WO2014061513A1 - Led classification method, led classification device, led classification program, recording medium, and liquid-crystal display device - Google Patents

Abstract

Provided is an LED classification device (21) whereby, when a chromaticity of a primary light of an LED, wherein an LED element which emits the primary light is combined with a fluorescent light body which is excited by the primary light and emits a secondary light of a longer wavelength than the primary light, is within a prescribed range, the LED is classified as being usable in a backlight of a liquid-crystal display device. A coefficient computation unit (26) and a correction chromaticity computation unit (27) compute, for the total number of LEDs which are to be classified, a correction value of a chromaticity which is obtained with the primary light envisioned as having passed through a color filter of the liquid-crystal display device, and correct the chromaticity by subtracting the correction value from the chromaticity which is obtained for each of the total number of LEDs which are to be classified. A chromaticity rank classification unit (28) classifies the LEDs by chromaticity rank on the basis of the corrected chromaticity.

Description

LED classification method, LED classification device, LED classification program, recording medium, and liquid crystal display device

The present invention relates to an LED classification method for classifying whether or not a plurality of LEDs (light emitting diodes) can be used for a backlight of a liquid crystal display device based on the chromaticity distribution.

In recent years, backlights using LEDs having a long life and low power consumption as light sources have become widespread as backlights for liquid crystal display devices. A white LED is usually used for such a backlight. The white LED is generally configured by combining a blue LED and a phosphor. In such a white LED, white light is obtained by mixing the blue light emitted from the blue LED chip and the light emitted when the phosphor is excited by the blue light. For example, in a white LED using a green phosphor and a red phosphor as a phosphor, green light and red light obtained by exciting the green phosphor and the red phosphor with blue light are mixed with blue light. I get white light.

In order to use such a white LED as a backlight, it is necessary to apply a phosphor so as to develop a desired white color according to the display characteristics of the liquid crystal panel in the liquid crystal display device.

For example, Patent Document 1 discloses a method capable of easily and quickly providing a phosphor capable of changing a white emission color obtained by a blue LED and a phosphor to a more uniform color tone in a manufacturing process. In this method, the light source color information of a specific white LED presented by the customer to the content in which the relationship between the light source color information of the white LED and the required light emission color information is related through the coefficient related to the phosphor material. Then, the phosphor material related to the coefficient obtained by applying the required emission color information is specified. Thus, until the actual acquisition of the light-emitting element is waited for, with the phosphor specific information including the type, composition ratio, and mixing ratio (part by weight) of the fluorescent material that substantially satisfies the required emission color information requested by the customer. It can be obtained quickly.

On the other hand, in Patent Document 2, since white LEDs have high color reproducibility, a method for quickly producing white LEDs by obtaining a phosphor mixture concentration by software calculation without trial and error. Is disclosed. In this method, first, a process is performed in which the mixed spectrum obtained by mixing the light of two types of phosphors with adjusted concentrations and the light of the LED is brought close to the standard spectrum. Next, an area surrounded by the chromaticity coordinates of the three primary colors obtained by dividing the light mixture spectrum by the color filter is obtained, and a process for obtaining the chromaticity coordinate position of the white light constituting the three primary colors is performed. Such processing is executed by calculation.

Further, Patent Document 3 describes that the backlight adjusts the blue leakage of the phosphor layer in the white LED according to the blue wavelength of the blue LED included in the white LED.

Furthermore, Patent Document 4 discloses a method for improving display uniformity in a display panel irradiated with light from a backlight. The method includes, for example, estimating a filter function of a transmissive display component through which backlight emission is transmitted, and estimating filtered chromaticity data corresponding to the filter function for a plurality of light emitters. .

Japanese Patent Publication “Japanese Patent Laid-Open No. 2001-107036” (published on April 17, 2001) Japanese Patent Publication “Japanese Patent Laid-Open No. 2010-93237 (published on April 22, 2010)” Japanese Patent Publication “Special Table 2012-503215 (published February 2, 2012)” Japanese Patent Publication “Special Table 2011-504605 (published on February 10, 2011)”

The methods disclosed in Patent Documents 1 and 2 as described above are methods for determining the phosphor concentration and the like at the time of manufacturing the white LED. In addition, the method disclosed in Patent Document 3 is a method of adjusting blue light when manufacturing a white LED.

However, when using a plurality of white LEDs combining a blue LED and a phosphor for the backlight, the phosphor has the desired concentration and amount even if the phosphor concentration is optimally determined as described above. It is very difficult to form a phosphor layer. For this reason, the density | concentration and quantity of a fluorescent substance do not become uniform between white LED at the time of manufacture. Moreover, since the characteristics of the blue LED and the light emitting layer vary among products, the peak wavelength of blue light varies among white LEDs. For this reason, since the balance of the light intensity of the excitation light of the phosphor and the blue light of the blue LED varies, the chromaticity varies among the white LEDs.

If such white LEDs with varying chromaticities are used as they are in the backlight, there is a disadvantage that the display color becomes non-uniform in the display surface. Conventionally, in order to eliminate such inconvenience, only white LEDs classified by chromaticity rank so that the chromaticity distribution falls within a predetermined range have been selected and used for the backlight.

FIG. 10 is a diagram showing an example of such chromaticity rank classification. As shown in FIG. 10, only white LEDs having chromaticity distribution within the rectangular frame F within the predetermined range are selected and used. The frame F is divided into finer ranges, and is configured so that chromaticity can be ranked for each division. Within this frame F, the chromaticity of the white LEDs in the group having a short peak wavelength of the blue light component is distributed in a range D11 indicated by a solid line. In the range D11, the peak wavelength is 444.7 nm, and the average value AVE11 of chromaticity is at a position indicated by a solid line circle. On the other hand, in the frame F, the chromaticity of the white LEDs of the group having a long blue light component peak wavelength is distributed in a range D12 indicated by a broken line. In the range D12, the peak wavelength is 446.2 nm, and the average value AVE12 of chromaticity is at a position indicated by a broken-line circle.

However, even if the white LED in which the chromaticity of the emitted light itself of the white LED itself falls within the predetermined range is selected as described above, the variation range of the chromaticity of the white LED on the panel display that is transmitted through the liquid crystal panel is expanded. Is done. This is because the chromaticity of the white LED on the panel display is divided into groups of chromaticity variation ranges corresponding to the peak wavelength of blue light, particularly due to the influence of the color filter. For this reason, a white LED appears out of the desired chromaticity rank range on the panel display of the liquid crystal panel. The reason for this will be described in detail below.

First, the maximum value of the luminance of blue light on the display surface of the liquid crystal panel is the transmittance of the color filter (blue filter) of the liquid crystal panel through which the blue light is transmitted (and the liquid crystal from the LED light source such as an optical sheet or a diffusion plate). It includes a luminance reduction generated when passing through the optical member up to the panel) and the light intensity of the blue light emitted from the blue LED of the white LED (light intensity × transmittance). On the other hand, even in the white LED having the chromaticity classified into the predetermined chromaticity rank range as described above, the deviation of the peak wavelength of the blue light component is about ± 5 nm. Further, the transmittance of the color filter (blue filter) tends to decrease as the wavelength is shorter. For this reason, when the peak wavelength of the blue light component is shifted as described above, the maximum value of the luminance of the blue light on the display surface of the liquid crystal panel differs.

FIG. 11 is a graph showing the relationship between the emission spectrum of a blue LED in a white LED and the transmission characteristics of a color filter (blue filter). In FIG. 11, the vertical axis represents the transmittance of the color filter and the intensity of the emitted light of the blue LED.

As shown in FIG. 11, when the center of the peak wavelength of the blue light component is set to 450 nm, the peak wavelength is shifted in the range of 445 nm to 455 nm. In FIG. 11, the spectrum of blue light having a peak wavelength of 455 nm is indicated by a broken line, and the spectrum of blue light having a peak wavelength of 445 nm is indicated by a one-dot chain line. Further, in the blue light spectrum, a portion exceeding the transmittance of the blue filter (shown by hatching in the figure) is cut.

For this reason, the amount of light cut by the blue filter differs between blue light having a peak wavelength of 455 nm and blue light having a peak wavelength of 445 nm. Specifically, the shorter the peak wavelength of blue light, the lower the transmittance of the blue filter, so the amount of light cut by the blue filter increases. Accordingly, the chromaticity of white light including blue light having a short peak wavelength is shifted to the yellow side by a small amount of the blue light when the white light passes through the color filter. In addition, the blue light component further decreases due to the effect of visibility (the ratio of the light component by the phosphor increases with respect to the blue light component).

