JP2002304129A - Backlight and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight which effectively use the external light for increasing the exiting light. SOLUTION: Backlight is disposed in the back side of a liquid crystal display panel 1. The back light consists of a light guide plate 2, a diffusion plate 3 disposed between the liquid crystal display panel 1 and the light guide plate 2, a light reflecting plate 4 formed on the other principal face of the light guide plate 2, and a fluorescent lamp structure disposed on the end face of the light guide plate 2. The fluorescent lamp structure consists of a light source 5 and a reflector 6. A phosphor 27 and/or a phosphorescence body 28 is present between the light-reflecting plate 4 (30) and the light guide plate 2. A window 7 is formed in a part of the chassis 8 which protects the liquid crystal display panel 1 and the backlight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a backlight used for display means such as a liquid crystal display device. Further, the present invention relates to a liquid crystal display device having the backlight.

[0002]

2. Description of the Related Art In recent years, a backlight has been used for a display means such as a liquid crystal display device in order to enhance the display performance, thereby increasing the luminance.

[0003] For example, in a liquid crystal display device, a backlight is provided in a transmissive or transflective liquid crystal display device.

[0004] Recently, the demand for liquid crystal display devices has been expanding also in portable telephones and portable information terminals. However, since they are used both outdoors and indoors, they can be visually recognized even when the surrounding environment is bright or dark. To reduce power consumption, transflective liquid crystal display devices have been developed and are already being used.

FIG. 6 shows an example of a transflective liquid crystal display device. Reference numeral 1 denotes a transflective liquid crystal panel.
The light guide plate 2 of the backlight is provided on the back surface side of the backlight. The light guide plate 2 is made of an acrylic resin, a polycarbonate resin,
It is made of a light guide material such as a norbornene resin. Further, a diffusion plate 3 is interposed between the transflective liquid crystal panel 1 and the light guide plate 2, and a light reflection plate 4 is provided on a surface facing the light guide plate 2.

Further, a light source 5 is arranged on the end face of the light guide plate 2,
This is a fluorescent lamp structure provided with a reflector 6 behind it.

According to this transflective liquid crystal display device, there are both functions when used as a reflection type device by external illumination such as sunlight and a fluorescent lamp, and when used as a transmission type device with a backlight mounted as internal illumination. Has both.

On the other hand, also in such display means, there is a need in the market for low power consumption. For example, for mobile phones and personal digital assistants, it is particularly desirable to reduce power consumption. However, on the other hand, in a reflection mode device that does not use a backlight, the brightness tends to decrease, and therefore visibility is reduced. We need to raise it further.

However, in the transflective liquid crystal display device having the above configuration, when the panel display is viewed using the external light in the reflection mode, only the reflected light of the external light reflected by the transflective plate is used. . Therefore, for the brightness,
The situation is not yet satisfactory, and higher brightness is required.

[0010] In a liquid crystal display device provided with a color filter for displaying a color image, such a problem is remarkable.

That is, the transmittance of light is reduced to 1/3 by the color filter, whereby the display becomes dark and cannot be sufficiently viewed.

In order to solve this problem, a technique using a fluorescent material for a backlight has been proposed (Japanese Patent Laid-Open No. Hei 9-1997).
26511).

FIG. 7 shows this backlight. Reference numeral 26 denotes a light guide plate into which a phosphor is mixed, and a light source accommodating hole 24 is provided on an end face of the light guide plate 26.
Thus, the irradiation light of the light source 25 is amplified by the phosphor inside the light guide plate 26 to improve the luminance.

[0014]

However, according to the backlight disclosed in Japanese Patent Application Laid-Open No. 9-26511, when this is combined with a liquid crystal display device, the backlight provided on the liquid crystal display device has a disadvantage.
The polarizing plates contain an ultraviolet absorber, and the only ultraviolet light that excites the phosphor is the irradiation light of the lamp light source. When used in the reflection mode, external light such as sunlight containing a large amount of ultraviolet light is used. The fluorescent material could not be reached, and the external light was not effectively utilized.

Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a backlight in which external light is more effectively used to enhance emitted light.

An object of the present invention is to provide a high-performance liquid crystal display device which has increased luminance and reduced power consumption.

[0017]

According to the backlight of the present invention, a light source is disposed on an end surface of a light guide plate having a light reflecting member formed on one main surface, and irradiation light of the light source entering the light guide plate is transmitted from the other main surface. In the configuration in which light is emitted, a phosphor and / or a light storage member is interposed between the light guide plate and the light reflection member, and an external light incident window for introducing ambient light is provided on another end surface of the light guide plate. Features.

