JP2009109537A - Liquid crystal device and method of manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal device, hardly separating a polarizer from a liquid crystal cell, and also causing no deterioration of characteristics in the main area such as a display area, and method of manufacturing it. <P>SOLUTION: A polarizer 1 stuck to a liquid crystal cell enclosing liquid crystal material between upper and lower substrates 2, 3 made of plastic includes an area 24 having high bonding strength and an area 25 having bonding strength lower than the area 24, and at least the peripheral part of the polarizer 1 is an area having high bonding strength. The area having high bonding strength is made by plasma cleaning using a mask or the like. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a structure of a liquid crystal device using a flexible substrate such as a plastic film and a manufacturing method thereof, and more particularly to a bonding structure of a flexible substrate and a polarizing plate and a manufacturing method thereof.

  A liquid crystal device made of a plastic film substrate has been put into practical use as a display panel of a mobile phone taking advantage of its light weight and thin properties. Recently, attention has been focused on the features of being hard to break, being bent, and having a high degree of freedom in planar shape, and various applied products have been proposed.

A widely used liquid crystal device has a structure in which a liquid crystal cell in which a liquid crystal material is sealed is sandwiched between two polarizing plates between upper and lower substrates. When we prototyped a liquid crystal device with this structure using a plastic substrate and conducted a long-term reliability test, the periphery of the polarizing plate was peeled off. As a cause of this, it has been found that the adhesion (adhesion) strength of the polarizing plate of a liquid crystal device using a plastic substrate is weaker than that of a liquid crystal device conventionally made of a glass substrate. This is presumably because the surface of the plastic substrate is more easily stained than the glass substrate.

As a basis for this, there is a method of improving the adhesive strength of the polarizing plate by cleaning the substrate surface (for example, see Patent Document 1 below). In Patent Document 1, UV light is applied to the substrate surface while ozone is supplied to improve the adhesion of the polarizing plate. The substrate was made of glass, and the contaminant was silicon resin.
JP-A-9-281474

  Therefore, we also applied a plasma cleaning method, which is said to be effective for removing contamination on the substrate surface of a liquid crystal device, to a liquid crystal cell made of a plastic substrate. However, although the adhesive strength of the polarizing plate was improved, the surface of the substrate was deteriorated and the display image quality of the liquid crystal device was lowered.

  In the plasma cleaning equipment we used, oxygen radicals obtained by discharge between dielectrics under atmospheric pressure chemically bond with surface contaminants to remove these contaminants, and there is no physical damage to the surface. It is said that there are few. Here, the layer structure of the plastic substrate we used will be described with reference to FIG. FIG. 4 is a cross-sectional view of the surface side of the plastic substrate. An undercoat layer 44, an organic gas barrier layer 43, an inorganic gas barrier layer 42, and a solvent-resistant coat layer 41 are laminated on a substrate support material 45 made of polycarbonate. The thickness of each layer is several tens of nm to several μm. The above-described deterioration in display image quality is considered to have been altered by plasma cleaning until the solvent-resistant coating layer or a layer below it is visible.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal device in which a polarizing plate is hardly peeled off from a liquid crystal cell and at the same time has no characteristic deterioration in a main region such as a display region and a manufacturing method thereof. To do.

In order to achieve the above object, the present invention includes a liquid crystal cell in which a liquid crystal material is sealed between upper and lower substrates, and at least one of the upper and lower substrates of the liquid crystal cell is a plastic substrate, and a polarizing plate is attached to the plastic substrate. In the attached liquid crystal device, the region to which the polarizing plate is attached has a first region having a high adhesive strength and a second region having a lower adhesive strength than the first region, and at least a peripheral portion of the polarizing plate. A part is the first region.

  It is preferable that the liquid crystal cell has a display area, and at least a part of the display area is the second area.

  The adhesive strength of the second region is preferably a strength that does not deteriorate the display image quality.

  The planar external shapes of the liquid crystal cell and the polarizing plate may be the same.

  The present invention also includes a liquid crystal cell in which a liquid crystal material is sealed between upper and lower substrates, at least one of the upper and lower substrates of the liquid crystal cell being a plastic substrate, and a polarizing plate attached to the plastic substrate. In the manufacturing method, a region including a part of the peripheral portion of the polarizing plate is selectively washed to increase the adhesive strength of the region.