FIG. 12 is a graph showing the spectra of a plurality of white LEDs showing the same chromaticity. FIG. 13 is a diagram illustrating the chromaticity rank range of the emitted light of the white LED and the chromaticity rank range of the emitted light transmitted through the liquid crystal panel.

In the spectrum of each white LED shown in FIG. 12, the peak wavelength of blue light is shifted, but the chromaticity of each white LED is the same in the frame F shown in FIG. When the light emitted from each white LED passes through the color filter (blue filter), the amount of blue light is cut in accordance with the transmission characteristics, so the chromaticity distribution is shifted in the direction of higher chromaticity. In this case, for the white LED whose peak wavelength of the blue light component is the center value (450 nm in the case of FIG. 11), the chromaticity is distributed in the frame Ftyp shifted from the frame F in the direction in which the x value and the y value increase. To do. On the other hand, for a white LED whose peak wavelength of the blue light component is shorter than the center value, chromaticity is distributed in a frame Fmin shifted in a direction in which the x value and the y value increase from the frame Ftyp. On the other hand, for a white LED in which the peak wavelength of the blue light component is longer than the center value, the chromaticity is distributed in a frame Fmax shifted in a direction in which the x value and the y value decrease from the frame Ftyp.

As described above, when the peak wavelength of the blue light component is short, in order to avoid the disadvantage that the chromaticity shifts to the yellow side, it is necessary to perform white balance adjustment in the liquid crystal panel. By this white balance, the maximum brightness of red light and green light is balanced with the maximum brightness of blue light that has been lowered from the desired brightness. However, such a white balance adjustment causes a new problem that the display brightness of the liquid crystal panel decreases as a whole.

On the other hand, in the method disclosed in Patent Document 4, the filtered chromaticity data corresponding to the estimated filter function is estimated for a plurality of light emitters, but the blue light cut in the color filter is considered. Absent.

The present invention has been made in view of the above-described problems, and the object thereof is chromaticity on a panel display which does not require a large white balance adjustment that leads to a decrease in display luminance on a liquid crystal panel. An object of the present invention is to provide a white LED that is selected so that the variation is within a desired range.

The LED classification method according to an aspect of the present invention includes a combination of an LED element that emits primary light and a phosphor that is excited by the primary light and emits secondary light having a longer wavelength than the primary light. An LED classification for classifying an LED that is used as a backlight of a liquid crystal display device if the chromaticity of the primary light of the LED that emits the combined light of the primary light and the secondary light is within a predetermined range. A chromaticity prediction step of predicting the chromaticity of the primary light transmitted through a color filter in a liquid crystal panel provided in the liquid crystal display device for all the LEDs to be classified, and the predicted chromaticity And a chromaticity rank classification step of classifying the LEDs according to chromaticity rank.

In addition, the LED classification device according to an aspect of the present invention combines an LED element that emits primary light and a phosphor that is excited by the primary light and emits secondary light having a longer wavelength than the primary light. If the chromaticity of the primary light of the LED that emits the combined light of the primary light and the secondary light is within a predetermined range, the LED is classified as an object used for the backlight of the liquid crystal display device. A chromaticity predicting unit that predicts the chromaticity of the primary light that has passed through a color filter in a liquid crystal panel provided in the liquid crystal display device with respect to the total number of LEDs to be classified; Chromaticity rank classification means for classifying the LED into chromaticity ranks based on the corrected chromaticity.

In addition, a liquid crystal display device according to one embodiment of the present invention includes a liquid crystal panel, a plurality of LEDs, a plurality of linear light sources provided adjacent to each other, and an output from the linear light source incident from at least one end side. A light guide plate that radiates light to the liquid crystal panel in a planar shape, and is closer to the light incident side than a central portion between the light incident side end of the light guide plate and the end facing the end. The LED mounted on the linear light source is selected so that the emitted light from each linear light source matches the chromaticity of the transmitted light that has passed through the liquid crystal panel through the light guide plate.

According to one embodiment of the present invention, it is possible to easily select LEDs that do not need to have reduced luminance even when mounted on a backlight.

It is a perspective view which shows the structure of the liquid crystal display device which uses LED classified by the LED classification method which concerns on one Embodiment of this invention for a backlight. It is a perspective view which shows the structure of the other liquid crystal display device which uses LED classified by the LED classification method which concerns on one Embodiment of this invention for a backlight. It is a graph which shows the transmission spectrum of the color filter in each liquid crystal display device. It is a longitudinal cross-sectional view which shows the structure of the said LED. It is a graph which shows the emission spectrum of said LED. It is a block diagram which shows the structure of the LED classification device for implement | achieving the said LED classification method. It is a graph which shows the variation | change_quantity of the chromaticity after the color filter permeation | transmission of the blue light with respect to the shift amount of the peak wavelength from the reference wavelength of the peak wavelength of the blue light from said LED used as classification | category object. It is a figure which shows the chromaticity rank classification | category by the correction | amendment chromaticity converted into the value after color filter permeation | transmission by the said LED classification device. It is a flowchart which shows the procedure of the classification | category of LED by the said LED classification device. It is a figure which shows the conventional chromaticity rank classification | category of white LED. It is a graph which shows the relationship between the emission spectrum of blue LED in white LED, and the permeation | transmission characteristic of a color filter. It is a graph which shows the emission spectrum of several white LED of the same chromaticity by the chromaticity rank classification | category of FIG. It is a figure which shows the rank range of chromaticity of the emitted light of white LED, and the rank range of chromaticity of the said emitted light which permeate | transmitted the liquid crystal panel. It is a perspective view which shows the structure of the liquid crystal display device which uses LED classified by the LED classification method which concerns on other embodiment of this invention for a backlight. It is a figure which shows distribution of the blue component of the light in a different area | region in the liquid crystal panel of each light radiate | emitted from two LED bar (light source) used for the backlight in the liquid crystal display device of FIG. (A) is the graph which shows the emission spectrum of the light from one said LED bar according to distribution of the blue component shown in FIG. 15, (b) is the other said above according to distribution of the blue component shown in FIG. It is a graph which shows the emission spectrum of the light from a LED bar. It is a graph which shows the relationship between the distance from said 2 LED bar, and the height of the peak of the blue component of the light from these LED bar. (A) and (b) are chromaticity corrections so that there is no chromaticity difference between the two systems of light from the two LED bars in the backlight at the center of the liquid crystal panel provided in the liquid crystal display device of FIG. 5 is a graph showing the relationship between the distance from the two LED bars using LEDs and the chromaticity x and chromaticity y of the two lights. (A) and (b) described above using LEDs that have been chromatically corrected so that there is no chromaticity difference between the two systems of light from the two LED bars in a region close to the two LED bars in the liquid crystal panel. It is a graph which shows the relationship between the distance from two LED bars, and chromaticity x and chromaticity y of said two lights, respectively.

Embodiment 1
An embodiment according to the present invention will be described below with reference to FIGS.

[Liquid Crystal Display]
[Configuration of liquid crystal display device]
FIG. 1 is a perspective view showing a schematic configuration of a liquid crystal display device 1 according to the present embodiment. FIG. 2 is a perspective view showing a schematic configuration of another liquid crystal display device 2 according to the present embodiment. FIG. 3 is a graph showing a transmission spectrum of the color filter 7 in the liquid crystal display devices 1 and 2.

As shown in FIG. 1, the liquid crystal display device 1 includes a backlight 3 and a liquid crystal panel 4.

The backlight 3 is disposed on the back side of the liquid crystal panel 4, is an edge light type backlight that irradiates light on the entire surface of the liquid crystal panel 4, and includes a plurality of light emitting devices 5 and a light guide plate 6. The light emitting device 5 is a white LED that is mounted on the side of the light guide plate 6 at a predetermined interval and emits light toward the light guide plate 6 side. As described above, the white LED includes a blue LED and a red phosphor and a green phosphor that are excited by the blue light of the blue LED. The light guide plate 6 deflects the light emitted from the light emitting device 5 so as to be emitted to the liquid crystal panel 4 side.

The liquid crystal panel 4 is filled with liquid crystal between two opposing transparent substrates, and the transmittance of light from the backlight 3 is changed by changing the alignment state of the liquid crystal in units of pixels configured in a matrix. change. Further, the liquid crystal panel 4 has a color filter 7 disposed on the display surface side. In the color filter 7, a filter for each color of red (R), green (G), and blue (B) having a transmission spectrum shown in FIG. 3 is formed for every three sub-pixels constituting each pixel. When light passes through each filter, the light of the color of each filter can be emitted. In the liquid crystal panel 4, based on the light color component ratio of red (R), green (G), and blue (B) corresponding to the color of each pixel determined for each display image, transmission of the liquid crystal layer corresponding to the sub-pixel is performed. By adjusting the rate individually, each pixel is displayed in a color to be displayed.

