JP4779859B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element used in a projection display device such as a projector or a projection TV (television), and more particularly, to provide a defocus substrate that prevents deterioration of image quality due to dust or scratches on a transparent substrate. The present invention relates to a liquid crystal display element.

  In recent years, projection display devices such as projectors and projection TVs (televisions) are widely used. These display devices are provided with an image display element in which incident light entering the liquid crystal is modulated by an image signal using the optical characteristics of the liquid crystal. Here, the optically modulated light is projected onto a screen or the like by an optical system having a projection lens or the like, thereby displaying an image.

  By the way, regarding the transparent substrate used for the liquid crystal display element, if the surface of the substrate is dusty or scratched, the depth of focus of the optical system, etc., even though the focus of the optical system is adjusted to the liquid crystal. This causes the transparent substrate surface located at a slight distance from the liquid crystal to be in a focused state, and as a result, the dust, scratches, etc. are displayed as a projected image on the screen, causing the image quality to deteriorate. It was.

  For this reason, in order to prevent deterioration of image quality due to dust or scratches on the transparent substrate, one side of the substrate used in the liquid crystal display element (in the case of a reflective liquid crystal display element) or both sides (transmission type liquid crystal display) In the case of an element), a technique is proposed in which a defocus substrate made of, for example, a transparent glass substrate is attached with an optical adhesive so that the dust, scratches, etc. are positioned away from the focus of the optical system. (Patent Document 1 etc.).

JP 2000-227768 A (Patent No. 36866560)

  By the way, when the defocus substrate is provided, even if dust or scratches are attached to the surface of the defocus substrate as described above, the position of the dust or scratches is out of focus from the optical system, that is, defocus. Therefore, the image quality is not reflected on the projected image, and the image quality can be improved in this respect.

  However, regarding the adhesive used when attaching the defocus substrate, there has been a need to control thickness unevenness due to the necessity of managing the internal stress of the adhesive and the amount of protrusion of the adhesive. For this purpose, it is necessary to control the variation in thickness, which is the gap between the defocus substrate that is pasted by the pasting device and the transparent substrate of the liquid crystal display element, with high precision, and control the equipment costs. There was a problem that forced us to.

  In addition, with regard to the method of curing the adhesive, since curing is performed in a short time using a photo-curing adhesive or the like, the deterioration of the liquid crystal due to strong light irradiation at the time of curing or the rapid adhesive An internal stress is generated in the defocus substrate made of a glass substrate due to the influence of curing shrinkage, and birefringence (shading) appears due to the internal stress, which may deteriorate the image quality.

  The present invention has been devised to pay attention to the above problems and to effectively solve them. An object of the present invention is to provide a liquid crystal display element capable of maintaining a high image quality by controlling the thickness of an adhesive for attaching a defocus substrate with a simple configuration.

  According to a first aspect of the present invention, there is provided a first substrate having a pixel effective area in which a plurality of pixel electrodes are formed, and a transparent second substrate bonded with liquid crystal sealed between the first substrate and the first substrate. The first substrate is bonded to the side surface opposite to the liquid crystal side of the first substrate and at least the side surface opposite to the liquid crystal side of the second substrate via an adhesive layer. In the liquid crystal display element having a transparent defocus substrate, the adhesive layer has no spacer made of a transparent spacerless adhesive in which a region including a region corresponding to the pixel effective area is not mixed with a spacer member An area outside the outer periphery of the spacer-free area is composed of two areas that are spacer areas made of a spacer-containing adhesive mixed with a spacer member. Is 示素Ko.

  According to the image display element of the present invention, it is possible to maintain high image quality by controlling the thickness of the adhesive to which the defocus substrate is attached with a simple configuration.

  FIG. 1 is an enlarged sectional view showing a liquid crystal display element according to the present invention, FIG. 2 is a process diagram showing an example of a method for manufacturing a liquid crystal display element, and FIG. 3 is a process diagram showing another example of a method for manufacturing a liquid crystal display element. FIG. 4 is a partially enlarged view showing a situation when the adhesive containing the spacer member is cured. Here, a reflective liquid crystal display element will be described as an example.

