United States Patent [19]
`Sakuma et al.
`
`[54] LIQUID CRYSTAL DISPLAY MODULE
`HAVING CUT-AWAY PORTIONS OF THE
`BACK FRAME FOR WEIGHT REDUCTION
`AND HEAT DISSIPATION
`
`[75]
`
`Inventors: Toshiyuki Sakuma; Hiroshi
`Nakamoto; Toru Watanabe;
`Shigeharu Hatayama; Toshimitsu
`Matsudo; Takayuki Iura, all of
`Mobara, Japan
`
`[73] Assignee: Hitachi, Ltd., Tokyo, Japan
`
`[21] Appl. No.: 250,429
`
`[22] Filed:
`
`May 27, 1994
`
`[30]
`
`Foreign Application Priority Data
`
`[JP]
`
`Japan .................................... 5-132171
`
`Jun. 2, 1993
`Int. Cl.6
`........................ G02F 111333; G02F 1/1335
`[51]
`[52] U.S. Cl . ................................................. 359/83; 359/49
`[58] Field of Search .......................................... 359/49, 83
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,146,354
`5,214,522
`5,299,038
`5,335,100
`
`9/1992 Plesinger ................................... 359/49
`5/1993 Tagawa ..................................... 359/49
`3/1994 Hamada .................................... 359/49
`8/1994 Obata ........................................ 359/83
`
`lllllllllllllllllllllllllllllllllllll 111111111111111 11111111111 11111111 1111
`US005504605A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,504,605
`Apr. 2, 1996
`
`5,432,626
`
`7/1995 Sasuga ...................................... 359/83
`
`FOREIGN PATENT DOCUMENTS
`
`Japan ....................................... 359/83
`3/1993
`5066390
`Japan ....................................... 359/83
`3/1993
`5072514
`Japan ....................................... 359/83
`5341285 12/1993
`Primary Examiner-Anita Pellman Gross
`Assistant Examiner-Tiep H. Nguyen
`Attorney, Agent, or Firm-Antonelli, Terry, Stout & Kraus
`
`[57]
`
`ABSTRACT
`
`It is possible to reduce the thickness and size of a liquid
`crystal display module and to suppress any display irregu(cid:173)
`larity due to the heat generation of a light source, by
`providing a liquid crystal display module which is charac(cid:173)
`terized by an upper frame 1 made of a thin stainless steel
`sheet and a lower frame 2 made of a thin aluminum sheet
`thereby to reduce the thickness of an intermediate frame 42,
`and to form the lower frame 2 with cut-away portions 55 and
`56, which extend in a direction perpendicular to a back light
`source 36 over at least the area of a liquid crystal display
`panel 62 and which are positioned symmetrically to the line
`perpendicular to the center portion of the back light source
`36, cut-away portions 57 and 58, which extend just below
`the back light source 36 in the longitudinal direction of the
`back light source 36, and notches 53 and 54 which are
`positioned below the two end portions of the back light
`source 36.
`
`14 Claims, 10 Drawing Sheets
`
`2
`
`'----..54
`
`TOYOTA EXHIBIT 1004
`
`Page 1 of 18
`
`

`

`U.S. Patent
`US. Patent
`
`Apr. 2, 1996
`Apr. 2, 1996
`
`Sheet 1 of 10
`Sheet 1 of 10
`
`5,504,605
`5,504,605
`
`FIG. 1
`
`6 3
`
`
`
`~54
`
`Page 2 of 18
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`Page 2 of 18
`
`

`

`U.S. Patent
`
`Apr. 2, 1996
`
`Sheet 2 of 10
`
`5,504,605
`
`FIG. 2
`
`~--------------1 --------------~
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`
`Page 3 of 18
`
`

`

`U.S. Patent
`US. Patent
`
`Apr. 2, 1996
`Apr. 2, 1996
`
`Sheet 3 of 10
`Sheet 3 of 10
`
`5,504,605
`5,504,605
`
`FIG. 3
`
`
`
`Page 4 of 18
`
`Page 4 of 18
`
`

