KR20090055023A - Flashing fluorescent lamp, backlight device, and liquid crystal display device - Google Patents

Abstract

Provided is a fluorescent lamp (2) including a fluorescent material layer (23) formed on the inner face of a glass container (21). The fluorescent material layer contains only the fluorescent material (as specified by a fluorescent material containing an activator selected from the group consisting of Sn2+, Pr3+, Eu2+, Eu3+, Ce3+ and Tb3+), which has a 90 % illumination rising time period of 5 milliseconds or less and a one-tenth residual time period of 5 milliseconds or less. This fluorescent lamp can flash quickly so that it can suppress the formation of a residual image if it is used as a backlight of the liquid crystal display device of the flashing type, in which the backlight is flashed in response to the drive of the liquid crystal.

Description

Fluorescent lamps, backlight units and liquid crystal displays for flashing lighting {FLASHING FLUORESCENT LAMP, BACKLIGHT DEVICE, AND LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a fluorescent lamp, a backlight device and a liquid crystal display device used for blinking lighting.

The lighting method of a backlight device used in a liquid crystal television or the like has been a mainstream method of always lighting a lamp (hereinafter, referred to as a conventional method), but recently, development of a method of turning on and off a lamp (hereinafter, a blinking lighting method) is in progress. have.

BACKGROUND ART The blinking lighting method is generally known as a blinking lighting method that lights up at the timing of on / off timing of a plurality of lamps arranged, and a scanning lighting method that lights up while scrolling sequentially by shifting the timing of on / off of the lamp. In any manner, there is a merit that, by combining with driving of the liquid crystal, it is possible to prevent motion blur caused during moving picture display.

That is, these blinking lighting systems are attracting attention as a means for solving the problems of liquid crystal televisions, which are generally weak in moving images. Such a flashing-lighting backlight device is disclosed in International Publication No. 04/053826, Japanese Patent Application Laid-Open No. 2004-87489, Japanese Patent Application Laid-Open No. 2003-84739, Japanese Patent Application Laid-Open No. 2002-6815, and the like. Is disclosed.

However, in the backlight device using such a blinking lighting method, it is possible to prevent some degree of motion blur caused during moving image display, but it cannot be prevented sufficiently, and it is a big problem that an afterimage remains.

As a result of the inventor's examination of this problem, it was found that the response speed of the fluorescent substance used for the fluorescent lamp which comprises a backlight apparatus also has a cause. That is, when the fluorescent lamp used in the conventional system was used for the flashing lighting system, the conclusion was reached that the above-mentioned problem occurred because the phosphor reacted slowly to the on / off input to the fluorescent lamp.

<Overview of invention>

As a result of the study of the fluorescent material of the fluorescent lamp suitable for this flashing lighting system, the present invention has been proposed since the flashing lighting fluorescent lamp, the backlight device and the liquid crystal display device which are hard to remain after image can be realized. .

An object of the present invention is to provide a fluorescent lamp for blinking, a backlight device, and a liquid crystal display device in which afterimages are hard to remain.

In order to achieve the above object, the flickering fluorescent lamp of the present invention is characterized in that a multi-wavelength phosphor composed of a plurality of phosphors having a 1/10 afterglow time of 5 msec or less is formed on the inner surface of the glass container.

Moreover, in the fluorescent lamp for blinking lighting of this invention, 90% of light emission rise time of the said fluorescent substance is 5 msec or less, It is characterized by the above-mentioned.

In the flickering lighting fluorescent lamp of the present invention, the phosphor contains an activator selected from Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , Ce ³⁺ , and Tb ³⁺ . will be.

In the flickering fluorescent lamp of the present invention, the phosphor is a multi-wavelength phosphor containing red, green, and blue phosphors, and the red phosphor is Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , green. The phosphor is characterized in that Eu ²⁺ , Ce ³⁺ , Tb ³⁺ , and the blue phosphor contains an activator selected from Eu ²⁺ .

