JP2803786B2 - Liquid crystal display device - Google Patents

Description

The present invention relates to a negative type liquid crystal display device.

[Related Art] In recent years, a liquid crystal display element is capable of displaying a large area with low power, and thus its use as a display device is increasing. The liquid crystal display device usually adopts a configuration in which a liquid crystal layer is sandwiched between substrates provided with electrodes, a peripheral portion of the liquid crystal layer is sealed with an adhesive, and a driving device for applying a voltage to the electrodes is provided. As an adhesive for the peripheral seal, a glass frit or an organic adhesive is used.

In the liquid crystal display device having such a configuration, the seal portion, which is a non-display portion, usually has a transparent or milky white color, and transmits light from the back side of the liquid crystal display device or the like to lower the contrast of the display portion. The so-called light leakage phenomenon has become a problem. In particular, recently, liquid crystal display devices used for displaying instruments, clocks, and the like of automobiles have often adopted a negative type display that displays bright characters and figures on a dark display surface. In this case, since the background becomes dark, it is very important to suppress the light leakage phenomenon.

In order to solve such problems, there has been proposed a method in which a powder such as carbon black or a black dye is mixed into a sealing material such as an organic adhesive to form a light-shielding black to prevent light leakage. .

[Problem to be Solved by the Invention] As described above, when a light-shielding sealing material is used in a negative-type liquid crystal display element, a phenomenon in which light escapes from the boundary between the sealing material and a light-shielding film provided on the substrate surface is caused by It often occurs and may result in product failure.

This is thought to be because the accuracy of the position where the light-shielding seal is provided on the substrate is poor, and the formation of a gap between the light-shielding film and the light-shielding film often causes light leakage.

Means for Solving the Problems The present invention has been made to solve such problems, and a light-shielding film is formed on at least one of the display pattern portions of a pair of substrates provided with electrodes, and the light-shielding film is formed on the substrate. An alignment film is formed on the substrate, the surfaces of the alignment film are opposed to each other, the periphery thereof is sealed with a sealing material, polarizing films are provided on both sides of a liquid crystal cell having liquid crystal sealed therein, and a means for applying a voltage to the electrodes is provided. In the negative type liquid crystal display element, the sealing material is a light-shielding sealing material, and the light-shielding film is provided so as to extend to the sealing material region,
A negative-type liquid crystal display element, comprising: a band-shaped region in which a light-shielding film formed thereby and a sealing material are arranged so as to overlap with each other, wherein the width of the band-shaped region is substantially smaller than the width of the sealing material. I will provide a.

 Hereinafter, the present invention will be described in detail.

FIG. 1 is a conceptual diagram showing an arrangement of a light shielding film and a sealing material provided on a substrate of a liquid crystal display element other than a display pattern portion in one of the embodiments according to the present invention. A light-shielding film 5 is provided on the substrate 3 other than the display pattern portion,
When viewed from above, a region 6 where the sealing material 1 and the light-shielding film 5 overlap exists in a band shape in a peripheral region of the light-shielding film 5.

It is preferable that the width of the band-shaped region is smaller than the width of the seal region in order to reduce a decrease in sealing strength. Furthermore, from the viewpoint of being able to sufficiently prevent light leakage, on average, preferably 1/30 to 1/3 times the width of the sealing material, more preferably 1/15 to 1/5 times. .

Although the above description has been made on the case where the light-shielding film is provided so as to extend over the sealing material region, the same effect can be obtained by providing the alignment film in addition to the light-shielding film also over the sealing material region.

As a method of manufacturing the liquid crystal display element according to the present invention, a commonly used method can be employed.

That is, an alignment film is formed on a pair of substrates provided with electrodes, alignment processing is performed, the alignment film surfaces are opposed to each other, the periphery is sealed with a sealing material, liquid crystal is sealed inside to form a liquid crystal cell, and polarized light is polarized on both sides. This is because a film is provided and voltage applying means for driving as a negative liquid crystal display element is provided. At this time, as described above, the light-shielding surface is provided so as to extend to the region where the sealing material exists.