As shown in FIG. 2, the liquid crystal display device 2 includes a backlight 8 and a liquid crystal panel 4.

The backlight 8 is disposed on the back side of the liquid crystal panel 4 and is a direct type backlight that irradiates light on the entire surface of the liquid crystal panel 4, and includes a plurality of light emitting devices 5 and a mounting substrate 9. The light emitting device 5 is mounted on the entire surface of the mounting substrate 9 at a predetermined interval and emits light directly to the liquid crystal panel 4. Since the backlight 8 can modulate the brightness for each small region (for example, pixel), it is excellent in energy saving and can increase the contrast ratio between light and dark.

[Configuration of LED]
FIG. 4 is a longitudinal sectional view showing a configuration of the LED 10 as the light emitting device 5 used in the above-described backlights 3 and 8. FIG. 5 is a graph showing an emission spectrum of the LED 10.

4 is a white LED used as the light emitting device 5, and includes a frame 11, an LED chip 12, a lead frame 13, a wire 14, a resin 15, and phosphors 16 and 17.

The frame 11 is disposed on the lead frame 13. The frame 11 is made of a nylon material and has a recess 11a. The inclined surface of the recess 11a is formed as a reflective surface that reflects the emitted light of the LED chip 12. The reflecting surface is preferably formed of a metal film containing silver or aluminum in order to efficiently extract the emitted light from the LED chip 12.

The lead frame 13 is insert-molded in the frame body 11. The upper end portion of the lead frame 13 is divided and formed, and a part of the lead frame 13 is exposed at the bottom surface of the concave portion 11 a of the frame body 11. The lower end portion of the lead frame 13 is cut to a predetermined length and is bent along the outer wall of the frame body 11 to form an external terminal.

The LED chip 12 (LED element) is, for example, a GaN-based semiconductor light-emitting element having a conductive substrate, and a bottom electrode is formed on the bottom surface of the conductive substrate, and an upper electrode is formed on the opposite surface. The outgoing light (primary light) of the LED chip 12 is blue light in the range of 430 to 480 nm and has a peak wavelength at 450 nm. The LED chip 12 is die-bonded with a conductive brazing material on one side of the upper end portion of the lead frame 13 exposed on the bottom surface of the recess 11a. Further, in the LED chip 12, the upper electrode and the other side of the upper end portion of the lead frame 13 are wire-bonded by a wire 14. Thus, the LED chip 12 is electrically connected to the lead frame 13.

Resin 15 seals the recess 11a by filling the recess 11a. Further, since the resin 15 is required to have high durability with respect to primary light having a short wavelength, a silicone resin is preferably used.

The phosphors 16 and 17 are dispersed in the resin 15. The phosphor 16 is a green phosphor that emits green secondary light having a longer wavelength than the primary light (peak wavelength is 500 nm or more and 550 nm or less), and is made of, for example, a Eu-activated β sialon phosphor material. On the other hand, the phosphor 17 is a red phosphor that emits red light having a longer wavelength than the primary light (peak wavelength is 600 nm or more and 780 nm or less). For example, the phosphor 17 is made of a phosphor material mixed with CaAlSiN3: Eu. Become. By using such phosphors 16 and 17, it is possible to obtain a three-wavelength type LED 10 having good color rendering properties.

In the LED 10 configured as described above, as the primary light emitted from the LED chip 12 passes through the resin 15, a part thereof is converted into secondary light by exciting the phosphors 16 and 17. The outgoing light (combined light) in which the primary light and the secondary light are mixed is radiated to the outside as substantially white light.

FIG. 5 is a graph showing the emission spectrum of the LED 10, where the vertical axis represents intensity (arbitrary unit) and the horizontal axis represents wavelength (nm).

As shown in FIG. 5, the emission spectrum of the three-wavelength type LED 10 is distributed so as to have peaks in blue, green and red, and the peak of blue light is the largest. The LED 10 uses specific phosphors 16 and 17 that are excited by blue light having a wavelength in the range of 430 to 480 nm in the primary light and emit light with high efficiency. Thereby, the light-emitting device 5 (LED10) which has the spectral characteristic adjusted according to the transmission characteristic of the liquid crystal display devices 1 and 2 can be obtained.

[LED classification device]
FIG. 6 is a block diagram showing the configuration of the LED classification device 21.

The LED classification device 21 shown in FIG. 6 realizes the LED classification method of this embodiment for classifying whether the LED 10 used as the light-emitting device 5 is a light-emitting device 5 suitable for the backlights 3 and 8. Used for. The LED classification device 21 includes a memory 22, a storage unit 23, a display unit 24, and an arithmetic processing unit 25 in order to classify the LEDs 10.

[Configuration of memory, storage unit and display unit]
The memory 22 is a volatile memory that temporarily stores a characteristic measurement value of the LED 10 from the LED characteristic measurement device 31 and temporarily stores calculation data generated by calculation processing by the calculation processing unit 25. The characteristic measurement values are stored in the memory 22 in a state in which codes assigned to the respective LEDs 10 are associated with each other so that the LEDs 10 can be identified with respect to the total number of the LEDs 10 to be classified. The LED characteristic measuring device 31 is a device that measures the characteristics of the LED 10, and measures the chromaticity, peak wavelength, and the like of each LED 10 in a state where a large number of LEDs 10 emit light, and outputs the measured values as characteristic measured values.

The storage unit 23 is a storage device that stores the classification result of the LED 10 obtained by the arithmetic processing of the arithmetic processing unit 25, and includes a hard disk device or the like.

The display unit 24 is a display device for displaying the above classification result.

[Configuration of arithmetic processing unit]
The arithmetic processing unit 25 performs processing for classifying the LEDs 10 based on the characteristic measurement values from the LED characteristic measurement device 31. The arithmetic processing unit 25 uses the following arithmetic expression to correct the chromaticity (x, y) of the emitted light from the LED 10 assuming that the emitted light from the LED 10 has passed through the color filter 7 (blue filter). Correction to chromaticity (x1, y1) (chromaticity correction means). Further, the arithmetic processing unit 25 performs chromaticity rank classification of the LED 10 based on the corrected chromaticity (x1, y1). Or the arithmetic processing part 25 performs chromaticity rank classification | category of LED10 based on the output chromaticity (xd, yd) about the light output from the liquid crystal panel 4 (display) previously calculated | required by simulation.

Note that, assuming that the light has passed through the color filter 7 (blue filter), correction is performed in consideration of a change in chromaticity until the light emitted from the light emitting device 5 passes through the liquid crystal panel 4. This change in chromaticity is caused when the emitted light from the light emitting device 5 is transmitted through optical members such as a diffusion plate, an optical sheet, and a light guide plate, the color filter 7 (blue filter), and the liquid crystal panel 4. Is a change in chromaticity of transmitted light with respect to. Thereby, the said correction | amendment becomes more preferable correction | amendment matched with the display in the actual liquid crystal panel 4. FIG.

In the present embodiment, as described above, the correction of the transmission characteristic of the color filter 7 is the correction of the transmission characteristic of the blue filter. As described in the problem to be solved by the invention, this is because the deviation of the peak wavelength of the blue light component in the light emitted from the light emitting device 5 is large at the mass production level of the light emitting device 5. This is because the chromaticity of the emitted light greatly affects the deviation before and after transmission through the color filter 7. On the other hand, by correcting the transmission characteristics of the red filter and the green filter, it is possible to perform correction in accordance with the actual display on the liquid crystal panel 4. However, the method of only correcting the transmission characteristics of the blue filter can be said to be a simple method of correcting the measurement data of the light emitting device 5 by a simple correction formula as will be described later. Moreover, since this correction method can eliminate the rank classification regarding the blue light peak, the characteristic classification items (management characteristic items) of the light emitting device 5 can be reduced.

x1 = x−α × (λp−λ0)
y1 = y−β × (λp−λ0)
In the above arithmetic expression, λp is a measured value of the peak wavelength of the blue light component in the light emitted from the LED 10. The influence of blue light on the chromaticity affects not only the peak wavelength but also the spectral shape. Therefore, this measured value is not the maximum point of the emission intensity, but a measured value of the dominant wavelength (main wavelength) to which the emission spectrum shape is added. The dominant wavelength is measured, for example, by measuring the dominant wavelength as blue monochromatic light by extracting an emission spectrum of 480 nm or less. This measurement takes into account the influence of the blue LED light in the light emitting device 5 being absorbed by the phosphor.