`

`U.S. Patent
`US. Patent
`
`Apr. 2, 1996
`Apr. 2, 1996
`
`Sheet 4 of 10
`Sheet 4 of 10
`
`5,504,605
`5,504,605
`
`FIG. 4
`FIG". 4
`
`62
`
`1 5
`
`2 1 d 1
`
`3:r
`l
`
`6
`
`3 2
`
`60
`
`Page 5 of 18
`
`
`
`22
`1 2
`
`16
`
`Page 5 of 18
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`

`

`U.S. Patent
`US. Patent
`
`Apr. 2, 1996
`Apr. 2, 1996
`
`Sheet 5 of 10
`Sheet 5 of 10
`
`5,504,605
`5,504,605
`
`FIG. 5
`FIG. 5
`
`
`
`Page 6 of 18
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`Page 6 of 18
`
`

`

`U.S. Patent
`
`Apr. 2, 1996
`
`Sheet 6 of 10
`
`5,504,605
`
`-........
`
`0
`0
`
`FIG. 6
`colored
`colored
`I< B/W >I
`<
`>
`
`60 70 80 90 100 110 120
`Angle a (Degree)
`
`FIG. 7
`
`Page 7 of 18
`
`

`

`U.s. Patent
`
`Apr. 2, 1996
`APP- 2, 1996
`
`Sheet 7 of 10
`Shee? 7 of 10
`
`5,504,605
`5,504,605
`
`PI G. 8( a)
`
`5
`
`PIG, 8(b)
`
`
`
`Page 8 of 18
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`Page 8 of 18
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`

`

`s,so4,605
`
`sneet s of 1 ()
`
`lJ .s. -patent
`
`Page 9 of 18
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`Page 9 of 18
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`

`

`U.S. Patent
`U.S. Patent
`
`Apr. 2, 1996
`Apr. 2, 1996
`
`Sheet 9 of 10
`Sheet 9 of 10
`
`5,504,605
`5,504,605
`
`F !G. 10
`
`49
`
`48
`
`34
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`6 2
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`
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`L31
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`
`—————
`
`Page 10 of 18
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`Page 10 of 18
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`

`

`U.S. Patent
`US. Patent
`
`Apr. 2, 1996
`Apr. 2, 1996
`
`Sheet 10 of 10
`Sheet 10 of 10
`
`5,504,605
`5,504,605
`
`F !G. 11
`FIG. I]
`
`64
`64
`
`63
`53
`
`
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`
`Page 11 of 18
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`Page 11 of 18
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`

