JP4029383B2 - Reflective liquid crystal display element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reflective liquid crystal display element, and more particularly to a storage structure of a liquid crystal display cell in a package.
[0002]
[Prior art]
In recent years, reflective liquid crystal display elements have been widely used as display elements mounted on projector devices and projection TVs.
In particular, a silicon substrate provided with a reflective electrode arranged in a matrix and a CMOS transistor driving circuit for supplying voltage thereto and a transparent substrate on which a common electrode is formed face each other, and a liquid crystal is sealed between them. Reflective liquid crystal display elements called LCOS (Liquid Crystal On Silicon) elements have been attracting attention because of their high display image quality.
[0003]
In this display element, a liquid crystal display cell in which a liquid crystal layer is sealed with a silicon substrate and a transparent substrate is fixed to another substrate on which a circuit is formed and wiring processing is performed, or a metal or resin package is flexible. It is configured by storing together with a printed circuit board (FPC).
[0004]
By the way, this display element rises in temperature in the projector or projection TV set as the internal temperature rises during the set operation, and receives an extremely strong light of several W / cm ² or more from the light source. The temperature rises due to light absorption when the light is reflected.
[0005]
At this time, birefringence develops in the glass material itself constituting the substrate due to the stress generated when the transparent substrate receives a force from the circuit substrate or the package or the thermal stress.
The manifestation of the birefringence of the glass material of the transparent substrate is that the liquid crystal display element originally obtains an image by utilizing the birefringence of the liquid crystal, so that the display image quality is superimposed on the birefringence of the liquid crystal layer. Is significantly deteriorated.
[0006]
In addition, if excessive thermal stress is applied to the display element, or if the temperature of the element itself rises too much, the cell gap of the liquid crystal layer changes due to the difference in the coefficient of thermal expansion between the constituent members, thereby degrading the image quality. It is something to be made.
Therefore, how to suppress the external stress applied to the liquid crystal display cell by the difference in coefficient of thermal expansion between the members constituting the reflective liquid crystal display element, and the irradiation of the display element with extremely strong light from the light source. On the other hand, how to dissipate heat is an important technique for maintaining good image quality.
[0007]
As conventional examples embodying such a technique, for example, (1) Japanese Patent Laid-Open No. 10-20324, (2) Japanese Patent Publication No. 2001-500633, and (3) Japanese Patent Laid-Open No. 11-64860 can be cited. The following is an overview of each technology.
[0008]
First, as shown in FIG. 5, a reflective liquid crystal display element 30 described in Japanese Patent Laid-Open No. 10-20324 in (1) is a reflective liquid crystal panel 36 comprising a silicon (IC) substrate 33, a transparent substrate 34, and the like. Is provided with a hole 32 that is larger than the IC substrate 33 and narrower than a first direction width (horizontal direction width in the figure) of the transparent substrate 34, and the IC substrate 33 is placed in the hole 32. The both ends of the transparent substrate 34 in the first direction are fixed to the circuit board 31 with an adhesive 35. The adhesive 35 is a conductive ultraviolet curable adhesive and has a structure in which wiring is performed between the IC substrate 33 and the circuit substrate 31. For convenience of explanation, the liquid crystal layer is not shown.
[0009]
As shown in FIG. 6, the reflective liquid crystal display element 40 described in (2) Special Table 2001-500633 is a reflective liquid crystal panel 45 comprising a transparent first substrate 43, an active matrix element 44, and the like. A window 42 is provided in the circuit board 41 for fixing the active matrix element 44 constituting a part of the reflective liquid crystal panel 45 and sinks into the heat radiating gel material 46 through the window 42. Yes.
The gel material 46 is placed in a recess of a base material 47, and the base material 47 has a structure that supports the circuit board 41. For convenience of explanation,
The liquid crystal layer is not shown.