Λ0 is the center value (reference wavelength) of the measured value of this peak wavelength, and is set in the range of 445 nm to 450 nm, preferably about 448 nm. The reference wavelength λ0 is, for example, a specific wavelength determined based on the user's request. The LED 10 is manufactured so that the peak wavelength λp becomes the reference wavelength λ0, but actually the peak wavelength λp varies in the range of 442 nm to 452 nm.

Α and β are coefficients (wavelength correction coefficients for chromaticity), and are set in the range of 0 to 0.01.

The chromaticity (x, y) and the peak wavelength λp are acquired from the LED characteristic measurement device 31 as characteristic measurement values of the LED 10.

The arithmetic processing unit 25 includes a coefficient calculation unit 26 (chromaticity prediction unit), a corrected chromaticity calculation unit 27 (chromaticity prediction unit), and a chromaticity rank classification unit 28 in order to realize the above processing. .

<Configuration of coefficient calculation unit>
The coefficient calculation unit 26 (coefficient calculation means) stores the coefficient α of the arithmetic expression based on the chromaticity (x, y) and the peak wavelength λp as the characteristic measurement value stored in the memory 22 as the characteristic measurement value. And the coefficient β is calculated. Specifically, the coefficient calculation unit 26 performs the following processing. FIG. 7 is a diagram for explaining the processing, and the change in chromaticity after transmission of the blue light through the color filter with respect to the shift amount of the peak wavelength from the reference wavelength of the peak wavelength of the blue light from the LED 10 to be classified. It is a graph which shows quantity.

As shown in FIG. 7, the coefficient calculation unit 26 includes straight lines Lx connecting two points respectively specified by two different peak wavelengths λp of the LEDs 10 and two change amounts Δx and Δy corresponding to these peak wavelengths λp. , Ly are obtained as coefficients α, β and stored in the memory 22. By using such coefficients α and β, the amounts of change Δx and Δy with respect to the shift amount of an arbitrary peak wavelength λp from the reference wavelength λ0 can be linearly obtained using the straight lines Lx and Ly.

<Configuration of correction chromaticity calculation unit>
The correction chromaticity calculation unit 27 (correction chromaticity calculation means) applies the coefficients α and β stored in the memory 22 to the arithmetic expression, and calculates the peak wavelength λp for all the LEDs 10 read from the memory 22. Thus, the corrected chromaticity (x1, y1) is calculated. The corrected chromaticity calculation unit 27 stores the calculated corrected chromaticity (x1, y1) in the memory 22.

(Λp−λ0) in the arithmetic expression is a difference (wavelength shift amount) between the peak wavelength λp and the reference wavelength λ0, and as shown in FIG. 7, chromaticity change amounts Δx and Δy with respect to the wavelength shift amount are linear. Approximately obtained. A correction value for chromaticity (x, y) can be obtained by multiplying the wavelength shift amount by the above-mentioned coefficients α and β. Then, the corrected chromaticity (x1, y1) is obtained by subtracting the correction value from the chromaticity (x, y) read from the memory 22.

<Configuration of chromaticity rank classification unit>
The chromaticity rank classification unit 28 (chromaticity rank classification means) reads the corrected chromaticity (x1, y1) from the memory 22, and performs the chromaticity rank classification of the LED 10 based on the corrected chromaticity (x1, y1). . FIG. 8 is a diagram illustrating an example of such chromaticity rank classification. As shown in FIG. 8, the chromaticity rank classification unit 28 classifies the LEDs 10 based on whether or not the corrected chromaticity (x1, y1) is distributed within a rectangular frame F within a predetermined range, and stores the result. The unit 23 is stored in a state associated with the code of the LED 10. Further, the chromaticity rank classification unit 28 causes the display unit 24 to display the classification result of the LED 10 stored in the memory 22 as the LED 10 to be selected together with the code.

The above frame F is divided into finer ranges, and is configured so that the chromaticity can be ranked for each division. Within this frame F, the corrected chromaticity (x1, y1) of the group of LEDs 10 having a short blue light wavelength is distributed in a range D1 indicated by a solid line. In the range D1, the peak wavelength is 444.7 nm, and the chromaticity average value AVE1 is at the position indicated by the solid line circle. On the other hand, in the frame F, the chromaticity of the group of LEDs 10 having a long blue light wavelength is distributed in a range D2 indicated by a broken line. In the range D2, the peak wavelength is 446.2 nm, and the average value AVE2 of chromaticity is at a position indicated by a broken-line circle.

<Configuration of chromaticity simulator>
The chromaticity rank classification unit 28 may perform the chromaticity rank classification of the LEDs 10 based on a predicted value (simulation value) obtained by predicting (simulating) the chromaticity of light transmitted through the liquid crystal panel 4 by the chromaticity simulator 32. . This eliminates the need to calculate the coefficients α and β and the corrected chromaticity (x1, y1).

The above simulation values are obtained by the chromaticity simulator 32 (chromaticity prediction means) shown in FIG. 6 on the basis of several peak wavelengths λp (dominant wavelengths) assumed in advance, and are associated with the peak wavelengths λp. Prepared in the form of a table. Thereby, the chromaticity rank classification | category part 28 performs chromaticity rank classification | category of LED10 based on the simulation value read from the table based on the peak wavelength (lambda) p actually measured. The chromaticity simulator 32 is included in the LED classification device 21.

The chromaticity simulator 32 performs transmission characteristics of optical members such as a diffusion plate, an optical sheet, and a light guide plate, and a color filter 7 (blue filter) with respect to spectrum data (specific measurement values) measured by the LED characteristic measurement device 31. The output chromaticity (xd, yd) on the display is calculated by a simulation considering the above.

Here, the above-described corrected chromaticity (x1, y1) is completely different from the output chromaticity (xd, yd). The reason will be described below.

The corrected chromaticity (x1, y1) is the chromaticity corrected to perform the chromaticity rank classification of the LED 10, and only the above-described changes Δx and Δy due to the difference in the wavelength of the LED 10 are reflected. On the other hand, output chromaticity (xd, yd) is chromaticity on the display.

The corrected chromaticity (x1, y1) and the output chromaticity (xd, yd) are related by the following equation. The following expression is an approximate expression because the corrected chromaticity (x1, y1) is approximated linearly.

xd≈x1 + Sx0
= X−α × (λp−λ0) + Sx0
yd≈y1 + Sy0
= Y-α × (λp-λ0) + Sy0
In the above equation, Sx0 is a constant and is expressed as a shift amount of chromaticity x when λp = λ0 (difference between chromaticity x on the display and chromaticity x of LED 10). This shift amount is about 2 / 100-3 / 100. Sy0 is a constant and is expressed as a shift amount of chromaticity y when λp = λ0 (difference between chromaticity y on the display and chromaticity y of LED 10). This shift amount is a value of about 5 / 100-6 / 100.

The form for providing the simulation value is not limited to the above example, and various forms can be applied.

<Realization form of arithmetic processing unit>
Each block of the coefficient calculation unit 26, the corrected chromaticity calculation unit 27, and the chromaticity rank classification unit 28 in the arithmetic processing unit 25 is realized by software (LED classification program) using a CPU as follows. That is, the LED classification program causes the computer to function as the LED classification device 21 (the coefficient calculation unit 26, the corrected chromaticity calculation unit 27, and the chromaticity rank classification unit 28).

Or each said block may be comprised by a hardware logic, and may be implement | achieved by the process by the program using DSP (Digital * Signal * Processor).

The program code (execution format program, intermediate code program, source program) of the above software may be recorded on a computer-readable recording medium. The object of the present invention can also be achieved by supplying the recording medium to the LED classification device 21 and reading and executing the program code recorded on the recording medium by the CPU.

Examples of the recording medium include magnetic tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, and optical disks such as CD-ROM / MO / MD / BD / DVD / CD-R. Can be used. In addition, as the recording medium, a card system such as an IC card (including a memory card) / optical card or a semiconductor memory system such as a mask ROM / EPROM / EEPROM (registered trademark) / flash ROM can be used. .

Alternatively, the LED classification device 21 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Further, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

[LED classification processing by LED classification device]
The classification processing of the LEDs 10 by the LED classification device 21 will be described with reference to the flowchart of FIG. FIG. 9 is a flowchart showing the procedure of the classification process.

As shown in FIG. 9, first, the characteristic measurement values from the LED characteristic measurement device 31 are acquired for the total number of LEDs 10 to be classified, and stored in the memory 22 (step S1). In addition, coefficients α and β are calculated in advance based on simulation using the acquired characteristic measurement values (coefficient calculation process, chromaticity correction process). At this time, the coefficient calculation unit 26 determines the slopes of the straight lines Lx and Ly connecting the two points as the coefficients α and β as described above.