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`5,504,605
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`2
`SUMMARY OF THE INVENTION
`
`1
`LIQUID CRYSTAL DISPLAY MODULE
`HAVING CUT-AWAY PORTIONS OF THE
`BACK FRAME FOR WEIGHT REDUCTION
`AND HEAT DISSIPATION
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to a liquid crystal display
`module and, more particularly, to a field effect type liquid
`crystal display module having excellent time sharing drive
`characteristics and the capability of using monochromatic
`and multi-color displays.
`In a liquid crystal display module of the "twisted nematic
`type", there is formed between two electrode substrates a
`helical structure which is twisted by 90 degrees by a nematic
`liquid crystal having a positive dielectric anisotropy, and
`polarizing plates are so arranged on the outer sides of the
`two electrode substrates that their polarizing axes (or
`absorbing axes) are perpendicular to or in parallel with the
`liquid crystal molecules adjacent to the electrode substrates
`(as disclosed in Japanese Patent Publication No. 13666/
`1976).
`In this liquid crystal display element having an angle of
`twist (a) of 90 degrees, a problem arises not only in the
`steepness (y) of the change in the transmittance of the liquid 25
`crystal layer with respect to the voltage applied to the liquid
`crystal layer, but also in the visual angle characteristics
`thereof. Thus, the time sharing number (corresponding to the
`number of scanning electrodes) is practically limited to 64.
`In order to obtain an improvement of the image quality and 30
`an increase in the amount of display data for the liquid
`crystal display element in recent years, however, there has
`been proposed a super twisted nematic (STN) module in
`which the angle of twist a of the liquid crystal molecules is
`made larger than 180 degrees. It has been discussed in
`Applied Physics Letter 45, No. 101,021, 1284 (entitled "A
`new, highly multiplexable liquidcrystal display" by T. J.
`Scheffer & J. Nehring) that the time sharing drive charac(cid:173)
`teristics of such a module are improved so as to increase the
`time sharing number by making use of a birefringence effect
`in that STN. There has also been proposed a (Super-twisted
`Birefringence Effect) display module.
`This kind of liquid crystal display module includes an
`upper frame having a display window; a liquid crystal 45
`display panel having a liquid crystal plate integrated with a
`driver substrate; a conductor assembly having an optical
`diffusion plate and a conductor plate; an intermediate frame
`equipped with a linear back light source on at least one side
`thereof; and a lower frame. The module is constructed by 50
`laminating the above-specified components in the recited
`order and by jointing and fixing the upper frame and the
`lower frame.
`Moreover, the aforementioned upper frame and lower
`frames are made of thin iron sheets, and the entirety is tightly 55
`laminated by sandwiching suitable spacers or adhesive
`tapes, if necessary, between the above-specified individual
`components so that it may be fixedly integrated.
`In the liquid crystal display module of the prior art, since
`the upper frame and the lower frame are made of thin iron 60
`sheets, the liquid crystal display module has the disadvan(cid:173)
`tage that the overall module has its thickness and weight
`increased, thereby imposing limitations on the reduction of
`the thickness and weight for purpose of maintaining its
`rigidity, and in that the heat generated by the back light 65
`source is transferred locally to the liquid crystal display
`panel to invite display irregularity.
`
`35
`
`40
`
`An object of the present invention is to solve the afore(cid:173)
