration of this embodiment showing the degree.

Further, a good surface light source could be obtained without the color tone unevenness seen in the second example.

The reason for this is that, in the case of the surface light source device of the second example, the ratio of incident light from the white LED elements of ranks b and c is considered to be high at the right end of the light exit surface. The emitted light has a color mixture of colors of the ranks b and c. On the other hand, in the case of the surface light source device according to the present embodiment, the LEDs of rank a and rank c are arranged adjacent to each other at the center of the LED board 21.
These colors are mixed, and the color becomes a b-rank color located in the middle, and it is considered that a surface light source device with little color tone unevenness can be configured as a whole.

In the above-described embodiment, the case where the point light sources 2 composed of six white LED elements are used has been described. However, the number of the point light sources 2 is not limited to six but may be two. When the above-mentioned point light sources 2 are used, the white LED elements having chromaticities farthest from each other in the opposite hue direction from the center of the chromaticity range are selected from the target and the two white LED elements are selected. When they are arranged adjacently on the substrate 21, color unevenness can be reduced. When the number of the point light sources 2 is four or more, the white LED elements having the distant chromaticities in the opposite hue directions are selected, and the selected two white LED elements are placed on the LED board 21. Adjacent to the plurality of point light sources 2...

As described above, when a surface light source device using a plurality of white LED elements is formed, the distribution of each white LED element on the xy chromaticity diagram indicates the center of the target chromaticity range of the surface light source device. In the case of the present embodiment, x = about 0.3
1, y = 0.31), the opposite hue directions (in this embodiment, the lower left (blue) direction and the upper right (yellow) on the chromaticity diagram)
Direction), the white LED elements having the most distant chromaticity are selected, and the two selected white LED elements are
By arranging them adjacently on one, it is possible to reduce color tone unevenness. As a result, a white LED element having a wide chromaticity range can be used, and the cost of the surface light source device can be reduced.

By devising the arrangement of the plurality of white LED elements as described above, the color tone unevenness can be reduced and a surface light emitting device satisfying the chromaticity range can be obtained.
In some surface light source devices, a device slightly deviating from the specification of the chromaticity range appears. The reason is that the chromaticity variation of the white LED elements within the same rank used is not constant. Therefore, in the present embodiment, the chromaticity correction means corresponding to the outgoing light is provided in the surface light source device outside the chromaticity range while using the white LED element having a wide chromaticity range in relation to the light propagation path of the light guide plate. By arranging, the chromaticity within the specification is adjusted.

Specifically, after assembling the point light sources of the white LED elements having the respective ranks as the LED board 21 based on the above rules, the white reflective sheet 5 having the standard chromaticity, that is, the target chromaticity is formed. The light guide plate 1 placed in advance has the LE
The point light source 2 is fully lit with the D board 21 mounted, and the chromaticity on the surface light source is measured.

As a result of the measurement, the chromaticity on the surface light source is
The non-defective product is determined as to whether or not it is within the target chromaticity range. If the product is determined to be good, the assembly as the surface light source device is continued.

On the other hand, the LED board 21 determined to be defective
Is separated from the light guide plate 1 and a light guide plate 1 including a colored reflection sheet 5 for correcting the chromaticity difference based on a chromaticity difference from a target chromaticity range is newly prepared and assembled. Such a colored reflection sheet 5 is prepared in advance as a chromaticity difference so that a chromaticity that corrects the chromaticity difference is automatically selected from the chromaticity difference obtained at the time of the chromaticity measurement. This is executed when the relationship between the plurality of coloring sheets 5 is stored in the table.

By selecting the colored reflection sheet 5 having a desired chromaticity in this way, a product out of the specification range can be made a good product within the specification range.

Since the chromaticity correcting means may be provided in relation to the propagation path of the light guide plate 1, it is not limited to the reflection sheet 5, but may be provided between the point light source 2 and the light guide plate 1. Even if the reflection sheet 5 is a surface light source device that does not require correction, the reflection sheet 5 itself needs a standard reflection sheet 5. Therefore, by providing the reflection sheet 5 with a correction function, the number of components can be reduced. I'm done.

FIG. 8 is an xy chromaticity diagram for explaining a chromaticity adjusting method according to another embodiment. This embodiment provides a method for performing the adjustment without devising the arrangement relationship of the white LED elements on the LED board 21 as in the above embodiment. That is, in this embodiment, the ranks (a, b, c) of the white LED elements have substantially no relation.

In the surface light source device of FIG. 8, the number of white LED elements is six (however, it is not necessary to stick to the number, and in this embodiment, it may be one). Is approximately a rank as plotted with a circle in the same figure, and the chromaticity on the surface light source is out of the target chromaticity range as a result of the measurement, as plotted with a diamond-shaped mark (displayed as conventional specification). .

From the result of the measurement, the colored reflection sheet 5 corresponding to the chromaticity difference is selected by the method described above, that is, by using a table prepared according to the chromaticity difference, and is set within the target chromaticity range. In this embodiment, the color temperature 3400 ° k can be converted to 3200 ° k by using the color temperature conversion filter part number A1 (displayed as y (A1)) manufactured by Tokyo Stage Lighting. As plotted, a surface light source device having a target chromaticity range was obtained.

