JPH1049065A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the number of parts and the man-hours for assembly or to enable the adjustment of the light emission characteristics of light emitting elements by adopting the constitution to package light emitting elements of a flexible circuit board and to execute connection to the outside by utilizing the flexibility thereof. SOLUTION: A light emitting element substrate 4 comprises the relatively thin circuit board material having flexibility. Many LED chips 41 which are back light sources are packaged thereon. The front ends 45 of the branch parts 43 sharing wiring parts 44 for liquid crystals are respectively connected by conductive adhesives, etc., to the driving electrode patterns 11 of a liquid crystal panel 1. The terminals of the wiring parts 44 for the liquid crystals are gathered together with the terminals of a lighting circuit 42 through the main surface of the light emitting element substrate 4 to the connector terminal parts 46 of the light emitting element substrate 4 and are connected to the power source existing on the base substrate on the outside of the light emitting element substrate 4 or the driving circuit of the liquid crystal panel 1. The light emitting element substrate 4 is bonded to the bottom surface of a reflection frame 3 and is integrated as a display device or is held and fixed between the front surface of the base substrate and the rear surface of the reflection frame 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device provided with backlight illumination.

[0002]

2. Description of the Related Art Liquid crystal displays are generally used in a great number of electronic information devices. Further, the liquid crystal display is often configured to be illuminated from the back side by a so-called backlight light source. The liquid crystal display panel and the backlight light source are often mechanically integrated (unitized).

[0003] In some cases, the backlight light source simply serves as bright background light of the liquid crystal display to increase the brightness of the display. However, a plurality of light sources having different peak wavelengths are simultaneously used to illuminate the display with a mixed color. Actively, for example,
As disclosed in Japanese Patent Application Laid-Open No. 3-41078 and Japanese Patent Publication No. Hei 8-27453, light sources of three primary colors emit light in a time-division manner, and a liquid crystal panel is opened and closed in accordance with the light emission timing of a light source of a specific color. It can also be used as an optical shutter to perform color display without expensive color dot filters. In this last example, a single color light emitting element such as an LED or a colored lamp is used as a backlight light source in combination with different colors.

[0004] Examples of the structure of a backlight light source using a light emitting element such as an LED combined with a liquid crystal panel are disclosed in JP-A-3-111886 and JP-A-4-55086. According to these, a large number of light emitting elements are arranged and mounted on a flat printed circuit board, and a resin frame which also serves as a spacer for a liquid crystal panel and a light source while forming an inclined reflecting wall on the upper surface (light emitting element side) is formed. Provided,
Further, a structure in which a light diffusion plate is provided on the upper surface to reduce illumination unevenness is disposed as a light shutter on the back side of a liquid crystal panel for displaying information.

[0005]

That is, in the conventional structure, only the light emitting elements are mounted on the printed circuit board. Also, a connector that supplies a drive signal to the liquid crystal panel from an external liquid crystal drive circuit is provided independently of other lighting components,
A flexible circuit board (which functions as a lead wire) having a wiring pattern is electrically conductively bonded to a surface electrode of a liquid crystal cell glass as a separate member. In addition, liquid crystal display panels tend to have poor responsiveness at low temperatures, and as a method of temperature compensation, the liquid crystal panel is heated with electric heat, but the heater at that time is independent of lighting components. It was provided. Further, since the light emitting element is mounted on a flat and highly rigid substrate, the mounting direction, that is, the directivity of light is limited.

In the present invention, except for the drawbacks of the conventional structure, a light emitting element and other parts are integrally provided on a substrate to reduce the number of parts and the number of assembling steps, or to adjust the light emitting characteristics of each element. It is an object to provide a liquid crystal display device.

[0007]

In a liquid crystal display device according to the present invention, a light emitting element is mounted on a flexible circuit board, and a structure for connecting to the outside by utilizing the flexibility is provided. The integration of related parts and the adjustment of the light emission direction are made possible.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view showing a liquid crystal display device according to a first embodiment of the present invention. Reference numeral 1 denotes a liquid crystal display panel, which has a super twisted nematic liquid crystal layer or a layer of ferroelectric or antiferroelectric liquid crystal, and has a pixel pattern such as a dot shape or a character segment shape, and has a display ON.
A polarizing plate is also integrated as necessary so that the pixel functions as a shutter for transmitting light. Of course, the driver circuit may be mounted on a glass substrate. Reference numeral 11 denotes a drive electrode pattern that appears at the end of the glass substrate. 2 is a light diffusion sheet, 3 is a reflection frame and is a molded product made of synthetic resin,
The liquid crystal display panel 1 has a light reflecting surface 31 for improving the efficiency of use of emitted light, and a hook portion 32 for fixing the liquid crystal display panel 1 and the light diffusion sheet 2.