  As shown in FIG. 1, the liquid crystal display element 2 includes a first substrate 6 having a plurality of reflective pixel electrodes 4 made of an aluminum alloy and the like, and is disposed so as to face the first substrate 6. The liquid crystal 8 is sealed between and the transparent second substrate 10 to be joined. Specifically, the first substrate 6 is made of an opaque semiconductor substrate such as a silicon wafer, for example, and the pixel electrodes 4 are arranged in a matrix form vertically and horizontally on the surface of the first substrate 6. An area where the pixel electrodes 4 are arranged is an image effective area 12 for actually forming an image.

  Further, a driving circuit (not shown) for driving the pixel electrode 4 is provided on the first substrate 6 so as to correspond to each pixel electrode 4. The second substrate 10 is made of a transparent glass substrate, for example, and a common transparent counter electrode 14 made of ITO (indium tin oxide) is formed on the surface of the second substrate 10. Then, with the pixel electrode 4 and the counter electrode 14 facing each other, the first and second substrates 6 and 10 are bonded together with the liquid crystal 8 sealed therebetween. At the time of bonding, an adhesive 16 is applied along the periphery of the first substrate 6 or the second substrate 10, and the substrates 6 and 10 are bonded and fixed with the adhesive 16 interposed therebetween.

  A transparent defocus substrate 22 is bonded to the surface of the second substrate 10 opposite to the liquid crystal 8 side through an adhesive layer 20 that is a feature of the present invention. Specifically, the defocus substrate 22 is made of, for example, a transparent glass substrate. As the adhesive layer 20, at least the region corresponding to the pixel effective area 12 is a spacerless region using a transparent spacerless adhesive 24 without a spacer member. On the outside of the outer periphery of the spacerless region where the adhesive 24 is provided, a spacer-containing adhesive 26 containing the spacer member 26A is provided to form a spacer-equipped region. That is, it is provided so that the region with spacers surrounds the region without spacers, and the adhesive layer 20 is formed in both regions.

  The spacerless adhesive 24 may be a photocurable adhesive such as an ultraviolet curable resin or a thermosetting adhesive. Preferably, the refractive index of the adhesive 24 and the second substrate 10 are matched. . More preferably, the refractive index of the spacerless adhesive 24 is matched with the refractive index of the defocus substrate 22. Thus, the spacerless adhesive 24 is thinly formed over the entire region corresponding to the pixel effective area 12.

  On the other hand, the spacer member 26A to be put in the spacer-containing adhesive 26 is made of a spacer ball having a diameter of about 2 μm, for example, and is formed into a fine spherical shape by, for example, quartz and the like when the defocus substrate 22 is bonded. It functions as a spacer. As shown in the drawing, the spacer-containing adhesive 26 is provided so as to correspond to the peripheral portion of the defocus substrate 22 and does not enter the region corresponding to the pixel effective area 12. As will be described later, the spacer-containing adhesive 26 may be provided along the periphery of the defocus substrate 22, or may be provided in an intermittent or continuous line shape.

  Since the spacer-containing adhesive 26 is located outside the pixel effective area 12, it may be transparent to the incident light L or may be opaque. As the spacer-containing adhesive 26, as will be described later, it is preferable to use a photo-curing adhesive such as an ultraviolet curable resin so that it can be temporarily fixed.

  Here, a method for forming the adhesive layer 20 will be described with reference to FIGS. First, as shown in FIGS. 2A and 3A, a spacerless adhesive 24 is applied to a region corresponding to the pixel effective area 12 on the surface of the second substrate 10 opposite to the liquid crystal 8. The spacer-containing adhesive 26 is applied to the outer peripheral side of the area corresponding to the pixel effective area 12. In this case, the spacer-less adhesive 24 may be formed in an appropriate amount with no excess or deficiency at the center, or may be applied thinly over substantially the entire area corresponding to the pixel effective area 12. Good.

  Further, as shown in FIG. 2A, the spacer-containing adhesive 26 may be applied by being scattered in the form of dots at corners or the like, or as shown in FIG. 3A. You may make it apply | coat intermittently linearly along the outer periphery of the area | region corresponding to the effective area 12. FIG. Although not shown, the spacer-containing adhesive 26 may be continuously applied in a line so as to surround the region along the outer periphery of the region. The spacer-containing adhesive 26 is applied in a state where the peripheral portion (end portion) of the defocus substrate 22 to be attached later is in slight contact. In this case, the first substrate 6 is bonded and fixed to the opposite side surface of the second substrate 10 with the liquid crystal 8 already sealed in the previous step.