A liquid crystal display device according to the present invention is characterized in that the backlight according to the present invention is arranged on the back surface of a liquid crystal display panel.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A backlight and a liquid crystal display device according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic sectional view of a liquid crystal display device provided with the backlight, FIG. 2 is an exploded perspective view of the liquid crystal display device, and FIG. 3 is a plan view of a structure in which a phosphor and a light storage material are arranged. is there. FIG.
The same parts as those of the liquid crystal display device shown in FIG.

In these figures, reference numeral 1 denotes a liquid crystal display panel, and a backlight is provided on the back side of the liquid crystal display panel 1. The backlight includes a light guide plate 2 made of an acrylic resin, a polycarbonate resin, a norbornene resin, or the like; a diffusion plate 3 interposed between the liquid crystal display panel 1 and the light guide plate 2; The light reflecting plate 4 is formed of an aluminum plate or the like which is the light reflecting member formed on the surface, and a fluorescent lamp structure disposed on an end face of the light guide plate 2.

This fluorescent lamp structure comprises a light source 5 which is a linear light source such as a cold cathode tube or a hot cathode tube, and a reflector 6. Reference numeral 8 denotes a housing for protecting the liquid crystal display panel 1 and the backlight, which is made of SUS, synthetic resin, or the like, and has a light shielding property.

According to the present invention, on the other end face of the light guide plate 2,
An external light entrance window for introducing ambient light is provided. According to this external light incident window, a window 7 for lighting is formed in a part of the housing 8. External light is made to enter from the end face of the light guide plate 2 through the window 7.

Desirably, the other end face of the light guide plate 2 may have a lens structure to enhance the light collecting property.

That is, as shown in FIG. 2, the other end face of the light guide plate 2 is formed as a converging lens 2a by forming a convex lens over its longitudinal direction, and forms a condensing lens 2a. Is introduced into the light guide plate 2 more, thereby further increasing the light use efficiency.

The condenser lens 2a may be processed as a lens integrally with the light guide plate 2, or may be arranged as a separate lens.

Next, in FIG. 1, the light source 5 is shown as a cold-cathode tube, and a reflector 6 is arranged behind the cold-cathode tube. A light source may be used. In particular, LEDs have low power consumption, and thus are suitable for small mobile phones and portable information terminals.

FIG. 3 shows an example of disposing phosphors and luminous bodies when such a point light source is used. According to the backlight shown in the figure, the condensing lens 29 is formed at the end of the light guide plate 2 as described above, and LEDs 31 are provided at the four corners of the light guide plate 2 respectively.

The present invention is characterized in that a phosphor 27 and / or a luminous body 28 are interposed between the light reflection plate 30 and the light guide plate 2.

The phosphors 27 and the light accumulators 28 are formed on the surface of the light reflecting plate 4 or the surface of the light guide plate 2, but in FIG. 3, they are formed on the surface of the light reflecting plate 4. 3 shows an arrangement structure of a phosphor 27 and a phosphorescent body 28. In addition, you may form similarly on the surface of the light-guide plate 2. FIG.

The phosphor 27 emits visible light fluorescence when excited by ultraviolet rays. For example, there is a phosphor 27 formed by coating a non-oxide material obtained by adding copper or the like to zinc sulfide.

The light accumulator 28 emits light during light reception,
It emits light temporarily after the end of the light reception, and for example, a material made of aluminum strontium oxide as a light emitting substrate is applied.

For example, based on a high-impact light-storing material N manufactured by Nemoto Special Chemical Co., Ltd., luminous luminova (a strontium aluminate compound), Picarico of Chemitech Co., Ltd., and zinc borosilicate glass of Sumita Optical Glass Co., Ltd. There is a substance to which a rare earth element is added as an active substance. In addition, Mitsui Bussan Co., Ltd., Nittetsu Building Materials Co., Ltd. and Japan Advertising Company Co., Ltd., jointly developed by the sunlight (ultraviolet light),
Acrylic resin plate that emits light at night (product name: "Ecoluna")
May be used.

By the way, the phosphor is a substance which emits light by exciting electrons when irradiated with ultraviolet rays or electron beams.
A substance that emits light even after these irradiations is called a luminous body, and the two are distinguished.

