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SEMI D36-1103 © SEMI 2003 2 5.2.2 reflection sheet — the sheet that reflects the light to prevent th e loss of the light toward b ack side of the BLU. 5.2.3 light gui de plate — the plate, one of im portant components of…

SEMI D36-1103 © SEMI 2003 1

SEMI D36-1103

TERMINOLOGY FOR LCD BACKLIGHT UNIT

This standard was technically approved by the Global Flat Panel Display Committee and is the direct

responsibility of the Japanese Flat Panel Display Committee. Current edition approved by the Japanese

Regional Standards Committee on August 8, 2003. Initially available at www.semi.org October 2003; to be

published July 2003.

1 Purpose

1.1 These terms and definitions describe various

components and characteristics of backlight unit used

for light source of liquid crystal display. This standard

will be helpful to unify terminologies used for backlight

unit, which will improve manufacturing efficiency

resulting in reduction of manufacturing cost and time.

2 Scope

2.1 This standard is applicable to backlight unit. This

standard includes the terminologies of components used

in Backlight unit, inspection and measurement used in

backlight unit field as well as panel and instrumentation

field. The other area is not dealt with other SEMI

standard document.

NOTICE: This standard does not purport to address

safety issues, if any, associated with its use. It is the

responsibility of the users of this standard to establish

appropriate safety and health practices and determine

the applicability of regulatory or other limitations prior

to use.

3 Limitations

3.1 In this standard, our target is only backlight unit

and general purpose for terminology. Hence a special

language used for critical purpose is not mentioned. For

example, we do not define special languages depending

to personal emotion and a detail or small components

depending on special or general purpose.

3.2 The definition of lamp components follows the

language used in lighting company or other optics

related standardization.

4 Referenced Standards

4.1 CIE Standards

CIE 1931 — color space, CIE 1976 UCS

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

1 CIE International Commission on Illumination, Kegelgasse 27, A-

1030 Vienna, Austria

5 Terminology

5.1 General Terminology

5.1.1 Definition of Backlight Unit

5.1.1.1 Backlight unit (BLU) is a kind of light source

positioned at the backside of liquid crystal panel. Since

LCD is non-emissive display device it needs essentially

light source.

5.1.2 Structure of BLU

5.1.2.1 As an initial light source cold cathode

fluorescence lamp (CCFL) is used at bottom and/or

topside of BLU. The light emitted from CCFL is

entered into light guide plate (LGP). Here light is

spread out two-dimensional light by scattering sites at

the back surface LGP or inside of LGP. Two-

dimensional light is sometimes diffused by diffusion

sheet or conversed by prism sheet respectively. And

final light comes into human eyes.

Figure 1

General structure of BLU; From a) to g), each

components are indicate CCFL, reflection sheet,

light guide plate, diffusion sheet, two prism sheets,

protection sheet and panel respectively.

5.2 Components — The following measurement items

are recommended for BLU but these items depend on

user requirements if they are specified.

5.2.1 cold cathode fluorescence lamp — the positive

column or cathode discharge lamp of the glow

discharge. Namely, the ultraviolet by the releasing of

the second electron of cathode stimulates the phosphor,

so the lamp radiates the visible ray.

SEMI D36-1103 © SEMI 2003 2

5.2.2 reflection sheet — the sheet that reflects the light

to prevent the loss of the light toward back side of the

BLU.

5.2.3 light guide plate — the plate, one of important

components of the BLU, that changes the path of the

light from line light source to face light source.

5.2.4 diffusion sheet — the sheet that diffuses the light

to the previous surface.

5.2.5 prism sheet — the film to enhance the brightness.

5.2.6 protection sheet — a kind of sheet placed on the

top of BLU for protecting other components from

damage outside.

5.2.7 frame — the frame to make the components of

the BLU stably combined.

5.2.8 electrode — the conductor, an electron source

inside the lamp, which releases the electron by the

electric current or flows the discharge current.

5.2.9 hot (electrode) — the electrode part receiving

current from the inverter, namely anode.

5.2.10 ground (electrode) — the opposite part against

the hot electrode of the lamp, namely cathode.

5.2.11 inverter — the device that transfers the voltage

of the power supply from low voltage DC to high

voltage AC to start the cold cathode fluorescence lamp.

5.2.12 lamp — the light source device mainly using the

cold cathode fluorescence lamp that lights the BLU.

