FR2514536A1 - LCD module with separate display and electronics - uses two circuit boards linked by printed circuit board connecting into flexible multi-conductor connectors on boards - Google Patents

Abstract

The module is formed from two readily separable parts, one being the display panel incorporating the liquid crystal cells and the other the electronic circuit which controls and drives the display. The electrical connections between the two parts use a system of separable connections having a flexible joint with multiple conductors. The flexible joints connect to a printed circuit board which connects the electronic control circuit to the display cells. The assembly is mounted in a box, having a rectangular window in one end, with the liquid crystals facing the window. The opposite end of the box is closed by the printed circuit board which couples the two parts of the unit. A light source is placed behind the liquid crystals for display in low ambient light conditions.

Description

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  Modular liquid crystal display element.

  The present invention relates to a modular element

  the liquid crystal display unit formed by at least two easily disconnectable parts, namely, an electro-optical display head and an electro-unit

  picnic including all or part of the com- ponents

display head command.

  In general, it is known that the liquid crystal cells currently available on the market, in particular for the digital display of quantities, are in the form of a plate having, on the peripheral border of one of

  its faces, a series of connected control electrodes

  tees to the internal electrical network of the cell and

  to be connected to the electronic control unit

  order. It turns out that due in particular to the large number of these control electrodes and the corresponding electrical connections, the cell and the control unit are generally mounted in the same case.

  of generally large cross section compared to the di-

cell mensions.

  Such a provision, however, presents a

  many disadvantages among which we mention-

  nera: the large size of the display element; the difficulty of mounting and, in particular, the wiring of the cell / control unit connections, and, the difficulty of maintenance (detection of

  breakdowns and replacement of defective components).

  The invention firstly aims to remove

all of these drawbacks.

  To this end, it offers a modular liquid crystal display element formed by at least two removable parts, namely, a display head.

  electro-optics and a control unit, and in the-

  what the electrical connections between these two parts

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  are carried out by means of a separate connection system

  rables. More precisely, the display head consists of a housing provided, on its front face, with a window in which is removably mounted, the liquid crystal cell, the rear face of this box intended to come and assemble on the unit of

order being opened.

  The part of the connection system included in this display head, consists of at least one seal

  flexible with multiple conductors, inserted between the terminal

  the inner surface of the cell provided with the control electrodes and the peripheral edge of a transfer card closing the rear opening of the

housing.

  This flexible joint comprises a plurality of discrete conductive elements, electrically isolated from each other and extending from one side to the other of the joint, preferably in planes perpendicular to the axis.

longitudinal of the joint.

  On the one hand, its role is to maintain the

  lule firmly pressed against the window sill

  and connect the individual electrodes

  command of the cell to corresponding contact pads

dants of the transfer card.

  This transfer card consists of a printed circuit board, possibly double-sided, which comprises, on a side, at its periphery, a plurality of primary contact pads corresponding in size and in layout, to the control electrodes of the

  cell and, on the other side 8, at its periphery, a greater

  reality of secondary contact pads connected each

  to a corresponding primary contact pad.

  These secondary contact pads can be arranged in different locations from those of the primary contact pads, and have different dimensions. The transfer card thus thus allows -3-

  to use a control unit whose connection pads

  tacts intended to ensure the electrical connections with the display head, may have a different implantation from that of the control electrodes of the liquid crystal cell.

  contact of the control unit can therefore be advanced

  markedly planned according to the manufacturing techniques

  cation and mounting of the electronic control unit.

  The electronic control unit includes-

  even a shoemaker containing at least part of the electronic control circuit and whose front face which holds

  location of assembly face of the display head presented

  at least one flexible joint with multiple conductors intended to come into contact with the secondary contact pads of the transfer card, when the display head is assembled to the electronic control unit. Furthermore, this flexible seal itself relates to a series of contact pads electrically connected to the

electronic control circuit.

  According to a particularly advantageous mode of the invention

  tion, this flexible seal comes directly to bear on

  contact pads on the printed circuit of the control unit

  which is then specially designed for this purpose.

  So when the display head is my-

  ted on the control unit, the electrical connection is obtained

  individual size of each of the control electrodes

  of the liquid crystal cell with the corresponding contact pads of the control unit (by

example of its printed circuit).

  Of course, in order to obtain good quality of the various electrical contacts which these connections comprise and to ensure good holding in position of the various elements, the display head must be locked by means of fixing elements (for example screw) tending to compress the display head on the case of the control unit

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  4 _ and to ensure pressure between the different studs

  contact and multiple conductor seals.