[0010]
The reflection type liquid crystal display element 50 described in Japanese Patent Laid-Open No. 11-64860 of (3) includes a first substrate 52, a second substrate 53, and the like attached to the package body 51 as shown in FIG. On the back side of the reflective liquid crystal panel 54 (the lower side in the figure), a metal heat dissipating plate 55 is installed with four sides embedded, and between the reflective liquid crystal panel 54 and the metal heat dissipating plate 55. Is a configuration in which a heat dissipation sheet 56 having elasticity is interposed.
The package body 51 has a cavity structure that is sealed with a metal heat dissipating plate 55 provided on the back side of the reflective liquid crystal panel 54 and a front glass plate 57. For convenience of explanation, the liquid crystal layer is not shown.
[0011]
[Problems to be solved by the invention]
In such a reflection type liquid crystal display element, in addition to the characteristic that the image display quality does not deteriorate due to mechanical stress and thermal stress, the price of component parts is required to meet the demand for lower prices recently required. It is also necessary to reduce the number of points.
However, in the case of the reflection type liquid crystal display element 30 described in Japanese Patent Laid-Open No. 10-20324 in (1), since there is no portion in contact with the back surface of the reflection type liquid crystal panel 36, the heat dissipation efficiency is poor, and the reflection type liquid crystal display Due to the light applied to the panel 36, the temperature of the reflective liquid crystal panel 36 itself rises remarkably.
Further, since the transparent substrate 34 is directly fixed to the circuit board 31, it receives mechanical and thermal stress from the circuit board. As a result, there is a problem that birefringence appears or the cell gap of the liquid crystal layer changes due to a difference in thermal expansion coefficient, resulting in image quality degradation.
[0012]
In the case of the reflective liquid crystal display element 40 according to (2) Japanese Translation of PCT International Publication No. 2001-500353, a part of the reflective liquid crystal panel 45 is formed in the heat dissipation gel agent 46 provided in the concave portion of the base material 47. Because of the structure in which the second substrate 44 is submerged, it is necessary to support adhesion between the three components of the base material 47, the circuit substrate 41, and the reflective liquid crystal panel 45, and the handling of the heat radiating gel agent 46 Is not easy, assembly is difficult, and productivity is poor.
[0013]
In the case of the reflective liquid crystal display element 50 described in Japanese Patent Laid-Open No. 11-64860 in (3), the heat radiation efficiency is increased through the heat radiation sheet 56 between the liquid crystal panel 54 and the metal heat radiation plate 55. However, since the package configuration is complicated and the cavities must be assembled in an airtight state, there is a problem in that productivity is poor and it is difficult to reduce the part price.
[0014]
In view of the above problems, the present invention has a configuration in which only a silicon substrate of a liquid crystal display cell is fixed to a base member having a cooling effect, thereby improving image quality due to the addition of direct mechanical stress or thermal stress from the outside. It solves problems, productivity, and costs at the same time.
That is, the problem to be solved by the present invention is to increase the heat dissipation effect from the liquid crystal panel to suppress the temperature rise, eliminate the cell gap change of the liquid crystal layer due to the difference in coefficient of thermal expansion between the constituent members, and prevent image quality deterioration. An object of the present invention is to provide a reflective liquid crystal display element that is high in productivity and low in cost.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration 1 ) as a means.
1) a transparent substrate (2), a silicon substrate (4) opposed to the transparent substrate (2) with a gap and supporting the transparent substrate (2) only by a sealant (7), and the gap in the gap A liquid crystal layer (5) sealed with a sealing agent (7), and a liquid crystal display cell (10) comprising:
Stepped portion includes a bottom consisting recess has a (11 a 1) (11a), said liquid crystal display cell (10), a bottom surface of the silicon substrate (4) only the recess with an adhesive (12) (11a) (11a3 ) And a base member (11) that is housed and supported in the recess (11a) ;
A space between the transparent substrate (2), said base member (11) of the stepped portion located on an opposite side of the silicon substrate with respect to the position of the transparent substrate (2) (4) A reflective liquid crystal display element (20) comprising an aperture (14) fixed to (11a) .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is an exploded perspective view for explaining an embodiment of a reflective liquid crystal display element of the present invention,
FIG. 2 is a schematic sectional view for explaining an embodiment of the reflective liquid crystal display element of the present invention.
