JPH10239677A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively protect a liquid crystal driving IC from light by absorbing light propagated with a transparent substrate as a light guide. SOLUTION: In a COG(chip on glass) liquid crystal display device where a liquid crystal driving IC 17 is face-down connected to a terminal part 121 and a light reflection layer 16 is provided on one outside face of a display part 15, at least the surface of a transparent substrate 12 between the liquid crystal driving IC 17 and the display part 15 is coated with a light absorbent 20 whose refractive index is approximately equal to that of the transparent substrate 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly, to a COG type liquid crystal display device in which a semiconductor element for driving a liquid crystal is face-down connected to a terminal portion of a transparent substrate.

[0002]

2. Description of the Related Art In recent years, with the spread of portable information terminals and the like, in the field of liquid crystal display devices, a so-called COG (a semiconductor device (IC)) for mounting a liquid crystal driving semiconductor element directly on a terminal portion of a transparent substrate in the form of a chip. Chip On Glas
s) Technology is being actively adopted.

[0003] There are two types of COG: a face-down type in which the connection terminals of the chip are mounted facing the substrate surface and a face-up type, that is, a face-down type. In the face-down type COG, one side of the liquid crystal display panel is used. In general, a method of connecting a connection electrode provided on a terminal portion of a transparent substrate and an IC pad (connection terminal) via a so-called anisotropic conductive film made of an adhesive and conductive particles (for example, Tokunosho 6
No. 2-6652).

[0004]

In general, a liquid crystal driving IC is packaged in a resin case, but in the case of a COG in a liquid crystal display device, it is mounted without a package due to its space. For,
As one of the problems of the COG type liquid crystal display device, a problem has been pointed out that an operation voltage of the liquid crystal driving IC is changed by external incident light to cause an operation failure or an operation stop state. .

Therefore, a light-shielding tape is attached to the surface of the transparent substrate opposite to the surface on which the liquid crystal driving IC is mounted (for example,
JP-A-4-172425), IC for driving liquid crystal
Countermeasures such as covering the periphery with black silicon resin have been taken.

[0006] However, such countermeasures are insufficient for face-down COG. In particular, in the case of a reflection type liquid crystal display device having a light scattering reflective layer, the COG portion is usually covered with an exterior material such as a housing, and the liquid crystal drive IC mounting portion is covered with a light shielding tape. Even if the surrounding area is covered with an exterior member, if the display surface is illuminated with strong light such as a strobe, the liquid crystal driving IC
There was a problem that the operation stopped.

When the cause was investigated, the liquid crystal driving I
It was found that the light applied to C was propagated using the transparent substrate as a light guide. In particular, when a light-scattering reflective layer is provided on the back surface of the display unit, the effect of scattering incident light inside the transparent substrate is strong, and the amount of light propagating inside the transparent substrate increases, resulting in a liquid crystal driving IC. Malfunctions.

[0008] Further, even if the surface on which the liquid crystal driving IC is mounted is covered with black silicon resin, the problem still cannot be solved because light entering through the transparent substrate as a light guide is more transparent than the refractive index of the silicon resin. The refractive index of the substrate is larger, and external light is used as an IC
It was also found that it was propagated to the mounting surface.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem of the prior art, and has as its object to protect a liquid crystal driving semiconductor element (IC) mounted on a terminal portion from external incident light. It also absorbs light propagating through the transparent substrate as a light guide, and
Is to provide a COG type liquid crystal display device capable of effectively protecting the liquid crystal from light.

[0010]

In order to achieve the above-mentioned object, the present invention provides a method in which transparent electrodes formed on a pair of transparent substrates are opposed to each other with a peripheral sealing material interposed therebetween, and a liquid crystal is sealed therein. And a terminal portion having a terminal pattern extending from the transparent electrode on the surface thereof, the terminal portion being connected to the side of the one transparent substrate, and having a terminal pattern drawn from the transparent electrode. In a liquid crystal display device having a liquid crystal driving semiconductor element (IC) connected face down and having a light reflecting layer on one of the outer surfaces of the display section, at least the liquid crystal driving semiconductor element and the display section are connected to each other. The surface of the transparent substrate is covered with a light absorber having a refractive index substantially equal to that of the transparent substrate.

The polymer material used in the present invention and having a refractive index substantially equal to that of the transparent substrate includes halogens such as poly (α-methyl methyl acrylate) and poly-2,3-dibromopropyl polyacrylate. High molecular compounds, high molecular compounds having an aromatic ring such as polyphenyl methacrylate, poly (vinyl benzoate), and polyvinyl naphthalene, high molecular compounds containing a sulfur element such as polyenthiol resin, bisphenol AF epoxy resin, or bisphenol AD epoxy resin And high-refractive index polymer materials and copolymers containing these as main components.