The phosphor 27 and the phosphor 28 are provided so as to form a dot pattern, and are formed by applying screen printing or the like during plate making.

In forming the dot pattern, the LE is controlled so as not to cause uneven brightness on the surface of the backlight.
It is preferable to reduce the area of each of these dots in the portion near D31 and the lighting window.

Thus, in the backlight having the above-described structure, the irradiation light of the light source 5 and the LED 31 is incident on the light guide plate 2, and in addition to the incident light, the phosphor 27 emits light and the light storage 28 also emits light. Absorbs light and emits light, so that even after the light source 5 and the LED 31 are turned off, or even when the surrounding environment suddenly darkens, the display can be visually recognized for a while, and the use state of the device becomes good. . In addition, the frequency of use of the light source 5 and the LED 31 is reduced, thereby reducing the total power consumption.

Further, according to the present invention, a window 7 for daylighting is formed in a part of the housing 8 and external light is made to enter from the end face of the light guide plate 2 through the window 7, so that the fluorescent material 27 Each light emitting function of the light storage body 28 is improved. In addition, the other end face of the light guide plate 2 is made into a lens structure to enhance the light collecting property, so that the light emitting function of each of the phosphor 27 and the luminous body 28 can be maximized.

Next, a specific configuration of the present invention will be described with a transflective liquid crystal display device. FIG. 4 is a schematic sectional view of the transflective liquid crystal display panel 1, and FIG. 5 is an enlarged sectional view of a main part thereof.

In FIG. 4, a retardation plate 34 made of polycarbonate or the like and an iodine-based polarizing plate 33 are sequentially stacked on one principal surface of a liquid crystal panel 35, and a retardation plate 36 made of polycarbonate or the like is laminated on the other principal surface. The iodine-based polarizing plate 37 is sequentially stacked. These are attached using an adhesive made of an acrylic material. Polarizer 3
The backlight 38 is disposed on the outer surface of the backlight 7.

The structure of the liquid crystal panel 35 will be described in detail with reference to FIG. The liquid crystal panel 22 in the figure corresponds to the liquid crystal panel 35, and 9 is a glass substrate on the segment side and a glass substrate on the common side which are opposed to each other. Transparent electrode 10
And an insulating layer 11 made of SiO ₂ and an alignment film 12 made of a polyimide resin rubbed in a certain direction.

The semi-permeable film 23 is formed on the inner surface of the other glass substrate 9.
Are formed, and the color filter 14 and the black matrix 15 are formed on the semi-transmissive film 23. The color filters 14 are arranged for each pixel, and a chromium metal or a black matrix 15 of a photosensitive resist is formed between the color filters 14.

The semi-transmissive film 23 has both light transmissive and light reflective properties, and prevents a phase difference from occurring when sandwiched between two polarizing plates. In addition, the semi-transmissive film 23 may be specular or scattering.

The transflective film 23 has a laminated structure in which, for example, a TiO ₂ layer as a high refractive index layer and a SiO ₂ layer as a low refractive index layer are alternately laminated. Alternatively, a metal film such as aluminum or chromium may be thinned. Further, a slit for transmitting light may be provided in the reflective film.

The color filter 14 is of a pigment dispersion type,
That is, a photosensitive resist prepared in advance with a pigment is applied on a substrate and formed by photolithography. R, G, and B in the figure indicate red, green,
The color filter 14 is colored blue.

An overcoat layer 16 made of an acrylic resin and a transparent electrode 18 made of ITO are formed thereon. The transparent electrode 18 is orthogonal to the transparent electrode 10. In addition, the alignment film 17 made of polyimide resin rubbed in a certain direction is formed on the transparent electrode 18.

The pair of glass substrates 9 formed as described above
Are bonded by a seal member 20 via a liquid crystal layer 19 made of chiral nematic liquid crystal twisted at an angle of, for example, 200 to 270 °. Furthermore, a large number of spacers 21 are arranged between the two glass substrates 9 to make the thickness of the liquid crystal layer 19 constant. In addition, although the insulating layer 11 and the overcoat layer 16 are provided in the liquid crystal panel 22 of the present example, they need not be provided.