Next, the corrected chromaticity (x1, y1) is calculated using the above-described arithmetic expression and the above-described coefficients α, β (step S2: corrected chromaticity calculating step, chromaticity correcting step). At this time, the corrected chromaticity calculation unit 27 calculates the corrected chromaticity (x1, y1) using the measured chromaticity (x, y) and the peak wavelength λp for the total number of LEDs 10 to be classified.

Then, the chromaticity rank classification of the LED 10 is performed based on the corrected chromaticity (x1, y1) (step S3: chromaticity rank classification process). At this time, the chromaticity rank classification unit 28 performs the chromaticity rank classification of the LEDs 10 depending on whether or not the correction chromaticity (x1, y1) is distributed within the frame F shown in FIG. If the corrected chromaticity (x1, y1) is within a predetermined range by this chromaticity rank classification, the LED 10 indicating the corrected chromaticity (x1, y1) is classified as an object to be used for the backlights 3 and 8.

Further, when the output chromaticity (xd, yd) described above is used, although not shown, the processing is performed according to the following procedure.

First, the characteristic measurement values from the LED characteristic measurement device 31 are acquired for the total number of LEDs 10 to be classified and stored in the memory 22 as in step S1. Further, the output chromaticity (xd, yd) is calculated in advance by the simulation by the chromaticity simulator 32. Then, the chromaticity rank classification of the LED 10 is performed based on the output chromaticity (xd, yd).

[Effects of LED classification device]
As described above, the LED classification device 21 corrects the chromaticity (x, y) after transmission through the color filter 7 as the corrected chromaticity (x1, y1) by the arithmetic processing unit 25, and this corrected chromaticity (x1) , Y1), the chromaticity rank classification of the LED 10 is performed.

Thereby, for the LED 10 whose peak wavelength λp is shifted to the longer side, the corrected chromaticity (x1, y1) is calculated so that the chromaticity (x, y) is shifted to blue (the lower chromaticity). (Reference: Average value AVE2 in FIG. 8). On the other hand, the corrected chromaticity (x1, y1) is calculated so that the chromaticity (x, y) shifts to yellow (the higher chromaticity) for the LED 10 whose peak wavelength λp is shifted to the shorter one ( Reference: Average value AVE1 in FIG.

Then, by using the corrected chromaticity (x1, y1) corrected in this way, a decrease in the intensity of blue light (shift amount) by the color filter 7 can be predicted and the chromaticity rank classification of the LED 10 can be performed. it can.

Alternatively, the chromaticity rank classification of the LED 10 can be similarly performed using the above-described output chromaticity (xd, yd).

By mounting the LEDs 10 selected based on the chromaticity rank classification on the backlights 3 and 8 in the liquid crystal display devices 1 and 2, it is possible to suppress variations in luminance of the blue light in the liquid crystal panel 4. it can. In particular, when the light emitted from the LED 10 having a short peak wavelength λp is transmitted through the liquid crystal panel 4 (color filter 7), the blue light component is largely cut by the color filter 7 and the chromaticity is shifted to the yellow side. Therefore, by performing the above chromaticity correction, it is possible to perform chromaticity rank classification more appropriate as a light source for a liquid crystal panel.

In addition, since the yield is low if only the LED 10 having the center rank in the frame F shown in FIG. 8 is used, the LED 10 having high and low chromaticity distribution is also used. This employs a known arrangement rule in which the LEDs 10 having greatly different chromaticities are arranged adjacent to each other to average the chromaticity of the entire liquid crystal panel 4.

[Additional Notes]
Since the LED 10 including the phosphors 16 and 17 has a shape in which the emission spectrum also includes a phosphor color component, the LED characteristic measurement device 31 can obtain the wavelength of blue light by measuring the peak wavelength. However, since the measurement of the peak wavelength is likely to cause noise, an error is likely to occur. In order to suppress the influence of noise, the LED characteristic measuring device 31 specifies a wavelength range from 400 nm until the phosphor color component does not appear on the long wavelength side, and calculates the dominant wavelength (main wavelength) in this wavelength range. do it. As described above, for example, a dominant wavelength as blue monochromatic light is measured by extracting an emission spectrum of 480 nm or less. This measurement takes into account the influence of the blue LED light in the light emitting device 5 being absorbed by the phosphor.

In addition, although this embodiment demonstrated the classification | category of LED10 containing a green fluorescent substance and a red fluorescent substance, the fluorescent substance which LED10 contains is not limited to this. For example, instead of the green phosphor and the red phosphor, a yellow phosphor that is excited by blue light of a blue LED may be included. Thereby, pseudo white can be obtained by mixing the blue light of the blue LED and the yellow light of the yellow phosphor.

In this embodiment, the LED characteristic measuring device 31 is provided outside the LED classification device 21, but may be provided as a part of the LED classification device 21.

<< Embodiment 2 >>
Another embodiment according to the present invention will be described below with reference to FIGS.

In the present embodiment, components having functions equivalent to those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

[Liquid Crystal Display]
[Configuration of liquid crystal display device]
FIG. 14 is a perspective view showing a schematic configuration of the liquid crystal display device 41 according to the present embodiment.

As shown in FIG. 14, the liquid crystal display device 41 includes a backlight 42 and a liquid crystal panel 4.

The backlight 42 is disposed on the back side of the liquid crystal panel 4 and is an edge light type backlight that irradiates light on the entire surface of the liquid crystal panel 4, and includes a light guide plate 6 and LED bars 43 and 44.

The LED bars 43 and 44 are linear light sources and are arranged adjacent to the end of the light guide plate 6 where light on at least one side is incident. The LED bars 43 and 44 are arranged on the lower side in the example shown in FIG. The LED bar 43 is disposed on the right side of the liquid crystal display device 41 and the LED bar 44 is disposed on the left side.

The LED bars 43 and 44 are each composed of a plurality of light emitting devices 5 and a substrate 45.

The substrate 45 is formed in an elongated strip shape (linear shape), and has a width that is slightly wider than the outer size (width) of the light emitting device 5. The substrate 45 is provided with a printed wiring (not shown) for supplying power to the light emitting device 5 on a mounting surface on which the light emitting device 5 is mounted. Further, a positive terminal and a negative terminal (not shown) connected to the printed wiring are provided at both ends or one end of the substrate 45. The light emitting device 5 is supplied with power by connecting wiring for supplying power from the outside to the positive terminal and the negative terminal.

The light emitting device 5 is a white LED, and is mounted on the substrate 45 at a predetermined interval so as to emit light toward the light guide plate 6 side. As this white LED, the chromaticity rank is classified based on the corrected chromaticity (x1, y1) obtained by the LED classification device 21 as in the white LED used in the liquid crystal display devices 1 and 2 of the first embodiment. The aforementioned LED 10 is used.

The light guide plate 6 has a structure in which light can be extracted from each part of the light emitting surface so that linear light incident from the LED bars 43 and 44 is emitted in a planar shape.

In the liquid crystal display device 41, the two LED bars 43 and 44 are used as the light source of the backlight 42, but three or more LED bars may be used.

[Attenuation of blue component of light by light guide plate]
FIG. 15 is a diagram showing the distribution of the blue component of light in different regions of the liquid crystal panel 4 of each light emitted from the LED bars 43 and 44. 16A is a graph showing an emission spectrum of light from the LED bar 43 corresponding to the distribution of the blue component shown in FIG. 15, and FIG. 16B is a graph showing the distribution of the blue component shown in FIG. 4 is a graph showing an emission spectrum of light from the LED bar 44. FIG. 17 is a graph showing the relationship between the distance from the LED bars 43 and 44 and the height of the peak of the blue component of the light from these LED bars 43 and 44.

The general light guide plate including the light guide plate 6 has a transmittance characteristic that absorbs the blue component of light as the distance from the light source increases. For this reason, the light emitted from the LED bars 43 and 44 and traveling through the light guide plate 6 gradually attenuates the blue component.

Here, as shown in FIG. 15, the wavelength at which the intensity of the blue component of the light emitted from the LED bar 43 reaches a peak (blue peak wavelength) is 451.5 nm, and the blue peak wavelength of the light emitted from the LED bar 44 is 441. 5 nm.

The light emitted from the LED bar 43 passes from the area A1 close to the LED bar 43 to the central area B1 of the liquid crystal panel 4 (display surface), and the area C1 far from the LED bar 43 (near the opposite side where the LED bar 43 is disposed). The peak value (blue peak) of the intensity of the blue component is attenuated in the process of proceeding to (). As shown in FIG. 16A, the blue peak is highest in the region A1, slightly lower in the region B1, and lowest in the region C1.