  Like most liquid crystal displays, the display head is also equipped with a liquid crystal cell lighting device placed either in front of the cell for reflective operation. either in arrears of the

  cell for operation by transmission of-

  radiation through the cell.

  In the case of a lighting device acting by reflection, the cell can be advantageously mounted oblique to the longitudinal axis of symmetry of the housing of the display head.

  case, the light source can be located on the

  internal hardness of the housing adjacent to the window, on the side where the cell is set back This light source can be removably mounted so that it can be easily changed without the need to carry out

  disassembly of the display head.

  In the case of a lighting device acting by transmission through the cell, the light source must be placed behind the cell,

  so inside the shoemaker There is therefore a pro-

  delicate problem for the implantation of the light source, its power supply and its removability without dismantling

the display head.

  The invention also aims to resolve these

  problems using the peculiarities of the struc-

  ture of the display head previously described.

  To this end, it therefore offers a display head

  comprising a casing of substantially parallel shape-

  pip 6 dique, fitted with a substantially rectangular window

  re against which is mounted a rectangular liquid crystal cell, the control electrodes of which are arranged along two of its opposite lateral edges. The display head then includes two seals -

  flexible multi-conductor side tubes

  bend against the two side edges of the cell

  which carry the control electrodes.

  Against these two seals (on the inside of the bot-

  tier) two guide elements are also provided

  which delimit a free volume between the trans-

  fert, the liquid crystal cell and the two sides

  free sides of the housing (perpendicular to the

  guide elements) Furthermore, on one of these c 8 free lateral tees is provided a section opening

  substantially equal to the section of the preceding free volume

  duly mentioned, and by which we introduce to the

  like a drawer, the light source.

  This light source can advantageously be

  present as a piece of trans-

  parent having a substantially parallelepepi-

  length of pedals substantially equal to the length of the boot and of width equal to the distance separating the two guide elements This part comprises, on the side of the cell a flat face, and on the other side, a slightly concave face coated with a layer

  in material capable of ensuring good distribution of the ray-

luminous.

  At the two ends of this concave face are provided two respective housings formed in the transparent material, which are each intended to receive a

  electric micro-bulb These two bulbs are

  same mounted on a plate, for example a circuit

  printed, of the same dimension as said part and which pre-

  feel, on the side 8 opposite to the bulbs, two studs

  tact connected to the wires of the bulbs.

  In the mounted position of the display head, these

  contact pads come to bear on contact pads

  corresponding tact of the transfer card, the assembly being designed to supply the bulbs

in electric current.

  Thus, in the event of failure of the bulbs, it suffices -6-

  simply remove, like a drawer, the set

  ble formed by the transparent material part and the

  insert the bulbs, then change the bulb

  the defective one (or even the whole plate).

  According to another characteristic of the invention, the boot housing containing the control unit is produced in two removable parts each comprising a seal

  flexible multi-conductor intended to come into con-

  tact of the transfer card of the display head, a printed circuit on which is targeted a part of the electronic control circuit, and, on the opposite side

  at the flexible seal, a series of plug-in terminals connected

  tees to said printed circuit and intended to come plugged in

  expensive on corresponding terminals of an external circuit

  laughing, the electrical connections between the two printed circuits being effected by means of transverse pins

  plugging in during assembly of the case.

  An embodiment of the invention will be described below, by way of nonlimiting example, with reference to the accompanying drawings in which s Figure 1 is an exploded perspective view

  of a modular display element.

  Figures 2 and 3 are two axial cross-sections

  tudinal, 900 from each other of the modular element

shown in Figure 1.

  Figures 4 and 5 are respectively a view of the rear face (Figure 4) and a view of the front face (Figure 5) of the modular element shown in Figures 1 to 3. As previously mentioned, the modular element

  liquid crystal display shown in these

  sins is formed of two removable parts, namely, an electreptic display head 1 and a unit of

command 2.

  The display head 1 comprises a casing 3 of substantially parallelepiped shape, provided on its front face with a substantially rectangular window 4 against which

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  -7- is mounted, in a removable manner, a rectangular liquid crystal cell 5 whose control electrodes are arranged along the two lateral edges

opposite 6 and 7.

  Against these two lateral edges 6 and 7 respectively apply, on the inside of the shoemaker Ideux flexible joints 8, 9 with multiple conductors

  in the form of a cord, of rectangular section

  gular, produced using a plurality of discrete conductive elements, electrically isolated from each other and extending from one side to the other of the joint,

  preferably in planes perpendicular to the long axis

gitudinal of the joint.

