JPH0534521U - Display for instrument - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a display device for an instrument, which has a small influence of heat generated by a cold cathode tube or a liquid crystal drive circuit and has a long life without uneven display on a liquid crystal panel. In a display device for an instrument having a rectangular transmissive liquid crystal panel 20, a backlight 30 provided on the back surface of the liquid crystal panel 20, and a printed circuit board on which a liquid crystal drive circuit is mounted, along a side of the backlight. A phototube 32 provided, a backlight case 31 provided on the back surface of the phototube, a light guide plate 33 for guiding the light emitted from the phototube along the backlight case, and a light guide side provided on the illuminated side of the light guide plate. The backlight is provided with a light diffusion plate 34, and an isothermal plate 35 made of a good heat conductor provided between the backlight case and the light guide plate and having one end in contact with the phototube.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for an instrument used in an industrial control device or the like, and more particularly, to an improvement in which a liquid crystal panel displays well.

[0002]

[Prior Art]

 The applicant of the present invention has proposed an instrument display device using a transmissive liquid crystal panel in Japanese Utility Model Publication No. 3-10214. FIG. 4 is a perspective view showing an assembled state of the conventional device. In the figure, the casing 10 has a box shape and holds the outer shape of the display. The liquid crystal panel 20 displays characters and figures, and flat cables 22 used for connection with the printed circuit board 50 are attached to the long sides and the short sides. The flat cable 22 is a cable having multi-core flexibility. The backlight 30 is mounted on the back surface of the liquid crystal panel 20 and emits light to the outside through the liquid crystal panel 20, and is a rectangular body that functions as a light source of the display device. The backlight guide 40 is a U-shaped frame member. The backlight 30 is mounted inside and also supports the back surface of the liquid crystal panel 20. The printed circuit board 50 is mounted on the back surface of the backlight 30 and has a connection portion 52 to which the flat cable 22 is connected. The printed circuit board 50 supplies control signals and drive signals necessary for the operation of the liquid crystal panel 20. ing.

FIG. 5 is a sectional view showing the structure of the backlight 30. The backlight case 31 is made of resin or the like and has a groove or the like that engages with the backlight guide 40 on the side surface. The cold-cathode tube 32 is a type of photoelectric cell that emits light when supplied with electric power from the outside, and is housed here in the up-down direction of the backlight 30. The light guide plate 33 is provided on the illuminated surface side of the backlight case 31, and guides the light emitted from the cold cathode tubes 32 so that the light emitted from the illuminated surface becomes uniform. The diffusing plate 34 is attached to the illuminating surface side of the light guide plate 33. Since the light directly radiated from the light guide plate 33 has unevenness, it is provided to reduce this unevenness when it reaches the liquid crystal panel. Has been.

[0004]

[Problems to be solved by the device]

 However, the conventional device has the following problems. Both electrodes of the cold cathode tube generate heat of about 15 to 20 degrees when emitting light. There is no problem if a sufficient space can be secured between the cold cathode tube and the liquid crystal panel, but when they are placed close to each other, the temperature of the liquid crystal panel surface near the electrodes rises by about 10 degrees, resulting in display mura. To do. The printed circuit board has a circuit that drives the liquid crystal of the liquid crystal panel, so it generates heat. On the other hand, the liquid crystal of the liquid crystal panel is a chemical, and it is desirable to use it at a temperature as low as possible since it changes over time even at room temperature. Therefore, if the liquid crystal drive circuit and the liquid crystal panel are placed close to each other, the life of the liquid crystal is shortened due to the temperature rise and the visibility of the display is reduced.

The present invention solves such a problem, and the influence of heat generated by the cold cathode tube of the backlight or the liquid crystal driving circuit on the print substrate is small, and the display of the liquid crystal panel is even and has a long life. An object is to provide a display device for measuring instruments.

[0006]

[Means for Solving the Problems]

 The first invention to achieve such an object is to supply a rectangular transmissive liquid crystal panel 20, a backlight 30 provided on the back surface of the liquid crystal panel 20, and a signal for driving the liquid crystal of the liquid crystal panel 20. A display device for an instrument having a printed circuit board having the following configuration has the following configuration.

That is, a phototube 32 provided along one side of the backlight, a backlight case 31 provided on the back surface of the phototube, and a guide for guiding the light emitted by the phototube along the backlight case. An optical plate 33, a light diffusion plate 34 provided on the illuminating side of the light guide plate, and an isothermal plate made of a planar good heat conductor provided between the backlight case and the light guide plate and having one end in contact with the photoelectric tube. 35 is provided in the backlight.

A second invention to achieve such an object is to provide a rectangular transmissive liquid crystal panel 20, a backlight provided on the back surface of the liquid crystal panel 20, and a signal for driving the liquid crystal of the liquid crystal panel. The instrument display device having a printed circuit board to be supplied has the following configuration.

That is, a short side flat cable 23 provided on one short side of the liquid crystal panel, and a long side flat cable 25 provided on one long side of the liquid crystal panel, A rectangular first printed circuit board 24 to which the other end of the short side flat cable 23 is connected, and another end of the long side flat cable 25 are connected to form a circuit for driving the liquid crystal panel. It is provided with a rectangular second printed circuit board 26 provided. The backlight is positioned on the back surface of the liquid crystal panel, and the first printed board and the second printed board are arranged in this order on the back surface of the backlight.

[0010]

[Action]

 In the first invention, the light emitted from the photoelectric tube is uniformly illuminated on the back surface of the liquid crystal panel by the photoelectric plate and the diffusion plate. In addition, the heat generated in the photocell is conducted to the entire backlight by the isothermal plate, thus making the temperature of the backlight illumination surface uniform and preventing the phototube from adversely affecting the temperature distribution on the liquid crystal panel surface.