On the other hand, the light emitted from the LED bar 44 passes from the region A2 close to the LED bar 44 to the region B2 in the central portion of the liquid crystal panel 4, and the region C2 far from the LED bar 44 (region on the opposite side where the LED bar 44 is disposed). ) The blue peak attenuates in the process of going to). As shown in FIG. 16B, the blue peak is the highest in the region A2, slightly lower in the region B2, and lowest in the region C2.

Thus, the amount of attenuation of the light emitted from the LED bars 43 and 44 varies depending on the distance L from the LED bars 43 and 44.

The central portion of the liquid crystal panel 4 is the center between the light incident side end of the light guide plate 6 (the end on the arrangement side of the LED bars 43 and 44) and the end facing the end. It shall correspond to the area | region of the predetermined range containing.

As shown in FIG. 17, the height of the blue peak of the light emitted from the LED bar 43 (blue peak wavelength 451.5 nm) and the light emitted from the LED bar 44 (blue peak wavelength 441.5 nm) The amount of attenuation differs according to the distance from 43 and 44. In FIG. 17, the horizontal axis represents the relative distance from the LED bars 43 and 44, the position closest to the LED bars 43 and 44 is represented by “0”, and the position farthest from the LED bars 43 and 44 is represented. It is represented by “10”. The vertical axis represents the relative height of the blue peak, with the minimum value represented by “0” and the maximum value represented by “100”.

As shown in FIG. 17, the height of the blue peak of the light from the LED bars 43 and 44 is the maximum value at a distance from the LED bars 43 and 44 (hereinafter simply referred to as “distance”) “0”. . However, the height of the blue peak of the light from the LED bar 43 decreases to about “90” at the distance “10”, whereas the height of the blue peak of the light from the LED bar 44 is the distance “10”. It falls below “80”.

As described above, the height of the blue peak is greatly attenuated as the blue peak wavelength is shorter.

[Adjustment of chromaticity]
18A and 18B show the chromaticity correction so that the chromaticity difference between the two systems of transmitted light from the LED bars 43 and 44 transmitted through the central portion (areas B1 and B2) of the liquid crystal panel 4 is eliminated. It is a graph which shows the relationship between the distance from LED bar 43,44 using the LED10 made, and the chromaticity x and chromaticity y of said two lights, respectively. 19A and 19B, the chromaticity correction is performed so that the chromaticity difference between the two systems of light emitted in the regions (regions A1 and A2) near the LED bars 43 and 44 in the liquid crystal panel 4 is eliminated. 4 is a graph showing the relationship between the distance from the LED bars 43 and 44 using the LED 10 and the chromaticity x and chromaticity y of the two lights.

18 and 19, as in FIG. 17, the horizontal axis represents the relative distance from the LED bars 43 and 44, and the position closest to the LED bars 43 and 44 is represented by “0”. The position farthest from the LED bars 43 and 44 is represented by “10”. In the following description, the distance from the LED bars 43 and 44 represented by the horizontal axis is simply referred to as “distance”.

Usually, the line of sight of a person with respect to the liquid crystal display device 41 is often concentrated in the central portion of the screen. Therefore, as shown by a one-dot chain line in FIG. 15, the light appearing in the central portion (regions B1 and B2) in the liquid crystal panel 4 It is preferable to eliminate the chromaticity difference. For this reason, the chromaticity correction and chromaticity rank classification according to the first embodiment are eliminated for the LED 10 in which the LED 10 is mounted on the LED bars 43 and 44 so that the chromaticity difference between the two systems of light emitted in the regions B1 and B2 is eliminated. The LED 10 in which the above is performed is used.

Thereby, as shown in FIGS. 18A and 18B, the chromaticities x and y of the light appearing at the position of the distance “5” corresponding to the centers of the regions B1 and B2 match.

However, when the LED 10 subjected to chromaticity correction and chromaticity rank classification as described above is mounted on the LED bars 43 and 44, the following inconvenience occurs.

In the areas A1 and A2 (distance “0” to “4”) close to the LED bars 43 and 44, as shown in FIGS. 18A and 18B, the light emitted from the LED bars 43 and 44, respectively. The difference between the chromaticities x and y of the light increases. In particular, at the distance “0”, the chromaticity difference of light becomes maximum. This is because in regions A1 and A2, the longer the blue peak wavelength, the higher the chromaticity, and the shorter the blue peak wavelength, the lower the chromaticity.

For this reason, as shown in FIG. 15, a chromaticity difference is generated between the lights appearing in the areas A1 and A2, and the boundary of chromaticity becomes visible at the boundary between the areas A1 and A2. This phenomenon is seen when the difference between the blue peak wavelengths of the LED bars 43 and 44 is 7.5 nm or more.

In addition, the blue peak wavelength of LED bar 43,44 here is an average value of the blue peak wavelength of all the light-emitting devices 5 (LED10) mounted in LED bar 43,44, respectively.

In order to avoid such inconvenience, if the chromaticities x and y of the light appearing in the areas A1 and A2 coincide with each other rather than the areas B1 and B2, the chromaticity difference generated in the boundary portion between the areas A1 and A2 is reduced. Can be relaxed. More preferably, as shown in FIGS. 19A and 19B, it appears at a position slightly closer to the LED bars 43 and 44 than the areas B1 and B2 (for example, a position at a distance “4” in the areas A1 and A2). It is only necessary that the chromaticities x and y of light match.

Thereby, the chromaticity difference generated at the boundary between the areas A1 and A2 can be made inconspicuous.

Also, the position where the chromaticity matches as described above is preferably set as follows. Specifically, as shown in FIG. 15, the distance between the end of the light guide plate 6 on the light incident side and the center of the light guide plate 6 (more specifically, the center of the regions B1 and B2). It is a position separated by a distance of 40% or more and less than 50% of L1. Thereby, the chromaticity difference which arises in the boundary part between area | region A1, A2 can be almost eliminated.

In addition, the difference in blue peak wavelength between the LED bars 43 and 44 was 7.5 nm or more, and the chromaticity boundary was seen. If the difference was 10 nm or less, the wavelength difference was such that the chromaticity boundary could not be seen. Can be relaxed. Thereby, the LED bar 43 whose blue peak wavelength is 451.5 nm and the LED bar 44 whose blue peak wavelength is 441.5 nm can be combined.

Further, as will be described below, the chromaticity difference generated at the boundary between the regions B1 and B2 can be made inconspicuous.

When the positions where the chromaticities of the light beams emitted from the LED bars 43 and 44 and output from the liquid crystal panel 4 match are shifted from the central portion of the liquid crystal panel 4 toward the LED bars 43 and 44 as described above, Since the chromaticity of each light in the portion is shifted, a chromaticity difference is generated. However, if the chromaticity difference is 3/1000 or less for chromaticity x and y, respectively, it is difficult for humans to recognize the chromaticity boundary due to the chromaticity difference. Conversely, if the above chromaticity difference is greater than 3/1000 for each of the chromaticity x and y, humans can easily recognize the chromaticity boundary due to the chromaticity difference.

Further, by shifting the position where the chromaticity matches as described above toward the LED bars 43 and 44, the chromaticity difference increases between the regions C1 and C2 far from the LED bars 43 and 44. However, in the areas C1 and C2, the light from the LED bars 43 and 44 mixes (mixes colors) with each other by spreading while traveling through the light guide plate 6. For this reason, the chromaticity boundary is not visible at the boundary between the regions C1 and C2, so that the color unevenness between the regions C1 and C2 is not noticeable.

In addition, it is necessary to provide many LED bars of the same type as the LED bars 43 and 44 as the screen size of the liquid crystal display device 41 is larger. Therefore, making the chromaticity boundary of transmitted light inconspicuous in the region near the LED bar as described above is effective in improving image quality as the screen size increases.

(Chromaticity correction)
In order to shift the position where the chromaticity matches as described above toward the LED bars 43 and 44, the coefficients α and β used by the coefficient calculation unit 26 to obtain the corrected chromaticity (x1, y1) are Set to a value smaller than the value when the chromaticity matches at the center. For example, the coefficient calculation unit 26 changes the coefficients αn and βn when shifting the position where the chromaticity matches with respect to the coefficients αm and βm when the chromaticity matches in the central portion as follows.

αn = αm × 0.75
βn = βm × 0.75
As a result of the correction chromaticity calculation unit 27 calculating using these coefficients αn and βn, the obtained correction chromaticity (x1, y1) is slightly larger than the value when the chromaticity matches in the central portion. Therefore, as shown in FIGS. 19 (a) and 19 (b), two systems of light radiated at a distance “4” closer to the LED bars 43 and 44 than a position “center” (distance “5”). The chromaticities x and y can be matched.

