1. Field of the Invention
The present invention relates to a liquid crystal display device having a spacer for holding a gap with which a liquid crystal is enclosed between two sheets of substrates referred to as so-called a drive substrate and a counter substrate, respectively, and a method of manufacturing the same.
2. Description of the Related Art
A liquid crystal display device has advantages such as thinning, lightweight, and low power consumption. For this reason, many liquid crystal display devices are used in electronic apparatuses for mobile applications such as a mobile phone and a digital camera.
The liquid crystal display device has a liquid crystal panel in which a liquid crystal is enclosed between a pair of substrates. With the liquid crystal display device, the liquid crystal panel modulates a light radiated from a flat surface light source such as a backlight provided on a back surface of the liquid crystal panel. Also, display of an image is carried out on a front surface (on a side of viewing a display surface) of the liquid crystal panel by the modulated light.
In recent years, a liquid crystal display device has been realized that has a sensor function called “a touch panel” with which data representing contents instructed by a user is directly inputted by utilizing an icon or the like displayed on a screen of the liquid crystal display device.
The touch panel is installed on the display surface side of the liquid crystal display device so that the instructed contents shown on the screen of the liquid crystal display device can be selected with a hand of an operator or an object (for example, a stylus pen). When the hand of the operator or the object directly touches the touch panel, the touch panel detects a position within the panel surface which the hand of the operator or the object touches. The liquid crystal display device receives the instructed contents as an input signal in accordance with the position where the contact is detected, and carries out an operation based on the input signal.
When the liquid crystal display device including the touch panel is used in a computer or the like, there is no need for providing an input unit as an attached accessory, other than a main body and a display device, such as a keyboard or a mouse. Or, the touch panel provides another input unit which assists such an input unit. In addition, when the touch panel is used in a mobile product such as a mobile phone, there is no need for providing an input unit such as a keyboard, or the number of keys can be reduced.
From the above, when the touch panel is mounted to the liquid crystal display device, the number of special attached accessories is reduced. For the side of the product provider, when the number of attached accessories is less, there is provided an advantage that the flexibility of the product design increases, and thus the miniaturization and the convenience enhancement are progressed, thereby increasing the product power. This provides the advantages such as the price-reduction, high functionality and convenience enhancement of the product for the user side as well. For this reason, the use of the touch panel has a tendency to increase yearly.
A liquid crystal display device in which a touch panel is added to a display surface side of a liquid crystal display panel is known in terms of a method of mounting the touch panel.
However, it is disadvantageous to add the touch panel externally for thinning the liquid crystal display device, which results in an increase in manufacturing cost. In addition, in the liquid crystal display device to which the touch panel is externally added, the optical characteristics in a phase of image display changes due to an influence of a refractive interface, so that the visibility of the image is reduced. For this reason, it is studied that the liquid crystal display panel and the touch panel are formed integrally with each other.
Moreover, when such a liquid crystal display panel is actually used, if a pressure is applied from the outside to the liquid crystal display panel, the spacer or a supporting body therefor is remarkably deformed due to surface pressing or the like because of the thinning of a glass.
With regard to the reason for this, it is given that when the liquid crystal display panel is used as the touch panel, a large load is applied to the touch panel, and when the glass is thinned, a pressure applied to the spacer determining a cell gap is not dispersed, and thus a load per one spacer becomes large.
With regard to measures to cope with this situation, it is the most effective measures to increase a disposition density of the spacer.
However, when an area occupancy as a rate of a spacer area per unit area is increased, there is caused a problem that when an impact is applied to the liquid crystal layer, vacuum babbles (so-called low-temperature bubbles) are generated.
This results from that although when the impact is applied to the spacers under a low-temperature environment, a cell gap saps downward and immediately restores to the original state, the bubbles are generated inside the cell because a restoration speed against the impact applied to the liquid crystal layer cannot follow a restoration speed of a member such as a glass.
The bubbles are generated because the glass quickly restores to the original state when the spacer area occupancy is high. Thus, the spacer area occupancy and the prevention of generation of the bubbles show a trade-off relationship.
With regard to the measures to cope with the low-temperature bubbles, there is known a technique for taking the measures to cope with the low-temperature bubbles by changing heights of spacers. This technique, for example, is described in Japanese Patent Laid-Open No. 2005-122150.