  The case 3 is also closed, from the c 8 side opposite to the window 4, by a transfer card 11 consisting of a double-sided printed circuit board which comprises at its periphery, from the inside case of the case, a plurality primary contact pads corresponding in size and location, to the control electrodes of the cell 5 and which come to bear on the two flexible seals 8, 9, and on the other side 8 t, at its periphery, a plurality of pads of secondary contact each connected to one (or possibly several) corresponding primary contact pad. Furthermore, against the two flexible seals with multiple conductors 8, 9, c 8 inside the boot, there are also two guide elements 12, 13

  parallel, forming slides in the case 3.

  These two guide elements 12, 13 delimit with the transfer card 11, the liquid crystal cell 5 and the two lateral sides 14, 15 of the case 3, a free volume 16 intended to receive a removable lighting device acting by transmission. through

from cell 5.

  -8- This lighting device consists of a part

  in transparent material 17 having a sensitive shape

  completely parallelepipedal, of length substantially equal to the length of the boot 3 and of width equal to the distance separating the two guide elements 12, 13. This part 17 comprises, from the side 8 of the cell 5, a flat face 18, and , on the other side, one side slightly

  concave 19 coated with a layer of material suitable for

  rer good diffusion of light radiation.

  At the two ends of this concave face are provided two respective housings 20 formed in the

  transparent material, which are intended to receive each

  cun an electric micro-bulb 21.

  These two bulbs 21 are themselves mounted on a printed circuit board 22 which has

  opposite side to the bulbs, two contact pads 23 con-

connected to the wires of the bulbs 21.

  These contact pads 23 are intended to come

  wear on corresponding contact pads on the

  transfer head 11, the assembly being designed to ensure

  the supply of the bulbs 21 with electric current.

  The entire lighting device (part 17 + printed circuit 22) is housed like a

  drawer in volume 16, thanks to an opening 24 mena-

  on side 15 of shoemaker 3 perpendicular to

guide elements 12, 13.

  Furthermore, the part 17 may comprise, at one of its ends, a latching stud 25 intended to cooperate with a bore 26 formed on the c 8 tee 14 of the

  shoemaker 3 opposite opening 24 and a gripping head

  sion 27 located c 8 opening tee 24.

  The control unit 2 comprises a case made of two removable parts 28, 29 each containing a printed circuit board 30, 31, the assembly having, once mounted, a parallelepiped shape, the front face of which is substantially rectangular, has substantially the same dimensions as the rear face of the display head 1 on which it must come to be assembled. At the rear face (figure 4), the two

  parts of the boot 28, 29 each include an opening

  rectangular shape 32, 33, provided with an axial rim 34-

  lying projecting outward, delimiting a volume

  open parallelepiped, in which are available

  ser a series of plug-in terminals 36 mounted on the

  rear edge of the corresponding printed circuit 30, 31.

  This arrangement is intended to allow the control unit 2 to be connected to a connector

  corresponding form of an external circuit.

  Slightly protruding from the front, both

  parts 28, 29 of the shoemaker include, in addition, near

  mite of two of their opposite lateral edges, two respective flexible seals 38, 39 with multiple conductors, intended to come into contact with the transfer card 11 of the display head 1, as well as, respectively, on contact pads provided on the front edge of

  two printed circuit boards 30, 31.

  These flexible seals 38, 39 therefore make it possible to ensure disconnectable electrical connections between the unit

  2 and the removable display head 1.

  Furthermore, the electrical connections between the two printed circuit boards 30, 31 are ensured by means of connectors with transverse pins 40 which are plugged in when the two parts 28, 29 of the case are assembled. For their assembly and fixing, the adjacent side edges of the two parts 28, 29 of the boot maker are provided with elements 41, 42 shaped so as to

  stinterpenetrate each other and in which are pra-

  coaxial holes 43 through which a screw 44 is passed intended to be screwed on a

  thread 45 provided in the case 3 of the display head

age 1.

  Thus, using two lateral screws 44, we obtain

  fixing the two parts 28, 29 of the control unit

  command 2, and the display head 1.