Moreover, the backlight device of this invention is equipped with the case, the said fluorescent lamp accommodated in the said case, and the lighting circuit which can flash and light up the said fluorescent lamp, It is characterized by the above-mentioned.

Moreover, the liquid crystal display device of this invention was equipped with said backlight device and the liquid crystal panel arrange | positioned at the light emitting surface side of this backlight device, It is characterized by the above-mentioned.

According to the present invention, it is possible to realize a flickering fluorescent lamp, a backlight device and a liquid crystal display device in which afterimages hardly remain.

BRIEF DESCRIPTION OF THE DRAWINGS The figure for demonstrating the backlight device of 1st embodiment of this invention.

FIG. 2 is a diagram for explaining a cross section of the fluorescent lamp shown in FIG. 1; FIG.

3 is a view for explaining the light emission characteristics of a fluorescent lamp coated with a phosphor of Y ₂ 0 ₃ : Eu ³⁺ .

4 is a diagram for explaining the presence or absence of an afterimage when a moving image of a liquid crystal image is projected by a fluorescent lamp having a different response speed.

FIG. 5 is a diagram for explaining light emission characteristics when the lamp of Example 1 is blinked and turned on by blinking lighting; FIG.

FIG. 6 is a diagram for explaining light emission characteristics when the lamp of Comparative Example 1 is blinked and turned on by blinking lighting; FIG.

7 is a view for explaining the difference between Example 1 and Comparative Example 1. FIG.

8 is a diagram for explaining a response speed of a fluorescent lamp when various phosphors are used.

9 is a view for explaining the response speed of the fluorescent lamp when the phosphor of FIG. 8 is combined;

10 is a diagram for explaining the backlight device according to the second embodiment of the present invention.

It is a figure for demonstrating the liquid crystal display device of 3rd Embodiment of this invention.

12 is a diagram for explaining light emission obtained in the liquid crystal display of the present invention.

EMBODIMENT OF THE INVENTION Below, the backlight device using the flickering fluorescent lamp of embodiment of this invention is demonstrated with reference to drawings.

<First Embodiment>

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the backlight device of 1st Embodiment of this invention.

The backlight device BL of this embodiment is a direct type system. The case of the backlight device BL is composed of the front frame 1a and the back frame 1b. An opening surface is formed in the front frame 1a. The back frame 1b has a bottomed opening shape, and a highly reflective reflective surface is formed inside.

Inside the back frame 1b, a plurality of elongated fluorescent lamps 2 are arranged so that their respective tube axes are substantially parallel. In addition, although a cold cathode fluorescent lamp is used in this embodiment, a hot cathode fluorescent lamp, an external electrode fluorescent lamp, a flat fluorescent lamp, etc. may be sufficient, and there is no restriction | limiting in a kind, shape, size, etc.

The specific structure of the fluorescent lamp 2 is shown in FIG.

The fluorescent lamp 2 is composed of, for example, a main portion of a glass container 21 made of soft glass, and a mixed gas and mercury made of Ne and Ar are enclosed therein. Electrode mounts 22a and 22b are sealed at both ends of the glass container 21. The electrode mounts 22a and 22b are composed of electrodes 22a1 and 22b1 and bead glasses 22a2 and 22b2.

The phosphor 23 is formed on the inner surface of the glass container 21. In the present invention, it is preferable to use a phosphor having a fast response speed. 3 is a diagram for explaining the light emission characteristics of a fluorescent lamp coated with a phosphor of Y ₂ O ₃ : Eu ³⁺ . 3, the horizontal axis represents time, and the vertical axis represents voltage or current values. Waveform A of FIG. 3 is an on-off signal that is a voltage waveform for controlling on / off a fluorescent lamp, waveform B is a lamp voltage waveform, waveform C is a lamp current waveform, and waveform D is a light emission intensity of the lamp. Is an output voltage waveform obtained by photoelectric conversion with a photodiode. These waveforms are measured and displayed by an oscilloscope.

