1. Field of the Invention
The present invention relates to a display device, and to a liquid crystal display device that secures the reliability of sealing and prevents liquid crystals from being contaminated while the device is provided with a narrow picture frame.
2. Description of the Related Art
A liquid crystal display device is provided with a TFT substrate and a counter substrate. The TFT substrate has pixels including a pixel electrode, a thin film transistor (TFT), and the like in a matrix configuration. The counter substrate is disposed opposite to the TFT substrate, and has a color filter and the like formed at a location corresponding to the pixel electrode of the TFT substrate. Liquid crystals are sandwiched between the TFT substrate and the counter substrate. The transmittance of light caused by liquid crystal molecules is controlled at every pixel to form images.
Since the liquid crystal display device is flat and light weight, the use is growing in various fields. Small-sized liquid crystal display devices are widely used for a mobile telephone, a DSC (Digital Still Camera), etc. The small-sized liquid crystal display device is strongly demanded that the outer shape be reduced while securing a predetermined display region. This means that a distance between the end portion of the display region and the end portion of the outer shape, a so-called picture frame, is reduced. In this case, the area of an encapsulation portion that encapsulates liquid crystals becomes small to cause a problem of securing the reliability of a seal portion.
The liquid crystals are encapsulated with a sealing material. In the case where liquid crystals are filled by a one drop fill (ODF) process, liquid crystals are dropped before curing the sealing material. Such a problem arises in that before a sealing material is cured, materials in the sealing material spread in the liquid crystals, and the quality of the liquid crystals is degraded. The following configuration is described in Japanese Patent Application Laid-Open Publication No. Hei 10-123537. In order to prevent an uncured sealing material from spreading in liquid crystals, an elastic seal is used for an encapsulation material to encapsulate liquid crystals. This elastic seal only serves to confine liquid crystals, and is not responsible for bonding a TFT substrate to a counter substrate. A thermosetting sealing material or an ultraviolet (UV) curable sealing material is formed on the outer side of the elastic seal to bond a TFT substrate to a counter substrate.
Moreover, a configuration is described in paragraph “0005” and FIG. 11 in Japanese Patent Application Laid-Open Publication No. Hei 10-123537 in which a UV curable seal is formed on the inner side of the elastic seal and a thermosetting seal is formed on the outer side. However, a gap is provided between the seal on the inner side and the seal on the outer side. Furthermore, no description is provided on the relationship between the UV curable seal and a light shielding portion formed on the TFT substrate.
A configuration is described in Japanese Patent Application Laid-Open Publication No. Hei 11-64862 in which a thermosetting bonding layer is formed as a sealing material on the inner side and a bonding layer made of a two-liquid adhesive resin or an ultraviolet curing resin is formed on the outer side of the thermosetting bonding layer. An object of Japanese Patent Application Laid-Open Publication No. Hei 11-64862 is to prevent a phenomenon in bonding a TFT substrate to a counter substrate using a thermosetting resin in which thermal strain deforms the substrates and a gap between the TFT substrate and the counter substrate is changed.
USPTO Backgrounds
USPTO Backgrounds