FIG. 3 is a cross-sectional view showing an embodiment of the reflective liquid crystal display element of the present invention.
[0017]
As shown in FIG. 3, the reflective liquid crystal display element 20 in this embodiment includes a reflective liquid crystal display cell 10, an aperture 14, a base member 11, and an adhesive 12.
First, the structure of the reflective liquid crystal display cell 10 will be described with reference to FIGS.
FIG. 2 is a cross-sectional view taken along the line aa after the assembly of the reflective liquid crystal display cell 10 of FIG.
The reflective liquid crystal display cell 10 includes a transparent substrate 2 having a transparent electrode 1 formed on one surface (the lower surface in the figure) and an antireflection film 8 formed on the other surface, a pixel electrode 3, and a driving CMOS transistor. A silicon (IC) substrate 4 on the surface of which a semiconductor process or the like (not shown) is formed is disposed so that the transparent electrode 1 and the pixel electrode 3 face each other.
[0018]
A liquid crystal layer 5 is provided between the transparent substrate 2 and the IC substrate 4, and both the substrates 2 and 4 include spacers 6 that are applied to surround the pixel electrode 3 and regulate a gap (cell gap). The liquid crystal layer 5 is sealed and fixed by an adhesive sealant 7.
The sealing port 9 is a part that finally seals the liquid crystal layer 5.
An alignment film (not shown) is provided on the surface of the transparent substrate 2 and the IC substrate 4 that are in contact with the liquid crystal layer 5.
[0019]
In FIG. 3, the base member 11 is formed in a substantially box shape having stepped recesses 11a composed of stepped portions 11a1 and 11a2 and a bottom surface 11a3 for accommodating the reflective liquid crystal display cell 10, and the opposite side of the recess is A plurality of grooves 11b are provided for heat dissipation.
The back surface of the IC substrate 4 of the reflective liquid crystal display cell 10 assembled as described above is fixed to the bottom surface 11 a 3 of the recess 11 a of the base member 11 with an adhesive 12.
An aperture 14 made of transparent glass for the purpose of protection and dust prevention is fixed to the outermost step portion 11a1 of the stepped recess 11a of the base member 11 with an adhesive (not shown), and the reflective liquid crystal display element 20 Assembly is complete.
The position of the stepped portion 11a1 in the depth direction is set so that the aperture 14 and the transparent substrate 2 do not come into contact with each other, and a space is provided between them, so that the transparent substrate 2 is interposed in the base member 11 with the sealant 7 interposed therebetween. It is supported only by the IC substrate 4. The term “support” as used herein refers to an integrated connection state in which force can be substantially transmitted, and it goes without saying that connections such as flexible leads are not included.
[0020]
As a material of the transparent substrate 2, a # 1737 glass substrate manufactured by Corning, Inc. is used, the transparent electrode 1 is formed of an ITO (Indium Tin Oxide) film, and the alignment film is formed of silicon oxide.
In addition, n-type nematic liquid crystal is used as the liquid crystal layer 5, the sealant 7 is a WR series main sealant manufactured by Kyoritsu Chemical Industry Co., Ltd., and a SW-3.2D1 spacer ball manufactured by Yakushi Chemical Co., Ltd. is used as the spacer 6. The mixed material was used.
[0021]
Next, the reliability evaluation of the reflective liquid crystal display element 20 assembled in this way under a high temperature environment will be described.
This evaluation is based on whether or not unevenness due to birefringence of the glass occurs on the projected image in a high-temperature environment of 70 ° C. by projecting an image with a projection apparatus equipped with each of the example and the comparative example shown below. went.