As can be seen from the figure, the fluorescent lamp 2 reacts to the on-off signal waveform A with the lamp voltage and the lamp current waveform B and C without delay, but the light emission waveform D of the lamp Reaction tends to be slow. This is the result of the response speed of the phosphor. Therefore, it is most preferable to use a phosphor having a response speed equal to that of the on-off signal A, but such a phosphor is difficult to realize.

Therefore, the inventors investigated the response speeds of various phosphors, and found that 1/10 afterglow time (the time until the brightness of the lamp became 0.1 A from 0.1 A when the maximum brightness was A) was about 1 msec to 10 msec. A wavelength fluorescent lamp was created. Then, a moving image of the liquid crystal image was projected by the fluorescent lamp, and ten subjects were tested whether or not an afterimage was felt on the moving image.

The result is shown in FIG. As can be seen from FIG. 4, it was found that when the 1/10 afterglow time was 5 msec or less, it was hardly seen as an afterimage to the human eye, and when it was 3 msec or less, it was hardly recognized as an afterimage. Incidentally, since the phosphor of Y ₂ 0 ₃ : Eu ^{3+ shown} in FIG. 3 is about 2.5 msec for both the 90% rise time and the 1/10 afterglow time, the response speed at the time of blinking lighting is fast, and the phosphor of the present invention is used. Suitable as. In most phosphors, it was found that there is a correlation between the rise of light emission and the decrease of light emission. For example, the phosphor of FIG. 3 has a 1/10 afterglow time of 2.5 msec, while the 90% emission rise time (time until the brightness of the lamp becomes 0 to 0.9 A) is also about 3 msec. That is, since the 1/10 afterglow time and the 90% emission rise time have almost the same result, the phosphor having a rapid drop in emission can be said to be a phosphor having a rapid rise in emission.

In FIG. 1, the diffusion plate 3 is disposed on the opening side of the back frame 1b. As the diffusion plate 3, it is desired to use a 50% to 85% transmittance so that the light emission unevenness can be reduced and the efficiency is not too low.

The optical sheet 4 is arrange | positioned on the diffuser plate 3. As the optical sheet 4, one sheet or a plurality of diffusion sheets, a prism sheet, or the like can be used according to the purpose.

The lighting circuit 5 is arrange | positioned at the back side of the back frame 1b. As this lighting circuit 5, what is necessary is just what fluorescent lamp 2 can flash and light, for example, PWM (Pulse Width Modulation) circuit is typical. In the case of this PWM circuit, it is preferable to turn on a lamp in the range of 50-300 Hz of frequency and 10-70% of duty ratio. In that case, of course, it is desired to set the frequency and the duty ratio so that the off period of the lamp becomes longer than the 1/10 afterglow time from the viewpoint of afterimage suppression.

Below, one specification of the Example and the comparative example of the backlight device of this invention is shown.

<Example 1>

Backlight device BL; size = 32 inches (approximately 760 mm x approximately 440 mm),

Fluorescent lamp 2; cold cathode fluorescent lamp, inner diameter = 2.0 mm, outer diameter = 3.0 mm, lamp current = 6.0 mA,

Number of uses = 16, lamp pitch = 23.8 mm, distance = 14 mm of fluorescent lamp 2 and diffuser plate 3,

Phosphor 23; Y ₂ 0 ₃ : Eu ³⁺ (R), Y ₂ Si ₅ : Tb ³⁺ (C), BaMg ₂ Al ₁₀ O ₁₇ : Eu ²⁺ (B),

Diffusion plate 3; transmittance = 60%,

Optical sheet 4; diffusion sheet, prism sheet,

Lighting circuit (5): PWM circuit, frequency = 50 Hz, duty ratio = 50%.

Comparative Example 1

Phosphor 23; Y ₂ 0 ₃ : Eu ³⁺ (R), LaPO ₄ : Ce ³⁺ , Tb ³⁺ (G), BaMg ₂ Al ₁₀ O ₁₇ : Eu ²⁺ (B),

Configuration other than the fluorescent substance 23 is the same specification as Example 1.