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Claims (11)

  1. Modular liquid crystal display element   formed from at least two easily removable parts, namely an electro-optical display head including the liquid crystal cell (5) and an electronic control unit for said cell (5) / characterized in that the electrical connections between these two parts   are carried out by means of a separate connection system   rables comprising at least one flexible seal (38, 39) to multiple conductors.   2. Modular display element as claimed   cation 1, characterized in that the display head (1) consists of a case (3) provided, in its front face, with a window (4) in which is removably mounted, the liquid crystal cell (5), the   rear side of this boot (3) intended to come stasse-   bler on the control unit being open, and in that the part of the connection system, included in this display head (1), consists of at least one flexible joint with multiple conductors 8, 9, interposed between the edge of the inner face of the cell (5)   equipped with commando electrodes and the peripheral border   risk of a transfer card (11) closing the opening   re back of the shoemaker (3), said transfer card   (11) consisting of a printed circuit board,   double face, which comprises, on a c 8 tee, at its periphery, a plurality of primary contact pads corresponding dimensions and implantation, to the control electrodes of the cell and, on the other c 8 tee,   at its periphery, a plurality of contact pads se-   condaries each connected to a corresponding primary contact pad. 3. Modular display element according to one of the   claims 1 and 2, characterized in that the unit of   electronic control (2) itself comprises a casing housing containing at least part of the electronic control circuit and the front face of which takes the place of the face 11 - assembly of the display head (1) has at least one seal flexible multiple conductor (38, 39) intended to come into contact with the secondary contact pads of the transfer card (11), when the display head (1) is assembled with the   electronic control (2), this flexible seal also bearing   also on a series of electric contact pads   connected to the electronic circuit of the control unit (2).   4. Modular display element according to one of the   previous claims characterized in that the   flexible seal of the electronic control unit (2) comes directly to contact pads of a printed circuit (30, 31) of the electronic control unit command (2).   5 Modular display element according to one of the   previous claims, characterized in that the   display head (1) is further equipped with a device   lighting of the liquid crystal cell (5).   6. Modular display element according to one of the   previous claims characterized in that in   in the case of a lighting device acting by reflection, the liquid crystal cell (5) is mounted oblique with respect to the longitudinal axis of symmetry of the case (3) of the display head (1), and in that the light source is located on the internal edge of the case (3) adjacent to the window (4), from the side 8 to the cell (5) is set back.   7. Modular display element according to one of the   Claims 1 to 5, characterized in that, for a   transmission lighting, the light source is   placed inside the case (3) of the display head   (1), behind the liquid crystal cell (5).   8. Modular display element as claimed   cation 7, characterized in that the above head of affi-   chage (1) comprises a case (3) of substantially parallelepiped shape, provided with a window (4) substantially rectangular against which is mounted a cell 12 - rectangular liquid crystal (5) whose electrodes   control are arranged along two of its edges-   opposite side res, in that, the t 8 te display   (1) includes two flexible side seals (8, 9) with   multiple conductors coming to bear against the two said lateral edges of the cell (5), in that, against these two seals (8, 9), on the inner side of the shoemaker, are also provided two guide elements (12, 13 ) which delimit a free volume (16) between the said transfer card (11), the liquid crystal cell (5) and the two free lateral sides (14, 15) of the case (3), and in that, on one of these c 8 free side tees (15) is provided with an opening (24) through which is introduced, in the manner of a drawer, the light source.   9. Modular display element as claimed   cation 8, characterized in that said light source   is in the form of a piece of trans-   parent (17) of shape corresponding substantially to that of the above free volume (16) and which comprises, on the side opposite the cell (5), a slightly concave face (19) coated with a layer of optically diffusing material and that, at the two ends of this concave face, are provided two respective housings (20) formed in the transparent material, each intended to receive a electric bulb (21).   10. Modular display element as claimed   cation 9, characterized in that the above two ampou-   the electrics (21) are mounted on a plate (22) having, from the side opposite to the bulbs, at least two contact pads (23) connected to the wires of the bulbs (21), these two contact pads (23) being intended to come to bear on corresponding contact pads of the transfer card (11).   11 Modular display element according to one of the   previous claims, characterized in that the   casing containing the control unit (2) is made 13 - in two removable parts (28, 29) each comprising a flexible joint with multiple conductors (38, 39) intended to come into contact with the transfer card (11) of the display unit (1), a printed circuit (30, 31) to which a part of the electronic control circuit is wired, and, from the side opposite the flexible seal (38, 39), a series of plug-in terminals (36) connected to said printed circuit (30, 31) and intended to be connected to corresponding terminals of an external circuit, the electrical connections between the two printed circuits (30, 31) being effected by means of transverse pins   (40) plugging in during assembly of the shoemaker