  It is preferable to clean the entire surface of the liquid crystal cell by masking the region to be selectively cleaned.

  The selective cleaning may be plasma cleaning.

  The selective cleaning may be a UV cleaning.

  By strengthening the adhesive strength of the peripheral part of the polarizing plate, it strengthened against peeling of the polarizing plate starting from the peripheral part. Increasing the adhesive strength can be achieved by applying a physicochemical treatment to the substrate surface as described above. The surface of the plastic substrate is easily affected by these physicochemical treatments, but by assigning areas with weak adhesive strength to the main parts of the liquid crystal device such as the display area, the surface of the main part does not deteriorate and looks good The characteristics related to are maintained. Further, since the main part is bonded to the substrate, it is difficult for interference fringes and bubbles to be held in due to the floating of the polarizing plate.

  In general, the planar outline of the liquid crystal cell is larger than the planar outline of the polarizing plate. However, when a design reason or a simple laminate structure is desired, the planar outlines of the liquid crystal cell and the polarizing plate may be substantially the same. However, the present invention is strong against peeling of the polarizing plate starting from the peripheral portion by increasing the adhesive strength of the peripheral portion of the polarizing plate.

  As described above, the adhesion strength is weakened mainly due to surface contamination. In order to increase the adhesive strength in a specific region, it is sufficient to selectively clean only this region. Since cleaning using liquid has various disadvantages, plasma cleaning and UV cleaning that are possible in the atmosphere are excellent.

  In order to perform selective cleaning, a specific region may be scanned by narrowing the plasma beam or UV light, or the entire surface of the liquid crystal cell may be masked with a shower-like plasma or UV light with a spread of light flux. It may be washed. The method using the mask is generally simpler and faster than the scanning method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted. The scale is changed as appropriate.
(First embodiment)

A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an exploded perspective view showing layers according to the first embodiment. FIG. 2 is a perspective view (a) of the cleaning process and a plan view (b) of the liquid crystal device after applying the polarizing plate.

  The layer structure of the liquid crystal device of this embodiment will be described with reference to FIG. From the bottom of the figure, a lower polarizing plate 4, a lower substrate 3, an upper substrate 2, and an upper polarizing plate 1 are laminated. The upper and lower substrates 2 and 3 are bonded at their peripheral portions with a seal (not shown), and liquid crystal is sealed in a space formed by the upper and lower substrates 2 and 3 and the seal. The upper and lower substrates 2 and 3 have the layer structure shown in FIG. 4 on the side of the polarizing plates 1 and 4, the substrate support material is made of polycarbonate, and is a sheet having a thickness of 0.1 mm. The upper and lower polarizing plates 1 and 4 are sheets having a thickness of 0.1 mm and sandwiching a polarizing layer with TAC (triacetyl cellulose), and have adhesive layers (not shown) on the upper and lower substrates 2 and 3 side. . The seal is an epoxy adhesive having a width of 1 mm and a thickness of 5 μm. In the present embodiment, the planar outer shapes of the polarizing plates 1 and 4 and the substrates 2 and 3 are all the same, but it is not always necessary to match, for example, the planar surface is larger than the substrate. The external shape may be different.

  The cleaning process will be described with reference to FIG. A mask 22 is placed in the center of the substrates 2 and 3 (hereinafter referred to as liquid crystal cells) into which liquid crystal has been injected, and a plasma shower 21 is sprayed from above. Plasma cleaning is performed under atmospheric pressure, and the distance from the electrode that generates plasma to the liquid crystal cell is 5 mm. The amount of cleaning is controlled by the amount of gas supplied to the electrode and the transport speed (more precisely, time) of the liquid crystal cell passing through the plasma shower 21. By the way, in this prototype, it was carried out at 100 mm / s. The mask used a rubber sheet, but black paper or aluminum foil can also be used.

The liquid crystal device with the polarizing plate attached in FIG. The peripheral portion of the polarizing plate 1 indicated by the oblique lines is the region 24 plasma-cleaned in FIG. The region 25 inside the region 24 is not plasma-cleaned by the mask 22, so that the adhesive strength remains weaker than the region 24. This area 25 has an image display unit 23.
(Second Embodiment)

  A second embodiment of the present invention will be described with reference to FIG. FIG. 3 is an exploded perspective view of the second embodiment.