For comparison, 5500 ° k is changed to 3200 ° k
When the color temperature conversion filter part number A5 (indicated as y (A5)) made by Tokyo Stage Lighting, which converted to, exceeded the target chromaticity range as plotted with a + sign.

As described above, in this embodiment, attention is paid to the existence of the conventional reflection sheet 5 and the reflection sheet 5 is provided with a function of chromaticity correction, so that the color can be added without adding a component. This makes it possible to use the LED substrate 21 outside the range.

[0056]

As described above, according to the adjustment method of the present invention, even when a point light source is used, the color tone and the color tone unevenness can be suppressed, and the cost of the surface light source device can be reduced.

Further, in addition to the white LED element consisting of only a b-rank product, a configuration in which an a-rank product and a c-rank product are added to a b-rank product, or a configuration of only an a-rank product and a c-rank product, It is possible to provide a surface light source device that is not inferior to that composed of only a b-rank product with central chromaticity, color tone unevenness, and the like without strict control of the LED. And the cost of the surface light source device can be reduced.

Further, a chromaticity difference from a target chromaticity range is measured, and based on the chromaticity difference as a result of the measurement, a colored reflecting member for correcting the emitted light to the target chromaticity range is provided close to the back surface of the light guide plate. By arranging the light sources in such a manner, a surface light source device having a target chromaticity range can be obtained, so that a light source having a wide chromaticity range can be used, and the cost of the surface light source device can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a surface light source device to which the present invention is applied.

FIG. 2 is a perspective view showing a schematic configuration of a surface light source device to which the present invention is applied.

FIG. 3 is a diagram illustrating an example of a color tone rank of a white LED element.
It is a y chromaticity diagram.

FIG. 4 is an xy chromaticity diagram showing a color tone of the surface light source device when a white LED element of rank b is used.

[Figure 5] White LED of rank a, rank b and rank c
FIG. 7 is an xy chromaticity diagram showing a color tone of a surface light source device when an element is used.

FIG. 6 is a schematic plan view of a surface light source device as a premise of the present invention.

[Fig. 7] White LED of rank a, rank b, rank c
FIG. 3 is an xy chromaticity diagram showing a color tone of a surface light source device which is a premise of this embodiment using elements.

FIG. 8 is an xy chromaticity diagram showing a color tone of the surface light source device according to the embodiment using a white LED element having an approximately rank a.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light guide plate 2 point light source 5 reflection sheet 11 light reflection surface 12 light emission surface 21 LED substrate

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 33/00 F21Y 101: 02 // F21Y 101: 02 G02F 1/1335 530 (72) Inventor Michiaki Sato Moriguchi, Osaka 2-5-5 Keihan Hondori Sanyo Electric Co., Ltd. (72) Inventor Nobuto Nishida 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Masato Ochiiwa Osaka 2-5-5 Keihanhondori, Moriguchi City, Sanyo Electric Co., Ltd. F term (reference) 2H038 AA52 AA55 2H091 FA14Z FA23Z FA45Z FC30 FD22 FD24 LA16 5F041 AA14 AA31 DC07 DC23 DC23 EE11 EE23 EE25 FF11 5G435 BB04 EE04 BB04 FF08 GG23 GG26 LL07

Claims (4)

[Claims] 1. A chromaticity adjusting method for a surface light source device that receives light from a plurality of point light sources disposed on one of side end surfaces of a light guide plate and emits light from a surface of the light guide plate, comprising: A step of arranging a plurality of point light sources having chromaticities deviated in the opposite hue directions from the center of the range, and measuring the light emitted from the light guide plate by causing the point light sources to emit light, to a target chromaticity range. A step of inspecting whether the light is included or not, and if the result of the inspection indicates that the light is not included in a target chromaticity range, a chromaticity correction unit corresponding to the emitted light is arranged in relation to the light propagation path of the light guide plate. And a step of adjusting the chromaticity of the surface light source device. 2. Light is incident from a light source disposed on one of the side end surfaces of the light guide plate, reflected by a reflection member disposed close to a back surface facing the front surface of the light guide plate, and reflected from the surface of the light guide plate. A chromaticity adjustment method for a surface light source device that emits light in a shape, wherein the light source emits light, the emitted light from the light guide plate is measured, and a chromaticity difference from a target chromaticity range is measured. Based on the chromaticity difference of the measurement result, selecting a colored reflective member that corrects the emitted light to a target chromaticity range as a reflective member disposed close to the back surface of the light guide plate. Chromaticity adjustment method for a surface light source device. 3. The point light source or the light source is a group of point light sources including four or more white light emitting diode elements, and has a chromaticity farthest from the center in a hue direction opposite to the center of the target chromaticity range. 3. The chromaticity adjusting method for a surface light source device according to claim 1, wherein the two white light emitting diode elements are arranged substantially at the center of the point light source group. 4. The surface light source device according to claim 1, wherein the chromaticity correcting main means is a colored reflecting member provided on a back surface of the light guide plate opposite to a surface on which light is emitted. Chromaticity adjustment method.