[0022]
As a comparative example, a reflective liquid crystal display element 200 shown in FIG. 4 was prepared.
In the reflective liquid crystal display element 200 of this comparative example, a portion 2 a protruding laterally and a step portion 11 a 2 of the base member 11 are fixed with a UV curable adhesive 13 in the transparent substrate 2 of the reflective liquid crystal display cell 10. The other parts are the same as those of the reflective liquid crystal display element 20 of the embodiment.
[0023]
(Evaluation results)
Comparative example: Generation of unevenness.
Example: No occurrence of unevenness.
Further, in the examples, no change in the cell gap was observed, and even when mounted on a projector optical system equivalent to 7000 ANSI lumens, there was no image irregularity or display image quality degradation at all.
[0024]
That is, in the reflective liquid crystal display element 20 of the embodiment, the IC substrate 4 and the base member 11 are fixed via the thermosetting adhesive 12, and the transparent substrate 2 is supported only by the IC substrate 4 via the sealant 7. Therefore, mechanical and thermal stress is not directly applied to the transparent substrate 2, and the birefringence of the glass of the transparent substrate 2 induced by the direct stress is suppressed to a very low level.
Moreover, since the temperature difference between each member is also suppressed, the influence by the difference in thermal expansion coefficient is extremely reduced, and the cell gap change can be eliminated.
Therefore, the display image quality does not deteriorate even when the temperature rises due to intense light irradiation or the temperature rises due to the operation of the apparatus in the projector or projection TV set.
The embodiment of the present invention is not limited to the above-described configuration, and can be modified without departing from the gist of the present invention.
For example, it is not essential to mix a spacer with the sealant. Further, the base member does not have to have a shape having a concave portion, and may have an arbitrary shape such as a plate shape.
[0025]
【The invention's effect】
As described above in detail, according to the present invention, the heat dissipation effect from the liquid crystal display cell is high and the temperature rise can be effectively suppressed, and the cell gap of the liquid crystal layer does not change due to the difference in thermal expansion coefficient between members. Thus, a high productivity and low cost reflective liquid crystal display element can be obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view illustrating an embodiment of a reflective liquid crystal display element of the present invention.
FIG. 2 is a cross-sectional view illustrating an embodiment of a reflective liquid crystal display element of the present invention.
FIG. 3 is a cross-sectional view showing an embodiment of a reflective liquid crystal display element of the present invention.
FIG. 4 is a cross-sectional view showing a comparative example of the reflective liquid crystal display element of the present invention.
FIG. 5 is a cross-sectional view illustrating an example of a conventional reflective liquid crystal display element.
FIG. 6 is a cross-sectional view illustrating another example of a conventional reflective liquid crystal display element.
FIG. 7 is a cross-sectional view illustrating another example of a conventional reflective liquid crystal display element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent electrode 2 Transparent substrate 3 Pixel electrode 4 Silicon (IC) substrate 5 Liquid crystal layer 6 Spacer 7 Sealing adhesive 8 Antireflection film 10 Liquid crystal display cell 11 Base member 11a Recessed part (storage part)
11a1, 11a2 Step portion 11a3 Bottom portion 12 Adhesive 14 Aperture 20 Reflective liquid crystal display element

Claims (1)

A liquid crystal display cell comprising: a transparent substrate; a silicon substrate facing the transparent substrate with a gap and supporting the transparent substrate only with a sealing agent; a liquid crystal layer sealed with the sealing agent in the gap; ,
With a recess comprising a bottom having a stepped portion, the liquid crystal display cell, a base member for supporting and accommodated in the recess by fixing only the silicon substrate to the bottom surface of the recess with an adhesive,
A space between the transparent substrate, the base member, the reflective provided with, and an aperture which is fixed to the stepped portion positioned on an opposite side of the silicon substrate with respect to the position of the transparent substrate Liquid crystal display element.

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