5 is a view for explaining the light emission characteristics when the lamp of Comparative Example 1 is blinked and turned on by blinking lighting. In these figures, the horizontal axis represents time, and the vertical axis represents voltage or current values. Waveform (A) of Figs. 5 and 6 is an on-off signal which is a voltage waveform for controlling on / off a fluorescent lamp, waveform (B) is a ramp voltage waveform, waveform (C) is a lamp current waveform, and waveform (D) is a lamp Is an output voltage waveform obtained by photoelectric conversion of the light emission intensity of the photodiode.

Comparing the light emission waveforms of Fig. 5 and Fig. 6, it can be seen that the response speed of the lamp is faster in Example 1 than in Comparative Example 1. Specifically, the 1/10 afterglow time of Example 1 was about 3 msec, and Comparative Example 1 was about 7 msec, and Example 1 was turned off quickly. In addition, also about 90% light emission rise time, Example 1 is slightly smaller than 3 msec, and Comparative Example 1 is slightly smaller than 8 msec.

In addition, when each lamp was mounted on a liquid crystal display and the moving image was illuminated, Example 1 hardly remained as an afterimage, but in Comparative Example 1, the afterimage remained and the moving image was blurred. In addition, when the liquid crystal was closed with the liquid crystal closed at the timing of the lamp off to erase the afterimage, that is, the luminance of both was compared in the state where the lamp luminance was obtained only during the period in which the lamp was on. As a result, both luminance with respect to the luminous flux of the lamp when the duty ratio was 100% were about 95% in Example 1, and about 70% in Comparative Example 1. That is, the liquid crystal display device using Example 1 felt clearly bright.

The reason for such a result is estimated as follows.

The difference between Example 1 and Comparative Example 1 is that only green phosphors having different response speeds are used for the on-off signal, as shown in FIG. 7. However, as is apparent from Figs. 5 and 6, when a three-wavelength phosphor is used, a large difference occurs in the rise and afterglow of the lamp. From this point of view, when one of the phosphors of R (red), G (green), and B (blue) has a slow response time when the lamp blinks using the fluorescent lamp 2 coated with three wavelength phosphors, It was speculated that the response speed would be slow.

Therefore, when a three-wavelength phosphor combining various phosphors was formed on a lamp and tested, it was confirmed that the phosphor having the slowest response speed determines the response speed of the three-wavelength phosphor. Therefore, in the three-wavelength fluorescent lamp for blinking lighting, it is necessary to use a combination of phosphors having a fast response speed in the entire RGB. In addition, even a four-wavelength phosphor in which phosphors such as red, green, blue, and crimson are mixed, or a multi-wavelength phosphor in which more than one phosphor is mixed, a fluorescent lamp having a fast response speed of light emission only when the response speed of all phosphors is fast. It is possible to realize.

Here, further studies by the inventors found that the response speed of the phosphor is mainly related to the activator of the phosphor. That is, the composition of the phosphor is expressed as Y ₂ 0 ₃ : Eu ^3+, and Y ₂ 0 ₃ is generally called the mother and Eu ³⁺ as the activator, but as can be seen from FIG. 8, the phosphor response The speed was found to depend almost on the Easter. Therefore, when the test was carried out by paying attention to the activator of the phosphor, if the phosphor was composed of an activator selected from Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , Ce ³⁺ , and Tb ³⁺ , 1/5 msec or less. It was found that afterglow time was easy to realize. However, since the activator of Eu ³⁺ and Tb ³⁺ has a response speed of several msec, there are also phosphors having a 1/10 afterglow time of more than 5 msec depending on the combination with the mother. Therefore, in these cases, only the phosphor whose 1/10 afterglow time is 5 msec or less is suitable for blinking lighting. On the other hand, the activators of Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , and Ce ^{3+ have} a 90% emission rise time and a 1/10 afterglow time of about 0.1 msec. Since it responds, it can be said that it is suitable for the use of flashing lighting especially. Incidentally, when a plurality of activators are used, there is a tendency for the characteristics of the activator having the slowest response speed to be obtained as the response speed of the phosphor. For example, Comparative Example 1, the green phosphor LaPO _4: In the case of Ce ^3+, Tb ^3+, but includes the response speed faster Ce ^3+, it is more than the response speed is slow in the response speed of the Tb ³⁺ . That is, in the case of plural activators, when one of them contains an activator with a slow response speed, it is not preferable as a phosphor to be used for blinking lighting.