[Additional Notes]
In the present embodiment, the LED bars 43 and 44 are disposed on the lower side (lower side) of the light guide plate 6, but are not limited thereto, and may be disposed on one of the left and right sides or the upper side of the liquid crystal panel 4. Further, LED bars may be provided on the two opposite sides of the light guide plate 6. Thereby, the boundary of chromaticity near the LED bar can be made inconspicuous on both sides, which is preferable to the configuration in which the LED bar is provided on one side of the light guide plate 6.

Further, the liquid crystal display device 41 produces good results particularly under the following conditions.

LED10 size: 4-8mm × 1-4mm
The pitch of the LEDs 10 in the LED bars 43 and 44: 0.5 to 2.0 cm
LED bars 43 and 44 length: 30 to 100 cm (for screen size 31 to 100 inches of liquid crystal display device 41)
Needless to say, the present invention is not limited to the above conditions.

[Summary]
An LED classification method according to an aspect of the present invention includes an LED element (LED chip 12) that emits primary light and a phosphor that emits secondary light having a longer wavelength than the primary light when excited by the primary light. If the chromaticity of the primary light of the LED (LED 10) that emits the combined light of the primary light and the secondary light by combining the LED chips 16, 17) is within a predetermined range, the LED is An LED classification method for classifying as an object to be used for a backlight ( backlight 3, 8, 42) of a liquid crystal display device (liquid crystal display device 1, 2, 41), wherein the primary light is provided in the liquid crystal display device A chromaticity prediction step (a coefficient calculation unit 26 and a corrected chromaticity calculation unit 27 or a chromaticity simulator 3) that predicts the chromaticity transmitted through the color filter in the liquid crystal panel for all the LEDs to be classified. ) And, and a chromaticity rank classification step of the LED chromaticity rank classification based on the predicted chromaticity (chromaticity rank classification section 28).

In addition, the LED classification device (LED classification device 21) according to one aspect of the present invention has an LED element (LED chip 12) that emits primary light and is excited by the primary light and has a longer wavelength than the primary light. The chromaticity of the primary light of the LED (LED 10) that emits the combined light of the primary light and the secondary light by combining the phosphors (LED chips 16, 17) that emit secondary light is within a predetermined range. An LED classification device for classifying the LED as an object to be used for a backlight ( backlight 3, 8, 42) of a liquid crystal display device (liquid crystal display device 1, 2, 41). Chromaticity prediction means (coefficient calculation unit 26 and correction chromaticity calculation) that predicts the chromaticity of light transmitted through a color filter in a liquid crystal panel provided in the liquid crystal display device for the total number of LEDs to be classified. 27 or chromaticity simulator 32), and a chromaticity rank classification means for chromaticity rank classifying the LED based on the predicted chromaticity (chromaticity rank classification section 28).

In the above configuration, the chromaticity assuming that the primary light has passed through the color filter is predicted by the chromaticity prediction step or the chromaticity prediction means. Then, the chromaticity rank classification step or the chromaticity rank classification means classifies the LEDs based on the predicted chromaticity.

By performing the chromaticity rank classification using the chromaticity predicted in this way, it is possible to predict the amount of change in light intensity due to the color filter and more appropriately classify the LEDs into the chromaticity rank classification. By mounting the LEDs selected based on the chromaticity rank classification on each backlight in the liquid crystal display device, it is possible to suppress variation in luminance of light transmitted from the backlight through the color filter.

In the LED classification method, the chromaticity prediction step calculates a correction value of the chromaticity due to transmission of the primary light through the color filter for all the LEDs to be classified, and classifies based on the correction value. A chromaticity correction step of correcting the chromaticity as a correction chromaticity for the total number of the target LEDs, wherein the chromaticity correction step transmits the primary light having a predetermined reference wavelength through the color filter. The reference chromaticity at the time when the chromaticity is changed and the change amount of the chromaticity with respect to the reference chromaticity are calculated, and the inclination of the change amount relative to the shift amount of the peak wavelength of the primary light from the reference wavelength is corrected for the chromaticity A coefficient calculation step (coefficient calculation unit 26) that calculates the coefficient of the value; and the correction value is calculated by multiplying the difference between the peak wavelength and the reference wavelength by the coefficient, and the correction value is divided. Preferably it contains a correction chromaticity calculating step of calculating the corrected chromaticity by subtracting from each of the chromaticity obtained on the LED of the total number of interest (correcting chroma calculating unit 27).

Further, in the LED classification device, the chromaticity prediction means calculates a correction value of the chromaticity due to transmission of the primary light through the color filter for the total number of LEDs to be classified, and based on the correction value. A chromaticity correction unit that corrects the chromaticity as a correction chromaticity for the total number of LEDs to be classified, and the chromaticity correction unit receives the primary light having a predetermined reference wavelength as the color. A reference chromaticity when passing through the filter and a change amount of the chromaticity with respect to the reference chromaticity are calculated, and an inclination of the change amount with respect to a shift amount of a peak wavelength of the primary light from the reference wavelength is calculated. A coefficient calculating means (coefficient calculating unit 26) that calculates the coefficient of the degree of correction value, and the correction value is calculated by multiplying the difference between the peak wavelength and the reference wavelength by the coefficient; Correction chromaticity calculation means (correction chromaticity calculation unit 27) for calculating the correction chromaticity by subtracting from the chromaticity obtained for the total number of LEDs to be classified. preferable.

In the above configuration, the chromaticity correction value assuming that the primary light has passed through the color filter is calculated for the total number of LEDs to be classified by the chromaticity correction step or the chromaticity correction means, and this correction value Based on the above, the chromaticity obtained for the total number of LEDs to be classified is corrected as the corrected chromaticity. In addition, since the coefficient of the correction value is calculated based on the gradient of the amount of change in chromaticity with respect to the reference chromaticity obtained by the coefficient calculating step or the coefficient calculating means assuming that the color filter has been transmitted, 1 A change in chromaticity due to the transmission of the next light color filter is reflected in the correction value. Then, the correction chromaticity is calculated by subtracting the correction value thus obtained from the chromaticity by the correction chromaticity calculation step or the correction chromaticity calculation means.

This makes it possible to easily reflect the change in chromaticity due to the color filter in the correction of chromaticity.

In the LED classification method, in the coefficient calculation step, the backlight includes a plurality of LEDs, and a plurality of linear light sources (LED bars 43 and 44) provided adjacent to each other and incident from at least one end side. With respect to the liquid crystal display device including a light guide plate that radiates light emitted from a linear light source in a planar manner to the liquid crystal panel, an end portion on the light incident side of the light guide plate and an end portion facing the end portion The coefficient is calculated so that the emitted light from each linear light source matches the chromaticity of the transmitted light that has passed through the liquid crystal panel through the light guide plate at a position closer to the light incident side than the central portion between It is preferable to do.

Further, in the LED classification device, the coefficient calculating means includes a plurality of linear light sources provided adjacent to each other, the backlight having the plurality of LEDs, and the linear light source incident at least from one end side. For the liquid crystal display device including the light guide plate that radiates the emitted light in a planar shape to the liquid crystal panel, between the end on the light incident side of the light guide plate and the end facing the end. It is preferable to calculate the coefficient so that the emitted light from each linear light source matches the chromaticity of the transmitted light transmitted through the liquid crystal panel through the light guide plate at a position closer to the light incident side than the central portion. .

In the above configuration, the LEDs are classified into chromaticity ranks based on the corrected chromaticity calculated using the coefficient calculated as described above. By producing a linear light source using this LED, the chromaticity of the transmitted light that is transmitted from the linear light source through the light guide plate through the liquid crystal panel is the same at a position closer to the light incident side than the central portion. To do. Thereby, as described above, the boundary of chromaticity in the region close to the linear light source can be made inconspicuous.

Further, it is preferable that the coefficient calculating step and the coefficient calculating means calculate the coefficient so that a chromaticity difference of the transmitted light at the central portion is 3/1000 or less.

In the above configuration, if the chromaticity difference of the transmitted light in the central portion is 3/1000 or less, it is difficult for humans to recognize the chromaticity boundary due to the chromaticity difference. As a result, the chromaticity boundary can be made inconspicuous even in the central portion.

In the LED classification method or the LED classification device, it is preferable that the primary light is blue light.

As described above, with respect to blue light, due to the shift in peak wavelength between LEDs, the light intensity after passing through the color filter varies and affects the display color. On the other hand, as described above, the chromaticity rank is appropriately classified based on the change in the chromaticity distribution by the color filter by correcting the chromaticity by predicting the change due to the transmission of the color filter as described above. Can do.