`mentioned inherent problems of the prior art and to provide
`a liquid crystal display module which can have its thickness
`5 and weight reduced while maintaining its entire rigidity and
`can suppress any display irregularity due to the heat gen(cid:173)
`eration of the back light source.
`In order to achieve the above-specified object, a liquid
`crystal display module 63 of the present invention includes
`10 a metallic upper frame 1 having a display window 3; a liquid
`crystal display panel 62 arranged below the upper frame 1
`and having a liquid crystal display element and a driver
`substrate 35 for the liquid crystal display element formed
`integrally around the liquid crystal display element; a con-
`15 ductor assembly 37 arranged below the liquid crystal display
`panel 62 and formed by laminating an optical diffusion plate
`and a conducting plate; an intermediate frame 42 arranged
`below the conductor assembly 37 for accommodating the
`same and formed on at least one side thereof with a space for
`20 mounting a linear back light source 36; and a lower frame 2
`arranged below the intermediate frame 42 and jointed to the
`upper frame 1 for fixing the liquid crystal panel 62, the
`conductor assembly 37 and the intermediate frame 42 being
`arranged between the lower frame 2 and the upper frame 1,
`wherein the lower frame 2 is formed with cut-away portions
`57 and 58 of predetermined shapes, which extend just below
`the back light source 36 in the longitudinal direction of the
`back light source 36.
`Moreover, the cut-away portions 57 and 58 are formed
`such that the ratio of the area (S 1+S2+S3) of the lower frame
`2, which is formed just below the back light source 36, to the
`area (L) occupied by the back light source 36 is set to 10%
`to 50%. In a more preferable mode, the cut-away portions 57
`and 58 are formed such that the ratio of the area (S 1+S2+S3)
`of the lower frame 2, which is formed just below the back
`light source 36, to the area (L) occupied by the back light
`source 36 is set to about 30%.
`The present invention is further characterized in that the
`lower frame 2 is formed with notches 53 and 54 in positions
`corresponding to the two end portions of the back light
`source 36. In this mode, the cutaway portions 57 and 58 and
`notches 53 and 54 are formed such that the ratio of the area
`(S 1 +S 2+S3 ) of the lower frame 2, which is formed just below
`the back light source 36, to the area (L) occupied by the back
`light source 36 is set to 10% to 50%. In a more preferable
`mode, the cut-away portions 57 and 58 and the notches 53
`and 54 are formed such that the ratio of the area (S 1+S2+S3)
`of the lower frame 2, which is formed just below the back
`light source 36, to the area (L) occupied by the back light
`source 36 is set to about 30%.
`The present invention is further characterized in that the
`lower frame 2 is formed with cut-away portions 55 and 56
`of predetermined shapes, which extend through the back
`light source 36 over the area corresponding to the liquid
`crystal display panel 62 and which are positioned symmetri-
`cally to the line perpendicular to the longitudinal direction of
`the back light source 36. In this case, the cut-away portions
`55 and 56 are formed such that the ratio of the area of the
`lower frame 2, which is formed below the liquid crystal
`display panel 62, to the area occupied by said liquid crystal
`display panel 62 is set to 10% to 50%. In a more preferable
`mode, the cut-away portions 55 and 56 are formed such that
`the ratio of the area (L) of the lower frame 2 formed below
`the liquid crystal display panel 62 to the area (S4+S5+S6 )
`occupied by the liquid crystal display panel 62 is set to
`about 30%.
`
`Page 12 of 18
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`