Moreover, since the characteristic of a fluorescent substance changes with the kind and valence of an activator, there are an activator which can be used for every desired luminescent color, and an activator which cannot be used. If Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , Ce ³⁺ , Tb ³⁺ is an activator, Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ is a red phosphor, Eu ²⁺ , Ce ³⁺ can be used for a green fluorescent substance, Tb ³⁺ , Eu ²⁺ can be used for a blue fluorescent substance.

Next, as shown in Fig. 9, a three-wavelength fluorescent lamp using various RGB phosphors was produced, and the response speed was tested. As a result, in Example 2, 3, 5 were about 3 msec, Example 4 was 1 msec or less, and Comparative Examples 2 and 3 were 10 msec or more in 90% of light emission rise time. In addition, 1/10 afterglow time was about 3 msec in Example 2, 3, and 5, Example 4 was 1 msec or less, Comparative Example 2 was about 6 msec, and Comparative Example 3 was 10 msec or more. As mentioned above, as long as it is a combination of fluorescent bodies with quick response speed, it was confirmed that any combination can be applied to the backlight device of a blinking lighting system with a quick response speed.

In addition, the fluorescent lamp of the present invention is also effective in performing dimming by the PWM system. That is, although dimming is mainly performed for the purpose of adjusting contrast, the effect that an afterimage hardly remains as a result can also be acquired.

Therefore, in the first embodiment, by using a fluorescent lamp coated with the phosphor 23 of RGB having a 1/10 afterglow time of 5 msec or less on the inner surface of the glass container 21, the blinking is turned on, whereby the backlight device is hard to remain after image. Can provide. In addition, since such a phosphor has a 90% emission rise time of 5 msec or less in most cases, when the liquid crystal display device is configured by synchronizing the on and off of the lamp and the liquid crystal, the luminance loss of the lamp is small, and high luminance can be realized. have.

Specifically, the red phosphor contains Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , the green phosphor contains Eu ²⁺ , Ce ³⁺ , Tb ³⁺ , and the blue phosphor contains an activator selected from Eu ²⁺ . When the lamp is composed of three wavelength phosphors, the above effects can be reproduced.

In the above embodiment, the blinking lighting method is used as the backlighting method of the backlight device, but the present invention can be effectively applied to the backlighting device of the scanning lighting method.

FIG. 10 is a diagram for explaining the backlight of the scanning lighting method. FIG. In this backlight device, 12 lamps are divided into two each to form six lamp groups, and on / off signals having shifted timings by 1/6 are input to each lamp group, and scanning lighting is performed. The on-off signal has a frequency of 60 Hz and a duty ratio of 50% and is generated by the PWM system. This scanning lighting method differs from the blinking lighting method in that one or a plurality of lamp groups are always on in any one of the lighting states. However, as described above, a backlight device having high brightness and low afterimage can be realized.

<2nd embodiment>

It is a figure for demonstrating embodiment of the liquid crystal display device using the fluorescent lamp of this invention.

As for the liquid crystal display device, the case is comprised by the front case FC and the back case BC. Liquid crystal panel LCP is arrange | positioned at the opening surface of front case FC. The back case BC is in the shape of a bottomed opening, and the backlight device BL is disposed therein.