5.2.13 lamp assembly — the total light source devices

to light lamp.

5.2.14 lamp cover — the part protecting the lamp

makes the light released from the luminance factor

incident over the light guide plate.

5.2.15 lamp holder — the part that protects the lamp

form external collision or contact.

5.2.16 lamp ring — the part that protects lamp from the

fragility.

5.2.17 mercury — as an ultraviolet light source,

elemental name in the periodic table is Hg.

5.2.18 mixing gas — the gas needed to open the

discharge consists of Neon and Argon gas etc

maintaining the discharge.

5.2.19 phosphor — the phosphor with commonly red,

blue and green color that transfers the ultraviolet came

from the mercury to the visible ray.

5.2.20 shrinkage tube — the part made of insulation

material to protect the wire.

5.2.21 adhesive tape — the tape to be used for adhering

the components of the BLU to each other.

5.2.22 back cover — the device that complements

fragile part of the lamp, etc. by means of utensil.

5.2.23 clip — the part fixing the sheet on the frame to

prevent flux and looseness of sheet.

5.3 Characteristics

5.3.1 luminance — the luminance flux from the surface

per unit solid angle per unit area in a given direction.

Unit: nit and/or cd/m

5.3.2 average luminance — average value of measured

luminance.

5.3.3 maximum luminance — maximum value among

the measured luminance.

5.3.4 minimum luminance – minimum value among the

measured luminance.

5.3.5 luminance uniformity — The value that indicates

the uniformity of luminance for the measured point.

And the value is obtained by selecting one or multiple

among below equations.

a) (maximum/minimum) × 100

b) (minimum/maximum) × 100

c) [(maximum-minimum)/Maximum] × 100

d) [(maximum-minimum)/Average] × 100

where average = Σ(i!n)/N

5.3.6 center point — The position corresponding to the

center of active area of BLU.

5.3.7 chromaticity — The indication of the suitable

color for the mark of same color, namely the spectro-

distribution-chart (λ) of the measured light source. The

light source color is indicated by the 3 measured

stimulus factors X, Y, Z (the quality of stimulus

evoking the primary color sense) at the sensitivity of

eye (2° ).

Tri

stimulus factors: X, Y, Z

x = X/(X + Y + Z),

y = Y/(X + Y + Z),

z = Z/(X + Y + Z),

x + y + z = 1

(Referred by CIE 1931 color space)

5.3.8 life time — The shorter period of the time during

no re-lit the lamp when lighting the lamp and during the

flux of light’s reaching the minimum value of

regulations.

5.3.9 correlated color temperature (CCT) — A term

used to describe the color of a light source whose

chromaticity lies close to the Planckian (black body)

locus on a CIE chromaticity chart. Specially, it is the

temperature of a black body radiator which produces

the chromaticity most similar to that of the light source

evaluated. It is usually expressed in degrees Kelvin.

5.3.10 surface temperature — The surface temperature

of the lamp and BLU.

Unit: ° C

5.3.11 turn-on test — The test for checking turn-on &

off of the BLU.

5.3.12 appearance test — The test for appearance

inspection of the BLU.

5.3.13 reliability test — The test for checking the

changes of the display quality and part size during

lighting of the BLU at the measurement condition (ex:

temperature 60° C, humidity 75%, aging time 96hr,

250hr, 500hr).

5.3.14 efficiency — The ratio

of total light fluxes

generated by the lamp and consumed electric power at

input part of the lamp.

Unit: lm / W (lumen/Watt)

5.4 Equipment

5.4.1 photometer — The equipment that measures the

luminance of the object at the point of the perpendicular

angle view for the surface of BLU.

5.4.2 colorimeter — The equipment that measures the

color of the object at the point of the perpendicular

angle view for the surface of BLU.

NOTICE: SEMI makes no warranties or

representations as to the suitability of the standards set

forth herein for any particular application. The

determination of the suitability of the standard is solely

the responsibility of the user. Users are cautioned to

refer to manufacturer' s instructions, product labels,

product data sheets, and other relevant literature,

respecting any materials or equipment mentioned

herein. These standards are subject to change without

notice.

By publication of this standard, Semiconductor

Equipment and Materials International (SEMI) takes no

position respecting the validity of any patent rights or

copyrights asserted in connection with any items

mentioned in this standard. Users of this standard are

expressly advised that determination of any such patent

rights or copyrights, and the risk of infringement of

such rights are entirely their own responsibility.

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