`

`5,504,605
`
`4
`FIG. 7 is an explanatory diagram illustrating the relations
`among the array directions of liquid crystal molecules, the
`twisting direction of liquid crystal molecules, the axial
`directions of polarizing plates and the optical axis of a
`5 birefringent member of Specific Embodiment 4 of the liquid
`crystal display module according to the present invention;
`FIG. 8 a diagram for explaining how to measure inter(cid:173)
`sectional angles a, ~ and y in the liquid crystal display
`module according to the present invention;
`FIG. 9 is a partially cut-away perspective view of an
`upper electrode substrate in the liquid crystal display module
`according to the present invention;
`FIG. 10 is a block diagram showing the case in which the
`liquid crystal display module according to the present inven(cid:173)
`tion is used for a display unit of a laptop personal computer;
`and
`FIG. 11 is an external view showing the case in which the
`liquid crystal display module according to the present inven(cid:173)
`tion is used for the display unit of a laptop personal
`computer.
`
`3
`The present invention is characterized by a combination
`of the above-specified characteristics suitably or by adopting
`one of them, and in that the upper frame 1 is made of a thin
`stainless steel sheet whereas the lower frame 2 is made of a
`thin aluminum sheet.
`Thanks to the cut-away portions 57 and 58 or the notches
`53 and 54 formed in the lower frame 2, as described above,
`it is possible to prevent any reduction of brightness by
`reducing the "leakage current" and the heat dissipation and
`to make the temperature distribution of the liquid crystal 10
`display panel 62 more uniform. Thanks to the cut-away
`portions 55 and 56, it is possible to make the temperature
`distribution of the liquid crystal display panel 62 more
`uniform by improving the heat dissipation and to reduce the
`weight of the liquid crystal display module. As described 15
`above, moreover, more preferable effects can be attained in
`the strength of the frame and in the brightness of the back
`light source by forming the aforementioned cut-away por(cid:173)
`tions 51 and 58 and notches 53 and 54 such that the area (S 1
`+S2+S3) of said lower frame formed just below the back 20
`light source 36 to the area (L) occupied by the back light
`source 36 is set to 10% to 50% (more preferably about 30% ),
`and by forming the aforementioned cut-away portions 55
`and 56 such that the area of the lower frame 2 formed below
`the aforementioned liquid crystal display panel 62 to the 25
`area occupied by said liquid crystal display panel 62 is set
`to 10% to 50% (more preferably about 30%). Moreover, the
`upper frame 1 is made of a thin stainless steel sheet, whereas
`the lower frame 2 is made of a thin aluminum sheet, so that
`the rigidity can be enhanced while reducing the thickness of 30
`the intermediate frame 42 thereby to reduce the overall
`weight of the liquid crystal display module.
`The foregoing and other objects, advantages, manner of
`operation and novel features of the present invention will be
`more readily understood from the following detailed 35
`description when read in connection with the accompanying
`drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`40
`
`FIG. 1 is an expanded perspective view of a liquid crystal
`display module according to one embodiment of the present
`invention;
`FIG. 2 is a top plain view showing a lower frame 45
`constituting the liquid crystal display module according to
`the present invention;
`FIG. 3 is an explanatory diagram illustrating the relations
`among the array directions of liquid crystal molecules, the
`twisting direction of liquid crystal molecules, the axial 50
`directions of polarizing plates and the optical axis of a
`birefringent member of Specific Embodiment 1 of the liquid
`crystal display module according to the present invention;
`FIG. 4 is a perspective view showing an essential portion
`of the laminated structure of the components of the liquid
`crystal display module according to the present invention;
`FIG. 5 is an explanatory diagram illustrating the relations
`among the array directions of liquid crystal molecules, the
`twisting direction of liquid crystal molecules, the axial 60
`directions of polarizing plates and the optical axis of a
`birefringent member of Specific Embodiment 2 of the liquid
`crystal display module according to the present invention;
`FIG. 6 is a graph plotting the contrast characteristics of
`Specific Embodiment 2 of the liquid crystal display module 65
`according to the present invention against an intersectional
`angle a for the colors of transmission light;
`
`55
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Here will be described in detail in the following in
`connection with its embodiments with reference to the
`accompanying drawings.
`FIG. 1 is an expanded perspective view for explaining the
`construction of a liquid crystal display module 63 according
`to the present invention. Reference numeral 1 designates an
`upper frame; numeral a liquid crystal display window;
`numeral 62 a liquid crystal display panel; numeral 35 a