In the case of the liquid crystal display device, it is possible to combine the operation of the opening and closing of the liquid crystal panel LCP with the blinking lighting of the backlight device BL. FIG. 12 is a diagram for explaining light emission characteristics when the lamp of the backlight device BL blinks and lights. In Fig. 12, the horizontal axis represents time, and the vertical axis represents voltage or current values. In addition, waveform (A) of Figure 12 is an on-off signal which is a voltage waveform for controlling the fluorescent lamp on-off, waveform (B) is a ramp voltage waveform, waveform (C) is a lamp current waveform, waveform (D) is a It is an output voltage waveform obtained by photoelectric conversion of light emission intensity by a photodiode. In addition, waveform E is a signal for opening and closing the liquid crystal which forms a liquid crystal panel LCP, waveform F is a light emission waveform obtained by liquid crystal panel LCP, and waveform G is a light emission waveform which is not obtained by liquid crystal panel LCP.

As shown in Fig. 12, since the afterglow of the lamp can be cut by closing the liquid crystal panel LCP at the same time as inputting the off signal to the backlight device BL, the combination of both almost prevents the occurrence of motion blur. It is possible. However, since the cut light cannot be used as the light of the liquid crystal, the luminance is reduced by that amount. For example, in Comparative Example 1, the luminance decreases by about 30%. In view of the above, in the backlight device using the fluorescent lamp of the present invention, since the response speed of the lamp is fast, the light to be cut is reduced, and high brightness can be achieved.

Therefore, in the second embodiment, a liquid crystal display device having high brightness and low afterglow can be realized even with blinking lighting.

Claims (12)

And a multi-wavelength fluorescence comprising a glass container in which a discharge medium is enclosed, a discharge electrode provided at an end of the glass container, and a plurality of kinds of phosphors formed on an inner surface of the glass container, and these phosphors have a 1/10 afterglow time of 5 msec. Fluorescent lamp for blinking lighting characterized by the following. The method of claim 1, The phosphor has a 90% light emission rise time of 5 msec or less, flicker lighting fluorescent lamp. The method of claim 1, And the phosphor contains an activator selected from Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , Ce ³⁺ , and Tb ³⁺ . The method of claim 2, And the phosphor contains an activator selected from Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , Ce ³⁺ , and Tb ³⁺ . The method of claim 1, The phosphor is a multi-wavelength phosphor containing red, green and blue phosphors, the red phosphor is Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , and the green phosphor is Eu ²⁺ , Ce ³⁺ , Tb ^{3 The} fluorescent lamp for blinking lighting characterized in that ⁺ , blue phosphor contains an activator selected from Eu ²⁺ . The method of claim 2, The phosphor is a multi-wavelength phosphor containing red, green and blue phosphors, the red phosphor is Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , Eu ³⁺ , and the green phosphor is Eu ²⁺ , Ce ³⁺ , Tb ^{3 The} fluorescent lamp for blinking lighting characterized in that ⁺ , blue phosphor contains an activator selected from Eu ²⁺ . The method of claim 1, The phosphor is a multi-wavelength phosphor containing red, green, and blue phosphors, the red phosphor is Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , the green phosphor is Eu ²⁺ , Ce ³⁺ , and the blue phosphor is Eu ²⁺ Fluorescent lamp for blinking lighting, characterized in that it contains an activator selected from. The method of claim 2, The phosphor is a multi-wavelength phosphor containing red, green, and blue phosphors, the red phosphor is Sn ²⁺ , Pr ³⁺ , Eu ²⁺ , the green phosphor is Eu ²⁺ , Ce ³⁺ , and the blue phosphor is Eu ²⁺ Fluorescent lamp for blinking lighting, characterized in that it contains an activator selected from. And a case, a fluorescent lamp of claim 5 housed in said case, and a lighting circuit capable of blinking and lighting said fluorescent lamp. And a case, a fluorescent lamp according to claim 6 housed in said case, and a lighting circuit capable of blinking and lighting said fluorescent lamp. The backlight device of claim 9, And a liquid crystal panel arranged on the light emitting surface side of the backlight device. The backlight device of claim 10, And a liquid crystal panel arranged on the light emitting surface side of the backlight device.

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