How to reverse the clock display

Colocación polarizador pantalla reloj

Today we're going to see how we can reverse the clock screen. We can make it black with light digits or the other way around, dark digits with a light background.

  1. Advantages of the dark number display on a light background
  2. Advantages of the inverted display (light numbers on a dark background)
  3. Necessary tools.
  4. Preliminaries.
  5. Dismantling the module
  6. Remove the polarizing filter
  7. Screen cleaning
  8. The new polarizing filter
  9. Reset the module
  10. Related video

Advantages of the dark number display on a light background

This type of display is the classic display of digital watches, the display of a lifetime.

Pantalla normal reloj
Example of "normal" display

Among the main advantages of this screen over the inverted one are Better visibility: these screens have better visibility than the inverted ones, regardless of the level and type of lighting. As they have a higher contrast of the digits with the background, they make it easier to read at a glance. Possible better battery consumption: it is not that the inverted screens consume more (they consume exactly the same), but having better visibility than the inverted ones, we will use the light better, so we will be able to save battery and extend the life of the battery.

Advantages of the inverted display (light numbers on a dark background)

This type of digital watch display has clear digits on a black background.

Pantalla invertida de reloj
Ejemplo de una pantalla "invertida"

The main advantage is aesthetics. As it is much less seen (although it is more common every day) than the traditional screen, it calls much more attention.

Necessary tools.

  • Screwdriver or jaxial key to remove the back cover of the watch
  • Tweezers for removing the watch module from the case
  • Alcohol to clean the glue residues from the previous polarizing filter
  • Cutter or sharp knife to separate the polarizing filter from the screen
  • Polarizing film to be placed back on the screen. It is preferable to choose one that already has the glue applied on one side
  • Isopropyl alcohol to clean the glue residues from the screen polarizing filter.


Obviously, the first step is to remove the back cover of the watch, and with the help of the tweezers, take the watch module out of the watch case. Care should be taken when removing the module from the case so as not to damage it.

Dismantling the module

Once removed from the box, we must dismantle the clock module. It is convenient to document each step in order not to have any problem when reassembling the module. Personally, what I do, is taking pictures with the mobile phone in each step, so it is easier to reassemble the caliber correctly. We proceed to disassemble the battery hitch and remove it from the module. We will release the tabs that fix the battery holder from the module. We will be careful not to lose small components, such as the spring that is in contact with the back cover and that allows the sound of the alarm to work. Carefully remove the plastic sheet where the battery is fitted. Then remove the electronic circuit from the module. Next, we will be able to see the zebra connectors and the screen. Carefully end the zebra connectors.

Remove the polarizing filter

LCD invertido reloj
Lcd screen with inverted polarizing filter

We dismantle the screen and resting the screen on a flat surface, with the cutter or the knife, we proceed to remove the polarizing filter. Insert the edge on the side between the polarizing filter and the screen. It's better to go slowly, it's better to go in 5 minutes than to break the screen in a hurry, which will make the watch useless.

Screen cleaning

Once the polarizing filter has been removed, we proceed to clean the remains of the glue from the screen with isopropyl alcohol. It is convenient not to leave any rest, as later when placing the new polarizing filter it will not be perfectly stuck to the screen and with the time it will give problems when detaching.

LCD sin polarizador
Screen without polarizing filter and without glue residues.

The new polarizing filter

When we have a clean screen, we should know the orientation of the new polarizing filter. We will have to mount the module completely again, and place the new polarizing film on the screen, taking into account the side that has the adhesive glue . We will turn the sheet until we see the digits perfectly (if we want it normal or inverted). Once we know the correct position, we can use the old polarizing filter as a template to cut the new polarizing film.

Colocación polarizador pantalla reloj
New polarizing filter on the screen before pasting

We disassemble the module again, and with the lcd of the screen on a flat surface, we stick the new polarizing filter on the screen. We try to be careful and go little by little to avoid leaving "bubbles" on the screen and that it is centered on the lcd.

Pantalla normal reloj
"Uninverted" screen, now normal as usual

Reset the module

We will proceed to reassemble the module, and an essential step in casio digital watches is to "reset" the module. The procedure consists of making contact in the connector marked "AC" on the back of the module with the positive pole of the battery. In some models it is with the negative pole, in that case there will be a sticker on the battery or on the back of the watch cover.

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