`driver substrate; numeral13 a spacer; numeral37 an optical
`conductor assembly composed of an optical diffusion plate,
`a conducting plate and a reflecting plate; numeral 42 an
`intermediate frame having a linear back light source
`mounted thereon; numeral36 a linear back light source (or
`lamp) composed of a cold-cathode tube; numeral17 a lamp
`cover; and numeral 2 a lower frame.
`Moreover, numeral 18 designates raised ears to be
`brought into contact with ground pads 24 formed at the
`driver substrate 35; numeral 20 pawls to be fixed on pawl
`retainers 25 formed in the lower frame 2; numeral 14 an
`adhesive tape for fixing the upper frame 1 and the liquid
`crystal display panel 62; numerals 55 and 56 cut-away
`portions formed in symmetrical positions with respect to a
`line perpendicular to the central portion of the back light;
`numerals 57 and 58 cut-away portions formed in the longi(cid:173)
`tudinal direction of the back light source 36; and numerals
`53 and 54 notches formed below the two end portions of the
`back light source 36. Still moreover, the upper frame 1 is
`made of a steel sheet having a thickness of 0.8 mm, and the
`lower frame 2 is made of an aluminum sheet having a
`thickness of 0.5 mm.
`In FIG. 1, the liquid crystal display panel 62 is sand(cid:173)
`wiched between the upper frame 1 and the lower frame 2 in
`the order, as shown. The intermediate frame 42 is equipped
`at its one end side with the linear light source (or back light
`source) 36 made of a cold-cathode tube, which has its direct
`light omitted toward the liquid crystal display panel 62
`shielded by the lamp cover 17, so that its emitted light may
`be directed toward the conductor assembly 37 composed of
`an optical diffusion plate and a conducting plate.
`
`Page 13 of 18
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`5,504,605
`
`15
`
`5
`The spacer 13 is sandwiched between the conductor
`assembly 37,which is mounted in the recess formed in the
`intermediate frame 42, and the liquid crystal display panel
`62 to establish a display area.
`The upper frame 1 is made of a thin stainless steel sheet, 5
`and the lower frame 2 is made of a thin aluminum sheet. The
`lower frame 2 is formed with at least one pair of cut-away
`portions 55 and 56, which extend in a direction perpendicu-
`lar to the back light source 36 over at least the area of the
`liquid crystal display panel 62 and which are positioned 10
`symmetrically to the line perpendicular to the center portion
`of the back light source 36. The lower frame 2 is further
`formed with at least two cut-away portions 57 and 58, which
`extend just below the back light source 36 in the longitudinal
`direction of the back light source 36. Further, the lower
`frame 2 is provided with notches 53 and 54, which are
`positioned below the two end portions of the back light
`source 36.
`As described above, according to the present embodi(cid:173)
`ment, the upper frame 1 is made of a thin stainless steel
`sheet, and the lower frame 2 is made of a thin aluminum
`sheet, so that the liquid crystal display module can be made
`thin and light without having its rigidity reduced. At the
`same time, the heat dissipation effect can be improved to
`establish a uniform temperature distribution all over the
`surface, thereby to prevent any display irregularity, by use of
`the cut-away portions 55 and 56, which extend in a direction
`perpendicular to the back light source 36 over at least the
`area of the liquid crystal display panel 62 and which are
`positioned symmetrically to the line perpendicular to the
`center portion of the back light source 36, by use of the
`cut-away portions 57 and 58, which extend just below the
`back light source 36 in the longitudinal direction of the back
`light source 36, and by use of the notches 53 and 54, which
`are positioned below the two end portions of the back light
`source 36.
`Moreover, the back light source 36 is driven by high(cid:173)
`frequency waves so that an electric current flows from the
`back light source 36 to the lower frame 2 through a stray
`capacity between the lower frame 2 and the back light source 40
`36. This current is called a "leakage current". Since the
`electric current to contribute to a lighting operation of the
`back light source 36 is reduced by that "leakage current", the
`brightness accordingly drops. On the other hand, the back
`light source 36 generates heat if it is lit for a long time 45
`period, so that the temperature in the vicinity thereof grows
`higher than the room temperature. If no counter-measure is
`taken, the heat in the vicinity of the back light source 36
`exerts direct influences upon the liquid crystal display panel
`62 so that the temperature distribution of the liquid crystal 50
`display panel cannot be made uniform. In the aforemen(cid:173)
`tioned embodiment, therefore, the cut-away portions 57 and
`58 are formed to prevent the reduction of the brightness due
`to the "leakage current" so that the temperature distribution
`of the liquid crystal display panel may be made uniform to 55
`prevent display irregularity. Moreover, the cut-away por(cid:173)
`tions 57 and 58 can prevent the brightness from being