  In such a state, the defocus substrate 22 is bonded to the second substrate 10 while being relatively aligned with a bonding apparatus (not shown). At this time, just by applying a certain pressing pressure between the two substrates 10 and 22, the function of the spacer-containing adhesive 26 interposed between the peripheral portion of the defocus substrate 22 and the peripheral portion of the second substrate 10 The gap between the substrates 10 and 22, that is, the thickness is made constant, and the spacerless adhesive 24 sandwiched between the substrates 10 and 22 spreads out over the entire surface with a uniform thickness, and an excessive amount of the spacerless adhesive 24 protrudes outward. It will be. FIG. 2B and FIG. 3B each show a state at this time.

  Thereby, since the thickness of the spacerless adhesive 24 can be accurately and stably controlled with a simple structure, the variation in the thickness of the spacerless adhesive 24 can be significantly suppressed. In addition, the amount of the adhesives 24 and 26 that protrudes to the outer peripheral side of the defocus substrate 22 can be reduced, and variation in the amount of adhesive that protrudes can also be suppressed. The bonding apparatus includes, for example, a mounting table on which one substrate side can be mounted and moved in a plane, and an arm mechanism that holds the other substrate side and is movable in the vertical direction. .

  When the defocus substrate 22 is bonded in this way, as shown in FIG. 4, the necessary light L <b> 2 propagated through the optical fiber 30 from the light irradiation device (not shown) is transmitted from the optical nozzle 32. The spacer-containing adhesive 26 is irradiated for a short time, for example, about 10 seconds or less, and the spacer-containing adhesive 26 is cured and temporarily fixed. Thereafter, the liquid crystal display element 2 is conveyed to the next step, and the spacerless adhesive 24 is completely cured by, for example, a batch-type thermosetting process. In this way, the liquid crystal display element 2 can be transported to the next process by temporarily fixing with the spacer-containing adhesive 26, so that the tact time can be shortened and the productivity can be improved.

As described above, according to the present invention, since the spacer-containing adhesive 26 is provided on the outer periphery of the region corresponding to the pixel effective area, the spacerless adhesive 24 for attaching the defocus substrate 22 with a simple configuration is provided. By controlling the thickness, high image quality can be maintained.
In the above embodiment, the case where the spacerless adhesive 24 and the spacer-containing adhesive 26 are applied to the second substrate 10 side has been described as an example. However, the present invention is not limited to this. You may make it apply | coat to the position corresponding to the focus board | substrate 22 side.

  Although the reflective liquid crystal display element 2 has been described as an example here, the present invention is not limited to this. The present invention is also applied to a transmissive liquid crystal display element in which the first and second substrates 6 and 10 are both transparent substrates. The invention can be applied. In this case, the defocus substrate 22 is provided on both the first and second substrates 6 and 10.

It is an expanded sectional view which shows the liquid crystal display element which concerns on this invention. It is process drawing which shows an example of the manufacturing method of a liquid crystal display element. It is process drawing which shows another example of the manufacturing method of a liquid crystal display element. It is the elements on larger scale which show the condition at the time of hardening the adhesive agent containing a spacer member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Liquid crystal display element, 4 ... Pixel electrode, 6 ... 1st board | substrate, 8 ... Liquid crystal, 10 ... 2nd board | substrate, 12 ... Pixel effective area, 14 ... Counter electrode, 20 ... Adhesive layer, 22 ... Defocus board | substrate, 24 ... Adhesive without spacer, 26 ... Adhesive with spacer, 26A ... Spacer member.

Claims (1)

A first substrate having a pixel effective area on which a plurality of pixel electrodes are formed;
A transparent second substrate bonded in a state of sealing liquid crystal with the first substrate;
The first substrate is provided on the side surface opposite to the liquid crystal side of the first substrate and at least the side surface opposite to the liquid crystal side of the second substrate via an adhesive layer. A transparent defocus substrate,
In a liquid crystal display element having
The adhesive layer is a spacerless region made of a transparent spacerless adhesive in which a region including the region corresponding to the pixel effective area is not mixed with a spacer member,
2. A liquid crystal display element according to claim 1, wherein a region outside the outer periphery of the region without spacer is constituted by two regions which are regions having a spacer made of a spacer-containing adhesive mixed with a spacer member.

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