Further, since the light-shielding treatment by the light absorber is performed after the liquid crystal cell is assembled, the treatment temperature is limited, and a light-curing resin or a material that cures at a low temperature near normal temperature is used. From this point of view, the acrylic-modified resin in the above materials is particularly preferable. Further, as such a material, a material having a glass transition point of −30 ° C. or less can be preferably used from the viewpoint of preventing cracks from occurring during cold storage.

The light absorbing pigment to be added to such a polymer material is carbon, a black organic pigment (the black pigment is not limited to a single material and includes a mixture of a plurality of color pigments), or TiOx ( (x is a real number less than 2).

The amount of the pigment to be added is 0.1 to 10 parts by weight based on 100 parts by weight of the polymer material.
This ratio is appropriately selected depending on the required light transmittance and film thickness. If this value is less than 0.1 part by weight, the degree of light shielding tends to decrease, while if it exceeds 10 parts by weight, problems may occur in the surface properties, adhesion, electrical insulation, etc. of the film. is there. The wavelength that must be absorbed is 1400 nm or less, which corresponds to the light absorption wavelength of the silicon substrate of the liquid crystal driving IC.

This light absorber is provided at least on the surface of the transparent substrate between the liquid crystal driving IC mounted on the terminal portion and the liquid crystal display portion. That is, the incident side (display unit)
To prevent light from propagating inside the transparent substrate from
It is preferable that the entire outer surface of the transparent substrate in the region from the incident side to the end face of the liquid crystal driving IC is coated with this light absorbing material, but the liquid crystal driving IC mounting surface and the opposite mounting surface of the transparent substrate are coated. A sufficient effect can be obtained only by performing the above.

The COG type liquid crystal display device is usually covered with an exterior member (housing) as a final product form.
Since there is no invasion of external light directly incident on the liquid crystal driving IC mounting surface, other portions that cannot be observed from the display unit, that is, the liquid crystal driving IC mounting surface and the transparent substrate surface outside the same, and It is desirable that the back surface of the liquid crystal driving IC mounting surface is also covered with this light absorbing material. A conventional method such as covering the liquid crystal driving IC mounting surface with the light absorbing material and photo-curing, and then attaching a light-shielding tape to the opposite surface side can also be used.

The light absorber according to the present invention functions as a normal light-shielding layer against direct incident light from the outside. In addition, since the light absorber has a refractive index substantially equal to that of the transparent substrate, light is not totally reflected at the interface between the transparent substrate and the polymer material, but is absorbed by the light absorbing pigment. That is, the light absorber reduces the light guide effect of the transparent substrate,
A sufficient light-shielding effect is exhibited even with strong light such as a strobe light.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Next, in order to better understand the technical concept of the present invention, an embodiment will be described with reference to the drawings.

FIG. 1 illustrates an example of a COG type liquid crystal display device according to the present invention. That is, the liquid crystal display device 10 includes first and second transparent substrates 11 and 12, and although not shown, transparent electrodes are formed on their opposing surfaces. In this case, a terminal portion 121 is continuously provided on a side of the second transparent substrate 12, and a terminal pattern (not shown) drawn from a transparent electrode of the transparent substrate 12 is provided on a surface of the terminal portion 121. Are formed.

The first and second transparent substrates 11 and 12 are
The transparent electrodes are superimposed on each other with the peripheral sealing material 13 interposed therebetween, and a liquid crystal 14 is sealed in a cell between them, thereby forming a display unit 15. A light reflection layer 16 is provided on one outer surface of the display unit 15, that is, on the second transparent substrate 12 side in this embodiment. This light reflection layer 16 may be either a scattering reflection layer or a semi-transmission / reflection layer. In addition, 18 and 19 are polarizing plates.

A liquid crystal driving IC 17 is mounted on the terminal section 121. In this case, the liquid crystal driving IC 17 is face-down connected to the terminal pattern of the terminal section 121. That is, the IC pad and the terminal pattern are connected via a so-called anisotropic conductive film made of, for example, an adhesive and conductive particles.