`reduced by the thermal dissipation of the back light
`source 36.
`On the other hand, the two end portions of the back light 60
`source 36 are locally reduced in brightness by the tempera(cid:173)
`ture drop so that their temperature has to be raised so that the
`temperature distribution of the liquid crystal display panel
`62 can be kept uniform. Thus, the notches 57 and 58 are
`formed to prevent the brightness reduction while making the 65
`temperature distribution of the liquid crystal display panel
`62 more uniformed. The notches 57 and 58 can functionally
`
`6
`achieve the same effects as those of the aforementioned
`cut-away portions.
`On the other hand, the cut-way portions 55 and 56, which
`are formed to extend over the area of the liquid crystal
`display panel62 and are positioned symmetrically to the line
`perpendicular to the center portion of the back light source
`36, can reduce the weight of the lower frame 2 and uniform
`render the temperature distribution of the liquid crystal
`display panel 62 more uniform.
`Further description will be made on the area ratios of the
`cut-away portions 57 and 58, the notches 53 and 54 and the
`cut-away portions 55 and 56, as described above, to the
`lower frame 2.
`FIG. 2 is a top plan view showing the lower frame 2. The
`aforementioned cut-away portions 57 and 58 and notches 53
`and 54 are arranged at specified positions with respect to the
`back light source 36. This back light source 36 is equipped
`with a power supply cable, although not shown, which is
`arranged generally in parallel with the back light source 36.
`20 If it is assumed that the length of the back light source 36 and
`the power supply cable are designated at L, the portions, in
`which the lower frame 2 excepting the cut-away portions 57
`and 58 and the notches 53 and 54 are present, can be
`designated at S1, S2 and S3 . The present invention is
`25 characterized in that the ratio of the portion (S 1+S 2+S3 ), in
`which the lower frame 2 is present, to the portion (L), in
`which the fluorescent lamp and the power supply cable of
`the back light source 36 are arranged, is set to 10% to 50%
`(preferably about 30%). This can be expressed in the fol-
`lowing relationship: 0.1~(S1+S2+S3)1L~0.05.
`Since the cut-away portions 57 and 58 and the notches 53
`and 54 are formed at the above-specified ratio, the reduction
`of the brightness due to the "leakage current" or the heat
`dissipation can be prevented to achieve more effectively the
`prevention of any display irregularity by means of the
`uniform temperature distribution of the liquid crystal display
`panel.
`As to the cut-away portions 55 and 56, too, the area ratio
`to the conductor assembly is an important point, as viewed
`from the standpoint of making the temperature distribution
`of the liquid crystal display panel more uniform.
`Specifically, the prevention of the display irregularity by
`making the temperature distribution of the liquid crystal
`display panel more uniform can be achieved more effec(cid:173)
`tively by setting the ratio of the portion, in which the lower
`frame 2 is present to the portion, in which the conductor
`assembly 37 is arranged, to 10% to 50% (preferably about
`30% ). This can be expressed in the following relationship:
`0.1 ~(S4+S5+S6)/L~ 0.5, if the width of the liquid crystal
`display element of the liquid crystal display panel 62 or the
`width of the conductor assembly 37 is designated at L, and
`if the portions, in which the lower frame 2 is present to
`correspond to the arranged portion of the conductor assem(cid:173)
`bly 37, are designated at S4 , S5 and S6 .
`Here will be described specific embodiments in which the
`construction described above is applied to a liquid crystal
`display module of super-twisted nematic (STN) type. Inci(cid:173)
`dentally, those portions having identical functions are des(cid:173)
`ignated by common reference numerals, and their repeated
`description will be omitted.
`[Specific Embodiment 1]
`FIG. 3 is an explanatory diagram illustrating the array
`directions (e.g., rubbing directions) of liquid crystal mol(cid:173)
`ecules, the twisting direction of liquid crystal molecules, the
`directions of the polarizing axes (or absorbing axes) of
`polarizing plates, and the direction of the optical axis of a
`
`30
`
`35
`
`Page 14 of 18
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`5,504,605
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`5
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`40
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`7
`member having a birefrigence effect, by taking a top plan
`view of the liquid crystal display panel 62 according to the
`present invention, and FIG. 4 is a perspective view showing
`an essential portion of the liquid crystal display panel 62
`according to the present invention.
`The twisting direction 10 and the angle of twist 8 ofliquid
`crystal molecules are regulated by the rubbing direction 6 of
`an oriented film 21 on an upper electrode substrate 11, by the
`rubbing direction 7 of an oriented film 22 on a lower
`electrode substrate 12, and by the kind and amount of an 10
`optically active substance to be added to a nematic liquid