The light emitting element substrate 4 is made of a relatively thin flexible circuit board material. A large number of LED chips 41 serving as a backlight light source are mounted thereon. Reference numeral 42 denotes a lighting circuit for the LED 41, which is formed by printing. Although not shown, a drive IC for the LED chip 41, a current limiting resistor, and the like may be mounted together as long as board space permits. Reference numeral 43 denotes a branch portion, which is a liquid crystal wiring portion 4 which is a plurality of printed conductive lines.
4 The distal end 45 of the branch 43 is connected to the drive electrode pattern 11 of the liquid crystal display panel 1 with a conductive adhesive or the like. The liquid crystal wiring section 44 passes through the main surface of the light emitting element substrate 4, and its end is gathered together with the end of the lighting circuit 42 in the connector terminal section 46 of the light emitting element substrate 4, and the base substrate outside the light emitting element substrate 4 ( (Not shown) and a drive circuit of the liquid crystal display panel 1 (neither is shown). The light emitting element substrate 4 is adhered to the lower surface of the reflection frame 3 to be integrated as a display device, or is sandwiched and fixed between the upper surface of the base substrate (not shown) and the lower surface of the reflection frame 3.

FIG. 2 is an assembled sectional view showing a liquid crystal display device according to a second embodiment of the present invention. In this embodiment, in order to illuminate the liquid crystal panel 1 from behind, a light guide plate 5 (made of a highly transparent acrylic resin or polycarbonate material plate) and a reflection sheet 6 are used instead of a diffusion sheet.
Is used. The light emitting element substrate 4 is made of a flexible circuit board, and a branch portion 43 (not necessarily a branch shape), which is a part thereof, rises to connect with the electrodes of the liquid crystal panel 1. Light emitting element 41 as an LED
Are arranged such that illumination light enters from the side surface of the light guide plate 5. Reference numeral 7 denotes a base substrate on which a liquid crystal driving circuit and a power supply circuit for a light emitting element are mounted, and a conductive pattern of a connector terminal portion 46 of the light emitting element substrate 4 is connected to a connecting portion 71 which is a part thereof. . The main part of the entire structure is tightened and integrated by the frame member 8 having the hook.

FIG. 3 shows a third embodiment of the present invention.
FIG. 3 is an exploded perspective view showing a liquid crystal display device provided with a temperature compensation mechanism. Liquid crystal display panel 1, light diffusion sheet 2, reflection frame 3,
Light reflecting surface 31, hook portion 32, light emitting element substrate 4, LED
The chip 41, the branch portion 43, the tip portion 45 of the branch portion, the connector terminal portion 46, and the like are substantially the same as those in the first embodiment. The same applies to the arrangement of the lighting circuit 42 and the liquid crystal wiring section 44, but the specific printed wiring patterns are not shown for other portions.

The light emitting element substrate 4 has a frame portion 48 connected to the second branch portion 47. When the liquid crystal display device is assembled, the frame-shaped portion comes into close contact with the peripheral portion of the liquid crystal panel 1 from the back and transmits heat to the liquid crystal panel 1. A pattern of a resistor serving as a heater is formed on the surface of the frame-shaped portion 48 by printing (not shown, but the resistor pattern makes substantially one round or almost all around the frame-shaped portion or along the long side of the liquid crystal panel. If the resistance pattern does not go around the frame, the shape of the frame itself does not necessarily have to be a closed hollow shape), and lead wires at both ends of the resistor are provided. Passes through the second branch portion and coexists with another pattern in the connector terminal portion 46. A limiting resistor 49 is connected in series with the LED to a power supply. Although not shown below, the connector terminal 46
The circuit on the base substrate connected to the device has a switching circuit controlled by a temperature sensor, and when the temperature of the device falls below a predetermined value, the heater resistor is energized to warm the liquid crystal and improve the responsiveness.

FIG. 4 shows a fourth embodiment of the present invention.
It is an assembly sectional view showing the liquid crystal display device which improved the illuminance distribution of illumination light utilizing the flexibility of the light emitting element substrate. It has a structure substantially similar to that of the first embodiment, and shows a cross section perpendicular to the longitudinal direction of the liquid crystal display panel, which cuts through one of the light emitting element groups. Reflection frame 3 in the first embodiment
An inner frame 33 having a curved bottom surface and a reflective surface 31;
The inner bottom surface also forms a curved surface, and is separated from an outer frame 34 having a hook portion 32. The inner frame 33 and the outer frame 34 sandwich the flexible light emitting element substrate 4 so as to form a curved surface. And the whole is united integrally by the hook part 32 of the outer frame 34. Further, the distal end portion 45 of the branch portion 43 of the light emitting element substrate 4 is sandwiched by the inner frame 33 at the same time as the rubber block 9, pressed against the glass substrate of the liquid crystal panel 1 from below, and connected to the display pattern.