Thus, when the liquid crystal display device 1 having the above configuration is used as a reflection type, the light irradiated by external illumination such as sunlight or a fluorescent light is applied to the polarizing plate 33, the phase difference plate 34, the liquid crystal panel 22 (the liquid crystal panel 35). ), And is reflected by the semi-transmissive film 23, the reflected light is enhanced by the enhanced reflection effect, and the liquid crystal panel 22 (the liquid crystal panel 3
5), passes through the phase difference plate 34 and the polarizing plate 33,
High brightness can be obtained.

When the liquid crystal display device 1 is used as a transmissive type, the irradiation light of the backlight 38 passes through the polarizing plate 37 and the phase difference plate 36 sequentially and passes through the liquid crystal panel 22 (liquid crystal panel 35). In this case, the panel which is sequentially passed through the phase difference plate 34 and the polarizing plate 33 and used in the reflection type can also be used in the transmission type under the same conditions, and is stable in either the reflection type or the transmission type. Vivid color display was achieved.

As described above, according to the transflective liquid crystal display device of the present invention, when the backlight 38 is turned off, as shown in FIG. 2, the liquid crystal display panel 1 (the liquid crystal panels 22 and 35) The external light (indicated by a in FIG. 2) such as sunlight directly incident on the panel is reflected by the semi-transmissive film 23 to display the panel, and the mode is changed to the reflection mode.

On the other hand, when the transmission mode is set, in addition to the conventional light irradiation of the backlight (indicated by c in FIG. 2), external light is further transmitted through the window 7 of the housing 8 to the light guide plate 2. The light is incident from the end face (indicated by b in FIG. 2).

Therefore, in the transmission mode, the light use means a in the reflection mode and the light use means c in the conventional mode are used.
In addition to the above, the addition of the light utilization means b significantly increased the light transmitted through the semi-transmissive liquid crystal panel, thereby increasing the luminance and brightening the display.

Further, according to the present invention, after the light source 5 is turned off, or after abrupt change to a state where light cannot be taken in through the window 7, the afterglow light emission from the luminous body 28 is maintained for a while. Subsequently, the display screen can be recognized.

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements may be made without departing from the scope of the present invention.

For example, in the above example, a transflective liquid crystal display device has been described, but a similar effect can be obtained with a transmissive liquid crystal display device instead.

Further, in the above case, both the phosphor and the luminous body are provided, but only one of the phosphor and the luminous body may be used instead.

[0056]

As described above, according to the backlight of the present invention, a phosphor and / or a phosphorescent material is interposed between the light guide plate and the light reflecting member, and ambient light is applied to the other end face of the light guide plate. By arranging the external light incident window to be introduced, the emitted light can be enhanced by effectively using the external light, and it has become an effective illumination unit for various display devices.

Further, in the liquid crystal display device of the present invention,
By using the backlight of the present invention, a high-performance liquid crystal display device with increased luminance and reduced power consumption can be provided. Furthermore, even when the surrounding environment is bright, when backlight is incident on the liquid crystal display device, or when the surrounding environment is dark, even when the battery that only turns on the lamp light source runs out, the liquid crystal display device can visually recognize information. Could be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display device provided with a backlight according to the present invention.

FIG. 2 is an exploded perspective view of a liquid crystal display device provided with a backlight according to the present invention.

FIG. 3 is a plan view of a structure in which a phosphor and a phosphor are arranged.

FIG. 4 is a schematic sectional view of a transflective liquid crystal display panel.

FIG. 5 is an enlarged sectional view of a main part of a transflective liquid crystal display panel.

FIG. 6 is a schematic sectional view of a conventional transflective liquid crystal display device.

FIG. 7 is a schematic sectional view of a conventional backlight.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel 2 ... Light guide plate 2a, 29 ... Condensing lens 3 ... Diffusion plate 4 ... Light reflection plate 5 ... Light source 6 ... Reflector 7 ... Window Reference numeral 8: Housing 27: Phosphor 28: Phosphor 31: LED

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G02F 1/13357 G02F 1/13357 // F21Y 101: 02 F21Y 101: 02 103: 00 103: 00

Claims (2)

[Claims] 1. A backlight in which a light source is disposed on an end surface of a light guide plate having a light reflecting member formed on one main surface and light emitted from the light source entering the light guide plate is emitted from the other main surface. A backlight, wherein a phosphor and / or a phosphorescent body is interposed between the reflector and a reflection member, and an external light entrance window for introducing ambient light is provided on another end surface of the light guide plate. 2. The liquid crystal display device according to claim 1, wherein the backlight according to claim 1 is arranged on the back surface of the liquid crystal display panel.