In this embodiment, the terminal 1
The entire substrate 21 is covered with a light absorber 20 having a refractive index substantially equal to that of the transparent substrates 11 and 12. That is, light is absorbed not only between the display section 15 and the mounting section of the liquid crystal driving IC 17, but also from the upper portion of the liquid crystal driving IC 17 to the end on the side opposite to the display section, and further to the back side of the terminal section 121. Body 20 is covered.

The light absorber 20 is formed by adding a predetermined amount of a black pigment typified by carbon to the polymer material exemplified above.
7 is protected from external light.

That is, the light absorber 20 functions as a normal light-shielding layer against direct incident light from the outside, and light that propagates through the inside of the transparent substrate 12 by total reflection using the transparent substrate 12 as a light guide. Is absorbed by the light absorption 20. As a result, a sufficient light-shielding effect is exhibited even with strong light such as a strobe light.

In this embodiment, the liquid crystal driving IC 17 is used.
Is entirely covered with the light absorber 20, but in an actual product form, the terminal portion 121 is usually
Is covered with an exterior member (housing), so if it is only necessary to reduce the light guide effect of the transparent substrate only, the light absorber is provided on the surface of the transparent substrate between the display section and the mounting section of the liquid crystal driving IC. 20 may be coated.

[0026]

【Example】

Example 1 Each of the transparent substrates was a glass substrate having a refractive index of 1.52, and a liquid crystal driving I
C is mounted face-down, and a scattering reflective plate is provided on the back side of the display unit.
N) A COG type liquid crystal panel as shown in FIG. 1 was produced. Then, bisphenol AF is placed on the liquid crystal driving IC mounting surface and the glass substrate surface opposite to the mounting surface.
One part by weight of carbon was mixed with 100 parts by weight of a mixture of an epoxy compound (see the following chemical formula (1)) and a cyclohexane epoxy acrylate compound (see the following chemical formula (2)) at a weight ratio of 1: 1. The resin was applied and cured by irradiating ultraviolet rays. The refractive index of this resin is 1.5
It was 2. A non-display portion of the COG type liquid crystal panel, that is, a black plate cover is provided on the terminal portion so that external light does not directly enter the terminal portion, and a strobe is placed directly above the display portion (display screen) to emit light. However, there was no effect on the display screen.

[0027]

Embedded image

[0028]

Embedded image

For reference, the following table shows the relationship between the mixing ratio of the bisphenol AF epoxy compound of formula (1) and the cyclohexane epoxy acrylate compound of formula (2) and the refractive index.

[Table 1]

Comparative Example 1 A COG type liquid crystal panel was prepared according to the reflective super-twisted nematic (STN) method as in Example 1, and the liquid crystal driving IC mounting surface and the glass substrate on the side opposite to the mounting surface were mounted. On the surface, a silicone resin that is usually used as a resin (SE manufactured by Dow Corning Toray)
-917) was applied and cured. The refractive index of this resin was 1.43. Then, when the strobe light was emitted under the same conditions as in Example 1, the phenomenon that the operation of the liquid crystal driving IC was stopped occurred.

[0031]

As described above, according to the present invention,
In a COG type liquid crystal display device, light propagating by total reflection inside a transparent substrate as a light guide is absorbed by a light absorber formed on the substrate surface.
The operation failure of the liquid crystal driving IC caused by the external light can be reliably prevented. In addition, since the light absorber is a light-curing type or a room-temperature curing type, it does not require heating equipment and the like, and therefore can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing one embodiment of a COG type liquid crystal display device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 COG type liquid crystal display device 11, 12 Transparent substrate 121 Terminal part 13 Peripheral sealing material 14 Liquid crystal 15 Display part 16 Reflector 17 Liquid crystal drive semiconductor element (IC) 20 Light absorber

Claims (3)

[Claims] 1. A display section having transparent electrodes formed on a pair of transparent substrates opposed to each other with a peripheral sealing material interposed therebetween, and a liquid crystal sealed therein. A terminal portion having a terminal pattern extending from the transparent electrode on the surface thereof, and a liquid crystal driving semiconductor element is face-down connected to the terminal pattern of the terminal portion, and In a liquid crystal display device having a light reflecting layer on one of the outer surfaces of at least one of the portions, at least a surface of a transparent substrate between the liquid crystal driving semiconductor element and the display portion has a refractive index substantially equal to that of the transparent substrate. A liquid crystal display device characterized by being covered with an absorber. 2. The liquid crystal display device according to claim 1, wherein the light absorber contains a light absorbing pigment and is made of a polymer material having a refractive index substantially equal to that of the transparent substrate. 3. The liquid crystal display device according to claim 2, wherein the light absorbing pigment contains carbon.