In this embodiment, it is assumed that the viewing direction 10 of the user is not perpendicular to the liquid crystal panel 1 but is slightly inclined and the light is emitted so that the illumination light intensity in the viewing direction becomes large. The mounting angle and curvature of the element substrate 4 are devised. Depending on the applied state, the light scattering property can be further enhanced, and when a different color element such as R, G, or B is used, color unevenness can be intentionally given to the display surface. The connector terminal portion 4 of the light emitting element substrate 4
Although 6 cannot be in close contact with the surface of the base substrate 7 in a natural state, it is connected by being slightly twisted by utilizing its original flexibility.

A liquid crystal panel, a heater section, a light diffusion sheet,
It is preferable that the reflection frame, the light emitting element substrate, and the like have an integrated structure. The reason is that if this part is collectively manufactured by the manufacturer as a part, the user can easily assemble it into the final product by purchasing it and preparing only the liquid crystal drive signal generation circuit, the LED driver and the power supply. Further, if the LED driver IC 100 is mounted on the light emitting element substrate, the liquid crystal driver IC is mounted on the liquid crystal panel, and the temperature sensor is mounted on the reflection frame, the burden on the user can be further reduced.
A liquid crystal display device is further unitized to promote industrial use.

[0016]

As is apparent from the above description of the various embodiments, in the present invention, a flexible substrate is used for mounting a light emitting element, and other substrates than the holding of the light emitting element are used for the substrate. New functions such as connection to liquid crystal panel, holding member for temperature compensation resistance, and improvement of directivity of lighting are added. Therefore, the number of parts and the number of assembly steps are reduced and the performance is improved as a liquid crystal display device. And a favorable effect can be obtained also in unitizing the light source for illumination in the liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a liquid crystal display device having a connection portion with a liquid crystal panel according to a first embodiment of the present invention.

FIG. 2 is an assembled sectional view of a liquid crystal display device having a connection portion with a liquid crystal panel according to a second embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a liquid crystal display device having a temperature compensation mechanism according to a third embodiment of the present invention.

FIG. 4 is an assembly sectional view showing a liquid crystal display device according to a fourth embodiment of the present invention in which the illuminance distribution of illumination light is improved by utilizing the flexibility of a light emitting element substrate.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal panel 11 drive electrode pattern 2 light diffusion sheet 3 reflection frame 31 light reflection surface 32 hook portion 33 inner frame 34 outer frame 4 light emitting element substrate 41 LED chip 42 lighting circuit 43 branch portion 44 liquid crystal wiring portion 45 tip portion 46 Connector terminal part 47 Second branch part 48 Frame part 5 Light guide plate 6 Reflective sheet 7 Base substrate 71 Connection part 8 Frame member 9 Rubber block 10 Viewing direction 100 Driver IC

Claims (4)

[Claims] 1. A liquid crystal display unit configured to illuminate the liquid crystal panel using a plurality of light emitting elements arranged on the rear side of the liquid crystal panel as a light source, the liquid crystal display unit being provided on the rear side of the liquid crystal panel via a frame member. At least a part of a lighting circuit of the light emitting element is formed on a flexible circuit board and the light emitting elements are arranged and mounted, and a part of the flexible circuit board is bent to form a connection portion with the outside. Liquid crystal display device. 2. The liquid crystal panel according to claim 2, further comprising a liquid crystal wiring section for carrying the liquid crystal panel driving wiring group, wherein one end of the liquid crystal wiring section bypasses or penetrates the frame member. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is connected to a panel, and the other end is connected to a liquid crystal drive circuit board outside the flexible circuit board. 3. The flexible circuit board further includes a heater section on which a resistor is printed, and the heater section is held close to the liquid crystal panel by the frame member.
3. The liquid crystal display device according to claim 1, wherein the resistor is a heating resistor for performing temperature compensation of a display operation of the liquid crystal panel. 4. The flexible circuit board according to claim 1, wherein the main portion on which the light emitting element is mounted is held by the frame member so as to be inclined or bent with respect to a surface of the liquid crystal panel. 3. The liquid crystal display devices according to 3.