`crystal layer 50 sandwiched between the upper electrode
`substrate 11 and the lower electrode substrate 12.
`In order that the liquid crystal molecules may be oriented
`to have a twisted helical structure between the two upper and
`lower electrode substrates 11 and 12 sandwiching the liquid
`crystal layer 50, as shown in FIG. 4, there is adopted the
`so-called "rubbing method" of rubbing the surfaces of such
`oriented films 21 and 22 on the upper and lower electrode
`substrates 11 and 12 in one direction with a cloth or the like 20
`in contact with the liquid crystal and as are made of an
`organic high-molecular resin, such as polyimide. The rub(cid:173)
`bing directions at this time, i.e., the rubbing direction 6 in the
`upper electrode substrate 11 and the rubbing direction 7 in
`the lower electrode substrate 12 are in the array directions of
`the liquid crystal molecules.
`The two upper and lower electrode substrates 11 and 12
`thus oriented are so opposed through a gap d1 to each other
`that they intersect with each other at their individual rubbing
`directions 6 and 7 at an angle of about 180 degrees to 360
`degrees, and are adhered to each other by a framed sealing
`member 52 which is formed with a notch 51 for injecting the
`liquid crystal. When the gap is filled up with a nematic liquid
`crystal to which is added a predetermined amount of an
`optically active substance having a positive dielectric anisot- 35
`ropy, the liquid crystal molecules are so arrayed between
`those electrode substrates as to have a helical structure of the
`shown angle of twist 8. Incidentally, reference numerals 31
`and 32 designate upper and lower electrodes, respectively.
`Over the upper electrode substrate 11 of a liquid crystal
`cell60 thus constructed, there is arranged a member (as will
`be called the "birefringent member") 40 having a birefrin(cid:173)
`gent effects. Upper and lower polarizing plates 15 and 16 are
`further provided across this member 40 and the liquid crystal
`cell 60.
`The angle of twist 8 of the liquid crystal molecules in the
`liquid crystal 50 is preferably at 200 degrees to 300 degrees,
`but more preferably falls within a range of 230 degrees to
`270 degrees from the practical standpoint to avoid the
`phenomenon that the lighting state in the vicinity of the
`threshold value in the curve of transmission-applied volt(cid:173)
`age is oriented to scatter the light so that excellent time
`sharing characteristics may be maintained.
`This condition basically acts to make the response of the
`liquid crystal molecules more sensitive to the voltage
`thereby to realize the excellent time sharing characteristics.
`In order to achieve an excellent display quality, on the other
`hand, the product &11·d1 of the refractive index anisotropy
`&11 and the thickness d1 of the liquid crystal layer 50 is 60
`desirably set preferably within a range of 0.5 !ffil to 1.0 !ffil,
`and more preferably within a range of 0.6 !ffi1 to 0.9 lffil·
`The birefringent member 40 acts to modulate the polar(cid:173)
`ized state of the light to be transmitted through the liquid
`crystal cell 60 thereby to convert the colored display of only
`the liquid crystal cell 60 to a monochromatic display. For
`this conversion, the product &12·d2 of the refractive index
`
`8
`anisotropy &12 and the thickness of the birefringent member
`40 is very important and is set preferably within a range of
`0.4 !ffi1 to 0.8 !ffil, and more preferably within a range of 0.5
`!ffi1 to 0. 7 !ffil.
`Moreover, the liquid crystal display panel 62 according to
`the present invention utilizes elliptical polarization resulting
`from the birefringence. In case, therefore, a uniaxial trans(cid:173)
`parent birefrigent plate is used as the birefringent member
`40, the relations among the axes of the polarizing plates 15
`and 16, the optical axis of the birefringent member 40, the
`array directions 6 and 7 of the electrode substrate 11 and 12
`of the liquid crystal cell 60, are extremely important.
`Here will be described the operations and effects of the
`aforementioned relations with reference to FIG. 3. This
`Figure illustrates the relations of the axes of the polarizing
`15 plates, the optical axis of the uniaxial transparent birefrin(cid:173)
`gent member, and the array directions of the liquid crystal
`molecules of the electrode substrates of the liquid crystal
`cell by taking a top plan view of the liquid crystal display
`module having the construction of FIG. 4.
`In FIG. 3, reference numeralS designates the optical axis
`of the uniaxial transparent birefringent member 40; numeral
`6 the array direction of the liquid crystal of the birefringent
`member 40 and the upper electrode substrate 11 adjacent to
`the former; numeral 7 the array direction of the liquid crystal
`of the lower electrode substrate 12; numeral 8 the axis of
`25 absorption or polarization of the upper polarizing plate 15;
`letter a an angle made between the liquid crystal array
`direction 6 of the upper electrode substrate 11 and the optical
`axis 5 of the uniaxial birefringent member 40; letter ~ an
`angle made between the axis of absorption or polarization 8
`30 of the upper polarizing plate 15 and the op