The LED classification program according to an aspect of the present invention is a program for causing a computer to function as each unit in the LED classification apparatus. A recording medium according to an aspect of the present invention is a computer-readable recording medium that records the LED classification program. These LED classification programs and recording media are also included in the technical scope of the present embodiment.

A liquid crystal display device according to one embodiment of the present invention includes a liquid crystal panel, a plurality of linear light sources that are provided adjacent to each other, and light emitted from the linear light source that is incident at least from one end side. A light guide plate that radiates the liquid crystal panel in a planar shape, and a position closer to the light incident side than a central portion between an end on the light incident side of the light guide plate and an end facing the end Thus, the LEDs mounted on the linear light source are selected so that the emitted light from each linear light source matches the chromaticity of the transmitted light transmitted through the liquid crystal panel through the light guide plate.
Included in the enclosure.

In this configuration, since the liquid crystal display device includes the linear light source using the LEDs selected as described above, the light emitted from each linear light source passes through the light guide plate at a position closer to the light incident side than the central portion. The chromaticity of the transmitted light that has passed through the liquid crystal panel is matched. Thereby, as described above, the boundary of chromaticity in the region close to the linear light source can be made inconspicuous.

In the liquid crystal display device, the position where the chromaticity matches is a distance of 40% or more and less than 50% of the distance between the light incident side end and the central portion from the light incident side end. It is preferable that it is a separated position. Thereby, the chromaticity difference in the region close to the linear light source can be almost eliminated.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments can be appropriately combined. Embodiments are also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

The LED classification method according to the present invention corrects the chromaticity of the LED by predicting the luminance change in the state of being transmitted through the color filter, and thus can be suitably used for a liquid crystal display device using an LED as a backlight.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Liquid crystal display device 3 Backlight 4 Liquid crystal panel 5 Light-emitting device 7 Color filter 8 Backlight 10 LED
12 LED chip (LED element)
16 phosphor 17 phosphor 21 LED classification device 22 memory 23 storage unit 24 display unit 25 arithmetic processing unit 26 coefficient calculation unit (chromaticity prediction means, chromaticity correction means, coefficient calculation means)
27 Correction chromaticity calculation unit (chromaticity prediction means, chromaticity correction means, corrected chromaticity calculation means)
28 Chromaticity rank classification part (chromaticity rank classification means)
31 LED characteristic measuring device 32 Chromaticity simulator (chromaticity prediction means)
41 Liquid crystal display device 42 Backlight 43 LED bar (Linear light source)
44 LED bar (linear light source)
A1 area A2 area B1 area B2 area C1 area C2 area F Frame (predetermined range)
Sx0 constant Sy0 constant (x, y) Chromaticity (x1, y1) Correction chromaticity Δx, Δy Change amount (xd, yd) Output chromaticity α coefficient β coefficient αm coefficient βm coefficient αn coefficient βn coefficient λ0 reference wavelength λp peak wavelength

Claims (14)

1. A combined light of the primary light and the secondary light by combining an LED element that emits primary light and a phosphor that is excited by the primary light and emits secondary light having a longer wavelength than the primary light. If the chromaticity of the primary light of the LED that emits light is within a predetermined range, the LED is classified as an object to be used for a backlight of a liquid crystal display device,
   A chromaticity prediction step of predicting the chromaticity of the primary light transmitted through a color filter in a liquid crystal panel provided in the liquid crystal display device with respect to the total number of LEDs to be classified;
   And a chromaticity rank classification step of classifying the LED according to a predicted chromaticity to a chromaticity rank classification.
2. The chromaticity prediction step includes
   The correction value of the chromaticity due to the transmission of the primary light through the color filter is calculated for the total number of the LEDs to be classified, and the chromaticity is corrected for the total number of the LEDs to be classified based on the correction value. Including a chromaticity correction step of correcting as chromaticity,
   The chromaticity correction step is
   A reference chromaticity when the primary light having a predetermined reference wavelength passes through the color filter and a change amount of the chromaticity with respect to the reference chromaticity are calculated, and the primary light from the reference wavelength is calculated. A coefficient calculating step of calculating a slope of the change amount with respect to the shift amount of the peak wavelength of the chromaticity as a coefficient of the correction value;
   By calculating the correction value by multiplying the difference between the peak wavelength and the reference wavelength by the coefficient, and subtracting the correction value from the chromaticity obtained for the total number of LEDs to be classified, respectively. The LED classification method according to claim 1, further comprising a corrected chromaticity calculation step of calculating the corrected chromaticity.
3. In the coefficient calculation step,
   The backlight includes a plurality of the LEDs, and radiates light from the plurality of linear light sources provided adjacent to each other and the linear light source incident from at least one end to the liquid crystal panel in a planar shape. For the liquid crystal display device including a light guide plate,
   In the light guide plate, light emitted from each linear light source passes through the light guide plate at a position closer to the light incident side than the central portion between the end on the light incident side and the end facing the end. 3. The LED classification method according to claim 2, wherein the coefficient is calculated so that chromaticities of transmitted light transmitted through the panel match.
4. In the coefficient calculation step,
   The LED classification method according to claim 3, wherein the coefficient is calculated so that a chromaticity difference of the transmitted light in the central portion is 3/1000 or less.
5. 5. The LED classification method according to any one of claims 1 to 4, wherein the primary light is blue light.
6. A combined light of the primary light and the secondary light by combining an LED element that emits primary light and a phosphor that is excited by the primary light and emits secondary light having a longer wavelength than the primary light. If the chromaticity of the primary light of the LED that emits light is within a predetermined range, the LED classification device classifies the LED as an object used for a backlight of a liquid crystal display device,
   Chromaticity prediction means for predicting the chromaticity of the primary light transmitted through a color filter in a liquid crystal panel provided in the liquid crystal display device with respect to the total number of LEDs to be classified;
   An LED classification apparatus comprising: a chromaticity rank classification unit that classifies the LEDs according to a predicted corrected chromaticity.
7. The chromaticity prediction means includes
   The correction value of the chromaticity due to the transmission of the primary light through the color filter is calculated for the total number of the LEDs to be classified, and the chromaticity is corrected for the total number of the LEDs to be classified based on the correction value. Chromaticity correction means for correcting as chromaticity,
   The chromaticity correction means is
   A reference chromaticity when the primary light having a predetermined reference wavelength passes through the color filter and a change amount of the chromaticity with respect to the reference chromaticity are calculated, and the primary light from the reference wavelength is calculated. Coefficient calculation means for calculating the slope of the change amount with respect to the shift amount of the peak wavelength as a coefficient of the chromaticity correction value;
   By calculating the correction value by multiplying the difference between the peak wavelength and the reference wavelength by the coefficient, and subtracting the correction value from the chromaticity obtained for the total number of LEDs to be classified, respectively. The LED classification device according to claim 6, further comprising a correction chromaticity calculation unit that calculates the correction chromaticity.
8. The coefficient calculating means includes
   The backlight includes a plurality of the LEDs, and radiates light from the plurality of linear light sources provided adjacent to each other and the linear light source incident from at least one end to the liquid crystal panel in a planar shape. For the liquid crystal display device including a light guide plate,
   In the light guide plate, light emitted from each linear light source passes through the light guide plate at a position closer to the light incident side than the central portion between the end portion on the light incident side and the end portion facing the end portion. The LED classification device according to claim 7, wherein the coefficient is calculated so that chromaticities of transmitted light transmitted through the panel match.
9. The coefficient calculating means includes
   The LED classification device according to claim 8, wherein the coefficient is calculated so that a chromaticity difference of the transmitted light in the central portion is 3/1000 or less.
10. The LED classification device according to any one of claims 6 to 9, wherein the primary light is blue light.
11. An LED classification program that causes a computer to function as each means in the LED classification device according to any one of claims 6 to 10.
12. A computer-readable recording medium on which the LED classification program according to claim 11 is recorded.
13. LCD panel,
    A plurality of linear light sources having a plurality of LEDs and provided adjacent to each other;
    A light guide plate that emits the light emitted from the linear light source incident from at least one end side in a plane to the liquid crystal panel;
    In the light guide plate, light emitted from each linear light source passes through the light guide plate at a position closer to the light incident side than the central portion between the end on the light incident side and the end facing the end. The liquid crystal display device, wherein the LEDs mounted on the linear light source are selected so that chromaticities of transmitted light transmitted through the panel match.
14. The position where the chromaticity matches is a position separated from the end on the light incident side by a distance of 40% or more and less than 50% of the distance between the end on the light incident side and the central portion. The liquid crystal display device according to claim 13.

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