  First, an outline of the apparatus will be described. In the liquid crystal device of the second embodiment, a lower polarizing plate 34, a liquid crystal cell including a lower substrate 33 and an upper substrate 32, and an upper polarizing plate 31 are stacked on an electroluminescence sheet 301 for illumination. It is a thing. The material is the same as in the first embodiment. The regions indicated by solid lines on the upper substrate 32 are a first image display region 35, a switch button display region 37, and a second image display region 38, respectively, and electrodes are formed on the liquid crystal layer side with respect to each. Has been. The first and second image display areas 35 and 38 and the switch button area 37 are turned on and can be visually recognized according to the operation mode. A switch sheet 30 is affixed to the lower part of the switch button area 37. When the switch button in the visible state is pressed, the switch sheet 30 detects the press and sends a signal to a control block (not shown).

  Next, the adhesive situation of the polarizing plate 31 will be described. The regions 36 and 39 on the upper substrate 32 are regions where a mask is placed during plasma cleaning. For this reason, when the polarizing plate 31 is attached to the upper substrate 32, the regions 36 and 39 become regions having low adhesive strength. The first and second display areas 35 and 38 are inside the areas 36 and 39 having low adhesive strength. Since the switch button area 37 is pressed, there is a concern about the generation of bubbles and the floating of the polarizing plate rather than display quality. It is preferable that the lower polarizing plate 34 is also provided with a region having a strong adhesive strength and a region having a weak adhesive strength.

In the first and second embodiments, the entire peripheral portion of the polarizing plate is a region having a high adhesive strength, but the adhesive strength may be increased only for a part of the peripheral portion. In this case, it is preferable to make the corner portion a region having a high adhesive strength to prevent peeling. In the first and second embodiments, the plasma cleaning method is adopted as the cleaning method, but UV light cleaning may be used. We used a mask and obtained the same effect at a feed rate of 2.2 m / min under UV light with a wavelength of 254 nm 1500 mJ / cm 2 to 2000 mJ / cm 2.

It is a disassembled perspective view of the 1st Embodiment of this invention. It is the perspective view (a) of the washing | cleaning process of the 1st Embodiment of this invention, and the top view (b) of a liquid crystal device. It is a disassembled perspective view of the 2nd Embodiment of this invention. It is sectional drawing of the prior art example 1. FIG.

Explanation of symbols

1, 31 Upper polarizing plate 2, 32 Upper substrate 3, 33 Lower substrate 4, 34 Lower polarizing plate 21 Plasma shower 22 Masks 23, 35, 38 Image display region 24 High bonding strength region (first region)
25, 36, 39 Area with weak adhesive strength (second area)
37 Switch button area 30 Switch sheet 301 Electroluminescence sheet

Claims (8)

In a liquid crystal device having a liquid crystal cell in which a liquid crystal material is sealed between upper and lower substrates, at least one of the upper and lower substrates of the liquid crystal cell is a plastic substrate, and a polarizing plate is attached to the plastic substrate,
In the region where the polarizing plate is attached, there are a first region having a strong adhesive strength and a second region having a weaker adhesive strength than the first region,
At least a part of the periphery of the polarizing plate is the first region.   The liquid crystal device according to claim 1, wherein the liquid crystal cell has a display area, and at least a part of the display area is the second area.   3. The liquid crystal device according to claim 1, wherein the adhesive strength of the second region is a strength that does not deteriorate display image quality.   The liquid crystal device according to claim 1, wherein the liquid crystal cell and the polarizing plate have a planar outer shape that matches. In a method of manufacturing a liquid crystal device having a liquid crystal cell in which a liquid crystal material is sealed between upper and lower substrates, at least one of the upper and lower substrates of the liquid crystal cell being a plastic substrate, and a polarizing plate attached to the plastic substrate ,
A method of manufacturing a liquid crystal device, wherein a region including a part of a peripheral portion of the polarizing plate is selectively washed to increase the adhesive strength of the region.   6. The method of manufacturing a liquid crystal device according to claim 5, wherein the selectively cleaned region is masked and the entire surface of the liquid crystal cell is cleaned.   The method for manufacturing a liquid crystal device according to claim 5, wherein the selective cleaning is plasma cleaning.   The method of manufacturing a liquid crystal device according to claim 5, wherein the selective cleaning is UV cleaning.

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