Note that the above manufacturing method is an example, and it goes without saying that other manufacturing methods can be adopted as long as the effects of the present invention are not impaired.

As this substrate, a transparent substrate made of glass, plastic, or the like can be used, and ITO (In ₂ O ₃ —SnO ₂ ), SnO ₂
Etc. are formed. Of course, a low-resistance metal lead may be provided on the transparent electrode, or a color filter, an insulating film, or the like may be formed above or below the transparent electrode.

The light transmittance of the light shielding film in the present invention is preferably 0.3% or less, particularly preferably 0.2% or less. Conventionally known light-shielding films may be used for these light-shielding films, and may be thin or thick. For example, it may be formed by printing or the like using an ink containing a non-conductive pigment or the like.

The light-shielding film on the inner surface of the liquid crystal cell is formed on the background portion of the display, and usually only needs to be formed on one substrate. Of course, it may be formed separately on both substrates, but forming it on one substrate requires fewer steps and improves productivity.

An alignment film is formed on the surface of the substrate with electrodes.
When the light-shielding film is provided on the electrode, an alignment film is formed thereon. As this alignment control method, a known alignment control method such as a method of forming an organic polymer film of polyimide, polyamide, polyvinyl alcohol or the like by a printing method or a spinner method, rubbing this, or an oblique vapor deposition method can be used.

Further, an insulating film such as SiO ₂ or TiO ₂ may be interposed between the alignment film and the light-shielding film or the electrode on the inner surface of the cell to improve the insulating property.

The sealing material may be a usual sealing material such as an epoxy resin or a silicone resin, and is used by mixing a colored, preferably black dye or pigment. Ordinarily, an opening may be formed in a part of the cell, the cell may be formed, and then liquid crystal may be injected from the opening to seal the opening.

The polarization axes of the pair of polarizing films may be arranged almost in parallel as in the case of a normal negative-type liquid crystal display element, and substantially orthogonal to each other as in the case of a normal positive-type liquid crystal display element. May be arranged as follows.

However, if the pixels are arranged orthogonally, the part to which the voltage is applied becomes black. It is necessary to employ a reverse driving method of applying a voltage to the driving. Such a liquid crystal display device has an advantage that a high contrast ratio can be obtained because the degree of light shielding in a dark portion is higher than that of a normal negative type liquid crystal display device.

As a driving unit for applying a voltage to the electrodes, a driving unit used in a normal liquid crystal display device can be used, and a driving unit capable of supplying an AC voltage equal to or higher than a normal threshold value is used.

In addition, the substrate may be a polarizing film substrate, or a touch switch, an ultraviolet cut filter, or an anti-reflection filter may be laminated on the outer surface of the substrate, and a normal liquid crystal display device may be used as long as the effects of the present invention are not impaired. May be applied.

Although the present invention can be used for a liquid crystal display device of a normal negative display, as described above, the polarizing axes of a pair of polarizing films are arranged so as to be orthogonal to each other, and as a whole, a negative display is performed, The effect of applying a voltage is great when applied to a liquid crystal display device using a driving unit that performs the same operation as in the positive type display.

That is, in a pixel that transmits light in a display portion, a voltage equal to or lower than a threshold value at which liquid crystal molecules rise is applied,
A voltage higher than the threshold voltage is applied to the light-shielded pixels. Note that as to the method of applying a voltage, each pixel may be individually driven, or multiplex driving in which a plurality of pixels are driven by a common signal may be used.

As the driving voltage, a voltage that can obtain a high contrast mainly at the observed angle may be selected. In general, the higher the driving voltage, the higher the contrast at a higher angle (perpendicular to the substrate). When driven at a low voltage, a high contrast can be obtained at a low angle, but when the voltage is too low, a sufficient contrast cannot be obtained. Generally, it is desirable to drive within a range of 1.5 to 6 times the threshold voltage in the vertical direction.

Usually, an illuminating means is provided behind the polarizing film on the back surface, but a reflecting plate may be provided behind the polarizing film, and display may be performed using light from the front. In addition, the present invention can be applied to a device in which a lighting unit and a transflective plate are installed, and light from both the back and the front is used.