In the second invention, the printed circuit board is divided into a common side and a liquid crystal drive circuit mounting side, and the liquid crystal panel and the liquid crystal drive circuit printed circuit board are housed in the instrument housing with the common side sandwiched therebetween. Therefore, the printed circuit board with heat-generating components faces the liquid crystal panel side with the printed circuit board without heat-generating components sandwiched between them, and since both are thermally insulated, the influence of the heat-generating components does not affect the liquid crystal panel and the liquid crystal panel is not used for a long time. Is stable.

[0012]

【Example】

 The present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the construction of a component according to an embodiment of the present invention. In FIG. 1, parts having the same functions as those in FIG. The short side flat cable 23 is connected to the short side of the liquid crystal panel 20. The printed board 24 is connected to the other end of the short side flat cable 23, and is provided, for example, on the common side of the liquid crystal panel drive circuit. The long side flat cable 25 is connected to the long side of the liquid crystal panel 20. The printed circuit board 26 is connected to the other end of the long side flat cable 25, and is provided, for example, on the segment side of the liquid crystal panel drive circuit. The liquid crystal panel 20 is of a so-called dot matrix type, and the transmission amount of light emitted from the back surface is controlled for each dot. This control may be an on / off binary type, or may be a multilevel type that allows transmission of an intermediate amount of light. The backlight 30 has a uniform light irradiation surface. For example, a cold cathode tube is used as a light source, and the backlight 30 is used by being connected to an external power source.

FIG. 2 is a sectional view of the display device in an assembled state. The front surface of the casing 10 faces the display surface of the liquid crystal panel 20, and is provided with a translucent protective surface so that the display can be visually recognized. If necessary, characters or figures are printed in advance. ing. On the back surface of the liquid crystal panel 20, a backlight 30 and printed boards 24 and 26 are stacked in this order.

The procedure for assembling the thus-configured apparatus will be described below. First, when connecting the liquid crystal panel 20 and the printed boards 24 and 26, the short side flat cable 23 and the long side flat cable 25 are connected in a state where they are developed on a plane. These inspections and corrections are also performed in the expanded state.

Further, the procedure for incorporating is as follows. The liquid crystal panel 20 is placed on the casing 10. The backlight guide 40 accommodating the backlight 30 is placed on the liquid crystal panel 20. The printed circuit board 24 is folded on the backlight guide 40. The printed circuit board 26 is folded on the printed circuit board 24. In this way, one-way assembly work is performed.

FIG. 3 is a sectional view of the backlight 30. Incidentally, in FIG. 3, the same elements as those in FIG. The isothermal plate 35 is provided between the backlight case 31 and the light guide plate 33, and is made of a material having a high thermal conductivity such as an aluminum plate. One end is in contact with the cold-cathode tube 32, and the heat generated from the cold-cathode tube 32 is diffused throughout the backlight 30 to provide a uniform heat distribution and use air convection from the back surface of the backlight case 31. Waste heat.

[0017]

[Effect of the device]

 As described above, according to the present invention, the heat generated in the cold cathode tubes 32 is conducted to the entire backlight by the isothermal plate 35, so that the temperature of the backlight illuminating surface is made uniform and the temperature distribution on the liquid crystal panel surface is improved. It is uniform. Therefore, uneven display due to uneven temperature does not occur on the liquid crystal panel surface. The printed circuit board is divided into a common side 24 and a liquid crystal drive circuit mounting side 26, and the liquid crystal panel 20 and the liquid crystal drive circuit printed circuit board 26 are housed in the instrument housing with the common side 26 sandwiched therebetween. Therefore, the effect of the heat-generating components does not affect the liquid crystal panel, and there is a practical effect that the display of the liquid crystal panel becomes stable for a long period of time.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure of a component according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the display device in an assembled state.

FIG. 3 is a sectional view of a backlight.

FIG. 4 is a perspective view showing an assembled state of a conventional device.

FIG. 5 is a cross-sectional view of a conventional backlight.

[Explanation of symbols]

 10 ... Casing 20 ... Liquid crystal panel 23, 25 ... Cable 24, 26 ... Printed circuit board 30 ... Backlight 31 ... Backlight case 32 ... Cold cathode tube (photoelectric tube) 33 ... Light guide plate 35 ... Isothermal plate

Claims (2)

[Scope of utility model registration request] 1. A display device for an instrument having a rectangular transmissive liquid crystal panel 20, a backlight 30 provided on the back surface of the liquid crystal panel 20, and a printed circuit board for supplying a signal for driving liquid crystal of the liquid crystal panel. , A photoelectric tube 3 provided along one side of the backlight
2. A backlight case 31 provided on the back surface of the phototube, a light guide plate 33 for guiding the light emitted by the phototube along the backlight case, and a diffusion of light provided on the illuminated side of the light guide plate. A display device for an instrument, characterized in that the backlight is provided with a plate 34, an isothermal plate 35 which is provided between the backlight case and the light guide plate and which has one end in contact with the phototube and is made of a good heat conductor. 2. A display device for an instrument having a rectangular transmissive liquid crystal panel 20, a backlight provided on the back surface of the liquid crystal panel 20, and a printed circuit board for supplying a signal for driving liquid crystal of the liquid crystal panel, Short side flat case provided on one short side of the liquid crystal panel
And a long side flat case provided on one long side of the liquid crystal panel.
And a rectangular first printed circuit board 24 to which the other end of the short-side flat cable 23 is connected, and the other end of the long-side flat cable 25 to connect the liquid crystal panel. A rectangular second printed circuit board 26 provided with a driving circuit, and a backlight is positioned on the back surface of the liquid crystal panel, and the first printed circuit board and the second printed circuit board are connected to the back surface of the backlight. A display device for measuring instruments, which is arranged in order.