[Operation] In the present invention, since the light-shielding sealing material and the light-shielding film are disposed so as to overlap with each other, it is possible to completely prevent light from leaking from the boundary region.

[Example 1] [Example 1] A glass substrate with ITO was patterned and a light-shielding film having a thickness of 2.5 µm was formed using black ink by offset printing inside the cell except for the portion corresponding to the display pattern.
Further, a 0.1 μm-thick polyimide film was formed thereon, and this was rubbed to form an alignment film, thereby manufacturing a segment electrode substrate.

Further, a glass substrate with ITO was patterned and a polyimide film having a thickness of 0.1 μm was formed thereon, and this was rubbed to form an alignment film, thereby producing a common electrode substrate.

The segment electrode substrate and the common electrode substrate were arranged so that the electrode surfaces faced each other, the periphery was sealed with a light-shielding sealing material, and a nematic liquid crystal was injected into the inside to manufacture a liquid crystal cell.

At this time, as shown in FIG. 1, the light-shielding film and the light-shielding sealing material were arranged so as to overlap. The ratio of the width of the overlapping strip-shaped region to the width of the sealing material region was 1:10.

A pair of polarizing plates was arranged on both sides of the liquid crystal cell. Further, an illuminating means was arranged on the back side to prepare a liquid crystal display device.

At this time, one polarizing film has its polarization axis orthogonal to the alignment processing direction of the adjacent substrate, and the other polarizing film has its polarization axis parallel to the alignment processing direction of the adjacent substrate. Was arranged so that its polarization axes were parallel to each other, and was driven in the same manner as a normal negative-type liquid crystal display device. As a result, a negative type liquid crystal display device was obtained.

The obtained negative liquid crystal display device had good contrast without light leakage from the boundary between the seal portion and the alignment film portion.

"Example 2" In Example 1, the pair of polarizing films of the liquid crystal display device were set so that their polarization axes were orthogonal to the alignment processing direction of the adjacent substrates, that is, the pair of polarizing films were orthogonal to each other. In contrast to the normal driving of the negative type display device, the pixel is driven by applying a reverse driving method in which a voltage is not applied to a pixel to be brightened and a voltage is applied to a pixel to be darkened. This allows
In the part corresponding to the display pattern, the degree of light shielding in the dark part, which is the part corresponding to the display pattern, is higher than that in the ordinary negative-type liquid crystal display device, so that the black in the background part is extremely effective. And a liquid crystal display having a high contrast ratio was obtained.

As in Example 1, the obtained negative liquid crystal element had extremely good contrast without light leakage from the boundary between the seal portion and the light-shielding film portion.

[Effects of the Invention] The present invention has an excellent effect of preventing light from leaking from the boundary between the light-shielding seal and the light-shielding film by partially overlapping the light-shielding seal with the light-shielding film.

[Brief description of the drawings]

 FIG. 1 is a conceptual diagram showing the features of the present invention. 1: Seal material 3: Substrate 5: Light shielding film 6: Overlapping area

──────────────────────────────────────────────────続 き Continuation of the front page (72) Motoo Okada, Inventor 1-11, Yabu City, Osaka Prefecture (56) References JP-A-63-273835 (JP, A) JP-A-60-181730 (JP, A) JP-A-62-69235 (JP, A) JP-A-62-46431 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1 / 1339 G02F 1/1337

Claims (1)

(57) [Claims] 1. A light-shielding film is formed on at least one of a pair of substrates provided with electrodes except for a display pattern portion, an alignment film is formed on the substrate, the alignment film surfaces are opposed to each other, and the periphery is sealed with a sealing material. In a negative-type liquid crystal display device having a polarizing film provided on both sides of a liquid crystal cell in which a liquid crystal is sealed inside and a liquid crystal is sealed therein, and a voltage applying means to the electrodes, the sealing material is a light-shielding sealing material. The light-shielding film is provided so as to extend to the sealing material region, and has a band-shaped region in which the light-shielding film and the seal formed thereby are arranged so as to overlap, and the width of the band-shaped region is
A negative-type liquid crystal display device characterized by being substantially narrower than a width of a sealing material.